排序方式： 共有34条查询结果，搜索用时 15 毫秒
11.
云杉种源苗期性状变异及种源选择初步研究 总被引：8，自引：0，他引：8
以7年生云杉苗为试材,对17个种源的10个生长性状进行测定,并对种源间生长性状的变异、种源地理变异模式、种源区划和种源苗期选择进行统计分析.结果表明:地径、苗高、当年高、一级侧枝数量、二级侧枝数量、最大侧根粗度、地上部分生物量和地下部分生物量8个生长性状种源间差异极显著,重要的生长性状是苗当年高、苗高、地径和地上部分生物量;云杉苗期地径生长量与年降水量呈极显著负相关,一级侧枝数量和地上部分生物量与年降水量也呈显著负相关;依据种源间生长性状的聚类分析结果,把17个种源划分为4个种源区;根据10个生长性状的综合指数对参试的17个种源进行排序和苗期初步选择. 相似文献
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We studied the damage caused to unfelled trees during skidding operations in four beech stands of northern and central Greece that were managed under differing harvesting systems.After timber was harvested we recorded and analyzed all damage to a width of 2 m along both sides of the skid trails.The percentage of damaged residual trees was 17–28 %.Higher numbers of saplings were uprooted or destroyed in parts of the stands with high natural regeneration.Most damaged trees suffered 1.33–1.90 wounds that were inflicted up to a height of 1 m above ground level.At all sites mean wound sizes were large,89–1190 cm2,and caused elevated risk of future fungal infection.The damage caused by skidding during timber harvesting can be minimized by better planning the harvest operations,and training forest workers in reduced impact logging. 相似文献
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浙江省早籼稻近期区试品种（系）蒸煮品质研究 总被引：11，自引：6，他引：11
对水稻区试中多品种(系)、多年、非平衡、无重复分析值的蒸煮品质性状数据,用作者提出的统计方法作了分析。分析结果表明,“八五”期间参试的早籼稻品种(系)蒸煮品质较“七五”参试品种有所改善,高直链淀粉含量的参试品种极显著减少,低直链淀粉含量的参试品种极显著增加;软胶稠度的品种极显著增加,硬胶稠度的品种极显著减少。但多数参试品种胶稠度仍偏硬,综合蒸煮品质不佳。各蒸煮品质性状均以品种效应为主,其次是品种×年份互作效应。蒸煮品质性状的提高,首先应注意品种(系)的主效。各蒸煮品质间有极显著的相关关系,其中直链淀粉与胶稠度的负相关最明显,其次为直链淀粉与糊化温度的负相关。为克服性状相关引起的早籼稻优质育种的难度,应抓好直链淀粉与胶稠度这一主要矛盾并应广泛筛选育种种质资源。 相似文献
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麦/玉/豆轮作制度下不同施肥措施对大豆产量的影响 总被引：2，自引：0，他引：2
在麦/玉/豆轮作制度下,通过在不同年份改变施肥量,研究前茬作物的肥料残效和不同施肥措施对大豆产量和农艺性状的影响.结果表明:麦/玉/豆轮作与大豆连作相比具有显著的增产效果.各处理平均株高较连作处理增加25.6%,单株荚数增加90.2%,单株粒数增加158.2%,茎粗增加10.5%.不同施肥水平间产量差异极显著.同样在轮作制度下,年际问调整化肥施用量,可以获得较好的作物产量. 相似文献
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We examined 5-year basal area growth of nearly 2600 trees in stem-mapped plots at five locations differing in site characteristics, species composition, and management history on the Olympic Peninsula in Western Washington, USA. Our objectives were to determine if internal edges, the boundaries within the stand between components of the variable-density thinning, influenced individual tree growth, and whether incorporation of individual tree local competition indices in growth prediction models could account for treatment and edge effects. Treatment significantly affected tree growth at all sites, with trees in the thinned matrix displaying on average over 25% greater basal area growth than trees in unthinned patches. Proximity to canopy gaps created as part of the variable-density thinning increased basal area growth of trees in the thinned matrix by nearly 11%. In addition, growth of trees close to skid trails was 11% greater than trees located away from the trails. Past thinning history, and its effect on initial stocking rate, appeared to affect the magnitude of the edge effects. Blocks that had received earlier commercial thinnings, and thus had lower stocking at the onset of the study, displayed lower growth responses than previously unthinned blocks. Including local competition indices in the models generally reduced growth prediction error; however, the indices examined did not fully account for treatment or edge effects. Our results suggest that not accounting for internal edges in spatially complex stands could result in errors in projected growth of trees, although these edge effects are highly variable. Failure to account for the effects of internal edges could affect not just estimates of future stand yield, but also projections of future stand structure. 相似文献
17.
美国的小径系统及其借鉴意义 总被引：1，自引：0，他引：1
文中介绍了美国小径系统的经营管理情况, 提出了在我国发展小径系统的建议和具体措施。 相似文献
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Dimitrios Baxevanos Christos Goulas Stergios Tzortzios Athanasios Mavromatis 《Euphytica》2008,161(3):371-382
Multi-environment trial data are required, to obtain variety stability performance parameters as selection tools for effective
cultivar evaluation. The interrelationship among seven stability parameters and their association with mean yield, along with
the repeatability of these parameters across consecutive years was the objective of this study. Cottonseed yield data of 31
cotton cultivars, proprietary of Delta and Pine Land Co and other companies, evaluated in 20 locations over the 1999–2005 year
period in Greece, Spain and Turkey were used for combined analysis of variance in four datasets. Across locations in a single
evaluation year (dataset A), across locations in each of two single consecutive evaluation year (dataset B), across locations
and two consecutive years (dataset C) and across locations and three consecutive years (dataset D). For each dataset, cultivar
phenotypic variance was appropriately partitioned in its components and the h2 and component estimated. Furthermore, following the appropriate stability analysis
and AMMI1 along with the GGE Biplot distance (GGED) and instability (GGEIN) parameters were obtained. The interrelationship
among the parameters and their association with mean yield based on Spearman rank correlation was studied in each of the seven
single evaluation years (dataset A). Rank correlation coefficients were also used as estimates of the repeatability of these
stability parameters across consecutive year combinations (dataset B, C and D). The parameters GGED and YSi were consistently highly correlated with each other and mean yield in five out of seven single evaluation years. The data
provided evidence that single year evaluation across locations might be sufficient to reliably rank cotton cultivars, based
on mean yield along with GGED and YSi. Combined analysis across two consecutive years (dataset C) was more effective as compared to single year evaluation. GGED
was relatively more repeatable than YSi and mean yield in single (dataset B) and 2-year comparisons (dataset C). Although GGED is an index depended and proportional
to yield, provides a superior way to integrate mean performance and stability into a single measure, which can be assessed
visually on biplots. Regarding the other stability parameters, the results were contradicting and of low repeatability across
single years and two consecutive years. Cultivar evaluation combined across locations in 3 years did not improve the repeatability
of cultivar variance effects but resulted in very high repeatability of GGED, YSi and mean yield. 相似文献
20.
通过对４．５年生的赤桉、邓恩桉、多枝桉等３种类１１种源的种类种源试验林的生长调查、形质指标调查和选林保存率的调查,采用单因素方差分析和多目标决策理论等综合分析评定方法,来评判种源的优劣。研究结果表明：到目前试验研究阶段,仍以赤桉１５０２５、１５０２２和贵溪赤桉为最佳种源。多枝按１５２１３、邓恩桉１７３３３和祁阳赤桉为淘汰种源。在资兴市或类似资兴市气候的湘南各县（市）可以对赤桉１５０２５、１５０２２ 相似文献