Conservation Ecology Center, Smithsonian's National Zoo & Conservation Biology Institute, Front Royal, VA, USA.
Department of Forestry and Natural Resources, Purdue University, West Lafayette, IN, USA.
Nature. 2022 Aug;608(7923):552-557. doi: 10.1038/s41586-022-05092-3. Epub 2022 Aug 10.
As the climate changes, warmer spring temperatures are causing earlier leaf-out and commencement of CO uptake in temperate deciduous forests, resulting in a tendency towards increased growing season length and annual CO uptake. However, less is known about how spring temperatures affect tree stem growth, which sequesters carbon in wood that has a long residence time in the ecosystem. Here we show that warmer spring temperatures shifted stem diameter growth of deciduous trees earlier but had no consistent effect on peak growing season length, maximum growth rates, or annual growth, using dendrometer band measurements from 440 trees across two forests. The latter finding was confirmed on the centennial scale by 207 tree-ring chronologies from 108 forests across eastern North America, where annual ring width was far more sensitive to temperatures during the peak growing season than in the spring. These findings imply that any extra CO uptake in years with warmer spring temperatures does not significantly contribute to increased sequestration in long-lived woody stem biomass. Rather, contradicting projections from global carbon cycle models, our empirical results imply that warming spring temperatures are unlikely to increase woody productivity enough to strengthen the long-term CO sink of temperate deciduous forests.
随着气候的变化，温暖的春季气温导致温带落叶林更早地落叶和开始吸收 CO2，从而导致生长季节长度和年度 CO2 吸收量呈增加趋势。然而，对于春季温度如何影响树木茎干生长（将碳储存在树木的木材中，而木材在生态系统中的停留时间很长），我们知之甚少。在这里，我们使用来自两个森林的 440 棵树木的树木年轮带测量结果表明，温暖的春季温度会使落叶树木的茎干直径生长提前，但对生长季节高峰期长度、最大生长速率或年生长没有一致的影响。这一发现得到了来自北美东部 108 个森林的 207 个树木年轮年表的百年尺度的证实，其中在生长季节高峰期，年轮宽度对温度的敏感程度远远高于春季。这些发现意味着，在春季温暖的年份中，任何额外的 CO2 吸收都不会显著增加对长寿命木质茎生物质的固碳。与全球碳循环模型的预测相反，我们的实证结果表明，春季变暖不太可能增加温带落叶林的木质生产力，从而增强其作为长期 CO2 汇的能力。
