A simple ecohydrological model captures essentials of seasonal leaf dynamics in semi-arid tropical grasslands

Abstract. Modelling leaf phenology in water-controlled ecosystems remains a difficult task because of high spatial and temporal variability in the interaction of plant growth and soil moisture. Here, we move beyond widely used linear models to examine the performance of low-dimensional, nonlinear ecohydrological models that couple the dynamics of plant cover and soil moisture. The study area encompasses 400 000 km2 of semi-arid perennial tropical grasslands, dominated by C4 grasses, in the Northern Territory and Queensland (Australia). We prepared 8 yr time series (2001–2008) of climatic variables and estimates of fractional vegetation cover derived from MODIS Normalized Difference Vegetation Index (NDVI) for 400 randomly chosen sites, of which 25% were used for model calibration and 75% for model validation. We found that the mean absolute error of linear and nonlinear models did not markedly differ. However, nonlinear models presented key advantages: (1) they exhibited far less systematic error than their linear counterparts; (2) their error magnitude was consistent throughout a precipitation gradient while the performance of linear models deteriorated at the driest sites, and (3) they better captured the sharp transitions in leaf cover that are observed under high seasonality of precipitation. Our results showed that low-dimensional models including feedbacks between soil water balance and plant growth adequately predict leaf dynamics in semi-arid perennial grasslands. Because these models attempt to capture fundamental ecohydrological processes, they should be the favoured approach for prognostic models of phenology.

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A simple ecohydrological model captures essentials of seasonal leaf dynamics in semi-arid tropical grasslands

Biogeosciences ◽

10.5194/bg-7-907-2010 ◽

2010 ◽

Vol 7 (3) ◽

pp. 907-920 ◽

Cited By ~ 34

Author(s):

P. Choler ◽

W. Sea ◽

P. Briggs ◽

M. Raupach ◽

R. Leuning

Keyword(s):

Soil Moisture ◽

Plant Growth ◽

Linear Models ◽

Nonlinear Models ◽

Plant Cover ◽

Spatial And Temporal Variability ◽

Tropical Grasslands ◽

Low Dimensional ◽

Semi Arid ◽

Leaf Dynamics

Abstract. Modelling leaf phenology in water-controlled ecosystems remains a difficult task because of high spatial and temporal variability in the interaction of plant growth and soil moisture. Here, we move beyond widely used linear models to examine the performance of low-dimensional, nonlinear ecohydrological models that couple the dynamics of plant cover and soil moisture. The study area encompasses 400 000 km2 of semi-arid perennial tropical grasslands, dominated by C4 grasses, in the Northern Territory and Queensland (Australia). We prepared 8-year time series (2001–2008) of climatic variables and estimates of fractional vegetation cover derived from MODIS Normalized Difference Vegetation Index (NDVI) for 400 randomly chosen sites, of which 25% were used for model calibration and 75% for model validation. We found that the mean absolute error of linear and nonlinear models did not markedly differ. However, nonlinear models presented key advantages: (1) they exhibited far less systematic error than their linear counterparts; (2) their error magnitude was consistent throughout a precipitation gradient while the performance of linear models deteriorated at the driest sites, and (3) they better captured the sharp transitions in leaf cover that are observed under high seasonality of precipitation. Our results showed that low-dimensional models including feedbacks between soil water balance and plant growth adequately predict leaf dynamics in semi-arid perennial grasslands. Because these models attempt to capture fundamental ecohydrological processes, they should be the favoured approach for prognostic models of phenology.

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Response of water vapour D-excess to land-atmosphere interactions in a semi-arid environment

10.5194/hess-2016-271 ◽

2016 ◽

Cited By ~ 2

Author(s):

Stephen D. Parkes ◽

Matthew F. McCabe ◽

Alan D. Griffiths ◽

Lixin Wang ◽

Scott Chambers ◽

...

Keyword(s):

Soil Moisture ◽

Relative Humidity ◽

Water Vapour ◽

Regional Scale ◽

Measurement Techniques ◽

Spatial And Temporal Variability ◽

Moisture Source ◽

Moisture Recycling ◽

Nocturnal Inversion ◽

Semi Arid

Abstract. The stable isotopic composition of water vapour provides information about moisture sources and processes that is difficult to obtain with traditional measurement techniques. Recently, it has been proposed that the D-excess (dv = δ2H − 8 × δ18O) of water vapour can provide a diagnostic tracer of continental moisture recycling. However, D-excess exhibits a diurnal cycle that has been observed across a variety of ecosystems and may be influenced by a range of processes beyond regional scale moisture recycling, including local evaporation (ET) fluxes. There is a lack of measurements of D-excess in evaporation (ET) fluxes, which has made it difficult to assess how ET fluxes modify the D-excess in water vapour (dv). With this in mind, we employed a chamber based approach to directly measure D-excess in ET (dET) fluxes. We show that ET fluxes imposed a negative forcing on the ambient vapour and could not explain the higher daytime dv values. The low dET observed here was sourced from a soil water pool that had undergone an extended drying period, leading to low D-excess of the soil moisture. A strong correlation between daytime dv and locally measured relative humidity was consistent with an oceanic moisture source, suggesting that remote hydrological processes were the major contributor to daytime dv variability. During the early evening, ET fluxes into a shallow nocturnal inversion layer caused a lowering of the dv values near the surface. In addition, transient mixing of vapour with a higher D-excess from above the nocturnal inversion modified these values, causing large within night variability. These results indicate dET can generally be expected to show large spatial and temporal variability and to depend on the soil moisture state. For long periods between rain events, common in semi-arid environments, ET would be expected to impose negative forcing on the surface dv. The variability of D-excess in ET fluxes therefore needs to be considered when using dv to study moisture recycling and during extended dry periods may act as a tracer of the relative humidity of the oceanic moisture source.

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SISTEM OTOMASI PENYIRAMAN TANAMAN BERBASIS TELEGRAM

SIGMA TEKNIKA ◽

10.33373/sigma.v2i1.1834 ◽

2019 ◽

Vol 2 (1) ◽

pp. 81

Author(s):

Muhammad Irsyam

Keyword(s):

Soil Moisture ◽

Plant Growth ◽

Water Intake ◽

Smart Phone ◽

Growth Failure ◽

Automation System ◽

Notification System ◽

Efficiency And Effectiveness ◽

Plant Automation

ABSTRAK Faktor yang menentukan kegagalan pertumbuhan suatu tanaman hampir dipengaruhi oleh teknik atau cara penyiraman tanaman yang salah. Hal ini disebabkan oleh teknik penyiraman yang dilakukan secara manual sehingga tidak semua tanaman mendapatkan asupan air yang merata untuk menghidari tanaman menjadi layu. Faktor lain yang menyebabkan kegagalan pertumbuhan tanaman adalah kelembaban tanah. Oleh karena itu, untuk mengurangi permasalahan tersebut dirancanglah “Sistem Otomasi Penyiraman Tanaman Berbasis Telegram”. Adapun sistem ini meliputi penyiraman tanaman secara otomatis berdasarkan kadar kelembaban tanah dengan sistem pemberitahuan atau notifikasi yang akan dikirimkan kepada petani dengan menggunakan aplikasi smart phone Telegram. Sistem ini telah mampu mengontrol penyiraman sesuai dengan kondisi yang diinginkan. Dengan adanya sistem otomasi penyiraman tanaman berbasis telegram maka dapat meningkatkan efesiensi dan efektivitas petani sehingga kualitas tanaman dapat terjaga dengan baik.Kata kunci -- Penyiraman Tanaman, Penyiraman Secara Otomatis, Telegram.ABSTRACT Factors that determine the failure of a plant's growth of almost are influenced by incorrect cropping techniques or methods. This is caused by the technique of watering is done manually so that not all plants get a uniform water intake to avoid crops withered. Another factor that causes plant growth failure is soil moisture. Therefore, to reduce the problem was designed "Telegram Based Water Planting Automation System". The system includes automatic watering of plants based on moisture level of the soil with a notification or notification system that will be sent to farmers using Telegram smart phone applications. This system has been able to control the watering according to the desired conditions. With the telegraph-based plant watering plant automation system can improve the efficiency and effectiveness of farmers so that the quality of the plant can be maintained properly. Keywords -- Watering Plants, Watering Automatically, Telegram.

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Comparative Analysis Of Plant Growth Regulators On Bud Break In Prosopsis And Tecomella For Sustainable Agriculture In Arid And Semi-Arid Regions Of India

Bioscience Biotechnology Research Communications ◽

10.21786/bbrc/11.2/3 ◽

2018 ◽

Vol 11 (2) ◽

pp. 208-215

Author(s):

Sunita Khatak

Keyword(s):

Comparative Analysis ◽

Plant Growth ◽

Sustainable Agriculture ◽

Plant Growth Regulators ◽

Growth Regulators ◽

Arid Regions ◽

Bud Break ◽

Semi Arid

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

Forests ◽

10.3390/f12030381 ◽

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.

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Suitability Evaluation of Typical Drought Index in Soil Moisture Retrieval and Monitoring Based on Optical Images

Remote Sensing ◽

10.3390/rs12162587 ◽

2020 ◽

Vol 12 (16) ◽

pp. 2587

Author(s):

Yan Nie ◽

Ying Tan ◽

Yuqin Deng ◽

Jing Yu

Keyword(s):

Remote Sensing ◽

Soil Moisture ◽

Arid Regions ◽

Drought Index ◽

Dynamic Monitoring ◽

Landsat 8 ◽

Landsat 8 Oli ◽

Rapid Acquisition ◽

Semi Arid ◽

Soil Moisture Inversion

As a basic agricultural parameter in the formation, transformation, and consumption of surface water resources, soil moisture has a very important influence on the vegetation growth, agricultural production, and healthy operation of regional ecosystems. The Aksu river basin is a typical semi-arid agricultural area which seasonally suffers from water shortage. Due to the lack of knowledge on soil moisture change, the water management and decision-making processes have been a difficult issue for local government. Therefore, soil moisture monitoring by remote sensing became a reasonable way to schedule crop irrigation and evaluate the irrigation efficiency. Compared to in situ measurements, the use of remote sensing for the monitoring of soil water content is convenient and can be repetitively applied over a large area. To verify the applicability of the typical drought index to the rapid acquisition of soil moisture in arid and semi-arid regions, this study simulated, compared, and validated the effectiveness of soil moisture inversion. GF-1 WFV images, Landsat 8 OLI images, and the measured soil moisture data were used to determine the Perpendicular Drought Index (PDI), the Modified Perpendicular Drought Index (MPDI), and the Vegetation Adjusted Perpendicular Drought Index (VAPDI). First, the determination coefficients of the correlation analyses on the PDI, MPDI, VAPDI, and measured soil moisture in the 0–10, 10–20, and 20–30 cm depth layers based on the GF-1 WFV and Landsat 8 OLI images were good. Notably, in the 0–10 cm depth layers, the average determination coefficient was 0.68; all models met the accuracy requirements of soil moisture inversion. Both indicated that the drought indices based on the Near Infrared (NIR)-Red spectral space derived from the optical remote sensing images are more sensitive to soil moisture near the surface layer; however, the accuracy of retrieving the soil moisture in deep layers was slightly lower in the study area. Second, in areas of vegetation coverage, MPDI and VAPDI had a higher inversion accuracy than PDI. To a certain extent, they overcame the influence of mixed pixels on the soil moisture spectral information. VAPDI modified by Perpendicular Vegetation Index (PVI) was not susceptible to vegetation saturation and, thus, had a higher inversion accuracy, which makes it performs better than MPDI’s in vegetated areas. Third, the spatial heterogeneity of the soil moisture retrieved by the GF-1 WFV and Landsat 8 OLI image were similar. However, the GF-1 WFV images were more sensitive to changes in the soil moisture, which reflected the actual soil moisture level covered by different vegetation. These results provide a practical reference for the dynamic monitoring of surface soil moisture, obtaining agricultural information and agricultural condition parameters in arid and semi-arid regions.

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