[Comparison on fungal molecular ecological networks of agricultural soils with different latitudes in the black soil region of Northeast China]. / 东北黑土区不同纬度农田土壤真菌分子生态网络比较.

To investigate the differences of fungal network structures and interaction among fungal species of in black soil region of Northeast China, Illumina MiSeq sequencing was used to reveal the fungal communities in the three long-term fertilization experimental fields. Fungal molecular ecological networks were constructed based on random matrix theory (RMT). The results demonstrated that Ascomycota, Basidiomycota and Zygomycota were the dominant phyla and Hypocreales, Pleosporales and Sordariales were the dominant order, but the relative abundance of some dominant taxa significantly varied in different locations. Fungal molecular ecological network structures in three locations showed significant difference, with more complex fungal network being observed in north location with more competitive relations among species. The fungal network in south location was more easily disturbed by environmental perturbations with less stability. Only seven shared nodes were detected among three fungal molecular ecological networks. There were large differences in connectivity of shared nodes within individual fungal network. The subnetwork of Hypocreales was gradual complex from south to north location while subnetwork of Pleosporales presented reversed trend. The key species of south, middle and north locations were Chaetomiaceae, Pleosporales and Penicillium coralligerum, respectively. Soil pH and total N content were the main soil properties simultaneously influencing three fungal networks.

[Study on Biochar Properties Analysis with Scanning Electron Microscope-EnergyDispersive X-Ray Spectroscopy (SEM-EDX)].

Scanning Electron Microscope-Energy Dispersive X-ray spectroscopy (SEM-EDX) was applied to analyze the chemical and structural properties of biochars produced under different temperatures. Results showed that average carbon content (SEM C aver.) and maximum carbon content (SEM C max.) of miscanthus (MS) biochar increased as temperature increasing. There were significant and positive relationships between SEM C max., SEM C aver. and highest treatment temperature (HTT) (r were 0.76 and 0.86). SEM C max., SEM C aver. and dry combustion total carbon content had significant and positive relationships (r were 0.83 and 0.91), SEM C max. which was better than SEM C aver. So the carbon content of MS biochar which had good correlationship with temperature analyzed by SEM-EDX, SEM C max. could be used for composition analysis of biochar, scanning results could analyze structural properties of biochar effectively. This method is rapid, simple and stable. It also could analyze structure and composition of biochar simultaneously. It is a promising method that would be useful to study the structure and composition of biochar and other materials.

[Distribution and enrichment characteristics of organic carbon and total nitrogen in mollisols under long-term fertilization].

The characteristics and changes of soil organic carbon (SOC) and total nitrogen (TN) in different size particles of soil under different agricultural practices are the basis for better understanding soil carbon sequestration of mollisols. Based on a 31-year long-term field experiment located at the Heilongjiang Academy of Agricultural Sciences (Harbin) , soil samples under six treatments were separated by size-fractionation method to explore changes and distribution of SOC and TN in coarse sand, fine sand, silt and clay from the top layer (0-20 cm) and subsurface layer (20-40 cm). Results showed that long-term application of manure (M) increased the percentages of SOC and TN in coarse sand and clay size fractions. In the top layer, application of nitrogen, phosphorus and potassium fertilizers combined with manure (NPKM) increased the percentages of SOC and TN in coarse sand by 191.3% and 179.3% compared with the control (CK), whereas M application increased the percentages of SOC and TN in clay by 45% and 47% respectively. For subsurface layers, the increase rates of SOC and TN in corresponding parts were lower than that in top layer. In the surface and subsurface layers, the percentages of SOC storage in silt size fraction accounted for 42%-63% and 48%-54%, TN storage accounted for 34%-59% and 41%-47%, respectively. The enrichment factors of SOC and TN in coarse sand and clay fractions of surface layers increased significantly under the treatments with manure. The SOC and TN enrichment factors were highest in the NPKM, being 2.30 and 1.88, respectively, while that in the clay fraction changed little in the subsurface layer.

[Effect of long-term fertilization on microbial community functional diversity in black soil].

In order to study the effects of long-term different fertilization on microbial community functional diversity in arable black. soil, we examined microbial metabolic activities in two soil la- yers (0-20 cm, 20-40 cm) under four treatments (CK, NPK, M, MNPK) from a 35-year continuous fertilization field at the Ministry of Agriculture Key Field Observation Station of Harbin Black Soil Ecology Environment using Biolog-ECO method. The results showed that: in the 0-20 cm soil layer, combined application of organic and inorganic fertilizer(MNPK) increased the rate of soil microbial carbon source utilization and community metabolism richness, diversity and dominance; In the 20-40 cm layer, these indices of the MNPK treatment was lower than that of the NPK treat- ment; while NPK treatment decreased soil microbial community metabolism evenness in both layers. Six groups of carbon sources used by soil microbes of all the treatments were different between the two soil layers, and the difference was significant among all treatments in each soil layer (P < 0.05) , while the variations among treatments were different in the two soil layers. Canonical correspondence analysis (CCA) showed that soil microbial community metabolic function of all the treatments was different between the two soil layers, and there was difference among all treatments in each soil layer, while the influences of soil nutrients on soil microbial community metabolic function of all treatments were similar in each soil layer. It was concluded that long-term different fertilization affected soil microbial community functional diversity in both tillage soil layer and down soil layers, and chemical fertilization alone had a larger influence on the microbial community functional diversity in the 20-40 cm layer.

[Response of black soil organic carbon, nitrogen and its availability to longterm fertilization].

Based on the long-term fertilization experiments, effects of various fertilization practices on the soil organic carbon (SOC) and total nitrogen (TN) in the surface (0-20 cm) and subsurface (20-40 cm) black soil in northeast China were studied. Results showed that, compared with the CK, long-term application of organic manure, especially the combination of mineral fertilizers and organic manure significantly increased the organic SOC and TN in the surface soil. Application of mineral fertilizers plus organic manure with conventional (NPM) and high application (N2P2M2) rate increased SOC significantly by 24. 6% and 25.1% , and TN by 29.5% and 32.8%, respectively. However, there was no significant difference among the treatments for SOC and TN at the subsurface. Compared with the CK (CKh), mineral fertilizer plus organic manure (NPM and N2P2M2) did not only increase the soil microbial biomass carbon (SMBC) and nitrogen (SMBN) , dissolved organic carbon (DOC) and nitrogen (DN), but also significantly increased the ratio of SMBC and DOC to SOC, SMBN and TN to TN. Application of the NPM and N2P2M2 increased the value of SMBC/SOC by 0.36 to 0.59 and SMBN/TN by 1.21 to 1.95 percentage points, respectively. The value of DOC/SOC and DN/TN ranged from 0.53% to 0.72% and 1.41% to 1.78%, respectively. This result indicated that SMBC, SMBN, DOC, DN and SMBC/ SOC, SMBN/TN, DOC/SOC, DN/TN were more sensitive than SOC and TN to long-term fertilization in the soil profile, and were better indicators for the impact of long-term fertilization soil fertility. The concluded that the application of manure especially manure plus mineral fertilizers can increase soil nutrients activity in the surface and subsurface black soil, acting as a helpful practice to improve soil fertility and the ability of nutrient supply, while it may cause potential environment pollution on carbon and nitrogen loss in the agroecosystem.

[Fluorescence spectroscopic characteristics of fulvic acid from the long-term located fertilization in black soil].

In order to investigate the effect of long-term located fertilization on soil fulvic acid (FA), in this study, four soil samples were taken from black soil with long-term located fertilization (about 30 year) in Harbin, Heilongjiang province. The fertilization treatments included control (CK), N, P and K fertilization (NPK), horse manure (OM), combination of organic manure and chemical fertilizations (MNPK). Soil FA was extracted from the samples and purified. The excitation, emission, synchronous, and three-dimensional-excitation emission matrix fluorescence spectroscopy (3DEEM) characteristics of the FA were determined. The excitation, emission and synchronous scan spectra all indicated that the main peaks of FA in the NPK treatment exhibited a significantly blue shift compared with CK, while those of MNPK, OM treatment caused a red shift to some extent. 3DEEM spectra of FA in all treatments exhibited four peaks (peak a, peak b, peak c, and peak d), compared with FA in CK, the wavelengths shift tendency of peak a, peak b, and peak c of FA 3DEEM in NPK, MNPK and OM treatments were similar to that of traditional spectra in FA. In order to provide quantitative information of FA humification degree in different treatments, we investigated the fluorescence index f450/500 (FI), area integration (A370-600 nm, A1 370-412 nm, A4 538-600 nm). Compared with CK, the f450/500, ratio of A1/A in NPK and A4/A in MNPK treatment increased by 4.62%, 6.12%, 7.22%, respectively. However, the f450/500, the ratio of A1/A in MNPK and A4/A in NPK treatment decreased by 3.86%, 15.31%, and 7.22% respectively. This indicated that NPK application gave a lower degree of FA humification, and combination of organic manure and chemical fertilizations would lead to a greater degree of FA aromatization in black soil with long-term located fertilization than CK.