Hua Yong Zhang

Morphological Responses, Biomass Yield, and Bioenergy Potential of Sweet Sorghum Cultivated in Cadmium-Contaminated Soil for Biofuel

This study was performed to assess morphological responses, biomass yield and bioenergy potential during the entire growth period (167 days) of sweet sorghum with different Cd stress, i.e. 0, 1, 5, 10, 30, 50, and 100 mg/kg in pot experiments. The results showed that the morphological characteristics of sweet sorghum, i.e. shoot length, leaf length and leaf numbers were not significantly changed with the Cd concentration ≤ 5 mg/kg in the soil. The aerial biomass of sweet sorghum treated by 10 mg/kg Cd was 82.71% of the control test, and was reduced to 70.67% when the Cd concentration in the soil was increased to 30 mg/kg. The root was the main location site of Cd in the sweet sorghum, thus the reutilization of the aerial biomass would not be seriously influenced. The predicted ethanol yields was 3.65, 3.05, 3.14, 2.69, 1.15, and 0.41 t/y/hm2 for 1, 5, 10, 30, 50, and 100 mg/kg Cd concentration, respectively. Due to its high biomass production and Cd accumulation capacity, sweet sorghum is a good candidate for bio-energy production in Cd-contaminated (<30 mg/kg) soil.

Photosynthetic Responses of Energy Plant Maize under Cadmium Contamination Stress

Cadmium’s (Cd) impact on the photosynthetic activities of energy plant maize was investigated in pot experiments containing different Cd contaminated levels during the whole growth period. The results showed that the ability of photosynthesis was not obviously inhibited by elevated Cd stress. Net photosynthetic rate (NPR) was decreased with the growth of maize, while transpiration rate (TR), stomatal conductance (gs>) and intercellular CO2 concentration (Ci) were enhanced in heading period, then decreased in maturity period. The change of fluorescence quenching and photosystem II (PSII) efficiency was consistent with NPR. Thus, the influence of photosynthesis under Cd stress mainly depended on the response of PSII reaction centre.

Dynamics on the Interaction between Vegetation Growth and Aeolian Dust Deposition

From the holistic perspective, a new dynamic model is proposed in this research to investigate the interaction between vegetation growth and aeolian dust deposition. Three cases of equilibrium distribution can be obtained and the stability of interior equilibriums is determined. When there is a stable interior equilibrium, a critical curve exists and separates the coexistent area where vegetation can survive in the environment of aeolian dust deposition, from the other area where vegetation is to be excluded. Simulation analysis further reveals the variation of the critical curve with the parameters and the anthropic influences. The critical curve and the coexistent equilibrium described by the model may be used as a theoretical basis to evaluate the feasibility of vegetation restoration in the environment of aeolian dust deposition.

Cadmium Stress on Wheat Morphology: Germination and Growth

In this study, the morphological responses of wheat to Cd during the whole growth stage were investigated in pot experiment with substrates containing 0, 1, 5, 10, 50 and 100 mg Cd/kg soil. The results showed that wheat was moderately tolerant to Cd stress, and the most sensitive endpoint to Cd toxicity was tiller number. The seed germination was not effected by Cd at all concentrations. The No Observed Adverse Effect Concentration (NOAEC) was 10 mg Cd/kg, and the Low Observed Adverse Effect Concentration (LOAEC) was 50 mg Cd/kg for the wheat.

Irregular Striped Vegetation Patterns in Arid and Semiarid Regions Resulted from Oscillatory Instability

Striped vegetation pattern formation in arid and semiarid regions has attracted many researchers in ecological field. In this research, we modify the classical Klausmeier model and study nonlinear mechanism of oscillatory instability which can also possibly lead to pattern formation in ecological systems. Via simulation, irregular striped vegetation patterns are numerically obtained for the modified model. From the mechanism of oscillatory instability, this research provides a theoretical explanation for the formation of irregular striped vegetation patterns in nature.

The Carbon Sequestration of Oak Forests in Shanxi Province, China

Oak forest is one of the most crucial zonal forests in Shanxi Province, China. A precise estimation of its carbon sequestration is of great value to the construction of regional carbon budgets. In this study, field measurement data from 47 oak forest stands and the 8th forest inventory data of Shanxi Province have been collected. Using the field measurement data, the relationship between stand volume and biomass is established with an accuracy test. By applying the relationship and a specific carbon concentration coefficient to the forest inventory data, the carbon sequestration of oak forests in Shanxi Province is estimated. The results show that the total carbon sequestration of the local oak forests is 16.19 × 106 t. Among the forests in different age classes, the mid-aged and premature forests are acting as the major carbon sink, with their carbon sequestration accounting for 28.2% and 44.2% of the total amount respectively.

Effects of Nutrient Enrichment on a Realistic Food Web

Nutrients supplies play a crucial role in population distribution of food webs, and it is one of the most important challenges in both theoretical and applied ecology to better understand the ‘bottom-up’ effect. Here we analyzed a realistic food web containing one limiting nutrient and two producer-consumer interactions. Through the simulations of the mean population size and the variability of each species, we found that 1) in infertile environment the coexistence of species increases with nutrient supply; 2) the mean values of species abundance increase dramatically at then remain constant with the increase of nutrient supply; and 3) the stability of each population also increases and then remains constant. These results are inconsistent with the traditional predictions known as the ‘paradox of enrichment’, and our analysis may provide a solution to this paradox.

The Study of Thermodynamics on the Development of Ecosystem

The study of the development of ecosystem is a very important problem in ecology. With the development of ecology, the study of ecosystem is gradually from description of natural phenomena to the understanding of mechanism of ecosystem development. Thermodynamics is full of highly scientific and universal theory, and thereby thermodynamic theories can provide the foundations for understanding ecosystem development rule. In this paper, we review the application and development of thermodynamic theories for the development of ecosystem. The limitations and future developments of these theories are also addressed.

A Study on Bacterioplankton Community Composition in a Nature Reservoir

The relationship between bacterioplankton community composition and environmental factors in a constructed small-scale reservoir was studied. Polymerase chain reaction (PCR) - denaturing gradient gel electrophoresis (DGGE) fingerprinting was used to detect plankton communities. Species composition of the sites was heterogeneous; 60 % of the total species were restricted to single samples and only 2 bands were found in all investigated samples. Clustering analysis illustrated a strong correlation between samples taken from same sites. Canonical correspondence analysis (CCA) results showed that bacterioplankton community composition was primarily correlated with NO3--N and CODCr. Bacterioplankton community composition could reflect the environmental conditions to some extent.

Phosphorus Fractionation in the Sediment of a Natural Lake

Seven typical surface sediments were collected along the flow direction in the hypertrophic Qixinghu lake located in Nansi Lake Basin. The sediments were evaluated on the basis of phosphorus (P) fractionation by sequential extraction scheme. Sedimentary phosphorus were fractioned into six forms (Ex-P, Al-P, Fe-P, BD-P, Ca-P and Org-P) to reveal phosphorus removal mechanism. The rank order according to the content of P-fractions was Ca-P > Org-P > Al-P > Fe-P > Ex-P > BD-P. The permanent Ca-P showed considerable contribution (41.97%-73.15%) to the sedimentary P-loads. The relative contributions of Ex-P to total sedimentary phosphorus (TP) ranged from 0.91% to 4.64%, which was positively correlated with alkaline phosphatase activity (r=0.8480). TP and Org-P were positively correlated with organic matter (OM) (r=0.8577 and r=0.9237, respectively). Total phosphorus concentration in the sediment fluctuated with changes in water quality and substrate characteristics. The high content of sedimentary metal elements and OM are contributed to the phosphorus accumulation and adsorption.