为揭示我国西北山地温带针叶林降水利用效率(RUE)的年际变化及其对气象因子响应的差异性, 在宁夏六盘山研究了华山松(Pinus armandii)天然林、华北落叶松(Larix principis-rupprechtii)和油松(Pinus tabulaeformis)人工林的RUE及其与气象因子间的关系。结果表明: 3种针叶林RUE及其年际变化存在种间差异。生产力高的林分(两种人工林)具有更高的RUE, 华北落叶松林年平均生产力和RUE分别为6.72 t·hm ^-2·a ^-1和1.12 g·m ^-2·mm ^-1, 是华山松林的2.53倍和2.49倍; 油松林分别为5.76 t·hm ^-2·a ^-1和0.97 g·m ^-2·mm ^-1, 也远高于华山松林。在林龄小于32年时, 3种林分RUE总体表现出随林龄而增加的趋势, 但存在着种间差异, 其中两种人工林增速更快; 华山松林在林龄为32-45年时, RUE呈波动变化, 之后呈下降趋势。RUE的年际变化趋势与林分生产力相似, 即在生产力较高的年份RUE也较高。气象因子对RUE的影响有明显的“滞后效应”和种间差异。RUE受年降水量及其年内分配格局的影响。随年降水量增加, 华山松林RUE逐渐减小, 而华北落叶松和油松林RUE均先升高后降低; 在干旱年份3种针叶林RUE趋向于相近的值(不一定是最大值), 而在湿润年份趋向于相同的最小值; 除受当年春季(4月)或秋季(9-11月)的降水量影响外, 3种针叶林的RUE还受上一年夏秋(8-9月)的降水量影响。3种针叶林的RUE都极显著地受到上年6月、当年3与6月气温的影响; 此外, 华山松林RUE与当年2月气温负相关, 两人工林均受到当年4、5月气温的显著促进作用。

Aims Rain-use efficiency (RUE), the ratio of vegetation productivity to annual precipitation, is an important measure of water use and a key determinant of the net primary production (NPP) of forest ecosystems. Our objective is to investigate the interannual variation of RUE of three conifer forests and their response to the variation of meteorological factors.
Methods We calculated the biomass and NPP of three coniferous forests (Pinus armandii natural forest, Larix principis-rupprechtii plantation and Pinus tablaeformis plantation) in Liupan Mountains of Ningxia, China by dendroecological methods, empirical biomass equations and collected meteorological data including monthly air temperature, humidity and precipitation. Then we calculated the RUE of these forests and analyzed their correlation with meteorological factors.
Important finding The NPP and RUE of L. principis-rupprechtii plantation, having the values of 6.72 t·hm ^-2·a ^-1and 1.12 g·m ^-2·mm ^-1, respectively, were 1.53 and 1.49 times higher than the Pinus armandii natural forest and 0.17 and 0.15 times higher than the P. tablaeformis plantation, respectively. The RUE increased with forest age when it was younger than 32 years, but RUE varied among species. The interannual variation of RUE of P. armandii natural forest was relatively stable when aged 32-45 years and then decreased with age. With increasing annual precipitation, the RUE of P. armandii natural forest decreased, but the RUE of the two plantations increased at first and then decreased. The RUE of all three forests tended to be similar in the driest years and tended to have the same minimum value in the wettest years. RUE, which was affected by meteorological factors of the previous year, responded to meteorological factors differently among tree species, but it was mainly influenced by meteorological factors of the current year and its annual variation pattern. The RUE of P. armandii natural forest was significantly negatively correlated with precipitation in August of the previous year and that in September, October and November of the current year. The RUE of the two plantations was significantly correlated with precipitation in September of the previous year and that in April of the current year and, in the case of the L. principis-rupprechtii plantation, to precipitation in September of the current year. The RUE of all three tree species was significantly correlated with the mean air temperature in June and March of the current year and that in June of the previous year. In addition, the RUE of P. armandii natural forest was significantly correlated with air temperature in February of the previous year, and the RUE of the two plantations was significantly positively correlated with air temperature in April and May of the current year.