Mountain Meadows of the Sierra Nevada An integrated means of determining ecological condition in mountain meadows Protocols and Results from 2006 Sabra E. Purdy and Peter B. Moyle Department of Water Resources Contract No. 4600004497 Acknowledgments We would like to acknowledge the Department of Water Resources (Contract No. 4600004497) for their support of this research project under the Integrated Regional Water Management Plans. We would also like to thank our sponsor, the Natural Heritage Institute (Agreement No. 06‐000470), in particular, Elizabeth Soderstrom and Carrie Monohan. In addition, we extend our gratitude to Amy Merrill, David Weixelman, Jeff Brown and Sagehen Field Station, Max Fish, Dan Wilson, Brett Baker, Jon Stead, Erik King, Morgan King, Ken Tate, and the administrative staff at the U.C. Davis Center for Watershed Sciences, Diana Cummings, Tanya Guilfoil, and Ellen Mantallica. 2 Introduction to Sierra Nevada Meadows Montane meadows are a distinctive form of riparian wetland that occur in the elevational belt between 4,000 and 8,000 feet in the Sierra Nevada. Riparian plant communities differ significantly from their corresponding upland communities because of their access to water and because the soil type provides conditions not found elsewhere (Kondolf et al. 1996). Riparian areas are generally limited to a narrow strip along the stream before the increased depth of the water table forces a change to an upland community (Kondolf et al. 1996). Therefore, riparian habitats tend to represent just a small fraction of the land in any given watershed, ranging from approximately 0.1 to 1 percent in the Sierra Nevada (Kattelmann and Embury 1996). Mountainous areas with steep gradients are frequently punctuated by alluvial basins with low gradients. In these areas, both the water table and riparian vegetation are able to spread out, creating meadows. Such meadows represent less than 0.01 percent of the landscape in the Sierra Nevada, but are very important in their function and biodiversity (Kattelmann and Embury 1996). These productive and diverse systems support more species of wildlife than any other habitat type in the Sierra Nevada (Kauffman and Krueger 1984). For example, approximately one‐fifth of the 400 species of terrestrial vertebrates found in the Sierra Nevada are strongly dependent on riparian areas, with a much higher percentage partially associated with riparian areas (Graber 1996). Meadows and riparian areas have been identified as the single most important habitat to birds in the western U.S. (DeSante 1995). In addition, amphibian species such as mountain yellow‐legged frog (Rana muscosa and Rana sierrae (Vredenburg), the Yosemite toad (Bufo canorus) (both endemic to the Sierra Nevada), and southern long‐toed salamander (Ambystoma macrodactylum sigillatum) all heavily rely on meadows, or meadow associated habitats. Although Sierra mountain meadows are disproportionately valuable for habitat and ecological services, they have generally received less attention than wetlands at lower elevations. They have withstood a long history of degradation (change to a state that is less productive and supports fewer species and individuals of native animals and plants) from timber harvest, dams and diversions, mining, livestock grazing, and invasions of alien species (Ratliff 1985). In spite of their importance, there is surprisingly little comprehensive information available regarding their status or the status of the streams they contain on which to base planning, restoration, and conservation priorities. Despite considerable and widespread impacts from grazing and other activities, a fairly high proportion of Sierran meadows appear to have not crossed the threshold into irreversible, long‐term ecological impairment. Meadows are comparatively resilient systems that can return to an apparent high state of ecological function once degrading influences, such as grazing or roads, are eliminated or reduced (Ratliff 1984, US Bureau of Land Management 1995). This resiliency is presumably the result of a combination of ample water, a large seedbank, and low gradients, but can be lost once a certain degradation threshold has been passed and the system cannot recover on its own. The single biggest factor that reduces meadow resiliency and hence promotes degradation in the Sierra Nevada is grazing, particularly in the way it can change meadow hydrology. 3 Grazing With few exceptions, nearly all meadows in the Sierra Nevada have been grazed by livestock at one time or another (Kattelmann and Embury 1996). Many areas have been badly damaged by grazing and the effects can be seen in many meadow streams. In the Sierra Nevada, grazing was virtually ubiquitous before 1930 (Kattelmann and Embury 1996) and only the most remote and inaccessible areas remained ungrazed (Kinney 1996). Grazing occurred primarily in riparian areas because they provided the best forage, shade, and easy access to water; the effects of the livestock quickly became evident (Kinney 1996). For example, years of persistent overgrazing in Plumas National Forest led to major degradation of the riparian meadows in the North Fork Feather River drainage (Kattelmann and Embury 1996). Severe gullying and soil loss was evident by 1900 (Kattelmann and Embury 1996). The Soil Conservation Service estimated soil losses in the watershed to be 15‐30 vertical cm (6‐12 in) since grazing began in the 1860s (Kattelmann and Embury 1996). Menke et al. (1996) provided a thorough look at the grazing history of California from the gold rush era to present times, and found that although considerable improvement has been made in range management, there was a great deal of residual damage in these systems, and they are not likely to recover without 1) further reduction or elimination of grazing, and 2) active restoration projects. For example an inventory of wet meadows in Inyo National Forest in the eastern Sierra indicated that 90% were damaged or threatened by damage from accelerated erosion due to poor grazing practices (Kattelmann and Embury 1996). Despite the large body of literature demonstrating the negative ecological impacts of livestock grazing, properly managed grazing is not necessarily detrimental to the environment (Menke et al. 1996, Allen‐Diaz et al. 1999). Techniques utilized for minimizing cattle impact to riparian areas include pasture rotation, grazing alternate years, decreased stock levels, and riparian exclosures (Menke et al. 1996). A common criticism in the literature is that few of these management tools receive premanipulation study and are therefore riddled with inferential mistakes, causal assumptions, and inconclusive evidence (Belsky et al. 1999, Sarr 2002). Additionally, many studies set out only to document patterns associated with overgrazing rather than quantitative analysis of processes (both degradation and recovery) (Sarr 2002). The contentious nature of economic interest versus ecosystem health has generated decades of debate; yet, there are relatively few conclusive studies about quantitative effects of grazing (Sarr 2002). Vegetation changes are fairly well‐documented, but references to impacts on fish and other aquatic organisms are surprisingly sparse. This may be in part due to the difficulty of separating causal interactions in already‐degraded streams, particularly in light of the long history of degradation in these systems. The dearth of sites that have never been impacted makes it difficult to reference historical conditions and quantitatively compare them to current conditions. Hydrology Mitsch and Gosselink (2000) contend that hydrology is the primary driver for the establishment and persistence of all wetlands. While hydrology drives botanical community structure, it is also driven by it. The connection between hydrology, vegetation, and stream geomorphology in meadows is generated by both positive and negative feedbacks, and an impact to one inevitably affects the others. Stream bank erosion is one of the most obvious and widespread negative effects of disturbance in meadow systems (Micheli and Kirchner 2002). While this may have a number of root causes, the most common causes of erosion and incision in Sierran meadows 4 have been 1) grazing of livestock and 2) poorly installed culverts, and 3) road cuts, that lead to head cutting, bank erosion, and drops in the water table. Generally, soil erosion is preceded by a loss of protective vegetation, though large scale flood events that mobilize large volumes of sediment can alter stream beds through both erosion and deposition. Hydric meadows are often dominated by sedges (Carex species), which generally possess densely matted root matrices that do an excellent job of holding together the unconsolidated and fine soils generally found in meadows (Chambers et al. 2004). Meadow vegetation protects stream banks from the erosive forces of water and helps to attenuate flooding when the stream overtops its banks. In combination, meadow soils and vegetation have a sponge‐ like effect and are able to store water that is available for a longer time over a greater surface area to meadow vegetation (Hammersmark et al. 2008). When stream bank vegetation is depleted past a certain threshold level, the dynamics of moving water quickly begin to erode the soft, unconsolidated meadow soils (Micheli and Kirchner 2002). This leads to a widening of the stream channel which in turn prevents the stream from overtopping its banks and accessing the floodplain in high runoff events. Rather than dissipating