Ahrends, Bernd

[["dc.bibliographiccitation.firstpage","87"],["dc.bibliographiccitation.issue","2"],["dc.bibliographiccitation.journal","LANDBAUFORSCHUNG VOLKENRODE"],["dc.bibliographiccitation.lastpage","93"],["dc.bibliographiccitation.volume","59"],["dc.contributor.author","Czajkowski, Tomasz"],["dc.contributor.author","Ahrends, Bernd"],["dc.contributor.author","Bolte, Andreas"],["dc.date.accessioned","2018-11-07T08:29:30Z"],["dc.date.available","2018-11-07T08:29:30Z"],["dc.date.issued","2009"],["dc.description.abstract","Due to climate change, heat waves and drought are expected to increase in frequency and intensity in Central Europe. Thus, assessments of critical constraints of water supply in forest trees are! needed to develop adequate forest adaptation measure;. We present a novel 'critical limit' approach to soil water availability (SWA) for the major central European forest tree species based on the physiological plant water status. In regards to the conductivity of trees' xylem, three thresholds of pre-dawn water potential (psi(wp)) were chosen, referring to (i) slight conductivity loss (10%), (ii) critical conductivity loss (50%) and (iii) complete conductivity loss (>90%). In times of drought, pre-dawn water potential relates to the soil water potential at the lowest soil depth in which plant's root system is able to deplete water resources; the 'effective rooting depth' (ERD). The critical limit of soil water availability (CL-SWA) represents the proportion of plant-available water within the variable effective rooting depth (ERD) that meets both the critical soil water potential at the lower limit of the ERD and the critical plant water status. The CL-SWA-approach can be implemented in water budget models like BROOK90."],["dc.description.sponsorship","German Federal Ministry of Education and Science (BMBF)"],["dc.identifier.isi","000269342400001"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/16668"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Forschungsanstalt Fur Landwirt Braunschweig Volkenrode"],["dc.relation.issn","0458-6859"],["dc.title","Critical limits of soil water availability (CL-SWA) for forest trees - an approach based on plant water status"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","132"],["dc.bibliographiccitation.journal","Environmental Pollution"],["dc.bibliographiccitation.lastpage","141"],["dc.bibliographiccitation.volume","164"],["dc.contributor.author","Hauck, Markus"],["dc.contributor.author","Zimmermann, Jorma"],["dc.contributor.author","Jacob, Mascha"],["dc.contributor.author","Dulamsuren, Choimaa"],["dc.contributor.author","Bade, Claudia"],["dc.contributor.author","Ahrends, Bernd"],["dc.contributor.author","Leuschner, Christoph"],["dc.date.accessioned","2018-11-07T09:10:55Z"],["dc.date.available","2018-11-07T09:10:55Z"],["dc.date.issued","2012"],["dc.description.abstract","Tree-ring width of Picea abies was studied along an altitudinal gradient in the Harz Mountains, Germany, in an area heavily affected by SO2-related forest decline in the second half of the 20th century. Spruce trees of exposed high-elevation forests had earlier been shown to have reduced radial growth at high atmospheric SO2 levels. After the recent reduction of the SO2 load due to clean air acts, we tested the hypothesis that stem growth recovered rapidly from the SO2 impact. Our results from two formerly damaged high-elevation spruce stands support this hypothesis suggesting that the former SO2-related spruce decline was primarily due to foliar damage and not to soil acidification, as the deacidification of the (still acidic) soil would cause a slow growth response. Increasing temperatures and deposited N accumulated in the topsoil are likely additional growth-promoting factors of spruce at high elevations after the shortfall of SO2 pollution. (C) 2012 Elsevier Ltd. All rights reserved."],["dc.identifier.doi","10.1016/j.envpol.2012.01.026"],["dc.identifier.isi","000302971400020"],["dc.identifier.pmid","22361051"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/26600"],["dc.language.iso","en"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Elsevier Sci Ltd"],["dc.relation.eissn","1873-6424"],["dc.relation.issn","0269-7491"],["dc.title","Rapid recovery of stem increment in Norway spruce at reduced SO2 levels in the Harz Mountains, Germany"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","30"],["dc.bibliographiccitation.journal","Ecological Modelling"],["dc.bibliographiccitation.lastpage","47"],["dc.bibliographiccitation.volume","346"],["dc.contributor.author","Thiele, Jan Christoph"],["dc.contributor.author","Nuske, Robert S."],["dc.contributor.author","Ahrends, Bernd"],["dc.contributor.author","Panferov, Oleg"],["dc.contributor.author","Albert, Matthias"],["dc.contributor.author","Staupendahl, Kai"],["dc.contributor.author","Junghans, Udo"],["dc.contributor.author","Jansen, Martin"],["dc.contributor.author","Saborowski, Joachim"],["dc.date.accessioned","2018-11-07T10:27:13Z"],["dc.date.available","2018-11-07T10:27:13Z"],["dc.date.issued","2017"],["dc.description.abstract","Projected climate change implies that site conditions can no longer be expected to remain constant over a tree's lifetime. The fast and complex changes in site characteristics and growth patterns diminish the value of traditional knowledge and profoundly alter the conditions of forest management. One way to tackle the inherent uncertainties are simulation studies addressing these new dynamics and mechanisms. The aim of this study is to present such a simulation model system comprising various established and validated process-based and statistical models assessing the complex and dynamic response of a forest stand to climate change. For a given climate scenario, these coupled models estimate the potential growth and yield and various risks considering changing site and stand conditions. As an example, the model system is applied to managed forest stands of Norway spruce (Picea abies (L) H. Karst.) in a forest district located in central western Germany. For the changing climate conditions according to SRES B1 and A1 B, the model results suggest a positive effect on the site index and, by contrast, a negative impact on tree survival of increasing risks regarding drought stress mortality, wind damage, and bark beetle infestation given the climate change scenario. The annual contribution margin of timber production under consideration of damage risks by drought stress mortality, wind, and bark beetle infestation reveals that, in this case, the increased growth is able to compensate for the higher risks with few exceptions. Furthermore, we discuss the advantages and challenges of employing a dynamic complex simulation model system for climate change impact assessment based on high-resolution climate data. (C) 2016 Elsevier B.V. All rights reserved."],["dc.identifier.doi","10.1016/j.ecolmodel.2016.11.013"],["dc.identifier.isi","000393248900004"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/43203"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","PUB_WoS_Import"],["dc.relation.issn","1872-7026"],["dc.relation.issn","0304-3800"],["dc.relation.orgunit","Abteilung Ökoinformatik, Biometrie und Waldwachstum"],["dc.title","Climate change impact assessment-A simulation experiment with Norway spruce for a forest district in Central Europe"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.subtype","original_ja"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","3763"],["dc.bibliographiccitation.issue","12"],["dc.bibliographiccitation.journal","Biogeosciences"],["dc.bibliographiccitation.lastpage","3779"],["dc.bibliographiccitation.volume","18"],["dc.contributor.author","Brumme, Rainer"],["dc.contributor.author","Ahrends, Bernd"],["dc.contributor.author","Block, Joachim"],["dc.contributor.author","Schulz, Christoph"],["dc.contributor.author","Meesenburg, Henning"],["dc.contributor.author","Klinck, Uwe"],["dc.contributor.author","Wagner, Markus"],["dc.contributor.author","Khanna, Partap K."],["dc.date.accessioned","2021-08-12T07:46:08Z"],["dc.date.available","2021-08-12T07:46:08Z"],["dc.date.issued","2021"],["dc.description.abstract","Abstract. Atmospheric deposition of nitrogen (N) has exceeded its demand for plant increment in forest ecosystems in Germany. High N inputs increased plant growth, the internal N cycling within the ecosystem, the retention of N in soil and plant compartments, and the N output by seepage water. But the processes involved are not fully understood, notably the effect of fructification in European beech (Fagus sylvatica L.) on N fluxes. The frequency of fructification has increased together with air temperature and N deposition, but its impact on N fluxes and the sequestration of carbon (C) and N in soils have been hardly studied. A field experiment using 15N-labeled leaf litter exchange was carried out over a 5.5-year period at seven long-term European beech (Fagus sylvatica L.) monitoring sites to study the impact of current mast frequency on N cycling. Mean annual leaf litterfall contained 35 kg N ha−1, but about one-half of that was recovered in the soil 5.5 years after the establishment of the leaf litter 15N exchange experiment. In these forests, fructification occurred commonly at intervals of 5 to 10 years, which has now changed to every 2 years as observed during this study period. Seed cupules contributed 51 % to the additional litterfall in mast years, which creates a high nutrient demand during their decomposition due to the very high ratios of C to N and C to phosphorus (P). Retention of leaf litter 15N in the soil was more closely related to the production of total litterfall than to the leaf litterfall, indicating the role of seed cupules in the amount of leaf N retained in the soil. Higher mast frequency increased the mass of mean annual litterfall by about 0.5 Mg ha−1 and of litterfall N by 8.7 kg ha−1. Mean net primary production (NPP) increased by about 4 %. Mean total N retention in soils calculated by input and output fluxes was unrelated to total litterfall, indicating that mast events were not the primary factor controlling total N retention in soils. Despite reduced N deposition since the 1990s, about 5.7 out of 20.7 kg N ha−1 deposited annually between 1994 and 2008 was retained in soils, notably at acid sites with high N/P and C/P ratios in the organic layers and mineral soils, indicating P limitation for litter decomposition. Trees retained twice as much N compared to soils by biomass increment, particularly in less acidic stands where the mineral soils had low C/N ratios. These results have major implications for our understanding of the C and N cycling and N retention in forest ecosystems. In particular the role of mast products in N retention needs more research in the future."],["dc.description.abstract","Abstract. Atmospheric deposition of nitrogen (N) has exceeded its demand for plant increment in forest ecosystems in Germany. High N inputs increased plant growth, the internal N cycling within the ecosystem, the retention of N in soil and plant compartments, and the N output by seepage water. But the processes involved are not fully understood, notably the effect of fructification in European beech (Fagus sylvatica L.) on N fluxes. The frequency of fructification has increased together with air temperature and N deposition, but its impact on N fluxes and the sequestration of carbon (C) and N in soils have been hardly studied. A field experiment using 15N-labeled leaf litter exchange was carried out over a 5.5-year period at seven long-term European beech (Fagus sylvatica L.) monitoring sites to study the impact of current mast frequency on N cycling. Mean annual leaf litterfall contained 35 kg N ha−1, but about one-half of that was recovered in the soil 5.5 years after the establishment of the leaf litter 15N exchange experiment. In these forests, fructification occurred commonly at intervals of 5 to 10 years, which has now changed to every 2 years as observed during this study period. Seed cupules contributed 51 % to the additional litterfall in mast years, which creates a high nutrient demand during their decomposition due to the very high ratios of C to N and C to phosphorus (P). Retention of leaf litter 15N in the soil was more closely related to the production of total litterfall than to the leaf litterfall, indicating the role of seed cupules in the amount of leaf N retained in the soil. Higher mast frequency increased the mass of mean annual litterfall by about 0.5 Mg ha−1 and of litterfall N by 8.7 kg ha−1. Mean net primary production (NPP) increased by about 4 %. Mean total N retention in soils calculated by input and output fluxes was unrelated to total litterfall, indicating that mast events were not the primary factor controlling total N retention in soils. Despite reduced N deposition since the 1990s, about 5.7 out of 20.7 kg N ha−1 deposited annually between 1994 and 2008 was retained in soils, notably at acid sites with high N/P and C/P ratios in the organic layers and mineral soils, indicating P limitation for litter decomposition. Trees retained twice as much N compared to soils by biomass increment, particularly in less acidic stands where the mineral soils had low C/N ratios. These results have major implications for our understanding of the C and N cycling and N retention in forest ecosystems. In particular the role of mast products in N retention needs more research in the future."],["dc.identifier.doi","10.5194/bg-18-3763-2021"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/88624"],["dc.language.iso","en"],["dc.notes.intern","DOI Import GROB-448"],["dc.relation.eissn","1726-4189"],["dc.title","Cycling and retention of nitrogen in European beech (<i>Fagus sylvatica</i> L.) ecosystems under elevated fructification frequency"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","282"],["dc.bibliographiccitation.issue","3-4"],["dc.bibliographiccitation.journal","Geoderma"],["dc.bibliographiccitation.lastpage","297"],["dc.bibliographiccitation.volume","158"],["dc.contributor.author","Penne, Carolin"],["dc.contributor.author","Ahrends, Bernd"],["dc.contributor.author","Deurer, Markus"],["dc.contributor.author","Boettcher, Juergen"],["dc.date.accessioned","2018-11-07T08:39:09Z"],["dc.date.available","2018-11-07T08:39:09Z"],["dc.date.issued","2010"],["dc.description.abstract","Forest ecosystems play an important role in the global carbon (C) cycle, acting as a carbon sink. Data on soil organic matter (SOM) stocks and turnover rates in relation to vegetation properties are important to understand carbon storage distribution mechanisms and to upscale carbon stocks to the stand scale. The canopy structure may influence the spatial variation of carbon input, firstly, by governing the throughfall and litterfall onto the organic layer, and, secondly, by influencing the climatic factors in the organic layer such as temperature and water content dynamics. Those climatic factors in turn have an impact on carbon mineralisation. In this study we investigated the influence of the canopy structure of a 55-year-old pine stand on the spatial distribution of forest floor carbon stocks (FFCS). The results showed that the spatial variation of FFCS was relatively low (cv 25%). The spatial variation of FFCS was partly caused by the small variation in needle litterfall (cv 8.8%) as a result of the heterogeneous canopy structure. The needle litterfall was significantly higher (7.5%) directly under the tree crowns compared with the areas without canopy cover. Also, the nutrient concentrations of the rain throughfall were significantly higher and its pH values were significantly lower under the crowns compared with the areas under the canopy gaps. However, the abiotic factors (pH, ion concentrations, N content, and C/N ratio) of the organic material sampled from the forest floor did not show any significant differences with respect to areas under tree crowns or in canopy gaps. Additionally, neither the carbon mineralisation nor enzyme activities of various steps of the mineralisation processes were related to the canopy structure. A geostatistical analysis revealed that the ranges of the FFCS and the thickness of the F layer were similar to the ranges of the crown structure. We concluded, firstly, that the needle litterfall is the main factor causing differences in FFCS and systematically varied as a function of tree canopy structure. Secondly, the reason for the small variations in litterfall and in carbon stocks was the high cover fraction of about 76% of the relatively young pine stand. We hypothesise that the litterfall variation will increase with the thinning of the stand. Finally, for upscaling the FFCS from the sample to the forest stand scale, the canopy structure can be neglected for pine stands with a cover fraction larger than 70-80%. (C) 2010 Elsevier B.V. All rights reserved."],["dc.description.sponsorship","German Research Foundation (DFG)"],["dc.identifier.doi","10.1016/j.geoderma.2010.05.007"],["dc.identifier.isi","000282000100021"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/18926"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Elsevier Science Bv"],["dc.relation.issn","1872-6259"],["dc.relation.issn","0016-7061"],["dc.title","The impact of the canopy structure on the spatial variability in forest floor carbon stocks"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","746"],["dc.bibliographiccitation.issue","6"],["dc.bibliographiccitation.journal","Agricultural and Forest Meteorology"],["dc.bibliographiccitation.lastpage","754"],["dc.bibliographiccitation.volume","151"],["dc.contributor.author","Sogachev, A."],["dc.contributor.author","Panferov, Oleg"],["dc.contributor.author","Ahrends, Bernd"],["dc.contributor.author","Doering, C."],["dc.contributor.author","Jorgensen, H. E."],["dc.date.accessioned","2018-11-07T08:55:06Z"],["dc.date.available","2018-11-07T08:55:06Z"],["dc.date.issued","2011"],["dc.description.abstract","There are many natural and anthropogenic reasons why a gap can occur inside the forest. When a gap appears within a studied stand (e.g. near a flux tower which operated for some time, providing information about the ecosystem-atmosphere exchange), an assessment of new measurement conditions should be carried out. Using a three-dimensional approach for footprint estimation based on numerical solution of Reynolds-Averaged Navier-Stokes (RANS) equations, we investigated possible changes in air flow and CO2 flux footprints resulting from two suggested forest management activities - clear-cut and stripe-cut - around the flux tower located in 130-year-old spruce forest in the Soiling highland, Germany. The model results show that degree of changes in flux footprints depends on the chosen management strategy. The clear-cut strategy produces the largest changes and the stripe-cut leads to weaker changes of investigated characteristics. The role of remote canopy sources increases, while the contribution of remote soil sources decreases with increased share of removed trees. In general, the investigated characteristics change differently for summer and winter due to the combined effects of phenology and upwind topography. (C) 2010 Elsevier B.V. All rights reserved."],["dc.identifier.doi","10.1016/j.agrformet.2010.10.010"],["dc.identifier.isi","000290193500009"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/22827"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Elsevier Science Bv"],["dc.publisher.place","Amsterdam"],["dc.relation.conference","International Conference on Atmospheric Transport and Chemistry in Forest Ecosystems"],["dc.relation.eventlocation","Bayreuth, GERMANY"],["dc.relation.issn","0168-1923"],["dc.relation.orgunit","Abteilung Bioklimatologie"],["dc.title","Numerical assessment of the effect of forest structure changes on CO2 flux footprints for the flux tower in Soiling, Germany"],["dc.type","conference_paper"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dspace.entity.type","Publication"]]