Scoping the impact of tidal and wave energy extraction on suspended sediment concentrations and underwater light climate

The depth to which sunlight penetrates below the sea surface is one of the key factors determining the species composition and productivity of marine ecosystems. The effects range from the rate and fate of primary production, through the performance of visual predators such as fish, the potential for refuge from predators by migrating to depth, to the scope for seabed stabilisation by algal mats. Light penetration depends partly on spectral absorption by seawater and dissolved substances, but mainly on the scattering caused by suspended particulate material (SPM). Some of this SPM may be of biological origin, but in coastal waters the majority is mineral material originating ultimately from seabed disturbance and land erosion, the latter being deposited in the sea by rivers and aerial processes. SPM is maintained in the water column or deposited on the seabed depending on combinations of hydrodynamic processes including baroclinic (density-driven) or barotropic (mainly tidal and wind driven) currents, and wave action (Ward et al. 1984; Huettel et al. 1996). Since tidal and wave energy extraction must alter these hydrodynamic properties at some scales depending on the nature of the extraction process, we can expect some kind of impact on the concentration of the SPM. If these are large enough, we may have to consider the extent to which these may impact the underwater light environment and the local or regional ecology. Whilst several coupled hydrodynamic-sediment models exist to predict SPM distributions in aquatic systems, their skill level in open coastal and offshore marine waters is acknowledged to be relatively low. This is largely because the processes are not well understood and the formulations are largely based on empirical relationships rather than fundamental physical principles. The models are also highly demanding in terms of calibration data and computational resources. Hence their utility for predicting relatively subtle effects arising from changes in flow or wave environments due to energy extraction devices seems rather low. Here, we summarise the key mathematical functions describing the processes involved in sediment suspension, and propose a lightweight one-dimensional (vertical) model which can be used to scope the effects of changes in flow and wave energy on SPM

Mineral-cycling Aspects Within the Sagebrush Ecosystem

All life forms absorb minerals, which are generally used in cellular metabolism. These minerals may be secreted during normal metabolism or mineralized after cellular death. The cycle can then be repeated. Our studies of mineral cycling within the sagebrush (Artemisia) ecosystem attempt to explain why the productivity of one site is different from that of another. We may also want to know if enough minerals are available to support a shrub-to-grass conversion project or if the site provides adequate nutrition to herbivores. The mineral content of Artemisia, for example, has been used as a means of detecting precious metals in the subsoil. This procedure, known as biogeochemical prospecting, is commonly used in north-central Asia. The mineral enrichment studies comparing Artemisia in areas downwind and upwind from factories provide a base line for monitoring mineral fallout (Conner et al. 1976, Gough and Severson 1976, Severson and Gough 1976). Mineral cycling information also helps us to interpret the effects of fire, grazing, or erosion on the mineral status of a given site

Pendekatan Joyful Learning Sebagai Metode Pembelajaran Pendidikan Kependudukan & Lingkungan Hidup (PKLH) di Madrasah Ibtidaiyah

Environmental damage is basically the state of the ecosystem is not in a normal state. Environmental problems arise due to human activities use the environment without regard to sustainability. If there is a disregard for the preservation of the environment, then people will feel the impact, both directly and indirectly. Madrasah as one of the first container and a major in the formation of man of faith and character, should support the Government in implementing education learning population and environment (PKLH). Therefore, in the learning environment needs to be designed such that students can learn the population and the environment in a relaxed, happy, and meaningful, so learning it is fun not a burden. PKLH correspond to the learning objectives, then the effective learning should use a variety of approaches that can be fun and attract the attention of students like Joyful Learning approac

Tall Forb SRM 409

The type is characterized by a large array of luxuriant, rather tall 16 to 48 inches (0.4 to 1.2 m) mesic forbs. In the climax condition many species are present without any species dominating (Ellison, 1954). Stands vary in number of species present and in those that are visually prominent. Certain grass and sedge species are found throughout the range of the type, but within the type, they are mostly inconspicuous and seldom comprise more than 10% of the composition. Shrubs are mostly absent. Most present day stands are in an early seral stage because of grazing disturbance or invasion of woody species, and are now dominated by a few species of seral forbs and grasses

Forage yield and quality trends of annual grasses in the Great Basin

Grazing animals readily eat medusahead (Taeniatherum asperum [Sim.] Neuski) and cheatgrass (Bromus tectorum L.) during the short time when plants are green and succulent. Cheatgrass, the more important of the two, is a primary source of spring forage in the Great Basin. It is characterized by a short green-feed period, large yearly variations in yield, and declining forage quality as plants dry. However, cattle eat mature cheatgrass and gain as well as cattle grazing on matured perennial grasses growing in the same area

Response of montane tall-forb communities to 2,4-D and mixtures of 2,4-D and picloram

Tall-forb communities occur on deep soils of the upper montane and subalpine zones of the Rocky Mountains and extend from southwestern Montana to southern Utah. In the Centennial Mountains of Montana, forbs comprise >80% of the annual yields, including 30-35% sticky geranium (Geranium viscosissimum) and 20-25% Potentilla spp. Tall-forb communities are rich in species diversity and very productive, but many of the forbs are not palatable to grazing ungulates. Suppression of the less palatable species, like sticky geranium, would increase the forage value for grazing. In 1983 and 1984 adjacent plots were sprayed during weeks 1, 2, 3, and 4 in July, with 2,4-D[(2,4 Dichlorophenoxy)acetic acid, isooctyl ester] applied at 1.1 or 2.2 kg 2,4-D/ha or 2.2 kg 2,4-D/ha plus 0.6 kg/ha of the potassium salt of picloram (4-amino-3,5,6-trichloropicolinic acid). Forage yields were measured in August of 1984, 85, and 86. Total forage yields ranged from 2,700 to 3,000 kg/ha on the untreated areas. Forb yields were significantly reduced, especially by the 2,4-D + picloram treatment. Herbicide treatments applied during flower-stalk development to first fower of sticky geranium were most effective. Grass and sedge production partially compensated for reductions in forb yields. Interseeding of introduced species into herbicide treated plots in 1983 was unsuccessful. Forb and grass production is expected to return to levels similar to those on untreated areas after 5 years

Seasonal Changes in Nutritional Quality of Agropyron desertorum Compared with Six Other Semiarid Grasses

Desert wheatgrass, (Agropyron desertorum (Fisch.) Schulte) an introduced perennial grass, is widely used to improve the forage resources in semi-arid regions of the western United States and Canada. The use of this species is based on trials that have shown that it provides early forage, is drought tolerant, often produces greater yields and animal gains, and is able to withstand heavier use than many native species. The nutritional attributes of this species are compared to those of certain other grass species in this paper

Growth and Nutritional Value to Cattle of Grasses on Cheatgrass Range in Southern Idaho

Seven grass species--desert wheatgrass (Agropyron desertorum), streambank wheatgrass (Agropyron riparium), cheatgrass (Bromus tectorum), basin wildrye (Elymus cirtereus), Sandberg's bluegrass (Poa sandbergii), bottlebrush squirreltail (Sitanion hystrix), and needle-and-thread grass (Stipa comata)--were harvested to a 1/2-inch (1.2-cm) stubble height periodically between mid-March and December in most years from 1962 through 1968 at the Saylor Creek Experimental Range in southern Idaho. These samples were analyzed for N, P, S, Ca, Mg, K, Na, Zn, Mn, Cu, and Fe. Certain digestibility fractions (NDF, NDF-ash, DCW, DCW-ash free, and TDDM) were also determined on these samples. In addition, estimates of the soil chemical status, soil moisture contents over depth and time, forage yields, and moisture contents over time, effects of ammonium nitrate fertilization on forage yields and mineral composition, and animal grazing responses to cheatgrass range are included

Highly variable friction and slip observed at Antarctic ice stream bed

The slip of glaciers over the underlying bed is the dominant mechanism governing the migration of ice from land into the oceans, with accelerating slip contributing to sea-level rise. Yet glacier slip remains poorly understood, and observational constraints are sparse. Here we use passive seismic observations to measure both frictional shear stress and slip at the bed of the Rutford Ice Stream in Antarctica using 100,000 repetitive stick-slip icequakes. We find that basal shear stresses and slip rates vary from 104 to 107 Pa and 0.2 to 1.5 m per day, respectively. Friction and slip vary temporally over the order of hours, and spatially over 10s of metres, due to corresponding variations in effective normal stress and ice–bed interface material. Our findings suggest that the bed is substantially more complex than currently assumed in ice stream models and that basal effective normal stresses may be significantly higher than previously thought. Our observations can provide constraints on the basal boundary conditions for ice-dynamics models. This is critical for constraining the primary contribution of ice mass loss in Antarctica and hence for reducing uncertainty in sea-level rise projections

Generalized empty-interval method applied to a class of one-dimensional stochastic models

In this work we study, on a finite and periodic lattice, a class of one-dimensional (bimolecular and single-species) reaction-diffusion models which cannot be mapped onto free-fermion models. We extend the conventional empty-interval method, also called {\it interparticle distribution function} (IPDF) method, by introducing a string function, which is simply related to relevant physical quantities. As an illustration, we specifically consider a model which cannot be solved directly by the conventional IPDF method and which can be viewed as a generalization of the {\it voter} model and/or as an {\it epidemic} model. We also consider the {\it reversible} diffusion-coagulation model with input of particles and determine other reaction-diffusion models which can be mapped onto the latter via suitable {\it similarity transformations}. Finally we study the problem of the propagation of a wave-front from an inhomogeneous initial configuration and note that the mean-field scenario predicted by Fisher's equation is not valid for the one-dimensional (microscopic) models under consideration.Comment: 19 pages, no figure. To appear in Physical Review E (November 2001