Climate shapes the distribution and abundance of species across space and time globally and is a major determinant of local biodiversity. Changes in precipitation, particularly drought, can alter biodiversity in temperate tallgrass prairie grassland ecosystems, where soil moisture is the primary driver of plant community structure. Hay harvest, a common management practice in this system, can also affect plant biodiversity. Thus, understanding how climatic changes co-occurring with hay harvest management will drive biodiversity responses in grasslands can anticipate some of the broader impacts on the plant community structure. We investigate how a gradient in precipitation alongside with clipping, to mimic hay harvest, shapes plant functional group responses and overall plant community diversity and species’ composition. In Central Oklahoma, we used rain interception shelters to impose a gradient of precipitation treatments (+50%, 0%, -20 %, -40 %, -60 %, -80%, -100%) nested with aboveground biomass clipping treatment (clipped vs. unclipped) in a fully factorial design (n=3, N=21). We asked: (1) What are the main effects of precipitation and clipping on functional group abundances, plant biodiversity and compositional similarity? (2) Does clipping mediate precipitation effects to shape the structure of a temperate prairie ecosystem, since clipping is known to increase plant richness?
Results/Conclusions
After two years, we found that precipitation and clipping acted independently to influence the plant diversity and overall plant species composition. In the first year, precipitation changes altered plant community metrics, extreme drought decreased diversity and evenness compared to increasing precipitation that promoted plant diversity by increasing the number of plant species. In the second year, clipping increased richness, but altered precipitation had no effect on community metrics. Interestingly, changes in community structure were not driven by functional groups, but by species-specific responses. Plant species composition tended to shift more with drought indicating that species’ identity and/or relative abundance diverged under stressful conditions. Overall, our results show that precipitation changes had an immediate effect on plant community responses, while clipping lagged to affect diversity metrics only during year two. Compositional similarity was consistently affected by precipitation changes, with drought promoting species turnover.