Eschenbach W.,Busgen Institute |
Eschenbach W.,Johann Heinrich Von Thunen Institute |
Well R.,Johann Heinrich Von Thunen Institute
Biogeosciences | Year: 2013
Knowledge about the spatial variability of denitrification rates and the lifetime of denitrification in nitrate-contaminated aquifers is crucial to predict the development of groundwater quality. Therefore, regression models were derived to estimate the measured cumulative denitrification of aquifer sediments after one year of incubation from initial denitrification rates and several sediment parameters, namely total sulphur, total organic carbon, extractable sulphate, extractable dissolved organic carbon, hot water soluble organic carbon and potassium permanganate labile organic carbon. For this purpose, we incubated aquifer material from two sandy Pleistocene aquifers in Northern Germany under anaerobic conditions in the laboratory using the 15N tracer technique. The measured amount of denitrification ranged from 0.19 to 56.2 mg N kg-1 yr-1. The laboratory incubations exhibited high differences between non-sulphidic and sulphidic aquifer material in both aquifers with respect to all investigated sediment parameters. Denitrification rates and the estimated lifetime of denitrification were higher in the sulphidic samples. For these samples, the cumulative denitrification measured during one year of incubation (D cum(365)) exhibited distinct linear regressions with the stock of reduced compounds in the investigated aquifer samples. D cum(365) was predictable from sediment variables within a range of uncertainty of 0.5 to 2 (calculated Dcum(365)/measured D cum(365)) for aquifer material with a Dcum(365) > 20 mg N kg-1 yr-1. Predictions were poor for samples with lower Dcum(365), such as samples from the NO-3 bearing groundwater zone, which includes the non-sulphidic samples, from the upper part of both aquifers where denitrification is not sufficient to protect groundwater from anthropogenic NO-3 input. Calculation of Dcum(365) from initial denitrification rates was only successful for samples from the NO3−-bearing zone, whereas a lag-phase of denitrification in samples from deeper zones of NO-3 free groundwater caused imprecise predictions. In our study, Dcum(365) of two sandy Pleistocene aquifers was predictable using a combination of short-term incubations and analysis of sediment parameters. Moreover, the protective lifetime of denitrification sufficient to remove NO-3 from groundwater in the investigated aquifers is limited, which demonstrates the need to minimise anthropogenic NO-3 input. © 2012 Author(s).
Hopf-Biziks A.,Julius Kuhn Institute |
Schroder T.,Julius Kuhn Institute |
Schutz S.,Busgen Institute
Journal of Plant Diseases and Protection | Year: 2016
The pine wood nematode, Bursaphelenchus xylophilus, can cause pine wilt disease on susceptible conifer species, mainly Pinus spp., outside its natural range. One of the management options for pine wilt disease in recent decades in affected countries such as Japan was the evaluation of potentially tolerant or resistant host species. In the framework of Pest Risk Assessment and Management as well in Contingency Planning in Germany, we studied the pathogenicity of B. xylophilus towards different German pine provenances. According to the German Legal Ordinance on Regions of Provenance, 2- to 3-year-old Pinus sylvestris saplings of eight provenances were artificially inoculated with B. xylophilus using a suspension of 4000 B. xylophilus in 300 ll of tap water per tree. No significant differences in tree death between the provenances were detected. All inoculated provenances reached a mortality of 100 %, but significant differences occurred in the time course of disease development. © Deutsche Phythomedizinische Gesellschaft 2016.
Schulte-Bisping H.,Busgen Institute |
Beese F.,Busgen Institute
European Journal of Forest Research | Year: 2016
Within the framework of the International Cooperative Programme on Integrated Monitoring (ICP IM), nitrogen pools and fluxes and their balance were determined for the German Integrated Monitoring (IM) site, Neuglobsow, characterized by very low soil nitrogen. From 1998 to 2013, total nitrogen (N) deposition in form of ammonium and nitrate was 6.80 ± 1.36 and 6.46 ± 1.09 kg N ha−1 year−1, respectively (in total 13.26 ± 2.01 kg N ha−1 year−1). Meanwhile, the average gaseous loss was 0.7 kg N ha−1 year−1 and the leaching loss was 2.38 kg N ha−1 year−1. Since the remaining atmospheric net N-inputs (10.18 kg N ha−1 year−1) exceeds plant uptake (8.36 kg N ha−1 year−1), there is a nitrogen surplus of 1.82 kg N ha−1 year−1. This surplus and the accelerated mineralization of the soil organic matter which was stored during the decades before the study began when temperatures were slightly cooler, combined with low leaching rates, explain the high nitrogen supply found in the leaves and needles. However, with decreasing nitrogen deposition, biomass export and with air temperatures rises expected the ecosystem N-supply will likely decline in the long run. © 2016 Springer-Verlag Berlin Heidelberg
Seven J.,Busgen Institute |
Polle A.,Busgen Institute
PLoS ONE | Year: 2014
Mycorrhizas are the chief organ for plant mineral nutrient acquisition. In temperate, mixed forests, ash roots (Fraxinus excelsior) are colonized by arbuscular mycorrhizal fungi (AM) and beech roots (Fagus sylvatica) by ectomycorrhizal fungi (EcM). Knowledge on the functions of different mycorrhizal species that coexist in the same environment is scarce. The concentrations of nutrient elements in plant and fungal cells can inform on nutrient accessibility and interspecific differences of mycorrhizal life forms. Here, we hypothesized that mycorrhizal fungal species exhibit interspecific differences in mineral nutrient concentrations and that the differences correlate with the mineral nutrient concentrations of their associated root cells. Abundant mycorrhizal fungal species of mature beech and ash trees in a long-term undisturbed forest ecosystem were the EcM Lactarius subdulcis, Clavulina cristata and Cenococcum geophilum and the AM Glomus sp. Mineral nutrient subcellular localization and quantities of the mycorrhizas were analysed after non-aqueous sample preparation by electron dispersive X-ray transmission electron microscopy. Cenococcum geophilum contained the highest sulphur, Clavulina cristata the highest calcium levels, and Glomus, in which cations and P were generally high, exhibited the highest potassium levels. Lactarius subdulcisassociated root cells contained the highest phosphorus levels. The root cell concentrations of K, Mg and P were unrelated to those of the associated fungal structures, whereas S and Ca showed significant correlations between fungal and plant concentrations of those elements. Our results support profound interspecific differences for mineral nutrient acquisition among mycorrhizas formed by different fungal taxa. The lack of correlation between some plant and fungal nutrient element concentrations may reflect different retention of mineral nutrients in the fungal part of the symbiosis. High mineral concentrations, especially of potassium, in Glomus sp. suggest that the well-known influence of tree species on chemical soil properties may be related to their mycorrhizal associates. © 2014 Seven, Polle.
Schulte-Bisping H.,Busgen Institute |
Beese F.,Busgen Institute |
Dieffenbach-Fries H.,German Federal Environment Agency
European Journal of Forest Research | Year: 2012
Carbon fluxes and C-turnover of a mature mixed forest were assessed over a 5-year period from 2004 to 2008 at the Integrated Monitoring site "Neuglobsow". The mature stand with European beech (Fagus sylvatica L.) and Scots pine (Pinus sylvestris L.) is located in the north-eastern German lowlands (Brandenburg). Soil carbon fluxes of the trenched and non-trenched plots were measured once a week with a closed chamber method to separate heterotrophic and autotrophic respiration. Annual wood increments were continuously measured by dendrometer bands. A strong correlation was found between observed and predicted soil respiration fluxes calculated on the basis of the measured soil temperatures and soil water contents. Carbon sequestration by accumulation in the aboveground biomass accounted for 1. 67 Mg C ha -1 year -1. Including the C-sequestration in coarse roots the net primary production (NPP) increased to 2. 0 Mg C per ha and year. Carbon release from soil by apparent heterotrophic respiration was overestimated due to higher soil moisture in the rootless trenching plots. Therefore we adjusted the apparent heterotrophic respiration by means of predicted water contents of the trenched plots, using a SVAT model. Accordingly the apparent heterotrophic respiration rate was 0. 94 Mg C ha -1 year -1 resulting in a net ecosystem production (NEP) of 1. 06 Mg C ha -1 year -1. The net C loss from the soil carbon pool may be caused by higher temperatures, which were increased by 1. 5 °C during the observation period compared to the long-term temperature average (1961-1990). These short-term changes have to be regarded carefully interpreting measured carbon sequestration rates of forest ecosystems in the global carbon cycle. © 2012 The Author(s).