宁夏六盘山三种针叶林初级净生产力年际变化及其气象因子响应

利用年轮生态学方法和生物量经验方程,在宁夏六盘山研究了华山松天然林及华北落叶松和油松人工林等3种针叶林的年初级净生产力(NPP)及其与气象因子间的关系。研究表明:3种针叶林生物量的年际变化均符合逻辑斯蒂方程,林分的现存生物量(t/hm2)为华北落叶松林最大(141.96),华山松林(130.99)次之,油松林最小(123.29)。3种针叶林NPP存在显著的年际差异和种间差异,林分的NPP(t.hm-.2a-1)为华北落叶松林(6.72)>油松林(5.76)>华山松林(2.66);NPP年际变化在华山松林呈现"快速增加-缓慢增加-缓慢减小"的趋势,而华北落叶松林和油松林为快速上升的趋势。3种针叶林的NPP随年降水量的变化行为不同,华山松林极轻微地增大,华北落叶松林和油松林均是先增加后降低;然而在极端干旱年份或极端湿润年份,3种针叶林的NPP都趋向于相同的较低值,其原因可能分别是水分胁迫和低温胁迫。气象因子对林分NPP的影响具明显的"滞后效应"和种间差异。华山松林NPP与上年11月和当年9、11月的降水量显著负相关;油松林NPP与上年9月及当年4月的降水量显著相关;上年和当年9月的降水量均与华北落叶松林NPP显著正相关。上年6月的温度和当年3与6月的月均温及月均最高温能显著影响3种针叶林的NPP,但存在种间差异,其中华山松林NPP与当年与上年生长季各月的温度均呈不同程度的负相关,而油松林和华北落叶松林则多呈不同程度的正相关。

The interannual variation of net primary productivity of three coniferous forests in Liupan Mountains of Ningxia and its responses to climatic factors

Using dendroecological methods and empirical biomass equations, we calculated the biomass and net primary productivity (NPP) of three coniferous forests (Pinus armandii natural forest, Larix principis-rupprechtii plantation, Pinus tablaeformis plantation) in Liupan Mountains of Ningxia, northwest China. Then we analyzed their relation with climatic factors, including monthly air temperature and precipitation. The results indicated that the interannual variation of biomass (t/hm²) of the three forests studied follows the logistic equation, with the order of L. principis-rupprechtii plantation (141.96) > P. armandii natural forest (130.99) > P. tablaeformis plantation (123.29). The interannual variation of NPP of P. armandii natural forest showed a trend of "fast increase-slow increase-slow decrease"; while the variation of NPP of other two plantations showed a trend of "rapid rising" with some fluctuations. There is a remarkable difference among the NPP (t·hm^-2·a^-1) of the three forests, with the order of L. principis-rupprechtii plantation (6.72)>P.tablaeformis plantation (5.76) > P. armandii natural forest (2.66). With increasing annual precipitation, the NPP varied much differently among the three forests, i.e., the NPP of P. armandii forest increased very slowly, but the NPP of other two plantations firstly increased and then decreased. However, in the driest or the rainfall-richest years, the NPPs of all three forests tended to their same lower values, but probably with different stresses of drought or low temperatur. The NPP response to climatic factors presnted a time lag and acted differently among the three forests. The NPP of P.armandii forest was significantly and negatively correlated with the precipitation in November of previous year and that in November and September of current year; while the NPP of P. tablaeformis plantation was significantly correlated with the precipitation in September of previous year and that in April in current year, and the NPP of L.principis-rupprechtii plantation was significantly and positively correlated with the precipitation in September of both previous and current year. The NPP of all three forests was significantly correlated with the mean temperature and minimum temperature in June and March of current year, and the temperature in June of previous year. However, the NPP response to temperature differently among the three forests, the NPP of P.armandii forest was more or less negatively correlated with the temperature in each month of growing season; while the NPP of P.tablaeformis and L.principis-rupprechtii forests was more or less positively correlated with the temperature in each month of gowth season.