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31.
Some indigenous fruit trees, in the drylands of southern Africa are worthy of interest because of their adaptation to environmental conditions prohibitive for traditional crops. Their fruits or their derivatives are traditionally used as an additional income by rural population, but little information is available about the properties of the soils that support their growth, although this information is necessary if the trees are subjected to sustainable domestication. Several soil properties are, however, to be considered as a whole and discriminant analysis provides a helpful tool to individuate the best conditions for the tree growth. Thirty-five soil samples were taken in areas where the trees naturally grow and produce, and the analytical data of the surface layer were used to relate soil properties to tree species. Four groups of trees were well separated using two discriminant functions that takes into account both the fertility characteristics (pH, organic C, N, texture, and properties of the exchange complex) and the Fe contents and distribution among the oxide forms. The discriminant functions allow a very acceptable reclassification of the data (more than 80% of cases correctly reclassified) and the classification coefficients were used to build an empirical equation that may help to identify the most suitable tree to be introduced at a new site. 相似文献
32.
Bonifacio Mostacedo Francis E. Putz Todd S. Fredericksen Armando Villca Turian Palacios 《Forest Ecology and Management》2009
A major impediment to the sustainable management of tropical dry forests in Bolivia is the scarcity of natural regeneration of commercial timber tree species. Where regeneration is present, true seedlings of many species are outnumbered by vegetative sprouts from roots, broken stems, and the stumps of felled trees. This study evaluates the importance of resprouts promoted by logging operations for the regeneration of commercially important canopy tree species. The objectives of the study were: (1) to characterize stump and root sprouting behaviors of canopy tree species harvested for timber; (2) to quantify the effect of logging on relative abundances and growth rates of stump sprouts, root sprouts, and true seedlings; (3) to relate the species-specific probabilities of stump sprouting to stump diameter and stump height; and (4) to explore how sprouting varies with the ecological requirements of canopy tree species. The study was carried out 1–5 years after logging of a privately owned land in a Bolivian tropical dry forest. Twenty-seven of the 31 species monitored resprouted at least occasionally, among which Centrolobium microchaete (Leguminosae-Fabaceae) and Zeyheria tuberculosa (Bignoniaceae) were the most frequent stump sprouters, and Acosmium cardenasii (Leguminosae-Fabaceae) and C. microchaete were the most frequent root sprouters. In all species the number of sprouts declined with increasing stump diameter and stump height. The probability of stump resprouting differed among species but did not vary consistently with stump diameter, except in Z. tuberculosa in which it declined. Approximately 45% of juveniles <2 m tall of canopy tree species originated from root or stem sprouts. Light-demanding species tended to regenerate more from seeds and root sprouts than from stumps. Seedling densities were higher in microsites opened by logging, while root and stem sprouts were equally common across microsites. Given their abundance and the fact that root and stem sprouts at least initially grew faster than true seedlings, we conclude that vegetative regeneration in this tropical dry forest is an important mode of post-logging regeneration especially for species that regenerate poorly from seed. Resprout management should be considered as a potentially effective strategy for the procurement of regeneration following logging, especially for species that do not readily recruit from seed. 相似文献
33.
Thymus vulgaris essential oil and thymol against Alternaria alternata (Fr.) Keissler: effects on growth,viability, early infection and cellular mode of action
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34.
The structure of the upper atmosphere of mars: In situ accelerometer measurements from mars global surveyor 总被引:1,自引:0,他引:1
GM Keating SW Bougher RW Zurek RH Tolson GJ Cancro SN Noll JS Parker TJ Schellenberg RW Shane BL Wilkerson JR Murphy JL Hollingsworth RM Haberle M Joshi JC Pearl BJ Conrath MD Smith RT Clancy RC Blanchard RG Wilmoth DF Rault TZ Martin DT Lyons PB Esposito MD Johnston al et 《Science (New York, N.Y.)》1998,279(5357):1672-1676
The Mars Global Surveyor (MGS) z-axis accelerometer has obtained over 200 vertical structures of thermospheric density, temperature, and pressure, ranging from 110 to 170 kilometers, compared to only three previous such vertical structures. In November 1997, a regional dust storm in the Southern Hemisphere triggered an unexpectedly large thermospheric response at mid-northern latitudes, increasing the altitude of thermospheric pressure surfaces there by as much as 8 kilometers and indicating a strong global thermospheric response to a regional dust storm. Throughout the MGS mission, thermospheric density bulges have been detected on opposite sides of the planet near 90 degreesE and 90 degreesW, in the vicinity of maximum terrain heights. This wave 2 pattern may be caused by topographically-forced planetary waves propagating up from the lower atmosphere. 相似文献
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Moro PL Lopera L Bonifacio N Gonzales A Gilman RH Moro MH 《Veterinary parasitology》2005,130(1-2):99-104
An epidemiological study was conducted in a highland rural community in Peru to determine risk factors for canine echinococcosis caused by Echinococcus granulosus. Dogs were diagnosed using a coproantigen enzyme-linked immunosorbent assay (ELISA). Dog owners were interviewed prior to stool collection and asked for attitudes, practices and beliefs likely to be associated with local patterns of E. granulosus transmission. Univariate and multivariate analysis were used to determine odds ratios (OR) and their 95% confidence intervals (CI). The main risk factors found to be significantly associated with canine echinococcosis by univariate analysis were dog age (3-25 months) (OR, 5.14; CI, 1.7-15.7), female sex (OR, 4.3; CI, 1.4-13.3) and having been fed hydatid infected offal (OR, 2.9; 95% CI, 1.0-8.6). There was complete lack of knowledge about echinococcosis transmission. In addition to periodic dog treatment, control programs need to emphasize education of the human population to increase knowledge of parasite transmission and to change human practices associated with high rates of infection. 相似文献
38.
M. Catoni M. E. D'amico M. C. Mittelmeijer‐Hazeleger G. Rothenberg E. Bonifacio 《European Journal of Soil Science》2014,65(5):763-773
In Podzols, organic matter (OM) is stabilized mainly by interaction with minerals, as a direct consequence of pedogenic processes. Metal–organic associations strongly affect OM surface features, particularly microporosity. Cemented ortstein horizons (CM) may form during podzolization, accompanied by a spatial arrangement of OM on mineral surfaces, which differs from that in non‐cemented horizons (N‐CM). To investigate the metal–organic associations and their changes during pedogenesis, we selected both N‐CM and CM podzolic horizons, isolated NaClO‐resistant OM and compared the specific surface area (SSA) before and after OM oxidation. The SSA was assessed by using N2, to detect the pores in the range of micropores (< 2 nm) and mesopores (2–50 nm), and CO2, to measure a smaller microporosity (< 0.5 nm), which is not accessible to N2. Only the N‐CM samples showed the typical increase in N2‐SSA after the removal of labile OM, while a decrease was found in all CM horizons. The CO2‐SSA revealed a large number of small micropores characterizing OM, both before and after oxidation. The smallest micropore classes (< 0.5 nm) were, however, more abundant in NaClO‐resistant OM, which had therefore a larger number of N2‐inaccessible surfaces than the labile pool. The N2‐SSA data thus indicated a more homogeneous coverage of mineral surfaces by stabilized OM in CM samples. Because of the abundance of small micropores, OM in these podzolic B horizons had extremely large CO2‐SSA values (about 800 m2 g?1), with sharp differences between the NaClO‐labile OM (290–380 m2 g?1) and the NaClO‐stabilized pool (1380–1860 m2 g?1), thus indicating very reactive illuvial organic materials. 相似文献
39.
BC Hosking TM Griffiths RG Woodgate RB Besier AS Le Feuvre P Nilon C Trengove KJ Vanhoff BG Kaye-Smith W Seewald 《Australian veterinary journal》2009,87(11):455-462
Objective To determine the efficacy of monepantel, a developmental compound from the amino-acetonitrile derivative class of anthelmintics, against field infections of gastrointestinal nematodes in sheep.
Procedures Comparisons of efficacy (using standard faecal worm egg count reduction tests) and safety (on the basis of visual observations) were made in a large-scale field study in Australia, between groups of sheep treated with either an oral solution of monepantel or a registered anthelmintic. The sheep were naturally infected with the major gastrointestinal nematode genera present in Australia.
Results The post-treatment efficacy results for monepantel were: at 7 days (±1 day) efficacy was >98%; at 14 days (±1 day) it was generally close to or >99%; and at 21 days (±1 day) efficacy was consistently >99%. A high proportion of the targeted nematode populations were confirmed as being resistant to one or more of the currently available anthelmintic classes.
Conclusions Monepantel when used under field conditions at a minimum dose rate of 2.5 mg/kg was highly effective against mixed-genus natural field infections of the major gastrointestinal nematode genera including Haemonchus , Teladorsagia ( Ostertagia ), Trichostrongylus , Nematodirus , Chabertia and Oesophagostomum . This result included efficacy against some populations resistant to the currently available broad-spectrum anthelmintics. Few Cooperia spp. were present to allow confirmation of efficacy against this genus. On no occasion after treatment did any commercial anthelmintic-treated groups have significantly lower faecal egg counts than the monepantel-treated groups. Monepantel was safe for the target animals and human operators when used in a field situation. 相似文献
Procedures Comparisons of efficacy (using standard faecal worm egg count reduction tests) and safety (on the basis of visual observations) were made in a large-scale field study in Australia, between groups of sheep treated with either an oral solution of monepantel or a registered anthelmintic. The sheep were naturally infected with the major gastrointestinal nematode genera present in Australia.
Results The post-treatment efficacy results for monepantel were: at 7 days (±1 day) efficacy was >98%; at 14 days (±1 day) it was generally close to or >99%; and at 21 days (±1 day) efficacy was consistently >99%. A high proportion of the targeted nematode populations were confirmed as being resistant to one or more of the currently available anthelmintic classes.
Conclusions Monepantel when used under field conditions at a minimum dose rate of 2.5 mg/kg was highly effective against mixed-genus natural field infections of the major gastrointestinal nematode genera including Haemonchus , Teladorsagia ( Ostertagia ), Trichostrongylus , Nematodirus , Chabertia and Oesophagostomum . This result included efficacy against some populations resistant to the currently available broad-spectrum anthelmintics. Few Cooperia spp. were present to allow confirmation of efficacy against this genus. On no occasion after treatment did any commercial anthelmintic-treated groups have significantly lower faecal egg counts than the monepantel-treated groups. Monepantel was safe for the target animals and human operators when used in a field situation. 相似文献
40.