Fresh Patch Research Articles

Germination and seedling establishment of Norway spruce (Picea abies) after clear-cutting is affected by timing of soil scarification

Natural regeneration of Norway spruce (Picea abies (L.) Karst.) is a relatively common practice in Norway on medium to low site indices. However, seedling establishment is often hampered by rapid regrowth of competing vegetation in scarified patches. The aim of our study was to examine the effect of coordinating scarification towards an expected seed-fall, by studying germination and seedling establishment in scarified patches of different age (fresh, one- and two-year-old). The experiment was conducted in two stands in southeast Norway that were clear-cut in 2007. Scarification was applied to subplots in autumn 2008–2010. To simulate seed-fall, seeds were sown in fresh scarification patches in spring 2009–2011, in one-year-old patches in 2010 and 2011, and in two-year-old patches in 2011. Both germination and seedling survival were negatively affected by the age of the scarified patches. Germination was higher, and mortality lower, at the small fern woodland site, compared with the bilberry woodland site. Sowing in fresh patches also resulted in increased height and root collar diameter of the seedlings compared with sowing in older patches. It is likely that the competing vegetation both on the site and in the scarification patches affected the growth of the seedlings. In conclusion, the age of the scarified patches affected both germination and mortality, as well as early growth of the seedlings.

Fishing for the Right Words: Decision Rules for Human Foraging Behavior in Internal Search Tasks

Animals depleting one patch of resources must decide when to leave and switch to a fresh patch. Foraging theory has predicted various decision mechanisms; which is best depends on environmental variation in patch quality. Previously we tested whether these mechanisms underlie human decision making when foraging for external resources; here we test whether humans behave similarly in a cognitive task seeking internally generated solutions. Subjects searched for meaningful words made from random letter sequences, and as their success rate declined, they could opt to switch to a fresh sequence. As in the external foraging context, time since the previous success and the interval preceding it had a major influence on when subjects switched. Subjects also used the commonness of sequence letters as a proximal cue to patch quality that influenced when to switch. Contrary to optimality predictions, switching decisions were independent of whether sequences differed little or widely in quality.

Bovine tunica vaginalis: a new material for umbilical hernioplasty in sheep

In this study, fresh patches of bovine tunica vaginalis (BTV), was used as implants for the repair of experimentally-created umbilical hernias in eight sheep. The scrotum were harvested immediately after slaughter and thoroughly washed with sterile distilled water for 5-7 times. The scrotal skin together with the fatty tissues and the loose connective tissues and the tunica adventitia were mechanically stripped by means of a sterile surgical knife, and finally washed with sterile physiological saline solution for 5-7 times. The prepared patches were immersed in the sterile saline solution and preserved at 2-4 oC in sterile jars, ready for use within 4 hrs from their harvesting for hernioplasty of sheep umbilical hernias. The eight implanted grafts were examined clinically and histologically, and all were successfully healed except one (87.5%). Clinically, the successfully implanted BTV patches didn't show signs of rejection, except for the presence of cardinal signs of local inflammatory reaction which were subsided 48 hrs post-operation, and disappeared within 4-5 days post-operation. The healing processes showed no significant abnormalities, except for the occurrence of a few simple multifocal stitch abscess infections. The histopathological examinations showed invasion of dense fibrous connective tissues, consisted of heavy bundles of collagen fibers, through which newly formed capillaries and mononuclear inflammatory cells and melanin pigments deposition, were infiltrated through the graft. As a first report on this new tissue implant in sheep, BTV is proved to be a suitable biocompatible heterogenic surgical patch for reconstruction of umbilical hernias, because of its availability as a cheap tissue, with a high tensile strength and flexibility. However, further investigation is required regarding preservation efficiency and employment for reconstruction of soft tissue defects in man and animals.

COMPARING LOCOMOTION WITH LEVER‐PRESS TRAVEL IN AN OPERANT SIMULATION OF FORAGING

An operant model of foraging was studied. Rats searched for food by pressing on the left lever, the patch, which provided one, two, or eight reinforcers before extinction (i.e., zero reinforcers). Obtaining each reinforcer lowered the probability of receiving another reinforcer, simulating patch depletion. Rats traveled to another patch by pressing the right lever, which restored reinforcer availability to the left lever. Travel requirement changed by varying the probability of reset for presses on the right lever; in one condition, additional locomotion was required. That is, rats ran 260 cm from the left to the right lever, made one response on the right lever, and ran back to a fresh patch on the left lever. Another condition added three hurdles to the 260‐cm path. The lever‐pressing and simple locomotion conditions generated equivalent travel times. Adding the hurdles produced longer times in patches than did the lever‐pressing and simple locomotion requirements. The results contradict some models of optimal foraging but are in keeping with McNair's (1982) optimal giving‐up time model and add to the growing body of evidence that different environments may produce different foraging strategies.

Aggregation and the maintenance of genetic diversity: An individual-based cellular model

A cellular model, where each individual is explicitly defined, is used to describe a population of a mycophagous species ofDrosophila. Patches represent single fungal fruiting bodies which are only available as oviposition sites for a single fly generation. Standard competition equations are used to describe the interaction between larval genotypes at each patch. Dispersal of adults is obligatory and uses a simple model of patch choice to produce aggregated arrivals of adults at fresh patches. The degree to which aggregation of adults and eggs can promote coexistence of genotypes in a one-locus, two-allele system with dominance is explored. When both phenotypes (A- andaa) are aggregated, a polymorphism can be maintained for over 1000 generations even when the selective disadvantage of one phenotype (aa) is great. This model enhances the degree of polymorphism in a population, using aggregation. It does not preclude the operation of other methods which enhance the coexistence of genotypes. Therefore, it is acting to augment the degree of polymorphism maintained in species which exploit patchy and ephemeral habitats, including allDrosophila and a wide range of other organisms.

Short Phase Efficacy of Autologous Peritoneum as a Pericardial Substitute

The risks associated with resternotomy are largely related to loss of pericardial integrity. No satisfactory substitute for pericardium has been identified. The structural similarity between pericardium and peritoneum prompted an assessment of the latter as a biologic substitute. Two peritoneal patches were harvested from four juvenile swine, which then underwent left thoracotomies. In each pig, two pericardial defects were created and repaired with fresh and glutaraldehyde treated autologous peritoneal patches. Three weeks post operatively, the chest and abdomen were re-explored and the patches evaluated. In all cases, extrapericardial adhesions were insignificant. On gross examination of the intrapericardial surfaces, the fresh patches appeared smooth and glistening, with neither degenerative changes nor adherence to the epicardium. The treated patches were easily separated from the epicardium in two cases, but the other two patches were moderately to severely adherent. Histologic examination demonstrated well preserved morphology in all patches. C proline uptake and autoradiography revealed preserved fibroblast viability in the fresh patches. Intra abdominally, in all cases, there was complete reperitonealization without adhesion formation. In conclusion, fresh autologous peritoneum performed well as a pericardial substitute after heart surgery.ASAIO Journal1995; 41:226-229.

Short Phase Efficacy of Autologous Peritoneum as a Pericardial Substitute

The risks associated with resternotomy are largely related to loss of pericardial integrity. No satisfactory substitute for pericardium has been identified. The structural similarity between pericardium and peritoneum prompted an assessment of the latter as a biologic substitute. Two peritoneal patches were harvested from four juvenile swine, which then underwent left thoracotomies. In each pig, two pericardial defects were created and repaired with fresh and glutaraldehyde treated autologous peritoneal patches. Three weeks post operatively, the chest and abdomen were re-explored and the patches evaluated. In all cases, extrapericardial adhesions were insignificant. On gross examination of the intrapericardial surfaces, the fresh patches appeared smooth and glistening, with neither degenerative changes nor adherence to the epicardium. The treated patches were easily separated from the epicardium in two cases, but the other two patches were moderately to severely adherent. Histologic examination demonstrated well preserved morphology in all patches. C proline uptake and autoradiography revealed preserved fibroblast viability in the fresh patches. Intra abdominally, in all cases, there was complete reperitonealization without adhesion formation. In conclusion, fresh autologous peritoneum performed well as a pericardial substitute after heart surgery.