C,N And P Ecological Stoichiometric Ratios Among Leaves-Litter-Soil Systems In Secondary Forest Of Different Degraded Stage In Middle Subtropics

The restoration and reconstruction of degraded secondary forest ecosystems has become the theme of today's subtropical regional development.In this study,the secondary forest of the different degraded stage of Xiangdong hills(Loropetalum chinensis-Vaccinium bracteatum Thunb-Rhododendron mariesii Hemsl.et Wils shrubs(LVR),Loropetalum chinensis-Cunninghamia lanceolata-Quercus fabri Hance shrubbery(LCQ),Pinus massoniana Lamb-Lithocarpus glaber-Loropetalum chinensis coniferous and broad-leaved mixed forest(PLL),Lithocarpus glaber-Adinandra millettii-Cyclobalanopsis glauca(Thunberg)Oersted evergreen broad-leaved forest(LAG)),The contents of C,N and P in the leaves,litter layers,soil layers and their stoichiometric characteristics of the main plantations in different degraded stages were studied.The limiting factors of the secondary forest in the subtropical degraded stage were studied.Change characteristics of contents of C,N,P in soil and the effect of degeneration of secondary forest on soil fertility in order to clarify the interaction and feedback mechanism between plant and soil,and to provide scientific basis for the restoration and reconstruction of scientific and effective secondary forest.The main conclusions are as follows:(1)The average C content of the main plant leaves in the secondary degraded forest was 368.75-438.25 g/kg,the average N content was 11.09-17.19 g/kg,the average P content was 0.46-0.77 g/kg,and the secondary forest degradation was the main The contents of C,N and P in the leaves of the main plants were decreased with the secondary forest degradation.The C/N ratio,C/P ratio,N/P ratio was 21.94-41.24,596.22-1172.86,21.97-28.32,respectively.With the increase of secondary forest degradation,the growth of plants in the secondary degraded forest in the subtropical region was mainly affected by P element.N content and P content had a significant linear positive correlation,C/N ratio,C/P ratio and plant leaf C,N,P content was extremely significant correlation,and N/P ratio and P content was very significant Negative correlation,N,P has a high degree of dependence and coupling,C/N ratio,C/P ratio was significantly controlled by C,N,P content,N/P ratio is mainly controlled by the P content.The contents of C,N and P in the leaves of the same plant were different in the secondary forest,and the C content,C/N ratio and C/P ratio of the same plant leaves were significantly different from those in the secondary forest Showing a gradual increase in the trend,N/P than there is no obvious changes in the law.(2)The contents of C,N and P in the litter layer of secondary forest were 227.20-424.09 g/kg,8.04-11.28 g/kg,and 0.26-0.38 g/kg,respectively.The contents of C,N and P were higher on the descending trend,and the performance of the decomposition layer>semi-decomposed layer>Has been broken down.The C/N ratio,C/P ratio and N/P ratio of the litter layer and different decomposition layers were significantly affected by secondary forest degradation,and the mixed forest of Pinus massoniana and Quercus mongolica-The C/N ratio and C/P ratio of litter layer were significantly higher than that of Quercus mongolica-red light ratio-Cyclobalanopsis glauca evergreen broad-leaved forest,Cunninghamia lanceolata-Cunninghamia lanceolata and Quercus variabilis.With litter decomposition,C/N,C/P ratio decreased,N/P ratio did not change significantly.The C/N ratio and the C/P ratio were significantly correlated with the contents of C,N and P in the litter layer,and the N/P was only negatively correlated with P content.There was no significant correlation between the content of C in plant leaves and the content of C in litter layer(P>0.05).The content of N and P in plant leaves was positively correlated with the content of N and P in litter layer(P<0.01)There was no significant correlation between C/N ratio and C/N ratio of litter layer,C/P ratio of plant leaf and C/P ratio of litter layer(P>0.05),plant N/P ratio and litter There was a significant linear positive correlation between the N/P ratio(P<0.01).(3)Soil organic C,total N and total P contents decreased significantly with the secondary forest degradation.The contents of organic C,total N and total P in soils of four different degraded stages decreased with the increase of soil depth.The C/N ratio of the secondary forest was higher than that of the C/N ratio(11.9)and the global C/N ratio(13.33),respectively.The C/P ratio was 88.58,the soil C/P ratio is 105 and the N/P ratio is 5.48,which is larger than the average N/P ratio(5.2)in China.It is shown that the soil P element may be an important factor in the secondary forest soil of the limiting factor.The mean values of C:N:P in secondary forest were higher than those in C:N:P in China(60:5:1).The correlation between soil C/N ratio and soil C content was not significant,and negatively correlated with N,P content,N/P ratio was positively correlated with soil C,N content,and soil P content content was not significant,And C/P ratio and P content was not significant,and C,N content was significantly positive correlation.(4)The contents of C,N and P in the secondary forest were in the order of leaf>litter layer>soil layer,leaf and litter layer,and the contents of C and P were different,Litter layer N content are:LAG>PLL>LCQ>LVR,leaf C content of LVR>PLL>LCQ>LAG,litter layer C content of PLL>LAG>LVR>LCQ.Leaf P content of PLL>LAG>LCQ>LVR,litter layer P content of LAG>LCQ>PLL>LVR.