Evaluating canopy transpiration and water use of two typical planted tree species in the dryland Loess Plateau of China

Abstract

Large-scale vegetation restoration has been conducted in China's Loess Plateau over the past several decades to control soil and water loss. However, these efforts have not followed any specific guidelines to select plant species that balance the twin goals of vegetation restoration and water demand. In the present study, we measured canopy transpiration characteristics of oriental arborvitae (Platycladus orientalis) and Chinese pine (Pinus tabulaeformis), two species that are commonly planted in restoration efforts, and recorded water input and output for these two species during the growing season. P. tabulaeformis had a higher tolerance than P. orientalis to warmer and drier environments and used water over a wider time span. Canopy transpiration significantly increased when rainfall exceeded 15 mm and was negatively correlated with net change of soil water content. Meanwhile, rainless intervals also affected canopy transpiration recovery. Canopy transpiration of P. tabulaeformis was 25.4% higher than that of P. orientalis. Soil water content under P. orientalis declined by 28.4% after the growing season, while it slightly increased under P. tabulaeformis (0.7%). Our results suggested that although P. tabulaeformis plantation had higher canopy transpiration, this water use did not drastically reduce soil water content, mainly due to the lower evaporation caused by the dense canopy cover. However, the low soil water content also implied that a better management, such as a mixed plantation of these two species and other supplemental water-conservation techniques, should be considered to better use water in this semiarid region.

Sap flow characteristics and physiological adjustments of two dominant tree species in pure and mixed plantations in the semi-arid Loess Plateau of China

“…This facilitative interaction has also been observed among species in plantations even in seasonal drought or semi-arid water limited regions (Wu et al, 2017;Zhang et al, 2017). For example, Zhang et al (2017) suggested the dense canopy cover of P. tabuliformis can reduce the evaporation of soil water in surface layers, which may benefit co-existing species, such as Platycladus orientalis, in the dryland Loess Plateau of China. However, in the semi-arid Loess Plateau of China in the present study, although contrasting physiological adjustments of P. tabuliformis and H. rhamnoides were observed in mixed plantations (Figs.…”

“…Co-existing species in natural forest usually exhibit different physiological or morphological adjustments to minimize competition for water during prolonged drought periods (Trubat et al, 2006;Yang et al, 2015). This facilitative interaction has also been observed among species in plantations even in seasonal drought or semi-arid water limited regions (Wu et al, 2017;Zhang et al, 2017). For example, Zhang et al (2017) suggested the dense canopy cover of P. tabuliformis can reduce the evaporation of soil water in surface layers, which may benefit co-existing species, such as Platycladus orientalis, in the dryland Loess Plateau of China.…”

“…Vegetation restoration and reforestation of degraded land are useful forest management practices for the soil erosion conservation and hydrological regime regulation (Swaffer et al, 2014;Jian et al, 2015). By increasing biodiversity and the variety of ecological niches, mixed plantations may be more resistant to external disturbances, such as storms or disease attacks, compared with pure plantations (Zapater et al, 2013;Zhang et al, 2017). However, vegetation deterioration and ecological degradation have been observed in some mixed plantations because water supplies could not meet the demand for co-existing species, especially in arid and semi-arid regions (Chen et al, 2008;Yang et al, 2015).…”

Improvements in the Root Morphology, Physiology, and Anatomy of Platycladus orientalis Seedlings from Air-root Pruning

“…Franco, a native Chinese Cupressaceae plant, is among the most intensively used cypress species for vegetation restoration projects in northern China (Jiang et al, 2014;. This indigenous species is a perennial evergreen coniferous tree with remarkable longevity that exhibits high tolerance to a diversity of adverse environmental conditions, including drought, freezing temperatures, hot weather, and nutrient imbalances (enrichment and depletion) (Jiang et al, 2014;Wu et al, 2017;Zhang et al, 2017). Other studies have demonstrated that P. orientalis provided considerable ecological benefits for vegetation restoration, especially in fragile ecosystems such as arid and semiarid regions (Yu et al, 2015;Zhang et al, 2017).…”

“…This indigenous species is a perennial evergreen coniferous tree with remarkable longevity that exhibits high tolerance to a diversity of adverse environmental conditions, including drought, freezing temperatures, hot weather, and nutrient imbalances (enrichment and depletion) (Jiang et al, 2014;Wu et al, 2017;Zhang et al, 2017). Other studies have demonstrated that P. orientalis provided considerable ecological benefits for vegetation restoration, especially in fragile ecosystems such as arid and semiarid regions (Yu et al, 2015;Zhang et al, 2017). However, its survival rate is low due to the poorly developed root systems of container seedlings (Yang et al, 2010;2011) coupled with the extreme environments in which they are transplanted .…”