氮素与水分添加对内蒙古温带典型草原生物量的影响

The influence of nitrogen and water addition on biomass in a typical steppe of Inner Mongolia

为了解大气氮沉降和降水格局改变对草原生物量的影响,在内蒙古温带典型草原开展氮、水添加控制试验.试验设置对照(CK),氮素添加(10 g m^(-2) a^(-1)),水分添加(60 mm m^(-2) a^(-1)),氮、水同时添加(N 10 g m^(-2) a^(-1)+水60 mm m^(-2) a^(-1))4种处理.经过两年试验处理,结果显示:(1)较对照处理,氮添加处理下总生物量(403.03 g/m^2)、地上生物量(279.97 g/m^2)、地下生物量(123.07 g/m^2)和禾类草地上生物量(165.35 g/m^2)均显著增加,而杂类草地上生物量变化不显著.(2)水添加较对照显著增加了地上生物量(200.93 g/m^2)、杂类草地上生物量(177.82 g/m^2),但显著降低了地下生物量(-110.39 g/m^2),而总生物量与禾类草地上生物量变化不显著.(3)氮添加处理下,水添加显著增加了地下生物量与禾类草地上生物量,但对总生物量、地上生物量、杂类草地上生物量没有显著影响.进一步分析显示,在不添加水分条件下,氮添加较对照显著增加禾类草地上生物量(107.15 g/m^2)与地下生物量(5.43 g/m^2);而在水分添加条件下,氮添加较对照分别增加58.2 g/m^2和117.64 g/m^2.本研究结果表明,禾类草地上生物量与其氮含量呈正相关关系,杂类草地上生物量与土壤含水量呈正相关关系,这可能是氮素添加提高禾类草地上生物量和水分添加提高杂类草地上生物量的重要机制之一;在内蒙古干旱半干旱地区仅氮素添加(10 g m^(-2) a^(-1))的措施可显著增加禾类草的地上生物量,有利饲草产量的增加,如需增加菊科、豆科等其他杂草的生物量,可考虑水分的补给.

This study aimed to understand the effects of atmospheric nitrogen deposition and precipitation pattern change on grassland biomass in a temperate steppe in northern China. Four treatments were set up, which included control （CK）, nitrogen addition （10 g m-2 a-1）, water addition （60 mm m-2 a-1）, and nitrogen and water addition （N 10 g m-2 a-1 ＋ water 60 mm m-2 a-1）. The results showed that nitrogen addition significantly increased total biomass （TB） （403.03 g/m^2）, aboveground biomass （AGB） （279.97 g/m^2）, underground biomass （BGB） （123.07 g/m^2）, and aboveground biomass of grass （AGBgrass） （165.35 g/m^2）, but had no significant effect on aboveground biomass of forbs （AGBforb）. Water addition significantly increased AGB （200.93 g/m^2） and AGBforb （177.82 g/m^2）, but it significantly reduced BGB （-110.39 g/m^2） and had no significant effects on TB and AGBgrass. Nitrogen and water addition in combination had additive effects on AGBgrass and BGB, but had non-additive effects on TB, AGB, and AGBforb. The results also showed that nitrogen addition significantly increased AGBgrass （107.15 g/m^2） and BGB （5.43 g/m^2） without water addition, while it increased AGBgras （58.2 g/m^2） and TB （117.64 g/m^2） with water addition. These results showed that AGBgrass was positively correlated with grass nitrogen concentration, while AGBforb was positively correlated with soil water content, suggesting that nitrogen and water additions could increase grass biomass and forb biomass, respectively, in the typical steppe of Inner Mongolia. Therefore, nitrogen addition can be adopted to increase forage grass productivity by increasing the grass aboveground biomass, while water addition can be adopted to increased forb biomass.