北京西山侧柏林可燃物调控措施的影响评价

Impact assessment of fuel regulation measures in Platycladus orientalis forest in Western Hills of Beijing

【目的】针对北京西山侧柏Platycladus orientalis林可燃物分布特征,实施不同强度可燃物调控措施,并依据调控后林下植被的生物多样性和光合特性的变化,对可燃物调控措施的影响进行评价。【方法】在北京西山试验林场,选取华北地区针叶林—侧柏林,通过对林分可燃物分布特征的调查和分析,制定以修枝、割灌为主的调控措施,分别为未调控(ck)、修枝高度2.5 m并适当清理地表凋落物(P1)、修枝高度3.0 m和割灌并适当清理地表凋落物(P2)、修枝高度3.5 m和割灌并适当清理地表凋落物(P3),每个处理设置3块20 m×20 m的标准地,对比调控与未调控林分的林下植物多样性和优势灌木的光合特性变化。【结果】不同强度可燃物调控措施均改变了林下植被的生物多样性,其中P2调控下灌木层和草本层的物种优势度和多样性及灌木层的物种均匀度显著高于对照;调控林分的林下优势灌木(主要是孩儿拳头Grewia biloba var.parviflora和构树Broussonetia papyrifera)的最大净光合速率、光饱和点、光补偿点、暗呼吸速率均比对照增加,而表观量子效率则减小,其中P2调控措施下的林下植物光合产物的积累更明显。【结论】调控措施改变了林分结构,使林下光照强度增加。不同调控强度对植被生物多样性和光合特性的影响存在差异,P2调控最有利于研究区域的林分恢复。

[Objective]Based on the fuel distribution characteristics of the Platycladus orientalis forest in Western Hills of Beijing,fuel regulation measures of different intensities were implemented,and effects of the fuel regulation measures were evaluated according to the biodiversity and photosynthetic characteristics of understory vegetation.[Method]P.orientalis,a typical coniferous tree species in North China was selected as the research object.By investigating and analyzing distribution characteristics of P.orientalis forest fuel,regulation measures focusing on pruning,cutting and irrigation were formulated,including:unregulated stands(ck),pruning height 2.5 m and cleaning the surface litter appropriately(P1),pruning height 3.0 m and cutting shrubs and cleaning the surface litter appropriately(P2),pruning height 3.5 m and cutting shrubs and cleaning the surface litter appropriately(P3).Three sample plots of 20 m×20 m were established for each treatment,and changes of plant diversity and photosynthesis attributes of dominant shrubs were compared between regulated and unregulated stands.[Result]The biodiversity of understory vegetation was altered after different fuel managements,among which the species dominance(D)and diversity(H)of shrub layer and grass layer and the species evenness(J)of shrub layer after P2 management were significantly higher than those of ck.Compared with ck,the maximum net photosynthetic rate,light saturation point,light compensation point,dark respiration rate of the understory vegetation(Grewia biloba var.parviflora and Broussonetia papyrifera)all increased,while the apparent quantum efficiency decresed after P2 management.We observed that the accumulation of understory vegetation photosynthetic products was more obvious with P2 management.[Conclusion]The implementation of regulation measures changed the forest structure and increased the light intensity.The effects of different regulation intensity on biodiversity and photosynthetic characteristics of understory vegetation were different.P2 management was most conducive to stand recovery in the study area.