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Leaf spectral responses of Poa crymophila to nitrogen deposition and climate change on Qinghai-Tibetan Plateau

Hua, Qiaoyi, Yu, Yi, Dong, Shikui, Li, Shuai, Shen, Hao, Han, Yuhui, Zhang, Jing, Xiao, Jianan, Liu, Shiliang, Dong, Quanming, Zhou, Huakun, Wessell, Kelly
Agriculture, ecosystems & environment 2019 v.284 pp. 106598
Poa, absorption, alpine meadows, chlorophyll, climate, ecosystems, forage, global warming, leaves, nitrogen, photochemistry, photosynthesis, reflectance, steppes, temperature, China
Temperature and nitrogen (N) are limited factors on the Qinghai-Tibetan Plateau (QTP). Climate change and increasing N deposition on the QTP have posed threats to the sustainability of alpine ecosystems. To examine plant spectral responses to N deposition and climate change, we measured leaf spectral reflectance of Poa crymophila, a common forage species grown in alpine meadow (AM) and alpine steppe (AS) on the eastern QTP under four N addition treatments (CK, 8, 40, 72 kg N ha −1 yr −1). We used natural climate gradients from colder and drier AS to warmer and wetter AM to simulate the climate change on the QTP. Results showed that both N deposition and climate change had significant effects on entire visible and near-infrared regions (p < 0.05), but the interactive effects were insignificant (p> 0.05). Enhanced visible absorption, increased near-infrared reflection, a red shift for red edge and a blue shift for green peak were observed with increasing N addition levels. The modified red edge simple ratio index and photochemical reflective index increased gradually in response to N addition (p < 0.05). These responses indicated that N deposition may make leaf wider and thicker, increase leaf chlorophyll content and photochemical efficiency, and enhance photosynthetic capacity. Climate warming and wetting had opposite effects from N deposition on leaf reflectance of Poa crymophila. These observations showed the potential to monitor the status of Poa crymophila under future climate change and N deposition with leaf spectral measurements.