模拟非生长季氮沉降增加对温带草原不同植物功能群氮吸收的贡献

Anthropogenic nitrous pollutant emissions significantly increased during the last decades, which contributed to the accelerated nitrogen (N) deposition. In temperate regions of China, N deposition in non-growing season account for approximate 20-30% of the total deposition fluxes. Therefore, the ecosystem retention capacity of deposited N in non-growing season is vital for plant growth in N-limited temperate regions. However, contribution of increased N deposition in non-growing season to plant growth has not yet been tested in different temperate grasslands. To examine these issues, we added 15N to simulated increased N deposition in non-growing season after snowmelt, and follewed its subsequent fate over three growing seasons, on three contrasting temperate grasslands including meadow steppe, typical steppe and desert steppe in northern China. Our major objectives are (1) elucidate the contribution of increased N deposition in non-growing season to different plant functional groups; (2) investigate the subsequent fate of deposited N in temperate grasslands after three growing seasons; (3) explore the major drivers to regulate biological availability of increased N deposition in non-growing season. These issues will improve our understanding on predictions of plant community composition and ecosystem productivity, and the responses of them to the climate changes.

近几十年人类的石化燃烧、化肥使用及火烧砍伐导致大气氮沉降急剧增加。来自我国温带地区的观测表明，非生长季氮沉降量约占年总量的20-30%。对于受氮素限制的温带地区，非生长季沉降的氮固持和保持的程度对植物生长十分重要。然而，非生长季氮沉降增加对温带草原不同功能群植物氮吸收的贡献尚未探究。本项目沿湿冷到干暖的气候梯度，选择草甸草原、典型草原和荒漠草原三种温带草原类型，施加同位素15N模拟非生长季氮沉降，量化非生长季氮沉降增加对不同植物功能群氮吸收的贡献，阐明沉降的氮在生态系统中的长期再分配，揭示非生长季沉降氮生物有效性的区域分异特征与主成因。本研究对于全面理解和预测植被生产力和植物群落组成变化及其对未来气候变化的响应具有重要的意义。

近几十年人类的石化燃烧、化肥使用及火烧砍伐导致大气氮沉降急剧增加。来自我国温带地区的观测表明，非生长季氮沉降量约占年总量的20-30%。对于受氮素限制的温带地区，非生长季沉降的氮固持和保持的程度对植物生长十分重要。然而，非生长季氮沉降增加对温带草原不同功能群植物氮吸收的贡献尚未探究。本以温带草原为研究对象，施加同位素15N模拟非生长季氮沉降，量化非生长季氮沉降增加对不同植物功能群氮吸收的贡献，阐明沉降的氮在生态系统中的长期再分配，揭示非生长季沉降氮生物有效性的主成因。春季融雪期，温带草地大量固持非生长季的氮源，土壤和微生物为初期的主要氮汇，随之植物则为主要的氮汇。不同种植物对氮的吸收能力不同。非生长季氮源在植物中滞留的时间最长，土壤次之，而在微生物中转化的最快。本研究对于全面理解和预测植被生产力和植物群落组成变化及其对未来气候变化的响应具有重要的意义。