Population Structure And Distribution Pattern Of Ulmuspumila L. Woodland Under Fencing Enclosure In The Otindag Sandy Land

Ulmus pumila woodland distributed in the sandy soil on a special distribution patterns, isthe most stable sand vegetation type and the most suitable for Saudy climatic conditions ofecological communities. The research on Ulmus pumila woodland has great significance toprotect sand ecological environment and guide the construction and recovery protection of theartificial and natural woodland grassland.By taking natural elm woodland as the research object in the Otindag Sandy land, thispaper analyzed the spatial distribution pattern of Ulmus pumila populations, seedlinggeneration pattern and diversity of understory herbaceous vegetation, with typical bulksample investigation and point pattern analysis.（1）On fixed sand dunes and in sandy lands between dunes, the number of the olderclass of Ulmus pumila elm population is less or missing, while the number of middle-agedtree and early mature tree is more. The populations are in the stage of vigorous growth andtrend to mature stage.（2）The whole population on fixed sand dunes has a clumped distribution on a smallerscale. With increasingly enlarged scales, the population tends to have random spatialdistributions. The spatial association of middle-aged tree and mature tree is positivelycorrelated with each other. The spatial associations of different developmental stages arelow.The whole population in sandy lands between dunes has a clumped distribution at thescales <10m. The young tree and middle-aged tree have random spatial distributions on agreater scale, however the mature tree has a clumped distribution. The spatial associationsbetween different developmental stages are showed on a smaller scale. With increasinglyenlarged scales, the spatial association between different developmental stages turns to benegative.（3）There are seedlings growth in two habitats, and the sandy lands between dunes ismore suitable for seedling growth. There is obvious dating on fixed sand dunes, lack of youngtree and middle-aged trees; but not in sandy lands between dunes. The Ulmus pumilaseedlings show aggregated distributions in two habitats, but the aggregation intensity ofseedlings is different. On fixed sand dunes, there is a negative correlation between seedlingsand mature trees population on a smaller scale. In sandy lands between dunes, there is a positively correlation between seedlings and mature trees population on a smaller scale. Andthey both have no association between them on a greater scale.（4）On fixed sand dunes and in sandy lands between dunes, the diversity index internalcrown are total less than external crown. On fixed sand dunes, the average of diversity indexin south transect is less than other directions, and the coefficient of variation is generallylarger than others. While in sandy lands between dunes the diversity index in transect of alldirections is not significant. In two habitats, the herb diversity index with increasing distanceaway from the tree base, shows parabola changes that firstly increase and then decrease. Andtheir relationship is accord with quadratic equation.The highest diversity index is present tothe crown edge and crown radius of1.5times and beyond this distance, diversity index issignificantly reduced and is consistent with the grassland.（5）We should follow the population distribution pattern of the law and intraspecificlinks, that based on habitat conditions, to keep the population stable and promote populationgrowth in woodland management. Moderate human interference can be taken in naturalregeneration of woodland for fencing, for example, thinning, mowing grass, removing turf,loosing soil, and singling measures to promote seedling regeneration, growth.