Conversion of Natural Ecosystems to Cropland Increases the Soil Net Nitrogen Mineralization and Nitrification in Tibet

A comparative study was conducted to determine the NH4+ and NO3- concentrations in soil profiles and to examine the net nitrogen (N) mineralization and nitrification in adjacent forest, grassland, and cropland soils on the Tibetan Plateau. Cropland soil showed significantly higher inorganic N concentrations in soil profiles compared with forest and grassland soils. NO3- -N accounted for 70%–90% of inorganic N in cropland soil, while NH4+ -N was the main form of inorganic N in forest and grassland soils. The average net N mineralization rate at 0–20 cm depth was approximately twice in cropland soil (1.48 mg kg-1 d-1) as high as in forest (0.83 mg kg-1 d-1) or grassland soil (0.72 mg kg-1 d-1). Cropland showed strong net nitrification, with the net rate almost equal to the total net N mineralization. Urea addition stimulated soil respiration, particularly in forest soil. Most urea-N, however, remained as NH4+ in forest and grassland soils, while NO3- was the main form of inorganic N to increase in cropland soil. Higher rates of net nitrification in cropland soils suggest that land use change on the Tibetan Plateau may lead to high N losses through nitrate leaching.

Expression of HIF-1α and Its Target Genes in the Nanorana parkeri Heart：Implications for High Altitude Adaptation

Hypoxia-inducible factor 1 alpha（HIF-1α） and its target genes vascular endothelial growth factor（VEGF） and transferrins（TF） play an important role in native endothermic animals＇ adaptation to the high altitude environments. For ectothermic animals – especially frogs – it remains undetermined whether HIF-1α and its target genes（VEGF and TF） play an important role in high altitude adaptation, too. In this study, we compared the gene sequences and expression of HIF-1α and its target genes（VEGF and TF） between three Nanorana parkeri populations from different altitudes（3008 m a.s.l., 3440 m a.s.l. and 4312 m a.s.l.）. We observed that the c DNA sequences of HIF-1A exhibited high sequence similarity（99.38%） among the three altitudinally separated populations; but with increasing altitude, the expression of HIF-1A and its target genes（VEGF and TF） increased significantly. These results indicate that HIF-1α plays an important role in N. parkeri adaptation to the high altitude, similar to its role in endothermic animals.

The Expression Plasticity of Hypoxia Related Genes in High-Altitude and Plains Nanorana parkeri Populations

For species that have a broad geographic distribution, adaptive variation may be attributable to gene expression plasticity. Nanorana parkeri is an anuran endemic to the southern Tibetan Plateau where it has an extensive altitudinal range（2850 to 5100 m asl）. Low oxygen concentration is one of the main environmental characteristics of the Tibetan Plateau. Hypoxia-inducible factor α subunits（HIF-1α and HIF-2α, encoded by Endothelial PAS domain protein 1（EPAS1）） and associated genes（e.g., vascular endothelial growth factor（VEGF） and Erythropoietin（EPO）） play crucial roles in maintaining oxygen homeostasis. In this study, we compared the expression of HIF-1A, VEGF, EPAS1 and EPO mRNA between two populations of N. parkeri： one population inhabiting the native high altitudes, and the second living in, and being acclimated to, the lower plains（70 m asl）. The expression of HIF-1A, VEGF and EPAS1 mRNA in the high altitude population were significantly higher than in the acclimated population, whereas there was no significant difference for EPO between two groups. Our results indicated that gene expression plasticity may make significant contributions to local adaptation of species that have broad altitudinal distributions. In addition, we deepen our understanding of the adaptive potential of this species by evaluating the experiments in the scope of its evolutionary history.

Rise and Prospects of Ecological Civilization

In recent decades, with the constant progress of society, the study of ecological civilization has attracted extensive attention of scholars at home and abroad, and more in-depth research on its theory and application has been conducted. In this paper, the historical background, theoretical and realistic bases of ecological civilization were analyzed, showing that the birth and development of ecological civilization is inseparable from the historical development of human society. Then the development prospects and application fields of ecological civilization were discussed further.

Study of the Amount of Forest Litter and Litter Decomposition

Based on the introduction of concept of forest litter, changes in the amount of forest litter with climate zone, elevation, forest type and age of stand were analyzed, and then the decomposition of forest litter was discussed.

Ecosystem Health and Its Evaluation

Firstly, the connotations and influencing factors of ecosystem health are discussed, and then the assessment principle, evaluation stand- ard and evaluation method of ecosystem health and the establishment and measurement of ecosystem health indicators are studied. Through the study of its connotation and evaluation, feasible measures to effectively promote the development of ecosystem health are put forward finally.

Control Approaches to Soil Pollution from Heavy Metals

With the continuous development of human society and economy and the continuous progress of industrial technology,more and more pollutants are discharged into the natural environment,and soil environment is also affected at the same time. Among pollutants leading to soil pollution,heavy metals have resulted in most serious soil pollution. Here,many control and restoration approaches to soil pollution from heavy metals are proposed,and characteristics and applicable conditions of various methods are compared,so as to provide theoretical references for the control and restoration of soil pollution from heavy metals in future.