Elliott Chaparral Reserve

23 Sep, 02 AM - 01 Nov, 02 AM

As anthropogenic activities continue to alter environmental conditions, ecologists are challenged to predict how natural systems will respond. Species vary in their tolerances to environmental constraints such as drought, as well as their capacity to compete for limiting nutrients with other species (Tilman 1982). Functional traits integrate these ecological tolerances and strategies for obtaining resources (Lavoral et al. 1999). This provides a framework for predicting how species composition is likely to respond to shifting environmental conditions and resource supplies (Suding et al 2008). In areas where the range of potentially successful ecological strategies are restricted by environmental conditions, species are likely to converge on a common set of functional traits associated with environmental tolerance (e.g. habitat filtering, Weiher & Keddy). In areas where resources are abundant, competition among species may become a more important predictor of community composition than environmental tolerance, hence permitting a broader array of strategies to co-exist. Further, the concept of limiting similarity predicts that species will be more likely to co-exist if they use different resources or use limiting resources at different times, such that the community may diverge in functional traits. In Southern California, precipitation levels are expected to decline overall and also become more variable in the coming decades. The proposed research seeks to better understand the role of precipitation as a habitat filter, influencing patterns of trait divergence and convergence in a chaparral community. I hypothesize that with lower levels of precipitation, highly adapted native chaparral species, will display a convergence in the following traits: high water use efficiency, low specific leaf area, similar flowering time and length of flowering and will outperform divergent alien species. I further expect that as levels of rainfall increase, native species will be unable to take advantage of the surplus resource (rainfall). As a result, divergent species with novel traits, such as invasive annual grasses, will be able to outcompete native species and establish within the community. Experimental plots will receive one of five levels of rainfall (0%, 50%, 100%, 150%, and 200% of ambient rainfall) with five replicates for a total of 20 experimental plots and 5 control plots. Also included will be an additional three covered plots to account for any unintended effects of the rain-out shelters (such as warming or shifts in humidity). Rain-out shelters will be utilized for rainfall manipulations with a shelter over each plot receiving the ?less than ambient rainfall? treatment. Each shelter will be positioned over existing focal native vegetation. Both evergreen and deciduous juvenile shrubs will be planted in a 1 x1 m subplot to monitor seeding establishment, growth rates and survivorship as well as trade-offs in major plant functional strategies. An additional 1 x1 m subplot will be monitored to evaluate shifts in species composition as compared to controls. Rainfall will then be distributed to experimental plots by the use of irrigation according to their prescribed treatment.

Visit #23198 @Elliott Chaparral Reserve

Approved

Under Project # 22674 | Research

Evaluating the Effects of Projected Precipitation Shifts on South Coastal Chaparral Communities

graduate_student - University of California, San Diego

Reservation Members(s)

Angelita Ashbacher Sep 23, 2010 - Nov 1, 2012 (771 days)
Angelita Ashbacher Sep 23, 2010 - Nov 1, 2012 (771 days)
Angelita Ashbacher Sep 23, 2010 - Nov 1, 2012 (771 days)
Angelita Ashbacher Sep 23, 2010 - Nov 1, 2012 (771 days)
Group of 2 Volunteer Sep 23, 2010 - Nov 1, 2012 (771 days)

Reserve Resources(s) | Create Invoice

Grounds use only 6 Sep 23, 2010 - Nov 1, 2012