Den här rapporten fokuserar på att ta fram en grund i hur skapandet av spelvegetation med polygonplan som korsar varandra kan göras, utan att få problem med oönskade artefakter och skuggor. Det finns givetvis flertalet metoder för att lösa detta som varierar beroende på vilken typ av ljussättning som implementerats i spelet samt vilken spelmotor som används. I den här undersökningen kommer endast en spelmotor med grund ljussättning användas.Målet var att undersöka flertalet metoder för att nå det önskade resultatet, vilket var fungerande spelvegetation med korsande polygonplan utan några skuggor eller artefakter. Moment som inte ingick i den här undersökningen var ingående undersökningar i hur vertexnormaler fungerar på en mer matematisk nivå, samt hur dessa tekniker kan överföras till andra spelmotorer. För att uppnå dessa mål gjordes en del undersökningar i hur spelvegetations geometri och vertexnormaler påverkar resultatet, samt materialinställningar i den valda spelmotorn.Vikten av en klar bild av vilken typ av spelvegetation som ska skapas innan arbetet påbörjas visade sig tidigt i undersökningen. Organiska och mjuka former är att föredra, och det är även viktigt att kontrollera hur vertexnormalernas riktning påverkar objektet i den valda spelmotorn. I själva spelmotor är det materialet på objektet som har störst inverkan på resultatet, framförallt materialets underlagsfärg. Genom att följa dessa riktlinjer kan målet av spelvegetation, med korsande polygonplan, utan alltför tydliga skuggor och artefakter uppnås. / This report focuses on establishing a foundation in how to create game foliage with criss-crossing polygon planes, without getting unwanted artefacts or shadows. There are several different methods to achieve this depending on what kind of lighting the game has implemented, but also which game engine is being used. In this research, only one game engine with basic lighting will be used.The goal was to research several different methods that would give the desired result, which as stated above, was to create working game assets with criss-crossing polygon planes without artefacts. Stages that are not included in this research are how vertex normals work from a mathematics perspective, and how these methods would work in other game engines. Research was focused on how geometry and vertex normals affect the object visual appearance, as well as the impact the material settings in the games engine provided.The survey quickly showed the importance of having a clear vision on what type of game foliage was sought to be created before the work began. Organic and soft shapes are preferred, and it is also important to check how the vertex normals affect the object in the selected game engine. In the game engine itself, it is the material on the object that has the greatest impact on the result, especially the material's subsurface colour. By following these guidelines, the goal was achieving game foliage with less visible shadows and artefact.

With the increase in and more diverse applications of microwave radio communications, the probability of a signal propagating through a medium of vegetation is increased. As a direct result of this demand for microwave communication systems, knowledge is required of the effects of vegetation media on the propagating microwave signal. This enables radio system planners to predict the signal loss more accurately, necessitating a detailed study of the propagation effects of vegetation. A vegetation depth attenuation model has been developed based on the International Telecommunications Union-Radio Sector model and validated against measurements conducted at two microwave frequencies of 11.2 GHz and 20 GHz. The measurements were conducted on a number of sites of differing geometries at different times of the year to obtain the two extreme states of foliage, in- and out-of-leaf. The trees found at the sites were of a number of indigenous species. A variety of species and environments were employed for the outdoor measurements as it was felt that any variation in the signal, occurring as a direct result of the species, climate, environment etc., would be reduced. A further study has been conducted in an anechoic chamber, the purpose being to investigate the depolarising effect of vegetation, to characterise and to ascertain how and to what extent the polarisation of the incident signal is changed as it passes through the vegetation without the effects of climate, location and environment affecting the resultant signal. To enable larger quantities of data to be obtained, collated and subsequently analysed and also to remove any scope for error during the collection of results, two data acquisition programs were written for the two main environments in which the measurements were to be undertaken, that is to say, outdoor and indoor (anechoic chamber) environments. In seeking to provide a model for the prediction of attenuation a radio wave will suffer as it is propagated through a body of vegetation, several models have been examined in turn and their relative merits discussed together with their applicability to the study. After examining the possible models available, the thesis provides a model which enables the prediction of additional attenuation a radiowave signal will suffer as a function of path length (depth) of the vegetation medium and frequency. The model can be recommended for use in the 10-30 GHz band. The study on the depolarisation of signals by vegetation has shown that the components of a vegetation medium e.g. tree trunks, branches and leaves, can cause considerable changes in the polarisation of the incident signal as it propagates through a volume of vegetation. The work presented in this thesis contains new measured results of the polarisation state of the radio wave as it emerges from a vegetation specimen. These results obtained in an anechoic chamber under controlled conditions have demonstrated that additional effects, other than attenuation by absorption and scatter need to be considered in order to characterise and subsequently model the overall effect of vegetation in the radio path of propagating signals.

No description available.

No description available.

Quick identification of loblolly pine nutrient deficiencies has troubled foresters who wish to increase productivity through fertilization. In the past, extensive field trials were established that did not allow for quick identification of a large number of possibly limiting nutrients in individual stands. This study used single-tree fertilization with macro-nutrients (N, P, K, Ca, Mg, S) and micro-nutrients (Mn, Zn, B, Cu, Fe, Mo) to identify deficiencies using foliar techniques in one growing season. Four study sites in TX, AL, GA, and SC were established in loblolly pine plantations at or near canopy closure. Nutrient concentrations relative to the critical level, optimal nutrient ratios, DRIS methodology, vector analysis, and changes in individual fascicle and total current year foliage weight/area were used to identify deficiencies. Phosphorus was repeatedly indicated as most limiting growth at TX while K was implicated at SC. The GA site revealed multiple deficiencies including N, K, and S. The AL site revealed only a very suspect B deficiency. Critical level methodology was effective in identifying deficiencies of N, P, and K, while B, S, and Cu appeared to be available at sufficient quantities when concentrations were below the published critical levels. Concentrations of S were especially below the critical levels and not increased by fertilization indicating that the critical levels were too high. Nutrient ratio interpretability was reduced by luxury uptake of N in comparison to other deficient nutrients. DRIS methodology was hampered by the inability to create effective comparative norms. Deficiency detection with vector analysis created problems when B and Mn displayed greater uptake relative to controls than the macro-nutrients that provided relative foliage mass increases. Resulting diagnosis indicated deficiencies when B and Mn were really taken up as luxury consumption. Vector analysis may not be as effective as its individual parts. Foliage weight/area responses detected fewer deficiencies than the other techniques. No significant foliar responses were seen at the TX or AL sites. However, K at the SC site was identified as deficient by all foliage mass variables, and multiple deficiencies were detectable at the GA site. / Master of Science

To date, there exists no complete, computationally efficient, physics-based model to compute the radar backscatter from forest canopies. Several models attempt to predict the backscatter coefficient for random forest canopies by using the Vector Radiative Transfer (VRT) Theory with success, however, these models often rely on purely time-harmonic formulations and approximations to integrals. Forms of VRT models have recently been developed which account for a Gaussian pulse incident waveform, however, these models often rely heavily on very specific and obfuscated approximations to solve the associated integrals. This thesis attempts to resolve this problem by outlining a method by which existing, proven, time harmonic solutions to the VRT equation can be modified to account for arbitrary pulse waveforms through simple path delay method. These techniques lend physical insight into the actual scattering mechanisms behind the returned waveform, as well as offer explanations for why approximations of previous authors' break down in certain regions. Furthermore, these radiative transfer solutions can be reformulated into a convolutional model which is capable of quickly and accurately predicting the radar return of random volumes. A brief overview of radiative transfer theory as it applies to remote sensing is also given. / Master of Science

This study presents the first attempt to combine the fields of ultraviolet (UV) photobiology, plant cell wall biochemistry, aerobic methane production and reactive oxygen species (ROS) mechanisms to investigate the effect of UV radiation on vegetation foliage. Following reports of a 17% increase in decomposition rates in oak (Quercus robur) due to increased UV, which were later ascribed to changes in cell wall carbohydrate extractability, this study investigated the effects of decreased UV levels on ash (Fraxinus excelsior), a fast-growing deciduous tree species. A field experiment was set up in Surrey, UK, with ash seedlings growing under polytunnels made of plastics chosen for the selective transmission of either all UV wavelengths, UV-A only, or no UV. In a subsequent field decomposition experiment on end-of-season leaves, a significant increase of 10% in decomposition rate was found after one year due to removal of UV-B. However, no significant changes in cell wall composition were found, and a sequential extraction of carbohydrate with different extractants suggested no effects of the UV treatments on cell wall structure. Meanwhile, the first observations of aerobic production of methane from vegetation were reported. Pectin, a key cell wall polysaccharide, was identified as a putative source of methane, but no mechanism was suggested for this production. This study therefore tested the effect of UV irradiation on methane emissions from pectin. A linear response of methane emissions against UV irradiation was found. UV-irradiation of de-esterified pectin produced no methane, demonstrating esters (probably methyl esters) to be the source of the observed methane. Addition of ROS-scavengers significantly decreased emissions from pectin, while addition of ROS without UV produced large quantities of methane. Therefore, this study proposes that UV light is generating ROS which are then attacking methyl esters to create methane. The study also demonstrates that this mechanism has the potential to generate several types of methyl halides. These findings may have implications for the global methane budget. In an attempt to demonstrate ROS generation in vivo by UV irradiation, radio-labelling techniques were developed to detect the presence of oxo groups, a product of carbohydrate attack by ROS. Using NaB3H4, the polysaccharides of ash leaflets from the field experiment were radio-labelled, but did not show any significant decrease in oxo groups due to UV treatments. However, UV-irradiation of lettuce leaves showed a significant increase in radio-labelling, suggesting increased UV irradiation caused an increase in the production of ROS. The study shows that the use of this radio-labelling technique has the potential to detect changes in ROS production due to changes in UV levels and could be used to demonstrate a link between ROS levels and methane emissions.

Forest soils store as much carbon (C) as the vegetation that grows on them, and the carbon in soil is more stable than the C in biomass. Quaking aspen (Populus tremuloides Michx.) is the most widespread tree species in North America, and aspen forests in the Western US have been found to store more soil organic carbon (SOC) in the mineral soil than nearby conifers. Fire exclusion and grazing often promote the succession of aspen to conifer dominated forests due to their effect on aspen regeneration. So far the factors driving the differential SOC accumulation, and the effects of the vegetation shift on SOC pools, are not well understood. In this dissertation I aimed to evaluate how various forest vegetation characteristics – tree type, detritus fluxes, detritus chemistry – affect SOC pools and stability from a global to a molecular level using two contrasting forest types – aspen and conifer. A meta-analysis showed that, while conifer forests worldwide had higher C pools in the forest floor, this difference did not translate into the mineral soil, suggesting that the mechanisms that control SOC storage differ between both soil compartments. Above- and belowground detritus input fluxes were similar between aspen and conifer forests, and did not explain the higher SOC pools under aspen. A sorption study revealed that the more labile aspen foliage dissolved organic carbon (DOC) was more effectively retained in soil than aspen root, and conifer substrate DOC. Furthermore, soils that contained aspen SOC retained new DOC better than soils with conifer SOC, irrespective of the source of the DOC. Finally, foliage and root specific compounds that were identified for aspen and subalpine fir provide a base for future studies aiming to identify the source of SOC under both overstory types. Overall, the results of the dissertation suggest that substrate chemistry more than detritus fluxes drive the differences between SOC pools under aspen and conifer forests in Utah. This finding indicates that the link between C input amounts and SOC pools is not as direct as currently assumed in most SOC models. Furthermore, a tree species effect on SOC as distinct as aspen vs conifer is not common between all hardwood and conifer comparisons worldwide, thus suggesting that the effect of vegetation can be overridden by other factors.

During this study two models were developed to predict growth of Pinus radiata D.Don plantations in Canterbury, New Zealand. The first, CanSPBL(1.2), is a model for whole rotations of stands owned by Selwyn Plantation Limited in Canterbury. The second model, CanSPBL(water) is a hybrid growth model for the Selwyn estate in Canterbury that incorporates an index of root zone water balance over the simulation period. An existing stand growth and yield model CanSPBL was examined using a validation dataset of PSP measurements that were not used in model fitting. Projection bias was shown for mean top height, basal area per hectare, and residual stand stocking particularly for stands at elevations exceeding 450 metres. The new model, CanSPBL(1.2) showed an increase in precision of 4 - 46% over CanSPBL(1.0) at a stand level. The components of the stand model include mean top height, basal area per hectare, stems per hectare, and diameter distribution. The mortality model was made in conjunction with managers at CanSPBL to exclude catastrophic mortality events from model projections. Data used for model fitting was filtered using a mortality index based on the -3/2 power law. An examination of this model with an independent dataset showed little apparent bias. The new model, CanSPBL(water) was developed to include an index of water balance over the simulation period. Water balance estimates were made using a sub model for root zone water balance included in the hybrid physiological model 3-PG (Landsberg and Waring, 1997). The new model showed an increase in precision of 1 - 4% over CanSPBL(1.2) at a stand level (with the exception of the model for maximum diameter which showed a decrease in precision of 0.78%) using climatic inputs that included yearly variation. However the model showed increases of precision from 0.5 to 8% (with the exception of maximum diameter again, showing a decrease in precision of 0.13%) using long term monthly average climatic inputs. The components of the stand model also include mean top height, basal area per hectare, stems per hectare, and diameter distribution. The mortality model was also fitted with a data set filtered using a mortality severity index based on the -3/2 power law to exclude catastrophic mortality events. An examination of this model with an independent dataset showed little apparent bias. Two models to predict a one sided canopy leaf area index (LAI) of radiata pine stands in the Canterbury Plains of New Zealand were also developed. The models were fitted using non-linear least squares regression of LAI estimates against stem measurements and stand characteristics. LAI estimates were derived from digital analysis of fisheye lens photography. The models were kept simple to avoid computational circularity for physiological modelling applications. This study included an objective comparison and validation of a range of model types. The models CANTY (Goulding, 1995), CanSPBL(1.2) (Pinjuv, 2005), CanSPBL-water (Pinjuv, 2005), and 3-PG (Landsberg and Waring, 1997) were compared and validated with the main criteria for comparison being each model s ability to match actual historical measurements of forest growth in an independent data set. Overall, the models CanSPBL(water), and CanSPBL(1.2) performed the best in terms of basal area and mean top height prediction. Both models CanSPBL(water), and CanSPBL(1.2) showed a slightly worse fit in predictions of stocking than did the model CANTY. The hybrid model 3PG showed a better fit for the prediction of basal area than the statistically based model CANTY, but showed a worse fit for the prediction of final stocking than all other models. In terms of distribution of residuals, CanSPBL(1.2) had overall the lowest skewness, kurtosis, and all model parameters tested significant for normality. 3PG performed the worst on average, in terms of the distribution of residuals, and all models tested positively for the normality of residual distribution.

No description available.