Different responses of plant N and P resorption to overgrazing in three dominant species in a typical steppe of Inner Mongolia, China

Abstract

Nutrient resorption from senesced leaves is an important mechanism for nutrient conservation in plants. However, little is known about the effect of grazing on plant nutrient resorption from senesced leaves, especially in semiarid ecosystems. Here, we evaluated the effects of grazing on N and P resorption in the three most dominant grass species in a typical steppe in northern China. We identified the key pathways of grazing-induced effects on N and P resorption efficiency. Grazing increased N and P concentrations in the green leaves of Leymus chinensis and Stipa grandis but not in Cleistogenes squarossa. Both L. chinensis and S. grandis exhibited an increasing trend of leaf N resorption, whereas C. squarrosa recorded a decline in both leaf N and P resorption efficiency under grazing. Structural equation models showed that grazing is the primary driver of the changes in N resorption efficiency of the three dominant grass species. For L. chinensis, the P concentration in green and senesced leaves increased the P resorption efficiency, whereas the senesced leaf P concentration played an important role in the P resorption efficiency of C. squarrosa. Grazing directly drove the change in P resorption efficiency of S. grandis. Our results suggest that large variations in nutrient resorption patterns among plant species depend on leaf nutritional status and nutrient-use strategies under overgrazing, and indicate that overgrazing may have indirect effects on plant-mediated nutrient cycling via inducing shifts in the dominance of the three plant species.

Groundwater Depths Affect Phosphorus and Potassium Resorption but Not Their Utilization in a Desert Phreatophyte in Its Hyper-Arid Environment

“…ex Ledeb.) Keng is significantly affected by green and senesced leaf P concentrations in overgrazing treatments ( Wang et al, 2020 ). Herein, the NRE of P in A. sparsifolia at 4.5 m groundwater depth was significantly higher than that at 2.5 m ( Table 1 ), suggesting that A. sparsifolia at 4.5 m groundwater depth could have translocated more P from the senescing tissues to the green tissues to support plant growth as indicated in our previous report that the soil P concentrations between 4.5 and 2.5 m groundwater depths in the same area were not significantly different ( Zhang et al, 2018a ).…”

“…Nutrient utilization and resorption are vital for plant growth and ecosystem processes in various ecosystems ( Aubrey et al, 2012 ; Zhao et al, 2017 ; Wang et al, 2020 ). First, the total net primary production per unit nutrient absorption is described as nutrient use efficiency (NUE) ( Vitousek, 1982 ).…”

“…Nutrient resorption from senescing tissues to green tissues has important consequences for plants that live in nutrient-limited habitats. Nutrient resorption helps plants re-use nutrients directly to become less dependent on external nutrient concentrations ( Aerts and Chapin, 2000 ; Wang et al, 2014 , 2020 ; Zhao et al, 2017 ; Huang et al, 2018 ). Hence, nutrient resorption is an important mechanism of nutrient conservation in plants.…”

“…NRE is usually higher in nutrient-limited habitats than in nutrient-rich ones ( Killingbeck, 1996 ; Yuan and Chen, 2009 ). Recently, evidence has suggested that NRE is affected by climate, soil/leaf nutrient and stoichiometry, plant functional group, plant age, spatial pattern, and land utilization ( Brant and Chen, 2015 ; Netzer et al, 2017 ; Xu et al, 2017 ; Zhao et al, 2017 ; Wang et al, 2020 ). Previous studies have shown that increasing water condition decreases the NRE of N, but increases that of P of three graminoid species, Agropyron cristatum , Achnatherum sibiricum , and Stipa grandis , and one forb species, Potentilla bifurca in Inner Mongolia, China ( Lü and Han, 2010 ).…”

Resorption Efficiency of Four Cations in Different Tree Species in a Subtropical Common Garden

“…These different results might be related to plant nutrient status across different plant functional types [3,18]. More importantly, most previous studies have not taken the homogeneity of site conditions into consideration [19,20]. Therefore, it is of great significance to study nutrient resorption of different tree species at the same site.…”