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Effect of shrub coverage on grassland ecosystem carbon pool in southwestern China
XUE Jing-Yue, WANG Li-Hua, XIE Yu, GAO Jing, HE Jun-Dong, WU Yan
Chin J Plant Ecol    2019, 43 (4): 365-373.   DOI: 10.17521/cjpe.2017.0062
Abstract   (1236 HTML135 PDF(pc) (1105KB)(1165)  

AimsThe grassland in southwestern China is mainly warm and tropical grass and shrub grassland, accounting for approximately one-tenth of the national grassland area. Analysis of the relationship between shrub coverage and the grassland carbon pool and its composition is of great significance for accurately assessing carbon storage in the southwestern grassland, which grassland is still in the secondary succession stage.
MethodsIn a field investigation, 41 representative plots of different geomorphic types in southwestern China were divided into three types according to shrub coverage: no shrub grassland community (shrub coverage is 0), low shrub coverage grassland community (shrub coverage is 0-10%) and high shrub coverage grassland community (shrub coverage is 10%-30%). Carbon density was calculated by measuring the aboveground and underground biomass and litter biomass of grassland communities at different shrub coverage levels, as well as plant and soil carbon content.
Important findings The results showed that with increasing shrub coverage and species richness in grasslands, the ecosystem vegetation carbon density increased from 0.304 kg·m -2 to 1.574 kg·m -2, and the roots and litter carbon density also showed growth trends. The soil carbon density increased from 7.215 kg·m -2 to 9.735 kg·m -2, and the ecosystem carbon density increased from 7.519 kg·m -2 to 11.309 kg·m -2, with increasing shrub coverage. Regarding the composition of the grassland carbon pool, the soil carbon pool of the low shrub coverage grassland accounted for the smallest proportion of the ecosystem carbon pool. In summary, the increase in shrub coverage changes the composition of the grassland ecosystem carbon pool and leads to an increase in the amount of ecosystem carbon. Therefore, when estimating the grassland ecosystem carbon pool, it is necessary to overall plan for and take into account the changes in grassland shrub coverage in southern China.


Fig. 1 Vegetation carbon pool of vegetation in grassland community with different shrub coverage in southwestern China. I, II, and III are the three different shrub coverage levels of the grassland community. I, II, and III represent no shrub grassland, low shrub coverage grassland, and high shrub coverage grassland, respectively. The data are the mean ± SE (I, II, n = 18; III, n = 5). Different lowercase letters indicate significant differences among sites with different shrub coverage of grassland levels (p < 0.05).
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不同灌木植物盖度草地群落的植被碳库差异显著(F = 11.459, p < 0.001), 随着草地群落灌木植物盖度逐渐增大, 植被碳库逐渐增加, 且低灌木植物盖度草地群落和高灌木植物盖度草地群落的植被碳库显著大于无灌木植物草地群落, 但低灌木植物盖度草地群落和高灌木植物盖度草地群落的植被碳库差异不显著(表3; 图1)。就地上植物碳密度而言, 无灌木植物草地群落、低灌木植物盖度草地群落和高灌木植物盖度草地群落分别为0.057、0.089和0.073 kg·m-2, 彼此之间地上植物碳库差异显著(F = 3.348, p = 0.046)。其次, 凋落物碳密度分别为0.005、0.014和0.015 kg·m-2, 三者间凋落物碳库差异显著(F = 9.223, p = 0.001), 低灌木植物盖度草地群落和高灌木植物盖度草地群落的凋落物碳库显著大于无灌木植物草地群落。另外, 三者的地下植物碳密度分别为0.242、1.304和1.486 kg·m-2, 彼此之间差异显著(F = 10.969, p < 0.001), 表现为低灌木植物盖度草地群落和高灌木植物盖度草地群落的根系碳库显著大于无灌木植物草地群落(图1)。随着草地群落灌木植物盖度增加, 包括凋落物和地下碳库在内, 植被碳库有逐渐增加的趋势, 但这种变化随着灌木植物盖度增加, 趋势有所减弱, 表现为低灌木植物盖度草地群落和高灌木植物盖度草地群落的植被碳库差异不显著。
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