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1.
为了探讨不同甜瓜种质资源叶部SPAD值分布,以210份甜瓜种质为试材,分析了甜瓜开花期和坐果期叶部SPAD值的变异。结果表明,开花期叶部SPAD值野生甜瓜最大,其次为厚皮甜瓜、薄皮甜瓜;坐果期厚皮甜瓜叶部SPAD值最大,叶部SPAD值基本符合正态分布,属于数量性状。开花期与坐果期叶部SPAD值之间均呈极显著相关,叶部SPAD值随着叶位升高而增加,中部叶位L14的叶部SPAD值最大,且变异系数最小,可作为甜瓜叶部SPAD值的测定叶位。基于种质的SPAD值、种质类型及来源,210份甜瓜种质可聚为4类,各类SPAD值分布范围出现一定差异。研究结果可为甜瓜种质资源的评价利用提供参考依据。  相似文献   
2.
荷兰人将中国茶带到美洲殖民地,英国人将饮茶习惯普及。独立后的美国迫切展开与中国直接贸易,1784年“中国皇后号”的首航标志着中美贸易的开端。从首次贸易到鸦片战争时期,茶叶始终占据了中美贸易的核心商品地位,且在美国对华贸易商品中所占比例整体呈稳步增长趋势。美国对茶叶的消费需求、经济发展的需要以及华商对美商提供的有利的交易方式等因素促进了中美茶叶贸易的发展,茶叶贸易也给美国早期的发展带来了重大的影响。  相似文献   
3.
The importance of soil aggregation in determining the dynamics of soil organic carbon (SOC) during erosion, transportation and deposition is poorly understood. Particularly, we do not know how aggregation contributes to the often-observed accumulation of SOC at depositional sites. Our objective was to assess how aggregation affects SOC stabilization in comparison to interactions of SOC with minerals. We determined and compared aggregate size distributions, SOC distribution in density fractions, and lignin-derived phenols from aggregated soil samples at both eroding and depositional sites. The stabilization effect of aggregation was quantified by comparing mineralization from intact and crushed macro-aggregates. Deposition of eroded soil material resulted in carbon (C) enrichment throughout the soil profile. Both macro-aggregate associated SOC and C associated with minerals (heavy fraction) increased in their importance from the eroding to the depositional site. In the uppermost topsoil (0–5 cm), SOC mineralization from intact aggregates was larger at the depositional site than at the eroding site, reflecting the large input of labile organic matter (plant residues) promoting aggregation. Contrastingly, in the subsoil, mineralization rates were lower at the depositional site because of effective stabilization by interactions with soil minerals. Aggregate crushing increased SOC mineralization by 10–80% at the eroding site, but not at the depositional site. The content of lignin-derived phenols did not differ between eroding and depositional sites in the topsoil (24.6–30.9 mg per g C) but was larger in the subsoil of the eroding site, which was accompanied by higher lignin oxidation. Lignin data indicated minor effects of soil erosion and deposition on the composition of SOC. We conclude that SOC is better protected in aggregates at the eroding than at the depositional site. During transport disaggregation and consequently SOC mineralization took place, while at the depositional site re-aggregation occurred mainly in the form of macro-aggregates. However, this macro-aggregation did not result in a direct stabilization of SOC. We propose that the occlusion of C inside aggregates serves as a pathway for the eroded C to be later stabilized by organo-mineral interaction.  相似文献   
4.
金沙江干热河谷区冲沟侵蚀极为发育,形成大量侵蚀劣地,对该区域侵蚀劣地不同坡位草被生长特征和土壤水分状况进行了调查分析。结果表明,1)侵蚀劣地不同坡位草被生长差异较大,草被盖度和地上生物量大小均表现为:坡上部坡中部坡下部,且坡下部与坡上部和坡中部之间草被生长状况存在极显著差异(P0.01);2)同等降雨状况下,不同坡位土壤水分含量随时间延长均呈现指数递减趋势,但其衰减速率不同,导致土壤水分含量存在差异,衰减速率表现为:坡上部坡中部坡下部,土壤水分含量表现为相反顺序;3)监测时段内土壤水分(土壤平均含水量和末次土壤含水量)与草被覆盖度和生物量之间均呈现极显著正相关关系(P0.01),说明侵蚀劣地不同坡位下土壤水分差异是决定草被生长差异的关键因素。  相似文献   
5.
以往生产中只能凭直观或用外圆打表测量方法来确定变形轴中心孔最佳位置,这既不方便又不准确.经分析与计算,得出变形轴中心孔最佳位置为0.35L.  相似文献   
6.
Variation of infiltration rates with landscape position influences the amount, distribution, and routing of overland flow. Knowledge of runoff patterns gives land managers the opportunity to affect changes that optimize water use efficiency and reduce the risk of water quality impacts. The objective of this study was to assess the effect of landscape position and associated soil properties on infiltration in a small (147 ha) forest/pasture watershed in the Ozark Highlands. Three previously reported studies measured infiltration rates using double ring, sprinkling, single ring, and tension infiltrometers on soils at varying landscape positions. Although large variation in infiltration rates was observed among measurement techniques, upland and side slope soils (Nixa and Clarksville) had consistently lower infiltration rates compared to the soil in the valley bottom (Razort). A conceptual understanding of watershed runoff is developed from these data that includes infiltration excess runoff from the Nixa and Clarksville soils and saturation excess runoff on the Razort soil. Management of the soil water regime based on this understanding would focus on increasing infiltration in upland soils and maintaining the Razort soil areas in forest. Forest productivity would be enhanced by increasing plant-available water in upland soils and decreasing flooding on the Razort soil. Surface water quality would be improved by reducing the transport of potential water contaminants from animal manure applied to upland pastures.  相似文献   
7.
Leaf-fall phenology was studied in a cool–temperate deciduous broad-leaved forest in central Japan in relation to the topographic environmental gradients that occur along a short mountain slope. Leaf-fall phenology was described quantitatively using data from leaf litter collected along the slope. In autumn, leaf fall at the study site tended to occur slightly earlier on the upper slope than on the lower slope. This pattern was found at both the stand and the species levels. Our results suggest that leaf-fall phenology may be affected by difference in microclimatic conditions, because environmental conditions are thought to be more severe on the upper slope than on the lower slope. The less intensive methods used in this study, the litter trap method, and Dixon’s model succeeded in quantifying the phenological patterns of leaf fall within stands and within species along the short mountain slope.  相似文献   
8.
卷荚相思在福建五台山林场的生长表现   总被引:3,自引:0,他引:3  
在五台山林场引种卷荚相思3年试验结果表明,卷荚相思能适应林场的立地和气候条件,生长快且好,胸径和树高年生长量分别为3 cm,2.5 m;不同坡向,坡位,立地条件下卷荚相思生长差异显著,试验结果表明,五台山地区比较适合种植卷荚相思,尽管在冬季有严重的霜冻,但试验林未出现严重寒害。  相似文献   
9.
随着全国野生动植物保护和自然保护区建设工程的实施 ,自然保护区在我省生态环境建设中的地位与作用越来越重要 ,运用生物多样性管护区的理论指导我省的自然保护区建设将是正确认识自然保护区地位与作用的关键所在。  相似文献   
10.
以温州蜜柑为中间砧,对高林温州蜜柑、太田椪柑进行不同部位高接的适宜性研究.结果表明,不同部位高接对成活率的影响无显著性差异,但树冠的恢复程度与嫁接部位的高低成正比,即高接部位越高,树冠恢复越快;含糖量和糖酸比以腹接最高,侧枝次之;外观以腹接、侧枝高接为好,副主枝高接次之,主枝高接最差.柑桔高接最高高度应控制在1.0 ~ 1.3m,早投产,树冠恢复快,果实品质好,以侧枝高接,腹接为好,侧枝高接易引起内膛空虚,可采取内膛腹接弥补.  相似文献   
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