Effects of climate, soil, and leaf traits on nutrient resorption efficiency and proficiency of different plant functional types across arid and semiarid regions of northwest China.

BACKGROUND

Plant nutrient resorption is crucial for the efficient conservation of nutrients. However, the mechanisms through which abiotic and biotic factors control nutrient resorption remain controversial. We investigated leaf nitrogen (N) and phosphorus (P) resorption efficiency (NRE and PRE) and resorption proficiency, as well as the underlying mechanisms for each plant functional type (PFT: non-legume herbs, non-legume shrubs, and legumes) by collecting green and senescent leaves of 59 species covering 106 sites from arid and semiarid regions of northwest China.

RESULTS

Legumes had much lower leaf NRE and much higher senesced leaf N than the other two PFTs; they had similar leaf PRE to non-legume shrubs. Non-legume herbs exhibited the highest leaf P resorption. Climate, particularly temperature, increased leaf N resorption in non-legume herbs; however, climate, particularly decreasing precipitation, decreased leaf P resorption in legumes. Leaf nutrient resorption in non-legume shrubs decreased with increasing soil fertility, but leaf NRE in legumes increased. Leaf traits contributed more to leaf N and P resorption than climate and soil. Senesced leaf N and P concentrations increased along the resource-conservative to resource-acquisitive strategy axis. There were strong negative relationships between leaf NRE and senesced leaf N concentration and between leaf PRE and senesced leaf P concentration, in which legumes had a lower slope than non-legumes.

CONCLUSIONS

These findings suggest that ecological strategies and N-fixing plant types modulate nutrient resorption. Plants with the resource-conservative strategy are highly proficient in nutrient resorption. We highlight the importance of leaf economics traits and spectrum in regulating leaf nutrient resorption in drylands in the context of global climate change, potentially modulating plant traits and community composition. The higher proficient and efficient N and P resorption of plant species suggests the crucial importance of nutrient resorption in the nutrient cycling of harsh drylands.