Fire impacts on surface heat, moisture and carbon fluxes from a tropical savanna in northern Australia

2003 ◽  
Vol 12 (4) ◽  
pp. 333 ◽  
Author(s):  
J. Beringer ◽  
L. B. Hutley ◽  
N. J. Tapper ◽  
A. Coutts ◽  
A. Kerley ◽  
...  
Keyword(s):  
Surface Energy ◽  
Ecosystem Respiration ◽  
Bowen Ratio ◽  
Heat Fluxes ◽  
Radiative Energy ◽  
Moderate Intensity ◽  
Fire Intensity ◽  
Monsoon Circulation ◽  
Radiative Balance ◽  
Low Intensity

Savannas form a large fraction of the total tropical vegetation and are extremely fire prone. We measured radiative, energy and carbon exchanges over unburned and burned (both before and after low and moderate intensity fires) open forest savanna at Howard Springs, Darwin, Australia. Fire affected the radiative balance immediately following fire through the consumption of the grass-dominated understorey and blackening of the surface. Albedo was halved following fire of both intensities (from 0.12 to 0.07 and from 0.11 to 0.06 for the moderate and low intensity sites, respectively), but the recovery of albedo was dependent on the initial fire intensity. The low intensity fire caused little canopy damage with little impact on the surface energy balance and only a slight increase in Bowen ratio. However the moderate fire resulted in a comprehensive canopy scorch and almost complete leaf drop in the weeks following fire. The shutdown of most leaves within the canopy reduced transpiration and altered energy partitioning. Leaf death and shedding also resulted in a cessation of ecosystem carbon uptake and the savanna turned from a sink to a source of carbon to the atmosphere because of the continued ecosystem respiration. Post-fire, the Bowen ratio increased greatly due to large increases in sensible heat fluxes. These changes in surface energy exchange following fire, when applied at the landscape scale, may have impacts on climate through local changes in circulation patterns and changes in regional heating, precipitation and monsoon circulation.

scholarly journals Competing Effects of Vegetation on Summer Temperature in North Korea

2021 ◽  
Author(s):  
Jieun Oh ◽  
Eungul Lee
Keyword(s):  
Surface Energy ◽  
North Korea ◽  
Large Scale ◽  
Vegetation Index ◽  
Bowen Ratio ◽  
Summer Temperature ◽  
Heat Fluxes ◽  
Cooling Effect ◽  
Western Region ◽  
The Western Region

Abstract Vegetation reduction could affect regional climate by perturbing the surface energy and moisture balances via changes in albedo and evapotranspiration. However, it is unknown whether vegetation effects on climate occur in North Korea, where a severe reduction in forest cover has been observed. This study aimed to identify the biogeophysical processes in vegetation and climate interactions in North Korea, using Normalized Difference Vegetation Index (NDVI) and climate reanalysis data over the period 1982‒2015. As per the NDVI regression trend results, the highest rates of decreasing NDVI were detected in the western region of North Korea during summer. Based on the detrended correlation analysis of NDVI with surface energy variables at each grid point, including solar radiation, sensible and latent heat fluxes, Bowen ratio, and temperature, we identified a cooling effect of vegetation in the western region (with lower NDVI and lower elevation), but a warming effect of vegetation in the northern region (with higher NDVI and higher elevation). The different biogeophysical effects were induced by the increasing and decreasing Bowen ratio with increasing vegetation in the northern and western regions, respectively. In the western region of North Korea, where large-scale human-induced forest loss has been observed, the increasing summer temperature caused by the decreasing cooling effect of vegetation would be up to 1.5 ℃ by the end of this century, if the current rate of deforestation continues. Thus, we urgently suggest that sustainable management and restoration of forests are needed in North Korea, which is among the countries most vulnerable to climate change now and in the future.

scholarly journals Observations of daytime surface energy balance in cloudy tropical conditions at Ile-Ife, Nigeria

MAUSAM ◽  
2022 ◽  
Vol 53 (3) ◽  
pp. 359-366
Author(s):  
O. O. JEGEDE
Keyword(s):  
Energy Balance ◽  
Surface Energy ◽  
Surface Energy Balance ◽  
Cloud Amount ◽  
Soil Surface ◽  
Bowen Ratio ◽  
Heat Fluxes ◽  
Sensible Heat ◽  
Average Value ◽  
Tropical Conditions

Daytime energy balance at the surface in cloudy tropical conditions for Ile-Ife; Nigeria (7°33'N, 4°34'E) is investigated based on a series of micrometeorological measurements performed in October/November of 1998. For the humid environment that it is (mixing ratio, 17 -25 g / kg), magnitudes of the latent heat flux were much larger than the values for the sensible heat. Of the morning hours the average value for the Bowen ratio obtained was 0.36, while for the afternoons it was 0.74. As the soil surface became dried up in the afternoons, magnitudes of both sensible heat and ground heat fluxes were found to be comparable.   Fluctuations in the magnitudes of the terms of the surface energy balance correlated well to the cloud amount, degree of soil wetness, air temperature and humidity. But of all these factors, the variation in the amount of cloudiness appeared most dominant.

scholarly journals Surface Energy Components and Land Characteristics of a Rice Paddy

2007 ◽  
Vol 46 (11) ◽  
pp. 1879-1900 ◽  
Author(s):  
Jeng-Lin Tsai ◽  
Ben-Jei Tsuang ◽  
Po-Sheng Lu ◽  
Ming-Hwi Yao ◽  
Yuan Shen
Keyword(s):  
Air Quality ◽  
Surface Energy ◽  
Bowen Ratio ◽  
Rice Paddy ◽  
Carbon Dioxide Flux ◽  
Heat Fluxes ◽  
Surface Energy Budget ◽  
Canopy Resistance ◽  
Rice Paddies ◽  
Quality Models

Abstract Many meteorological and air-quality models require land characteristics as inputs. A field experiment was conducted to study the surface energy budget of a rice paddy in Taiwan. During the day, the energy balance ratio measured by an eddy covariance (EC) system was found to be 95% after considering the photosynthetic and local advected heat fluxes. The observations by the EC system suggest that the Bowen ratio was about 0.18 during the daytime. The EC system also measured the daytime absorbed carbon dioxide flux. The equivalent photosynthetic energy flux was about 1% of the net solar radiation. A reference table describing the land characteristics of rice paddies for use in meteorological and air-quality models is listed that shows that the albedo and the Bowen ratio measured over rice paddies were lower than those listed in many state-of-the-art models. This study proposes simulating latent heat flux by assigning proper values for canopy resistance rather than by assigning constant values for Bowen ratio or surface moisture availability. The diurnal pattern of the canopy resistance of the rice paddy was found to be “U” shaped. Daytime canopy resistance was observed to be 87 s m−1, and a high canopy resistance (∼900 s m−1) should be assigned during nighttime periods.

scholarly journals Prescribed burning in a mediterranean-climate region mitigates the disturbance by bushfire to a critical food resource for an endangered bird, the Carnaby’s cockatoo

Fire Ecology ◽  
2019 ◽  
Vol 15 (1) ◽  
Author(s):  
Valerie S. Densmore ◽  
Emma S. Clingan
Keyword(s):  
Seed Production ◽  
Prescribed Burning ◽  
Fire Regime ◽  
Fire Hazard ◽  
Food Resource ◽  
Management Tool ◽  
Fire Intensity ◽  
Prescribed Burns ◽  
Low Intensity ◽  
Percentage Survival

Abstract Background Prescribed burning is used to reduce fire hazard in highly flammable vegetation types, including Banksia L.f. woodland that occurs on the Swan Coastal Plain (SCP), Western Australia, Australia. The 2016 census recorded well over 1.9 million people living on the SCP, which also encompasses Perth, the fourth largest city in Australia. Banksia woodland is prone to frequent ignitions that can cause extensive bushfires that consume canopy-stored banksia seeds, a critical food resource for an endangered bird, the Carnaby’s cockatoo (Calyptorynchus latirostris, Carnaby 1948). The time needed for banksias to reach maturity and maximum seed production is several years longer than the typical interval between prescribed burns. We compared prescribed burns to bushfires and unburned sites at three locations in banksia woodland to determine whether low-intensity prescribed burns affect the number of adult banksias and their seed production. Study sites were matched to the same vegetation complex, fire regime, and time-since-fire to isolate fire intensity as a variable. Results Headfire rates of spread and differenced normalized burn ratios indicated that prescribed burning was generally of a much lower intensity than bushfire. The percentage survival of adult banksias and their production of cones and follicles (seeds) did not decrease during the first three years following a prescribed burn. However, survival and seed production were significantly diminished followed high-intensity bushfire. Thus, carrying capacity for Carnaby’s cockatoo was unchanged by prescribed burning but decreased markedly following bushfire in banksia woodland. Conclusions These results suggest that prescribed burning is markedly different from bushfire when considering appropriate fire intervals to conserve canopy habitats in fire-resilient vegetation communities. Therefore, low-intensity prescribed burning represents a viable management tool to reduce the frequency and extent of bushfire impacts on banksia woodland and Carnaby’s cockatoo.

scholarly journals Evaluation of LDL goal achievement in statin consumption, south east of Iran

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Malihe Aghasizadeh ◽  
Saeede Khosravi Bizhaem ◽  
Mahin Baniasadi ◽  
Mohammad Reza Khazdair ◽  
Toba Kazemi
Keyword(s):  
Cardiovascular Risk ◽  
Statin Therapy ◽  
Goal Achievement ◽  
Moderate Intensity ◽  
Cvd Risk ◽  
Intensity Pattern ◽  
Cross Sectional ◽  
Low Intensity ◽  
Very High ◽  
Statin Use

AbstractLipid goal achievement and statin consumption were estimated at extreme/very-high/high/moderate and low cardiovascular risk categories. In the cross-sectional study, 585 patients treated with statin therapy referring to the heart clinic of Birjand were recruited. Patients were classified and examined LDL-C values and the proportion reaching targets according to the American Association of Clinical Endocrinologists guideline. Three patterns of statin use (high/moderate/low-intensity statin therapy) in all patients were examined and attainments of LDL-C goal in cardiovascular risk groups have been demonstrated. Over half the populations (57.6%) were in the very-high CVD risk group. The results showed that the proportion of patients meeting total LDL-C goal values according to the guidelines was 43.4%. The frequency of patient had achievement LDL goal lower in high-intensity pattern (N = 13, 2.3%), compared with moderate (N = 496, 86.1%) and low-intensity patterns (N = 67, 11.6%). In general, LDL-C goal achievement was greatest with moderate-intensity statin use. LDL-C reduction after statin consumption was estimated about one-third of the studied population. It seems likely that the achievement of a therapeutic target for serum lipids such as LDL-C improved is far more cost-effective and would be able to reach the target LDL as well changing the type and intensity of statins.

Position of cones within cone clusters determines seed survival in black spruce during wildfire

2019 ◽  
Vol 49 (2) ◽  
pp. 121-127 ◽  
Author(s):  
T.B. Splawinski ◽  
D.F. Greene ◽  
S.T. Michaletz ◽  
S. Gauthier ◽  
D. Houle ◽  
...  
Keyword(s):  
Black Spruce ◽  
Seed Viability ◽  
Heat Fluxes ◽  
Wake Flow ◽  
Windward Side ◽  
Fire Intensity ◽  
Burned Area ◽  
Individual Plant ◽  
Buoyant Plumes ◽  
Porous Bodies

It has recently become clear that the regeneration density of serotinous species within a burned area declines with local fire intensity. It is assumed that this occurs because variation in local fire intensity leads to variation in incident heat fluxes and, ultimately, seed necrosis. We argue here that this same relationship between incident heat flux and seed necrosis is important at the scale of individual plant crowns. Using Picea mariana (Mill.) B.S.P. (black spruce), we show that postfire seed viability increases with crown height, depth into the crown, and angle from wind direction (with the windward side enjoying greater viability). All three effects are what one would expect given the physics of buoyant plumes, interactions of moving fire lines with wake flow around cylinders, and heat transfer in porous bodies such as a tree crown. We conclude by discussing the broader consequences of cone cluster size and global change on regeneration in serotinous species.

Impacts of fire radiative flux on mature Pinus ponderosa growth and vulnerability to secondary mortality agents

2017 ◽  
Vol 26 (1) ◽  
pp. 95 ◽  
Author(s):  
Aaron M. Sparks ◽  
Alistair M. S. Smith ◽  
Alan F. Talhelm ◽  
Crystal A. Kolden ◽  
Kara M. Yedinak ◽  
...  
Keyword(s):  
Dose Response ◽  
Pinus Ponderosa ◽  
Radial Growth ◽  
Unit Area ◽  
Radiative Energy ◽  
Fire Intensity ◽  
Response Relationship ◽  
Fire Behaviour ◽  
Dose Response Relationship ◽  
Resin Duct

Recent studies have highlighted the potential of linking fire behaviour to plant ecophysiology as an improved route to characterising severity, but research to date has been limited to laboratory-scale investigations. Fine-scale fire behaviour during prescribed fires has been identified as a strong predictor of post-fire tree recovery and growth, but most studies report these metrics averaged over the entire fire. Previous research has found inconsistent effects of low-intensity fire on mature Pinus ponderosa growth. In this study, fire behaviour was quantified at the tree scale and compared with post-fire radial growth and axial resin duct defences. Results show a clear dose–response relationship between peak fire radiative power per unit area (W m–2) and post-fire Pinus ponderosa radial growth. Unlike in previous laboratory research on seedlings, there was no dose–response relationship observed between fire radiative energy per unit area (J m–2) and post-fire mature tree growth in the surviving trees. These results may suggest that post-fire impacts on growth of surviving seedlings and mature trees require other modes of heat transfer to impact plant canopies. This study demonstrates that increased resin duct defence is induced regardless of fire intensity, which may decrease Pinus ponderosa vulnerability to secondary mortality agents.

Substrate metabolism when subjects are fed carbohydrate during exercise

1999 ◽  
Vol 276 (5) ◽  
pp. E828-E835 ◽  
Author(s):  
Jeffrey F. Horowitz ◽  
Ricardo Mora-Rodriguez ◽  
Lauri O. Byerley ◽  
Edward F. Coyle
Keyword(s):  
Plasma Insulin ◽  
Fat Oxidation ◽  
Insulin Concentration ◽  
Peak Oxygen Consumption ◽  
Moderate Intensity ◽  
Moderate Intensity Exercise ◽  
Plasma Insulin Concentration ◽  
Carbohydrate Ingestion ◽  
Low Intensity ◽  
Low Intensity Exercise

This study determined the effect of carbohydrate ingestion during exercise on the lipolytic rate, glucose disappearance from plasma (Rd Glc), and fat oxidation. Six moderately trained men cycled for 2 h on four separate occasions. During two trials, they were fed a high-glycemic carbohydrate meal during exercise at 30 min (0.8 g/kg), 60 min (0.4 g/kg), and 90 min (0.4 g/kg); once during low-intensity exercise [25% peak oxygen consumption (V˙o 2 peak)] and once during moderate-intensity exercise (68%V˙o 2 peak). During two additional trials, the subjects remained fasted (12–14 h) throughout exercise at each intensity. After 55 min of low-intensity exercise in fed subjects, hyperglycemia (30% increase) and a threefold elevation in plasma insulin concentration ( P < 0.05) were associated with a 22% suppression of lipolysis compared with when subjects were fasted (5.2 ± 0.5 vs. 6.7 ± 1.2 μmol ⋅ kg−1 ⋅ min−1, P < 0.05), but fat oxidation was not different from fasted levels at this time. Fat oxidation when subjects were fed carbohydrate was not reduced below fasting levels until 80–90 min of exercise, and lipolysis was in excess of fat oxidation at this time. The reduction in fat oxidation corresponded in time with the increase in Rd Glc. During moderate-intensity exercise, the very small elevation in plasma insulin concentration (∼3 μU/ml; P < 0.05) during the second hour of exercise when subjects were fed vs. when they were fasted slightly attenuated lipolysis ( P < 0.05) but did not increase Rd Glc or suppress fat oxidation. These findings indicate that despite a suppression of lipolysis after carbohydrate ingestion during exercise, the lipolytic rate remained in excess and thus did not limit fat oxidation. Under these conditions, a reduction in fat oxidation was associated in time with an increase in glucose uptake.

The Local Biophysical Response to Land-Use Change in HadGEM2-ES

2019 ◽  
Vol 32 (22) ◽  
pp. 7611-7627 ◽  
Author(s):  
E. Robertson
Keyword(s):  
Land Use ◽  
Land Use Change ◽  
Latent Heat ◽  
Temperature Response ◽  
Bowen Ratio ◽  
Heat Fluxes ◽  
Turbulent Heat ◽  
Available Energy ◽  
Turbulent Heat Fluxes ◽  
The Tropics

Abstract The biophysical response to a local change in land use is calculated using the HadGEM2-ES Earth system model. The biophysical temperature response is found to be a small residual of three large opposing flux responses: available energy, sensible heat, and latent heat. Deforestation reduces available energy, which is balanced by a reduction in heat lost via turbulent fluxes. However, the changes in turbulent heat fluxes are not simply a response to the reduction in available energy; rather, they are a direct response to land-use change, caused by reduced roughness length and, in the tropics, an increase in the Bowen ratio. Evaluation against satellite-derived observational datasets shows that in response to deforestation, the model has too much albedo-driven cooling and too little latent-heat-driven warming, leading to a large cooling bias.

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