Aspen (Populus tremuloides) stands and their contribution to plant diversity in a semiarid coniferous landscape

Abstract

We conducted a field study to determine the relative contributions of aspen (Populus tremuloides), meadow, and conifer communities to local and landscape-level plant species diversity in the Sierra Nevada and southern Cascade Range, northeastern California, USA. We surveyed plant assemblages at 30 sites that included adjacent aspen, conifer, and meadow communities across a 10,000-km 2 region. We statistically investigated patterns in local and landscape-scale plant diversity within and among the three vegetation types. Summing across sites, aspen stands supported more plant species overall and more unique plant species than either meadow or conifer communities. Local richness and diversity did not differ between aspen and meadow plots; conifer forest plots were significantly lower in both measures. Heterogeneity in species composition was higher for aspen forest than for meadows or conifer forest, both within sites and between sites. Plant communities in aspen stands shared less than 25% of their species with adjacent vegetation in conifer and meadow plots. Within aspen forest, we found a negative relationship between total canopy cover and plant diversity. Our results strongly support the idea that plant communities of aspen stands are compositionally distinct from adjacent meadows and conifer forest, and that aspen forests are a major contributor to plant species diversity in the study region. Current patterns of aspen stand succession to conifer forest on many sites in the semiarid western US are likely to reduce local and landscape-level plant species diversity, and may also have negative effects on other ecosystem functions and services provided by aspen forest.

Tamm Review: Management of mixed-severity fire regime forests in Oregon, Washington, and Northern California

“…In the case of relatively pure patches of aspen (Populus tremuloides), cottonwood (Populus trichocarpa & Populus fremontii), and birch (Betula papyrifera & Betula occidentalis), fire exclusion has dramatically reduced their abundance, patch sizes, and vigor (Hessburg et al, 1999a). For their influence on habitat for certain species, landscape biodiversity, and fire behavior (Kuhn et al, 2011;Shinneman et al, 2013), there are clear advantages to revitalizing existing clones and patches, or to restoring their abundance (Jones et al, 2005) near wet meadows and seeps, in areas of seasonally high water table, and in floodplain and riparian areas (Bartos and Campbell, 1998;Campbell and Bartos, 2001;Seager et al, 2013). …”

Climate change refugia and habitat connectivity promote species persistence

“…Montane meadows are key to alpine and subalpine animal communities, hydrological function, and human recreation, agriculture, and economy [11][12][13]. Recent work [4] used high resolution, dynamically downscaled climate models to map refugial meadow networks to identify where climate-sensitive species could persist, and restoration and conservation actions could be focused.…”

Phenology and climate relationships in aspen ( Populus tremuloides Michx.) forest and woodland communities of southwestern Colorado

“…This condition, called Sudden Aspen Decline (SAD), is characterized as a drought and disease cycle, where terrain and edaphic features predispose stands to decline, severe drought initiates decline, and finally, opportunistic insects and pathogens cause extensive damage and frequent mortality Rehfeldt et al, 2009;Worrall et al, 2008). Researchers have suggested that aspen is undergoing a range contraction in the warmest, driest, and most southerly regions of its distribution (Kuhn et al, 2011;Worrall et al, 2013;Zegler et al, 2012). Aspen decline and mortality is largely attributed to drought events and to the gradual warming and drying conditions brought about by global climate change (Worrall et al, 2013).…”