Results 21 to 30 of about 4,252 (135)
Ultrasound in Obstetrics &Gynecology, Volume 66, Issue 1, Page 24-32, July 2025.ABSTRACT Objectives To investigate the impact of aspirin administration on the incidence of preterm birth, according to the type of delivery and gestational age at preterm birth, and to examine the hypothesis that aspirin delays preterm delivery. Methods This was a secondary analysis of a multicenter stepped‐wedge cluster randomized trial of a first ...
H. H. Y. Leung +29 more
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Ultrasound in Obstetrics &Gynecology, Volume 64, Issue 6, Page 768-775, December 2024.Abstract Objective Lower urinary tract obstruction (LUTO) is a chronic condition with a spectrum of outcomes. It is usually suspected prenatally based on ultrasound features (USFs). Given the unknown postnatal trajectory and the potential for significant morbidity and mortality, many families choose termination of pregnancy (TOP), often based on USFs ...
J. Richter +10 more
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Biotropica, Volume 56, Issue 6, November 2024.This study examines the distribution and environmental correlations of 1081 large old trees (LOTs) across 74 species in Hainan Island, South China. The findings reveal uneven spatial patterns, with species diversity varying across the island and influenced by factors such as GDP, urbanization, and forest cover.
Chunping Xie +3 more
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Integrative Conservation, Volume 3, Issue 1, Page 58-75, March 2024.Local populations are aware of the decline and disappearance of Detarium species in their habitats, attributing this trend to excessive human exploitation and the effects of climate change. Thus, Detarium plant resources may face challenges in forests with different levels of protection status due to habitat fragmentation and the effects of climate ...
Adama Taonda +4 more
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Shuitu Baochi Xuebao, 2017 为研究杉木人工林土壤团聚体分布特征及其稳定性，探索杉木人工林土壤结构状况，以不同发育阶段杉木人工林0—100 cm土层为研究对象，采用干筛法测定土壤团聚体组成，采用湿筛法测定团聚体稳定性，结果表明：在干筛处理下，各发育阶段杉木人工林土壤团聚体以大团聚体（＞0.25 mm）为主，大团聚体比例皆达80%以上，中龄林和成熟林土壤大团聚体比例在各土层中均高于幼龄林，且在0—20 cm土层差异显著（P＜0.05）；在各土层中，不同发育阶段杉木人工林＞5 mm粒径的土壤团聚体皆占较高比例，且不同发育阶段对＞5 ...
庄 +5 more
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Shuitu Baochi Xuebao, 2011 采用对比分析方法,揭示了不同发育阶段落叶松人工林根际与非根际土壤有机氮、水解氮、全磷、有效磷、有效钾和酸度的变化规律。结果表明:不同发育阶段落叶松人工林根际与非根际土壤酸性氨基酸、碱性氨基酸、游离氨基酸总量和水解氮,以及根际土壤中性氨基酸、速效钾、全磷和有效磷从幼龄林到中龄林增加,中龄林以后降低。根际活性酸、非根际土壤速效钾随林龄增加呈显著下降趋势,根际与非根际土壤交换性酸、交换性铝、非根际活性酸则相反,随林龄的增大呈明显增加趋势。
陈立新, 段文标, 乔璐
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Shuitu Baochi Xuebao, 2023 为探究大气氮沉降增加导致的土壤团聚体结构变化规律及其对土壤水分入渗性能的影响,在贡嘎山针叶成熟林和中龄林内分别设计2种氮肥形态[(NH4)2SO4、KNO3]和4个浓度水平(0,10,20,40 kg/(hm2·a)N)的添加试验,研究不同形态大气氮沉降对亚高山森林土壤团聚体结构和土壤水分入渗特征的影响。结果表明:(1)随施氮量增加,中龄林土壤大团聚体含量逐渐增加,土壤持水量、孔隙度和水分稳定入渗率逐渐增大;成熟林土壤大团聚体含量、土壤持水量、孔隙度和水分稳定入渗率均表现出先增加后降低的趋势;(2 ...
郭海云, 王根绪, 孙守琴
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Shuitu Baochi Xuebao, 2008 为了解连作杨树人工林不同生长阶段林地内的土壤微生态环境特征,分别选取山东省莒县招贤镇和峤山镇境内的连作杨树人工林地为研究对象,研究结果表明:土壤的物理性状随着林龄的增加先变差后又逐渐改善,而pH值随着林龄的增加是逐渐降低的。土壤养分和土壤脲酶活性随着林龄的增加呈现先增加后减小的趋势,过氧化物酶和多酚氧化酶活性随着林龄的增加而降低,过氧化氢酶活性随林龄的增加没有规律。除1龄林地外,细菌、放线菌数量及微生物总量随着林龄的增加先增加后减少,真菌数量随林龄的增加规律性不强。在土壤剖面上 ...
刘福德 +5 more
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Shuitu Baochi Xuebao, 2017 为了定量研究燕山山地不同林龄华北落叶松人工林的碳密度特征及其分配格局，为森林碳汇服务功能提升提供科学依据。以河北省木兰围场国有林场管理局新丰林场3种林龄（11，21，32 a）华北落叶松人工林为研究对象，基于9块样地本底调查和27株标准木树干解析数据，采用标准木回归分析法、样方收获法、土壤剖面取样法和重铬酸钾—浓硫酸氧化外加热法等，获取不同林龄华北落叶松人工林的碳密度，分析了其特征及变化趋势。结果表明：不同林龄华北落叶松人工林生态系统总碳密度表现为32 a（97.29 t/hm2）＞21 a（90.56
马长明, 赵, 牟洪香, 刘炳响
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Shuitu Baochi Xuebao, 2007 利用经典统计学与地统计学相结合的方法对毛乌素沙地不同林龄沙柳表层土壤（0-20 cm）水分空间异质性进行研究。结果表明,随着林龄的增长,表层土壤水分含量有增加的趋势,增加幅度为5.46%-6.60%;不同林龄沙柳表层土壤之间水分含量差异极显著（p〈0.01）。变异函数分析显示,2-4年的沙柳林中,随着林龄的增长,使得基台值和空间结构比增大,沙柳表层土壤水分含量具有高度的空间异质性,其空间异质性以空间自相关部分为主,从占总空间异质性的63%增大到87%;各向异性分析也表明 ...
姚月锋, 满秀玲
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