乐昌含笑人工林的土壤肥力和涵养水源功能研究

通过对乐昌含笑和杉木人工林生物量和土壤肥力的调查,进行乐昌含笑人工林培肥土壤和涵养水源功能的研究,结果表明:营造乐昌含笑人工林后林地土壤水稳性团聚体含量增加,团聚体的稳定性增强,容重降低,总孔隙度增加,林地土壤结构、孔隙和养分状况得到不同程度的改善,乐昌含笑人工林具有比杉木林更好的培肥土壤功能;乐昌含笑叶的最大持水率明显高于杉木叶,其林分地上部分最大持水量是杉木林的1.14倍,同时由于乐昌含笑林土壤结构及孔隙状况的改善,林地蓄水能力增强,使得乐昌含笑人工林表现出比杉木林更好的水源涵养功能。     

基于Oracle Spatial的水土保持监测空间数据管理方法

水土保持监测工作中包含了大量的空间数据,如何科学、合理、有效地组织管理这些空间数据和属性数据,促进水土保持的信息化和现代化建设,成为水土保持监测工作迫切需要解决的问题。本文以水土保持工作中的空间数据作为研究对象,分析比较了几种空间数据管理的方法,采用基于Oracle 9i数据库平台的Oracle Spatial存储水土保持空间数据,实现了水土保持空间数据和属性数据的一体化存储和管理。     

牙克石市水土保持生态修复的途径研究

文章在分析牙克石市自然条件及水土流失特点的基础上,提出牙克石市水土保持生态修复的可行性及生态修复的措施,以及近年来牙克石市生态修复所取得的可喜成果。     

广西大青山石灰岩山土壤理化性质的演变及其造林绿化

研究得知:该范围的石山(石灰岩山)上,在北热带气候及植被条件相互作用下,演变为一类特别肥沃的土壤——石灰土;该类土壤有机质及氮素丰富,保蓄水性能强;钙、镁、钾、铁、锰、锌等元素含量也十分丰富,故称“热带黑钙土”;石山石多土少,整体环境恶劣,而局部生境却十分优越,又因该区雨量充沛,即使石山中的石缝、石槽内,只保存5％土质,上面就会覆盖较繁茂的草、灌植被,其中不少具有较高的经济价值,同时,也易于栽培喜钙、喜肥的优良或珍贵树种。     

Productivity of intensified crop—fallow rotations in the Trenbath model

Management of crop—fallow rotations should strike a balance between exploitation, during cropping, and restoration of soil fertility during the fallow period. The Trenbath model describes build-up of soil fertility during a fallow period by two parameters (a maximum level and a half-recovery time) and decline during cropping as a simple proportion. The model can be used to predict potential crop production for a large number of management options consisting of length of cropping period and duration of fallow. In solving the equations, the model can be restricted to sustainable systems, where fallow length is sufficient to restore soil fertility to its value at the start of the previous cropping period. The model outcome suggests that the highest yields per unit of land can be obtained by starting a new cropping period after soil fertility has recovered to 50–60% of its maximum value. This prediction is virtually independent of the growth rate of the fallow vegetation. The nature of the fallow vegetation (natural regrowth, planted trees, or cover crops) mainly influences the crop yield by modifying the required duration of fallow periods. Intensification of land use by shortening fallow periods will initially increase returns per unit land at the likely costs of returns per unit labor. When fallows no longer restore soil fertility to 50% of the maximum, overall productivity will decline both per unit land and per unit labor, unless external inputs replace the soil fertility restoring functions of a fallow.This revised version was published online in November 2005 with corrections to the Cover Date.     

换土垫层法处理地基及分析

本文作者通过多年实验,结合大庆工程实际,详细对比了四种施工方案,以及计算方法,并从中论述了如何选择最佳方案,具有指导意义。     

Carbon, water and nutrient flux in Maya homegardens in the Yucatán peninsula of México

The Yucatán Peninsula of México has shallow soils and receives low amounts of precipitation, and has therefore low agricultural potential. Lacking large-scale irrigation from rivers and adequate rainfall, the indigenous Maya groups maintain agricultural productivity by adapting a variety of practices. Multistrata homegardens, one of their agricultural systems, have provided goods for trade, sale and personal consumption for many centuries. Nevertheless, an understanding of the controlling biological factors and interactions within these systems can lead to yield improvements. Photosynthetic rates, water use and litter production for a variety of species have been studied in these gardens to determine how Maya management impacts resource flow, productivity and diversity. When irrigated, diurnal photosynthetic rates nearly doubled for Manilkara zapota and water use increased two fold for M. zapota and Cordia dodecandra. Total litter production in traditional homegardens varied from 1,000 to 4,000 kg ha⁻¹ yr⁻¹ and ten arboreal species were found to contribute more than 33% of total litterfall biomass. Nutrient concentrations in the leaves of the predominant species were analyzed; Meliococcusbijugatus and Spondias purpurea were found to contribute the largest quantities of N, P and C. Our research indicates that species and structural diversity are critical to sustainability of homegardens, allowing efficient use and transfer of carbon, nutrients and water. This revised version was published online in June 2006 with corrections to the Cover Date.     

Determination of drought tolerance using root activities in Robinia pseudoacacia ''Idaho'' transformed with mtl-D gene

Idaho locust (Robinia pseudoacacia 'Idaho') is an exotic multi-purpose tree used in landscaping, soil and water conservation, fodder sources and others. To improve its drought tolerance for reclaiming arid land, five lines of transformed mtl-D gene, as osmotic regulator in plant cells, have been selected and managed to determine their drought tolerance under experimental conditions.Qualitative and quantitative variables of transformed plants were studied. The critical value of drought tolerance was determined by detecting the 2,3,5-triphenyl tetrazolium chloride (TTC) reductants in roots and soil water content (SWC). The critical value for drought tolerance was SWC 6% while for the control plants the critical SWC was 8%; a moderate level of SWC is 13% and the highest SWC for plant endurance was 18%. The method proved to be reliable and sensitive in the evaluation of drought tolerance for forest trees.     

马尾松飞播林土壤肥力研究

湖南省马尾松飞播林林地土壤肥力低下是制约其林分生长和发育的重要因素.通过土壤养分主成分分析,对马尾松飞播林土壤肥力级别进行了排序和分类,在此基础上,运用方差分析和灰色关联分析对土壤养分含量和土壤肥力水平进行了分析和评价.将湖南省马尾松飞播林地土壤肥力分为Ⅰ、Ⅱ、Ⅲ类,全K、全N,微量元素Zn、Fe,以及土壤有机质含量在各肥力级别土壤中均存在显著差异,Ca、Mg、全P在各类土壤中的含量相差不大,全P在土壤中的含量极低,同时研究结果也表明,林分所处立地条件越好,土壤肥力水平就越高,这为马尾松飞播林林分施肥提供了科学依据.     

树桩盆景的养护管理技术

通过介绍生境管理，盆土管理和树上管理来讲述树桩盆景的养护管理技术。