Scaling Up Sap Flow Measurements from the Stem Scale to the Individual Scale for Multibranched Caragana Korshinskii on the Chinese Loess Plateau

Abstract

The traditional heat balance method for measuring plant sap flow (SF) becomes troublesome and uneconomic for multibranched shrub species if all their stems are used for the measurement. The objectives of this study were to explore specific relationships between stem-scale SF and plant morphological traits and then to scale up SF measurements from the stem scale to the individual scale for Caragana korshinskii Kom., a dominant shrub species on the Chinese Loess Plateau. Sap flow was measured for twenty-one stems from three representative individuals from July to September 2018 during the rainy season. The results indicated that the stem-scale SF in C. korshinskii presented a positive linear correlation with the stem base diameter (SBD), stem length (SL), primary branch numbers in the stem (PBN), and estimated stem biomass (W). The SBD-based statistical models performed well in estimating the stem-scale SF, with an R2 value of 0.9726 and root mean squared error (RMSE) of 2.5389 g h−1. Over the canopy projection area, the individual-scale transpiration flows for the three selected C. korshinskii were 1.91, 1.10, and 1.59 mm·d−1. In addition, stem-scale SF was positively and linearly correlated with air temperature, photosynthetically active radiation, vapor pressure deficit, reference crop evapotranspiration, and variable transpiration. This study sheds light on morphological and meteorological influences on stem-scale SF and has made contributes to the accurate and rapid estimation of the plant sap flow from easily available morphological traits for multibranched shrub species in semiarid regions. Limitations, however, may exist for the established model when it is used to estimate SF of C. korshinskii during the water-limited dry season. Our study deserves further exploration of a more general model to have a better estimation of SF for C. korshinskii in both dry and rainy seasons.

Thinning promoted the rejuvenation and highly efficient use of soil water for degraded Caragana korshinskii plantation in semiarid loessal regions

“…The average soil bulk density is 1.2 g cm −3 in the 0–180 cm soil layer. Rain‐fed farmlands, native shrub–grasslands, sparse forestlands, and fallow croplands are the main land use types in the watershed (Wang, Shen, et al, 2019). Moreover, the natural vegetation in the study area included sparse grasses, such as Stipa bungeana and Heteropappus altaicus .…”

“…Our previous study in this area identified a satisfactory method to upscale SF from measured stem scales to individual scales for C. korshinskii (Wang, Shen, et al, 2019). The individual‐scale total canopy transpiration (T, kg shrub −1 ) and water use efficiency (WUE, kg m −3 shrub −1 ) of C. korshinskii were calculated during the growing seasons from the stem‐scale SF data (Tsuruta et al, 2020).…”

“…Reducing the leaf area of the canopy by pruning decreases the loss of transpiration, thus ensuring better plant growth under extreme drought conditions (Chen et al, 2016). Studies have investigated the effects of thinning and pruning on soil water retention, vegetation growth, renewal, production, and water use (Ma et al, 2019; McDowell & Allen, 2015; Nunes et al, 2014; Tsamir et al, 2019; Wang, Shen, et al, 2019). These studies improved our knowledge of the response of plant and soil water to different thinning and pruning treatments.…”

The Stem Sap Flow and Water Sources for Tamarix ramosissima in an Artificial Shelterbelt With a Deep Groundwater Table in Northwest China

“…Plant transpiration is conducted via stomatal processes and the hysteresis between environmental factors and the SSF can be regarded as the adaptation of plants to environmental factors caused by water limitation (Matheny et al, 2014;Ma et al, 2017;Zha et al, 2017;Hong et al, 2019;Wang et al, 2019). Our results show that the daily cycle for PAR, Ta, and VPD (24 h) lags behind that for the SSF (Figure 6), which is in agreement with previous studies (Ma et al, 2017;Hong et al, 2019;Wang et al, 2019). Generally, the maximum PAR occurs at noon, while the maximum temperature and the maximum VPD usually appear in the afternoon.…”

Complex canopy structures control tree transpiration: A study based on 3D modelling in a tropical rainforest

“…In general, per‐tree transpiration often scales with tree size. Variations among trees are thus often explained by biometric variables, among which stem diameter is often applied (Dierick & Hölscher, 2009; Kotowska et al, 2021; Meinzer et al, 2001; Vertessy et al, 1995; Wang et al, 2019; Yue et al, 2008). However, crown dimension‐related metrics such as crown projection area were reported to perform better than stem diameter for predicting transpiration, for example, across 32 study sites in lowland Sumatra (Röll et al, 2019).…”