Environmental Factors at Different Canopy Heights Had Significant Effects on Leaf Water-Use Efficiency in Cold-Temperate Larch Forest

Abstract

It is of great significance to study short-term water-use efficiency (WUEs) at different canopy heights for accurately evaluating the adaptability of cold-temperate larch (Larix gmelinii) forest to climate change. The stable isotope method combining data of gradient meteorology, photosynthetic properties and leaf structure were used to assess the influence of different canopy heights on short-term water-use efficiency (WUEs) in larch forests in the northern Da Hinggan Mountains. The results show that: (1) The rank of leaf WUEs at different canopy heights was upper canopy > middle canopy > lower canopy. The leaf WUEs in upper canopy was significantly higher than those in the middle and lower canopy (p < 0.01), and no significant difference was found between the middle and lower canopy (p > 0.05). (2) The environmental factors, the photosynthetic characteristics, the specific leaf weight (LMA) and stomatal density (SD) had significant impact (p < 0.05) on leaf WUEs at different canopy heights of larch forest. (3) The results of the weighted random forest analysis show that the main factor affecting WUEs in larch forests at different canopy heights was vapor pressure deficit (VPD), followed by relative humidity (RH) and net photosynthetic rate (Pn), while LMA and SD made relatively small contributions. This indicates that the variation of leaf WUEs at different canopy heights is mainly due to environmental factors. Our results highlight that the difference of environmental factors at different canopy heights should be considered in the future study of leaf WUE. Our results contribute to a better understanding of water utilization strategies and carbohydrate relations in the boreal forest ecosystems, which is of great significance for improving the sustainable management measures and strategies of boreal forest resources.

Linking stomatal size and density to water use efficiency and leaf carbon isotope ratio in juvenile and mature trees

“…SLA can reflect the differences of leaf anatomical structure that can influence the variability of iWUE between species via changes in mesophyll conductance (Mediavilla et al 2001;Tomás et al 2013;Carriquí et al 2015;Trueba et al 2021). Previous studies reported that SLA was negatively correlated with iWUE and δ 13 C in crops (Craufurd et al 1999;Reddy et al 2020a,b), shrubs (Horike et al 2023) and trees (Wang et al 2013;Ge et al 2022;Zhong et al 2023). Our results also show the tendency of a negative correlation between SLA and both iWUE and δ 13 C, though this was significant only for the relationship with δ 13 C of juvenile species inter-specifically and with the iWUE of mature trees intra-specifically.…”

“…SLA decreases in plants with thicker leaves (Vile et al 2005;Homeier et al 2021). Multiple studies have found that SLA is negatively related to iWUE and δ 13 C in crops (Reddy et al 2020a;Reddy et al 2020b), shrubs (Horike et al 2021) and tree species (Ge et al 2022). The correlation between SLA and iWUE might be caused by anatomical differences that affect the mesophyll tissue surface area and mesophyll conductance (Baird et al 2017).…”

Leaf physiological and morphological constraints of water-use efficiency in C3 plants

“…A study by Medrano et al (2009) also reported a positive correlation between WUE i and LMA in Mediterranean herbs and shrubs. Similarly, LMA was positively correlated with WUE 13C among trees ( Betula, Larix, Pinus ) in the boreal forest ( Ge et al 2022 ). A thicker leaf can be associated with a thicker boundary layer, which lowers transpiratory losses and ultimately improves WUE bio ( Bramley et al 2013 ).…”