The self-organization of step-pools in mountain streams

Spontaneous, autogenic self-organization has been described in numerous geomorphic systems, but it has not been investigated in detail with respect to coarse bedforms in general or step-pools in particular. In this paper, we review the spatial organization of step-pool systems and present example evidence of step-pool development as an autogenic self-organization process. We then outline the mathematical language for defining spatially divergent self-organization and test these ideas using two unique field examples from Oregon (Andrews Experimental Forest) and California (Baxter Creek), where step-pools developed from planar beds in artificially manipulated channels. Results show that step-pool development is consistent with a spatially divergent self-organization phenomenon. Entropy increases as initially undifferentiated planar channels diverge into steps and pools, then declines when a series of steps and pools of consistent size and spacing is established, signifying stability in the system. The self-organization process is accompanied by increasing flow resistance and decreasing slope (through increasing the “vertical sinuosity” of the step-pool profile and creation of low- or negative gradient pool areas), suggesting a minimization of stream power. The self-adjustment of the step-pool bed profile over time represents another manifestation of a general process that results in rhythmic patterns on the surface of Earth.     

Natural diversion of the ramu river in Papua New Guinea

At present, the Ramu River in Papua New Guinea flows directly into the Bismarck Sea, while the adjacent Keram flows into the Sepik River. There is evidence to suggest that the Ramu previously occupied the existing Keram water course, and has been gradually diverting its discharge into its present channel, probably over the last 4,000 years. The diversion process is not complete yet, and during the wet season flood water still travels across these two rivers. The most direct evidence to support this proposal of river diversion is that there are much larger meander bends on which the existing Keram stream channel is superimposed. The diversion of the Ramu is believed to be a result of relative sea‐level rise in the late Quaternary which altered the gradients of the Keram and Ramu rivers, and may have been facilitated through neo‐tectonic movement of the floodplain.     

A catchment-scale model of mountain stream channel morphologies in southeast Australia

The position of mountain streams high in the channel network and their proportional dominance mean that channel modifications and adjustments within these systems will have important implications for downstream processes and linkages. This study develops an analysis framework for examining the catchment-scale distribution of reach morphologies, and the relationship among reach type, catchment lithology and flow competence in southeast Australian mountain streams. The analysis framework is applied to three catchments which have contrasting proportions of the two dominant lithologies of the region, Devonian granites and Ordovician metasediments.The model successfully delineated 68% of reach types, and the resultant spatial maps allowed the effects of stream network position and catchment specific controls on channel morphology to be evaluated. Maximum lengths of the majority of reach morphology types were in second-order streams and the maximum number of morphology types (six) was present in third-order streams, with dramatic reductions in reach type variability as the network expands. The position of catchment lithology within the channel network structure was recognized as more important than the aerial extent of a particular lithology on the distribution and abundance of reach morphologies. The model provides an important tool in the management of channel networks for the protection or restoration of ecological diversity, by identifying river segments and tributaries with high morphological diversity.     

Diatom-temperature transfer functions based on the altitudinal zonation of diatom assemblages in Papua New Guinea: a possible tool in the reconstruction of regional palaeoclimatic changes

Indirect and direct gradient ordination techniques were used to study the relationship between present-day benthic and periphytic diatom assemblages and environmental factors along an altitudinal gradient in Papua New Guinea. Both within the screened initial data-set and a narrowly-defined subset of soft-water lakes, shifts in diatom assemblages are clearly related to altitudinal differences. This relation is used to construct transfer functions for inferring altitude (and hence average water temperature) from the diatom records. Calibration by canonical correspondence analysis (CCA) and simple weighted averaging calibration proved to be superior to models using WA with tolerance downweighting and to a simple WA model based on a selection of 52 indicator taxa. From the calibration models and the linear relationship between altitude and epilimnetic water temperature, the average lake water temperature can be predicted with an accuracy of 3.2°C. After further refinement, a transfer function for palaeotemperature based on diatoms would be of potential value for climatic reconstructions in tropical regions.     

Large wood potential,piece characteristics,and flood effects in Swiss mountain streams

We present results of two studies on the (1) potential wood load in steep headwater streams and (2) properties of large wood (LW) transported in mountain rivers during the large August 2005 flood event in Switzerland. Ten headwater reaches of 1000 m length were surveyed in different regions of Switzerland. The potential wood load was estimated for in-channel deadwood, and possible driving factors were explored. Correlations were found with dead wood volume on hillslopes and mean channel width. We established size distributions of LW pieces and identified probable recruitment processes. Four reaches were resurveyed after an exceptionally severe flood in August 2005, showing limited LW transport in channels but considerable wood input by mass wasting processes. In addition, characteristics of deposits of LW along mountain rivers affected by the 2005 flood were investigated. Diameter and length distribution of transported and deposited pieces were comparable to those of LW from steep headwater streams, yet with considerably fewer long pieces in the deposits of mountain rivers. Most LW pieces were fresh wood, indicating that the portion of in-channel deadwood transported during the 2005 flood was limited. Findings of the study contribute to a better understanding of LW dynamics in Alpine mountain streams.     

Environmental Refugees? A tale of two resettlement projects in coastal Papua New Guinea

ABSTRACT

Environmental change in small islands may be associated with migration as a means of adaptation. Both Manam and the Carteret Islands in Papua New Guinea (PNG) have experienced rapid- and slow-onset changes, respectively. These have been accompanied by the forced migration and ‘temporary’ resettlement of the Manam population and attempts at resettlement by Carteret Islanders. Neither has proved successful, thwarted by ‘host’ landowners, the impossibility of gaining adequate access to land and land rights, and government inactivity. Settlers have been perceived as outsiders and rival claimants to valuable coastal resources. Inability to resettle in national contexts raises issues of ambiguity, identity and citizenship. The problems experienced by quite small population groups moving short distances in similar cultural contexts are indicative of the potential future problems facing environmental migrants in other contexts.     

The storage of bed material in mountain stream channels as assessed using Optically Stimulated Luminescence dating

A detailed understanding of channel forming and maintenance processes in mountain streams requires some measurement and/or prediction of bed load transport and sediment mobility. Traditional field based measurements of such processes are problematic because of the high formative discharges characteristic of such streams. The application of Optically Stimulated Luminescence (OSL) dating is proposed here as a new way of determining actual residency times of fine sediments and consequently validating selected predictions for the entrainment of sediment in these streams. Model predictions of sediment mobility for selected step-pool and plane-bed channels in a mountain catchment in south eastern Australia are initially calculated using equations of hydraulic competence and the one-dimensional HEC-RAS model. Results indicate that floods exceeding bankfull with recurrence intervals up to 13 years are competent to mobilise the maximum overlying surface grain sizes at both sites. OSL minimum age model results from 7 samples of well bleached quartz in the fine matrix particles indicate general agreement with selected competence equations. The apparent long (100–1400 y) burial age of most of the mineral quartz, however, suggests that competent flows are not able to flush all subsurface fine-bed material. The depth of maximum bed load exchange (flushing) was limited to ≤ twice the depth of the overlying D₉₀ grain size. Application of OSL in this study provides important insight into the nature of storage and flushing of matrix material in mountain streams.     

城市"新经济"发展的空间效应及其启示——以西安市为例

以知识为基础、以计算机与信息技术为依托、技术与制度创新驱动、兼跨第二与第三产业并以服务业居重、高度外向而趋于全球化的当代"新经济"的兴起,正从诸多方面影响和改变着城市。本文以西安市为实证分析案例,依据对"新经济"内在禀赋特性的认识,从城市"产业区"格局重构、城市办公楼宇设施增长、高新技术产业区的CBD化、产业与居住功能分区的模糊化、城市经济与社会空间的极化等方面对城市"新经济"发展的空间影响效应进行了分析,并就其对于城市规划与决策的启示予以探讨。     

Responses of Two New Hampshire (USA) Lakes to Human Impacts in Recent Centuries

This study contrasts the effects of human disturbances on two very different lake/catchment systems: Hatch Pond and Beaver Lake, New Hampshire. Hatch is in a steep mountain catchment remote from urban/industrial centers, and is a small, relatively deep, primarily seepage lake with moderate flushing rate. The catchment has been continuously forested, but disturbed by partial loggings and a forest fire. Beaver’s more extensive and gently sloping catchment is much closer to urban/industrial centers, and has been agricultural and recently suburban. Beaver is a larger but shallower drainage lake with much more rapid flushing than Hatch. We compared the sedimentary records and inferred limnological responses to catchment land uses and air pollution inputs of these mesotrophic lakes, and interpreted differing responses as a function of basic differences between the lakes and their catchments. Some chemical and biological variables in the sediment of both lakes respond sensitively to the first disturbances of the catchments by Euro-American settlers. Diatom-inferred Cl at both lakes indicates a modest increase of salinity at this time. Hatch sediment contains a record of soil erosion starting 1810 with first logging and fire. For ~125 years, erosion was largely of upper eluviated soil, but by 1935 it reached deeper into the illuviated (enriched) horizon. Maximal lake trophic state based on diatom-inferred limnological variables occurred in the mid-1900’s period of maximum sedimentation of illuviated soil. The sediment record since 1964 reflects forest maturation, and soil stabilization and acidification, but not lake acidification. At Beaver, the limnological effects of forest clearance and agriculture starting ~1700 were relatively mild due to gentleness of slopes and soil characteristics favoring stability. A near doubling of earth elements, and major increases in trace metal pollutants and coal combustion particles (CCP) occurred in sediment dating around 1900. Landscape analysis as well as historical and sedimentary records preclude the catchment as the major source of these increases. The most likely source is atmospheric fallout of CCP with its metal load. Despite controls on CCP and other emissions starting 1960, concentrations of earth elements and trace metals in Beaver sediment remain high due to soil mobilization by residential development of the catchment. The trophic state of Beaver Lake has increased, but the relative increase has been smaller than at Hatch, despite more intensive land uses and greater aerial inputs at Beaver. We propose that this lesser eutrophication is due to rapid flushing of Beaver Lake with stream water from relatively undeveloped parts of the extensive catchment, and lower sensitivity to nutrient inputs of this naturally more eutrophic lake. A major shift from unicellular to colonial chrysophytes at Hatch starts in the late-1800’s, and at Beaver in the early 1900’s. Colonial taxa in lesser quantities appear at the time of first settlement of the Beaver catchment. At both lakes the shifts are correlated with increasing metal fluxes from the opening of catchment biogeochemical cycles, as with the aforementioned erosional sequence at Hatch. But at Hatch aerial inputs of trace metals, and at Beaver aerial inputs major and trace metals associated with CCP are also correlated with the major chrysophyte shift. It appears that the chrysophytes have responded to stressors associated with both catchment disturbance and regional atmospheric inputs.     

Paleolimnological assessment of human impacts in Lake Blanca, SE Uruguay

Paleolimnological techniques were used to assess human impacts onLake Blanca, a small (0.6 km²), coastal fresh waterbodyin southern Uruguay, which is the drinking water source for 100,000 localresidents. We retrieved a core that extends to about 1100 ¹⁴Cyr BP. ²¹⁰Pb ages, organic mater, CO₃, totalcarbon, nutrients, fossil pigments and diatoms allowed us to establishlimnological conditions before and after cultural impacts. Soil removal(1880–1960) and intensive cattle and sheep grazing (1943–1966) ledto gully formation in the catchment. This watershed erosion resulted inincreased sedimentation rates. The aquatic system appeared to be mesotrophicwith dominance of epibenthic diatoms until 1966, at which timeeutrophication intensified with forestry activities. Increases in nutrients, aswell as blooms of planktonic diatoms, were observed. During the last decade,tourist/urban development as well as high drinking water demand caused areduction in lake area. Subsequent marked increases in rainfall led to furtherphytoplankton blooms and macrophyte proliferation.     

High spatial resolution hyperspectral mapping of in-stream habitats, depths, and woody debris in mountain streams

This article evaluates the potential of 1-m resolution, 128-band hyperspectral imagery for mapping in-stream habitats, depths, and woody debris in third- to fifth-order streams in the northern Yellowstone region. Maximum likelihood supervised classification using principal component images provided overall classification accuracies for in-stream habitats (glides, riffles, pools, and eddy drop zones) ranging from 69% for third-order streams to 86% for fifth-order streams. This scale dependency of classification accuracy was probably driven by the greater proportion of transitional boundary areas in the smaller streams. Multiple regressions of measured depths (y) versus principal component scores (x₁, x₂,…, x_n) generated R² values ranging from 67% for high-gradient riffles to 99% for glides in a fifth-order reach. R² values were lower in third-order reaches, ranging from 28% for runs and glides to 94% for pools. The less accurate depth estimates obtained for smaller streams probably resulted from the relative increase in the number of mixed pixels, where a wide range of depths and surface turbulence occurred within a single pixel. Matched filter (MF) mapping of woody debris generated overall accuracies of 83% in the fifth-order Lamar River. Accuracy figures for the in-stream habitat and wood mapping may have been misleadingly low because the fine-resolution imagery captured fine-scale variations not mapped by field teams, which in turn generated false “misclassifications” when the image and field maps were compared.The use of high spatial resolution hyperspectral (HSRH) imagery for stream mapping is limited by the need for clear water to measure depth, by any tree cover obscuring the stream, and by the limited availability of airborne hyperspectral sensors. Nonetheless, the high accuracies achieved in northern Yellowstone streams indicate that HSRH imagery can be a powerful tool for watershed-wide mapping, monitoring, and modeling of streams.     

Finding common ground: relational concepts of land tenure and economy in the oil palm frontier of Papua New Guinea

In the oil palm frontier regions of West New Britain and Oro provinces, Papua New Guinea, customary land tenure arrangements are changing in response to the growing demand for land for agricultural development. This paper examines one aspect of these changes, namely the gifting and selling of customary land for oil palm development to people who have no customary birthrights to the land. By analysing how access rights are maintained over the relatively long cultivation cycle of oil palm (approximately 25 years), and in the context of the rapidly changing socio-economic and demographic environments of the oil palm frontiers, the paper demonstrates that while land transactions seemingly entail the commodification of land, land rights and security of land tenure remain embedded in social relationships. For customary landowners, the moral basis of land rights is contingent on 'outsiders' maintaining particular kinds of social and economic relationships with their customary landowning 'hosts'. In exploring how these social relationships are constituted through the performance of particular kinds of exchange relationships, the paper provides insights into relational concepts of land rights and how these are able to persist in Papua New Guinea's oil palm frontier regions where resource struggles are often intense and where large migrant populations are seeking land for agricultural development.     

Reflections on use of participatory research for disaster risk reduction

Participatory research approaches are increasingly popular with academic researchers and development organisations working to facilitate change in collaboration with local communities. This paper contributes to recent debates over the use of participatory approaches by examining the use of participatory research within disaster risk reduction. Drawing on research in Papua New Guinea in which participatory techniques were used with indigenous communities to determine strategies for dealing with environmental hazards, the value of such techniques is critiqued. Finally the significance of participatory research as a research methodology is discussed as is its possible contribution to disaster risk reduction policy.     

Paleolimnological assessment of human impacts on an urban South African lake

North End Lake is a polluted and eutrophic freshwater system located in Port Elizabeth, South Africa. Since the lake is expected to be used for recreational/tourist purposes by 2010, a rehabilitation program will have to be designed. For this reason, we retrieved a sediment core from the central region of the lake to decipher the effect of historical human impacts on the water body. Pre-disturbance paleolimnological inferences indicate that the lake was likely mesotrophic. After ∼1831, when sheep farming activities were undertaken in the catchment, increases in trophic state and changes in sediment composition were observed. After ∼1937, increases in trace metal levels, organic matter, spheroidal carbonaceous particles (SCP) and changes in sediment composition were recorded. The system became eutrophic as indicated by the dominance of the diatom Actinocyclus normanii, a cosmopolitan species often observed in systems where water quality has been dramatically degraded. The conditions worsened after 1986 because of the construction of a storm-water retention system, which intentionally channeled storm-water runoff into the lake. Because of this, extremely high values of fecal coliforms (i.e. 2 × 10⁶ every 100 ml) have been measured in the water column. The paleolimnological information identified the sharp increase in organic content in the uppermost section of the core, and this could be correlated to the operation of the storm-water retention system. Therefore, as an immediate management measure, we suggest that the storm-water retention system should either no longer be utilized, or the storm-water runoff should be treated before disposal into the lake. In addition, an effective sewage system has to be constructed.     

高新区科技金融发展过程及其空间效应——以无锡新区为例

科技金融是伴随着中国科技体制改革和金融发展不断深化、服务于自主创新和创新型国家建设战略而逐渐产生的新生事物。以中国科技金融创新的主要发源地之一的无锡国家级高新区为例,通过实地调查,对科技金融体系的产生、发展及其空间效应进行实证研究。研究发现,无锡新区的科技金融服务已基本形成一个完整的体系;政策、市场和社会因素是科技金融发展的主要推动力;科技金融体系的建立推动了产业转型,专门的科技金融空间出现,同时在科技金融支持下新的产业空间出现,并引发人口空间转移和社会空间转型等。本文可丰富科技金融和高新区转型的理论,并为其他地区的科技金融实践提供借鉴。     

Human impacts on headwater fluvial systems in the northern and central Andes

South America delivers more freshwater runoff to the ocean per km² land area than any other continent, and much of that water enters the fluvial system from headwaters in the Andes Mountains. This paper reviews ways in which human occupation of high mountain landscapes in the Andes have affected the delivery of water and sediment to headwater river channels at local to regional scales for millennia, and provides special focus on the vulnerability of páramo soils to human impact. People have intentionally altered the fluvial system by damming rivers at a few strategic locations, and more widely by withdrawing surface water, primarily for irrigation. Unintended changes brought about by human activities are even more widespread and include forest clearance, agriculture, grazing, road construction, and urbanization, which increase rates of rainfall runoff and accelerate processes of water erosion. Some excavations deliver more sediment to river channels by destabilizing slopes and triggering processes of mass-movement.The northern and central Andes are more affected by human activity than most high mountain regions. The wetter northern Andes are also unusual for the very high water retention characteristics of páramo (high elevation grass and shrub) soils, which cover most of the land above 3000 m. Páramo soils are important regulators of headwater hydrology, but human activities that promote vegetation loss and drying cause them to lose water storage capacity. New data from a case study in southern Ecuador show very low bulk densities (median 0.26 g cm^− 3), high organic matter contents (median 43%), and high water-holding capacities (12% to 86% volumetrically). These data document wetter soils under grass than under tree cover. Effects of human activity on the fluvial system are evident at local scales, but difficult to discern at broader scales in the regional context of geomorphic adjustment to tectonic and volcanic processes.     

The impacts of sustained heavy grazing on plant diversity and composition in lowland and upland habitats across the Kamiesberg mountain range in the Succulent Karoo, South Africa

This study explored the impacts of sustained heavy grazing in six vegetation types across an altitudinal and rainfall gradient in the Kamiesberg mountain range in Namaqualand. The study was carried out across the fence separating the Leliefontein communal area and surrounding privately owned farms. The communal area has been stocked over decades at approximately twice the government recommended stocking rate, while adjacent privately owned farms have generally adhered to recommended rates. Plant community data were collected from 66, 0.1 ha modified Whittaker plots and analysed for diversity and compositional changes. Consideration of community-wide responses through NMDS ordination showed that heavy grazing did not result in the dominance of a few wide-spread, weedy species in communal areas. Species richness at the 0.1 ha scale was also not affected by different land use practices. However, there was a significant compositional shift away from large woody and succulent shrubs, and an associated increase in dwarf shrubs and herbaceous perennial plants on the communal areas. This shift was only evident on the sandy lowland habitats, while a reduction in perennial grass was recorded in the rocky upland habitats on the communal areas. Compositional shifts towards smaller and more ephemeral species in the communal area are indicative of a system more closely dependent on rainfall. This has implications for people's livelihoods in the region, particularly in light of predicted climate change.     

中国全球气候变化影响研究方法的进展

着重介绍了中国全球气候变化影响研究中有关方法的最新进展,其中包括实验室、农田和野外观测实验;冰芯、树木年轮和历史文献方法;数值模式研究,特别是静态模式和动态模式研究。最后,指出了存在的问题,以及研究展望。