Contrasting changes in above- and below-ground biomass allocation across treeline ecotones in southeast Tibet
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- 作者：Xin-sheng Liu ; Yu-qin Nie ; Gao-qiang Kong ; Tian-xiang Luo
- 关键词：Treeline ecotone ; Fine root biomass ; Above ; ground biomass ; Vegetation type ; Southeast Tibet
- 刊名：Journal of Mountain Science
- 出版年：2016
- 出版时间：November 2016
- 年：2016
- 卷：13
- 期：11
- 页码：2036-2045
- 全文大小：230 KB
- 刊物主题：Earth Sciences, general; Geography (general); Environment, general; Ecology;
- 出版者：Springer Berlin Heidelberg
- ISSN：1993-0321
- 卷排序：13
文摘
Under conditions of a warmer climate, the advance of the alpine treeline into alpine tundra has implications for carbon dynamics in mountain ecosystems. However, the above- and below-ground live biomass allocations among different vegetation types within the treeline ecotones are not well investigated. To determine the altitudinal patterns of above-/below-ground carbon allocation, we measured the root biomass and estimated the above-ground biomass (AGB) in a subalpine forest, treeline forest, alpine shrub, and alpine grassland along two elevational transects towards the alpine tundra in southeast Tibet. The AGB strongly declined with increasing elevation, which was associated with a decrease in the leaf area index and a consequent reduction in carbon gain. The fine root biomass (FRB) increased significantly more in the alpine shrub and grassland than in the treeline forest, whereas the coarse root biomass changed little with increasing altitudes, which led to a stable below-ground biomass (BGB) value across altitudes. Warm and infertile soil conditions might explain the large amount of FRB in alpine shrub and grassland. Consequently, the root to shoot biomass ratio increased sharply with altitude, which suggested a remarkable shift of biomass allocation to root systems near the alpine tundra. Our findings demonstrate contrasting changes in AGB and BGB allocations across treeline ecotones, which should be considered when estimating carbon dynamics with shifting treelines.