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The Qinghai鄄Tibet Plateau (QTP) is usually regarded as an ideal place to study the response of natural ecosystems to climate change because this mountainous region supports one of the most fragile environments within the global ecosystem. After the QTP experienced a distinct warming in recent decades, scientists have realized that a remarkable variation in vegetation in the QTP could potentially result from climate change. In this paper, the temporal variation of phenology for the alpine Gramineae was analyzed for the dates of the onset of growth in spring, blossoming, and withering from 1988 to 2010 based on the observations from five in鄄situ sites in the northeastern QTP. Additionally, the relationships between temperature or precipitation and the duration of the growth period for alpine Gramineae were investigated using the stepwise regression and partial correlation analysis. Seasonal trends were found to be advancing significantly in the last20 years in the southern QTP, which includes the Three鄄Rivers Source Area for the dates of onset, blossoming and withering of grasses. Specifically, the trendsare-4d / 10a for onset,-13d / 10a for blossoming, and-9 d / 10a for withering in the Qumalai fescue grassland, all of which are statistically significant (P < 0.01) .Additionally, the Haibei Stipa sareptanavar

In order to elucidate the activity and ecological distribution of arbuscular mycorrhizal (AM) fungi in Saibei desert steppe, we sampled soil from three different sites at Erniudian,Shangduzhen and Qinggeletu in Saibei desert steppe in June 2013. Roots of Caragana korshinskii and rhizosphere soil were collected from each site at five depths in the soil profile: 0-10, 10-20, 20-30, 30-40 and 40-50 cm, respectively. The results indicated that C. korshinskii formed strong symbiotic relationship with AM fungi. AM fungal spore density and colonization rates were significantly affected by sampling sites and soil depths. The highest spore density occurred at the 0-10cm layer and gradually decreased with soil depths. Hyphal colonization rate was the highest in samples collected at Shangduzhen among the three sites. However, vesicular colonization was the lowest in samples from Qinggeletu, and there were no significant differences among soil layers. Arbuscular colonization differed among the three sites. Both the total colonization rates and colonization intensity of AM fungi http: / / www.ecologica.cn in root samples from Shangduzhen were the highest compared to the other two sites, respectively. Spore density strongly correlated with soil organic C, total N, easily extractable glomain (EEG) and total extractable glomalin (TG) (all P < 0郾 01) , soil pH (P<0郾 05) , and negatively correlated with available P (P<0郾 01). Hyphal colonization rate had negative correlation with soil pH, available P, total N and acid phosphatase (all P< 0郾 05). Vesicular and arbuscular colonization rates were strongly correlated with available N and alkaline phosphatase (all P<0郾 01). EEG and TG had significant positive correlation with available N, total N, alkaline phosphatase and acid phosphatase (all P<0郾 01) , urease (P < 0郾 05) , but had no significant correlation with available P. Principal component analysis showed that acid and alkaline phosphatase, TG, total N and organic carbon were the key factors affecting soil nutrient status. The average contents of TG and EEG were 3.19 mg / g and 1.17 mg / g accounting for 7.77% and 3.83% of the total soil organic carbon, and 20郾 81% and 9.57% of the total soil nitrogen, respectively. Multiple linear regression analysis showed significant linear correlation between TG or EEG and soil organic C and total N, respectively. The results suggest that AM fungal colonization and glomalin are useful indicators for evaluating soil quality and function of desert ecosystem on the basis of its relationship with AM fungal distribution, soil nutrient dynamics, carbon and nitrogen cycle.

The influence of diversity in agricultural landscapes on pest abundance remains controversial despite several studies on the subject. For example, the ecological role of crop diversity in determining the source鄄sink dynamics of populations of polyphagous Heliothis spp. is complex, and varies at field, farm, region and national scales. Recently, the cropping structures within farms in Xinjiang, China, were adjusted due to changes in market conditions. The effects of these rapid changes in cropping structure at the landscape scale on the dynamics of Helicoverpa armigera have, however, not been well studied. This is particularly so for intensive agriculture in isolated oasis ecosystems, such as the irrigated cropping regions within the deserts of northern Xinjiang. The influence of a mosaic landscape on the population dynamics of H. armigera was measured using light traps in 16-17 farms covering 240 km 2 in 2007-2009. Light traps were placed in clusters on commercial farms which varied in the relative amounts of cotton, tomatoes, sugar beet, corn and wheat that they grew. Moths were collected and identified every morning from the beginning of May to the middle of August in each of the three years of the study. The average number of moths caught each day / trap and each month / trap were calculated for