浑善达克沙地稀树疏林草地植被生物量及净初级生产力

 森林和草原等陆地生态系统在全球碳循环中扮演非常重要的角色,而发育在半干旱地区沙地上的疏林草地植被在这方面的作用还不清楚.本文对内蒙古浑善达克沙地榆树(Ulmus pumila L.)疏林草地的生物量、生产力(NPP)以及降水利用效率(RUE)区分不同生境,即固定沙地、半固定沙地、流动沙地、丘间低地、柳灌丛和低湿地进行了研究;分析和比较了植被碳库及NPP的分配情况.结果表明,疏林草地的平均生物量(21.30Mg·hm^-2)与NPP(11.06Mg·hm^-2·a^-1)分别比典型草原地带的平均值高90%和59%,RUE近于后者的2倍,沙地水平上的地下与地上生物量之比为2.9,说明大量的植被碳贮藏于地下,沙地中乔木对生物量和NPP的贡献不大,分别为10%和1.3%,但对于维持疏林草地的完整性具有重要功能.浑善达克沙地的疏林草地生态系统与地带性的典型温带草原不同,应属于一类温带萨王那生态系统类型,合理的管理和恢复措施将有助于其在畜牧业和碳固持方面生态系统服务功能的实现.

Vegetation Biomass and Net Primary Production of Sparse Forest Grassland in Hunshandake Sandland

Terrestrial ecosystems are playing important roles in the global carbon cycling. However, the information is still limited with regard to the semiarid sandland, comparing with the thorough studies on forest and grassland. The biomass carbon storage, Net Primary Production (NPP), and Rain Use Efficiency (RUE) of Hunshandake Sandland, a semiarid sandy region in Inner Mongolia covered with vegetation of Siberian elm (Ulmus pumila L.) sparse forest grassland, were estimated. Six main habitats, i.e. fixed dunes, semi-fixed dunes, shifting dunes, lowland, willow scrub, and wetland, were compared with each other to analyze the patterns of carbon storage and NPP distribution. The average biomass (21.30Mg·hm^-2) and NPP (11.06Mg·hm^-2·a^-1) of the sparse forest grassland are 90% and 59% higher than the mean level for the surrounding temperate grassland, respectively. Governed by the same climate, the RUE for sparse forest grassland ecosystem is almost twice than that for surrounding grassland. The ratio of below to above ground biomass is 2.9 in the sandland, the fact indicates that most of the vegetation carbon are stored in a below ground pool. Although trees are functionally critical for maintaining the integrity of sparse forest grassland, they only account for 10% and 1.3% of the biomass and NPP, respectively. The sparse forest grassland in Hunshandake Sandland should be recognized as a temperate savanna ecosystem which is distinctively different from typical temperate grassland in the same region indicated by the higher NPP and vegetation carbon storage. Well designed management and restoration efforts could potentially realize ecosystem services in both forage production and carbon sequestration.