Sap flow of a wild cherry tree plantation growing under Mediterranean conditions: Assessing the role of environmental conditions on canopy conductance and the effect of branch pruning on water productivity

Abstract

In recent decades, wild cherry has been one of the species most widely used for reforestation in Europe. Studies aiming to select and improve trees to give them the best growth rates and wood properties have increased in response to growers' demands.However, information relating to key physiological processes such as transpiration or stomatal conductance and to the effect of the common practice of pruning on plant-water relations is scarce. The main objective of this study was to assess the effects of environmental conditions on canopy conductance dynamics. Its secondary objective was to examine the short-and medium-term effects of branch pruning on tree transpiration, growth and derived water productivity. To this end, we measured sap flow in an experimental plantation where trees were subjected to drip irrigation and rain-fed conditions and where variables characterizing climate, soil and tree growth were also monitored. The results demonstrated that the Jarvis-Stewart approach was appropriate for studying the responses of canopy conductance to environmental factors. As well as the role of vapour pressure deficit and net radiation in controlling the daily variations of canopy conductance, the single effects of decreasing soil water content (optimum relative extractable water, REW, higher than 0.4) and increasing air temperature (optimum of 21ºC), as summer conditions approached, were correctly incorporated into the modelling exercise. Soil water content exerted the greatest control on canopy conductance for trees growing under rain-fed conditions, while air temperature did for irrigated trees. Pruning significantly reduced transpiration to about 35% when pre-and post-sub-periods were compared, but also affected annual water productivity regardless of the irrigation treatment. To assess the long-term effects of pruning on water productivity, measurements in both pruned and unpruned trees would be desirable.

Water Storage of Plants Cannot Be Ignored During The Process of Water Movement

“…We observed clear differences in the use of water and distribution of water proportion between the two tree species, which could be related to the characteristics of tree species themselves. Molina et al (2019) also found that the aboveground biomass and defoliation cycle were the main factors that affected the sap flow rate. In our study, the sap flow rate of P. orientalis was higher than that of Q. variabilis during the dormant period, probably because broad-leaved deciduous species, such as Q. variabilis, have already shed their leaves, while P. orientalis retained its leaves.…”

“…Water is a key factor that affects the circulation of materials and plant growth in forest ecosystems (Nadezhdina et al 2020). Soil water is absorbed by plants through the roots and stored in the xylem or used for photosynthesis; it also evaporates and reaches the atmosphere through leaf stomata (Weatherley et al 1982;Buckley et al 2012;Adrià et al 2015;Huang et al 2017;Molina et al 2019). Stable hydrogen and oxygen isotope technology provides a new technical manner to explore the source of water for plants and solves the difficulty of quantifying the ratio of absorption of plants to each layer of water source (Wang et al 2017).…”

Do Extreme Climate Events Cause the Degradation of Malus sieversii Forests in China?

“…Extreme high temperature events occur frequently in July in the study region, and are conducive to outbreaks of diseases and insect pests. Human measures of sawing branches further reduced the leaf area of M. sieversii trees, resulting in the reduction of photosynthetic production, which hindered the growth of M. sieversii trees in the area ( Molina et al, 2019 ). Overall, the occurrence of extreme precipitation and temperature promoted the growth of wild apple tree rings in the degraded area.…”

“…Because of their excellent resistance, the vitality of good tree individuals can be strengthened, with poor trees suffering from human disturbance can become worse. For example, improper pruning by humans reduces the water use efficiency of trees ( Molina et al, 2019 ), extreme high temperature exacerbates insect and disease outbreaks, and extreme precipitation can cause outbreaks of Valsa mali Miyabe et Yamada. These resulted in the growth of M. sieversii showing a decreasing trend, and the correlation between tree-ring chronology in the degraded area and extreme precipitation, and high temperature indices showed negative correlations ( Supplementary Figures 3 , 4 and Figure 9 ).…”

Verification of sap flow characteristics and measurement errors of Populus tomentosa Carr. and Salix babylonica L. based on the liquid level equilibrium method

“…The thermal dissipation probe method (TDP) is a way of measuring stem sap flow velocity obtained by Granier after experiments, and it is widely used because of its relatively reliable measurement results, simple operation, and low cost (Liu et al, 2011;Molina et al, 2019). However, in recent years, many scholars have begun to question its accuracy, and it is generally believed that the measured values of trunk sap flow are lower than the actual values (Liu et al, 2012;Rana et al, Abbreviations: LLE, liquid level equilibrium method; TDP, thermal diffusion probe method; F d , flow velocity; A s , area.…”