Insight into the variation of soil hydraulic properties under beech and spruce forest—A case study in the forest of Tharandt, NE Germany

Abstract

Background

The increasing vulnerability of forests in the temperate zone due to climate change has led to modification in the forest structure to secure woody raw materials and ecosystem benefits. Such changes will influence hydrological processes both at the stand and catchment scale. Soil hydraulic properties (SHP) play an important role in assessing the water cycle in these ecosystems. Yet, knowledge regarding the effect of forest- and site-specific conditions on SHP in temperate climates is scarce.

Aims

This work addresses this research gap by assessing the variation of SHP under two common European forest stands, Fagus sylvatica and Picea abies (1) with comparable site conditions, and (2) across differing site conditions.

Methods

We determined the soil water retention curve (WRC) and the hydraulic conductivity curve (HCC) in several plots with the bimodal Kosugi–Mualem's hydraulic model. These functions were determined using combined field and laboratory measurements, including hydraulic conductivity and water content from soil samples.

Results

(1) We observed distinct variations in SHP between beech and spruce forest stands with comparable site conditions; however, no clear pattern in the variation was discernible. (2) A noticeable effect of the site-specific characteristics on the SHP was detected. Moreover, SHP in each analysed forest type presented individual variations.

Conclusions

This study demonstrates that SHP present a wide range of variations in terms of both forest- and site-specific conditions. Hence, due to its heterogeneity, we emphasise the need for more research to better characterise SHP in temperate zone forests. Moreover, this study underlines the urgent use of a minimum set of parameters in studies when addressing SHP (e.g., tree age, soil texture).