Short-term responses of soil decomposer and plant communities to stump harvesting in boreal forests

Recently, in addition to logging residues, stumps have become an important component in energy production since there is growing global interest in the use of renewable energy sources in order to decrease anthropogenic carbon emissions. Harvesting of stumps influences the forest floor by changing vegetation and soil organic layers and exposing mineral soil across large areas. We studied whether stump harvesting after clear felling poses further short-term changes in boreal forest soil decomposer community (microbes and mesofauna) and vegetation when compared to the traditional site preparation practice (mounding). In general, stump harvesting caused decline in enchytraeid abundance but did not induce further major changes in decomposer community otherwise nor in vegetation of each soil micro-habitat (intact soil and exposed mineral soil). However, the abundances of almost all decomposer animals were lower in the exposed mineral soil than in the intact soil. Stump removal increased the area of exposed mineral soil in the clear felled areas, leading to lower amount of high quality habitat for most decomposer organisms. Hence, it is obvious that there are (or will be) differences in the decomposer community dynamics between the treatments at the forest stand level. Both species richness and coverage of plants benefitted from large-scale exposure of mineral soil. Because the stump removal procedure disturbs soil organic layers and negatively affects the decomposer community, it has the potential to alter nutrient dynamics in forests.     

Effects of bioenergy extraction on visual preferences in boreal forests: a review of surveys from Finland,Sweden and Norway

Increased forest biomass production for bioenergy will have various consequences for landscape scenery, depending on both the landscape features present and the character and intensity of the silvicultural and harvesting methods used. We review forest preference research carried out in Finland, Sweden and Norway, and discuss these findings in relation to bioenergy production in boreal forest ecosystems. Some production methods and related operations incur negative reactions among the public, e.g. stump harvesting, dense plantation, soil preparation, road construction, the use of non-native species, and partly also harvest of current non-productive forests. Positive visual effects of bioenergy production tend to be linked to harvesting methods such as tending, thinning, selective logging and residue harvesting that enhance both stand and landscape openness, and visual and physical accessibility. Relatively large differences in findings between studies underline the importance of local contextual knowledge about landscape values and how people use the particular landscape where different forms of bioenergy production will occur. This scientific knowledge may be used to formulate guiding principles for visual management of boreal forest bioenergy landscapes.     

Partial cutting as a conservation alternative for oak (Quercus spp.) forest—Response of bryophytes and lichens on dead wood

Semi-open oak-rich forests may support many species adapted to large trees and coarse woody debris. Currently many oak-rich forests in northern Europe have more or less closed canopies due to lack of natural and cultural disturbances. In these forests, conservation oriented partial harvesting of biofuel may restore a desired forest structure and light regime that potentially may favour many species that have declined during the last century. We quantified effects of such cutting on lichens and bryophytes living on dead wood in southern Sweden, using a design with paired cutting and control plots (each 1 ha) in 15 forests. In each plot we surveyed the same five logs and three stumps before and after harvest (25% of the tree basal area removed). The epixylic species composition shifted towards a flora typical for dryer dead wood. The mean species number of lichens per stump increased (clear effect) and the mean number of bryophytes per stump decreased (nearly significantly) due to harvesting. The species composition, but not species richness, on logs was affected. No increases or decreases in species of conservation concern could be detected. Since the overall negative effects were weak, we suggest that partial harvesting of dense oak forests is compatible with maintenance of the diversity of lichens and bryophytes on dead wood. However, the amount of such forest harvested needs to be carefully assessed in relation to demands of other taxa.     

Quality,productivity and costs of spot mounding after slash and stump removal

Abstract

In Nordic countries, the harvesting of slash and stumps from regeneration areas for energy purposes has rapidly increased, and will increase further in the future. This development has unknown technoeconomic effects on soil scarification. This study investigated three spot mounding methods and factors affecting their quality, productivity and costs in regeneration areas after slash and stump removal. The methods were integrated stump lifting and spot mounding (INTE), separate excavator-based spot mounding (BLADE), and separate spot mounding by a continuously working mounding unit (CONT). The average quality of work was worst in INTE, while CONT was the most sensitive to stoniness. Average work times per spot mound were 4.1 and 3.1 times higher in INTE and BLADE, respectively, than in CONT. Altogether, the cost–quality ratio of CONT was better than that of the other methods, except in very small areas.     

Impact of slash removal,drag scarification,and mounding on lodgepole pine cone distribution and seedling regeneration after cut-to-length harvesting on high elevation sites

Excessive slash loading could pose a problem for the regeneration of the serotinous lodgpole pine especially in forests at higher elevation where soil temperature is limiting. In the past, these forests have commonly been harvested using full-tree harvesting where trees are processed at roadside; however, recently cut-to-length harvesting has become a more frequent harvesting method. In cut-to-length harvesting the harvested trees are processed in the block, as a result slash accumulation is much higher on these cutblocks. In an experimental field trial, the cone distribution, natural lodgepole pine regeneration, and the growth and establishment of planted lodgepole pine were evaluated in response to slash load, drag scarification, and mounding after cut-to-length harvesting of high elevation lodgepole pine stands in the Rocky Mountains. Twelve sites were established, each contained six plots which were randomly assigned to six treatment combinations of two slash removal (slash and slash removed) and three mechanical soil preparation treatments (no soil preparation, drag scarifying, and mounding). The slash removal reduced slash volume by more than 50% but also reduced the number of lodgepole pine cones available for regeneration by over 33%. However, soil mechanical treatments offset this effect as fewer cones were necessary to achieve high natural pine regeneration densities. Drag scarification of plots resulted in 12 times the number of pine seedlings compared to the non-prepared plots. Although slash removal did not have an effect on the number of naturally regenerated lodgepole pine seedlings, it had a positive effect on their growth performance. Conversely, planted pine seedlings had lower mortality and better growth in soils that had been mechanically prepared and had the slash removed; however, the growth effects became only apparent 4 years after planting. While slash removal and mechanical soil preparation did increase soil temperatures; the slash removal treatment had a more transient effect on soil temperatures than soil preparation. Differences in soil temperature decreased over time which appeared to be mostly driven by a warming of the soils in the plots with no soil preparation, likely a result of the decomposition of the finer slash and feathermosses. Overall, it appears that surface disturbance on these high elevation sites had a far greater effect on lodgepole pine regeneration and growth than the increased accumulation of slash as a result of cut-to-length harvesting.     

Responses of polypore fungi following disturbance-emulating harvesting treatments and deadwood creation in boreal Norway spruce dominated forests

ABSTRACT

The emulation of natural disturbances in harvesting has become a widely accepted approach to reach ecologically sustainable forest management. The purpose of this study was to examine the responses of polypore fungi (species richness and composition) on four different cutting methods (selection, gap, patch, and clear-cutting) plus uncut controls, and the creation of high stumps and cut logs in combination with harvesting. Polypores were inventoried one year before, and two and seven years after cutting. A total of 71 polypore species were found, but no red-listed species were recorded seven years after cutting. Irrespective of the treatment, the variation in polypore richness was best explained by the number of deadwood objects in the stands. Species richness per deadwood object was the highest on natural logs. Species richness per volume of spruce deadwood was the highest on small-diameter deadwood and stumps, intermediate on natural logs and lower on cut logs and high stumps. These results indicate that cut logs created in harvesting cannot compensate the loss of deadwood in cutting and energy wood harvesting. Our results demonstrate the difficulty in rapidly creating habitats for red-listed polypores in commercially managed forests.     

Soil-CO2 flux after patch scarification,harrowing and stump harvest in a hemi-boreal forest

Abstract

Stump harvesting is one way of increasing the amount of bioenergy, but little is known about the consequences of tree-stump harvesting on the carbon balance in the forest. Therefore, soil-surface CO₂ flux (soil respiration, R _s) was determined two years after clear-cutting for common soil disturbances occurring after patch scarification, harrowing and stump harvest in southern Sweden. R _s from intact soil was found to be of the same magnitude as emissions from areas of mixed humus, indicating only small effects of disturbance. Elevated mounds produced lower emissions than in the intact soil during the second year despite larger amounts of organic matter, probably due to low soil moisture. The lowest R _s was found in soil surfaces with exposed mineral soil. The treatment effects on R _s were estimated considering the actual area of different disturbances. During the first year, there was no difference in R _s among the treatments, whereas in the second year the flux was 10% higher after harrowing and stump harvesting than after patch scarification, implying that the effects on CO₂ flux after stump harvest were comparable to conventional harrowing. However, it is unclear whether this finding basically applies to regions where decomposition is limited by soil moisture during the summer.     

Effects of forest harvesting on runoff and sediment characteristics in the Hyrcanian forests,northern Iran

Loss of canopy cover by forest harvesting generally increases the average surface runoff volume and sediment. Selective cutting (single and group selection method) is the most usual forest harvesting method in the Hyrcanian forests in the north of Iran. The purpose of this study is to find the effect of selective logging technique on the hydrological behavior of runoff and sediment in the Kheyrud forests located in northern Iran over 1 year. Four treatments were implemented: natural forest without harvesting (C), forest with selective harvesting (H) and area without canopy cover (WC) and skid trail (S). Three types of data were measured in each plot including soil chemical and physical properties, runoff and sediment load after each rainfall. The results indicate significant differences (P ≤ 0.05) in runoff generation and sediment production with respect to the treatments cover. The runoff in all treatments showed relatively similar response to rainfall, while the highest runoff and sediment were observed in skid trails, and the area without canopy cover (1.13 and 0.62 mm, and 1.2 and 0.51 g m^?2), averagely. In contrast, the natural forest without harvesting and the forest with selective harvesting treatments exhibited the lowest amounts of runoff (0.2 and 0.44 mm) and sediment (0.1 and 0.17 g m^?2), averagely. Implementation of low logging technique was useful to control the effects of logging on the runoff and sediment yield.     

Soil disturbance and post-logging forest recovery on bulldozer paths in Sabah, Malaysia

We examined the extent of soil disturbance associated with bulldozer yarding and the regrowth of woody vegetation on bulldozer paths (skid trails) in selectively logged dipterocarp forest. In an area logged in 1993, using conventional, i.e., uncontrolled, harvesting methods, about 17% of the area was covered by roads and skid trails. In contrast, in a 450-ha experimental area where reduced-impact logging guidelines were implemented, 6% of the area was similarly disturbed. Skid trails in the reduced-impact logging areas were less severely disturbed than those in conventional logging areas; the proportion of skid trails with subsoil disturbance was less than half that in conventional logging areas. Four years after logging, woody plant recovery on skid trails was greater in areas logged by reduced-impact than by conventional methods. Skid trails where topsoil had been bladed off had less woody vegetation than skid trails with intact topsoil. In a chronosequence of logging areas (3, 6, and 18 years after logging), species richness and stem densities of woody plants (>1 m tall, <5 cm dbh) were lower on skid trail tracks than on skid trail edges or in adjacent forest. Both richness and density increased with time since logging, but even 18 years after logging, abandoned skid trails were impoverished in small woody stems compared with adjacent forest. Minimizing soil and stand disturbance during logging appears to allow a more rapid recovery of vegetation on bulldozed soils, but the long-term fate of trees growing on compacted soils remains uncertain.     

Whole-tree harvesting with stump removal versus stem-only harvesting in peatlands when water quality,biodiversity conservation and climate change mitigation matter

This article examines alternative forest harvesting regimes when ecosystem services in terms of water quality, biodiversity conservation and climate change mitigation are included in the analysis. The harvesting regimes are whole-tree harvesting with stump removal and conventional stem-only harvesting. The harvesting regimes are evaluated under two alternative climate policy contexts. The first alternative is a carbon neutral bioenergy policy, which assumes the carbon dioxide (CO₂) neutrality of bioenergy and produces substitution benefits, as bioenergy replaces fossil fuels. The second alternative climate policy, a carbon non-neutral bioenergy policy, takes into account the fact that bioenergy causes carbon dioxide emissions, producing substitution costs, and that harvested woody biomass affects the ability of a forest to act as a carbon sink. We extend the traditional Faustmann (1849) rotation model to include nutrient load damage, biodiversity benefits, and climate impacts. The empirical analysis is based on Finnish data from a catchment experiment carried out on drained peatland forests. The empirical results show that under a carbon neutral bioenergy policy, whole-tree harvesting with stump removal produces the highest net social benefits. However, if a carbon non-neutral bioenergy policy is assumed, the net social benefits are greater under stem-only harvesting.     

Long-term effects of stump harvesting on soil properties and tree growth in Scots pine and Norway spruce stands

Abstract

Effects of stump harvesting on the properties of surface soil and on the density, structure and growth of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) stands were estimated in a field trial in western Finland. The experiment was established in 1977 and measured in 2010. Stems and logging residues were harvested after clear-cutting, and stumps were lifted and removed from half of the experimental area. Sixteen plots were planted with pine seedlings and 16 with spruce. The main effects of stump harvesting were improved survival of planted trees and an increase in natural regeneration. No clearly negative effects were noted in the stand development. Stump harvesting had no or minimal effects on the properties of the organic layer and those of the 0- to 10-cm mineral-soil layer. Soil properties did not differ between tree species. Pine production was higher on plots with stump removal compared to plots without soil treatment.     

A continuum of dead wood with various habitat elements maintains the diversity of wood-inhabiting fungi in an old-growth boreal forest

Evidence on habitat associations of threatened wood-inhabiting species in boreal forests may contribute to a better understanding of their ecology and conservation needs. We examined the diversity of wood-inhabiting fungal communities in an old-growth boreal forest with high substrate availability and continuity based on repeated surveys of fruit bodies. The number of species in morphological and functional groups in relation to coarse woody debris (CWD) attributes was estimated with generalized linear models. Additionally, we calculated species interaction networks of CWD attributes and fungal species. The composition of fungal communities was analysed using a non-metric multidimensional scaling with subsequent environmental fitting. Old conifer (especially spruce) logs and large aspen logs with branches represented the most important substrates for the red-listed species and the indicator species of old-growth boreal forests. Among “dynamic” CWD attributes such as time since tree death, decay class and stage of epixylic succession, the latter was the most important indicator of diversity of all species and their morphological and functional groups. The interaction network provided evidence of the importance of tree species diversity for fungal diversity. The composition of fungal communities was tree species specific and related to dynamic attributes, bark cover and diameter of logs. Our results suggest the importance of a continuum of dead wood from different tree species with a variety of niches such as branches, exposed wood, fragmented and complete cover of bark and patches of epixylic vegetation to maintain the assemblages of wood-inhabiting fungi in an old-growth boreal forest.     

Short-term effects of whole-tree harvesting on understory plant species diversity and cover in two Norway spruce sites in southern Norway

Effects of clear-cut harvesting on ground vegetation plant species diversity and their cover are investigated at two Norway spruce sites in southern Norway, differing in climate and topography. Experimental plots at these two sites were either harvested conventionally (stem-only harvesting) or whole trees including crowns, twigs and branches were removed (whole-tree harvesting), leaving residue piles on the ground for some months. We compare the number of plant species in different groups and their cover sums before and after harvesting, and between the different treatments, using non-parametric statistical tests. An overall loss of ground vegetation biodiversity is induced by harvesting and there is a shift in cover of dominant species, with negative effects for bryophytes and dwarf shrubs and an increase of graminoid cover. Differences between the two harvesting methods at both sites were mainly due to the residue piles assembled during whole-tree harvesting and the physical damage made during the harvesting of residues in these piles. The presence of the residue piles had a clear negative impact on both species numbers and cover. Pile residue harvesting on unfrozen and snow-free soil caused more damage to the forest floor in the steep terrain at the western site compared to the eastern site.     

Invasion of Non-Commercial Tree Species After Selection Logging in a Bolivian Tropical Forest

Abstract

Single-tree selection logging will likely result in a 4.3% loss in the relative abundance and a 4.1% loss in basal area of trees of commercial species in one cutting cycle due to their removal by harvesting combined with their potential recolonization of only 31% of logging gaps in a Bolivian tropical dry forest. Densities of the most valuable species, Amburana cearensis and Cedrela fissilis, were particularly reduced by logging. To sustain the current harvesting rate, uses need to be developed for more non-commercial species and/or silvicul-tural treatments employed that increase regeneration of commercial species and remove non-commercial species using timber stand improvement techniques.     

The effects of burning and dead-wood creation on the diversity of pioneer wood-inhabiting fungi in managed boreal spruce forests

The loss of natural forest habitats due to forestry is the main reason for the decline in boreal forest biodiversity of the Nordic countries of Europe. Ecological rehabilitation may provide means to recover and sustain biodiversity. We analyzed the effects of controlled burning and dead-wood creation (DWC) on the diversity of pioneer wood-inhabiting fungi in managed Norway spruce (Picea abies) forests in southern Finland. Altogether 18 stands were first subjected to a partial cutting with ordinary logging residues in form of cut stumps and treetops left on site. The subsequent rehabilitation treatments consisted of a controlled burning applied in half of the stands and three levels of dead-wood creation (5, 30 and 60 m³ ha⁻¹). The DWC involved creation of logs; felling of whole trees to mimic downed logs formed by natural disturbance processes. Each treatment was replicated three times. Inside each stand, substrates were sampled in two different biotopes; one on mineral soil and one on mineral soil with a thin peat layer. We surveyed the fungal flora on the logs (n = 364) and the ordinary residue stumps (n = 1767) and tops (n = 845) five years after the treatments.When comparing different stands, controlled burning had a significant effect on species composition; certain species were significantly more frequent on substrates in burned stands than in unburned stands, indicating that these species were favored by controlled burning. By contrast, we found no significant effects of DWC levels or biotope on species composition or richness. When comparing different substrates, 99% of the logs hosted at least one species and the occurrence probability of certain species was significantly higher on logs than on ordinary residue stumps and tops. Yet, volume-based rarefaction analyses showed that residues were more species dense than the logs, indicating that ordinary logging residues constitute important resources for many pioneer species.We conclude that controlled burning combined with DWC have strong effects on biodiversity; it modifies the composition of the pioneer wood-inhabiting fungal species found in managed forests and may thereby also influence the further succession and diversity of the secondary fungal flora.     

Ant community responses to experimental fire and logging in a eucalypt forest of south-eastern Australia

Sustainable forest management requires a sound understanding of the impacts of forestry management practices, especially prescribed fire and timber harvesting, on biodiversity. Many studies have examined the impacts of fire and logging separately, but few have considered them together. Here we describe the combined effects of selective logging and repeated prescribed fire on ants in eucalypt forest near Eden in south-eastern Australia. The study was conducted within 18 experimental coupes comprising three replicates of each of six treatments, representing combinations of two logging (selectively logged and unlogged) and three prescribed burning (unburnt, routine and high fire frequency over 20 years) practices. Ants were sampled using terrestrial and arboreal pitfall traps in two plots within each of the 18 coupes. A total of 92 species from 35 genera were recorded, with ant species richness increasing with both increasing fire frequency and selective harvesting. We also found significant differences in ant species composition between management treatments; however, these differences were rather modest, and apparent only between extremes of fire and harvesting combinations. Logging on its own was not a significant factor contributing to variation in ant species composition. However, the responses of two common species and a key functional group to fire depended on logging treatment; in each case their abundance decreased with increasing fire frequency at unlogged sites, but increased at logged sites. The general resilience of ant communities suggests that forests remain in good functional health even when subject to a combination of selective logging and frequent burning. However, our study under-sampled species with specialist microhabitat requirements, and these might have been more heavily impacted. We have also revealed some significant interactions between the effects of fire and logging, which highlights the importance of considering combined impacts of forest management practices.     

采伐方式对海南岛霸王岭热带山地雨林恢复的影响

比较3种采伐方式(重复采伐、径级择伐和采育择伐)对海南岛霸王岭热带山地雨林恢复群落中物种多样性、群落结构和功能群组成的影响。结果表明:3种方式采伐后(20～25年)的山地雨林恢复群落物种丰富度呈增加趋势,主要表现为小径级(胸径<10cm)的长寿命先锋种增加;与老龄林相比,径级采伐和采育择伐没有增加伐后林中成年树的物种丰富度;3种采伐恢复林中幼树和小树的物种累积速度低于老龄林;森林采伐后恢复群落中的个体密度显著高于老龄林,但胸高截面积显著低于老龄林;伐后林群落中胸高截面积减少最多的为采育择伐,其次为径级择伐和重复采伐;森林采伐恢复群落内长寿命先锋种的物种丰富度、个体密度和胸高截面积均增加,而后期耐荫种物种丰富度变化较小;采育择伐在短期降低了森林木材蓄积量,但没有显著改变群落中功能群组成,因而能够在相对较短的时间内恢复到干扰前的水平。     

Understory plant communities of boreal mixedwood forests in western Canada: Natural patterns and response to variable-retention harvesting

We examined patterns of variation in richness, diversity, and composition of understory vascular plant communities in mixedwood boreal forests of varying composition (broadleaf, mixedwood, conifer) in Alberta, Canada, before and for 2 years following variable-retention harvesting (clearcut, 20 and 75% dispersed green tree retention, control). Broadleaf-dominated forests differed from mixedwood or conifer-dominated forests in that they had greater canopy cover, litter depth, soil nitrogen, warmer soils, as well as greater shrub cover, herb and shrub richness and diversity (plot scale). In contrast, conifer, and to a lesser extent mixedwood, forest had greater β diversity than broadleaf forest. Overall, mixedwood and conifer forests were similar to one another, both differed from broadleaf forest. Several species were found to be significant indicators of broadleaf forest but most of these also occurred in the other forest types. Understory composition was related to canopy composition and edaphic conditions. Variable-retention harvesting had little effect on understory cover, richness, or diversity but resulted in reduced richness and β diversity at a larger scale. The clearcut and 20% treatments affected composition in all forest types. Early successional species and those common in disturbed sites were indicators of harvesting while evergreen, shade-tolerant understory herbs were indicators of the control forest and 75% retention harvest. We conclude that it is important to maintain a range of variation in canopy composition of mixedwood forests in order to conserve the associated understory communities. The presence of conifers in these forests has a particularly important influence on understory communities. The threshold for a lifeboat effect of variable-retention harvesting is between 20 and 75% retention. Examination of richness and β diversity at a variety of scales can provide interesting information on effects of harvesting on spatial reorganization and homogenization of understory plant communities.     

Floristic and structural recovery of a laurel forest community after clear-cutting: A 60 years chronosequence on La Palma (Canary Islands)

We analyzed a post-clearcut chronosequence (0.5 to 60 years after harvesting) in the laurel forest of La Palma island (Canarian Archipelago) to determine the recovery of the stands with respect to species composition, richness, life strategies and structural parameters of the canopy. Multivariate analysis showed that exotic species, as well as annual ruderal species were confined to early-successional stages, while native perennials, typical of laurel forests, dominated the late-successional stages. Total species richness decreased significantly with time after clear-cutting. The relative fast recovery of understory native species may be due to low forest floor disturbance during harvesting. Shade-intolerant pioneer, pioneer-remnant and shade-tolerant late-successional species were the main life strategies of native tree species. Most structural parameters showed a continuous and monotonic increase (basal area, biomass) or decrease (density, percentage of photosynthetic biomass) during succession. Once clear-cutting, here performed with an interval of 8 years, is abandoned, the recovery of the laurel forest seems possible due to careful logging that protects the soil and a rapid asexual regeneration of native tree species, revealing this to be a sustainable management practice.     

Post-harvest windthrow and recruitment of large woody debris in riparian buffers on Vancouver Island

Large woody debris (LWD) provides structural complexity to small streams. Riparian buffers are intended to provide long-term vegetation cover and supplies of LWD, but post-harvest windthrow often occurs. To evaluate the impacts of windthrow in riparian buffers and identify the components for a small stream LWD recruitment model, we sampled 26 streams in immature and older stands in wind-exposed areas of southwestern and northern Vancouver Island. These treed buffer strips had been exposed following clearcut harvest of adjacent timber on both sides 1–20 years previously. For stream sections 100 m long in each buffer, all logs greater than 7.5 cm diameter that spanned at least part of stream channel were measured. A total of 658 logs were recorded. Windthrown trees were comparable in characteristics to the trees that made up the buffer. The majority of logs derived from windthrown trees were oriented perpendicular to the stream channel and were suspended above the stream channel. Even 20 years after harvesting, two-thirds of the logs were still suspended above the stream. Logs in older buffers were more decayed, and the decay rate depended on tree species and initial diameter. Log height above stream was negatively correlated with log decay class and time since logging. Log length declined with time since harvest exposure and decay class. Sediment was exposed on upturned roots and within mineral soil pits. The volume of soil retained on upturned rootwads declined over time, but some soil remained even after 20 years. Very little of this exposed sediment was close enough to the creek to result in sediment delivery.