Abstract:

Aims Our objective was to understand the population structure, spatial pattern and recruitment mechanism of Betula albo-sinensisforest at Taibai Mountain, northwestern China.

Methods Using data collected from 0.75 hm² plots, we determined the life table, age structure and survivorship curve of the B. albo-sinensis population. Univariate and bivariate Ripley’sK functions were employed to determine spatial distribution of standing trees and snags in different age classes and correlate standing trees and snags.

Important findings The B. albo-sinensis population had high mortality of seedlings and saplings, stable growth of adult trees and then gradually increased mortality. The survivorship curve of B. albo-sinensis population matched Deevey Type I. Snags mostly developed by uprooting and snapping, producing disturbed microsites that recruitment probably relied on. Standing trees and snags were clustered by each age class but randomly distributed when all classes were combined. Standing trees above a given size formed snags in pulses at a scale that was also the optimum canopy gap size for establishing. Population dynamics are related to spatial pattern and provide a measure of ecological significance between population structure and spatial patterns. As a sun-loving species,B. albo-sinensis requires disturbed microsites (e.g., sites of uprooting and snapping) and canopy openings for regeneration in the forest. Patterns in the distribution of standing trees appear to persist and were consistent with highly aggregated patterns of snags caused by natural disturbances across the stand. Findings suggest that cohorts of the B. albo-sinensis population at Taibai Mountain are spatially clumped and the aggregation of different cohorts represents pulsed recruitment that might be capable of maintaining population stability.

Key words: spatial pattern, point pattern analysis, age structure, canopy gap, recruitment, snags, population, Betula albo-sinensis