黄土高原中部针叶树与灌木径向生长对气候的响应差异

为揭示黄土高原中部不同树种径向生长对气候变化的响应及应对极端干旱能力的差异,构建延安任家台林场油松、狼牙刺和黄刺玫树轮宽度年表,利用帕默尔干旱指数(PDSI)定义极端干旱事件,计算干旱频率及强度;利用树轮宽度量化径向生长应对极端干旱事件的抵抗力(Rt)、恢复力(Rc)及恢复弹力(Rs)。结果表明,油松与5月平均气温和平均最高气温显著负相关,与9月平均最高气温显著正相关,与前一年11月降水和7月相对湿度显著正相关;狼牙刺与前一年9月平均气温,当年7月平均最高气温,8月平均气温和平均最高气温显著负相关;黄刺玫与7月平均气温和平均最高气温显著负相关;3个树种径向生长均与PDSI正相关。干旱程度加剧使树木抗旱性降低,导致油松、狼牙刺Rt和Rs减弱。树种间差异表现为,Rt:狼牙刺>油松,Rc:油松>狼牙刺>黄刺玫,Rt:黄刺玫>狼牙刺。

Different response of conifer and shrubs radial growth to climate in the middle Loess Plateau

In order to reveal the responses of the radial growth of different tree species to climate and its adaptability to extreme drought in the middle of the Loess Plateau, the tree-ring width chronologies of Pinus tabulaeformis, Sophora viciifolia and Rosa xanthina were developed based on the samples collected from Renjiatai Forest Farm in Yan''an. The Palmer Drought Index (PDSI) were used to define the extreme drought events, and calculate the drought frequency and drought intensity. The tree-ring widths were used to quantify the resistance, recovery and resilience of radial growth to extreme drought events. The Pearson correlation analysis results showed that Pinus tabulaeformis was negatively correlated with monthly mean temperature and monthly mean maximum temperature in May, but was positively correlated with monthly mean maximum temperature in September, monthly total precipitation in November of the previous year, and monthly mean relative humidity in July; Sophora viciifolia was negatively correlated with monthly mean temperature in September of the previous year, monthly mean maximum temperature in July, monthly mean temperature and monthly mean maximum temperature in August. Rosa xanthine was negatively correlated with monthly mean temperature and monthly mean maximum temperature in July. Radial growth of all species were positively correlated with the monthly mean PDSI. Increased drought intensity reduced the drought resistance of the trees, and thus weakened resistance and resilience of Pinus tabulaeformis and Sophora viciifolia. The results also showed that the resistance of Sophora viciifolia was stronger than that of Pinus tabulaeformis, the recovery of Pinus tabulaeformis was stronger than that of shrubs, the recovery of Sophora viciifolia was stronger than that of Rosa xanthine, and the resilience of Rosa xanthine was stronger than that of Sophora viciifolia.