Effect of Some Tree Forest Species on Soils, Studied by an in Situ Experimental Method

1990

S. 529-550

8 Abb., 1 Tab., 41 Lit. Ang.

Unselbständiges Werk

200041210

The changes in forest soil function due to silvicultural modifications were studied by an in situ experimental method. This method used the evolution of a test-mineral as an indicator of change in the physico-chemical environment of the soil. The processes operating in the soil can be identified with reference to laboratory data obtained on the same mineral. After 3 years in acidic soils, the test-mineral (an interstratified mineral containing vermiculite) was studied; CEC, exchangeable and non exchangeable elements, mineralogy (XRD traced), and compared with the control. The results showed that if the chemical data and the mineralogy are studied, one can characterize the effects of soil types, soil horizons and forest species. In the acid brown soils the test mineral is highly desaturated while exchangeable acidity increases. In this soil, Al is rapidly hydroxylated. The change of forest species (spruce versus mixed broadleaved) produces an important mobilization of Al and forms a more shable Al integrate. In the podzol, the quantity of Al is greater than in the acid brown soil but the formation of a very stable Al intergrade mineral was not observed. The change of forest species (spruce versus beech) tends to produce the same relative effect as observed in the acid brown soil. The processes of soil function can be defined as follows: - acidolysis is the processes whichdiscriminates the function of acid brown soils; - acido-complexolysis characterizes the A1, A2 horizons of the podzolic soils. We can identify the mechanisms ivolved in the effect of species on soil function; for example the spruce increases acidity which mobilizes more Al and which tends to form a more stable Al integrate than the broadleaved species; there is a strong interaction between soil and species. Statistical analyses show the level of significance of the effects (soils, species) and allow a clear vizualisation of the results. This method with its unique experimental reference allows us to compare numerous situations and to characterize the mechanisms of soil function in relation to soil type and species. The different processes of soil function that we have recognized, correspond to very different aluminium speciation and cation distribution on the CEC, and consequently to different behavious for the nutrition and the development of forest species.