Tree Regeneration and Species Diversity Following Conventional and Uniform Spacing Methods of Selective Cutting in a Subtropical Humid Forest Reserve1

There are a variety of ways to diminish the negative impacts of forest management for timber on biodiversity. A pilot project using a uniform spacing method of selective cutting was recently implemented in the 5340 ha Guarani Reserve, Misiones, Argentina, to design adequate management schemes for the subtropical forests of the region. Uniform spacing involves moderate timber harvesting and careful selection of remnant trees. In this article we compare tree regeneration in forests experimentally cut by diameter limit and uniform spacing methods. Seedlings of five size classes from 10 cm to 3 m in height were sampled using rectangular nested plots. Three years after cutting, an average of 54,330 and 22,270 seedling/ha (all height classes combined) of commercial and non-commercial species were found in the forest cut by uniform spacing and by minimum diameter, respectively. In an adjacent uncut forest there were 34,900 seedlings/ha, and in another forest cut by minimum diameters 30 years ago there were 50,000 seedlings/ha, The forest cut by uniform spacing had the highest number of commercial seedlings/ha, with three times as many as the forest cut by minimum diameter three years ago and twice as many as the forest treated by minimum diameters 30 years ago. The forest cut by uniform spacing and the forest treated by minimum diameters 30 years ago had the highest diversity of understory plants other than trees, as well as heterogeneous canopy cover, while the other two forests had a predominance of bamboo in the understory and more open canopy conditions. Although lack of site replication limits interpretation of the results, these early findings suggest that the uniform spacing method can be an ecologically sound forest management option for the region.     

Social relationships of mountain baboons: Leadership and affiliation in a non-female-bonded monkey

Instead of close and differentiated relationship among adult females, the accepted norm for savanna baboons, groups of Drakensberg mountain baboons (Papio ursinus) showed strong affiliation of females towards a single male. The same male was usually the decision-making animal in controlling group movements. Lactating or pregnant females focused their grooming on this “leader” male, producing a radially patterned sociogram, as in the desert baboon (P. hamadryas); the leader male supported young animals in the group against aggression and protected them against external threats. Unlike typical savanna baboons, these mountain baboons rarely displayed approach-retreat or triadic interactions, and entirely lacked coalitions among adult females. Both groups studied were reproductively one-male; male-female relationships in one were like those in a unit of hamadryas male at his peak, while the other group resembled the unit of an old hamadryas male, who still led the group, with a male follower starting to build up a new unit and already monoplizing mating. In their mountain environment, where the low population density suggests conditions as harsh for baboons as in deserts, adults in these groups kept unusually large distances apart during ranging; kin tended to range apart, and spacing of adults was greatest at the end of the dry, winter season. These facts support the hypothesis that sparse food is responsible for convergence with hamadryas social organization. It is suggested that all baboons, though matrilocal, are better categorized as “cross-sex-bonded” than “female bonded”.     

Territorial behavior of Western Sandpipers on their nonbreeding grounds: effect of sex and foraging interference

ABSTRACT Nonbreeding shorebirds often alternate social structure between anonymous flocks and territorial behavior in response to different environmental factors. To evaluate specific drivers for one species, we studied the spacing behavior of wintering Western Sandpipers (Calidris mauri) at Bahía Santa María, northwestern Mexico, using behavioral observations. The density, population structure, and territorial behavior of Western Sandpipers differed among three habitat types. Cattail marshes supported 110 birds per ha, 49% males, and no territorial birds. Mangrove flats supported 288 birds per ha, 58% males, and 5% territorial birds. Brackish flats supported 365 birds per ha, 76% males, and 7% territorial birds. Territories consisted of rectangular strips (5–9 m long, N= 77). Territory length was not related to either bird density or number of territorial birds by plot, but was positively related to nearest bird distance. Aggression rate was inversely related to territory length, suggesting that territory length is set by the costs of defense. Foraging rate was independent of territory length, and prey densities in territories did not differ from those in areas used by nonterritorial birds. Males were more likely to be territorial and had a higher aggression rate than females, suggesting that males, which forage more on surface prey, were more affected by foraging interference. Our results suggest that the territorial behavior of Western Sandpipers in our study was an opportunistic strategy to reduce foraging interference. The variation in spacing behavior we documented provides evidence that interference competition affects the social structure of Western Sandpipers during the nonbreeding season.     

Competition causes regular spacing of alder in Alaskan shrub tundra

Summary Alders (Alnus crispa) in shrub tundra in northern Alaska showed significant regularity of spacing. Removal of neighboring alder shrubs stimulated nutrient accumulation and growth of remaining alders but did not stimulate nutrient accumulation or growth of any other shrub species. This demonstrates that neighboring alders competed with one another and that, when alders were removed, the resources made available were used preferentially by remaining alders rather than by the community in general. Neither patterns of seedling establishment nor patterns of frostrelated features could explain the regular distribution of alder. We suggest that regular patterns of plant distribution are restricted to sites of low-resource availability, because in these habitats (1) there is strong competition for a scarce resource, and (2) there are only one or a few dominant species to compete for these resources in a given canopy height or rooting depth.     

Effects of distance to crop rows and to conspecific neighbours on the size of Brassica napus and Veronica persica weeds

We tested the hypothesis that local competitive conditions are a determinant of the size of individual weeds in cereal crops by investigating the relationship between individual weed size and (a) distance from the crop row and (b) distance to the nearest conspecific neighbour in cereal crops. There were significant but weak effects of distance to rows of summer and winter wheat (Triticum aestivum), and distance to conspecific individuals on individuals of two weed species, Brassica napus and Veronica persica. Our results suggest that local neighbourhood competitive conditions, although detectable, have only limited effects on weed growth. Size-asymmetric competition from the crop population and plasticity in weed growth reduce the importance of a weed individual's exact location relative to crop individuals and to other weed individuals. A static, two-dimensional view of space is not sufficient to describe competitive effects because the third dimension can be the most important in competition, and because many plants can change their locations through plastic growth.Wir überprüften die Hypothese, dass lokale Konkurrenzbedingungen ein Bestimmungsfaktor für die Größe einzelner Unkräuter in Getreidefeldern sind, indem wir die Beziehung zwischen der individuellen Unkrautgröße und (a) der Distanz zu den Pflanzenreihen und (b) der Distanz zu den nächsten, artgleichen Nachbarpflanzen in Getreidefeldern untersuchten. Es gab signifikante jedoch geringfügige Effekte der Distanz zu den Reihen von Sommer- und Winterweizen (Tritium aestivum) sowie der Distanz zu den artgleichen Individuen auf die Individuen von zwei Unkrautarten, Brassica napus und Veronica persica. Unsere Ergebnisse lassen vermuten, dass Konkurrenzbedingungen in der unmittelbaren Nachbarschaft nur einen begrenzten Effekt auf das Unkrautwachstum haben, auch wenn sie wahrnehmbar sind. Größenasymmetrische Konkurrenz seitens der Getreidepopulation und die Plastizität des Pflanzenwachstums reduzieren die Bedeutung der exakten Position einer einzelnen Unkrautpflanze in Beziehung zu einzelnen Getreide- oder anderen, einzelnen Unkrautwpflanzen. Eine statische, zweidimensionale Betrachtung des Raumes reicht nicht aus, um die Konkurrenzeffekte zu beschreiben, weil die dritte Dimension die wichtigste für die Konkurrenz sein kann und weil viele Pflanzen ihre Position durch plastisches Wachstum verändern können.     

Field experiments on the trapping of stoats (Mustela erminea)

Abstract

Steel Fenn traps spaced at 100 m, 200 m, 400 m, and 800 m intervals (total 88 traps) were set in the Eglinton and Hollyford valleys, Fiordland, New Zealand, for 14 days a month from November 1974 to March 1976. A total of 173 stoats were caught, mostly in the two summers. The number of stoats caught and the proportion of females did not change with trap spacing, but both were higher than in an earlier, informal trapping campaign in the same area (20 traps at 2.1 km average interval; 124 stoats caught). The capture rate on the experimental lines declined from 1.07 stoats per 100 trap-nights at the beginning of the average 14-day session to 0.42 at the end, a reduction of 60%. Immigration between trapping sessions probably occurred in all months, but was most marked in summer. The usefulness of the data for the formulation of management policies concerning stoats in the National Parks of New Zealand will be discussed, along with other relevant information, elsewhere.     

Secondary structure propensity and chirality of the amyloidophilic peptide p5 and its analogues impacts ligand binding - In vitro characterization

BackgroundPolybasic helical peptides, such as peptide p5, bind human amyloid extracts and synthetic amyloid fibrils. When radiolabeled, peptide p5 has been shown to specifically bind amyloid in vivo thereby allowing imaging of the disease. Structural requirements for heparin and amyloid binding have been studied using analogues of p5 that modify helicity and chirality.MethodsPeptide-ligand interactions were studied using CD spectroscopy and solution-phase binding assays with radiolabeled p5 analogues. The interaction of a subset of peptides was further studied by using molecular dynamics simulations.ResultsDisruption of the peptide helical structure reduced peptide binding to heparin and human amyloid extracts. The all-D enantiomer and the β-sheet-structured peptide bound all substrates as well as, or better than, p5. The interaction of helical and β-sheet structured peptides with Aβ fibrils was modeled and shown to involve both ionic and non-ionic interactions.ConclusionsThe α-helical secondary structure of peptide p5 is important for heparin and amyloid binding; however, helicity is not an absolute requirement as evidenced by the superior reactivity of a β-sheet peptide. The differential binding of the peptides with heparin and amyloid fibrils suggests that these molecular interactions are different. The all-D enantiomer of p5 and the β-sheet peptide are candidates for amyloid targeting reagents in vivo.General SignificanceEfficient binding of polybasic peptides with amyloid is dependent on the linearity of charge spacing in the context of an α-helical secondary structure. Peptides with an α-helix or β-sheet propensity and with similar alignment of basic residues is optimal.     

Spacing behaviour in resting Culex pipiens (Diptera, Culicidae): a computer modelling approach

Abstract. We compared two models based on Monte Carlo simulations with the spacing patterns of resting adults of the mosquito Cx pipiens L. (form molestus ) (Diptera, Culicidae). The comparison with the first model which assumed a distribution of complete spatial randomness showed that there was a tendency for mosquitoes to repel other mosquitoes which were too close, resulting in high local regularity. The second model took this repulsion into account. A final test of global patchiness using Model 2 indicated that the spacing behaviour of Cx pipiens was not sufficiently described by local regularity only, but also required a gregarious element. This supports the hypothesis that the molestus form of Cx pipiens shows spaced-out gregariousness in the sense of Kennedy & Crawley (1967).