共查询到20条相似文献，搜索用时 484 毫秒
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我国省级耕地非农化适度性评判研究 总被引：1，自引：0，他引：1
对我国省级耕地非农化的适度性做出评判,将有助于耕地保护政策的有效实施.为此,从耕地非农化与经济发展关系的角度提出了一种评判区域耕地非农化适度性的方法,并运用此方法对我国近年来各省市区耕地非农化的适度性进行了实证研究.结果表明:即使在全国耕地非农化总体适度的情况下,仍然存在某些耕地非农化过度或滞后的省份.因此,对于那些耕地非农化过度的省份必须采取紧的土地供应政策,而对于那些耕地非农化滞后的省份则应采取松的土地供应政策,这样做才能既调控了耕地非农化,又不会影响经济的正常发展. 相似文献
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中国水利学会2007年学术年会于10月29-31日在苏州市召开.本届年会的主题是"现代水利与河湖管理",水利部各司局、长江水利委员会、黄河水利委员会、各省市自治区水利厅局的领导、以及来自全国有关水利科研、设计、施工、管理和教学一线的技术骨干近600人参加了大会.与中国科协其他学会的年会相比,水利学会年会除了学术讨论的性质外,还带有一定的工作会议内容.来自各方面的10位专家作了大会特邀报告. 相似文献
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没有想到的是,在特克斯县城周边的高山上,是那么平坦开阔,有着丘陵般起伏绵延的大草原。原以为是原始草原。是哈萨克的最最重要的生产资料,却看见了农区才有的大片收割过的金黄的麦茬,和一垄垄开着寂寞的白色花朵的洋芋。黑土地上最适宜生长这类块根作物了。问县上的陪同人员,答复是： 相似文献
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金秋时节,我们共庆辽宁省孤儿学校南朝阳市搬迁到沈阳市新址。在此,我受李立国部长的委托,代表民政部,也代表关注、支持学校搬迁的李学举老部长向辽宁省孤儿学校新校园的落成表示热烈的祝贺!向孤儿学校的全体同学和教职员工致以亲切的问候!向多年来一直关心支持儿童福利事业发展的辽宁省委、省政府的领导,相关部门的同志和社会各界的朋友表示衷心的感谢! 相似文献
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陈重潘 《云南地理环境研究》2010,22(2):39-42
全球气候变化已是当今世界研究的热点。近年来,气候变化对陆地植被以及土壤的影响研究已经广泛开展。通过系统收集和整理气候变化对植被和土壤影响国内外相关研究结果,有利于进一步认识气候变化给生存环境带来的影响。大量野外定量分析以及经验模型预测等方法研究表明:气候变化对陆地植被产生了重要影响,主要表现在植被分布范围、生产力以及多样性的改变。气候变化也会使土壤基本性质发生变化,同时土壤作为全球碳循环过程中重要的中间碳库,土壤有机碳库与气候变化有着密切的关系,气候变暖与土壤有机碳库的分解互为反馈。 相似文献
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The Holocence paleolimnology of Lake Sämbosjön is described using geochemical and diatom analyses. The objective of this study is the reconstruction of major changes in trophic state and productivity, and to interpret the major causative processes. The accumulation of organic matter indicates a relatively high productivity in early Holocene, and the diatom analysis indicates a relatively high trophic state and pH. A succeeding decrease in productivity and trophic state and lowering in pH is recorded from about 8000 BP. If lake development had been primarily edaphically conditioned, viz. determined by nutrient supply from catchment soils, such a progressive oligotrophication would represent the common development of temperate lakes. Between about 6000 BP and 4000 BP Lake Sämbosjön was characterized by relatively stable productivity and pH. From about 4000 BP the analyses reveal an increase again in trophic state, productivity, and in pH. This eutrophication, which continued throughout the late Holocene, was caused by an exceptionally strong human influence on the catchment of Lake Sämbosjön. The increased supply of nutrients from cleared and deforested catchment soils changed the trophic state and provided the basis for increased lake productivity. 相似文献
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Studies of soil productivity must compensate for the effects of temporal trends in order to examine the pattern of crop yields along spatial gradients. An analysis of the published yield estimates for 30 soils in 233 counties, however, did not find consistent yield increases over the past three decades. On the contrary, the yield estimates for many soils were markedly uniform since 1972. The uniformity appears to have two causes: the acknowledged difficulty of making yield estimates in a time of increasing variability in soil and crop management, both within and between regions, and surveyors' awareness of data stored in a national soils data base. The effect is to cast doubt on soil productivity data reported in county soil surveys published between 1973 and 1988. 相似文献
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Michael E. Folkoff 《自然地理学》2013,34(4):328-336
In previous studies, models of the climatic controls on pH in the A (pHA) and B horizons (pHB) of U.S. soils were developed which differ in the functional forms and variables incorporated into each model. This study suggests that the differences in the models are explained by climate's control over the soil properties that determine pH buffering. Climatic control of pHA and pHB buffering in most acid soils is through its control over clay mineralogy. However in very acid soils, organic matter content (OM) is a stronger buffer of pHA than is clay mineralogy because in these highly leached soils, OM contents are very high and most OM is concentrated in the A horizon. In basic soils, climate dominates buffering through its control over the chemical reactions involving calcium carbonate (CaCO3) formation. The pHA model suggests that in basic soils as moisture decreases CaCO3 content increases causing pHA buffering to increase. In contrast, the pHB model suggests that as moisture decreases pHB buffering decreases. Although leaching of basic soils is limited, when it occurs a highly-concentrated pulse of calcium (Ca2+) is illuviated to the B horizon, causing pHB to increase. As leaching decreases, the magnitude of this pulse of Ca2+ increases because more Ca 2+ is available for leaching and depth of leaching of Ca2+ decreases. Studies of basic soils support only the results of the pHA model, but they are based mainly on laboratory studies which do not consider the influence of climate on B horizon chemistry. [Key Words: Soil acidity, pH buffering, climate, modeling, U.S. soils.] 相似文献
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A numerical index of soil development, the POD Index, was developed and applied to 723 pedons of United States soils that either exhibit, or are developing, Podzol (Spodosol) morphology. The index is determined solely from morphologic (field) criteria, and provides the first soil development index for Podzol and Podzol-like soils that does not use chemical data. The index assumes that pedogenesis and profile development in these soils produces the following morphologic changes; (1) the E (eluvial) horizon becomes “whiter,” (2) the B (illuvial) horizon becomes “redder” and “darker,” and (3) the number of B subhorizons increases. Results indicated that the index was useful for differentiating between non-Podzols and Podzols, and between Entic and Typic subgroups of Spodosols. A comparison of POD Indices for Spodosols of differing drainage revealed that maximum development occurred in wet soils (somewhat poorly drained), with minimal development on the driest sites. This finding is consistent with current theory on the effects of drainage/water table relations on Podzol development. Additionally, the index has usefulness in chrono-sequences of Podzol soil development [Key words: soils, Podzol, Spodosol.] 相似文献
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磷酸酶在土壤生物释磷过程中起着重要作用。本文以极地苔原鸟粪土为研究对象,测定了不同环境条件下土壤剖面中碱性磷酸酶(APA)的活力,研究了APA在土壤中随深度的变化规律,并同步测定了相应土壤中有机碳、总氮、各形态磷、pH,分析了酶活力与这些因子的相关性。结果表明:同一采样点土壤剖面中碱性磷酸酶活力大小呈现一定规律性,最大值出现在表层,且随采样深度的增加而递减,变化范围为1.00—1403.49ppm,平均约为408.31ppm。碱性磷酸酶活性与土壤中有机碳含量(r=0.70,p0.01)、氮含量(r=0.43,p0.01)呈显著正相关性,表明土壤中碳、氮等有机物含量是影响极地苔原土壤磷酸酶活力的主要因素。另外,碱性磷酸酶活性与总磷(r=0.39,p0.05)、无机磷(r=0.40,p0.05)和有机磷(r=0.11,p=0.67)含量也呈正相关性,表明各形态磷在一定程度上也影响着土壤中碱性磷酸酶活力;与土壤中铜含量(r=-0.38,p0.05)和锌含量(r=-0.28,p=0.05)呈显著负相关,表明土壤中Cu、Zn等金属离子对极地苔原土壤磷酸酶活力具有抑制和破坏作用。结果证实土壤磷酸酶活性可作为指示极地土壤肥力的一个重要指标。 相似文献
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河南土壤中某些微量元素的含量与分布 总被引：3，自引：0，他引：3
本文对河南省108个县1160多个土壤样品进行了一万多样次分析,查明了河南省存在着大面积的缺钼、缺硼和缺锌土壤;揭示了微量元素Mo、B、Cu、Zn、Fe和Mn在各种类型土壤中的全量和有效态含量及其分布规律等。 相似文献
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Seabird guano influences on desert islands: soil chemistry and herbaceous species richness and productivity 总被引：4，自引：0，他引：4
An understanding of the effects of guano deposition on arid soil chemistry and the consequences for plant communities is lacking. This study examined patterns of herbaceous species richness and productivity, soil chemistry, soil moisture and soil respiration on 11 islands in the Gulf of California, six of which receive seabird guano deposition. Species richness was significantly lower on islands with guano (“Bird” islands) than islands without guano (“Non-bird” islands), with very little overlap in species composition; however, productivity was significantly greater on Bird than on Non-bird islands. As expected, Bird island soils had higher concentrations of NO3−, NH4+ and total nitrogen (N) than Non-bird island soils; and, measurements of δ15N indicate that the higher concentrations of N were derived from guano. We also found that soil moisture and respiration were significantly higher, but pH was significantly lower, on Bird than Non-bird islands. These results suggest that guano deposition in deserts stimulates productivity—even in dry years—due to elevated N and, indirectly, soil moisture. Guano deposition also results in a decrease in species richness and a change in species composition probably due to elevated N, N toxicity, or low pH. However, we also found that pH varied more on Bird than on Non-bird islands; and that salinity—while not different between island types—was significantly patchier on Bird than on Non-Bird islands. These results suggest that guano deposition affects not only the general chemical composition of soils, but also results in greater spatial variation in soil chemical composition, which may ultimately affect species richness and composition. Therefore, understanding spatial patterning in soil chemistry as a result of guano deposition is critical for understanding guano effects on plant richness and productivity. 相似文献
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酸性硫酸盐土的酸害暴发机制及其环境影响 总被引：4，自引：0，他引：4
酸性硫酸盐土广泛分布于热带亚热带滨海地区,当其中的硫铁矿物质与空气接触或直接暴露地表时会发生氧化而形成强烈酸害,从而导致土壤、水、大气和区域生态系统的退化,最终对动植物生长和人类的健康产生较大影响而成为全球性的热带亚热带滨海环境问题。酸性硫酸盐土的酸害暴发主要包括：（１）硫铁矿的形成、累积与埋藏过程;（２）硫铁矿的氧化与致酸过程;（３）土壤对酸的中和与缓冲过程;（４）土壤中酸的稀释与迁移过程。酸性硫酸盐土的酸害影响是上述四个过程相对强弱与综合作用的结果。酸性硫酸盐土酸害暴发可导致区域土壤环境、水环境和大气环境的酸化,以及大量金属与重金属元素的溶解与释放,引起生物生存环境的恶化与栖息地的丧失,动植物出现变态生长,而且疾病频繁,生产力下降,区域生态系统的结构和功能发生异常,生物多样性下降。 相似文献