Harukuni Tachibana

Water chemistry in Sarobetsu Mire and their relations to vegetation composition

Abstract The changes in water chemistry regime and their effect on the composition of the vegetation were studied in Sarobetsu Mire, northern Hokkaido, Japan, an exotic plant-invaded bog. Water chemistry and plant species data were collected along the invasion stage which depicts the degradation gradient. Analysis of Variance (ANOVA) was conducted to assess the source of the variances in water chemistry and Canonical Correspondence Analysis (CCA) was then used to relate vegetation gradients to environmental factors. The water chemistry regimes between the natural and degraded area were found to be significantly different. They were found to change gradually from ombrotrophic to minerotrophic state along the invasion pattern. Sampling points (i.e. locations along the degradation gradient) accounted for most of the variation in water chemistry. It accounted for 30 – 80% of the total variation in pH, EC, NH4 +, DN, Na+, K+, Ca2+, Mg2+, alkalinity 4.3Bx, Si and Dissolved Organic Carbon. CCA ordination also revealed that besides hydrological parameters, nutrient contents, acidity-alkalinity gradient and base cation content (excluding K+) were also closely related to the composition of the vegetation. The results highlight the influence of hydrological parameters on water chemistry regime; they control the chemical as well as biotic processes in mire ecosystems.