scholarly journals Overview of a prescribed burning experiment within a boreal forest in Finland

2013 ◽  
Vol 13 (8) ◽  
pp. 21703-21763 ◽  
Author(s):  
A. Virkkula ◽  
J. Levula ◽  
T. Pohja ◽  
P. P. Aalto ◽  
P. Keronen ◽  
...  
Keyword(s):  
Boreal Forest ◽  
Radiative Forcing ◽  
Prescribed Burning ◽  
Geometric Mean ◽  
Sonic Anemometer ◽  
Ground Level ◽  
Organic Layer ◽  
Available Nitrogen ◽  
Mean Diameter

Abstract. A prescribed burning of a boreal forest was conducted on 26 June 2009 in Hyytiälä, Finland, to study aerosol and trace gas emissions from wildfires and the effects of fire on soil properties in a controlled environment. A 0.8 ha forest near the SMEAR II was cut clear; some tree trunks, all tree tops and branches were left on the ground and burned. The amount of burned organic material was ~46.8 t (i.e., ~60 t ha−1). The flaming phase lasted 2 h 15 min, the smoldering phase 3 h. Measurements were conducted on the ground with both fixed and mobile instrumentation, and from a research aircraft. In the middle of the burning area, CO2 concentration peaks were around 2000–3000 ppm above the baseline and peak vertical flow velocities were 6 ± 3 m s−1, as measured a 10-Hz 3-D sonic anemometer placed within the burn area. Peak particle number concentrations were approximately 1–2 × 106 cm−3 in the plume at a distance of 100–200 m from the burn area. The geometric mean diameter of the mode with the highest concentration was at 80 ± 1 nm during the flaming phase and in the middle of the smoldering phase but at the end of the smoldering phase the largest mode was at 122 nm. In the volume size distributions geometric mean diameter of the largest volume mode was at 153 nm during the flaming phase and at 300 nm during the smoldering phase. The lowest single-scattering albedo of the ground-level measurents was 0.7 in the flaming-phase plume and ~0.9 in the smoldering phase. The radiative forcing efficiency was negative above dark surfaces, in other words, the particles cool the atmosphere. Elevated concentrations of several VOCs (including acetonitrile which is a biomass burning marker) were observed in the smoke plume at ground level. The forest floor (i.e., richly organic layer of soil and debris, characteristic of forested land) measurements showed that VOC fluxes were generally low and consisted mainly of monoterpenes, but a clear peak of VOC flux was observed after the burning. After one year, the fluxes were nearly stabilised close to the level before the burning. The clearcutting and burning of slash increased the total long-term CO2 release from the soil, altered the soil's physical, chemical and biological properties such as increased the available nitrogen contents of the soil, which in turn, affected the level of the long-term fluxes of greenhouse gases.

scholarly journals Prescribed burning of logging slash in the boreal forest of Finland: emissions and effects on meteorological quantities and soil properties

2014 ◽  
Vol 14 (9) ◽  
pp. 4473-4502 ◽  
Author(s):  
A. Virkkula ◽  
J. Levula ◽  
T. Pohja ◽  
P. P. Aalto ◽  
P. Keronen ◽  
...  
Keyword(s):  
Soil Properties ◽  
Prescribed Burning ◽  
Geometric Mean ◽  
Sonic Anemometer ◽  
Ground Level ◽  
Organic Layer ◽  
Available Nitrogen ◽  
Clear Cutting ◽  
Mean Diameter

Abstract. A prescribed fire experiment was conducted on 26 June 2009 in Hyytiälä, Finland, to study aerosol and trace gas emissions from prescribed fires of slash fuels and the effects of fire on soil properties in a controlled environment. A 0.8 ha forest near the SMEAR II measurement station (Station for Measuring Ecosystem-Atmosphere Relations) was cut clear; some tree trunks, all tree tops and branches were left on the ground and burned. The amount of burned organic material was ~46.8 tons (i.e., ~60 tons ha−1). The flaming phase lasted 2 h 15 min, the smoldering phase 3 h. Measurements were conducted on the ground with both fixed and mobile instrumentation, and in the air from a research aircraft. In the middle of the burning area, CO2 concentration peaked around 2000–3000 ppm above the baseline, and peak vertical flow velocities were ~9 m s−1, as measured with a 10 Hz 3-D sonic anemometer placed within the burn area. In the mobile measurements the peak particle number concentrations were approximately 1–2 × 106 cm−3 in the plume at a distance of 100–200 m from the burn area. On the ground at the SMEAR II station the geometric mean diameter of the mode with the highest concentration was 80 ± 1 nm during the flaming phase and in the middle of the smoldering phase, but, at the end of the smoldering phase, the largest mode was 122 nm. In the volume size distributions, geometric mean diameter of the largest volume mode was 153 nm during the flaming phase and 300 nm during the smoldering phase. The lowest single-scattering albedo of the ground-level measurements was 0.7 in the flaming-phase plume and ~0.9 in the smoldering phase. Elevated concentrations of several volatile organic compounds (VOC) (including acetonitrile, a biomass burning marker) were observed in the smoke plume at ground level. Measurements at the forest floor (i.e., a richly organic layer of soil and debris, characteristic of forested land) showed that VOC fluxes were generally low and consisted mainly of monoterpenes, and VOC flux peaked after the burning. After one year, the fluxes had nearly stabilized close to the level before the burning. The clear-cutting and burning of slash increased the total long-term CO2 release from the soil, and altered the physical, chemical and biological properties of the soil, such as increased the available nitrogen contents of the soil, which in turn, affected the long-term fluxes of greenhouse gases.

Long-Term Protective Immunity of Recipients of the OKA Strain of Live Varicella Vaccine

PEDIATRICS ◽  
1985 ◽  
Vol 75 (4) ◽  
pp. 667-671 ◽  
Author(s):  
Yoshizo Asano ◽  
Takao Nagai ◽  
Takao Miyata ◽  
Takehiko Yazaki ◽  
Shigemitsu Ito ◽  
...  
Keyword(s):  
Varicella Zoster Virus ◽  
Skin Reaction ◽  
Protective Immunity ◽  
Geometric Mean ◽  
Varicella Vaccine ◽  
Geometric Mean Titer ◽  
Positive Skin ◽  
Varicella Zoster ◽  
Mean Diameter

In spite of close contacts with patients who had varicella, 101 of 106 (95%) healthy and sick children (142 of 147 (97%) exposures of these children) who had received the OKA strain of live varicella vaccine 7 to 10 years earlier were protected against the disease completely. Among them, 37 of 38 (97%) vaccine recipients who received immunologic testing had varicella-zoster virus (VZV) antibodies tested by fluorescent antibody to membrane antigen method with a geometric mean titer of 1:9.3, and 37 of the 38 (97%) showed positive skin reaction to varicella-zoster virus antigen with erythema (mean diameter 13.4 mm). These findings were compared with those for 29 children who had contracted typical varicella 7 to 10 years earlier, whose seropositive rate was 100% with a geometric mean titer of 1:10.5, and 97% of whom (28/29) had positive skin reaction with mean diameter of 12.9 mm. These results indicate that the vaccine-induced protective immunity persists for approximately one decade and is almost equal to the long-term immunity following natural infection.

scholarly journals Thinning and Burning Effects on Long-Term Litter Accumulation and Function in Young Ponderosa Pine Forests

2020 ◽  
Vol 66 (6) ◽  
pp. 761-769
Author(s):  
Matt Busse ◽  
Ross Gerrard
Keyword(s):  
Ponderosa Pine ◽  
Forest Floor ◽  
Prescribed Burning ◽  
Mineral Soil ◽  
Pine Forests ◽  
Organic Layer ◽  
Litter Accumulation ◽  
Ponderosa Pine Forests ◽  
Essential Components

Abstract We measured forest-floor accumulation in ponderosa pine forests of central Oregon and asked whether selected ecological functions of the organic layer were altered by thinning and repeated burning. Experimental treatments included three thinning methods applied in 1989 (stem only, whole tree, no thin—control) in factorial combination with prescribed burning (spring 1991 and repeated in 2002; no burn—control). Forest-floor depth and mass were measured every 4–6 years from 1991 to 2015. Without fire, there was little temporal change in depth or mass for thinned (270 trees ha−1) and control (560–615 trees ha−1) treatments, indicating balanced litterfall and decay rates across these stand densities. Each burn consumed 50–70 percent of the forest floor, yet unlike thinning, postfire accumulation rates were fairly rapid, with forest-floor depth matching preburn levels within 15–20 years. Few differences in forest-floor function (litter decay, carbon storage, physical barrier restricting plant emergence, erosion protection) resulted from thinning or burning after 25 years. An exception was the loss of approximately 300 kg N ha−1 because of repeated burning, or approximately 13 percent of the total site N. This study documents long-term forest-floor development and suggests that common silvicultural practices pose few risks to organic layer functions in these forests. Study Implications: Mechanical thinning and prescribed fire are among the most widespread management practices used to restore forests in the western US to healthy, firewise conditions. We evaluated their effects on the long-term development of litter and duff layers, which serve dual roles as essential components of soil health and as fuel for potential wildfire. Our study showed that thinning and burning provided effective fuel reduction and resulted in no adverse effects to soil quality in dry ponderosa pine forests of central Oregon. Repeated burning reduced the site carbon and nitrogen pools approximately 9–13 percent, which is small compared to C located in tree biomass and N in mineral soil. Litter accumulation after burning was rapid, and we recommend burning on at least a 15–20-year cycle to limit its build-up.

Soil aggregation as influenced by cultural practices in Saskatchewan: I. Black Chernozemic soils

1993 ◽  
Vol 73 (4) ◽  
pp. 579-595 ◽  
Author(s):  
C. A. Campbell ◽  
D. Curtin ◽  
A. P. Moulin ◽  
L. Townley-Smith ◽  
G. P. Lafond
Keyword(s):  
Organic Matter ◽  
Cultural Practices ◽  
Geometric Mean ◽  
Organic Matter Content ◽  
Water Stable Aggregates ◽  
Cropping Frequency ◽  
Mean Diameter ◽  
The Impact ◽  
Erodible Fraction

The impact of cultural practices on soil aggregate characteristics which determine the susceptibility of the soil to wind and water erosion was studied at two long-term (> 30-yr) crop rotation sites on Black Chernozemic soils at Indian Head and Melfort, Saskatchewan. Surface soil (top 5 cm) taken in spring and fall, 1991, was air-dried and sieved by rotary sieve to measure aggregate size distribution. The water-stability of soil aggregates (1–2 mm) was determined after: (i) slow wetting, and (ii) fast wetting. Both rotation studies employed conventional tillage management until 1990 when the Indian Head experiment was converted to zero-tillage. Summerfallowing increased the wind-erodible (< 0.84-mm) fraction of soil and decreased the geometric mean diameter (GMD) of aggregates. One year of cropping was sufficient to significantly reduce the proportion of wind-erodibile aggregates. Fertilization and legume green manure and hay crops reduced the wind-erodible fraction at Indian Head, but had no effect on the higher organic matter soil at Melfort. In monoculture wheat systems at Indian Head there was an inverse relationship between the wind-erodible fraction and cropping frequency; this was credited to the positive influence of cropping frequency on crop residue production. The wind-erodible fraction (Y) was related to GMD at Indian Head: Y = 11.8 + 117/GMD (r2 = 0.80***), and at Melfort, Y = 11.9 + 91/GMD (r2 = 0.82***). When subjected to rapid wetting, both the difference between cropped and native grassland soils, and the influence of cultural practices on water stable aggregates were pronounced. Aggregate stability was more closely related to the long-term management than to recent (< 1 yr) cultural treatments. Frequent cropping, fertilization, and use of legumes increased water stable aggregates, particularly at the Indian Head site with its lower organic matter content. Key words: Wet sieving, dry sieving, legumes, fertilization, geometric mean diameter, wind erosion

A Post-fire Ecological Study of Xanthorrhoea australis Following Prescribed Burning in the Warby Range State Park, North-eastern Victoria, Australia

1998 ◽  
Vol 46 (2) ◽  
pp. 253 ◽  
Author(s):  
N. Peter Curtis
Keyword(s):  
Ecological Study ◽  
Prescribed Burning ◽  
Plant Density ◽  
Ground Cover ◽  
Ground Level ◽  
Adaptive Traits ◽  
High Soil Moisture ◽  
North Eastern ◽  
A Site

Xanthorrhoea australis R.Br. is considered a fire-tolerant species, a statement evidently based on established adaptive traits rather than fire recorded studies. This two-year post-fire study of X. australis in areas that have been subjected to prescribed burning in 1976 and 1991 compares results with a site unburnt for about 100 years. In the sites burnt in 1991, arborescent plants had a mortality of between 10% and 40% (average 21%), with highest mortality in the youngest and oldest plants, and in the site with the lowest plant density. In the site burnt in 1976, plants were still dying. Mortality of plants in the unburnt site was 4%. Flowering in the first post-fire spring varied from 0–100% throughout the size classes, with no flowering observed in plants smaller than 0.5 m. In the unburnt sites and the 1976 burnt sites, where understorey protected seedlings, recruitment was significantly higher (P < 0.001) than in the areas burnt in 1991 that had little ground cover. Plants with severe burn damage to stems at ground level often developed leans (P < 0.001) that were more often opposite to the burnt side (P < 0.001). Leans increased from 2.5˚ to 35˚, and some plants continued to grow, lying horizontally. In all fire sites the horizontal plants had a mortality of 44–92% compared with 29% for those in the unburnt site. In some sites, particularly in areas of high soil moisture, 3–10% of plants developed epicormic shoots after their stems fractured, or their shoot apices died. The study showed that fire has a long-term deleterious effect on large plants of this species. These data should be taken into account by authorities engaged in prescribed burning in forests with significant stands of this species.

scholarly journals Simultaneous generalized and low-layer SCIDAR turbulence profiles at san pedro mártir observatory

2019 ◽  
Vol 490 (1) ◽  
pp. 1397-1405 ◽  
Author(s):  
R Avila ◽  
O Valdés-Hernández ◽  
L J Sánchez ◽  
I Cruz-González ◽  
J L Avilés ◽  
...  
Keyword(s):  
High Altitude ◽  
Wind Direction ◽  
Close Agreement ◽  
Baja California ◽  
Ground Level ◽  
Combined Effect ◽  
Moderate Altitude ◽  
San Pedro ◽  
Simultaneous Measurements

ABSTRACT We present optical turbulence profiles obtained with a Generalized SCIDAR (G-SCIDAR) and a low-layer SCIDAR (LOLAS) at the Observatorio Astronómico Nacional in San Pedro Mártir (OAN-SPM), Baja California, Mexico, during three observing campaigns in 2013, 2014, and 2015. The G-SCIDAR delivers profiles with moderate altitude-resolution (a few hundred metres) along the entire turbulent section of the atmosphere, while the LOLAS gives high altitude resolution (on the order of tens of metres) but only within the first few hundred metres. Simultaneous measurements were obtained on 2014 and allowed us to characterize in detail the combined effect of the local orography and wind direction on the turbulence distribution close to the ground. At the beginning of several nights, the LOLAS profiles show that turbulence peaks between 25 and 50 m above the ground, not at ground level as was expected. The G-SCIDAR profiles exhibit a peak within the first kilometre. In 55 per cent and 36 per cent of the nights stable layers are detected between 10 and 15 km and at 3 km, respectively. This distribution is consistent with the results obtained with a G-SCIDAR in 1997 and 2000 observing campaigns. Statistics computed with the 7891 profiles that have been measured at the OAN-SPM with a G-SCIDAR in 1997, 2000, 2014, and 2015 campaigns are presented. The seeing values calculated with each of those profiles have a median of 0.79, first and third quartiles of 0.51 and 1.08 arcsec, which are in close agreement with other long term seeing monitoring performed at the OAN-SPM.

scholarly journals Long-term O<sub>3</sub>–precursor relationships in Hong Kong: field observation and model simulation

2017 ◽  
Vol 17 (18) ◽  
pp. 10919-10935 ◽  
Author(s):  
Yu Wang ◽  
Hao Wang ◽  
Hai Guo ◽  
Xiaopu Lyu ◽  
Hairong Cheng ◽  
...  
Keyword(s):  
Hong Kong ◽  
Model Simulation ◽  
Ground Level ◽  
Effective Control ◽  
Photochemical Pollution ◽  
Mixing Ratios ◽  
The Past ◽  
Total Volatile Organic Compounds

Abstract. Over the past 10 years (2005–2014), ground-level O3 in Hong Kong has consistently increased in all seasons except winter, despite the yearly reduction of its precursors, i.e. nitrogen oxides (NOx =  NO + NO2), total volatile organic compounds (TVOCs), and carbon monoxide (CO). To explain the contradictory phenomena, an observation-based box model (OBM) coupled with CB05 mechanism was applied in order to understand the influence of both locally produced O3 and regional transport. The simulation of locally produced O3 showed an increasing trend in spring, a decreasing trend in autumn, and no changes in summer and winter. The O3 increase in spring was caused by the net effect of more rapid decrease in NO titration and unchanged TVOC reactivity despite decreased TVOC mixing ratios, while the decreased local O3 formation in autumn was mainly due to the reduction of aromatic VOC mixing ratios and the TVOC reactivity and much slower decrease in NO titration. However, the decreased in situ O3 formation in autumn was overridden by the regional contribution, resulting in elevated O3 observations. Furthermore, the OBM-derived relative incremental reactivity indicated that the O3 formation was VOC-limited in all seasons, and that the long-term O3 formation was more sensitive to VOCs and less to NOx and CO in the past 10 years. In addition, the OBM results found that the contributions of aromatics to O3 formation decreased in all seasons of these years, particularly in autumn, probably due to the effective control of solvent-related sources. In contrast, the contributions of alkenes increased, suggesting a continuing need to reduce traffic emissions. The findings provide updated information on photochemical pollution and its impact in Hong Kong.

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