共查询到10条相似文献，搜索用时 46 毫秒
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We present a new approach for selecting seed sources of Eucalyptus to be grown on saline land. We evaluated our method using 22 seed sources, 11 tree-form species and 11 mallee-form species.
We found that the commonly used strategy of selecting seed sources on the basis of average productivity was inappropriate,
as average productivity was poorly correlated with the relationship between productivity and salinity that was actually observed.
Using our new approach, we categorized seed sources as salt-sensitive or salt-tolerant based on the strength of the observed
relationship between salinity and productivity. Seed sources defined as sensitive were associated with relatively large (−24.8
to −64.2%) productivity losses, while the changes in productivity for tolerant seed sources ranged from −17.1 to 10.5%. On
average, reductions in height due to increased salinity were about 30% greater for sensitive seed sources than tolerant ones,
although the effect was smaller for mallee-form and greater for tree-form seed sources. The difference between sensitive and
tolerant seed sources was similar after 1, 2 and 4 years of growth. 相似文献
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王珊子 《绿色中国(A版)》2006,(15):66-68
“民以食为天”,“人命关天”,这两句古话阐明了食品安全无以复加的重要性。实际上,食品安全的重要性还远不止于此,这个问题不仅关系到人的健康和生命,而且关系到经济发展、社会稳定,乃至公民对整个社会和政府的信心。 相似文献
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王珊子 《绿色中国(综合版)》2006,(8):66-68
“民以食为天”，“人命关天”，这两句古话阐明了食品安全无以复加的重要性。实际上，食品安全的重要性还远不止于此，这个问题不仅关系到人的健康和生命，而且关系到经济发展、社会稳定，乃至公民对整个社会和政府的信心。[编者按] 相似文献
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《Journal of Sustainable Forestry》2013,32(3-4):307-316
Concerns for maintaining biodiversity have led to the adoption of ecosystem management as the paradigm for federal land management. This approach will identify desired future conditions as the goal for management, based on ecological objectives for a given landscape. Some management efforts attempt to identify desired future conditions based on existing successional stages as defined by a classification of overstory vegetation types. Such an approach ignores most of the underlying ecological parameters of the landscape, and is inadequate for identifying past disturbance regimes and future successional pathways. An assessment of desired future conditions based on an ecological classification system is essential to overcome these inadequacies. The strategy proposed in this paper uses an appropriate ecological land classification, based on either ecological land types or habitat types, included in a broader hierarchical classification system. It also uses a vegetation map of existing overstory vegetation. These two maps are overlaid to generate polygons of ecological units that can then be used to create an ecosystem diversity matrix. Each polygon (stand) can be evaluated as to its composition and structure relative to its possible placement within the ecosystem diversity matrix through comparisons with historical ranges of variability. The overall ecosystem diversity matrix can then be examined in terms of the distribution of successional stages within each habitat type or ecological land type. The goal should be to maintain at least adequate ecological representation of all successional stages within each habitat type that occurred historically, based on past disturbance regimes. Adequate ecological representation is defined as sufficient size and distribution of inherent ecosystems to maintain viable populations of all endemic species dependent on these ecosystems. This approach can maintain and enhance regional biodiversity, but also maintain flexibility in land management options. 相似文献
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12个桃品种的花芽休眠需冷量和开花需热量 总被引：3，自引：0，他引：3
在浙西南地区研究12个桃品种花芽休眠需冷量和开花需热量生态指标.犹他模型测定结果显示:12个桃品种中,花芽休眠需冷量低的品种为春蜜、超红、中油11号、中油7号、中油4号,约为550～650 cu;其次是丽油5号、仓方早生、燕红、丽油3号、早凤凰,约为650～ 800 cu;需冷量高的品种为新川中岛和赤月,约为900～ 950cu.同一地区不同品种需热量差异较大,同一品种年际间差异相对较小.以生长度天模型试验结果表明:开花需热量低的品种为赤月和丽油3号,大约400 ～ 500 d·℃;其次是新川中岛,大约500～600 d·℃;春蜜、丽油5号、早凤凰、中油4号、中油7号、仓方早生和燕红大约600 ～ 700 d·℃;需热量较高的是中油11号和超红,约为700～800 d·℃.12个桃品种花芽休眠需冷量与开花需热量之间呈乘幂函数曲线显著负相关. 相似文献
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Summary Effects of moisture content on bending strength and section capacity have been studied assuming that strength properties are linearly related to moisture content below the fiber saturation point. The models developed using the linear strength vs. moisture content relationships are compared with quadratic models developed earlier. The linear representation of strength variation with moisture content leads to predicted member bending capacity relationships which show that increases in member bending strength with moisture content will compensate for section property decreases at all bending strength property levels. Comparisons of bending strength and bending capacity models show that the two modelling approaches lead to similar predicted member performance. Simplified procedures are provided for adjusting member bending strength for moisture content which are suitable for materials properties codes or standards. 相似文献