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首页> 外文期刊>Ecosphere >Historic declines in growth portend trembling aspen death during a contemporary leaf miner outbreak in Alaska
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Historic declines in growth portend trembling aspen death during a contemporary leaf miner outbreak in Alaska

机译：在阿拉斯加当代叶矿工爆发时，增长的历史衰退颤抖

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Climate change‐driven droughts and insect outbreaks are becoming more frequent and widespread, increasing forest vulnerability to mortality. By addressing the impacts of climate and insects on tree growth preceding death, we can better understand tree mortality risk under a changing climate. Here, we used tree stature and interannual growth (basal area increment; BAI) to assess processes leading to trembling aspen (Populus tremuloides ) survival or mortality during an unprecedented leaf miner (Phyllocnistis populiella ) outbreak in boreal North America. We identified eight sites (22 plots) in the longest running forest monitoring network in Alaska, spanning ~350?km of latitude, that experienced ≥0.25?Mg·ha~(?1)·yr~(?1)aspen mortality during the outbreak. We compared the size and canopy position, growth patterns, and sensitivity to climate and leaf mining of aspen that survived (living;n ?=?84) vs. died (dying;n ?=?76) and linked the normalized difference vegetation index (NDVI) to plot‐level aspen growth and stand biomass recruitment, growth, and mortality. Dying aspen were in the subcanopy, smaller in diameter, and after a drought in 1957 had lower growth than living aspen until death. Before the outbreak, growth of all trees was positively influenced by moisture and negatively by temperature, but only living trees maintained this climate response during the outbreak. Leaf mining reduced growth of both groups, exerting at least a twofold greater impact than climate. The NDVI captured plot‐level tree growth and stand biomass growth and mortality, yet it was nearly two times more strongly associated with living than dying tree growth and 12 times more strongly associated with biomass growth than mortality. These differences suggest that NDVI may inadequately detect insect‐driven dieback and dispersed mortality of aspen across the boreal biome. Our findings reveal that a historic drought triggered a multi‐decadal growth decline that predisposed aspen to mortality during the leaf miner outbreak and that while aspen growth is influenced by moisture and temperature, it is more strongly affected byP.?populiella . We conclude that as the climate warms and insect outbreaks increase in frequency and magnitude at high latitudes, we should expect to see persistent and greater declines in aspen growth and increases in mortality.
机译：气候变化驱动的干旱和昆虫爆发正在变得更加频繁和普遍，增加对死亡率的森林脆弱性。通过解决气候和昆虫对死亡后树脂的影响，我们可以在不断变化的气候下更好地了解树死亡率风险。在这里，我们使用树立和持续增长（基础区域增量; Bai），以评估导致颤抖的Aspen（仙群颤抖）生存或死亡率在北美前所未有的叶片矿工（ Phyllocnistis populiella）爆发期间。我们在阿拉斯加最长的森林监测网络中确定了八个站点（22个地块），跨越〜350？KM纬度，经历了≥0.25？mg·ha〜（？1）·Yr〜（？1）在此期间的白杨死亡率暴发。我们将尺寸和冠层位置，增长模式和敏感性的敏感性和叶片开采的敏感性（生存; n？=？84）与死亡（死亡; n？76）进行了比较将归一化差异植被指数（NDVI）联系起来的情节级白杨生长和培养生物量招募，生长和死亡率。染色的白杨在瓣膜复制中，直径较小，1957年干旱后，生长低于生长直至死亡。在爆发之前，所有树木的生长受到水分的积极影响，受到温度的负面影响，但只有生活树在爆发期间保持这种气候响应。叶矿矿床降低了两组的生长，施加至少比气候更大的撞击。 NDVI捕获的情节级树生长和兼容生物量生长和死亡率，但它与生生树生长的生活近似近两倍，与生物质生长比死亡率更强。这些差异表明，NDVI可能不充分地检测昆虫驱动的死回和分散在北方生物群系中的白杨的死亡率。我们的调查结果表明，历史悠久的干旱引发了一种多截止的增长率下降，即在叶片矿工疫情中倾向于白杨，虽然白杨生长受水分和温度的影响，但它受到 P.?populiella更强烈的影响。我们得出结论，随着气候温暖和昆虫爆发在高纬度地区的频率和幅度增加，我们应该期望在白杨生长中看到持续和更大的下降，并增加死亡率。

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