| Quercus glauca is a constructive species of top-level community in karst ecosystem,and also one of the main components constituting subtropical forest in China.It has strong adaptability and plays an important role in karst forest vegetation.Guilin is one of the main distribution areas of karst hills in Guangxi,with typical karst landform characteristics.It has the characteristics of high landscape heterogeneity,obvious hydrogeological structure,high bare rock ratio,strong carbonate dissolution,and poor soil.Quercus glauca,as a pioneer tree species for vegetation restoration and reconstruction in karst area,plays an important role in the restoration and protection of karst forest ecosystem,and plays an important role in regulating climate,protecting water source,inhibiting sandstorm,carbon and oxygen fixation,and maintaining biodiversity and many other ecological functions.In order to explore that community characteristics of Quercus glauca in karst hills of guilin and its relationship with environmental factor,we set up 23,25 and 25 plots in beitou village of yangshuo county,yanpo mountain in the suburb of guilin and long village of yongfu county respectively.The Quercus glauca community in karst hills was taken as the research object,based on the community survey and environmental factor measurement data,the species composition,floristic composition,community structure,environmental characteristics,quantitative classification and sequencing of Quercus glauca community in karst hills were discussed,as well as the relationship between community distribution and environmental factors,aiming to provide a scientific basis for vegetation restoration and reconstruction of degraded ecosystem in karst area.The results are as follows.(1)The comparative analysis of 9 environmental factors in 3 Quercus glauca community plots shows that: the soil p H in Long village was the lowest,the soil water content,organic matter,available phosphorus and available potassium lower than those in Beitou and Yanpo sites.The total phosphorus content in Beitou site was significantly higher than that in the other two sites.The available nitrogen content in Long village site was significantly higher than that in Yanpo and Beitou sites.In general,the soil nutrient content of long village site was relatively low among the three sites.(2)A total of 144 species of vascular plants were found in the Beitou Village,belonging to 54 families and 111 genera.Among those there are 7 family,14 genus and 18 species of Pteridophyta piants,47 families,97 genera and 126 species of Angiospermae piants.A total of 97 species of vascular plants were found in the Yanpo Village,belonging to 46 families and 76 genera.Among those there are 8 family,12 genus and 18 species of Pteridophyta piants,38 families,64 genera and 79 species of Angiospermae piants.A total of 110 species of vascular plants were found in the Longcun Village,belonging to 54 families and 93 genera.Among those there are 10 family,17 genus and 23 species of Pteridophyta piants,44 families,76 genera and 87 species of Angiospermae piants.The families and categories with more species in the three plots are basically the same,including Leguminosae,Euphorbiaceae,Pteridaceae,Rutaceae,and Lauraceae.(3)The floristic composition of internal medicine in the three sites is mainly dominated by pantropical distribution,while that of genus is dominated by pantropical distribution,tropical Asia(India–Malaysia)distribution and Old World tropical distribution.On the whole,it shows obvious tropical and subtropical characteristics.(4)The structure of plant diameter grade and height grade in Beitou Village presented typical inverted "J" distribution,indicating that there were sufficient sapling reserves in the site,the community regeneration was good,and it was in a stable growth stage.The structure of diameter grade and height grade of plants in Yanpo and Longcun Villages showed a single peak distribution to the left,indicating that there were more trees of medium diameter grade and less trees of two diameter grades in the sample plots.(5)The Quercus glauca community in the karst hills could be classified into three community types based on quantitative methods:Quercus glauca-Pittosporum planilobum+Mallotus philippensis-Pteris ensiformis(Association Group Ⅰ),Quercus glauca-Quercus glauca+Decaspermum gracilentum-Ophiopogon bodinieri(Association Group Ⅱ),Quercus glauca-Mallotus philippensis+Callicarpa bodinieri-Diplazium donianum(Association Group Ⅲ).(6)The results of Monte Carlo replacement test and redundancy analysis well reflect the distribution pattern of each community type and its relationship with environmental gradient,among which nine environmental factors,such as canopy openness,bare rock rate,soil p H,organic matter,total phosphorus,available nitrogen,available phosphorus,available potassium and water content,have significant effects on the distribution of the community.The results of variation decomposition show that the interaction of soil factors and spatial factors is the main factor affecting the species distribution in karst hills.Among them,soil water content,soil p H value,soil organic matter and soil total phosphorus may be important ecological factors affecting the species composition and distribution of plant communities in this study area. |
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