养分添加对内蒙古不同草地生态系统生物量的影响

Effects of Nutrient Additions on Community Biomass Varied among Different Grassland Ecosystems of Inner Mongolia

为了比较不同气候条件下草地生态系统对养分添加的响应,在内蒙古的草甸草原、典型草原和荒漠草原区分别建立长期养分添加试验。在三年试验数据的基础上,分析不同养分（N和P）添加、不同梯度（N：10,5和2.5 g/m2;P：10 g/m2）对这3种代表性草地群落生物量及其分配的影响。结果表明,施氮导致内蒙古温带草原地上生物量增加27%-53.3%,平均增加37.8%,并且施氮浓度越高,地上生物量增加越多。地下生物量对施肥的响应比地上生物量小,整体上,高浓度的氮添加使内蒙古草原的群落总生物量平均增加10.2%。较干旱的荒漠草原对氮限制的响应比典型草原和草甸草原更明显。磷肥对群落地上、地下生物量的影响不明显。施氮肥促进草甸草原和荒漠草原的根冠比（R/S）降低,典型草原的根冠比则轻度增加。施肥对内蒙古温带草原根系的垂直分布没有显著影响。位于不同环境条件下的草地生态系统对施肥的响应存在时间和空间差异,意味着在碳循环模型预算和草地管理中需要考虑不同草地生态系统对养分添加的响应。草地地上生物量对施肥的响应高于地下部分,如果不考虑地下部分,可能会高估整个生态系统对施肥的响应。

In order to compare the response of community biomass to nutrient additions among different grassland ecosystems, the authors established nutrient addition experiments on three grassland ecosystems along the climate gradient, including meadow steppe, typical steppe and desert steppe in Inner Mongolia. On the basis of the threeyear experiment, the impacts of different nutrients（N, P） on different nutrient gradient（N： 10, 5 and 2.5 g/m2; P： 10 g/m2） on above- and belowground biomass of these grassland ecosystems was analyzed. The results show that nitrogen leads to a significant increase in the aboveground biomass of grassland in Inner Mongolia by 27% to 53.3%, an average increase of 37.8%. In addition, the response of biomass to N addition increases with the N gradients. Belowground biomass has a less response to fertilization than aboveground biomass. There is an average of 10.2% increase in the total biomass of grassland community in response to N addition. Biomass responds to P addition less deeply than N addition. Furthermore, the response of biomass to nutrient addition varies among three grassland ecosystems. In arid desert steppe, community biomass is more sensitive to N limitation than the typical steppe and meadow steppe. N addition reduces belowground biomass and R/S ratio in meadow steppe and desert steppe, whereas promotes the values in typical steppe. In contrast, nutrient additions have relatively less and insignificant impacts on the root distribution of temperate grasses. These observations indicate that nutrient addition has different effects on community biomass under different environmental conditions, which means it is necessary to consider the changed response of different grassland ecosystems to nutrient addition in the carbon cycle models budget and grassland management.