Abstract
Hydraulic redistribution (HR) can buffer drought events of tree individuals, however, its relevance for neighbouring trees remains unclear. Here, we quantified HR to neighbouring trees in single- and mixed-species combinations. We hypothesized that uptake of HR water positively correlates with root length, number of root tips and root xylem hydraulic conductivity and that neighbours in single-species combinations receive more HR water than in phylogenetic distant mixed-species combinations. In a split-root experiment, a sapling with its roots split between two pots redistributed deuterium labelled water from a moist to a dry pot with an additional tree each. We quantified HR water received by the sapling in the dry pot for six temperate tree species. After 7 days, one quarter of the water in roots (2.1 ± 0.4 ml), stems (0.8 ± 0.2 ml) and transpiration (1.0 ± 0.3 ml) of the drought stressed sapling originated from HR. The amount of HR water transpired by the receiving plant stayed constant throughout the experiment. While the uptake of HR water increased with root length, species identity did not affect HR as saplings of Picea abies ((L.) Karst) and Fagus sylvatica (L.) in single- and mixed-species combinations received the same amount of HR water.
Highlights
Hydraulic redistribution (HR) is the passive reallocation of water through roots and other tissues of plants along a water potential (ψ) gradient (Nadezhdina et al, 2010)
On day 6 it was significantly enriched when compared to δ2H values before the labelling in P. abies, P. menziesii, F. sylvatica and Q. robur (Table 4); no enrichment in transpired water was found on any day after the labelling in A. pseudoplatanus and C. sativa (δ2H on day 6: −58 ± 1 ‰ and − 69 ‰, respectively, Table 4)
Especially root proximity between same and different species need to be investigated as close proximity and even direct contact might have an important influence on the amount of HR water neighbouring trees take up
Summary
Hydraulic redistribution (HR) is the passive reallocation of water through roots and other tissues of plants along a water potential (ψ) gradient (Nadezhdina et al, 2010). Under drought, neighbouring trees may take up HR water released by plants with root access to moist soil. The additional water acquired by neighbouring plants was hypothesized to support higher stomatal conductance and growth (Dawson, 1993; Magh et al, 2018), with up to nine times higher biomass production in dry regions (Bogie et al, 2018), increasing drought resistance and to potentially improve survival (Pang et al, 2013). We quantify how much HR water drought stressed neighbouring saplings of six common temperate tree species received from a redistributing tree in a growth chamber split-root experiment. We hypothesized that flux of HR water to neighbour trees is higher within individuals of the same species than across species for phylogenetically distant F. sylvatica and P. abies trees
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