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261.
火烧迹地落叶松八齿小蠹种群扩散蔓延规律 总被引:1,自引:0,他引:1
1987年大兴安岭发生特大森林火灾,为落叶松八齿小蠹猖獗发生提供了优良的环境条件.经过1988、1989两年的研究,发现落叶松八齿小蠹种群扩散已从重度火烧林转向中、轻度火烧林,每年扩散危害的距离在10m左右;提出扩散蔓延的数学模型为Y=0.67+1.66X,落叶松八齿小蠹扩散蔓延程度与虫源基地中其种群密度和被扩散林分的生理状况有关.其相关数学模型为Y=2.70X+0.25X_2-1.76,落叶松八齿小蠹种群在火烧迹地上扩散属于聚集型扩散. 相似文献
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在分析当前我国农村税费改革存在的四大主要问题的基础上,有针对性地提出了政策建议和主张。 相似文献
264.
在旱地覆膜栽培条件下,临丰116具有良好的苗型结构和产量结构,抗旱节水优势强,叶片功能期长,耐高温,抗干热风,根穗比值大,抗倒伏,不早衰,穗大,粒重,产量高。该品种是旱地覆膜栽培较理想的配套品种。同时探讨了覆膜栽培配套品种的育种目标。 相似文献
265.
林安红 《福建农业大学学报(哲学社会科学版)》2008,(6):30-34
我国农村公共产品供给缺失、不足的现状积弊已久,应更多地予以其关注,加大供给投入和力度。鉴于医疗供给上的特殊性,及长期以来医疗供给存在的诸多弊端,本文以此为例,着重从空间布局和结构布局两个维度分析当前农村卫生服务体系建设的相关突出问题,并进行规避路径探析,俾使新型农村合作医疗的构建与完善能更贴近实际需求,能更快、更好地产生实效。 相似文献
266.
阐述目前德州地区园林树种选择存在的问题,以及德州市自然环境和植被状况,总结德州地区耐盐碱园林树种的选择和应用情况,并为今后耐盐碱园林树种的应用提出可行性建议。 相似文献
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268.
Grain Yield and Quality of Durum Wheat Landraces in a Dry Mediterranean Region of Northern Syria 总被引:1,自引:0,他引:1
Twenty-two durum wheat landraces of various origins were evaluated for performance and stability of grain yield, protein content and gluten strength (SDS sedimentation volume) at two sites of Northern Syria situated in the drought-prone part of the local durum wheat belt. Yield was recorded in three seasons, while protein content and SDS volume were assessed in two seasons only. A high “entry X environment” interaction was observed for all traits, which was significantly attributable to heterogeneity of entry regressions on the environmental mean for grain yield only. Compared to the recently-bred, widely-grown variety ‘Sham I’, some landraces showed somewhat similar yield responses, whereas others proved more stable without being significantly lower yielding. Significant variation was found for SDS volume, though only few of the best-ranking landraces for this trait also possessed an acceptable yield level. The entries did not significantly differ for protein content. The broad sense heritability estimates obtained for grain yield (0.59) and SDS volume (0.89) highlighted the interest in some of the landraces examined for improving grain yield and quality in the region. 相似文献
269.
S. Ceccarelli 《Euphytica》1987,36(1):265-273
Summary Using the traditional approach (selection for grain yield) it has been found that F3 families derived from F2's selected under unfavourable conditions were more vigorous in the early stages of growth, taller, earlier in heading and with larger yields than F3 families derived from F2's selected under favourable conditions. A high and negative correlation coefficient was found between the drought susceptibility index and grain yield at the driest site, whereas at the wettest site the correlation coefficients were lower and in some cases positive, indicating the existence of traits which are desirable under drought and undesirable under favourable conditions, or vice versa.Expected responses to selection for grain yield using different selection criteria indicated that selection under stress conditions is expected to be more efficient than selection under favourable conditions when dry areas is the target environment.Expected responses to selection for grain yield using different selection criteria indicated that selection under stress conditions is expected to be more efficient than selection under favourable conditions when dry areas is the target environment.Part of this work was supported by Opec Fund for International Development. 相似文献
270.