Root Features Determine the Increasing Proportion of Forbs in Response to Degradation in Alpine Steppe, Tibetan Plateau

Abstract

Understanding the response of plant community to degradation is fundamentally important for grassland conservation and management. The objective of this study is to examine the changes in soil properties and plant characteristics along a degradation gradient in alpine steppe, and explore the potential mechanisms that biotic and abiotic controls regulate plant community variations. We chose seven sequent degrees of degradation, and conducted a field survey as well as soil and plant samplings in an alpine steppe in Northern Tibet. The results showed that soil water content (SWC), soil compaction (SCOM), soil total carbon (STC), and total nitrogen (STN) dramatically decreased along the degradation gradient. The species richness, overall aboveground biomass (AGB), and AGB of graminoids were apparently reduced with increasing degradation, while AGB of forbs slightly increased. The increasing degradation levels induced a significant increase in the trade-off value of AGB of forbs, which was negatively associated with SWC, SCOM, STC, STN, and soil available nitrogen. The mean root length of forbs was significantly longer than that of graminoids (P < 0.05). Moreover, the mean root diameter of the top 1/3 part of forbs was remarkably thicker than that of graminoids (P < 0.05). These findings indicate that the degradation-induced cohesionless soils with insufficient water and nutrients together with the divergent root morphological traits of graminoids and forbs determine the plant community structure shift with grassland degradation. This study can improve the understanding of community succession of grassland degradation, and provide guidance for the management of degraded alpine steppe on the Tibetan Plateau.

Community species diversity mediates the trade‐off between aboveground and belowground biomass for grasses and forbs in degraded alpine meadow, Tibetan Plateau

“…Similar to the results of previous studies, our results suggested that, with an increase in degradation, the trade‐off value of forbs significantly shifted from negative to positive (Zhang et al., 2020 ; Zhang & Sun, 2020 ). Specifically, from ND to SD, the increased AGB ratio was higher than that of BGB for forbs in our study (Figure 6b,c ), which moved the trade‐off away and above the 1:1 line (Figure 3b ).…”

Effect ofElymus nutans on the assemblage of arbuscular mycorrhizal fungal communities enhanced by soil available nitrogen in the restoration succession of revegetated grassland on theQinghai‐TibetanPlateau

“…This indicates the strong linkage between plant community and soil available nitrogen during restoration succession as found in other studies (Jiang et al, 2018; Liu et al, 2012; Wang et al, 2018). In addition, the change in the plant communities is the result of the competition between grasses and forbs as found in other studies (Wu et al, 2019; Xing et al, 2020; Zhang & Sun, 2020); moreover, the regulation of soil nitrogen nutrients on the competition between grasses and forbs has been confirmed in the alpine meadow ecosystem of the Qinghai‐Tibetan Plateau (Li et al, 2020; Wang et al, 2018; Wang et al, 2020). Thus, it could be deduced that the strong linkage was achieved through the regulation of soil available nitrogen on the competition between grasses and forbs.…”

Comparison of Soil Total Nitrogen Content Prediction Models Based on Vis-NIR Spectroscopy

“…Agricultural production [ 35 , 36 , 37 ], soil structure [ 38 ], soil properties [ 39 ], soil sample data characteristics [ 40 ], along with the methods of data preprocessing [ 16 , 41 ], all affect the STN concentration prediction modeling and model performance. Due to the results we achieved in this paper, the STN prediction models with good performance and generalization come from the data set with greater size and more evenly distributed within a country.…”