Comparison of transpiration between different aged black locust (Robinia pseudoacacia) trees on the semi-arid Loess Plateau, China

Abstract

Black locust (Robinia pseudoacacia) is widely planted throughout the semi-arid Loess Plateau of China. The spatial distribution of this species at different ages is highly heterogeneous due to restoration and management practices. In this study, we aimed to compare the transpiration levels between different aged black locusts at the tree and stand scales, clarifying the physiological status of this species with different ages. Black locust trees with two representative age classes (12 and 28 years) were selected in the Yangjuangou catchment on the semi-arid Loess Plateau. Sap flux density (Fd) and environmental variables (solar radiation, air temperature, relative humidity and soil water content) were simultaneously monitored throughout the growing season of 2014. Tree transpiration (Et) was the product of Fd and sapwood area (AS), and stand transpiration (Ec) was calculated basing on the stand sap flux density (Js) and stand total sapwood area (AST). Stomatal conductance (gs) was measured in a controlled environment and hydraulic conductance was estimated using the relationship between transpiration rate and vapor pressure deficit (VPD). Our results showed that Et and Ec were higher in the 28-year-old stand than in the 12-year-old stand. The gs and hydraulic conductance of 28-year-old trees were also higher than those of 12-year-old trees, and the two parameters were thus the causes of variations in transpiration between different age classes. After rainfall, mean Fd increased by 9% in 28-year-old trees and by 5% in 12-year-old trees. This study thus suggests that stand age should be considered for estimating transpiration at the catchment and region scales in this area. These results provide ecophysiological evidences that the older black locust trees had more active physiological status than the younger ones in this area. These findings also provide basic information for the management of water resources and forests on the semi-arid Loess Plateau.

Canopy transpiration and stand water balance between two contrasting hydrological years in three typical shrub communities on the semiarid Loess Plateau of China

“…Accordingly, the Tr values were higher in 2016 than in 2015 in the three communities (Figure ). The ET 0 is a compound index that characterizes local meteorological conditions (Jiao et al, ), and no significant differences in ET 0 were observed between the two years. Therefore, the increased Tr between 2015 and 2016 was attributable to soil moisture primarily, and the influence of the SWC at 0–200 cm on Tr variations was greater during the drier than the wetter year for the three communities (Table ).…”

“…Accordingly, the Tr values were higher in 2016 than in 2015 in the three communities ( Figure 3). The ET 0 is a compound index that characterizes local meteorological conditions (Jiao et al, 2016), and no significant differences in ET 0 were observed between the two years.…”

Improved Water Consumption Estimates of Black Locust Plantations in China’s Loess Plateau

“…These values are much larger than the ones (≤0.5 mm d −1 ) reported by some previous sap flow studies (Table 1) on black locust plantations [23][24][25][28][29][30]. A few studies quantified the water consumption of black locust stands in the Loess Plateau region with other methods.…”

“…Table 1 shows that the ratio of total sapwood area to the stand ground surface in our study was much lower than other studies for black locust stands in the Loess Plateau region. This is due to the significantly different sapwood thicknesses that were taken into account for upscaling the stand transpiration in the different studies [25,29]. Other experimenters estimated a significantly larger sapwood thickness (ranging from 5.0 to 15.4 mm) suggesting possibly no limitation to the outermost growth, which may lead to uncertainties.…”

Soil moisture variations in response to precipitation in different vegetation types: A multi‐year study in the loess hilly region in China

“…Stand density is another key factor that impacts soil moisture conditions. Vegetation with higher density would more easily lead to soil desiccation due to high transpiration demand (Jiao et al, ; Wang et al, ). Therefore, the strong consumption capacity combined with high stand density contributed to the intensive consumption of soil water in black locust land, especially in the deep soil layers, where a dry layer had developed (Table and Figure ).…”