抚育间伐对秦岭南坡油松中龄林生长的影响

Thinning effects on growth of Pinus tabulaeformis middle-age forest on southern slope of Qinling Mountains

在陕西省宁陕县境内的平河梁自然保护区内油松典型分布地段,按不同立地条件、不同抚育间伐强度设置油松中龄林研究样地48块,对不同抚育间伐强度处理的单株木和林分平均胸径的生长以及林分生产力的变化进行测定。研究结果表明:在不同立地条件下抚育间伐后林木胸径生长量均随径级的增大而增加,较小的林木在间伐强度为25%的林分中胸径生长量最大,较大的林木在间伐强度为15%的林分中胸径生长量最大;在不同立地条件下抚育间伐均能在一定程度上提高林分平均胸径的生长量,间伐强度为15%的林分平均胸径生长量均最高;间伐强度为15%在不同立地条件下均能显著提高乔木层的生产力,间伐强度为25%能够显著提高高海拔阳坡乔木层生产力,间伐强度为5%能显著提高低海拔阳坡和阴坡乔木层生产力;不同立地条件下抚育间伐对乔木层生产力的促进作用存在差异,但在抚育间伐后3 a的较短时期内这些差异并不显著;在不同的立地条件下均以强度为15%的间伐对秦岭南坡油松中龄林的生长最为有利,在适宜的强度范围内,高海拔阳坡可采取较大的间伐强度,而低海拔阴坡则应该采取较小的间伐强度。

In order to research thinning effects of different intensity on growth Pinus tabulaeformis middle-age forest, explore the suitable thinning intensity of it on the southern slope of the Qinling Mountains. 48 experimental plots were established at different site conditions in Pinus tabulaeformis middle aged stands on the southern slope of the Qinling Mountains. The experimental plots were investigated 3 years after thinned from below with different intensity. The thinning intensity were grouped according to the percentage of removed trees volume, i.e. CK（no thinning was conducted）, 5%（T5）, 15%（T15）, 25%（T25）. The effects of thinning on growth of diameter at breast height（DBH） of residual trees, stand average breast diameter and net primary productivity（NPP） of tree layer in unit area on different site conditions were analyzed. The results showed that with the increase of residual trees size the growth of DBH increased, little trees grew fastest in T25 thinned stands but big trees grew fastest in T15 thinned stands. All thinning intensity significantly improved stand average DBH growth and T15 thinned stands was the best on all site conditions. T15 thinning improved NPP of tree layer significantly on all site conditions, T25 thinning improved NPP of tree layer significantly in high elevation-sunny slop stands, T5 thinning improved NPP of tree layer significantly in low elevation-sunny slope and low elevation-shady slope stands. Thinning can improve the growth of DBH and biomass of middle-age Pinus tabulaeformis forest on the southern slope of the Qinling Mountains. Thinning intensity about 15% could be the best. The thinning intensity may be heavily in high elevation-sunny slope stands and lightly in low elevation-shady slop stands.