Soil And Water Conservation Effects And Mechanisms By Hedgerow Ecosystems In Red Soil Fields On Slopes

The functions of hedgerows in effectively preventing and controlling soil and water loss have been shown in numerous studies all over the world. However, only a few studies have conducted research in their soil and water conservation effects and mechanisms (abbreviated as SWCEM), and this necessitates further research. To provide the improvement and establishment of the hedgerow ecosystem models with scientific guidance, this paper takes red soil slope fields as the object study area to discuss the SWCEM of hedgerows, through field experiments and on site investigation.1. Effects and Mechanisms on Reducing Soil and Water Loss in Hedgerow Ecosystems(1) Hedgerows are capable of retaining water and soil under actual and simulated rainfall conditions. Rain erosive power and rainfall were higher in June and August than in other months in 2001. Results from Weather Monitoring Stations from the area showed that precipitation in the two months accounted for 37.70% total annual rainfall during the year under review and a significant positive correlation between the rainfall erosivity and rainfall intensity was found, which indicated that the erosive ability of rainfall could be better expressed by its intensity than the total amount of rain. For our study we used two common hedge plants, Hemercoallis citrina Baroni and P. Rotatum Flligg which on average, reduced annual runoff and soil loss by 10. 14~ 11.56 times and 135. 34 ~ 165. 84 times, compared with the spring soybean mono-cropping pattern. Significant positive correlation was observed between the aggressive rainfall, runoff and soil loss under the hedgerow ecosystems on one hand and the soybean monocropping pattern on the other, with a significant positive correlation between runoff and soil loss. Regression models were established to simulate the relationship between runoff, soil loss and aggressive rainfall. Moreover, hedgerow ecosystems were effective in controlling water and soil loss in June and August. Under simulated rainfall, Hemercoallis Citrina Baroni and P. Rotation Flligg hedgerow ecosystems had a significant effect on reducing water and soil loss in their later stages of plant growth, and there was a significant positive correlation between the effect on reducing water and soil loss and the rain intensities. Moreover, hedgerow ecosystems decreased more soil loss than runoff, and the initial time of runoff incidences could well represent the water and soil conservation effects of hedgerow ecosystems. Significant negative correlation was observed between the initial time of runoff incidence, runoff and soil loss under the hedgerow ecosystems and soybean monocropping pattern, with significant positive correlation between runoff and soil loss. Regression models were established to simulate the relationships between runoff, soil lossand the initial time of runoff incidence. The higher the rain intensity was, the more the differences were among the treatments during the runoff and soil loss periods; the difference of soil loss was more significant than that of runoff and this trend was similar between runoff and soil loss.(2) The results showed that rainfall capacity and rain erosivity (abbreviated as Rv) during the typhoon rain season of 2001 accounted for 24.50%, 73.35% of the annual rainfall and Rv, respectively, with significant correlation between each rainfall capacity and Rv. There was a highly significant correlation between the highest rain intensity in 30 minutes (abbreviated asI30 ) and Rv, and no significant correlation between rainfall capacity and 130. The soilconservation effects were better than the water conservation effects. The order of importance for water and soil conservation effects in different treatments was Eragrostis curvula, Kummerowia atriata, Ixeris denticulata, with the most significantly positive correlation between each runoff and soil loss. There was significant positive correlations not only between the runoff of different treatments and rainfall, between barren slope and Ixeris denticula...