Meteorological variables affect composition, structure, growth, health, and dynamics of forest ec... more Meteorological variables affect composition, structure, growth, health, and dynamics of forest ecosystems. The measurement of meteorological data at forest monitoring plots is essential for the interpretation of climate change effects. Within an ecological monitoring network, standard meteorological variables such as precipitation, air temperature, relative humidity, solar radiation, wind velocity, and direction should be measured. These variables are essential for the calculation of total deposition of air pollutants, for the interpretation of biological processes or for the derivation of water budgets and percolation from the rooting zone. Additional variables of interest are soil temperature, stand precipitation, and soil moisture. The magnitude and changes in time of the meteorological variables can be assessed as explanatory factors for other observations made in forest ecological monitoring. A detailed description of different methods is given. As an example for an integrated analysis, the application of meteorological data in water budget modeling is described and results of a pilot study are shown.
<p>The Austrian Research Infrastructure LTER-CWN (Long-Term... more <p>The Austrian Research Infrastructure LTER-CWN (Long-Term Ecosystem Research Infrastructure for Carbon, Water and Nitrogen) aims for measuring extreme events in high temporal resolution. Within the framework of this project a measuring weir was installed near Klausen-Leopoldsdorf (Lower Austria) in order to collect high-resolution data of stream-water quantity and quality. The measuring weir is located in the western part of the „Wienerwald“, the north-eastern edge of the Alps, at about 475m a.s.l. Especially in the year 2020 this area showed humid weather conditions with an annual precipitation of 904mm. The observed catchment has an area of about 46 hectares. The dominating soil types in the catchment are Planosoils and Stagnosols. The observations at the weir with a time resolution of 5 minutes started in February 2019. The plot was set up for recordings of carbon (C), nitrogen (N) and water fluxes theparameters TOC-N, DOC-N, NO<sub>3,</sub> water level, water temperature, electrical conductivity, turbidity and organic matter values being measured. To answer one of the main research issues - the impact of heavy rainfall events on the runoff regime of a catchment within a dense beech forest in relation to the soil, specific time, the influence of interception and corresponding water level in the observed river - a water level sensor (OTT) and a multifunction spectrolyzer (S:CAN) were installed at the weir. During the measuring period 2019/2020 11 heavy rainfall events (corresponding to more than 20mm daily precipitation sum) were recorded. Due to the small catchment area the average time interval between heavy rainfall events and the corresponding increase of the water level at the measuring weir is about 2 hours. The time and intensity of the rainfall event together with the level of soil moisture before the precipitation event are the key factors for the amount of runoff. Additionally, other measured parameters like the turbidity or the electrical conductivity of the water correspond very well with the amount of runoff. Data with such a high time resolution will help to get a better understanding of extreme events and the consequences of these events in respect to climate change.</p>
Windbreaks are key structural elements in the rural environment and affect the functionality of l... more Windbreaks are key structural elements in the rural environment and affect the functionality of landscapes in multiple ways. A broad interdisciplinary view on these functions lacks in scientific literature and common knowledge. This led to under informed management decisions, a decrease in the number of windbreaks in wide areas, and a subsequent loss of landscape functionality. Therefore, the knowledge on windbreaks and associated ecosystem services (ES) was systematically reviewed to guide the way for a holistic comprehension of such structural landscape elements. We defined eight bundles of ES on the basis of the Common International Classification of ES scheme. Search terms that allowed to include only vegetative windbreaks consisting of at least one tree row were combined with appropriate search terms for the eight ES bundles in individual searches resulting in a total of 6094 hits. We considered only publications that provided quantitative data and allowed to derive a clear eff...
<p>Wind erosion of arable soil is considered a risk factor for Austrian fields, but... more <p>Wind erosion of arable soil is considered a risk factor for Austrian fields, but direct measurements of soil loss are not available until now. Despite this uncertainty, vegetated windbreaks have been established to minimize adverse wind impacts on arable land. The study addresses these questions: i) How relevant is wind erosion as a factor of soil degradation? ii) How important is the protective effect of vegetated windbreaks? iii) Are systematic patterns of spatial and temporal variability of wind erosion rates detectable in response to weather conditions? </p><p>Two experimental fields adjacent to windbreaks were equipped with sediment traps, soil moisture sensors, and meteorological measurement equipment for microclimatic patterns. Sediment traps were arranged in high spatial resolution from next to the windbreak to a distance of ten times the windbreak height. Beginning in January 2020, the amount of trapped sediment was analyzed every three weeks. The highest wind erosion rates on bare soil were observed in June and July. For unprotected fields with bare soil, upscaled annual erosion rates were as high as 0.8 tons per hectare, and sediment trapped increased in a linear fashion with distance from the windbreak. Soil water content near the surface (5 cm depth) was three percent higher at a distance of two times the height of the windbreak than at a distance of six times the height. For the same respective distances from the windbreak, we observed 29 days of soil water contents below the wilting point compared with 60 days.</p><p>The preliminary outcomes confirmed the expected effects of windbreaks on soil erosion and microclimate in agricultural fields. Prospective results from multiple vegetation periods will be used in an upscaling approach to gain informations for the whole basin. That is meant to be done by a combination with a soil wind erosion model which was so far used for regional modelling of wind erosion susceptibility.</p>
The Leaf-Area-Index (LAI) is commonly used to characterize the plant canopy and is a fundamental ... more The Leaf-Area-Index (LAI) is commonly used to characterize the plant canopy and is a fundamental indication of plant vitality and photosynthetic activity. The forest health status is not only vital for economical reasons, but also has a significant impact on global carbon sequestration. The LAI has a highly dynamic character among deciduous forests and is prone to significant seasonal fluctuations. Accurate continuous LAI measurements do provide valuable information on growth characteristics, but they require considerable measurement effort. In this study, we tested a novel method that would allow for continuous low-effort LAI parameterizations. For our study we used temperature measurements from 2011 to 2019 obtained at two meteorological stations: Station one is an open land station, station two is located inside a forest stand characterized by European beech (measurements were undertaken as part of the ICP Forests program), both are located in Klausen Leopoldsdorf (Austria). We c...
<p>... more <p>The degrading impact of wind on agricultural soils has been observed throughout centuries in the Pannonian region of central Europe. Nevertheless, soil loss was not yet quantified and the extent or relevance of the problem are unknown for this agriculturally important region. Especially dry soil surface is highly prone to erosion and as drought periods are expected to become more frequent and severe with changing climate, the risk of wind erosion will increase accordingly. Living windbreaks and similar agro-forestry systems are supposed to be highly effective measures against wind erosion. In an extensive research project, multiple approaches are integrated to obtain a broad view onto the relevance of soil degradation by wind on plot scale and its regional distribution.</p><p>More in detail, case studies are conducted where the soil loss by wind erosion is measured in sediment traps. Data about driving and stabilizing factors like wind speed, soil moisture, vegetation density etc. are measured in high spatial and temporal resolution. The measurements started in December 2019. Besides, wind erosion risk is modelled and mapped on regional scale applying state-of-the-art model procedures. The measurement results are used in an attempt to down-scale the model application and thus create a link to ground-truth data. Information about spatial and temporal variability of the driving factors is used for implementation of stochastic calculation procedures in a sensitivity study which determines the most relevant factors for wind erosion mitigation.</p><p>The used modelling approach also includes the effects of wind shelters what enables a partly evaluation of the existing network of such elements in the Pannonian region. There, the Authority of Land Reform has been supporting and documenting the installation of wind shelters for more than 60 years. Incorporating this data base, quantitative and qualitative statements will be developed about the state of the shelter belts and their relevance concerning erosion rates. Additionally, the potential and actual value of living windbreaks will be determined with special regards to physiological and ecological characteristics, stability under future climate conditions and further ecosystem services in agricultural landscapes.</p>
ABSTRACT The management of manmade spruce forests under the aspect of climate change is an import... more ABSTRACT The management of manmade spruce forests under the aspect of climate change is an important issue in Central Europe. The results of climate scenarios indicate that the growth conditions in low elevations will deteriorate significantly. For Austria’s lowlands the vulnerability is analyzed and regional maps of different risk classes for spruce dominated forests are presented. Local site conditions, however, play a crucial role. In two case studies, where Norway spruce is growing on heavy soils, the influence of soil properties and tree mixture on the water demand of Norway spruce, especially during drought stress periods, is illustrated. On heavy, clayey soils restricted root formation and consequently the inability to exhaust water reserves in deeper parts of the soil is an important factor for drought stress. In mixed spruce/beech stands there is some evidence that the belowground competition leads to a very shallow rooting of spruce with negative consequences in drought stress periods. Thinning strategies and the reduction of the rotation period are tools to improve the growth conditions for spruce. On very unfavourable sites a stand conversion seems to be unavoidable. After large scale disturbances, like wind throw, natural regeneration of pioneer tree species can help to overcome the critical early regeneration phase.
ABSTRACT Sap flow measured by the Heat Field Deformation technique, HFD, is sensitive to flow res... more ABSTRACT Sap flow measured by the Heat Field Deformation technique, HFD, is sensitive to flow responses to small changes in water potential gradients within the tree hydraulic systems. When these changes occur abruptly, under experimental treatments (severing, localized irrigation, heavy loading), sap flow movement can be used as a marker to study root functionality, for example root ability to redistribute water and withstand heavy machinery pressure. Experiments also showed that a compensation mechanism may operate in trees, with a temporary increase in the absorbed water due to a preferential use of one part of the root system when another part is damaged or when a water source is lost. Long-term measurements of root sap flow allow distinguishing between water uptake from shallow and deep rooted trees, at different exposures at a forest edge and from healthy and infected trees. Root sap flow can be used as an indicator of tree stress or of the prevailing mechanisms used by trees to survive drought, under irrigation or rain-fed conditions.
Meteorological variables affect composition, structure, growth, health, and dynamics of forest ec... more Meteorological variables affect composition, structure, growth, health, and dynamics of forest ecosystems. The measurement of meteorological data at forest monitoring plots is essential for the interpretation of climate change effects. Within an ecological monitoring network, standard meteorological variables such as precipitation, air temperature, relative humidity, solar radiation, wind velocity, and direction should be measured. These variables are essential for the calculation of total deposition of air pollutants, for the interpretation of biological processes or for the derivation of water budgets and percolation from the rooting zone. Additional variables of interest are soil temperature, stand precipitation, and soil moisture. The magnitude and changes in time of the meteorological variables can be assessed as explanatory factors for other observations made in forest ecological monitoring. A detailed description of different methods is given. As an example for an integrated analysis, the application of meteorological data in water budget modeling is described and results of a pilot study are shown.
<p>The Austrian Research Infrastructure LTER-CWN (Long-Term... more <p>The Austrian Research Infrastructure LTER-CWN (Long-Term Ecosystem Research Infrastructure for Carbon, Water and Nitrogen) aims for measuring extreme events in high temporal resolution. Within the framework of this project a measuring weir was installed near Klausen-Leopoldsdorf (Lower Austria) in order to collect high-resolution data of stream-water quantity and quality. The measuring weir is located in the western part of the „Wienerwald“, the north-eastern edge of the Alps, at about 475m a.s.l. Especially in the year 2020 this area showed humid weather conditions with an annual precipitation of 904mm. The observed catchment has an area of about 46 hectares. The dominating soil types in the catchment are Planosoils and Stagnosols. The observations at the weir with a time resolution of 5 minutes started in February 2019. The plot was set up for recordings of carbon (C), nitrogen (N) and water fluxes theparameters TOC-N, DOC-N, NO<sub>3,</sub> water level, water temperature, electrical conductivity, turbidity and organic matter values being measured. To answer one of the main research issues - the impact of heavy rainfall events on the runoff regime of a catchment within a dense beech forest in relation to the soil, specific time, the influence of interception and corresponding water level in the observed river - a water level sensor (OTT) and a multifunction spectrolyzer (S:CAN) were installed at the weir. During the measuring period 2019/2020 11 heavy rainfall events (corresponding to more than 20mm daily precipitation sum) were recorded. Due to the small catchment area the average time interval between heavy rainfall events and the corresponding increase of the water level at the measuring weir is about 2 hours. The time and intensity of the rainfall event together with the level of soil moisture before the precipitation event are the key factors for the amount of runoff. Additionally, other measured parameters like the turbidity or the electrical conductivity of the water correspond very well with the amount of runoff. Data with such a high time resolution will help to get a better understanding of extreme events and the consequences of these events in respect to climate change.</p>
Windbreaks are key structural elements in the rural environment and affect the functionality of l... more Windbreaks are key structural elements in the rural environment and affect the functionality of landscapes in multiple ways. A broad interdisciplinary view on these functions lacks in scientific literature and common knowledge. This led to under informed management decisions, a decrease in the number of windbreaks in wide areas, and a subsequent loss of landscape functionality. Therefore, the knowledge on windbreaks and associated ecosystem services (ES) was systematically reviewed to guide the way for a holistic comprehension of such structural landscape elements. We defined eight bundles of ES on the basis of the Common International Classification of ES scheme. Search terms that allowed to include only vegetative windbreaks consisting of at least one tree row were combined with appropriate search terms for the eight ES bundles in individual searches resulting in a total of 6094 hits. We considered only publications that provided quantitative data and allowed to derive a clear eff...
<p>Wind erosion of arable soil is considered a risk factor for Austrian fields, but... more <p>Wind erosion of arable soil is considered a risk factor for Austrian fields, but direct measurements of soil loss are not available until now. Despite this uncertainty, vegetated windbreaks have been established to minimize adverse wind impacts on arable land. The study addresses these questions: i) How relevant is wind erosion as a factor of soil degradation? ii) How important is the protective effect of vegetated windbreaks? iii) Are systematic patterns of spatial and temporal variability of wind erosion rates detectable in response to weather conditions? </p><p>Two experimental fields adjacent to windbreaks were equipped with sediment traps, soil moisture sensors, and meteorological measurement equipment for microclimatic patterns. Sediment traps were arranged in high spatial resolution from next to the windbreak to a distance of ten times the windbreak height. Beginning in January 2020, the amount of trapped sediment was analyzed every three weeks. The highest wind erosion rates on bare soil were observed in June and July. For unprotected fields with bare soil, upscaled annual erosion rates were as high as 0.8 tons per hectare, and sediment trapped increased in a linear fashion with distance from the windbreak. Soil water content near the surface (5 cm depth) was three percent higher at a distance of two times the height of the windbreak than at a distance of six times the height. For the same respective distances from the windbreak, we observed 29 days of soil water contents below the wilting point compared with 60 days.</p><p>The preliminary outcomes confirmed the expected effects of windbreaks on soil erosion and microclimate in agricultural fields. Prospective results from multiple vegetation periods will be used in an upscaling approach to gain informations for the whole basin. That is meant to be done by a combination with a soil wind erosion model which was so far used for regional modelling of wind erosion susceptibility.</p>
The Leaf-Area-Index (LAI) is commonly used to characterize the plant canopy and is a fundamental ... more The Leaf-Area-Index (LAI) is commonly used to characterize the plant canopy and is a fundamental indication of plant vitality and photosynthetic activity. The forest health status is not only vital for economical reasons, but also has a significant impact on global carbon sequestration. The LAI has a highly dynamic character among deciduous forests and is prone to significant seasonal fluctuations. Accurate continuous LAI measurements do provide valuable information on growth characteristics, but they require considerable measurement effort. In this study, we tested a novel method that would allow for continuous low-effort LAI parameterizations. For our study we used temperature measurements from 2011 to 2019 obtained at two meteorological stations: Station one is an open land station, station two is located inside a forest stand characterized by European beech (measurements were undertaken as part of the ICP Forests program), both are located in Klausen Leopoldsdorf (Austria). We c...
<p>... more <p>The degrading impact of wind on agricultural soils has been observed throughout centuries in the Pannonian region of central Europe. Nevertheless, soil loss was not yet quantified and the extent or relevance of the problem are unknown for this agriculturally important region. Especially dry soil surface is highly prone to erosion and as drought periods are expected to become more frequent and severe with changing climate, the risk of wind erosion will increase accordingly. Living windbreaks and similar agro-forestry systems are supposed to be highly effective measures against wind erosion. In an extensive research project, multiple approaches are integrated to obtain a broad view onto the relevance of soil degradation by wind on plot scale and its regional distribution.</p><p>More in detail, case studies are conducted where the soil loss by wind erosion is measured in sediment traps. Data about driving and stabilizing factors like wind speed, soil moisture, vegetation density etc. are measured in high spatial and temporal resolution. The measurements started in December 2019. Besides, wind erosion risk is modelled and mapped on regional scale applying state-of-the-art model procedures. The measurement results are used in an attempt to down-scale the model application and thus create a link to ground-truth data. Information about spatial and temporal variability of the driving factors is used for implementation of stochastic calculation procedures in a sensitivity study which determines the most relevant factors for wind erosion mitigation.</p><p>The used modelling approach also includes the effects of wind shelters what enables a partly evaluation of the existing network of such elements in the Pannonian region. There, the Authority of Land Reform has been supporting and documenting the installation of wind shelters for more than 60 years. Incorporating this data base, quantitative and qualitative statements will be developed about the state of the shelter belts and their relevance concerning erosion rates. Additionally, the potential and actual value of living windbreaks will be determined with special regards to physiological and ecological characteristics, stability under future climate conditions and further ecosystem services in agricultural landscapes.</p>
ABSTRACT The management of manmade spruce forests under the aspect of climate change is an import... more ABSTRACT The management of manmade spruce forests under the aspect of climate change is an important issue in Central Europe. The results of climate scenarios indicate that the growth conditions in low elevations will deteriorate significantly. For Austria’s lowlands the vulnerability is analyzed and regional maps of different risk classes for spruce dominated forests are presented. Local site conditions, however, play a crucial role. In two case studies, where Norway spruce is growing on heavy soils, the influence of soil properties and tree mixture on the water demand of Norway spruce, especially during drought stress periods, is illustrated. On heavy, clayey soils restricted root formation and consequently the inability to exhaust water reserves in deeper parts of the soil is an important factor for drought stress. In mixed spruce/beech stands there is some evidence that the belowground competition leads to a very shallow rooting of spruce with negative consequences in drought stress periods. Thinning strategies and the reduction of the rotation period are tools to improve the growth conditions for spruce. On very unfavourable sites a stand conversion seems to be unavoidable. After large scale disturbances, like wind throw, natural regeneration of pioneer tree species can help to overcome the critical early regeneration phase.
ABSTRACT Sap flow measured by the Heat Field Deformation technique, HFD, is sensitive to flow res... more ABSTRACT Sap flow measured by the Heat Field Deformation technique, HFD, is sensitive to flow responses to small changes in water potential gradients within the tree hydraulic systems. When these changes occur abruptly, under experimental treatments (severing, localized irrigation, heavy loading), sap flow movement can be used as a marker to study root functionality, for example root ability to redistribute water and withstand heavy machinery pressure. Experiments also showed that a compensation mechanism may operate in trees, with a temporary increase in the absorbed water due to a preferential use of one part of the root system when another part is damaged or when a water source is lost. Long-term measurements of root sap flow allow distinguishing between water uptake from shallow and deep rooted trees, at different exposures at a forest edge and from healthy and infected trees. Root sap flow can be used as an indicator of tree stress or of the prevailing mechanisms used by trees to survive drought, under irrigation or rain-fed conditions.
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