轿子山国家级自然保护区气候变化特征及对NDVI的影响

轿子山国家级自然保护区保存有最完整的滇中高原植被与生境,是气候敏感性热点地区之一。采用一元线性回归、Pettitt突变检验、Spearman相关系数等方法识别1961—2019年气候要素和极端气候指数变化特征,1999—2016年归一化植被指数（NDVI）时空变化趋势特征及对极端气候指数的响应,旨在辨识轿子山植被变化特征及对极端气候变化的动态响应,以期为保护区的气候风险评估提供参考依据。结果表明：（1）全球变暖下,1961—2019年气候要素（平均气温、日照时间、风速、雾日）变化趋势显著,垂直温度带组合动态变化,2017—2019年基带由南亚热带转为北热带;（2）整体来看,1961—2019年极端气温指数变化率和突变点较极端降水指数显著;（3）1999—2016年NDVI增速随海拔升高降低,以海拔2 736,3 236 m为界,NDVI增长速率的变化率表现为"高—低—高";（4） NDVI_mean、NDVI_max、NDVI_min对极端气温指数的相关性总体上强于极端降水指数,对暖指数、降水强度指数、极端降水日指数响应最为敏感;（5）如果（极端）气候变化超过植被耐受阈值,则可能抑制植被生长。鉴于未来气候变化的不确定性,有必要进一步识别极端气候变化对保护区NDVI的影响,加强保护区极端气候风险预警、监测和管控。

Climate Change Characteristics of Jiaozishan National Nature Reserve and Its Impact on NDVI

Jiaozishan National Nature Reserve preserves the most complete vegetation and habitat of the central Yunnan Plateau, and is one of the hot spots with climate sensitivity. Univariate linear regression, Pettitt mutation test and Spearman correlation and other methods were used to analyze the change characteristics of climate elements and the extreme climate index from 1961 to 2019 in this area, as well as the temporal and spatial change trend characteristics of NDVI and its response to extreme climate index from 1999 to 2016. The aim was to study the climate change characteristics and the dynamic response of vegetation in Jiaozi Mountain, providing a reference for climate risk management in the reserve. The results showed that:(1) Global warming led to a significant change in the climate elements (average temperature, sunshine hours, wind speed and foggy day) from 1961 to 2019. The vertical temperature zones changed dynamically, and the baseband changed from a south subtropical zone to a north tropical zone in 2017-2019. (2) On the whole, the change rate and abrupt change point of the extreme temperature index from 1961 to 2019 were more significant than those of the extreme precipitation index. (3) From 1999 to 2016, the growth rate of NDVI decreased with the increasing of altitude. Taking the altitude of 2 736 m and 3 236 m as the boundary, the change rate of NDVI growth rate showed the trend of "high-low-high". (4) The correlation of NDVI_mean, NDVI_max and NDVI_min to extreme temperature index was stronger than that to extreme precipitation index, and NDVI_mean, NDVI_max, NDVI_min were most sensitive to warm index, precipitation intensity index and extreme precipitation day index. (5) If (extreme) climate change exceeds the vegetation tolerance threshold, vegetation growth might be inhibited. In view of the uncertainty of future climate change, it is necessary to further identify the impact of extreme climate change on NDVI in the reserve and strengthen the early warning, monitoring and control of extreme climate risk in the reserve.