Light modification in a developing silvopastoral system in the UK: a quantitative analysis

Transmitted photosynthetically active radiation (PAR) was measured in eight-year-old silvopastoral stands at three different locations in the UK by using PAR sensors randomly distributed between four adjacent trees planted in a square pattern. Two densities (100 stems.ha^-1 and 400 stems.ha^-1 were compared. The annual carrying capacity (live weight of the animals that a plot supports) was also recorded as an indirect figure of the overall agricultural production of the system. The silvopastoral plots received less radiation than the agricultural plot without trees, the 400 stems.ha^-1 treatment being more shaded than the 100 stems.ha^-1. Over the measurement period, on some special days, a maximum of 30% of the incoming radiation was intercepted on the 400 stem.ha^-1 treatment with the largest trees. The amount of light intercepted was highly correlated with the type of weather and the leaf area development of the trees: the brighter the day and more expanded the leaf area, the higher was the proportion of radiation intercepted by the tree. However, over the measuring period, a small amount of radiation was intercepted by the tree canopies. As a consequence, no differences were observed in the annual carrying capacity. This revised version was published online in June 2006 with corrections to the Cover Date.     

Use of goats as biological agents for the renovation of pastures in the Appalachian region of the United States

Much of hill-land pasture in the Appalachian region of the United States is dominated by herbaceous weeds and brush. Low cost, low input and environmentally acceptable reclamation procedures are needed to maintain the productivity of these pastures. This experiment evaluated the effectiveness of using goats (Capra hircus hircus) alone (30 mature, brush does/ha) or cattle (Bos taurus) with goats (17 mature, brush does/ha + two to three steers/ha -- 225 kg average live weight) to reclaim a pasture from an abandoned, overgrown 5.9 ha orchard left untouched for 15 years. Over four grazing seasons, managed defoliation resulted in a substantial increase in herbaceous vegetative cover in plots grazed by goats alone (65 to 86%) and by goats with cattle (65 to 80%) while vegetative cover decreased from 70 to 22% in the control plot. Similarly, the cover by grass species increased in the grazed plots (goats: 16 to 63%; goats + cattle: 13 to 54%) while averaging 10% in the control plot. Multiflora rose (Rosa multiflora Thumb.) bushes were practically eliminated after four grazing seasons as quantified by an average reduction in height from 2.1 m to 0.6 m, and by the number of dead canes (stems) in both the goat (100%) or goat + cattle (92%) treatments. Results indicated that the foraging habits of goats resulted in the elimination of multiflora rose bushes and in a significant increase in desirable forage species. This revised version was published online in June 2006 with corrections to the Cover Date.     

美国阻燃处理木材的现状

总结美国阻燃处理木材的规范与标准,介绍美国主要阻燃处理木材生产商的阻燃木材产品,分析主要阻燃剂的配方及合成工艺、处理木材的工艺与技术特点,为国内阻燃处理木材行业的技术发展提出建议.     

Agroforestry potential in the southeastern United States: perceptions of landowners and extension professionals

The first steps in developing an agroforestry extension and training program involve compilation, synthesis, and analysis of current knowledge on existing practices. Equally important is to understand the perceptions of landowners and professionals of agroforestry as a land use option. No systematic effort has been made to assess these critical issues in the southeastern United States. Therefore, needs assessment surveys were developed following an analysis of major demographic issues that frame land use in the region and synthesis of information obtained from informal site visits and interviews with people engaged in resource and land use in the Atlantic and Gulf Coastal Plain. Surveys of extension professionals and landowners were then undertaken in the states of Alabama, Florida, and Georgia to represent the southeastern region. In addition to getting insights into the perceived benefits and concerns about agroforestry practices, the surveys indicated that the extent of alley cropping, forest farming and silvopasture practiced by landowners was less than anticipated, and that the prominence of windbreaks was overlooked by professionals. Managed riparian forest buffers or streamside management zones and windbreak technologies were the most widely used forms of agroforestry in the study area, although landowners did not recognize influence of agroforestry practices on quality or quantity of water among benefits of highest importance to them. Multistrata patio- or home gardens were also a prominent landowner-practice and acknowledged by professionals. These survey results can be useful for developing a relevant agroforestry extension and training program in the subtropical Southeast and may be of interest to agroforestry efforts in other similar settings. This revised version was published online in August 2006 with corrections to the Cover Date.     

An Overview of Non-Timber Forest Products in the United States Today

Summary

As people become more interested in personal health and family activities, demand for wild forest products has increased. This increased demand coupled with an increased concern for sustainable m anagement practices has focused attention on the variety of issues and products involved in the non-timber forest products industry. Forest management organizations have gradually increased funding for research and management of non-timber forest products over the past two decades. The broad categories of U.S. non-timber forest products include floral greens, Christmas greens, ornamentals and craft materials, wild edibles, medicinals, ceremonials/culturals, and native transplants. The increase in resource pressure has had many policy reactions, including restricted access, harvesting fees, and harvest limits. Opportunities for public input to policy decisions on federal, state and private land are often unclear or nonexistent. Researchers, managers, and policy makers are working to understand the multitude of issues surrounding non-timber forest products, including biology, management, public policy and equity issues.     

An indicator of tree migration in forests of the eastern United States

Changes in tree species distributions are a potential impact of climate change on forest ecosystems. The examination of tree species shifts in forests of the eastern United States largely has been limited to simulation activities due to a lack of consistent, long-term forest inventory datasets. The goal of this study was to compare current geographic distributions of tree seedlings (trees with a diameter at breast height ≤2.5 cm) with biomass (trees with a diameter at breast height > 2.5 cm) for sets of northern, southern, and general tree species in the eastern United States using a spatially balanced, region-wide forest inventory. Compared to mean latitude of tree biomass, mean latitude of seedlings was significantly farther north (>20 km) for the northern study species, while southern species had no shift, and general species demonstrated southern expansion. Density of seedlings relative to tree biomass of northern tree species was nearly 10 times higher in northern latitudes compared to southern latitudes. For forest inventory plots between 44° and 47° north latitude where southern tree species were identified, their biomass averaged 0.46 tonnes/ha while their seedling counts averaged 2600 ha⁻¹. It is hypothesized that as northern and southern tree species together move northward due to greater regeneration success at higher latitudes, general species may fill their vacated niches in southern locations. The results of this study suggest that the process of northward tree migration in the eastern United States is currently underway with rates approaching 100 km/century for many species.     

An analysis of the public discourse about urban sprawl in the United States: Monitoring concern about a major threat to forests

Urban sprawl has been identified as a serious threat to forests and other natural areas in the United States, and public concern about the impacts of sprawling development patterns has grown in recent years. The prominence of public concern about sprawl is germane to planners, managers, and policymakers involved in efforts to protect interface forests from urban encroachment because the level of concern will influence the acceptance of policies and programs aimed at protecting forests. A new indicator of public concern about urban sprawl is presented, based on computer content analysis of public discussion contained in the news media from 1995–2001. More than 36,000 news stories about sprawl were analyzed for expressions of concern. Overall concern about sprawl grew rapidly during the latter half of the 1990s. The environmental impacts of sprawl were the most salient concern overall, and concern about loss of open space and traffic problems has increased since 1995 as a share of all sprawl concerns. The method described in this paper provides a new approach for planners and policymakers to monitor change in public attitudes about a wide range of social issues over time.     

Nitrogen-fixation dynamics in a cut-and-carry silvopastoral system in the subhumid conditions of Guadeloupe, French Antilles

This paper summarizes several studies on N recycling in a tropical silvopastoral system for assessing the ability of the system to increase soil fertility and insure sustainability. We analyzed the N₂ fixation pattern of the woody legume component (Gliricidia sepium), estimated the recycling rate of the fixed N in the soil, and measured N outputs in tree pruning and cut grass (Dichanthium aristatum). With this information, we estimated the N balance of the silvopastoral system at the plot scale. The studies were conducted in an 11-year-old silvopastoral plot established by planting G. sepium cuttings at 0.3 m × 2 m spacing in natural grassland. The plot was managed as a cut-and-carry system where all the tree pruning residues (every 2-4 months) and cut grass (every 40-50 days) were removed and animals were excluded. No N fertilizer was applied. Dinitrogen fixation, as estimated by the ¹⁵N natural abundance method, ranged from 60-90% of the total N in aboveground tree biomass depending on season. On average, 76% of the N exports from the plot in tree pruning (194 kg [N] ha^–1 yr^–1) originated from N₂ fixation. Grass production averaged 13 Mg ha^–1 yr^–1 and N export in cut grass was 195 kg [N] ha^–1 yr^–1. The total N fixed by G. sepium, as estimated from the tree and grass N exports and the increase in soil N content, was about 555 kg [N] ha^–1 yr^–1. Carbon sequestration averaged 1.9 Mg [C] ha^–1 yr^–1 and soil organic N in the 0-0.2 m layer increased at a rate of 166 kg [N] ha^–1 yr^–1, corresponding to 30% of N₂ fixation by the tree. Nitrogen released in nodule turnover (10 kg [N] ha^–1 yr^–1) and litter decomposition (40 kg [N] ha^–1 yr^–1) contributed slightly to this increase, and most of the recycled N came from the turnover or the activity of other below-ground tree biomass than nodules. This revised version was published online in June 2006 with corrections to the Cover Date.     

A financial analysis of a silvopasture system in southern Mississippi

Silvopasture is reemerging as a land use in the southern US. Alternate land use treatments based on field trials for timber and pasture for beef cattle production were financially evaluated. Multiple-use management aspects of these systems were further illustrated by the addition of fee hunting. Land Expectation Values (LEVs) were lower when silvopasture treatments were compared to steer grazing only. However, silvopasture treatments compared favorably to some grazing treatments. LEVs were higher when silvopasture treatments were compared to commercial forest plantation applications on similar sites. Silvopasture systems promote multiple-use management of the land under an environmentally friendly cropping system whereby certain types of wildlife can thrive. This is particularly relevant in light of recent increases in fee hunting in the South. LEVs were reduced by $289, $200, and $151 ha⁻¹ at discount rates of 5%, 7%, and 9% respectively, when fee hunting was excluded in the recommended silvopasture treatment. The monetary value of a wildlife component in this system can be interpreted as the expected value gained per hectare per rotation in perpetuity when fee hunting is part of the management plan. On average, it represented an 8.6% gain in LEVs for this treatment. Results from this study support the potential for silvopasture applications in the South for private landowners. Cattle grazing of improved forage in commercially productive loblolly pine (Pinus taeda) stands can relieve annual cash flow problems inherent in tree production. This revised version was published online in June 2006 with corrections to the Cover Date.     

Post-wildfire seeding in forests of the western United States: An evidence-based review

Broadcast seeding is one of the most widely used post-wildfire emergency response treatments intended to reduce soil erosion, increase vegetative ground cover, and minimize establishment and spread of non-native plant species. We conducted an evidence-based review to examine the effectiveness and effects of post-wildfire seeding treatments on soil stabilization, non-native species invasion, and plant community recovery in the western U.S. We reviewed 94 scientific papers and agency monitoring reports identified using a systematic search protocol. As sampling designs have become more rigorous in recent years, evidence that seeding is effective in reducing erosion has decreased. Of highest and high quality studies evaluating soil erosion, 92% (11 of 12) were published since 2000, none of which showed an effective result. Before 2000, the majority of the studies (71%) fell into the lowest quality categories, of which 72% showed seeding to be effective. The majority of studies (20 of 27, 74%) evaluating soil erosion in seeded versus unseeded controls showed that seeding did not reduce erosion relative to unseeded controls. Even when seeding significantly increased vegetative cover, seeded sites rarely supported plant cover levels considered sufficient to stabilize soils within the first and second year post-wildfire. Of the 11 studies evaluating seeding effectiveness for curtailing invasions of non-native plant species, an almost equal percentage found seeding treatments to be either effective (54%, 6 studies) or ineffective (45%, 5 studies). However, the majority of effective and ineffective treatments (83% and 80%, respectively) used non-native species. Sixteen of 26 studies (62%) evaluating seeding effects on plant communities reported that seeding suppressed recovery of native plants, although data on long-term impacts of this reduction are limited. The literature suggests that post-wildfire seeding does little to protect soil in the short-term, has equivocal effect on invasion of non-native species, and can have negative effects on native vegetation recovery, although long-term studies are needed to assess lasting impacts of seeded species.     

Pasture production in a silvopastoral system in relation with microclimate variables in the atlantic coast of Spain

Grasses and legumes of high productivity and nutritional quality are a good alternative as pasture supplements in rangelands of low quality forage. Orchardgrass (Dactylis glomerata L. cv. `Artabro') and white clover (Trifolium repens L. cv. `Huia') are known as shade tolerant and low flammability species that have been successfully used in agroforestry systems in Galicia, both diminishing fire hazard compared with natural shrublands. In this study, annual and seasonal production of a grass mixture of both species was quantified during 3 years in a pinewood under different tree canopy covers. Regardless of cover, pasture production increased in summer, and decreased from fall to spring. We obtained a significant correlation between annual pasture production and light transmission through the tree canopy (R² = 0.96, P<0.05). Light transmittance through a maritime pine canopy (Pinus pinaster Ait.) was higher than through a Scots pine canopy (P. sylvestris L.), corresponding to 36–57% and 16–21% of full sunlight respectively. The highest herbage production was obtained in no tree stands and the lowest under a P. sylvestris canopy. Fluctuations inlight transmission, temperature and PAR (Photosynthetically Active Radiation) under tree canopy were less apparent compared with no tree stands. Variation in seasonal production was more pronounced in stands without trees, and appeared more uniform when percentage of light intercepted by tree canopy increased.This revised version was published online in November 2005 with corrections to the Cover Date.     

An application of data envelopment analysis to investigate the efficiency of lumber industry in northwestern Ontario, Canada

This study aims at exploring the technical efficiency of lumber industry in northwestern Ontario,Canada using data envelopment analysis(DEA).The DEA model analyzes relative technical efficiency of lumber mills with disproportionate inputs and outputs by dividing the 10year time series data,for inputs and outputs of 24 lumber mills,over two periods(1999-2003 and 2004-2008).Four inputs,namely,material(log volume),labour(man-hours),two types of energy(hog-fuel and electricity),and one output(lumber volume) are used in this study.The trend analysis shows an annual reduction of 10%,13% and 13% for lumber output,log consumption(input) and number of employees,respectively,during the period 1999-2008.The results from DEA with two scenarios with energy inputs and without energy inputs,for the two periods are found to be mixed and interesting.While some mills have improved their performance in terms of best use of available scarce inputs in the second period,some have shown negative per cent change in efficiency.In the with energy input and the without energy input scenario,some of the mills show a reduction in efficiency in the second period from the first period,with the highest estimated reductions of-13.9% and-47.6%,respectively.A possible explanation for these negative performances of mills in the latter period is the decline in production in the second period compared to the first period,where these mills were not able to adjust their inputs(mostly labour) as proportional lay-offs might not have been possible.These results provide policy makers and industry stakeholders with an improved understanding of the trends of efficiency and employment as well as reallocation opportunities of future inputs in order to increase benefits from this sector.     

The effect of cattle grazing on soil physical and chemical properties in a silvopastoral system in the Peruvian Amazon

In a six-year-old peach palm (Bactris gasipaes) plantation, centrosema (Centrosema macrocarpum), a leguminous forage plant, was established as a cover crop which was eventually grazed. This experiment was designed to monitor probable changes in soil physical and chemical properties and measure peach palm fruit production and live-weight gain of cattle grazing this silvopastoral system. The experiment was installed on land that was previously cleared by a D7 bulldozer having a straight blade that mixed the thin layer of topsoil with the acid subsoil (20–40 cm) and severely compacted the soil. The results demonstrated that the centrosema cover crop reduced soil bulk density, increased water infiltration rates and reduced mechanical resistance. In general soil physical properties were improved with the use of Centrosema as forage and cover crop. Soil acidity and aluminum saturation decreased considerably, while potassium concentrations increased. Calcium and magnesium concentrations decreased over time as these minerals were stored in the pasture biomass, translocated to fresh peach palm fruits and/or exported to animals. A strong competition for nutrients was observed between the peach palm plants and Centrosema. The low production of peach palm fruits was in response to mechanized land clearing during initial establishment of the plantation, and also probably due to deficits of N, P, K, Ca and Mg in the soil instead of being a consequence to the presence of cattle. The average increase in live-weight gains of the cattle was at a rate of 445 g/animal/day during the four-years of the study. Such an increase is substantially greater than those registered in the area under traditional grazing systems used in the region. This revised version was published online in August 2006 with corrections to the Cover Date.     

美国的造林过程及启示

通过200多年的发展, 美国林业形成了一个相对完备、科学性强、有着良好收益的造林激励体系。文中从美国的造林工程、造林扶持政策等方面介绍美国的造林过程, 并结合我国的林业发展现状提出了明晰产权、尊重价值规律、健全林业政策保障体系和提高林业科技水平等建议。     

Relationship between tree canopy height and the production of pasture species in a silvopastoral system based on alder trees

Silvopastoral systems in New Zealand that incorporate trees planted to control soil erosion on hills largely rely on the productivity of the pastoral system for financial returns. The effect on pasture productivity of increasing the tree canopy height by pruning Italian gray alder (Alnus cordata) was investigated by measuring the response of light, soil moisture, soil temperature, pasture production of major pasture species, and grazing behaviour of sheep. A split-plot design with four replicates was used. The main plot treatments were three levels of shade (81, 23, and 12% of available photosynthetic photon flux (PPF)), created by pruning 11 year old alder grown at the same density. The sub-plot treatments were four pasture mixes: perennial ryegrass (Lolium perenne), Yorkshire fog (Holcus lanatus), and cocksfoot (Dactylis glomerata), each sown with white clover (Trifolium repens), and cocksfoot sown with lotus (Lotus pedunculatus). Soil temperature was highest under light shade. Total herbage yield at 50 mm stubble height from October to May under heavy and medium shade was 60 and 80%, respectively, of the total herbage harvested under light shade. Cocksfoot had the greatest herbage yield, either with lotus or white clover. The tillering of perennial ryegrass was suppressed by shade more than for the other grass species making ryegrass unsuitable for use in this silvopastoral system. More sheep grazed in the light shade than in the heavy shade, but there was no difference in sheep preference for cocksfoot or Yorkshire fog. Lotus was grazed more frequently than white clover. Pruning of alder to increase canopy height has the potential to improve the productivity of the understorey pasture and its acceptability to sheep.     

以林地为主的土地利用类型对生态系统服务功能影响研究——以长沙市岳麓区莲花镇为例

土地利用结构的改变对生态系统服务功能影响深远。参照前人提出的陆地生态系统价值当量因子表并结合研究区实际情况,计算出研究区2005~2013年生态系统服务价值VESV。结果表明:莲花镇生态系统服务价值构成中,林地占主要部分,达到75%以上,其次是水域。研究区总VESV由2005年的45.73×107元减少到2013年的44.81×107元,林地面积的减少以及建设用地面积的增加是生态系统服务价值减少的主要原因;对开展"综合土地整理"项目的五村进行分析,结果表明大华村和立马村的单位面积ESV较高,说明两村生态效益较高,土地利用规划更加合理;桐木村的单位面积ESV最小,在今后的发展中应增加林地面积,保护耕地,减少未利用地向建设用地转变。研究期内各土地利用类型的敏感性指数均小于1,说明研究结果可信。     

美国俄勒冈州的生物入侵问题及其启示

重点介绍了俄勒冈州的生物入侵问题, 指出其生物入侵现状, 采取的主要防治措施, 以及遇到的主要困难。最后指出在处理生物入侵问题方面我们应该汲取的经验教训。     

Guidelines for Managing Wildlife Habitats in Southwestern Ponderosa Pine Forests of the United States

IntroductionEcoledcalrelahonshipsanddePendenceofwildlifesPe-ciesonsouthwesternPOnderosapine(Pineponderosa)fOrestsarecloselyrelat6dtohabitatuse.Foraginghabits,seasOndfoodPreferences,anduseoftreesforfeedingarelawtydePendentuponthestrUctureandspahalar-rangme…     

Soil physical factors affecting the growth of sycamore (Acer pseudoplatanus L.) in a silvopastoral system on a stony upland soil in North-East Scotland

Tree growth and soil physical properties were compared on two grazed plots planted with sycamore at 5 and 10 m square spacing on an upland Scottish site. Both plots received fertilizer and stocking density of ewes and lambs was adjusted to maintain a constant sward height.Mean tree height in 1990 and height increment (1988–90) were significantly greater in the 5 m spaced plot (P<0.05). Although matric potential under the trees was generally greater than in the grassed rows between trees, mean penetration resistance (37–107 mm depth) was significantly greater (P<0.01) under the trees. Even when the soil was close to field capacity, less than 10% of penetrometer readings were < 1 MPa under the trees, in comparison to 44% in grassed areas between trees. This demonstrates that surface compaction due to preferential treading by sheep near the base of trees was sufficient to have seriously reduced tree root growth. Penetration resistance under the 5 m spaced trees was significantly less (P<0.05) than under the 10 m spaced trees. A technique for estimating the probability of root deflections by stones (in 35 mm depth intervals), Ps, from penetrometer readings was used. A significant relationship (P<0.1) was found between tree height increment and depth to Ps0.4 in the 10 m plot.