Abstract
Plants may maintain long-term xylem function via efficiency-safety tradeoff and segmentation. Most studies focus on the growing season and community level. We studied species with different efficiency-safety tradeoff strategies, Quercus acutissima, Robinia pseudoacacia, Vitex negundo var. heterophylla, and Rhus typhina, to determine the seasonality of this mechanism. We separated their branches into perennial shoots and terminal twigs and monitored their midday water potential (Ψmd), relative water content (RWC), stem-specific hydraulic conductivity (Ks), loss of 12, 50, and 88% of maximum efficiency (i.e., P12, P50, P88) for 2 years. There were no correlations between water relations (Ψmd, RWC, Ks) and embolism resistance traits (P12, P50, P88) but they significantly differed between the perennial shoots and terminal twigs. All species had weak annual hydraulic efficiency-safety tradeoff but strong segmentation between the perennial shoots and the terminal twigs. R. pseudoacacia used a high-efficiency, low-safety strategy, whereas R. typhina used a high-safety, low-efficiency strategy. Q. acutissima and V. negundo var. heterophylla alternated these strategies. This mechanism provides a potential basis for habitat partitioning and niche divergence in the changing warm temperate zone environment.
Highlights
Precipitation patterns have been substantially altered as consequence of global climate change (Easterling et al, 2000; Högy et al, 2013; Gimbel et al, 2015; Ge et al, 2017)
The correlations among water relations were positive for Q. acutissima but only the associations between md and stem-specific hydraulic conductivity (Ks) were significant for this species and between perennial shoots (PS) and terminal twigs (TT)
air-entry point (P12)−PS, fastest drop point (P50)−TT, and upper inflection point (P88)−TT were positively correlated with T, s, and water relations
Summary
Precipitation patterns have been substantially altered as consequence of global climate change (Easterling et al, 2000; Högy et al, 2013; Gimbel et al, 2015; Ge et al, 2017). This phenomenon has aggravated the existing uneven seasonal water distribution (and, by extension, soil, and air moisture status) in the warm temperate zone (Luan et al, 2011; Corlett, 2016). Xylem-dependent hydraulic traits including water relations and embolism resistance traits are crucial for plant growth and adaptation
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