We investigated the effects of a long-term thinning experiment on the distribution of above-ground biomass of Douglas-fir （Pseudotsuga menziesii [Mirb.] Franco var. menziesii） in a plantation in southern Italy. Allo...We investigated the effects of a long-term thinning experiment on the distribution of above-ground biomass of Douglas-fir （Pseudotsuga menziesii [Mirb.] Franco var. menziesii） in a plantation in southern Italy. Allometric equations were used to estimate biomass and partitioning to stem and crown compartments. Variation in biomass stock estimated with allometric equations were evaluated according to seven thinning treatments： geo- metric-systematic （1 row every 3）, selective （light-moderate-heavy）, mixed systematic-selective （1 row every 4, 1 row every 5）, unthinned （control）. Over the experimental period of 13 years, current annual increments of carbon were lower （3.4 Mg ha^-1 year^-1） in control plots than in treated plots. At age 30, plots subjected to light selective thinning showed higher values of above-ground biomass （249.7 Mg ha^-1）. The biomass harvested with this treatment was 29.3 Mg ha^-1, and the mean annual increment of carbon over 13 years was 4.8 Mg ha^-1. Our results showed that light thinning stimulated increase in carbon stock, with a minimal loss of carbon during the treatment and a current annual increment of carbon higher than in control sub-plots and sub-plots thinned using systematic methods. This treatment yielded least carbon emissions and we affirm it has discrete global warming mitigation potential.展开更多
In order to study the dynamics of uneven-aged stands of interior Douglas-fir, Pseudotsuga menzesii var.glouca (Mirb.) Franco in future, six permanent sample plots wer set up on the Knife Creek Block of the Alex Fraser...In order to study the dynamics of uneven-aged stands of interior Douglas-fir, Pseudotsuga menzesii var.glouca (Mirb.) Franco in future, six permanent sample plots wer set up on the Knife Creek Block of the Alex Fraser Researh Forcst of University of British Columbia. The measurements and observations for all living trees within theboundaries of a plot wer madc, including DBH(diameter at breast height), TTH(total tree height), height to lowest livingbranch, crown diameter, tree vigor, angle of lean, distance of lean, direction of lean and tree location. Based on the data,some stand characteristics of the plots were analyzed simply and preliminarily. Results showed that most of the interiortrees on the plots are ranged 10-20 cm in distribution of DBH class, and 2-6 m in distribution of rm class. Trees withdifferent fors, however, are distributed unevenly. The relationship between total tree height and diameter at breast heightfollows a quadratic distribution, Y=a+bX+cX2.展开更多
The aim of the article was to study the growth of Douglas-fir plantations in the region of the Training Experimental Forest Enterprise, Yundola （Central South Bulgaria）. The study sites were three Douglas-fir planta...The aim of the article was to study the growth of Douglas-fir plantations in the region of the Training Experimental Forest Enterprise, Yundola （Central South Bulgaria）. The study sites were three Douglas-fir plantations, ranging between 50 and 55 years of age at altitudinal range between 1,400 m and 1,600 m above sea level （masl）. The mean height, diameter at breast height, site class, stem volume as well as the mechanical resistance （H/D ratio） of Douglas-fir were measured for each plantation. The results showed that Douglas-fir had the best height growth of the studied plantations on slope facing South at altitude 1,600 masl and Douglas-fir with age 55 years old reached a mean height of 32.4 m. The average diameter at breast height of the studied plantations reaches approximately 30 cm, which shows that they are suitable for large scale wood harvesting. The average stem volume of Douglas-fir in the observed plantations up to age of 55 is within the range of 400-600 m3/ha, with an average annual volume increment from 7 m3/ha to 12 m3/ha each year. The high index of mechanical resistance （H/D ratio） indicated a risk for abiotic damages, which implicated the need for the immediate implementation of felling.展开更多
Large trees have disproportionally large competitive advantage in access to light, which has been proposed to increase growth dominance of large trees (e.g., a larger proportion of volume growth than standing volume i...Large trees have disproportionally large competitive advantage in access to light, which has been proposed to increase growth dominance of large trees (e.g., a larger proportion of volume growth than standing volume is in large trees in a stand). Tree growth may also be limited by the availability of other resources besides light.Nutrient deficiency, especially of nitrogen, is considered common among temperate forests including mixedconifer forests of the Inland Northwest of the United States. Data from a long-term forest nutrition study across four Inland Northwest states were analyzed to evaluate nitrogen×potassium fertilization?s effects on growth dominance over an eight-year period following treatment. Our results show that growth dominance varied substantially across plots in each vegetation series and fertilization treatment, and its mean values generally were at minuscule magnitudes, negative, and not significantly different from 0. We propose that this lack of a clear pattern in growth dominance was the result of the mixed-species composition where shade-tolerant species remained in lower crown positions, yet their relative growth kept pace with large trees. Limited moisture availability at dry sites may have hampered the development of growth dominance. Growth dominance also was lowered by mortality observed among relatively large trees. The largely negative growth dominance across fertilization treatments indicated that small trees seem to have maintained higher relative growth rates than large trees, even if absolute growth was higher among large trees. In the case fertilization does improve stand growth, a significant part of this improved growth will be lost in density-dependent mortality over time if not captured through thinning/harvesting.展开更多
Conventional clear-cut timber harvest is a widespread industrial practice across the Pacific Northwest;however,information regarding how these practices impact soil microbial community structure at the regional scale ...Conventional clear-cut timber harvest is a widespread industrial practice across the Pacific Northwest;however,information regarding how these practices impact soil microbial community structure at the regional scale is limited.With evidence of consistent and substantial impact of harvest on soil microbial functional profiles across the region(despite a range of environmental conditions),the objective of this study was to determine the extent to which harvest also influences the structure of prokaryotic and fungal soil microbial communities,and how generalized these trends are throughout the geographic region.Paired soil samples were collected one year before and after harvest across nine second-growth Douglas-fir forests in the Pacific Northwest.Total community DNA was extracted from the soils,and high-throughput targeted gene sequencing of the 16 S r RNA gene for prokaryotes and the internal transcribed spacer(ITS)gene for fungi was performed.Alpha diversity was consistently and significantly higher after harvest;it was moderately so for fungal communities(+14.6%),but only marginally so for prokaryotic communities(+2.0%).Similarly,on average,a greater proportion of the variation in the community structure of fungi(20.1%)at each site was associated with forest harvest compared to that of prokaryotes(13.2%).Overall,the greatest influence of timber harvest on soil microbial communities appeared to be a relative depletion of ectomycorrhizal fungi,with a concomitant enrichment of saprotrophic fungi.Understanding the short-term responses of soil microbial communities across the region,particularly those of tree root-associated symbionts,may aid our understanding of the role soil microbial communities play in ecological succession.展开更多
文摘We investigated the effects of a long-term thinning experiment on the distribution of above-ground biomass of Douglas-fir （Pseudotsuga menziesii [Mirb.] Franco var. menziesii） in a plantation in southern Italy. Allometric equations were used to estimate biomass and partitioning to stem and crown compartments. Variation in biomass stock estimated with allometric equations were evaluated according to seven thinning treatments： geo- metric-systematic （1 row every 3）, selective （light-moderate-heavy）, mixed systematic-selective （1 row every 4, 1 row every 5）, unthinned （control）. Over the experimental period of 13 years, current annual increments of carbon were lower （3.4 Mg ha^-1 year^-1） in control plots than in treated plots. At age 30, plots subjected to light selective thinning showed higher values of above-ground biomass （249.7 Mg ha^-1）. The biomass harvested with this treatment was 29.3 Mg ha^-1, and the mean annual increment of carbon over 13 years was 4.8 Mg ha^-1. Our results showed that light thinning stimulated increase in carbon stock, with a minimal loss of carbon during the treatment and a current annual increment of carbon higher than in control sub-plots and sub-plots thinned using systematic methods. This treatment yielded least carbon emissions and we affirm it has discrete global warming mitigation potential.
文摘In order to study the dynamics of uneven-aged stands of interior Douglas-fir, Pseudotsuga menzesii var.glouca (Mirb.) Franco in future, six permanent sample plots wer set up on the Knife Creek Block of the Alex Fraser Researh Forcst of University of British Columbia. The measurements and observations for all living trees within theboundaries of a plot wer madc, including DBH(diameter at breast height), TTH(total tree height), height to lowest livingbranch, crown diameter, tree vigor, angle of lean, distance of lean, direction of lean and tree location. Based on the data,some stand characteristics of the plots were analyzed simply and preliminarily. Results showed that most of the interiortrees on the plots are ranged 10-20 cm in distribution of DBH class, and 2-6 m in distribution of rm class. Trees withdifferent fors, however, are distributed unevenly. The relationship between total tree height and diameter at breast heightfollows a quadratic distribution, Y=a+bX+cX2.
文摘The aim of the article was to study the growth of Douglas-fir plantations in the region of the Training Experimental Forest Enterprise, Yundola （Central South Bulgaria）. The study sites were three Douglas-fir plantations, ranging between 50 and 55 years of age at altitudinal range between 1,400 m and 1,600 m above sea level （masl）. The mean height, diameter at breast height, site class, stem volume as well as the mechanical resistance （H/D ratio） of Douglas-fir were measured for each plantation. The results showed that Douglas-fir had the best height growth of the studied plantations on slope facing South at altitude 1,600 masl and Douglas-fir with age 55 years old reached a mean height of 32.4 m. The average diameter at breast height of the studied plantations reaches approximately 30 cm, which shows that they are suitable for large scale wood harvesting. The average stem volume of Douglas-fir in the observed plantations up to age of 55 is within the range of 400-600 m3/ha, with an average annual volume increment from 7 m3/ha to 12 m3/ha each year. The high index of mechanical resistance （H/D ratio） indicated a risk for abiotic damages, which implicated the need for the immediate implementation of felling.
基金Funding for study establishment and remeasurements was provided by members of the Intermountain Forest CooperativeFunding was also provided by the National Science Foundation award IIP-1916699。
文摘Large trees have disproportionally large competitive advantage in access to light, which has been proposed to increase growth dominance of large trees (e.g., a larger proportion of volume growth than standing volume is in large trees in a stand). Tree growth may also be limited by the availability of other resources besides light.Nutrient deficiency, especially of nitrogen, is considered common among temperate forests including mixedconifer forests of the Inland Northwest of the United States. Data from a long-term forest nutrition study across four Inland Northwest states were analyzed to evaluate nitrogen×potassium fertilization?s effects on growth dominance over an eight-year period following treatment. Our results show that growth dominance varied substantially across plots in each vegetation series and fertilization treatment, and its mean values generally were at minuscule magnitudes, negative, and not significantly different from 0. We propose that this lack of a clear pattern in growth dominance was the result of the mixed-species composition where shade-tolerant species remained in lower crown positions, yet their relative growth kept pace with large trees. Limited moisture availability at dry sites may have hampered the development of growth dominance. Growth dominance also was lowered by mortality observed among relatively large trees. The largely negative growth dominance across fertilization treatments indicated that small trees seem to have maintained higher relative growth rates than large trees, even if absolute growth was higher among large trees. In the case fertilization does improve stand growth, a significant part of this improved growth will be lost in density-dependent mortality over time if not captured through thinning/harvesting.
基金supported by Weyerhaeuser Natural Resource Company.
文摘Conventional clear-cut timber harvest is a widespread industrial practice across the Pacific Northwest;however,information regarding how these practices impact soil microbial community structure at the regional scale is limited.With evidence of consistent and substantial impact of harvest on soil microbial functional profiles across the region(despite a range of environmental conditions),the objective of this study was to determine the extent to which harvest also influences the structure of prokaryotic and fungal soil microbial communities,and how generalized these trends are throughout the geographic region.Paired soil samples were collected one year before and after harvest across nine second-growth Douglas-fir forests in the Pacific Northwest.Total community DNA was extracted from the soils,and high-throughput targeted gene sequencing of the 16 S r RNA gene for prokaryotes and the internal transcribed spacer(ITS)gene for fungi was performed.Alpha diversity was consistently and significantly higher after harvest;it was moderately so for fungal communities(+14.6%),but only marginally so for prokaryotic communities(+2.0%).Similarly,on average,a greater proportion of the variation in the community structure of fungi(20.1%)at each site was associated with forest harvest compared to that of prokaryotes(13.2%).Overall,the greatest influence of timber harvest on soil microbial communities appeared to be a relative depletion of ectomycorrhizal fungi,with a concomitant enrichment of saprotrophic fungi.Understanding the short-term responses of soil microbial communities across the region,particularly those of tree root-associated symbionts,may aid our understanding of the role soil microbial communities play in ecological succession.
