Nutrient loss and water quality under extensive grazing in the upper Burdekin river catchment, North Queensland

Increased sediment and nutrient losses resulting from unsustainable grazing management in the Burdekin River catchment are major threats to water quality in the Great Barrier Reef Lagoon. To test the effects of grazing management on soil and nutrient loss, five 1 ha mini-catchments were established in 1999 under different grazing strategies on a sedimentary landscape near Charters Towers. Reference samples were also collected from watercourses in the Burdekin catchment during major flow events. Soil and nutrient loss were relatively low across all grazing strategies due to a combination of good cover, low slope and low rainfall intensities. Total soil loss varied from 3 to 20 kg ha(-1) per event while losses of N and P ranged from 10 to 1900 g ha(-1) and from 1 to 71 g ha(-1) per event respectively. Water quality of runoff was considered moderate across all strategies with relatively low levels of total suspended sediment (range: 8-1409 mg l(-1)), total N (range: 101-4000 microg l(-1)) and total P (range: 14-609 microg l(-1)). However, treatment differences are likely to emerge with time as the impacts of the different grazing strategies on land condition become more apparent. Samples collected opportunistically from rivers and creeks during flow events displayed significantly higher levels of total suspended sediment (range: 10-6010 mg l(-1)), total N (range: 650-6350 microg l(-1)) and total P (range: 50-1500 microg l(-1)) than those collected at the grazing trial. These differences can largely be attributed to variation in slope, geology and cover between the grazing trial and different catchments. In particular, watercourses draining hillier, grano-diorite landscapes with low cover had markedly higher sediment and nutrient loads compared to those draining flatter, sedimentary landscapes. These preliminary data suggest that on relatively flat, sedimentary landscapes, extensive cattle grazing is compatible with achieving water quality targets, provided high levels of ground cover are maintained. In contrast, sediment and nutrient loss under grazing on more erodable land types is cause for serious concern. Long-term empirical research and monitoring will be essential to quantify the impacts of changed land management on water quality in the spatially and temporally variable Burdekin River catchment.     

李泽冈环带及其它沉淀型式的自组织

沉淀/溶解与搬运的动力学过程的偶合能导致许多有趣型式,其中研究最细的是李泽冈环带。这里我们将对这些现象以及对这些现象的解释模式作一回顾。关于这一理论的地质应用将在后面章节中予以讨论。     

21世纪地质调查所的作用

地质调查所的建立最初是为了从事地质测图（与实际地质工作有关的，如采矿、建筑和运输）。尽管有些地调所已把重点放在更加基础的地质工作上，但测图仍然是地调所的主要工作，很多地调所已更加注重市场，部分原因是为了适应政府经费的缩减。技术的进步也将影响地调所从事调查研究工作的方式。国家地质调查所将来的工作也将受到广泛的社会经济趋势的影响。２１世纪地质调查所工作的重点将依赖于国家关注资源开发、工业发展、人口高度     

地电化学勘查方法的现状与前景

对地电化学勘查方法的刺状和前景作了评述，并提出了我国电化学勘查方法的发展战略。     

Demographic response to rural restructuring and counterurbanisation in South Australia, 1981-1991

"Using South Australia as a case study, this paper seeks to trace and demonstrate two processes (counterurbanisation and rural restructuring) whose effects overlap to differentiate and characterise the population geography of...two zones, separated by a transition along the outer fringe of Adelaide's urban field.... In the demographic core zone [rural restructuring] has been partly offset by continued counterurbanisation, resulting in demographic mixing and rural dilution. The 1981-91 population growth in rural communities is shown to be more a function of population density at the outset of the period than of initial population size. Demographic growth...is shown to conform to a simple unidimensional scale, allowing the production of a clear, easily interpretable typology of rural demographic change with few non-conforming statistical areas. At a local level within individual rural communities, demographic decline is shown to be accompanied by increased concentration of the population into small towns, while demographic growth is associated with deconcentration."     

中国金矿床分形分布及对超大型矿床的勘查意义

根据中国４４２个岩金矿床的空间坐标和储量数据,研究了中国岩金矿床的空间和储量分布分形特征。研究表明,在两个尺度范围内金矿床在空间上呈分形分布,其群集分布的分维Ｄ分别为０．２２９３（２０￣１５０ｋｍ）和１．３０７３（１５０￣５０００ｋｍ）;矿床密度分布的Ｄ值分别为０．４２８９（２￣１００ｋｍ）和１．４６２１（１００￣１５００ｋｍ）。通过研究还发现,矿床储量与频数之间也呈分形关系。在此基础上,提出了中     

隐伏矿勘查经验与启示 ——从《信息找矿战略与勘查百例》谈起

以大型隐伏矿床的发现历史为依据,系统地总结了隐伏矿勘查的经验与策略,并从矿产勘查哲学的角度进行了深入的思考。针对拟寻矿床的地质特征。抓住深部关键的地质因素,查明地球物理和地球化学特征与它们的对应关系,把地球物理和地球化学判据转化成找矿标志,是提高隐伏矿找矿效率的关键。成矿作用的分带现象是一个普遍的规律,对于指导隐伏矿预测和矿床深部勘探具有重要的意义。直接信息是矿产勘查最可靠的信息。直接信息和间接信息并不是以学科划分的,在一定的条件下和一定的研究程度上两者可以转化。以直接信息为先导,实现从区域到局部的转变,使找矿迅速突破。必须充分重视各类方法的应用条件与前提。重视各种直接信息的挖掘与印证,加强各类方法的集成与综合。对于一个重要的成矿区（带）来说,随着地质研究与找矿工作的深入,需要不断地修订和调整勘查准则。矿产勘查投资是一种高风险、高效益的投资,是一项创造性很强的实践．集调查与研究于一体。矿产勘查不以研究“水平”论高低,而以“成败”论英雄;要看勘查的实效,而非理论的高深;要看是否见矿,而非勘查过程的简繁。经验与理论、科学与技术的交叉与融合是通向矿产勘查的成功之路。