摘要
Vegetation green-up is occurring earlier due to climate warming across the Northern Hemisphere,with substantial infuences on ecosystems.However,it is unclear whether temperature responses differ among various green-up stages.Using high-temporal-resolution satellite data of vegetation greenness and averaging over northern vegetation(30-75°N),we found the negative interannual partial correlation between the middle green-up stage timing(50%greenness increase in spring-summer)and temperature(R_(P)=-0.73)was stronger than those for the onset(15%increase,R_(P)=-0.65)and end(90%increase,R_(P)=-0.52)of green-up during 2000-2022.Spatially,at high latitudes,the middle green-up stage showed stronger temperature responses than the onset,associated with greater low-temperature constraints and stronger control of snowmelt on green-up onset as well as greater spring frost risk.At middle latitudes,correlations with temperature were similar between the onset and middle stages of green-up,except for grasslands of the Mongolian Plateau and interior western USA,where correlations with temperature were weaker for the middle stage due to water limitation.In contrast,the end of the green-up showed weaker temperature responses than the middle due to insuffcient water and high climatic temperature during the end of the green-up in most of the study region,except for cold regions in the interior western USA,western Russia and the Tibetan Plateau,where temperature was still a main driver during end of green-up.Our fndings underscore the differences in temperature responses among green-up stages,which alters the temporal alignment between plants and environmental resources.
北半球气候变暖导致春季植被提前返青,并对生态系统产生了重要影响。然而,目前尚不清楚不同返青阶段对温度的响应是否存在差异。本研究基于高时间分辨率的遥感植被绿度数据,发现在2000-2022年间,北半球中高纬度地区植被的返青中期(植被绿度在上半年增加年振幅50%对应的时间)与温度之间的年际偏相关关系(空间平均R_(P)=-0.73)强于返青初期(植被绿度增加15%,R_(P)=-0.65)和末期(植被绿度增加90%,R_(P)=-0.52)。在高纬度地区,由于低温限制更大、春季融雪控制更强以及春季霜冻风险更大,返青初期对温度的响应弱于返青中期。在中纬度地区,返青初期和中期对温度的响应整体上相近;但是在蒙古高原和美国西部内陆的草原地区,返青中期因受水分限制,对温度的响应弱于初期。相比而言,在研究范围内的大部分地区,返青末期因水分不足和气温较高,对温度的响应弱于中期;仅在美国西部内陆、俄罗斯西部和青藏高原这些寒冷地区,温度仍是返青末期的主要驱动因素。我们的研究结果强调了不同返青阶段对温度响应的差异及其空间变化,这种差异可能会改变植物与环境资源之间在时间上的匹配关系,需进一步研究。
基金
supported by the National Natural Science Foundation of China(42301388)
the Fundamental Research Funds for the Central Universities,and the Top-Notch Young Talents Program of China(to M.Shen).
