Abstract
Numerous studies have concluded that carbon (C):nitrogen (N):phosphorus (P) stoichiometry in both soils and plants tends to be decoupled under global change. We consequently hypothesized that plants will adjust nutrient conservation strategies to balance the altered elemental stoichiometry accordingly. To test our hypothesis, we conducted two pot-cultured experiments (with 8-level water and 6-level N addition treatments) using N-fixing species Glycyrrhiza uralensis Fisch from a desert steppe in northwestern China. We observed that high water availability lowered total N content and the N:P ratio in soils, further promoting both N and P resorption from senescing leaves of G. uralensis. High N addition enhanced soil N availability and the N:P ratio, thereby reducing N resorption, but increasing P resorption of G. uralensis. Comparatively, there were also great changes in senescing leaf C:N:P stoichiometry while no clear changes were observed in either green leaf or root C:N:P stoichiometry of G. uralensis. As expected, the altered C:N:P stoichiometry may, in turn, modify N and P conservation strategies through their close linkages with N and P uptake in green leaves of G. uralensis. This modification may also further exert effects on N and P cycling of the desert steppe.
Highlights
As consequences of anthropogenic activities, changing precipitation patterns and increasing atmospheric nitrogen (N) deposition have become two serious global environmental problems for terrestrial ecosystems[1], especially for those limited by precipitation and N
Increasing water supply greatly increased aboveground biomass, root biomass and total biomass of G. uralensis with the highest values displayed in W2 treatment (Fig. S1)
Increasing N addition promoted the growth of G. uralensis with the highest values shown in N20 treatment (Fig. S2)
Summary
As consequences of anthropogenic activities, changing precipitation patterns and increasing atmospheric nitrogen (N) deposition have become two serious global environmental problems for terrestrial ecosystems[1], especially for those limited by precipitation and N. Previous studies estimated that the amount of N deposition has reached two to seven times the pre-industrial rates in some developed countries[7], increasing at a rate of 0.41 kg hm−2 yr−1 during 1980–2010 in China[8] Both precipitation and N deposition closely relate to soil nutrient availability and regulate nutrient tradeoff between plants and soils[9,10]. Plant nutrient conservation is considered an important nutrient-use strategy for plants from the most nutrient-poor ecosystems[20] It determines litter decomposition quality, and soil nutrient availability, and plays a significant role in the nutrient cycling of ecosystems. Low nutrient uptake and/or high nutrient resorption are suggested as useful mechanisms to conserve nutrients for plants in nutrient-poor habitats[22] Both nutrient uptake and nutrient resorption by plants are species-specific processes, affected by meteorological factors and vegetation types. Plant nutrient conservation strategies have been remarkably well-studied in grasslands (i. e., moderate grasslands in northern China), though our knowledge of desert steppe species is still lacking, especially regarding P conservation strategies
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