2001—2017 年三江源区典型草地群落碳源/ 汇模拟及动态变化分析

碳源/汇是解释地球大气碳循环过程的重要指标，探究三江源的碳源/汇特征对于理解该地 区植被对全球气候变化的响应具有重要意义。三江源以脆弱的草地生态系统为主，且对全球气候 变化非常敏感。该地区生态环境极其脆弱，大部分地区条件恶劣导致实测数据稀缺，很难对该地 区的碳源/汇时空格局进行完整剖析。因此通过以三江源 5 种典型草地群落（金露梅、紫花针茅、风 毛菊、小蒿草、及青藏薹草群落）为研究对象，基于 BIOME-BGC 模型，利用地理数据、气象数据和植 被生理参数等数据，得出 2001—2017 年三江源草地群落的净初级生产力（NPP）、净生态系统生产 力（NEP）模拟值，并对草地群落 NPP、NEP 变化特征与气温、降水相关性以及碳利用效率变化等特 征进行了综合分析。结果表明：三江源区 NPP、NEP 在空间格局上，表现为由东南向西北数值逐渐 递减趋势；5 种典型草地群落多年 NPP 均呈现逐年增高趋势，其平均值为 196.06 g C·m ^-2·a ^-1。其 中，金露梅群落 NPP 平均值最高为 342.00 g C·m^-2·a^-1，青藏薹草群落 NPP 平均值最低为 55.93g C·m^-2·a^-1；5 种草地群落 NEP 的多年平均值为 49.02 g C·m^-2·a^-1，金露梅、紫花针茅及青藏薹草 3 种植 被群落的 NEP 值呈缓慢的上升趋势，风毛菊和小蒿草群落呈缓慢下降趋势。研究发现三江源草地 生态系统具有显著的碳汇作用，且不同群落 NPP、NEP 对气温和降水的响应程度有所差异，5 种群 落 NPP 与气温均呈显著正相关，但 NPP、NEP 与降水量的相关性较低；5 种群落均具有较强固碳潜 力，除金露梅外其余植被群落的碳利用率均在 0.625 以上。

Simulation and dynamic change of carbon source/sink in the typical grassland communities in the Three River Source Area from 2001 to 2017

In this paper, five typical grassland communities (Potentilla fruticosa, Stipa purpurea, Saussurea japonica, Kobresia pygmaea, and Carex moorcroftii communities) in the Three River Source Area, Qinghai Province, China were selected as research objects. Basic geographic data, meteorological data, and vegetation physiological parameters data were used to estimate the net primary productivity (NPP) and the net ecosystem productivity (NEP) in these grassland communities from 2001 to 2017 based on the BIOME-BGC model. This paper also investigated the change characteristics of NPP and NEP and their correlation with temperature and precipitation. The characteristics of the change of the carbon use efficiency (CUE) were also explored. Results showed that the spatial pattern of the values of NPP and NEP in the Three River Source Area reduced gradually from southeast to northwest. The multi-year average value of NPP in 5 typical grassland communities was 196.06 g C·m-2·a-1, which showed an increasing trend year by year. Among them, the annual average value of NPP in Potentilla fruticosa was the highest (342.00 g C·m-2·a-1), and the annual average value of NPP in Carex moorcroftii seagrass was the lowest (55.93 g C·m- 2 ·a- 1). The annual mean value of NEP of the five grassland communities was 49.02 g C·m- 2 ·a- 1. The NEP values of Potentilla fruticosa, Stipa purpurea and Carex moorcroftii increased slowly, while the NEP values of Saussurea japonica and Kobresia pygmaea decreased slowly. Therefore, the grassland ecosystem in the Three River Source Area has significant carbon sequestration function of absorbing CO2. A significant positive correlation between NPP and temperature was observed, while a low correlation between NPP, NEP, and precipitation existed. All the five communities have great potential for carbon sequestration. The carbon utilization rate of other vegetation communities was above 0.625, except the Potentilla fruticosa.