Northeast Institute of Geography and Agroecology, Chinese Academy Of Sciences
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Elevated CO2 alters distribution of nodal leaf area and enhances nitrogen uptake contributing to yield increase of soybean cultivars grown in Mollisols
No full textUnderstanding how elevated CO2 affects dynamics of nodal leaf growth and N assimilation is crucial for the construction of high-yielding canopy via breeding and N management to cope with the future climate change. Two soybean cultivars were grown in two Mollisols differing in soil organic carbon (SOC), and exposed to ambient CO2 (380 ppm) or elevated CO2 (580 ppm) throughout the growth stages. Elevated CO2 induced 4-5 more nodes, and nearly doubled the number of branches. Leaf area duration at the upper nodes from R5 to R6 was 4.3-fold greater and that on branches 2.4-fold higher under elevated CO2 than ambient CO2, irrespective of cultivar and soil type. As a result, elevated CO2 markedly increased the number of pods and seeds at these corresponding positions. The yield response to elevated CO2 varied between the cultivars but not soils. The cultivar-specific response was likely attributed to N content per unit leaf area, the capacity of C sink in seeds and N assimilation. Elevated CO2 did not change protein concentration in seeds of either cultivar. These results indicate that elevated CO2 increases leaf area towards the upper nodes and branches which in turn contributes yield increase
Nitrogen removal in wood chip combined substrate baffled subsurface-flow constructed wetlands: impact of matrix arrangement and intermittent aeration
No full textIn this study, two lab-scale baffled subsurface-flow constructed wetlands (BSFCWs), including gravel-wood chips-slag and gravel-slag-wood chips, were operated at different intermittent aeration to evaluate the effect of artificial aeration and slow-released carbon source on the treatment efficiency of high-strength nitrogen wastewater. Results indicated that gravel-slag-wood chips extended aerobic/anaerobic alternating environment to gravel and slag zones and maintained anaerobic condition in the subsequent wood chip section. The order of gravel-slag-wood chip was more beneficial to pollutant removal. Sufficient carbon source supply resulted from wood-chip-framework substrate simultaneously obtained high removals of COD (97%), NH4+-N (95%), and TN (94%) in BSFCWs at 2 h aeration per day. The results suggest that intermittent aeration combined with wood chips could achieve high nitrogen removal in BSFCWs
Effects of alternate flooding-drought conditions on degenerated Phragmites australis salt marsh in Northeast China
No full textThe hydrological regime is the dominant factor associated with the degradation and restoration of inland salt marshes in Northeast China. This study investigates whether alternate flooding-drought conditions could be used to actively restore degraded inland salt marshes with the native plant Phragmites australis. Pot experiments were designed to examine changes in the growth and physiology of P. australis, as well as the saline-alkaline soil characteristics, in response to different hydrological regimes, alternate flooding-drought treatments, and single treatments of moisture, flooding, and drought. After 4 months of treatments, the P. australis population that grew in alternate flooding-drought conditions exhibited substantially more biomass accumulation and less Na+ absorption compared with the single treatments of moisture, flooding, and drought. Photosynthesis physiology served as regulating and adaptive responses to different water regimes, with increased values after the short-term flooding, long-term drought, and flooding-drought cycles. In addition, the saline-alkaline soil properties changed in response to the flooding-drought cycles. The flooding-drought cycles increased organic matter and total nitrogen contents, but decreased pH, electrical conductivity, and saline ion levels. Plant growth and saline-alkaline soil were improved by flooding-drought cycles (not drought-flooding cycles), which suggests that this may be an effective approach for restoration inland salt marshes
Growth and physiology responses of Phragmites australis to combined drought-flooding condition in inland saline-alkaline marsh, Northeast China
No full textAs a special ecosystem in western Songnen Plain, Northeast China, Phragmites australis saline-alkaline marsh degrade to saline meadow or even alkaline spots progressively, due to the interruption of the water supply. It was the basis to restore the saline-alkaline marsh successfully, that understanding the responses of P. australis to flooding in dried saline-alkaline marsh. Pot experiments were conducted to explore an optimum flooding time for restoring inland saline-alkaline marshes by determining the changes in the growth and physiology of P. australis in response to five different combined drought-flooding treatments (DF04, DF13, DF22, DF31 and DF40). The results showed that the long-term flooding without drought condition (DF04) was not the most favorable condition for the largest effective accumulation of plants biomass, although it gave rise to the highest population height. The combined drought-flooding treatment that drought in one month and flooding in subsequent three months (DF13) was proved as the optimum flooding time, not only obtaining the largest biomass, but also effectively reducing the sodium ion absorbed by plant shoots. Subsequently, the accumulation of sodium ion in plant shoots increased significantly with the delay of flooding from DF22 to DF40 treatments, and the significant enhanced photosynthetic activity implied the evident physiological responses to drought stress.As a special ecosystem in western Songnen Plain, Northeast China, Phragmites australis saline-alkaline marsh degrade to saline meadow or even alkaline spots progressively, due to the interruption of the water supply. It was the basis to restore the saline-alkaline marsh successfully, that understanding the responses of P. australis to flooding in dried saline-alkaline marsh. Pot experiments were conducted to explore an optimum flooding time for restoring inland saline-alkaline marshes by determining the changes in the growth and physiology of P. australis in response to five different combined drought-flooding treatments (DF04, DF13, DF22, DF31 and DF40). The results showed that the long-term flooding without drought condition (DF04) was not the most favorable condition for the largest effective accumulation of plants biomass, although it gave rise to the highest population height. The combined drought-flooding treatment that drought in one month and flooding in subsequent three months (DF13) was proved as the optimum flooding time, not only obtaining the largest biomass, but also effectively reducing the sodium ion absorbed by plant shoots. Subsequently, the accumulation of sodium ion in plant shoots increased significantly with the delay of flooding from DF22 to DF40 treatments, and the significant enhanced photosynthetic activity implied the evident physiological responses to drought stress
Genetic diversity of indigenous soybean-nodulating rhizobia in response to locally-based long term fertilization in a Mollisol of Northeast China
No full textThe influences of five different fertilizer treatments on diversity of rhizobia in soybean nodule were investigated in a long-term experiment with with four replicates: (1) control (without fertilization), (2) balanced NPK fertilizer (NPK), and (3-5) unbalanced chemical fertilizers without one of the major elements (NP, PK, and NK) in Mollisol in Northeast China. The highest soybean yield was observed in the NPK treatment. Total of 200 isolates were isolated and grouped into four Bradyrhizobium genospecies corresponding to B. japonicum, B. diazoefficiens, B. ottawaense and Bradyrhizobium sp. I, based upon the multilocus sequence analysis of 6 housekeeping genes. The Bradyrhizobium sp. I was extensively distributed throughout the study site and was recorded as the dominant soybean rhizobia (82.5-87.5%). Except the NK treatment, the other fertilizer treatments had no effect on rhizobial species composition. Compared with the CK treatment, all the fertilizer treatments decreased species richness, diversity and evenness. The soil organic carbon contents, available N content and pH were the key soil factors to rhizobial community structure. Results suggest that long-term fertilization can decrease rhizobial species diversity, while balanced fertilization with NPK is the most suitable fertilization regime if taking both soybean yields and rhizobial diversity into account
Influence of snow cover changes on surface radiation and heat balance based on the WRF model
No full textThe snow cover extent in mid-high latitude areas of the Northern Hemisphere has significantly declined corresponding to the global warming, especially since the 1970s. Snow-climate feedbacks play a critical role in regulating the global radiation balance and influencing surface heat flux exchange. However, the degree to which snow cover changes affect the radiation budget and energy balance on a regional scale and the difference between snow-climate and land use/cover change (LUCC)-climate feedbacks have been rarely studied. In this paper, we selected Heilongjiang Basin, where the snow cover has changed obviously, as our study area and used the WRF model to simulate the influences of snow cover changes on the surface radiation budget and heat balance. In the scenario simulation, the localized surface parameter data improved the accuracy by 10 % compared with the control group. The spatial and temporal analysis of the surface variables showed that the net surface radiation, sensible heat flux, Bowen ratio, temperature and percentage of snow cover were negatively correlated and that the ground heat flux and latent heat flux were positively correlated with the percentage of snow cover. The spatial analysis also showed that a significant relationship existed between the surface variables and land cover types, which was not obviously as that for snow cover changes. Finally, six typical study areas were selected to quantitatively analyse the influence of land cover types beneath the snow cover on heat absorption and transfer, which showed that when the land was snow covered, the conversion of forest to farmland can dramatically influence the net radiation and other surface variables, whereas the snow-free land showed significantly reduced influence. Furthermore, compared with typical land cover changes, e.g., the conversion of forest into farmland, the influence of snow cover changes on net radiation and sensible heat flux were 60 % higher than that of land cover changes, indicating the importance of snow cover changes in the surface-atmospheric feedback system
Exogenous application of methyl jasmonate induces defence against Meloidogyne hapla in soybean
No full textPhytohormones play important roles in plant defence against plant-parasitic nematodes, although the role of jasmonate (JA) in defence against root-knot nematodes (RKN, Meloidogyne spp.) in soybean (Glycine max) was unknown. In this study, two commercial soybean cultivars, cvs DongSheng1 (DS1) and SuiNong14 (SN14), were identified as susceptible and resistant, respectively, to M. hapla. Quantitative reverse transcription (qRT)-PCR analysis showed that the expression of genes involved in JA synthesis or signalling was significantly induced in both susceptible and resistant roots at 24 and 48 h after inoculation. Exogenous application of methyl jasmonate induced defence against RKN in susceptible cv. DS1, which might be involved in altered activities of defence-related enzymes (chitinase and beta-1,3 glucanase) and pathogenesis-related gene PR5 expression. The results indicate that exogenous application of JA might be an alternative strategy to induce soybean resistance against RKN
Modeling and Predicting of MODIS Leaf Area Index Time Series Based on a Hybrid. SARIMA and BP Neural Network Method
No full textThe modeling and predicting of vegetation Leaf area index (LAI) is an important component of land surface model and assimilation of remote sensing data. The MODIS LAI product (i.e. MOD15A2) is one of the most widely used LAI data sources. However, the time series of MODIS LAI contains some data of low quality. For example, because of the influence of the cloud, aerosol, etc., the MODIS LAI presents the characteristics of the discontinuous in time and space. In fact, the time series of MODIS LAI include both linear and nonlinear components, which cannot be accurately modeled and predicted by either linear method or nonlinear method alone. In this paper, the original LAI time series data were first smoothed with Savitzky-Golay (SG) filtration and linear interpolation; SARIMA, BP neural network and a hybrid method of SARIMA-BP neural network were then used for modeling and predicting MODIS LAI time series. The SARIMA-BP neural network combined both SARIMA and BP neural network, which could model the linear and the nonlinear component of MODIS LAI time series respectively. That is, the final result of SARIMA-BP neural network was the sum of results of the two methods. Experiments showed that the time series of MODIS LAI that were smoothed with the SG filtration and linear interpolation were more smooth than original time series, with a determination coefficient up to 0.981, closer to 1 than that of SARIMA (0.941) and BP neural network (0.884); the correlation coefficient between SARIMA-BP neural network and the observation is 0.991, higher than that of between SARI MA (0.971) or BP neural network (0.942) SARIMA and the observation. Thus, it can be concluded that, the proposed SARI MA-BP neural network method can better adapt to the LAI time series, and it outperforms the SARIMA and BP neural network methods
Chemical Attraction of Conspecifics in Folsomia candida (Collembola)
No full textChemical substances excreted from individuals are regarded as chemo-sensory signals that induce aggregation in Collembola. However, chemical or physiological evidence is required to identify the chemical composition of signals responsible for aggregation behavior. Present study applied solvent extraction and gas chromatograph-mass spectrometer-computer technology to separate and identify the chemical compounds in cuticle extracts from the model Collembola species, Folsomia candida. The occurrence of aggregation behavior was confirmed by conspecific attractiveness using a trap bioassay. Eight chemical compounds were obtained from F. candida's cuticle solvent. The trap assay detected fatty acid combinations from the body extracts of F. candida that induced attractiveness behavior among conspecific individuals and small molecules with higher concentration induced repellent. However, single sensillum recordings of two thin-wall chemical receptors at the second segment of the distal position of the antenna did not receive any positive responses to fatty acids, either single or in combination. The way F. candida used fatty acid combinations as chemical signal for conspecific aggregating was discussed
Carbon, Nitrogen and Phosphorus Contents of Wetland Soils in Relation to Environment Factors in Northeast China
No full textSoil organic carbon (OC) is sensitive to climatic change, and it can be expected to manifest measurable responses to global warming. Globally, nitrogen (N) and phosphorus (P) are the most common nutrients limiting plant growth and soil carbon storage. We collected soil samples at 17 marsh sites in August 2012 across Northeast China. These samples were analysed for variations in soil organic carbon (OC), total nitrogen (TN) and total phosphorus (TP) levels, and multiple controlling of environmental and biotic factors. Results showed the means to be as follows: 16,850.7 mmol kg(-1) (OC), 540.5 mmol kg(-1) (TN), 30.0 mmol kg(-1) (TP), 29.9 (C:N), 516.5 (C:P) and 16.8 (N:P). The OC, TN, TP and C:N:P ratios decreased with increases in the mean annual temperature (MAT) and flooding depth, whereas the C:N ratio did not change significantly with the flooding depth. Quadratic relationships were observed between the OC, TN and TP and soil pH. Linear mixed-effect models showed that climate exerted great influences on soil nutrients. These results will improve our understanding of the ecological patterns of nutrient fluxes and the biogeochemical mechanisms of the response of vegetation to climate changes