Foster Jane R, Finley Andrew O, D'Amato Anthony W, Bradford John B, Banerjee Sudipto
Department of Forest Resources, University of Minnesota, 115 Green Hall, 1530 Cleveland Ave. N., St. Paul, MN, 55108, USA.
Department of Forestry and Geography, Michigan State University, 126 Natural Resources Building, East Lansing, MI, 48824, USA.
Glob Chang Biol. 2016 Jun;22(6):2138-51. doi: 10.1111/gcb.13208. Epub 2016 Mar 3.
As global temperatures rise, variation in annual climate is also changing, with unknown consequences for forest biomes. Growing forests have the ability to capture atmospheric CO2 and thereby slow rising CO2 concentrations. Forests' ongoing ability to sequester C depends on how tree communities respond to changes in climate variation. Much of what we know about tree and forest response to climate variation comes from tree-ring records. Yet typical tree-ring datasets and models do not capture the diversity of climate responses that exist within and among trees and species. We address this issue using a model that estimates individual tree response to climate variables while accounting for variation in individuals' size, age, competitive status, and spatially structured latent covariates. Our model allows for inference about variance within and among species. We quantify how variables influence aboveground biomass growth of individual trees from a representative sample of 15 northern or southern tree species growing in a transition zone between boreal and temperate biomes. Individual trees varied in their growth response to fluctuating mean annual temperature and summer moisture stress. The variation among individuals within a species was wider than mean differences among species. The effects of mean temperature and summer moisture stress interacted, such that warm years produced positive responses to summer moisture availability and cool years produced negative responses. As climate models project significant increases in annual temperatures, growth of species like Acer saccharum, Quercus rubra, and Picea glauca will vary more in response to summer moisture stress than in the past. The magnitude of biomass growth variation in response to annual climate was 92-95% smaller than responses to tree size and age. This means that measuring or predicting the physical structure of current and future forests could tell us more about future C dynamics than growth responses related to climate change alone.
随着全球气温上升，年气候变率也在发生变化，这对森林生物群落的影响尚不明朗。生长中的森林有能力捕获大气中的二氧化碳，从而减缓二氧化碳浓度的上升。森林持续的碳固存能力取决于树木群落如何应对气候变化。我们对树木和森林对气候变化的反应的了解大多来自树木年轮记录。然而，典型的树木年轮数据集和模型并未捕捉到树木和物种内部及之间存在的气候反应多样性。我们使用一个模型来解决这个问题，该模型在考虑个体大小、年龄、竞争状态和空间结构潜在协变量变化的同时，估计单株树木对气候变量的反应。我们的模型允许推断物种内部和之间的方差。我们从生长在北方和温带生物群落过渡带的15种北方或南方树种的代表性样本中，量化各种变量如何影响单株树木地上生物量的增长。单株树木对年平均温度波动和夏季水分胁迫的生长反应各不相同。一个物种内个体之间的差异比物种之间的平均差异更大。平均温度和夏季水分胁迫的影响相互作用，因此温暖年份对夏季水分供应产生积极反应，凉爽年份产生消极反应。随着气候模型预测年平均温度将显著上升，糖槭、红栎和白云杉等物种的生长对夏季水分胁迫的反应将比过去更加多样化。生物量增长对年气候的变化幅度比对树木大小和年龄的反应小92 - 95%。这意味着，测量或预测当前和未来森林的物理结构，可能比仅与气候变化相关的生长反应更能让我们了解未来的碳动态。
