Temporal variation of soil water and its influencing factors in hilly area of Chongqing,China

The paper studied the temporal variation of soil water content and its influencing factors in hilly area of Chongqing by the yearly data of 2006 and 2007.According to precipitation anomaly percentage,the year 2006 was a dry year and 2007 a normal year.In the dry year 2006,the variations of soil moisture in all three layers(0-10 cm,10-20 cm,20-40 cm)were medium(10%<CV<30%);in the normal year 2007,the variation in the layer of 0-10 cm was strong(CV>30%),and those of the two deeper layers were weak(CV<10%).Hence,the seasonal variation of soil moisture in the humid area was large in the dry year and small in the wet year.The probability distributions of soil moisture in all three layers in both dry and normal years showed single-peak shapes.However,peak locations and values varied with different layers and years.Among factors affecting the temporal variation of soil moisture in the 0-10 cm layer,during March to May,the meteorological factors including temperature,sunshine and precipitation were all inversely correlated with soil water content variation.The correlations with average temperature and accumulated temperature were both highly significant P<0.01(P=0.00).The inverse correlations with sunshine and precipitation were significant P<0.05(P=0.01).Among soil physical properties,except for bulk density which was inversely correlated with soil moisture,all other properties were positively correlated.Organic material was positively correlated with soil moisture,which suggested that organics had the sponge effect and contributed to soil water storage and movement.During the period of June to September,there was no significant correlation between soil water content and total storage.The meteorological factors of temperature,accumulated temperature and sunshine were all inversely and highly significantly correlated with soil water content P<0.01(P=0.00).