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Berlin Brandenburg

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  • 1
    Language: English
    In: Plant and Soil, 2011, Vol.340(1), pp.157-167
    Description: In semi-arid grassland ecosystems, soil biogeochemical processes are controlled by seasonal and inter-annual rainfall variation and temperature, which may override the long-term impact of grazers on N availability and N dynamics. In a three-year (2004–2006) case study of an Inner Mongolian grassland, we analysed time-integrated (ion-exchange resins) and instantaneous (soil mineral N extractions) inorganic N availability at three sites of varying grazing intensities and combined these data with information on soil water content (SWC), aboveground net primary productivity (ANPP) and plant N uptake. Additionally, the effects of rainfall and grazing on N-form availability (NO 3 − -N, NH 4 + -N) were considered. Grazing had less impact on N availability compared to seasonal and annual rainfall distribution. One of the three study years (2004) showed a grazing effect with higher resin-N availability at the ungrazed site compared to the heavily grazed site. Inorganic N availability was low in the driest year (2005) and highest in a year of average rainfall amount and favourable distribution (2004). In general, we found a positive relationship between inorganic N availability and both plant productivity and plant N uptake. Rainfall also controlled the plant available NO 3 − -N and NH 4 + -N pools; NH 4 + -N dominated the available inorganic N-form in times of low SWC, while the available NO 3 − -N increased with SWC. We observed N availability and plant productivity in a temporal synchronized pattern. Increased rainfall variability and land-use practices affecting SWC will likely alter N availability dynamics (and the relation of N-forms) and, therefore, important processes of semi-arid natural grassland carbon and N cycling.
    Keywords: Resin-N ; Soil mineral-N ; N-form ; ANPP ; Soil water content ; Climate variability ; Steppe ; Inner Mongolia
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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  • 2
    Language: English
    In: Oecologia, 2011, Vol.165(4), pp.855-864
    Description: Productivity of semiarid grasslands is affected by soil water and nutrient availability, with water controlling net primary production under dry conditions and soil nutrients constraining biomass production under wet conditions. In order to investigate limitations on plants by the response of root–shoot biomass allocation to water and nitrogen (N) availability, a field experiment, on restoration plots with rainfed, unfertilized control plots, fertilized plots receiving N (25 kg urea-N ha −1 ) and water (irrigation simulating a wet season), was conducted at two sites with different grazing histories: moderate (MG) and heavy (HG) grazing. Irrigation and N addition had no effect on belowground biomass. Irrigation increased aboveground (ANPP) and belowground net primary production (BNPP) and rain-use efficiency based on ANPP (RUE ANPP ), whereas N addition on rainfed plots had no effect on any of the measured parameters. N fertilizer application on irrigated plots increased ANPP and RUE ANPP and reduced the root fraction (RF: root dry matter/total dry matter), resulting in smaller N effects on total net primary production (NPP) and rain-use efficiency based on NPP. This suggests that BNPP should be included in evaluating ecosystem responses to resource availability from the whole-plant perspective. N effects on all measured parameters were similar on both sites. However, site HG responded to irrigation with higher ANPP and a lower RF when compared to site MG, indicating that species composition had a pronounced effect on carbon allocation pattern due to below- and aboveground niche complementarity.
    Keywords: Above- (ANPP) and belowground net primary production (BNPP) ; Land use history ; Irrigation ; N fertilizer ; Restoration
    ISSN: 0029-8549
    E-ISSN: 1432-1939
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  • 3
    Language: English
    In: Plant and Soil, 2011, Vol.340(1), pp.73-88
    Description: Grazing of grasslands changes soil physical and chemical properties as well as vegetation characteristics, such as vegetation cover, species composition and biomass production. In consequence, nutrient allocation and water storage in the top soil are affected. Land use and management changes alter these processes. Knowledge on the impacts of grazing management on nutrient and water fluxes is necessary because of the global importance of grasslands for carbon sequestration. Soil water in semi-arid areas is a limiting factor for matter fluxes and the intrinsic interaction between soil, vegetation and atmosphere. It is therefore desirable to understand the effects of grazing management and stocking rate on the spatial and temporal distribution of soil moisture. In the present study, we address the question how spatio-temporal soil moisture distribution on grazed and ungrazed grassland sites is affected by soil and vegetation properties. The study took place in the Xilin river catchment in Inner Mongolia (PR China). It is a semi-arid steppe environment, which is characterized by still moderate grazing compared to other regions in central Inner Mongolia. However, stocking rates have locally increased and resulted in a degradation of soils and vegetation also in the upper Xilin River basin. We used a multivariate geostatistical approach to reveal spatial dependencies between soil moisture distribution and soil or vegetation parameters. Overall, 7 soil and vegetation parameters (bulk density, sand, silt and clay content, mean weight diameter, mean carbon content of the soil, vegetation cover) and 57 soil moisture data sets were recorded on 100 gridded points on four sites subject to different grazing intensities. Increasing stocking rates accelerated the influence of soil and vegetation parameters on soil moisture. However, the correlation was rather weak, except for a site with high stocking rate where higher correlations were found. Low nugget ratios indicate spatial dependency between soil or plant parameters and soil moisture on a long-term ungrazed site. However, the effect was not found for a second ungrazed site that had been excluded from grazing for a shorter period. Furthermore the most important soil and vegetation parameters for predicting soil moisture distribution varied between different grazing intensities. Therefore, predicting soil moisture by using secondary variables requires a careful selection of the soil or vegetation parameters.
    Keywords: Soil moisture ; Multivariate geostatistics ; Spatial dependency ; Grazing ; Grassland
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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  • 4
    In: PLoS ONE, 2013, Vol.8(9)
    Description: Water use efficiency (WUE) is a key indicator to assess ecosystem adaptation to water stress. Rain use efficiency (RUE) is usually used as a proxy for WUE due to lack of transpiration data. Furthermore, RUE based on aboveground primary productivity (RUE ANPP ) is used to evaluate whole plant water use because root production data is often missing as well. However, it is controversial as to whether RUE is a reliable parameter to elucidate transpiration efficiency (TE), and whether RUE ANPP is a suitable proxy for RUE of the whole plant basis. The experiment was conducted at three differently managed sites in the Inner Mongolia steppe: a site fenced since 1979 (UG79), a winter grazing site (WG) and a heavily grazed site (HG). Site HG had consistent lowest RUE ANPP and RUE based on total net primary productivity (RUE NPP ). RUE ANPP is a relatively good proxy at sites UG79 and WG, but less reliable for site HG. Similarly, RUE ANPP is good predictor of transpiration efficiency based on aboveground net primary productivity (TE ANPP ) at sites UG79 and WG but not for site HG. However, if total net primary productivity is considered, RUE NPP is good predictor of transpiration efficiency based on total net primary productivity (TE NPP ) for all sites. Although our measurements indicate decreased plant transpiration and consequentially decreasing RUE under heavy grazing, productivity was relatively compensated for with a higher TE. This offset between RUE and TE was even enhanced under water limited conditions and more evident when belowground net primary productivity (BNNP) was included. These findings suggest that BNPP should be considered when studies fucus on WUE of more intensively used grasslands. The consideration of the whole plant perspective and “real” WUE would partially revise our picture of system performance and therefore might affect the discussion on the C-sequestration and resilience potential of ecosystems.
    Keywords: Research Article
    E-ISSN: 1932-6203
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  • 5
    Language: English
    In: Plant and Soil, 2010, Vol.328(1), pp.495-505
    Description: Productivity of semiarid grasslands is primarily limited by seasonal rainfall amount and becomes increasingly limited by nutrient availability under wet conditions. Interactive effects of water and N availability on grassland productivity and parameters related to water use were studied on a grassland site in Inner Mongolia, China, in a 2-factorial experiment with two levels of water (rainfed: 158 mm; irrigated: 839 (N0) and 972 (N1) mm) and N supply (0 or 180 kg N ha −1 ). RUE was calculated from ANPP and cumulative water supply. Bare soil evaporation (E) was calculated from climatic data and leaf area dynamics, and percolation (D) and transpiration (T) were estimated with HYDRUS-1D. Water-use efficiency (WUE, ANPP / (T + D)) and transpiration efficiency (TE, ANPP / T) were calculated. Resource availability had pronounced effects on the water-use efficiency of semiarid grassland. RUE, WUE, and TE all decreased under irrigated compared to rainfed conditions and were significantly increased with N fertilizer application at both levels of water supply. While the irrigation effect on parameters of water-use efficiency were accordingly reflected in stable carbon isotope signatures, N supply resulted in significantly less negative δ 13 C-values under rainfed but not irrigated conditions. It is concluded, that spatial or temporal gradients in resource availability have pronounced effects on the water-use efficiency of semiarid grassland. The decrease of water use-efficiency under high water supply was related to differences in TE and not to a relative increase of unproductive water loss. Carbon isotope discrimination was highly correlated with WUE and TE, but can be a poor predictor of RUE.
    Keywords: Carbon isotope discrimination ; Bare soil evaporation ; Rain-use efficiency ; Transpiration efficiency
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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  • 6
    Language: English
    In: Plant and Soil, 2011, Vol.340(1), pp.35-58
    Description: Semiarid steppe ecosystems account for large terrestrial areas and are considered as large carbon (C) sinks. However, fundamental information on topsoil sensitivity to grazing is lacking across different spatial scales including the effects of topography. Our interdisciplinary approach considering soil chemical, physical, and vegetation properties included investigations on pit scale (square-metre scale), plot scale (hectare scale), and the scale of a landscape section (several hectares). Five different sites, representing a grazing intensity gradient, ranging from a long-term grazing exclosure to a heavily grazed site were used. On the pit scale, data about aggregate size distribution, quantity of different soil organic carbon (SOC) pools, SOC mineralisation, hydraulic conductivity and shear strength was available for topsoil samples from representative soil profiles. Spatial variability of topographical parameters, topsoil texture, bulk density, SOC, water repellency, and vegetation cover was analysed on the basis of regular, orthogonal grids in differently grazed treatments by using two different grid sizes on the plot scale and landscape section. On the pit scale, intensive grazing clearly decreased soil aggregation and the amount of fresh, litter-like particulate organic matter (POM). The weak aggregation in combination with animal trampling led to an enhanced mineralisation of SOC, higher topsoil bulk densities, lower infiltration rates, and subsequently to a higher risk of soil erosion. On the plot scale, the effects of soil structure disruption due to grazing are enhanced by the degradation of vegetation patches and resulted in a texture-controlled wettability of the soil surface. In contrast, topsoils of grazing exclosures were characterised by advantageous mechanical topsoil characteristics and SOC-controlled wettability due to higher POM contents. A combined geostatistical and General Linear Model approach identified topography as the fundamental factor creating the spatial distribution of texture fractions and related soil parameters on the scale of a landscape section. Grazing strongly interfered with the topography-controlled particle relocation processes in the landscape and showed strongest effects on the aboveground biomass production and biomass-related soil properties like SOC stocks. We conclude that interdisciplinary multi-scale analyses are essential (i) to differentiate between topography- and grazing-controlled spatial patterns of topsoil and vegetation properties, and (ii) to identify the main grazing-sensitive processes on small scales that are interacting with the spatial distribution and relocation processes on larger scales.
    Keywords: Steppe soils ; Soil organic matter fractions ; Organic carbon mineralisation ; Wind erosion ; Texture ; Vegetation cover ; Shear strength ; Hydraulic conductivity ; Water repellency ; Anisotropy
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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  • 7
    Language: English
    In: Ecological Research, Nov, 2013, Vol.28(6), p.1029(15)
    Description: Byline: Yingzhi Gao (1,2), Marcus Giese (3), Holger Brueck (3), Haijun Yang (1,2), Zhijian Li (1) Keywords: Crop growth rate; Leaf nitrogen content; Net assimilation rate; Relative growth rate; Luxury nitrogen consumption Abstract: The analyses of plant leaf traits that strongly influence aboveground net primary production (ANPP) are indispensable for understanding the process of plant biomass formation. However, there are few studies that have attempted to relate patterns of ANPP under contrasting management practices to plant leaf-level traits. To assess how leaf traits affect plant biomass accumulation under different land-use practices, we examined leaf traits and biomass production in three differently managed sites in the Inner Mongolia steppe: a site fenced since 1979 (UG), a winter grazing site (WG), and a heavily grazed site (HG). Low soil water content, leaf area index, and potential growth ability of species at site HG led to low crop growth rate (CGR), net assimilation rate (NAR), and relative growth rate (RGR) resulting in lower ANPP as compared to sites WG and UG. Irrespective of land-use management, prolonged drought significantly decreases ANPP even though it systematically increases mean CGR and RGR. However, leaf N content and leaf weight ratio are the crucial components necessary to determine the RGR at site WG. This suggests that low leaf N and availability of soil N due to haymaking may be responsible for neither over-compensatory nor compensatory growth in this site. The low ANPP in dry years is not due to the low mean CGR and RGR but rather to the short effective growing days (referring to the days the vegetation actually grows), suggesting that production-adjusted grazing regimes may be the most suitable measures for precision land management and avoiding grassland degradation. Author Affiliation: (1) Key Laboratory of Vegetation Ecology, Northeast Normal University, Changchun, 130024, China (2) State Environmental Protection Key Laboratory of Wetland Ecology and Vegetation Restoration, Northeast Normal University, Changchun, 130024, China (3) Institute for Crop Production and Agroecology in the Tropics and Subtropics, Section Crop Water Stress Management, University of Hohenheim, Garbenstr. 13, 70599, Stuttgart, Germany Article History: Registration Date: 10/09/2013 Received Date: 08/01/2013 Accepted Date: 09/09/2013 Online Date: 08/10/2013 Article note: Electronic supplementary material The online version of this article (doi: 10.1007/s11284-013-1086-1) contains supplementary material, which is available to authorized users.
    Keywords: Rain ; Land Use ; Land Use Controls
    ISSN: 0912-3814
    E-ISSN: 14401703
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  • 8
    Language: English
    In: Environmental and Experimental Botany, May, 2013, Vol.89, p.1(10)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.envexpbot.2012.12.007 Byline: Suchit Shrestha (a)(b), Folkard Asch (b), Holger Brueck (b), Marcus Giese (b), Julie Dusserre (c), Alain Ramanantsoanirina (d) Keywords: Crop duration; Phenology; Sowing date; Spikelet sterility; Temperature; Thermal stress Abstract: a* Knowledge on genotypic variability is required for assessing adaptability of rice production to changing climate. a* Phenotypic responses to variable temperature are genotype specific. a* Genotypic thermal responses with regard to spikelet sterility provide valuable information to improve rice growth models. a* Phenological responses determining crop duration and yield help to develop adapted cropping calendars to climate change. Author Affiliation: (a) Africa Rice Center (AfricaRice), 01 BP 2031 Cotonou, Benin (b) University of Hohenheim, Dept. of Plant Production and Agroecology in the Tropics and Subtropics, Stuttgart, Germany (c) Agricultural Research for Developing Countries (CIRAD), Research Unit in Partnership for Sustainable Farming and Rice Cropping Systems (URP SCRiD), Antsirabe, Madagascar (d) National Centre for Applied Research and Rural Development (FOFIFA), Research Unit in Partnership for Sustainable Farming and Rice Cropping Systems (URP SCRiD), Madagascar Article History: Received 23 February 2012; Revised 19 November 2012; Accepted 24 December 2012
    Keywords: Cropping Systems -- Analysis
    ISSN: 0098-8472
    Source: Cengage Learning, Inc.
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  • 9
    Language: English
    In: The journal of physical chemistry. B, 23 February 2012, Vol.116(7), pp.2284-93
    Description: Charge transfer within and between biomolecules remains a highly active field of biophysics. Due to the complexities of real systems, model compounds are a useful alternative to study the mechanistic fundamentals of charge transfer. In recent years, such model experiments have been underpinned by molecular simulation methods as well. In this work, we study electron hole transfer in helical model peptides by means of molecular dynamics simulations. A theoretical framework to extract Marcus parameters of charge transfer from simulations is presented. We find that the peptides form stable helical structures with sequence dependent small deviations from ideal PPII helices. We identify direct exposure of charged side chains to solvent as a cause of high reorganization energies, significantly larger than typical for electron transfer in proteins. This, together with small direct couplings, makes long-range superexchange electron transport in this system very slow. In good agreement with experiment, direct transfer between the terminal amino acid side chains can be dicounted in favor of a two-step hopping process if appropriate bridging groups exist.
    Keywords: Electrons ; Molecular Dynamics Simulation ; Peptides -- Chemistry
    ISSN: 15206106
    E-ISSN: 1520-5207
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  • 10
    Language: English
    In: Catena, October 2016, Vol.145, pp.180-192
    Description: Rubber plantations are strongly increasing in Xishuangbanna, Southwest China. Herbicide applications controlling the undergrowth may increase erosion potential and carbon export by decreasing plant and litter cover. Quantitative evaluation of the erodibility of rubber systems and the impact of herbicides has not been studied. This study aimed at assessing the impact of herbicide application on soil loss and the induced carbon export in a rubber plantation. Runoff, sediment yield, and total organic carbon (TOC) content in sediments were measured under natural rainfall for one year in a 12-year old rubber plantation subjected to three different herbicide treatments: i) standard application twice per year practiced by the majority of farmers (Hs); (ii) no application to maintain a high understory plant cover (H −); and (iii) bimonthly application (adopted by some farmers) in order to largely avoid understory plant cover (H +). The infiltration rate under different treatments was measured with a rainfall simulator. Monthly measurements of fine root density using soil coring, surface cover, and understory plant cover making photography were carried out. The highest soil and TOC in sediment losses (425 g m , 15 g C m respectively) were observed under H + treatment, while under H − treatment they were strongly reduced (50 g m and 2 g C m respectively). Compared to Hs, H + increased soil and sediment TOC loss by 34 and 52%, while H − reduced soil and TOC loss, both by 82%. Notably, H − presented high conservation efficiency, reducing sediment yields by 86% for highly erosive rainfall events. The cover and management ( ) factor and support practice factor ( ) are essential components of the common Universal Soil Loss Equation (USLE) model. We combined the and factors into a single value ( ) and, for the first time, derived estimations of annual values for a rubber plantation (0.005–0.04) using our data. The dynamic change of the factor of plantations during the rainy season was quantified by relating relative soil loss to changes in understory plant cover (PC), which can be expressed as = 0.04e ( = 0.88, 〈 0.0001). Understory plant cover as affected by herbicide application was thus a key factor controlling the soil loss of established rubber systems. This suggests options to improve the soil conservation and biodiversity through reduced herbicide management.
    Keywords: Erosion ; Herbicide Application ; Rubber Plantation ; Cover and Management Factor ; Usle ; Sciences (General) ; Geography ; Geology
    ISSN: 0341-8162
    E-ISSN: 1872-6887
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