Effects of landscape structure on nest predation in roadsides of a midwestern agroecosystem: a multiscale analysis

Nest predation is an important cause of mortality for many bird species, especially in grassland ecosystems where generalist predators have responded positively to human disturbance and landscape fragmentation. Our study evaluated the influence of the composition and configuration of the surrounding landscape on nest predation. Transects consisting of 10 artificial ground nests each were set up in 136 roadsides in six watersheds in south-central Iowa. Nest predation on individual roadside transects ranged from 0 to 100% and averaged 23%. The relationship of landscape structure within spatially-nested landscapes surrounding each roadside transect (within 200, 400, 800, 1200, and 1600 m of the transect line) to nest predation was evaluated by using multiple regression and canonical correlation analyses. The results of this multiscale landscape analysis demonstrated that predation on ground nests was affected by the surrounding landscape mosaic and that nest predators with different-sized home ranges and habitat affinities responded to landscapes in different ways. In general, wooded habitats were associated with greater nest predation, whereas herbaceous habitats (except alfalfa/pasture) either were associated with less nest predation or were not important. Different landscape variables were important at different spatial scales. Whereas some block-cover habitats such as woodland were important at all scales, others such as rowcrops and alfalfa/pasture were important at large scales. Some strip-cover habitats such as gravel roads and paved roads were important at small scales, but others such as wooded roadsides were important at all all scales. Most landscape metrics (e.g., mean patch size and edge density) were important at large scales. Our study demonstrated that the relationships between landscape structure and predator assemblages are complex, thus making efforts to enhance avian productivity in agricultural landscapes a difficult management goal.     

Extraction of newly immobilized n from an illinois mollisol using aqueous phenol

Studies were conducted on an ¹⁵N-enriched Illinois Mollisol (Flanagan silt loam) to determine the extractability of newly immobilized N with aqueous phenol (45%, v/v). In comparison to mild extradants proposed as indexes of plant available N (i.e. 10 mw NaHCO₃ and hot 10 m CaCl₂), phenol showed the highest selectivity for the immobilized N, both with regard to the amount of biomass N extracted and the magnitude of the extractability ratio (ER). Aqueous phenol was also more selective in removing the immobilized N than reagents used for extraction of soil organic matter (i.e. 150 m Na₄P₂O₇ and 100 m KOH). Results with soils incubated for up to 120 days showed that the amount of ¹⁵N extracted with aqueous phenol fluctuated with time and was related to changes in the soil microbial population, e.g. ER was highest when the bacterial population was maximal. Aqueous phenol shows promise as a selective extradant of potentially-available (labile) organic N in soils.     

The effect of different HUFA enrichment emulsions on the nutritional value of rotifers (Brachionus plicatilis) fed to larval haddock (Melanogrammus aeglefinus).

A feeding study was conducted in the winter 2001 to determine the effects of feeding rotifers (Brachionus plicatilis) enriched with various levels of essential fatty acids on the growth and survival of haddock larvae (Melanogrammus aeglefinus). Rotifer enrichment treatments were: 1) mixed algae, 2) high DHA (docosahexaenoic acid, 22:6n-3), 3) high DHA and EPA (eicosapentaenoic acid, 20:5n-3), and 4) DHA, EPA, and AA (arachidonic acid, 20:4n-6). Larvae were fed rotifers enriched with the different treatments from days 1 to 16 post-hatch. From day 17 until 25 all treatment groups were fed rotifers reared on mixed algae and then weaned onto the International Council for Exploration of the SEA (ICES) Standard Reference Weaning diet (http://allserv.rug.ac.t/aquaculture/rend/rend.htm) over a five day period. The experiment was terminated on day 41 post-hatch. The enrichment treatments affected the fatty acid composition of the rotifers and correlated with the accumulation of these fatty acids in the haddock larvae. However, no significant differences in larval growth or survival to 40 days post hatch were detected, suggesting that all treatments provided the minimal essential fatty acid requirements for haddock.     

Mitochondrial NAD(P)-dependent malic enzyme from herring testicular tissue: Purification,kinetic behaviour and regulatory properties

Mitochondrial NAD(P)-dependent malic enzyme [EC 1.1.1.39, L-malate: NAD⁺ oxidoreductase (decarboxylating)] was purified from herring testicular tissue to a specific activity of 26.4 μmol NADH/min/mg protein. Herring testicular tissue is one of the most abundant sources of this enzyme. The purification procedure involved differential centrifugation of mitochondria and then chromatography on DEAE-Sephacel, Red Agarose and Sephacryl S-300. This enzyme catalyzes the oxidative decarboxylation of malate in the presence of Mn²⁺ and either NAD or NADP. Under V_max conditions the ratios for the rate of NAD/NADP reduction was 1.8. A study of the reductive carboxulation reaction indicated that this enzyme reaction is reversible; at pH 7.0 the reverse reaction exhibited 22% of the activity of forward reaction. Some kinetic characteristics of the enzyme were determined. ATP was found to be a competitive inhibitor with respect to malate. Fumarate reversed ATP inhibition. Regulation of NAD(P)-dependent malic enzyme from herring testicular tissue mitochondria could respond to changing levels of mitochondrial ATP and fumarate in vivo.     

Scale-dependent habitat use in three species of prairie wetland birds

We evaluated the influence of scale on habitat use for three wetland-obligate bird species with divergent life history characteristics and possible scale-dependent criteria for nesting and foraging in South Dakota, USA. A stratified, two-stage cluster sample was used to randomly select survey wetlands within strata defined by region, wetland density, and wetland surface area. We used 18-m (0.1 ha) fixed radius circular-plots to survey birds in 412 semipermanent wetlands during the summers of 1995 and 1996. Variation in habitat use by pied-billed grebes (Podilymbus podiceps) and yellow-headed blackbirds (Xanthocephalus xanthocephalus), two sedentary species that rarely exploit resources outside the vicinity of nest wetlands, was explained solely by within-patch variation. Yellow-headed blackbirds were a cosmopolitan species that commonly nested in small wetlands, whereas pied-billed grebes were an area-sensitive species that used larger wetlands regardless of landscape pattern. Area requirements for black terns (Chlidonias niger), a vagile species that typically forages up to 4 km away from the nest wetland, fluctuated in response to landscape structure. Black tern area requirements were small (6.5 ha) in heterogeneous landscapes compared to those in homogeneous landscapes (15.4–32.6 ha). Low wetland density landscapes composed of small wetlands, where few nesting wetlands occurred and potential food sources were spread over large distances, were not widely used by black terns. Landscape-level measurements related to black tern occurrence extended past relationships between wetlands into the surrounding matrix. Black terns were more likely to occur in landscapes where grasslands had not been tilled for agricultural production. Our findings represent empirical evidence that characteristics of entire landscapes, rather than individual patches, must be quantified to assess habitat suitability for wide-ranging species that use resources over large areas.     

Economic trade-offs to limit nonpoint sources of agricultural pollution

A national model has been built which allows analysis of physical and economic trade-offs as soil loss per acre is limited to specified levels in each major land group of the nation. Crop variables with their associated conservation practices are developed for each of 1891 land groups in 223 agricultural producing regions and 51 water supply regions. The regions and soil groups are made interdependent through regional commodity demands and a transportation submodel. Hence, changes in cropping systems and erosion control practices in one region are simultaneously expressed in effects on other regions. Soil loss limits are set at 10, 5, and 3 t per acre. The 10 t limit does not have a large impact on interregional production patterns and farm comodity prices. However, the 5 and 3 t limits, either singularly or in combination with different export levels, cause rather marked increases in commodity prices. Also at limits of 5 and 3 t, considerable shifts take place among regions in the crops grown and the erosion control methods used. Regions with erosive soils sacrificed in reduced income; regions with level soils can crop more intensely and gain greater income. Conservation practices such as reduced tillage increase the amount of pesticides needed in some regions and pose special environmental problems. The South Atlantic region is affected most by soil loss limits to control nonpoint pollution. The Great Plains regions with more level land and limited rainfall are affected least.     

Production of Lectins from Marine Algae: Current Status,Challenges, and Opportunities for Non-Destructive Extraction

Marine algae are an excellent source of novel lectins. The isolation of lectins from marine algae expands the diversity in structure and carbohydrate specificities of lectins isolated from other sources. Marine algal lectins have been reported to have antiviral, antitumor, and antibacterial activity. Lectins are typically isolated from marine algae by grinding the algal tissue with liquid nitrogen and extracting with buffer and alcohol. While this method produces higher yields, it may not be sustainable for large-scale production, because a large amount of biomass is required to produce a minute amount of compound, and a significant amount of waste is generated during the extraction process. Therefore, non-destructive extraction using algal culture water could be used to ensure a continuous supply of lectins without exclusively disrupting the marine algae. This review discusses the traditional and recent advancements in algal lectin extraction methods over the last decade, as well as the steps required for large-scale production. The challenges and prospects of various extraction methods (destructive and non-destructive) are also discussed.     

Use of treated mine water for rainbow trout (Oncorhynchus mykiss) culture: a production scale assessment

In previous proof-of-concept work, it was shown that the use of treated coal mine water for rainbow trout (Oncorhynchus mykiss) culture in a cage was technically feasible, though only a 50-fish bioassay was grown and no work on production-related issues was conducted. To further advance the use of treated mine water, an under-utilized water resource throughout Mid Appalachia, work was conducted to assess the effects of using treated coal mine water for the intensive production of rainbow trout in a flow-through system. During this study, comprehensive water quality data were collected to supplement fish weight and length data taken during routine monthly sampling events. The 8000 fish grew well in the raceway system over the 9 months of production, where a feed conversion ratio of 1.4 and a condition factor of 5.1 × 10⁻⁴ were measured with stocking and harvest densities of 26.4 and 50.2 kg/m³, respectively. Further, total net production was 3275 kg (7220 lb) with 98.6% survival. Throughout the study, dissolved ion concentrations (Fe, Al, Mg, Ca, and SO₄) often exceeded recommended tolerance limits. Further, elevated ammonia nitrogen concentrations generated from a component of the mine water-treatment process were identified as a potential limiting factor for aquaculture development. However, when the non-ideal effects of high ionic strength and the speciation of dissolved metal–ligand complexes were taken into account, the concentrations of free metal ions were within recommended tolerance limits.