An aggregation index (AI) to quantify spatial patterns of landscapes

There is often need to measure aggregation levels of spatial patterns within a single map class in landscape ecological studies. The contagion index (CI), shape index (SI), and probability of adjacency of the same class (Qi), all have certain limits when measuring aggregation of spatial patterns. We have developed an aggregation index (AI) that is class specific and independent of landscape composition. AI assumes that a class with the highest level of aggregation (AI =1) is comprised of pixels sharing the most possible edges. A class whose pixels share no edges (completely disaggregated) has the lowest level of aggregation (AI =0). AI is similar to SI and Qi, but it calculates aggregation more precisely than the latter two. We have evaluated the performance of AI under varied levels of (1) aggregation, (2) number of patches, (3) spatial resolutions, and (4) real species distribution maps at various spatial scales. AI was able to produce reasonable results under all these circumstances. Since it is class specific, it is more precise than CI, which measures overall landscape aggregation. Thus, AI provides a quantitative basis to correlate the spatial pattern of a class with a specific process. Since AI is a ratio variable, map units do not affect the calculation. It can be compared between classes from the same or different landscapes, or even the same classes from the same landscape under different resolutions.     

Physicochemical requirements in the environment of the earthworm Eisenia foetida

Survival and/or growth were used to assess optimum and potentially deleterious physico-chemical conditions in the environment of the earthworm Eisenia foetida. Maximum weight was gained between 20 and 29°C with horse manure or activated sludge as food. Maximum weight gain as a function of moisture in activated sludge occurred between 70 and 85%. All worms died within a week at pH values <5 or >9; optimum pH for gain in weight centered around 7.0 Soluble salts in excess of 0.5% were lethal, though ammonium acetate caused 100% mortality at a concentration of 0.1%; concentrations in manures contaminated by urine or cattle slurry may be lethal, while those present in noncontaminated manure, with an electrolytic conductivity of 1.5–3mmhos, support weight gain. Inorganic chemicals that are commonly used to coagulate sludges, often as a preliminary to land application, were innocuous at concentrations higher than those normally used at wastewater treatment plants. Anaerobically digested sludges are toxic to earthworms, and are characterized by low oxidation-reduction potentials; when placed upon a soil substrate the redox potential increases slowly, and though the sludge tested in this study was nontoxic at Eh values in excess of 250 mV, it provided insufficient nutriment to E. foetida to allow weight gain. With activated sludge as food, growth of E. foetida occurred more rapidly when soil was present, independently of whether it was placed as a substrate beneath the sludge or mixed into the sludge. Growth occurred more rapidly when activated sludge was placed on substrates which allowed drainage, though loam or ashed loam appeared superior to others, such as glass beads or sand; the growth promoting factor is related to the inorganic fraction of the soil.     

The utilisation of poison hoppers designed for grey squirrel (Sciurus carolinensis Gmelin) control

The grey squirrel is recognised as a pest species of economic importance but the justification of the view appears to be founded on local areas of severe damage. Despite evidence that damage may not be alleviated by squirrel population destruction, Warfarin poisoning was introduced as an alternative to trapping.The utilisation by wildlife of a poison hopper designed for grey squirrel control was investigated by automatic photography. Results confirmed that a number of species may feed from the grain presented via the hopper. However, the majority of the bait was removed during the hours of darkness when grey squirrels were not active. It is a conservative estimate that between 55 and 65% of the grain entered the environment via animals other than squirrels.In addition, the removalof bait by night visitors resulted in the accumulation of large quantities of bait at and around the entrance to the hopper tunnel. This increased accessibility to the potentially poisoned bait by animals other than squirrels.Until such time as evidence is produced to show these results as exceptional, it can only be concluded that fears expressed over the lack of specificity of this method of control are justified.     

Fine-scale vegetation patches decline in size and cover with increasing rainfall in Australian savannas

Fine-scale vegetation patches (<5 m in width) are critically important in many landscapes because they function to obstruct surface flows of water and wind. These obstructions increase the infiltration of runoff and the capture of nutrients in runoff sediments and in wind-blown soil and litter. The importance of redistribution of runoff into runon patches from spaces between patches (fetches) is likely to be greater in drier than in wetter environments. In this paper we examine the hypothesis that the ratio of fetch to patch decreases as rainfall increases, and that this trend will be most evident on intermediate-textured soils because these soils are more prone to runoff. We measured fine-scale patches on 38 sites with sand, loam or clay soils. Sites were located along a 1000-mm rainfall gradient in the savannas of northern Australia. The width and intercept length of patches and the fetch between patches was measuring along line transects of 100–120 m oriented down slope. We found that the ratio of fetch to patch area did not decrease with decreasing rainfall, but increased on both sand and loam soils. This result was because with increasing rainfall mean spacing between patches disproportionally increased while mean patch size and cover declined. The cover of patches was negatively correlated with tree canopy cover, which significantly increased with rainfall. This negative correlation suggests that in higher rainfall savannas the size and spacing of ground-layer patches is controlled by the tree layer, and that as rainfall decreases this control decreases and runoff-runon processes increasingly structure the landscape. For savannas on clay soils these trends were not significant except that on the highest rainfall sites the cover of ground-layer patches was nearly 100% while trees were absent.     

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.     

The Immune System of Marine Organisms as Source for Drugs against Infectious Diseases

The high proliferation of microorganisms in aquatic environments has allowed their coevolution for billions of years with other living beings that also inhabit these niches. Among the different existing types of interaction, the eternal competition for supremacy between the susceptible species and their pathogens has selected, as part of the effector division of the immune system of the former ones, a vast and varied arsenal of efficient antimicrobial molecules, which is highly amplified by the broad biodiversity radiated, above any others, at the marine habitats. At present, the great recent scientific and technological advances already allow the massive discovery and exploitation of these defense compounds for therapeutic purposes against infectious diseases of our interest. Among them, antimicrobial peptides and antimicrobial metabolites stand out because of the wide dimensions of their structural diversities, mechanisms of action, and target pathogen ranges. This revision work contextualizes the research in this field and serves as a presentation and scope identification of the Special Issue from Marine Drugs journal “The Immune System of Marine Organisms as Source for Drugs against Infectious Diseases”.     

Body weight of newborn and suckling piglets affects their intestinal gene expression

Modern hyperprolific sows must deal with large litters (16–20 piglets) which reduce piglet birthweight with a concomitant increase in the proportion of small and intrauterine growth retarded piglets. However, larger litters do not only have a greater variation of piglet weights, but also a greater variation in colostrum and milk consumption within the litter. To further understand the impact that body weight has on piglets, the present study aimed to evaluate the degree of physiological weakness of the smallest piglets at birth and during the suckling period (20 d) compared to their middle-weight littermates through their jejunal gene expression. At birth, light piglets showed a downregulation of genes related to immune response (FAXDC2, HSPB1, PPARGC1α), antioxidant enzymes (SOD2m), digestive enzymes (ANPEP, IDO1, SI), and nutrient transporter (SLC39A4) (P < 0.05) but also a tendency for a higher mRNA expression of GBP1 (inflammatory regulator) and HSD11β1 (stress hormone) genes compared to their heavier littermates (P < 0.10). Excluding HSD11β1 gene, all these intestinal gene expression differences initially observed at birth between light and middle-weight piglets were stabilized at the end of the suckling period, when others appeared. Genes involved in barrier function (CLDN1), pro-inflammatory response (CXCL2, IL6, IDO1), and stress hormone signaling (HSD11β1) over-expressed compared to their middle-weight littermates (P < 0.05). In conclusion, at birth and at the end of suckling period, light body weight piglets seem to have a compromised gene expression and therefore impaired nutrient absorption, immune and stress responses compared to their heavier littermates.     

Behaviour of bentazon as influenced by water and tillage management in rice‐growing conditions

Bentazon is a widely used herbicide in rice agroecosystems that has commonly been found in water resources. To assess how tillage and water regimes affect sorption/desorption, dissipation and leaching of bentazon in Mediterranean rice‐growing conditions, field experiments were carried out using tillage and flooding (TF), tillage and sprinkler irrigation (TS), no‐tillage and sprinkler irrigation (NTS) and long‐term no‐tillage and sprinkler irrigation (NTS7). After 3 years, the K_d values in TS were 2.3, 1.6 and 1.7 times lower than the values in NTS7, NTS and TF respectively. Greater sorption of bentazon was related to higher contents in total organic carbon and, although to a lesser extent, in humic acids and dissolved organic carbon. The persistence of bentazon was significantly greater under anaerobic (half‐life DT₅₀ = 94.1–135 days) than under aerobic (DT₅₀ = 42.4–91.3 days) incubation conditions for all management regimes. Leaching losses of bentazon were reduced from 78 and 74% in TS and TF to 61 and 62% in NTS7 and NTS respectively. The mid‐ and long‐term implementation of sprinkler irrigation in combination with no‐tillage could be considered a management system that is effective at reducing water contamination by bentazon in Mediterranean rice‐growing agroecosystems. © 2017 Society of Chemical Industry