Landscape Ecology - Landscape resistance surfaces are often used to address questions related to movement, dispersal, or population connectivity. However, modeling landscape resistance is... 相似文献
Grazing livestock has strong impact on global nitrous oxide (N2O) emissions by providing N sources through excreta. The scarcity of information on factors influencing N2O emissions from sheep excreta in subtropical ecosystems such as those of Southern Brazil led us to conduct field trials in three different winter pasture seasons on an integrated crop–livestock system (ICL) in order to assess N2O emission factors (EF-N2O) in response to variable rates of urine and dung.
Materials and methods
The equivalent urine-N loading rates for the three winter seasons (2009, 2010, and 2013) ranged from 96 to 478 kg ha?1, and the dung-N rates applied in 2009 and 2010 were 81 and 76 kg ha?1, respectively. Air was sampled from closed static chambers (0.20 m in diameter) for approximately 40 days after excreta application and analyzed for N2O by gas chromatography.
Results and discussion
Soil N2O-N fluxes spanned the ranges 4 to 353 μg m?2 h?1 in 2009, ??47 to 976 μg m?2 h?1 in 2010, and 46 to 339 μg m?2 h?1 in 2013. Urine addition resulted in N2O-N peaks within for up to 20–30 days after application in the 3 years, and the strength of the peaks was linearly related to the N rate used. Emission factors of N2O (EF-N2O, % of N applied that is emitted as N2O) of urine ranged from 0.06 to 0.34% and were essentially independent of N rate applied. By considering a ratio of N excreted by urine and dung of 60:40, a single combined excretal EF-N2O of 0.14% was estimated.
Conclusions
Our findings showed higher mean EF-N2O for sheep urine than that for dung (0.21% vs 0.03%), irrespective of the occurrence or not of urine patches overlap. This value is much lower than default value of 1% of IPCC’s Tier 1 and reinforces the needs of its revision.
The aim was to evaluate the effect of different concentrations of caffeine added in activating solution over sperm motility in fresh and thawed semen of pacu, Piaractus mesopotamicus, and curimba, Prochilodus lineatus. The activating solutions were prepared with sodium bicarbonate solution of 0.76% (NaHCO3) and caffeine was added at concentrations of 2.5, 5.0, 10.0, and 20.0 mM. As control, a solution of NaHCO3 0.76 without caffeine was used. Eight males of pacu and 20 males of curimba were used. Aliquots of 200 μL of semen were diluted in 800 μL extender solution (DMSO 10% and BTS 5%), placed in 0.5 mL straws and cryopreserved for 7 d in a liquid nitrogen tank. There was a linear increase in sperm motility for fresh semen of pacu, and for curimba fresh and thawed semen (P < 0.05), due to the increase in the concentration of caffeine. There was a quadratic response for duration of motility for thawed semen of pacu and for fresh semen of curimba (P < 0.05), respectively. These results indicate that addition of caffeine in the activator solution can improve sperm motility parameters, however, is dependent on the species and concentration used. 相似文献
The aqueous extract of Hyptis suaveolens leaves was studied for their antinociceptive property in chemical and thermal models of nociception in mice. Oral administration of the aqueous extract (100, 200, and 400 mg/kg) dose-dependently reduced the number of writhings induced by acetic acid, decreased the licking activity of the early phase in formalin test and increased the reaction time in hot-plate test. The antinociceptive effect was significantly antagonized by naloxone (3 mg/kg; i.p.). Preliminary acute toxicity study showed that no animal death with doses up to 5 g/kg (p.o.). 相似文献
Seven species of Solanum were screened for their molluscicidal properties against Biomphalaria glabrata, the intermediated host of Schistosoma mansoni, Solanum agrarium, S. jabrense, S. melissarum, S. megalonyx, S. paludosum, S. paraibanum and S. stipulaceum. Four extracts showed molluscicidal activity with LC(50) from 22 to 56 microg/ml. 相似文献
In non-anesthetized normotensive rats, Hyptis fruticosa essential oil (HFEO, 5, 10, 20 and 40 mg/kg; i.v.) induced hypotension associated with tachycardia. In intact and isolated rings of rat superior mesenteric artery (control), HFEO (1-1000 microg/ml, n=6, cumulatively) induced concentration-dependent relaxations of tonus induced by 10 microM phenylephrine (Phe) (pD(2)=2.6+/-0.27; E(max)=64+/-8.3%). In denuded endothelium pre-contracted rings with Phe or K(+)-depolarizing solution (80 mM), the concentration-response curves to HFEO were not shifted (pD(2)=2.3+/-0.25 and 2.3+/-0.28, respectively), but their maximal responses were significantly (P<0.05 vs control) increased (E(max)=122.3+/-18.2% and 92+/-3.6%, respectively). HFEO was also capable of antagonizing the concentration-response curves to CaCl(2) (3 microM-30 mM) in a dose-dependent manner. 相似文献
The layout of 32 permanent plots in the most important cork production regions of Portugal and the measurement of the most
representative tree parameters were performed for statistically sound cork weight modelling. The establishment of cork weight
equations is presented for the different cork oak study areas considered alone or grouped according to the most representative
tree parameters. For the presented cork weight models was chosen independent variable the total stripping surface (artmax). For the selection criteria five statistic were used, including PRESS, APRESS and Mallows's statistic. The crossvalidation
of the best classified models was performed and to discuss the importance of the “study area” factor, a regression analysis
with “dummy” variables was performed. 相似文献
Soybean rust is caused by an obligate parasite (Phakopsora pachyrhizi) which has spread in Brazil in each new season since 2001 and, despite the efforts to control the disease, losses have occurred
every year. Its control demands several tactics amongst which chemical control with fungicides is the main method and remains
indispensable. Control strategies such as the use of cultivars with partial resistance are desirable, but are not yet commercially
available. The present study analyzed the existing differences in the reactions of short, medium and long cycle soybean cultivars
against Asian rust and their responses to fungicide sprays. The experiment was conducted at Uberlandia-MG, Brazil, under field
conditions from December 2007 to May 2008, in the Syngenta Seeds Experimental Station. The high pressure of the disease in
the experiment simulated the natural pressure that the disease often reaches in Brazil. The studied variables were: visual
severity (percentage of infected leaf area), percentage defoliation and productivity (kg ha−1). Disease severity was expressed as AUDPC (area under disease progress curve). Variance analysis and comparison of means
by the Tukey test (5% significance) were done for all variables studied. Significant differences were observed between cultivar
effects and chemical control programs. The results obtained here indicate that the cultivars M-Soy 8199RR and Emgopa 315RR
were less susceptible to disease, and that a control program termed “monitoring” (in which the appearance of new pustules
of the pathogen were monitored to make the decision at each fungicide spray) was the most effective. 相似文献