中文摘要：

稀树灌草丛作为干热河谷区特殊的植被类型，其碳储量等一直缺乏必要的研究。以元江干热河谷稀树灌草丛植被为对象，利用典型样地法研究该区稀树灌草丛植被的碳储量与净初级生产力。结果表明：元江稀树灌草丛植被的碳储量为32.13 t C/hm2，其中乔木、灌木和草本各层次的碳储量为26.70、4.04、1.40 t C/hm2，分别占到总碳储量的83.02%、12.57%、4.4%。乔木层中地上部分碳储量占到66.70%。另外，元江稀树灌草丛的净初级生产力为3.88 t C hm-2 a-1，其中林分的净初级生产力为1.90 t C hm-2 a-1，凋落物量为1.98 t C hm-2 a-1；林下植被层对林分净初级生产力的贡献达到了46.92%。说明元江稀树灌草丛具有较高的碳储量和碳汇能力。结果为稀树灌草丛碳循环及碳汇功能研究提供了基础，同时也为干热河谷区植被的保育与可持续经营提供了科学依据。

英文摘要：

Savanna is a unique vegetation type that predominantly occurs in dry-hot valleys, yet its carbon storage capacity and net primary productivity （NPP） remain poorly understood. In the present study, we estimated carbon storage and NPP of savanna vegetation using permanent field plots in the dry-hot valley of Yuanjiang, Yunnan Province, southwestern China. We estimated tree carbon storage using allometric equations, and carbon storage in shrubs and herbs was estimated by the harvesting method. The NPP was calculated using two years of data from plot surveys. We found that the total carbon storage of the savanna in Yuanjiang was 32.13 t C/hm2. Carbon storage in the tree, shrub, and herb layers was 26.70 t C/hm2, 4.04 t C/hm2, and 1.40 t C/hm2, which contributed 83.02%, 12.57%, and 4.35% of the total carbon storage, respectively. Aboveground carbon storage accounts for 66.70% of tree layer carbon storage. Similarly, the NPP of the savanna was 3.88 t C hm-2 a-1. NPP from the forest biomass and litter was 1.90 t C hm-2 a-1 and 1.98 t C hm-2 a-1, respectively. The contribution to the NPP of forest biomass from the understory （shrubs and herbs） approached 46.92%. Thus, we conclude that, owing to its high carbon storage and NPP values, savanna vegetation is an important component of the carbon cycle; this finding provides a rationale for the conservation of vegetation and the sustainable management of savanna ecosystems in dry-hot valleys.