| The flood of Minjiang River basin is serious, which has brought great losses on agriculture production, national economy etc While forests have great hydrological effect and play important role in the reduction of flooding disaster through their canopy, undergrowth, forest floor and soil layers. In situ monitoring station and runoff plots have been established in Jian'ou city in 2000. We systemically analyzed the characteristics of throughfall, stemfiow, intercepting of canopy and forest floor, water storage of soil in plantations of Schima superba (SS) and Chinese fir (Cunninghamia lanceolata, CF), enclosing and tending forest and the controls (bare land). Further, the relations between rainfall and some hydrological parameters, such as throughfall, stemfiow, canopy intercepting, water storage of forest floor and soil, runoff, are discussed. Due to few detailed studies on this aspect, the ecological comparisons of hydrological characteristics among different utilized lands on the basis of various parameters are necessary in providing the implications for sustainable management of lands and alleviation of harms of floods in Minjiang River Basin. The results showed that:1. When the rainfall is smaller than 1mm, there is generally no throughfall in the SS and CF plantations. On the contrary, throughfall and rainfall are related positively when the rainfall is more than lmm. Also, throughfall in the CF is greater than that in the SS on basis of the same amount of rainfall. The throughfall rates of the SS and CF were 67. 69% and 79. 69% respectively.2. Stemfiow in the SS and CF plantations increased with the increase of rainfall, and linear relationship between stemfiow and rainfall was found. Regression analysis showed that there was obvious stemfiow in case of P>2.48mm and P>5.56mm in the SS and CF, respectively. Stemfiow rates in the SS and CF were 7.43% and 2.07% respectively. In addition, the increase of stemfiow in the SS was more than that in the CF during whole observation.3. Water intercepting through canopy of the SS and CF increased slowly with increase of rainfall and tend to constant. The saturated water intercepting of canopy for two forestswere 20mm (SS) and 8mm (CF) respectively. Intercepting rates for the SS and CF were 21.41% and 12.07% respectively. For the same rainfall, there was opposite relation between water intercepting of canopy and rainfall intensity.4. There are distinct differences in rainfall interception among three treatments. Compared with the SS, rainfall interception for treatment 1, 2 and 3 in the CFare 16.55%, 16.26 % and 21.17 % higher. Also, water storage in forest floor of the two forests for treatment III were both significantly higher than those for treatment I (PO.05).5. Runoff in bare land (the control) was significantly greater than those in other land use types, which indicated the role of forest lands in the conservation of soil and water. The amount of rainfall influenced the production of runoff greatly, while rainfall intensity did not. Significant parabola relationship between runoff and rainfall amount was found (.PO.01). The sequence of mean annual runoff coefficient in different lands was the control (30.93%) > enclosing and tending forest (2.58%) >the CF forest (1.69%) > the SS forest(1.39%). Further, runoff coefficients in March-June were higher than those in July-December, while in January and February, the runoff coefficient increased again. This monthly pattern may be related to the change of rainfall amount.6. Mean annual water storage of soils to lm depth in the SS, CF and enclosing and tending forest was 392.38mm, 375.95mm and 344.25mm, respectively, being 146.56mm, 130.13mm, 98.43mm higher than that in the control (245.82mm). The patterns of annual water storage of soils in four land use types were similar and showed as "W". In general it was high in June, thereafter decreased until the lowest values in September or October, then increased again. Monthly mean water storage of soils in different land use types followed the order: the SS> the CF> enclosing and tending forest> the control.7. There was obvious difference in monthly change of water storage in soil layers for the four land use types. Change of water storage in top 20cm soil in the control was more obvious in comparison with those in other three land use types. Water storage of soils in the SS, CF and the control increased with soil depth. While in enclosing and tending forest, water storage increased from topsoil until the soil depth of 60cm, then decreased to 1 m depth. The order of water storage in different layers for the four land use types was same, that was the SS> the CF> enclosing and tending forest > the control.8. Simulation experiments through minitype plot inside and outside forest are carried out to determine effects of forest floor on runoff and sediment yield. When forest floors are... |
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