Regeneration of commercial tree species in a logged forest in the Selva Maya, Mexico

One of the main threats to the sustainability of community forestry in the Selva Maya is insufficient regeneration of commercial tree species. We evaluated the regeneration status of 22 commercial tree species in a managed semideciduous tropical rain forest in Southern Mexico. The study was carried out in six harvesting areas along a 16-year chronosequence. In each area, 10 transects (1000 m²) were established and all trees >50 cm height and <10 cm diameter were recorded. We evaluated the relationships between seedling and sapling abundance, and canopy cover and disturbance condition (closed forest, canopy gap, log landing, skid road, primary road and secondary road). The area occupied by closed forest canopy increased with age of harvesting area (65–91% of sampled area), while the area occupied by canopy gaps decreased (22–9%). Log landings occupied less than 1% of the sampled area. The predominant canopy cover was 75–80% in all harvesting areas, even in the most recently harvested areas. The highest densities of seedlings and saplings, of both shade tolerant and intolerant species, were found in log landing and skid trails, followed by secondary roads. Even Simarouba glauca, a shade tolerant species, displayed higher densities in sites with ≤65% of canopy cover. Our results support previous findings and indicate that the levels of disturbance caused by existing harvesting procedures may be inadequate to promote sufficient regeneration of not only light demanding desirable species but also for some of the evaluated shade tolerant species of commercial interest. Seedling and sapling densities exhibited by Swietenia macrophylla, for example, are insufficient to support current harvesting rates. The application of a spatial mixed system with patch-cuts of different sizes, a consequence of group felling, could be applied to provide the necessary conditions for the regeneration of the main commercial species.     

Nursery fertilization enhances survival and physiological status in Canary Island pine (<Emphasis Type="Italic">Pinus canariensis</Emphasis>) seedlings planted in a semiarid environment

We tested the hypothesis that fertilized containerized Pinus canariensis seedlings increases survival when planted in semiarid sites through the improvement of their physiological status during the establishment phase by an increment in root growth. Seedlings were cultured under two different regimes: traditional (in non-fertilized natural soil) and alternative (in fertilized peat). Morphological attributes and nitrogen content were measured before planting. Measurements of survival and growth in the plantation were made periodically for 2 years and physiological plant responses (leaf water potential, gas exchange and chlorophyll fluorescence) during the third summer after planting were tested and finally a set of plants were excavated to measure the same parameters as before planting. Seedlings cultivated using fertilized peat achieved the highest values for all of evaluated parameters. During the third dry season, big seedlings exhibited better physiological status. Therefore, enhanced root growth can result in better water uptake during the dry period thereby increasing survival and growth in the next few years after planting. A feed-back physiological model is proposed to explain P. canariensis establishment in a semiarid environment.     

Understanding Conflicts between People and Parks at Ranomafana, Madagascar

The national park model originating in the unique circumstances of mid-19th century North America has been widely applied in the developing countries of the late 20th century, provoking numerous land-use conflicts between parks and resident peoples. Key factors in understanding these conflicts are examined using the field experience of the Ranomafana National Park in Madagascar. A conflict management strategy is suggested for alleviating such antagonism and facilitating the investigation of mutually acceptable conservation and development pathways.     

Die Konservierung von entomologischen und zoologischen Präparaten in dem Kunststoff P 1

Ohne Zusammenfassung     

Improving food quality through new technology

New technological developments make it possible to improve the quality of animal disease therapy, prophylaxis and diagnosis, and to improve animals' growth and fertility. The term 'quality' includes not only objective measurements, such as the fatness or leanness of meat, but also organoleptic factors such as flavour and others which are of increasing importance to consumers, such as animal welfare. Is new technology consistent with the improvement of quality? For example, beta-agonists and porcine somatotrophin reduce the fatness and increase the protein content of carcases, but there are also subtle positive relationships between fatness and eating quality. In contrast, bovine somatotrophin appears to have no effect on milk composition but there are indications that it may affect the perception of milk quality by some consumers. Improved vaccines can increase food quality by improving animal health and welfare and increasing the uniformity of the product; immunological techniques may also be used to improve meat quality. A gulf has developed between the benefits from new technology and consumer perceptions; indeed there is evidence of political resistance to some technological advances. Despite the stringent regulation of veterinary medicinal products in the United Kingdom and other countries, there is continued pressure for greater political control over their approval. The exchange of information between scientists, industry, the legal regulators and consumers must be improved so that advances in technology are acceptable to the majority and used to the advantage of all.     

Digestibility of vegetative and mature tall fescue greenchop with or without alfalfa greenchop substitution.

Nine ruminally and duodenally cannulated steers (average BW 355 kg) were used to evaluate effects of prebloom alfalfa greenchop substitution at 20% of DMI on utilization of late-May (high quality; HQ; Period 1) and mid-August (low quality; LQ; Period 2) tall fescue greenchop. Alfalfa inclusion did not influence (P greater than .10) diet ad libitum DMI during Period 1 but it decreased (P less than .10) DMI during Period 2. Ruminal and total tract DM, cell wall, and GE digestibility of HQ were unaffected (P greater than .10) by alfalfa inclusion; however, digestibility of these constituents in LQ was increased (P less than .03) by alfalfa substitution. Alfalfa substitution did not influence (P greater than .10) dietary cell wall monosaccharide disappearance. Ruminal CP digestibility was greater (P less than .10) when steers received alfalfa, but microbial efficiency (grams of bacterial N/kilogram of OM truly digested in the rumen) was not enhanced (P greater than .10) by alfalfa inclusion in either HQ or LQ diets. There was a trend (P = .15) for greater microbial efficiency with alfalfa substitution to LQ. Ruminal particulate passage rate did not differ (P greater than .10) between treatments for either stage of maturity. Fluid passage rate was faster (P less than .10) in steers that received only LQ (7.1%/h) than in those fed LQ substituted with 20% alfalfa (5.0 %/h). Our data suggest that alfalfa inclusion in a low-quality fescue diet enhanced cell wall and GE digestibility.     

Induction of parturition in dairy cows with dexamethasone.

Sixty Holstein cows were paired by parity and sire, and one of each pair was allocated at random to treatment or control; 17 cows were injected with 7.5 mg/100 kg dexamethasone trioxa undecanoate 14 days before the predicted date of calving, 13 cows received the same dose five days before term and 30 cows were left untreated. The treatment significantly advanced parturition and 29 of the 30 induced cows calved within 72 hours of the injection. Induction at day 14 before term was safe for calf and dam, the calves were 3.2 kg lighter than control calves and there was a high incidence of retained placenta. Treatment for this condition resulted in increased veterinary costs of 14.50 pounds per cow exclusive of dexamethasone treatment. Treatment at this stage was also associated with low pregnancy rates in the next breeding season. Calves born after induction at five days before term were not significantly lighter than calves from control cows, the problem of retained placenta was less marked and there were no subsequent effects on fertility. There were no significant effects of induction on milk yield or milk quality up to 200 days of lactation.     

An analysis of the diphenylamine reaction in sap of healthy and leaf roll virus infected potato plants

Summary An analysis was made of a difference in colour development between saps from healthy and leaf roll virus (PLRV) infected potato plants, manifested in the diphenylamine reaction ofDische. The colour development was found to be caused by sugars. The differences in colour development were due to the sugar concentration which could be different in healthy and diseased leaves, and not to DNA in the latter. We could correlate the increases in sugar concentration with the severity of virus symptoms. The mechanical transmission of the PLRV, as suggested byBrandenburg (1962), could not be confirmed.Samenvatting Een verschil in kleur, dat tussen sap van gezonde en bladrolviruszieke aardappelplanten door de difenylmaine-reactie vanDische kan optreden, werd geanalyseerd. Het bleek dat de kleurontwikkeling werd veroorzaakt door suikers. De verschillen in kleur van de reactiemengsels waren te wijten aan het feit dat de suikerconcentratie in bladeren van zieke planten een hogere waarde kan bereiken dan in bladeren van gezonde planten en niet aan een hoger desoxyribonucleïnezuurgehalte in zieke bladeren. Er bleek een duidelijke correlatie te bestaan tussen de stijging van de suikerconcentratie en de sterkte van de bladrolsymptomen. De mechanische overdracht van het bladrolvirus, zoals die doorBrandenburg (1962) was gesuggereed, kon niet worden bevestigd.     

Effect of intestinal inflammation on fecal elastase concentration in dogs

BACKGROUND: A commercially available ELISA kit for fecal elastase measurement can be used in the diagnosis of exocrine pancreatic insufficiency (EPI) in dogs. However, other causes of diarrhea also may affect fecal elastase concentration. OBJECTIVE: This study was undertaken to determine whether intestinal inflammation alters fecal elastase concentration in dogs. METHODS: Fecal elastase concentration was measured with an ELISA kit in the following groups of dogs: group 1 (n=16), control dogs, without gastrointestinal disease; group 2 (n=14), dogs with diarrhea and no histopathologic evidence of intestinal inflammation; and group 3 (n=12), dogs with diarrhea and histopathologic evidence of intestinal inflammation. Serum trypsin-like immunoreactivity (TLI) was determined in dogs with diarrhea to rule out EPI. RESULTS: All dogs in groups 2 and 3 had serum TLI concentrations >5 microg/L, ruling out EPI. No statistically significant difference was found in fecal elastase concentration among the 3 groups of dogs (P=.969). CONCLUSIONS: The results indicate that intestinal inflammation does not affect fecal elastase concentration, such that test results may be used to exclude a diagnosis of EPI even in animals with inflammatory bowel disease.