Biomass Regressions for Understory Species in Young-Growth Sitka Spruce–Western Hemlock Forests of Southeast Alaska

2021 ◽  
Vol 95 (1) ◽  
Author(s):  
Annelise Z. Rue-Johns ◽  
Justin S. Crotteau ◽  
David V. D'Amore ◽  
Jeffrey C. Barnard
Keyword(s):  
Sitka Spruce ◽  
Western Hemlock ◽  
Southeast Alaska ◽  
Understory Species ◽  
Young Growth

Modeling specific gravity and diameter inside bark of western hemlock and Sitka spruce growing in southeast Alaska

2021 ◽  
Author(s):  
Joseph Dahlen ◽  
David Auty ◽  
Eini C. Lowell
Keyword(s):  
Specific Gravity ◽  
Fixed Effects ◽  
Sitka Spruce ◽  
Western Hemlock ◽  
Fit Indices ◽  
Southeast Alaska ◽  
Important Species ◽  
Explanatory Variables ◽  
Cambial Age ◽  
Young Growth

Western hemlock and Sitka spruce are two commercially important species in Alaska with harvests beginning to focus on naturally regenerated young-growth. We developed within-tree models of ring specific gravity (SG) and diameter inside bark (DIB) for young-growth western hemlock and Sitka spruce. Eight even-aged stands (age < 75 years) in southeast Alaska were felled and disks collected from multiple height levels; 128 trees and 451 disks were collected for western hemlock, and 217 trees and 952 disks were collected for Sitka spruce. Radial strips were prepared and scanned using X-ray densitometry. We fitted non-linear mixed-effects models to the data, with cambial age, height within tree, and dominance class used as explanatory variables. The R2 values (fixed effects only) for the SG models were 0.48 and 0.42 for western hemlock and Sitka spruce, respectively. The corresponding fit indices for the DIB models were 0.86 and 0.85 percent for western hemlock and Sitka spruce, respectively. Tree maps depicting the within tree variation in SG showed more variability in Sitka spruce than in western hemlock. The wood and growth properties of young-growth trees in Alaska will continue to become more important as the U.S. Forest Service transitions away from harvesting old-growth trees.

scholarly journals Porcupine Feeding Damage in Precommercially Thinned Conifer Stands of Central Southeast Alaska

1997 ◽  
Vol 12 (4) ◽  
pp. 115-121 ◽  
Author(s):  
Andris Eglitis ◽  
Paul E. Hennon
Keyword(s):  
Host Selection ◽  
Sitka Spruce ◽  
Tsuga Heterophylla ◽  
Picea Sitchensis ◽  
Western Hemlock ◽  
Feeding Damage ◽  
Southeast Alaska ◽  
Erethizon Dorsatum ◽  
Young Growth

Abstract This study describes feeding damage by porcupines (Erethizon dorsatum) in precommercially thinned young growth stands of Sitka spruce (Picea sitchensis) and western hemlock (Tsuga heterophylla) on Mitkof Island in central southeast Alaska. We examined 641 trees from 54 sampling plots along transect lines in three 12 to 20 yr old stands. Porcupine feeding was monitored each spring and fall from 1985 to 1987. Four categories of feeding damage are described: complete girdling of the bole, partial girdling (bole scars), branch clipping, and "tasting wounds" (small basal bole scars). Sitka spruce, the primary crop tree in these thinned stands, sustained significantly higher damage (52% of trees affected) than western hemlock (26% of trees affected). Porcupine feeding was greater on taller than shorter Sitka spruce. Although only 8 of 59 trees initially girdled in 1985 were killed, many later sustained additional feeding damage. Following the 1987 season 3 yr after thinning, nearly 30% of the spruce and 14% of the western hemlock crop trees had been partially or completely girdled. Issues deserving future attention include the role of thinning in predisposing stands to porcupine damage, methods of population assessment, and mechanisms of host selection by porcupines. West. J. Appl. For. 12(4):115-121.

Effects on understory biomass and forage 8–10 years after precommercial thinning of Sitka spruce – western hemlock stands in southeast Alaska

2020 ◽  
Vol 50 (2) ◽  
pp. 215-225
Author(s):  
Justin S. Crotteau ◽  
Annelise Z. Rue-Johns ◽  
Jeffrey C. Barnard
Keyword(s):  
Forest Type ◽  
Sitka Spruce ◽  
Picea Sitchensis ◽  
Wildlife Habitat ◽  
Western Hemlock ◽  
Stand Age ◽  
Southeast Alaska ◽  
Precommercial Thinning ◽  
Clear Cutting ◽  
Understory Biomass

In southeast Alaska, United States, multiple-use forest management objectives include both timber production and wildlife habitat. Following stand-replacing disturbances such as clear-cutting, Sitka spruce (Picea sitchensis (Bong.) Carrière) and western hemlock (Tsuga heterophylla (Raf.) Sarg.) naturally regenerate and competitively dominate resources, excluding understory biomass and biodiversity. Thinning may mitigate the effects of canopy closure and permit understory development, but evidence of the effect on understories 8–10 years after thinning is lacking. We report results 4–5 and 8–10 years after thinning experiments on the Tongass National Forest to demonstrate the effects of precommercial thinning (thinned versus control), stand age (15–25, 25–35, and 35–50 years), and weather on understory dynamics and Sitka black-tailed deer (Odocoileus hemionus sitkensis Merriam, 1898) forage availability. Stand density negatively affected understory biomass, whereas temperature and precipitation positively interacted to increase biomass. Thinning had an enduring effect on understories, with biomass at least twice as great in thinned versus unthinned stands through year 10. We identified compositional differences from thinning as stand age class increased. Deer forage responded similarly to biomass, but thinning-induced differences faded with increased winter snowfall scenarios, especially in older stands. This study aids the understanding of stand overstory and understory development following silvicultural treatments in the coastal temperate rain forest of Alaska and suggests management implications and applications for balancing objectives throughout the forest type.

Composition and development of conifer regeneration in thinned and unthinned natural stands of western hemlock and Sitka spruce in southeast Alaska

1994 ◽  
Vol 24 (5) ◽  
pp. 976-984 ◽  
Author(s):  
Robert L. Deal ◽  
Wilbur A. Farr
Keyword(s):  
Sitka Spruce ◽  
Western Hemlock ◽  
Age Classes ◽  
Forest Canopies ◽  
Southeast Alaska ◽  
Thinning Intensity ◽  
Open Forest ◽  
Closed Forest ◽  
Conifer Regeneration ◽  
Natural Stands

Natural regeneration of understory conifers was studied in 1988, 9–14 years after thinning of even-aged stands of western hemlock (Tsugaheterophylla (Raf.) Sarg.) and Sitka spruce (Piceasitchensis (Bong.) Carr.) on upland sites in southeast Alaska. Two age-classes of stands were compared: young stands, <30 years old that before thinning had open forest canopies and understories of conifer regeneration, shrubs, herbs, and forbs; and older stands, 31–98 years old, that before thinning had closed forest canopies and little or no understory vegetation. In 1988, dominant understory conifers in young stands were 2–4 m tall, and about the same age as trees in the overstory. In the older stands there was dense new regeneration that germinated 2–3 years after thinning and averaged 0.6–1.5 m tall. Seventy-two to 100% of all regeneration was hemlock. The rest was Sitka spruce. The amount of regeneration increased and the percentage of hemlock decreased with increasing thinning intensity. Thinning of young stands on upland sites appears to benefit understory conifers, which rapidly expand to fill in the available growing space. Heavy thinning in older stands promotes dense germination of understory conifers making it difficult for other understory plants to become established.

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