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Effects of very intensive forest biomass harvesting on short and long term site productivity:chapter 3
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Effects Of Very Intensive Forest Biomass Harvesting On Short And Long Term Site Productivity
No full textIntensified forest biomass utilisation causes export of substantial amounts of nutrients from the forest ecosystem. Compared to conventional stems-only harvesting, the most intensive biomass sce nario causes increases in nutrient exports of up to 6-7 times whereas the biomass export increases only up to 2 times (Stupak et al. 2007a). High concentrations of nutrients in small branches, twigs, and leaves compared to stems are the main reason. The extensive export of nutrients related to intensive biomass extraction have for many years caused concern for the long-term fertility of the system among forest ecologists (Burger 2002, Blanco et al. 2005, Dyck et al. 1994, Egnell et al. 1998, Egnell et al. 2006). In this chapter we focus on the nutritional consequences of intensified biomass utilisation by use of the nutrient balance approach. Specific attention is given to quantification of the nutrient export and to the soil nutrient release capability. We suggest distinction of sensitive and robust soils. Six case studies are used to exemplify the approach and illustrate the importance of deposition, harvesting and soil properties. The distinction of sites and the quantification of nutrient balances are used for compensation recommendations. We do not discuss effects like decrease in soil organic matter, or other indirect effects like soil compaction, weed problems, and microclimatic effects
Towards better estimates of carbon stocks in Bornean logged-over Dipterocarp forests
Full text linkTropical forests are a major reservoir of biodiversity and carbon (C), playing a pivotal role in global ecosystem function and climate regulation. However, most of the tropical forests, especially Bornean forests in Southeast Asia, are under intense pressure and threatened by anthropogenic activities such as logging, mining industry, agriculture and conversion to industrial plantation. In 2010, the area of production forests in Borneo was 26.8 million ha (approx. 36% of the total land area of Borneo) including 18 million ha (approx. 24%) of logged forests. Production forests are thus emerging as a dominant land-use, playing a crucial role in trading-off provision of goods and maintenance of ecosystem services, such as C and biodiversity retention. Selective logging is known to reduce both above- and below-ground biomass through the removal of a few large trees, while increasing deadwood stocks through collateral damages. By creating large gaps in the canopy, microclimates in the understory and on the forest floor change locally speeding up the decomposition of litter and organic matter. The extent of incidental damages, canopy openness, as well as the speed of C recovery, was shown to be primarily related to logging intensity. However, empirical evaluations of the long-term effect of logging intensity on C balance in production forests remain rare. The present thesis aims to assess the long-term effect of logging intensity on C sequestration in a north Bornean Dipterocarp forests (Malinau District, North Kalimantan) logged in 1999/2000. Five main C pools, namely above-ground (AGC) and below-ground (BGC) carbon in living trees, deadwood, litter, and soil organic carbon (SOC) were estimated along a logging intensity gradient (ranging from 0 to 57% of initial biomass removed). Our result showed that total C stocks 16 years after logging, ranged from 218-554 Mg C ha-1 with an average of 314 Mg C ha-1. A difference of 95 Mg C ha-1 was found between low logging intensity (19%). Most C (approx. 77%) was found in living trees, followed by soil (15%), deadwood (6%), and a minor fraction in litter (1%). The imprint of logging intensity was still detectable 16 years after logging, and logging intensity thus was the main driver explaining the reduction of AGC>20, BGC>20, deadwood, and total C stocks and an increase in deadwood. Solely, logging intensity explained 61%, 63%, 38%, and 48% of variations of AGC>20, BGC>20, deadwood, and total C stocks, respectively. Logging intensity also significantly reduced SOC stocks in the upper 30 cm layer. For total SOC stocks (0-100 cm), the negative influence of logging intensity was still perceptible, being significant in conjunction with other variables. Our results quantify the long-term effect of logging on forest C stocks, especially on AGC and deadwood. High logging intensity (50% reduction of initial biomass) reduced total C stocks by 27%. AGC recovery was lower in high logging intensity plots, suggesting lowered forest resilience to logging. Our study showed that maintaining logging intensity, below 20% of the initial biomass, limit the long-term effect of logging on AGC and deadwood stocks
Effect of tree species and soil properties on nutrient immobilization in the forest floor
No full textTo investigate the effect of tree species and soil properties on organic matter accumulation and associated nutrients, an area-based sampling of the forest floor was carried out in a 28 years old species trial including Norway spruce, Douglas fir, beech, and common oak at two sites, a poor and sandy soil, and a fertile loamy soil. The accumulation of C, N and P in the forest floor was significantly higher at the sandy site than at the loamy site under all species. At the loamy site, oak was characterized by lesser accumulation of C, N and P than the other species. Remarkably, the C/N-ratios showed no substantial differences, whereas the C/P-ratios were significantly higher at the sandy site for all species. pH was significantly lower at the sandy site for all species, and among the species, pH was lower in the conifer forest floors than in the broadleave forest floors. The concentration of ammonium, nitrate and phosphate in the soil solution was much higher at the loamy site under all species showing a stronger microbial activity. It is therefore hypothesized that the differences in accumulation rates were, at least partly, caused by differences in the mineralization regimes. Strong root infiltration in the forest floors at the sandy site compared to almost none at the loamy site, is probably responsible for the differences in mineralization rate due to competition between the organic matter decomposers and the tree-roots/mycorrhiza for nutrients. Author Keywords: EFFECTS OF ROOTS; NUTRIENT IMMOBILIZATION; SOIL PROPERTIES; SOIL SOLUTION; TREE SPECIE
Aluminium contamination of acid soil solution isolated by means of porcelain suction cups:a reply to a paper by Hughes & Reynolds (1990) and an interpretation of aluminium release
No full textEffect of the artificial acid rain and liming on the base status in an acid forest (<em>Picea abies</em> (L.), Karst ) soil (typic haplohumod)
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