黄土高原子午岭林区典型树种叶片N、P再吸收特征

为揭示黄土高原子午岭林区不同演替阶段和植被类型主要树种养分再吸收特征,研究选取4种次生植被树种(白桦、山杨、辽东栎和油松)和2种人工植被树种(刺槐和侧柏),测定其成熟叶、凋落叶和林下土壤碳(C)、氮(N)、磷(P)含量,研究了叶片N、P再吸收率及其与养分指标的关系。结果表明:(1)不同树种叶片养分和林下土壤养分含量存在显著差异,土壤C、N含量和C∶N∶P计量比均表现为演替后期林地(辽东栎和油松)演替前期林地(山杨和白桦)人工林(侧柏和刺槐);(2)不同树种叶片N、P再吸收率分别为17.18%—43.34%和27.13%—58.12%,均表现为演替后期林地人工林演替前期林地,且P的再吸收率总体高于N的再吸收率;(3)不同树种叶片N、P再吸收率与叶片养分指标的关系强于土壤,与养分计量比的相关性大于养分含量的相关性。说明子午岭典型植被会通过叶片N、P再吸收来适应养分限制环境,尤其是演替后期植被再吸收能力更强,研究可为黄土高原植被恢复提供理论依据。

Leaf N and P resorption characteristics of typical tree species in the Ziwuling forest area on Loess Plateau

In order to reveal the nutrient resorption characteristics of the main tree species of different succession stages and vegetation types in Ziwuling forest area on Loess Plateau, we selected four secondary succession forest tree species (Quercus wutaishansea Mary, Pinus tabuliformis Carr., Betula platyphylla Suk., and Populus davidiana Dode) and two artificial forest tree species (Robinia pseudoacacia L., and Platycladus orientalis (L.) Franco). The C, N and P concentrations of soil, green leaves, and senesced leaves were determined, and the N and P resorption efficiency (NRE and PRE) and C:N:P stoichiometry ratios were calculated. The results showed that (1) the soil and leaves nutrients were significantly different among different tree species.The soil C and N contents and C:N:P stoichiometry ratios showed the order of late succession stages forests (Quercus wutaishansea Mary and Pinus tabuliformis Carr.) > early succession stages forests (Betula platyphylla Suk. and Populus davidiana Dode) > artificial vegetation forests (Robinia pseudoacacia L. and Platycladus orientalis (L.) Franco). (2) The NRE and PRE of different tree species was 17.18%-43.34% and 27.13%-58.12%, respectively, with the order of late succession stages forests > artificial vegetation forests > early succession stages forests. The PRE were mostly higher than the NRE. (3) The NRE and PRE showed stronger relationship with leaves nutrient than with soil nutrient, and also showed stronger relationship with C:N:P stoichiometry ratios than with C, N and P concentrations. It indicated that N and P resorption was an important mechanism for typical tree species in the Ziwuling forest area to adapt to nutrient limitation, especially for the late succession stages forests. This can provide basis for vegetation restoration in the Loess Plateau.