Effects Of Stump Harvesting Research Articles

Short-term response to stump harvesting by the ground flora in boreal clearcuts

ABSTRACTWe studied short-term ground vegetation responses to stump harvesting by recording the occurrence of all species of bryophytes, vascular plants and the cover of soil disturbance on 20 clearcuts in the Southern and Middle Boreal zone in northern Scandinavia. All 20 clearcuts were slash-harvested and scarified and 10 of the clearcuts were also stump-harvested. The added effect of stump harvesting was assessed by comparing stump-harvested clearcuts with non-stump-harvested clearcuts. We tested whether stump harvesting causes extra soil disturbance compared to conventional forestry and if stump harvesting is affecting the assemblage, species richness and occurrence of individual species of vascular plants and bryophytes in boreal clearcuts. Our results revealed that stump harvesting causes an increase in the area of disturbed soil surface compared to conventional harvesting. Four of the most commonly occurring plant species in this area were significantly affected by stump harvesting, and Vaccinium vitis-idaea had a median occurrence of only 20% of that in non-stump-harvested clearcuts. The large impact on some plant species from a relatively modest increase of soil disturbance caused by stump harvesting suggest that stumps, with their slightly elevated bases, contributes to the survival of certain species on clearcuts.

Impact of Tree Stump Harvesting on Soil Carbon and Nutrients and Second Rotation Tree Growth in Mid-Wales, UK

The drive to develop renewable energy is increasing the interest in energy forestry. Woody biomass from forest residues has the potential to make a significant contribution to greenhouse gas emission reduction through fossil fuel substitution. However, there is a danger of operational practice running ahead of the understanding of the environmental impacts of such activities. Consequently, there is an urgent requirement for scientifically underpinned guidance on the best management practices to ensure soil and water protection, including sustaining forestry’s key role in carbon capture. This study addresses the main issues associated with stump harvesting practices and their impacts on soil carbon and nutrient capital and effects on the second rotation tree growth. It reports results from a clearfell site in the UK where experimental stump harvesting was carried out in 2005 before replanting with Sitka spruce Picea sitchensis (Bon.)Carr. Both stump harvested and conventional harvested areas (Control) were studied in 2009 and 2010, five years after harvesting, on the two distinct soil types at the site: podzolised brown earth and peaty gley soils. Results show impacts of stump harvesting on soil carbon and nitrogen stocks, residual water, base cations (K+, Ca2+ and Mg2+) concentrations and stocks and bulk density in both soil types. The organic peaty gley soil showed larger and deeper profile changes after stump harvesting compared with the podzolised brown mineral soil, where some of the negative changes in C, N and base cations in the top soil were compensated by increases at depth. Tree assessment showed positive effect of stump harvesting on K and Ca uptake by young seedlings, but N and P nutrient status was reduced on the peaty gley soils. The overall results support the current UK forestry guidance for stump harvesting which identifies that soil type is the most important site factor determining the sustainability of the practice.

Long-term effects of stump harvest on mercury and general chemistry in discharge water

ABSTRACTThis synoptic study evaluates water chemistry in stump-harvested and conventionally logged reference areas, located in South-Central Sweden, 20–30 years after harvest and reforestation. Electrical conductivity, pH, alkalinity (), nitrate nitrogen () and total organic carbon (TOC) were measured in discharging groundwaters and in low-order streams and ditches. The groundwaters were further analysed for total mercury (THg) and methyl mercury (MeHg). Additionally, solid phase Hgtot and MeHg were measured in stream mudbottoms. The mean MeHg concentration and mean MeHg/TOC ratio were significantly (p < .05) higher in discharging groundwater from stump-harvested compared to reference areas. In contrast, the concentration of THg did not differ. Likewise, there were no significant treatment differences for electrical conductivity, pH, or TOC. In the stream-/ditchwaters also no significant differences were found, but electrical conductivity (p = 0.07) and pH (p = .08) tended to be lower in stump-harvested areas. Hgtot and MeHg concentrations in stream-/ditch sediments did not differ between treatments. These results suggest that weakly enhanced MeHg concentrations may be present in the riparian groundwater zone 20–30 years after stump harvest.

Long-term effects of stump harvesting and site preparation on pools and fluxes of soil carbon and nitrogen in central Sweden

ABSTRACTClear-cutting and subsequent site preparation is a common forest management practice in the Nordic countries. Slash and stumps have been suggested to replace fossil fuels in district heating plants. Stump/root removal from clear-cuts will reduce the amount of decomposable substrate in the soil and thus decrease soil CO2 emission, but stump lifting is also supposed to stimulate CO2 efflux and counteract CO2 reduction. To determine the effects of stump/root harvesting in relation to site preparation (stumps retained) on pools and fluxes of carbon (C) and nitrogen (N) after a period of 20–30 years, soil sampling was performed in four pairs of stump/root harvesting (S) and patch scarification (P) stands in central Sweden in 2009. Stump/root harvesting resulted in a significantly lower soil C pool in the humus layer. Annual heterotrophic respiration (RH) in the whole soil profile was significantly lower after the S than after the P treatment, the mean difference being 38 ± 23 g CO2–C m−2 year−1 (95% CI). This difference was larger than corresponding data from stump/root decomposition models (11–18 g CO2–C m−2 year−1), but both empirical and model data showed that stump/root harvesting will reduce heterotrophic soil CO2 emissions to the atmosphere during the actual period.

Effects of stump harvest and site preparation on N2O and CH4 emissions from boreal forest soils after clear-cutting

Harvesting stumps after clear-cutting can increase bioenergy supplies and thus reduce needs for fossil fuels, but more knowledge is required about associated changes in greenhouse gas emissions from forest soils to assess the climatic impact of extracting stumps for this purpose. The soil disturbance caused by harvesting stumps may alter soil processes, including N mineralization. N availability is an important determinant of emissions of the potent greenhouse gases N2O and CH4. Effects of stump harvest on these gases are largely unknown. Therefore, they were explored in this study by monitoring differences in N2O and CH4 emissions associated with different types of disturbance during two years following stump harvest and site preparation (as well as their overall effects) at three mesic sites, using the chamber technique. N2O emissions at two of the sites were affected by the type of soil disturbance, but not at the other site. At one site, the N2O emissions were highest from undisturbed soil and mounds and significantly lower from mixed soil, bare mineral soil and wheel ruts. At this site the emission rates were clearly correlated with N availability across the disturbances. At the second site showing significant treatment effects, N2O emissions were higher from the bare mineral soil after site preparation than from other types of disturbed soil. At the third site there were no significant N2O emissions, possibly due to reductions in nitrogen availability caused by the fast establishment of vegetation at that site. The CH4 fluxes included both uptakes and losses, but were generally low following all types of soil disturbances, although they were substantial from wheel ruts and soil pits. In conclusion there were no, or minor, between-treatment differences in N2O and CH4 emissions. Furthermore, the radiative forcing potential of these emissions was small compared to mean CO2 emissions from Swedish clear-cuts. Thus, our results indicate that stumps can be harvested without causing elevated emissions of N2O and CH4 on mesic sites. The effects on wetter sites remain to be illuminated.

Effects of stump harvesting on soil C and N stocks and vegetation 8–13 years after clear-cutting

Effects of stump harvesting on coarse woody debris (CWD), soil and vegetation were investigated 8–13years after clear-cutting of eight forest stands located at two sites, Honkola and Haukilahti, in Central Finland. Norway spruce (Picea abies) was the dominant tree species in the harvested stands. Four of the stands were subjected to mounding and four were stump-harvested. Logging residues were removed at harvest from all eight stands.The amount of CWD remaining after stump harvesting was estimated from basal area of remaining stumps, diameter and length of logs and by weighing smaller pieces of dead wood. Moss and field layer vegetation cover was estimated by a point-intercept method and the diameter of young trees was measured to estimate basal area. Soil carbon and nitrogen stocks and pH were determined in the humus layer and down to 25cm depth in the mineral soil. The degree of soil disturbance was visually assessed in the field.Basal area measurements on remaining stumps suggested that about 75% of the stumps had been removed from the stump-harvested stands, which is a typical stump harvesting rate in Finland. The amount of remaining stumps and root biomass was significantly lower in stump-harvested stands than in stands where stumps had been retained, whereas differences between mounding and stump harvesting were not significant for the other types of CWD. Stump harvesting had no significant effect on the cover of field layer species, total moss cover or vegetation composition. Total stem density was almost twice as high in stump-harvested stands as in stands where stumps were not harvested, due to significantly higher stem density of Betula pendula Roth., whereas no effect was observed on the basal area of the other tree species. No significant treatment effect on soil carbon and nitrogen stocks or on degree of soil disturbance was detected, but the higher density of Betula indicates higher exposure of mineral soil during the years following stump removal. In conclusion, stump harvesting seems to promote natural establishment of Betula seedlings, but does not change tree productivity.

Overlooked subterranean saproxylic beetle diversity in clear-cut stumps and its implications for stump extraction

Stump extraction (which include removal of coarse roots) will reduce the available habitat for insects breeding in dead wood (saproxylic species). The root-living diversity is largely unknown which is unsatisfactory as 68% of the wood harvested at stump extraction is root wood. We compared the diversity of saproxylic beetles in Norway spruce, Picea abies, coarse roots with that in the above-ground part of the same stumps. Five below-ground (root) and eight above-ground (stump) samples were collected from early-decay stumps at each of twelve Swedish clear-cuts. In total 8314 saproxylic beetles of 60 species were reared from the 156 wood samples. The estimated species richness in roots (47 species) was 51% of that in stumps (93). When root and stump samples were pooled the total estimate was 116 species. The phylogenetic diversity (average taxonomic distinctness) in individual roots was only 63% of that in stumps. Species composition differed between substrate types, and only 28% of the species were common to both substrates. Most root samples were numerically dominated by Dryocoetes autographus (33% of the samples) or Hylobius abietis (10%). Most stump samples were dominated by Crypturgus spp. (66%) or Rhagium inquisitor (19%). Of the 17 most abundant species, five were associated with roots and two of those used roots exclusively. Ten species were associated with stumps. We conclude that the root-living beetles constitute an important part of the stump/root assemblage and should not be overlooked when the effects of stump harvest on biodiversity is evaluated.

The arthropod community of boreal Norway spruce forests responds variably to stump harvesting

Forest fuel harvesting increases the need to collect not just logging residues but also tree stumps from harvested stands. This biomass removal has raised concern over forest biodiversity. Here, the effects of stump harvesting on spiders, ants, harvestmen, ground beetles and epiedaphic springtails occupying boreal Norway spruce (Picea abies) forest floor were studied two and five years after harvesting by comparing pitfall trap samples from clear-cut sites with and without subsequent stump harvesting and from unharvested mature forests in central Finland. At harvested sites, traps were placed both on intact and exposed mineral soil surface. Open-habitat and generalist ground beetles benefitted from the stump harvesting, but generally the numbers of arthropods between stump harvesting treatments and different aged clear-cuts were rather similar. The intact forest floor hosted more ants, springtails and harvestmen than did the exposed mineral soil. Moreover, the community structure of spiders, ground beetles and springtails was affected by stump harvesting, forest-floor quality (intact or exposed), and time elapsed since harvesting. Based on these results we recommend minimizing the exposure of mineral soil during management practices. However, more long-term studies are required to document the development of fauna in the harvested areas and the ecosystem-level impacts of utilization of forest biomass for energy.

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

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.

Carbon balance of a forest ecosystem after stump harvest

Stump harvest in forests can cause both reductions of CO2 emissions through a decrease of decomposable substrate (direct effect) and emission increases as a consequence of deep and extensive soil disturbance (indirect effect). Here, the effects of stump harvest on net ecosystem CO2 exchange (NEE) in a former Norway spruce stand in mid Sweden are presented. CO2 exchange was continuously followed by eddy-covariance measurements during the first years after harvest. Differences in NEE from stump harvested and mounded (reference) plots were determined by soil-surface respiration measurements. Respiration from decaying stumps was estimated by a decomposition model. Fluxes indicated a direct effect (decreased efflux) during the first year after harvest that corresponded to the absence of decomposing stumps. During the following years, this emission reduction was increasingly counteracted by an indirect effect (increased efflux) of similar magnitude. This means that the expected emissions caused by extra soil disturbance occur with a certain delay and seem to increase with time. By these emissions, the substitution efficiency of stumps as bioenergy resource is reduced. Furthermore, at a time scale of centuries, instant combustion of stumps leads to a larger contribution to global warming than slow decomposition, because the stump carbon is available earlier in form of greenhouse gas. This is estimated by the time integral of emissions. Thus, despite the surprisingly low initial emissions, the overall substitution efficiency and climate benefits of stump harvest are likely to be small. The long-term consequences of stump harvest for the carbon budget are, however, still uncertain.

Which macroarthropods prefer tree stumps over soil and litter substrates?

Tree stumps are a potential bioenergy resource to replace fossil fuels and meet the targets for reduced CO2 emissions. However, the effects of stump harvesting on wood-dependent organisms are poorly known. This study assessed the abundances of macroarthropods, especially non-coleopteran groups, in wood, bark and ‘periphery’ of stumps in comparison with soil to evaluate which species/taxa prefer stumps over soil and would risk a significant population decline following extensive stump harvesting. To assess the effects of stump age on species and individual numbers, 5-, 10- and 20-yr-old stumps were studied at three sites in southern and central Sweden. For each site and age class, stumps of Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) were compared. Samples of wood and bark were taken from the full height of the stump and samples of periphery and soil to a depth of 10cm. The samples were placed in Tullgren funnels for animal extraction during 4days. A total of 56 species or other taxonomic groups not belonging to Coleoptera were identified. Bark (including the space between bark and wood) had significantly lower species richness of non-coleopteran macroarthropods but higher abundance per m2 (of cut stump surface) than soil in 10-yr-old stands, which on average contained higher abundances than the other age classes. No significant differences were found between spruce and pine stumps, indicating that one of the tree species can act as a substitute after stump harvesting of the other. Viewed over all substrates, Diplopoda, Coleoptera, Diptera (larvae) and Homoptera contributed most to the total abundance (29, 20, 17 and 15%, respectively). Of these groups, Diplopoda were much more abundant in bark (98%) than in soil (2%). The most common diplopod species was Proteroiulus fuscus, which often demonstrated 100-fold higher abundances (per sample unit) in bark and wood than in soil. Six species/taxa had clearly higher abundances in stumps than in soil. Stump harvesting would thus markedly reduce preferred habitats for these taxa. It is also possible that some species generally considered as soil animals might be occasionally dependent on stumps for, e.g. egg-laying and hatching. For such species, stump harvesting would be more detrimental than indicated by this population survey.

Soil CO2 flux during the first years after stump harvesting in two Swedish forests

One way of increasing the supply of renewable energy, thereby decreasing the use of fossil fuels, is to extract the stumps that remain after final stem harvesting. However, little is known about the environmental consequences of stump harvesting, and how ecosystem services, such as carbon sequestration, are affected by the practice. In the present paper, the effects on the soil carbon pool during the first months and years after stump harvesting in former Norway spruce stands are presented. The study was performed at two sites in mid- and southern Sweden. At both sites, the soil CO flux was measured on several occasions with a portable respiration system, to compare plots on which stump harvesting had occurred, with reference plots. At one of the sites, CO exchange was also followed continuously by means of eddy-covariance measurements before and after stump harvesting. Since there was no vegetation at the beginning of the study, almost all emitted CO could be assumed to come from heterotrophic sources, and the soil CO flux was measured. This study shows that the effect of stump harvesting on CO flux or soil decomposition processes is small or absent compared to site preparation such as mounding in a short-term perspective of months and years. The long-term consequences of stump harvesting are, however, still uncertain.22222