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A dramatic decline in forest cover in eastern Africa along with a growing population means that timber and poles for building
and fuelwood are in short supply. To overcome this shortage, the region is increasingly turning to eucalyptus. But eucalyptus
raises environmental concerns of its own. Fears that it will deplete water supply, affect wildlife and reduce associated crop
yields have caused many countries in the region to discourage farmers from planting this exotic. This paper is part of a series
of investigations on the growth and water use efficiency of faster growing eucalyptus hybrids, which was introduced from South
Africa to Kenya. The hypothesis is that the new hybrids are more efficient in using water and more suitable for the semi-arid
tropics than existing eucalyptus and two popular agroforestry species. Gas exchange characteristics of juvenile Eucalyptus grandis (W. Hill ex Maiden), two eucalyptus hybrids (E. grandis × Eucalyptus camaldulensis Dehnh.), Grevillea robusta (A. Cunn) and Cordia africana (Lam) was studied under field and pot conditions using an infrared gas analyzer was used to measure photosynthetic active
radiation (PAR), net photosynthetic rate (A), stomatal conductance (g
s) and transpiration rate (E) at CO2 concentrations of 360 μmol mol−1 and ambient humidity and temperature. A, E and g
s varied between species, being highest in eucalyptus hybrid GC 15 (24.6 μmol m−2 s−1) compared to eucalyptus hybrid GC 584 (21.0 μmol m−2 s−1), E. grandis (19.2 μmol m−2 s−1), C. africana (17.7 μmol m−2 s−1) and G. robusta (11.1 μmol m−2 s−1). C. africana exhibited high E values (7.0 mmol m−2 s−1) at optimal soil moisture contents than G. robusta (3.9 mmol m−2 s−1) and eucalyptus (5.3 mmol m−2 s−1) in field experiment and G. robusta (3.2 mmol m−2 s−1) and eucalyptus (4.2 mmol m−2 s−1) in pot-grown trees. At very low soil moisture content, extremely small g
s values were recorded in GC 15 and E. grandis (8 mmol m−2 s−1) and G. robusta (14 mmol m−2 s−1) compared to GC 584 (46.9 mmol m−2 s−1) and C. africana (90.0 mmol m−2 s−1) indicating strong stomatal control by the species. Instantaneous water use efficiency ranged between 3 and 5 μmol mmol−1 and generally decreased with decline in soil moisture in pot-grown trees but increased with declining soil moisture in field-grown
trees. 相似文献
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The effect of supplementation with three levels of Leucaena leucocephala leaf meal (LLM) added to a diet composed of cotton seed hulls (CSH) and maize bran (MB) on milk yield, milk composition and body weight changes of grazing lactating cows was studied in a completely randomised design. Marginal product analysis for the different levels of LLM as a substitute to cotton seed cake (CSC) was also calculated. The following treatment diets were used in the experiment: Diet 1, (control) composed of 1.8 kg DM CSH and 1.8 kg DM MB. Diet 2, 3 and 4 had an addition of 1.2, 2.0 and 2.6 kg DM of LLM respectively. Diet 5 was composed of 1.8 kg DM of CSC and 1.8 kg DM of MB. Treatments, number of lactations, farm and initial milk yields significantly (P < 0.01) influenced milk production. LLM supplementation to grazing cows significantly increased milk production, weight gain and milk composition (P > 0.05). Cows on treatment 1 achieved no significant (P < 0.05) increase in milk yield compared to cows on treatment 2, 3, 4 and 5 which attained net milk increase of 3.6, 4.1, 6.7 and 4.4 litres/cow/day respectively. There was no significant (P > 0.05) difference in net milk produced by cows on treatment 2, 3 and 5 compared to treatment 1. LLM supplementation significantly (P < 0.05) increased total solids (TS) in milk compared to that of cows under control, but there was no significant (P > 0.05) influence on milk crude protein (CP), butter fat (BF), solids not fat (SNF) and ash in all the diets. Body weight was significantly (P < 0.05) increased by LLM supplementation. Degradation coefficients of the treatment diets were high and varied significantly (P < 0.01) and had an influence on the metabolizable energy value of the treatment diets. Cows on diet 2 to 4 had a weight gain of 190.9, 101.8 and 80.9 g/cow/day respectively and cows on diet 5 attained the highest weight gain (234.5 g/cow/day). Diet 4 had the highest marginal productivity of 4.3 followed by diets 2, 3 and 1 with marginal productivities of 2.8, 0.6 and 0 respectively. It was therefore, concluded that the optimal supplementation level using LLM as a substitute for the more expensive CSC was diet 4.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
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Shem T. Oliver Joanne Hardy 《The Canadian veterinary journal. La revue veterinaire canadienne》2015,56(4):382-386
This study investigated 15 horses diagnosed with temporohyoid osteoarthopathy (THO) and treated by ceratohyoidectomy between 2004 and 2012. The presenting complaint, duration and nature of the clinical signs, additional diagnostic procedures, and complications were reviewed retrospectively. Long-term follow-up on horses was used to determine prognosis. All horses were diagnosed by guttural pouch endoscopy. Follow-up was available for 14 horses that survived to discharge. Eight of 10 horses that were used athletically prior to surgery returned to previous levels of use. Persisting clinical signs included mild facial nerve paralysis (3/14; 21.4%) or head tilt (6/14; 42.8%) but these were not functionally limiting. It was concluded that equine THO affects a wide range of breeds, disciplines, and ages of horses, and has a variety of presenting clinical signs most commonly associated with vestibular and facial nerves. Prognosis following ceratohyoidectomy is good for resolution of ataxia but some cranial nerve deficits may persist. 相似文献
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C?D.?K.?Rubanza M.?N.?Shem R.?Otsyina T.?FujiharaEmail author 《Agroforestry Systems》2005,65(3):165-174
Information is lacking on the potential of leguminous fodder trees such as Leucaena leucocephala as a feed resource to supplement the native forages in traditional grazing management systems in the tropics. Two studies
were conducted (1) to assess traditional fodder banks’ forage nutritive potential on animal production, and (2) to investigate
the effect of Leucaena leucocephala leaf meal (LLM) supplementation on growth of steers grazing standing hay basal forages in the dry season. The traditional
forages had low nutritive values indicated by low mean crude protein (CP) of 23 g kg−1 dry matter (DM), and high fibre contents of 717, 546 and 153 g kg−1 DM for neutral detergent fibre (NDF), acid detergent fibre (ADF) and acid detergent lignin (ADL), respectively. The forages
were poorly degraded in sacco and had low metabolisable energy (ME) (4.2–4.6 MJ kg−1 DM). Mean washing losses A, slowly degradable DM fraction, B, potential degradability, (A+B) and mean 48 h DM degradability
(DMD) of grazing land forages were 70, 471, 541 and 326 g kg−1 DM, respectively. In the supplementation study, 16 growing steers (160.8±0.24 kg) were randomly allocated into four groups,
in a completely randomized design. Four LLM treatment diets (T1, T2, T3 and T4), with four levels: 0, 0.4, 0.6 and 0.8 kg
DM for control, low, medium and high LLM levels, respectively, were randomly allocated to the animals in the four groups for
70 days (d). LLM supplementation (p<0.05) improved mean weight gain from −0.30 to 0.26 kg steer−1 d−1, for T1 and T4, respectively. Steers on T4 gained (p<0.05) more weight compared to the animals in T1 and T2, though there was no (p>0.05) difference in weight gains between animals on T3 and T4 (0.14 vs. 0.26 kg steer−1 d−1, respectively). Standing hay basal forages alone could not sustain animal productivity during dry seasons unless corrected
for protein. Higher levels of LLM supplementation prevented weight losses and improved the performance of grazing steers,
a management practice thought appropriate to low income pastoralists in semiarid western Tanzania. 相似文献
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Two experimental models simulating the traditional storage conditions prevalent in Kenya, i.e. the open basket model and the modern wooden box model, were used to study the rate of dissipation and fate of malathion residues in maize grains and beans stored for periods of up to one year at ambient temperatures averaging 23°C. The grain samples were initially treated with 10·36 mg kg−1 of radiolabelled malathion dust prior to storage and portions analysed at regular intervals for malathion, malaoxon and the transformation products isomalathion, malathion α-monocarboxylic acid and malathion β-monocarboxylic acid using a combination of chromatographic, radioisotopic and mass-spectrometric techniques. The findings showed a gradual penetration of malathion into the grains in amounts which were slightly higher in maize than in beans irrespective of the method of storage. After 51 weeks of storage, 34–60% of the initial residues persisted in all the grains. The total residual levels were slightly higher in beans than in maize irrespective of the storage methods though the persistence was a little higher in the wooden box than in the open basket. The rates of dissipation of the pesticide from the grains decreased with storage time and followed a biphasic pattern. Applying first-order reaction kinetics, the following half-lives were obtained: maize grains stored in open basket: 194 days; maize grains stored in closed wooden box: 261 days; beans stored in open basket: 259 days; beans stored in closed wooden box: 405 days. Beans stored in the wooden box had higher levels of bound residues than those sampled from the open basket. This trend was similar in maize grains although the concentrations were lower. The analysis of malathion metabolites confirmed the degradation trend of the residues. 相似文献
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Shem Kuyah Catherine Muthuri Ramni Jamnadass Peter Mwangi Henry Neufeldt Johannes Dietz 《Agroforestry Systems》2012,86(2):267-277
Classical allometries determine biomass from measurements of diameter at breast height or volume. Neither of these measurements is currently possible to be derived directly from remote sensing. As biomass estimates at larger scales require remotely sensed data, new allometric relations are required using crown area and/or tree height as predictor of biomass, which can both be derived from remote sensing. Allometric equations were developed from 72 trees semi-randomly selected for destructive sampling in three 100?km2 sentry sites in western Kenya. The equations developed fit the data well with about 85?% of the observed variation in aboveground biomass explained by crown area. Addition of height and wood density as second predictor variables improved model fit by 6 and 2?% and lowered the relative error by 7 and 2?%, respectively. The equation with crown area in combination with height and wood density estimated representative aboveground biomass carbon to be about 20.8?±?0.02?t?C?ha?1; which is about 19?% more than the amount estimated using an allometry with diameter at breast height as predictor. These results form the basis for a new generation of allometries using crown area as a predictor of aboveground biomass in agricultural landscapes. Biomass predictions using crown area should be supported by height and wood density and the application of crown area equations for remote sensing based up-scaling should consider crown interactions with competing or coexisting neighboring trees. 相似文献
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Lack of availability, poor quality forages and cost of concentrate feeds, especially during the dry season, are some of the major problems faced by smallholder dairy producers in the tropics. Therefore, two experiments were conducted to evaluate the nutritive value and economic benefits of substituting cottonseed cake (CSC) by Gliricidia sepium (GS) for milk yield and composition of crossbred dairy cattle. In experiment one chemical composition of the two feeds and their dry matter degradability (DMD) were determined. GS had (P < 0.05) higher dry matter degradability (DMD) than CSC. Potential DM degradability (PDMD) and degradation rate constants (c) of CSC and GS did not vary (P > 0.05). In experiment two, four treatment diets, all based on Napier grass, maize bran, mineral/vitamin mixture and two levels each of GS and CSC, were fed to milk cows in a 4 × 4 Latin square experiment. The treatments were, T1 = 0 GS + CSC 18%, T2 = 18% GS + CSC, T3 = 23.4% GS + CSC and T4 = 39.7% GS + CSC. Cows on T1 and T3 showed (P < 0.05) higher total DMI, metabolizable energy intake (MEI) and milk yield than cows on T2 and T4. There were no differences (P > 0.05) in milk protein, butterfat and total solids contents between the treatments. Cost analyses showed diet T3 to be more profitable than the other treatments, suggesting that the use of GS in combination with CSC is more profitable than when either of the two was used alone.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
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A low cost field‐survey method for mapping seagrasses and their potential threats: an example from the northern Gulf of Aqaba,Red Sea 
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下载免费PDF全文 Gidon Winters Dor Edelist Rachamim Shem‐Tov Sven Beer Gil Rilov 《水产资源保护:海洋与淡水生态系统》2017,27(2):324-339
1. In the Gulf of Aqaba (GoA), coral reefs are considered the dominating ecosystem, while seagrass meadows, recognized worldwide as important ecosystems, have received little attention. Absence of comprehensive seagrass maps limits awareness, evaluations of associated ecosystem services, and implementation of conservation and management tools. 2. Presented here are the first detailed maps of seagrass meadows along the Israeli coast of the northern GoA. Mapping was performed by snorkelling along transects perpendicular to the shore above meadows growing at 15–25 m. Measurements along these transects included position, meadow depth and visual estimations of seagrass cover. Shallow boundaries of meadows, parallel to shore, were recorded by GPS tracking. Supplementary work included drop‐camera boat surveys to determine the position of the deeper edge of meadows. In addition, GIS layers were created that indicated shoreline infrastructures, near‐shore human activities and potential pollution threats. Ecosystem services of seagrass meadows mapped were valuated using a benefit transfer approach. 3. In total, 9.7 km of the 11 km shoreline were surveyed and 2830 data points collected. Seagrasses were growing along 7.5 km of the shoreline, with shallow (15–25 m) meadows found to cover an area of 707 000 m2 and valued at more than US$ 2 000 000 yr‐1 in associated ecosystem services. Pilot drop‐camera surveys (additional 283 data points) indicated that meadows can extend down to 50 m in some places. Coastal uses and threats varied in character and location. A municipality runoff point and drainage canal located close to the largest meadow were identified as the main threats to local seagrasses. 4. These low‐cost methods enhance our understanding of seagrass distribution in the northern GoA. They demonstrate a GIS‐based tool for assessing how environmental changes might affect the cover and state of seagrasses, improving efforts to conserve seagrass, and have particular relevance to seagrass mapping in developing countries and/or island nations. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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