Patterns of Gap‐Phase Replacement in a Subalpine, Old‐Growth Forest

Lertzman, Kenneth P.

doi:10.2307/1940772

Cited by 141 publications

(128 citation statements)

References 47 publications

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“…the new ecological paradigm and understanding of disturbance in old-growth forests, it is now recognized that fine-scale disturbance is ubiquitous in coastal forests of British Columbia (Lertzman and Krebs 1991, Lertzman 1992, Beese and Sandford 1992, Lertzman et al 1996. The uneven-age structures of western redcedar suggest that regeneration following catastrophic disturbance is not necessarily the dominant mode of regeneration in these forests.…”

Section: Resultsmentioning

confidence: 99%

Western redcedar population dynamics in old-growth forests: Contrasting ecological paradigms using tree rings

Daniels¹

2003

The Forestry Chronicle

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In coastal British Columbia, late-successional forests dominated by western redcedar (Thuja plicata Donn ex D. Don) are structurally complex, with deep multi-layered canopies, large trees that are > 250 years old, and abundant coarse woody debris (CWD). These forests are presumed to be "old-growth" forests in which fine-scale gaps are the dominant disturbance regime, accounting for their structural diversity. In this study, I have used tree-ring analyses to investigate western redcedar regeneration dynamics in these old-growth forests. Western redcedar dominates canopies of many stands, but is rare in the understorey although it tolerates shade. The traditional interpretation is that western redcedar depends on catastrophic disturbance to regenerate and that it is replaced through succession by western hemlock (Tsuga heterophylla (Raf.) Sarg.) and Pacific silver fir (Abies amabilis (Dougl. ex Loud.) Dougl. ex J. Forbes), which are abundant in the understorey. Dominant trees are perceived to represent an even-aged, post-disturbance cohort and the lack of regeneration indicates a population decline in the absence of catastrophic disturbances. In this paper, I investigate four assumptions underlying this interpretation: (1) Tree size indicates age. (2) Populations establish as even-aged, post-disturbance cohorts. (3) Abundant CWD represents recent mortality. (4) Regeneration is insufficient to maintain canopy dominance. Using tree-ring evidence, I show that population dynamics of western redcedar are a combination of gap-phase establishment and a continuous mode of recruitment from the subcanopy to the canopy. Specifically, size is a poor surrogate for tree age. Age distributions from 15 sites revealed uneven-aged populations, rather than single post-disturbance cohorts. Both logs and snags of western redcedar may persist more than 270 years; they do not represent recent mortality that is disproportionate to the number of live western redcedar in canopy. The regeneration niches of western redcedar and western hemlock overlap. For both species, gap-phase disturbances result in substrate suitable for successful seedling establishment. Preliminary results from dendroecological analysis of radial growth rates of trees in the subcanopy and canopy strata suggest that western hemlock and Pacific silver fir depend on gaps to recruit to the upper canopy, but recruitment of western redcedar may be independent of canopy gaps. I propose that differences in mode of recruitment to the canopy may explain the differences in population structures between western redcedar, western hemlock, and Pacific silver fir in the old-growth forest. These results provide an ecological precedent for use of a range of silvicultural systems, including clearcuts through single-tree harvesting and protection forests, when managing western redcedar in coastal British Columbia.Key words: Coastal British Columbia, disturbance regimes, regeneration dynamics, Thuja plicata, variable retention silviculture Dans la région côtière de la Colombie-Britannique...

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Section: Resultsmentioning

confidence: 99%

Western redcedar population dynamics in old-growth forests: Contrasting ecological paradigms using tree rings

Daniels¹

2003

The Forestry Chronicle

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“…communities is a simple and well-studied system that can be useful in improving our understanding of coexistence in highly shade-tolerant species (e.g., Forcier 1975, Woods 1979, Poulson and Platt 1996. The dynamics of this community type are similar to those observed in other systems around the world (e.g., Yamamoto 1989, Lertzman 1992, Lusk and Smith 1998, Russo et al 2005. A conceptual model of coexistence for these two species was proposed by Forcier (1975) and further developed by Canham (1989), Poulson and Platt (1996), and Arii and Lechowicz (2002).…”

Section: Introductionmentioning

confidence: 95%

Partitioning the Factors of Spatial Variation in Regeneration Density of Shade-Tolerant Tree Species

Gravel

Beaudet

Messier

2008

Ecology

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Abstract. Understanding coexistence of highly shade-tolerant tree species is a longstanding challenge for forest ecologists. A conceptual model for the coexistence of sugar maple (Acer saccharum) and American beech (Fagus grandifolia) has been proposed, based on a lowlight survival/high-light growth trade-off, which interacts with soil fertility and small-scale spatiotemporal variation in the environment. In this study, we first tested whether the spatial distribution of seedlings and saplings can be predicted by the spatiotemporal variability of light availability and soil fertility, and second, the manner in which the process of environmental filtering changes with regeneration size. We evaluate the support for this hypothesis relative to the one for a neutral model, i.e., for seed rain density predicted from the distribution of adult trees. To do so, we performed intensive sampling over 86 quadrats (5 3 5 m) in a 0.24-ha plot in a mature maple-beech community in Quebec, Canada. Maple and beech abundance, soil characteristics, light availability, and growth history (used as a proxy for spatiotemporal variation in light availability) were finely measured to model variation in sapling composition across different size classes. Results indicate that the variables selected to model species distribution do effectively change with size, but not as predicted by the conceptual model. Our results show that variability in the environment is not sufficient to differentiate these species' distributions in space. Although species differ in their spatial distribution in the small size classes, they tend to correlate at the larger size class in which recruitment occurs. Overall, the results are not supportive of a model of coexistence based on small-scale variations in the environment. We propose that, at the scale of a local stand, the lack of fit of the model could result from the high similarity of species in the range of environmental conditions encountered, and we suggest that coexistence would be stable only at larger spatial scales at which variability in the environment is greater.

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“…Many gap makers which opened a gap by the Typhoon Milenyo, were almost completely deprived of their crowns just after the typhoon, but only 1 or 2 years later they flourished and became canopy trees again. Reciprocal replacement or strong self-replacement could act to stabilize community composition (Lertzman 1992), but self-replacement of gap makers is not common in temperate forests.…”

Section: Discussionmentioning

confidence: 99%

Gap characteristics and natural regeneration in Mt. Makiling rainforest, the Philippines

Kim¹,

Kim²,

Kim³

et al. 2011

J. Ecol. Environ.

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This study was conducted to determine the characteristics of gaps and natural regeneration of trees on Mt. Makiling, the Philippines. Canopy gaps in or around two 1-ha permanent plots and on 3-km line transects were investigated. Most of the gaps studied were formed or affected by Typhoon Milenyo, which hit the study site in September 2006. The most frequent mode of gap maker death was snap-off, whereas uprooting was relatively less important. The most frequent gap maker was balobo (Diplodiscus paniculatus) followed by magabuyo (Celtis luzonica) and katmon (Dillenia philippinensis). In contrast, the most frequent gap filler was magabuyo (C. luzonica). At the sapling layer, the most important species was magabuyo (C. luzonica), but there was a high proportion of lianas and palms. Most of the gaps had leaf area index (LAI) values between 3 and 5. A clear trend of a decrease in gap size and an increase in LAI was observed for 2 years from 2007 to 2009. New seedlings emerged very abundantly during the same time period. The rapid changes in the gaps were partially due to the excellent capability of tropical trees to resprout after the crown or stem was damaged by the typhoon. This study on gap dynamics may contribute to a better understanding of the natural regeneration process of trees in tropical rainforests.

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Patterns of Gap‐Phase Replacement in a Subalpine, Old‐Growth Forest

Cited by 141 publications

References 47 publications

Western redcedar population dynamics in old-growth forests: Contrasting ecological paradigms using tree rings

Western redcedar population dynamics in old-growth forests: Contrasting ecological paradigms using tree rings

Partitioning the Factors of Spatial Variation in Regeneration Density of Shade-Tolerant Tree Species

Gap characteristics and natural regeneration in Mt. Makiling rainforest, the Philippines

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