Native forest pathogens facilitate persistence of Douglas-fir in old-growth forests of northwestern California

2011 ◽  
Vol 41 (6) ◽  
pp. 1256-1266 ◽  
Author(s):  
Ashley E. Hawkins ◽  
Terry W. Henkel
Keyword(s):  
Bark Beetles ◽  
Tree Mortality ◽  
Douglas Fir ◽  
Native Forest ◽  
Gap Formation ◽  
Old Growth ◽  
Forest Pathogens ◽  
Canopy Trees ◽  
White Fir ◽  
Closed Canopy

Forest pathogens and insects can accelerate tree mortality, increase stand structural heterogeneity, and alter tree community composition. In northern California, the canopy trees Abies concolor var. lowiana (Gord. & Glend.) Lemmon (white fir) and Pseudotsuga menziesii var. menziesii (Mirbel) Franco (Douglas-fir) co-occur but vary in shade tolerance and regenerative abilities following disturbance. Field observations suggested that mortality and turnover of white fir exceeded that of Douglas-fir and that native pathogens may be important drivers in the absence of fire. Pathogens and bark beetles were sampled in old-growth white fir – Douglas-fir stands in northwestern California to assess their contribution to tree mortality, gap formation, and regeneration. We determined abundances and size class distributions of canopy trees, presence of pathogens and bark beetles, and causes of tree mortality. We sampled canopy gaps and closed-canopy forests for overstory species composition, cause of mortality of gap-maker trees, and regeneration of white fir and Douglas-fir. Root-rot fungi accounted for significantly higher mortality and gap formation in white fir than in Douglas-fir. Relative seedling–sapling density of Douglas-fir was higher in pathogen-induced canopy gaps than in closed-canopy forest. In the absence of fire, native forest pathogens enable regeneration and persistence of Douglas-fir by enhancing mortality of white fir, resulting in canopy gap formation.

scholarly journals Successional dynamics of a regenerated forest in a plantation landscape in Southern India

2019 ◽  
Vol 35 (2) ◽  
pp. 57-67
Author(s):  
Ashish N. Nerlekar ◽  
Vignesh Kamath ◽  
A. Saravanan ◽  
R. Ganesan
Keyword(s):  
Species Richness ◽  
Basal Area ◽  
Primary Forest ◽  
Native Forest ◽  
Plantation Forest ◽  
Old Growth ◽  
Eucalyptus Plantation ◽  
Canopy Trees ◽  
Closed Canopy ◽  
Over Time

AbstractWe monitored native forest regeneration over 11 y in a eucalyptus plantation and compared it with the neighbouring primary forest. For the plantation forest, we hypothesized that species richness, density, basal area and densities of old-growth species would increase over time, and compared to the primary forest, plantation forest would have higher species richness and density, but lower densities of old-growth species. In 2016, we repeated the protocol of a study that sampled the plantation forest in 2005, with thirty 10 × 10-m plots and enumerating trees (≥10 cm diameter), saplings (>1 to <10 cm diameter) and seedlings (<1 cm diameter). In the plantation forest, for trees, the species richness, density of gap, bird-dispersed and mammal-dispersed species increased by 67%, 156%, 116% and 238% respectively; whereas for saplings, density of gap, bird-dispersed and small-seeded species declined by 45.2%, 51% and 18.2% respectively over time; and seedling densities did not change across functional groups. Stand basal area increased by 80.1% in the plantation forest. The primary forest had 446% greater density of closed-canopy trees compared with plantation forest. Contrary to our prediction, the plantation forest did not accumulate significant densities of old-growth species over time, probably due to demographic filters that prevent them from attaining maturity.

Variation in canopy gap formation among developmental stages of northern hardwood stands

1996 ◽  
Vol 26 (10) ◽  
pp. 1875-1892 ◽  
Author(s):  
Sally E. Dahir ◽  
Craig G. Lorimer
Keyword(s):  
Sugar Maple ◽  
Tree Mortality ◽  
Developmental Stages ◽  
Turnover Time ◽  
Gap Formation ◽  
Old Growth ◽  
Northern Hardwood ◽  
Hardwood Species ◽  
Shade Tolerant Species ◽  
Mature Stands

Trends in gap dynamics among pole, mature, and old-growth northern hardwood stands were investigated on eight sites in the Porcupine Mountains of western upper Michigan. Recent gaps (created between 1981 and 1992) were identified using permanent plot records of tree mortality, while older gaps (1940–1981) were identified using stand reconstruction techniques. Although canopy gaps were somewhat more numerous in pole and mature stands, gaps were <25% as large as those in old-growth stands because of smaller gap-maker size, and the proportion of stand area turned over in gaps was only about half as large. Gap makers in younger stands generally had mean relative diameters (ratio of gap-maker DBH to mean DBH of canopy trees) <1.0 and were disproportionately from minor species such as eastern hophornbeam (Ostryavirginiana (Mill.) K. Koch). Gap makers in old-growth stands had mean relative diameters >1.5 and were predominantly from the dominant canopy species. Even in old-growth forests, most gaps were small (mean 44 m2) and created by single trees. Based on the identity of the tallest gap tree in each gap, nearly all shade-tolerant and midtolerant species have been successful in capturing gaps, but gap capture rates for some species were significantly different from their relative density in the upper canopy. The tallest gap trees of shade-tolerant species were often formerly overtopped trees, averaging more than 60% of the mean canopy height and having mean ages of 65–149 years. Canopy turnover times, based on gap formation rates over a 50-year period, were estimated to average 128 years for old-growth stands dominated by sugar maple (Acersaccharum Marsh.) and 192 years for old-growth stands dominated by hemlock (Tsugacanadensis (L.) Carrière). While these estimates of turnover time are substantially shorter than maximum tree ages observed on these sites, they agree closely with independent data on mean canopy residence time for trees that die at the average gap-maker size of 51 cm DBH. The data support previous hypothetical explanations of the apparent discrepancy between canopy turnover times of <130 years for hardwood species and the frequent occurrence of trees exceeding 250 years of age.

Effects of a native forest pathogen, Phellinusweirii, on Douglas-fir forest composition in western Oregon

1993 ◽  
Vol 23 (12) ◽  
pp. 2473-2480 ◽  
Author(s):  
Jenny C. Holah ◽  
Mark V. Wilson ◽  
Everett M. Hansen
Keyword(s):  
Tree Mortality ◽  
Vascular Plant ◽  
Douglas Fir ◽  
Forest Composition ◽  
Native Forest ◽  
Forest Pathogen ◽  
Vascular Plant Diversity ◽  
Center Edge ◽  
Ordination Techniques ◽  
Root Grafts

The fungal pathogen Phellinusweirii (Murrill) Gilbertson (Family: Hymenochaetaceae) causes extensive rot in the roots and bole of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) and true firs, eventually leading to tree mortality. The native pathogen spreads slowly via root grafts and root contacts between conifers, leaving behind areas of tree mortality commonly called infection centers. This study determines (i) whether the slow, systematic removal of the Douglas-fir overstory by P. weirii changes the community composition of old-growth and mature forests, (ii) if composition is significantly affected, to what degree P. weirii influences the composition, (iii) what effects the disease has on individual populations, and (iv) whether vascular plant diversity is affected by disease presence. The herb, shrub, and tree strata were randomly sampled within and adjacent to six P. weirii infection centers located in the low-elevation Cascade and Coast ranges of western Oregon. Statistically significant (P ≤ 0.05) differences in species composition between infected and adjacent noninfected forest were found across all sites. Ordination techniques showed that the distance of vegetation to the infection center edge was a major factor underlying the forest community's structure. The average cover of all herbaceous species was higher inside infection centers as compared with outside, for all locations, though statistically significant at only two sites. In general, species differed in their responses to disease presence. Changes in diversity due to the presence of the root rot were statistically significant in three of the six cases (P ≤ 0.05) but the patterns of change differed from site to site. The removal of Douglas-fir overstory has strong effects on the plant community, but the specific patterns depend on the species and site involved.

scholarly journals Changes in Transpiration and Leaf Water Potential in Douglas-Fir Trees following Douglas-Fir Beetle Attack and Mechanical Girdling

Forests ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1722
Author(s):  
Javier E. Mercado ◽  
Robert T. Walker ◽  
Scott Franklin ◽  
Shannon L. Kay ◽  
Susana Karen Gomez ◽  
...  
Keyword(s):  
Water Potential ◽  
Bark Beetle ◽  
Leaf Water Potential ◽  
Bark Beetles ◽  
Tree Mortality ◽  
Douglas Fir ◽  
Leaf Water ◽  
Lodgepole Pines ◽  
And Control ◽  
Phloem Feeding

Bark beetles and their associated fungi kill trees readily, but we often ignore which organism is the leading cause of tree mortality. While phloem feeding beetles inhibit photosynthate transport, their associated fungi block the tracheids disrupting transpiration. Within the family Pinaceae, knowledge of tree physiological decline following bark beetle and associated fungi colonization is limited to the genus Pinus. Here we investigate the physiological response of Pseudotsuga (P. menziesii) to bark beetles or its fungi. We hypothesized that fungi block water transport in Douglas-fir causing faster mortality than by bark beetle activity alone. We successfully lured Douglas-fir beetle to attack a subset of trees in our experimental area using pheromones and compared Beetle-Killed trees with mechanically Girdled, and Control trees. During spring snowmelt, nine months after treatments were applied, Control, Girdled, and five trees that Survived beetle attack had higher transpiration rates and less negative pre-dawn water potential than five Beetle-Killed trees. Declines in transpiration and leaf water potential in our Beetle-Killed trees occurred much earlier than those in studies of beetle-attacked lodgepole pines, suggesting stronger defensive traits in Douglas-fir. Our data suggest that, as in pines, bark beetle-associated fungi are the leading cause of mortality in Douglas-fir beetle-attacked trees.

Stand development in an old-growth subalpine forest in southern interior British Columbia

1999 ◽  
Vol 29 (9) ◽  
pp. 1347-1356 ◽  
Author(s):  
R Parish ◽  
J A Antos ◽  
M -J Fortin
Keyword(s):  
Bark Beetles ◽  
Subalpine Forest ◽  
Radial Increment ◽  
Abies Lasiocarpa ◽  
Old Growth ◽  
Engelmann Spruce ◽  
Dryocoetes Confusus ◽  
Old Growth Forest ◽  
Canopy Trees ◽  
Short Period

The dynamics of an old-growth Engelmann spruce (Picea engelmannii Parry) - subalpine fir (Abies lasiocarpa (Hook.) Nutt.) forest were investigated using stand-history reconstruction. Age and size structures, tree location, and radial increment patterns were used to link establishment and growth to disturbances. The spatial distribution of trees was used to infer patterns of establishment and mortality. The forest originated in the 1650s, probably after fire. Initial establishment took almost 80 years, after which fir continued to recruit effectively, but spruce did not. The tree-ring record showed no evidence of widespread disturbance during the first 200 years, but from about 1855 to 1900 a major period of canopy mortality caused by bark beetles released suppressed trees and provided opportunities for establishment and rapid growth of seedlings of both species. Most current canopy trees established or released during this period of disturbance; thus, many canopy trees are fairly young in this old-growth forest and canopy turnover is high. A short period of disturbance (1927-1932) caused by the balsam bark beetle (Dryocoetes confusus Swaine) resulted in release of suppressed trees but did not promote seedling establishment. At the time of study (1994), the stand was undergoing another minor disturbance caused by this insect. Bark beetles appear to be of fundamental importance in controlling the dynamics of spruce-fir forests during the long intervals that often occur between fires in cool, wet climates.

Microclimatic and soil moisture responses to gap formation in coastal Douglas-fir forests

2002 ◽  
Vol 32 (2) ◽  
pp. 332-343 ◽  
Author(s):  
Andrew N Gray ◽  
Thomas A Spies ◽  
Mark J Easter
Keyword(s):  
Soil Moisture ◽  
Solar Radiation ◽  
Pacific Northwest ◽  
Air Temperature ◽  
Douglas Fir ◽  
Organic Substrates ◽  
Gap Formation ◽  
The North ◽  
Soil Temperatures ◽  
Closed Canopy

The effects of gap formation on solar radiation, soil and air temperature, and soil moisture were studied in mature coniferous forests of the Pacific Northwest, U.S.A. Measurements were taken over a 6-year period in closed-canopy areas and recently created gaps in four stands of mature (90–140 years) and old-growth (>400 years) Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) forest in the western Cascade Range of central Oregon and southern Washington. Gap sizes ranged from 40 to 2000 m2. Summer solar radiation levels and soil temperatures differed significantly among gap sizes and positions within gaps and were driven primarily by patterns of direct radiation. Nevertheless, effects on air temperature were slight. Soil moisture was more abundant in gaps than in controls, was most abundant in intermediate gap sizes, and tended to decline during the growing season in single-tree gaps and on the north edges of large gaps. However, there was substantial variation in moisture availability within individual gaps, primarily related to the variety of organic substrates present. Moisture in gaps declined over multiple years, likely caused by encroachment of vegetation within and around gaps. Low light levels probably limit filling of natural gaps in these forests, but the variety of microenvironments in large gaps may facilitate diverse plant communities.

Canopy gaps in Douglas-fir forests of the Cascade Mountains

1990 ◽  
Vol 20 (5) ◽  
pp. 649-658 ◽  
Author(s):  
Thomas A. Spies ◽  
Jerry F. Franklin ◽  
Mark Klopsch
Keyword(s):  
Canopy Structure ◽  
Douglas Fir ◽  
Western Hemlock ◽  
Permanent Plots ◽  
Gap Size ◽  
Gap Formation ◽  
Seedling Density ◽  
Old Growth ◽  
Mature Stand ◽  
Mature Stands

Types and rates of mortality were measured and canopy gap formation rates were estimated from 5- to 15-year records of mortality in 34 permanent plots in mature (100- to 150-year-old) and old-growth (>200-year-old) Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco)/western hemlock (Tsugacanadensis (Raf.) Sarg.) forests in western Oregon and Washington. Gap surveys were conducted in a mature and an old-growth stand, and characteristics of 40 gaps and regeneration were measured. Most canopy trees died without disrupting the forest in both mature (87.6%) and old-growth stands (73.3%). The amount of forest area per year representing new gaps was 0.7% in mature stands and 0.2% in old-growth stands. The gap survey found a higher proportion of gaps in the mature stand than in the old-growth stand. Most regeneration (> 1 m tall) in gaps was western hemlock; Douglas-fir regeneration did not occur. The ratio of seedling density in gaps to density under canopies was about 3 for the mature stand and about 9 for the old-growth stand. Seedling density was correlated with measures of gap age but not gap size. The study suggests that gap disturbances and vegetative responses are important processes in the dynamics of these forests. However, gap formation rates and vegetative responses appear to be slow relative to other forest types. In addition to gap size, canopy structure and disturbance severity are important determinants of gap response.

Short- and long-term growth characteristics associated with tree mortality in southwestern mixed-conifer forests

2014 ◽  
Vol 44 (10) ◽  
pp. 1227-1235 ◽  
Author(s):  
Jeffrey M. Kane ◽  
Thomas E. Kolb
Keyword(s):  
Tree Mortality ◽  
Douglas Fir ◽  
Growth Characteristics ◽  
Conifer Forests ◽  
Mixed Conifer ◽  
Dead Trees ◽  
White Fir ◽  
Mixed Conifer Forests ◽  
Short And Long Term

Continued increases in global temperatures and incidences of drought have been implicated in elevated tree mortality in many regions, prompting interest in better understanding tree mortality processes. A recent extreme drought in the southwestern U.S. (1996–2003) contributed to elevated tree mortality throughout the region. We used this event to investigate the relationship of short- and long-term tree growth characteristics to recent (1996–2008) tree mortality in the mixed-conifer forests in northern Arizona. We compared radial growth characteristics over a 50-year period between paired live and recently dead white fir (Abies concolor (Gordon & Glend.) Lindl. ex Hildebr.), limber pine (Pinus flexilis E. James), trembling aspen (Populus tremuloides Michx.), and Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco). We found that (i) dead trees of all species typically had lower mean growth rates than live trees, (ii) dead trees of most species had a greater coefficient of variation in growth over long time periods (>20 years) than live trees, (iii) dead aspen and dead Douglas-fir trees had larger negative growth trends than live trees for some time periods, (iv) dead trees of most species had larger numbers of abrupt growth declines than live trees, and (v) a combination of short- and long-term growth characteristics distinguished live and dead trees, with greater importance of short-term growth for aspen, long-term growth for limber pine, and a mix of short- and long-term growth for white fir and Douglas-fir. These results strongly suggest that recent tree mortality in southwestern mixed-conifer forests is caused by a mixture of short- and long-term processes.

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