Li Wen-Yu, Zhang Yang-Jian, Shen Ruo-Nan, Zhu Jun-Tao, Cong Nan
Lhasa Plateau Ecosystem Research Station, Key Laboratory of Ecosystem Network Observation and Modeling, 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. 2022 Jan;33(1):51-58. doi: 10.13287/j.1001-9332.202201.004.
Alpine grassland is threatened by the import of chemicals, fertilizers and other external resources with increasing human activities on the Qinghai-Tibet Plateau. It is unclear how carbon cycle of alpine grasslands is affected by the inputs of external resources such as nitrogen, phosphorus, and potassium (N, P, K) and their interactions. We conducted a 3 year experiment on the interactive addition of N, P and K with alpine grassland as the research object to clarify ecosystem carbon exchange process in response to resource addition by measuring community coverage and ecosystem carbon exchange. The results showed the alpine meadow was represented by carbon sequestration during the growing season. The mean value of net ecosystem CO exchange (NEE) was -13.0 μmol·m·s under the control treatment. NEE, ecosystem respiration (ER), and gross ecosystem productivity (GEP) showed no significant responses when N, P and K were added separately. NEE was significantly increased by 95.3% and 63.9%, GEP was significantly increased by 45.5% and 33.0% under the combined addition of NP and NPK, but ER remained stable. The combined addition of NP or NPK mainly increased NEE and GEP by increasing the coverage of plant communities and affecting ecosystem water use efficiency. Plant community coverage was increased by 18.1% and 21.4%, respectively. The addition of NP increased productivity and autotrophic respiration in alpine meadow. It might cause soil acidification to inhibit heterotrophic respiration, thereby did not change ER due to the two aspects canceling each other out. The addition of N, P, K alone and NK and PK did not change ecosystem carbon exchange, while the combined addition of NP increased NEE and GEP on the nutrient-deficient alpine meadows, indicating that ecosystem carbon uptake was co-limited by N and P in alpine meadow.
随着青藏高原人类活动的增加，高山草原受到化学品、化肥和其他外部资源输入的威胁。目前尚不清楚氮、磷、钾（N、P、K）等外部资源输入及其相互作用如何影响高山草原的碳循环。我们以高山草原为研究对象，进行了为期3年的氮、磷、钾交互添加实验，通过测量群落覆盖度和生态系统碳交换，以阐明生态系统碳交换过程对资源添加的响应。结果表明，生长季高山草甸以碳固存为主。对照处理下净生态系统CO交换（NEE）的平均值为-13.0 μmol·m·s。单独添加氮、磷、钾时，NEE、生态系统呼吸（ER）和总生态系统生产力（GEP）均无显著响应。NP和NPK组合添加时，NEE显著增加了95.3%和63.9%，GEP显著增加了45.5%和33.0%，但ER保持稳定。NP或NPK组合添加主要通过增加植物群落覆盖度和影响生态系统水分利用效率来增加NEE和GEP。植物群落覆盖度分别增加了18.1%和21.4%。NP添加增加了高山草甸的生产力和自养呼吸。这可能导致土壤酸化抑制异养呼吸，从而因两方面相互抵消而使ER不变。单独添加氮、磷、钾以及NK和PK均未改变生态系统碳交换，而NP组合添加使养分缺乏的高山草甸NEE和GEP增加，表明高山草甸生态系统碳吸收受到氮和磷的共同限制。
