Northeast Institute of Geography and Agroecology, Chinese Academy Of Sciences
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Root-associated bacterial diversities of Oryza rufipogon and Oryza sativa and their influencing environmental factors
No full textOryza rufipogon is the ancestor of human-cultivated Oryza sativa. However, little is known about the difference between the root-associated microorganisms of O. rufipogon and O. sativa. In this study, the root-associated bacteria of O. rufipogon, Leersia hexandra, and O. sativa from different latitudes in China were studied by DGGE analysis. Their bacterial community structures were compared by principal component analysis. The relationship between root-associated bacteria and soil properties was explored by canonical correspondence analysis. The relationships of glomalin-related soil protein (GRSP) content, soluble sugar content, proline content of the plant, and bacterial diversity indices of their root-associated microorganisms were also investigated. We found both broad-spectrum and host-specific bacteria, and the similarity, diversity and abundance indices of O. rufipogon and L. hexandra were higher than O. sativa root-associated bacteria. However, even living in the same habitat, O. rufipogon and L. hexandra selected different root-associated bacteria. Microbial composition was primarily correlated with available N, P, and K and the annual precipitation. We also found a positive correlation between the soluble sugar content of the plant and GRSP content of the root soil. The above results indicated that the community structure of root-associated bacteria differs between wild rice and cultivated rice. Human activity and the natural selection of the host plants shaped the differences, consistent with our hypothesis
Priming of rice (Oryza sativa L.) seedlings with abscisic acid enhances seedling survival, plant growth, and grain yield in saline-alkaline paddy fields
No full textSaline-alkaline (SA) stress is one of the major constraints to crop production worldwide. It is characterized by high salinity and high alkalinity (high pH), with the latter being the primary inhibiting factor to rice growth. We previously reported that pretreatment with abscisic acid (ABA) primed rice seedlings for enhanced tolerance to alkaline stress. In the present study, we conducted a 3-year field experiment to further assess the ABA-priming effect on the stress tolerance of rice plants in two paddy fields with different SA levels (field-A: non-reclaimed field, pH = 10.13 +/- 0.009, EC1:5 = 0.50 +/- 0.004; field-B: reclaimed field, pH = 9.74 +/- 1 0.005, EC1:5 = 0.48 +/- 0.001). Rice seedlings were treated with ABA at concentrations of 0 (control), 1, and 10 mu M by root-drenching for 24 h prior to transplanting to the two paddy fields with different SA levels. Compared to the control treatment, ABA application substantially reduced the occurrence of leaf withering by 22%-50% and seedling death by 11%-17%. Further, ABA application also significantly improved subsequent plant growth and the final grain yield by 8%-55%; a more profound effect was observed in the harder SA field. Expressions of the ABA-responsive genes SalT and OsWsi18 were highly induced by ABA treatment, and the induced levels were sustained until at least 8 d after transplanting. Collectively, these results suggest a potent priming effect of ABA on the SA stress tolerance of rice plants, providing an effective and practical approach to improving rice production in SA paddy fields. (C) 2016 Elsevier B.V. All rights reserved
The temporal variation of farmland soil surface roughness with various initial surface states under natural rainfall conditions
No full textSoil surface roughness not only affects the hydrological and erosive behavior of soils, but also influences their spectral reflectivity in the optical and microwave bands. Field measurement of soil surface roughness is time-consuming, laborious, costly, and, for vegetated areas, impractical. We attempt to find a method to predict the dynamics of soil surface roughness for various soil surface states for black soils in Northeast China. In this study, four soil surfaces with different roughness were designed, and three kinds of roughness parameters, root-mean square height (rmsh), correlation length (cl) and rmsh/c1, of each soil surface were measured. The results of soil surface roughness were as follows: (1) a decrease over time was observed for rmsh and rmsh/cl as well as an increase in cl over time; (2) an exponential relationship was confirmed between roughness parameters (rmsh, c1, and rmsh/c1) and cumulative rainfall (CR) for soil plots without ridge, as well as for the relative change (RC) of roughness parameters and CR; (3) a significant difference in change of soil surface roughness with CR existed for soil surfaces with ridge and without ridge, and a Gaussian function was more suitable for describing the dependence of soil roughness evolution on CR than an exponential function. These results indicate that the temporal change of soil surface roughness in the black soil of Northeast China could be predicted by CR based on the empirical relationship achieved in this study regardless of whether soil surface has a ridge and of different initial roughness
Conversion of cropland to forage land and grassland increases soil labile carbon and enzyme activities in northeastern China
No full textSoil labile carbon (C) and enzyme activities are valuable indicators of changes in soil quality and health. Understanding the changes in soil labile C and enzyme activities under different land uses is important to maintain soil quality and health and for sustainable land use. The primary objective of this study was to investigate the short-term influences of different land uses on SOC, soil labile C and enzyme activities in semiarid alkaline grassland of northeastern China. The experiment was organized as a block design with four replications of each land use treatment. Land use treatments were corn cropland (Corn), alfalfa forage land (Alfalfa), Lyemus chinensis grassland (AG), Lyemus chinensis grassland for mowing (AG + Mow) and restored grassland (RG), which were applied for five years. Total soil organic carbon (SOC), three labile C pools (oxidizable labile C; water-extractable organic C; microbial biomass C) and the activities of four soil enzymes (catalase; urease; alkaline phosphatase; invertase) were determined at the 0-20 cm depth in the five land use treatments. Results showed that soil labile C and enzyme activities were sensitive indicators of land use change. Conversion of cropland to forage land and grassland increased SOC (40.42%), soil labile C measures (25.50%) and enzyme activities (55.60%). However, the responses of different forms of soil labile C and enzyme activities to different land uses were not similar. Under Corn, AG + Mow, AG and RG land uses, the geometric means of labile C (27.01%, 10.95%, 17.52% and 5.11%, respectively) and enzyme activities (40.92%, 13.54%, 11.38% and 7.38%, respectively) were lower than those under Alfalfa, demonstrating that soil labile C and enzyme activities improved more under Alfalfa than under other land uses in northeastern China. Significant correlations were also obtained between SOC, soil labile C measures and enzyme activities. To conclude, soil labile C and enzyme activities can be expected to gradually increase with the conversion of cropland to grasslands and forage land, and planting to alfalfa offers a profitable and sustainable solution to our requirement for pairing forage production with rapid restoration of soil quality in the areas in which soils are not suitable for growing crops in the Songnen Grassland
Evaluation of CDOM sources and their links with water quality in the lakes of Northeast China using fluorescence spectroscopy
No full textThe spatial distributions of the fluorescence intensities F-max), for chromophoric dissolved organic matter (CDOM) components, the fluorescence indices (FI370 and FI310) and their correlations with water quality of 19 lakes in the Songhua River Basin (SHRB) across semiarid regions of Northeast China were examined with the data collected in September 2012 and 2015. The 19 lakes were divided into two groups according to EC (threshold value = 800 mu S cm(-1)): fresh water (N = 13) and brackish water lakes (N = 6). The fluorescent characteristics of CDOM in the 19 lakes were investigated using excitation-emission matrix fluorescence spectroscopy (EEM) coupled with parallel factor (PARAFAC) and multivariate analysis. Two humic-like components (C1 and C3), one tryptophan-like component (C2), and one tyrosine-like component (C4) were identified by PARAFAC. The component C4 was not included in subsequent analyses due to the strong scatter in some colloidal water samples from brackish water lakes. The correlations between F-max for the three EEM-PARAFAC extracted CDOM components C1-C3, the fluorescence indices (FI370 and FI310) and the water quality parameters (i.e., TN, TP, Chl-a, pH, EC, turbidity (Turb) and dissolved organic carbon (DOC)) were determined by redundancy analysis (RDA). The results of RDA analysis showed that spatial variation in land cover, pollution sources, and salinity/EC gradients in water quality affected F-max for the fluorescent components C1-C3 and the fluorescence indices (FI370 and FI310). Further examination indicated that the CDOM fluorescent components and the fluorescence indices (FI370 and F1310) did not significantly differ (t-test, p > 0.05) in fresh water (N = 13) and brackish water lakes (N = 6). There was a difference in the distribution of the average F-max for the CDOM fluorescent components between Cl to C3 from agricultural sources and urban wastewater sources in hypereutrophic brackish water lakes. The F-max for humic-like components Cl and C3 spatially varied with land cover among the 19 lakes. Our results indicated that the spatial distributions of F-max for CDOM fluorescent components and their correlations with water quality can be evaluated by EEM-PARAFAC and multivariate analysis among the 19 lakes across semiarid regions of Northeast China, which has potential implication for lakes with similar genesis. (C) 2017 Elsevier B.V. All rights reserved
Eight-Year Cattle Manure Amendment Alters Chemical and Biochemical Properties of Eroded Mollisols
No full textSoil chemical and biochemical properties are important indicators in assessing soil quality. To investigate the effect of manure application on eroded Mollisols, soil organic carbon (SOC), total nitrogen (TN), C/N ratio, and potentially mineralizable nitrogen (PMN), microbial biomass carbon (MBC), urease activity, and sucrase activity were determined aft er 8-yr application of cattle manure in combination with chemical fertilizers in a soil erosion simulation facility by removing the topsoil by 0, 5, 10, 20, and 30 cm in a typical Mollisols region in China. All parameters except C/N ratio showed a declining trend with the increasing of erosion depth. Soil organic C, TN, PMN, MBC, urease activity, and sucrase activity were 11 to 23, 5 to 9, 5 to 16, 11 to 19, 18 to 32 and 13 to 37% higher under the chemical fertilizer + manure treatment than the chemical fertilizer alone plots, respectively. The C/N ratios did not change significantly with the increase of erosion depth, but they were also 5 to 17% higher in the chemical fertilizer + manure treatment than that in the chemical fertilizer alone treatment. Eight-year application of cattle manure in combination with chemical fertilizers improved soil quality of eroded Mollisols, but was not good enough to restore the fertility of eroded Mollisols to that of non-eroded soils
Optimum water supplement strategy to restore reed wetland in the Yellow River Delta
No full textIn order to supply optimum water to restore reed wetlands used for bird habitats, a field investigation and greenhouse experiment were conducted. Three water supplementation stages (early stage at 20 May, middle stage at 20 July and later stage at 20 September, respectively) and five depths (0, 10, 15, 20 and 35 cm over the surface, respectively) were established, with three replicates for each treatment combination. Reed growth characteristics (survival rate, height, density and biomass) and soil properties of field investigation and experiment were recorded to determine the impacts of water supplementation on reed wet-land restoration. The field investigation showed that reeds in natural wetlands grow better than those in degraded wetlands and soil properties in degraded wetlands were significantly different from soils in natural wetlands. With freshwater supplementation, reed growth characteristics and soil properties greatly improved. As water depth increased, reed growth decreased gradually. Reeds grew best in shallow water depth (<= 10cm) than in the greater flooding depths. Saturated soils with no standing water at the early stage of reed growth increased reed survival and water depth can be increased as the reeds grow. During the process of water supplementation, soil salinity was reduced significantly. Soil salinity was reduced dramatically at early and middle stages of reed growth, but it increased slightly at the later stage. Soil pH increased greatly during the experiment. Soil total nitrogen (TN) and total organic carbon (TOC) showed contrasting changes, with soil TN decreasing and TOC increasing. To best manage reed wetlands restoration, we suggest saturating wetland in the spring to stimulate reed germination, increasing surface water depth up to 15cm at the stage of reed rapid growth, and then reducing water depth during the later growth stage
Agrobacterium salinitolerans sp nov., a saline-alkaline-tolerant bacterium isolated from root nodule of Sesbania cannabina
No full textTwo Gram-staining-negative, aerobic bacteria (YIC 5082(T) and YIC4104) isolated from root nodules of Sesbania cannabina grown in a high-salt and alkaline environment were identified as a group in the genus Agrobacterium because they shared 100 and 99.7% sequence similarities of 16S rRNA and recA+ atpD genes, respectively. These two strains showed 99.2/100% and 93.9/95.4% 16S rRNA and recA+ atpD gene sequence similarities to Agrobacterium radiobacter LMG140 T and Agrobacterium. pusense NRCPB10 T, respectively. The average nucleotide identities (ANI) of genome sequences were 89.95% or lower between YIC 5082 T and the species of the genus Agrobacterium examined. Moreover, these two test strains formed a unique nifH lineage deeply separated from other rhizobia. Although the nodC gene was not detected in YIC 5082(T) and YIC4104, they could form effective root nodules on S. cannabina plants. The main cellular fatty acids in YIC 5082(T) were summed feature 8 (C-18 : 1 omega 7c/C-18 : 1 omega 6c), C-19 : 0 omega 8c, summed feature 2 (C-12 : 0 aldehyde/unknown equivalent chain length 10.9525) and C16 : 0. The DNA G+C content of YIC 5082 T was 59.3 mol%. The failure to utilize D-sorbitol as a carbon source distinguished YIC 5082(T) from the type strains of related species. YIC 5082 T could grow in presence of 5.0% (w/v) NaCl and at a pH of up to 10.0. Based on results regarding the genetic and phenotypic properties of YIC 5082(T) and YIC4104 the name Agrobacterium salinitolerans sp. nov. is proposed and YIC 5082 T (= HAMBI 3646 T = LMG 29287(T)) is designed as the type strain
Amelioration Effect of Horizontal Flushing Times on Sodic Soil Remediation
No full textHorizontal flushing after amendment application to ameliorate low-permeability sodic soil is a site-specific method. Based on a pot experiment, the impacts of horizontal flushing on moderately and extremely sodic soils were studied. The effects of desulfurized gypsum (DG) on horizontal flushing were observed, and the influence of DG on total soluble salts (TSS) flushed and the removal of sodium (TNaF) was analyzed. The experiment had a completely randomized design with four treatments, and each treatment had five replications. Four treatments were designed as MCK (moderately sodic soil), ECK (extremely sodic soil), MGR (moderately sodic soil with 100% gypsum requirement), and EGR (extremely sodic soil with 100% gypsum requirement). All treatments received three consecutive horizontal flushing events. The monitored sodic parameters included Na+ removed by horizontal flushing, total soluble salts removed by horizontal flushing, pH and electronic conductivity (EC) in ponded water, pH, EC, total alkalinity, and sodium adsorption ratio (SAR) in two soil layers (0 - 10 and 10 - 20 cm). The results indicated that horizontal flushing combined with DG amendments is an effective measure for the reclamation of sodic soil. Horizontal flushing could effectively remove the soluble sodium in soil water, which resulted in a significant decrease in the sodicity (SAR) of the soil. The SAR of MCK, MGR, ECK and EGR decreased by 36.6%, 70.8%, 18.6% and 43.1%, respectively. The second horizontal flushing removed a significantly greater (p 0.05) between the second and third horizontal flushing except in the ECK treatment. As the horizontal flushing increased, the quantity of soluble sodium and total salts removed from the ponded water did not increase accordingly. The MGR and EGR treatments performed better, and the ideal horizontal flushing is two events considering the water scarcity problem in local areas