MULTIVARIATE MODELING OF SOIL MICROBIAL VARIABLES IN FOREST SOIL CONTAMINATED BY HEAVY-METALS USING WET CHEMICAL-ANALYSES AND PYROLYSIS GC MS/

Microbial activity, biomass and community patterns were measured in th e forest soils surrounding a large smelter emitting heavy metals and s ulphur in northern Sweden. The chemical background to the high variati on of the microbial variables in mor samples with a content of Cu + Zn between 100 and 1000 mu g g(-1) organic matter was investigated. Soil respiration rate was modelled using different combinations of wet che mistry data and pyrolysis. A combination of carbohydrate data, humus f ractionation data and physicochemical data explained 86% of the varian ce in soil respiration rate. Pyrolysis data explained less variance an d was more difficult to interpret. Phospholipid fatty acid (PLFA) patt erns in the soils were also analysed. A multivariate (MVP-PLS) model o f basal respiration rate, substrate induced respiration (SIR), lag tim e after glucose addition and the scores from the first component of a principal components analysis (PCA) of 33 phospholipid fatty acids (PL FAcompl) was made. The explained variance for basal respiration rate w as 75%, for SIR 85%, for lag time 52% and for PLFAcompl 82%. Respirati on rate and SIR were negatively correlated to the amount of soil organ ic matter in the mor layer (SOM m(-2)), nitrogen content and humic aci ds and positively correlated to glucans and humins. The content of bas e cations and pH were positively correlated to respiration rate and SI R and negatively correlated to lag time. The phospholipid fatty acid p atterns (PLFAcompl) showed that fungal fatty acid patterns dominated i n shallow mor layers with higher cellulose content, while gram-positiv e bacteria were more abundant in thicker mor layers with more humic ac ids and a higher nitrogen content. The variation in the microbial vari ables was partitioned into a heavy metal dependent and an organic matt er quality dependent part, which increased the correlation between hea vy metals and the microbial variables. (C) 1998 Elsevier Science Ltd. All rights reserved.