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Biodiversity
functional traits
leaf carbohydrates
leaf nitrate
photosynthesis
species performance
stable isotopes
source-sink relations
temperature response functions
air CO2
enrichment
species richness
fructan metabolism
photosynthesis
biodiversity
leaves
communities
ryegrass
Abstract:
Positive species richness effects on aboveground community productivity in experimental grasslands have been reported to correlate with variable responses of individual species. So far, it is largely unknown whether more complete use of resources at the community level correlates with resource limitation of particular species and may explain their decreasing performance with increasing plant diversity. Using the subordinate grass species Lolium perenne L. as a model, we monitored populations in 82 experimental grasslands of different plant diversity (Jena Experiment) from year 2 to 6 after establishment, and measured ecophysiological leaf traits related to light and nutrient acquisition and use. Population and plant individual sizes of L. perenne decreased with increasing species richness. A decrease in transmitted light with increasing species richness and legume proportion correlated with increasing specific leaf area (SLA). Despite this morphological adaptation to lower light availability, decreasing foliar delta 13C signatures with increasing species richness and low variation in leaf gas exchange and chlorophyll concentrations suggested a low capacity of L. perenne for adjustment to canopy shade. Leaf nitrogen concentrations and foliar delta 15N signatures indicated a better N supply in communities with legumes and a shift in the uptake of different N forms with increasing species richness. Leaf blade nitrate and carbohydrate concentrations as indicators of plants nutritional status supported that light limitation with increasing species richness and legume proportions, combined with a N limitation in communities with increasing proportions of non-legumes, correlated with the decreasing performance of L. perenne in communities of increasing plant diversity.
