Tree Hydraulic Functioning

A special issue of Forests (ISSN 1999-4907). This special issue belongs to the section "Forest Ecophysiology and Biology".

Deadline for manuscript submissions: closed (30 September 2019) | Viewed by 9026

Special Issue Editors

ETSI Montes, Forestal y del Medio Natural. C/ José Antonio Novais, Universidad Politécnica de Madrid, 10, 28040 Madrid, Spain
Interests: plant hydraulics; water relations; drought resistance; wood anatomy; phenotypic plasticity
Special Issues, Collections and Topics in MDPI journals
Fundación CEAM, Joint research unit University of Alicante-CEAM, PO Box 99, 03080 Alicante, Spain
Interests: plant functional ecology; forest restoration; ecological restoration; drought stress; climate change; forest decline
French National Institute for Agricultural Research (INRA), 5 chemin de Beaulieu, 63000 Clermont-Ferrand, France
Interests: plant ecophysiology; xylem anatomy; plant hydraulics; drought stress; xylem embolism; cavitation; plant water use; drought-induced tree mortality

Special Issue Information

Dear Colleagues,

Plant growth, reproduction and photosynthesis critically depend on maintaining an adequate supply of water to the leaves and meristems. Cavitation, and the resulting gas emboli that block the xylem conduits and impairs water transport, is considered one of the major challenges for the ascent of sap. During severe or prolonged droughts or due to the expansion of air bubbles in the freeze-thaw cycles in winter, hydraulic failure can result in loss of hydraulic conductance with the resulting reduction in water supply to leaves, lowering of photosynthetic rates, canopy dieback and eventually whole plant death. Xylem embolism is thus a limiting factor for plant survival and distribution. Besides the construction of a xylem resistant to embolism, drought and freezing tolerance is determined by a number of key hydraulic traits which aid to maintain plant water content within xylem functional limits. These traits, such as stomatal sensitivity, leaf turgor loss point, capacitance, refilling of embolized conduits or rooting depth, vary enormously across species. According to projected scenarios of global change, the expected rise in global mean temperature and frequency of extreme events over the next century will impact forest ecosystems and shift species distribution ranges. This has made hydraulic traits to emerge as crucial parameters to understanding species ecology and distribution, differences in water use strategies, and for predicting future mortality events. This special issue will focus on functional variation of plant hydraulic traits with particular interest in embolism resistance and how plants, populations and communities deal with reductions in hydraulic conductivity. We encourage submissions of original studies and critical reviews related with the following topics:

  • Variation in embolism resistance in response to abiotic (water, light, CO2, temperature) and biotic factors (competition, diseases).
  • New techniques or revisions of established techniques to evaluate hydraulic traits both in the field and in the laboratory.
  • Impact of xylem embolism and reductions of hydraulic conductivity on plant function and how plants deal with these phenomena in relation to gas exchange and plant performance.
  • Intraspecific variability and phenotypic plasticity of hydraulic traits.
  • Hydraulic traits in the framework of the plant economic spectrum. Strategies of adaptation to hydraulic failure of different functional groups.

Dr. Rosa Ana López Rodríguez
Dr. Alberto Vilagrosa
Dr. José Manuel Torres Ruiz
Guest Editors

Manuscript Submission Information

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Keywords

  • vulnerability to embolism
  • hydraulic traits
  • xylem anatomy and hydraulic functioning
  • water relations
  • tree mortality

Published Papers (3 papers)

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Research

16 pages, 2892 KiB  
Article
The Mechanism of Changes in Hydraulic Properties of Populus euphratica in Response to Drought Stress
by Duan Li, Jianhua Si, Xiaoyou Zhang, Yayu Gao, Huan Luo, Jie Qin and Guanlong Gao
Forests 2019, 10(10), 904; https://doi.org/10.3390/f10100904 - 15 Oct 2019
Cited by 9 | Viewed by 2954
Abstract
Stable hydraulic conductivity in forest trees maintains the survival of trees which contribute to productivity in forest ecosystems. Drought conditions break down this relationship, but the mechanisms are poorly known. To increase the understanding of the mechanism of hydraulic characteristics during drought, we [...] Read more.
Stable hydraulic conductivity in forest trees maintains the survival of trees which contribute to productivity in forest ecosystems. Drought conditions break down this relationship, but the mechanisms are poorly known. To increase the understanding of the mechanism of hydraulic characteristics during drought, we determined hydraulic parameters in Populus euphratica Oliv. (P. euphratica) in a time-series of drought using a high-pressure flow meter. We found that P. euphratica could enhance hydraulic transport in severe drought stress under a threshold of soil water content. Drought-induced loss of hydraulic conductance could seriously impair water transport capacity. The soil water content of about 4.5% in the rhizosphere could lead to canopy mortality yet maintain live roots. Hydraulic conductance could be changed under drought stress as a consequence of changes in the anatomical structure and physiology. Furthermore, there was also a trade-off between hydraulic efficiency and safety. The consideration of hydraulic efficiency was first within the range of hydraulic safety limit. Once the hydraulic safety limit was reached, safety would be taken as the first consideration and hydraulic efficiency would be reduced. Research on the mechanism of hydraulic properties in riparian plants in arid areas provides a scientific basis for riparian forest restoration. Full article
(This article belongs to the Special Issue Tree Hydraulic Functioning)
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13 pages, 1719 KiB  
Article
Drought-Induced Mortality Is Related to Hydraulic Vulnerability Segmentation of Tree Species in a Savanna Ecosystem
by Shubin Zhang, Guojing Wen and Daxin Yang
Forests 2019, 10(8), 697; https://doi.org/10.3390/f10080697 - 17 Aug 2019
Cited by 7 | Viewed by 2894
Abstract
Vulnerability segmentation (VS) has been widely suggested to protect stems and trunks from hydraulic failure during drought events. In many ecosystems, some species have been shown to be non-segmented (NS species). However, it is unclear whether drought-induced mortality is related to VS. To [...] Read more.
Vulnerability segmentation (VS) has been widely suggested to protect stems and trunks from hydraulic failure during drought events. In many ecosystems, some species have been shown to be non-segmented (NS species). However, it is unclear whether drought-induced mortality is related to VS. To understand this, we surveyed the mortality and recruitment rate and measured the hydraulic traits of leaves and stems as well as the photosynthesis of six tree species over five years (2012–2017) in a savanna ecosystem in Southwest China. Our results showed that the NS species exhibited a higher mortality rate than the co-occurring VS species. Across species, the mortality rate was not correlated with xylem tension at 50% loss of stem hydraulic conductivity (P50stem), but was rather significantly correlated with leaf water potential at 50% loss of leaf hydraulic conductance (P50leaf) and the difference in water potential at 50% loss of hydraulic conductance between the leaves and terminal stems (P50leaf-stem). The NS species had higher Huber values and maximum net photosynthetic rates based on leaf area, which compensated for a higher mortality rate and promoted rapid regeneration under the conditions of dry–wet cycles. To our knowledge, this study is the first to identify the difference in drought-induced mortality between NS species and VS species. Our results emphasize the importance of VS in maintaining hydraulic safety in VS species. Furthermore, the high mortality rate and fast regeneration in NS species may be another hydraulic strategy in regions where severe seasonal droughts are frequent. Full article
(This article belongs to the Special Issue Tree Hydraulic Functioning)
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14 pages, 2289 KiB  
Article
Hydraulic Characteristics of Populus euphratica in an Arid Environment
by Duan Li, Jianhua Si, Xiaoyou Zhang, Yayu Gao, Chunlin Wang, Huan Luo, Jie Qin and Guanlong Gao
Forests 2019, 10(5), 407; https://doi.org/10.3390/f10050407 - 10 May 2019
Cited by 9 | Viewed by 2478
Abstract
Stable hydraulic conductivity in forest trees maintains healthy tree crowns and contributes to productivity in forest ecosystems. Drought conditions break down this relationship, but the mechanisms are poorly known and may depend on drought severity. To increase the understanding of changes in hydraulic [...] Read more.
Stable hydraulic conductivity in forest trees maintains healthy tree crowns and contributes to productivity in forest ecosystems. Drought conditions break down this relationship, but the mechanisms are poorly known and may depend on drought severity. To increase the understanding of changes in hydraulic conductivity during drought, we determined hydraulic parameters in Populus euphratica Oliv. (P. euphratica) in naturally arid conditions and in a simulated severe drought using a high-pressure flow meter. The results showed that leaf-specific hydraulic conductance (LSC) of leaf blades was less variable in mild drought, and increased significantly in severe drought. Plants attempted to maintain stability in leaf blade LSC under moderate water stress. In extreme drought, LSC was enhanced by increasing hydraulic conductance in plant parts with less hydraulic limitation, decreasing it in other parts, and decreasing leaf area; this mechanism protected the integrity of water transport in portions of tree crowns, and induced scorched branches and partial mortality in other parts of crowns. We conclude that limitation in water supply and elastic regulation of hydraulic characteristics may drive the mortality of tree branches as a result of severe drought. Evaluation of adaptive water transport capacity in riparian plants in arid areas provides a scientific basis for riparian forest restoration. Full article
(This article belongs to the Special Issue Tree Hydraulic Functioning)
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