Study On Rainfall Hydrochemical Characteristics Of Larix Gmelinii Forest In Great Xingan Mountains Of Inner Mongolia

The hydrochemical characteristics in forest ecosystems could reflect the regional ecological forest conditions and pysiological characteristics of the different plant communities. The types and amount of elements in open-rainfall, through-fall and stem-flow were investigated in order to reveal the changes and balance of nutrients in forest ecosystems.This research could be important for nutrient management trees in forest and for protection of water resource. In our experiment, the chemical components(N, P, NO3--N, NH4+-N, CO32-, HCO3-, Cl-, Ca, Mg, K, Na, Mn, Zn, Fe, Cu, Cr, Pb, Cd, Se, As, pH, EC, salinity) in open-rainfall, through-fall and stem-flow for Larix gmelinii natural forest ecosystems, were analyzed. The results were shown as follows.1. Through the reseach that was showed the content of 11 conventional elements(N, P, NO3-, NH4+, CO32-, HCO3-, Cl-, Ca, Mg, K, Na) in open-rainfall, through-fall and stem-flow of Larix gmelinii forest from May 2008 to Septemper, the concentration of HCO3- and Ca were higher than other elements, while P was lower than other elements. The tatal number of conventional elements increases through forest canopies. It showed that in through-fall and stem-flow was enriched remarkably. The content of conventional elements sequence in open-rainfall, through-fall and stem-flow goes as follows: open-rainfall: HCO3->Ca>CO32->NO3->N>Na>K>NH4>Cl->Mg>P;through-fall:HCO3->Ca>Na>CO32->N>NO3->K>NH4+>Mg>Cl->P;stem-flaw:HCO3->Ca>Cl->P>K>N>CO32->NH4+>NO3->Mg>Na.2. The input of trace elements(Mn,Zn,Fe,Cu) was lower than other elements in precipitation. After canopy leaching, Mn and Fe increased in through-fall and stem-flow. The concentration of Zn in through-fall and stem-flow were lower than those in precipitation, and Zn was absorbed by tree crows. The leaching of volume sequence in stem-flow goes as follows: Mn>Fe>Cu>Zn. The content of high polluted heavy metal were lower than other elements in precipitation(15～0.25μg/L). The content of heavy metal elements sequence precipitation and stem-flow goes respectively as follows: Cr>BP>Cd>Se=As and Cr>Pb>Cd>As>Se.3. The pH value of open-rainfall and through-fall near-neutral from May 2008 to September in Larix gmelinii forest. However, the stem-flow was significantly acidified(pH value 4.4～6.3). The monthly change of EC was obviously in open-rainfall and through-fall, consistently with minimum in July (1.4 and 1.6ms/m), and maximum in September (22 and 8 ms/m).4. The inputs in rainfall in growth seasonal at larix geminii forest of Great Xingan Mountains (Inner Mongolia) were 0.191kg/hm2 for nitrogen, 0.106kg/hm2 for NO3_N, 0.049kg/hm2 for NH4+-N and 0.036kg/hm2 for TN, respectively.