Northeast Institute of Geography and Agroecology, Chinese Academy Of Sciences
Not a member yet
4476 research outputs found
Sort by
Long-term phosphorus addition enhances the biodegradability of dissolved organic carbon in a nitrogen-limited temperate freshwater wetland
No full textPhosphorus (P) enrichment is expected to strongly influence dissolved organic carbon (DOC) biodegradation. However, the relationship between P availability and DOC biodegradation is largely unknown in nitrogen (N)limited ecosystems. Here, we investigated the changes in the ratio of DOC to dissolved total nitrogen (DTN), specific UV absorbance at 254 nm(SUVA(254)), and DOC biodegradation in surface water and soil pore water (0-15 cm depth) following eight years of multi-level P addition (0, 1.2, 4.8, and 9.6 g Pm-2 year(-1)) in an N-limited freshwater marsh in Northeast China. We found that P addition caused an increase in DOC biodegradation in surface water and soil pore water, irrespective of the P addition levels. Compared with the control treatment, the P addition rates of 1.2, 4.8, and 9.6 g Pm-2 year(-1) increasedDOC biodegradation by 20.7%, 15.2%, and 14.5% in surface waters, and 11.3%, 9.4%, and 12.0% in soil pore waters, respectively. The DOC biodegradationwas separately negatively correlated with the DOC: DTN ratio and SUVA(254), indicating that the positive effect of P addition on DOC biodegradation was caused by the elevated N concentration and the reduced DOC aromaticity. Our findings suggest that P enrichment enhances the biodegradability of DOC through increased N availability and altered DOC chemical composition, which would accelerate DOC loss from the waters and alter ecosystem C balance in N-limited temperate wetlands. (C) 2017 Elsevier B.V. All rights reserved
Ecosystem Service Comparison before and after Marshland Conversion to Paddy Field in the Sanjiang Plain, Northeast China (vol 37, pg 593, 2017)
No full textAgraphorura Xuae Sp Nov., the First Record of Onychiuridae (Collembola) from Continental Ecuador, with a Key to the Known Species of the Genus
No full textThe new species Agraphorura xuae sp. nov. is described from continental Ecuador, the first onychiurid species record in this region. The new species is most similar to A. gambiarius (Murphy, 1965) from West Africa, but they can be separated easily by the number and length of p-chaetae between two inner posterior pso on the head, the number of chaetae on Th. I tergum, the presence of the male ventral organ and the ratio of the empodial appendage/unguis. A key to the world known species is provided. The list of all known species from continental Ecuador is presented
Estimation of Usle K Values with a Process-Based Approach
No full textThe Universal Soil Loss Equation (USLE) soil erodibility (K) factors for different soils have often been estimated using a soil erodibility nomograph. The USDA-NRCS requested assistance in evaluating nomograph estimates of K for two soils that exhibit very different erodibilities based on field observations and expert opinion. In this study, we used a combination of laboratory measurements and process-based WEPP model simulations to estimate USLE K factors for four soils: a Miami silt loam from Indiana, an Opal clay from South Dakota, a Vergennes silty clay loam from Vermont, and a Mexico silty clay loam from Missouri. Experiments to estimate WEPP erosion parameters included: (1) simulated rainfall experiments to estimate WEPP model interrill erodibility (K-i) and (2) V-shaped mini-flume experiments to estimate WEPP model rill erodibility (K-r) and critical shear stress (tau(cr)). These estimates were made under three soil moisture conditions: initially dry, pre-wetted and then drained, and pre-wetted and saturated. Results showed that for the reference Indiana and Missouri soils, the back-calculated USLE K values from the dry and saturated soils were not significantly different from either the nomograph or RUSLE2 database values. For the South Dakota and Vermont NRCS test soils, the nomograph K was significantly lower than the experimentally derived K for initially dry and saturated soils and was also below the RUSLE2 database value. Saturated/drained soil moisture conditions resulted in the lowest back-calculated USLE K values for all soils. The process-based WEPP model with laboratory measurements of K-i, K-r, and tau(cr) allowed computation of USLE K and provided more conservative estimates of K for the South Dakota clay and Vermont silty clay loam soils. More science-based K values have soil conservation policy implications in that the RUSLE2 database may provide better estimates for K values than use of the nomograph for some soils
Distinct soil bacterial communities in response to the cropping system in a Mollisol of northeast China
No full textCropping systems such as monoculture and rotation can affect soil microbial communities, however, the mechanisms of how bacterial community are affected and the possible links between these effects and cropping systems remain unclear. To address this question, we comparatively investigated the bacterial abundance, diversity and structure in the bulk and rhizosphere soils of soybean grown in two cropping systems, i.e., continuous cropping of soybean (CC) and cropping rotation with maize (CR) using real-time PCR and Illumina Miseq sequencing methods The results showed that soil pH, total N, total P, and available nutrients such as N, P and K were significantly higher in the bulk soil of CR than in CC. No significant variation of bulk soil total C content was detected between the two cropping systems. The bacterial abundance and diversity were higher in the bulk and rhizosphere soils of CR than in corresponding soil samples of CC. In addition, higher abundance and lower diversity of bacterial communities were observed in rhizosphere soil than in bulk soil within each cropping system. Compared with CC treatment, 12 and 17 bacterial phyla/classes were significantly increased for CR in bulk soil and rhizosphere, respectively. Among the altered bacterial phyla/classes, Betaproteobacteria, Acidobacteria, Actinobacteria and Alphaproteobacteria were the most important taxa contributing to the variation between the two crop systems in both bulk and rhizosphere soils. The results of principal coordinate analysis (PCoA) and three nonparametric multivariate statistical tests revealed that the bacterial communities were distinctly separated between CC and CR both in the bulk and rhizosphere soils; the variation of Bray-Curtis difference in rhizosphere soil was greater than in bulk soil. Furthermore, the composition and diversity of the soil bacterial communities in bulk soil were affected by soil pH, total nitrogen (TN), total phosphorus (TP) and soil available potassium, nitrogen and phosphorus (AK, AN and AP), and the effect of soil pH was a primary factor in determining bacterial community composition