Effects Of Whole-tree Harvesting Research Articles

Effects of intensive biomass harvesting on forest soils in the Nordic countries and the UK: A meta-analysis

The use of biomass from forest harvesting residues or stumps for bioenergy has been increasing in the northern European region in the last decade. The present analysis is a regional review from Nordic and UK coniferous forests, focusing on the effects of whole-tree harvesting (WTH) or whole-tree thinning (WTT) and of WTH followed by stump removal (WTH + S) on the forest floor and mineral soil, and includes a wider array of chemistry data than other existing meta-analyses. All intensified treaments led to significant decreases of soil organic carbon (SOC) stock and total N stock in the forest floor (FF), but relative responses compared with stem-only harvesting were less consistent in the topsoil (TS) and no effects were detected in the subsoil (SS). Exchangeable P was reduced in the FF and TS both after WTT and WTH, but significant changes in exchangeable Ca, K, Mg and Zn depended on soil layer and treatment. WTH significantly lowered pH and base saturation (BS) in the FF, but without apparent changes in cation exchange capacity (CEC). The only significant WTH-effects in the SS were reductions in CEC and BS. Spruce- and pine-dominated stands had comparable negative relative responses in the FF for most elements measured except Mg and for pH. Relative responses to intensified harvesting scaled positively with growing season temperature and precipitation for most variables, most strongly in FF, less in the TS, but almost never in the SS, but were negative for P and Al. The greater reduction in FF and TS for soil organic carbon after intensive harvesting decreased with time and meta-regression models predicted an average duration of 20–30 years, while many other chemical parameters generally showed linear effects for 30–45 years after intensified harvesting. Exchangeable acidity (EA), BS and pH all showed the reversed effect with time, i.e. an initial increase and then gradual decrease over 24–45 years. The subsoil never showed a significant temporal effect. Our results generally support greater reductions in nutrient concentrations, SOC and total N in forest soil after WTH compared with SOH in northern temperate and boreal forest ecosystems.

Effects of whole-tree harvesting on soil, soil water and tree growth – A dynamic modelling exercise in four long-term experiments

Whole tree harvesting (WTH) following final felling of productive forests is increasingly promoted as a method to extract biomass for energy purposes. Despite its importance, there is a limited number of experimental studies investigating the impacts of WTH on forest ecosystem sustainability. Modelling studies have previously been carried out to complement and explain empirical observations from four long-term WTH experiments in Sweden. The literature shows a significant discrepancy between these studies, and open questions remain as to the fate of the base cations that are not removed in the absence of WTH. This study uses the integrated ecosystem model ForSAFE, which simulate a forest ecosystem’s biogeochemical processes and the feedbacks between these processes, to trace the fate of base cations for the said four long-term WTH experiments. The study shows that the model generally captures the observed effects of WTH on the stocks of base cations in the biomass and in the soil. The modelled results were also used to map how the base cations removed through WTH would otherwise (if left at the site) have been distributed in the ecosystem. The results indicate that the soil organic pool may be more important to the long-term base cation balance than the exchangeable pool, and should receive more attention in future research.

Recovery of understorey vegetation after stem-only and whole-tree harvesting in drained peatland forests

The demand for small-sized trees, logging residues, stumps, and lateral roots for energy production has increased during recent decades and therefore whole-tree harvesting (WTH) has become a more common harvesting method in forests. However, this may cause a more pronounced delay in the recovery of forest vegetation than conventional stem-only harvesting (SOH), especially in sensitive peatlands, and thus increase soil erosion. The effects of WTH have not been investigated on peatlands before this study. Recovery of understorey vegetation of drained peatland forests after two different tree harvesting methods, stem-only harvesting and whole-tree harvesting, was investigated in Eastern Finland at eight silviculturally managed peatland forests largely comprising Scots pine, Pinus sylvestris, and Norway spruce, Picea abies. In SOH, trunks only were removed from the sites whereas in WTH, tree trunks, branches, and stumps were removed. In each site, understorey vegetation (tree seedlings, dwarf shrubs, graminoids, herbs, and bryophytes) was inventoried on both mounded and unprepared soil (surfaces) on 220 permanent sample plots one and five years after harvesting. WTH had more pronounced effects on vegetation than SOH. Five to six years after the treatments, the occurrence of dwarf shrubs was lower in WTH than in SOH, whereas the cover of graminoids increased from both SOH and WTH. Soil preparation affected negatively on the recovery of peat and forest bryophytes, but positively on the recovery of some graminoid and herb species. Peat properties, e.g., pH and water table level, were found to regulate the recovery. WTH caused a longer delay on the recovery of understorey vegetation than SOH, especially if soil had been prepared. Thus, WTH cannot be recommended in drained peatland forests.

Ground vegetation composition and diversity in drained Norway spruce (Picea abies (L.) Karst.) stands 50 years after whole-tree harvesting management: case study in Latvia

Abstract The long-term (50 years) effect of whole-tree harvesting (stump harvesting) on ground vegetation in experimental drained Norway spruce (Picea abies (L.) Karst.) stands was studied. We used a chronosequence approach to assess the long-term impact of whole-tree harvesting (WTH) on stands’ ground vegetation. WTH stands were compared with four control stands with different age and with the same forest type: young stand (15 years), middle-aged stand (45 years), mature stand (110 years) and over-mature stand (140 years). Species richness was similar between the WTH stand and middle-aged stand (61 and 60 species, respectively). Shannon-Wiener diversity indices in the WTH and middle-aged stand (3.40 and 3.19, respectively) indicated that the stands were similar to each other. A community similarity analysis showed that the composition of vegetation was similar between the WTH and middle-aged stand, although some species like Lycopodium clavatum and Diphasiastrum complanatum occurred only in the WTH stand. The study showed that a period of 50 years is sufficient for ground vegetation of a typical drained spruce forest to recover after WTH management.

Effects of whole-tree harvest on soil-water chemistry at five conifer sites in Sweden

Logging residues, such as tops and branches, can provide a useful biofuel for large-scale energy production. However, increasing the harvest intensity may affect the soil nutrient stores and water quality. Here, effects on soil-water chemistry after stem-only and whole-tree harvesting were investigated using data from five experimental sites in Sweden, representing medium- to high-fertility sites. They were located in recharge areas on mineral soil and harvested between the years 1995 and 2001. Soil-water samples had previously been collected from below the main part of the root zone in study plots subjected to stem-only or whole-tree harvest. Soil-water chemistry data from the five sites were jointly analyzed by ANOVA using seasonal mean concentrations from the first six seasons after clear-cutting. The concentrations of NO3–-N, K+, and Mg2+were significantly different (p < 0.05) between the two harvest regimes, indicating lower levels after whole-tree harvest than after stem-only harvest. No significant differences were detected for electrical conductivity, pH, or the concentrations of NH4+-N, Al, Ca2+, SO42–-S, and Cl–. Measurements at one site suggested that the logging residues left on the ground increased the influx of Cl–to the soil. Simple budget calculations indicated that the nutrient export by logging-residue harvest was greater than the export by leaching during the regeneration phase.

Effects of Whole-Tree Harvesting on Species Composition of Tree and Understory Communities in a Northern Hardwood Forest

In the northeastern United States, whole-tree harvesting is widely used to supply fuel to biomass energy facilities, but questions remain regarding its long-term sustainability. We have previously reported findings indicating no short-term decrease in forest productivity in whole-tree harvested sites when compared with similar conventionally (stem-only) harvested sites. Here we present additional results of the same study, but focus on the effect harvest treatment has on the species composition of the regenerating forest. Within northern hardwood forests in central New Hampshire and western Maine, regeneration surveys were conducted on four (4) small clearcuts in 2010 and twenty-nine (29) small clearcuts in 2011. The species and diameter of trees > 2 m in height were recorded within 1 m or 2 m-radius plots and used to calculate the biomass fraction of each species. The 2010 study additionally measured the density of trees 2 m in height and the diversity of understory non-tree species. Non-metric multidimensional scaling and multi-response permutation procedures were used to determine the effect of harvest treatment had on community-wide tree species composition. Potential differences were also examined on a species-by-species basis. Both analytic methods indicated no significant differences in species composition of tree species or understory communities. Within the limits of our data, we conclude that no significant effects of residue removal on species composition are observed within our sample of northern hardwood sites at this early stage of stand development.

Effects of whole-tree harvesting on growth of pine and spruce seedlings in southern Finland

The effects of harvesting logging residue on the survival and growth of planted Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst) seedlings and on number and growth of natural seedlings were studied at five sites in southern Finland. Trees were harvested either conventionally, i.e. harvesting only the stems, or harvesting all the aboveground tree biomass (WTH). One of the experiments had been planted with pine and four experiments with spruce 10 years ago. When the spruce experiments were analysed together, WTH had significantly increased the average number of planted seedlings, but had not affected basal area, stem volume or biomass of the planted seedlings. When both planted and natural seedlings were studied together, WTH significantly increased the average number of seedlings and the average total biomass of all tree species. In the pine experiment, WTH had no effect on stand or tree characteristics. In this study, within the first 10 years after reforestation, WTH did not have any negative effect in stand or tree characteristics that could be explained by nutrients removed with logging residue.

Changes in the effects of whole-tree harvesting on soil chemistry during 10 years of stand development

Whole tree harvesting depletes soil nutrients and increases soil acidification more than conventional stem harvesting. This study examined whether this effect persists through stand development and to what extent forest growth and associated nutrient accumulation in biomass determined changes in soil chemistry over time. Changes in soil chemistry and nutrient capital in the forest floor and soil were determined over a period of 10years (i.e., 15–25years following harvesting) in two young stands of Scots pine and two young stands of Norway spruce in different parts of Sweden. Conventional harvesting of stems (CH) in these stands was compared with harvesting of stems and branches but with needles left on site (BSH), and whole tree harvesting (WTH). The effects of WTH on calcium and manganese concentrations in the forest floor and uppermost mineral soil (0–5cm) were found to diminish over time, mainly due to more rapidly declining concentrations of these elements in CH and to some extent in BSH plots than in WTH plots. A similar pattern was found for total calcium and manganese concentrations in the forest floor and soil to 20cm depth. The declining calcium and manganese concentrations in the forest floor were accompanied by more rapidly increasing levels of acidity and declining base saturation and effective cation exchange capacity in the forest floor in CH and BSH plots than in WTH plots. However, differences between harvesting treatments in aluminium concentration in the forest floor and calcium concentration in the deepest part of the mineral soil (10–20cm) persisted over time. Differences in site yield capacity and expected nutrient accumulation in biomass among sites did not explain patterns of change in total amounts of nutrients in the forest floor and soil over time and the observed changes were generally small.

The effects of whole-tree harvesting on three sites in upland Britain on the growth of Sitka spruce over ten years

Summary Three experiments were established in the 1990s to examine the impact of complete residue (brash) and above-ground biomass removal (i.e. ‘whole-tree harvesting’, WTH) at clearfelling on the subsequent growth and yield of replanted Sitka spruce (Picea sitchensis). The sites were of varying fertility; two would now be considered to be of ‘medium’ risk for brash removal, while one would be a ‘high’-risk site. The interactions between brash removal and regular remedial fertilizer applications and weed control regimes were also investigated at each site. After 10 years, trees had been successfully established at all sites, and in most cases, the treatments were close to canopy closure. The main effects observed at all sites were due to brash retention and fertilizer application. The benefits from the former were not evident until the last stages of the establishment period, whereas benefits from fertilizer application were evident once the trees had reached 5–6 years of age. The impacts of weed control were inconsistent, providing temporary benefits on the more fertile sites, and having a negative effect on the poorest site, primarily because the herbicide regime favoured the development of ericaceous vegetation which competed with the planted trees for nutrients. After 10 years at the two medium-risk sites, the difference in growth between plots with brash retained and those where brash was removed was 5–9 per cent for height growth and 5–7 per cent for diameter. However, at the poorest site, the equivalent differences were ~9 per cent and 19 per cent. The results show that the impact of brash removal due to WTH are significantly affected by site type and soil fertility and also that it may take nearly a decade before the impacts of such practices are evident.

The long-term effects of logging residue removal on forest floor nutrient capital, foliar chemistry and growth of a Norway spruce stand

This study compared the nutrient capital of the forest floor, the nutrient status of trees, and the growth of a stand of Norway spruce (Picea abies L. (Karst.)) planted on a whole-tree harvesting treatment (needles left on site) with a conventional stem-only harvesting treatment 30 years after clearcutting. No significant treatment effects were detected in the amount of organic matter, the amounts of nutrients in the forest floor, or the concentrations of foliar nutrients. The results indicate that whole-tree harvesting with the needles left on the site did not reduce the long-term nutrient capital of the forest floor or the nutritional status of trees. Whole-tree harvesting significantly reduced the height of dominant spruce compared to stem-only harvesting, however the stem volume of dominant spruce did not differ between the harvesting treatments. The greater height growth of the dominant trees in the stem-only harvesting treatment could be attributed to indirect factors other than changes in site resource availability (e.g. protection against frost damage), and hence the effect of whole-tree harvesting on potential site productivity was inconclusive due to the confounding effect of site factors. In the whole-tree harvesting treatment, the total stem volume of the stand and, consequently, the actual site productivity, was lower when compared to stem-only harvesting due to the lower density of naturally regenerated seedlings.

Long term effects of whole tree harvesting on soil carbon and nutrient sustainability in the UK

The practice of harvesting forest residues is rapidly increasing due to rising demand for renewable energy. However, major concerns have been raised about the sustainability of this practice and its net impact on long term soil ability to support forest productivity, particularly through second and subsequent rotations. In this study, soil chemical properties such as acidity, total N and C, available NO3–N and NH4–N and exchangeable cations were measured in all horizons in peaty gleys soils under one of the oldest experiments in Europe—a 28-year-old second rotation stand of Sitka spruce (Picea sitchensis), in Kielder forest, UK. Treatments included Whole Tree Harvesting (WTH—of all above ground biomass), Conventional stem-only harvesting (CH) of the first rotation crop, and repeated Fertilisation (FE) after the planting of the second rotation forest. This study demonstrates the soil changes underpinning the reduced second rotation tree productivity on these acidic upland sites under WTH, a further 18 years after the investigation by Proe and Dutch (1994). Overall, WTH increased soil acidity significantly (p < 0.05) and reduced soil base saturation whilst FE reduced soil acidity (p < 0.05) and increased soil base saturation as compared to CH. Soil moisture was significantly higher (p < 0.01) under WTH compared to CH and FE plots. There was no evidence that WTH decreased soil organic carbon (SOC) and soil nitrogen (N), but to the contrary there were significantly (p < 0.01) higher concentrations and stocks of total C and N in the WTH soils compared with CH and FE. The depletion of SOC and N in CH and FE plots was attributed to much higher soil mineralisation rates associated with the brash and fertilisation as compared to the WTH plots, where significantly less soil available NO3–N (p < 0.01) was found. In the long term WTH on peaty gley soils appears positive for soil C and N storage. However, WTH had a long term negative impact on soil and tree nutrition of K+ and P, which are currently at deficient levels, but has had a stabilising effect on tree N nutrition as measured in twigs and needles. These results suggest that whilst WTH lead to a reduction in aboveground tree biomass compared to conventional harvest, these practices on selected soil types and certain sites may be beneficial for soil C and N sequestration. The overall findings of this study imply that cost benefit analyses for each site should be carried out before decisions are made on the appropriate type of forest operations (harvesting and replanting), considering both geology and soils in order to serve both environmental benefits, long term sustainability and the available biomass production for timber and biofuel.

Good-practice guidelines for whole-tree harvesting in Sweden: Moving science into policy

Concerns over climate change, peak oil and energy security have prompted countries such as Sweden to develop policies that promote alternative energy sources, including forest-based bioenergy. Sweden is at the forefront of research and development on forest-based bioenergy and has employed a model of science-based policy development to implement bioenergy production systems. In response to environmental concerns over whole-tree harvesting for bioenergy in Sweden, a number of government-funded research programs on forest-derived bioenergy have been undertaken with the intent of generating knowledge about the effects of whole-tree harvesting, ash recycling and bioenergy-related silvicultural practices on ecological systems and values such as soil, nutrient balances, water, biodiversity, greenhouse gas balances and recreation. Sweden developed a series of recommendations and good-practice guidelines for whole tree harvesting starting in 1986 and ending with the most recent revision in 2008. These guidelines and regulations are based on various scientific studies and include prescriptions and mandates to minimize environmental damage caused by whole tree harvesting for bioenergy. From the beginning, the process of developing effective guidelines and regulations governing whole tree harvesting in Sweden has been informed by science. Guidelines and regulations govern the areas of site productivity, utilization of recycled wood ash, biodiversity and physical damage to trees and soils. Overall, Sweden’s experience demonstrates the way in which science can be used to inform guidelines and policies. Key words: Sweden, bioenergy, ash recycling, energy policy, good-practice guidelines, regulations, environment

Effect of whole-tree harvesting on microclimate during establishment of second rotation forestry

The effect of whole-tree harvesting on microclimate during the restocking of three upland forest sites in the UK was studied from January 1994 to November 1999. Mean soil temperatures at 0.1 m depth were greater during summer months and reduced during winter months at all three sites in whole-tree harvested treatments compared to those where harvest residues were retained on site. Whole-tree harvesting also affected mean shoot temperatures (0.3 m above ground level) at each of the three sites and, for much of the time, the effects on shoot temperatures were the reverse of those observed for the soil. In comparison to conventional harvesting, shoots on whole-tree harvested plots tended to be cooler in spring and summer whereas the same shoots were warmer during winter. Whole-tree harvesting increased mean wind speeds measured at 0.3 m by around 40% at each of the three sites during the first year after replanting. This effect diminished to 26, 20 and 5% over the following 3 years at the one site studied for the longest period, located in Kielder Forest, Northumberland. The biomass of 4-year-old Sitka spruce trees was greater on whole-tree harvested plots at two sites where growth was increased by fertiliser applications but was not affected by harvesting treatment at the more fertile third site in which no response to fertiliser was observed.

The effects of whole-tree harvest on benthic insects in small New Hampshire streams

(2000). The effects of whole-tree harvest on benthic insects in small New Hampshire streams. SIL Proceedings, 1922-2010: Vol. 27, No. 2, pp. 1079-1089.

Effects of biomass removal in thinnings and compensatory fertilization on exchangeable base cation pools in acid forest soils

The effects of whole-tree harvesting and fertilization at first thinning on the exchangeable pools of base cations in the soil were examined on four sites five years after thinning. One site with Norway spruce ( Picea abies (L.) Karst.) is located in southwestern Sweden and three other sites with Scots pine ( Pinus sylvestris L.) are located in southeastern, south-central and northern Sweden. On all sites, the stands were thinned, and the following treatments were applied in a randomized block design ( n = 3): (i) stem-only harvest, logging residues left on site; (ii) whole-tree harvesting; (iii) whole-tree harvesting combined with compensatory fertilization (N–P–K were applied one year after thinning in the form of inorganic fertilizers, and the amounts were equal to the nutrient content of the harvested logging residues); (iv) stem-only harvesting in combination with N (pine sites) or NP (spruce site) fertilization (ammonium nitrate, 150 kg N ha −1, superphosphate, 30 kg P ha −1) and (v) whole-tree harvesting and nitrogen fertilization as in treatment (iv). There were no general treatment effects revealed from analysis across all sites. Effects of harvesting intensity were detected on two sites, indicating reduced pools of exchangeable K, Mg and Ca after whole-tree harvesting. The reductions were less pronounced than the effects observed in other studies from experiments with whole-tree harvesting at clear-felling of mature forests. Effects of application of nitrogen alone were more frequently observed than effects of harvesting of logging residues. In most cases, base cation pools were lower after N treatment than after other treatments, and this effect was probably due to exchange and translocation phenomena. However, Ca pools had increased after NP treatment on the spruce site due to high content of Ca in P fertilizer. No effect of compensatory fertilization with N–P–K was detected. A comparison between exchangeable nutrient pools before thinning and five years after indicated that K was generally lost from the soil profile.

Effects of different levels of biomass removal in thinning on short‐term production of pinus sylvestris and picea abies stands

Effects of harvest intensity in thinnings on the productivity of the remaining stands were studied in two Scots pine (Pinus sylvestris L.) and two Norway spruce (Picea abies (L.) Karst.) stands in Sweden. Treatments were: conventional stem wood harvest with short‐wood system (CH); whole‐tree harvest (WTH); whole‐tree harvest + compensation fertilization with NPK (WTH + F). No significant treatment differences in basal area increment could be detected during the first 10 yrs after harvest. However, in all four stands mean basal area increment was lower on WTH plots than on CH plots. The effects of WTH + F were inconsistent. The results indicate that WTH could be practiced in thinnings without significant short‐term production losses in Scots pine and Norway spruce stands in Sweden. However, it is to early to draw any definite conclusion on long‐term effects of WTH on site productivity.

The effect of whole-tree harvesting on the growth of second rotation Sitka spruce

Summary Stem analysis has been used to examine the effects of two harvesting techniques upon growth of second rotation Sitka spruce planted in 1981 on a peaty gley site of low fertility in Kielder Forest, Northumberland. The effect of NPK fertilizer upon tree growth on conventionall y harvested plots was also determined. Weed competition was reduced by hand weeding and the application of herbicides. Repeated measures analysis was used to identify the time at which significant growth responses occurred. Whole-tree harvesting reduced mean tree volume from 1986 onwards while the addition of fertilizer to conventionall y harvested plots increased volume growth from 1990. By 1993, whole-tree harvesting had decreased mean tree volume by 32 per cent and the addition of fertilizer to conventionally harvested plots had increased mean tree volume by 13 per cent. Observed treatment effects are most likely due to the increased removal of nutrients during whole-tree harvesting. The release of nutrients from decomposing residues is expected to meet uptake requirements for approximately 7-9 years following replanting. Effects of shelter and weed competition should also be considered on sites where herbicides have not been used to control ground vegetation. Repeated measures analysis and the use of suitable growth functions provide powerful analytical tools to examine historical treatment effects derived from stem analysis.

The effects of whole-tree harvest on insects associated with leaf packs in small streams in New Hampshire

(1994). The effects of whole-tree harvest on insects associated with leaf packs in small streams in New Hampshire. SIL Proceedings, 1922-2010: Vol. 25, No. 3, pp. 1483-1491.

Effects of Whole-Tree Harvest on Epilithic Algal Communities in Headwater Streams

ABSTRACT The effects of whole tree harvest on the stream algal community within the Hubbard Brook Experimental Forest, New Hampshire were studied by comparing harvested streams with reference streams and by experimental manipulations of light, acidity and nitrate levels. The most marked effect was a large increase in algal standing crop in the summer in the streams of the harvested area. Light plays a key role in this increase, but other factors such as pH, nutrients, and water flow are probably also important.

Effects of whole-tree harvest on epilithic bacterial populations in headwater streams

Bacteria attached to rock and glass surfaces were studied in streams draining a whole-tree harvested watershed (WTH) and a nonharvested (CONTROL) watershed in the Hubbard Brook Experimental Forest, New Hampshire, U.S.A. Seasonal trends in numbers of cells/cm(2), mean cell volume, cell size-frequency distribution, and bacterial biomass were determined using 4'6-diamidino-2-phenylindole (DAPI) epifluorescent microscopy and scanning electron microscopy (SEM); the response of these parameters to decreased pH and increased nitrate concentration in the WTH stream was assessed via controlled manipulation of stream water chemistry in artificial channels placed in the CONTROL stream. Bacterial distribution varied significantly between the two streams and seasonally within each stream in apparent response to differential availability of dissolved organic carbon from algae and autumn-shed leaves. Decreased pH similar to that in the WTH stream had a significant effect on cell numbers, mean cell volume, and biomass in the CONTROL stream. Decreased pH accounted for some aspects of the altered bacterial distributions observed in the WTH stream. Nitrate at concentrations similar to those in the WTH stream had no effect on bacterial distribution in the CONTROL stream suggesting that headwater stream epilithic bacteria were carbon limited.