| A series of questions were caused by degradation of karat ecological environment and rocky desertification such as the loss of biodiversity.Now one of hot questions is exploring the mechanism of formation and maintenance of biodiversity from the studies soil environment in ecological research.The karst ecosystem is special and complex.And it have many hypotheses about the mechanism of biodiversity formation,however It is no conclusiones about that these reasons were unclear about the species diversity pattern and maintenance.In this paper,we were used the research methods of“space series instead of time series”with different times“soil-plant”relationship as the main line,and combined with horizontal and vertical characteristics of the phytocoenosium as the auxiliary study.And then we used soil moisture and nutrients as the entry point for the study to revealed the maintenance mechanism from the perspective of the correlation between species diversity and soil habitat in the restoration process of degraded vegetation in Maolan karst forest through these series of analysis of succession and horizontal and vertical characteristics of the forest phytocoenosium（below,three sequences for short）.Total number of phytocoenosium and analysis of soil moisture,nutrient and of which coefficient variation in ecological niches to know the habitat pattern of soil moisture and nutrients.The study explain the characteristics of species diversity and its variation trend and found out dominant factors.By these analysis of measurement and correlation of multiple indicators,which include species diversity of forest community,arbor,shrub,herb layers.And in combination with the correlate dominant plant nutrients with soil water and nutrients to explored the maintenance mechanism of species diversity in karst forest.These main results were summarized as follows.（1）The pattern of soil moisture:Temporary drought of soil moisture occurs frequently and contents are highly heterogeneous in“three sequences”of karst forest.The general trend of soil moisture content in ecological niches are stone gutter（SG）>soil surface（TM）>stone surface（SM）.But the trend is different due to these differences of small terrain,slope position,aspect and forest coverage.In the primary of vegetation succession,there are small different of soil moisture content in various ecological niches.But with the restoration of degraded vegetation,soil moisture content will increasing,this difference in soil moisture will also increased in below ecological niches:stone gutter（SG）,soil surface（TM）,stone surface（SM）.The best time of soil water holding capacity is climax forest phytocoenosium stage.From the perspective of horizontal and vertical distribution of soil moisture in the niche and the climax forest phytocoenosium,the spatial variability is very large.（2）The pattern of soil nutrient:soil nutrients are also highly heterogeneous in“three sequences”of karst forest.The general trend of soil contains content of C,N（all N and alkaline N）,P（all P and effective P）is stone surface（SM）>stone gutter（SG）>soil surface（TM）.But the stone surface（SM）just has few soil,weak capacity of soil nutrient.The trend is also highly volatile and different because of the various kind of minor irreqularities,slope position,aspect and forest coverage rate in karst area.With the restoration process of degraded vegetation,there are increase which of the contents of soil C,N and P,and then the soil nutrient status improved,the climax forest phytocoenosium stage achieve the best level.With the process of vegetation restoration,These changes decrease about the proportions of soil C/N,C/P and C/N/P and showed a downtrend,and the N/P relative change ratio become relatively flat.From the perspective of horizontal and vertical distribution of soil nutrients in the climax forest and ecological niche,the spatial variability is large.Compared with forest soil with other surrounding area,the content of soil organic matter,total N and alkaline solution N is higher in the study area.it is lower for total P and effective P in the preliminary and middle stage of succession,after it will improve in the later stage,however,sometime lower or slightly higher.The ratio of C/N is close to other surrounding forest soil,and these ratios of C/P,N/P and C/N/P are slightly higher than other surrounding areas.（3）The diversity pattern of soil nutrient and water correlation and their combinations:There are different degrees of correlation of“three sequences”in the forest phytocoenosium and soil nutrient pattern in the ecological niches and water pattern in the study areas.Especially in these testes for forest phytocoenosium of degraded vegetation restoration process and the 3 types of ecological niches soils with the stone gutter（SG）,stone surface（SM）and soil surface（TM）,there are relevant tests of 95.00%for correlation in the five indicators of C,N（all N and alkaline solution N）,P（all P and effective P）soil moisture content and reached a significant level with 65.00%.It was very complex in highly heterogeneous soil nutrients and moisture,further forming different combinations of water and nutrient gradients,of which them add the diversity and complexity of soil habitat patterns in karst forests.（4）The pattern of plant species diversity:The plant species diversity of forest phytocoenosium were riches and special in the study area.On matter what it are high that its species richness,diversity,3 types of ecological niches,tree layers,shrub layers and herb layers in the forest phytocoenosium,and the diversity index is complex and variable in“three sequences”of forest phytocoenosium.Among them,the species richness index(dma)showed an increasing trend with the succession process of degraded vegetation.the vertical distribution of species richness index(dma)is decreased with altitude.it was no significant difference for that the species dominance index（D）,diversity index（H’）and uniformity index（Je）in each sequence.But,the fluctuation and heterogeneity is large or high.There is higher for The species substitution rate of“three sequences”of succession,horizontal and vertical sequences which is the Whittaker index（βw）and the Cody index（βc）.There are no identical plots and niches types even if in the 22 adjacent apical horizontal transects at the same altitude and with 660m altitude of climax forest phytocoenosium.（5）Correlation between plant species diversity and soil moisture and nutrients:Canonical Correlation Analysis（CCA）showed,the correlation is highly significant with species diversity,soil water and nutrients in karst forest phytocoenosium in the study area.The first typical correlation coefficient reached a significant level（correlation coefficientλ1=0.9556）with between the indicators of species diversity and the linear combination of soil moisture and nutrient indicators.the secondly typical correlation coefficient reaches a significant level（correlation coefficientλ2=0.8280）.In the Correlation between species diversity and 10 soil factors,soil nutrient combinations（especially C/N,C/N/P）and soil water content are the most important dominant factors;species diversity with 10correlation coefficients of soil factor content in the study area,the coefficient of variation of soil C/P,N/P and effective P are most important dominant factors.（6）Plant nutrient pattern and its correlation with soil moisture and nutrient environment in vegetation restoration process:In the study area,the average value of C,N and P contents for dominant plant leaves are lower than world,but the average ratio of C/N,C/P and N/P ratio of is higher than the world average and national average in the karst forest.With the succession of degraded vegetation to a higher stage,the average content of C,N,and P for dominant plants increased to a high degrees.Even in the some species of different recovery stages and different niches,it is the difference of C,N,and P contents and their ratio.The study showed that when the dominant plants absorbing N,P,the characteristics of high efficiency assimilation is some to C in karst forests.The ability of assimilate C with high efficiency,when absorbing low-concentration soil P,maybe it is an adaptation mechanism of forest plants for the general lack of P for the soil environment in the karst region.Through the researches,we systematically and comprehensively revealed the basic characteristics of the spatial and temporal distribution patterns of soil moisture,soil nutrients（C,N,P content and combinations）and plant species diversity in the paper from“three sequences”in the Maolan karst forest community and its niches.And a series of coupling relationships between their distribution patterns.Explain the formation and maintenance mechanism of plant species diversity pattern based on soil moisture and nutrient pattern in Maolan karst forest.On the one hand,the study of the“soil-plant”system of the karst forest ecosystem further enriches the theoretical content,and on the other hand it provides a further theoretical basis for the scientific protection and rational management of plant species diversity in the region. |
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