Functional Effects of Vegetation on the Radiant Energy Budget of Boreal Forest

In contrast to tundras, where the mass of vegetation is low and its effect on energy exchange relatively small, boreal forest vegetation exerts a more important buffering effect on energy flux to and from the ground surface. Air movement below the canopy is reduced, and a relatively high proportion of solar radiation is absorbed by the canopy directly, to be lost as sensible or latent heat. Removal of the buffer provided by stratified vegetation results in increased soil heat flux and ground temperatures, and increased depth of the active layer, which in areas of ice rich permafrost can lead to surface subsidence.

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Soil-Surface Straw Influences Micrometeorological Conditions Affecting Canola Mortality During Nighttime Frosts

Journal of Agricultural Science ◽

10.5539/jas.v12n11p246 ◽

2020 ◽

Vol 12 (11) ◽

pp. 246

Author(s):

Samuel Kovaleski ◽

Arno B. Heldwein ◽

Genei A. Dalmago ◽

Jorge A. de Gouvêa ◽

Gilberto R. da Cunha ◽

...

Keyword(s):

Heat Flux ◽

Ground Surface ◽

Soil Surface ◽

Soil Heat Flux ◽

Growth Cycle ◽

The Other ◽

Net Radiation ◽

Plant Mortality ◽

Seedling Mortality ◽

Micrometeorological Conditions

Our objective was to measure alterations in the micrometeorological conditions surrounding canola seedlings during frost periods, and to quantify seedling mortality as a function of straw distribution on the ground surface. The data was acquired from 15 frosts in 2014. We used four treatments, comprising ground surface without straw (SWS), ground surface entirely straw-covered (SEC), sowing line without straw (SLW), and soil with preexisting surface straw (SES), over three experiments. Net radiation (NR), soil heat flux (G), air (Ta), leaf (Lf), rosette (Tr), and surface temperature (Ts), and plant mortality were evaluated. NR was higher in the SEC treatment and lower in the SLW treatment, whereas G was higher on straw-covered ground; Ts and Ta were lower in the SEC than in the other treatments during the most intense frosts. On 06/19, Tr in the SEC and SLW treatments was -0.66 °C and 0.42 °C, respectively; on 08/14, Lf was -3.62 °C and -2.88 °C in the SEC and SLW treatments, respectively. Plant mortality due to the frost on 06/19 was 30% in the SEC treatment, but 0% in the SLW treatment; the frost of 08/14 caused 33.8% mortality in the SEC treatment and 1.25% in the SLW treatment. This therefore showed that removing straw from the sowing line improved the microclimate around the plants, thus reducing canola mortality at the beginning of the growth cycle, which is when frost events most frequently occur.

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Fluxo de calor no solo modelado a partir de dados de temperatura em dois níveis de profundidade em uma floresta tropical na Amazônia Ocidental

Ciência e Natura ◽

10.5902/2179460x30726 ◽

2018 ◽

Vol 40 ◽

pp. 138

Author(s):

Antônio Vinicius do Prado Rodrigues ◽

Nelma Tavares Dias Soares ◽

Renata Gonçalves Aguiar ◽

Alberto Dresch Webler ◽

Bruno Soares de Castro

Keyword(s):

Heat Flux ◽

Energy Balance ◽

Soil Temperature ◽

Tropical Forest ◽

Large Scale ◽

Energy Exchange ◽

Global Climate ◽

Soil Heat Flux ◽

Measured Data ◽

Biological Reserve

The global climate is dependent of ecological balance of forests, especially tropical. The heat flux in the soil is an important factor in studies of energy balance representing the main form of energy exchange between soil and atmosphere. The aim of the present work was to estimate soil heat flux using soil temperature measurements at two depth levels in a tropical forest in the Western Amazon, in order to obtain coherent data for both the use of the values and for the filling of failures in database. Had been used data on temperature and soil heat flux collected in a micrometeorological tower belonging to the towers network of the Large Scale Biosphere-Atmosphere Program in the Amazon, located in the Jaru Biological Reserve. The estimated data presented 94% agreement with the measured data, the two have similar behaviors that allow the use in filling of failures in a demonstrative way. However, there is a delay in the estimated values of the heat flux in the soil in relation to the measured one, which interferes in the result of the model, provoking more studies to improve it.

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The Evaluation and Effects of Soil Heat Flux on Ground Surface Heat Balance.

JOURNAL OF JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES ◽

10.3178/jjshwr.12.492 ◽

1999 ◽

Vol 12 (6) ◽

pp. 492-501

Author(s):

Masahiro KOJIMA ◽

Kimiteru SADO ◽

Takashi NAKAO

Keyword(s):

Heat Flux ◽

Heat Balance ◽

Ground Surface ◽

Soil Heat Flux ◽

Surface Heat

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An Assessment of Using Remote Sensing-based Models to Estimate Ground Surface Soil Heat Flux on the Tibetan Plateau during the Freeze-thaw Process

Remote Sensing ◽

10.3390/rs12030501 ◽

2020 ◽

Vol 12 (3) ◽

pp. 501 ◽

Cited By ~ 1

Author(s):

Yang ◽

Wu ◽

Yao ◽

Li ◽

Xie ◽

...

Keyword(s):

Remote Sensing ◽

Heat Flux ◽

Ground Surface ◽

Soil Heat Flux ◽

The Tibetan Plateau ◽

Frozen Ground ◽

Group Schemes ◽

Freeze Thaw ◽

Thaw Cycle ◽

Freeze Thaw Cycle

The ground surface soil heat flux (G0) is very important to simulate the changes of frozen ground and the active layer thickness; in addition, the freeze-thaw cycle will also affect G0 on the Tibetan Plateau (TP). As G0 could not be measured directly and soil heat flux is difficult to be observed on the TP in situ due to its high altitude and cold environment, most of previous studies have directly applied existing remote sensing-based models to estimate G0 without assessing whether the selected model is the best one of those models for those study regions. We use in-situ observation data collected at 12 sites combined with Moderate Resolution Imaging Spectroradiometer (MODIS) data (MOD13Q1, MODLT1D, MOD09CMG, and MCD15A2H) and the China meteorological forcing dataset (CMFD-SRad and CMFD-LRad) to validate the main models during the freeze-thaw process. The results show that during the three stages (complete freezing (CF), daily freeze-thaw cycle (DFT), and complete thawing (CT)) of the freeze-thaw cycle, the root mean square error (RMSE) between the models' G0 simulated value and the corresponding G0 "measured value" is the largest in the CT phase and smallest in the CF phase. The simulated results of the second group schemes (SEBAL, Ma, SEBALadj, and Maadj) were slightly underestimated, more stable, and closer to the measured values than the first group schemes (Choudhury, Clawson, SEBS, Choudhuryadj, Clawsonadj, and SEBSadj). The Maadj scheme is the one with the smallest RMSE among all the schemes and could be directly applied across the entire TP. Then, four possible reasons leading to the errors of the main schemes were analyzed. The soil moisture affecting the ratio G0/Rn and the phase shift between G0 and net radiation Rn are not considered in the schemes directly; the scheme cannot completely and correctly capture the direction of G0; and the input data of the schemes to estimate the regional G0 maybe bring some errors into the simulated results. The results are expected to provide a basis for selecting remote sensing-based models to simulate G0 in frozen ground dynamics and to calculate evapotranspiration on the TP during the freeze-thaw process. The scheme Maadj suitable for the TP was also offered in the study. We proposed several improvement directions of remote sensing-based models in order to enhance understanding of the energy exchange between the ground surface and the atmosphere.

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Application of fractional calculus in ground heat flux estimation

Thermal Science ◽

10.2298/tsci110131075p ◽

2012 ◽

Vol 16 (2) ◽

pp. 373-384 ◽

Cited By ~ 1

Author(s):

Milan Protic ◽

Miomir Stankovic ◽

Dragan Mitic ◽

Branimir Todorovic

Keyword(s):

Heat Flux ◽

Surface Temperature ◽

Land Surface ◽

Ground Surface ◽

Physical Factor ◽

Soil Heat Flux ◽

Analytic Solutions ◽

Ground Heat Flux ◽

Balance Analysis ◽

Energy Balance Analysis

Ground (soil) heat flux is important physical factor primarily because of its role in surface energy balance, analysis of atmospheric boundary layer and land surface-atmosphere interaction. Direct measurement of this property is often associated with difficulties arising from need for adequate calibration of measuring devices, determination of proper depth for probes, upward water migration and accumulation below measuring plates to lack of understanding of the governing thermal processes occurring at the ground surface. In the following paper approach for inferring heat flux indirectly, from known ground surface temperature time-dependant functions, using previously developed fractional diffusion equation for ground heat conduction is elaborated. Fractional equation is solved for two, most frequently encountered harmonic surface temperature functions. Yielded results were compared with analytic solutions. Validation results indicate that solutions obtained with fractional approach closely correspond to analytic solutions with remark that former are more general, containing the term covering the transitional effect.

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EFFECTS OF THE SOIL MOISTURE ON THE NET RADIATION FLUX AND SOIL HEAT FLUX AT THE GROUND SURFACE

Geographical Review of Japan ◽

10.4157/grj1984a.58.1_39 ◽

1985 ◽

Vol 58 (1) ◽

pp. 39-46 ◽

Cited By ~ 1

Author(s):

Soo-Jin HWANG

Keyword(s):

Heat Flux ◽

Soil Moisture ◽

Radiation Flux ◽

Ground Surface ◽

Soil Heat Flux ◽

Net Radiation

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Patterns of surface energy exchange and evapotranspiration in relation to water availability in an oasis-desert ecotone

10.22541/au.161855581.17552627/v1 ◽

2021 ◽

Author(s):

Xibin Ji ◽

Wenzhi Zhao ◽

Bowen Jin ◽

Jane Liu ◽

Feinan Xu ◽

...

Keyword(s):

Heat Flux ◽

Surface Energy ◽

Arid Regions ◽

Energy Exchange ◽

Soil Heat Flux ◽

Valuable Insight ◽

Management Guidelines ◽

Surface Energy Fluxes ◽

The Arid Regions ◽

Insight Into

A knowledge of the exchanges of energy and water over the terrestrial surface is the first step to understand the ecohydrological mechanisms, particularly in water-limited ecosystems in the dryland environments. However, patterns of energy exchange and evapotranspiration (ET) are not well understood in the oasis-desert ecotone, which plays an important role in protecting oasis against the threat of desertification in northwestern China’s arid regions. Here the continuous measurements of surface energy fluxes were made using eddy covariance in conjunction with auxiliary measurements for two years (2014-2015) at a shrubland within an oasis-desert ecotone in the arid regions, northwestern China. Statistical analysis on 30-min time scale indicates that about 50% of daytime net radiation (Rn) over the shrubland is dissipated as H on average, which peaks in spring; one third Rn is consumed by soil heat flux (G). Only 9% of Rn was consumed for latent heat flux (λE), which peaks in summer (21% in 2014 and 16% in 2015), corresponding to the season with highest rainfall among all seasons. Daily mean ET is about 1 mm·d−1 during growing season of the shrub species. The rapid and transient increase in ET occurs following a rainfall event. A switch in surface soil moisture from 0.04 to 0.11 m3·m−3 causes an increase in Rn by about 11% and λE by 151% at the shrubland, respectively. Accumulated annual ET were 195 and 181 mm in 2014 and 2015, respectively, exceeding the corresponding P by about 87 and 77 mm, indicating that groundwater may be another important source of water for ET over the shrubland aside from P. These results provide valuable insight into the mechanisms of sustaining energy and water balance at the ecotone, and then produce some management guidelines for allocating water resources and protecting vegetation.

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