Abstract
The relationships between community-weighted mean (CWM) functional traits and ecosystem functions have been extensively studied. However, how CWM traits and ecosystem functions respond to grazing types and whether the relationships between CWM traits and ecosystem functions mediate the response of ecosystem functions to grazing types remains controversial. In the present study, we set up a seven-year grazing experiment with four grazing types: no grazing (NG), cattle grazing (CG), sheep grazing (SG), and mixed grazing by sheep and cattle (MG) on Inner Mongolia grassland. Nine functional traits of dominant species and five ecosystem functions under different grazing types were determined, and the relationships between CWM traits and ecosystem functions were analyzed. The results showed that the CWM height decreased after grazing, while the CWM nitrogen and phosphorus contents increased after CG. SG caused a greater decrease in aboveground biomass (AGB) and a greater increase in the net ecosystem CO2 exchange (NEE) of grassland ecosystems than did CG. This result may be partially because the CWM nutrient content and NEE were more negatively related after CG; and the increase in the CWM nitrogen and phosphorus contents suppressed NEE after CG. Therefore, to protect the sustainability of grassland ecosystem functions, SG should be reduced. Additionally, our work emphasizes that the relationships between plant functional traits and ecosystem functions may mediate the response of ecosystem functions to grazing types.
Highlights
Functional trait-based methodologies have created new ways to link plant and ecosystem processes and functions and can be used to solve problems related to global climate change, biodiversity loss and ecological protection [1,2,3,4]
The CWM_SPC of cattle grazing (CG) alone was significantly higher than that of the control (NG), but there was no significant difference between sheep grazing (SG) and MG (Figure 1g)
Our study showed that the community-weighted mean (CWM) height presented a decreasing trend regardless of grazing types
Summary
Functional trait-based methodologies have created new ways to link plant and ecosystem processes and functions and can be used to solve problems related to global climate change, biodiversity loss and ecological protection [1,2,3,4]. Many scholars have focused on the relationships between plant functional traits and environmental factors. They have focused on the relationship between plant functional traits and environmental gradients and disturbance intensity [6,7,8,9]. The study of plant functional traits involves multiple scales, such as species level, community level and ecosystem level [12,13,14,15]. The study of the plant functional traits can reveal the underlying mechanism of ecosystem function [13,16,17]. Functional diversity and community-weighted average are two main approaches used to study the relationships between community-level plant functional traits and ecosystem function [18,19,20]. Based on the biomass ratio hypothesis, in which the contribution of a species determines the extent of its influence on the characteristics of the ecosystem [23], community-weighted mean (CWM) traits focus on the importance of dominant species and are useful for explaining the litter decomposition rate, aboveground net primary productivity, and soil moisture [13,24,25,26]
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