Varying characteristics of soil seed banks during the succession process of Nitraria Tangutorum vegetation in an arid desert area.

Specific leaf area(SLA, leaf area per unit dry mass) and Leaf dry matter content(LDMC, the ratio of leaf dry mass to fresh mass) as important variables in plant ecology, scientists research leaves traits mainly by the SLA and LDMC because they are associated with many critical aspects of plant growth and surviva1in different environment and they are can be simple measured. In this paper, the typical plants Nitraria tangutorum leaves was chosen as research materials, and according to years average precipitation of Dengkou and plant growth regulation, designed the two precipitation enhancement period (May to July, August to September) , each precipitation enhancement period set two rain enhancement gradients (72.5mm / year (50%) , 145mm / years (100%)) , conducted the artificial simulation of precipitation enhancement to natural Nitraria tangutorum shrubs. We examined changes of SLA and LDMC of Nitraria tangutorum leaves during growing season in 2012 and 2013. The results showed that the artificially simulated precipitation (B / C / D / E treatment) added SLA and LDMC of Nitraria tangutorum leaves, at the same simulated precipitation period, effect of SLA and LDMC in 100% treatment was greater than 50% treatment, however, there was no significant difference between tow treatments in the same simulated precipitation period; SLA response to simulated precipitation in the early stage of the growing season was obviously, on the contrary, LDMC was sensitive to simulated precipitation in the late stage of the growing season. The same

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Low鄄covered vegetation is one of typical vegetation patterns in arid and semi鄄arid areas of China through a long term nature succession. These vegetation types consist of a lot natural sparse woodland and shrubbery, the sandland is under semi鄄shifting and semi鄄fixing. However, we found that at low vegetation coverage, the horizontal distribution pattern of trees and shrubs can have marked effects on fixation of shifting sands, and different horizontal distribution patterns have the different restoration degrees of the soil and vegetation. In this paper, for clarify impacts of low鄄covered sand fixing forest belts on natural vegetation restoration and soil development, the variation and rule of soil nutrients and vegetation with different distribution patterns were researched in Aohan, Chifeng City, Inner Mongolia. The characteristics of community and structure, the physical and chemical characteristics of soil, the amount of soil microbes in different distribution patterns were investigated. The data obtained from the experiment were analyzed with the principal components, the canonical correlation and fuzzy comprehensive evaluation, which obtain coefficient of different recovery scale. Results show: Belt

Our previous research showed an increasing trend of rainfall in a temperate arid region of China. In this study, to address potential effects of additional rain on carbon emissions of an arid ecosystem, we conducted a field manipulative experiment with five simulated rain addition treatments ( four rain addition treatments and one for comparison ) . Each treatment included four repetitive plots, each with an area of approximately 113 m 2 , in Dun Huang, Gansu. The design simulated rain increases of 0% ( CK) , 50% , 100% , 200% and 300% of the long鄄term average annual precipitation (40 mm) at the study site. We used the Li鄄8100 automated soil CO 2 flux system in a Nitraria sphaerocarpa community during the growing season, from May to September 2010. Our results showed a linear positive correlation in soil carbon emissions between 09:00-11:00 and 24:00 hours for vegetated and bare soil ( bare soil R 2 = 0. 31-0. 76, P < 0郾 001; vegetated soil R 2 = 0. 85-0. 96, P<0. 001) . The rain increases accelerated vegetated and bare soil respiration in the plots. Compared with the control group, soil carbon emissions of bare soil increased by 8. 83, 11. 03, 26. 64, 31. 69 g / m 2 ,and the emissions of vegetated soil increased by 30. 02, 45. 34, 98. 08, 133. 90 g / m 2 with the 0% ( CK) , 50% , 100% , 200% and 300% treatments, respectively. Soil carbon emissions of vegetated soil were three times greater than those of bare soil during the growing season, which was statistically significant. There was a significant linear correlation between soil carbon emissions and precipitation during the growing season, in both bare soil and vegetated soil. With a 1 mm increase in rainfall, soil carbon emissions in vegetated and bare soils increased 1. 12 g / m 2 and 0. 27 g / m 2 , respectively. With a given community cover, every 1 mm rainfall increase produced an additional 0. 69 g / m 2 of soil carbon