Northeast Institute of Geography and Agroecology, Chinese Academy Of Sciences
Not a member yet
4476 research outputs found
Sort by
Delimiting species of Protaphorura (Collembola: Onychiuridae): integrative evidence based on morphology, DNA sequences and geography
No full textSpecies delimitation remains a significant challenge when the diagnostic morphological characters are limited. Integrative taxonomy was applied to the genus Protaphorura (Collembola: Onychiuridae), which is one of most difficult soil animals to distinguish taxonomically. Three delimitation approaches (morphology, molecular markers and geography) were applied providing rigorous species validation criteria with an acceptably low error rate. Multiple molecular approaches, including distance-and evolutionary model-based methods, were used to determine species boundaries based on 144 standard barcode sequences. Twenty-two molecular putative species were consistently recovered across molecular and geographical analyses. Geographic criteria were was proved to be an efficient delimitation method for onychiurids. Further morphological examination, based on the combination of the number of pseudocelli, parapseudocelli and ventral mesothoracic chaetae, confirmed 18 taxa of 22 molecular units, with six of them described as new species. These characters were found to be of high taxonomical value. This study highlights the potential benefits of integrative taxonomy, particularly simultaneous use of molecular/geographical tools, as a powerful way of ascertaining the true diversity of the Onychiuridae. Our study also highlights that discovering new morphological characters remains central to achieving a full understanding of collembolan taxonomy
Impact of soil water erosion processes on catchment export of soil aggregates and associated SOC
No full textSoil erosion is a complex process which causes loss of soil mineral material together with soil organic carbon (SOC). Little is known about the impact of soil water erosion on catchment exports of soil aggregates and associated SOC, especially at a small agricultural catchment SOC delivered from a small catchment located in Northeast China was assessed for three erosive rainfall events in 2011. The quantity and size of the exported soil aggregates and their concentration of SOC were assessed along with runoff rate, sediment loss and rainfall characteristics to further the understanding of SOC erosion and its potential fate. Aggregate size distribution in sediments was different from that in source soil and was significantly correlated to sediment concentration in runoff. Fine size aggregate fractions in the sediments were the most abundant. The SOC was enriched in the sediments and indicated a high selectivity of the erosion processes. The SOC concentration differed among different sizes of aggregate fractions with coarse size aggregate fractions generally having the largest concentration. We concluded that the soil water erosion processes impact the aggregate size distribution and SOC enrichment in the delivered sediment, which subsequently influence the catchment exports of SOC. Additional measurements over several rainy seasons are required to further quantify the impact of soil water erosion on catchment exports of soil aggregates and associated SOC. (C) 2017 Elsevier B.V. All rights reserved
Removal of nutrients in saline wastewater using constructed wetlands: Plant species, influent loads and salinity levels as influencing factors
No full textThis study aims to evaluate how plant species, influent loads and salinity levels affect the removal of nutrients from saline wastewater using constructed wetlands (CWs). CWs planted with Canna indica showed the greatest removal percentages among the four tested species for nitrogen (N) (similar to 100%) at both low and high influent loads, and similar to 100% and 93.8% for phosphorus (P) at low and high influent loads, respectively at an electrical conductivity (EC) of 7 mS/cm (25 degrees C). The influence of different salinity levels on plant assimilation of N and P varied with their respective concentrations; salinity (e.g., EC at 7,10 and 15 mS/cm) even enhanced plant absorption of N and P under specific conditions. In conclusion, CWs planted with selected species can be used for the removal of N and P under a range of different salinity levels (e.g., EC at 7, 10 and 15 mS/cm, 25 degrees C). (C) 2017 Published by Elsevier Ltd
Effect of long-term phosphorus addition on the quantity and quality of dissolved organic carbon in a freshwater wetland of Northeast China
No full textUnderstanding how P enrichment alters the quantity and quality of dissolved organic carbon (DOC) is important, because of their role in regulating the C cycle. Here, we established a four-level P addition experiment (0, 1.2,4.8, and 9.6 g Pm-2 year(-1)) in a N-limited freshwater wetland in the Sanjiang Plain, Northeast China. The aim of this study was to examine the effects of eight years of P addition on DOC concentration, SUVA(254) (Abs(254)/DOC concentration, indicating the aromaticity of DOC), C:C ratio (Abs(400)/DOC concentration, indicating the proportion of colored humic substances in DOC), and E4:E6 ratio (Abs(465)/Abs(665), indicating the molecular size of humic substances) in surface water and soil pore water (0-15 cm depth) during the growing season (June through September). Our results showed similar changing trends in concentration and optical properties of DOC following eight years of P addition in the both surface water and soil pore water across the sampling dates. Generally, P addition decreased DOC concentration, SUVA254, and C:C ratio, and increased E4:E6 ratio, irrespective of P addition levels. These altered optical properties of DOC indicated that P addition decreased the molecular weight and aromaticity of DOC, and thus increased the quality of DOC. These results suggest P enrichment substantially reduces the quantity of DOC in N-limited temperate freshwater wetlands, and imply that increased DOC quality following P addition can further provide a positive feedback to decreased DOC pool. (C) 2017 Elsevier B.V. All rights reserved
Quantitative Trait Locus Mapping of Soybean Maturity Gene E6
No full textSoybean [ Glycine max (L.) Merr.] sensitivity to photoperiod determines adaptation to a specific range of latitudes for soybean cultivars. When temperate-adapted soybean cultivars are grown in low latitude under short day conditions, they flower early, resulting in low grain yield, and consequently limiting their utility in tropical areas. Most cultivars adapted to low-latitude environments have the trait of delayed flowering under short day conditions, and this trait is commonly called long juvenile (LJ). In this study, the E6 locus, the classical locus conditioning the LJ trait, was molecularly mapped on Gm04 near single-nucleotide polymorphism marker HRM101. Testcross, genetic mapping, and sequencing suggest that the E6 and J loci might be tightly linked. Genetic interaction evaluation between E6 and E1 suggests that E6 has a suppressive effect on E1 and that the function of E6 is dependent on E1. The tagging markers for E6 are very useful for molecular breeding for wide adaptation and stable productivity of soybean under lowlatitude environments. Molecular identification and functional characterization of the E6 gene will greatly facilitate the understanding of the genetic and molecular mechanisms underlying the LJ trait
Potassium Application Affects Key Enzyme Activities of Sucrose Metabolism during Seed Filling in Vegetable Soybean
No full textPot experiments were conducted in 2014 and 2015 with two vegetable soybean [Glycine max (L.) Merr.] cultivars ('Zhongkemaodou 1' and '121') under normal rates of nitrogen and phosphorus application with three potassium (K) fertilization treatments: no K application (K0), 120 kg K2SO4 ha(-1) at seeding (K1), and 120 kg K2SO4 ha(-1) at seeding + 1% K2SO4 foliar application at flowering (K2). Potassium application significantly increased seed sucrose concentration, and the highest seed sucrose concentrations were uniformly observed in the treatment of foliar K application after flowering. At 7 wk after flowering, the highest stage of seed sucrose concentration, K1 and K2 treatments increased sucrose concentration by 19.8 to 44% and 29.1 to 86.4% for Zhongkemaodou 1, and 7.2 to 42.1% and 26.2 to 63.8% for 121, respectively. Changes of net activities of sucrose-metabolizing enzymes in seed paralleled the trend of sucrose accumulation. Potassium application increased the activities of sucrose phosphate synthase and sucrose synthase with increased sucrose synthesis but reduced the activity of sucrose synthase with increased sucrose decomposition. Potassium application also reduced the activities of acid invertase and neutral invertase, especially around seed ripening. Potassium fertilization enhanced seed net activities of key enzymes in sucrose metabolism and subsequently induced the increase in sucrose concentration of vegetable soybean
Nitrogen additions affect litter quality and soil biochemical properties in a peatland of Northeast China
No full textNitrogen (N) is a limiting nutrient in many peatland ecosystems. Enhanced N deposition, a major component of global climate change, affects ecosystem carbon (C) balance and alters soil C storage by changing plant and soil properties. However, the effects of enhanced N deposition on peatland ecosystems are poorly understood. We conducted a two-year N additions field experiment in a peatland dominated by Eriophorum vaginatum in the Da Xing'an Mountains, Northeast China. Four levels of N treatments were applied: (1) CK (no N added), (2) N1 (6 g N m(-2) yr(-1)), (3) N2 (12 g N m(-2) yr(-1)), and (4) N3 (24 gN m(-2) yr(-1)). Plant and soil material was harvested at the end of the Second growing season. N additions increased litter N and phosphorus (P) content, as well as S-glucosidase, invertase, and acid-phosphatase activity, but decreased litter C:N and C:P ratios. Litter carbon content remained unchanged. N additions increased available NH4+-N and NO3--N as well as total Gram-positive (Gram+), Gram-negative (Gram-), and total bacterial phospholipid fatty acids (PLFA) in shallow soil (0-15 cm depth). An increase in these PLFAs was accompanied by a decrease in soil labile organic C (microbial biomass carbon and dissolved organic carbon), and appeared to accelerate decomposition and reduce the stability of the soil C pool. Invertase and urease activity in shallow soils and acid-phosphatase activity in deep soils (15-30 cm depth) was inhibited by N additions. Together, these findings suggest that an increase in N deposition in peatlands could accelerate litter decomposition and the loss of labile C, as well as alter microbial biomass and function. (C) 2016 Elsevier B.V. All rights reserved
Urbanization Drives SOC Accumulation, Its Temperature Stability and Turnover in Forests, Northeastern China
No full textGlobal urbanization is a vital process shaping terrestrial ecosystems but its effects on forest soil carbon (C) dynamics are still not well defined. To clarify the effects of urbanization on soil organic carbon (SOC) variation, 306 soil samples were collected and analyzed under two urban-rural gradients, defined according to human disturbance time and ring road development in Changchun, northeast China. Forest SOC showed a linear increase with increasing human disturbance time from year 1900 to 2014 (13.4 g C m(-2) year(-1)), and a similar trend was found for the ring road gradient. Old-city regions had the longest SOC turnover time and it increased significantly with increasing urbanization (p = 0.011). Along both urban-rural gradients SOC stability toward temperature variation increased with increasing urbanization, meaning SOC stability in old-city regions was higher than in new regions. However, none of the urban-rural gradients showed marked changes in soil basal respiration rate. Both Pearson correlation and stepwise regression proved that these urbanization-induced SOC patterns were closely associated with landscape forest (LF) proportion and soil electrical conductivity (EC) changes in urban-rural gradients, but marginally related with tree size and compositional changes. Overall, Changchun urbanization-induced SOC accumulation was 60.6-98.08 thousand tons, accounting for 12.8-20.7% of the total forest C biomass sequestration. Thus, China's rapid urbanization-induced SOC sequestration, stability and turnover time, should be fully estimated when evaluating terrestrial C balance
Assessment of Ammonia Volatilization Losses and Nitrogen Utilization during the Rice Growing Season in Alkaline Salt-Affected Soils
No full textThe objectives of this study were to evaluate the effects of different fertilizer types and application rates on ammonia volatilization loss and to explore nitrogen distribution and nitrogen use efficiency using the N-15 isotope tracing technique in different alkaline salt-affected conditions in the Songnen Plain, Northeast China. The results showed a decreasing trend in ammonia volatilization loss from ammonium nitrate and ammonium sulfate, but not that from urea, as the electrical conductivity gradient increased, whereas the reverse trend was found as the pH gradient increased. Ammonia volatilization loss increased in moderately salt-affected soil compared with that in slightly salt-affected soil, particularly during the tillering stage, regardless of the N fertilizer rate. The percentage of N absorbed by rice plants increased from urea but decreased from the soil as the amount of nitrogen was increased. Interestingly, the N retention rate in soil decreased and rice grain yield and nitrogen agronomic efficiency increased as the amount of nitrogen increased in both salt-affected soil conditions. The nitrogen application amount of highest N physiological efficiency was 225 kg.N/ha. Considering high rice production and a minimal environmental threat, we should fully consider controlling ammonia volatilization losses by adjusting the fertilizer type and the crop stage when the fertilizer is applied
New species of the family Steganacaridae (Acari, Oribatida, Phthiracaroidea) from Northeast China with keys to known species of Austrophthiracarus and Hoplophthiracarus from the Palaearctic Region
No full textIn this study, two new species of steganacarid mites (Oribatida: Phthiracaroidea) from Northeast China, Austrophthiracarus setiformis Liu sp. nov. and Hoplophthiracarus acuminatus Liu sp. nov., are described and illustrated. Keys to known species of Austrophthiracarus and Hoplophthiracarus from the Palaearctic Region are provided to facilitate further studies of these groups