Acidic Deposition and Climate Warming as Drivers of Tree Growth in High-Elevation Spruce-Fir Forests of the Northeastern US
Acidic Deposition and Climate Warming as Drivers of Tree Growth in High-Elevation Spruce-Fir Forests of the Northeastern US
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DOI：
10.3389/ffgc.2019.00063
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发表时间：
2019-10
影响因子：
3.2
通讯作者：
J. Wason;C. Beier;J. Battles;M. Dovciak
中科院分区：
文献类型：
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作者：
J. Wason;C. Beier;J. Battles;M. Dovciak
北美东部的酸雨导致了高海拔云冷杉林中红云杉的广泛衰退。随着最近酸沉降的减少和气候变暖，据报道，一些山区的红云杉生长复苏。基于一个广泛的树木年轮采样网络建立跨越海拔（海拔600至1200米）在云杉冷杉林在美国东北部（纽约，佛蒙特州，新罕布什尔州，和缅因州），我们调查是否这种复苏是特定的红云杉或如果它也发生在共显性香脂冷杉。此外，我们测试了这两个物种的树木生长变化是否与最近的酸性沉积和气候趋势有关。急剧增加的增长率的红云杉是显而易见的，在所有海拔高度和最密切相关的增加雨水pH值。虽然前一年的气候（凉爽的7月和温暖的11月）解释较高的云杉生长在某些年份，最近的气候趋势并没有驱动观察到的云杉增长。与此相反，香脂冷杉表现出没有区域增长激增期间云杉恢复。因此，云杉生长复苏似乎是介导的主要是下降的酸沉降，而不是气候变化或林分动态，也会影响冷杉生长。虽然高海拔森林最终可能面临未来变暖相关的高温和干旱压力的风险，但最近观察到的云杉生长的急剧复苏说明了政策驱动的酸性沉积物减少对美国东北部森林健康和生产力的好处。
Acid rain in eastern North America contributed to the widespread decline of red spruce in high-elevation spruce-fir forests. With recent reductions in acid deposition and a warming climate, resurgence of red spruce growth has been reported in some mountain areas. Based on an extensive tree-ring sampling network established across elevations (600 to 1200 m above sea level) in spruce-fir forests on 10 mountains in the northeastern US (New York, Vermont, New Hampshire, and Maine), we investigated whether this resurgence was specific only to red spruce or if it occurred also in the codominant balsam fir. Furthermore, we tested if tree growth changes for both species were related to recent trends in acidic deposition and climate. Sharply increasing growth rates of red spruce were evident at all elevations and most closely correlated with increasing rainwater pH. Although climate of the previous year (cool July and warm November) explained higher spruce growth in certain years, recent trends in climate did not drive observed increases in spruce growth. In contrast, balsam fir exhibited no regional growth surge during the period of spruce recovery. Thus, spruce growth resurgence appears to be mediated primarily by declining acid deposition and not climatic changes or stand dynamics that would also impact fir growth. Although high-elevation forests may ultimately be at risk for future warming-related heat and drought stress, the observed recent dramatic resurgence of spruce growth illustrates the benefits of policy-driven reductions in acidic deposition for the health and productivity of northeastern US forests.