scholarly journals Microclimatic comparison of lichen heaths and shrubs: shrubification generates atmospheric heating but subsurface cooling during the growing season

2021 ◽  
Vol 18 (5) ◽  
pp. 1577-1599
Author(s):  
Peter Aartsma ◽  
Johan Asplund ◽  
Arvid Odland ◽  
Stefanie Reinhardt ◽  
Hans Renssen
Keyword(s):  
Heat Flux ◽  
Soil Temperature ◽  
Longwave Radiation ◽  
Growing Season ◽  
Soil Heat Flux ◽  
Net Radiation ◽  
Mountain Area ◽  
Atmospheric Heating ◽  
Air Temperatures ◽  
The Difference

Abstract. Lichen heaths are declining in abundance in alpine and Arctic areas partly due to an increasing competition with shrubs. This shift in vegetation types might have important consequences for the microclimate and climate on a larger scale. The aim of our study is to measure the difference in microclimatic conditions between lichen heaths and shrub vegetation during the growing season. With a paired plot design, we measured the net radiation, soil heat flux, soil temperature and soil moisture on an alpine mountain area in southern Norway during the summer of 2018 and 2019. We determined that the daily net radiation of lichens was on average 3.15 MJ (26 %) lower than for shrubs during the growing season. This was mainly due to a higher albedo of the lichen heaths but also due to a larger longwave radiation loss. Subsequently, we estimate that a shift from a lichen heath to shrub vegetation leads to an average increase in atmospheric heating of 3.35 MJ d−1 during the growing season. Surprisingly, the soil heat flux and soil temperature were higher below lichens than below shrubs during days with high air temperatures. This implies that the relatively high albedo of lichens does not lead to a cooler soil compared to shrubs during the growing season. We predict that the thicker litter layer, the presence of soil shading and a higher evapotranspiration rate at shrub vegetation are far more important factors in explaining the variation in soil temperature between lichens and shrubs. Our study shows that a shift from lichen heaths to shrub vegetation in alpine and Arctic areas will lead to atmospheric heating, but it has a cooling effect on the subsurface during the growing season, especially when air temperatures are relatively high.

scholarly journals The decline of alpine lichen heaths generates atmospheric heating but subsurface cooling during the growing season

2020 ◽  
Author(s):  
Peter Aartsma ◽  
Johan Asplund ◽  
Arvid Odland ◽  
Stefanie Reinhardt ◽  
Hans Renssen
Keyword(s):  
Heat Flux ◽  
Soil Temperature ◽  
Longwave Radiation ◽  
Growing Season ◽  
Soil Heat Flux ◽  
Net Radiation ◽  
Mountain Area ◽  
Atmospheric Heating ◽  
Air Temperatures ◽  
The Difference

Abstract. Lichen heaths are declining in abundance in alpine and arctic areas partly due to an increasing competition with shrubs. This shift in vegetation types might have important consequences for the microclimate and climate on a larger scale. The aim of our study is to measure the difference in microclimatic conditions between lichen heaths and shrub vegetation during the growing season. With a paired plot design, we measured the net radiation, soil heat flux, soil temperature, and soil moisture on an alpine mountain area in south Norway during the summer of 2018 and 2019. We determined that the daily net radiation of lichens was on average 3.15 MJ (26 %) lower than for shrubs during the growing season. This was mainly due to a higher albedo of the lichen heaths, but also due to a larger longwave radiation loss. Subsequently, we estimate that a shift from a lichen heath to shrub vegetation leads to an average increase in atmospheric heating of 3.35 MJ per day during the growing season. Surprisingly, the soil heat flux and soil temperature were higher below lichens than below shrubs during days with high air temperatures. This implies that the relatively high albedo of lichens does not lead to a cooler soil compared to shrubs during the growing season. We hypothesize that the thicker litter layer, the presence of soil shading, and a higher evapotranspiration rate at shrub vegetation are far more important factors in explaining the variation in soil temperature between lichens and shrubs. Our study shows that a shift from lichen heaths to shrub vegetation in alpine and arctic areas will lead to atmospheric heating, but has a cooling effect on the subsurface during the growing season, especially when air temperatures are relatively high.

scholarly journals Forest Evapotranspiration and Energy Flux Partitioning Based on Eddy Covariance Methods in an Arid Desert Region of Northwest China

2017 ◽  
Vol 2017 ◽  
pp. 1-10
Author(s):  
Xiaohong Ma ◽  
Qi Feng ◽  
Yonghong Su ◽  
Tengfei Yu ◽  
Hua Jin
Keyword(s):  
Heat Flux ◽  
Energy Flux ◽  
Moisture Transfer ◽  
Sensible Heat Flux ◽  
Growing Season ◽  
Northwest China ◽  
Soil Heat Flux ◽  
Heat Fluxes ◽  
Net Radiation ◽  
Flux Partitioning

In this study, the characteristics of energy flux partitioning and evapotranspiration of P. euphratica forests were examined in the extreme arid region of Northwest China. Energy balance closure of the ecosystem was approximately 72% (H + LE = 0.72 ∗ (Rn-G)+7.72, r2=0.79, n=12095), where Rn is the net radiation, G is the soil heat flux, H is the sensible heat flux, and LE is the latent heat flux. LE was the main term of energy consumption at annual time scale because of higher value in the growing season. The ratios of the latent (LE) and sensible (H) heat fluxes to net radiation were 0.47 and 0.28 throughout the year, respectively. Moreover, the yearly evapotranspiration of P. euphratica forests was 744 mm year−1. And the mean daily ET was 5.09 mm·d−1 in the vibrant growing season. In particular, a small spike in the actual evapotranspiration distribution occurred during the soil ablation period due to the higher temperature and sufficient soil moisture associated with soil thawing. This period is accompanied by a series of physical processes, such as moisture transfer and heat exchange.

scholarly journals Characteristics of radiative and non-radiative energy fluxes over monsoon trough zone

MAUSAM ◽  
2022 ◽  
Vol 52 (3) ◽  
pp. 581-592
Author(s):  
T. N. JHA
Keyword(s):  
Heat Flux ◽  
Global Radiation ◽  
Longwave Radiation ◽  
Soil Heat Flux ◽  
Radiative Energy ◽  
Net Radiation ◽  
Energy Fluxes ◽  
Diurnal Variability ◽  
Response Data ◽  
Soil Flux

In order to describe behaviour of radiative and non-radiative erergy fluxes in the surface layer, computation of net radiation, sensible, latent and heat soil flux has been done using hourly global radiation, slow response data of MONTBLEX-90 and surface observation of Varanasi and Jodhpur during rainy and non-rainy days in July 1990. Daily and hourly ground temperature is calculated solving one dimensional heat conduction equation and soil heat flux is computed using force restored method .Outgoing Longwave Radiation (OLR) is calculated by Stefan-Boltzrnann law of radiation and the largest diurnal variability was found over dry convective zone. Results show that OLR from the ground lies in the range 473.0-537.6 Wm-2 at Jodhpur and 497.4 -548.4 Wm-2 at Varanasi during generally cloudy day. The dip in OLR is increascd by 10% with increase of relative humidity and cloudiness. Daily mean of the largest downward soil heat flux are found as 206.4 and 269.4 Wm-2 at Varanasi and Jodhpur respectively during cloudy day. About 40-50% of net radiation is imparted to soil heat flux at Varanasi and  Jodhpur. Sum of the hourly non- radiative energy fluxes has not been balanced by net radiation while daily cumulative value of the fluxes balances the net radiation during non-rainy day.

scholarly journals Seasonal dynamics of methane emissions from a subarctic fen in the Hudson Bay Lowlands

2013 ◽  
Vol 10 (7) ◽  
pp. 4465-4479 ◽  
Author(s):  
K. L. Hanis ◽  
M. Tenuta ◽  
B. D. Amiro ◽  
T. N. Papakyriakou
Keyword(s):  
Soil Temperature ◽  
Air Temperature ◽  
Growing Season ◽  
Near Surface ◽  
Growing Seasons ◽  
Air Temperatures ◽  
Soil Temperatures ◽  
Surface Soil Temperature ◽  
Filling Method ◽  
Highly Correlated

Abstract. Ecosystem-scale methane (CH4) flux (FCH4) over a subarctic fen at Churchill, Manitoba, Canada was measured to understand the magnitude of emissions during spring and fall shoulder seasons, and the growing season in relation to physical and biological conditions. FCH4 was measured using eddy covariance with a closed-path analyser in four years (2008–2011). Cumulative measured annual FCH4 (shoulder plus growing seasons) ranged from 3.0 to 9.6 g CH4 m−2 yr−1 among the four study years, with a mean of 6.5 to 7.1 g CH4 m−2 yr−1 depending upon gap-filling method. Soil temperatures to depths of 50 cm and air temperature were highly correlated with FCH4, with near-surface soil temperature at 5 cm most correlated across spring, fall, and the shoulder and growing seasons. The response of FCH4 to soil temperature at the 5 cm depth and air temperature was more than double in spring to that of fall. Emission episodes were generally not observed during spring thaw. Growing season emissions also depended upon soil and air temperatures but the water table also exerted influence, with FCH4 highest when water was 2–13 cm below and lowest when it was at or above the mean peat surface.

scholarly journals Characteristic Variation of Ground Heat Flux and Net Radiation at Tropical Station in Ile-Ife, Osun State, Nigeria

2020 ◽  
pp. 35-42
Author(s):  
A. Usman ◽  
B. B. Ibrahim ◽  
L. A. Sunmonu
Keyword(s):  
Heat Flux ◽  
Research Work ◽  
Soil Heat Flux ◽  
Entire Period ◽  
Net Radiation ◽  
Sampled Data ◽  
Minimum Value ◽  
Maximum Value ◽  
Characteristic Variation ◽  
Ground Heat Flux

Characteristic variation of ground heat flux and net radiation enhances the understanding of the significance of indicated trends of variability to everyday life and factors that might be responsible for such variations. This research work critically analyses some specific days with field data over grass-covered surface at Ile-Ife, Nigeria between ground heat flux and net radiation. For the field observations, an instrumented meteorological mast was set up at an experimental site (7°33’N, 4°35’E) located at Obafemi Awolowo University campus, Ile-Ife, Nigeria for a period of two weeks (31st May-14th June, 2013). The soil heat flux, net radiation and soil temperature from the soil heat flux plate; an all-wave net radiometer, and soil thermometer were recorded every 10 seconds and averaged over 2 minutes interval. The sampled data was stored in the data logger (Campbell Scientific, Model CR10X) storage module. After the removal of spurious measurement values (Quality Assurance and Quality Control), the data stored was further reduced to 30 minutes averages using the Microcal Origin (version 7.0) data analysis software. The results showed that the measured ground heat flux, HGM during the daytime increases until 1400 hrs with maximum value of about 136.86 Wm-2 and minimum value of about -72.87 Wm-2 at 0830 hrs (DOY 156). The measured net radiation, Rn value of 649.65 Wm-2 observed at 1400 hrs (DOY 156), represented the maximum value for the entire period of the study. -10.75 Wm-2 value observed at1800 hrs (DOY 154), represented the minimum value for the entire period of the study due to the cloudy condition of the sky which reduces the amount of incoming solar radiation reaching the earth surface.

ENERGY BALANCE OVER PRAIRIE GRASS

1972 ◽  
Vol 52 (2) ◽  
pp. 215-225 ◽  
Author(s):  
LAWRENCE C. NKEMDIRIM ◽  
SHUJI YAMASHITA
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Bowen Ratio ◽  
Soil Heat Flux ◽  
Daily Basis ◽  
Net Radiation ◽  
Large Variability ◽  
Prairie Grass ◽  
Latent Flux ◽  
Evaporative Flux

The energy balance over prairie grass was computed for four cloudless days using the Bowen ratio and the Fourier heat conduction equation. For the 3 advection-free days evaporation accounted for an average of 55% of daytime net radiation. Turbulent flux of heat and soil heat flux shared the remaining portion almost equally. Hourly evaporation can be related to net radiation by the empirical equation: E = 1.2 + 0.75 R cal cm−2 hr−1, where E is the evaporative flux and R the net radiation. The patterns of the soil heat flux was fairly steady from day to day. The relation between hourly flux of sensible heat and soil heat flux was linear on a daily basis. The linearity of the two fluxes when the hourly value for the whole period of investigation was pooled was poor. The proportion of net radiation used as latent flux and sensible flux showed large variability under advection conditions.

scholarly journals Forest Soil Respirations are More Sensitive to Nighttime Temperature Change in Eastern China

2018 ◽  
Vol 47 (1) ◽  
pp. 249-254
Author(s):  
Zhaoyong SHI ◽  
Ke LI ◽  
Yongming WANG ◽  
Bede S. MICKAN ◽  
Weikang YUAN ◽  
...  
Keyword(s):  
Soil Respiration ◽  
Soil Temperature ◽  
Temperature Change ◽  
Global Climate ◽  
Eastern China ◽  
Growing Season ◽  
Mean Value ◽  
Apparent Temperature ◽  
Effect Of Temperature ◽  
The Difference

Soil respiration is one of the main fluxes in the global carbon cycle. The effect of temperature on soil respiration is well understood. The response of soil respiration to temperature warming is called apparent temperature sensitivity (Q10) of soil respiration, which is an important parameter in modeling soil CO2 effluxes under global climate warming. The difference of Q10 between daytime and nighttime was hardly reported although attentions are attracted by the differences of temperature change and its effects on vegetation productivity. In this study, we investigated the Q10 of soil respiration in daytime and nighttime by modeling empirical functions based on the in situ measurement of soil respiration and temperature in temperate and subtropical forests of eastern China. Our results showed that the Q10 of soil respiration is higher in nighttime with the mean value of 2.74 and 2.35 than daytime with the average of 2.49 and 2.18 in all measured months and growing season, respectively. Moreover, the explanatory rate of soil temperature to soil respiration in nighttime is also higher than in daytime in each site in both all measured and growing seasons. The Q10 and explanatory rate of soil temperature to soil respiration in nighttime is 1.08 and 1.15 times in daytime in growing season. These findings indicate that soil respiration has a bigger sensitivity to temperature in nighttime than daytime. The change of soil temperature explains more variation of soil respiration in nighttime than daytime.

scholarly journals Modeling the Interaction of Plastic Film Mulch and Potato Canopy Growth with Soil Heat Transport in a Semiarid Area

Agronomy ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 190 ◽  
Author(s):  
You-Liang Zhang ◽  
Feng-Xin Wang ◽  
Clinton C. Shock ◽  
Shao-Yuan Feng
Keyword(s):  
Heat Flux ◽  
Heat Transport ◽  
Solanum Tuberosum L ◽  
Thermal Conditions ◽  
Soil Heat Flux ◽  
Gansu Province ◽  
Water Evaporation ◽  
Plastic Film ◽  
Net Radiation ◽  
Plastic Mulch

Plastic film mulch is an important agricultural technology to reduce water evaporation and modify the soil thermal conditions for crop production. The optical properties of plastic film mulch and the crop canopy growth are both key factors impacting soil heat transport in the soil-film-canopy-atmosphere ecosystem. In this study, a process-oriented model was developed to better understand the interaction among the plastic film mulch, potato (Solanum tuberosum L.) canopy growth, and soil thermal conditions. Canopy growth, photosynthetically active radiation transmittance, net radiation, soil heat flux, and temperature were monitored in a two-year plastic mulch field experiment in Wuwei (Gansu Province, China). Results showed that the simulation of daily soil surface temperature had a good performance with 2.8 and 1.5 °C of root mean square error (RMSE) for the transparent film mulch (TM) and black film mulch (BM), respectively. Moreover, the simulation of the daily net radiation and soil heat flux model indicated reasonable fluctuations with potato phenological development with the daily R2 ranging from 0.89 to 0.98 in 2014 and 2015 for the TM and BM treatments. It was shown that the canopy temperature under BM was greater than that in TM treatment, and the maximum value difference could be up to 7 °C during the early potato growing period, which implied that the BM may perform better in modifying the canopy thermal condition. The model could provide heat distribution information for plastic film choosing in potato field to avoid heat stress.

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