Zong Ning, Duan Cheng, Geng Shou Bao, Chai Xi, Shi Pei Li, He Yong Tao
Key Laboratory of Ecosystem Network Observation and Modelling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
Ying Yong Sheng Tai Xue Bao. 2018 Jan;29(1):59-67. doi: 10.13287/j.1001-9332.201801.006.
A long-term experiment, involving exogenous N addition and simulated warming, was conducted in an alpine meadow in Damxung, northern Tibet, to study how warming and N addition influence community production and biomass allocation. The results showed that warming resulted in a warm but dry microsite, that was, air temperature increased by 1.6 ℃ and soil surface temperature increased by 1.4 ℃, and soil water content decreased by 4.7%. Under no N addition treatments, warming significantly decreased plant aboveground biomass by 61.5%, 108.8% and 77.1% in 2012, 2013 and 2014, respectively. Under high N treatments (40 and 80 kg N·hm·a), warming had no significant effect on aboveground biomass. These findings indicated that the effect of warming might be dependent on N addition level, and N addition could compensate for soil N loss caused by warming. Warming led to an increase in root/shoot by 98.6%, 60.7% and 97.8% in 2012, 2013 and 2014 under no N addition treatments, respectively. Under the ambient condition, the change percentages of aboveground and belowground biomass of plant communities first increased and then decreased along an N gradient, with the saturation thresholds of above- and below-ground biomass for N addition 56.0 and 55.5 kg N·hm·a, respectively. Under the warming condition, above- and belowground biomass increased linearly with increasing N addition. These findings suggested that warming modulated the response patterns of alpine meadows to exogenous N input, which was mainly caused by decreased soil inorganic N under warming. The estimation of N thresholds highlights that alpine meadows are more sensitive to future N deposition than other types of grasslands.
在西藏北部当雄的一个高寒草甸开展了一项长期试验，该试验涉及外源氮添加和模拟增温，以研究增温和氮添加如何影响群落生产力和生物量分配。结果表明，增温导致形成了温暖但干燥的微生境，即气温升高了1.6℃，土壤表面温度升高了1.4℃，土壤含水量降低了4.7%。在不添加氮的处理下，2012年、2013年和2014年增温分别使植物地上生物量显著降低了61.5%、108.8%和77.1%。在高氮处理（40和80 kg N·hm·a）下，增温对地上生物量没有显著影响。这些结果表明，增温的影响可能取决于氮添加水平，并且氮添加可以补偿增温导致的土壤氮损失。在不添加氮的处理下，2012年、2013年和2014年增温分别使根冠比增加了98.6%、60.7%和97.8%。在环境条件下，植物群落地上和地下生物量的变化百分比沿氮梯度先增加后降低，地上和地下生物量氮添加的饱和阈值分别为56.0和55.5 kg N·hm·a。在增温条件下，地上和地下生物量随氮添加量的增加呈线性增加。这些结果表明，增温调节了高寒草甸对外源氮输入的响应模式，这主要是由增温下土壤无机氮减少所致。氮阈值的估计突出表明，高寒草甸比其他类型的草地对未来氮沉降更敏感。
