Krasnoyarsk, Russia
Krasnoyarsk, Russia

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Zhu Z.,CAS Institute of Subtropical Agriculture | Ge T.,CAS Institute of Subtropical Agriculture | Hu Y.,CAS Institute of Subtropical Agriculture | Zhou P.,CAS Institute of Subtropical Agriculture | And 7 more authors.
Plant and Soil | Year: 2017

Background and aims: The turnover of plant- and microbial- derived carbon (C) plays a significant role in the soil organic C (SOC) cycle. However, there is limited information about the turnover of the recently photosynthesized plant- and soil microbe-derived C in paddy soil. Methods: We conducted an incubation study with four different 13C–labeled substrates: rice shoots (Shoot-C), rice roots (Root-C), rice rhizodeposits (Rhizo-C), and microbe-assimilated C (Micro-C). Results: Shoot- and Root-C were initially rapidly transformed into the dissolved organic C (DOC) pool, while their recovery in microbial biomass C (MBC) and SOC increased with incubation time. There were 0.05%, 9.8% and 10.0% of shoot-C, and 0.06%, 15.9% and 16.5% of root-C recovered in DOC, MBC and SOC pools, respectively at the end of incubation. The percentages of Rhizo- and Micro-C recovered in DOC, MBC, and SOC pools slowly decreased over time. Less than 0.1% of the Rhizo- and Micro-C recovered in DOC pools at the end of experiment; while 45.2% and 33.8% of Rhizo- and Micro-C recovered in SOC pools. Shoot- and Root-C greatly increased the amount of 13C–PLFA in the initial 50 d incubation, which concerned PLFA being indicative for fungi and actinomycetes while those assigning gram-positive bacteria decreased. The dynamic of soil microbes utilizing Rhizo- and Micro-C showed an inverse pattern than those using Shoot- and Root-C. Principal component analysis of 13C–PLFA showed that microbial community composition shifted obviously in the Shoot-C and Root-C treatments over time, but that composition changed little in the Rhizo-C and Micro-C treatments. Conclusions: The input C substrates drive soil microbial community structure and function with respect to carbon stabilization. Rhizodeposited and microbial assimilated C have lower input rates, however, they are better stabilized than shoot- and root-derived C, and thus are preferentially involved in the formation of stable SOC in paddy soils. © 2017 Springer International Publishing Switzerland

Atere C.T.,CAS Institute of Subtropical Agriculture | Ge T.,CAS Institute of Subtropical Agriculture | Zhu Z.,CAS Institute of Subtropical Agriculture | Tong C.,CAS Institute of Subtropical Agriculture | And 7 more authors.
Biology and Fertility of Soils | Year: 2017

This study aimed to better understand the stabilisation of rice rhizodeposition in paddy soil under the interactive effects of different N fertilisation and water regimes. We continuously labelled rice (‘Zhongzao 39’) with 13CO2 under a combination of different water regimes (alternating flooding-drying vs. continuous flooding) and N addition (250 mg N kg−1 urea vs. no addition) and then followed 13C incorporation into plant parts as well as soil fractions. N addition increased rice shoot biomass, rhizodeposition, and formation of 13C (new plant-derived C) in the rhizosphere soils under both water regimes. By day 22, the interaction of alternating flooding-drying and N fertilisation significantly increased shoot and root 13C allocations by 17 and 22%, respectively, over the continuous flooding condition. The interaction effect also led to a 46% higher 13C allocation to the rhizosphere soil. Alone, alternating water management increased 13C deposition by 43%. In contrast, N addition increased 13C deposition in rhizosphere soil macroaggregates under both water regimes, but did not foster macroaggregation itself. N treatment also increased 13C deposition and percentage in microaggregates and in the silt and clay-size fractions of the rhizosphere soil, a pattern that was higher under the alternating condition. Overall, our data indicated that combined N application and a flooding-drying treatment stabilised rhizodeposited C in soil more effectively than other tested conditions. Thus, they are desirable practices for improving rice cropping, capable of reducing cost, increasing water use efficiency, and raising C sequestration. © 2017 Springer-Verlag Berlin Heidelberg

Boy J.,Leibniz University of Hanover | Godoy R.,Austral University of Chile | Shibistova O.,Leibniz University of Hanover | Shibistova O.,VN Sukachev Institute of Forest | And 6 more authors.
Revista Chilena de Historia Natural | Year: 2016

Background: Maritime Antarctica is severely affected by climate change and accelerating glacier retreat forming temporal gradients of soil development. Successional patterns of soil development and plant succession in the region are largely unknown, as are the feedback mechanisms between both processes. Here we identify three temporal gradients representing horizontal and vertical glacier retreat, as well as formation of raised beaches due to isostatic uplift, and describe soil formation and plant succession along them. Our hypotheses are (i) plants in Antarctica are able to modulate the two base parameters in soil development, organic C content and pH, along the temporal gradients, leading to an increase in organic carbon and soil acidity at relatively short time scales, (ii) the soil development induces succession along these gradients, and (iii) with increasing soil development, bryophytes and Deschampsia antarctica develop mycorrhiza in maritime Antarctica in order to foster interaction with soil. Results: All temporal gradients showed soil development leading to differentiation of soil horizons, carbon accumulation and increasing pH with age. Photoautptroph succession occurred rapidly after glacier retreat, but occurrences of mosses and lichens interacting with soils by rhizoids or rhizines were only observed in the later stages. The community of ground dwelling mosses and lichens is the climax community of soil succession, as the Antarctic hairgrass D. antarctica was restricted to ornithic soils. Neither D. antarctica nor mosses at the best developed soils showed any sign of mycorrhization. Conclusion: Temporal gradients formed by glacier retreat can be identified in maritime Antarctic, where soil development and plant succession of a remarkable pace can be observed, although pseudo-succession occurs by fertilization gradients caused by bird feces. Thus, the majority of ice-free surface in Antarctica is colonized by plant communities which interact with soil by litter input rather than by direct transfer of photoassimilates to soil. © 2016 Boy et al.

Hellmann L.,Swiss Federal Institute of forest | Hellmann L.,Oeschger Center for Climate Change Research | Tegel W.,Albert Ludwigs University of Freiburg | Kirdyanov A.V.,Vn Sukachev Institute Of Forest | And 13 more authors.
Arctic, Antarctic, and Alpine Research | Year: 2015

Recent findings indicated spruce from North America and larch from eastern Siberia to be the dominating tree species of Arctic driftwood throughout the Holocene. However, changes in source region forest and river characteristics, as well as ocean current dynamics and sea ice extent likely influence its spatiotemporal composition. Here, we present 2556 driftwood samples from Greenland, Iceland, Svalbard, and the Faroe Islands. A total of 498 out of 969 Pinus sylvestris ring width series were cross-dated at the catchment level against a network of Eurasian boreal reference chronologies. The central Siberian Yenisei and Angara Rivers account for 91% of all dated pines, with their outermost rings dating between 1804 and 1999. Intensified logging and timber rafting along the Yenisei and Angara in the mid-20th century, together with high discharge rates, explain the vast quantity of material from this region and its temporal peak ca. 1960. Based on the combined application of wood-anatomical and dendrochronological techniques on a well-replicated data set, our results question the assumption that Arctic driftwood mainly consists of millennial-old larch and spruce. Nevertheless, data from other species and regions, together with longer boreal reference chronologies, are needed for generating reliable proxy archives at the interface of marine and terrestrial environments. © 2015 Regents of the University of Colorado.

Buntgen U.,Swiss Federal Institute of forest | Buntgen U.,Oeschger Center for Climate Change Research | Buntgen U.,Academy of Sciences of the Czech Republic | Hellmann L.,Swiss Federal Institute of forest | And 8 more authors.
Journal of Ecology | Year: 2015

Summary: The effects of climate change on Arctic ecosystems can range between various spatiotemporal scales and may include shifts in population distribution, community composition, plant phenology, primary productivity and species biodiversity. The growth rates and age structure of tundra vegetation as well as its response to temperature variation, however, remain poorly understood because high-resolution data are limited in space and time. Anatomical and morphological stem characteristics were recorded to assess the growth behaviour and age structure of 871 dwarf shrubs from 10 species at 30 sites in coastal East Greenland at 70°N. Recruitment pulses were linked with changes in mean annual and summer temperature back to the 19th century, and a literature review was conducted to place our findings in a pan-Arctic context. Low cambial activity translates into estimated average/maximum plant ages of 59/204 years, suggesting relatively small turnover rates and stable community composition. Decade-long changes in the recruitment intensity were found to lag temperature variability by 2 and 6 years during warmer and colder periods, respectively (r = 0.851961-2000 and 1881-1920). Synthesis. Our results reveal a strong temperature dependency of Arctic dwarf shrub reproduction, a high vulnerability of circumpolar tundra ecosystems to climatic changes, and the ability of evaluating historical vegetation dynamics well beyond the northern treeline. The combined wood anatomical and plant ecological approach, considering insights from micro-sections to community assemblages, indicates that model predictions of rapid tundra expansion (i.e. shrub growth) following intense warming might underestimate plant longevity and persistence but overestimate the sensitivity and reaction time of Arctic vegetation. Our results reveal a strong temperature dependency of Arctic dwarf shrub reproduction, a high vulnerability of circumpolar tundra ecosystems to climatic changes, and the ability of evaluating historical vegetation dynamics well beyond the northern treeline. The combined wood anatomical and plant ecological approach, considering insights from microsections to community assemblages, indicates that model predictions of rapid tundra expansion (i.e. shrub growth) following intense warming might underestimate plant longevity and persistence but overestimate the sensitivity and reaction time of Arctic vegetation. © 2014 British Ecological Society.

Gentsch N.,Leibniz University of Hanover | Mikutta R.,Leibniz University of Hanover | Shibistova O.,Leibniz University of Hanover | Shibistova O.,VN Sukachev Institute of Forest | And 18 more authors.
European Journal of Soil Science | Year: 2015

Permafrost degradation may cause strong feedbacks of arctic ecosystems to global warming, but this will depend on if, and to what extent, organic matter (OM) is protected against biodegradation by mechanisms other than freezing and anoxia. Here, we report on the amount, chemical composition and bioavailability of particulate (POM) and mineral-associated OM (MOM) in permafrost soils of the East Siberian Arctic. The average total organic carbon (OC) stock across all soils was 24.0 ± 6.7 kg m-2 within 100 cm soil depth. Density fractionation (density cut-off 1.6 g cm-3) revealed that 54 ± 16% of the total soil OC and 64 ± 18% of OC in subsoil horizons was bound to minerals. As well as sorption of OM to clay-sized minerals (R2 = 0.80; P < 0.01), co-precipitation of OM with hydrolyzable metals may also transfer carbon into the mineral-bound fraction. Carbon:nitrogen ratios, stable carbon and nitrogen isotopes, 13C-NMR and X-ray photoelectron spectroscopy showed that OM is transformed in permafrost soils, which is a prerequisite for the formation of mineral-organic associations. Mineral-associated OM in deeper soil was enriched in 13C and 15N, and had narrow C:N and large alkyl C:(O-/N-alkyl C) ratios, indicating an advanced stage of decomposition. Despite being up to several thousands of years old, when incubated under favourable conditions (60% water-holding capacity, 15°C, adequate nutrients, 90 days), only 1.5-5% of the mineral-associated OC was released as CO2. In the topsoils, POM had the largest mineralization but was even less bioavailable than the MOM in subsoil horizons. Our results suggest that the formation of mineral-organic associations acts as an important additional factor in the stabilization of OM in permafrost soils. Although the majority of MOM was not prone to decomposition under favourable conditions, mineral-organic associations host a readily accessible carbon fraction, which may actively participate in ecosystem carbon exchange. © 2015 British Society of Soil Science.

Pflugmacher D.,Oregon State University | Krankina O.N.,Oregon State University | Cohen W.B.,U.S. Department of Agriculture | Friedl M.A.,Boston University | And 8 more authors.
Remote Sensing of Environment | Year: 2011

Information on land cover at global and continental scales is critical for addressing a range of ecological, socioeconomic and policy questions. Global land cover maps have evolved rapidly in the last decade, but efforts to evaluate map uncertainties have been limited, especially in remote areas like Northern Eurasia. Northern Eurasia comprises a particularly diverse region covering a wide range of climate zones and ecosystems: from arctic deserts, tundra, boreal forest, and wetlands, to semi-arid steppes and the deserts of Central Asia. In this study, we assessed four of the most recent global land cover datasets: GLC-2000, GLOBCOVER, and the MODIS Collection 4 and Collection 5 Land Cover Product using cross-comparison analyses and Landsat-based reference maps distributed throughout the region. A consistent comparison of these maps was challenging because of disparities in class definitions, thematic detail, and spatial resolution. We found that the choice of sampling unit significantly influenced accuracy estimates, which indicates that comparisons of reported global map accuracies might be misleading. To minimize classification ambiguities, we devised a generalized legend based on dominant life form types (LFT) (tree, shrub, and herbaceous vegetation, barren land and water). LFT served as a necessary common denominator in the analyzed map legends, but significantly decreased the thematic detail. We found significant differences in the spatial representation of LFT's between global maps with high spatial agreement (above 0.8) concentrated in the forest belt of Northern Eurasia and low agreement (below 0.5) concentrated in the northern taiga-tundra zone, and the southern dry lands. Total pixel-level agreement between global maps and six test sites was moderate to fair (overall agreement: 0.67-0.74, Kappa: 0.41-0.52) and increased by 0.09-0.45 when only homogenous land cover types were analyzed. Low map accuracies at our tundra test site confirmed regional disagreements and difficulties of current global maps in accurately mapping shrub and herbaceous vegetation types at the biome borders of Northern Eurasia. In comparison, tree dominated vegetation classes in the forest belt of the region were accurately mapped, but were slightly overestimated (10%-20%), in all maps. Low agreement of global maps in the northern and southern vegetation transition zones of Northern Eurasia is likely to have important implications for global change research, as those areas are vulnerable to both climate and socio-economic changes. © 2011 Elsevier Inc.

Zhao N.-N.,Lanzhou University | Guggenberger G.,Leibniz University of Hanover | Guggenberger G.,King Saud University | Shibistova O.,Leibniz University of Hanover | And 4 more authors.
Plant and Soil | Year: 2014

Background: Meadows and shrublands are two major vegetation types on the Qinghai-Tibetan Plateau, but little is known about biochemical characteristics and its relation to decomposability of soil organic carbon (OC) under these two vegetation types. The present study was designed to evaluate effects of aspect-vegetation complex on biochemical characteristics and decomposability of soil OC.Methods: Two hills were randomly selected; both with vegetation being naturally divided into southward meadows and northward shrublands by a ridge, and soils were sampled at depths of 0–15 and 15–30 cm, along contours traversing the meadow and shrubland sites. Particulate (particle size 2–0.05 mm) OC and nitrogen (N), microbial biomass C and N, non-cellulosic sugars, and CuO lignin were analyzed, and OC mineralization was measured for 49 days at 18 and 25 °C under laboratory incubation, respectively.Results: More than half of soil OC was present as particulate fraction across all samples, indicating the coarse nature of soil organic matter in the region. Averaging over depths, shrublands contained 87.7 − 114.1 g OC and 7.7 − 9.3 g N per kg soil, which were 63 − 78 and 26 − 31 % higher than those in meadows, respectively. Meanwhile the C/N ratio of soil organic matter was 11.4 − 12.3 under shrublands, being 29 − 40 % higher than that under meadows. Soil OC under meadows was richer in noncellulosic carbohydrates and microbial biomass in the 0–15 and 15–30 cm depths but contained less lignin in the 15–30 cm depth. Ratios of microbially- to plant-derived monosaccharides and between acid and aldehyde of the vanillyl units were greater in soils under shrublands, showing more abundant microbially-derived sugars and microbially-transformed ligneous substances in OC as compared to meadow soils. By the end of 49 days’ incubation, total CO2–C evolution from soils under meadows was 15.0–16.2 mg g−1 OC averaging over incubation temperatures and soil depths, being 27–55 % greater than that under shrublands. Across all soil samples over two sites, total CO2 − C evolved per g OC at either 18 or 25 °C was closely correlated to enrichments of noncellulosic carbohydrates and microbial biomass. This indicates that the greater soil OC decomposability under meadows was associated with its larger abundances of readily mineralizable fractions compared with shrublands. However, temperature increase effect on soil OC decomposability did not differ between the two types of vegetation.Conclusions: Our findings suggest that the aspect-vegetation complex significantly affected pool size, biochemical characteristics, and decomposability of soil OC on the northeastern edge of Qinghai-Tibetan Plateau. However, the response of soil OC decomposability to temperature was similar between southward meadows and northward shrublands. © 2014, Springer International Publishing Switzerland.

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