SP12c Root trait variation and plasticity in relation to phosphorus availability in phosphorus-poor subtropical forests (sp12c phosporus)

Root traits are critical for nutrient uptake in nutrient-poor environments. For phosphorus (P)- poor subtropical forests of BEF China, important research questions are how root morphological and physiological traits have adapted to low P conditions, and how different coexisting species have evolved different adaptive strategies of P uptake and cycling. Preliminary data have shown that coexisting species in these forests differ markedly in root morphology and architecture. In this project, we will examine how these differences in morphology and architecture are related to P uptake and cycling. We hypothesize that: 1) species with larger-diameter root tips are more dependent on root hairs or mycorrhizal fungi for P uptake than those with smaller-diameter root tips; 2) the larger-root-diameter species have greater growth rate and explore greater volume of soil per unit whole-plant biomass production; 3) the larger-root-diameter species have higher P use efficiency as reflected in lower tissue P concentrations and higher P retranslocation rates at the whole plant level. We also hypothesize that differences in root morphological and chemical traits are highly conserved such that they show limited change when soil P levels are modified, whereas root physiological intensity (as measured by tissue respiration) is highly plastic. Testing of these hypotheses is likely to lead to a much better understanding of how root trait differences contribute to species coexistence in P-poor environments.