Spatio-Temporal Variation Analysis of Precipitation during 1960-2008 in the Poyang Lake Basin, China

Long-term monthly precipitation data from 1960 to 2008 at 17 rain stations are analyzed to explore spatio-temporal variation of the seasonal and annual precipitation in the Poyang Lake basin, China, using anomaly analysis, simple linear regressive technique, Mann-Kendall trend test and Continuous Wavelet Transform. The results indicate that: (1) increasing precipitation trend is observed in summer and winter, while decreasing precipitation trend is identified in spring and autumn, and the above mentioned precipitation trends are not statistically significant;(2) changing trend of the areal average annual precipitation is non-significantly increasing, and increasing trend happens in almost the whole basin except in western and south-eastern small parts;(3) the spatial distribution of the seasonal and annual precipitation anomalies between 1991-2008 and 1960-2008 is similar to that of seasonal and annual precipitation trend during 1960-2008;(4) three main time-frequency distributions are observed in annual precipitation series during 1960- 2008, and they are 18 - 26 years, 8 - 14 years and 2 - 8 years, respectively;accordingly, there are three main periods in annual precipitation series, and they are 11-year, 22-year and 5-year respectively. This result will be helpful for further research on availability, scientific management and assessment of the water resources of the Poyang Lake basin.

Variations of Farming Systems and Their Impacts on Surface Water Environment in Past 60 Years in Intensive Agricultural Area of Taihu Region, China

Based on agricultural nitrogen (N) balance model and field experiments, the impacts of farming system changes of Taihu Region of China on surface water environment were studied. During past 60 years, farming systems changed greatly in Taihu Region. The traditional method of manure collection and application was replaced by chemical fertilizer utilization gradually. Chemical N fertilization intensity decreased greatly due to the abolition of “3 crops per year” and reduction of cropland area in 1990-2010. Crops depleting soil fertility increased, while those improving soil fertility decreased, leading to an excessive dependence on chemical fertilizer application, which increased the risks of soil N loss to surface water environment in Taihu region. However, field experiments showed that the agricultural N loss with runoff only accounted for 2% of fertilizer N application rate. The majority of N was exported by crop harvesting. Our findings showed that the agricultural N loss might not be the main source of N pollution in Lake Tai after 2000. To control N pollution of Lake Tai, more attention should be paid to industrial and domestic wastewater from urban and rural areas, wastes from livestock and poultry breeding, bait input for aquaculture, etc in the Taihu Region, China.

Impact of seasonal water-level fluctuations on autumn vegetation in Poyang Lake wetland,China

Water level fluctuations (WLF) are natural patterns that are necessary for the survival of various plants,and WLF guarantee both the productivity and the biodiversity of wetlands.However,the underlying mechanisms of how changes in vegetation are linked to seasonal WLF remain unclear.Using vegetation and hydrological data from 1989 to 2009,we identified the key seasonal fluctuations and their impacts on vegetation in the Poyang Lake wetland by utilizing a tree-based hierarchical model.According to our results: 1) WLF in summer had significant impacts on both sedges and reeds.The severe summer floods promoted the expansion of sedges,while they inhibited the expansion of reeds;2) WLF in autumn also greatly impacted sedges,while reeds were severely affected in spring.Specifically,we found that low water levels in autumn led to the expansion of sedges,and low water levels in spring led to the expansion of reeds.The results were well corroborated through comparisons of the vegetation distribution patterns over the last two decades (i.e.,the 1990s and 2000s),which may shed light on corresponding water resource and wetland management.

Analyzing and quantitatively evaluating the organic matter source at different ecologic zones of tidal salt marsh, North Jiangsu Province, China

In order to explore the effect of different eco-logical zones and their above plants in the organic matter cycling of the whole tidal salt marsh,indicators such as total organic carbon(TOC),total nitrogen(TN),C/N ratio,δ13C and d15N of surface,core sediments,and plants of tidal salt marshes in North Jiangsu Province are analyzed.Subse-quently,distribution regularities of these measurement indi-cators are discussed,and the biogeochemistry processes between sediments and plants are also analyzed.Lastly,the organic matter sources of different ecologic zones in tidal salt marsh are evaluated,and the organic matter accumu-lations in different ecologic zones induced by their plants are also compared.These results indicate that TOC,TN,C/N ratio and δ13C showed obvious zonal distribution.The organic matter sources are dominated by marine input in the silt flat,artemisia schrenkiana flat,and the transition zone between silt and spartina alterniflora flat,and are controlled by terrigenous input in spartina alterniflora flat.Spartina alterniflora plays an important role in the accumulation of organic matter in the whole tidal salt marshes ecosystem.In the study area,the annually increased TOC,organic matter and TN in the spartina alterniflora,artemisia schrenkiana and reed flats reach 6,451,12,043 and 536 t,respectively.The amount of TOC,organic matter and TN accumulated in the spartina alterniflora flat is more than that in other ecological zones,which shows that the spartina alterniflora flat exert a non-replaceable effect on the material cycle and exchange in the whole tidal salt marshes ecosystem.