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Adjacent Fields (adjacent + field)
Selected AbstractsColony productivity and foundress behaviour of a native wasp versus an invasive social waspECOLOGICAL ENTOMOLOGY, Issue 6 2003Tracy R. Armstrong Abstract., 1.,Colony productivity, prey utilisation, and foundress behaviour of a North American native wasp (Polistes fuscatus) versus an European invasive wasp (Polistes dominulus) were investigated in a controlled field experiment with optimal versus natural foraging conditions. Colonies with the optimal prey foraging conditions were provided with prey ad libitum within an enclosed area. The other colonies foraged in the adjacent field,woodland but had the same nest conditions as the other treatment. 2.,When given prey ad libitum, both wasp species captured similar amounts of prey and the conversion to total offspring biomass was similar. But P. dominulus colonies produced 2.5 times the number of workers as P. fuscatus colonies, reflecting the smaller size of P. dominulus wasps. 3.,Foundresses of P. dominulus were observed more often building or repairing the nest, thereby contributing to the production of colonies with twice as many cells as colonies of P. fuscatus. Foundresses of P. dominulus showed more acts of aggression toward workers than did P. fuscatus foundresses, which was not a function of adult density on the nest. 4.,At the end of the experiment, P. dominulus colonies with optimal prey foraging conditions still had a high level of egg-laying and peaked in the number of pupae then, whereas egg-laying and the number of pupae per colony of the other treatments began to decline 2,3 weeks earlier. These results indicate that P. dominulus is more opportunistic than P. fuscatus, which may account in part for P. dominulus's success as an introduced species in North America. [source] Allometric growth relationships of East Africa highland bananas (Musa AAA-EAHB) cv. Kisansa and MbwazirumeANNALS OF APPLIED BIOLOGY, Issue 3 2009K. Nyombi Abstract Highland bananas are an important staple food in East Africa, but there is little information on their physiology and growth patterns. This makes it difficult to identify opportunities for yield improvement. We studied allometric relationships by evaluating different phenological stages of highland banana growth for use in growth assessment, understanding banana crop physiology and yield prediction. Pared corms of uniform size (cv. Kisansa) were planted in a pest-free field in Kawanda (central Uganda), supplied with fertilizers and irrigated during dry periods. In addition, tissue-cultured plants (cv. Kisansa) were planted in an adjacent field and in Ntungamo (southwest Uganda), with various nutrient addition treatments (of N, P, K, Mg, S, Zn, B and Mo). Plant height, girth at base, number of functional leaves and phenological stages were monitored monthly. Destructive sampling allowed derivation of allometric relationships to describe leaf area and biomass distribution in plants throughout the growth cycle. Individual leaf area was estimated as LA (m2) = length (m) × maximum lamina width (m) × 0.68. Total plant leaf area (TLA) was estimated as the product of the measured middle leaf area (MLA) and the number of functional leaves. MLA was estimated as MLA (m2) = ,0.404 + 0.381 height (m) + 0.411 girth (m). A light extinction coefficient (k = 0.7) was estimated from photosynthetically active radiation measurements in a 1.0 m grid over the entire day. The dominant dry matter (DM) sinks changed from leaves at 1118 °C days (47% of DM) and 1518 °C days (46% of DM), to the stem at 2125 °C days (43% of DM) and 3383 °C days (58% of DM), and finally to the bunch at harvest (4326 °C days) with 53% of DM. The allometric relationship between above-ground biomass (AGB in kg DM) and girth (cm) during the vegetative phase followed a power function, AGB = 0.0001 (girth)2.35 (R2 = 0.99), but followed exponential functions at flowering, AGB = 0.325 e0.036(girth) (R2 = 0.79) and at harvest, AGB = 0.069 e0.068(girth) (R2 = 0.96). Girth at flowering was a good parameter for predicting yields with R2 = 0.7 (cv. Mbwazirume) and R2 = 0.57 (cv. Kisansa) obtained between actual and predicted bunch weights. This article shows that allometric relationship can be derived and used to assess biomass production and for developing banana growth models, which can help breeders and agronomists to further exploit the crop's potential. [source] Evaluation of the SWEEP model during high winds on the Columbia Plateau ,EARTH SURFACE PROCESSES AND LANDFORMS, Issue 11 2009G. Feng Abstract A standalone version of the Wind Erosion Prediction System (WEPS) erosion submodel, the Single-event Wind Erosion Evaluation Program (SWEEP), was released in 2007. A limited number of studies exist that have evaluated SWEEP in simulating soil loss subject to different tillage systems under high winds. The objective of this study was to test SWEEP under contrasting tillage systems employed during the summer fallow phase of a winter wheat,summer fallow rotation within eastern Washington. Soil and PM10 (particulate matter ,10 µm in diameter) loss and soil and crop residue characteristics were measured in adjacent fields managed using conventional and undercutter tillage during summer fallow in 2005 and 2006. While differences in soil surface conditions resulted in measured differences in soil and PM10 loss between the tillage treatments, SWEEP failed to simulate any difference in soil or PM10 loss between conventional and undercutter tillage. In fact, the model simulated zero erosion for all high wind events observed over the two years. The reason for the lack of simulated erosion is complex owing to the number of parameters and interaction of these parameters on erosion processes. A possible reason might be overestimation of the threshold friction velocity in SWEEP since friction velocity must exceed the threshold to initiate erosion. Although many input parameters are involved in the estimation of threshold velocity, internal empirical coefficients and equations may affect the simulation. Calibration methods might be useful in adjusting the internal coefficients and empirical equations. Additionally, the lack of uncertainty analysis is an important gap in providing reliable output from this model. Published in 2009 by John Wiley & Sons, Ltd. [source] Spatial relationships between intensive land cover and residual plant species diversity in temperate farmed landscapesJOURNAL OF APPLIED ECOLOGY, Issue 6 2006SIMON M. SMART Summary 1In temperate farmed landscapes conservation policies increasingly emphasize large-scale reductions in land-use intensity. Yet despite a managed reversion to more favourable abiotic conditions, depleted regional species pools may prevent the re-assembly of target communities. 2Using national-scale survey data recorded across Great Britain in 1998, we investigated the extent to which grassland indicator plant species persisted on potential refuge habitats across a spatial gradient of intensive land cover in lowland 1-km squares. These habitats comprised road verges, field boundaries, watercourse banks and small biotope fragments. Intensive land cover comprised built land, arable and improved grassland. 3The rate of reduction in indicator species richness across the intensive land cover gradient was significantly lower in all potential refuge features than in surrounding fields and larger areas of habitat. 4The best refuge locations were watercourse banks and small biotopes. In both cases, indicator species richness was higher than adjacent fields at the lowest intensive land cover and stayed higher as intensive land cover increased. 5However, as intensive land cover increased, plant traits associated with higher nutrient availability were more prominently represented among indicator species. 6Although richer assemblages of indicator species persisted on refuge features, population sizes are likely to be small, because of species,area effects, and also vulnerable to nutrient surpluses and reduced or inappropriate disturbance. 7Synthesis and applications. Across the British lowlands, linear landscape features and small habitat fragments can provide limited safe havens for unimproved grassland plant species. However, the identity of refuge features and their species richness and composition are likely to vary with local conditions. Three activities are therefore paramount in assessing their role in larger scale extensification schemes: (i) development of rapid ways of assessing the plant diversity and distribution of refuge features in local areas; (ii) quantification of the risks posed to the viability of residual source populations through implementation of different options for incorporating them into extensification schemes; (iii) maximization of scheme performance by targeting landscapes with sufficient residual diversity to enable increases in population size of the target species in the medium term. [source] Refuge habitats modify impact of insecticide disturbance on carabid beetle communitiesJOURNAL OF APPLIED ECOLOGY, Issue 2 2001Jana C. Lee Summary 1Carabid beetles are polyphagous predators that can act as biological control agents of insect pests and weeds. While current agricultural practices often create a harsh environment, habitat management such as the establishment of within-field refuges has been proposed to enhance carabid beetle abundance and impact. We examined the joint effects of refuge habitats and insecticide application on carabid activity density (parameter of population density and relative activity) and species composition in a cornfield. 2Our 2-year study comprised four treatments: (i) ,refuge/,insecticide; (ii) +refuge/,insecticide; (iii) ,refuge/+insecticide; (iv) +refuge/+insecticide. Refuge strips consisted of grasses, legumes and perennial flowering plants. ,,Refuge' strips were planted with corn and not treated with insecticide. 3Before planting and insecticide application, carabid activity density in the crop areas was similar across all treatments. Insecticide application immediately reduced carabid activity density and altered community composition in the crop area. 4Refuge strips had significantly higher activity density of beetles than ,refuge strips before planting and during the summer. 5During summer, as new carabids emerged and insecticide toxicity declined, the presence of refuge strips influenced carabids in the adjacent crop area. Carabid activity density within crop areas previously treated with insecticide was significantly higher when adjacent to refuge strips. Also, carabid communities within insecticide-treated crop areas were affected by the presence or absence of a refuge strip. 6The presence of refuge strips did not consistently augment carabid numbers in crop areas where insecticide was not applied. One explanation may be that insecticides decreased the quality of crop habitat to carabids by depletion of prey and direct mortality. However, subsequent rebounds in prey density and the absence of competing predators may make these areas relatively more attractive than unperturbed crop habitats to carabid colonization from refuges. 7This study demonstrates that refuges may buffer the negative consequences of insecticide application on carabids in adjacent fields. Diversifying agro-ecosystems with refuge habitats may be a viable strategy for maintaining carabid populations in disturbed agricultural landscapes to keep pests below outbreak levels. [source] BURIAL HISTORY RECONSTRUCTION AND THERMAL MODELLING AT KUH-E MOND, SW IRANJOURNAL OF PETROLEUM GEOLOGY, Issue 4 2003M. R. Kamali At the Kuh-e Mond anticline (Fars Province, SW Iran) and in nearby offshore structures, large volumes of natural gas are reservoired in the Permian , Early Triassic Dehram Group while heavy oil has been discovered in the Cretaceous Sarvak and Eocene Jahrum Formations. In this paper, we use data from six exploration wells and from nearby surface exposures to reconstruct the burial history at Kuh-e Mond. Regional observations show that the thick sedimentary fill in this part of the Zagros Basin was subjected to intense tectonism during the Zagros Orogeny, with a paroxysmal phase during the late Miocene and Pliocene. Thermal modelling and geochemical data from Kuh-e Mond and adjacent fields allows possible hydrocarbon generation and migration mechanisms to be identified. Maturities predicted using Lopatin's TTI model are in accordance with maturities obtained from vitrinite reflectance measurements. We show that formations which have source potential in the nearby Dezful Embayment (including the Pabdeh, Gurpi, Gadvan and Kazhdumi Formations) have not reached the oil window in the Mond wells. Moreover, their organic carbon content is very low as they were deposited in oxic, shallow-water settings. Underlying units (including the Ordovician and Cambrian) could have reached the gas window but contain little organic matter. Silurian shales (Sarchahan Formation), which generate gas at Kuh-e Gahkum and Kuh-e Faraghan (north of Bandar Abbas) and in Saudi Arabia and elsewhere in the Middle East, are absent from the Mond structure. The absence of source rocks suggests that the gas and heavy oil accumulations at Kuh-e Mond and at nearby fields have most probably undergone long-distance lateral migration from distant source kitchens. [source] | |||||||||||||