Contrasting effects of ecosystem engineering by the cordgrass Spartina maritima and the sandprawn Callianassa kraussi in a marine-dominated lagoon

Ecosystem engineering by plants and animals significantly influences community structure and the physico-chemical characteristics of marine habitats. In this paper we document the contrasting effects of ecosystem engineering by the cordgrass Spartina maritima and the burrowing sandprawn Callianassa kraussi on physico-chemical characteristics, microflora, macrofaunal community structure and morphological attributes in the high shore intertidal sandflats of Langebaan Lagoon, a marine-dominated system on the west coast of South Africa. Comparisons were made at six sites in the lagoon within Spartina and Callianassa beds, and in a “bare zone” of sandflat between these two habitats that lacks both sandprawns and cordgrass. Sediments in Spartina habitats were consolidated by the root-shoot systems of the cordgrass, leading to low sediment penetrability, while sediments in beds of C. kraussi were more penetrable, primarily due to the destabilising effects of sandprawn bioturbation. Sediments in the “bare zone” had intermediate to low values of penetrability. Sediment organic content was lowest in bare zones and greatest in Spartina beds, while sediment chl-a levels were greatest on bare sand, but were progressively reduced in the Spartina and Callianassa beds. These differences among habitats induced by ecosystem engineering in turn affected the macrofauna. Community structure was different between all three habitats sampled, with species richness being surprisingly greater in Callianassa beds than either the bare zone or Spartina beds. In general, the binding of surface sediments by the root systems of Spartina favoured rigid-bodied, surface-dwelling and tube-building species, while the destabilising effect of bioturbation by C. kraussi favoured burrowing species. The contrasting effects of these ecosystem engineers suggest that they play important roles in increasing habitat heterogeneity. Importantly, the role of bioturbation by C. kraussi in enhancing macrofaunal richness was unexpected. By loosening sediments, reducing anoxia and enhancing organic content, C. kraussi may engineer these high shore habitats to ameliorate environmental stresses or increase food availability.     

砂泥岩间互地层裂缝延伸规律探讨

目前裂缝预测主要集中在对开度、密度和发育强度等参数的半定量或定量化预测方面,对裂缝的延伸规律和穿透性研究缺少深入研究。针对这种情况,文中以天山山前某油田沙泥岩间互地层为例,采用应力场数值模拟法建立应力场与裂缝参数之间的定量关系,从而实现裂缝在沙泥岩间互地层中的的延伸规律与穿透性研究。模拟结果显示,越薄的砂岩层越容易产生构造裂缝,而砂岩厚度对砂岩中产生的裂缝在泥岩中的延伸长度影响很小,几乎可以忽略,且对延伸到泥岩中裂缝的孔隙度影响也不大,即不管泥岩上下砂岩层的厚度如何,延伸到泥岩中的裂缝孔隙度变化不大,均在038％左右;砂泥岩互层处裂缝在泥岩中延伸长度一般为15~2 m,当泥岩厚度为4 m左右时,砂岩裂缝恰好无法穿透泥岩,泥岩可作为有效的封盖层。     

青平川油田储层地质特征与注水开发试验

通过对岩石矿物、储层物性、油层敏感性和水驱油效果分析,在储层地质研究基础上,评价青平川油田长2油藏注水开发效果。研究结果表明,长2油藏含油砂岩以细粒长石砂岩为主,粘土矿物中绿泥石含量较高。储层物性差,属于典型的低渗透岩性油藏。水驱油实验结果表明,青平川油田长2油层水驱油效果较好,油田最终驱油效率可达49.4%。先导性注水试验表明,注水开发可以使青平川油田产量在较短时间内得到大幅度提高,在注水后的第4到第7个月达到产量高峰期,第8个月后进入稳产期。油田注水开发产量递减规律分析表明初始递减律为0.019 1(1/月)。根据青平川长2油藏实际情况,认为注水开发能达到提高采油速度和油田最终采收率的目的。     

Prey versus substrate as determinants of habitat choice in a feeding shorebird

Many shorebirds on their non-breeding grounds feed on macrobenthic fauna which become available at low tide in coastal intertidal flats. The Eastern Curlew Numenius madagascariensis in Moreton Bay Australia, varies greatly in density among different tidal flats. This study asks: how important is the abundance of intertidal prey as a predictor of this variation? We quantified feeding curlews’ diet across 12 sites (different tidal flats, each re-visited at least eight times), through 970 focal observations. We also estimated the abundance of total macrobenthic fauna, potential prey taxa and crustacean prey on each tidal flat; measured as the number of individuals and a relative biomass index per unit substrate surface area obtained from substrate core samples. We estimated curlew density at each site using low-tide surveys from every site visit.     

从红外遥感图像提取地下热信息的透热指数法

红外遥感影像主要反映的是地表温度。然而气象因素对地表温度的影响远大于来源于地下的地质因素 ,可能存在的地下热异常信号淹没在气象信息之中。如何从中提取地下热信息 ,成为一个关键问题。文中由热传导理论出发 ,根据地下热信号通过不同热扩散率材料传到地表时将产生较大时间差的特点 ,提出了提取地下热异常的新指标“透热指数”。通过对实验数据和遥感数据的试算 ,分析了使用“透热指数”法的条件及影响因素