Hydrological functions of forests in small lowland catchments - Jan Tyszka

Jan Tyszka. Instytut Badawczy Leśnictwa, Sękocin Stary, 2008, ISBN 978-83-878647-76-6, 216 pp. In Polish, with abstract, summary, list of abbreviations and symbols, tables and figures in English. 38 EUR.

The study attempts to estimate and to interpret the impact of forest on water circulation in small lowland catchments of the Vistula river basin taking into consideration the climatic, physiographic and habitat conditions. It uses the findings of the hydrological research conducted between 1966 and 2006 within 46 small catchments with different forest cover, habitat and stand characteristics representative of the majority of larger forest complexes in eastern Poland. The period under study featured variable climatic conditions and marked trends towards a decrease in water resources, as well as changes in the fertility of forest habitats, species and age structure, as well as in stand volume.

 The declining rainfall/runoff ratio and the lowering of the groundwater table in wet habitats points to the downward trend in water resources. This is due to the growing demand of stands for water caused by a rise in air temperature and increase in standing volume. The lowering of snow retention and improvement of habitat productivity as a result of the contamination of water circulating in forest ecosystems and catchments are the major factors causing disturbances in water relations.

 The growing water deficit is a limiting factor for the development of stands and species diversity of forest ecosystems. Nevertheless, forests in the post-drought period fulfil their positive hydrological function accelerating the small water cycle. The impact of forests in the temperate climatic zone on the increase of evapotranspiration rate is compensated in part by relatively higher precipitation than on arable fields. Even if there are small topographic differences, the impact of forests is conditioned by slope exposition and land inclination of a catchment.