Once forests have achieved a full canopy, their growth rate declines progressively with age. This work used a global data set with estimates from a wide range of forest types, aged 20‒795 years, of their annual photosynthetic production (gross primary production, GPP) and subsequent above- plus below-ground biomass production (net primary production, NPP). Both GPP and NPP increased with increasing mean annual temperature and precipitation. GPP was then unrelated to forest age whilst NPP declined progressively with increasing age. These results implied that autotrophic respiration increases with age. It has been proposed that GPP should decline in response to increasing water stress in leaves as water is raised to greater heights as trees grow taller with age. However, trees may make substantial plastic adjustment in morphology and anatomy of newly developing leaves, xylem and fine roots to compensate for this stress and maintain GPP with age. This work reviews the possibilities that NPP declines with age as respiratory costs increase progressively in, any or all of, the construction and maintenance of more complex tissues, the maintenance of increasing amounts of live tissue within the sapwood of stems and coarse roots, the conversion of sapwood to heartwood, the increasing distance of phloem transport, increased turnover rates of fine roots, cost of supporting very tall trees that are unable to compensate fully for increased water stress in their canopies or maintaining alive competitively unsuccessful small trees.

森林一旦形成完整的树冠，其生长速度就会随着年龄的增长而逐渐下降。这项工作使用了全球数据集，其中估计了20至795年的各种森林类型的年光合生产量（主要初级生产总值，GPP）以及随后的地上和地下生物量产量（净初级生产量， NPP）。GPP和NPP均随着年均温度和降水的增加而增加。GPP与森林年龄无关，而NPP随着年龄的增长而逐渐下降。这些结果暗示自养呼吸随年龄增加。已经提出，随着树随着年龄的增长，水被升高到更高的高度，GPP应该响应于叶片中水分压力的增加而下降。然而，树木可能会对新发育的叶片，木质部和细根的形态和解剖结构进行实质性的塑性调整，以补偿这种压力并随着年龄的增长保持GPP。这项工作回顾了NPP随着年龄增长而下降的可能性，因为在任何或全部复杂和复杂的组织的构造和维护，茎和粗根的边材内不断增长的活组织的维护中，呼吸费用逐渐增加。边材到心材的距离，韧皮部运输距离的增加，细根的周转率增加，无法支撑高高的树木的成本，这些高高的树木无法完全补偿其冠层水分压力的增加或无法维持竞争性未成功的小树。