Diversity did not influence soil water use of tree clusters in a temperate mixed forest

Abstract

Abstract. Compared to monocultures, diverse ecosystems are often expected to show more comprehensive resource use. However, with respect to diversity-soil-water-use relationships in forests, very little information is available. We analysed soil water uptake in 100 tree clusters differing in tree species diversity and species composition in the Hainich forest in central Germany. The clusters contained all possible combinations of five broadleaved tree species in one-, two-and three-species clusters (three diversity levels), replicated fourfold (20 one-species, 40 two-species and 40 three-species clusters). We estimated soil water uptake during a summer dry period in 0-0.3 m soil depth, based on throughfall and soil moisture measurements with a simple budgeting approach. Throughout the whole vegetation period in 2009, soil water uptake was additionally determined at a higher temporal resolution and also for a greater part of the soil profile (0-0.7 m) on a subset of 16 intensive clusters. During the dry spell, mean soil water uptake was 1.9 ± 0.1 mm day −1 in 0-0.3 m (100 clusters) and 3.0 ± 0.5 mm day −1 in 0-0.7 m soil depth (16 clusters), respectively. Besides a slightly higher water use of Fraxinus clusters, we could not detect any effects of species identity or diversity on cluster water use. We discuss that water use may indeed be a conservative process, that differences in tree-species-specific traits may be compensated for by other factors such as herb layer coverage and tree spatial arrangement, and that diversitydriven differences in water use may arise only at a larger scale. We further conclude that with respect to stand water use "tree diversity" alone is not an appropriate simplification of the complex network of interactions between species traits, stand properties and environmental conditions that have varying influence on stand water use, both in space and time.

High‐resolution isotope measurements resolve rapid ecohydrological dynamics at the soil–plant interface

“…Little experimental information is available on the relationship between tree mixture and water use in temperate forests (Grossiord et al, 2013), but our analysis aligns with recent results for a mixed European forest undergoing desiccation (Meißner et al, 2013) to contradict a common paradigm that more diverse ecosystems use available resources more comprehensively (e.g. Hector et al, 1999).…”

“…We further note that the suggested complementarity in resource exploitation by beech and oak did not significantly enhance relative daily water use of the mixed over the two monocultures (combined data) under dry or rewetted conditions (Welch's t ‐tests on data for each day of the experiment, with Holm–Bonferroni correction, P > 0.05). Little experimental information is available on the relationship between tree mixture and water use in temperate forests (Grossiord et al ., ), but our analysis aligns with recent results for a mixed European forest undergoing desiccation (Meißner et al ., ) to contradict a common paradigm that more diverse ecosystems use available resources more comprehensively (e.g. Hector et al ., ).…”

Transpiration patterns and water use strategies of beech and oak trees along a hillslope

“…This species‐specific plasticity might be key for their survival and competitiveness under increasing water scarcity (Volkmann et al, 2016). The spatial and temporal water source partitioning between different species is still poorly tested and contrasting results have been found (Allen et al, 2019; Bello et al, 2019; Grossiord et al, 2014; Meißner et al, 2013; Volkmann et al, 2016). While Meinzer et al (2001) highlighted the potential of niche complementarity as a competition avoidance strategy, Grossiord (2019) and Gillerot et al (2020) suggested that tree diversity does not systematically increase the performance of forest communities.…”

Species diversity and identity effects on the water consumption of tree sapling assemblages under ample and limited water supply

“…The latter observations are mirrored by patterns of soil water extraction conducted during the same period with a soil water balance modeling approach (Krämer and Hölscher ). Also in the Hainich forest, Meißner et al () found no systematic differences in water consumption among small‐sized tree clusters that differed in species composition and species richness (1–3 species). Different deuterium signatures in the xylem water of coexisting tree species in mixed stands pointed, however, at partitioning of soil water among species during a soil desiccation period and thus may indicate a certain complementarity in water use (Meißner et al ).…”