National Institute of Agricultural Technology (INTA), Agricultural Experimental Station of Delta del Paraná, Campana, B2804, Argentina.
Graduate Degree Program in Ecology, Department of Ecosystem Science and Sustainability, Colorado State University, Fort Collins, CO, 80523, USA.
New Phytol. 2024 Jun;242(5):1932-1943. doi: 10.1111/nph.19764. Epub 2024 Apr 19.
Large trees in plantations generally produce more wood per unit of resource use than small trees. Two processes may account for this pattern: greater photosynthetic resource use efficiency or greater partitioning of carbon to wood production. We estimated gross primary production (GPP) at the individual scale by combining transpiration with photosynthetic water-use efficiency of Eucalyptus trees. Aboveground production fluxes were estimated using allometric equations and modeled respiration; total belowground carbon fluxes (TBCF) were estimated by subtracting aboveground fluxes from GPP. Partitioning was estimated by dividing component fluxes by GPP. Dominant trees produced almost three times as much wood as suppressed trees. They used 25 ± 10% (mean ± SD) of their photosynthates for wood production, whereas suppressed trees only used 12 ± 2%. By contrast, dominant trees used 27 ± 19% of their photosynthate belowground, whereas suppressed trees used 58 ± 5%. Intermediate trees lay between these extremes. Photosynthetic water-use efficiency of dominant trees was c. 13% greater than the efficiency of suppressed trees. Suppressed trees used more than twice as much of their photosynthate belowground and less than half as much aboveground compared with dominant trees. Differences in carbon partitioning were much greater than differences in GPP or photosynthetic water-use efficiency.
人工林里的大树通常比小树每单位资源利用生产更多的木材。这一模式可能有两个原因：光合作用资源利用效率更高，或者将更多的碳分配到木材生产中。我们通过将蒸腾作用与桉树的光合用水效率相结合，在个体尺度上估计了总初级生产力（GPP）。通过使用异速生长方程和模拟呼吸作用来估计地上生产力通量；通过从 GPP 中减去地上通量来估计总地下碳通量（TBCF）。通过将组件通量除以 GPP 来估计分配。优势树木产生的木材几乎是被抑制树木的三倍。它们将 25±10%（平均值±标准差）的光合作用产物用于木材生产，而被抑制的树木仅使用 12±2%。相比之下，优势树木将 27±19%的光合作用产物用于地下，而被抑制的树木将 58±5%的光合作用产物用于地下。中间树木介于这两个极端之间。优势树木的光合用水效率比被抑制树木高出约 13%。与优势树木相比，被抑制树木将超过两倍的光合作用产物用于地下，而用于地上的光合作用产物不到一半。碳分配的差异远远大于 GPP 或光合用水效率的差异。
