Natural Windbreaks Research Articles

A Call For Improving Winter Windbreak Design for Lowbush Blueberry Production in the Saguenay–Lac-Saint-Jean Region of Québec, Canada

ABSTRACTWind exposure may reduce the snowpack and increase frost damage to lowbush blueberry (Vaccinium angustifolium Ait.). Farmers in the Saguenay-Lac-Saint-Jean region (Québec) have therefore installed natural windbreaks to maintain a deep snow cover. We verified the efficiency of 39 windbreaks distributed over two farms. Over two consecutive years, snow depth was measured along transects established perpendicular to these windbreaks. In the first summer, frost damage and yields were assessed at each point where snow depth had been measured. We found large fluctuations in snow depth along most transects, with deeper snow occurring within 20 m on either side of windbreaks. Relative snow depth distribution was correlated between years on 19 transects. On one farm, one third of total transect length was below the recognized critical depth of 30 cm. On this farm, the proportion of damaged stems, the mean length of stem damage and the damaged-to-total stem length decreased exponentially with increasing snow depth. Likewise, the number of fruits per stem decreased exponentially with the length of stem damage and increased linearly with snow depth. Given current trends in climate change, our results serve as a timely call for improving winter windbreak design in the Saguenay-Lac-Saint-Jean region.

Efficient Exploitation of Local Fruit Resources Through Sustainable Production and High Added Value Processing

Fruit production in Europe has a dual system organization: an industrial type with high density planting systems in large extension farms and a small size orchard type in family owned farms. Certainly, the two systems are quite different in terms of fruit varieties, planting systems, orchard management and fruit production valorisation. In recent years, the smart family fruit farms became more and more important for the rural economy by increasing the efficient use of local resources, by offering social security and comfort and by reducing the environmental fruit finger print. Besides the already existing orchards, new ones are planted with trees produced using local species and varieties, better adapted to soil and climate conditions, grafted on resistant rootstocks. Low input orchard technologies, organic fertilization and integrated pest management are generally used. Natural windbreaks and shelters, grass soil cover management are generalized in order to ensure a higher biodiversity and the protection of wild life. Local fruits are produced in many cases under registered Protected Designation of Origin (PDO), Protected Geographical Indication (PGI), and Traditional Specialties Guaranteed (TSG). Those insure the product authenticity, a quality control system and a better marketing. Fruits are sold fresh on the local markets and in modern distribution network but also processed in the farm or in cooperative processing units. Special products are obtained following traditional recipes, some of the being sugar free, rich in vitamins, active principles and considered functional food. Continuous science and technology development brings innovation also in orchard technologies in European small fruit farms aiming to maintain their sustainability and competitiveness, by producing top quality fruits, with nearly to zero residues and no environmental negative impact. The European model of small smart fruit farms could be introduced and tested to Indonesian condition. Keywords: small smart farms; local varieties; planting systems; sustainable orchard management; plant protection; local fruit processing

Numerical analysis of wind microclimatic effects on a plastic greenhouse protected by a windbreak in different seasonal periods

Windbreaks are frequently used to protect greenhouses. Agricultural plastic nets are widely used for the construction of such windbreaks replacing the traditional natural windbreaks formed by trees. When installed against the dominant wind direction at an optimized distance from the greenhouse side walls, windbreaks may reduce wind loads. An additional effect of the provided protection against strong cold winds is the reduction of heat losses during the winter period. However, the effect of windbreaks in situations when cooling is necessary, particularly in cases of low wind speeds during summer period, has not been investigated so far. The present work aims to analyse the energy efficiency and the wind flow around and through an arched-roof greenhouse with two side and one roof opening (windows) in two extreme cases, namely a) a high velocity cold wind causing important heat losses on the greenhouse (closed windows), and b) a low velocity wind speed resulting to buoyancy-driven ventilation in the greenhouse (open windows). In the first case the reduction of heat losses due to the windbreak are explored. In the second case, the possible dissipation of the ventilation airflow and the corresponding temperature variations by the windbreak is investigated. Computational Fluid Dynamics (CFD) numerical simulations are used in the present work.

Проблемы страхования рисков в сельском и лесном хозяйствах от стихийных бедствий

In recent years, due to an increase the number of natural disasters such as droughts, in the territory of the Russian Federation, the insurance and insurance ways of business activities in agriculture and forestry from natural disasters is becoming increasingly important. In addition, with transfer of land and forest areas in the long-term lease, the well-being of agricultural firms, farmers and tenants, both on land and in the forest areas are under threat of bankruptcy and failure of entrepreneurial activity. The insured event in the form of environmental insurance is a sudden, unexpected damage to crops as a result of various kinds of undesirable weather conditions, natural disasters. However, the insurance of land from land runoff, landslides have occurred as a result of heavy rains, floods in agriculture requires further consideration, as every year in the Russian Federation to increase the area of arable land emerged from agricultural use. In forestry, the position of forests insurance from various types of natural disasters is not well developed in agriculture. Thus, with the adoption of the “Forest Code” of the Russian Federation in 2007, various types of logging and timber harvesting, reforestation work-related should be carried out by tenants of forest plots. However, today the tenants of forest plots (individuals and businesses) do not have the so-called economic stimulus in the form of insurance against natural disasters, fires, windbreaks and windfalls. They remain one to one with a past event, which can not take any action to save their businesses. Now insurance of farmland and forest land from various kinds of environmental disasters and emergencies by the state plays a critical role in the development of small and medium-sized businesses in these sectors to strengthen food security and increase the productivity of forests of the Russian Federation.

Influence of windbreaks and forest borders on abundance and species richness of native pollinators in lowbush blueberry fields in Québec, Canada

AbstractLowbush blueberry (Vaccinium angustifoliumAiton (Ericaceae)) production is highly dependent on insect pollination to maximise yields. The current losses in honey bee (Apis melliferaLinnaeus (Hymenoptera: Apidae)) colonies pose a serious threat to the blueberry industry, raising interest in alternative pollinators. Abundance and diversity of native pollinators usually decreases with distance from natural habitats. In this study, we evaluated the effects of distance from wooded habitats such as windbreaks and forest borders on the presence of native pollinators in blueberry fields in Lac-St-Jean (Québec, Canada). Four treatments were compared: single-row, double-row, natural windbreaks, and forest borders. Pan-traps were placed at 5, 30, and 60 m from the windbreak or forest border. A total of 3878 native pollinators were collected and 81% were ground-nesting bees. The forest border was the only treatment with higher abundance and species richness on the periphery (5 m) of the field than at further distances, supporting the hypothesis that the presence of pollinators is favoured by habitats potentially offering more abundant and diverse nutritional resources. Our overall results reveal that native pollinators are distributed quite homogeneously in blueberry fields, suggesting that windbreaks are beneficial to native pollinator communities.

Quantification of the environmental effect on citrus canker intensity at increasing distances from a natural windbreak in northeastern Argentina

Citrus canker, caused by the bacterium Xanthomonas citri pv. citri (Xcc), is an endemic quarantine disease in northeastern Argentina. The objective of this study was to quantify the effect of weather variables on mid-season fruit canker intensity in an experimental grove of the “Red Blush” grapefruit cultivar in Bella Vista, Corrientes Province (Argentina), at two contrasting distances from a natural windbreak (closer, wd = 0; farther, wd = 1). For the 1991–2010 growing seasons, disease observations were analyzed at both windbreak distances. The variable that best correlated with the disease levels (S: severe, M: moderate and L: light) at both windbreak distances was DPrecWsBl (days with precipitation > 12 mm and wind speed > 2.6 km.h−1; Kendall Tau-b coefficient (rk) = 0.71), different from the rk = 0.60 obtained with DPrec (days with precipitation > 12 mm). Daily wind speed values at both windbreak distances were estimated from wind speeds recorded at Bella Vista meteorological station after fitting linear regression equations. The best ordinal response logistic regression models included DPrecWsBl and DT (days with temperatures in the interval 17–27 °C), and DPrec, DDMaxT (sum of the exceeding amounts of daily maximum temperature from 33 oC) and windbreak distance (wd) coded as strong (wd = 0) and moderate (wd = 1) wind protection (prediction accuracy = 90 and 88.6 % respectively). Both models classified the nine observations with a severe canker intensity level correctly and their respective precipitation-driven predictors (DPrecWsBl and DPrec) achieved a highly satisfactory separation of two observed canker levels (S and M-L). The results may allow us to release canker risk warnings for scenarios with strong (wd = 0) and moderate (wd = 1) wind protection. These warnings may assist producers to make bactericide spray applications.

Simulation of odour dispersion downwind from natural windbreaks using the computational fluid dynamics standard k-ε model

If natural windbreaks create air turbulence and can help disperse odours from livestock operations, their dispersion effect has not been extensively researched. This paper introduces a model simulating odour dispersion downwind from natural windbreaks. The standard k-ε model of the FLUENT software was used to incorporate the effect of climatic conditions and windbreak structure. The model was calibrated for wind velocity recovery, odour concentration (OC) from field observations and inertial resistance. Once calibrated, the model accurately reproduced the odour plume developing downwind from the windbreak. The correlation between OC for 11 field trials and that simulated were statistically significant (P < 0·01), indicating that the model was accurate. The model demonstrated that a windbreak did alter the magnitude and direction of the wind velocity, thus creating a pressure jump across its width. This pressure jump produces a strong downwind turbulence forming a mixing layer capable of enhancing odour dispersion.

INVESTIGATION OF WINDBREAK SYSTEMS TO CONTROL DUST GENERATION AND DISPERSION IN A RECLAIMED LAND: A NUMERICAL APPROACH

INVESTIGATION OF WINDBREAK SYSTEMS TO CONTROL DUST GENERATION AND DISPERSION IN A RECLAIMED LAND: A NUMERICAL APPROACH

Natural Windbreaks Sustain Bird Diversity in a Tea-Dominated Landscape

Windbreaks often form networks of forest habitats that improve connectivity and thus conserve biodiversity, but little is known of such effects in the tropics. We determined bird species richness and community composition in windbreaks composed of remnant native vegetation amongst tea plantations (natural windbreaks), and compared it with the surrounding primary forests. Fifty-one, ten-minute point counts were conducted in each habitat type over three days. Despite the limited sampling period, our bird inventories in both natural windbreaks and primary forests were nearly complete, as indicated by bootstrap true richness estimator. Bird species richness and abundance between primary forests and windbreaks were similar, however a difference in bird community composition was observed. Abundances of important functional groups such as frugivores and insectivores did not vary between habitat types but nectarivores were more abundant in windbreaks, potentially as a result of the use of windbreaks as traveling routes, foraging and nesting sites. This preliminary study suggests that natural windbreaks may be important habitats for the persistence of bird species in a production landscape. However, a better understanding of the required physical and compositional characteristics for windbreaks to sustain bird communities is needed for effective conservation management.

Relation of peel damage in citrus fruit to wind climate in orchard and its control

Peel damage originated by wind is the main abiotic cause of citrus fruit discards for export in Uruguay. Natural windbreaks such as Eucalyptus and Casuarinas have not been effective in reducing it. This research was carried out during three years in a citrus orchard situated in the coastal plain of Uruguay (35° SL). The purpose of this work was to study wind climate inside the orchard, fruit seasonal sensitivity, basal leaf effect on the onset and evolution of peel damage, and the efficiency of artificial windbreaks to reduce fruit discard of ‘Ellendale’ tangor. Average wind velocity in the orchard did not exceed 5 m s −1. First peel scars were evident two weeks after petal fall and damaged fruit percentage importantly increased during the first stage of fruit growth. Low energy vortexes caused almost permanent friction between basal leaves and the developing fruitlets growing in their axil. Removal of the basal leaf decreased significantly wind damaged fruit. Natural wind flow modification through the use of semi-porous artificial windbreak nets (5 cm by 10 cm mesh) modified low energy vortexes and increased significantly the percentage of export quality fruit. We conclude that this type of net is more efficient than natural windbreaks or classical nets to reduce wind damage in citrus fruit.

A wind tunnel study on aerodynamic porosity and windbreak drag

Natural windbreaks such as trees are very efficient barriers to high velocity winds. The windbreaks exert drag force causing a net loss of momentum and thus disturb the characteristics of flow. The main factors which can affect the efficiency of the windbreaks are tree height, width, tree arrangement, porosity, etc. However, tree porosity which is strongly related to the windbreak drag is very difficult to establish. In this study, the results of a wind tunnel test were introduced to find the aerodynamic porosity and resistance factor of a tree windbreak. Black pine tree (Pinus thunbergii), a typical tree windbreak in Korea was chosen as the experimental tree. With the main factors of wind velocity, static pressure and density of the tree, the aerodynamic porosity as well as the resistance factor of the tree was found. The average porosity at varied tree density were found to be 0.91, 0.69 and 0.42 for one, two and three trees, respectively. The resistance factors which can be equaled to the drag coefficient were 0.55, 0.82 and 1.08 for one, two and three trees, respectively. The determined aerodynamic porosity and windbreak drag will be used later as input data in computer simulation studies such as computational fluid dynamics (CFD). Moreover, the experimental procedure as well as the use of real trees in the wind tunnel experiment of finding the aerodynamic porosity and windbreak drag of various tree windbreaks was established through this study.

Structural design of a natural windbreak using computational and experimental modeling

Computational and experimental approaches are employed for the structural design of a natural windbreak. It is intended to find the optimum tree shelterbelt to obviate the uneven wind speed distribution across the width dimension of a high-level competition rowing channel. The experimental results, obtained in a wind tunnel, and consisting of erosion-technique images and local wind-speed measurements, are used to benchmark the computational model. A good agreement between the two sets of results is obtained. Several windbreak configurations, considering one or two rows of different cross-sectional shape and porosity, are computationally modeled. For the shortest row a rectangular shape, with porosity of 35%, is considered; for the tallest row, which aims the modeling of a poplar tree, a porosity of 87% is assumed at the trunk level, and 60% at the crown. The optimum shelterbelt consists of two rows, composed by bamboo and poplar trees, which allows the attainment of a low and nearly uniform wind flow across the width of the channel.

Effect of weather conditions on windbreak odour dispersion

Natural windbreaks are planted to enhance the dispersion of livestock odours and improve the rural environment, although the best implementation strategies still need to be better defined. Using computational fluid dynamic modelling, the objective of this paper was to verify the effect of climatic conditions on odour dispersion downwind from natural windbreaks. The Fluent shear stress transport (SST) k– ω model was used to simulate odour dispersion as released by an odour source, and as dispersed downwind from a single-row coniferous windbreak measuring 9.2 m in height and 7 m in thickness, with an aerodynamic porosity of 0.4. The simulation was limited to a single-point emission source. A total of 21 simulations demonstrated the effects of wind velocity and direction, and air temperature under unstable, neutral, and stable atmospheric conditions. Generally, higher wind velocities produced shorter odour plumes for all atmospheric conditions, but a shorter odour plume was observed also at lower wind velocities under unstable atmospheric stability because of stronger vertical convection. As opposed to air temperature at the ground surface, temperature gradient had a much stronger effect on the odour dispersion domain. Wind direction had an impact on the direction and length of the odour plume, which decreased for wind directions of 0–45° (0° being perpendicular to the windbreak) due to air flowing along and near the leeward side of the windbreak. Neutral atmospheric stability conditions produced a shorter odour plume length compared with unstable and stable conditions because of stronger convective effects.

Simulation of odour dispersion downwind from natural windbreaks using the computational fluid dynamics standard k-ε modelA paper submitted to the Journal of Environmental Engineering and Science.

If natural windbreaks create air turbulence and can help disperse odours from livestock operations, their dispersion effect has not been extensively researched. This paper introduces a model simulating odour dispersion downwind from natural windbreaks. The standard k-ε model of the FLUENT software was used to incorporate the effect of climatic conditions and windbreak structure. The model was calibrated for wind velocity recovery, odour concentration (OC) from field observations and inertial resistance. Once calibrated, the model accurately reproduced the odour plume developing downwind from the windbreak. The correlation between OC for 11 field trials and that simulated were statistically significant (P < 0.01), indicating that the model was accurate. The model demonstrated that a windbreak did alter the magnitude and direction of the wind velocity, thus creating a pressure jump across its width. This pressure jump produces a strong downwind turbulence forming a mixing layer capable of enhancing odour dispersion.

Cultural and Environmental Factors Associated with Winter Injury to Apple in Northern Eastern Canada

ABSTRACT A survey was conducted in 1995/1996 to identify factors responsible for apple tree mortality in Quebec during the winter of 1993/ 1994. ‘Golden Delicious’, ‘Wealthy’, ‘Mutsu’, ‘Red Delicious’, ‘Golden Russet’ and ‘Yellow Transparent’ were severely injured or killed in all regions, the mortality of other cultivars was mainly affected by certain combinations of cultural and environmental factors. Generally, percent mortality was lower at higher altitudes and in orchards with sufficient snow cover and low density trees. Higher mortality was observed for very young or very old trees, specifically those that had a heavy crop in the previous year or were exposed to wind. Vigorous trees were more susceptible to winter injury than trees of moderate vigor. Less mortality was observed with trees that had been harvested early in the season. Trees on dwarf rootstocks planted in sandy soil, sandy loam, gravel loam, or any soil in combination with sandy or gravel soil type were more susceptible to winter damage. The orchard site and the location of trees in each orchard were the most important factors that affected apple tree mortality. The maximum tree mortality was observed for trees that were exposed to cold air accumulation or in orchards where the flow of cold air was prevented due to obstructions like a natural windbreaks or land topography. The least damage was observed in orchards planted on a slight slope. The absence of a river, or a large body of water nearby increased mortality in all regions. Selection of a good site is the most important factor in controlling winter damage. Our results revealed that even the most hardy cultivar and rootstocks combinations can undergo winter damage when they are planted in an unsuitable site. This is particularly critical for dwarf and semi-dwarf rootstocks.

Simulation of the effect of windbreaks on odour dispersion

Computational fluid dynamic (CFD) models are capable of defining best management practices associated with the wide use of natural windbreaks to help disperse livestock odours. The Fluent shear stress transport (SST) k – ω model was used to simulate odour dispersion downwind from natural windbreaks and to test the effect of tree characteristics (tree porosity, type and height, and windbreak distance from the odour source). The airflow inertial resistance of windbreaks was defined as proportional to the square of the tree diameter. The SST k – ω model was initially calibrated for air velocity recovery rate on the downwind side of the windbreak, using a two-dimensional simulation. Following calibration with field odour measurements, the model was used to compare the size and length of odour plumes developing downwind from windbreaks with different tree characteristics and odour source position. With the air velocity recovery rate calibration, the SST k – ω model predicted the wind velocity profile with an acceptable error of 4.5%. The calibration of the SST k – ω model for odour dispersion required the use of a function transforming the simulated odour mass concentration into simulated absolute hedonic tone. Once calibrated for odour dispersion, the SST k – ω model was able to accurately predict odour concentration downwind from the windbreak. By comparison, the SST k – ω simulations indicated that a dense (aerodynamic porosity of 0.2 compared to 0.66) and tall (9.2 m compared to 4.6 m) natural windbreak produced a shorter odour plume, but the odour concentration immediately downwind from the windbreak was much higher. For the same aerodynamic porosity, tree type or structure had limited effect on odour plume size. As compared to a source located further away (60 m), an odour source located close (15 m) to the windbreak produced a shorter plume because a closer source resulted in less dilution upwind from the windbreak and a greater mass of odourous air trapped downwind from the windbreak. Thus, a tall and dense natural windbreak, located no more than 15 m downwind from the odour source, minimises the length of the odour plume, but increases the intensity of the odour level immediately downwind from its position.

Filtering of windborne particles by a natural windbreak

New measurements of the transport and deposition of artificial heavy particles (glass beads) to a thick 'shelterbelt' of maize (width/height ratioW/H ≈ 1.6) are used to test numerical simulations with a Lagrangian stochastic trajectory model driven by the flow field from a RANS (Reynolds-averaged, Navier-Stokes) wind and turbulence model. We illustrate the ambiguity inherent in applying to such a thick windbreak the pre-existing (Raupach et al. 2001; Atmos. Environ. 35, 3373-3383) 'thin windbreak' theory of particle filtering by vegetation, and show that the present description, while much more laborious, provides a reasonably satisfactory account of what was measured. A sizeable fraction of the particle flux entering the shelterbelt across its upstream face is lifted out of its volume by the mean updraft induced by the deceleration of the flow in the near-upstream and entry region, and these particles thereby escape deposition in the windbreak.

Livestock Odour Dispersion as Affected by Natural Windbreaks

Natural windbreaks have been planted around livestock shelters to improve odour dispersion without substantial knowledge of their best implementation practices. Using three groups of four trained panellists and an odour generator, the objective of the present research was to measure and compare the length of odour plumes (LOP) produced in the field in the absence of, and in the presence of four natural windbreaks exposed to various climatic conditions. During 39 mornings in August, September and December 2003, panellists observed the resulting odour plumes using hedonic tone (HT) as scale and in the afternoon, evaluated the odour concentration (OC) of the odorous air sampled at the generator. By correlating HT with to their corresponding OC, filed HT values were converted into OC units, and 2 OU m−3 contours were used to establish LOP. A multiple factor analysis verified the effect significance on LOP of the presence of a windbreak, of windbreak properties and of climatic conditions. While being diluted, OC decreased exponentially with HT as observed by panellists (P < 0.05). Secondly, the windbreaks significantly reduced LOP by 22% as compared to the site without a windbreak. Thirdly, the denser windbreaks had a greater impact on reducing LOP. The LOP of windbreaks with an optical porosity of 0.55 was not significantly different compared to that created in the absence of a windbreak. The wind speed, direction and ambient temperature had a strong influence on LOP while atmospheric stability, windbreak position downwind from the odour source within 60 m and odour emission rate had little impact, based on the analysis of 36 field tests in the presence of a windbreak.

USE OF WINDBREAKS IN LOWBUSH BLUEBERRY (VACCINIUM ANGUSTIFOLIUM AIT.) PRODUCTION

Windbreaks have long been used to reduce wind travel over crops and therefore, reduce mechanical stress, increase crop yield, reduce evaporation, and decrease water use. The objectives of this investigation were to acquire a fundamental understanding of both the microclimatic changes brought about by windbreaks, and the manner in which these changes are translated into growth, development, and yield of wild blueberries. The experiment was conducted at three locations in Nova Scotia (Earltown, Fox Point, and West Brook NS), and three treatments were used at all sites. The wind shelter treatments used consisted of (1) exposed plants, (2) plants that were encircled by a 50% permeable, wooden lath shelter, and (3) plants that were encircled with a wooden lath shelter and covered prior to winter with a floating row cover which was removed prior to bloom the following spring. The shelter treatments had a significant effect on microclimate especially snow cover and ground level temperatures during the winter. This coincided with reduced winter floral bud damage, and greater stem weights, berry number, and harvestable yields (g·m-2) compared to plants that were exposed. Natural windbreaks were also observed to have a beneficial effect on yield with harvested yield decreased at a linear rate from the windbreak [i.e., y = 353 – 4.25 x, where y = harvestable yield (g×m-2) and x is the distance from the windbreak)]. These results indicate that wind shelters can reduce floral bud winter injury and increase the vegetative growth and yield of lowbush blueberries.

Influence d'un brise-vent sur les pertes convectives et radiatives d'une serre

An experimental study of air flow near the walls of a greenhouse protected by a natural windbreak shows that a low speed reversed flow is produced between the two obstacles and relatively large wind speeds and gradients are located at the top of the greenhouse (Figure 1). Estimation of the convective heat fluxes from the different zones of the greenhouse cover to the surroundings shows that heat losses by convective processes are most important from the top of the greenhouse. This implies a need for good greenhouse roof insulation in order to save energy.