BACTERIAL COMMUNITY SUCCESSION AND INFLUENCING FACTORS OF IMPERATA CYLINDRICA LITTER DECOMPOSITION IN A DEGRADED COPPER TAILINGS DAM OF CHINA

Litter decomposition is a critical component of the ecological nutritional transformation process. It is particularly important to investigate characteristics and interactions of bacterial communities in litter decomposition in heavy metal polluted degrade areas, which will help clarify driving mechanisms of organic matter and nutrient cycling in mining areas that harbor contaminated soil. Imperata cylindrical was the dominant plant species in the degrade area investigated; thus, we selected this species as research object. Here we explore bacterial community characteristics and key microbial groups as well as driving factors of litter decomposition using in-situ litter decomposition experiments. The nutrient content of I. cylindrica decreased, while the litter pH status increased as decomposition progressed in one of the three sub-dams investigated (i.e., S516). Proteobacteria and Actinobacteriota were the dominant bacterial phyla during the different litter decomposition stages. Moreover, the role of Friedmanniella was critical in sustaining both structure and function of the bacterial community during the early decomposition stage. Quadrisphaera became the dominant species as litter decomposition progressed. Litter properties and enzyme activities both had significant effects on litter bacterial community characteristics, whose driving factors varied during different restoration stages. The bacterial community dynamics of litter were affected primarily by litter properties during the decomposition process. Furthermore, the most crucial factors that impacted bacterial litter structure were pH and copper content. Findings will help to deepen our understanding of litter decomposition mechanisms in degraded ecosystems, while also providing a scientific basis for improving effectiveness of material circulation and nutrient transformation in degrade ecosystems.

In Vitro Evaluation of Hen Eggshells Addition in Rice Husk on Litter Properties

Ammonium (NH3) is released from uric acid of chicken feces. Good management practices are required to depress ammonium concentration in a litter. Several research findings showed that application of CaCO3 (calcium carbonate) can decrease ammonium concentration in a litter. Eggshell as a by-product of hennery (hen stable) and hatchery is mainly constructed from CaCO3. This research aimed to evaluate the addition of hen eggshell powder at different concentration in litter on water content, pH, microorganism, and NH3 concentration of litter. Rice husk as litter material, hen eggshell powder at a concentration of 0%, 5%, 10%, and 15% and hen manure were thoroughly mixed. After 24 hours, the concentration of water content, pH, microorganisms amount and NH3 in each treatment were measured. This research was completely randomized designed with 3 repetitions. Results showed the progressive addition of hen eggshell powder in litter until 15% increased pH and decreased water content, number of microorganisms and NH3 concentration. The addition of 15% hen eggshell powder in litter revealed best litter properties.Keywords: ammonium, hen eggshell, litter, pH, water content

Contribution of Topography and Incident Solar Radiation to Variation of Soil and Plant Litter at an Area with Heterogeneous Terrain

Natural processes that determine soil and plant litter properties are controlled by multiple factors. However, little attention has been given to distinguishing the effects of environmental factors from the effects of spatial structure of the area on the distribution of soil and litter properties in tropical ecosystems covering heterogeneous topographies. The aim of this study was to assess patterns of soil and litter variation in a tropical area that intercepts different levels of solar radiation throughout the year since its topography has slopes predominantly facing opposing geographic directions. Soil data (pH, C, N, P, H+Al, Ca, Mg, K, Al, Na, sand, and silt) and plant litter data (N, K, Ca, P, and Mg) were gathered together with the geographic coordinates (to model the spatial structure) of 40 sampling units established at two sites composed of slopes predominantly facing northwest and southeast (20 units each). Soil and litter chemical properties varied more among slopes within similar geographic orientations than between the slopes facing opposing directions. Both the incident solar radiation and the spatial structure of the area were relevant in explaining the patterns detected in variation of soil and plant litter. Individual contributions of incident solar radiation to explain the variation in the properties evaluated suggested that this and other environmental factors may play a particularly relevant role in determining soil and plant litter distribution in tropical areas with heterogeneous topography. Furthermore, this study corroborates that the spatial structure of the area also plays an important role in the distribution of soil and litter within this type of landscape, which appears to be consistent with the action of water movement mechanisms in such areas.