Abstract
Alpine steppe is considered to be the largest grassland type on the Tibetan Plateau. This grassland contributes to the global carbon cycle and is sensitive to climate changes. The allocation of biomass in an ecosystem affects plant growth and the overall functioning of the ecosystem. However, the mechanism by which plant biomass is allocated on the alpine steppe remains unclear. In this study, biomass allocation and its relationship to environmental factors on the alpine grassland were studied by a meta-analysis of 32 field sites across the alpine steppe of the northern Tibetan Plateau. We found that there is less above-ground biomass (MA) and below-ground biomass (MB) in the alpine steppe than there is in alpine meadows and temperate grasslands. By contrast, the root-to-shoot ratio (R:S) in the alpine steppe is higher than it is in alpine meadows and temperate grasslands. Although temperature maintained the biomass in the alpine steppe, precipitation was found to considerably influence MA, MB, and R:S, as shown by ordination space partitioning. After standardized major axis (SMA) analysis, we found that allocation of biomass on the alpine steppe is supported by the allometric biomass partitioning hypothesis rather than the isometric allocation hypothesis. Based on these results, we believe that MA and MB will decrease as a result of the increased aridity expected to occur in the future, which will reduce the landscape’s capacity for carbon storage.
Highlights
Biomass allocation was an important character for the process of characterization of plant physiological ecology [1], it was the result of the plant long-term adapted to different environmental conditions [2].The Biomass allocation reflect show photosynthates are allocated between above-ground and below-ground biomass [3]
Yang et al (2009a) reported that on the Tibetan alpine grasslands, the relationship between roots and shoots supports the isometric allocation hypothesis [32]. They found that this isometric relationship is independent of soil nitrogen and moisture [32]. These results indicate that the mechanism of biomass allocation in the alpine steppe is still misunderstood and unverified in alpine and arid environments
MA ranged from 2.32 g?m22 to 73.6 g?m22, while MB ranged from 22.40 g?m22 to 587.32 g?m22
Summary
Biomass allocation was an important character for the process of characterization of plant physiological ecology [1], it was the result of the plant long-term adapted to different environmental conditions [2].The Biomass allocation reflect show photosynthates are allocated between above-ground and below-ground biomass [3]. Biomass allocation above-ground and below-ground affects plant growth as well as the overall function of the ecosystem and biogeochemical cycles [4,5]. The mechanism by which plants respond to variations in the availability of resources in their environment is a major question in plant ecology [6]. The optimal partitioning hypothesis suggests that plants respond to variations in the environment by partitioning biomass among various plant organs to maximize the plants’ growth rate [9,10]. The isometric allocation hypothesis predicts the net primary productivity of the roots vs the net primary productivity of the shoots (BNPP:ANPP) isometrically without considering the differences in plant species or community types [13,14,15]. No conclusion about biomass allocation has yet been presented
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