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Christoph Leuschner - One of the best experts on this subject based on the ideXlab platform.
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canopy transpiration of pure and mixed Forest Stands with variable abundance of european beech
Journal of Hydrology, 2012Co-Authors: Tobias Gebauer, Viviana Horna, Christoph LeuschnerAbstract:Summary The importance of tree species identity and diversity for biogeochemical cycles in Forests is not well understood. In the past, Forestry has widely converted mixed Forests to pure Stands while contemporary Forest policy often prefers mixed Stands again. However, the hydrological consequences of these changes remain unclear. We tested the hypotheses (i) that significant differences in water use per ground area exist among the tree species of temperate mixed Forests and that these differences are more relevant for the amount of stand-level canopy transpiration ( E c ) than putative complementarity effects of tree water use, and (ii) that the seasonal patterns of E c in mixed Stands are significantly influenced by the identity of the present tree species. We measured xylem sap flux during 2005 (average precipitation) and 2006 (relatively dry) synchronously in three nearby old-growth Forest Stands on similar soil differing in the abundance of European beech (pure beech stand, 3-species stand with 70% beech, 5-species stand with E c was 50% higher in the beech-poor 5-species stand than in the two Stands with moderate to high beech presence (158 vs. 97 and 101 mm yr −1 ); in the dry summer 2006, all Stands converged toward similar E c totals (128–139 mm yr −1 ). Species differences in E c were large on a sapwood area basis, reflecting a considerable variation in hydraulic architecture and leaf conductance regulation among the co-existing species. Moreover, transpiration per crown projection area ( E CA ) also differed up to 5-fold among the different species in the mixed Stands, probably reflecting contrasting sapwood/crown area ratios. We conclude that E c is not principally higher in mixed Forests than in pure beech Stands. However, tree species-specific traits have an important influence on the height of E c and affect its seasonal variation. Species with a relatively high E CA (notably Tilia ) may exhaust soil water reserves early in summer, thereby increasing drought stress in dry years and possibly reducing ecosystem stability in mixed Forests.
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Productivity of temperate broad-leaved Forest Stands differing in tree species diversity
Annals of Forest Science, 2010Co-Authors: Mascha Jacob, Christoph Leuschner, Frank M. ThomasAbstract:Understanding the effects of tree species diversity on biomass and production of Forests is fundamental for carbon sequestration strategies, particularly in the perspective of the current climate change. However, the diversity-productivity relationship in old-growth Forests is not well understood.* We quantified biomass and above-ground production in nine Forest Stands with increasing tree species diversity from monocultures of beech to Stands consisting of up to five deciduous tree species (Fagus sylvatica, Fraxinus excelsior, Tilia spp., Carpinus betulus, Acer spp.) to examine (a) if mixed Stands are more productive than monospecific Stands, (b) how tree species differ in the productivity of stem wood, leaves and fruits, and (c) if beech productivity increases with tree diversity due to lower intraspecific competition and complementary resource use.* Total above-ground biomass and wood production decreased with increasing tree species diversity. In Fagus and Fraxinus, the basal area-related wood productivity exceeded those of the co-occurring tree species, while Tilia had the highest leaf productivity. Fagus trees showed no elevated production per basal area in the mixed Stands.* We found no evidence of complementary resource use associated with biomass production. We conclude that above-ground productivity of old-growth temperate deciduous Forests depend more on tree species-specific traits than on tree diversity itself.
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Root Growth and Recovery in Temperate Broad-Leaved Forest Stands Differing in Tree Species Diversity
Ecosystems, 2009Co-Authors: Catharina Meinen, Dietrich Hertel, Christoph LeuschnerAbstract:In contrast to studies on aboveground processes, the effect of species diversity on belowground productivity and fine-root regrowth after disturbance is still poorly studied in Forests. In 12 old-growth broad-leaved Forest Stands, we tested the hypotheses that (i) the productivity and recovery rate (regrowth per standing biomass) of the fine-root system (root diameter
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rainfall partitioning in relation to Forest structure in differently managed montane Forest Stands in central sulawesi indonesia
Forest Ecology and Management, 2006Co-Authors: Johannes Dietz, Dirk Holscher, Christoph LeuschnerAbstract:Management activities alter the structure of many tropical Forest Stands which can be expected to influence the magnitude of canopy water fluxes. The objectives of this study were to determine throughfall, stemflow and rainfall interception in differently managed Forest Stands, and to relate the observed pattern of rainfall partitioning to stand structural characteristics. The study was conducted in a lower montane rainForest region (800–1140 m asl) in Central Sulawesi, Indonesia. Stands of four management types (natural Forest, Forest subject to small-diameter timber extraction, Forest subject to selective logging of large-diameter timber, and cacao agroForest under trees remaining from the natural Forest) were analyzed with three replicates per use type. The tree basal area decreased from the natural Forest (52.5 m 2 ha 1 ) to the agroForest (19.4 m 2 ha 1 ) which was paralleled by a reduction in mean tree height (trees 10 cm dbh) from 21.3 to 17.5 m. The estimated leaf area index (LAI), as derived from hemispherical photos, averaged 6.2 m 2 m 2 in the natural Forest, 5.3 in Forests with small timber extraction, 5.0 in Forests with large timber extraction, and 5.3 in the agroForest. The annual gross precipitation close to our different study plots varied locally between 2437 and 3424 mm during the time of the study. Throughfall was measured on 15–17 rain days per plot with a median of 70% of gross precipitation over all the natural Forest plots, 79 and 80% in Forest with small and large timber extraction respectively, and 81% in the agroForest. Stemflow was less than 1% in all studied use types. Thus, rainfall interception was highest in the natural Forest where 30% (median) of the gross precipitation was re-evaporated back into the atmosphere, and much lower in the three other use types (18–20%). Variability in structure and rainfall partitioning was high even within the same Forest use types, thus further analysis focused on gradual changes rather than categories. In the 12 Stands, LAI alone did not correlate significantly with the pattern of rainfall partitioning, the throughfall percentage increased signifi cantly with decreasing tree height (r 2 = 0.63). In a multiple linear regression with tree height and LAI as influencing factors, 81% of the variation in throughfall percentage is explained. A possible reason for this tree height-LAI-throughfall relationship is that under the conditions prevailing in our study region the canopy may not completely dry up between subsequent rainfall events. Therefore, the actual water storage at the start of a rainfall event would be below its potential. We hypothesize that tall trees increase the vertical distribution of foliage and other canopy components contributing to the canopy water storage, resulting in a higher canopy roughness and a more effective energy exchange with the atmosphere. This would consequently lead to an increased re-evaporation of intercepted water, larger available water storage and, thus, a reduced throughfall in Stands with tall trees. # 2006 Elsevier B.V. All rights reserved.
Santa Neimane - One of the best experts on this subject based on the ideXlab platform.
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ultraviolet radiation accelerates photodegradation under controlled conditions but slows the decomposition of senescent leaves from Forest Stands in southern finland
Plant Physiology and Biochemistry, 2020Co-Authors: Marta Pieriste, Santa Neimane, Twinkle Solanki, Line Nybakken, Alan G Jones, Estelle Forey, Matthieu ChauvatAbstract:Abstract Depending on the environment, sunlight can positively or negatively affect litter decomposition, through the ensemble of direct and indirect processes constituting photodegradation. Which of these processes predominate depends on the ecosystem studied and on the spectral composition of sunlight received. To examine the relevance of photodegradation for litter decomposition in Forest understoreys, we filtered ultraviolet radiation (UV) and blue light from leaves of Fagus sylvatica and Betula pendula at two different stages of senescence in both a controlled-environment experiment and outdoors in four different Forest Stands (Picea abies, Fagus sylvatica, Acer platanoides, Betula pendula). Controlling for leaf orientation and initial differences in leaf chlorophyll and flavonol concentrations; we measured mass loss at the end of each experiment and characterised the phenolic profile of the leaf litter following photodegradation. In most Forest Stands, less mass was lost from decomposing leaves that received solar UV radiation compared with those under UV-attenuating filters, while in the controlled environment UV-A radiation either slightly accelerated or had no significant effect on photodegradation, according to species identity. Only a few individual phenolic compounds were affected by our different filter treatments, but photodegradation did affect the phenolic profile. We can conclude that photodegradation has a small stand- and species-specific effect on the decomposition of surface leaf litter in Forest understoreys during the winter following leaf fall in southern Finland. Photodegradation was wavelength-dependent and modulated by the canopy species filtering sunlight and likely creating different combinations of spectral composition, moisture, temperature and snowpack characteristics.
Marta Pieriste - One of the best experts on this subject based on the ideXlab platform.
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ultraviolet radiation accelerates photodegradation under controlled conditions but slows the decomposition of senescent leaves from Forest Stands in southern finland
Plant Physiology and Biochemistry, 2020Co-Authors: Marta Pieriste, Santa Neimane, Twinkle Solanki, Line Nybakken, Alan G Jones, Estelle Forey, Matthieu ChauvatAbstract:Abstract Depending on the environment, sunlight can positively or negatively affect litter decomposition, through the ensemble of direct and indirect processes constituting photodegradation. Which of these processes predominate depends on the ecosystem studied and on the spectral composition of sunlight received. To examine the relevance of photodegradation for litter decomposition in Forest understoreys, we filtered ultraviolet radiation (UV) and blue light from leaves of Fagus sylvatica and Betula pendula at two different stages of senescence in both a controlled-environment experiment and outdoors in four different Forest Stands (Picea abies, Fagus sylvatica, Acer platanoides, Betula pendula). Controlling for leaf orientation and initial differences in leaf chlorophyll and flavonol concentrations; we measured mass loss at the end of each experiment and characterised the phenolic profile of the leaf litter following photodegradation. In most Forest Stands, less mass was lost from decomposing leaves that received solar UV radiation compared with those under UV-attenuating filters, while in the controlled environment UV-A radiation either slightly accelerated or had no significant effect on photodegradation, according to species identity. Only a few individual phenolic compounds were affected by our different filter treatments, but photodegradation did affect the phenolic profile. We can conclude that photodegradation has a small stand- and species-specific effect on the decomposition of surface leaf litter in Forest understoreys during the winter following leaf fall in southern Finland. Photodegradation was wavelength-dependent and modulated by the canopy species filtering sunlight and likely creating different combinations of spectral composition, moisture, temperature and snowpack characteristics.
Frank M. Thomas - One of the best experts on this subject based on the ideXlab platform.
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Productivity of temperate broad-leaved Forest Stands differing in tree species diversity
Annals of Forest Science, 2010Co-Authors: Mascha Jacob, Christoph Leuschner, Frank M. ThomasAbstract:Understanding the effects of tree species diversity on biomass and production of Forests is fundamental for carbon sequestration strategies, particularly in the perspective of the current climate change. However, the diversity-productivity relationship in old-growth Forests is not well understood.* We quantified biomass and above-ground production in nine Forest Stands with increasing tree species diversity from monocultures of beech to Stands consisting of up to five deciduous tree species (Fagus sylvatica, Fraxinus excelsior, Tilia spp., Carpinus betulus, Acer spp.) to examine (a) if mixed Stands are more productive than monospecific Stands, (b) how tree species differ in the productivity of stem wood, leaves and fruits, and (c) if beech productivity increases with tree diversity due to lower intraspecific competition and complementary resource use.* Total above-ground biomass and wood production decreased with increasing tree species diversity. In Fagus and Fraxinus, the basal area-related wood productivity exceeded those of the co-occurring tree species, while Tilia had the highest leaf productivity. Fagus trees showed no elevated production per basal area in the mixed Stands.* We found no evidence of complementary resource use associated with biomass production. We conclude that above-ground productivity of old-growth temperate deciduous Forests depend more on tree species-specific traits than on tree diversity itself.
Erik Næsset - One of the best experts on this subject based on the ideXlab platform.
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comparing regression methods in estimation of biophysical properties of Forest Stands from two different inventories using laser scanner data
Remote Sensing of Environment, 2005Co-Authors: Erik Næsset, Ole Martin Bollandsas, Terje GobakkenAbstract:Mean tree height, dominant height, mean diameter, stem number, basal area, and timber volume of 233 field sample plots were estimated from various canopy height and canopy density metrics— derived by means of a small-footprint laser scanner over young and mature Forest Stands— using ordinary least-squares (OLS) regression analysis, seemingly unrelated regression (SUR), and partial least-squares (PLS) regression. The sample plots were distributed systematically throughout two separate inventory areas with size 1000 and 6500 ha, respectively. The plots were divided into three predefined strata. Separate regression models were estimated for each inventory as well as common models utilizing the plots of both inventories simultaneously. In the models estimated by combining data from the two areas, the statistical effect of inventory was found to be significant (p<0.05) in the mean height models only. A total of 115 test Stands and plots with size 0.3–11.7 ha were used to validate the estimated regression models. The bias and standard deviations (parenthesized) of the differences between predicted and ground reference values of mean height, dominant height, mean diameter, stem number, basal area, and volume were −5.5% to 4.7% (3.1–7.3%), −6.0% to 0.4% (2.9–8.2%), −0.2% to 7.9% (5.5–15.8%), −21.3% to 12.5% (13.4–29.3%), −7.3% to 8.4% (7.1–13.6%), and −3.9% to 10.1% (8.3–14.9%), respectively. It was revealed that only minor discrepancies occurred between the three investigated estimation techniques. None of the techniques provided predicted values that were superior to the other techniques over all combinations of strata and variables.
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determination of mean tree height of Forest Stands by digital photogrammetry
Scandinavian Journal of Forest Research, 2002Co-Authors: Erik NæssetAbstract:The mean tree height of 73 Forest Stands in a 1000 ha Forest area was determined from canopy heights generated by automatic image matching using a digital photogrammetric workstation and digitized panchromatic aerial photographs with a scale of 1:15 000. First, the mean height of each stand was computed as the arithmetic mean of the quantile corresponding to the 75th percentile of the distribution of the canopy heights from the image matching within square grid cells with cell sizes of 236-400 m2. The mean heights from the image matching underestimated the true heights by 5.42 m. Secondly, field-measured mean tree heights of 165 georeferenced sample plots distributed systematically throughout the 1000 ha Forest area were regressed against the mean heights derived from the image matching. The regression equations were used to predict the mean heights of the 73 Stands. In very young Forest Stands, the predicted mean heights overestimated the true heights by 0.4 m and the precision was 0.9-1.0 m. In young an...
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estimating tree heights and number of stems in young Forest Stands using airborne laser scanner data
Remote Sensing of Environment, 2001Co-Authors: Erik Næsset, Kjellolav BjerknesAbstract:The mean heights of dominant trees and the stem numbers of 39 plots of 200 m2 each were derived from various canopy height metrics and canopy density measured by means of a small-footprint airborne laser scanner over young Forest Stands with tree heights .05) and a standard deviation of the differences between predicted and ground-truth mean height of 0.56 m (8.4%).
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Determination of mean tree height of Forest Stands using airborne laser scanner data
ISPRS Journal of Photogrammetry and Remote Sensing, 1997Co-Authors: Erik NæssetAbstract:The mean tree height of Forest Stands is a crucial stand characteristic in Forest planning. Currently, the mean tree height is determined by field measurements or by photogrammetric measurements utilizing aerial photographs. In this study, mean tree height of 36 test Stands is derived from tree canopy heights measured by means of an airborne laser scanner. On the average the laser recorded 505-1070 canopy heights per stand. First, the laser mean height is computed as the arithmetic mean of the canopy heights within each stand. The laser mean height underestimates the ground truth mean height by 4.1-5.5 m. Second, a weighted mean of the laser canopy heights is computed. The individual height values are used as weights. The weighted mean height underestimates the true height by 2.1-3.6 m. Finally, the laser mean height is computed as the arithmetic mean of the largest laser values within square grid cells with cell sizes of 15-30 m. The bias of the laser estimates is in the range -0.4 m to 1.9 m. The standard deviation for differences between the laser mean heights and the ground truth mean height is 1.1-1.6 m.
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Derivation of stumpage value and logging costs for individual Forest Stands using aerial photographs and cartographic modelling
Scandinavian Journal of Forest Research, 1996Co-Authors: Erik NæssetAbstract:A procedure for calculation of stumpage value and logging costs of individual mature Forest Stands using aerial photo‐interpretation and a grid‐based geographical information system (GIS) is presented. The stumpage value may be computed from characteristics related to the trees, i.e. site index, stand mean height, crown closure, and tree species distribution, using price equations. By means of cost equations, the logging costs may be calculated from the tree characteristics and the terrain characteristics of slope gradient and skidding distance. The practical application of the procedure was demonstrated by a case study in a 710 ha Forest area in southern Norway. The tree characteristics were determined by photo‐interpretation of individual Stands. Skid paths for wood transportation from the Stands to landings along the Forest roads were delineated by photo‐interpretation of the ground conditions. Slope and skidding distances were derived by a digital elevation model and cartographic modelling. Finally, t...