Divergent responses of plant biomass and its allocation to the altered precipitation regimes among different degraded grasslands in China

Abstract

Purpose Climate models predict shifts in precipitation patterns characterized by increased precipitation amount and decreased frequency for semi-arid grasslands in northeast China. However, under these novel climatic conditions, potential differences in plant biomass and its allocation among different degraded grasslands remain unclear.Methods We conducted a mesocosm experiment to test the effects of higher precipitation amount (increased by 50% from the long-term mean) and lower frequency (decreased by 50%) on plant biomass and allocation in the lightly degraded (LDG), moderately degraded (MDG), and severely degraded grasslands (SDG).Results Lower precipitation frequency promoted belowground biomass (BGB), while reducing aboveground biomass (AGB) allocation through enhancing soil water variability. Higher precipitation amount enhanced AGB in LDG and MDG, but not in SDG due to less soil inorganic nitrogen. Lower precipitation frequency weakened the positive effects of higher precipitation amount on biomass. Under altered precipitation, adjustment of AGB vs. BGB allocation was the primary biomass allocation strategy in LDG and SDG. However, to maintain water acquirement, plants in MDG preferred to adjust root vertical distribution, and allocated more roots to the deep soil layer where had a relatively stable water source. This strategy was driven by the changes in plant community composition of the dominant species in MDG.Conclusions The ndings of this research emphasized the importance of considering the degradation level of grasslands when predicting the responses of the ecosystem functions to the projected changes in precipitation regime. These ndings are critical for making feasible decisions for the sustainable management of degraded grasslands.

Ecosystem‐level decoupling in response to reduced precipitation frequency and degradation in steppe grassland

“…For this study, several sites with three degradation levels (light, moderate and severe) were randomly selected for the construction of the mesocosm (Figure S1). Distances between sites were less than 2 km, ensuring the same original soil and vegetation type (Yang et al, 2022). We did not need permission for this fieldwork.…”

“…On the one hand, we preferred to reduce precipitation frequency as much as possible to investigate the effects of extremely lower frequency on coupling and functions, while ensuring that precipitation frequency was well within the range of documented rainfall regimes of the past 50 years in this region (Figure S3). On the other hand, to avoid drought‐induced plant mortality and to ensure that soil water content was above the permanent wilting point (about 5% in this study), seven rainfall events were identified as the minimum number of rainfall events possible (Meng et al, 2021; Yang et al, 2022). All mesocosms received 305 mm precipitation, which is the 50‐year mean for the experimental period.…”

“…The annual mean temperature is 6.5°C with a frost‐free period of ~130–150 days. The annual mean wind speed is 3.4 m s −1 (Yang et al, 2022). The original soil type is Chernozem, with sand and silt dominating its surface layer (Zeng et al, 2018).…”

“…erosion by wind) have resulted in significant grassland desertification and salinization (Dong et al, 2020). As a result of degradation, the perennial climax species has been gradually replaced by annual pioneer species, such as Chloris virgata , resulting in decreased vegetation cover and productivity (Yang et al, 2022). Meanwhile, soil water retention, nutrient availability and carbon (C) sequestration have been greatly reduced by degradation (Chen et al, 2021).…”

“…Despite mounting evidence about how changes in rainfall frequency and degradation affect grassland plants and soil organisms, such as microbes and nematodes (Chen et al, 2021; Heisler‐White et al, 2009; Wang, Shi, et al, 2019; Yang et al, 2022), relatively little is known about how these changes may alter the way in which these organisms and their surrounding environment interact, for example, through shifts in above‐ground–belowground linkages (Sayer et al, 2017). Plants and their associated soil organisms are inextricably linked through plant‐derived inputs to soil (e.g.…”