亚热带人工和天然马尾松、杉木林生长对干旱的生态弹性差异

选取福建中西部地区相似气候条件下马尾松和杉木的天然林和人工林进行研究,利用年轮宽度、年轮宽度指数和断面积增量重建了4种林型共109株松树20年(1993—2012年)的年生长量,计算其对连续两次极端干旱事件(2003—2004年和2011年)的抵抗力、恢复力和弹性指数,分析人工林和天然林在抵抗力和弹性方面的差异。结果表明:马尾松和杉木对水分的需求在时间上存在差异,这解释了其对2003—2004年干旱事件的响应不一致。干旱压力极大地降低了马尾松和杉木的生长,但树木生长并未表现出干旱遗留效应。受干旱强度的影响,4种林型径向生长对2003—2004年干旱的响应强于2011年。干旱事件后马尾松比杉木具有更强的恢复能力;天然林比人工林对干旱的敏感性更高,同时弹性也更大。杉木人工林更容易受到频发的极端干旱事件的影响,在人工林抚育管理中应选择抗旱能力较强的遗传种源,以应对气候变暖导致的干旱频发。

Differences in the ecological resilience of planted and natural Pinus massoniana and Cunninghamia lanceolata forests in response to drought in subtropical China

We sampled Pinus massoniana and Cunninghamia lanceolata in both plantation and natural forests in central and western Fujian Province, China. Using tree-ring width, tree-ring width index, and basal area increment, we reconstructed the annual growth of 109 conifer individuals from four sites for the 20-year period from 1993 to 2012. We then calculated resistance, recovery, and resilience indices of those trees in response to two consecutive extreme droughts (2003-2004 and 2011) and analyzed the differences in resistance and resilience between plantations and natural fore-sts. The results showed that there were temporal differences in moisture requirements between P. massoniana and C. lanceolata, which accounted for their inconsistent responses to drought in 2003-2004. For both species, drought induced a marked growth reduction, without any clear lag effect. The growth responses during and following the 2003-2004 drought were significantly stronger than that for the 2011 drought. Those results indicated that P. massoniana was more resilient to drought stress than C. lanceolata, and the natural forests were more sensitive than plantations, but with stronger capacity to recover. C. lanceolata plantations were more susceptible to frequent extreme drought events. To mitigate the vulnerability of plantation trees to more frequent droughts in the future, we suggested select trees from genetic provenances with strong drought resistance.