Water use strategies for two dominant tree species in pure and mixed plantations of the semiarid Chinese Loess Plateau

Abstract

Understanding the water sources and physiological responses to soil moisture pulses for plantation species, particularly in mixed plantations, are essential to assess the water use strategy and vegetation restoration in semiarid regions. We used hydrogen stable isotopes in plant and soil water to determine the potential water sources for Pinus tabuliformis and Hippophae rhamnoides in both pure and mixed plantations in the semiarid Chinese Loess Plateau during the vigorous growing season (June–August) in 2016. Stomatal conductance (gc), midday leaf water potential (Ψm) and photosynthetic rate (Pr) were measured concurrently to analyse the physiological response. The P. tabuliformis in the pure plantation depended largely on shallow and middle soil layers regardless of precipitation amount, permitting this species to maintain stable Ψm at the expense of Pr through stomatal control. In contrast, H. rhamnoides in the pure plantation shifted its water source from shallow to deep soil layers following decreases in precipitation, allowing this species to maintain stable gc and Pr at the expense of Ψm. Thus, P. tabuliformis and H. rhamnoides displayed isohydric and anisohydric behaviour, respectively. Additionally, both species in mixed plantations largely absorbed water from shallow soil layers and shifted to deep soil layers when precipitation decreased. Mixed afforestation significantly reduced (p < .05) Pr for P. tabuliformis and Ψm for H. rhamnoides. Although contrasting physiological responses were adopted by these species, the major proportion of water resources were competitively obtained from similar soil depths—indicating that their mixed afforestation requires further investigation.

Rainfall pulse response of carbon fluxes in a temperate grass ecosystem in the semiarid Loess Plateau

“…Plant physiological response is expected only when the rainfall amount promotes soil water status. Previous studies indicated that a small rainfall amount (e.g., 5 mm) was the lower threshold to stimulate plant activities (Tang et al., ; Zeppel et al., ;; Zhao & Liu, ). However, Thomey et al.…”

“…Plant physiological response is expected only when the rainfall amount promotes soil water status. Previous studies indicated that a small rainfall amount (e.g., 5 mm) was the lower threshold to stimulate plant activities (Tang et al, 2018;Zeppel et al, 2008;;Zhao & Liu, 2010). However, Thomey et al (2011) indicated that small rainfall events may only increase microbial respiration in shallow soil layers and could not trigger plan root activities in relative deeper soil layers.…”

Responses of Amygdalus pedunculata Pall. in the sandy and loamy soils to water stress

“…In the northern region of the Loess Plateau, especially in the arid and semi-arid zones, efficient use of water resources is critical for sustainable plant growth. Plant water use strategy is controlled by many factors, including soil properties, water condition and functional plant root (Yu et al, 2015;Tang et al, 2018). The effect of soil texture and water conditions on the growth of A. pedunculata was analyzed in this study.…”

Lack of effect of admixture proportion and tree density on water acquisition depth for European beech (Fagus sylvatica L.) and sycamore maple (Acer pseudoplatanus L.)

“…Second, mycorrhizal fungal plant partners also contribute to water acquisition and transport, extending the soil volume explored by roots (Lehto and Zwiazek 2011). Thus, contrasted results in the literature make it impossible to conclude whether or not water uptake patterns correspond to the distribution of fine roots in woody species (Green and Clothier 1995;Midwood et al 1998;Liu et al 2011;Tang et al 2018).…”