摘要
日益加剧的氮沉降已经对陆地生态系统生产力和碳循环过程产生了显著影响。草原生态系统近90%的碳储存在土壤中,明确土壤呼吸及其组分对氮添加的响应对评估大气氮沉降背景下草原生态系统碳平衡和土壤碳库稳定性是非常重要的。以往关于草原土壤呼吸对氮沉降响应的理解多是基于短期(<5年)和低频(每年1–2次)氮添加实验研究,而关于长期氮添加和不同施氮频率对土壤呼吸及其组分的影响尚缺乏实验证据。该研究基于2008年建立在内蒙古半干旱草原的长期氮添加实验平台,包括6个氮添加水平和2个施氮频率处理,通过连续两年(2018–2019年)土壤呼吸及其组分的测定,发现:1)氮添加显著降低了土壤总呼吸速率(Rs),且Rs下降程度随着氮添加量的增加而增强。土壤异养呼吸速率(Rh)的显著下降是Rs下降的主要原因。2)不同氮添加频率并未显著影响土壤呼吸及其组分对氮添加处理的响应。3)长期氮添加造成的土壤酸化降低了土壤微生物活性并改变了微生物群落结构(真菌/细菌比),进而导致土壤呼吸及其异养组分呈现显著的负响应。以上结果表明,长期(>10年)氮添加对土壤地下碳循环过程的抑制作用非常明显,特别是异养呼吸组分的下降会降低土壤有机碳分解速率,有助于土壤碳库稳定性的维持。同时,随着氮添加处理时间的延长,不同施氮频率影响效应的差异减弱,表明目前长期的低频氮添加实验监测数据可以为评估自然生态系统对大气氮沉降的响应提供较为可靠的参考。
Aims Increasing global nitrogen(N) deposition has exerted significant influences on productivity and carbon cycle of terrestrial ecosystems. More than 90% of the carbon in grasslands is stored in the soil, therefore any changes in soil total respiration(Rs) might have a vital impact on the carbon balance and the stability of soil carbon pool of grassland ecosystems. Most of our understanding about the responses of Rs to N deposition was based on N deposition manipulative experiments with short-term(<5 years) and low frequency(1–2 times per year) N addition treatments. It is still unclear how the long term N addition and different N addition frequency will affect Rs and its components in semiarid grasslands. Methods Our study is based on a long term N addition manipulative experiment platform conducted in a typical temperate semiarid steppe, Nei Mongol. The experimental treatment consisted of six N addition amounts and two N addition frequencies. N addition treatments began at 2008. Soil respiration and its components were measured every two weeks during the growing season in 2018 and 2019. Important findings 1) Rs significantly decreased with increasing N addition amount. The negative impact of N addition on Rs was mainly resulted from the inhibition of heterotrophic respiration(Rh). 2) No significant differences were observed in responses of Rs and its components to low and high frequency N addition treatments. 3) Soil acidification caused by long term N addition inhibited soil microbial activity and changed soil microbial community composition, consequently decreased Rs and Rh. Our results suggested that the negative effect of N addition on soil carbon release still lasted after a decade of N addition treatment. In particular, the decrease of Rh would enhance the stability of soil carbon pool. No significant differences in the two N addition frequency treatments indicated that the potential impacts caused by simulated N addition with different frequencies would be diminished with prolonged treatment period. T
作者
杨泽
嘎玛达尔基
谭星儒
游翠海
王彦兵
杨俊杰
韩兴国
陈世苹
YANG Ze;GAMADAERJI;TAN Xing-Ru;YOU Cui-Hai;WANG Yan-Bing;YANG Jun-Jie;HAN Xing-Guo;CHEN Shi-Ping(State Key Laboratory of Vegetation and Environmental Change,Institute of Botany,Chinese Academy of Sciences,Beijing 100093,China;University of Chinese Academy of Sciences,Beijing 100049,China)
出处
《植物生态学报》
CAS
CSCD
北大核心
2020年第10期1059-1072,共14页
Chinese Journal of Plant Ecology
基金
国家自然科学基金(41773084)
国家重点研发计划(2017YFA0604801)。
关键词
长期氮添加
施氮频率
土壤呼吸
自养呼吸
异养呼吸
long-term nitrogen addition
nitrogen addition frequency
soil respiration
autotrophic respiration
heterotrophic respiration
