Phosphorus (P) is an important nutrient element in the photosynthesis process of plants. The effect of stand age on P nutrient dynamics in subtropical plantations is unclear. In this study, the mechanisms of above- and belowground P cycling in subtropical P. massoniana plantations of different stand ages (5, 9, 19, 29 and 35 years) were investigated. The percentage of metabolic P in leaves exhibited an initial rise and subsequent decline with stand age of P. massoniana throughout the growing season, culminating in a metabolic P proportion of 34%–68% in litter. During the non-growing season, the main change in the P components of P. massoniana fine roots was a transition from metabolic P to residual P. Relative to during the growing season, soil ligand P fractions decreased by 7%–22% and exchangeable P fractions increased by 0–16% in the non-growing season. Organ P components tended to decrease with increasing stand age, mainly due to the gradual decrease in soil-bioavailable P, a trend alleviated by litter input. The generation of dissolved P by soil phosphatases would limit the reduction in soil-bioavailable P caused by leaf P resorption to some extent. The differences in leaf organ P components between the growing and non-growing seasons are attributed to the allocation of P by the P. massoniana. Overall, the results of this study provide a basis for exploring the mechanisms of soil bioavailable P and soil P enzyme-mediated organ P component allocation in P. massoniana forests. These findings will help improve the management of P-limited P. massoniana plantations to enhance their productivity.

中文翻译：

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磷吸收对不同龄马尾松人工林生物活性磷的影响


磷 （P） 是植物光合作用过程中的重要营养元素。林龄对亚热带人工林 P 养分动态的影响尚不清楚。本研究研究了不同林龄 （5、9、19、29 和 35） 的亚热带马尾松 人工林地上和地下磷循环机制。在整个生长季节，叶片中代谢 P 的百分比随着马尾松 的林龄而最初上升，随后下降，最终在凋落物中代谢 P 比例为 34%–68%。在非生长季，马尾松 细根 P 组分的主要变化是从代谢 P 向残余 P 的转变。相对于生长季，土壤配体 P 组分减少了 7%–22%，可交换 P 组分在非生长季增加了 0–16%。器官 P 成分随着林龄的增加而趋于减少，主要是由于土壤生物可利用的 P 逐渐减少，这一趋势被凋落物输入所缓解。土壤磷酸酶产生溶解的 P 将在一定程度上限制叶 P 再吸收引起的土壤生物可利用 P 的减少。生长季节和非生长季节之间叶器官 P 成分的差异归因于马尾松 对 P 的分配。本研究结果为探究马尾松 林土壤生物可利用磷和土壤磷酶介导的器官磷成分分配机制提供了依据。这些发现将有助于改善对 P 限制的马尾松 人工林的管理，以提高其生产力。