Discordance in spatial patterns of white pine (Pinus strobus) size-classesin a patchy near-boreal forest

Citation
M. Dovciak et al., Discordance in spatial patterns of white pine (Pinus strobus) size-classesin a patchy near-boreal forest, J ECOLOGY, 89(2), 2001, pp. 280-291
Citations number
50
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Environment/Ecology
Journal title
JOURNAL OF ECOLOGY
ISSN journal
0022-0477 → ACNP
Volume
89
Issue
2
Year of publication
2001
Pages
280 - 291
Database
ISI
SICI code
0022-0477(200104)89:2<280:DISPOW>2.0.ZU;2-R
Abstract
1 White pines (Pinus strobus) in a c. 1 ha near-boreal aspen-red maple stan d in the western Great Lakes region, USA, were allocated to five size-class es that were tested for discordance of their spatial patterns (i.e. within- size-class spatial distribution of individuals and spatial associations amo ng different size-classes). The size-classes were 0.5-1 m tall, 1-2 m tall, 2-4 m tall, > 4 m tall but < 20 cm diameter at breast height (d.b.h.), and > 20 cm d.b.h. The size-classes also differed in age. Their spatial patter ns were analysed using formulae for spatial autocorrelation with categorica l data at neighbourhood (0-14 m) and stand (0-70 m) scales. 2 Size-classes clustered in neighbourhoods that differed in size ranging fr om 6 m in diameter (size-class 2) to 40 m (size-class 3), suggesting that t he pattern of each size-class is due to a different set of environmental fa ctors. Similar size-classes tended to be randomly or positively associated at neighbourhood scales, while the most dissimilar size-classes occupied di fferent neighbourhoods. 3 Size-classes 1 and 2 were located farther away from seed trees than size- class 3, which was farther away than size-class 4. Thus periodic seedling i nvasion of a deciduous matrix may be followed by the gradual retraction of older size-classes into a refuge near the mature seed source where competit ion from shrubs and overstorey trees is lower. Although the lack of fine-sc ale clustering suggests density-dependent mortality within the refuge, few older individuals were found outside this area. 4 Two regeneration bottlenecks may structure white pine populations. First, recruitment into size-class 2 is restricted to small patches (possibly in understorey gaps) within neighbourhoods with abundant size-class 1. Relativ ely unrestricted recruitment to size-class 3 follows, and after that recrui tment to size-class 4 is again limited, this time to refugia with sparse ca nopy near adult trees.