Effect Of Terrain Slope Research Articles

Using simulated GEDI waveforms to evaluate the effects of beam sensitivity and terrain slope on GEDI L2A relative height metrics over the Brazilian Amazon Forest

The vertical structure of forests provides important parameters for estimating aboveground biomass (AGB) and it can be measured by lidar sensors. The Global Ecosystem Dynamics Investigation (GEDI) full-waveform lidar sensor collects data systematically over the Earth's surface from the International Space Station. Since GEDI became operational, it has collected billions of ∼25-m diameter footprints. This massive dataset has been used to create higher level gridded and non-grided products. However, GEDI's ∼25-m footprints can be subject to errors associated with effects of geolocation, terrain slope, and beam sensitivity, among others, which are likely transferred to the downstream products. This study aims to (1) evaluate the effect of beam sensitivity and terrain slope on the accuracy of relative heights (RH) of GEDI product L2A version 2 through comparison with discrete-return airborne lidar data collected over transects in the Brazilian Amazon Forest biome, (2) assess GEDI's geolocation uncertainty and investigate its combined effects with beam sensitivity and terrain slope, and (3) re-evaluate beam sensitivity and terrain slope effects on the GEDI L2A RHs using footprints that were geolocation-adjusted through a simple novel approach. The analysis separates GEDI footprints by acquisition time, i.e., daytime, nighttime, and combined (all-data). The discrete-return airborne lidar point clouds are used to derive terrain slope within the GEDI footprints and to simulate GEDI waveforms and derive RHs comparable to the GEDI L2A product. Results indicate that terrain slope only causes significant effects on GEDI data collected during daytime because solar radiation affects waveform signal-to-noise ratio. Beam sensitivity causes significant effects on nighttime and all-data GEDI L2A RHs. If geolocation uncertainty is considered, the effects of beam sensitivity and terrain slope have just minor changes. Geolocation-adjusted data continue showing significant effects on nighttime and all-data RH differences caused by beam sensitivity but produce unbiased results. This study improves the understanding of how beam sensitivity, terrain slope, and their combined effect with geolocation uncertainty may affect the GEDI L2A RH collected over the Brazilian Amazon forest during daytime and nighttime.

Estimating water distribution of the rotating sprinkler with pulsating pressure on sloping land

Pulsating pressure plays an important role in improving the poor irrigation quality and the uneven water distribution caused by the terrain slope. Water distribution is one of the key factors in design of the sprinkler irrigation system, however, it is difficult to measure in practice. To provide appropriate technical parameters for the design of sprinkler irrigation system with pulsating pressure on sloping land, a mathematical model was established according to the water conservation principle and finite element idea, and its accuracy was experimentally verified. The model was applied to study the effects of terrain slope, sprinkler arrangement, sprinkler spacing and average pulsating pressure on water distribution on sloping land. The results showed that the water distribution was more favorable under the gentle terrain slope, when slope decreased from 25% to 5%, the uniformity increased from 74.47% to 86.22%. Sprinklers arranged in equilateral triangle and with the spacing close to R0 had the best water distribution uniformity, the uniformity coefficient (CU) of which was 11.43% and 8.75% higher than that in square and rectangular arrangement, respectively. The CU increased with the increase of the average pulsating pressure. However, the effect of increasing water pressure on promoting the uniformity of water distribution gradually decreases. Therefore, when using the Rainbird R5000 sprinkler on sloping land with pulsating pressure, it is suggested that the sprinkler irrigation systems should be arranged below the terrain slope of 20%, and operated at the average pulsating pressure of 300 kPa. The suitable sprinkler arrangement is the equilateral triangle, and with the spacing of 0.8R0 to 1.0R0. Keywords: sprinkler irrigation, water distribution on sloping land, estimation model, pulsating pressure DOI: 10.25165/j.ijabe.20221502.6662 Citation: Fu B Y, Huang Y, Zhang L. Estimating water distribution of the rotating sprinkler with pulsating pressure on sloping land. Int J Agric & Biol Eng, 2022; 15(2): 39–47.

The Pathways to Healthy Ageing: Evidence From Longitudinal Studies and Real-Time Data

The WHO has replaced its active ageing policy framework developed in 2002 with the new Healthy Ageing framework developed in 2015 and declared the decade between 2020 and 2030 as the Decade of Healthy Ageing. Healthy Ageing framework emphasizes the pivotal role of functional ability (FA) among older adults and conceptualizes that FA can be determined by intrinsic capacity (IC), environments (EN), and their interaction. WHO calls for global research to advance theoretical understanding of Healthy Ageing framework and translate the evidence into policy actions. This symposium provides the latest findings on Healthy Ageing from multi-country studies using real-time data and longitudinal study design. Dr. Röcke explored daily time-out-of-home and place visit diversity with daily emotional and stress processes in Zurich, using sensor-based and self-reported mobility and activity indicators to capture FA. Dr. Lu investigated the EN and 4-year trajectories of IC and their impact on FA trajectories among older adults in Hong Kong. Dr. Liu explored the longitudinal associations between neighborhood physical EN and depressive symptoms of older adults in Hong Kong and the moderating effects of terrain slope and declining daily activity of living. Dr. Guo investigated the relationship between perceived EN (environmental cognition) and mental health and the mediating roles of physical activity and place attachment. Dr. Chan explored neighborhood physical EN and cognition among older people and identified whether this association varies among different older age groups. Based on these findings, this symposium will discuss the future research direction on Healthy Ageing and its policy implication.

Longitudinal associations between neighbourhood physical environments and depressive symptoms of older adults in Hong Kong: The moderating effects of terrain slope and declining functional abilities.

Little is known about the accumulative impacts of neighbourhood physical environments on older adults' depressive symptoms over time. Based on a cohort study of 2081 older adults in Hong Kong, this study examined longitudinal relationships between neighbourhood physical environments and depressive symptoms among older adults, with a particular focus on the moderating effects of terrain slope and individual functional ability using latent growth curve modelling. Results indicated that the availability of community centres and passive leisure facilities reduced depressive symptoms over time. The protective effects of residential surrounding greenness on depressive symptoms among older adults differed by the terrain slope types. Longitudinal associations between neighbourhood physical environments and depressive symptoms varied between older adults with and without functional limitations. This study has implications for the Ecological Theory of Ageing by identifying the dynamic interplay of environment demands and individual functional ability. Planning policies for building age-friendly neighbourhoods are discussed.

Wearable Tendon Kinetics.

This study introduces a noninvasive wearable system for investigating tendon loading patterns during outdoor locomotion on variable terrain. The system leverages shear wave tensiometry, which is a new approach for assessing tendon load by tracking wave speed within the tissue. Our wearable tensiometry system uses a battery-operated piezoelectric actuator to induce micron-scale shear waves in a tendon. A data logger monitors wave propagation by recording from two miniature accelerometers mounted on the skin above the tendon. Wave speed is determined from the wave travel time between accelerometers. The wearable system was used to record Achilles tendon wave speed at 100 Hz during 1-km outdoor walking trials in nine young adults. Inertial measurement units (IMUs) simultaneously monitored participant position, walking speed, and ground incline. An analysis of 5108 walking strides revealed the coupled biomechanical effects of terrain slope and walking speed on tendon loading. Uphill slopes increased the tendon wave speed during push-off, whereas downhill slopes increased tendon wave speeds during early stance braking. Walking speed significantly modulated peak tendon wave speed on uphill slopes but had less influence on downhill slopes. Walking speed consistently induced greater early stance wave speeds for all slopes. These observations demonstrate that wearable shear wave tensiometry holds promise for evaluating tendon tissue kinetics in natural environments and uncontrolled movements. There are numerous practical applications of wearable tensiometry spanning orthopedics, athletics, rehabilitation, and ergonomics.

Estimation of Aerosol-Corrected Surface Solar Irradiance at Local Incidence Angle over Different Physiographic Subdivisions of India and Adjoining Areas Using MODIS and SRTM Data

AbstractSurface solar irradiance is considered as an important component of the surface radiation budget and constitutes one of the essential climate variables. In the present study, clear-sky instantaneous solar irradiance was estimated over 15 physiographic regions of India during January. Dewpoint temperature profiles were extracted from Moderate Resolution Imaging Spectroradiometer (MODIS) instrument onboard the Aqua satellite to calculate actual vapor pressure following Clausius–Clapeyron equation, which was further used in the Zillman parameterization for solar irradiance. The effect of terrain slope and aspect on direct radiation was taken into account by modifying the parameterized incoming shortwave flux by introducing the local incidence angle. A significant positive correlation was found between terrain-corrected MODIS irradiance and measured radiation data but the RMSE was very high (187 W m−2). Further, the effect of aerosol extinction was introduced by multiplying the terrain-corrected flux by a transmission factor obtained from satellite-derived aerosol optical depth and Ångström exponent. Due to the inclusion of the aerosol transmittance, the correlation was significantly improved (R2 = 0.84) and RMSE was reduced (31 W m−2). Further the effect of surface orientation on surface irradiance was evaluated on six hilly subdivisions. A large variation in the flux (135 to 161 W m−2) was noticed among different aspect classes. The variability was highest in the Eastern Himalayas subdivision (>250 W m−2) and was a minimum in the Eastern Hills subdivision (<28 W m−2). In absence of ground radiation data in hills, Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2), was used for validation of model output but it performed poorly and got saturated at higher surface irradiance values.

LES simulation of terrain slope effects on wind enhancement by a point source fire

Fire-driven flows associated with wind intervention can dangerously threaten buildings in bushfire-prone areas by increasing pressure load on the structures through fire-wind enhancement phenomenon. This phenomenon through which wind is enhanced by interacting with fire is exacerbated when the affected terrain is located in a positive slope area. This study employs LES simulations using FireFOAM platform to investigate the extent to which the wind enhanced by a point source of fire is affected by terrain slope. A module was appended to the FireFOAM solver to extract and output fire-induced forces and acceleration components for the analysis. The effects of terrain slope on wind velocity enhancement as well as the location at which local maximum wind enhancement occurs were studied. The LES results showed that with the increase of terrain upslope angle, wind enhancement along the centerline is significantly intensified, whereas local maximum wind enhancement that occurs at each side of the centerline is less affected. It was also shown that global maximum wind enhancement occurs immediately downstream of the fire source for all upslope angles. Moreover, similar to the local maximum wind enhancement, the rate of increase in global maximum wind enhancement reduces with the increase of terrain upslope angle.

Assessing the Impacts of Various Factors on Treetop Detection Using LiDAR-Derived Canopy Height Models

Canopy height models (CHMs) were utilized to detect treetops and estimate individual-tree parameters. The treetop detection based on CHMs was affected by surface topography and crown characteristics. However, their effects have not been well studied. Therefore, this paper aimed at assessing the impacts of aforementioned factors to facilitate treetop identification from LiDAR-derived CHMs. To fulfill this objective, we first extended and improved the previous models for cases with various terrains. Then, a new theoretical model was developed to quantify treetop displacements for ellipsoidal tree crowns. Finally, we further analyzed the treetop displacements due to terrain slope, crown radius, crown shape, and offset distance to the slope surface. Our analysis indicates that the vertical displacement increases exponentially with terrain slope; thus, the effect of terrain slope must be considered over extremely steep areas; larger errors are observed for trees with a large crown radius; the treetop displacements are highly correlated with crown shape, the effect of topographic normalization can be neglected for conical crowns with a large crown angle, and the elliptical crown shape can reduce the treetop detection errors; and treetop displacements increases with offset distance to the slope surface in Case 2 , while opposite results are observed in Case 5 . In addition, the results also demonstrate that the effect of slope-distorted CHMs may be quite different for different types of tree crowns and terrains. Overall, this paper makes a significant contribution to the development of theoretical models for quantifying treetop displacements. Furthermore, our findings provide a theoretical basis and guidance for better identifying treetops from LiDAR-derived CHMs.

Investigation of terrain slope effects on wind enhancement by a line source fire

Wind enhancement triggered by fire-wind interaction can potentially pose significant damage to structures built in bushfire prone areas. The effect of terrain slope is one of the parameters contributing to the enhancement of wind by fire that needs to be taken into account. This study employs a validated model of Computational Fluid Dynamics to assess the effects of terrain slope on this phenomenon. A module was developed and appended to the FireFOAM solver to output individual component of flow acceleration. Multiple analyses were used to explain the effects of terrain upslope and downslope on the phenomenon. The results reveal that although the enhancement of wind velocity due to fire increases with an increase in terrain upslope, a terrain downslope reduces flow enhancement by fire. The results also established that while an upslope terrain reinforces the Coanda effects and intensifies attachment of the plume to the ground, the downslope condition mitigates Coanda effects and reduces the flow's tendency to attach to the ground downstream of the fire source. Furthermore, under a constant heat release rate and upstream wind velocity, the maximum magnitude of wind enhancement linearly increases with the increase of upslope angle.

Slope-adaptive waveform metrics of large footprint lidar for estimation of forest aboveground biomass

The effect of terrain slope on large footprint lidar waveforms is still a great challenge to the accurate mapping of forest aboveground biomass (AGB), although previous studies have made significant progress for slopes lower than 15°. A new method was proposed to calculate slope-adaptive waveform metrics for forest AGB mapping over mountainous areas. First, a theoretical model was proposed to calculate lidar waveforms of bare ground with known terrain slopes. The forest waveform and its corresponding calculated bare ground waveform were then aligned by the signal ending points. Their energy quartiles were extracted separately by taking the signal ending points as references. The height differences between the corresponding energy quartiles were defined as slope-adaptive waveform metrics, which were then used as independent variables for the estimation of the forest AGB. The proposed method was examined with both simulated lidar waveforms of forest stands and real waveforms acquired by the Geoscience Laser Altimeter System (GLAS). Two typical footprint sizes (i.e., 25 m and 70 m in diameter) and 21 terrain slopes (i.e., from 0° to 40° at an interval of 2°) were used in the simulation of the lidar waveforms. The terrain slopes of the GLAS waveforms were between 5.54° and 34.08°. The results showed that the terrain stretching on the forest waveform could be compensated for by the bare ground waveform. Compared with the Gaussian decomposition and waveform parameter methods, the proposed method gave the best estimation of the forest AGB with R2 = 0.92 and RMSE = 15.95 Mg/ha using simulated waveforms with a footprint size of 70 m and R2 = 0.84 and RMSE = 34.99 Mg/ha using the GLAS waveforms. The results demonstrated that the proposed method had great potential for the estimation of forest AGB using lidar waveforms over mountainous areas.

黄土高原生态系统服务权衡与协同时空变化及影响因素——以延安市为例

PDF HTML阅读 XML下载 导出引用 引用提醒 黄土高原生态系统服务权衡与协同时空变化及影响因素——以延安市为例 DOI: 10.5846/stxb201808141730 作者: 作者单位: 陕西师范大学 地理科学与旅游学院 作者简介: 通讯作者: 中图分类号: 基金项目: 教育部人文社会科学重点研究基地项目（14JJD840004）；国家自然科学基金项目（41371523） Spatial and temporal changes in the synergy and trade-off between ecosystem services, and its influencing factors in Yanan, Loess Plateau Author: Affiliation: School of Geography and Tourism，Shaanxi Normal University Fund Project: The Major Project of Key Research Institute of Humanities and Social Science of the Ministry of Education; National Nature Science Foundation of China 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:明确黄土高原生态系统服务权衡与协同的时空变化特征及影响因素，深刻理解能源开发和经济发展背景下黄土高原多种生态系统服务之间的相关关系，为实现经济与生态保护的协调发展提供理论依据。以黄土高原典型区延安市为例，探讨1993-2013年间生态服务价值（植被净初级生产力、土壤保持、水源涵养和食物供给）之间权衡与协同关系的时空变化特征，以及退耕还林政策和地形坡度对生态系统服务权衡与协同关系动态变化的影响。结果表明：①各类生态系统服务之间呈现不同的相关关系，食物供给与土壤保持、水源涵养以及NPP之间均为权衡关系，NPP与土壤保持、水源涵养之间为协同关系，土壤保持与水源涵养呈现协同关系；②20年来延安市生态系统服务整体表现为权衡加强协同减弱的趋势；③对比退耕还林区与非退耕还林区权衡与协同的动态变化，发现退耕还林区各类生态服务多呈协同关系且不断加强，而在非退耕还林区多表现为权衡关系；④坡度为15°-25°地区生态服务冲突最为显著，大于25°地区生态服务协同作用显著；⑤NPP与水源涵养的协同关系呈现北部高南部低的分布规律，NPP与食物供给权衡程度在延安市北部较强而东部较弱，水源涵养与食物供给的权衡关系在延安市西南部更为突出而北部最弱。 Abstract:Clarifying the temporal and spatial changes in the trade-off and synergy between ecosystem services and its influencing factors in the Loess Plateau (LP) provides the basis for a better understanding of the interaction of ecosystem services in the background of energy and economic development. It also provides a theoretical basis for the coordinated development of economy and ecological protection. Using the partial correlation spatial statistical analysis, we investigated the spatio-temporal variation in the trade-off and synergy between ecosystem services (net primary productivity (NPP), soil conservation, water conservation, and food supply) and analyzed its influencing factors through the study of Grain-for-Green Program (GFGP) and non-Grain-for-Green Program (non-GFGP). We also assessed the effect of terrain slope on the dynamic changes in the trade-off and synergy during 1993-2013. The results obtained were as follows. (1) Various kinds of ecosystem services in Yanan have different correlations. We found that food supply and soil conservation, food supply and water conservation, and food supply and NPP have a trade-off relationship. There was a synergistic relationship between NPP and soil conservation, NPP and water conservation, and soil conservation and water conservation. (2) In addition, between 1993 and 2013, this synergistic relationship showed a downward trend, whereas, the trade-off relationship demonstrated an upward trend. (3) Furthermore, a comparison of the dynamic changes in the trade-off and synergy between GFGP and non-GFGP showed that various ecosystem services in GFGP have a synergistic relationship, and it continued to increase, but it showed a conflicting relationship in non-GFGP. (4) The conflict between ecosystem services in the area of 15°-25° was obvious, but in the area of > 25°, the synergistic relationship was evident. (5) In terms of the synergistic relationship between NPP and water conservation, the strongest evidence was found in the north of Yanan and the lowest was observed in the south. Moreover, the strongest trade-off relationship between NPP and food supply was in the north, whereas, the weakest was in the east. While exploring the trade-off between water conservation and food supply, we found that it is the strongest in the southest of Yanan and the lowest in the north. 参考文献 相似文献 引证文献

Effects of terrain slope and aspect on the error of ALS-based predictions of forest attributes

Effects of terrain slope and aspect on the error of ALS-based predictions of forest attributes

Effect of terrain slope on water distribution and application uniformity for sprinkler irrigation

In order to provide practical parameters for sprinkler irrigation system design on slope land, the effects of terrain slope on water distribution, sprinkler throw radius and water application uniformity were analyzed for the Rainbird LF1200 sprinkler. The results show that, the water distribution curve is roughly “heart-shape” on slope land, and the water has the trend of focusing on the upslope with the increase of the slope. Throw radius decreases for the upslope and increases for the downslope as the slope increases. For the convenience of sprinkler irrigation system design on slope land, a formula for computing throw radius on slope land was put forward by the theoretical derivation, and it was verified by the experimental data. The impact of sprinkler pressure and spacing on CU for slope land is more significant than that for flat ground. Under the experimental condition, no significant change is found regarding the influence of terrain slope on water application uniformity at the confidence level of 95%. Taking irrigation quality and economy into account, the Rainbird LF1200 sprinkler should be operated at the manufactures’ recommended pressure, rather than low pressure, with sprinkler spacing from 8 m×8 m to 10 m×10 m below the slope of 0.15 in practice. Keywords: sprinkler irrigation, slope land, water distribution, water application uniformity, throw radius DOI: 10.25165/j.ijabe.20181103.2901 Citation: Zhang L, Hui X, Chen J Y. Effects of terrain slope on water distribution and application uniformity for sprinkler irrigation. Int J Agric & Biol Eng, 2018; 11(3): 120–125.

A revised terrain correction method for forest canopy height estimation using ICESat/GLAS data

Although spaceborne Geoscience Laser Altimeter System (GLAS) can measure forest canopy height directly, the measurement accuracy is often affected by footprint size, shape and orientation, and terrain slope. Previous terrain correction methods only took into account the effect of terrain slope and footprint size when estimating forest canopy height. In this study, an improved terrain correction method was proposed to remove the effect of all aforementioned factors when estimating canopy height over sloped terrains. The revised method was found significantly better than the traditional ones according to the canopy height tested using small footprint LiDAR data in China. It reduced the RMSE of the canopy height estimates by up to 1.2m. The effect of slope on canopy height estimation is almost eliminated by the proposed method since the slope had little correlation with the canopy heights estimated by revised method. When the footprint eccentricity is small, the canopy height error due to the footprint shape and orientation is small. However, when the footprint eccentricity is large enough, the height estimation error due to footprint shape and orientation is large. Therefore, it is necessary to take into account the influence of footprint shape and orientation on forest canopy estimation.

Interpolation Routines Assessment in ALS-Derived Digital Elevation Models for Forestry Applications

Airborne Laser Scanning (ALS) is capable of estimating a variety of forest parameters using different metrics extracted from the normalized heights of the point cloud using a Digital Elevation Model (DEM). In this study, six interpolation routines were tested over a range of land cover and terrain roughness in order to generate a collection of DEMs with spatial resolution of 1 and 2 m. The accuracy of the DEMs was assessed twice, first using a test sample extracted from the ALS point cloud, second using a set of 55 ground control points collected with a high precision Global Positioning System (GPS). The effects of terrain slope, land cover, ground point density and pulse penetration on the interpolation error were examined stratifying the study area with these variables. In addition, a Classification and Regression Tree (CART) analysis allowed the development of a prediction uncertainty map to identify in which areas DEMs and Airborne Light Detection and Ranging (LiDAR) derived products may be of low quality. The Triangulated Irregular Network (TIN) to raster interpolation method produced the best result in the validation process with the training data set while the Inverse Distance Weighted (IDW) routine was the best in the validation with GPS (RMSE of 2.68 cm and RMSE of 37.10 cm, respectively).

Effects of terrain slope on long-term and seasonal water balances in clayey, subsurface drained agricultural fields in high latitude conditions

Water outflow pathways affect environmental loads from agricultural fields, but the pathways and effects of terrain topography on their proportions and on drainage design are not known in detail. In this study, a long-term hydrological dataset and 3D FLUSH model were applied to a field-scale assessment of multi-yearly and seasonal water balance in two adjacent clayey subsurface drained agricultural fields with different slopes (1% and 5%). The model was calibrated and then run with an hourly time step of input data throughout five studied years, and it was able to reproduce the measured water balance components. The results suggested that macropore flow had an essential role in the field-scale hydrological processes in clayey agricultural fields. The model provided a quantification how terrain slope increased the amount of groundwater outflow and correspondingly decreased the amount of drain discharge. The implication is that the hydrological effects of topography of the field and surrounding areas should be taken into account when optimizing drainage intensities. Though most of the groundwater outflow occurred outside the growing periods, sustained groundwater outflow occurred throughout all seasons. A correspondence was observed between the near-saturated surface soil conditions and tillage layer runoff (TLR) events, which suggests that TLR events in high-latitude clayey fields are mainly triggered by saturation excess mechanism. During two springs (once in both field section) TLR was clearly higher than during other seasons, which was likely induced by soil frost. However, the model without computational schemes for frost-induced changes on soil hydraulic properties satisfactorily reproduced drain discharge during most spring periods, and the amount of measured TLR was low during most springs, which indicates that typically frost-induced changes on TLR generation may be small. However, inaccuracies in the quantification of TLR induced by snowmelt formed uncertainty to the estimate of the water balance components during snowmelt.

Assessing the performance of nonparametric estimators of species richness in meadows

To accurately measure the number of species in a biological community, a complete inventory should be performed, which is generally unfeasible; hopefully, estimators of species richness can help. Our main objectives were (i) to assess the performance of nonparametric estimators of plant species richness with real data from a small set of meadows located in the Basque campina (northern Spain), and (ii) to apply the best estimator to a larger dataset to test the effects on plant species richness caused by environmental conditions and human practices. Two non-asymptotic and seven asymptotic accumulation functions were fitted to a randomized sample-based rarefaction curve computed with data from three well sampled meadows, and information theoretic methods were used to select the best fitting model; this was the Morgan-Mercer-Flodin, and its asymptote was taken as our best guess of true richness. Then, five nonparametric estimators were computed: ICE, Chao 2, Jackknife 1 and 2, and Bootstrap; MMRuns and MMMeans were also assessed. According to the criteria set for our performance assessment (i.e., bias, precision, and accuracy), the best estimator was Jackknife 1. Finally, Jackknife 1 was applied to assess the effects of terrain slope and soil parent material, and also fertilization, grazing, and mowing, on plant species richness from a larger dataset (20 meadows). Results suggested that grass cutting was causing a loss of richness close to 30%, as compared to unmowed meadows. It is concluded that the use of nonparametric estimators of species richness can improve the evaluation of biodiversity responses to human management practices.

Directional Connectivity of Wolf (Canis lupus) Populations in Northwest Spain and Anthropogenic Effects on Dispersal Patterns

In view of the extensive information available on wolf ecology and habitat suitability, and on the fragmentation of wolf populations by motorways and similar infrastructures, a key factor in their conservation, the aim of the present study was to model the directional connectivity of wolf populations in the region of Galicia in northwest Spain, and to quantify anthropogenic effects on wolf dispersal patterns. To this end, we map the probability of wolf movement by means of known relationships between wolf movement and anthropogenic, vegetation and topographic factors. The relative importance of each factor was quantified by sensitivity analyses. Three types of cost surface were constructed: (a) isotropic surfaces, (b) anisotropic cost surfaces taking into account terrain slope effects in the movement, and (c) surfaces obtained by combining the isotropic and anisotropic surfaces. The results obtained by approaches (a) and (c) indicate that one of the region’s motorways (the AP-9) probably acts as a significant barrier to wolf movement, possibly isolating two subpopulations, while the remaining motorways probably do not have major effects on dispersal. Estimation of lowest-cost routes for wolf displacement allowed identification of areas critical for connectivity, in which it would be of interest to perform detailed studies with more precise input data on motorway course and the location of drainage channels and underpasses, etc. (these being the factors identified by sensitivity analysis to be those with the most marked effects on the cost surfaces). The visualization of connectivity enabled by this approach will allow wolf management and conservation efforts to be focused on critical areas: such efforts might include measures aimed to encourage wolf dispersal through areas in which conflict with human activity is minimized, thus contributing positively to the management of a socially conflictive species. Finally, evaluation of the different cost surfaces suggests that it would be of interest to introduce two modifications to the anisotropic algorithm, to allow the user to weigh the importance of the different input factors, and to allow the inclusion of more than one anisotropic factor in the model.

Experimental study and large eddy simulation of effect of terrain slope on marginal burning in shrub fuel beds

This paper presents a combined study of laboratory scale fire spread experiments and a three-dimensional large eddy simulation (LES) to analyze the effect of terrain slope on marginal burning behavior in live chaparral shrub fuel beds. Line fire was initiated in single species fuel beds of four common chaparral plants under various fuel bed configurations and ambient conditions. An LES approach was developed to model fire spreading through a fuel bed with a subgrid scale turbulent combustion model based on a flame surface density concept. By examining two fuel bed slope configurations, it was found that upslope fire spread depends not only on the increased radiant heat transfer but also on the aerodynamic effect created by the interaction of the flame with the inclined surface. Under certain conditions, the convective heat transfer induced by this interaction becomes the dominant mechanism in determining fire spread success. Seventy-three (or 42%) of 173 experimental fires successfully propagated for slopes ranging from −70% to 70%. It was found there exists a critical slope above which fire spread in these live fuel beds was successful, and below which fire spread was unsuccessful. This critical slope for marginal burning varied widely with fuel moisture content and fuel loading. A stepwise logistic regression model was developed from experimental data to predict the probability of successful fire spread. It is expected that this model may be helpful in providing guidelines for prescribed fire application.

Parameterization of the thermal impacts of sub-grid orography on numerical modeling of the surface energy budget over East Asia

A parameterization scheme for the thermal effects of subgrid scale orography is incorporated into a regional climate model (developed at Nanjing University) and its impact on modeling of the surface energy budget over East Asia is evaluated. This scheme includes the effect of terrain slope and orientation on the computation of solar and infrared radiation fluxes at the surface, as well as the surface sensible and latent heat fluxes. Calculations show that subgrid terrain parameters alter the diurnal cycle and horizontal distributions of surface energy budget components. This effect becomes more significant with increased terrain slope, especially in winter. Due to the inclusion of the subgrid topography, the surface area of a model grid box changes over complex terrain areas. Numerical experiments, with and without the subgrid scale topography scheme, show that the parameterization scheme of subgrid scale topography modifies the distribution of the surface energy budget and surface temperature around the Tibetan Plateau. Comparisons with observations indicate that the subgrid topography scheme, implemented in the climate model, reproduces the observed detailed spatial temperature structures at the eastern edge of the Tibetan Plateau and reduces the tendency to overestimate precipitation along the southern coastal areas of China in summer.