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The spatial distribution of plant populations is an important feature of population structure and it determines the population’s ecological preferences,biological characteristics and relationships with environmental factors.The point pattern analysis method was adopted to study the distribution pattern of Picea schrenkiana individuals of different size classes and the correlations between two size classes as well as the impact of topographical attributes on the population distribution.With increasing diameter at breast height,the plant density of the P.schrenkiana population showed a declining trend.Old trees showed a random distribution at a small spatial scale(0-12 m),whereas saplings,small trees and big trees all had an aggregated distribution at all scales.With the increase of tree age,the scales at which maximal aggregation occurred gradually increased and the aggregation strength decreased.At a small scale(0-16 m),all size classes showed a negative correlation and the larger the difference between tree size,the more significant the negative correlation.The number of medium,big and old trees had a significantly positive correlation with elevations,whereas the number of saplings and small trees was not significantly correlated with elevations.The numbers of saplings,small and medium trees showed a significant positive correlation with slope gradient,whereas the number of big trees was not significantly correlated,and the number of old trees was negatively correlated with gradient.With the exception of old trees,saplings,small,medium and big trees showed negative correlations with convexity index.The study provides a theoretical basis for the conservation,rehabilitation and sustainable management of forest ecosystems in the Tianshan Mountains.
The spatial distribution of plant populations is an important feature of population structure and it determines the population of ecological preferences, biological characteristics and relationships with environmental factors. The point pattern analysis method was adopted to study the distribution pattern of Picea schrenkiana individuals of different size classes and the correlations between two size classes as well as the impact of topographical attributes on the population distribution. Increasing diameter at breast height, the plant density of the P. schrenkiana population showed a declining trend. Old trees showed a random distribution at a small spatial scale (0-12 m), saplings, small trees and big trees all had an aggregated distribution at all scales. What the increase of tree age, the scales at which maximal increased incidence of condensation and the aggregation strength decreased. At small scale (0-16 m), all size classes showed a negative correlation and the larger the difference between tree size, the more significant the negative correlation.The number of medium, big and old trees had a significantly positive correlation with elevations, as the number of saplings and small trees was not significantly correlated with elevations.The numbers of saplings, small and medium trees showed a significant positive correlation with slope gradient, whereas the number of big trees was not significantly correlated with gradient .With the exception of old trees, saplings, small, medium and big trees showed negative correlations with convexity index. The study provides a theoretical basis for the conservation, rehabilitation and sustainable management of forest ecosystems in the Tianshan Mountains.