The response of land snail assemblages below aspens to forest fire and clear-cutting in Fennoscandian boreal forests

Species can persist in a landscape with recurrent disturbances either through local survival or by dispersing to sites of a preferred successional stage. This study investigated in what extent forest floor dwelling land snails survived forest fires and clear-cutting. Snail fauna in LFH (litter, fermenting litter and humus) samples below retained aspen trees in disturbed areas were compared with samples under scattered aspens in adjacent forests by extracting snails from LFH samples below five aspens in several stands of each type (five forest fires, six clear-cuts, and seven undisturbed forests). LFH samples from burnt sites had a higher pH than from forests, but on average a lower abundance of individual snails (11 vs. 30 in 0.5 l LFH) and 50% lower species density (3 vs. 6 species). The abundances and species densities in the clear-cuts were less affected. There was generally a positive relationship between pH and both species density and abundance in all the stand types. Burning apparently depleted the snail fauna considerably and some species may be dependent on dispersal if they are to recover within the burnt area, while the snail assemblages at clear-cuts did not differ significantly in species composition from adjacent forests. The positive relationship between pH and snail prevalence on the burnt sites raises questions regarding the pre- and post-fire spatial variation in pH (and available minerals) within and among stands and how it relates to snail survival rates and their capacity to track suitable places after the disturbance. Retained aspens at clear-cuts seem to harbour a forest like land snail fauna.     

Persistent effects of fire severity on early successional forests in interior Alaska

There has been a recent increase in the frequency and extent of wildfires in interior Alaska, and this trend is predicted to continue under a warming climate. Although less well documented, corresponding increases in fire severity are expected. Previous research from boreal forests in Alaska and western Canada indicate that severe fire promotes the recruitment of deciduous tree species and decreases the relative abundance of black spruce (Picea mariana) immediately after fire. Here we extend these observations by (1) examining changes in patterns of aspen and spruce density and biomass that occurred during the first two decades of post-fire succession, and (2) comparing patterns of tree composition in relation to variations in post-fire organic layer depth in four burned black spruce forests in interior Alaska after 10-20 years of succession. We found that initial effects of fire severity on recruitment and establishment of aspen and black spruce were maintained by subsequent effects of organic layer depth and initial plant biomass on plant growth during post-fire succession. The proportional contribution of aspen (Populus tremuloides) to total stand biomass remained above 90% during the first and second decades of succession in severely burned sites, while in lightly burned sites the proportional contribution of aspen was reduced due to a 40-fold increase in spruce biomass in these sites. Relationships between organic layer depth and stem density and biomass were consistently negative for aspen, and positive or neutral for black spruce in all four burns. Our results suggest that initial effects of post-fire organic layer depths on deciduous recruitment are likely to translate into a prolonged phase of deciduous dominance during post-fire succession in severely burned stands. This shift in vegetation distribution has important implications for climate-albedo feedbacks, future fire regime, wildlife habitat quality and natural resources for indigenous subsistence activities in interior Alaska.     

The effects of mechanical site preparation and subsequent wildfire on trembling aspen (Populus tremuloides Michx.) regeneration in central Alberta,Canada

The objective of this study was to assess the regeneration response oftrembling aspen (Populus tremuloides Michx.) to differentmechanical site preparation (MSP) techniques commonly used in operationalforestry (disc trenching, drag scarifying and blading) and the specificmicrosites created by each treatment. This study was designed to measureregeneration after at least the first two growing seasons, however a largewildfire burned 80% of the study sites at the beginning of the second growingseason. Consequently, only limited second year data were presented, butregeneration from the first growing season following the fire was alsoassessed.Results indicated that microsites where the forest floor was disturbed and theparent root system was only lightly injured were more conducive to suckeringthan undisturbed microsites or where the root system was severely injured.Also,the fire disturbance after the first growing season resulted in increasedsuckering relative to the untreated controls in the first year. These resultssuggest that aspen sites with thick organic layers or vigorous competition fromother species can benefit from MSP when applied before the first growingseason.In addition, if first year suckering is inadequate, subsequent disturbancessuchas prescribed fire have the potential to improve suckering provided the parentroot system remains intact.     

Soil solution,foliar concentrations and tree growth response to 3-year of ammonium-nitrate addition in two boreal forests of Québec,Canada

Ammonium nitrate (NH₄NO₃) was applied monthly (from June to October) for 3 years in a balsam fir (Abies balsamea (Linné) Miller) and a black spruce (Picea mariana (Mill.) BSP) boreal forest in Québec (Canada). The design was composed of nine experimental units of 10 m × 10 m for each site. Application rates were 3 and 10 times the atmospheric N deposition measured at each site which was 6 and 3 kg ha⁻¹ year⁻¹ for the fir and the spruce sites, respectively. Soil solution composition (30 and 60 cm), tree growth, and foliar concentrations were analysed. The inorganic N in the soil solution of the control plots of both sites was low, particularly at the spruce site indicating that these forests are actively accumulating the atmospheric deposited N. Nitrogen additions regularly caused sudden and large inorganic N increases in the soil solution at both sites, both treatments and both sampling depths. However, these increases were transitory in nature and no persistent changes in inorganic N were observed. It was estimated that more than 95% of the added N was retained above the rooting zone at both sites. Nitrogen addition increased N, Ca, Mg and Mn foliar concentrations at the black spruce site but had no effects at the balsam fir site. After 3 years of N application, tree growth was similar in the control and the treated plots at both sites. Our results show that slow growing black spruce boreal forests with low ambient N deposition are responsive (in term of foliar N, Ca, Mg and Mn concentrations) to even small increases in N inputs, compared to higher growth balsam fir boreal forests with higher N deposition.     

The effect of red wood ant (<Emphasis Type="Italic">Formica rufa</Emphasis> group) mounds on root biomass,density, and nutrient concentrations in boreal managed forests

Red wood ants (Formica rufa group, RWAs) are common insects in boreal forests in Fennoscandia, and they build large, long-lived mounds as their nests. RWA mounds are enriched with carbon and nutrients, but little information is available about how they affect root distribution and the nutrient uptake of trees. In this study, we investigated the biomass, biomass density, nutrient concentrations, and amounts of fine (<2 mm) and coarse (>2 mm) roots in RWA mounds, and compared them with those of surrounding forest soil in mixed coniferous stands of different age classes in Finland. Neither fine nor coarse root biomasses differed significantly between the aboveground parts of the mounds and the organic layer of the soil. Root biomass density was lower in mounds than in the organic layer. However, fine root biomass and biomass density were higher in the belowground parts of mounds than in the surrounding mineral soil. Macroelement (N, Ca, K, P, S, Mg) and Zn and Cu concentrations in roots in the mounds were significantly higher than those in the organic layer. Root biomass and biomass density did not differ between stands of different age classes. The results of this study indicate that RWA mounds increase heterogeneity in root distribution in forest ecosystems, and also increase the availability of nutrients for plants that extend their roots inside RWA mounds.     

Long-term influence of fire and harvesting on boreal forest age structure and forest composition in eastern Québec

In boreal forests, historical variations in the area disturbed by natural disturbances or harvesting have rarely been compared. We measured temporal and spatial variations in areas affected by severe fires and clearcutting throughout the 20th century in a 57, 332 km² section of the eastern Canadian boreal forest. We examined the effects of these disturbances on spatio-temporal variations in the abundance of forests >60 years. Natural variability for the abundance of forests >60 years was estimated from simulations of natural disturbance regimes. We also measured compositional and structural differences between three categories of stands originating from relatively recent disturbances (∼50 years; clearcutting, fires, and clearcutting followed by fires), and one category of stands that were undisturbed for at least 200 years. At the regional level, we observed that forests >60 years gradually became scarcer throughout the 20th century due to a gradual expansion of harvested areas, an effect most pronounced in the southern part of the region, where mature and old forest abundance was clearly outside the range of natural variability at the end of the studied period. At the stand level, forest composition and structure differed between stand-origin categories: clearcutting-origin stands contained more balsam fir (Abies balsamea), fire-origin stands more black spruce (Picea mariana), and fire/clearcutting-origin stands more hardwoods (Betula papyrifera and Populus tremuloides). Overall, we estimate that strict forest management targets based on natural disturbance regimes will be difficult to achieve in eastern North-American boreal forests, most notably because contemporary disturbance rates, including both clearcutting and fire, have gradually become higher than the fire rates observed during the preindustrial period.     

Logging history (1820–2000) of a heavily exploited southern boreal forest landscape: Insights from sunken logs and forestry maps

Over the last two centuries, logging has caused major, but unquantified, compositional and structural changes in the southern portion of the North American boreal forest. In this study, we used a series of old forest inventory maps coupled with a new dendrochronological approach for analyzing timber floating histories in order to document the long-term transformation (1820–2000) of a southern boreal landscape (117 000 ha) in eastern Quebec, Canada, in response to logging practices. Landscape exploitation became increasingly severe throughout this time period. During the ninetieth century (1820–1900) of limited industrial capacity, selective logging targeted pine and spruce trees and excluded balsam fir, a much abundant species of the forest landscape. Logging intensity increased during the first half of the twentieth century, and targeted all conifer species including balsam fir. After 1975, dramatic changes occurred over the landscape in relation to clear-cutting practices, plantations, and salvage logging, which promoted the proliferation of regenerating areas and extensive plantations of the previously uncommon black spruce. Overall, logging disturbance resulted in an inversion in the forest matrix, from conifer to mixed and deciduous, and from old to regenerating stands, thus creating significant consequences on forest sustainability. If biodiversity conservation and sustainable forestry are to be management goals in such a heavily exploited forested landscape, then restoration strategies should be implemented in order to stop the divergence of the forests from their preindustrial conditions.     

Long-term impacts of prescribed burning on regional extent and incidence of wildfires—Evidence from 50 years of active fire management in SW Australian forests

Prescribed burning is advocated for the sustainable management of fire-prone ecosystems for its capacity to reduce fuel loads and mitigate large high-intensity wildfires. However, there is a lack of comprehensive field evidence on which to base predictions of the benefits of prescribed burning for meeting either wildfire hazard reduction or conservation goals. Australian eucalypt forests are among the very few forest types in the world where prescribed burning has been practised long enough and at a large enough spatial scale to quantify its effect on the incidence and extent of unplanned fires. Nevertheless even for Australian forests evidence of the effectiveness of prescribed burning remains fragmented and largely unpublished in the scientific literature.     

湖南省森林火灾应急资源规模测度指标体系研究

从影响森林火灾应急资源建设规模的因素入手,分析其与应急资源规模之间的关系,并采用统计学的变异系数法和相关系数法对指标进行筛选,从而构建起确定森林火灾应急资源规模的指标体系.结果表明,湖南省森林火灾应急资源的建设规模与当地的经济、交通、人口密度、森林资源分布、火灾频度等密切相关.     

Effects of drought on isolates of <Emphasis Type="Italic">Bradyrhizobium elkanii</Emphasis> cultured from <Emphasis Type="Italic">Albizia adianthifolia</Emphasis> seedlings of different provenances

Albizia adianthifolia (Schumach) W. F. Wright, a N-fixing legume tree, has a wide distribution in Africa, in Ghana occurring in high rainfall forests and in seasonally droughted forests, and is associated in the Ghanaian forest zone with dry, infertile sites. We hypothesised that A. adianthifolia hosted different rhizobial strains in different forest types, and that these different strains would show different growth responses to moisture stress and different motility and mortality in droughted soil. Three isolates, extracted from seedlings of A. adianthifolia growing in three forest types differing in seasonal drought, were identified as Bradyrhizobium elkanii and exposed to varying levels of osmotic stress. Growth responses varied between the three strains, one of which displayed clear signs of drought tolerance. A novel approach using soil leaching columns was used to test the effects of soil pore water (in terms of neck diameter) on both the survival and movement of wet and dry forest rhizobial isolates through soil columns. The responses of the isolates were significantly different, the pore neck diameter, marginally insignificant and the drought treatment insignificant. Thus the dry forest isolate survived better in all treatments, and showed less response to the treatments, than the isolate from the wet forest. The results offer preliminary evidence that Bradyrhizobium elkanii strains from A. adianthifolia in Ghana have evolved in response to local differences in seasonal water availability. These differences could assist the selection of A. adianthifolia provenances for agroforestry or land rehabilitation.     

不同抚育方式对杉木幼林生长与地力维持的效果分析

对杉木二代幼林采用３种抚育方式：①全面劈草;②全面劈草,局部松土除草;③全面松土除草。通过３年试验观测,结果表明：①和②方式比③方式植被覆盖度分别大２４．３％～４１．３％和２２．８％～３４．６％,表层土壤的侵蚀度下降５０．１％和４０．６％,Ａ０层覆盖率分别提高５７．１％和５４．７％;３种抚育方式对杉木幼林的树高和冠幅生长无显著差异,但对胸径生长有极显著差异;抚育效果以②方式最佳。     

The formation of small-scale forestry in countries with economies in transition: Observations from Lithuania

Lithuania has been undergoing a transition from one political culture (based on a centrally planned economy and a one-party system) to a radically different political culture (market economy and a democratic political system). After the declaration of independence in Lithuania, some new phenomena emerged in forestry: the privatisation of forest industry, the formation of a free timber market; increasing timber export levels; and new modes of ownership (private forests) and enterprise (private business logging companies). Private forest owners control approximately 680,000 ha of forest, 33% of the total forest area, projected to increase to 40–45% in the future. Small-scale private forestry is developing in Lithuania but there is a lack of information about the objectives and problems of private forest owners. This paper presents the main results of a survey carried out in 2004 by the Lithuanian Forest Research Institute. The most important forest ownership objectives are firewood production for home consumption, income generation from wood and non-wood product sales, and protection of nature and biodiversity. The main problems for private forest owners are that the forest properties are too small to achieve efficiency, owners lack money for silviculture activities and there is a heavy bureaucratic system for forest-related activity documentation. A cluster analysis of respondents’ ratings of importance for various forest management objectives reveals four groups of private forest owners. These groups are named according to their dominant management objective, as multi-objective owners, businessmen, consumers and ecologists.     

低效马尾松水保林林下植被及生态功能恢复研究Ⅰ恢复技术优化经营模式

在湖南省茶陵县设置了 10hm2 试验地 ,进行了低效马尾松水保林林下植被及生态功能恢复技术试验 ,建立了低效马尾松水保林林下植被及其生态功能恢复技术经营模式 ,以期为长江中上游防护林体系建设提供科学依据     

1977-2010年广西森林资源变化动态及其主要驱动因素分析

1977～2010年,广西森林资源发生了巨大变化,林地面积由1 396.32万hm2增加到1 527.17万hm2,增长9.37%;有林地面积由531.36万hm2增加到1 116.38万hm2,增长110.10%;活立木蓄积由2.56亿m3增加到5.58亿m3,增长117.97%。根据广西历次森林资源连续清查结果,阐明不同时期广西森林资源变化动态,并对政策和效益2个方面的驱动因素进行分析研究,提出新时期森林经营对策和建议。     

低效马尾松水保林林下植被及生态功能恢复研究Ⅱ恢复成效的分析与评价

对湖南省茶陵县低效马尾松水保林林下植被及生态功能恢复技术试验及其技术模式研究 ,通过 5a的定位观测 ,试验林的林下植被及生态功能均较对照林分有大幅度的增长     

思茅松阔叶混交林的生长及其土壤理化性状研究

为探讨思茅松与不同阔叶树种混交林对生长量以及土壤肥力的影响。2000年7月在景谷县选择红木荷、西南桦、冬樱花、喜树四个树种与思茅松进行不同比例的混交造林。结果表明思茅松与红木荷混交时,较好的混交比例是针阔比5∶1;与西南桦混交时为2∶1或者1∶1。     

Biomass and greenhouse-gas emissions from land-use change in Brazil's Amazonian “arc of deforestation”: The states of Mato Grosso and Rondônia

We calculate greenhouse-gas emissions from land-use change in Mato Grosso and Rondônia, two states that are responsible for more than half of the deforestation in Brazilian Amazonia. In addition to deforestation (clearing of forest), we also estimate clearing rates and emissions for savannas (especially the cerrado, or central Brazilian savanna), which have not been included in Brazil's monitoring of deforestation. The rate of clearing of savannas was much more rapid in the 1980s and 1990s than in recent years. Over the 2006–2007 period (one year) 204 × 10³ ha of forest and 30 × 10³ ha of savanna were cleared in Mato Grosso, representing a gross loss of biomass carbon (above + belowground) of 66.0 and 1.8 × 10⁶ MgC, respectively. In the same year in Rondônia, 130 × 10³ ha of forest was cleared, representing gross losses of biomass of 40.4 × 10⁶ MgC. Data on clearing of savanna in Rondônia are unavailable, but the rate is believed to be small in the year in question. Net losses of carbon stock for Mato Grosso forest, Mato Grosso savanna and Rondônia forest were 29.0, 0.5 and 18.5 × 10⁶ MgC, respectively. Including soil carbon loss and the effects of trace-gas emissions (using global warming potentials for CH₄ and N₂O from the IPCC's 2007 Fourth Assessment Report), the impact of these emission sources totaled 30.9, 0.6 and 25.4 × 10⁶ Mg CO₂-equivalent C, respectively. These impacts approximate the combined effect of logging and clearing because the forest biomasses used are based on surveys conducted before many forests were exposed to logging. The total emission from Mato Grosso and Rondônia of 56.9 × 10⁶ Mg CO₂-equivalent C can be compared with Brazil's annual emission of approximately 80 × 10⁶ MgC from fossil–fuel combustion.     

The impact of SFM-certification on forest product markets in Western Europe — an analysis using a forest sector simulation model

In the international discussion on labels for sustainably produced wood products based on the certification of sustainable forest management (SFM), little attention has been paid to what is probably the most crucial part of any market-based instrument: the potential impact on forest products markets. This paper analyses the potential impact of SFM-certification on forest products markets using a simulation model of the Western European forest sector. Two scenarios with assumptions regarding certification (chain-of-custody costs, timber supply reduction from certified forests) are projected for the period 1995–2015 and tested against the results of a base scenario (‘business as usual’). In general, the results show that rather modest changes are to be expected from SFM-certification in forest products markets. The market impact of a timber supply reduction from certified forest would be more distinct than the impacts of chain-of-custody costs. Industry gross profits would decrease more than production. Due to the large share of roundwood costs in total costs, the sawmill industry would be affected more by even small changes in raw-material prices than the panel and paper industry.     

The contribution of root respiration of<Emphasis Type="Italic">Pinus koraiensis</Emphasis> seedlings to total soil respiration under elevated CO<Subscript>2</Subscript> concentrations

The impacts of elevated atmospheric CO₂ concentrations (500 μmol·mol⁻¹ and 700 μmol·mol⁻¹) on total soil respiration and the contribution of root respiration ofPinus koraiensis seedlings were investigated from May to October in 2003 at the Research Station of Changbai Mountain Forest Ecosystems, Chinese Academy of Sciences, Jilin Province, China. After four growing seasons in top-open chambers exposed to elevated CO₂, the total soil respiration and roots respiration ofPinus koraiensis seedlings were measured by a Li-6400-09 soil CO₂ flux chamber. Three PVC cylinders in each chamber were inserted about 30 cm into the soil instantaneously to terminate the supply of current photosynthates from the tree canopy to roots for separating the root respiration from total soil respiration. Soil respirations both inside and outside of the cylinders were measured on June 16, August 20 and October 8, respectively. The results indicated that: there was a marked diurnal change in air temperature and soil temperature at depth of 5 cm on June 16, the maximum of soil temperature at depth of 5 cm lagged behind that of air temperature, no differences in temperature between treatments were found (P>0.05). The total soil respiration and soil respiration with roots severed showed strong diurnal and seasonal patterns. There was marked difference in total soil respiration and soil respiration with roots severed between treatments (P<0.01); Mean total soil respiration and contribution of root under different treatments were 3.26, 4.78 and 1.47 μmol·m⁻²·s⁻¹, 11.5%, 43.1% and 27.9% on June 16, August 20 and October 8, respectively. Foundation item: This study was supported by the Knowledge Innovation Project of the Chinese Academy of Sciences (KZCX1-SW-01) and the National Natural Science Foundation of China (30070158). Biography: LIU Ying (1976-), female, Ph. D. Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, P. R. China. Responsible editor: Song Funan