Chemistry Of Mobile Constituents In Mt. Lushan Forest Ecosystem And The Response Dynamics To Acid Deposition

Taking an example of an eco-tessera in Botanical Garden, Mt. Lushan under strong acid deposition, chemistry and dynamics of mobile constituents in forest ecosystem was studied. Both the rooting zone soil and bulk soil under different vegetation and in different seasons were sampled, and the forest ecosystem response to acid deposition was monitored in situ. The purpose of this work is to describe the ecological effects from soil acidification induced by the acid deposition and to help enhancement of scientific data for atmospheric deposition control. The results were as follows: 1. Mobile aluminum forms were analyzed using various digesting technique. No variation could be found between the mobile Al forms under coniferous forest and those under deciduous one. However, large difference in organo-complexed Al was found between in rooting zone soil and in bulk soil. Thus, depletion of organo-complexed Al in rooting zone soil could be an example of intense chemical change in soils under acidification. 2 Concentration of dissolved aluminum forms in soil solution and its seasonal change with vegetation type and root activities were studied. The total acid soluble aluminum(Ala) ranged from 0.6 mg/kg to 3.8 mg/kg, of which monometric Al was a dominant form. Higher concentration and ratio of Alm to Al appeared in autumn and winter, and under coniferous forest compared to that under deciduous forest. The results indicated Al mobilization in the studied soils was stimulated by soil acidification and potential phyto-toxicity of Al in regions with acid deposition impact should be addressed. 3 Dissolved organic carbon(DOC) contents in soil solution and the relation to the vegetation activity and to seasonal dynamics were also studied. The content of DOC varied in range of 289. 85 111. 04 mg/kg. High concentrations of DOC could be found in bottom soil except for the peak concentration in surface soil. Soil DOC concentration is higher under coniferous forest than under deciduous one, and higher in rooting zone soil than in bulk soil; Seasonal change of DOC concentration occurred with higher contents in winter and spring. There was very significant positive correlation between the concentrations of DOC and of dissolved aluminum or of the ratio of Al o Al indicating mobile organic species was closely associated with Al mobilization. 4 Base cations (Ca2 Mg2 K.. Nat) in soil solution were analyzed seasonally. Large variation of base cations in surface soil indicated leaching of base cations was occurred. Soil solution Ca/Ala molar concentration ratios ranged from 1.42 to 17. 13 for soil samples studied, with high values in autumn. 5 The chemical dynamics of precipitation, throughfall, stemflow and stream water was monitored both during the course of precipitation and after raining. Acidity, conductivity and cation concentration(Ca2 Mg2 K) of precipitation decreased in the course of raining. The properties of precipitation were closely related to the span of precipitation, the duration of raining and rainfall. Momentary properties of precipitation during raining had no significant variation with season. Acidity, conductivity and cation concentration of throughfall was higher than that of precipitation, pH of coniferous throughfall is lower than that of deciduous one; Compared to throughfall and precipitation, stemflow bad a lower pH value. Seasonal variation of stream water chemistry was revealed, whiled deciduous forest displayed b...