Tree Windbreaks Research Articles

Fine root distributions of shelterbelt trees and their water sources in an oasis of arid northwestern China

Shelterbelt trees play an important role in maintaining the sustainability of oases agricultural ecosystems, but the trees require a considerable amount of water for survival. The objectives of this study were to investigate the root distributions, transpiration and water sources of shelterbelt trees (Gansu Poplar; Populus gansuensis) in order to improve water management efficiency. Fine root and soil water distributions were investigated along three transects that passed through cropland and an adjacent shelterbelt, while sap flow measurements were conducted on six Gansu Poplar trees. Results showed that roots were mainly distributed within 5 m of both sides of an irrigation channel passing between the first and second tree rows. The maximum distance to which trees extended fine roots horizontally was about 18 m from the shelterbelt. In 2-m soil profiles, fine roots were mainly distributed in the 1.4–2.0 m and 0–0.4 m layers depending on the available water sources. A positive relationship was observed between soil water and fine root mass density. Trees grown near the cropland-shelterbelt border exploited water from cropland irrigation and irrigation channel leakage, greatly enhancing their transpiration. During the growing season of 2013, the mean total transpiration of trees grown farther away from the border (10.75 and 17.45 m) was 216.9 mm, whereas for trees grown nearer to the border (0.85 and 6.30 m) the amounts were 670.1 and 488.7 mm, respectively. If the trees were assumed to absorb the same amount of water from soil, rainfall and groundwater sources, then irrigation water sources provided 67.6% and 55.6% of the water meeting the transpiration requirements of the trees closest to the border. The results have important implications for water management in oasis agricultural areas by limiting the extension of shelterbelt tree roots into adjacent cropland in order to improve irrigation water use efficiency.

Carbon sequestration by white spruce shelterbelts in Saskatchewan, Canada: 3PG and CBM-CFS3 model simulations

For more than a century, planted shelterbelts in Saskatchewan, Canada have protected farmyards from the elements, decreased soil erosion, sequestered atmospheric carbon, as well as provided many other ecological functions. It is estimated that there are >60,000km of planted shelterbelts throughout the province, and considerably more in all of the Canadian Prairies. This paper details the overall process of quantifying and mapping the carbon stocks in white spruce (Picea glauca) shelterbelts planted in Saskatchewan. Shelterbelt data collected from field sampling sites, which were identified by a unique site selection approach, were used to parameterize two models for use in shelterbelt systems; an independent data set was used to validate model predictions. Shelterbelt tree growth was modeled with the Physiological Principles in Predicting Growth (3PG) model, and carbon flux and stocks in shelterbelts were modeled with the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3). Annual total ecosystem carbon (TEC) flux in white spruce shelterbelts increased one order of magnitude, from −0.33 to 4.4Mg Ckm−1yr−1, for age 1–25 years, and reached a peak of 5.5Mg Ckm−1yr−1 (age 39 years). An initial soil carbon loss from the shelterbelt, caused by the land-use change, was offset in full by tree growth by age 17, 18, and 21 years for trees planted at 2.0, 3.5, and 5.0m spacing within a row, respectively. Increase in carbon stocks, after 60 years of growth, was predicted in the litter layer (21.8Mg Ckm−1), belowground biomass (26.1Mg Ckm−1), and aboveground biomass (117.6Mg Ckm−1). Across all the different provincial soils, carbon additions were 106–195Mg Ckm−1 in 60-yr-old white spruce shelterbelts. Cumulatively, accounting for eight decades of white spruce shelterbelt planting and tree growth, carbon additions totaled 50,440Mg C province-wide in 991km of white spruce shelterbelts. The C additions represented 38% of the province-wide TEC stocks, which totaled 131,750Mg C. The cumulative carbon storage in all components of planted white spruce shelterbelts far exceeded the initial carbon levels present at the time of shelterbelt planting.

Estimating carbon storage in windbreak trees on U.S. agricultural lands

Assessing carbon (C) capture and storage potential by the agroforestry practice of windbreaks has been limited. This is due, in part, to a lack of suitable data and associated models for estimating tree biomass and C for species growing under more open- grown conditions such as windbreaks in the Central PlainsregionoftheUnitedStates (U.S.).Weevaluated 15 allometric models using destructively sampled Pinus ponderosa (Lawson & C. Lawson) data from field windbreaks in Nebraska and Montana. Several goodness-of-fit metrics were used to select the optimal model. The Jenkins' et al. model was then used to estimate biomass for 16 tree species in windbreaks projected over a 50 year time horizon in nine conti- nental U.S. regions. Carbon storage potential in the windbreak scenarios ranged from 1.07 ± 0.21 to 3.84 ± 0.04 Mg C ha -1 year -1 for conifer species and from 0.99 ± 0.16 to 13.6 ± 7.72 Mg C ha -1 year -1 for broadleaved deciduous species during the 50 year period. Estimated mean C storage potentials across species and regions were 2.45 ± 0.42 and 4.39 ± 1.74 Mg C ha -1 year -1 forconifer and broad- leaved deciduous species, respectively. Such infor- mation enhances our capacity to better predict the C sequestration potential of windbreaks associated with whole farm/ranch operations in the U.S.

The taxocene of lichen-feeding darkling beetles (Coleoptera, Tenebrionidae: Helopini) in a forest-steppe ecotone

The taxocene of lichen-feeding darkling beetles from the tribe Helopini is studied in the steppes of the south of Rostov Province. The species of lichens grazed on by the representatives of this tribe are identified for the first time and dependence of circadian activity and spatial distribution of adults on temperature and air humidity is shown. Global warming and human activities may have caused degradation of steppe lichen communities that formed the dietary base for the lichen-feeding darkling beetles in natural ecosystems. As a result, 3 out of 4 beetle species completely left steppe biotopes for tree shelterbelts. This caused a change in the trophic relationships (transition from epigeic to epiphytic lichens) and in the spatial distribution of darkling beetles, promoted the establishment of competitive interactions, and increased the duration of circadian and seasonal activity due to the lengthening of the periods with optimum temperature and air humidity for each species.

Queuing up the Olives: Confronting an Invasive Tree

The Russian olive tree (eleagnus angustifolia—no relation to the real olive) was brought to North America from southern Europe in the early 1900s, first as a windbreak tree and later as a drought-tolerant ornamental.

History of East European Chernozem Soil Degradation; Protection and Restoration by Tree Windbreaks in the Russian Steppe

The physiographic region of the Central Russian Upland, situated in the Central part of Eastern Europe, is characterized by very fertile grassland soils—Chernozems (Mollisols in the USDA taxonomy). However, over the last several centuries this region has experienced intense land-use conversion. The most widespread and significant land-use change is the extensive cultivation of these soils. As a result, Chernozems of the region that were some of the most naturally fertile soils in the world with thick A horizons had become, by the second half of the 19th century, weakly productive, with decreased stocks of organic matter. When not protected by plant cover, water and wind erosion degraded the open fields. The investigation of methods for rehabilitation and restoration of Chernozems resulted in the practice of afforestation of agricultural lands (mainly by windbreak planting). Preferences of agroforestry practices were initially connected with protection of cropland from wind and water erosion, improvement of microclimate for crop growth, and providing new refugia for wild animal and plant habitats. During the last several decades, tree windbreaks have begun to be viewed as ecosystems with great potential for atmospheric carbon sequestration, which plays a positive role in climate change mitigation. For the evaluation of windbreak influence on Chernozem soils, a study was developed with three field study areas across a climatic gradient from cool and wet in the north of the region to warm and dry in the south. Windbreak age ranged from 55–57 years. At each site, soil pits were prepared within the windbreak, the adjacent crop fields of 150 years of cultivation, and nearby undisturbed grassland. Profile descriptions were completed to a depth of 1.5 m. A linear relationship was detected between the difference in organic-rich surface layer (A + AB horizon) thickness of soils beneath windbreaks and undisturbed grasslands and a climate index, the hydrothermal coefficient (HTC). These results indicate that windbreaks under relatively cooler and wetter climate conditions are more favorable for organic matter accumulation in the surface soil. For the 0–100 cm layer of the Chernozems beneath windbreaks, an increase in organic C stocks comparable with undisturbed grassland soils (15–63 Mg·ha−1) was detected. Significant growth of soil organic matter stocks was identified not only for the upper 30 cm, but also for the deeper layer (30–100 cm) of afforested Chernozems. These findings illustrate that, in the central part of Eastern Europe, tree windbreaks improve soil quality by enhancing soil organic matter while providing a sink for atmospheric carbon in tree biomass and soil organic matter.

Analysis of Air Purification in a Woodland by Field Observation and Wind Tunnel Experiment

As part of a comprehensive study of the harmonious coexistence between man and nature focusing on woodland, we evaluated the role of the Ryukoku forest in air purification. The Ryukoku forest, located at Seta Hill in Shiga Prefecture, Japan, is composed of a mixture of conifer and deciduous trees. There are two mechanisms in purifying forest air: the deposition of air pollutants onto leaf surfaces and the effect of a tree wind break (air pollutant break). We measured the vertical distributions of nitrogen dioxide (NO2) concentration inside and outside the Ryukoku forest using passive samplers attached to a 25-m-tall observation tower and to the neighbouring university campus buildings, respectively. Wind tunnel experiments that treat atmospheric dispersion in model trees but cannot consider the effect of deposition have been conducted to evaluate the effect of a tree wind break. The observed NO2 concentrations in the Ryukoku forest showed a 5 - 20 percent decrease depending on the season towards the forest floor from the top of the canopy. Within the forest canopy layer, the average NO2 concentration was approximately 30 percent lower than that outside the forest. The results of the wind tunnel experiment showed a similar decrease in the concentration of air pollutants inside the forest. However, the decrease in the concentration of air pollutants towards the forest floor from the top of the canopy was not observed in the wind tunnel experiment. It is deduced that the low NO2 concentration inside the forest compared with that outside is mainly due to tree wind break effect and that the variation in NO2 concentration with height from the forest floor is mainly due to the deposition of air pollutants onto leaf surfaces.

A New Approach in Converting Desert into Pasture: Fengning County, Hebei Province, China

The thematic focus of this paper is to introduce a way to prevent desertification in the steppe climatic region by reducing wind velocity on ground surface and introducing a know-how of a specially designed drip-irrigation system that is sustainable in arid climate. The current desertification processes are rapidly expanding over the steppe climatic region worldwide, closely overlapping with Steppe Climatic Region (BS) of Koppen Climatic Classification. The basic thought in my study is to prevent desertification in the steppe climatic region by reducing wind velocity so that evaporation does not exceed precipitation. By applying Bernoulli’s equation for a one-kilometer-square pilot project in Fengning County, Hebei Province, China, it is estimated that four layers of tree windbreak in a square shape are sufficient to reduce wind velocity for the reforestation (Kim 2011). To avoid frequent failure of reforestation in the arid area owing to buildup of calcium layers and salt flat, a specially designed drip-irrigation system is introduced. Utilizing the favorable physical settings in the high altitude in arid area, a rotating solar power plant is planned to provide for pumping underground water for the drip irrigation. It is estimated that six kilowatts are sufficient power to support irrigation for a one-kilometer-square area, with a few dwelling units in the innermost 400-square-meter area. Once the Fengning pilot project is proven to be successful, it is hoped that the same system may be extended to the adjacent arid region and beyond.

Successful control of brown root rot disease in windbreak tree stands in Okinawa, Japan

Successful control of brown root rot disease in windbreak tree stands in Okinawa, Japan

Maize yield patterns on the leeward side of tree windbreaks are site-specific and depend on rainfall conditions in eastern Canada

Tree windbreaks may offer a range of potential advantages in terms of increased crop productivity and stability under climate change while providing multiple external benefits to society. The effects of windbreak on maize yields have not been assessed in a well-documented manner in eastern Canada, which is a major influential barrier limiting their adoption by farmers. In this study, we investigated the spatial distribution of maize grain yield in the leeward side of mature (average age, 30-years-old) single-tree row windbreaks that were located on four farm sites in southern Quebec, Canada. We determined whether the sign and magnitude of windbreak effects on spatial patterns of maize yield varied across contrasting years with respect to rainfall conditions. The greatest yield variation was observed at the tree-crop interface (within 0.5–1H, where H = tree height), where substantial yield reductions occurred. In two sites, the magnitude of negative windbreak effects on maize yield at the tree-crop interface decreases in the wetter years. We found important maize yield variation among sampling positions between 2H and 20H (here considered as the shelter zone), with yield values often significantly higher than at 24H (here considered as a control zone with negligible tree shelter effects). The magnitude of this yield variation in the shelter zone generally decreased in the wetter years. In most cases, we estimated that the net effect of windbreak on maize yield (0.5–20H vs. 24H) was negligible. Significant net positive (16 %) or negative (−6 %) effects of windbreaks on maize production were found at one site only and occurred on two different years. We conclude that the sign and magnitude of windbreak effects on spatial patterns of maize grain vary considerably across farms and depend upon temporal variation in rainfall conditions in eastern Canada.

Mapping and quantification of planted tree and shrub shelterbelts in Saskatchewan, Canada

The Government of Canada’s farm assistance programs have affected >80 % of Canada’s agricultural land base. One important program in the Prairie Provinces was the prairie shelterbelt program (PSP). A significant aspect of the PSP was shelterbelt tree planting to protect farmyard infrastructure and reduce soil erosion. The main goal of this paper was to map historical shelterbelt establishment, total expected shelterbelt length, and total expected number of six common planted shelterbelt species: caragana (Caragana arborescens), green ash (Fraxinus pennsylvanica), Manitoba maple (Acer negundo), Scots pine (Pinus sylvestris), white spruce (Picea glauca Monch), and hybrid poplar (Populus spp.). A clustering approach was designed to group all agricultural ecodistricts (106 total) into clusters (31 total) based on their similarity in 42 variables within five soil zones of Saskatchewan. Correlations between trees ordered through the PSP and observed shelterbelt length (across 2.1 Mha cumulative study area) were used for shelterbelt probability mapping. Mapping accuracy of planted shelterbelts was 48–86 %. Total shelterbelt length (of any species) ranged from 322 to 45,231 km for (in descending order) dark brown > brown > black > dark gray > gray soil zones. Novel decadal time-lapse maps and species-specific shelterbelt maps were produced to capture the progression of shelterbelt establishment for the first time at a province-wide scale which gave a new perspective, in map format, of the expansive impact of the living legacy of the PSP. Shelterbelt data gaps and high priority clusters of agricultural land in Saskatchewan were identified for future shelterbelt research.

Early fertilization and absorbent treatments continuously enhanced windbreak tree growth and soil properties in the Hetao Plain of Inner Mongolia, China

Intensive and continuous management has rarely been applied in forestation designed to combat desertification, except for a few instances of fertilization and irrigation in the early stage in northern China. We hypothesized that early and discontinuous fertilization and absorbent treatments would continuously increase tree growth and improve soil properties in an arid region. In 2003 and 2004, treatments of nitrogen fertilization and absorbents were applied to Populus alba var. pyramidalis trees in an experimental windbreak site in the Hetao Plain of Inner Mongolia, China. Nevertheless, the current study results have demonstrated that early and discontinuous nitrogen fertilization and absorbent treatments continuously increased tree growth (2003–2009) without any significant improvement in soil properties in 2010. The study results suggest that early and discontinuous fertilization and absorbent practices may be sufficiently effective in forestation aimed at combating desertification in arid lands where continuous maintenance cannot be expected.

Profiles in History

2012 USDA-NRCS Soil Scientist Bry Schmidt (retired), in blue vest, records a soil profile description of Tulare clay while working on the Rapid Assessment of U.S. Soil Carbon (RaCA) in 2012 in the historic Tulare Lakebed of Kings County, California. Dr. Robin Roberts, historian and USDA-NRCS Earth Team Volunteer, photographs the soil profile. RaCA in Kings County, California. Schmidt retired in 2013 after 25 years of federal service, including service in the United States Navy and a tour in Vietnam. During his career with USDA-SCS/NRCS, Schmidt made valuable contributions while working on several soil surveys in California, including the Soil Surveys of Northeast Kern County, Southwest Kern County, Western Tulare County, Western Fresno County, and Yosemite National Park. He is a co-author of the Soil Survey of Kern County, Southwestern Part. During his career with USDA-NRCS, he was highly regarded for his proficiency in working with the NASIS database. Dr. Robin Roberts has served as a USDA-NRCS Earth Team Volunteer since 2005 and authored the “History and Development” sections for the Soil Surveys of Western Fresno County, Southwest Kern County, and Northeast Kern County. Photo courtesy of Kerry Arroues, USDA-NRCS, Hanford, California. 2013–2014 The steppes of the Central Russian Uplands and the U.S. Great Plains both have extensive histories of the use of tree windbreaks to improve the local climate for crop growth. When V.V. Dokuchaev was sent to southern Russia in 1892, tree windbreaks had been used for more than a century to protect crops from hot, dry winds blowing from deserts to the southeast. Dokuchaev recommended an aggressive tree planting campaign, and today the region has an extensive windbreak network. During the Dust Bowl, a similar scenario played out in the United States. In this case, U.S. Forest Service personnel were charged with planting windbreaks to control wind erosion in six drought-stricken plains states. A key figure in the Prairie States Forestry Project (PSFP) was a Russian-born forester, Raphael Zon, who applied knowledge from his experiences in Russia to the PSFP in the Great Plains. Dr. Chendev (in pit) confers with North Dakota State Soil Scientist Wade Bott in a crop field in southern North Dakota. In 2013 and 2014, Yury Chendev of Belgorod State University (BSU) led expeditions to Nebraska, North and South Dakota, and Montana to study soil transformation following windbreak planting. A 1942 PSFP planting near Norfolk, NE was included in this study. Dr. Chendev and colleagues from BSU and Moscow State University were joined by U.S. partner Tom Sauer of the USDA-ARS and colleagues from Iowa State University. This project, funded by the U.S. Civilian Research and Development Foundation found strong similarities in soil organic carbon changes beneath the windbreaks that varied with climate and were consistent with findings from comparable sites in Russia. The results of this study will enable prediction of potential soil carbon sequestration and biomass production with tree planting in semiarid regions of the United States and Russia. Photo courtesy of Yury Chendev. Contributed by Tom Sauer. 2014 Resource Soil Scientist Greg Granger and State Soil Scientist Tony Jenkins analyze depth to bedrock distributions in potato fields of Northern Maine using ground penetrating radar. With the early April snowpack ranging from 0.5 to 1.5 m; snowshoes and a child's sled provide a relatively convenient way to traverse areas normally inaccessible to GPR due to crops and/or mud during warmer weather. The information gathered serves dual purposes: (i) field office assistance with on-site evaluation for planning conservation practices (specifically Subsurface Drainage 606) and (ii) Soil survey map unit evaluation pertinent to MLRA and National Initiative projects. NRCS Maine Soils Staff Use GPR for Bedrock Study. In the photo above, Resource Soil Scientist Greg Granger operates the GPR on a potato field buried under the snowpack. Information and Photo courtesy of Tony Jenkins, State Soil Scientist, USDA-NRCS, Maine.

Inventory of fruit species and ethnobotanical aspects in Sultepec, Mexico State, Mexico

Sultepec, State of Mexico, located on the central part of Mexico, belongs to the Physiographic province “Sierra Madre del Sur” and to the Subprovince “Depresión del Balsas”. Although it is known for its floristic richness, it lacks an inventory of vascular plants, including the fruit species. The aim of this work was to elaborate a database including family, scientific name, local name, biological form, origin, use, management, production and service of the fruit species. Plants were collected continuously from June 2010 to June 2011. Subsequently, they were determined in the herbarium “Eizi Matuda” (CODAGEM) from the Facultad de Ciencias Agrícolas of the Universidad Autónoma del Estado de México. The Principal Component Analysis was performed to show that management, use, origin and biological form explained the highest variability (41%) associated to the Principal Component 1. Meanwhile, plant height showed the highest association with the Principal Component 2 (18%). There were 25 families, 43 genus and 64 species. The best represented families by their species richness were Rosaceae, Rutaceae and Mimosaceae; at the genus level prevailed Citrus (7 species). The predominant biological form were trees (76.6%); 22 species provided firewood, 11 had ornamental value, 11 possessed medicinal properties, 8 were a forage source and 7 had wood value. The services they can provide include physical fence, shade, shelter for domestic animals and windbreak trees. Most of the species (62.5%) are for sale and own consumption; 37.5% is just obtained for own consumption. The main species management was in the backyard category.

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

Research on Yield and Quality Prediction Model of Poplar Based on Modern Information Technologies

The poplar is important part of shelterbelt trees, so the farmland shelterbelts based on poplar play an important part in the plain, in recent years the research on structure and efficiency mode of farmland shelterbelt are more, while the prediction models of the yield and quality of the polar are much less. The growth model is main material base of poplar growth, the development of information technology provides new methods for the quantitative study of poplar growth model and evaluation. The information technology is used to extract growth character parameters of poplar, and the neural networks is used to establish the relational model of the character parameters and wood materials and wood production of poplar, these models are used to monitor and analyze growth situation and materials of poplar and potential utilization value, so can correctly assess the reasonable use of the poplar, meanwhile provide the basis for the oriented cultivation of poplar management, which have important theory value and practical significance.

Brown root rot of trees caused by Phellinus noxius in the Ryukyu Islands, subtropical areas of Japan

SummaryThe fungus Phellinus noxius has a broad host range and causes brown root rot in a variety of tree species of various ages, irrespective of their original health. The fungus is widely distributed in tropical countries of Southeast Asia, the Pacific Islands and Australia, Central America and Caribbean, and Africa. Since 1988, when brown root rot was first found on Ishigaki Island, Okinawa Prefecture, the disease has been reported on several islands in Okinawa and Kagoshima Prefectures, and it has been causing serious problems to shade, windbreak, ornamental and landscape trees in the Ryukyu Islands, located in the subtropical region of southern Japan. Here, we report on the current status of P. noxius‐caused brown root rot in the Ryukyu Islands, Japan, including symptoms, occurrence, dispersal, distribution and host tree species of the disease, pathogenicity and/or virulence of the pathogen, and disease management based on our surveys and previously published reports from Japan. Brown root rot has been confirmed in 53 tree species from 32 plant families at different sites on 10 of the 12 islands surveyed. Among the 53 tree species, 34 were first recorded in Japan as host plants of P. noxius. The disease occurs mainly in shade, ornamental and windbreak trees at sightseeing places, parks, roadsides, agricultural land such as sugar cane fields, and around residences or other places associated with human activities.

Numerical simulation study of a tree windbreak

In this study, computational fluid dynamics (CFD) was utilised to investigate the flow characteristics around tree windbreaks. The efficiency of windbreaks depends on many factors which can be investigated in field experiments, though this is limited due to several reasons such as unstable weather conditions, few measuring points, etc. Fortunately, the investigation is possible via computer simulations. The simulation technique allows the trees to be modelled as a porous media where the aerodynamic properties of the trees are utilised in the model. The trees employed are Black pine trees (Pinus thunbergii) with a drag coefficient value of 0.55. The simulation provides analysis of the effect of gaps between trees, rows of trees, and tree arrangements in reducing wind velocity. The simulations revealed that 0.5 m gap between trees was more effective in reducing wind velocity than 0.75 and 1.0 m. The percentage reduction in velocity at the middle of the tree section for 0.5, 0.75 and 1.0 m gap distance was found to be 71, 65 and 56%, respectively. Two-rows of alternating trees were also found to be more effective than one-row and two-rows of trees. The reduction at the middle of the tree region for one-row and two-rows of trees and two-rows arranged alternately was 71, 88 and 91%, respectively. Results revealed that the percentage reduction in wind velocity measured at distance 15H, where H is the tree height, for one-row, two-rows of trees and two-rows arranged alternately was approximately 20, 30 and 50%, respectively.

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.

A laser scanning system for estimating wind velocity reduction through tree windbreaks

The performance of trees as windbreaks is principally determined by their geometric characteristics. This paper reports the development of a laser scanning system to measure tree geometric characteristics on-the-go and its use to estimate percent wind velocity reduction in a windbreak. The laser scanning system was built by mounting a laser sensor, a global positioning system (GPS) receiver, and a notebook computer on a test vehicle. A windbreak was established by arranging a set of large potted trees in a pattern that provided two porosities for wind velocity measurements (windbreaks I and II). Winds generated by a blower at low and high wind velocities were directed at the centers of the tree windbreaks. Wind velocities were measured using a vane anemometer in four areas of the windbreaks, both on the windward and leeward sides. Percent wind velocity reductions between the windward and leeward sides were calculated. The laser scanning system measured the tree canopy geometric characteristics in the same areas where the wind velocities were collected. The linear correlations between the tree canopy geometric characteristics and the percent wind velocity reductions were analyzed. In tree windbreak I, the highest correlation coefficient ( r) of 0.97 (root mean square deviation – RMSD = 3.61%) and 0.96 (RMSD = 3.29%) were obtained at the low (<16 m s −1) and high (<20 m s −1) wind velocity conditions, respectively. On the other hand, in tree windbreak II, the highest r values of 0.93 (RMSD = 4.59%) and 0.98 (RMSD = 2.26%) were estimated at the low (<12 m s −1) and high (<18 m s −1) wind velocity conditions, respectively.