Root-Water Relations and Interactions in Mixed Forest Settings

Abstract

Mixed forests harbor a great variety of living conditions and interactions among individual plants both above- and belowground. Because of the limited access to the belowground, the subsurface complexity of those ecosystems is far less investigated than the aboveground. Root systems support the canopy's needs by supplying water and nutrients. Thus, the root systems need to be adapted to the water demand of the canopy, with abiotic limits imposed by the length and severity of droughts as well as the accessibility to the deep subsurface. This chapter reviews the current understanding of root-water relations and interactions in mixed forests across disciplines. Research shows that above- and belowground traits are strongly coordinated and, despite some plasticity, are species specific. At the community level, the relative drought susceptibly and rooting strategy also determines canopy position. Depending on the assembly, combined niche partitioning for water and light, as well as facilitation by hydraulic redistribution can enhance ecosystem functions like drought resilience and productivity. Mycorrhizae play an important role for facilitating water interactions and increasing the resource space, e.g. by enhancing access to bedrock. The effects of those interactions on forest hydrology are not well understood. Future work should address the effect of forest structure on soil water patterns and fluxes.