Abundance, correlations and spatial patterns of nutrients and metals in till, humus, moss and pine needles in a boreal forest, western Finland

Abstract

Moss, humus, till and needle samples from coniferous forests at 87–103 sites were used to elucidate how natural processes and human activities throughout a 500 km 2 area in western Finland have affected the content, accumulation and dispersion of P, K, Ca, Mg, Fe, S, B, Cu, Zn, Mn, Cd, Cr, Ni and Pb in the environment. Abundance, correlations and spatial trends between and within the organic, biological and inorganic compartments were determined. No evident spatial trends existed for K, P, S, Mn, Mg and Ca. The distribution of these macronutrients in and between the media is controlled, to a high degree, by biological cycling; thus the nutrient levels are optimized in the various media. Low correlation coefficients for Ca, P, K, S and Mg between humus and moss, and the low spread of these nutrients in moss and needles, are other strong indications of efficient recycling. No correlation existed between the concentrations of B and the distance from the coast, suggesting that the B patterns are unaffected by deposition of marine salts. There was a strong spatial pattern for B in humus, moss and needles, probably connected with anthropogenic emissions from a nearby town centre. Geogenic dust affected the spatial distribution and the high correlation between Fe and Cr in moss, while natural processes were associated with the Fe anomaly found in the needles. The spatial accumulation patterns of Zn, Cd, Cu, Ni and Pb in humus and moss were strong and diverse and related to current industry, the former steel industry, traffic, coal combustion, and natural geochemical processes. An intriguing Cu anomaly in moss, probably caused by corrosion of the railway line's electric cables, was identified.