Soil Biological Response In Typical Forestry Land Of Qinling Mountain

Litter, largely produced in the forest, is the important soil nutrient source, especially for the soil carbon. The forest soil carbon change would affect the entire terrestrial ecosystem carbon balance, lead to the greenhourse effect and climate warming, finally impede the development of human beings. The study about soil enzymes change in Qinling typical soil will play an important role in understanding the forest system function, protecting and reasonably utilizing forest resources. Therefore, in our study, typical type of forest in Qinling region was chosen as the target sampling zone, including three conifers(chinese pine, armand pine, spruce) and two broadleaf(tooth oak 1, tooth oak 2). Outdoor and lab simulation experiments of carbon decay were respectively carried out to explore the change of soil basic physical and chemical properties, easily oxidized carbon(EOC), soil enzyme and soil microbial biomass. The results are listed in the following:1. The labile organic carbon(LOC) showed an irregular change with the seasonal variation. This is owe to the multiple impact factors in the labile organic change, including temperature, light, rainfall and the vegetation chemical composition in forest. Both EOC and LOC content in the O layer(humus layer) is greater than A layer(0-10 cm), due to the more litter in the O layer, which containing more abundant microbes and nutrients accumulated during the litter decomposition and mineralization. More specifically, in the O layer, the EOC and LOC content change is consistent, which is shown that the needles(chinese pine, armand pine, spruce) are greater than broadleaf(tooth oak 1, tooth oak 2). It might be determined by the needles feature, which has lignification cell and thicker cuticle(insect and water resistant),leading to the slow decomposition. Moreover, the EOC and LOC contents are higher in summer than that in spring because of the stronger rainfall in summer benefit to the litter decomposition.2. The soil enzyme activity in O layer is significantly higher than that in A layer. The results showed that the same soil enzyme activity is differential among different type of forest,which indicated that soil enzyme activity is strongly affected by vegetation type. Moreover, in A layer, soil sucrase, cellulose, and alkaline phosphatase showed the highest activity in summer. While, amylase, urease, protease, and dehydrogenase showed the highest activity in spring. For acid phosphatase, the highest activity is shown in different season with differentforest type(summer, in broad-leaved forest; autumn, in pinus tabulaeformis forest; spring, in Pinus armandi and spruce forest). This indicated that there is difference in soil enzyme response to temperature change. Thus, soil enzyme showed the different change in various forests and seasons.3. Soil microbial biomass, determined by the soil microbes amount, is the indicator of soil nutrient cycle and fertility and showed the seasonal change characteristics. The results showed that soil microbial biomass carbon(MBC) has the greatest content in autumn in O layer and in summer in A layer. Compared with needle leaved forest, MBC is higher in broad-leaved forest in O layer, while the contrast result is shown in A layer. Soil microbial biomass nitrogen(MBN) in O layer and A layer have the similar changes, which showed the highest content in summer. In needle leaved forest, MBN content is more stable compared with broad-leaved forest. For microbial biomass phosphorus, it showed irregular change in different forests and seasons. Based on the comprehensive comparison of three indicators, it is concluded that the highest microbial activity and soil fertility are shown in the tooth oak 2 in O layer and spruce in A layer.4. The broad-leaved forest(tooth oak) had the higher decomposition rate than needles(chinese pine). The addition of urea(to adjust the C:N ratio) could increase MBN, however,had no effect on soil organic carbon and MBC. In other words, it is said that urea addition could not enhance the decay of chinese pine and not improve the soil carbon storage. During the process of sharp tooth oak decay, the carbon release ability increased with the addition of leaves, while, there is no incensement for chinese pine decay. In the lower amount leaves addition in chinese pine decay, the adjustion of C:N ratio could enhance the decomposition.5. Chinese pine(the representative needles) and sharp tooth oak(the representative broad-leaved forest) are both typical forest in Qingling region. The comprehensive results of soil enzyme and carbon change in the decay of two forests showed that acidic phosphatase is most sensitive to carbon changes. Different soil enzymes have various changes in litter decay.Therefore, the specific regular exists in specific soil enzyme in the specific litter decomposition, which might be relevant to litter chemical composition. Shortly, soil enzyme could show higher activity when the decomposition occurred at 7 d and 30 d.