National Park Service Mojave National Preserve U.S. Department of the Interior

Science Newsletter

Sweeney Granite Mountains Desert Research Center: an Interview with Director Dr. Jim André James M. André1 and Debra L. Hughson2

A significant factor in the amount of high quality research conducted in Mojave National Preserve is the Sweeney Granite Mountains Desert Research Center, part of the University of California Natural Reserve System. In this issue we interview its Director, Dr. Jim André. Dr. André is a research botanist who completed the Preserve’s Vascular Plant Inventory for the National Park Service Inventory and Monitoring Program. The Sweeney Granite Mountains Desert Research Center (GMDRC) is one of 37 protected research sites operated by the University of California Natural Reserve System (UC NRS). This system of outdoor classrooms and laboratories The Sweeney Granite Mountains Desert Research Center is located in Granite Cove at the base of the Granite Mountains. makes relatively undisturbed examples of the state’s diverse ecosystems available with support facilities for long-term Debra – Some of the people who were to researchers, teachers, and students research projects and multi-week field instrumental in the formation of the UC In this Issue: courses. Established in 1978, the Natural Reserve System, such as Ken Sweeney Granite Mountains Desert Norris and Wilbur Mayhew, were very • Page 1. Sweeney Granite Mountains active in this area of the Mojave Desert. Desert Research Center: an Interview with Research Center encompasses 3,496 Director Dr. Jim André hectares (8,639 acres) of the pristine and In fact one of the student camps is called rugged Granite Mountains in the East Norris Camp. How did the Sweeney • Page 7. Reptile Diversity Following the Mojave Desert ranging from piñon-juniper Granite Mountains Desert Research Hackberry Fire woodlands to creosote scrub bajadas. Center come to be and why did they • Page 12. Physiological Responses of Housing, laboratories, and a conference choose this site? Mojave Desert Shrubs to a Simulated room at the reserve can accommodate Summer Wash Flow: Preliminary Results up to 12 researchers for long-term Jim – Before we get started, I wish to • Page 17. Resource Management Issue: projects and field classes of up to 35 thank Debra Hughson for inviting me to Managing the Effects of Climate Change people. In 1994 with the passage of the this interview and for her continuing 1Sweeney Granite Mountains Desert Research California Desert Protection Act, the leadership in facilitating research and Center, P.O. Box 101, Kelso, CA 92351. 2Mojave reserve was enclosed inside the science education throughout the National Preserve, 2701 Barstow Road, Barstow, boundary of the newly created Mojave California Deserts. And to the Mojave CA 92365. National Preserve. National Preserve for the initiation of the

Mojave National Preserve Science Newsletter November 2009, Number 2 This Science Newsletter: Science Newsletter, an effort that is plants, population ecology of large strongly supported by the staff at the mammals such as the desert bighorn The Mojave Desert is internationally GMDRC, as well as many of our sheep, and studies of landscape-level known as a place to conduct scientific colleagues at the University of California. processes, such as erosion dynamics of research on desert ecosystems. In fact Mojave National Preserve was The Granite Mountains played a alluvial surfaces. A number of projects at designated in part to "retain and significant historical role in the the GMDRC focus on long-term enhance opportunities for scientific development of the UC Natural Reserve processes, such as global climate research in undisturbed ecosystems" System (NRS). Use of the Granite change, soil disturbance recovery as stated in the California Desert Mountains in the 1960s by UC professors monitoring, or the survivorship of long- Protection Act of 1994. Significant research is conducted through the Dr. Ken Norris (UCLA/UCSC) and Dr. lived shrub species. By design, such Sweeney Granite Mountains Desert Wilbur Mayhew (UCR) as a favorite studies may span decades, if not Research Center, part of the destination for their natural history field centuries. University of California Natural courses helped spur the idea for the Reserve System, and the Desert creation of the entire UC Natural Reserve As a hub of research activity in the Studies Center, operated by the System in 1965, which now includes 37 Mojave Desert, the question of why California Desert Studies Consortium of California State Universities. Both reserves located throughout California. researchers seek the GMDRC and the are located in the Preserve. Joined by Ken’s brother, Dr. Bob Norris eastern Mojave Desert in general is one (UCSB), and Dr. Mildred Mathias (UCLA), that has drawn our interest, and probably The purpose of this newsletter is it was the enthusiasm of this prominent requires a more lengthy discussion than threefold. First, we would like to group of four professors that led to the we have room for here. But every reserve highlight some of the research being done by university scientists in the University of California’s purchase of is unique in its capabilities and what it Preserve and to distribute this several sections of railroad lands and emphasizes in its mission. What the information to park staff and parcels of private lands in the eastern GMDRC offers to visiting researchers and management. Second, this periodical Granite Mountains. After several years of classes, as much perhaps as any field will allow us to inform the public and dogged persistence and diplomacy with station in the western U.S., is access to a research community about science land owners and a very supportive tremendous natural area—pristine, wild, being done by Preserve staff or funded through the National Park Bureau of Land Management, their efforts and expansive. The 9,000-acre GMDRC Service. And most importantly, we culminated in the establishment of the is located within a region of unparalleled would like to build collaboration Granite Mountains Desert Research biological and geological diversity in between scientists and resource Center in 1978. California. And while the facilities and managers so that scientists are made staff here are vital to its operation, it really aware of the needs of managers and top quality science is brought to bear Debra – The UC Natural Reserve System is the quality of this natural area that on the problems facing resource is available for use by institutions outside represents the single greatest asset of managers. of the University of California. What the field station. Embedded within proportion of researchers and students millions of acres of federal wilderness, Our intention is to publish this come from out of the state and what do including the Mojave National Preserve, newsletter twice per year, once in the you think brings them here to Granite ecological processes are still functioning spring and again in the fall; distributed in print at our Visitor Mountains and the Mojave Desert? here. The GMDRC provides not only a Centers and electronically on the quality setting to researchers, but a site web. Articles will range from non- Jim – Perhaps more than any NRS that will be protected over the long term. technical news stories to highly reserve, the GMDRC sustains a very For visiting students, the Granite technical research reports. All diverse array of research from scientists Mountains and surrounding region material in this newsletter has been peer-reviewed by subject-matter who come from all parts of the world. Of represents not only an outdoor experts. In each issue we will discuss the more than 350 research projects that classroom, but an adventure into a a resource management issue or have been conducted at the GMDRC in frontier. Here visiting students can make research need along with possible the past 30 years, about 40% were by UC observations that contribute significantly means of obtaining funding. The scientists, while roughly one-third were by to our knowledge base, inspiring resource management concern scientists from outside of California. discovery and appreciation for the highlighted in this issue is managing the effects of climate change. Presently, we support more than 155 complexity of our natural world. active research projects, including studies Debra Hughson, Science Advisor in microbiotic soil crust development, Debra – Research projects tend to build taxonomy and evolution of insects and on each other. The reserve makes this

2 Mojave National Preserve Science Newsletter 2009, Number 2 possible and also enables projects to be website (http://nrs.ucop.edu) that includes are few remaining taxonomic discoveries designed to go on for decades. How can a Research Database, where research left for science. Nothing could be farther researchers new to the area tap into this applications, metadata, and from the truth. The California deserts body of work? Is it primarily through the bibliographies are accessible to the collectively make up 28% of California’s published literature, or are there public. In addition, OBFS landmass, yet contain 37% of its native mechanisms for sharing data internally (http://www.obfs.org) offers a Data plant taxa. Some of the mid-elevation within the reserve system? Registry, where a variety of datasets and zones of the eastern Mojave support 60 protocols are made available. Finally, we to 70 species of shrubs per hectare— Jim – Over the past 30 years the do house a small collection of some of the highest shrub diversity found GMDRC has supported more than 350 dissertations, reports, and datasets from in North America! New species are being academic research projects that have projects completed here at the GMDRC; discovered every year. I estimate that 6 generated over 450 publications. But one you can also see a list of current research to 9% of the California deserts flora is of the great surprises for me in my tenure and publications on our website presently undescribed. So next time as resident director for the past 15 years (http://granites.ucnrs.org/). you’re out and about looking down at has been the near exponential growth of those desert plants, do not assume they our research program. It took 20 years to As is the case at all reserves in the NRS, all have names! reach 50 active research projects. Today, it has in fact been a great challenge to just 10 years later, the number of active obtain raw data from researchers who are I was immediately drawn to the Mojave research projects has tripled. wary to part with it prior to completion of National Preserve by its geographical their analyses and publications. And position and high-elevation linkages. The Many factors have contributed to this because data management can be time- Preserve lies at the hub of the Mojave, rapid growth in research, including the consuming, the GMDRC may select Great Basin and Sonoran Deserts with addition of lodging and laboratory space, certain datasets over those with low lowland and mountain corridors collaboration with agencies, staff probability of being used again. Thus, interdigitating in all directions. And while expertise, organization of workshops and most of the projects that build from these corridors promote a dynamic long- symposiums, and the protected lands – previous projects do so through the distance flux of genotypes into the region, some of the only lands protected for personal correspondence and the complex local topography, soils, and research in the 25 million-acre Mojave cooperation among individual geomorphic diversity found in the Desert. But the single most important researchers. The GMDRC has been Preserve create niches where species factor that stands out more than any successful as a conduit for linking may persist on the margin of their range, other is the phenomena of building a researchers with similar academic or act as isolating mechanisms where body of research. Like stepping stones, interests, and that has likely been our speciation may be facilitated. Additionally, over time one research project builds on greatest active influence on this stepping- in contrast to the west Mojave, the the previous one. For example, a site stone process. eastern Mojave Desert flora is becomes especially interesting to a plant significantly influenced by summer physiologist after a soil scientist has Debra – Your own research interests monsoonal precipitation. There exists a mapped the age of the surfaces there. include the flora of the Mojave Desert. In whole suite of plant species (mostly Some research is only made possible by your floristic inventory for the National summer annuals) in the Preserve’s flora the data collected by a prior investigation. Park Service Inventory and Monitoring that occur nowhere else in California. This nurturing process takes time to Program you added 85 new taxa to the These are species that rapidly germinate, evolve, but after 30 years we are known 831 species of vascular plants in flower, and set seed in a matter of weeks beginning to cultivate and sustain an the Preserve, including several that are following summer rain events. active research program at GMDRC new to science, and 885 occurrences of because we have developed a body of special-status plants. What makes this My work on a Flora of the Mojave research. Plant a seed and it will grow. region so floristically diverse? National Preserve and surrounding areas has been ongoing since 1994 when I first As a member of the NRS and national Jim – There is a broad misconception by arrived at the GMDRC. I wish to again Organization of Biological Field Stations the public and even by some scientists thank NPS and the Inventory and (OBFS), the GMDRC has several that the California deserts lack botanical Monitoring Program for the financial mechanisms for storing data collected by diversity, and perhaps an even bigger support of this project several years ago. researchers and making it available to misconception is that the desert has The three-year grant helped fund a major future investigators. The NRS maintains a already been well documented, that there push in the botanical inventory of the

3 Mojave National Preserve Science Newsletter 2009, Number 2 Preserve by bringing in additional field as unique plant assemblages throughout like a Sisyphean task. If you were to lead assistance for the surveys. Though we the park. It will be important to assess the an effort to prevent biological invasions continue to add new vascular plant taxa needs of each of the approximately 120 into Mojave National Preserve, how (1) to the overall park list (total number of special-status plant species that occur in would you go about it? known taxa in the Preserve stands today the park, starting with the rarest and most at 928), the rate of new finds has slowed imperiled taxa and developing detailed Jim – This is a very difficult question, and down considerably. Still, additional spring management guidelines for each. Often one that often leads to a lively discussion surveys in remote areas and during fall threats are obvious, such as those in some circles of conservation biology. following summer rains will likely add an caused by the direct impacts of vehicles And being tasked with the job of additional 15-20 taxa to the overall list. or livestock trampling. Yet other threats preventing biological invasions into are more cryptic, requiring fairly Mojave National Preserve is like trying to The floristic effort at the Preserve sophisticated biological research prevent drinking at Burning Man, one is underscores two significant truths: 1) the (population genetics, demography, doomed to fail. The management of Mojave National Preserve is indeed reproductive biology) or modeling/long invasive plants usually comes down to a floristically diverse with a high term monitoring (climate change, soil triage decision that balances the concentration of rare and endemic nutrient, hydrological alteration) before likelihood for success with available species, and 2) the Preserve lies within a remedial actions or protection measures resources (budget, labor force, available region of California where taxonomic are taken. It is human nature to feel expertise). In the case of Sahara inventory is far from complete. With the compelled to take action to heal the mustard, we have a superstar weed that near completion of the flora, the Preserve wounds of an impact, but actions must be disperses at extraordinary rates, can now represents one of the few areas in tempered with the very risks they pose colonize undisturbed desert, and has the California Deserts that has been well- and be based upon the best science. For already structurally altered millions of documented. The only other recent and example, removal of invasive alien plants acres of lowland sandy habitats. Many comprehensive floristic inventories are at using either mechanical or herbicide millions of dollars are being spent on both the Whipple Mountains (2) and at Joshua applications may or may not adversely herbicide and mechanical removal in an Tree National Park, led by GMDRC impact rare plant populations, but should attempt to stem the tide. Optimists scientist Dr. Tasha La Doux. One does be carefully assessed prior to believe there is still an opportunity to not need to go to New Guinea or the implementation. control this species from spreading Brazilian rainforest to make important further into the California Deserts. The botanical discoveries, as 90% of the Considerations for the long-term viability unfortunate reality, however, is that it has California Deserts remain a floristic of native plants in the Preserve extend already entrenched itself throughout frontier ripe for taxonomic discovery. well beyond its borders. With the much of the Mojave, and control of its increasing fragmentation of the eastern spread is probably only worthwhile, or Debra – Threats to rare plant Mojave Desert by energy and other possible, in localized cases to protect assemblages in Mojave National development, the long-term viability of unique or rare habitats and populations. Preserve include local factors such as many populations within the park cannot We actually know very little about the life cattle grazing and fire and larger global be sustained without the preservation of history and ecology of Sahara mustard issues such as climate change. How do external corridors and trans-boundary (e.g., tolerance to drought, seed bank you think the National Park Service could processes such as dispersal of pollen by and dispersal ecology, impacts on soil best protect these populations? Are there pollinators and the movement, or nutrients, etc...). Given that there is little specific management actions that could colonization, of plants through seed we can do to control the spread of the be developed into project funding dispersal. As large as the Preserve is, it species on the landscape level, I would requests? will require collaboration with neighboring recommend that a higher proportion of agencies to develop regional the management funds be directed Jim – Inventory of the botanical conservation strategies. towards research into the biology of resources is obviously critical to this Sahara mustard, as we have a lot to gain management mission, as we can only Debra – Controlling invasive non-native by improving our understanding of its protect what we know exists. While the weeds, such as Sahara mustard, is a impacts to our natural systems. And inventory of the Preserve has focused high natural resource management perhaps we might identify weak links or initially on developing a park species list, priority for the Preserve. Although we are stages in its life history that might be we are now working to map many fortunate compared with much of the rest helpful to our management. hundreds of rare plant populations as well of the Mojave Desert, at times this seems

4 Mojave National Preserve Science Newsletter 2009, Number 2 As you know, there are many other rare plant species were impacted by the alleviate them. For example, habitat invasive species that pose existing or Hackberry Fire, and that each species fragmentation caused by developments future threats to the Mojave National endured and responded to the event along I-15 between the Clark Range and Preserve. Some of these, such as differently, depending upon their the Ivanpah Range impacts numerous Erodium cicutarium (storksbill), have individual life-history characteristics. rare plant populations, but how? If we been here for decades and have Because we lacked sufficient pre-fire assume that larger populations that are naturalized into the native vegetation. information (distribution, population sizes, broken into smaller ones leading to Unless a very sophisticated control etc…) for the majority of the rare species, restricted exchange of pollen or seed, mechanism is developed, such our assessment of impacts was limited to then this has important genetic and naturalized invasives are here to stay. a post-fire snapshot. demographic consequences. But The point here is that as difficult as it is to fragmentation also creates edge effects prevent invasions, it is far less an option We observed that with the sudden and deterioration of habitat quality. It may to eradicate aliens once they have release of nutrients into the soil and the alter plant-pathogen and plant-herbivore become established. Thus, it is vital to sunlight gaps that were opened among dynamics. Due to lack of time, funding or develop a coordinated multi-agency previously dense shrub and tree available expertise, the full range of monitoring program that detects canopies, many of the rare herbaceous demographic- versus genetic- invasions early on when eradication is perennials and/or annuals showed a very stochasticity parameters are rarely still a feasible option. positive initial response (e.g., Cima integrated into a population viability milkvetch). Rare plants that were most analysis. Until such detailed analyses Finishing this discussion on a more adversely affected by fire were those become available, managers must work positive note; although invasive alien lacking the ability to survive the burn with scientists to maintain natural plants pose perhaps the greatest threat to (e.g., woody such as Thorne’s ecological processes and provide the native ecosystems throughout California, buckwheat), poor re-sprouters, or not best natural conditions for populations the eastern Mojave Desert remains the likely to regenerate quickly from the seed and metapopulations to persist, while least impacted region of the state. While bank. In the Hackberry Fire report I delineating the most likely threats for invasive aliens comprise 15 to 35% of the provided a general discussion of other each species and minimizing or species in any given subregion potential threats that pertain to these eliminating them where possible. throughout cismontane California, they particular species (3). Examples of these make up only 7 to 9% of the California threats included grazing/trampling, road In general, threats come in three types: Desert flora. maintenance, and invasion of alien 1) threats imposed by changes in the species that may or may not be related to environment, either by natural or human Debra – The Hackberry Complex Fire in post-fire management or processes. causes, 2) threats resulting from 2005 was quite possibly the most disturbance of important interactions with dramatic natural disaster in this area in Rather than focus on the Hackberry Fire, other species, and 3) genetic threats. some decades. But in your rare plant however, I believe your question relates Although the Preserve and its report on that fire you identified a number to the Preserve’s entire rare plant surrounding lands are considered well- of other threats to rare plant populations management program and the protected, environmental threats are, in besides fire. Would you care to elaborate development of management priorities for fact, considerable. These include climate on these and perhaps prioritize them in rare plant protection in general. Many of change (e.g., altered precipitation and fire terms of the most immediately needed the 120 or so rare plant species in the regimes), habitat fragmentation (e.g., management actions? Preserve are being threatened by a roads), direct disturbance (e.g., livestock variety of factors. In most cases, threats trampling, hydrological alterations, Jim – I agree that the Hackberry Fire are associated with human actions of deposition of atmospheric nitrogen) and event was dramatic and natural, but the some sort, which implies we can often exploitation (e.g., cactus collecting). term disaster does not necessarily apply take action to remove or adapt these Disturbance of biotic interactions might in describing its impacts upon rare plant actions to reduce the threat. However, for include destruction of key pollinator populations. Most plant ecologists agree many threats it is difficult to understand guilds, altered pathogen and herbivore that fire regimes are in flux, but the role of how they ultimately affect the viability of interactions, and hybridization with fire and its effect upon native vegetation specific plant populations or introduced natives (e.g., CalTrans and rare species in the eastern Mojave metapopulations, to untangle their revegetation programs). Desert is complex and remains poorly interaction with other threats, and to understood. We know that several dozen come up with effective methods to Despite the complexity and multitudes of

5 Mojave National Preserve Science Newsletter 2009, Number 2 threats, there are a number of options for made in heaven as our missions are, if broader long-term commitments to reducing their effect on rare plant not compatible, highly complementary. events and conferences that advance populations in the Preserve. Some of Numerous successful collaborations communication about research and these need to be implemented on the already exist between the UC NRS and education. We can re-energize our MNP landscape level and require cooperation NPS. The UC Santa Cruz Island Reserve science group that includes the California from adjacent land owners, for example, collaborates with NPS Channel Islands to State University Desert Studies Center maintaining large expanses of facilitate research and teaching on the and meet on a regular basis to share unfragmented habitat, increasing island. More recently, Yosemite National ideas. And we can jointly participate in connectivity, creating buffer zones, and Park has been working with the NRS to national programs such as the National restoring original hydrological conditions. establish a similar relationship at the UC Science Foundation’s National Ecological In other cases, managers must act more Merced Wawona Field Station. Observation Network (NEON) or a Long on the local scale by providing protection Term Ecological Research network from livestock trampling, invasive As a hub for research throughout the (LTER). These are just a few thoughts. species, or recreational activities. And eastern Mojave Desert, the GMDRC The sky is the limit. perhaps most important of all, lack of functions within this concept of a information can be one of the greatest “gateway reserve” where it impacts a References threats to rare species. In order to much larger area than what is contained 1. J. M. André, “Inventory of vascular plants at prioritize management of rare plants in within the GMDRC boundaries. And as Mojave National Preserve and Manzanar the Preserve, we must first know you alluded to, the success of the Historic Site” (National Park Service Inventory something about their distributions, life- University of California alliance (via the and Monitoring Program 2006 history attributes, and identify any threats GMDRC) in the eastern Mojave depends http://www.nps.gov/moja/naturescience/indepe to their viability. Finally, conservation largely upon the extraordinary quality of ndentresearch.htm). management for rare plants should the ecosystem found in this region. Thus, 2. S. De Groot, Aliso. 24, 63-96 (2007). always take place in the context of the we greatly appreciate the opportunity to 3. J. M. André, “Hackberry Complex BAER key processes of their ecosystem (i.e., work with NPS, the leader among federal Stabilization Plan: Monitor Listed Plant practices developed in the Nebraska land management agencies in Species” (National Park Service Mojave prairies may not be appropriate in the preservation, research, and ecosystem National Preserve 2006). California deserts). management.

Debra – One of the attractions of Over the past 15 years the GMDRC and Sweeney Granite Mountains Desert Mojave National Preserve have teamed Research Center is its setting in a fairly up to facilitate over 100 academic expansive region of federally protected research projects, developed and public land and designated wilderness supported student research grants, areas. In fact a number of the engaged the media and public about researchers who come to the reserve do important desert issues, collaborated on much of their work in Mojave National a number of programs, including the Preserve. The Preserve, in turn, benefits Inventory and Monitoring Program from the work of these researchers and (e.g.Vital Signs Workshop, NPSpecies the scientific expertise concentrated at certification), rare plant inventory and the reserve. Knowing that this monitoring (e.g. after the Hackberry Fire), relationship is built for the long term, what and we have collaborated to organize kind of policies and practices would you several regional workshops and have in place for optimizing this symposiums. relationship? There are a number of directions I hope Jim – The continuing development of our to see our collaboration continue to collaboration is perhaps the most evolve. We can develop a more important goal of the GMDRC and, structured protocol of information and indeed, ranks as one of the highest data sharing. We can exchange expertise priorities of the UC Natural Reserve and resources to enable specific projects System. I truly believe this is a match and programs to occur. We can develop

6 Mojave National Preserve Science Newsletter 2009, Number 2 Reptile Diversity Following the Hackberry Fire Kirsten E. Dutcher1

The Hackberry Complex Fire in Mojave years after the fires. Burned and serve as refugia for reptile populations National Preserve stimulated research unburned habitats had comparable reptile that survive wildfire, and vegetated areas on seed banks (1), small mammals (2), diversity, and Uta stansburiana was the produce shaded microclimates where soil and effects on reptile diversity (3). most abundant reptile recorded. The temperatures are less extreme and Changing fire regimes in the Mojave numbers of individuals and species moisture is preserved (7–9). Desert is an ongoing land-management recorded during this study suggest that issue. Much attention is given to the the wildfire negatively impacted the The Mojave is home to an incredible relationship between fire and invasive herpetological community. array of reptiles, and the Hackberry annual plants. But fire regimes can also region supported many species. The be exacerbated by precipitation Introduction objective of this study was to determine variability, which may become more Historically, large wildfires in desert the effects of the wildfires on the prevalent in the future. The work by communities have been uncommon herpetofaunal community. Because of the Dutcher presented here provides because without a relatively large, need for thermoregulatory, foraging, and managers with information on how continuous fuel source, wildfires have protected sites, reptiles are highly reptile diversity was affected by a major reduced size and intensity (1). In North dependent on habitat structure, and fire fire. American deserts, wildfires have become has been shown to reduce their increasingly frequent since the 1970s. abundance and limit movements (10, 11). References This is largely due to the introduction of A review of herpetofaunal response to 1. M.L. Brooks, J.V. Draper, “Fire effects on exotic plant species, particularly Erodium fire found that many animals exhibit panic seed banks and vegetation in the Eastern cicutarium (fillaree), Bromus sp. (foxtail, and experience high rates of mortality. Mojave Desert: implications for post-fire cheatgrass), and Schismus sp. Often, dramatic disturbance also results management” (U.S. Geological Survey, (Mediterranean grass). These species, in habitats dominated by invasive plants Western Ecological Research Center, native to Europe, Africa, and Asia, are and decreased numbers of invertebrates. Henderson, Nevada, 2006). adapted to fire regimes in arid This reduction in thermoregulatory and 2. P. Stapp, Mojave National Preserve ecosystems and create a blanket of dry food resources results in a decrease in Science Newsletter. 1, 10-16 (2009). vegetation that facilitates the spread of reptile abundance and diversity (11, 12). 3. K.E. Dutcher, this issue. wildfire by creating a layer of dry, fast- burning fuel. Recurrent fire amplifies the Study During the summer of 2005, lightning presence of these species, which have Permits were obtained from the National caused numerous wildfires in the Mojave been shown to replace long-lived natives, Park Service, California Department of National Preserve, California. The fires changing the floral composition (2–4). Fish and Game, and California State burned 287 km2 and created a mosaic of Wildfire is currently considered to be one University to allow for collecting, unburned patches surrounded by burned of the main threats to native populations identifying and releasing reptiles within vegetation. This study examined the in the Mojave (5). the National Preserve. Sampling for this effects of these wildfires in 2006 and study was concentrated in what was 2007 on reptile diversity by conducting The Mojave Desert is subjected to predominantly juniper woodland between transect surveys at unburned patches frequent lightning strikes during the the elevations of 1,370 m-1,675 m (13). and along the fire perimeter in burned summer monsoons (6). On 22 June 2005 Sites were located near Cedar Canyon and unburned habitats. Temperature and lightning caused multiple fires in the and Black Canyon Roads, in the Mid-Hills vegetation cover data were also recorded Mojave National Preserve (MNP), area (Figure 1). All sampled sites had at each site. These surveys showed that California. The fires merged to become similar influence from cattle grazing, average environmental temperatures the Hackberry Complex Fire, which camping, and roads, and were more than were higher in burned areas as compared burned for seven days and was 100 m from roads, trails, or developed to unburned areas. Unburned areas also contained on 28 June 2005. A total of areas, with the exception of one site, showed a greater vegetative cover two 287 km2 burned between elevations of which was 30 m from an unmaintained 1,097-2,012 m. The fire did not consume dirt road. Seven unburned habitat 1San Diego Zoo's Institute for Conservation all the vegetation and the burned patches, surrounded by burned Research, Desert Tortoise Conservation Center, landscape contained a mosaic of landscape on all sides, and seven Las Vegas, Nevada. unburned habitat. Habitat patches may perimeter locations along the fire edge

7 Mojave National Preserve Science Newsletter 2009, Number 2 length and bisected the habitat, with 25 m in each habitat type. Transects were separated from replicates by 20 m (Figure 2). Transects were measured using a 25 m Lufkin tape measure, and GPS waypoints marked the start and end locations.

Vegetation point-intercept transects were conducted by walking the transect lines and recording vegetation height every five meters. At each point a 7-cm diameter pole was placed directly on the point, and the height of each plant that touched the pole was recorded (15). Plant height was classified as <10 cm, 10-30 cm, 30-50 cm, 50 cm-1 m, and >1 m. Data from dead or severely burned vegetation was not included. Vegetation transects were conducted once a month from May through October 2006 and March through August 2007. A total of 504 vegetation transects were conducted (14 sites x 3 replicates x 12 times).

During the fall and spring, transect surveys were conducted throughout the day; however, in the summer, when temperatures were high, transect surveys were conducted in the morning and late afternoon. In order to find lizards by direct observation in both burned and unburned areas, each transect line was walked two times and a snake stick used to flush lizards from grasses and shrubs. Sighting Figure 1. Habitat patch locations within the Hackberry region of the Mojave National Preserve. Habitat patches are approximate. The inset map shows the location of the Hackberry wildfire effort was concentrated to 5 m on either in Mojave National Preserve (MNP), Southern California. side of the transect line. During the were surveyed. Patch sites were mapped recorded after holding the thermometer course of this study a total of 1,542 using a handheld Global Positioning several feet above the ground, ground transects (14 sites x 3 replicates x 36 System (GPS) unit and ranged in size temperature was recorded after placing times) were conducted. from 1,527 to 36,580 m2. the thermometer on the soil surface, and subterranean temperature was recorded Analyses involving herpetological Ambient, ground, and subterranean after placing the tip of the thermometer 3- community structure were conducted temperatures were collected from May 5 cm into the soil. using PRIMER. All other analyses were through October 2006 and March through completed with PRISM statistical August 2007 using a handheld Ashcroft Transects were used to assess species software. The mean, standard deviation, dial thermometer. All temperatures were diversity and abundance across distinct and minimum/maximum temperatures recorded after the thermometer was habitat types with clearly defined borders were calculated. Air and ground surface placed in a temporarily shaded area for 2 (14). At each sampling site three parallel temperatures in warm (May through minutes and collected at the start of each transects that crossed the transition zone August 2006 and 2007) and cold seasons transect on both the burned and from burned into unburned habitat were (September through October 2006 and unburned sides. Air temperature was monitored. Each transect was 50 m in March through April 2007) were analyzed

8 Mojave National Preserve Science Newsletter 2009, Number 2 temperature data for 2006 and 2007 were divided by habitat type, season, and year. Burned habitats in the warm season had significantly higher ground surface temperatures (t = 11.61, df = 415, px

The total number of plants in the unburned areas (1,440; 68.58% total cover) was higher than in burned areas (846; 40.28% total cover). There were differences in the distribution of Figure 2. Transect design. Each site had three 50 m transects separated by 20 m. Half (25 m) vegetation heights in each habitat (χ2 = of each transect was located in burned habitat and 25 m in unburned habitat. 389.9, df = 1, p < 0.0001). In the burned using paired t-tests. Vegetation data were (analysis of similarity) of species diversity areas plants under 10 cm in height analyzed using χ2, with the mean and between years and in burned and significantly outnumbered plants in all standard deviation of each plant height vegetated habitats and SIMPER other height classes (Table 1). In class calculated to compare heights in (similarity percentages) analyses were addition, the number of plants in the burned and unburned areas. The reptile conducted. U. stansburiana data were under-10 cm height class increased from species observation rate during transect analyzed using χ2 and Fisher’s Exact test. the 2006 to 2007 growing season (264 to surveys was calculated. ANOSIM 345 total plants). For all heights, except Average air temperature in the warm <10 cm, unburned habitats had more season of 2007 was significantly higher plants per site than burned. All plants than 2006 (t = 5.420, df = 195, seen were not recorded to species. Of px

(b) (c) Figure 3. Ambient, ground, and subterranean temperatures ( ± SD). (a) Average ambient temperatures by year in the warm and cold seasons. (b) Average ground temperatures for unburned and burned habitats by year in each season. (c) Average subterranean temperatures for both habitats by year in each season.

9 Mojave National Preserve Science Newsletter 2009, Number 2 Table 1. Percent Vegetation Cover in Unburned and Burned habitats by Height Class the burned areas had more than twice Height Class (cm) Unburned Burned the number of plants in the <10 cm height Number Percent Cover Number Percent Cover class, and very few grew to over 10 cm <10 220 10.48 631 30.05 10-30 295 14.05 133 6.33 during the course of this study. This is 30-50 248 11.81 63 3.00 consistent with long term studies of plant 50-100 345 16.43 16 0.76 communities in the Southwest that have >100 332 15.81 3 0.14 found areas affected by wildfire are Total 1440 68.58 846 40.28 rapidly colonized by low growing ground

cover species that are predominantly During transect surveys five lizard and order to compare burned to unburned alien (3, 5). one snake species were observed areas yielded more individuals in (Tablex2). Species found at perimeter unburned habitat (n = 77 compared to Uta stansburiana was the dominant and patch sites did not differ significantly nx= 62); however, there were no reptile species in all surveys; however, (R = 0.038, p = 0.272); however, significant differences (Fisher’s Exact the absence of other species may have differences were found (R = 0.220, test; p = 0.0624). Combining burned and been due to the fact that they were not px=x0.022) between unburned and unburned areas in order to compare present or visible along the transect lines burned locations. A SIMPER analysis perimeter to patch sites found perimeter conducted. In 2006 the highest number of showed that in the unburned areas, U. sites to have significantly more U. U. stansburiana were found along the fire stansburiana accounted for 88.0% of stansburiana (Fisher’s Exact test; perimeter on the burned side, which is individuals, with A. tigris and S. px=x0.0258). similar to a study conducted after a occidentalis making up 14.7% and 13.5% wildfire in Arizona that found reptiles of individuals, respectively. In the burned Conclusion exhibited a preference for disturbed sites areas U. stansburiana comprised 98.6% Due to air temperature variation, 2007 (16). However, in 2007 the number of of individuals. Differences were found was warmer than 2006, but both surface individuals found in this area decreased between habitat types (χ2 = 9.952, df = 3, and subterranean temperatures were by more than half. It may be that p = 0.0190) and most U. stansburiana higher in burned areas than in unburned individuals utilized the burned area more were recorded in burned areas along areas in both years. The plant community heavily initially because the higher perimeter sites in 2006, followed by in unburned areas had almost 30% more ground temperatures allowed for optimal unburned patch sites in 2007 (Figure 4). cover than burned areas and remained basking sites. In 2007 temperatures may Combining perimeter and patch sites in relatively stable through time. However, have become too high, creating a habitat

Table 1. Reptile Species Observed During Transect Surveys Species 2006 2007 Unburned Burned Number Rate Number Rate Number Rate Number Rate Aspidocelus tigris 7 0.3684 4 0.2105 11 0.2895 0 0 Western whiptail

Gambelia wislizenii 2 0.1053 0 0 1 0.0263 1 0.0263 Long-nosed leopard lizard

Masticophis taeniatus 1 0.0526 0 0 0 0 1 0.0263 Striped whipsnake

Phrynosoma 0 0 1 0.0526 0 0 1 0.0263 platyrhinos Desert horned lizard

Sceloporus occidentalis 8 0.4211 7 0.3684 5 0.1316 10 0.2632 Western fence lizard

Uta stansburiana 80 4.2105 56 2.9474 75 1.9737 61 1.6053 Side-blotched lizard Total 98 5.1579 68 3.5789 92 2.4211 74 1.7105

Note: Observation rates were calculated using number of observations/number of transects conducted.

10 Mojave National Preserve Science Newsletter 2009, Number 2

National Preserve (National Park Service 2005). 14. D.W. Morris, in Mosaic Landscapes and Ecological Processes, L. Hansson, L. Fahrig, G. Merriam, Eds. (Chapman & Hall, London, 1995), chap. 5. 15. M.G. Barbour, J.H. Burk, W.D. Pitts, F.S. Gilliam, M.W. Schwartz, Terrestrial Plant Ecology (Benjamin Cummings, Menlo Park, 1999). 16. S.C Cunningham, R.D. Babb, T.R. Jones, B.D. Taubert, R. Vega, Biol. Conserv. 107, 193-201 (2002).

Acknowledgements Funding for this work was provided by the California Desert Research Fund at the Community Foundation, the California Figure 4. Total number of Uta stansburiana observed during transect surveys in each habitat Desert Studies Consortium, and California type by year. State University. Also, thanks to the Desert Studies Center at Zzyzx for use of type that did not provide a 52 (1971). equipment and facilities. I would like to thermoregulatory gradient or enough 2. M.L. Brooks, Biological Invasions. 1, 325 - thank J. Archie, T. Christopher, E. cover. The number of individuals in 337 (1999). Fernandez-Juricic, A. Fox, D. Hughson, S. unburned perimeter locations was 3. M.L. Brooks, J.R. Matchett, Western North Malcomber, D. Nichols, D. Underwood, and relatively constant through time, American Naturalist. 63, 283-298 (2003). L. Zimmerman for their assistance with this indicating that this population was the 4. T.C. Esque, paper presented at the Mojave research. I am grateful to M. Aguirre, M. most stable. The numbers found at Desert Science Symposium, Las Vegas, Baxter, J. Dutcher, R. Dutcher, C. Francois, patches increased from 2006 to 2007 in NV, February 25-27, 1999. E. Guinn, A. Jones, S. Jones, S. Louwsma, burned and unburned areas, with http://www.werc.usgs.gov/mojave- J. Putzi, J. Toenjis, and members of the unburned sites having more individuals. symposium/ California Conservation Corps for field 5. M.L. Brooks, Ecological Applications. 12, assistance. Although the results of a study conducted 1088-1102 (2002). in a single location and affected by a 6. T.C. Esque, C.R Schwalbe, L.A DeFalco, single event may not be fully extrapolated T.J Hughes, R.B. Duncan, The to other locations and events, it is clear Southwestern Naturalist. 48, 103-110 that wildfire is a serious threat to (2003). biodiversity in the Mojave. Information on 7. A.S. Faria, A.P. Lima, W.E. Magnusson, J. floral community succession and faunal Tropical Ecology. 20, 591-594 (2004). survival is useful to help understand the 8. G.R. Friend, Biol. Conserv. 65, 99-114 long-term consequences of altering (1993). landscapes and could lead to a better 9. D.T. Patten, E.M. Smith, Environmental understanding of how to control invasive Physiology of Desert Organisms (Academic species. Invasive species have created Press 1975). an unnatural grass-fire cycle in the 10. K. Setser, J.F. Cavitt, Natural Areas Journal. Mojave, resulting in habitats that are 23, 315-319 (2003). increasingly homogeneous and provide 11. L.E. Valentine, B. Roberts, L. Schwarzkopf, few resources for native species (4, 6, J. Appl. Ecol. 44, 228-237 (2007). 11). 12. K.R. Russell, D.H. Van Lear, D.C. Guynn Jr., Wildl. Soc. Bull. 27, 374-384 (1999). References 13. S. Dingman, GIS maps and data of the 1. T.L. Hanes, Ecological Monographs. 41, 27- Hackberry Complex Fire created for Mojave

11 Mojave National Preserve Science Newsletter 2009, Number 2 Physiological Responses of Mojave Desert Shrubs to Simulated Summer Wash Flow: Preliminary Results April R. Newlander,1 David R. Bedford,2 David M. Miller,2 and Darren R. Sandquist1

Research into the nature of vegetation are known to be highly variable (8). response to soil moisture and Rainfall during the winter months (Oct- geomorphology has been ongoing in April) is longer in duration, of lower Mojave National Preserve for about ten intensity, and occurs broadly across the years through the U.S. Geological Mojave region; whereas summer rainfall Survey Priority Ecosystems Science (July-Sept) is localized, more intense, program. This summer a directed and less frequent (9, 10). As a result, infiltration experiment was conducted summer rainfall events more commonly using isotope-labeled water to see how lead to wash flow. As a winter-rainfall Mojave perennial vegetation would dominated ecosystem, climate changes respond to a simulated summer A water truck and perforated hose were used in the Mojave that increase summer thunderstorm. These preliminary results to simulate runoff in a small alluvial channel. precipitation may play an important role will help managers understand how unpredictable water inputs” (4). Water in altering vegetation processes predicted increasing temperatures, inputs into desert ecosystems are what influenced by washes. An increase in the increasing summer precipitation, and drive plant productivity and are strongly frequency and intensity of summer increasing precipitation variability may linked to soil water availability and its rainfall events could increase the amount affect desert ecosystems. distribution in the soil profile (5). of water available to plants, especially Therefore, the frequency and magnitude those adjacent to washes. Over the past century the climate of the of precipitation events strongly affect soil To investigate how plants in the Mojave United States has experienced a 0.6°C moisture availability and, in turn, plant Desert might respond to increases in warming and by 2100 it is projected to water availability. summer precipitation, we simulated wash increase an additional 4-6°C, depending flow that would occur following an early on region (1). Average annual Soil moisture models simulating summer rain event. Specifically, we precipitation has also increased 5-10% in increased intensity of precipitation events replicated wash flow that would occur the past 100 years, which has been revealed altered soil moisture patterns in down-slope on an alluvial fan when an attributed to increased frequency and the upper (10-20 cm) and lower (80-90 isolated summer rain storm occurs intensity of rainfall events (1–3). Some cm) soil layers, thus affecting plant water higher-up. Several previous studies have climate models for the 21st century availability and overall vegetation quantified summer precipitation use by predict that the largest increases in composition in arid lands (6). Model applying watering treatments to the extreme weather events will occur in the results (6) indicate a greater amount of plants at the surface (11–15) or by arid Southwest region, altering both plant-available water in lower layers due measuring plant responses to natural winter and summer precipitation patterns to increased runoff and lateral summer rain events (8, 16, 17); however, (1). Biogeographic models predict that redistribution of runoff water. Soil there is limited information on how plants changes resulting in increased substrate and age further influence plant- utilize water derived specifically from precipitation would have a dramatic effect water availability as runoff is enhanced in water pulses in washes. on desert ecosystems, potentially leading older soil substrates, increasing to habitat conversion and a complete loss infiltration into younger substrates with Collaborators from the USGS and the of desert vegetation (1). excess runoff water made available to Plant Physiological Ecology Laboratory at plants bordering washes (7). Water California State University, Fullerton are Desert ecosystems have been defined as infiltration is highest in washes, and collectively working as part of the “water-controlled ecosystems with provides the greatest availability of water Recoverability and Vulnerability of Desert infrequent, discrete, and largely for plants across a typical Mojave bajada, Ecosystems (RVDE) project, funded by 1 Department of Biological Science, California underscoring the importance of washes in USGS, to understand how changes in State University, Fullerton.800 N State College the hydrogeology of desert landscapes. precipitation patterns might affect the Blvd, Fullerton, CA 92834. physiological functioning of perennial 2 U.S. Geological Survey, 345 Middlefield Road, The Mojave Desert is the driest desert in plants and the hydrogeology of desert MS-973, Menlo Park, CA 94025 North America, and precipitation patterns landscapes. The objectives of the present

12 Mojave National Preserve Science Newsletter 2009, Number 2 study are to: 1, quantify the responses of Values of xylem water potential were application, we found that plants both the native perennial species Larrea measured in the field with a Scholander- bordering and near the wash exhibited tridentata (creosotebush) and Ambrosia type pressure chamber (19). One to two decreased water stress (increased Ψpd), dumosa (white bursage) to simulated Ψ measurements per plant were taken at while those farther away did not. Plants wash flow that would occur during a pre-dawn (Ψpd) and at mid-day (Ψmd). (In farthest from the wash (3-5 m) had less summer precipitation event; and 2, this report we discuss only the former, as than a 2% increase in water potential for assess how these responses vary based patterns for both were very similar.) Due both species, whereas plants bordering on plant proximity to the wash. These to the time-consuming nature of these the wash (0-1 m) increased by 39% and measures will allow us to quantify the measurements and to minimize damage 37% for Larrea and Ambrosia, influence of washes on plant-water to plants, only 24 Larrea and 18 respectively. Plants in the intermediate availability in desert landscapes and, Ambrosia plants were sampled per day. area (1-3 m) also increased by 23% and specifically, how runoff events in these Stomatal conductance measurements 16%, respectively (Figures 1 and 2). One washes affect plant activity. were taken on all Larrea and Ambrosia month (day 35) following the pulse, plants using a hand-held leaf porometer Larrea plants at bordering and The study site is located at the foot of the (20). All measurements were taken 1 day intermediate distances from the wash still

Providence Mountains within the Mojave before the pulse to serve as baseline had significantly higher Ψpd values than National Preserve. It is approximately 50 data, and then again on days 1, 3, 6, 13, those farthest from the wash (p < 0.001), km SE of Baker, CA and 5 km NE of the 21, and 35 following the event. Additional whereas, Ambrosia plants were Kelso train depot. The site is on an sampling was done in August and significantly different across all distances alluvial fan that is dominated by the September 2009. (p < 0.001) (Figures 1 and 2). perennial shrubs Larrea tridentata and

Ambrosia dumosa. The Larrea-Ambrosia For each species, data for Ψpd and gs In all, we detected reduced water stress desert scrub vegetation type occupies were analyzed using a repeated for all plants within 3 m of the wash, and approximately 70% of the total area of the measures analysis of variance this persisted for up to a month. Post- Mojave Desert (18). (ANOVAR). The independent variable pulse water potentials of plants more than used was the distance category 3 m from the wash were indistinguishable To simulate water runoff into a wash (bordering, intermediate, distant), and from pre-pulse values, indicating no during a summer storm event, 2,000 day was the repeated measure variable. benefit from watering. gallons of water were distributed along a Results from day -1 were excluded from 30-m stretch of a 1-m wide wash using a the ANOVAR analysis; they were Stomatal conductance for Larrea fire hose that was perforated with two 6- analyzed with a one-way ANOVA to test significantly increased after just one day mm holes (on opposite sides of the hose) the null hypothesis that plants in the three following the water application (p = every 25 cm, thus allowing uniform water distance categories were not significantly 0.0075) and rose rapidly through day 3, distribution to the soil along the 30-m different from each other before the after which it steadily declined. Plants stretch. On each side of the wash, equal simulated rain event. Mean values for bordering and intermediate to the wash numbers of Larrea (n=28; 14 per side) each distance category of the above experienced > 2x and > 3x higher values, and Ambrosia (n=36; 18 per side) plants parameters on individual days were respectively, on day 1 than on day -1 were selected at three distances from the compared with Tukey’s post-hoc analysis. (Figure 3). The rate of increase for wash: bordering (0-1 m), intermediate (1- All data was analyzed using JMP 8 Ambrosia plants was much slower, 3 m), and distant (3-5 m). statistical software (SAS) and reported as however, not peaking until 21 days statistically significant if p < 0.05. following the water pulse. The Before and after the pulse of wash water proportional response for Ambrosia was was administered, a suite of physiological Preliminary Results greater than for Larrea, with plants measurements were taken. They ANOVA results revealed that on day -1 all bordering the wash increasing nearly 6x, included, pre-dawn and mid-day xylem distance groups were not significantly and plants intermediate to the wash water potential (Ψ), measures of different for both Ψpd (Larrea, p = 0.14; increasing more than 2x relative to values minimum and maximum daily plant-water Ambrosia, p = 0.88) and gs (Larrea, p = measured before the event (Figure 4). stress respectively; and leaf stomatal 0.10; Ambrosia, p = 0.59). Water status, conductance (gs), a measure of active based on Ψpd, significantly differed among By day 35, gs values for Larrea had water release from the plant. (Stomatal distance groups one day after the pulse declined considerably, but bordering and conductance is also related to leaf uptake for both Larrea (p = 0.004) and Ambrosia intermediate plants were still significantly of carbon dioxide for photosynthesis.) (p < 0.001). Following the water higher than those farthest from the wash

13 Mojave National Preserve Science Newsletter 2009, Number 2 (p = 0.003) (Figure 3). In contrast, on day Larrea tridentata 35, values for bordering and intermediate Ambrosia plants were still 4x and 3x -0.0 greater, respectively, than gs values on

-1.0 day -1. They were also significantly greater than those farthest from the wash -2.0 (p < 0.0001).

-3.0 Discussion 0-1 m Following the simulated wash flow event, -4.0 1-3 m plants bordering and at intermediate 3-5 m distances from the pulsed wash became -5.0 significantly less water-stressed and more physiologically active. By day 6 Pre-dawn water potential (MPa) -6.0 there was a large amount of new growth on both species, and greenness of plants -7.0 -1 1 3 6 13 21 35 adjacent to wash was noticeably greater wash flow than for those farther from the wash. simulation Day Ambrosia had new leaves in large Figure 1. Pre-dawn water potential values after a simulated water pulse for Larrea tridentata numbers on plants near the wash. Larrea plants at different distances from the pulsed wash. Each point is the mean +SE. n=9, 5, and 10 had broader, greener leaves, and by day at distances 0-1, 1-3, and 3-5 m, respectively. Values were not significantly different on day -1 13 some plants even had flower buds (ANOVA, f =2.09, p = 0.14). Following the simulated rain pulse plants were significantly different from each other based on distance from wash (ANOVAR; f = 42.35; p < 0.0001). The (21). These results show that a summer interaction of day*distance was also statistically significant (ANOVAR; f = 3.33; p = 0.0083). precipitation event causing wash flow for ~2 hr duration results in responses for perennial plants within ~3 m of the wash

Ambrosia dumosa and that these plants take up water through root biomass that is close to, or -0.0 beneath, the wash.

-1.0 Stomatal conductance response of Ambrosia initially lagged behind that of -2.0 Larrea, but eventually exceeded Larrea, on days 13, 21 and 35. This could be -3.0 0-1 m attributed to the differences in leaf 1-3 m -4.0 3-5 m phonologies whereby the response of Ambrosia, like other drought-deciduous

-5.0 shrubs, is constrained early-on by the lack of leaf area. After new leaves are

Pre-dawn water potential (MPa) -6.0 produced, however, these species typically exhibit greater activity leading to

-7.0 higher growth rates and more rapid water -1 1 3 6 13 21 35 use than evergreen shrubs, such as wash flow simulation Day Larrea (22). These results indicate some degree of resource-use partitioning, in Figure 2. Pre-dawn water potential values after a simulated water pulse for Ambrosia dumosa that these two species make use of wash plants at different distances from the pulsed wash. Each point is the mean +SE. n=10, 14, and 12 at distances 0-1, 1-3, and 3-5 m, respectively. Values were not significantly different on day water by different mechanisms, at least -1 (ANOVA, f =0.12, p = 0.88). Following the simulated rain pulse, plants in each distance temporally. category were significantly different from each other on days 1, 6, and 21 (ANOVAR; f = 14.01; p = 0.0004) and on days 3, 13, and 35 (ANOVAR; f = 25.95; p < 0.0001). The interaction of day*distance was statistically significant on days 1, 6, and 21 (ANOVAR; f = 3.92; p = 0.0083) Little is known about how increased but was not significant on days 3, 13, and 35 (ANOVAR; f = 1.52; p > 0.05). summer rains will affect the balance between Larrea and Ambrosia in the

14 Mojave National Preserve Science Newsletter 2009, Number 2 Mojave Desert. Ambrosia is a drought Larrea tridentata avoider, a growth strategy that allows the plant to drop its leaves and go dormant 250

when there is not sufficient water for new ) -1

growth. Larrea, on the other hand, is a s -2 drought tolerator, staying active year- 200 round. Thus, it must utilize water efficiently and exhibit good stomatal 150 control. Understanding the physiological 0-1 m responses of these two species to 1-3 m 3-5 m increased summer rain pulses will help 100 identify how plant distributions may change in response to changes in the precipitation regime of the Mojave Desert. 50

Our studies will also reveal how plant Stomatal conductance (mmol m functions are related to wash proximity in 0 desert landscapes—an important -1 1 3 6 13 21 35 wash flow consideration given the importance of simulation Day washes to plant production, distribution, and success. Figure 3. Stomatal conductance values (mmol m-2 s-1) following a simulated water pulse for Larrea tridentata plants at three distances from the pulsed wash. Each point is the mean +SE. n=12, 6, and 10 for the 0-1, 1-3, and 3-5 m distances, respectively. Values were not significantly Repeated photography and field different on day -1 (ANOVA, f = 2.52, p = 0.10). Following the simulated rain pulse, plants in observations have shown that plant each distance category were significantly different from each other (ANOVAR; f = 43.65; p < 0.0001). The interaction of day*distance was also statistically significant (ANOVAR; f = 3.59; p populations and communities have = 0.0016). changed over the past 100 years in the Mojave Desert in response to climate variability, such as prolonged drought or Ambrosia dumosa wet periods (9). These changes could 250 result from fine-scale changes, such as ) ephemeral pulses of summer water as -1 s shown in this study, yet the majority of -2 200 climate models are created at large temporal scales (e.g. annual or 150 seasonal). Such models do not make 0-1 m predictions about the magnitude or 1-3 m 3-5 m variation of precipitation changes at 100 smaller scales, the scale that is shown to strongly influence plant and ecosystem responses to climate change (24). 50 Therefore, research on smaller spatial Stomatal conductance (mmol m (regional and local) and temporal (days or 0 months) scales is crucial to improving -1 1 3 6 13 21 35 long-term predictions about vegetation wash flow simulation Day changes in response to altered precipitation patterns. Figure 4. Stomatal conductance values (mmol m-2 s-1) following a simulated water pulse for Ambrosia dumosa plants at three distances from the pulsed wash. Each point is the mean References and Notes +SE. n=10, 14, and 12 for distances 0-1, 1-3, and 3-5 m, respectively. Values were not significantly different on day -1 (ANOVA, f =0.53, p = 0.59). Following the simulated rain pulse 1. Climate Change Impacts on the United plants in each distance category were significantly different from each other on days 1, 6, and States: The Potential Consequences of 21 (ANOVAR; f = 11.22; p = 0.0003) and on days 3, 13, and 35 (ANOVAR; f = 17.12; p < 0.0001). The interaction of day*distance was statistically significant on days 1, 6, and 21 (ANOVAR; f = Climate Variability and Change (National 6.23; p = 0.0003) and on days 3, 13, and 35 (ANOVAR; f = 3.93; p = 0.006). Assessment Synthesis Team, US Global

15 Mojave National Preserve Science Newsletter 2009, Number 2

Change Research Program, Cambridge 1981) pp. 1-12. Information for Authors

Univ. Press, New York, 2000). 19. Model 1000 pressure chamber instrument, The Mojave National Preserve 2. D.R. Easterling, G.A. Meehl, C. Parmesan, PMS Instrument Company, Albany, OR, Science Newsletter accepts S.A. Changnon, T.A. Karl, L.O. Mearns, USA. contributions from qualified researchers on scientific work in Science. 289, 2068-2074 (2000). 20. Leaf Porometer, Decagon Devices, Inc., progress or completed in Mojave 3. T.R. Karl, R.W. Knight, Bull. Am. Meteorol. Pullman, WA, USA. National Preserve. Articles can Soc. 79, 231-241 (1997). 21. Personal observation of the first author. range from general interest stories 4. I. Noy-Meir, Desert ecosystems: 22. S.D. Smith, R.K. Monson, J.E. Anderson, intended for a broad audience to technical research reports. If you are environment and producers. Annu. Rev. Physiological Ecology of North American interested in publishing in this Ecol. Syst. 4, 25-41 (1973). Desert Plants (Springer-Verlag, Berlin, Science Newsletter, please contact 5. J.F. Reynolds, P.R. Kemp, K. Ogle, R.J. 1997). the editor. Manuscripts, including figures, photographs, maps, Fernandez, Oecologia. 141, 194-210 (2004). 23. Weltzin JF, Loik ME, Schwinning S, Williams references, and acknowledgements, 6. B. Tietjen, E. Zehe, F. Jeltsch, Water DG, Fay PA, Haddad BM, Harte J, should be less than 5,000 words. Resour. Res. 45 (2009). 24. T.E. Huxman et al., BioScience. 53, 941-952 References and notes should be in the Science reference style1. 7. D.M. Miller, D.R. Bedford, D.L. Hughson, (2003).

E.V. McDonald, S.E. Robinson, K.M. Send an idea for an article, or Schmidt, in The Mojave Desert: Ecosystem Acknowledgments manuscript for review including the Processes and Sustainability, R.H. Webb, Special thanks to Matthew Sutton and names of two potential peer reviewers, to: L.F. Fenstermaker, J.S. Heaton, D.L. Miguel Macias for their continued Hughson, E.V. McDonald, D.M. Miller Eds. participation and hard work with field data Mojave National Preserve (Univ. Nevada Press, Reno, 2009), pp. 225- collection and to all other CSUF lab 2701 Barstow Road Barstow, CA 92311 251. members that have assisted with field data attn: Debra Hughson 8. E. Naumburg, D.C. Housman, T.E. Huxman, collection. This study was supported by the or email: T.N. Charlet, M.E. Loik, S.D. Smith, Global U. S. Geological Survey – Priority [email protected]

Change Biol. 9, 276-285 (2003). Ecosystems Program. We thank the 1http://www.sciencemag.org/about/authors/ 9. R. Hereford, R.H. Webb, C.I. Longpre, J. National Park Service, Mojave National prep/res/refs.dtl Arid Environ. 67, 13-34 (2006). Preserve for facilitating and encouraging 10. C.S. Wilcox, J.W. Ferguson, G.C.J. this study. Fernandez, R.S. Nowak, J. Arid Environ. 56, 129-148 (2004). 11. D.H. Barker et al., New Phytol. 169, 799-808 (2005). 12. H. BassiriRad, D.C. Tremmel, R.A. Virginia, J.F. Reynolds, A.G. de Soyza, M.H. Brunell, Plant Ecol. 145, 27-36 (1999). 13. G. Lin, S.L. Phillips, J.R. Ehleringer, Oecologia. 106, 8-17 (1996). 14. T.E. Huxman et al., Oecologia. 141, 295- 305 (2004). 15. K.A. Snyder, L.A. Donovan, J.J. James, R.L. Tiller, J.H. Richards, Oecologia. 141 325- 334 (2004). 16. J.R. Ehleringer, S.L. Phillips, S.F. Schuster, D.R. Sandquist, Oecologia. 88, 430-434 (1991). 17. A.C. Franco, A.G. de Soyza, R.A. Virginia, J.F. Reynolds, W.G. Whitford, Oecologia. 97, 171-178 (1994). 18. J.L. Thames, D.D. Evans, in Water in Desert Ecosystems, D.D. Evans, J.L. Thames Eds. Larrea tridentata leaves have unfolded, and some new growth has appeared on Day 6 following the simulated rain pulse. (Dowden, Hutchinson & Ross, Stroudsburg,

16 Mojave National Preserve Science Newsletter 2009, Number 2 Resource Management Issue: Managing the Effects of Climate Change Global climate models (GCMs) generally to show that areas of the southwestern agree that a drying trend is already under United States and northern Mexico are way in the desert southwest and will the most persistent hotspots for climate continue through the century. Seager and change. Much of the responsiveness of others (1) analyzed time series of the southwestern hotspot comes, not precipitation from 19 GCMs used in the from progressive warming or a long-term Intergovernmental Panel on Climate rise or fall in precipitation, but from Change (IPCC) Fourth Assessment increased variability in precipitation from Report to show a general drying trend one year to the next. through mid 21st century in Southwestern North America. There was broad The two driest years on record (2002 and A trend towards drier conditions, increasing temperatures, and precipitation consensus among the climate models 2007) and the wettest year on record variability is likely to exacerbate wildfires. that this region will dry in the 21st century (2005) in the Mojave Desert have already A consequence may be vegetation type conversion from perennials to annual and and that the transition to a more arid caused significant impacts in Mojave more weedy species. climate may already be underway. National Preserve. Record winter precipitation in the winter of 2004-2005 measurable impacts from climate Although much uncertainty remains, followed by two dry summer months variability and change and are expected especially at resolutions smaller than resulted in abundant fuel. Lightning to receive serious consequences of single grid cells of a model, variability in strikes then ignited the Hackberry climate change in the near future. Priority precipitation is expected to increase. The Complex Fire, the largest wildfire in the resources and ecosystems include proportion of precipitation that comes park’s history. coastal, marine, and riverine systems, from extreme events is expected to high elevations, high latitudes, and arid increase as well as the duration and Surveys conducted over the past five lands. Projects must identify known or intensity of droughts. Diffenbaugh and years of sparse, groundwater-dependent expected threats from climate change to others (2) used the results of 15 GCMs wetlands that sustain wildlife and often specific resources and address how from the IPCC Fourth Assessment Report endemic biota indicate that most of these proposed actions will ameliorate those water sources are sensitive to threats.” This Science Newsletter is a publication of Mojave National Preserve, 2701 Barstow precipitation variability. Springs in Mojave Road, Barstow, CA 92311. Information National Preserve appear to respond Mojave National Preserve is interested in reported here has been reviewed by subject rapidly to annual rainfall and, on average, working with scientists to understand and matter experts. may have aquifer storage capacity to mitigate the effects of climate change on Editor persist through only a few years of park resources. Projects can range from Debra Hughson, Science Advisor extreme drought. Understanding and $30,000 to $900,000 and must be

Superintendent preserving natural resources in the face completed in three years. We would like Dennis Schramm of climate change is one of the great to work with interested researchers to challenges facing resource managers. develop proposal ideas for fiscal year Contributors 2011 and 2012 competition. Proposal James M. André David R. Bedford The National Park Service has created a ideas would be vetted at the 2010 fall Kirsten E. Dutcher new natural resource funding category meeting of the Mojave Network, and full David M. Miller called Climate Change Response (3) “to proposals for regional competition are April R. Newlander Darren R. Sandquist assist parks with natural and cultural due October 1, 2010. resource-management issues related to Reviewers detrimental consequences of climate References Ron Ruppert, Cuesta College William Presch, California State University, variability and change. Projects must 1. R. Seager et al., Science. 316, 1181-1184 Fullerton promote or plan for on-the-ground (2007). Susan Schwinning, Texas State University, conservation actions or communication 2. N.S. Diffenbaugh, F. Giorgi, J. S. Pal, San Marcos activities that promote resource Geophys. Res. Lett. 35, L16709 (2008).

stewardship and protect park resources. 3. National Park Service, FY 2012 Natural Contact: Priority for funding will be directed Resources SCC Guidance. (NPS, 2009). Debra Hughson, 760-252-6105 towards projects that demonstrate [email protected] tangible benefits to resources and ecosystems that are experiencing

17 Mojave National Preserve Science Newsletter 2009, Number 2