Nonstructural Carbohydrates in Forest Trees at Harvard Forest 2007-2010

Forest trees accumulate and store surplus nonstructural carbohydrates (NSC) as resources to be used to support future growth. This can be viewed as a conservative investment strategy, providing reserves that the tree can utilize in times of stress. NSC reserves are thus important in the context of forest responses to climate change, and forest ecosystem carbon cycling. At quarterly intervals over a three year period, we have monitored stemwood nonstructural carbohydrate (NSC) reserves of the dominant tree species of New England at three sites along a forest composition gradient: an oak-dominated transition hardwood forest (Harvard Forest), a maple-beech-birch northern hardwood forest (Bartlett Experimental Forest), and a spruce-fir boreal transition forest (Howland Forest). Adding to recent evidence indicating that in mature forest trees the nonstructural carbohydrate pool is surprisingly large, our results suggest that this pool is also highly dynamic, and unexpectedly old. In most species, seasonal dynamics in starch (2-4x higher in the growing season, lower in the dormant season) mirrored those of sugars. This data set contains 3 y of quarterly NSC concentration measurements (stemwood starch and sugars - sucrose, glucose, fructose, raffinose, stachyose - in mg per g OD wood tissue) for red maple, eastern hemlock, and red oak at the Harvard Forest.林木会积累并储存过剩的非结构性碳水化合物（nonstructural carbohydrates，NSC），将其作为支持未来生长的资源储备。这可被视为一种保守的投资策略，为树木在逆境时期提供可动用的储备。因此，非结构性碳水化合物储备在森林应对气候变化以及森林生态系统碳循环的研究中具有重要意义。 本研究于三年周期内按季度开展监测，对象为新英格兰地区沿森林组成梯度分布的三个样地的优势树种的茎干木质组织非结构性碳水化合物储备：分别为以栎树为主的过渡性落叶阔叶林（哈佛大学森林保护区，Harvard Forest）、以槭树-山毛榉-桦木为主的北方落叶阔叶林（巴特利特实验林，Bartlett Experimental Forest）以及云杉-冷杉为主的寒带过渡林（豪兰森林，Howland Forest）。 本研究结果补充了近期相关证据：此前已有研究证实成熟林木的非结构性碳水化合物库规模惊人庞大，而我们的结果进一步表明，该库同时具有高度动态性，且其留存周期亦出乎意料地久。在多数树种中，淀粉的季节动态变化（生长季含量为休眠季的2-4倍，休眠季含量更低）与糖类的变化趋势一致。 本数据集涵盖了哈佛大学森林保护区内红枫、东部铁杉与红栎三种优势树种为期三年的季度非结构性碳水化合物浓度测定数据，测定指标包括茎干木质组织中的淀粉与糖类物质——蔗糖、葡萄糖、果糖、棉子糖与水苏糖——单位为每克烘干木材组织（mg/g OD wood tissue）。