Effects Of Close-To-Nature Management On Biomass And Species Diversity In Chinese Fir Plantations

Through survey and study on growth and biomass and species diversity of Chinese fir plantation in the south subtropical regions,which was managed close-to-nature eight years later,this paper learn about the evolvement mechanism of the stand growing development and sub-layer structure,and expound the relations between biomass and species diversity by different thinning treatments and interplanting broad-leaved trees.The results are as following:①Thinning can improve DBH and tree height growth of fir in the transfor-stand.The average DBH of fir has reached (22.97±0.57) cm by high intensity,while the average height is (16.40±0.62) m.In moderate and light intensities stands,the average DBH are (19.83±0.76) cm and (18.20±0.70) cm respectively,the average height are (14.80±1.56) m and (14.63±0.57) m.The average DBH of comparison is (18.75±0.33) cm,but its average height, which has reach (17.57±1.06) m, is higher than other thinning stands.In addition,only heavy thinning can improve individual volume of fir significantly.②Thinning has no significant effect on Castanopsis hystrix, Quercus griffithii、Machilus pingii, and significant between the difference species. however, Mytilaria laosensis should be prioritized that its average DBH which has reach8.83cm is1.80、2.01、2.11times respectively than Castanopsis hystrix、Quercus griffithii、Machilus pingii.③Thinning can promote the natural regeneration significantly.Test have showed that the natural regeneration density in moderate and light and high intensity thinning of Chinese fir plantation are15.72trees/hm2,15.33trees/hm2,10.33trees/hm2respectively, which are significantly higher level than comparison(0.61trees/hm2).The average DBH from4.41cm to4.98cm while the average height from4.84m to5.93m.Both of them increase along with the thinning intensity.④Concerning the average individual tree biomass and the distribution ratio of organs in chinese fir plantation, the moderate and high intensity thinning have the better effect.The individual biomass of average trees described as H (229.21kg/tree)>CK(167.92kg/tree)>M(159.27kg/tree)>L(136.17kg/tree)。 The average individual tree biomass and its distribution ratio have the same order as bole>root>branch>bark>needle.⑤There is significant difference in the biomass of the arborous layer between thinning and control stands,and with the thinning intensity increased the stand biomass decreased.The stand biomass are that H (123.42t/hm2),M (161.29t/hm2),L (214.74t/hm2),CK (262.14t/hm2) respectively.Biomass distribution ratio in organs have an order as bole (50.19%～56.48%)>root (25.08%～25.48%)>branch (8.00%～14.22%)> bark(5.27%～6.06%)>needle (4.27%～5.25%).Thinning improve the biomass of sub-layer and its distribution ratio which from75.57%to77.26%in overground part and from22.89%～25.87%in underground part.The biggest contribution of biomass is Mytilaria laosensis,which the larger intensity the biomass accumulation the favor.There is not significant difference in the biomass of the Understorey,the biomass in an order as the arborous layer>the ground layer>Understorey.⑥The species composition and importance value of chinese fir plantation have some change after close-to-nature management.These are186species which belongs to76families and143categorie in all treated plot.Fern is rich that consist of17families and23categorie and33species.The abundance index is herbaceous layer> shrub layer>arborous layer>vine laye.With the increase of thinning intensity the important value of fir have a little decreased.The important value of Mytilaria laosensis and Castanopsis hystrix and Quercus griffithii have more than10%.The species which updates to the tree layer include Evodia lepta,Ficus auriculata,Mussaenda philippica,Ficus hirta,Oreocnide obovata.In shrub layer,The species such as Oreocnide obovata, Pilea notata, Evodia lepta,Clerodendrum cyrtophyllum et al,with important value above10%. Meanwhile,the partial sun tree species with Mallotus repandus,Mallotus philippensis, Macaranga denticulata et.al also grow. Piper mutabile, Trachelospermum jasminoides, Dioscorea fordii,Mussaenda pubescens,Piper nigrum,Ficus sarmentosa play a major role in vine laye while Allantodia virescens,Cibotium barometz,Angiopteris fokiensis Pteris semipinnata,Pteris setuloso-costulata,Pronephrium triphyllum in herbaceous layer.⑦Close-to-nature management promote species diversity to a better development.Compare to comparison,the Gleason species richness of tree layer,Shannon-Wiener index,Simpson index and Pielou index have a significant differences after thinning. But there is no significant difference between thinning intensity.The thinning (74%) stand species richness was19.67,moderate thinning was17.67which was the weakest,reach24.00. The Comparison was only4.33.Close-to-nature management has a little effect on Gleason species richness of understory shrub and herb layers,Shannon-Wiener index,Simpson index and Pielou index.This is consistent with the law of Close-to-nature management.