运用空间代替时间的方法研究了25年生柳杉人工林(对照)采伐后形成的柳杉人工幼龄林、经济林、苗圃地、皆伐迹地、农耕地5种土地利用类型初期土壤有机碳含量和碳储量变化。结果表明,5种土地利用类型和对照的土壤有机碳含量和碳储量均随...运用空间代替时间的方法研究了25年生柳杉人工林(对照)采伐后形成的柳杉人工幼龄林、经济林、苗圃地、皆伐迹地、农耕地5种土地利用类型初期土壤有机碳含量和碳储量变化。结果表明,5种土地利用类型和对照的土壤有机碳含量和碳储量均随土层的加深而降低;除经济林外,苗圃地、柳杉人工幼龄林、农耕地和皆伐迹地的土壤平均有机碳含量分别比对照降低了10.8%,28.1%,37.8%,40.1%;5种不同土地利用类型土壤碳储量排序为:皆伐迹地(214.2±17.0 t C/hm2)>经济林(191.3±13.4 t C/hm2)>柳杉人工幼龄林(173.5±15.1t C/hm2)>苗圃地(171.9±9.2 t C/hm2)>农耕地(132.7±12.1 t C/hm2),分别比对照(272.9±21.8 t C/hm2)减少了21.5%,29.9%,36.4%,37.0%,51.4%。人工林采伐后形成的不同土地利用类型,土壤有机碳含量和碳储量减小的程度与采伐后紧接着采取的人为措施有关。展开更多
The study evaluated the productivity and energy balance of the harvesting and the extraction of wood in plantation of exotic tree species, i.e., Pinus patula （Schiede ex Schlectendahl et Chamisso） and Cupressus lusi...The study evaluated the productivity and energy balance of the harvesting and the extraction of wood in plantation of exotic tree species, i.e., Pinus patula （Schiede ex Schlectendahl et Chamisso） and Cupressus lusitanica （Mill.）. The harvesting and extraction operations concerned clear-cut felling on two different types of terrain （gentle and steep terrain） and two levels of prun- ing. The results show that cutting is not affected by the terrain gradient whereas the pruning condition shows a significant effect on the delimbing operation. The productivity of cutting is evaluated at 28.1 m3.d-1 for unpruned trees and at 30.2 m3.d t for pruned trees. For the extraction phase, rolling was significantly affected by terrain conditions. On steep terrain, the gross productivity can be evaluated at 22.5 m3.d 1 for an extraction distance of 40 m, while for the same distance on gentle terrain the productivity decreases to 14.1 m3.d~. As a result, the steep terrain condition showed higher energy efficiency, suggesting that it is the more efficient system of extraction. The productivity model and the energy balance resulting from the study provide a better understanding of the variables af- fecting motor-manual cutting and rolling extraction in exotic plantations in Uganda.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
It is widely believed that intensive forestry has influenced small mammal population dynamics,and thereby the entire mammalian community in Fennoscandian boreal forests.The nature of these impacts on the different spe...It is widely believed that intensive forestry has influenced small mammal population dynamics,and thereby the entire mammalian community in Fennoscandian boreal forests.The nature of these impacts on the different species is subject to debate.We live-trapped voles between 2006 and 2009 in 2 commercially harvested forests in south-eastern Norway.We investigated the variation in vole abundance among habitat types(e.g.mature forest and clear-cut)and the hypothesis that graminivorous species such as field voles(Microtus agrestis L.)benefit from clear-cuts at the expense of forest dwellers(i.e.the bank vole,Myodes glareolus Schreb.),using fine-scale descriptors of the ground vegetation.We could not find support for the hypothesis that field voles show a preference for clear-cuts,and their overall abundance was low,while bank voles were the dominant species in all habitat types,including clear-cuts in the peak and pre-peak years.We found a positive association between bank vole abundance and bilberry(Vaccinium myrtillus L.)availability rather than a specific habitat type.Low field vole density in clear-cuts might be due to variation in local productivity and ground vegetation as well as to large variation in the species temporal dynamics.The latter is particularly associated with the widespread decline of field voles in Scandinavia.Logging has the potential to negatively affect bank vole population dynamics because of the negative effect on bilberry development.展开更多
文摘运用空间代替时间的方法研究了25年生柳杉人工林(对照)采伐后形成的柳杉人工幼龄林、经济林、苗圃地、皆伐迹地、农耕地5种土地利用类型初期土壤有机碳含量和碳储量变化。结果表明,5种土地利用类型和对照的土壤有机碳含量和碳储量均随土层的加深而降低;除经济林外,苗圃地、柳杉人工幼龄林、农耕地和皆伐迹地的土壤平均有机碳含量分别比对照降低了10.8%,28.1%,37.8%,40.1%;5种不同土地利用类型土壤碳储量排序为:皆伐迹地(214.2±17.0 t C/hm2)>经济林(191.3±13.4 t C/hm2)>柳杉人工幼龄林(173.5±15.1t C/hm2)>苗圃地(171.9±9.2 t C/hm2)>农耕地(132.7±12.1 t C/hm2),分别比对照(272.9±21.8 t C/hm2)减少了21.5%,29.9%,36.4%,37.0%,51.4%。人工林采伐后形成的不同土地利用类型,土壤有机碳含量和碳储量减小的程度与采伐后紧接着采取的人为措施有关。
文摘The study evaluated the productivity and energy balance of the harvesting and the extraction of wood in plantation of exotic tree species, i.e., Pinus patula （Schiede ex Schlectendahl et Chamisso） and Cupressus lusitanica （Mill.）. The harvesting and extraction operations concerned clear-cut felling on two different types of terrain （gentle and steep terrain） and two levels of prun- ing. The results show that cutting is not affected by the terrain gradient whereas the pruning condition shows a significant effect on the delimbing operation. The productivity of cutting is evaluated at 28.1 m3.d-1 for unpruned trees and at 30.2 m3.d t for pruned trees. For the extraction phase, rolling was significantly affected by terrain conditions. On steep terrain, the gross productivity can be evaluated at 22.5 m3.d 1 for an extraction distance of 40 m, while for the same distance on gentle terrain the productivity decreases to 14.1 m3.d~. As a result, the steep terrain condition showed higher energy efficiency, suggesting that it is the more efficient system of extraction. The productivity model and the energy balance resulting from the study provide a better understanding of the variables af- fecting motor-manual cutting and rolling extraction in exotic plantations in Uganda.
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.
文摘It is widely believed that intensive forestry has influenced small mammal population dynamics,and thereby the entire mammalian community in Fennoscandian boreal forests.The nature of these impacts on the different species is subject to debate.We live-trapped voles between 2006 and 2009 in 2 commercially harvested forests in south-eastern Norway.We investigated the variation in vole abundance among habitat types(e.g.mature forest and clear-cut)and the hypothesis that graminivorous species such as field voles(Microtus agrestis L.)benefit from clear-cuts at the expense of forest dwellers(i.e.the bank vole,Myodes glareolus Schreb.),using fine-scale descriptors of the ground vegetation.We could not find support for the hypothesis that field voles show a preference for clear-cuts,and their overall abundance was low,while bank voles were the dominant species in all habitat types,including clear-cuts in the peak and pre-peak years.We found a positive association between bank vole abundance and bilberry(Vaccinium myrtillus L.)availability rather than a specific habitat type.Low field vole density in clear-cuts might be due to variation in local productivity and ground vegetation as well as to large variation in the species temporal dynamics.The latter is particularly associated with the widespread decline of field voles in Scandinavia.Logging has the potential to negatively affect bank vole population dynamics because of the negative effect on bilberry development.
