氮磷添加对内蒙古温带草地地上生物量的影响

干旱半干旱地区植物生长不仅受到水分的限制，同时也受到养分的限制.为进一步明确养分在多大程度上能促进半干旱区植物的生长，本研究在内蒙古温带草原开展了连续2年的养分添加控制试验，设置10和40 g·m^-2·a^-1的N添加水平以及10 g·m^-2·a^-1的P添加水平.结果表明： N添加能够显著促进植物生长，10和40 g N·m^-2·a^-1处理地上生物量在2012年分别较对照增加50.8%和65.9%，2013年增加71.6%和93.3%，2个N添加处理之间地上生物量无显著差异.与单独10和40 g·m^-2·a^-1的N添加处理相比，P添加后地上生物量在2012年分别提高98.4%和186.8%，2013年分别提高111.7%和141.4%.N添加普遍提高了3种植物功能群(禾本科、菊科和其他科)的地上生物量，但较对照差异不显著，而N、P同时添加显著提高了菊科植物的地上生物量.养分添加使植被盖度升高，从而改善了表层土壤的水分条件，这可能是N、P添加促进植物生长和提高降水利用效率的重要机制之一.

Influence of nitrogen and phosphorus addition on the aboveground biomass in Inner Mongolia temperate steppe,China.

The plants in arid environment are constrained not only by water availability, but also by soil nutrient conditions. In order to clarify to what extent nutrient addition would facilitate the growth of plants in semi arid region, we conducted a nitrogen (N) and phosphorus (P) addition experiment in Inner Mongolia temperate grassland in 2012 and 2013. In our experiment, N was added at 10 and 40 g N·m^-2·a^-1 alone or in combination with P addition (10 g P·m^-2·a^-1). N addition significantly improved plant aboveground biomass (AGB) during the two study years. AGB in the treatments of 10 and 40 g·m^-2·a^-1 was enhanced by 50.8% and 65.9% in 2012, and 71.6% and 93.3% in 2013, respectively. However, no significant difference in AGB enhancement was found between two N addition treatments. Compared with N addition treatments at the rates of 10 and 40 g·m^-2·a^-1, N plus P addition improved AGB by 98.4% and 186.8% in 2012, and 111.7% and 141.4% in 2013, respectively. N addition generally increased all the three main functional types (i.e., Gramineae, Asteraceae and others), and the three functional types contributed nearly equally to the increase of the community AGB. In comparison, Asteraceae contributed largest to the increments of AGB under the N plus P addition treatments. Our results also indicated that N and P addition remarkably increased the ground coverage, resulting in improved surface soil moisture condition, which might be one important reason that N and P addition could facilitate plant growth in arid environment.