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971.
Elizabeth Rice 《Genetic Resources and Crop Evolution》2007,54(4):701-713
Using survey data from Jala, Mexico, this case-study evaluates in situ maize conservation of the variety ‘Jala’ (Zea mays L.). Though historically ‘Jala’ was the dominant variety grown in the valley of Jala, today less than 20% of farmers grow
it on only 5% of the maize area. Younger growers of the ‘Jala’ variety specialize in it, growing relatively large amounts
for niche markets. Older, diversified farmers grow small areas for household use and to compete in a local contest. Conservation
of the ‘Jala’ variety has been heavily influenced by shifting ideal concepts of maize, as determined by market and consumption
demands and by a contest designed to promote in situ conservation. The current move away from nationalized purchasing may
favor ‘Jala’s’ continued conservation. 相似文献
972.
Abrie J. van der Merwe Albertus L. Pretorius 《Journal of Agricultural, Biological & Environmental Statistics》2003,8(3):328-343
This article applies Bayesian nonparametric techniques of analysis to the mixed linear model. The distribution of the random
effects is specific as a nonparametric prior. A Dirichlet process prior is specified on the space of prior distributions.
A modified Dirichlet process is described and applied using a Gibbs sampler. The approach is demonstrated in an investigation
of the changes over time of packed cell volume in two breeds of cattle. 相似文献
973.
Anthropogenic N-deposition represents a significant input of N into semi-arid chaparral and coastal sage scrub (CSS) shrublands
of southern California. High levels of atmospheric N deposition have the potential to increase soil C and N mineralization,
and we hypothesize that semi-arid shrubland soil exposed to long-term (decades) high N deposition will have significantly
higher C and N mineralization potentials. This hypothesis was tested in a laboratory incubation where the inorganic N (NH4+NO3) and CO2 production of soils maintained at a constant temperature of 25°C and a soil moisture of 0.25 g H2O/g (65% water-filled pore space) were sampled sequentially over a 50-week period. The temporal trend in cumulative C and
N mineralization was well described by a first- and zero-order model, respectively. Long-term atmospheric N deposition significantly
increased potential N mineralization but not C mineralization, and both the rate and total N mineralization were significantly
positively correlated with the surface (0–10 cm) soil δ
15N natural abundance and negatively correlated with the surface soil C:N ratio. While the incubation techniques used here do
not provide realistic estimates of in situ C or N mineralization, these assays indicate that atmospheric N deposition has
significantly altered ecosystem N storage and cycling. 相似文献
974.
A micropropagation method for Jaal (Salvadora persica)—a tree of arid horticulture and forestry has been developed. Nodal segments of fresh shoot sprouts originated from axillary
buds obtained from a plant around 35–40 years old lopped plant were used as explants for establishment of in vitro cultures.
Surface-sterilized explants produced optimum number of shoots through activation of axillary buds on Murashige and Skoog’s
(MS) medium containing 8.88 μM BA (6-benzyladenine) + additives (25 mgl−1 each of adenine sulphate, arginine, citric acid, 50 mgl−1 ascorbic acid). The shoot multiplication was influenced by the successive transfer of the mother explants for 4–5 passages.
The maximum number (23.1 ± 0.73 shoots per explant) of shoots were regenerated on MS supplemented with 1.11 μM BA + 1.16 μM
Kn (Kinetin) + 0.54 μM NAA (α-naphthalene acetic acid). About 90% shoots pulse-treated with a combination of 2460.27 μM Indole-3-butyric
acid (IBA) + 494.56 μM NOA (2-naphthoxy acetic acid) were rooted ex vitro on soilrite within 15–18 days. Over 80% cloned plantlets
were hardened successfully in a green house and transferred to polybag/pots. 相似文献
975.
Juan Valencia Chris Harwood Russell Washusen Andrew Morrow Matthew Wood Peter Volker 《Wood Science and Technology》2011,45(1):15-34
Peripheral longitudinal growth strain (LGS) was measured on a total of 81, 22-year-old pruned Eucalyptus nitens trees from five thinning treatments in a plantation thinning trial in Tasmania. Growth strain data were gathered at breast
height on each tree using the CIRAD-Forêt method. The effects of thinning treatment and tree diameter on LGS and its relationships
to solid-wood traits determined in a processing trial were examined. LGS was significantly higher in the direction of the
prevailing wind and was not significantly affected by either thinning treatment or tree diameter. An index of log end splitting
was positively related to tree diameter, sawlog position (upper/lower), and LGS, which explained up to an additional 20% of
the variance after tree diameter and log position were accounted for in a linear regression model. High LGS and log end splitting
were significant indicators of increased board end splitting. 相似文献
976.
R. S. Yadav B. L. Yadav B. R. Chhipa S. K. Dhyani Munna Ram 《Agroforestry Systems》2011,81(3):195-202
An investigation was carried out in an Entisol at farmers’ field in Jaipur district, Rajasthan, India during 2002–2004 to evaluate the effect of traditionally grown trees
on soil biological characteristics. Traditionally grown trees in farm lands for study consisted of Prosopis cineraria (L.), Dalbergia sissoo (Roxb.) ex DC, Acacia leucophloea (Roxb.) and Acacia nilotica (L.) Del. having a canopy diameter of 8 m. Results revealed significant and substantial improvement in soil biological activity
in terms of microbial biomass C, N and P, dehydrogenase and alkaline phosphatase activity under different tree based agroforestry
systems as compared to a no tree control (cropping alone). Soil microbial biomass C, N and P under agroforestry varied between
262–320, 32.1–42.4 and 11.6–15.6 μg g−1 soil, respectively, with corresponding microbial biomass C, N and P of 186, 23.2 and 8.4 μg g−1 soil under a no tree control. Fluxes of C, N and P through microbial biomass were also significantly higher in P. cineraria based land use system followed by D. sissoo, A. leucophloea and Acacia nilotica in comparison to a no tree control. Thus, it is concluded that agroforestry system at farmers’ field enhance soil biological
activity and amongst trees, P. cineraria based system brought maximum and significant improvement in soil biological activity. 相似文献
977.
The wood–adhesive interface was analyzed using five methods with the objective of quantitatively assessing penetration of adhesive into the porous wood network. Methods included fluorescence microscopy, scanning electron microscopy, backscatter electron imaging, wavelength dispersive spectroscopy, and X-ray microtomography (XMT). Each method provided a visual inspection, and all of the analysis methods were applied to the same field of view. XMT was the primary technique of interest. Rubidium hydroxide was used in place of sodium hydroxide in the formulation of phenol–formaldehyde adhesive. Rubidium was found to increase the X-ray attenuation of the adhesive. However, rubidium migrated beyond the adhesive interphase during specimen preparation, thus reducing its effectiveness for image contrast enhancement. The wood species studied included red oak (Quercus rubra), Douglas-fir (Pseudotsuga menziesii), and hybrid poplar (Populus deltoides × Populus trichocarpa). All techniques used for this study were useful, but each presented some limitations for bondline analysis. Despite the problem with rubidium migration, XMT for this application was promising. 相似文献
978.
Parklands are mixtures of trees and shrubs that farmers select for certain functions. In the Sahel, parklands are cultivated
together with staple food crops, such as millet and sorghum. Parkland trees are sources of foods, including fruits, fats,
oils, leafy vegetables, nuts and condiments that complement food crops in the local diet. Despite their socio-economic and
ecological role, many studies have shown that the parklands are degrading very rapidly. Therefore, there is a need to undertake
restoration actions that are based on a clear understanding of the livelihood context, such as the wealth status of the farmers,
in which these agroecosystems are evolving. Thus, we conducted a wealth survey with rural communities in two different farming
systems of Burkina Faso that are the cereal-based system in the “Plateau Central” and the cotton-based system in the “Boucle
du Mouhoun”. A total of twelve villages were sampled, six villages for each system. The Participatory Analysis of Poverty
and Livelihood Dynamics (PAPoLD) method was used by rural farmers to rank farmer households of their communities according
to their wealth status. The results revealed that 70% of households in the Plateau Central and 56% in the “Boucle du Mouhoun”
managed to escape poverty, and became wealthy. However, 2% of households of the villages in the Plateau Central and 6% in
“Boucle du Mouhoun” fell into poverty in the same period whereas 9 and 12% remained poor in these zones, respectively. The
main causes associated with households getting out of poverty are subsidies for cotton, external revenues from relatives working
in towns and gardening activities. Death of spouse, illness, high number of people in the household and indebtedness are the
main causes that lead into poverty. The implications of these findings in designing appropriate policies and management options
for a sustainable management of agroforestry parklands under different land use systems were finally discussed. 相似文献
979.
Keith E. Woeste 《林业研究》2011,22(3):353-359
Three kinds of plant growth regulators, gibberellinA 4/7 (GA 4/7 ), 6-benzylaminopurine (BA), and chlormequat chloride (CCC), were evaluated for their ability to promote strobilus and cone production in a Chinese pine (Pinus tabuliformis Carr.) clonal seed orchard. Treatments (0, 250, 500, or 1000 mg L -1 ) were applied during three periods (June- July, July-August and August-September) in 2005. Of the three plant growth regulators, GA 4/7 was the best for promoting flower and cone production. Trees sprayed... 相似文献
980.
Species diversity and stability of natural secondary communities in different layers with different cutting intensities 10
years later were investigated by calculating Marglef Richness index (R), Shannon-Wiener diversity index (H), Simpson diversity index (P), and Pielou Evenness index (J). Results show that the values of R, H and P among different layers are listed in a decreasing order: the shrub layer > the arbor layer > the herb layer, all the three
indices values reach the maximum under medium selective cutting intensity after 10 years. The J value of the shrub layer shows a concave parabolic change with the increase in cutting intensity; it shows a linear increase
for the arbor layer, whereas the J value of the herb layer shows an opposite change pattern. The values of R at different cutting intensities had high significant difference, but other indices had not significant difference. The stability
of communities at different cutting intensities after 10 years is non-cutting> low selective cutting intensity > medium selective
cutting intensity > high selective cutting intensity > extra-high intensity > clear cutting. The stability of communities
at different cutting intensities after 10 years shows that the greater cutting intensities, the worse the stability is. 相似文献