By introducing levy-lindeberg theorem to raingauge networks planning, the authors obtain a linear relationship between the measurement precision of areal rainfall (relative error or permissible error) and raingauge networks density (average station spacing). The slope of relative error growing is directly proportional to the mean square error of random observation error, inversely proportional to square root of the areal rainfall and region area. Based on simulated rainfall fields and highdensity rainfall data during Mei-yu season in Anhui Province, conclusion above is validated by the statistic analysis reducing the raingauge stations method. The slope of the linear relationship is also investigated. This research is significant to provide certain reference for optimization of raingauge networks location planning. Based on the relationship, the authors calculate 2005-2008 rainfall data during Mei-yu season in Anhui Province and conclude that correlation coefficient between the measurement precision of areal rainfall and raingauge networks density in Huaibei Plain is 0.49 to 0.80, in the mountains of Southern Anhui Province is 0.70 to 1.41. Assuming that permissible error is 20%, the minimum average station spacing (the maximum Raingauge networks density) in Huaibei Plain is 25 km and in the mountains of Southern Anhui Province is 14 km.

To examine patterns of nutrient concentrations in different organs, stoichiometry of various nutrients, and the relation of nutrient concentrations with species and the environment, the concentrations of total non-structural carbohydrate (TNC), nitrogen (N), and phosphorus (P) among leaves, stems, tap roots, and first order roots in Asian white birch (Betula platyphylla) and Meyer spruce (Picea meyeri) were studied. The two species were located in the southeastern edge of Inner Mongolia. For TNC, leaves had the highest and first order roots had the lowest concentrations ; the largest difference between them was less than 53%. For N and P, however, there were much higher concentrations in leaves and first order roots than that in stems and the tap roots; the largest difference between them was about 98%. These patterns were determined by the physiological roles (carbohydrate production, nutrient uptake and storage, etc.) that different organs play. In addition, both TNC∶ N and TNC∶ P of Meyer spruce were higher than those of Asian whiter birch, reflecting the physiology of different species and variations in soil nutrient conditions.