间伐和施肥对杉木成熟林生长和材种结构的影响

  目的  分析不同间伐保留密度及不同氮、磷肥施用量对杉木Cunninghamia lanceolata成熟林生长和材种结构的影响，为高效培育大径材杉木提供理论依据。  方法  选择27年生立地指数大于22的杉木人工林，采用正交试验设置9块标准地，间伐保留密度设为300、600和825株·hm?2，氮肥施用量设为0、100、200 g·株?1，磷肥施用量设为0、250、500 g·株?1。  结果  间伐保留密度过大会限制杉木成熟林胸径增加，间伐保留密度过小会降低林分蓄积量，间伐和施肥均能有效促进单株材积增长，较高氮肥施用量能够促进杉木胸径、树高和平均单株材积的生长，氮、磷肥混合施用能够更有效地增加林分蓄积量的积累。间伐保留密度及氮、磷肥施用量3个因素均显著影响杉木成熟林大径材出材量 (P＜0.05)，间伐保留密度和磷肥施用量对杉木成熟林大径材出材率具有显著影响 (P＜0.05)，而氮肥施用量的影响较小。在立地指数为22条件下，能够使杉木成熟林大径材出材量和出材率最高的处理为间伐保留密度825株·hm?2、氮肥施用量200 g·株?1、磷肥施用量250 g·株?1。  结论  高立地指数下，杉木成熟林大径材培育过程中，保留适宜的间伐密度，并增施氮肥和磷肥，能有效促进杉木大径材出材率和出材量。图6表4参27

Effects of thinning and fertilization on growth and timber structure of mature Chinese fir forest

  Objective  This study aims to investigate the effects of different thinning retention density and different proportion of N and P fertilizer application on the growth and timber structure of mature Chinese fir forest.  Method  The 27 year-old Chinese fir plantation with a site index greater than 22 was selected, and 9 standard plots were set up by orthogonal experimental design. The thinning retention densities were 300, 600 and 825 plants·hm?2. The application rates of N fertilizer were 0, 100 and 200 g·plant?1, and the application rates of P fertilizer were 0, 250 and 500 g·plant?1.   Result  Excessive thinning retention density limited the diameter at breast height (DBH) increase of mature Chinese fir. Too small thinning retention density reduced the stand stock. Thinning and fertilization could effectively promote the growth of individual tree volume. Higher N application rate could promote the growth of DBH, tree height and average individual tree volume of Chinese fir, and the mixed application of N and P could increase the accumulation of stand volume more effectively. The thinning retention density, the application rate of N and P fertilizer all significantly affected the yield of large-diameter timber of mature Chinese fir forest (P＜0.05). The thinning retention density and the application rate of P fertilizer had a significant impact on the yield of large-diameter timber of mature Chinese fir forest (P＜0.05), while the application rate of N fertilizer had little impact. Under the site index of 22, the combination that produced the maximum yield and outturn rate of large-diameter timber of mature Chinese fir forest was thinning retention density of 825 plants·hm?2, N fertilizer application rate of 200 g·plant?1 and P fertilizer application rate of 250 g·plant?1.   Conclusion  Under the condition of high site index, the outturn and yield of large-diameter timber of Chinese fir could be effectively promoted by keeping appropriate thinning density and increasing N and P fertilizer application in the cultivation process of mature Chinese fir forest. [Ch, 6 fig. 4 tab. 27 ref.]