Spatiotemporal variations in groundwater and evaporative demand drive ecophysiological functioning of a phreatophyte in drylands

AbstractWater is the main limiting factor for groundwater-dependent ecosystems (GDEs) in drylands. Predicted climate change (precipitation reductions and temperature increases) and anthropogenic activities such as groundwater drawdown jeopardise the functioning of these ecosystems, presenting new challenges for their management. We developed a trait-based analysis to examine the spatiotemporal variability in the ecophysiology of Ziziphus lotus, a long-lived phreatophyte that dominates one of the few terrestrial GDEs of semiarid regions in Europe. We assessed morpho-functional traits and stem water potential along a naturally occurring gradient of depth-to-groundwater (DTGW, 2–25 m) in a coastal aquifer, and throughout the species-growing season. Increasing DTGW and salinity negatively affected photosynthetic and transpiration rates, increasing plant water stress (lower predawn and midday water potential), and positively affected Huber value (sapwood cross-sectional area per leaf area), reducing leaf area and likely, plant hydraulic demand. However, the species showed greater salt-tolerance at shallow depths. Despite groundwater characteristics, higher atmospheric evaporative demand in the study area, which occurred in summer, fostered higher transpiration rates and water stress, and promoted carbon assimilation and water loss more intensively at shallow water tables. This multiple-trait analysis allowed us to identify plant ecophysiological thresholds related to the increase in salinity, but mostly in DTGW (13 m), and in the evaporative demand during the growing season. These findings highlight the existence of tipping points in the functioning of a long-lived phreatophyte in drylands and can contribute to the sustainable management of GDEs in southern Europe, paving the way for further studies on phreatophytic species.

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Corrigendum to: Influence of climatic factors on variation in the Normalised Difference Vegetation Index in Mongolian Plateau grasslands

The Rangeland Journal ◽

10.1071/rj16073_co ◽

2018 ◽

Vol 40 (2) ◽

pp. 205

Author(s):

Xu-Juan Cao ◽

Qing-Zhu Gao ◽

Ganjurjav Hasbagan ◽

Yan Liang ◽

Wen-Han Li ◽

...

Keyword(s):

Climate Change ◽

Land Use ◽

Vegetation Index ◽

Climatic Factors ◽

Growing Season ◽

Limiting Factor ◽

Spatial And Temporal Variability ◽

Climate Factors ◽

Mongolian Plateau ◽

Normalised Difference Vegetation Index

Climate change will affect how the Normalised Difference Vegetation Index (NDVI), which is correlated with climate factors, varies in space and over time. The Mongolian Plateau is an arid and semi-arid area, 64% covered by grassland, which is extremely sensitive to climate change. Its climate has shown a warming and drying trend at both annual and seasonal scales. We analysed NDVI and climate variation characteristics and the relationships between them for Mongolian Plateau grasslands from 1981 to 2013. The results showed spatial and temporal differences in the variation of NDVI. Precipitation showed the strongest correlation with NDVI (43% of plateau area correlated with total annual precipitation and 44% with total precipitation in the growing season, from May to September), followed by potential evapotranspiration (27% annual, and 30% growing season), temperature (7% annual, 16% growing season) and cloud cover (10% annual, 12% growing season). These findings confirm that moisture is the most important limiting factor for grassland vegetation growth on the Mongolian Plateau. Changes in land use help to explain variations in NDVI in 40% of the plateau, where no correlation with climate factors was found. Our results indicate that vegetation primary productivity will decrease if warming and drying trends continue but decreases will be less substantial if further warming, predicted as highly likely, is not accompanied by further drying, for which predictions are less certain. Continuing spatial and temporal variability can be expected, including as a result of land use changes.

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Climate change influence on a forested urban park: a forecast of tree growth and mortality

10.32920/ryerson.14647239.v1 ◽

2021 ◽

Author(s):

Geet K Grewal

Keyword(s):

Climate Change ◽

Leaf Area ◽

Tree Growth ◽

Climate Change Scenario ◽

Growing Season ◽

Forecast Model ◽

Change Scenario ◽

Climate Change Scenarios ◽

Growing Season Length ◽

Management Plans

Climate change is expected to lengthen the growing season for plants in many temperate regions. The purpose of this study is to develop future growth estimates for trees in Earlscourt Park, Toronto. The i-Tree Forecast model, in combination with climate change scenarios provided by the Canadian Climate Change Scenario Network, were used to build trajectories of future tree growth and mortality. Tree growth forecasts were greatest for the climate change scenario with the longest growing season length. Results highlight future vulnerability in two tree species common to the park, honey locust and Norway maple. A comparison of the leaf area estimates produced by i-Tree Streets and i-Tree Eco was also conducted. These models showed differences in their prediction of leaf area, a key metric for ecological service provision. Forecasting tree growth and mortality in urban parks can inform management plans that seek to maximize the flow of future ecological benefits.

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Functional responses of recently emerged seedlings of an endemic Mexican oak (Quercus eduardii) under climate change conditions

Botanical Sciences ◽

10.17129/botsci.1988 ◽

2018 ◽

Vol 96 (4) ◽

pp. 582

Author(s):

Ernesto I. Badano ◽

Francisco A. Guerra-Coss ◽

Sandra M. Gelviz-Gelvez ◽

Joel Flores ◽

Pablo Delgado-Sánchez

Keyword(s):

Climate Change ◽

Seedling Emergence ◽

Canopy Cover ◽

Growing Season ◽

Climatic Conditions ◽

Tree Seedlings ◽

Functional Responses ◽

Climate Change Simulation ◽

Survival And Growth ◽

Growth Of Seedlings

Background: Climate change will increase temperature and reduce rainfall across temperate forests of Mexico. This can alter tree establishment dynamics within forest and in neighbouring man-made clearings.Hypotheses: Climate change will reduce emergence and survival of tree seedlings, and surviving plants will display functional responses matching with these changes. These effects should be more noticeable in clearings due to the lack of canopy cover.Studied species: Quercus eduardii (Fagaceae, section Lobatae) an oak species endemic to Mexico.Study site and years of study: Tree growing season 2015-2016 (rainy season) in a mature oak forest and a neighbouring clearing in Sierra de Álvarez, state of San Luis Potosí.Methods: In both habitats, we established control plots (under current climatic conditions) and climate change simulation plots (increased temperature and reduced rainfall). At the beginning of the growing season, we sowed acorns of Q. eduardii in these plots and monitored the emergence, survival and growth of seedlings. At the end of the growing season, we assessed functional responses on surviving seedlings.Results: Seedling emergence and survival were lower in climate change plots from both habitats. However, differences in survival between climate treatments were larger within the forest. Seedlings from climate change plots displayed functional responses indicating higher levels of thermal and water stress.Conclusions: This study indicates that climate change will constrain tree recruitment in Mexican oak forests. However, contrary to our expectations, it seems that these effects will be higher within forests than in man-made clearings.

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The Effects of Climate Change on Variability of the Growing Seasons in the Elbe River Lowland, Czech Republic

Advances in Meteorology ◽

10.1155/2015/546920 ◽

2015 ◽

Vol 2015 ◽

pp. 1-16 ◽

Cited By ~ 5

Author(s):

Vera Potopová ◽

Pavel Zahradníček ◽

Luboš Türkott ◽

Petr Štěpánek ◽

Josef Soukup

Keyword(s):

Climate Change ◽

Climate Models ◽

Regional Climate ◽

Regional Climate Models ◽

Growing Season ◽

Spatiotemporal Variability ◽

Elbe River ◽

Study Region ◽

The Elbe River ◽

Projected Changes

This research aimed to identify an approach for adaptation of agriculture to increased climate variability and projected changes, taking into account regional specificity of climate change. Changes in the timing of growing season (GS) parameters for both observation and models data were computed using daily mean temperatures for three thresholds that correspond to the physiological requirements of the vegetable types. This research included a new assessment of the potential impacts of climate change on the GS of vegetables grown in the Elbe River lowland, one of the largest farmed vegetable regions in Central Europe. To accomplish this, a comprehensive analysis was conducted of the spatiotemporal variability of the date of the beginning of the growing season (BGS), the date of the end of the growing season (EGS), and the length of the growing season (GSL) for the period 1961–2011. In addition, an assessment was made of the potential changes in the dates of the BGS, EGS, and GSL for the Elbe River lowland, simulated using the regional climate models. Prospective areas for growing thermophilic vegetables in the study region were also determined.

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Influence of climatic factors on variation in the Normalised Difference Vegetation Index in Mongolian Plateau grasslands

The Rangeland Journal ◽

10.1071/rj16073 ◽

2018 ◽

Vol 40 (2) ◽

pp. 91 ◽

Cited By ~ 4

Author(s):

Xu-Juan Cao ◽

Qing-Zhu Gao ◽

Ganjurjav Hasbagan ◽

Yan Liang ◽

Wen-Han Li ◽

...

Keyword(s):

Climate Change ◽

Land Use ◽

Vegetation Index ◽

Climatic Factors ◽

Growing Season ◽

Limiting Factor ◽

Spatial And Temporal Variability ◽

Climate Factors ◽

Mongolian Plateau ◽

Normalised Difference Vegetation Index

Climate change will affect how the Normalised Difference Vegetation Index (NDVI), which is correlated with climate factors, varies in space and over time. The Mongolian Plateau is an arid and semi-arid area, 64% covered by grassland, which is extremely sensitive to climate change. Its climate has shown a warming and drying trend at both annual and seasonal scales. We analysed NDVI and climate variation characteristics and the relationships between them for Mongolian Plateau grasslands from 1981 to 2013. The results showed spatial and temporal differences in the variation of NDVI. Precipitation showed the strongest correlation with NDVI (43% of plateau area correlated with total annual precipitation and 44% with total precipitation in the growing season, from May to September), followed by potential evapotranspiration (27% annual, and 30% growing season), temperature (7% annual, 16% growing season) and cloud cover (10% annual, 12% growing season). These findings confirm that moisture is the most important limiting factor for grassland vegetation growth on the Mongolian Plateau. Changes in land use help to explain variations in NDVI in 40% of the plateau, where no correlation with climate factors was found. Our results indicate that vegetation primary productivity will decrease if warming and drying trends continue but decreases will be less substantial if further warming, predicted as highly likely, is not accompanied by further drying, for which predictions are less certain. Continuing spatial and temporal variability can be expected, including as a result of land use changes.

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The influence of water table depth on evapotranspiration in the Amazon arc of deforestation

10.5194/hess-2019-47 ◽

2019 ◽

Author(s):

John O'Connor ◽

Maria J. Santos ◽

Karin T. Rebel ◽

Stefan C. Dekker

Keyword(s):

Soil Moisture ◽

Water Stress ◽

Growing Season ◽

Dry Season ◽

Rooting Depth ◽

Limiting Factor ◽

Recycling System ◽

Moisture Recycling ◽

Growing Season Length ◽

Arc Of Deforestation

Abstract. The Amazon rainforest evapotranspiration (ET) flux provides climate regulating and moisture provisioning ecosystem services through a moisture recycling system. The dense complex canopy and deep root system creates an optimum structure to provide large ET fluxes to the atmosphere forming the source for precipitation. Extensive land use and land cover change (LULCC) from forest to agriculture in the arc of deforestation breaks this moisture recycling system. Crops such as soybean are planted in large homogeneous monocultures and the maximum rooting depth of these crops is far shallower than forest. This difference in rooting depth is key as forests can access deep soil moisture and show no signs of water stress during the dry season while in contrast crops are highly seasonal with a growing season dependant on rainfall. As access to soil moisture is a limiting factor in vegetation growth, we hypothesised that if crops could access soil moisture they would undergo less water stress and therefore would have higher evapotranspiration rates than crops which could not access soil moisture. We combined remote sensing data with modelled groundwater table depth (WTD) to assess whether vegetation in areas with a shallow WTD had higher ET than vegetation in deep WTD areas. We randomly selected areas of forest, savanna and crop with deep and shallow WTD and examined whether they differ on MODIS Evapotranspiration (ET), Land Surface Temperature (LST) and Enhanced Vegetation Index (EVI), from 2001 to 2012, annually and during transition periods between the wet and dry season. As expected, we found no differences in ET, LST, and EVI for forest vegetation between deep and shallow WTD, which because of their deep roots could access water and maintain evapotranspiration for moisture recycling during the entire year. We found significantly higher ET and lower LST in shallow WTD crop areas than in deep WTD during the dry season transition, suggesting that crops in deep WTD undergo higher water stress than crops in shallow WTD areas. The differences found between crop in deep and shallow WTD, however, are of low significance with regards the moisture recycling system as the difference resulting from conversion of forest to crop has an overwhelming influence (ET in forest is ≈ 2 mm day−1 higher than that in crops) and has the strongest impact on energy balance and ET. However, access to water during the transition between wet and dry seasons may positively influence growing season length in crop areas.

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Trait-based responses of seven annual crops to elevated CO2and water limitation

Renewable Agriculture and Food Systems ◽

10.1017/s1742170517000692 ◽

2018 ◽

Vol 33 (3) ◽

pp. 259-266 ◽

Cited By ~ 4

Author(s):

Devan Allen McGranahan ◽

Brittany N. Poling

Keyword(s):

Climate Change ◽

Leaf Area ◽

Water Availability ◽

Crop Production ◽

Close Association ◽

Carbon Dioxide Concentration ◽

Small Scale ◽

Functional Responses ◽

Water Limitation ◽

Species Specific

AbstractBy potentially disrupting crop production, climate change has been implicated as a threat to global food security. We focus on two elements of climate change: elevated atmospheric carbon dioxide concentration, or e[CO2], and reduced water availability, as caused by drought. Both variables have been shown to have effects on crop physiology, although there is considerable evidence of interactions and moderation by species-specific differences. Measuring traits helps scale environmental effects up to functional responses, and we focused on traits connected to photosynthesis, which has a close association with crop yield. We measured the response of four physiological traits—quantum photosynthetic yield, chlorophyll content, root:shoot ratio and leaf area—across a diverse set of seven annual crop species grown under three levels of e[CO2] (450, 575 and 700 ppm) and two levels of water availability (minimum ~45 and ~15% VWC) in a growth chamber. Species included barley, durum wheat, maize, oats, sorghum, pinto bean and sunflower. Our regression analysis focused on testing for interactions between e[CO2] and water limitation and determining relative effect sizes of climate change impacts across species, data that can be used for species-specific modeling or determining appropriate levels of environmental variables in free-air CO2enrichment studies designed to extend small-scale experimental results to the field. Across all species and all traits, the strongest effect of e[CO2] occurred from 450 to 575 ppm, with only marginal differences from 575 to 700 ppm. We found substantial declines in leaf area across all species as a result of e[CO2] and wide variability in leaf area responses to water limitation. Other traits showed weak and variable responses to both e[CO2] and water limitation. While our data confirm that elements of global change, especially increased atmospheric CO2concentration, do affect traits related to photosynthesis, we found no discernible pattern to suggest which crops might be more resistant to e[CO2].

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Climate change influence on a forested urban park: a forecast of tree growth and mortality

10.32920/ryerson.14647239 ◽

2021 ◽

Author(s):

Geet K Grewal

Keyword(s):

Climate Change ◽

Leaf Area ◽

Tree Growth ◽

Climate Change Scenario ◽

Growing Season ◽

Forecast Model ◽

Change Scenario ◽

Climate Change Scenarios ◽

Growing Season Length ◽

Management Plans

Climate change is expected to lengthen the growing season for plants in many temperate regions. The purpose of this study is to develop future growth estimates for trees in Earlscourt Park, Toronto. The i-Tree Forecast model, in combination with climate change scenarios provided by the Canadian Climate Change Scenario Network, were used to build trajectories of future tree growth and mortality. Tree growth forecasts were greatest for the climate change scenario with the longest growing season length. Results highlight future vulnerability in two tree species common to the park, honey locust and Norway maple. A comparison of the leaf area estimates produced by i-Tree Streets and i-Tree Eco was also conducted. These models showed differences in their prediction of leaf area, a key metric for ecological service provision. Forecasting tree growth and mortality in urban parks can inform management plans that seek to maximize the flow of future ecological benefits.

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Photosynthesis and growth of spring barley: some effects of drought

The Journal of Agricultural Science ◽

10.1017/s0021859600028628 ◽

1980 ◽

Vol 94 (3) ◽

pp. 623-635 ◽

Cited By ~ 9

Author(s):

J. E. Leach

Keyword(s):

Water Stress ◽

Leaf Area ◽

Dry Matter ◽

Spring Barley ◽

Net Photosynthesis ◽

Growing Season ◽

Large Field ◽

Single Leaf ◽

Unit Leaf ◽

Effects Of Drought

SummaryDuring the dry summer of 1976, measurements were made of the photosynthesis, transpiration, respiration, and growth of irrigated (I) and non-irrigated (NI) spring barley growing in large field plots. Using a field enclosure, the photosynthesis of the irrigated barley was measured on 19 separate days during the latter two-thirds of the growing season when the plants were large enough to have measurable gas exchanges. The response of photosynthesis to water stress was determined from 3 days' comparative measurements on the I and NI crops, using both the field enclosure and, on 2 days only, a single-leaf photosynthesis chamber.Water stress in the NI crop caused large decreases in yield: the dry-matter yields of grain and straw were respectively reduced by 19 and 27%; number of grains (but not grain mass) was also reduced. Field enclosure measurements, which were in good agreement both with values for canopy net photosynthesis derived from the leaf chamber measurements and with estimates of dry-matter production derived from plant weighings, indicated that the net CO2 uptake per unit leaf area was little affected by water stress. Results from the plant weighings and mensurations showed that, during the growing season, the main effect of water stress, mediated by the survival of fewer tillers and the premature senescence of leaves, was a reduction of leaf area (by 40%).

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