Abstract:

Hydraulic redistribution (HR), one of the common bio-physical processes, plays key roles in mediating plant drought stress, regulating plant interspecific relations and community composition, as well as in influencing water and carbon balance of ecosystems. Great improvements have been achieved in HR research with fast development of isotopic labelling and tracing technologies. This paper summarizes the effects of HR on nutrient cycling of soil-plant system, based on studies over the past decade. HR increases soil water content in dry soil layers, thus helping to prevent embolism in roots, increasing the survival rate and the growth rate of fine roots and improving microbial activities. Such effects improve plant nutrient uptake, i.e., hydraulic lift promotes nitrogen uptake from upper soil layers and hydraulic descent promotes phosphorus uptake from deep soil layers. HR may facilitate nutrient exchange between upper and lower soil nutrient pools, improve nutrient flows and regulate the N:P ratio in both plants and soil. These effects may ultimately affect global ecosystems. Under the global change scenarios (e.g. nitrogen deposition), it is necessary to further explore the effects of HR on biogeochemical cycles. HR should be taken into account when using ecosystem models for future predictions.

Key words: biogeochemical cycle, hydraulic lift, N:P ratio, nutrient uptake, root traits