| Pinus massoniana is an important timber tree species and the pioneer tree species on afforestation of barren hills in southern China, it has great significance to the ecological management and the ecological service function. But the P. massoniana plantation area is large and it is mainly even-aged pure forest, so its fragile ecological system and poor ecological service function can’t meet the needs of the multi-objective forestry management. To explore and research its approach for near-nature transformation become a new task of forestry development. This research took P. massoniana plantation as object that planted in Experimental Center of Tropical Forestry of Chinese Academy of Forestry at1993, set up12permanent sample plots(each area is600m2) after thinning under4different intensities(20%,30%,40%,50%), then interplanted3fine native hardwood tree species which are Mytilaria laosensis, Castanopsis hystrix and Machilus pingii respectively at the density of120plants/hm2, set up3control sample plots(with no-thinning) at the same time. Investigated the community ecology and measured the biomass in each permanent sample plot on2013, research the influence on species diversity and biomass of P. massoniana plantation under different thinning treatments and interplanting native hardwood tree species. The results are as following:(1) There was different influence on species diversity of each communitie layer under different thinning intensities treatments. There was significant difference on Species Richness and Diversity Index of tree layer under different thinning intensities treatments. Thinning increase the Species Richness, Margalef Index(D’), Sinpson Index(D), Shannon-Wiener Index(H’) and Peiluo Index(Jsw) of tree layer significantly. There was no significant influence on Species Richness and Diversity Index of shrub layer and herb layer under thinning treatment. This paper, relatively high intensities thinning can increase the species diversity of tree layer significantly, has a certain role in promoting the species diversity of shrub layer, but didn’t alter the species diversity of herb layer significantly.(2) There was different influence on the growth at height and DBH of interplanting tree species under different thinning intensities treatments. The height increment rank is:M. laosensis(9.23±0.26m)> C. hystrix(5.13±0.26m)> M. pingii(4.89±0.26m); The DBH rank respectively is:M. laosensis(8.16±0.33cm)> M. pingii (3.85±0.33cm)> C. hystrix(3.73±0.33cm). Among the interplanting tree species, with the increase of thinning intensities, there was significant difference on the height and DBH of M. laosensis compare with C. hystrix and M. pingii, but no significant difference between C. hystrix and M. pingii. The maximum of height and DBH of M. laosensis all were found in the forest stand under50%thinning intensity, and the maximum of height and DBH of C. hystrix and M. pingii all were found in the forest stand under40%thinning intensity. Therefore, M. laosensis is suitable for being interplanted in the forest stand under higher thinning intensities, and the C. hystrix and M. pingii are more suitable for the lower one.(3) There was different influence on the growth at height of natural regeneration trees under different thinning intensities treatments. Compare with the control forest stand, the height of natural regeneration trees under20%,30%,40%,50%thinning intensity respectively increase53.11%,41.05%,39.20%and47.96%. After low density thinning treatment, the crown canopy close again through8years of recovery. This would had a negative effect on natural regeneration trees. Therefore, in order to promote the growth of natural regeneration trees, accelerate the formation of uneven-aged of mixed needle-coniferous forest, there should be a new round of thinning to the forest stand.(4) The effect of thinning on individual biomass and community biomass of P. massoniana is different. In this paper, the biomass of average tree in different thinning intensity is50%thinning(486.77kg)>40%thinning(413.01kg)>30%thinning(302.36kg)> control treatment(205.11kg)>20%thinning(198.82kg) in turn. The average biomass of individuals increase with the enhance of thinning intensity, and improve significantly. On the contrary, the community biomass is control treatment(267.21t/hm2)>30%thinning(191.67t/hm2)>20%thinning(178.01t/hm2)>40%thinning (159.49t/hm2)>50%thinning(125.66t/hm2) in turn. Total biomass of P. massoniana plantation decrease with the enhance of thinning intensity, and significantly reduce.(5) After8years of near-nature transformation in P. massoniana plantation, the species and individuals of tree layer improve significantly at processing of natural regeneration under different thinning intensities. In the600m2of sample plot, the average species of tree layer increase from (4.00±0.58) kinds of species in control stand to (12.67±1.77～21.00±1.73) kinds of species in thinning stand, the individuals increase from (5.00±1.16) plants of control stand to (69.33±11.35～102.67±9.56) plants of thinning stand. The importance values of P. massoniana decreases with the thinning intensity increasing, dropped from242.86of control stand to97.94of50%thinning stand, the importance values of other trees increase from57.14of control stand to202.06of50%thinning stand. After8years of transformation, some dominant species and co-dominant species from the local natural forest appear in tree layer, such as Mussaenda esquirolii, Mussaenda philippica, Canarium pimela, Canarium album, Choerospondias axillaris, Liquidambar formosana, Bischofia javanica and Cyclobalanopsis glauca. It’s worth pointing out that the3introduced native broadleaf trees(M.laosensis, C. hystrix, M. pingii) had been entered into sub-layer, M. laosensis had even become subdominant species of tree layer, the natural regeneration plants of C. hystrix, M. pingii have also appeared in tree layer. Consequently, this paper holds that even-aged pure forest of P. massoniana plantation completely could transform into uneven-aged of mixed needle-coniferous forest by thinning and interplanting native broad-leaved species. |
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