Rooting patterns, root growth, and water uptake in response to interspecific competition

PhD Student

Christina Hackmann

Research Outline

The forests of central Europe, providing numerous goods and services, are projected to experience increasingly prolonged and intense drought periods in summer. When investigating drought response of forest stands, the soil-root interface is of major importance for tree hydraulics. Species-specific differences in form and functionality of roots are known to occur, however, the effect of inter- and intraspecific competition on root traits, water uptake and resulting ecosystem functioning has rarely been researched.
In the second phase of subproject 1, we will assess spatial and temporal patterns of root water uptake in pure and mixed stands of European beech, Norway spruce and Douglas-fir at four different sites in north-western Germany. Stable water isotopes (2H, 18O) will be analyzed in soil and tree xylem water to estimate individual tree water uptake depths during drought periods throughout the growing seasons of 2021 and 2022.
We hypothesize that species identity has a significant influence on root water uptake depth. Yet, as water availability, soil type and tree nutrition are closely related, the effect of site conditions will also be considered. We further hypothesize to encounter complementarity effects (i.e. spatial or temporal differentiation of water uptake) in mixed stands in response to interspecific competition for water. In order to link belowground and aboveground hydraulic processes, the results will be analyzed along with growth and water status data of the investigated trees derived from high-resolution dendrometers.
In the light of climate change and increasing societal demands on forests, we aim for a better understanding of mixing effects on root functionality and tree-water relations in beech forests enriched with conifers, providing conclusive management implications.

Principal Investigator / Supervisor

Prof. Dr. Christian Ammer, Silviculture and Forest Ecology of the Temperate Zones, Faculty of Forest Sciences and Forest Ecology