1,446 publications from this institution
Grasslands are very important regionally and globally because they store large amounts of carbon (C) and nitrogen (N) and provide food for grazing animals.
The conversion of natural forests to tree plantations alters the quality and decreases the quantity of litter inputs into the soil, but how the alteration
Summary Demand of all living organisms on the same nutrients forms the basis for interspecific competition between plants and microorganisms in soils. This competition is especially strong in the rhizosphere. To evaluate competitive and mutualistic interactions between plants and microorganisms and to analyse ecological consequences of these interactions, we analysed 424 data pairs from 41 15 N‐labelling studies that investigated 15 N redistribution between roots and microorganisms. Calculated M ichaelis– M enten kinetics based on K m (Michaelis constant) and V max (maximum uptake capacity) values from 77 studies on the uptake of nitrate, ammonia, and amino acids by roots and microorganisms clearly showed that, shortly after nitrogen ( N ) mobilization from soil organic matter and litter, microorganisms take up most N . Lower K m values of microorganisms suggest that they are especially efficient at low N concentrations, but can also acquire more N at higher N concentrations ( V max ) compared with roots. Because of the unidirectional flow of nutrients from soil to roots, plants are the winners for N acquisition in the long run. Therefore, despite strong competition between roots and microorganisms for N , a temporal niche differentiation reflecting their generation times leads to mutualistic relationships in the rhizosphere. This temporal niche differentiation is highly relevant ecologically because it: protects ecosystems from N losses by leaching during periods of slow or no root uptake; continuously provides roots with available N according to plant demand; and contributes to the evolutionary development of mutualistic interactions between roots and microorganisms. Contents Summary 656 I. Introduction 657 II. General solution: trade of C for nutrients 657 III. Methods 658 IV. Interactions between roots and rhizosphere microorganisms 659 V. Potential of plants and microorganisms for N uptake by their competition 661 VI. Ecological relevance of competition between roots and microorganisms for N 662 VII. Effect of biotic and abiotic factors on N flows between microorganisms and roots 663 VIII. Conclusions and outlook 665 Acknowledgements 666 References 666
Die Stundenwerte der Temperatur eines Sandbodens wurden schichtweise bis zur Tiefe von 1 m mit Hilfe der Zeitreihenanalyse untersucht. Es wurden die Verzögerung des Tagesganges der Bodentemperatur gegenüber der der Lufttemperatur und die Dämpfung der täglichen Amplitude der Lufttemperatur in Abhängigkeit von der Bodentiefe berechnet. Die Verzögerung des Temperaturverlaufs in Abhängigkeit von der Bodentiefe wurde durch die Krosskorrelation zwischen einzelnen Temperaturmeßreihen bestimmt. Diese Abhängigkeit war linear: je 10 cm Bodenschicht wurde eine Verzögerung der Temperaturausbreitung um ca. 2 Stunden berechnet. Die Dämpfung der Amplitude des Tagesganges der Temperatur wurde als Zusammenhang zwischen den “saisonalen”; Komponenten des Tagesganges der Temperatur bei “additiver Census‐1‐Decomposition”; und der Bodentiefe bestimmt. Diese Abhängigkeit war exponentiell. Ein Pflanzenbestand wirkte als ein zusätzlicher Puffer sowohl auf die Dämpfung als auch auf die Verzögerung. Die ermittelten Parameter ermöglichen es, die Bodentemperatur bis zur Tiefe von 30 cm in Abhängigkeit von der Lufttemperatur in 5 cm Höhe mit einer mittleren Abweichung von < + 1,1 K und einem Korrelationskoeffizienten > 0,97 zu berechnen. Die Simulation der Bodentemperatur in 50 und 100 cm Tiefe war mit dem gewählten Ansatz ungenauer.
We developed a software tool enabling user-friendly and standardized pre- and post-processing of images of rooted soil by combining image processing techniques such as image registration, calibration, and segmentation in a graphical user interface. The added benefits of this image processing approach include an improved workflow in soil zymography. For evaluation, we conducted a rhizobox experiment with maize and determined the activity of leucine-aminopeptidase before and after glucose addition based on soil zymography. The temporal and spatial distribution of enzyme activity at the root-soil interface can be visualized by Root-o-Mat which offers 1) standardized image pre-processing, 2) calibration, 3) identification of hotspots of various intensity thresholds, 4) spatial analysis for selected roots, 5) inter-active illustration of enzyme activity profile lines, 6) image viewer, and 7) detection of temporal changes of enzyme activity. Registering images of the same rhizobox taken in successive periods allows further temporal and spatial analysis. We conclude that Root-o-Mat simplifies and firmly anchors image processing and image analyses in soil zymography. The new software can be downloaded for free (www.root-o-mat.de).
No abstract is provided for this article.
The gap formation due to forest thinning regulates the understorey microclimate, ground vegetation, and soil biodiversity. However, little is known about abundant and rare taxa's various patterns and assemblage mechanisms under thinning gaps. Thinning gaps with increasing sizes (0, 74, 109, and 196 m2) were established 12 years ago in a 36-year-old spruce plantation in a temperate mountain climate. Soil fungal and bacterial communities were analyzed by MiSeq sequencing and related to soil physicochemical properties and aboveground vegetation. The functional microbial taxa were sorted by FAPROTAX and Fungi Functional Guild database. The bacterial community stabilized under varied thinning intensities and was not different from the control plots, whereas the richness of the rare fungal taxa was at least 1.5-fold higher in the large gaps than in the small ones. Total phosphorus and dissolved organic carbon were the main factors influencing microbial communities in soil under various thinning gaps. The diversity and richness of the entire fungal community and rare fungal taxa increased with the understorey vegetation coverage and shrub biomass after thinning. Gap formation by thinning stimulated the understorey vegetation, the rare saprotroph (Undefined Saprotroph), and mycorrhizal fungi (Ectomycorrhizal-Endophyte-Ericoid Mycorrhizal-Litter Saprotroph-Orchid Mycorrhizal and Bryophyte Parasite-Lichen Parasite-Ectomycorrhizal-Ericoid Mycorrhizal-Undefined Saprotroph), which may accelerate nutrient cycling in forest ecosystems. However, the abundance of Endophyte-Plant Pathogens increased by eight times, which showed the potential risk for the artificial spruce forests. Thus, fungi may be the driving force of forest restoration and nutrient cycling under the increasing intensity of thinning and may induce plant diseases. Therefore, vegetation coverage and microbial functional diversity should be considered to evaluate the sustainability of the artificial forest ecosystem and forest restoration.
Raw data for the article: Kyle Mason-Jones*, Yakov Kuzyakov (2017)<br> “Non-metabolizable” glucose analogue shines new light on priming mechanisms: Triggering of microbial metabolism Soil Biology and Biochemistry 107, 68-76 https://doi.org/10.1016/j.soilbio.2016.12.015 * corresponding author: kmasonj@gwdg.de
The radiocarbon method has been frequently used to date mollusk shell carbonate. The accuracy of estimated ages, however, depends on the degree and completeness of shell carbonate recrystallization. Although the effect of contamination of the shell CaCO3 with environmental carbon (C) is well known, the role of Ca2+ in diagenetic processes remains unclear. Addition of young C to shells during diagenesis occurs in soil solution, where the Ca2+ concentration is in equilibrium with exchangeable Ca2+ and/or weathering of Ca-bearing minerals. While the exchange process takes place within seconds, the dissolution equilibrium requires longer timescales (on the order of months). It has therefore been hypothesized that the dissolution and recrystallization of shell carbonate in soils with higher cation exchange capacity (CEC) should proceed slower compared to those with low CEC. The objective was to determine the effects of soil CEC and exchangeable cations on shell carbonate recrystallization using the 14C labeling approach. Shell particles of the bivalve Protothaca staminea were mixed with carbonate-free sand (CEC=0.37cmol+ kg−1) (Sand), a loamy soil (CEC=16cmol+ kg−1) (Loam) or the same loamy soil saturated with KCl, where exchangeable cations were replaced with K+ (Exchanged). The high-sensitivity 14C labeling/tracing approach was used to determine carbonate recrystallization rates. Shell carbonate recrystallization after 120days in Loam and Exchanged (0.016 and 0.024mg CaCO3, respectively) showed one order of magnitude lower recrystallization than in Sand (0.13mg CaCO3). A high level of soil exchangeable Ca2+ decreased the solubility of shell carbonate and consequently its recrystallization because the exchange is faster than dissolution. Therefore, soil CEC and cation composition are determinant factors of shell carbonate recrystallization. Shells in soils with low CEC may undergo more intensive recrystallization; hence they may need further pretreatments before the dating procedure.
The turnover and residence time of carbon (C) and nitrogen (N) in soil is a fundamental parameter reflecting the rates of soil organic matter (SOM) transformation and the contribution of soils to greenhouse gases fluxes. Based on the global database of the stable isotope composition of C (δ13C) and N (δ15N) depending on soil depth (171 profiles), we assessed С and N turnover and related them to climate, biome types and soil properties. The 13C and 15N discrimination between the litter horizon and mineral soil was evaluated to explain the key processes of litter transformation. The 13C and 15N discrimination by microbial utilization of litter and SOM, as well as the continuous increase of δ13C and δ15N with depth, enabled to assess C and N turnover within SOM. N turnover was two times faster than that of C, which reflects i) repeated N recycling by microorganisms accelerating N turnover, ii) C loss as CO2 and input of new C atoms to cycling, which reduces the C turnover within soil, and iii) generally slower turnover of N free persistent organic compounds (e.g. lignin, suberin, cellulose) compared to the N containing compounds (e.g. amino acids, ribonucleic acids). An increase in temperature and precipitation accelerated C and N turnover because: i) higher microbial activity and SOM decomposition rate, ii) larger soil moisture and fast diffusion of dissolved organics towards exoenzymes, iii) downward transport of 13C-enriched organic matter (e.g. sugars, amino acids), and iii) leaching of 15N-depleted nitrates from the topsoil into subsoil and losses from the whole soil profile. Temperature accelerates SOM turnover stronger than precipitation. The temperature increase by 10 °C accelerates the C and N turnover for 40 %. SOM turnover is boosted by decreasing C/N ratio because: i) SOM with a high C/N ratio originated from litter is converted to microbially-derived SOM in mineral soil characterized by a low C/N ratio; ii) litter with a low C/N ratio is decomposed faster than litter with a high C/N; iii) microbial carbon-use efficiency increases with N availability. The biome type affects SOM decomposition by i) climate: slower turnover under wet and cold conditions, and ii) by litter quality: faster utilization of leaves than needles. Thus, the fastest C turnover is common under evergreen forests and the lowest under mixed and coniferous ones, whereas temperature and C/N ratio are the main factors controlling SOM turnover. Concluding, the assessment of SOM turnover by δ13C and δ15N approach showed two times faster N turnover compared to C, and specifics of SOM turnover depending on the biomes as well as climate conditions.
