摘要: |
【目的】探究择伐对林分结构的长期影响,为林分科学经营提供理论依据。【方法】以吉林省汪清县金沟岭林场内的20块云冷杉天然针阔混交林固定样地为研究对象,20块样地分为5组,每组分别设置对照(0%)、弱度(20%)、中度(30%)和重度(40%)4种初始择伐强度(按蓄积量计算)。1986年所有样地初次择伐,1992年第3组样地二次择伐,1994年第1和2组样地二次择伐,1997年第4组样地二次择伐,第5组样地未经历二次择伐,共获取初次择伐后8期(1986-2019年)监测数据。采用Weibull分布密度函数拟合林分直径结构,分析2次择伐对林分非空间结构的动态影响;计算林分角尺度、混交度、胸径大小比数及林分空间结构指数(FSSI)、林分空间结构距离(FSSD),分析不同择伐强度下林分空间结构的动态变化。【结果】① 初次择伐后33年(2019年),与期初相比,择伐样地大径级林木增幅大于对照样地,其中中度(30%)和重度(40%)择伐样地大径级林木占比分别增加28和33个百分点,对照样地增加27个百分点。② 1986-2019年,第5组样地Weibull分布曲线最高峰位置对应的胸径值整体随时间增加而增大,由8~10 cm(1986年)增加到18~20 cm(2019年);在相同年份,初始择伐强度越大,曲线最高峰对应的胸径值总体越大。③ Weibull分布曲线显示,1~4组样地二次择伐后,总体上中、小径阶林木株数频率升高,大径阶林木株数频率降低。④ 各样地FSSI随时间增加整体呈上升趋势,二次择伐后FSSI进一步上升,初次择伐后33年间,各样地FSSI由55.813~70.426(1986年)增加到64.211~74.194(2019年)。⑤ 1986-2019年,第5组样地FSSD随时间增加整体呈下降趋势,其中弱度(20%)择伐林分FSSD由57.419降低到49.381,且始终低于其他林分,表明其与其他林分相比拥有更理想的林分空间结构。【结论】通过调控择伐强度可优化调整金沟岭林场云冷杉天然针阔混交林林分结构,择伐强度以20%~30%为宜。 |
关键词: 择伐 林分结构 云冷杉天然林 |
DOI:DOI:10.13207/j.cnki.jnwafu.2024.12.005 |
分类号: |
基金项目:中国地质调查局项目“北京市永定河上游生态涵养区自然资源综合调查评价”(DD20230473) |
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Structural dynamics of natural spruce-fir forests based on selective cutting |
LIU Li1, GUO Weiwei1, LIU Xiaodong1, WANG Ping1, BAI Jie1, ZHAO Enquan2, WEN Hui1, ZHOU Dayou1, HU Xiaosheng1, ZHANG Zhigang3, LI Ming1
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1.Natural Resources Comprehensive in Vestigation and Command Center,China Geological Survey,Beijing 100055,China;2.Langfang Comprehensive Survey Center of Natural Resources,China Geological Survey,Langfang,Hebei 065000,China;3.Geophysical Investigation Center,China Geological Survey,Langfang,Hebei 065000,China
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Abstract: |
【Objective】To provide theoretical basis for the scientific management of stands,this study explored the long-term effects of selective cutting on stand structure.【Method】A total of 20 permanent sample plots of natural spruce-fir mixed coniferous and broad-leaved forest in Jingouling Forest Farm in Wangqing,Jilin were analyzed.The 20 plots were divided into 5 groups and four initial selection intensities of contrast (0%),weak (20%),moderate (30%) and heavy (40%) were set in each group (stock selection cutting).In 1986,all the plots were cut for the first time.In 1992,Group 3 sample plots were cut for the second time.In 1994,Groups 1 and 2 plots were cut for the second time.In 1997,Group 4 sample plots were cut for the second time. Group 5 had no secondary selection.A total of 8 periods (1986-2019) of monitoring data were obtained after the initial selective cutting.Weibull distribution density function was used to fit the stand diameter structure to analyze the dynamic effects of two selective cuts on non-spatial structure of stands.The stand uniform angle index,mingling degree,neighborhood comparison of diameter breast height (DBH),forest spatial structure index (FSSI) and forest spatial structure distance (FSSD) were calculated to analyze the dynamic changes of stand spatial structure under different selection intensities.【Result】① In 2019,33 years after initial selective cutting,the growth rate of large-diameter trees in selected plots was greater than that in contrast plots.The proportions of large-diameter trees in moderate (30%) and heavy (40%) selection plots were increased by 28% and 33%,respectively,where that of contrast plots was increased by 27%.② From 1986 to 2019,the DBH corresponding to the highest peak of Weibull distribution curve in Group 5 continued to increase from 8-10 cm (1986) to 18-20 cm (2019) with time.In the same year,larger initial cutting intensities had larger DBH corresponding to curve peak.③ After secondary selective cutting of plots from Groups 1 to 4,Weibull distribution curve showed that the frequency of middle and small diameter classes increased as a whole,while the frequency of large diameter classes decreased.④ The FSSI in each plot showed an increasing trend with the increase of time,increasing further after secondary selection cutting.Thirty-three years after initial selective cutting,FSSI in each plot increased from 55.813-70.426 (1986) to 64.211-74.194 (2019).⑤ From 1986 to 2019,the FSSD of Group 5 decreased with time. FSSD of weak (20%) group decreased from 57.419 to 49.381,and it was always lower than other stands and had more ideal stand spatial structure than other stands.【Conclusion】The stand structure of natural spruce-fir mixed coniferous and broad-leaved forest in Jingouling Forest Farm can be optimized by adjusting selective cutting intensity,and the appropriate intensity of selective cutting is 20%-30%. |
Key words: selective cutting stand structure natural spruce-fir forest |