中国北方天然草地的生物量分配及其对气候的响应

通过收集我国近20年来草地生物量的有关文献,估算了我国北方天然草地根冠比(R/S)及地下生产力占总生产力比例(fBNPP)的大小及其对气候变化的响应。结果表明:不同草地类型R/S比及fBNPP变异较大,根冠比为1.66~15.21,fBNPP为0.29~0.98;荒漠草原的R/S比及fBNPP较大,但变幅较小;森林草原R/S比和fBNPP较小,但变幅较大;R/S比及fBNPP随年降水的增加而显著降低,随年平均气温增加而降低的趋势不明显。采用生长季最大生物量估算的方法可能高估了R/S比及fBNPP。长期、高质量的生物量观测数据,尤其是地下生物量的数据以及开展不同研究方法对生产力估算结果的影响,对于准确评价草地在区域及全球碳循环中的作用是十分必要的。

Biomass Distribution of Natural Grasslands and It Response to Climate Change in North China

Aboveground and belowground biomasses and their distribution are the important parameters of carbon cycle.Many achievements about the distribution pattern of aboveground biomass have been achieved,but the studies about belowground biomass are very limited.In this paper,the root-shoot ratios and fBNPP(defined as the fraction of belowground net primary productivity(BNPP) in total NPP) as well as their relationships with climatic variables are lucubrated by synthesizing the references about biomass of grasslands in north China.The results show that the root-shoot ratios and fBNPP are obviously different from different grasslands types,and they vary in ranges of 1.66~15.21 and 0.29~0.98 respectively.In general,the root-shoot ratio and fBNPP of desert steppe are high,but their change extent is low;the root-shoot ratio and fBNPP of forest grasslands are low,but their change extent is high.There is a negative correlation between the root-shoot ratio and fBNPP and the climatic factors,that is the rootshoot ratio and fBNPP are significantly decreased with the increase of annual precipitation,but their decrease trend with the increase of annual temperature is not so significant.The study results also reveal that the values of root-shoot ratio and fBNPP might be overestimated if the maximum biomass in the growth season of grasslands is used.It is necessary to research the effects of different study methods on estimating the NPP of grasslands and veraciously evaluate the importance of grasslands in regional and global carbon circle using the long-term measured biomass data,especially the data of belowground biomass.