Comparison of Soil Properties, Understory Vegetation Species Diversities and Soil Microbial Diversities between Chinese Fir Plantation and Close-to-Natural Forest

With the continuous increase in plantation areas, the reduction of natural forest areas, and the unreasonable management of plantations by human beings, the service function of forest ecosystems has gradually reduced. Therefore, close-to-natural forestry has become important for the sustainable development of modern forestry. However, the differences in soil properties, enzyme activities, microbial diversities, and undergrowth vegetation species diversities have not been systematically explained for Chinese fir (Cunninghamia lanceolata). How do these indicators interact? The purpose of this paper was to study the difference in soil properties and biodiversity in different aged Chinese fir plantations and close-to-natural forests to explore their interactions and to provide direction for close-to-nature management. The results showed that the above indicators were significantly different in different aged Chinese fir plantations, soil pH, organic matter, total nitrogen, total phosphorus, total potassium, alkali-hydrolyzed nitrogen, available phosphorus concentrations, and urease activities in close-to-natural forests were significantly higher than plantations. It is worth mentioning that the richness of undergrowth vegetation species diversity (especially shrubs) and soil microbial diversities (especially fungi) in the close-to-natural forests were obviously higher than those in plantations. The correlation analysis results showed that the diversity of shrub species with respect to soil properties presented a higher correlation than herb species, the diversity of fungi with respect to soil properties presented a higher correlation than that observed for bacteria, and the diversity of fungi were significantly correlated with the diversity of undergrowth vegetation species diversities, but the correlation between bacteria and undergrowth vegetation species diversities was not significant. Our results suggest that the above factors are fundamental factors for the transformation of Chinese fir plantations to close-to-natural forests. To realize close-to-natural forestry, we must change the tree structure, combine the difference of those factors in different aged plantations, restore undergrowth vegetation species diversity, and thus improve microbial diversity and increase decomposition, transformation, and improvement of soil properties.

Effects of the dietary grain content on rumen and fecal microbiota of dairy cows

Six non-lactating Holstein dairy cows received diets with forage to grain mixture ratios of 100:0 (G0), 75:25 (G25), and 50:50 (G50) that contained 0.5, 10.0, and 19.5 % DM of starch, respectively. Rumen fluid and feces were sampled and methane emissions were determined during the last week of 5 wk experimental periods. Taxonomic compositions of microbiota were determined using Illumina s16S rRNA sequencing. Increased grain feeding increased the acidity and VFA concentrations of rumen fluid and feces, and decreased methane emissions expressed as L/kg DM. Microbial diversities were highest for G25. The numbers of identified genera in rumen fluid were 185, 182, and 171 for G0, G25, and G50, respectively. In feces, these numbers were 197, 182, and 171 for these diets respectively. In rumen digesta, 7 genera were correlated positively to G0 and negatively to G50, and 6 genera were correlated negatively to G0 and positively to G50. In feces, 16 genera were correlated positively to G0 and negatively to G50, and 13 genera were correlated negatively to G0 and positively to G50. Increasing grain feeding affected a limited number of genera in rumen digesta and feces. This could not explain treatment effects on the functionalities of microbiota.

Effects of Dietary Protein Levels on Bamei Pig Intestinal Colony Compositional Traits

Diets containing different crude protein levels (16%, 14%, and 12%) were created to feed Bamei pigs in order to study the effect of these compositions on intestinal colonies. Therefore, 27 healthy Bamei pigs of similar weight ( 20.99 kg ± 0.16 kg ) were selected and randomly divided into three groups for microbial diversity analysis. The results of this study show that microbial diversities and abundances in Bamei pig jejunum and caecum samples after feeding with different dietary protein levels were significantly different. Dietary crude protein level exerted no significant effect on the Shannon index for cecum microbes in these pigs, while Simpson, ACE, and Chao1 indices for group I were all significantly higher than those of either the control group or group II ( P < 0.05 ). Indeed, data show that microbial diversities and abundances in the 14% protein level group were higher than those in either the 16% or 12% groups. Dominant bacteria present in jejunum and cecum samples given low-protein diets were members of the phyla Firmicutes and Bacteroidetes. Data show that as dietary crude protein level decreases, representatives of the microbial flora genus Lactobacillus in jejunum and cecum samples gradually increases. Values for the KEGG functional prediction of microbial flora at different dietary protein levels also show that genes of jejunum and cecum microorganisms were mainly enriched in the “metabolism” pathway and indicate that low protein diets increase intestinal metabolic activity. Therefore, we recommend that Bamei pig dietary protein levels are reduced 2% from their existing level of 16% crude protein. We also suggest that essential synthetic amino acids (AA) are added to optimize this ideal protein model as this will increase intestinal flora diversity in these pigs and enhance health. These changes will have a positive effect in promoting the healthy growth of Bamei pigs.

Anaerobic digestion of dairy manure in a fixed bed CSTR: Methane production performance and microbial diversity

To improve the fixed bed and continuous stirred-tank reactor (CSTR) technology relative to the rate of treatment of dairy manure (DM), a continuous stirred tank-treated DM with immobilized carrier biofilm was investigated for 20 days (hydraulic retention time (HRT) was 10 d). Methane productivity, biofilm characteristics, and microbial diversities of the biofilm and digestate were measured. The highest content of extracellular polymeric substances (EPS), proteins, and polysaccharides occurred at 15 days of digestion. An agglomeration phenomenon was observed using a scanning electron microscope on the biofilm. This indicated that the biofilm consisting of EPS was stable during the second HRT. Microbial diversities in digestate and carrier biofilm were characterized using a 16S rRNA sequencing technique. Results showed that the dominant bacterial communities were Pseudomonas (17% to 26%), Clostridium (13% to 21%), and Bacteroidetes (7% to 16%), while the archaea communities were Methanocorpusculum (25% to 37%), Methanosarcina (15% to 33%), Methanoculleus (11% to 15%), and Methanosaeta (13% to 18%). The methane production rate was significantly correlated with bacterial communities (Pseudomonas, Clostridium, Altererythrobacter atlanticus), archaeal communities (Methanosarcina, Methanoculleus, Methanosaeta, and Methanoplanus), and biofilm characteristics (chemical oxygen demand (COD) and EPS). These findings showed that a carrier biofilm could efficiently increase methane production.

The soil bacterial and fungal diversity were determined by the stoichiometric ratios of litter inputs: evidence from a constructed wetland

Plant litter is an important component in wetland ecosystems, and the role of plant litter decomposition is considered to be important for wetland ecosystem functions and services. However, the consequences of litter inputs have seldom been experimentally tested in real ecosystems such as constructed wetlands (CWs). The enriched nutrients in CWs might weaken the role of litter inputs on soil carbon and nitrogen cycling. Here, we conducted a two-month field experiment to examine the effects of litter inputs on the soils in CWs. Our results showed that litter inputs significantly affected soil microbial (bacterial and fungi) diversities and properties (soil total nitrogen and nitrogen isotopes), and litter species with higher stoichiometry ratios, i.e. C/N, C/P and N/P led to higher microbial diversities. However, litter species had no or weak effects on microbial activities (CO2 and CH4 flux) or on the relative abundance of microbial communities, indicating that other environmental factors in such a CW might have stronger effects on those factors than litter inputs. These results highlighted the importance of submerged plant litter in nutrient-rich wetland ecosystems and provide potential tools for managers to improve the ecosystem functions and/or services via altering microbial diversities.