Effects of extreme drought on plant nutrient uptake and resorption in rhizomatous vs bunchgrass-dominated grasslands

Abstract

Both the dominance and the mass ratio hypotheses predict that plant internal nutrient cycling in ecosystems is determined by the dominant species within plant communities. We tested this hypothesis under conditions of extreme drought by assessing plant nutrient (N, P and K) uptake and resorption in response to experimentally imposed precipitation reductions in two semiarid grasslands of northern China. These two communities shared similar environmental conditions, but had different dominant species-one was dominated by a rhizomatous grass (Leymus chinensis) and the other by a bunchgrass (Stipa grandis). Results showed that responses of N to drought differed between the two communities with drought decreasing green leaf N concentration and resorption in the community dominated by the rhizomatous grass, but not in the bunchgrass-dominated community. In contrast, negative effects of drought on green leaf P and K concentrations and their resorption efficiencies were consistent across the two communities. Additionally, in each community, the effects of extreme drought on soil N, P and K supply did not change synchronously with that on green leaf N, P and K concentrations, and senesced leaf N, P and K concentrations showed no response to extreme drought. Consistent with the dominance/mass ratio hypothesis, our findings suggest that differences in dominant species and their growth form (i.e., rhizomatous vs bunch grass) play an important nutrient-specific role in mediating plant internal nutrient cycling across communities within a single region.

Species asynchrony stabilises productivity under extreme drought across Northern China grasslands

“…These sites are representatives of the major grassland (steppe) types in Northern China and were distributed along a broad precipitation gradient in Inner Mongolia (Table 1). Mean annual precipitation (MAP) ranged from 175 to 363 mm (Table 1; see Figure ; Luo, Xu, et al., 2018; Luo, Zuo, et al., 2018 for further description of the sites).…”

Anthropogenic global shifts in biospheric N and P concentrations and ratios and their impacts on biodiversity, ecosystem productivity, food security, and human health

“…The projected total land surface occupied by warm semiarid surfaces may become 38% larger in 2100 compared to the present (Huang, Ji, et al, ; Huang et al, ; Rajaud & de Noblet‐Ducoudré, ). “The effects of aridity (combination of high temperatures with low precipitation) on plant N:P ratios” along natural long‐term climatic gradients also differ from the effects in field studies with climatic manipulation (Luo, Xu, et al, ; Luo, Zuo, et al, ; Yuan et al, ). Increases in canopy N and P concentrations and decreases in plant C:P and N:P ratios have been recorded along transects of increasing aridity.…”

“…Delgado‐Baquerizo et al () observed a negative effect of aridity on the concentration of soil organic C and total N, but a positive effect on the concentration of inorganic P in semiarid and arid areas. In these conditions, P and N shift from soil to plants, so plant communities adapted to long‐term drought conditions retain higher levels of N and P (Luo, Xu, et al, ; Luo, Zuo, et al, ). These effects are consistent with observations of lower ratios of N:P in water from deeper soil layers and indicate P limitation in soil under arid climatic conditions (Sardans & Penuelas, ).…”

“…In contrast, plant N and P concentrations have tended to decrease and N:P ratios have tended to increase (He & Djistra, ; Yuan & Chen, ) in short‐term manipulation studies where water availability decreased (Jiao et al, ; Luo, Zuo, et al, ; Figure ), despite between‐site variations in foliar N and P concentrations (Luo, Zuo, et al, ; Sardans & Penuelas, , , ; Sardans, Grau, et al, ; Sardans, Penuelas, Estiarte, et al, ; Sardans, Penuelas, Prieto, & Estiarte, ). These increases in foliar N:P ratios in response to experimental drought are generally because low soil‐water contents limit P uptake more than N uptake (Luo, Xu, et al, ; Luo, Zuo, et al, ; Sardans, Grau, et al, ; Sardans & Penuelas, ; Urbina et al, ). Plants notably respond to sudden conditions of drought and warming in manipulated field experiments with increased allocations of N, P, and potassium (K) to roots, leading to lower root N:P ratios associated with higher primary metabolism linked to growth, protein synthesis, and pathways of energy transfer (Gargallo‐Garriga et al, , ).…”

Under drought conditions NaCl improves the nutritional status of the xerophyte Zygophyllum xanthoxylum but not of the glycophyte Arabidopsis thaliana

“…About 25% of the world's agricultural land is affected by drought stress ( Jajarmi , ). Global climatic change is predicted to alter growth‐season precipitation‐patterns, potentially increasing the risk of drought, and in particular extreme drought events during this century ( Anand et al., ; Luo et al., ). Drought stress induces a set of physiological and biochemical reactions including reducing water use efficiency in plants, which impair normal growth and water status ( Farooq et al., ; Sahin et al., ).…”