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1.
马茹 《山西水土保持科技》2010,(3):30-31
保护天然林,对于生态脆弱的山西来讲,是扭转生态环境恶化的重要措施,是控制水土流失、涵养水源的有效途径,是保护生物多样性的重大举措。以大同市为例,论述了林权制度改革对天然林生态质量的影响。根据林改实际,从政策调控、加强管理、金融支持、宣传教育等方面提出了建议。 相似文献
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J. Guretzky M. Kering J. Mosali E. Funderburg J. Biermacher 《Journal of plant nutrition》2013,36(12):1819-1834
Our objectives were to document effects of nitrogen (N), phosphorus (P), and potassium (K) fertilizer rates on forage yields and uptake of N, P, and K by Midland bermudagrass [Cynodon dactylon (L.) Pers.] on a Minco fine, sandy loam in southern Oklahoma. After six years of this long-term experiment, forage yield responses to fertilization were mixed and depended on year. Stability analysis indicated forage yields responded positively to N fertilization during favorable weather conditions but negatively during poor weather conditions. Application of 112 kg N ha?1 provided the best yield stability and mean annual forage yield among treatments, 11.5 Mg ha?1, across years. In years with near-average weather conditions, uptake of N, P, and K increased linearly with N application rate. Limited water holding capacity of the soil and high soil P and K may have contributed to the limited yield responses to fertilization in this semi-arid environment. 相似文献
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Evaluation of carbon sequestration and thinning regimes within the optimization framework for forest stand management 总被引：2，自引：0，他引：2
Due to the urgent demand for thinning in planted forests and the tend towards sustainable forest resource management, the
forest stand age class eligible for the thinning subsidy in Japan was expanded during the period from 2000 to 2004. Currently,
further expansion is under consideration in line with meeting the Kyoto Protocol target of carbon sequestration. In this paper,
we conducted evaluation analyses of carbon sequestration and subsidy effects within the optimization framework for the forest
stand management. The optimal forest stand management model called Dynamic Programming model for Kyushu Stand Simulator (DP-KYSS)
was utilized for the analysis of the target sugi (Cryptomeria japonia) forest stand in the Kyushu region, Japan. Our results showed that the thinning subsidy was effective to stimulate thinning
activities at the eligible age class for the subsidy, and that 20% of the current or proposed payment was appropriate to give
an incentive to forest owners for conducting the same optimal thinning regime. The amount of carbon sequestered in remaining
trees at final harvest was not always shown to increase over time. Depending upon the subsidy condition, it could decrease.
The average annual amount of carbon sequestered under no subsidy showed its maximum at age 35, while under the other subsidy
conditions, it was shortened to age 25. The net present value of cost per unit carbon loss associated with subsidy became
the highest for the rotation age of 35 years for all subsidy policies considered here. 相似文献
4.
Tree growing by smallholder farmers is an emerging livelihood strategy in Lake Tana catchment. The objectives of this study were to (1) identify the most important tree species grown, (2) investigate the drivers of the existing pattern, and (3) identify determinants of the number and diversity of tree species and their spatial patterns. Survey data were collected from 200 households. Multiple linear regression was employed to identify the determinants of tree growing behaviour of households and spatial variables affecting the abundance of tree species. Eucalyptus globulus, Acacia decurrens and E. camaldulensis dominate woodlots. Only a fraction of the forest production is used by the households, the rest being sold as poles or charcoal. Location in relation to market centres, number of livestock owned, landholding size and age of household head were found to positively affected the number of tree species and trees grown. Gender affected the species and spatial pattern of trees. Woodlots, farm boundaries and homesteads were found to be important tree growing niches. These results substantiate the proposition that farmers assign their parcels of land to uses that increase the rent value of the land, and this value is affected by access to roads. Woodlots are on the increase at the cost of productive agricultural land. Provision of a tree planting extension service may increase participation of farmers in tree planting, and a management-oriented tree planting extension service may give desirable results. 相似文献
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? Context
The current paradigms for the sustainable development of forests and agriculture involve territorial organization of these activities as well as the multifunctionality of the related landscapes. Accordingly, the new management strategies need to take into account the suitability of the resulting landscapes to produce the goods and services expected by society.? Aims
The aim of the study was to assess the preferred landscape patterns by different groups of users. In focus were the relations between the landscape metrics of preferred patterns and the individual characteristics of respondents.? Methods
A regional quantitative survey of both production and different consumption landscape users was conducted in the Alentejo region, southern Portugal. Respondents composed their preferred patterns on a block diagram representing an area of landscape seen from a single view according to the existing topographic conditions in the study area.? Results
In general, the visually complex landscape patterns were preferred more than the homogeneous ones. However, the metrics of preferred patterns varied between the user groups. The montado was the only land cover class that was present in the majority of preferred patterns.? Conclusion
For landscape users in southern Portugal, the visually complex landscapes including the montado are essential to satisfy their expectations. This may be an important fact to be taken into account for policy and landscape management in the future. 相似文献6.
Crop loss due to plant pathogens has provoked renewed interest in bacteriophages as a feasible biocontrol strategy of plant diseases. Phage cocktails in particular present a viable option for broadening the phage host range, limiting the emergence of bacterial resistance while maintaining the lytic activity of the phages. It is therefore important that the design used to formulate a phage cocktail should result in the most effective cocktail against the pathogen. It is also critical that certain factors are considered during the formulation and application of a phage cocktail: their stability, the production time and cost of complex cocktails, the potential impact on untargeted bacteria, the timing of phage application, and the persistence in the plant environment. Continuous monitoring is required to ensure that the efficacy of a cocktail is sustained due to the dynamic nature of phages. Although phage cocktails are considered as a plausible biocontrol strategy of phytobacteria, more research needs to be done to understand the complex interaction between phages and bacteria in the plant environment, and to overcome the technical obstacles. © 2019 Society of Chemical Industry 相似文献
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Kindu Mekonnen Roland J. Buresh Richard Coe Kering Maru Kipleting 《Agroforestry Systems》1998,42(3):265-282
Measurements of root and nutrient distributions in agroforestry systems have often been obtained from unreplicated plots.
We, therefore, measured the vertical and horizontal distribution of root length and soil nitrate in replicated plots of sesbania
[Sesbania sesban (L.) Merr.] to assess plot-to-plot variation and identify appropriate sampling schemes. Sampling was on profile
walls exposed from pits at two on-farm sites (Ochinga and Muange) in Kenya. At Ochinga, soil was sampled at 27 0.15-m depth
intervals and eight 0.15-m-wide locations perpendicular to 2.25-m-wide rows of 19-month-old sesbania. At Muange, sampling
was 18 months after establishment of sesbania from seedlings with a 1 m by 1 m spacing. Soil was sampled at 17 0.15-m depth
intervals and nine 0.15-m-wide sampling locations – one exactly below the tree and four each on opposite sides of the tree.
Root length density generally decreased with distance from sesbania and with soil depth. Soil nitrate, however, followed different
trends in the four replications at Ochinga and the three replications at Muange. At Ochinga, nitrate above 2.5-m depth clearly
increased with distance from the tree in two replications but followed no distinct trend in another replication. At Muange,
nitrate above 1.2-m depth decreased with distance from the tree in one replication, increased with distance from the tree
in another replication and followed no clear trend in another replication. The suitability of various sampling schemes for
measuring root length and nitrate was accessed from percent bias between measured values at sampling locations in the scheme
and actual values for an entire transect of sampling locations. Bias associated with selection of sampling locations tended
to be higher within the 2.25-m-wide sesbania rows than the 1 m by 1 m sesbania spacing. Soil sampling in systems with rows
of young trees should be at several locations along a transect perpendicular to tree rows in order to minimize bias.
This revised version was published online in June 2006 with corrections to the Cover Date.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
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Five polymeric black tea polyphenol fractions (PBP-1-5) were isolated from a popular brand of black tea. The effect of these PBPs and epigallocatechin gallate (EGCG), a major green tea polyphenol, was studied on the formation of [(3)H]-B(a)P-derived DNA adducts in vitro, employing rat liver microsomes. PBP-1-3 inhibited microsome-catalyzed [(3)H]-B(a)P-derived DNA adduct formation in vitro in a dose-dependent manner. This inhibition was further enhanced on preincubation of microsomes with each of the PBPs. PBP-4 was not effective per se and required preincubation with microsomes to exhibit its inhibitory effect, whereas PBP-5 remained ineffective with or without preincubation with microsomes. Further investigations revealed that the observed decrease in [(3)H]-B(a)P-DNA adduct formation was due to inhibition of isozymes of CYP450s by PBPs. Overall, results suggest that polymeric black tea polyphenol fractions retain one of the chemopreventive effects exhibited by the monomeric green tea polyphenol EGCG in vitro. 相似文献