Coniferous forests of the Pacific Northwest

Lassoie, James P.; Hinckley, Thomas M.; Grier, Charles C.

doi:10.1007/978-94-009-4830-3_6

Cited by 34 publications

(11 citation statements)

References 110 publications

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“…Despite their broad similarity in shade tolerance when compared with intolerant species, the four species do differ substantially in the life history characters and physiological parameters used to distinguish regeneration guilds. They vary in drought and snow tolerance, maximum growth rate, in the frequency of reproduction, seed size, and longevity (Powells 1965, Kotar 1972, USDA 1974, Long 1976, Arno and Hammerly 1977, Waring and Franklin 1979, Franklin and Waring 1980, Grant 1980, Lassoie et al 1986).…”

Section: Study Sitesmentioning

confidence: 99%

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

Lertzman¹

1992

Ecology

140

122

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Small—scale natural disturbances involving the death of one to a few trees and creating gaps in the forest canopy are key processes in the population and community ecology of many forests. I examined the patterns of replacement in gaps in a subalpine old—growth forest in southern coastal British Columbia to assess their role in the forest community. I found no evidence that self replacement or reciprocal replacement act to maintain the current community composition. Gapmaker—gapfiller comparisons indicated preferential replacement of all species by Pacific silver fir (Abies amabilis), suggesting that the community is undergoing successional change. Nor did gap size, location within a gap, or local canopy composition appear to exert a strong influence on the species composition of regeneration within the gap. The only circumstance where Pacific silver fir was not overwhelmingly dominant among gapfillers was on stumps, where almost all successful western hemlock (Tsuga heterophylla) gapfillers were located. These patterns suggest that neither species—specific interactions between gapmakers and gapfillers nor variability in gap environments is adequate to maintain the current composition of the forest canopy. However, caution is indicated in projecting a long—term trend from this short—term assessment of community trajectory.

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Section: Study Sitesmentioning

confidence: 99%

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

Lertzman¹

1992

Ecology

140

122

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“…T . heterophylla is a species with one of the highest moisture requirements among conifers (Lassoie et al ., 1986), hence its occurrence at high AET. In contrast, the variable set commonly used in bioclimatic models replaces AET with GDD5 (Table 2), which does not capture the interaction of energy and water availability (Stephenson, 1998).…”

Section: Discussionmentioning

confidence: 99%

“…We initially examined nine potential bioclimatic variables (Table 1), focusing on summer moisture stress, which is a known physiological limit on the T . heterophylla range (Waring & Franklin, 1979; Lassoie et al ., 1986). Potential annual evapotranspiration (PET) and actual annual evapotranspiration (AET) were estimated using the water‐balance model presented in Willmott et al .…”

Section: Methodsmentioning

confidence: 99%

Bioclimatic modelling using Gaussian mixture distributions and multiscale segmentation

Gavin

2005

Global Ecology and Biogeography

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Aim To introduce Gaussian mixture distributions and sequential maximum a posteriori image segmentation (GM-SMAP) as a model that predicts species ranges from mapped climatic variables, and to compare its predictive capacity with two commonly used bioclimatic models: regression tree analysis (RTA) and smoothed response surfaces (SRS).Location North-west North America. MethodsWe compared models for their ability to predict the distributional range of western hemlock ( Tsuga heterophylla ). We calculated and projected nine climatic and water-balance variables to a 2-km grid up to 140 km from the T. heterophylla range. Models were trained using the five variables selected by RTA, as well as subsets of three variables. Goodness of fit was assessed using models trained and tested on the entire study area. Predictive capacity was assessed using 100 cross-validation tests, each trained on a randomly sampled 1% of the study area and tested on the complement of the study area.Results Models using all five variables were significantly better than three-variable models. Model fit was greatest for SRS. GM-SMAP misclassified slightly more area and RTA misclassified almost twice the area compared to SRS. However, crossvalidation showed that the predictive capacity was clearly greatest for GM-SMAP and lowest for SRS, indicating that GM-SMAP makes more accurate predictions from sparse data.Main conclusions GM distributions prevent overfitting using an informationtheoretic approach, and the SMAP algorithm minimizes the spatial extent of the largest misclassified area using a multiscale method. These properties, useful for image classification, also aid their strong predictive capacity as a bioclimatic model. SRS overfit the data, lowering its predictive capacity, and RTA failed to capture details of interactions among variables, yielding a poor fit. These results demonstrate the strong potential of GM-SMAP as a bioclimatic model.

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“…Thus, recent climatic changes, especially increasing temperatures over the last 100 yr, have had major impacts on the productivity of high-elevation Washington forests. Temperature and precipitation influence NPP through a variety of processes (Lassoie et al 1985). Increasing precipitation might slightly increase the snowpack, but during the summer it would also moisten litter and enhance nutrient cycling.…”

Section: Period (Yr)mentioning

confidence: 99%

Long‐Term Trends in Forest Net Primary Productivity: Cascade Mountains, Washington

Graumlich¹,

Brubaker²,

Grier³

1989

Ecology

Self Cite

126

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Estimates of annual net primary productivity since 1880 for four high—elevation forest stands in western Washington indicated that productivity has increased 60% during the 20th century. Because these stands were separated by up to 200 km and differed in species composition, elevation, and time since establishment, the observed trends in productivity imply a response to regionwide changes in environmental factors rather than to site—specific stand dynamics. Annual production is significantly correlated with long—term variation in summer temperature and short—term variation in annual precipitation since 1983, the beginning of continuous local meteorological records. Production is uncorrelated with atmospheric CO2 concentrations, suggesting that direct CO2 fertilization is currently unimportant in these forests.

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Coniferous forests of the Pacific Northwest

Cited by 34 publications

References 110 publications

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

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

Bioclimatic modelling using Gaussian mixture distributions and multiscale segmentation

Long‐Term Trends in Forest Net Primary Productivity: Cascade Mountains, Washington

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