Grass Surface Research Articles

Monitoring of the refraction coefficient in the lower atmosphere using a controlled setup of simultaneous reciprocal vertical angle measurements

A great deal of empirical studies have investigated the characteristics of terrestrial refraction. However, only few of these are concerned with short‐term fluctuations of refraction influences. The aim of the present work is to analyze the short‐term characteristics (amplitudes and variations at scales of minutes to hours) of terrestrial refraction in the lower atmosphere around 1.8 m above the grass surface. We apply the known method of simultaneous reciprocal vertical angle measurements to derive time series of the refraction coefficient k as a measure for refraction. Our study uses a new setup of two pairs of total stations for parallel observations of the refraction coefficient along adjacent lines of sight. Such a controlled experiment not only allows us to determine refraction coefficients independently but also to assess measurement errors from the residuals between refraction coefficient pairs. Over five observation days in the summer of 2008, a total of 33 h of parallel observation data of the refraction coefficient were collected at sampling frequencies of 1 min. On one observation day, unique parallel observations of the refraction coefficient along three lines of sight with a total of six total stations were possible. For mostly sunny days, we found wave‐like and sawtooth‐like fluctuations of the refraction coefficient with amplitudes of 1–1.5 at time scales of 10–30 min. On cloudy days, the amplitudes of fluctuations were on the order of 0.5. Our refraction experiments show a variation range of k between −4 and +16 near the ground on sunny summer days. This equates to vertical temperature gradients between −0.5 and −0.1 K/m during the day and 1–2 K/m shortly after sunset. Cloud cover reduces the variability of k to a range of −2 to +5. Our results show that the frequently used Gaussian refraction coefficient of +0.13 is not suited for describing refraction effects in the lower atmosphere. As a conclusion, our results may be helpful to better assess the role of refraction in near‐ground precision surveys, such as geometric levelling or trigonometric heighting.

The Effect of Playing Surface on Injury Rate

Synthetic playing surfaces are widely used for field and court sports. Artificial turf surfaces are commonly used as an alternative to natural grass, while outdoor surfaces like clay and acrylic are also prevalent. The effect of these synthetic surfaces on injury rates has not been clearly established. The available literature is largely limited to football and soccer data and the majority of studies are short-term. Confounding variables such as climate, player position and footwear, as well as varying definitions of injury, also make it difficult to draw firm conclusions about the general effect of artificial playing surfaces on injury rates. Many peer-reviewed studies cite a higher overall rate of injury on first- and second-generation artificial turf surfaces compared with natural grass. Despite differences in injury type, the rate of injury on third-generation and natural grass surfaces appears to be comparable. It also appears that clay is significantly safer than either grass or hard court tennis surfaces, but this is a conclusion drawn with limited data. Further research investigating overall injury trends as well as sport-specific data is needed to draw more definitive conclusions regarding the effect of artificial playing surfaces on injury rates.

Ecological Risk Assessment of Pesticide Runoff from Grass Surfaces

An ecological risk assessment was performed for runoff of 37 pesticides registered for use on grass surfaces (lawns and golf courses) in the U.S. The assessment was based on 100-yr simulations using TPQPond, a newly developed model of pesticide runoff and subsequent accumulation in a receiving pond. One-in-10 yr pond concentrations were compared with acute toxicity end points for fish, invertebrates, and algae. Simulations were performed for pesticides applied at label rates on lawns, fairways, and greens using weather data for nine U.S. locations. Runoff of 4 of the 37 pesticides produced potential acute risk to invertebrates or fish. Two chemicals posed a comparable danger to plants. Risk was highest with fairways and lowest for greens. Locations with long growing seasons and large amounts of precipitation produced the highest risks. The risk assessment followed the general protocols recommended by USEPA, but with different models, weather data, and scenarios. In spite of the differences, the results confirmed that most but not all of the pesticides which had survived the USEPA registration process were also demonstrated safe, with respect to acute risks, by this independent assessment. The five exceptions were explained by differences in models, simulation scenarios, and input data. These results do not mean that the studied pesticides are free of any ecological dangers. In particular, no attempt was made to evaluate chronic risk.

The predicted risk of head injury from fall-related impacts on to third-generation artificial turf and grass soccer surfaces: A comparative biomechanical analysis

The risk of soccer players sustaining mild traumatic brain injury (MTBI) following head impact with a playing surface is unclear. This study investigates MTBI by performing headform impact tests from varying heights onto a range of third-generation artificial turf surfaces. Each turf was prepared as per manufacturers specifications within a laboratory, before being tested immediately following installation and then again after a bedding-in period. Each turf was tested dry and when wetted to saturation. Data from the laboratory tests were compared to an in situ third-generation surface and a professional grass surface. The surface performance threshold was set at a head impact criterion (HIC) = 400, which equates to a 10% risk of the head impact causing MTBI. All six third-generation surfaces had a >10% risk of MTBI from a fall >0.77 m; the inferior surfaces required a fall from just 0.46 m to have a 10% MTBI risk. Wetting the artificial turf did not produce a statistically significant improvement (P > 0.01). The in situ third-generation playing surface produced HIC values within the range of bedded-in experimental values. However, the natural turf pitch was the superior performer – necessitating fall heights exceeding those achievable during games to achieve HIC = 400.

Modeling the Thermal Effects of Artificial Turf on the Urban Environment

Abstract The effects of artificial turf (AT) on the urban canopy layer energy balance, air and surface temperatures, and building cooling loads are compared to those of other common ground surface materials (asphalt, concrete, and grass) through heat transfer modeling of radiation, convection, and conduction. The authors apply the Temperatures of Urban Facets in 3D (TUF3D) model—modified to account for latent heat fluxes—to a clear summer day at a latitude of 33° over a typical coastal suburban area in Southern California. The low albedo of artificial turf relative to the other materials under investigation results in a reduction in shortwave radiation incident on nearby building walls and an approximately equal increase in longwave radiation. Consequently, building walls remain at a relatively cool temperature that is similar to those that are adjacent to irrigated grass surfaces. Using a simple offline convection model, replacing grass ground cover with artificial turf was found to add 2.3 kW h m−2 day−1 of heat to the atmosphere, which could result in urban air temperature increases of up to 4°C. Local effects of AT on building design cooling loads were estimated. The increased canopy air temperatures with AT increase heat conduction through the building envelope and ventilation in comparison with a building near irrigated grass. However, in this temperate climate these loads are small relative to the reduction in radiative cooling load through windows. Consequently, overall building design cooling loads near AT decrease by 15%–20%. In addition, the irrigation water conservation with AT causes an embodied energy savings of 10 W h m−2 day−1. Locally, this study points to a win–win situation for AT use for urban landscaping as it results in water and energy conservation.

Biomechanical loading of the hip during side jumps by soccer goalkeepers

There is a risk of hip injury in dives to the side by soccer goalkeepers. In this study, we assessed hip loading in goalkeepers when performing such dives. The experiments were conducted in a laboratory setting using an in-ground force plate as well as on a grass surface when the athletes were equipped with force sensors. The forces acting on the hip were measured and high-speed video analysis was performed, allowing the investigation of the dive characteristics and techniques. The peak force values recorded in the laboratory setting ranged from 3 to 8 kN, which corresponded to 4.2–8.6 times body weight. The vertical impact velocities reached 3.25 m · s−1. In the field experiments, a hip loading of 87–183 N · cm−2 was determined. We found that goalkeepers who perform a rolling motion reduce their hip loading. The data provided by this study add to the biomechanics database and contribute to the establishment of injury criteria. Such information is necessary to develop and implement strategies to help prevent hip injuries.

504 ガラスの押し込みクラック発生に対する圧子形状等の影響(切削・研削・研磨加工I)

504 ガラスの押し込みクラック発生に対する圧子形状等の影響(切削・研削・研磨加工I)

The Potential for Brain Injury on Selected Surfaces Used by Cheerleaders

Although playground surfaces have been investigated for fall impact attenuation, the surfaces that cheerleaders use have received little attention. To determine (1) the critical height for selected surfaces used by cheerleaders at or below which a serious head impact injury from a fall is unlikely to occur, (2) the critical heights for non-impact-absorbing surfaces for comparison purposes, and (3) the effect of soil moisture and grass height on g(max) (which is defined as the multiple of g [acceleration due to gravity at the earth's surface at sea level: ie, 32.2 feet x s(-1) x s(-1)] that represents the maximum deceleration experienced during an impact) and the Head Injury Criterion (HIC) at the critical height for a dry grass surface. Observational study. A local cheerleading gym, indoor locations within the authors' institution, and various outdoor locations. g(max), HIC, and critical height. Critical heights for the surfaces tested ranged from 0.5 ft (0.15 m) for concrete and vinyl tile installed over concrete to more than 11 ft (3.35 m) for a spring floor. Increases in grass height and soil moisture resulted in an increase in the critical height for grass surfaces. Only spring floors and 4-in (0.10-m)-thick landing mats placed on traditional foam floors had critical heights greater than 10.5 ft (3.20 m), thus providing enough impact-absorbing capacity for performance of 2-level stunts. The potential for serious head impact injuries can be minimized by increasing the shock-absorbing capacity of the surface, decreasing the height from which the person falls, or both. Cheerleaders and cheerleading coaches should use the critical heights reported in this study to compare the relative impact-absorbing capacities of the various surfaces tested, with critical height as an indicator of the impact-absorption capacity of the surface. The findings of this study can be used to select the most appropriate surface for the type of maneuver to be performed, based on the maximum height expected to be achieved by the cheerleader(s) during execution of the maneuver. Cheerleaders should not perform maneuvers at heights that exceed the critical height for the surface on which they are performing.

Injury Rates On Fieldturf And Natural Grass For High School Football And Soccer.

PURPOSE: Few studies have compared injury rates on natural grass and FieldTurf surfaces, especially in interscholastic sport populations. Prior studies have not reported differences in injury rates between FieldTurf and natural grass during practice and games in football and soccer. The purpose of our study was to compare the incidence of injury in high school football and soccer on natural grass and FieldTurf surfaces. METHODS: A total of 539 athletes who participated on eight boys' football (283 boys) and sixteen soccer (131 boys, 125 girls) teams in Western Washington were followed between the 1998 to 2001 interscholastic seasons for injury occurrence on FieldTurf and natural grass surfaces. All injuries were reported and verified by an athletic trainer/physical therapist. Injury rates were calculated per 1,000 athletic exposures. RESULTS: Injury rates on natural grass were significantly higher on FieldTurf for football (p<0.0001) and girls' soccer (p=0.0005). Injury rates were significantly higher on natural grass than FieldTurf for practices and games for football (p<0.0001) and girls' soccer (p=0.008). No significant differences were found between natural grass and FieldTurf in head-related trauma for football players (p=0.55). For other body locations, higher rates of knee injury for football (p=0.002) and ankle injury for girls' soccer (p=0.01) occurred on natural grass compared to FieldTurf. By injury type, higher rates of sprains for girls' soccer (p=0.03) and strains for football (p=0.003) occurred on natural grass compared to FieldTurf. By position, for football, higher rates of injury occurred on natural grass than FieldTurf for lineman (p<0.0001) and defensive backs (p=0.03). For girls' soccer, defenders had higher rates of injury on natural grass than FieldTurf (p=0.006). CONCLUSION: The results of this study suggest that a new generation of synthetic turf, FieldTurf, may lower the risk of injury in football and girls' soccer at the high school level. Further studies are needed to compare the risk of injury between the two surfaces in other high school sports like field hockey or lacrosse that also play on these field surfaces. Keywords: FieldTurf, injuries, prospective, high school

Training Surface and Intensity

This investigation assessed the effects of training intensity and ground surface type on hemolysis, inflammation, and hepcidin activity during running. Ten highly trained male endurance athletes completed a graded exercise test, two continuous 10-km runs on a grass (GRASS) and a bitumen road surface (ROAD) at 75%-80% peak VO2 running velocity, and a 10 x 1-km interval running session (INT) at 90%-95% of the peak VO2 running velocity. Venous blood and urine samples were collected before, immediately after, and at 3 and 24 h after exercise. Serum samples were analyzed for circulating levels of IL-6, free hemoglobin (Hb), haptoglobin (Hp), iron, and ferritin. Urine samples were analyzed for changes in hepcidin expression. After running, the IL-6 and free Hb were significantly greater, and serum Hp was significantly lower than preexercise values in all three conditions (P < 0.05). Furthermore, IL-6 levels and the change in free Hb from baseline were significantly greater in the INT compared with those in the GRASS (P < 0.05). There were no differences between the GRASS and ROAD training surfaces (P > 0.05). Serum iron and ferritin were significantly increased after exercise in all three conditions (P < 0.05) but were not different between trials. Greater running intensities incur more inflammation and hemolysis, but these variables were not affected by the surface type trained upon.

Football Playing Surface and Shoe Design Affect Rotational Traction

Background High rotational traction between football shoes and the playing surface may be a potential mechanism of injury for the lower extremity. Hypothesis Rotational traction at the shoe-surface interface depends on shoe design and surface type. Study Design Controlled laboratory study. Methods A mobile testing apparatus with a compliant ankle was used to apply rotations and measure the torque at the shoe-surface interface. The mechanical surrogate was used to compare 5 football cleat patterns (total of 10 shoe models) and 4 football surfaces (FieldTurf, AstroPlay, and 2 natural grass systems) on site at actual surface installations. Results Both artificial surfaces yielded significantly higher peak torque and rotational stiffness than the natural grass surfaces. The only cleat pattern that produced a peak torque significantly different than all others was the turf-style cleat, and it yielded the lowest torque. The model of shoe had a significant effect on rotational stiffness. Conclusion The infill artificial surfaces in this study exhibited greater rotational traction characteristics than natural grass. The cleat pattern did not predetermine a shoe's peak torque or rotational stiffness. A potential shoe design factor that may influence rotational stiffness is the material(s) used to construct the shoe's upper. Clinical Relevance The study provides data on the rotational traction of shoe-surface interfaces currently employed in football. As football shoe and surface designs continue to be updated, new evaluations of their performance must be assessed under simulated loading conditions to ensure that player performance needs are met while minimizing injury risk.

Impact of Microclimatic Data Measured above Maize and Grass Canopies on Penman-Monteith Reference Evapotranspiration Calculations

Estimation of reference evapotranspiration (ETref) using measured microclimatic data and the Penman-Monteith (PM) method provides a powerful means of quantifying actual plant evapotranspiration (ETa) needed for use in various disciplines. When applying the PM method to estimate ETref, it is desirable to measure the required microclimatic data over a reference grass or alfalfa surface rather than above non-reference surfaces. However, in reality, establishing and maintaining a reference surface for long periods of time is a difficult task. Other surface energy balance systems, such as the Bowen ratio energy balance system (BREBS), eddy covariance system, and surface renewal, are increasingly used to measure surface energy fluxes along with the microclimatic data above various plant canopies. These systems could be another source of data for ETref estimations when reference weather station data are not available due to logistical difficulties associated with establishing and maintaining a separate reference weather station. In many cases, data measured above other vegetation surfaces using the surface energy balance systems are the only source of data for ETref and ETa estimations due to the absence of reference weather stations. There is little information on how microclimatic data measured above different plant canopies impact the calculated ETref if used in the PM method in place of data collected from a reference surface. This study compares data measured above grass and maize (Zea mays L.) canopies and assesses how the variables measured above two canopies impact ETref calculated using the ASCE standardized Penman-Monteith (ASCE-EWRI PM) equation. Two years (2005 and 2006) of hourly microclimatic data measured above a grass surface using an automated weather station and above a maize canopy using BREBS installed on a well-watered maize field were used. The results obtained indicate very good agreements between the microclimatic variables measured above grass and maize, and between ETref calculated with data measured above the two surfaces. The measured rainfall was the same for both sites (316 and 323 mm in 2005 for the weather station and BREBS, respectively, and 368 and 366 mm in 2006). The main difference between the two surfaces was in u2 and aerodynamic resistance (ra). On a seasonal average basis, wind speed (u2) was 15% and 20% higher over the grass canopy than the maize canopy for 2005 and 2006, respectively. The maximum difference in ra between the two surfaces occurred when the maize was at its maximum height (2.45 m). On a seasonal average, the ra above the maize canopy was 37 s m-1 higher than the ra above the grass surface. However, the impact of u2 and ra on ETref was insignificant. The grass and alfalfa-reference ET (ETo and ETr) estimated using the data measured above maize (ETo-maize and ETr-maize) and above grass (ETo-grass and ETr-grass) were very similar in both years. In 2005, ETo-maize (816 mm) and ETo-grass (824 mm) were within 1%, and ETr-maize (1,033 mm) and ETr-grass (1,070 mm) were within 3%. The same percentages were obtained in 2006 (ETo-maize = 671 mm, ETo-grass = 675 mm, ETr-maize = 838 mm, ETr-grass = 868 mm). Thus, in practice, data measured above a well-watered maize canopy can be a substitute for the microclimatic data measured above a reference surface in ETref estimations when reference weather station data are not available to solve the PM equation in areas with similar rainfall (>300 mm) during the growing season, as observed in this study.

FIELD OBSERVATIONS OF RADIATION AND HEAT BALANCES ON A GRASS SPOT AND AN ARTIFICIAL GROUND IN AN URBAN AREA

In order to evaluate the effects of grass spots on mitigating urban heat-island phenomena, radiation and heat balances were observed on a grass spot and an artificial ground in summer season. In the daytime, the air and the surface temperatures on the grass spot were much the same as those on the artificial ground, but the downward conductive heat flux on the grass surface was much lower, due to the latent-heat consumption. The surface temperature on the grass spot dropped rapidly in the evening, and the air on the cold grass surface was cooled through the nighttime.

Parametrization of turbulent fluxes over inhomogeneous landscapes

Reasons for the nonclosure of the heat balance in the atmospheric boundary layers over natural land surfaces are analyzed. Results of measuring the heat-balance components over different land surfaces are used. The Cabauw (Netherlands) data (obtained throughout 1996 over a grass surface with intermittent shrubs and single trees) and the data from the Anchor station in Germany (measured over coniferous forest in 2000–2001) are analyzed. In all, the analysis involves about fifty thousand independent values of the heat-balance components measured in the experiments, which should be indicative of the reliability of the results obtained in the paper. The data have shown that the heat balance is not closed and the imbalance is 50–250 W/m2. The sum of the latent and sensible heat fluxes λE + H = STF is found to be systematically smaller than the difference between the net radiation and the heat flux into the ground Rn − G. It is shown that the main cause of a systematic heat imbalance in the atmospheric boundary layers over inhomogeneous land surfaces is that the methods of surface-flux measurement and estimation are based on the theory that requires the hypothesis of stationarity and horizontal homogeneity. Direct data analysis has shown that the heat imbalance increases with landscape inhomogeneity. In the paper, a parametrization of the heat imbalance is carried out and the coefficient kf(z0ef/Lef) is introduced as a measure of inhomogeneity. For this, data from the experiments FIFE, KUREX, TARTEX, SADE, etc., are also used. Empirical formulas are presented to refine the results of direct measurements and calculations of surface fluxes over natural (inhomogeneous) land surfaces from profile and standard (using bulk parametrizations) data. These formulas can also be used to determine surface fluxes over inhomogeneous underlying land surfaces in order to take into account so-called subgrid-scale effects in constructing prediction models.

Modeling Studies of Ammonia Dispersion and Dry Deposition at Some Hog Farms in North Carolina

A modeling study was conducted on dispersion and dry deposition of ammonia taking one hog farm as a unit. The ammonia emissions used in this study were measured under our OPEN (Odor, Pathogens, and Emissions of Nitrogen) project over a waste lagoon and from hog barns. Meteorological data were also collected at the farm site. The actual layout of barns and lagoons on the farms was used to simulate dry deposition downwind of the farm. Dry deposition velocity, dispersion, and dry deposition of ammonia were studied over different seasons and under different stability conditions using the short-range dispersion/air quality model, AERMOD. Dry deposition velocities were highest under near-neutral conditions and lowest under stable conditions. The highest deposition at short range occurred under nighttime stable conditions and the lowest occurred during daytime unstable conditions. Significant differences in deposition over crop and grass surfaces were observed under stable conditions.

Application of the ISO 13472-1 in situ technique for measuring the acoustic absorption coefficient of grass and artificial turf surfaces

This paper presents the applicability of an in situ technique based on ISO 13472-1 standard for measuring the acoustic absorption coefficient of grass and artificial turf surfaces for normal incidence from a sound source. The in situ method is based on acoustic impulse response measurement of the material surface. A maximum length sequence (MLS) signal is played through a loudspeaker and the acoustic response from the surface is recorded using a single microphone. The fast Hadamard transform and fast Fourier transform based digital signal post-processing algorithm provides the acoustic absorption coefficient of the surface under test. The normal incidence acoustic absorption coefficient of a commercial artificial quash surface of Dow Co. obtained from this method was compared with the results from the ASTM E1050 impedance tube method for the same surface. The acoustic absorption coefficients of a test-site grass surfaces were measured for 30mm and 100mm length of grass blades in wet and dry soil conditions. Substantial difference in the acoustic absorption coefficient was observed for a similar grass-like artificial surface used for estimating sound power of commercial garden equipments and lawnmowers. The advantage of the in situ method lies in its ability to measure the normal incident acoustic absorption coefficient of any planar surface as installed or in situ. Additionally a quick testing time of less than a minute with the use of a laptop sound card based inexpensive data acquisition system is the main feature of this robust method.

Some insight into the influence of urban ground surface properties on the air-surface exchange of total gaseous mercury

Abstract Experiments utilizing meteorologically normalized sampling conditions were used to illustrate the role and function of urban pavement, bare soil and turf grass surface properties with respect to the air-surface exchange of total gaseous Hg (TGM). After ensuring uniform meteorological effects to each surface, resultant TGM fluxes from turf grass, bare soil and pavement were specifically representative of their diverse physical and biogeochemical properties. Results spanning the entire sampling year show distinct TGM flux signatures for each surface (5.69 ± 5.79 (ng/m 2 h) for bare soil, 0.53 ± 1.25 for turf grass, 0.26 ± 0.41 for pavement). Based on medians, the surface limitations of pavement decreased TGM flux by a factor of 22 compared to bare soil and by a factor of 2 compared to turf grass. Turf surface limitations decreased TGM flux by a factor of 11 compared to bare soil. By comparing these results to a parallel study, meteorological effects were found to develop 24% of the TGM flux signature for pavement, 53% for turf and 60% for bare soil. The remaining percentage contributions to each TGM flux signature were from the cumulative surface property effects of each surface. These results suggest that the greater the TGM flux magnitude for a particular surface, the more measurements are needed under a wide variety of meteorological conditions to develop a broad understanding of its TGM flux characteristics. Seasonal observation allowed closer investigation of a large shift to TGM deposition for the turf surface during the fall season. The large shift toward deposition was suspected to be linked to the formation of a thatch layer on the unexposed soil surface just beneath the turf layer.

Survival of enteric microorganisms on grass surfaces irrigated with treated effluent

Treated effluent can be reused for the irrigation of parks and sports grounds but there is an associated potential public health risks from microbial pathogens present on the grass surface, particularly when used for contact sports. The main aim of this study was to investigate the survival of pathogenic and indicator microorganisms on the grass surface of a sports ground irrigated with treated effluent under differing climatic conditions. Results showed that Salmonella enterica serotype typhimurium, Escherichia coli, Enterococcus faecalis and Staphylococcus aureus decayed faster under direct sunlight than MS2 with one log(10) reduction (T(90)) varying from 3 to 11 hours. Rapid decay (T(90) 3 to 4 hours) of bacterial pathogens occurred in both sunlight and shade during the summer. In contrast, T(90) times for the bacteria during the winter varied from 6 to 11 hours in direct sunlight and from 23 to 38 hours in shade. No significant seasonal variation was observed in the inactivation of the bacteriophage MS2. Enteric viruses are expected to show inactivation rates similar to MS2. The results show that rapid inactivation of enteric bacteria can be expected on grass surface irrigated with treated effluent at higher ambient temperatures, in direct sunlight and low moisture content.

Evaluation of hyperspectral data for pasture estimate in the Brazilian Amazon using field and imaging spectrometers

We used two hyperspectral sensors at two different scales to test their potential to estimate biophysical properties of grazed pastures in Rondônia in the Brazilian Amazon. Using a field spectrometer, ten remotely sensed measurements (i.e., two vegetation indices, four fractions of spectral mixture analysis, and four spectral absorption features) were generated for two grass species, Brachiaria brizantha and Brachiaria decumbens. These measures were compared to above ground biomass, live and senesced biomass, and grass canopy water content. The sample size was 69 samples for field grass biophysical data and grass canopy reflectance. Water absorption measures between 1100 and 1250 nm had the highest correlations with above ground biomass, live biomass and canopy water content, while ligno-cellulose absorption measures between 2045 and 2218 nm were the best for estimating senesced biomass. These results suggest possible improvements on estimating grass measures using spectral absorption features derived from hyperspectral sensors. However, relationships were highly influenced by grass species architecture. B. decumbens, a more homogeneous, low growing species, had higher correlations between remotely sensed measures and biomass than B. brizantha, a more heterogeneous, vertically oriented species. The potential of using the Earth Observing-1 Hyperion data for pasture characterization was assessed and validated using field spectrometer and CCD camera data. Hyperion-derived NPV fraction provided better estimates of grass surface fraction compared to fractions generated from convolved ETM+/Landsat 7 data and minimized the problem of spectral ambiguity between NPV and Soil. The results suggest possible improvement of the quality of land-cover maps compared to maps made using multispectral sensors for the Amazon region.

Long-term changes of air temperature within a pine forest as compared to those above a grass surface

We have analysed time series covering 30 years (1974-2003) of air temperature observations in the stand of the Hartheim pine forest (South-west Germany): daily mean values, daily maxima and minima and the diurnal range. These data, in form of monthly averages, are compared with the air temperature measurements of the Eschbach site (Deutscher Wetterdienst), which is situated in open country nearby. We discuss the differences between these two sites with particular reference to the development of the pine stand (tree height and stand density). The greatest influence upon the temperature development at both sites is that produced by oscillations of the weather. The respective curves generally run parallel to one another. The weather fluctuations are represented by the monthly mean wind at the 500 hPa level. The temperature properties of both sites Hartheim and Eschbach considered here converged during the 30-year period of observation, so that today they no longer present any notable differences.