| In this paper, considering characteristics of social economic,landform and physiognomyin hilly areas, we mainly focused on the distribution, ecological niche by investigatingOncomelania snail （hereafter referred to as snail）and testing habitat factors，as well as forestclimate, soil moisture and litter accumulation. The effects of controlling snail for13kinds ofplant materials are tested with indoor experimental method. These studies intended to revealthe mechanism of forest plantation on snail control and schistosomiasis prevention and toprovide technical supports for schistosomiasis-control in hilly area.The main results as follows:(1) Field investigation showed that snails are widely distributed in various land use typesin hilly region, but mainly in acetone area such as ditches, field edge with a punctuate andlinear pattern. The population density of snail per0.11m2were that paddy (7.32)> ditch(6.25)> barren grassland (5.71)> river beach land (3.62)> dry land (1.29)>woodland (0.12).(2) My investigation showed that the suitable herbaceous species richness for snail was4～14, the suitable herb community coverage was70%～90%, the suitable plant height was20～50cm; the most suitable soil moisture was nearby the capillary water; the suitabletemperature range was between15～30℃, suitable conductivity was between60～120mS/m.(3) By the quantitative analysis of connectivity，those plants with moss, Parathelypterisglanduligera, Pteris multifida are negative for snail distribution, and Humulus japonicas,Cardamine hirsute, EupHorbia helioscopia, Galium aparine, Mazus japonicas, Ranunculusjaponicas, Impatiens noli-tangere were positive species, which are be used as indicator forsnail habitat.(4) Understory vegetation types were scarce in Eucalyptus forest, and only few herbs andferns existed, hardly any ground herbs is in bamboo forest stand. According to thephenomenon，the conclusion that the disappearance of the herb layer is one of the main reasonsof controlling snail by forest. (5)Results of the routine meteorological factor showed that air humidity inside the forestand grass was different, and the maximum difference value was more than20%: air humidity(14:00) in bamboo forest was43.30%, but it was60.30%in grassland. Maybe this is one of thereason why herb layer was suitable for snail survival. After forest plantation, the directinfluence of changes of temperature and light for snail is less, but the indirect impact isbigger by adjusting coverage and species of herb.(6) Two forest stands with Eucalyptus and Bamboo can save water content up to32.65-178.51T/hm2in their body; water loss was up to24.9T/hm2in high yield cultivation ofbamboo every year, and it was about0.25%of annual rainfall. The canopy can intercept11%～40%of the rainfall. Rainfal interception proportion by canopys of five stands inchangning (Pleioblastus amarus, Cunninghamia lanceolata, phyllostachys pubescens,Dendrocalamus membramaceus and oak forest) were among21%～32%; After afforestation,forest transpiration was20%～40%more than the original marsh, together with theimprovement on soil infiltration capacity, forest made water infiltrate into deeper soil mor andreduced hydrcele in the soil surface. As a result, the total forest water input reduced30%ormore than that into woodland. Experimental result also showed that soil moisture in0～20cmsoil layer was0.5%lower in Eucalyptus plantation, and it was4.08%～11.57%lower inbamboo grove. Forest plantation mostly affected soil water content, which showed thatafforestation improved soil texture and soil infiltration condition and made water transferringfrom surface to deep soil easier, and this reduced soil surface water storage and result in acompression of the snail suitable space.(7) After planting, forest litters accumulated on soil surface, and the litters replaced theoriginal herb layer. The litter fall and decomposition not only inhibited the germination andgrowth of herbs, but also negatively affected snail movement, and acquirement for food andlight. Experimental results showed that snail density was correlated with litter thickness andcoverage, and snail was weak with pale shell and has high mortality.(8) Main plant materials in experimental zone had very good molluscicidal effect. alcoholextract of Eucalyptus leaves, Ailanthus altissima and camphor has highly toxic group, and the LC50was lower than0.1ppm.Walnut, vetiver and orange were also with molluscicidal effect,the LC50value was between0.2-1.0ppm; Vetiver grass, Melia azedarach, pepper leaf,Oleander Leaf, orange peel were also with toxicity, the LC50value was between1.0-5.0ppm;the LC50value was between10.0-20.0ppm for Wingnut and ginger shoots.Main innovations are as follows:(1) The rationality that indicator plant is named as index of recognizing and evaluatingsnail habitat. is demonstrated.(2) The plants with eucalyptus,ailanthus and vetiver are selected provide the mostpotential material for developing plant molluscacide.(3) For the first time, the mechanism of controlling snail by forest is revealed. |
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