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1.
Wild pigs are a free-ranging invasive species capable of inflicting significant damage on rural property. Wildlife management personnel may benefit from understanding the negative societal impact of wild pigs. A statewide mail survey of randomly selected landowners was conducted in rural Tennessee counties known to have wild pigs. The economic value of damage caused by wild pigs in 2015 in these counties was estimated at $26.22 million, whereas the cost incurred in control and eradication was $2.09 million. Input-output modeling of damage in these counties on the state’s economy showed $32.8 million in lost industrial output, $4.6 million in lost labor income, and 332 jobs or job equivalents affected. Findings are useful in understanding the types of damage, and the extent of these impacts on the rural economy. They could also facilitate comparing the expected benefit with the cost of control programs in Tennessee and comparable areas facing similar invasions from wild pigs.  相似文献   
2.
We studied variations in water relations and drought response in five Himalayan tree species (Schima wallichii (DC.) Korth. (chilaune) and Castanopsis indica (Roxb.) Miq. (dhale katus) at an elevation of 1400 m, Quercus lanata Smith (banjh) and Rhododendron arboreum Smith (lali gurans) at 2020 m, and Quercus semecarpifolia Smith (khasru) at 2130 m) at Phulchowki Hill, Kathmandu, Nepal. Soil water potential at 15 (Psi(s15)) and 30 cm (Psi(s30)) depths, tree water potential at predawn (Psi(pd)) and midday (Psi(md)), and leaf conductance during the morning (g(wAM)) and afternoon (g(wPM)) were observed from December 1998 to April 2001, except during the monsoon months. There was significant variation among sites, species and months in Psi(pd), Psi(md), g(wAM) and g(wPM), and among months for all species for Psi(s15). Mean Psi(pd) and Psi(md) were lowest in Q. semecarpifolia (-0.40 and -1.18 MPa, respectively) and highest in S. wallichii (-0.20 and -0.63 MPa, respectively). The minimum Psi value for all species (-0.70 to -1.79 MPa) was observed in March 1999, after 4 months of unusually low rainfall. Some patterns of Psi(pd) were related to phenology and leaf damage. During leafing, Psi(pd) often increased. Mean g(wAM) and g(wPM) were highest in Q. semecarpifolia (172 and 190 mmol m(-2) s(-1), respectively) and lowest in C. indica (78 and 74 mmol m(-2) s(-1), respectively). Soil water potential (Psi) at 15 cm depth correlated with plant Psi in all species, but rarely with g(wAM) and not with g(wPM). Plant Psi declined with increasing elevation, whereas g(w) increased. As Psi(pd) declined, so did maximal g(w), but overall, g(w) was correlated with Psi(pd) only for R. arboreum. Schima wallichii maintained high Psi, with low stomatal conductance, as did Castanopsis indica, except that C. indica had low Psi during dry months. Rhododendron arboreum maintained high Psi(pd) and g(w), despite low soil Psi. Quercus lanata had low g(w) and low Psi(pd) in some months, but showed no correlation between tree Psi and g(w). Quercus semecarpifolia, which grows at the highest elevation, had low soil and plant Psi and high g(w).  相似文献   
3.
从果树种植到果品消费,果树生理代谢紊乱现象均有发生,即使采取科学合理的培养方法也频繁发生.生物因素并非诱导代谢紊乱发生的主要因素,而非生物因素如光、温度、水和果实生长期不适宜的气候条件、运输条件和贮藏条件是其主要诱因,不科学的果园管理也会引起紊乱病变.另外,某些果树种类较容易发生某种代谢紊乱.  相似文献   
4.
Francisella orientalis is a highly virulent, emerging bacterium that causes mass mortalities in tilapia. This pathogen also affects numerous other warm-water fish species, including three-line grunt, hybrid striped bass and various ornamental fish. This study sheds light on two new species of fish that are susceptible to F. orientalis. Asian seabass and largemouth bass showed variable levels of susceptibility in a bacterial challenge experiment. After intraperitoneally injected with a dose of 106 CFU/fish, a total of 64.28% and 21.42% mortalities were obtained in Asian seabass and largemouth bass, respectively. Meanwhile, Nile tilapia showed acute mortality of 100%. All fish showed typical lesions of francisellosis, including multifocal granulomas in the spleen and head kidney. Immunohistochemical analysis revealed strong positive signals inside the granulomas of all fish. The bacterial recovery in solid media from infected fish was highest in Nile tilapia (85.71%), followed by Asian seabass (35.71%) and largemouth bass (21.42%). PCR results tested 100% positive for Nile tilapia, and 78.57% and 21.42% for Asian seabass and largemouth bass, respectively. In conclusion, Asian seabass and largemouth bass are susceptible to this pathogen, which warrants new management strategies when employing predation polyculture systems of these species with tilapia.  相似文献   
5.
Prescribed burning is a widely used tool in forest and grassland management. However, because fire that escapes from a prescribed burn accidentally may cause property damage, injuries, and even human casualties, purchasing insurance to cover such damages may be beneficial for prescribed burn practitioners. Given that insurance coverage for prescribed fire is recently emerging, factors that determine burners’ decisions to purchase such insurance are largely unknown. On the basis of data from a survey of prescribed burn practitioners in 14 southern and midwestern states, we modeled prescribed burners’ likelihood of purchasing insurance with respect to demographic characteristics, land management objectives, and importance placed on regulatory compliance and land use practices. Results suggest that prescribed burn practitioners are more likely to obtain such insurance if they are landowners themselves or have a written prescribed burn plan. Age of respondents and the level of importance they place on compliance with environmental laws also had a significant positive effect on the likelihood of obtaining insurance coverage. Respondents were less likely to purchase insurance if their land management objective was to control invasive plants or they considered the availability of lower-cost alternatives for woody plant removal an important factor in deciding whether or not to conduct prescribed burns. These findings shed light on underlying factors influencing insurance coverage for prescribed burning and are potentially beneficial for promoting the acquisition of insurance among burn practitioners.  相似文献   
6.
Yali is one of the best pear cultivars cultivated extensively in China and other countries. However, mortality rates of explants during the initial phase of tissue culture were found to be very high during the summer particularly from the shoot tip explants. A thorough investigation on the browning problem of Yali Aikansui and Abbe Fetel pears was done and their control measures are suggested in this paper. Emphasis has been given to the Yali pear. Shoot explants were collected from the field as well as from the plantlets grown in vitro during different months and observed for browning. The explants were excised and cultured in Murashige and Skoog (MS) solid and liquid medium as needed. The cultures were maintained in the dark as well as in a 16/8 hours light/dark photoperiod regime as needed and were kept in a growth room at (25±2)°C temperature. According to the experimental results, Yali was found more severely infected by browning than the other two cultivars. Similarly, it was also found that, the intensity of browning was less during spring and increased with time and reached the maximum during summer. Shoot tips of Yali were found more severely infected by browning than the second node and other nodes. This accelerated the mortality rate up to 81% of shoot explants during the summer months of July and August. Browning was greatly influenced by water-soluble polyphenols, more of which were found in the shoot tip of explants collected from the field (significantly higher at P ⩽ 0.05 and P ⩽ 0.01). Total polyphenol contents were found less in the explants from plantlets grown in vitro, and less browning of medium appeared resulting in a lower mortality rate of explants. Collections of explants during early spring (P ⩽ 0.05 and P ⩽ 0.01) and use of other nodes rather shoot tip because explants (P ⩽ 0.05 and P ⩽ 0.01) were found to be better in preventing the browning problem. Finally, for curative measures to control browning, use of ascorbic acid at the rate of 100 mg·L−1 (P ⩽ 0.05 and P ⩽ 0.01), 0.02%polyvinyl pyrrolidone (PVP) in the culture medium (P ⩽ 0.05), 96 hours dark treatment of other nodes (P ⩽ 0.05), and 12 hours cold treatments of explants at 4°C (P ⩽ 0.05 and P ⩽ 0.01) prior to sterilization of explants, were found to be the best methods to control browning and therefore to increase the survival rate of cultured explants of the Yali pear.  相似文献   
7.
The effects of regulators on the respiratory enzymes of Qiyuesu’s pear branches during dormant period were studied. The results showed that enzyme activities of SDH, G-6-PDH and 6-PGDH were increased by 0.02 mmol/L SA and 120 mg/L GA3. The enzyme activities of phosphohexoisomerase were reduced by 0.02 mmol/L SA and 120 mg/L GA3. Compared with the control, the PGI activity was reduced by 20.5% and 13.6% using 0.02mmol/L SA and 120mg/L GA3. Similarly, the SDH activity was increased by 6.1% and 29.2%, respectively. Likewise, the activity of G-6-PDH and 6-PGDH was increased by 93.9% and 24.8%. Changes of respiratory enzymes were consistent with respiratory pathway of regulators, which indicated that SA and GA3 were helpful to break the dormancy by enhancing activities of SDH, G-6-PDH and 6-PGDH.  相似文献   
8.
The effects of growth regulators on the respiration metabolism of pear buds during dormant period were studied in this experiment. The results showed that, during early dormant period, the respiration intensity of pear buds was infirm and increased slowly. As the weather became very cold, the respiration intensity rapidly declined, and after that it changed a little. In the later stage of dormant period, the respiration intensity rose rapidly. The maximum value appeared on January 4th, at 0.390 mo1 O2·g−1 FW·min−1, but thereafter declined to its original level. Under natural conditions, three respiratory pathways showed different changes. Pentose phosphate pathway might be the main reason for dormancy release in pear buds. The exogenous gibberellins were more efficient than salicylic acid in increasing the respiration rate. The exogenous SA appeared to play a more important role than exogenous GA3 in phosphopentose pathway. The effect of gibberellins would be more effective than SA in tricarboxylic acid cycle (TCA). The respiration rate of glycolysis was not affected by gibberellins and salicylic acid.  相似文献   
9.
This study examined the effect of natural resource amenities on human life expectancy. Extending the existing model of the life expectancy production function, and correcting for spatial dependence, we evaluated the determinants of life expectancy using county level data. Results indicate that after controlling for socio-demographic and economic factors, medical facilities and risk factors, counties with natural amenities such as high proportion of land in forests, farmland, rangeland and water bodies, as well as mild climate such as longer sunlight hours during winter and cooler year around temperature exhibited longer life expectancies at birth. In addition, counties containing state parks and outdoor recreation facilities, and those located near federal wilderness parks were associated with the longer expectancies at birth. Findings from this study have several implications for natural resource economics and management, public health, and human development. An important message of our findings is that the traditional approach of public health should be extended beyond just controlling diseases or treating patients to a more comprehensive approach that also acknowledges the preservation and utilization of natural resources, environmental amenities, and outdoor recreation opportunities in maintaining public health, quality of life, and overall human development.  相似文献   
10.
This study evaluates how urban residents value variety, spatial configuration, and patterns of open space in their neighborhoods. Quantitative matrices that were borrowed from landscape ecology were first used to measure the variety and spatial arrangement of open space plots and landuses around houses. Amenity values of those measures were then evaluated in a hedonic regression that was corrected for identification problem caused by the endogeneity of landuse variables. Empirical estimates from this research reveal that urban residents positively valued the varieties of open space but negatively valued the diversity within developed land uses in their neighborhoods. Similarly, open space plots with square shape and smooth, straight edges were preferred to those with more complex shapes and irregular edges. Further, residents preferred open spaces in few larger plots to many smaller pieces that are scattered throughout the neighborhood. Findings from this study will be useful in enhancing the quality and amenity value of open spaces and conceivably increase local property tax base.  相似文献   
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