Whole-tree Harvesting Plots Research Articles

DEVELOPMENT OF YOUNG STANDS AFTER WHOLE TREE HARVESTING AND WHOLE TREE HARVESTING COMBINED WITH STUMP BIOMASS EXTRACTION

Forest management pressures on ecosystems are expected to rise due to increased use of renewable resources and environmental, economic and political reasons. Extraction of nutrient rich logging residues from felling sites has become a common practice, therefore risks of negative impact on the nutrient cycling as well as site future productivity must be assessed. To evaluate effect of whole-tree harvesting (WTH) and whole-tree harvesting combined with stump biomass extraction (WTH+SB) on productivity of next rotation young stands measurements were carried out in eight sites for four to six years in typical forest site types in Latvia (Oxalidosa turf. mel. – eutrophic peat soil site; Hylocomiosa, Oxalidosa – mesotrophic mineral soil sites, Mytrillosa – oligotrophic mineral soil site). Harvesting in the sites was carried out in 2012-2013 and regeneration was carried out after one to two years with Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies L. (Karst.)) and black alder (Alnus glutinosa L. (Gaertn.)). Comparing conventional harvesting or so-called stem only harvesting (SOH) to WTH no statistically significant differences were observed regarding tree height, but in eutrophic Norway spruce site WTH plot smaller stem diameters were observed. Comparing WTH to WTH+SB statistically significantly higher Norway spruce and black alder heights in mono-stands were observed in WTH plots, while no significant differences were detected in Norway spruce and black alder mixed stand. No explicit differences were found regarding height/diameter ratio between WTH and WTH+SB treatments.

Harvesting of logging residues affects diameter growth and pine weevil attacks on Norway spruce seedlings

ABSTRACTRemoval of logging residues causes significant nutrient losses from the harvesting site. Furthermore, collection of residues into piles could lead to small-scale differences in establishment conditions for seedlings. We studied the effects of stem-only (SOH) and aboveground whole-tree harvesting (WTH) on Norway spruce (Picea abies) seedling growth and pine weevil (Hylobius abietis) damage at two sites (SE and W Norway). We also compared two planting environments within the WTH plots (WTH-0: areas with no residues, WTH-1: areas where residue piles had been placed and removed before planting). In practice, one-third of the residues were left on site after WTH. After three growing seasons there were no differences for height or diameter increment between SOH and WTH (WTH-1 and WTH-0 combined) treatments. However, relative diameter increment was largest for WTH-1 seedlings and lowest for WTH-0 seedlings. Few seedlings sustained pine weevil attacks at the W Norway site, with no differences among treatments. At the SE Norway site, the percent of seedlings damaged by pine weevils and average debarked area were significantly higher after WTH (82% and 3.3 cm2) compared to SOH (62% and 1.7 cm2). We conclude that WTH may lead to spatial differences in establishment conditions.

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.

Logging residue removal after thinning in Nordic boreal forests: Long-term impact on tree growth

The aim of this study was to determine the effect of whole-tree harvesting (WTH) on the growth of Scots pine ( Pinus sylvestris L.) and Norway spruce ( Picea abies (L.) Karst.) as compared to conventional stem harvesting (CH) over 10 and 20 years. Compensatory (WTH + CoF) and normal nitrogen-based (CH + F or WTH + F) fertilisation were also studied. A series of 22 field experiments were established during 1977–1987, representing a range of site types and climatic conditions in Finland, Norway and Sweden. The treatments were performed at the time of establishment and were repeated after 10–13 years at 11 experimental sites. Seven experiments were followed for 25 years. Volume increment was on average significantly lower after WTH than after CH in both 10-year periods in the spruce stands. In the pine stands thinned only once, the WTH induced growth reduction was significant during the second 10-year period, indicating a long-term response. Volume increment of pine stands was 4 and 8% and that of spruce stands 5 and 13% lower on the WTH plots than on CH during the first and the second 10-year period, respectively. For the second 10-year period the relative volume increment of the whole-tree harvested plots tended to be negatively correlated with the amount of logging residue. Accordingly, the relative volume increment decreased more, the more logging residue was harvested, stressing the importance of developing methods for leaving the nutrient-rich needles on site. If nutrient (N, P, K) losses with the removed logging residues were compensated with fertiliser (WTH + CoF), the volume increment was equal to that in the CH plots. Nitrogen (150–180 kg ha −1) or N + P fertilisation increased tree growth in all experiments except in one very productive spruce stand. Pine stands fertilised only once had a normal positive growth response during the first 10-year period, on average 13 m 3 ha −1, followed by a negative response of 5 m 3 ha −1 during the second 10-year period. The fertilisation effect of WTH + F and WTH + CoF on basal area increment was both smaller and shorter than with CH + F.

Whole-tree harvesting at clear-felling: Impact on soil chemistry, needle nutrient concentrations and growth of Scots pine

The effects of logging residue removal on soil chemical properties and the needle nutrient concentrations and growth of Scots pine (Pinus sylvestris L.) were studied after clear-felling on two sites of different fertility in eastern Finland. Harvesting was carried out either conventionally, i.e. harvesting only the stems [conventional harvesting (CH)], or totally, i.e. harvesting all of the above-ground tree biomass [whole-tree harvesting (WTH)]. The seedlings were planted in ploughing tilts on 50×50 m sample plots. The number of replications was 24 on the more fertile site and 12 on the less fertile site. Compared with CH, WTH had no effects on either the survival or growth of Scots pine trees during the first 22 years. Apart from the statistically significant increase in needle nitrogen concentration in the WTH treatment on the less fertile site, the needle concentrations were not affected by the harvesting intensity. On the more fertile site, the total amounts of carbon, nitrogen and calcium, as well as exchangeable calcium and extractable phosphorus in the organic layer, were significantly lower on the WTH than on the CH plots. Although the pH remained unchanged, the exchangeable aluminium concentrations increased on the more fertile site, and on both sites the calcium/aluminium ratio was significantly lower on the WTH plots than on the CH plots.

Chemical composition of forest floor and consequences for nutrient availability after wildfire and harvesting in the boreal forest

In boreal forests of eastern Canada, wildfire has gradually been replaced by clearcut harvesting as the most extensive form of disturbance. Such a shift in disturbance may influence the chemical properties of the forest floor and its capacity to cycle and supply nutrients, with possible implications for forest productivity. We compared the effects of stem-only harvesting (SOH), whole-tree harvesting (WTH) and wildfire on the chemical composition of forest floor organic matter and nutrient availability for plants, 15–20 years after disturbance in boreal coniferous stands in Quebec (Canada). The forest floor on plots of wildfire origin was significantly enriched in aromatic forms of C with low solubility, whereas the forest floor from SOH and WTH plots was enriched with more soluble and labile C compounds. The forest floor of wildfire plots was also characterized by higher N concentration, but its high C:N and high concentration of 15N suggest that its N content could be recalcitrant and have a slow turnover rate. Total and exchangeable K were associated with easily degradable organic structures, whereas total and exchangeable Ca and Mg were positively correlated with the more recalcitrant forms of C. We suggest that the bulk of Ca and Mg cycling in the soil–plant system is inherited from the influx of exchangeable cations in the forest floor following disturbance. The buildup of Ca and Mg exchangeable reserves should be greater with wildfire than with harvesting, due to the sudden pulse of cation-rich ash and to the deposition of charred materials with high exchange capacity. This raises uncertainties about the long-term availability of Ca and Mg for plant uptake on harvested sites. In contrast, K availability should not be compromised by either harvesting or wildfire since it could be recycled rapidly through vegetation, litter and labile organic compounds.

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.

Nutrient losses after clearfelling in Beddgelert Forest: a comparison of the effects of conventional and whole-tree harvest on soil water chemistry

The effects of conventional, bole only harvesting (CH) and whole-tree harvesting (WTH) on major inorganic nutrient concentrations (K, NO3-N, NH4-N, PO4-P and Ca) in soil water are described from Beddgelert forest in North Wales. Monitoring of nutrient leaching losses, and the timing thereof, from brash through the soil and into streams draining the CH areas allowed assessments to be made of the value of brash as a nutrient source for second rotation crops. Most of the K (around 100 kg ha-1) and one-third of the P (10 out of 30 kg ha-1) leached out of the brash lying on the CH plots within one year of felling. A pulse of K passed through the soil profile, but less than half this K reached the streams. In contrast, the P was immobilized in the soil. The lack of brash resulted in the absence of K and P pulses on the WTH plots. On the CH plots, brash was a net sink for inorganic-N for 3 years after felling. However, in both CH and WTH, a pulse of nitrate was observed in the soil and also in streams draining CH areas. The source of this nitrate may have been death of fine tree roots, followed by rapid mineralization and nitrification. Calculation of a nutrient budget for a complete crop rotation indicates that P and Ca losses in harvested material are likely to result in long-term depletion of these elements, and that the effects will be significantly more severe if WTH is practised.

Effect of harvest intensity and ground flora establishment on inorganic-N leaching from a Sitka spruce plantation in north Wales, UK

Inorganic-N concentrations in soil solution of whole tree harvest (WTH) and conventional fell (CF) plots were monitored for two years before felling and four years after felling. Concentrations in the mineral soil after felling were higher than in standing forest for up to 14 months in both felling treatments. In the WTH plots inorganic-N concentrations then dropped steadily until four years after felling they approached zero. In contrast, inorganic-N concentrations of the CF plots remained comparatively large. Inorganic-N was dominated by nitrate throughout the period of the study, and especially in the mineral horizons.