California Grassland Restoration Literature

Author : Jennifer Anna Balachowski
Publisher :
ISBN 13 : 9781339543581
Total Pages : pages
Book Rating : 4.5/5 (435 download)

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Download or read book Functional and Drought Survival Strategies of California Perennial Grasses in the Context of Restoration written by Jennifer Anna Balachowski and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Over the next 100 years, ecosystems in California are expected to experience warmer temperatures and an increase in the frequency and intensity of droughts. California grasslands are also heavily invaded by European annual grasses, and climate change may further favor these exotic invaders over native species. Restoration efforts in California grasslands would benefit from ways to identify taxa that are best suited to withstand increasing drought stress, including the traits that are common among the most successful drought survivors. The traits and strategies promoting severe drought survival in native perennial grasses have been relatively little explored, and drought survival is rarely studied in conjunction with seasonal patterns of growth or ecologically important (i.e., "functional") traits. In the first chapter of this dissertation, we integrated physiological and functional trait-based approaches to characterize seasonal growth dynamics and drought survival strategies in eight California wildland perennial grass species. We paid special attention to summer dormancy, an adaptation to drought that is known to be expressed by several California perennial grasses, but has received very little empirical study. Summer dormant species in our study were characterized by greater springtime productivity; earlier reproduction; a shallower, finer root system; and high tolerance of tissue dehydration. Together, these traits suggest that in spring, summer dormant taxa exhibit a resource acquisitive functional strategy, escaping drought via efficient competition for resources and early reproduction. Owing to functional similarity with many exotic annual grasses, we suggest that summer dormancy may play an important ecological role in restoring native perennial species to California grasslands. Local plant populations are recommended for ecological restoration to avoid maladaptation to current site conditions; however, whether they will be well adapted to future climate scenarios, including increasing drought stress, is a major concern for practitioners. In the second chapter, we extended the approach from Chapter 1 to characterize intraspecific variation in drought survival, seasonal growth dynamics, and functional traits in a suite of five populations of Elymus glaucus, a native perennial bunchgrass commonly used in restoration. We chose populations from sites with contrasting climates to determine how trait and environmental variability are related. We found strong intraspecific variation in dehydration tolerance, which was tightly correlated with summer dormancy. Dehydration tolerance was associated with a conservative functional strategy, and with increasing summer climatic water deficit at populations' sites of origin. Trait variation was most associated with annual climatic water deficit, rather than summer aridity, which highlights the need to measure traits during both the drought period and the more productive growing season when considering species from temporally variable climates. Our results suggest that restoration practitioners may be able to predict dehydration tolerance from summer aridity alone, but that climate during the growing season may be just as important for ecological restoration. Local adaptation evolves in response to both abiotic and biotic selective pressures. Biotic factors like competition have received far less empirical study, but functional ecology predicts that they will be more important in productive environments. In the third chapter, we used a reciprocal transplant experiment to determine whether patterns of trait variation expressed in Chapter 2 were indicative of local adaptation. Because populations were collected from contrasting productive and stressful sites, we asked whether intraspecific competition was a more important modulator of plant fitness in productive coastal sites, and whether coastal populations were more competitive. We did not find consistent evidence of local adaptation in our populations. We found that competition was more important to reproductive output at coastal sites, but only for resident populations. This result suggests that, especially at coastal sites, receiving all the benefits of locally sourced plant materials in grassland restoration requires careful consideration of the optimal intraspecific planting neighborhood.