1
|
Uni D, Sheffer E, Klein T, Shem-Tov R, Segev N, Winters G. Responses of two Acacia species to drought suggest different water-use strategies, reflecting their topographic distribution. FRONTIERS IN PLANT SCIENCE 2023; 14:1154223. [PMID: 37342134 PMCID: PMC10277743 DOI: 10.3389/fpls.2023.1154223] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Accepted: 05/02/2023] [Indexed: 06/22/2023]
Abstract
Introduction Soil water availability is a key factor in the growth of trees. In arid deserts, tree growth is limited by very dry soil and atmosphere conditions. Acacia tree species are distributed in the most arid deserts of the globe, therefore they are well adapted to heat and long droughts. Understanding why some plants do better than others in some environments is a key question in plant science. Methods Here we conducted a greenhouse experiment to continuously and simultaneously track the whole-plant water-balance of two desert Acacia species, in order to unravel their physiological responses to low water availability. Results We found that even under volumetric water content (VWC) of 5-9% in the soil, both species maintained 25% of the control plants, with a peak of canopy activity at noon. Moreover, plants exposed to the low water availability treatment continued growing in this period. A. tortilis applied a more opportunistic strategy than A. raddiana, and showed stomatal responses at a lower VWC (9.8% vs. 13.1%, t4= -4.23, p = 0.006), 2.2-fold higher growth, and faster recovery from drought stress. Discussion Although the experiment was done in milder VPD (~3 kPa) compared to the natural conditions in the field (~5 kPa), the different physiological responses to drought between the two species might explain their different topographic distributions. A. tortilis is more abundant in elevated locations with larger fluctuations in water availability while A. raddiana is more abundant in the main channels with higher and less fluctuating water availability. This work shows a unique and non-trivial water-spending strategy in two Acacia species adapted to hyper-arid conditions.
Collapse
Affiliation(s)
- Daphna Uni
- Institute of Plant Sciences and Genetics in Agriculture, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel
- Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Efrat Sheffer
- Institute of Plant Sciences and Genetics in Agriculture, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel
| | - Tamir Klein
- Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Rachamim Shem-Tov
- Acacia Research Center, The Dead Sea-Arava Science Center, Masada, Israel
| | - Nitzan Segev
- Acacia Research Center, The Dead Sea-Arava Science Center, Masada, Israel
| | - Gidon Winters
- Acacia Research Center, The Dead Sea-Arava Science Center, Masada, Israel
- Department of Life Sciences, Ben-Gurion University of the Negev, Eilat, Israel
| |
Collapse
|
2
|
Protas H, Ghisays V, Goradia DD, Bauer R, Devadas V, Chen K, Reiman EM, Su Y. Individualized network analysis: A novel approach to investigate tau PET using graph theory in the Alzheimer's disease continuum. Front Neurosci 2023; 17:1089134. [PMID: 36937677 PMCID: PMC10017746 DOI: 10.3389/fnins.2023.1089134] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Accepted: 02/14/2023] [Indexed: 03/06/2023] Open
Abstract
Introduction Tau PET imaging has emerged as an important tool to detect and monitor tangle burden in vivo in the study of Alzheimer's disease (AD). Previous studies demonstrated the association of tau burden with cognitive decline in probable AD cohorts. This study introduces a novel approach to analyze tau PET data by constructing individualized tau network structure and deriving its graph theory-based measures. We hypothesize that the network- based measures are a measure of the total tau load and the stage through disease. Methods Using tau PET data from the AD Neuroimaging Initiative from 369 participants, we determine the network measures, global efficiency, global strength, and limbic strength, and compare with two regional measures entorhinal and tau composite SUVR, in the ability to differentiate, cognitively unimpaired (CU), MCI and AD. We also investigate the correlation of these network and regional measures and a measure of memory performance, auditory verbal learning test for long-term recall memory (AVLT-LTM). Finally, we determine the stages based on global efficiency and limbic strength using conditional inference trees and compare with Braak staging. Results We demonstrate that the derived network measures are able to differentiate three clinical stages of AD, CU, MCI, and AD. We also demonstrate that these network measures are strongly correlated with memory performance overall. Unlike regional tau measurements, the tau network measures were significantly associated with AVLT-LTM even in cognitively unimpaired individuals. Stages determined from global efficiency and limbic strength, visually resembled Braak staging. Discussion The strong correlations with memory particularly in CU suggest the proposed technique may be used to characterize subtle early tau accumulation. Further investigation is ongoing to examine this technique in a longitudinal setting.
Collapse
Affiliation(s)
- Hillary Protas
- Banner Alzheimer’s Institute, Phoenix, AZ, United States
- Arizona Alzheimer’s Consortium, Phoenix, AZ, United States
| | - Valentina Ghisays
- Banner Alzheimer’s Institute, Phoenix, AZ, United States
- Arizona Alzheimer’s Consortium, Phoenix, AZ, United States
| | - Dhruman D. Goradia
- Banner Alzheimer’s Institute, Phoenix, AZ, United States
- Arizona Alzheimer’s Consortium, Phoenix, AZ, United States
| | - Robert Bauer
- Banner Alzheimer’s Institute, Phoenix, AZ, United States
- Arizona Alzheimer’s Consortium, Phoenix, AZ, United States
| | - Vivek Devadas
- Banner Alzheimer’s Institute, Phoenix, AZ, United States
- Arizona Alzheimer’s Consortium, Phoenix, AZ, United States
| | - Kewei Chen
- Banner Alzheimer’s Institute, Phoenix, AZ, United States
- Arizona Alzheimer’s Consortium, Phoenix, AZ, United States
- Department of Neurology, The University of Arizona, Tucson, AZ, United States
- Department of Psychiatry, The University of Arizona, Tucson, AZ, United States
- Department of Neuroscience, School of Computing and Augmented Intelligence, Biostatistical Core, School of Mathematics and Statistics, College of Health Solutions, Arizona State University, Tempe, AZ, United States
| | - Eric M. Reiman
- Banner Alzheimer’s Institute, Phoenix, AZ, United States
- Arizona Alzheimer’s Consortium, Phoenix, AZ, United States
- Department of Neurology, The University of Arizona, Tucson, AZ, United States
- Department of Psychiatry, The University of Arizona, Tucson, AZ, United States
- Department of Neuroscience, School of Computing and Augmented Intelligence, Biostatistical Core, School of Mathematics and Statistics, College of Health Solutions, Arizona State University, Tempe, AZ, United States
- Translational Genomics Research Institute, Phoenix, AZ, United States
| | - Yi Su
- Banner Alzheimer’s Institute, Phoenix, AZ, United States
- Arizona Alzheimer’s Consortium, Phoenix, AZ, United States
- Department of Neuroscience, School of Computing and Augmented Intelligence, Biostatistical Core, School of Mathematics and Statistics, College of Health Solutions, Arizona State University, Tempe, AZ, United States
| |
Collapse
|
3
|
Uni D, Lerner D, Smit I, Mzimba D, Sheffer E, Winters G, Klein T. Differential climatic conditions drive growth of Acacia tortilis tree in its range edges in Africa and Asia. AMERICAN JOURNAL OF BOTANY 2023; 110:e16132. [PMID: 36706279 DOI: 10.1002/ajb2.16132] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Revised: 12/28/2022] [Accepted: 12/29/2022] [Indexed: 06/18/2023]
Abstract
PREMISE Tree growth is a fundamental biological process that is essential to ecosystem functioning and water and element cycling. Climate exerts a major impact on tree growth, with tree species often requiring a unique set of conditions to initiate and maintain growth throughout the growing season. Still, little is known about the specific climatic factors that enable tree growth in savannah and desert tree species. Among the global tree species, Acacia tortilis occupies one of the largest distribution ranges (crossing 6500 km and 54 latitudes), spanning large parts of Africa and into the Middle East and Asia. METHODS Here we collected climate data and monitored Acacia tortilis tree growth (continuous measurements of stem circumference) in its southern and northern range edges in South Africa (SA) and Israel (IL), respectively, to elucidate whether the growth-climate interactions were similar in both edges. RESULTS Growth occurred during the summer (between December and March) in SA and in IL during early summer and autumn (April-June and October-November, respectively). Surprisingly, annual growth was 40% higher in IL than in SA. Within the wide distribution range of Acacia tortilis, our statistical model showed that climatic drivers of tree growth differed between the two sites. CONCLUSIONS High temperatures facilitated growth at the hot and arid IL site, while high humidity permitted growth at the more humid SA site. Our results confer an additional understanding of tree growth adaptation to extreme conditions in Acacia's world range edges, a major point of interest with ongoing climate change.
Collapse
Affiliation(s)
- Daphna Uni
- Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, Israel
- Institute of Plant Sciences and Genetics in Agriculture, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel
| | - David Lerner
- Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Izak Smit
- Scientific Services, South Africa National Parks, Skukuza, 1350, South Africa
- Sustainability Research Unit, Nelson Mandela University, George, South Africa
- Department of Zoology and Entomology, University of Pretoria, Pretoria, 0001, South Africa
| | - Duduzile Mzimba
- Scientific Services, South Africa National Parks, Skukuza, 1350, South Africa
| | - Efrat Sheffer
- Institute of Plant Sciences and Genetics in Agriculture, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel
| | - Gidon Winters
- The Dead Sea-Arava Science Center, Tamar Regional Council, Neve Zohar, 86910, Israel
- Eilat Campus, Ben-Gurion University of the Negev, Hatmarim Blv, Eilat, 8855630, Israel
| | - Tamir Klein
- Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, Israel
| |
Collapse
|
4
|
Ferrante M, Möller D, Möller G, Menares E, Lubin Y, Segoli M. Invertebrate and vertebrate predation rates in a hyperarid ecosystem following an oil spill. Ecol Evol 2021; 11:12153-12160. [PMID: 34522367 PMCID: PMC8427564 DOI: 10.1002/ece3.7978] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Revised: 07/07/2021] [Accepted: 07/15/2021] [Indexed: 11/16/2022] Open
Abstract
Extreme temperatures and scarce precipitation in deserts have led to abiotic factors often being regarded as more important than biotic ones in shaping desert communities. The presumed low biological activity of deserts is also one reason why deserts are often overlooked by conservation programs. We provide the first quantification of predation intensity from a desert ecosystem using artificial sentinel prey emulating caterpillars, a standardized monitoring tool to quantify relative predation pressure by many invertebrate and vertebrate predators. The study was conducted in a protected natural area affected by oil spills in 1975 and 2014; hence, we assessed the potential effects of oil pollution on predation rates. We found that predation was mostly due to invertebrate rather than vertebrate predators, fluctuated throughout the year, was higher at the ground level than in the tree canopy, and was not negatively affected by the oil spills. The mean predation rate per day (12.9%) was within the range found in other ecosystems, suggesting that biotic interactions in deserts ought not to be neglected and that ecologists should adopt standardized tools to track ecological functions and allow for comparisons among ecosystems.
Collapse
Affiliation(s)
- Marco Ferrante
- Mitrani Department of Desert EcologyBlaustein Institutes for Desert ResearchBen‐Gurion University of the NegevMidreshet Ben‐GurionIsrael
- Ce3C ‐ Centre for Ecology, Evolution and Environmental ChangesAzorean Biodiversity GroupFaculty of Agricultural Sciences and EnvironmentUniversity of the AzoresAngra do HeroísmoPortugal
| | - Daniella Möller
- Mitrani Department of Desert EcologyBlaustein Institutes for Desert ResearchBen‐Gurion University of the NegevMidreshet Ben‐GurionIsrael
| | - Gabriella Möller
- Mitrani Department of Desert EcologyBlaustein Institutes for Desert ResearchBen‐Gurion University of the NegevMidreshet Ben‐GurionIsrael
| | - Esteban Menares
- Mitrani Department of Desert EcologyBlaustein Institutes for Desert ResearchBen‐Gurion University of the NegevMidreshet Ben‐GurionIsrael
- Department of EcologyBrandenburg University of Technology Cottbus‐SenftenbergCottbusGermany
| | - Yael Lubin
- Mitrani Department of Desert EcologyBlaustein Institutes for Desert ResearchBen‐Gurion University of the NegevMidreshet Ben‐GurionIsrael
| | - Michal Segoli
- Mitrani Department of Desert EcologyBlaustein Institutes for Desert ResearchBen‐Gurion University of the NegevMidreshet Ben‐GurionIsrael
| |
Collapse
|
5
|
Al Ashhab A, Meshner S, Alexander-Shani R, Dimerets H, Brandwein M, Bar-Lavan Y, Winters G. Temporal and Spatial Changes in Phyllosphere Microbiome of Acacia Trees Growing in Arid Environments. Front Microbiol 2021; 12:656269. [PMID: 34322096 PMCID: PMC8312645 DOI: 10.3389/fmicb.2021.656269] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Accepted: 05/31/2021] [Indexed: 02/01/2023] Open
Abstract
Background: The evolutionary relationships between plants and their microbiomes are of high importance to the survival of plants in general and even more in extreme conditions. Changes in the plant's microbiome can affect plant development, growth, fitness, and health. Along the arid Arava, southern Israel, acacia trees (Acacia raddiana and Acacia tortilis) are considered keystone species. In this study, we investigated the ecological effects of plant species, microclimate, phenology, and seasonality on the epiphytic and endophytic microbiome of acacia trees. One hundred thirty-nine leaf samples were collected throughout the sampling year and were assessed using 16S rDNA gene amplified with five different primers (targeting different gene regions) and sequenced (150 bp paired-end) on an Illumina MiSeq sequencing platform. Results: Epiphytic bacterial diversity indices (Shannon-Wiener, Chao1, Simpson, and observed number of operational taxonomic units) were found to be nearly double compared to endophyte counterparts. Epiphyte and endophyte communities were significantly different from each other in terms of the composition of the microbial associations. Interestingly, the epiphytic bacterial diversity was similar in the two acacia species, but the canopy sides and sample months exhibited different diversity, whereas the endophytic bacterial communities were different in the two acacia species but similar throughout the year. Abiotic factors, such as air temperature and precipitation, were shown to significantly affect both epiphyte and endophytes communities. Bacterial community compositions showed that Firmicutes dominate A. raddiana, and Proteobacteria dominate A. tortilis; these bacterial communities consisted of only a small number of bacterial families, mainly Bacillaceae and Comamonadaceae in the endophyte for A. raddiana and A. tortilis, respectively, and Geodematophilaceae and Micrococcaceae for epiphyte bacterial communities, respectively. Interestingly, ~60% of the obtained bacterial classifications were unclassified below family level (i.e., "new"). Conclusions: These results shed light on the unique desert phyllosphere microbiome highlighting the importance of multiple genotypic and abiotic factors in shaping the epiphytic and endophytic microbial communities. This study also shows that only a few bacterial families dominate both epiphyte and endophyte communities, highlighting the importance of climate change (precipitation, air temperature, and humidity) in affecting arid land ecosystems where acacia trees are considered keystone species.
Collapse
Affiliation(s)
- Ashraf Al Ashhab
- Dead Sea and Arava Science Center, Masada, Israel.,Ben-Gurion University of the Negev, Eilat Campus, Be'er Sheva, Israel
| | | | | | | | - Michael Brandwein
- Dead Sea and Arava Science Center, Masada, Israel.,Biofilm Research Laboratory, Faculty of Dental Medicine, Hebrew University of Jerusalem, Jerusalem, Israel
| | | | - Gidon Winters
- Dead Sea and Arava Science Center, Masada, Israel.,Ben-Gurion University of the Negev, Eilat Campus, Be'er Sheva, Israel
| |
Collapse
|
6
|
Evolutionary history and genetic connectivity across highly fragmented populations of an endangered daisy. Heredity (Edinb) 2021; 126:846-858. [PMID: 33608651 PMCID: PMC8102499 DOI: 10.1038/s41437-021-00413-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Revised: 01/24/2021] [Accepted: 01/25/2021] [Indexed: 01/31/2023] Open
Abstract
Conservation management can be aided by knowledge of genetic diversity and evolutionary history, so that ecological and evolutionary processes can be preserved. The Button Wrinklewort daisy (Rutidosis leptorrhynchoides) was a common component of grassy ecosystems in south-eastern Australia. It is now endangered due to extensive habitat loss and the impacts of livestock grazing, and is currently restricted to a few small populations in two regions >500 km apart, one in Victoria, the other in the Australian Capital Territory and nearby New South Wales (ACT/NSW). Using a genome-wide SNP dataset, we assessed patterns of genetic structure and genetic differentiation of 12 natural diploid populations. We estimated intrapopulation genetic diversity to scope sources for genetic management. Bayesian clustering and principal coordinate analyses showed strong population genetic differentiation between the two regions, and substantial substructure within ACT/NSW. A coalescent tree-building approach implemented in SNAPP indicated evolutionary divergence between the two distant regions. Among the populations screened, the last two known remaining Victorian populations had the highest genetic diversity, despite having among the lowest recent census sizes. A maximum likelihood population tree method implemented in TreeMix suggested little or no recent gene flow except potentially between very close neighbours. Populations that were more genetically distinctive had lower genetic diversity, suggesting that drift in isolation is likely driving population differentiation though loss of diversity, hence re-establishing gene flow among them is desirable. These results provide background knowledge for evidence-based conservation and support genetic rescue within and between regions to elevate genetic diversity and alleviate inbreeding.
Collapse
|
7
|
Ferrante M, Möller DM, Möller GM, Lubin Y, Segoli M. Seed Predation on Oil-Polluted and Unpolluted Vachellia ( Acacia) Trees in a Hyper-Arid Desert Ecosystem. INSECTS 2020; 11:insects11100665. [PMID: 32998405 PMCID: PMC7600291 DOI: 10.3390/insects11100665] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Accepted: 09/24/2020] [Indexed: 11/20/2022]
Abstract
Simple Summary Bruchid beetles are the pests of many plant species worldwide. One or more grubs can develop inside a seed by consuming it and impairing its germination. Vachellia trees are important for preserving diverse and healthy arid ecosystems, but they are often threatened by human activities and hostile environmental conditions. Seed predation by bruchid beetles is one of the major causes of the decline in the populations of Vachellia trees in Israel. In a hyper-arid desert ecosystem affected by two major oil spills (in 1975 and 2014), we evaluated whether oil pollution increases seed predation rates of the seeds of Vachellia tortilis and V. raddiana. We recorded remarkably high predation rates for both species, particularly at the ground level, which suggests that conservation measures to reduce repeated infestations on fallen pods may be important to preserve these tree species. However, we found no clear evidence of a negative effect of oil pollution on seed predation, indicating that it did not increase the vulnerability of the seeds to bruchids even in trees affected by the recent oil spill. Abstract Acacia trees are keystone species in many arid environments, supporting high levels of plant and animal diversity. In Israel, the populations of Vachellia (formerly Acacia) tortilis (Forssk.) and V. raddiana (Savi) are declining at an alarming rate. Severe infestations by bruchid beetles (Coleoptera, Chrysomelidae) are among the major causes of seed mortality, but additional environmental stressors can reduce the defence level of the seeds, exacerbating their susceptibility to predators. In a hyper-arid desert ecosystem affected by two major oil spills (in 1975 and 2014), we quantified seed predation rates caused by insect granivores before and after the pods dropped to the ground. We recorded predation rates of up to 84% for both tree species, and higher predation rates at the ground level than in the canopy, suggesting that repeated infestations occur. These results reinforce the call to protect the populations of large ungulates such as gazelles, which kill the bruchids by feeding upon the pods, and promote seed germination and dispersion. We found no clear evidence of a negative effect of the oil spill on seed predation, indicating that oil pollution did not increase the vulnerability of the seeds to granivores even in trees affected by the recent oil spill.
Collapse
Affiliation(s)
- Marco Ferrante
- Mitrani Department of Desert Ecology, Ben-Gurion University of the Negev, Midreshet Ben-Gurion 8499000, Israel; (D.M.M.); (G.M.M.); (Y.L.); (M.S.)
- CE3C-Centre for Ecology, Evolution and Environmental Changes, Azorean Biodiversity Group, Faculty of Agricultural and Environmental Sciences, University of the Azores, PT-9700-042 Angra do Heroísmo, Portugal
- Correspondence: ; Tel.: +351-926-042-036
| | - Daniella M. Möller
- Mitrani Department of Desert Ecology, Ben-Gurion University of the Negev, Midreshet Ben-Gurion 8499000, Israel; (D.M.M.); (G.M.M.); (Y.L.); (M.S.)
| | - Gabriella M. Möller
- Mitrani Department of Desert Ecology, Ben-Gurion University of the Negev, Midreshet Ben-Gurion 8499000, Israel; (D.M.M.); (G.M.M.); (Y.L.); (M.S.)
| | - Yael Lubin
- Mitrani Department of Desert Ecology, Ben-Gurion University of the Negev, Midreshet Ben-Gurion 8499000, Israel; (D.M.M.); (G.M.M.); (Y.L.); (M.S.)
| | - Michal Segoli
- Mitrani Department of Desert Ecology, Ben-Gurion University of the Negev, Midreshet Ben-Gurion 8499000, Israel; (D.M.M.); (G.M.M.); (Y.L.); (M.S.)
| |
Collapse
|
8
|
Winters G, Otieno D, Cohen S, Bogner C, Ragowloski G, Paudel I, Klein T. Tree growth and water-use in hyper-arid Acacia occurs during the hottest and driest season. Oecologia 2018; 188:695-705. [PMID: 30120548 DOI: 10.1007/s00442-018-4250-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Accepted: 08/13/2018] [Indexed: 10/28/2022]
Abstract
Drought-induced tree mortality has been recently increasing and is expected to increase further under warming climate. Conversely, tree species that survive under arid conditions might provide vital information on successful drought resistance strategies. Although Acacia (Vachellia) species dominate many of the globe's deserts, little is known about their growth dynamics and water-use in situ. Stem diameter dynamics, leaf phenology, and sap flow were monitored during 3 consecutive years in five Acacia raddiana trees and five Acacia tortilis trees in the Arid Arava Valley, southern Israel (annual precipitation 20-70 mm, restricted to October-May). We hypothesized that stem growth and other tree activities are synchronized with, and limited to single rainfall or flashflood events. Unexpectedly, cambial growth of both Acacia species was arrested during the wet season, and occurred during most of the dry season, coinciding with maximum daily temperatures as high as 45 °C and vapor pressure deficit of up to 9 kPa. Summer growth was correlated with peak sap flow in June, with almost year-round activity and foliage cover. To the best of our knowledge, these are the harshest drought conditions ever documented permitting cambial growth. These findings point to the possibility that summer cambial growth in Acacia under hyper-arid conditions relies on concurrent leaf gas exchange, which is in turn permitted by access to deep soil water. Soil water can support low-density tree populations despite heat and drought, as long as recharge is kept above a minimum threshold.
Collapse
Affiliation(s)
- Gidon Winters
- The Dead Sea-Arava Science Center, Tamar Regional Council, 86910, Neve Zohar, Israel
| | - Dennis Otieno
- Department of Biological Sciences, Jaramogi Oginga Odinga University of Science and Technology, Bondo, Kenya
| | - Shabtai Cohen
- Institute of Soil, Water, and Environmental Sciences, Agricultural Research Organization, Rishon LeZion, Israel
| | - Christina Bogner
- Ecological Modelling, BayCEER, University of Bayreuth, Bayreuth, Germany
| | - Gideon Ragowloski
- The Dead Sea-Arava Science Center, Tamar Regional Council, 86910, Neve Zohar, Israel
| | - Indira Paudel
- Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Tamir Klein
- Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, Israel.
| |
Collapse
|