Research On The Characteristics Of Acid Deposition And Its Effects On Soil Based On The Hydrologic Cycle Of Forests In Jinyun Mountain

Due to the use of coal with high sulfur content causing emissions of SO2and NO3-, acid deposition has become a serious environment problem in the world and also the serious problem. Chongqing is one of the areas receiving the highest surfur deposition with a high frequency of acid rain, strength in China. It may has an negative effect on the health of forest ecosystem under long-term acid rain. Now the impact of nitrogen deposition is also increasing. In this paper, a comprehensive study of canopy and soil response and feedback mechanisms of acid deposition based on hydrologic cycle was conducted, which provide support to the control measure of acid pollution, forest protection, and solve the soil acidification and water environmental problems.Evergreen broad-leaved forest and mixed forest of coniferous and broad-leaved were selected. Rainfall and runoff samples were collected in this two typical forest stands among April to October of2012, then the chemistry variations of rainfall and runoff were analysed in the hydrologic cycle. Discussion on the water quality effects in different levels of typical forests (forest canopy, the soil layer) and the influencing factors. Simulated acid deposition experiments were conducted in April to November of2012, which aimed at discussing the effects of acid deposition under the soil physical and variation of chemical properties.(1) In the forest hydrological processes, the change of pH from high to low in both forest stands was:stemflow<throughfall<rainfall<interflow<surface runoff, which showed that precipitation acidification aggravated after passed through the forest canopy and the soil layer and litter layer has some acid buffering effect, making the interflow and surface runoff pH rise. (2) The acid deposition in Jinyun Mountain was mainly sulfur deposition. Variations of chemical properties were found after rainfall passed through the forest canopy. The factors affecting throughfall chemistry and flux included canopy exchange and wash-off of the dry substances atmospherically deposited on leaf surface.(3) The canopy leaching of SO42-was the largest, followed by Ca2+, K+. The canopy leaching of trace elements Na+and Mg2+were very low or even negative leaching. This may be due to different adsorption capacity of trees of the different elements. The total amount of canopy leaching performance was mixed conifer forest (4.357)> evergreen broad-leaved forest (2.754), which showed that conifer forest was more susceptible to canopy leaching under the effect of acid rain.(4) In rainfall-surface runoff-interflow process, except NH4+, the sum of Ca2+, Mg2+, K+, Na+surface runoff and interflow output were higher than the sum of precipitation input and, indicating that base cations loss and the soil has a certain of retain the ability of NH4+.(5) In terms of the total amount of base cations, the runoff output of base cations increased compared with the rainfall:mixed coniferous forest>evergreen broad-leaved forest, which indicates that evergreen broad-leaved forest is better choice in the construction of forest in acid rain area. It has correlation between the runoff output of base cations (K+, Ca2+, Mg2+and Na+) and the amount of runoff except NH4+, respectively, which means the loss of cations rise with the increase of runoff. In addition to the impact of runoff, the changes of NH4+may also be affected by other factors such as micro-organisms, season and so on.(6) Results showed that when N deposition level rise, pH values and exchangeable base cations in the soils decreased, indicating that soil acidification was more serious after nitrogen deposition treatment and nutrient loss. The longer duration of nitrogen deposition treatment, the greater the harm caused to soil. Meanwhile, activity of microorganism contributes the accumulation of NH4+-N and NO3--N as the nitrogen application goes on. Due to the increasing of soil active nitrogen, soil acidification was accelerated, accordingly results in the leaching of soil base cations and heavy metal and the negative influence on the health of forest ecosystems.