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加拿大安大略中部衰退中的糖枫树轮化学性质
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作者 Shaun Watmough Tom Hutchinson +1 位作者 Tom Brydges 于云江 《AMBIO-人类环境杂志》 1999年第7期612-617,634,共6页
生长在由安大略前寒武纪地盾风化而来的贫瘠土壤上健康的和正在衰退的糖枫林,其树轮大小和化学性质被用来记载自1940年以来树木养分的变化历史。从1986年起,在Dorset每年可以观察到树木大幅度衰退的症状,在40年代期间形成的树轮其宽度... 生长在由安大略前寒武纪地盾风化而来的贫瘠土壤上健康的和正在衰退的糖枫林,其树轮大小和化学性质被用来记载自1940年以来树木养分的变化历史。从1986年起,在Dorset每年可以观察到树木大幅度衰退的症状,在40年代期间形成的树轮其宽度已经减小,而1950年以后树轮大小和Ca、Mg、Mn的浓度均没有变化。但是,Ca浓度(680mg/kg)和Mg浓度(100mg/kg)已经属于最低糖枫树木的记录。Loring的糖枫比Dorset的要健康些,可在60年代也发生了树轮宽度减小现象,比Dorset晚减20年,并伴随着Ca和Mg浓度的显著降低,Mn浓度的降低尤为突出。微量元素或A1的毒性不可能是对衰减症状的直接响应。如果Loring是安大略中部看上去比较健康的糖枫林的代表地,那么在未来20年中,由养分短缺引起的衰退症状将更广泛地发生。 展开更多
关键词 糖枫树轮 化学性质 树木衰退 加拿大 森林退化
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Soil Phosphorus Fractions Change in Winter in a Corn-Soybean Rotation with Tillage and Phosphorus Fertilization 被引量:2
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作者 Yi-Chao SHI Noura ZIADI +2 位作者 Aimé J.MESSIGA Roger LALANDE HU Zheng-Yi 《Pedosphere》 SCIE CAS CSCD 2015年第1期1-11,共11页
Determining how agricultural management practices affect soil phosphorus(P) over the winter may further our understanding of the soil P cycle under specific environmental conditions in eastern Canada. This study asses... Determining how agricultural management practices affect soil phosphorus(P) over the winter may further our understanding of the soil P cycle under specific environmental conditions in eastern Canada. This study assessed changes over winter for soil P fractions and other selected chemical properties as affected by tillage and P fertilization. In 1992, a long-term corn(Zea mays L.) and soybean(Glycine max L.) rotational experiment was established in the province of Quebec, Canada. Soil samples(0–15 cm) were collected in fall 2001 and 2007 after a soybean harvest, and in the following spring 2002 and 2008 before corn seeding, in main plots under moldboard plow and no-till managements and selected subplots fertilized with 0, 17.5, or 35 kg P ha-1and 160 kg N ha-1. Soil samples were analyzed for P fractions and other chemical properties to assess changes over winter for 2001–2002 and 2007–2008. Changes over winter of all soil P fractions were significant for the two periods, indicating the occurrence of soil P transformation and movement over winter. The Mehlich-3-extractable Fe, Al, Ca, and Mg decreased during the two studied periods. Tillage had no significant effect on all soil P fractions. The resin-extractable P in 2001–2002 and Na HCO3-extractable inorganic P and Na OH-extractable organic P during the two winters were significantly increased under P fertilization. This study demonstrated that P in cultivated soils changed during winter as a result of changes in labile P fractions possibly due to the solubilization of residual fertilizer P combined with environmental factors. 展开更多
关键词 agricultural management practices environmental factors inorganic P labile P organic P
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