Effects of tropical rainforest conversion to rubber plantation on soil quality in Hainan Island, China

Land-use changes can alter soil properties and thus affect soil quality. Our understanding of how forest conversion (from tropical rainforest to rubber plantations) affects soil properties and soil quality is limited. An ideal testing ground for analyzing such land-use change and its impacts is Hainan Island, the largest tropical island in China. Based on 21 soil physicochemical and biological properties, a soil quality index (SQI) employed principal component analysis to assess soil quality changes from the conversion of tropical rainforests to rubber plantations. The results showed that (i) soil available potassium, available phosphorus, microbial biomass carbon, cellulose decomposition, acid phosphatase, and urease were vital soil properties for soil quality assessment on Hainan Island. (ii) The SQI of rubber plantations decreased by 26.48 % compared to tropical rainforests, while four investigated soil properties (soil pH, total phosphorus, cellulose decomposition, and actinomyces) increased. (iii) The SQI of both the tropical rainforests and rubber plantations showed significant spatial differences, which, under tropical rainforests, was more sensitive to seasonal changes than those under rubber plantations. (iv) Structural equation modeling suggested that forest conversion directly impacted soil quality and, indirectly impacted soil qualities' spatial variation by their interaction with soil types and geographical positions. Overall, though the conversion of tropical rainforest to rubber plantation did not decrease all soil properties, the tropical rainforest with its high soil quality should be protected.

Organic Matter Decomposition in River Ecosystems: the Role of Microbial Interactions Regulated by Environmental Factors

Microbes are the critical contributors to the organic matter decomposition (OMD) in river ecosystems. However, the role of microbial interactions on the OMD in river ecosystems and the regulation of environmental factors to the microbial interactions were not considered previously thus tacked in this study. Cotton strip (CS) as a substitute for organic matter was introduced to Luanhe River Basin in China. The results indicated that CS selectively enriched bacterial and fungal groups related to cellulose decomposition, leading to the cotton strip decomposition (CSD). In these groups, bacterial phyla Proteobacteria, fungal phyla Rozellomycota and Ascomycota were the dominant groups associated with the CSD. Bacteria and fungi on CS cooperatively formed a co-occurrence network to achieve the CSD. In the network, the key modules 2 and 4, mainly composed of phyla Proteobacteria and Ascomycota, directly promoted the CSD. Keystone taxa maintained the stability of microbial network structure and function, and regulated microbial groups associated with CSD in the key modules, rather than directly decomposing the CS. Notably, this study profoundly revealed that water temperature and total nitrogen (TN) regulated the keystone taxa and key modules in microbial interactions and then promoted the OMD. The two key modules 2 and 4 were significantly correlated with water temperature and TN in water, and two keystone taxa (bacterial genera Emticicia and Flavihumibacter) were significantly associated with TN. The research findings help us to understand the microbial mechanism of the OMD in rivers, which provides valuable insights into improving effective management strategies for river ecosystems.

Analysis of the Physicochemical Characteristics of Biochar Obtained by Slow Pyrolysis of Nut Shells in a Nitrogen Atmosphere

The process of slow pyrolysis of seven nut shell samples, in a nitrogen-purged atmosphere, has been studied, as well as characteristics of biochar obtained. The heat carrier with a temperature of 400–600 °C (with a step of 100 °C) was supplied indirectly using a double-walled reactor. The heating rate was 60 °C/min. At increased temperature of the heating medium, a decrease in the amount of the resulting carbon residue averaged 6.2 wt%. The release of non-condensable combustible gas-phase compounds CO, CH4, and H2, with maximum concentrations of 12.7, 14.0, and 0.7 vol%, respectively, was registered. The features of the obtained biochar sample conversions were studied using thermal analysis in inert (nitrogen) and oxidative (air) mediums at 10 °C/min heating rate. Kinetic analysis was performed using Coats–Redfern method. Thermal analysis showed that the main weight loss (Δm = 32.8–43.0 wt%) occurs at temperatures ranging between 290 °C and 400 °C, which is due to cellulose decomposition. The maximum carbon content and, hence, heat value were obtained for biochars made from macadamia nut and walnut shells. An increased degree of coalification of the biochar samples affected their reactivity and, in particular, caused an increase in the initial temperature of intense oxidation (on average, by 73 °C). While technical and elemental composition of nut shell samples studied were quite similar, the morphology of obtained biochar was different. The morphology of particles was also observed to change as the heating medium temperature increased, which was expressed in the increased inhomogeneity of particle surface. The activation energy values, for biochar conversion in an inert medium, were found to vary in the range of 10–35 kJ/mol and, in an oxidative medium—50–80 kJ/mol. According to literature data, these values were characteristic for lignin fibers decomposition and oxidation, respectively.

Composition of microorganisms in carbonated mineral waters of the Mukhen deposit (Khabarovsk territory)

The chemical composition, distribution, structure, number of physiological groups of cultivated bacteria and their biodiversity in the cold carbonic mineral waters of Mukhen and in microbial mats were studied. It is shown that the mineral waters are cold, hydrocarbonate-calcium-magnesium, enriched with iron, manganese, barium. Carbon dioxide predominates in the gaseous composition of waters. Microbiological studies have shown that no sanitary-indicative microflora was found in mineral waters, which indicates the purity of underground waters. Carbonic waters were characterized by a low number of physiological groups of autochthonous bacteria. Among the studied microorganisms, chemolithotrophic thionic bacteria predominated, which indicates the predominance of oxidation processes of reduced sulfur compounds with the participation of bacteria in groundwater. In the microbial mats, various chemolithotrophic and heterotrophic microorganisms were identified, participating in the geochemical cycles of carbon, nitrogen, sulfur, iron, manganese, and silicon. The number of physiological groups of bacteria was higher than in mineral waters, along with this saprophytic bacteria predominated significantly. A sufficiently high rate of protein and cellulose decomposition by microorganisms of microbial mats was shown. A low diversity of cultured heterotrophic bacteria with the dominance of microorganisms of the genus Bacillus was found in mineral waters and in microbial mats. By using the methods of X-ray phase analysis, the important role of microorganisms of microbial mats in the precipitation of silicate minerals and the formation of calcium carbonates was shown.

Biological activity of meadow-chernozem and sod-taiga permafrost soils of the Yeravninsky basin

The biological and biochemical parameters of two types of permafrost soils of the Yeravninsky basin (the carbon content of the microbial mass, different groups of microorganisms, protease, catalase and the intensity of cellulose decomposition) were studied, depending on the water-thermal properties and the type of soil formation. It is established that permafrost soils do not have an optimal combination of potential and real (actual) enzymatic activity. It is also noted that the acidic reaction of the soil solution and the low availability of nutrients in sod-taiga soils increases the development of fungal microflora. The most significant soil-ecological factor that determines the microbiological activity of meadow-chernozem and sod-taiga permafrost soils is humidity, as evidenced by a direct correlation. In turn, these microbiological indicators can be used for diagnostic assessment of the biological state of soils, and also, along with other soil properties, should be taken into account when developing methods to increase the productivity of existing hayfields and pastures on them.

Diversity In Intestinal Microorganisms Contributes To The Bodysize Difference In Chinese Horses And Ponies

Background: Intestinal microbiota communities can reflect the digestion and metabolism of the host, as well as the appearance of the host. In China, there are various excellent horse and pony breeds with rich diversity in wither height. However, little is known about the community structure of the intestinal microbiota in horses, let alone the profound effects it causes. Results: Here in, we generated 16S rRNA sequences of intestinal microorganisms from 118 Chinese horses including Guanzhong horse, Debao pony, and Ningqiang pony. We found that the intestinal microbiota of horses is full of diversity, and Firmicutes, Bacteroidetes, and Spirochaetes, which is consistent with the special structure of the horse digestive tract. Interestingly, the abundance of Firmicutes and Bacteroidetes at the phylum level, showed a strong correlation with horse height, with R values of 0.82 and -0.86 respectively. Moreover, at the genus level, Coprococcus, Streptococcus, Treponema, and Prevotella demonstrated higher significance in terms of height, the prediction of PICRUSt2 function and multiple analyses of the metabolic pathways, and additionally, the metabolic pathways of energy intake and utilization were significantly enriched in horses relative to ponies (P<0.01). Notably, flora colonization in mouse littermates contributed to their broad development compared to the control group. Conclusions: Compared with ponies, the intestinal microbiota enabled better cellulose decomposition and energy uptake in horses; Thus horses could get more energy from food to meet their higher demand for larger body development than ponies. Therefore, our study helps to understand the gut microbiota patterns across equine breeds, which has the potential to advance approaches aimed at personalized microbial modifications in horse breeding.

Study on Microbial Community Succession and Functional Analysis during Biodegradation of Mushroom Residue

In this study, 16S rRNA high-throughput sequencing technology was used to analyze the composition and diversity of bacterial and fungal communities in mushroom residue samples at different composting stages. During the composting process, the maximum temperature in the center of the pile can reach 52.4°C, and the temperature above 50°C has been maintained for about 8 days. The results showed that Actinobacteria, Firmicutes, Proteobacteria, Bacteroidetes, and Chloroflexi were the main microorganisms in the composting process, accounting for 98.9%-99.7% of the total bacteria. Furthermore, in order to obtain the protein expressed in each stage of composting, the nonstandard quantitative method (label free) was used to analyze it quantitatively by mass spectrometry, anda total of 22815 proteins were identified. It indicated that the number of identified proteins related to cellulose decomposition and the number of differentially expressed proteins were significantly enriched, and the functional proteins related to cellulose decomposition had significant stage correspondence.