子午岭林区两种天然次生林叶片C、N、P化学计量特征的季节变化

为阐明不同天然林叶片C、N、P化学计量特征及季节变化规律,了解植物对环境的适应策略,以陕西省子午岭林区桥山林场的油松和辽东栎天然次生林为研究对象,对其生长季内不同月份叶片的C、N、P含量及其计量比进行了分析。结果表明:(1)油松叶片C、N、P含量及其计量比分别为48.06%,1.15%,0.11%和42.58,473.22,11.02,辽东栎叶片C、N、P含量及其计量比分别为43.16%,2.10%,0.19%和25.47,380.18,14.49;两树种叶片各指标季节间变异系数表现为C含量最小,P含量最大。(2)两树种叶片C、N、P含量及其计量比在整个生长季内的变化规律不一致,油松叶片C含量在4—6月显著下降,之后保持平稳状态,8月后显著上升,至10月基本与4月持平;而辽东栎叶片C含量在整个生长季内变化不明显。油松叶片N含量在6月前较稳定,6—8月显著下降,随后显著上升,至10月基本与6月持平;辽东栎叶片N含量在4—6月显著下降,随后保持稳定,8月后再次显著下降,并在10月达到最低值。油松叶片P含量在8月前变化不明显,8月后显著上升,并在10月达到最高值;辽东栎叶片P含量在4月到6月显著下降,随后基本不变。两树种C∶N和C∶P的变化与N、P浓度相反;油松叶片N∶P在4—6月显著下降,6—8月显著上升,8—10月再次显著下降,辽东栎叶片N∶P在6月前显著上升并达到最高值,6—10月显著下降。(3)叶片C含量和C∶N主要受树种的影响,其他各指标受树种与月份交互作用的影响最大。(4)油松叶片C含量显著高于辽东栎,N含量显著低于辽东栎,因此,C∶N显著高于辽东栎,而辽东栎叶片的N∶P显著高于油松,但P含量和C∶P在两者之间无显著性差异。除叶片C含量外,各指标季节间变异系数均表现为油松小于辽东栎。研究结果丰富了天然林生态化学计量学的研究,同时也为黄土丘陵沟壑区的森林恢复与管理工作提供了一定的理论依据。

Seasonal Variations of C, N and P Stoichiometric Characteristics in Leaves of Two Natural Secondary Forests in Ziwuling Forest District

In order to explore the seasonal variations of carbon (C), nitrogen (N) and phosphorus (P) stoichiometric features in leaves of different natural secondary forests and understand the strategies of plant adaptation to the environment, we chose Piuns tabulaeformis and Quercus liaotungensis natural forests in Ziwuling Forest district as study area, and subsequently investigated their C, N and P stoichiometric parameters in leaves from April to October. The results showed: (1) Leaf C, N and P contents and stoichiometric ratios of Q. liaotungensis were 43.16%, 2.10%, 0.19% and 25.47, 380.18, 14.49, respectively, and the same parameters for P. tabulaeformis were 48.06%, 1.15%, 0.11% and 42.58, 473.22, 11.02, respectively. There were less seasonal dynamics in leaf C contents and more seasonal dynamics in leaf P contents than others through the whole growth season. (2) Leaf C content of P. tabulaeformis significantly decreased from April to June, then remained stable, but it significantly increased from August to October, which was almost equal to April; while leaf C content of Q. liaotungensis was almost constant. Leaf N content of P. tabulaeformis remained stable before June, then significantly decreased from June to August, then it significantly increased from August, and in October it was almost equal to April. Leaf N content of Q. liaotungensis significantly decreased from April to June, then remained stable, but it significantly decreased again from August and reached the lowest value in October. Leaf P content of P. tabulaeformis remained stable before August, then significantly increased and reached the maximum value in October. Leaf P content of Q. liaotungensis significantly decreased from April to June, then remained stable. The changes of C/N, C/P of two species were averse to their N, P content. Leaf N/P of P. tabulaeformis significantly decreased from April to June, then significantly increased, and it significantly decreased from August to October. The N/P of Q. liaotungensis increased significantly and reached the maximum value before June and then significantly decreased. (3) Factorial analysis showed that leaf C content and C/N mainly determined by tree species. For other parameters, they were mainly affected by the interaction between tree species and month. (4) Leaf C content of P. tabulaeformis significantly higher than that of Q. liaotungensis, however, leaf N content of P. tabulaeformis was significantly lower than that of Q. liaotungensis, therefore, leaf C/N of P. tabulaeformis was significantly higher than that of Q. liaotungensis. However, leaf N/P of Q. liaotungensis was significantly higher than that of P. tabulaeformis. There was no significant difference in leaf P content and C/P between these two species. The coefficient of seasonal variation of leaf N, P contents and C/N, C/P, N/P of P. tabulaeformis were smaller than those of Q. liaotungensis. The results could enrich the study of ecological stoichiometry in natural forests, and provide a theoretical basis for the forest restoration and management in the hilly and gully region of Loess plateau.