Specific leaf area variability along a natural gradient of soil texture and fertility

Background/Question/Methods

Species functional traits are the foundation of both complementarity theory of community assembly and biodiversity and ecosystem functioning relationships. In order to assess the functional importance of individual species in a community, and community assemblages on important ecosystem processes like nutrient and carbon cycling, it is crucial to determine which factors affect the variability of functional traits. My study explores how soil characteristics affect plant functional traits at the community level from 807 field permanent plots (0.5m²) across 17 restored and 18 remnant prairies in central Nebraska. I measured soil texture (sand, silt, clay), and soil C and N to address how key abiotic variables drive the magnitude of functional plant diversity across soil gradients. Over 300 plant species present at the fields were analyzed for specific leaf area, aboveground biomass allocation and plant height. Specific leaf area is a functional trait that has been identified as a primary component of the leaf economic spectrum and is highly correlated to N concentrations, A_max, and relative growth rate. Plant growth habit, duration, native and invasive status were determined from available databases and field observations.

Results/Conclusions

Specific leaf area (SLA) was quite varied, ranging from 5.3 to 463.2cm²/g, and a mean of 118.9±63.2cm²/g across sites. Across plant growth habit types, SLA was significanly lower in grasses and legumes, and high in forbs and woody plants (p < 0.05). Invasive species had generally higher SLA than the community as a whole (n=9). The fields host a wide range of soil texture and fertility conditions; among fields, there was no detectable difference in aggregate community SLA across N and C gradients, but there was a significant increase in community SLA with increasing silt, and corresponding decrease with sand content (p < 0.10). Community SLA differences are due mostly to different species presence at different sites, but there is also a component of within-species variability that will be explored as a result of these preliminary findings. Abiotic drivers of soil fertility and texture and drive differences in community assemblages and individual species’ functional traits, both of which help determine community wide functionality which in term has the potential to inform whole ecosystem dynamics.