摘要
有研究表明长期观测的植物花期物候变化温度敏感性与野外控制恒定增温试验所得出的花期物候温度敏感性结果不一致,这可能是由于两种观测方法具有不同的增温模式引起的。因为长期观测的气候变暖实际上是气温逐渐升高的情景,而野外控制增温试验所增加的温度是突然增加且每年保持不变。不同的增温模式是否会导致不同的结果目前还缺乏野外试验证据。此外,不同增温模式的效应还受到降水变化的调控。因此,我们于2015–2018年在高寒高山嵩草草甸开展了一项恒定增温(和对照相比,每年保持恒定增温1°C)和逐步增温(和对照相比,2015年增温0.25°C,以后逐年在前一年基础上再增温0.25°C,到2018年相比对照增温1°C)以及与增水(100%/50%)耦合的野外控制试验。研究结果发现,增温模式并没有显著改变群落花期物候。然而,增水显著提前了早花植物和中花植物的初花期,提前了早花植物的末花期,推迟了中花植物的末花期。增水处理并没有显著改变早花植物的开花持续期,但却显著延长了中花植物的开花持续期,进而延长了该群落的开花持续期。增温速率和增水处理并没有显著的交互作用。前一年的干旱会显著抑制第二年该植物群落的现存最大开花数。因此,无论增温模式如何,降水的改变对该高山嵩草植物群落花期物候的影响要大于增温对其的影响。
There is a debate about unmatched results between manipulative warming using constant warming rates every year(CW)and long-term observations warming affect temperature sensitivity of flowering phenology.This may be because long-term observations represent the actual yearly increase in temperature(i.e.a yearly stepwise warming rate per year,SW)which would differ from CW and their effects would be regulated by precipitation alteration.We conducted a warming experiment with CW(temperature increase by+1°C and sustained this elevated temperature for the duration of the study)and SW(temperature increase by+0.25°C progressively each year)with precipitation addition in an alpine grassland for four years.Our results showed that neither warming rate affected community flowering phenology.However,precipitation addition advanced onsets of flowering for early-spring flowering(ESF)and midsummer flowering(MSF)groups,and advanced the end date of flowering for ESF but delayed it for the MSF group.Therefore,flowering duration remained stable for the ESF group and prolonged for the MSF group,and further prolonging the flowering duration of the community.There were no interactions between warming rates and precipitation addition on the community’s flowering phenology.A severe drought in a year significantly decreased the maximal number of community flowers in the following year.Therefore,a change in precipitation has a greater effect than warming on the community flowering phenology in the semi-arid alpine grassland.
基金
supported by grants from the National Natural Science Foundation of China(41731175 and 41988101)
the Strategic Priority Research Program A of the Chinese Academy of Sciences(XDA20050101)
the Joint Key Research Fund under a cooperative agreement between the National Natural Science Foundation of China(NSFC)and Tibet Autonomous Region(TAR)(U20A2005)
the Second Tibetan Plateau Scientific Expedition and Research(STEP)program(2019QZKK0608 and 2019QZKK0302).
关键词
恒定增温和逐步增温
增水
群落花期物候
初花期和末花期
开花功能群
高寒草原
青藏高原
constant and stepwise warming
precipitation addition
flowering phenology of Kobresia pygmaea community
onset and end date of flowering
flowering functional groups
alpine grasslands
Tibetan Plateau