| Phoebe zhennan S.Lee,also known as Phoebe zhennan,is a large evergreen tree belonging to the genus Phoebe of Lauraceae.Phoebe zhennan S.Lee is a national second-class key protection tree species.Phoebe zhennan S.Lee,China ’s unique precious timber species,are mainly distributed in Sichuan,Chongqing,Guizhou,Hubei and other places in China.It is the main species of evergreen broad-leaved forests.Phoebe zhennan S.Lee,known as ’ the head of white wood ’ and ’king of cork ’,is historically used by royal nobility.However,due to the slow natural growth of Phoebe zhennan,coupled with the abuse of its timber in past dynasties and the neglect of its cultivation,there are fewer natural resources of Phoebe zhennan in China and much less natural forests with area distribution.With the increasing material living standards of people,the demand for Phoebe zhennan timber has increased sharply,and the contradiction between supply and demand has being intensified.Accelerating the cultivation of Phoebe zhennan artificial timber forest is the main way to solve this issue.Currently,the artificial afforestation area of Phoebe zhennan is massive,but the cultivation status of artificial forest is chaotic,and it is difficult to cultivate fast-growing and high-yield timber forest suitable for social needs.At present,China has carried out large-scale afforestation activities of Phoebe zhennan.Our previous survey provide that site conditions(especially soil acid-base environment)and forest vegetation are critical factors to restrict the growth of Phoebe zhennan plantation.However,forest vegetation and acid-base environment affect the growth of Phoebe zhennan stand and soil characteristics is unclear,and the relevant research theory is still lacking.Therefore,this study took Phoebe zhennan plantation under different soil acid-base environments in the state-owned forest farm as the research object in Chongqing,Yongchuan,discussed that how forest vegetation removal or retention measure sand forest acidbase environment effect the growth and soil characteristics of Phoebe zhennan forest,and then determined the key soil factors affecting the stand growth of Phoebe zhennan,revealed the correlation between forest vegetation community pattern and soil environmental factors of Phoebe zhennan plantation,solved the key problems hindering the efficient cultivation of Phoebe zhennan plantation,and provided certain theoretical basis for the selection of afforestation land and forest vegetation management in Phoebe zhennan production practice.The main results are as follows:(1)Effects of forest vegetation and soil p H on the growth of Phoebe zhennan: The growth of Phoebe zhennan was significantly affected by forest vegetation,but there were differences under different soil p H environments.Removal of forest vegetation significantly increased the growth of tree height,canopy width and leaf area(P<0.05),by 15.41%,18.74% and 48.08%,respectively,in acidic soil,but the growth of ground diameter was not significant(P>0.05).Average tree height,ground diameter,canopy width and leaf area were significantly increased by 10.09%,10.28%,8.09%and 38.99%,respectively,under neutral soil condition.The canopy width and leaf area were increased by 18.57% and 62.81%(P<0.05)in alkaline soil,and the average tree height and ground diameter were higher than those of CK,but there was no significant difference between them(P>0.05).Under the removal of forest vegetation,the leaf area of Phoebe zhennan in alkaline soil was significantly higher than that in neutral soil and acid soil(P<0.05),and the growth of tree height was alkaline soil > neutral soil > acid soil.In the removal of forest vegetation measures,ground diameter and crown growth showed neutral soil > acid soil > alkaline soil;In undergrowth vegetation conservation,ground diameter growth showed neutral soil > alkaline soil > acid soil,crown growth showed neutral soil > acid soil > alkaline soil.(2)Effects of forest vegetation and soil p H on photosynthetic characteristics of Phoebe zhennan: The photosynthetic characteristics of Phoebe zhennan were significantly effected by forest vegetation,but there were differences under different soil p H environments.In acidic soil environment,the removal of forest vegetation significantly increased the contents of chlorophyll a(Chla),chlorophyll b(Chlb),carotenoid(Car)and net photosynthetic rate(Pn)(P<0.05).In neutral soil environment,the removal of forest vegetation significantly increased Chla,Chlb and stomatal conductance(Gs)(P<0.05).In alkaline soil environment,the removal of photosynthetic pigments from forest vegetation of Phoebe zhennan was less affected by forest vegetation,and the removal of forest vegetation significantly increased Pn,Tr and Gs(P<0.05).The net photosynthetic rate(Pn)was alkaline soil > neutral soil > acid soil,and the transpiration rate(Tr)and stomatal conductance(Gs)were neutral soil > alkaline soil > acid soil,with significant differences among the three(P<0.05).(3)Effects of forest vegetation and soil p H on soil properties of Phoebe zhennan forest land :soil properties of Phoebe zhennan forest land were significantly affected by forest vegetation,but the effects of forest vegetation on soil properties of forest land were different under different soil p H environments.In acidic soil environment,the removal of forest vegetation significantly increased soil bulk density(BD),organic matter(OM),alkali-hydrolyzable nitrogen(AN)content and acid phosphatase(ACP),catalase(CAT),invertase(SC)and urease(UE)activity(P<0.05),but significantly increased OM,total nitrogen(TN),TK,AN,AK content and ACP,UE activity(P<0.05),and significantly decreased OP content and CAT and SC activity(P<0.05).In alkaline soil environment,removal of forest vegetation significantly increased OM,TN,TP,AN,OP,AK content and CAT,SC,UE activity,and significantly decreased NCO and ACP(P<0.05).Soil acidbase environment had significant influence on soil characteristics of Phoebe zhennan forest land.TPO,CPO,NCO,FCA,CAT,SC,UE,OM and soil nitrogen,phosphorus and potassium contents were alkaline soil > neutral soil > acid soil,and the difference was significant(P<0.05).The main soil environmental factors affecting the growth of Phoebe zhennan were ACP,TK and CPO.The main soil environmental factor affecting the photosynthetic characteristics of Phoebe zhennan was soil nutrients.(4)Correlation between forest vegetation diversity and soil environment of Phoebe zhennan :Forest vegetation diversity is closely related to soil acid-base environmentt.In acidic soil environment,the number of forest vegetation groups(G)was significantly negatively correlated with soil non-capillary porosity(APO)(P<0.05).Shannon-Wiener diversity index(SH)was significantly negatively correlated with available phosphorus(OP),saturated water content(SCA)and available potassium(AK);simpson dominance index(SI)was significantly negatively correlated with field capacity(FCA)and capillary porosity(CPO)(P<0.05).In neutral soil environment,G and Richness richness index(R)were significantly negatively correlated with total potassium(TK)(P<0.05).SH was significantly negatively correlated with sucrase(SC)and urease(UE)(P<0.05).SI was significantly negatively correlated with bulk density(BD)and total porosity(TPO)(P<0.05).In alkaline soil environment,N was significantly positively correlated with catalase(CAT),SC and CPO(P<0.05).R was negatively correlated with natural moisture content(NCO)(P<0.05).SH and CPO were significantly negative(P<0.05);SI was significantly positively correlated with OP,and SI was significantly negatively correlated with APO(P<0.05). |
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