Abstract
Aim of study: The objective of this study was to analyze the stand structure and spatial pattern of two A. chilensis stands with contrasting soil conditions and different site qualities in order to explore if these differences lead to patterns similar to the ones observed under different precipitation conditions.Area of study: The study was carried out in two stands located near the city of El Bolsón (41° 56’S - 71° 33’ W), Rio Negro, Argentina.Material and Methods: We evaluated age difference between canopy strata (upper and lower) in two stands with different site qualities by means of a Mann-Whitney test. Dead individuals by diameter class were compared by means of a chi square test. Spatial distribution pattern was analyzed using the pair-correlation function and the mark-correlation function.Main results: Both sites exhibited a random spatial distribution of A. chilensis but different processes seem to underlie the patterns. In the low-quality site facilitation and continuous establishment led to a transient clumped spatial pattern. Mortality mediated by competition occurred mainly on small trees resulting in the current random pattern. On the other hand, spatial pattern in the high-quality site does not reflect a facilitation mediated recruitment. The upper strata established synchronously and subsequent regeneration was episodic.Research highlights: The results show that the differences in site quality may lead to different establishment spatial patterns, showing the importance of facilitation processes in sites with drier soil conditions and lower quality, although results may be site specific, due to the lack of replications.Keywords: Spatial analysis; regeneration; mortality; competition; facilitation.Abbreviations used: LQ: low-quality site; HQ: high-quality site.
Highlights
The structure of a stand is the result of the interaction between different factors such as species composition, site quality and disturbance (Oliver and Larson, 1996)
In the low-quality site facilitation and continuous establishment led to a transient clumped spatial pattern
Research highlights: The results show that the differences in site quality may lead to different establishment spatial patterns, showing the importance of facilitation processes in sites with drier soil conditions and lower quality, results may be site specific, due to the lack of replications
Summary
The structure of a stand is the result of the interaction between different factors such as species composition, site quality and disturbance (Oliver and Larson, 1996). These factors have different effects on the establishment, survival and growth of trees in the first stages influencing the subsequent development of the stands (Harper et al, 2006). The spatial pattern of trees determines competitive relationships that are stronger between neighbour trees leading to a decrease in growth of plants located close to each other and in cases where competition is strong enough, an increase in mortality. Facilitation and competition influence spatial patterns that reflect the interaction between two species or between different cohorts of the same species (Rejmánek and Leps¢, 1996)
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