scholarly journals Soil moisture control on sap-flow response to biophysical factors in a desert-shrub species, <i>Artemisia ordosica</i>

2016 ◽  
Author(s):  
Tianshan Zha ◽  
Duo Qian ◽  
Xin Jia ◽  
Yujie Bai ◽  
Yun Tian ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Leaf Area ◽  
Sap Flow ◽  
Environmental Variables ◽  
Temporal Dynamics ◽  
Artemisia Ordosica ◽  
Shrub Species ◽  
Desert Shrub ◽  
Environmental Controls ◽  
Biophysical Factors

Abstract. Current understanding of acclimation processes in desert-shrub species to drought stress in dryland ecosystems is still incomplete. In this study, we measured sap flow in Artemisia ordosica and associated environmental variables throughout the growing seasons of 2013–2014 (May–September period of each year) to better understand the environmental controls on the temporal dynamics of sap flow. We found that the occurrence of drought in the dry year of 2013 during the leaf-expansion and leaf-expanded periods caused sap flow per leaf area (Js) to decline significantly, resulting in a sizable drop in transpiration. Sap flow per leaf area correlated positively with radiation (Rs), air temperature (T), and vapor pressure deficit (VPD), when volumetric soil water content (VWC) was > 0.11 m3 m−3. Diurnal Js was generally ahead of Rs by as much as 6 hours. This lag time, however, decreased with increasing VWC. Relative response of Js to the environmental variables (i.e., Rs, T, and VPD) varied with VWC, Js being more biologically controlled with low decoupling coefficient and thus being less sensitive to the environmental variables during dry periods. According to this study, soil moisture is shown to control sap-flow (and, therefore, plant-transpiration) response in Artemisia ordosica to diurnal variations in biophysical factors. The findings of this study add to the knowledge of acclimation processes in desert-shrub species under drought-associated stress. This knowledge is essential to model desert-shrub-ecosystem functioning under changing climatic conditions.

scholarly journals Soil moisture control of sap-flow response to biophysical factors in a desert-shrub species, <i>Artemisia ordosica</i>

2017 ◽  
Vol 14 (19) ◽  
pp. 4533-4544 ◽  
Author(s):  
Tianshan Zha ◽  
Duo Qian ◽  
Xin Jia ◽  
Yujie Bai ◽  
Yun Tian ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Leaf Area ◽  
Sap Flow ◽  
Environmental Variables ◽  
Conservation Strategy ◽  
Artemisia Ordosica ◽  
Shrub Species ◽  
Desert Shrub ◽  
Environmental Controls ◽  
Biophysical Factors

Abstract. The current understanding of acclimation processes in desert-shrub species to drought stress in dryland ecosystems is still incomplete. In this study, we measured sap flow in Artemisia ordosica and associated environmental variables throughout the growing seasons of 2013 and 2014 (May–September period of each year) to better understand the environmental controls on the temporal dynamics of sap flow. We found that the occurrence of drought in the dry year of 2013 during the leaf-expansion and leaf-expanded periods caused sap flow per leaf area (Js) to decline significantly, resulting in transpiration being 34 % lower in 2013 than in 2014. Sap flow per leaf area correlated positively with radiation (Rs), air temperature (T), and water vapor pressure deficit (VPD) when volumetric soil water content (VWC) was greater than 0.10 m3 m−3. Diurnal Js was generally ahead of Rs by as much as 6 hours. This time lag, however, decreased with increasing VWC. The relative response of Js to the environmental variables (i.e., Rs, T, and VPD) varied with VWC, Js being more strongly controlled by plant-physiological processes during periods of dryness indicated by a low decoupling coefficient and low sensitivity to the environmental variables. According to this study, soil moisture is shown to control sap-flow (and, therefore, plant-transpiration) response in Artemisia ordosica to diurnal variations in biophysical factors. This species escaped (acclimated to) water limitations by invoking a water-conservation strategy with the regulation of stomatal conductance and advancement of Js peaking time, manifesting in a hysteresis effect. The findings of this study add to the knowledge of acclimation processes in desert-shrub species under drought-associated stress. This knowledge is essential in modeling desert-shrub-ecosystem functioning under changing climatic conditions.

How to differentiate nighttime transpiration and water recharge in nocturnal sap flow?

2020 ◽  
Author(s):  
Zuosinan Chen ◽  
Zhiqiang Zhang ◽  
Lixin Chen
Keyword(s):  
Soil Moisture ◽  
Wind Speed ◽  
Water Loss ◽  
Sap Flow ◽  
Northern China ◽  
Mountainous Area ◽  
Nighttime Transpiration ◽  
Environmental Controls ◽  
Water Recharge ◽  
Semi Arid

&lt;p&gt;Nocturnal sap flow (&lt;em&gt;Q&lt;sub&gt;n&lt;/sub&gt;&lt;/em&gt;) affect not only forest carbon and water budgets but also their responses to climate change as it consists of two ecohydrological and ecophysiological significant components: nighttime transpiration and water recharge. A vapor pressure deficit (&lt;em&gt;VPD&lt;/em&gt;) based sap flow partitioning method has been developed to estimate nighttime transpiration, which is normally quantified through the discretely measured nighttime stomatal conductance, from the widely and continuously measured sap flow. However, given the increasing knowledge of &lt;em&gt;Q&lt;sub&gt;n&lt;/sub&gt;&lt;/em&gt; mechanisms, whether &lt;em&gt;Q&lt;sub&gt;n&lt;/sub&gt;&lt;/em&gt;&amp;#160;could be partitioning simply by &lt;em&gt;VPD&lt;/em&gt; and whether this method is valid in semi-arid regions remain unclear. We measured sap flow of &lt;em&gt;Pinus tabuliformis&lt;/em&gt; and &lt;em&gt;Acer truncatum&lt;/em&gt; in a middle-aged and a young monoculture forest stand, respectively, in a semi-arid mountainous area of northern China. We found the influence of &lt;em&gt;VPD&lt;/em&gt; on &lt;em&gt;Q&lt;sub&gt;n&lt;/sub&gt;&lt;/em&gt; conditioned by soil moisture. Meanwhile, a considerable impact of wind speed on &lt;em&gt;Q&lt;sub&gt;n&lt;/sub&gt;&lt;/em&gt; was observed. In the stands with relatively dry soils, both increased and decreased soil moisture promoted &lt;em&gt;Q&lt;sub&gt;n&lt;/sub&gt;&lt;/em&gt;, which might be due to enhanced nighttime water recharge for two distinct purposes, i.e., capacitance refilling and avoiding hydraulic failures. For these three environmental factors (i.e., &lt;em&gt;VPD&lt;/em&gt;, wind speed, and soil moisture) that have been considered most in previous studies, their total effect explained less than 55% of the &lt;em&gt;Q&lt;sub&gt;n&lt;/sub&gt;&lt;/em&gt; variations. This study highlights that physiological influences of &lt;em&gt;VPD&lt;/em&gt; on nighttime stomatal water loss were uncertain. Furthermore, it suggests that there could exist considerable nighttime water loss induced by wind, possible region-specific patterns of nighttime water recharge, and limited concurrent environmental controls on &lt;em&gt;Q&lt;/em&gt;&lt;sub&gt;n&lt;/sub&gt;. Our findings are helpful to improve the &lt;em&gt;VPD&lt;/em&gt;-based sap flow partitioning method to differentiate nighttime transpiration and water recharge.&lt;/p&gt;

scholarly journals Global soil moisture data derived through machine learning trained with in-situ measurements

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Sungmin O. ◽  
Rene Orth
Keyword(s):  
Machine Learning ◽  
Soil Moisture ◽  
Large Scale ◽  
Short Term Memory ◽  
Temporal Dynamics ◽  
Soil Moisture Data ◽  
Wide Range ◽  
Global Soil

AbstractWhile soil moisture information is essential for a wide range of hydrologic and climate applications, spatially-continuous soil moisture data is only available from satellite observations or model simulations. Here we present a global, long-term dataset of soil moisture derived through machine learning trained with in-situ measurements, SoMo.ml. We train a Long Short-Term Memory (LSTM) model to extrapolate daily soil moisture dynamics in space and in time, based on in-situ data collected from more than 1,000 stations across the globe. SoMo.ml provides multi-layer soil moisture data (0–10 cm, 10–30 cm, and 30–50 cm) at 0.25° spatial and daily temporal resolution over the period 2000–2019. The performance of the resulting dataset is evaluated through cross validation and inter-comparison with existing soil moisture datasets. SoMo.ml performs especially well in terms of temporal dynamics, making it particularly useful for applications requiring time-varying soil moisture, such as anomaly detection and memory analyses. SoMo.ml complements the existing suite of modelled and satellite-based datasets given its distinct derivation, to support large-scale hydrological, meteorological, and ecological analyses.

scholarly journals Investigating the Spatio-Temporal Variation of Soil Moisture and Agricultural Drought towards Supporting Water Resources Management in the Red River Basin of Vietnam

2021 ◽  
Vol 13 (9) ◽  
pp. 4926
Author(s):  
Nguyen Duc Luong ◽  
Nguyen Hoang Hiep ◽  
Thi Hieu Bui
Keyword(s):  
Soil Moisture ◽  
River Basin ◽  
Temporal Dynamics ◽  
Regional Scale ◽  
Dry Season ◽  
Red River ◽  
Agricultural Drought ◽  
Severe Drought ◽  
Red River Basin ◽  
Spatio Temporal

The increasing serious droughts recently might have significant impacts on socioeconomic development in the Red River basin (RRB). This study applied the variable infiltration capacity (VIC) model to investigate spatio-temporal dynamics of soil moisture in the northeast, northwest, and Red River Delta (RRD) regions of the RRB part belongs to territory of Vietnam. The soil moisture dataset simulated for 10 years (2005–2014) was utilized to establish the soil moisture anomaly percentage index (SMAPI) for assessing intensity of agricultural drought. Soil moisture appeared to co-vary with precipitation, air temperature, evapotranspiration, and various features of land cover, topography, and soil type in three regions of the RRB. SMAPI analysis revealed that more areas in the northeast experienced severe droughts compared to those in other regions, especially in the dry season and transitional months. Meanwhile, the northwest mainly suffered from mild drought and a slightly wet condition during the dry season. Different from that, the RRD mainly had moderately to very wet conditions throughout the year. The areas of both agricultural and forested lands associated with severe drought in the dry season were larger than those in the wet season. Generally, VIC-based soil moisture approach offered a feasible solution for improving soil moisture and agricultural drought monitoring capabilities at the regional scale.

scholarly journals Climate Differently Impacts the Growth of Coexisting Trees and Shrubs under Semi-Arid Mediterranean Conditions

Forests ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 381
Author(s):  
J. Julio Camarero ◽  
Cristina Valeriano ◽  
Antonio Gazol ◽  
Michele Colangelo ◽  
Raúl Sánchez-Salguero
Keyword(s):  
Soil Moisture ◽  
Radial Growth ◽  
Pinus Halepensis ◽  
Growth Dynamics ◽  
Early Summer ◽  
Growth Responses ◽  
Shrub Species ◽  
High Soil Moisture ◽  
Semi Arid ◽  
Mediterranean Conditions

Background and Objectives—Coexisting tree and shrub species will have to withstand more arid conditions as temperatures keep rising in the Mediterranean Basin. However, we still lack reliable assessments on how climate and drought affect the radial growth of tree and shrub species at intra- and interannual time scales under semi-arid Mediterranean conditions. Materials and Methods—We investigated the growth responses to climate of four co-occurring gymnosperms inhabiting semi-arid Mediterranean sites in northeastern Spain: two tree species (Aleppo pine, Pinus halepensis Mill.; Spanish juniper, Juniperus thurifera L.) and two shrubs (Phoenicean juniper, Juniperus phoenicea L.; Ephedra nebrodensis Tineo ex Guss.). First, we quantified the intra-annual radial-growth rates of the four species by periodically sampling wood samples during one growing season. Second, we quantified the climate–growth relationships at an interannual scale at two sites with different soil water availability by using dendrochronology. Third, we simulated growth responses to temperature and soil moisture using the forward, process-based Vaganov‒Shashkin (VS-Lite) growth model to disentangle the main climatic drivers of growth. Results—The growth of all species peaked in spring to early summer (May–June). The pine and junipers grew after the dry summer, i.e., they showed a bimodal growth pattern. Prior wet winter conditions leading to high soil moisture before cambium reactivation in spring enhanced the growth of P. halepensis at dry sites, whereas the growth of both junipers and Ephedra depended more on high spring–summer soil moisture. The VS-Lite model identified these different influences of soil moisture on growth in tree and shrub species. Conclusions—Our approach (i) revealed contrasting growth dynamics of co-existing tree and shrub species under semi-arid Mediterranean conditions and (ii) provided novel insights on different responses as a function of growth habits in similar drought-prone regions.

Diversity of phenolic compounds and plant traits in coexisting Patagonian desert shrub species of Argentina

Plant Ecology ◽  
2013 ◽  
Vol 214 (11) ◽  
pp. 1335-1343 ◽  
Author(s):  
Hebe Saraví Cisneros ◽  
Mónica B. Bertiller ◽  
Analía L. Carrera ◽  
Cecilia Larreguy
Keyword(s):  
Phenolic Compounds ◽  
Plant Traits ◽  
Shrub Species ◽  
Desert Shrub

Water transport in European Beech roots (<5mm) under drought in the south of Lower Saxony

2021 ◽  
Author(s):  
Eva Messinger ◽  
Heinz Coners ◽  
Dietrich Hertel ◽  
Christoph Leuschner
Keyword(s):  
Soil Moisture ◽  
Water Transport ◽  
Water Uptake ◽  
Sap Flow ◽  
Climate Models ◽  
European Beech ◽  
Root Surface Area ◽  
Lower Saxony ◽  
Tree Roots ◽  
Small Roots

&lt;p&gt;Climate models predict hotter and dryer summers in Germany, with longer periods of extreme droughts like in summer 2018. How does this affect the water uptake and transport in tree roots growing in the top- and subsoil?&lt;/p&gt;&lt;p&gt;In summer 2018 and 2019 we measured the water transport in fine roots (&lt;5mm) of European Beech on tertiary sand and triassic sandstone up to 2 m depth. We adapted the well-established HRM technique to enable measurements of very small sap flow rates in small roots. Thus, we measured the water transport as a temperature ratio of a stretching heat pulse.&lt;/p&gt;&lt;p&gt;Relating sap flow to root surface area, root depth, anatomy, soil moisture, and VPD allows for interesting insights in tree water uptake rates: Where are the limits of drought intensity and duration, for water uptake and recovery of small roots? Are there differences in the function of top- and subsoil roots? Are roots specialized for water transport or nutrient uptake? The investigated data gives a first hint on how the water transport in Beech roots differs with changes in the soil moisture and VPD under changing climate.&lt;/p&gt;

Hydrological implications of vegetation change in a subarctic, alpine catchment, Yukon Territory, Canada 

2021 ◽  
Author(s):  
Erin Nicholls ◽  
Gordon Drewitt ◽  
Sean Carey
Keyword(s):  
Soil Moisture ◽  
Interannual Variability ◽  
Sap Flow ◽  
Vegetation Change ◽  
Vegetation Type ◽  
Growing Season ◽  
White Spruce ◽  
Yukon Territory ◽  
Precipitation Regimes ◽  
Tall Shrub

&lt;p&gt;As a result of altitude and latitude amplified impacts of climate change, widespread alterations in vegetation composition, density and distribution are widely observed across the circumpolar north. The influence of this vegetation change on the timing and magnitude of hydrological fluxes is uncertain, and is confounded by changes driven by increased temperatures and altered precipitation (P) regimes. In northern alpine catchments, quantification of total evapotranspiration (ET) and evaporative partitioning across a range of elevation-based ecosystems is critical for predicting water yield under change, yet remains challenging due to coupled environmental and phenological controls on transpiration (T). In this work, we analyze 6 years of surface energy balance, ET, and sap flow data at three sites along an elevational gradient in a subarctic, alpine catchment near Whitehorse, Yukon Territory, Canada. These sites provide a space-for-time evaluation of vegetation shifts and include: 1) a low-elevation boreal white spruce forest (~20 m), 2) a mid-elevation subalpine taiga comprised of tall willow (Salix) and birch (Betula) shrubs (~1-3 m) and 3) a high-elevation subalpine taiga with shorter shrub cover (&lt; 0.75 m) and moss, lichen, and bare rock. Specific objectives are to 1) evaluate interannual ET dynamics within and among sites under different precipitation regimes , and 2) assess the influence of vegetation type and structure, phenology, soil and meteorological controls on ET dynamics and partitioning.&amp;#160; Eddy covariance and sap flow sensors operated year-round at the forest and during the growing season at the mid-elevation site on both willow and birch shrubs for two years. Growing season ET decreased and interannual variability increased with elevation, with June to August ET totals of 250 (&amp;#177;3) mm at Forest, 192 (&amp;#177;9) mm at the tall shrub site, and 180 (&amp;#177; 26) mm at the short shrub site. Comparatively, AET:P ratios were the highest and most variable at the forest (2.4 &amp;#177; 0.3) and similar at the tall and short shrub (1.2 &amp;#177; 0.1).&amp;#160; At the forest, net radiation was the primary control on ET, and 55% was direct T from white spruce. At the shrub sites, monthly ET rates were similar except during the peak growing season when T at the tall shrub site comprised 89% of ET, resulting in greater total water loss. Soil moisture strongly influenced T at the forest, suggesting the potential for moisture stress, yet not at the shrub sites where there was no moisture limitation. Results indicate that elevation advances in treeline will increase overall ET and lower interannual variability; yet the large water deficit during summer implies a strong reliance on early spring snowmelt recharge to sustain soil moisture. Changes in shrub height and density will increase ET primarily during the mid-growing season. This work supports the assertion that predicted changes in vegetation type and structure will have a considerable impact on water partitioning in northern regions, and will also vary in a multifaceted way in response to changing temperature and P regimes.&amp;#160;&amp;#160;&lt;/p&gt;

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