西南地区草地群落灌木植物盖度对生态系统碳库的影响

中国西南地区草地主要为暖性及热性草丛、灌草丛, 约占全国草地面积的1/10, 分析灌木植物盖度与草地碳库及其构成的关系对于准确评估尚处于次生演替阶段的南方草地碳储量具有重要意义。该研究基于野外实地调查, 将西南地区不同地貌类型的41个代表性草地样地依据灌木植物盖度划分为3种类型: 无灌木植物草地群落(灌木植物盖度为0)、低灌木植物盖度草地群落(灌木植物盖度0-10%)和高灌木植物盖度草地群落(灌木植物盖度10%-30%), 测定了群落地上、地下生物量和凋落物生物量以及植物和土壤碳含量, 计算碳密度。结果表明: 随着草地群落灌木植物盖度增大, 生态系统植被碳密度从0.304 kg·m ^-2增加到1.574 kg·m ^-2, 其中根系和凋落物碳库也呈增长趋势; 土壤碳密度从7.215 kg·m ^-2增加到9.735 kg·m ^-2, 生态系统碳密度从7.519 kg·m ^-2增加到11.309 kg·m ^-2。草地碳库构成中, 低灌木植物盖度草地群落的土壤碳库占生态系统碳库比例最小。草地群落灌木植物盖度增加改变了草地生态系统碳库构成并导致生态系统碳库增加, 建议在估算草地生态系统碳库时, 需要统筹考虑并兼顾南方地区草地群落灌木植物盖度变化。

Effect of shrub coverage on grassland ecosystem carbon pool in southwestern China

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.