Research Notes for Land Managers

Cottonwood Ecology Group, Northern Arizona University Fall 2010 Volume 1, Issue 1 Research Notes for Land Managers Inside this issue: Editor’s Note Climate change and the future 1 The following data sets, Ogden Nature Center, Utah of cottonwood riparian areas in implications, and manage- Department of Natural Re- the Southwest ment recommendations are sources and the National Range location, isolation, and 4 based upon ongoing field Science Foundation to climatic stress impact genetic and common garden studies merge basic research and diversity with Fremont (Populus fre- restoration. This issue in- montii) and narrowleaf cludes brief reports on 10 Genetic diversity in cottonwood 5 (Populus angustifolia) cotton- major topics. We empha- and its implications for a diverse dependent community ranging wood throughout Arizona, size that many of these from microbes to vertebrates New Mexico, Utah, Nevada, findings are preliminary, Colorado, Montana and and many have not yet Diversity is more than meets the 7 Idaho. They involve ongo- gone through the formal eye ing collaborations between review process for publi- Interspecific indirect genetic 8 the Blue Ridge Forest Ser- cation, which can take ings listed as 1) Key Find- effects: the influence of tree genet- vice, AZ Game and Fish, years. These notes are ings, 2) Major Lines of Evi- ics reaches far into the surround- Natural Resources Conser- meant to inform manag- dence, 3) Major Conserva- ing community and ecosystem vation Service, Bar T Bar ers of our most current tion and Restoration Impli- Ranch, NAU grounds, research findings and cations, and 4) Practical Beavers drive biological diversity 10 Natural Channel Design, their management impli- Recommendations. We City of Flagstaff, Pinetop cations. Findings are pre- welcome your feedback on Stand age, competition, planting 12 densities affect biodiversity and Game and Fish, Pinetop sented in a short, readily these topics habitat quality of restored com- Forest Service, Bureau of accessible format. Each ([email protected]; munities Reclamation, Cibola Na- major topic is organized [email protected]). tional Wildlife Refuge, according to four subhead- Restoration sites should aim to 13 mirror the genetic structure of wild populations Climate change and the future of cottonwood riparian areas in the Southwest Invasion ecology: Interactions 14 with exotic tamarisk Key Finding – Record stand the scope of the prob- distribution of cotton- droughts in the Southwest lem for riparian habitat woods will be dramati- Tamarisk alter the structure of 15 since 1996 have taken a throughout the Southwest cally altered and will be ectomycorrhizal fungal commu- toll on major vegetation and to take an aggressive eliminated from former nities of cottonwoods types. Although mortality stance on preventing future areas of abundance References cited and recent pub- 16 was highest for pinyon losses for a habitat type that (Gitlin & Whitham, un- lications from the Cottonwood pine in common PJ wood- is already considered threat- pub. data). The following Ecology Group lands, Fremont cotton- ened (Noss et al. 1995). figure shows the current woods in rare riparian Three major lines of distribution of cottonwoods Brian Layton Cardall Memo- 18 habitat suffered 20.7% (broadleaf Fremont and rial Scholarship Fund evidence – 1.1 - Climate mortality (Gitlin et al. change models predict Eastern, narrowleaf and 2006). These findings argue their naturally occurring that with continued that it is important to under- warming and drought, the hybrids) in a 4 state area of Page 2 Research Notes for Land Managers Volume 1, Issue 1 Utah, Arizona, Colorado, and New Mexico. Using the Genetic Algorithm for Rule-set Prediction (GARP) model, panel (a) shows the potential niche distribution for narrowleaf (black) and broadleaf (light grey) cottonwoods, with medium grey showing the potential hybrid zone between species. The broadleaf cottonwoods currently have the largest niche of the cross types. Because cottonwoods only occur along creeks and rivers, panel (b) shows the potential niche Figure 1. This panel shows the potential niche distribution of cottonwood modeled with GARP. map masked to show riparian areas only (species des- ignations same as (a). If you compare the current distribution of these cottonwoods (above Figure 1) with their projected distributions (right Future climate models predict greatly reduced potential distributions for cottonwood. Figure 2) based upon increasing tempera- tures and declining moisture, note the dra- matic shift in their distributions. For ex- ample, the white area denotes regions of the Southwest that are largely devoid of cottonwoods; note how that area vastly increases with a climate change scenario that is generally accepted as being realistic (e.g., contrast above panel (a) with lower right hand panel below) (Gitlin and Whitham unpub. data). 1.2 - Broadleaf cottonwoods (Fremont and Eastern) and narrowleaf cottonwood are suffering much higher mortality than their naturally occurring hybrids (Gitlin & Whitham unpub- lished data). Across the Colorado Pla- teau, mortality levels of narrowleaf cottonwood, broadleaf and hybrid cottonwoods differed in 2003 and 2004 (Figure 3). Hy- Figure 2. These panels indicate the potential distribution of cottonwood under several different combinations of increased temperature and decreased moisture. Research Notes for Land Managers Volume 1, Issue 1 Page 3 brids survived significantly better than either of their parental species. In 2003, 4% of F1 type hybrids died, which was ~1/3 the mortality of narrowleaf and ~1/4 the mortality of broadleaf cottonwoods (panel a). The same patterns emerged in 2004; F1 type hybrid mortality remained at 4%, while we recorded 23.3% of narrowleaf and 11.3% of broadleaf cottonwoods dead in that year (panel b). Panel (c) shows that although the mortality patterns vary among individual rivers, the overall pattern is for natural hybrids to outperform their parental species. Panel (d) shows the patterns of reproduction in which broadleaf cottonwoods are lower than either natural Figure 3. Natural hybrids show lower mortality than parental species (a-c), and broad- hybrids or narrowleaf cottonwood. leaf cottonwoods were found to have the lowest rates of reproduction (d). This is largely due to the fact that 6 hybrids and narrowleaf cottonwood outperform those can reproduce via sprouting from the from farther away, we 5 roots, whereas broadleaf cottonwoods found that environ- such as Fremont can only reproduce mental distance is 4 via seedlings. So, in the absence of more important than flooding events, which are largely elimi- geographic distance 3 nated by flood control, plants that for initial survivorship clone have a reproductive advantage 6 months after plant- 2 and are likely to better survive drought ing (Ferrier unpub. PRODUCTIVITY and reduced water flows due to agricul- data). 1 tural and other human demands on As with initial sur- water. vivorship, we also 0 1.3 - Local source populations found that Fremont AF AL CNWR GR3W HD ML PVER RL SC SP may be best adapted to their current local environments. In 2007, we Figure 4. Fremont productivity significantly varies across populations. planted over 2000 Fremont cottonwoods that had been propagated productivity (p=0.0001) is signifi- from cuttings collected throughout cantly different across populations the Basin and Range Hydrogeologic (Figure 4 above), and significantly Province in Arizona (174,000 km2). correlates to a generalized environ- They were planted at Palo Verde mental cline, elevation (Figure 5 left) Ecological Reserve, near Blythe, CA (Grady unpub. data). The popula- in collaboration with the Bureau of tion variation and clinal association Reclamation and California Fish and we see in these plant traits may indi- Game. In addition to the restoration cate that selection is driving evolu- goals of the planting, we sought to tionary differences within this spe- find out if local source populations cies. More importantly, environ- would perform better than source mental similarity of source popula- populations from more distant loca- tions to the restoration site will be an Figure 5. Plant productivity correlates tions. Although it is commonly be- important predictor of survival and with elevation of the source population. lieved that local source populations will subsequent performance. We show this to be true for current climatic con- Page 4 Research Notes for Land Managers Volume 1, Issue 1 source populations may no findings that naturally oc- years ago, today, and 200 longer be best adapted to curring hybrids are better years into the predicted fu- the local environment. than their parents in surviv- ture. We emphasize that a Findings are beginning to ing drought argues that field trial approach, to deter- emerge in ongoing studies these hybrids should be mine what ‘native’ popula- in Canada, and Europe that considered for use in resto- tions are best able to survive provide supporting evidence ration. Furthermore, if the in a changing environment, of this concern. The resto- environment will change as may be crucial to conserva- ration implications are so much as models predict, tion and restoration efforts. great that we can’t afford to then managers will need to The genetic differences ignore them. Together, the seriously consider restora- among different tree geno- H. Bothwell above 3 independent data tion with non-local geno- types are so pronounced -ditions, but as

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