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.

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.

Relations between red alder composition and understory vegetation in young mixed forests of southeast Alaska

2006 ◽  
Vol 36 (3) ◽  
pp. 738-748 ◽  
Author(s):  
Thomas A Hanley ◽  
Robert L Deal ◽  
Ewa H Orlikowska
Keyword(s):  
Carrying Capacity ◽  
Basal Area ◽  
Picea Sitchensis ◽  
Understory Vegetation ◽  
Wildlife Habitat ◽  
Red Alder ◽  
Southeast Alaska ◽  
Net Production ◽  
Understory Biomass ◽  
Young Growth

Interest in mixed red alder (Alnus rubra Bong.) – conifer young-growth stands has grown in southeast Alaska, USA, because they appear to provide much more productive understory vegetation and wildlife habitat than do similar-aged pure conifer stands. We studied understory vegetation in nine even-aged young-growth stands (38–42 years old) comprising a gradient of red alder – conifer overstory composition, with red alder ranging from 0% to 86% of stand basal area. Conifers were Sitka spruce (Picea sitchensis (Bong.) Carr.), western hemlock (Tsuga heterophylla (Raf.) Sarg.), and western redcedar (Thuja plicata Donn ex D. Don). We measured understory biomass and net production (current annual growth) in each stand by species and plant part and estimated carrying capacity for black-tailed deer (Odocoileus hemionus sitkensis Cowan) with a food-based habitat model. Highly significant positive relations (P < 0.002) were found between red alder basal area and all of the following: total understory biomass (r2 = 0.743), net production of shrubs (r2 = 0.758) and herbs (r2 = 0.855), and summer carrying capacity for deer (r2 = 0.846). The high correlation between red alder and herbaceous production is especially important, because herbs are least abundant and most difficult to maintain in young-growth conifer forests of this region. Red alder offers prospects for increasing understory vegetation biomass and its food value for deer and other wildlife when included as a hardwood overstory species in mixed hardwood–conifer young-growth forests.

scholarly journals Spatial aspects of structural complexity in Sitka spruce – western hemlock forests, including evaluation of a new canopy gap delineation method

2017 ◽  
Vol 47 (8) ◽  
pp. 1033-1044 ◽  
Author(s):  
Eryn E. Schneider ◽  
Andrew J. Larson
Keyword(s):  
Structural Complexity ◽  
Canopy Cover ◽  
Sitka Spruce ◽  
Picea Sitchensis ◽  
Canopy Gap ◽  
Western Hemlock ◽  
Small Scale ◽  
Southeast Alaska ◽  
Tree Patterns ◽  
Overstory Tree

Structural complexity in long-lived forests where stand-replacing disturbances are rare is thought to emerge from chronic small-scale disturbances and competitive interactions between trees. We analyzed tree size distributions, tree spatial patterns, and canopy gap attributes in ten 1.42 ha stem mapped plots in old-growth Sitka spruce (Picea sitchensis (Bong.) Carrière) – western hemlock (Tsuga heterophylla (Raf.) Sarg.) forests in southeast Alaska. Most plots had rotated sigmoid or reverse-J-shaped diameter distributions. Overstory tree patterns were uniform at short distance (<5 m) and random or aggregated at larger distances (>5 m); understory trees were spatially random or aggregated at most scales. Tree patterns were highly variable across plots. Overstory and understory tree populations were spatially independent in most medium canopy cover (40%–70%) plots but spatially repelled in most high canopy cover (>70%) plots. Canopy gap delineation using a traditional geometric approach identified more gaps and greater forest area in gaps compared to a new method based on canopy tree shadow lengths. We recommend defining the lower limit of canopy gap size using overstory tree crown diameter; gap delineation based on overstory tree shadow length is overly conservative at higher latitude sites. Our analyses show that, despite their low species richness, the temperate rainforests of southeast Alaska are highly structurally diverse.

scholarly journals Sitka Spruce and Western Hemlock Stand and Tree Growth 10 Years after Precommercial Thinning in Southeast Alaska

2012 ◽  
Vol 27 (1) ◽  
pp. 5-11 ◽  
Author(s):  
Mike Newton ◽  
Liz Cole
Keyword(s):  
Sitka Spruce ◽  
Tsuga Heterophylla ◽  
Picea Sitchensis ◽  
Western Hemlock ◽  
Diameter Growth ◽  
Southeast Alaska ◽  
Steady Rate ◽  
Increasing Trend ◽  
Naturally Regenerated Stands ◽  
Understory Plant

Abstract Ten years after precommercially thinning 16–18-year-old naturally regenerated stands of Sitka spruce (Picea sitchensis [Bong.] Carr.) and western hemlock (Tsuga heterophylla [Raf.] Sarg.) in southeast Alaska, neither species responded in height growth to spacing. Spruce diameter growth increased significantly following all thinning treatments, and among thinning treatments, there was a weak but increasing trend toward more rapid diameter growth at the wider spacings. Spruce basal areas increased almost twice as fast after thinning as without thinning, and radial growth continued to increase, whereas unthinned stands grew at a slower but steady rate. Western hemlock also showed a trend for increased diameter, but growth response was less than for spruce. Shrub control to enhance understory plant development for deer forage did not improve growth of either tree species. Branch diameter of Sitka spruce increased with spacing. Pruning led to epicormic sprouting in the 3 years following pruning with numbers inversely related to spacing. Sprouts developed and persisted in stands thinned to 200 or fewer stems per acre. Overall, pruning led to a small reduction in diameter growth at breast height.

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.

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

What influences the long-term development of mixtures in British forests?

2020 ◽  
Vol 93 (4) ◽  
pp. 545-556 ◽  
Author(s):  
W L Mason ◽  
T Connolly
Keyword(s):  
Functional Traits ◽  
Scots Pine ◽  
Shade Tolerance ◽  
Basal Area ◽  
Sitka Spruce ◽  
Picea Sitchensis ◽  
Silver Birch ◽  
Western Hemlock ◽  
Larix Kaempferi ◽  
Pure Stand

Abstract Six experiments were established between 1955 and 1962 in different parts of northern and western Britain which used replicated randomized block designs to compare the performance of two species 50:50 mixtures with pure stands of the component species. The species involved were variously lodgepole pine (Pinus contorta Dougl.), Japanese larch (Larix kaempferi Lamb. Carr.), Scots pine (Pinus sylvestris L.), silver birch (Betula pendula Roth.), Sitka spruce (Picea sitchensis Bong. Carr.) and western hemlock (Tsuga heterophylla Raf. Sarg.). The first four species are light demanding, while Sitka spruce is of intermediate shade tolerance and western hemlock is very shade tolerant: only Scots pine and silver birch are native to Great Britain. In three experiments (Bickley, Ceannacroc, Hambleton), the mixtures were of two light-demanding species, while at the other three sites, the mixture tested contained species of different shade tolerance. The experiments were followed for around 50 years, similar to a full rotation of even-aged conifer stands in Britain. Five experiments showed a tendency for one species to dominate in mixture, possibly reflecting differences in the shade tolerance or other functional traits of the component species. In the three experiments, the basal area of the mixtures at the last assessment was significantly higher than predicted based on the performance of the pure stands (i.e. the mixture ‘overyielded’). In two of these cases, the mixture had had a higher basal area than found in the more productive pure stand indicating ‘transgressive overyielding’. Significant basal area differences were generally more evident at the later assessment date. The exception was in a Scots pine: western hemlock mixture where greater overyielding at the earlier date indicated a nursing (‘facilitation’) effect. In the remaining experiments, the performance of the mixture conformed to predictions from the growth of the component species in pure stands. Taken overall, the results suggest that functional traits can be used to interpret the performance of mixtures but prediction of the outcome will require better understanding of the interplay between species and site characteristics plus the influence of silvicultural interventions.

Lateral Root Pruning of Sitka Spruce and Western Hemlock Seedlings

1972 ◽  
Vol 2 (3) ◽  
pp. 223-227 ◽  
Author(s):  
S. Eis ◽  
J. R. Long
Keyword(s):  
Lateral Root ◽  
Lateral Roots ◽  
Root Systems ◽  
Growing Season ◽  
Sitka Spruce ◽  
Picea Sitchensis ◽  
Short Length ◽  
Western Hemlock ◽  
Root Pruning

Roots of Sitka spruce (Picea sitchensis) and western hemlock (Tsugaheterophylla) seedlings were side pruned in nursery beds at semimonthly intervals to produce dense and compact root systems. Root pruning early in the growing season stimulated the growth of existing roots and also initiated new roots. The densest root systems were produced by pruning before the end of June. However, because of the short length of lateral roots on seedlings early in their second growing season, pruning equidistant between rows 18 cm apart was ineffective. The best compromise appeared to be to prune spruce at the beginning of July, and hemlock around the middle of July. Earlier pruning equidistant between rows can be effective on larger seedlings during their third growing season. If early pruning is carried out on 2 + 0 seedlings, a pruning distance of about 6 cm from the row is recommended.

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