Effects of soil fauna on litter decomposition in Chinese forests: a meta-analysis

Litter quality and climate have been presumed to be the dominant factors regulating litter decomposition rates on broad spatial scales. However, the role of soil fauna on litter decomposition is poorly understood, despite the fact that it could strongly influence decomposition by fragmentation and subsequent modification of the activities of microorganisms.In this study, we carried out a meta-analysis on the effects of soil fauna on litter decomposition rates in Chinese forests, ranging from boreal to tropical forests, based on data from 20 studies. The effects of climatic factors on decomposition rate were assessed by comparing the contribution of soil fauna to litter decomposition from studies carried out at different latitudes.The degree of influence of the soil fauna was in the order tropical (200%) > subtropical (47%) > temperate forest (28%). Comparing the effect size of soil fauna, it was found that when soil fauna was excluded, the decomposition rate, calculated using Olson’s equation, was most affected in tropical forest (−0.77), while the litter decomposition rate both subtropical (−0.36) and temperate forest (−0.19) were also suppressed to varying degrees (P < 0.001). These results highlight that soil fauna could promote litter decomposition to different extents. Using stepwise multiple linear regression, the effect size of the soil fauna was negatively correlated with the cellulose and nitrogen concentrations of the initial litter material. In Chinese forests, litter decomposition rates were reduced, on average, by 65% when soil fauna was excluded. The impact of soil fauna on decomposition was shown to be closely related to climate and litter quality.

Evidence of sodium limitation in ants and termites in a Neotropical savanna

Nutritional ecology of ropical ecosystems like Neotropical savannas, which are of high conservation concern, is understudied. Sodium is essential for heterotrophs but availability often falls short relative to plant consumer requirements. Savanna plant consumers like ants and termites should be sodium-limited due to high temperatures, nutrient-poor soils, and lack of oceanic sodium deposition. We tested the hypothesis that Neotropical savanna ants and termites are sodium-limited. Termites were tested by supplementing 0.25 m2 plots with H2O (control), 0.1%, 0.5%, or 1.0% NaCl and measuring termite presence and artificial substrate mass loss after 1 week. Ants were tested by collecting ants that recruited to H2O (control), 0.1%, 0.5%, and 1.0% NaCl and 1.0%, 10%, and 20% sugar baits on paired diurnal–nocturnal transects. Termites were 16 times more likely to occur on 1% NaCl than H2O plots and wood-feeding termites were most frequent. However, the decomposition rate did not differ among treatments. Ant bait use increased with increasing NaCl concentration and 1% NaCl usage was similar to sugar bait usage. Ants were 3.7 times more active nocturnally than diurnally, but contrary to predictions bait type (water, sugar or NaCl) usage did not differ between day and night. Together, these results provide strong evidence of sodium limitation in Neotropical savannas.

How do visible and UV light affect the structure and function of leaf-associated aquatic fungal communities polluted by TiO2 nanoparticles?

We assessed the phototoxicity of TiO2 nanoparticles on fungal structure and function. The fungal diversity was reduced by long-term exposure. However, the leaf decomposition rate was not inhibited rather than promoted under natural photoperiod.

Decomposition Rate of Avicennia lanata in Bakau Kecil Mangrove Forest Area, Mempawah District

Avicenna lanata is a type of mangrove that dominates the Mempawah Kecil Mangrove Forest. As many as 10 bacterial genera were identified from station 1 which is close to the influence of sea water, and 8 bacterial genera from station 2 which are close to residential areas. This study aims to determine the rate of decomposition of A. lanata leaf litter with 4 observation time periods with an interval of 15 days, namely the 15th, 30th, 45th and 60th days. The observations show that the rate of decomposition of the litter on the 15th day of observation is higher. Namely 0.206 gram/day at station I and 0.19 gram/day at station II, while the lowest rate of decomposition of litter occurred on the 60th day of observation, namely 0.112 gram/day at station I and 0.106 gram/day at station II. In addition, the parameters of physical and chemical of the environment such as DO, temperature, pH and salinity are in the range of their optimum values.

Effect of Metal Sequestrants on the Decomposition of Hydroxylammonium Nitrate

Hydroxylammonium nitrate (HAN) is an energetic salt used in flight-proven green monopropellants such as ASCENT (formerly AF-M315E), flown in NASA’s 2019 Green Propellant Infusion Mission, and SHP163, flown in JAXA’s Rapid Innovative Satellite Technology Demonstration-1. The decomposition of HAN is catalyzed by metals commonly found in storage tanks, a factor limiting its use. This work investigates the ability of metal-sequestering chelating agents to inhibit the decomposition of HAN. Isothermal and dynamic thermogravimetric analysis (TGA) were used to find isothermal decomposition rates, decomposition onset temperatures, and first-order Arrhenius reaction rate parameters. In the present research, 2,2′-bipyridine (Bipy), triethanolamine (TEA), and ethylenediaminetetraacetic acid (EDTA) were studied as 0.05, 0.1, 0.5, 1, and 5% by weight additives in 90% aqueous HAN. An isothermal decomposition rate of 0.137%/h at 348 K was observed for HAN. The addition of 1% Bipy and 1% TEA reduced the isothermal decomposition rate by 20.4% to 0.109%/h, and by 3.65% to 0.132%/h, respectively, showing that Bipy can inhibit decomposition. The addition of 1% EDTA increased the isothermal decomposition rate by 12.4% to 0.154%/h. Bipy was found to increase the decomposition onset temperature from 454.8 K to 461.8 K, while the results for TEA and EDTA were inconclusive. First order reaction rates calculated by the Ozawa-Flynn-Wall method were found to be insufficient to capture the effects of the tested additives. Bipy was found to inhibit the decomposition of HAN, while TEA and EDTA produced little or negative effect, a result believed to be due to poor metal complex stability at low pH and high acidity, respectively. Spectrophotometry, used for colorimetric analysis of Bipy+iron complexes, showed that Bipy forms chelate complexes with trace iron impurities when added to HAN solutions.

Impact of Tree Litter Identity, Litter Diversity and Habitat Quality on Litter Decomposition Rates in Tropical Moist Evergreen Forest.

Background: Attempts to restore degraded highlands by tree planting are common in East Africa. However, up till now, little attention has been given to effects of tree species choice on litter decomposition and nutrient recycling. Method: In this study, three indigenous and two exotic tree species were selected for a litter decomposition study. The objective was to identify optimal tree species combinations and tree diversity levels for the restoration of degraded land via enhanced litter turnover. Litterbags were installed in June 2019 into potential restoration sites (disturbed natural forest and forest plantation) and compared to intact natural forest. The tested tree leaf litters included five monospecific litters, ten mixtures of three species and one mixture of five species. Standard green and rooibos tea were used for comparison. A total of 1033 litters were retrieved for weight loss analysis after one, three, six, and twelve months of incubation. Results: The finding indicates a significant effect of both litter quality and litter diversity on litter decomposition. The nitrogen-fixing native tree Millettia ferruginea showed a comparable decomposition rate as the fast decomposing green tea. The exotic conifer Cupressus lusitanica and the native recalcitrant Syzygium guineense have even a lower decomposition rate than the slowly decomposing rooibos tea. A significant correlation was observed between litter mass loss and initial leaf litter chemical composition. Moreover, we found positive non-additive effects for litter mixtures including nutrient-rich and negative non-additive effects for litter mixtures including poor leaf litters respectively. Conclusion: These findings suggest that both litter quality and litter diversity play an important role in decomposition processes and therefore in the restoration of degraded tropical moist evergreen forest.

Biomass Estimation, Nutrient Content, and Decomposition Rate of Shoot Sheath in Moso Bamboo Forest of Yixing Forest Farm, China

The biomass, nutrient content and decomposition rate of shoot sheaths remain unexplored in the study of Moso bamboo forests. The rapid growth of shoots means many bamboo sheaths are produced each year, and therefore should not be neglected in the study of the Moso bamboo ecosystem. In our study, we selected 160 bamboo shoots of different sizes in Yixing forest farm, Jiangsu Province. Our analysis was based on the allometric growth equation, using diameter at breast height (DBH), internode length of bamboo at breast height (IL), and bamboo height (H) as independent variables to establish the biomass model of shoot sheaths using all samples. In addition, we also measured the nutrient content of shoots and estimated the decomposition rate of shoots by setting up litter decomposition bags. Our results found that logarithmic regression should be used to fit the biomass model of shoot sheaths. From the perspective of practical application, model W3 fitting DBH and IL was determined. The order of the nutrient elements in the shoot sheath is C > N > K > P. Decomposition tests showed that it took 0.47 years for 50% of sheaths to decompose, and 3.15 years for all sheaths to decompose.

Effects of C/N Ratio on Lignocellulose Degradation and Enzyme Activities in Aerobic Composting

Lignocellulosic materials have a complex physicochemical composition and structure that reduces their decomposition rate and hinders the formation of humic substances during composting. Therefore, a composting experiment was conducted to evaluate the effects of different C/N ratios on lignocellulose (cellulose, hemicellulose and lignin) degradation and the activities of corresponding enzymes during aerobic composting. The study had five C/N ratios, namely, T1 (C/N ratio of 15), T2 (C/N ratio of 20), T3 (C/N ratio of 25), T4 (C/N ratio of 30) and T5 (C/N ratio of 35). The results showed that treatments T3 and T4 had the highest rate of degradation of cellulose and hemicellulose, while treatment T3 had the highest rate of degradation of lignin. Among the five treatments, treatment T3 enhanced the degradation of the lignocellulose constituents, indicating a degradation rate of 6.86–35.17%, 15.63–44.08% and 31.69–165.60% for cellulose, hemicellulose and lignin, respectively. The degradation of cellulose and lignin occurred mainly at the thermophilic and late mesophilic phases of composting, while hemicellulose degradation occurred at the maturation phase. Treatment T3 was the best C/N ratio to stimulate the activities of manganese peroxidase, lignin peroxidase, polyphenol oxidase and peroxidase, which in turn promoted lignocellulose degradation.