Environmental response to land use at Lake Curlip,East Gippsland,Victoria

A palaeoecological approach was undertaken to investigate the last 400 years of change in vegetation, fire, nutrient mobility, lake productivity and erosion associated with Aboriginal and European land-use practices in a forested environment in eastern Victoria. Melaleuca ericifolia scrub, although present prior to European settlement, has expanded around Lake Curlip in the last 200 years, primarily due to the action of fire on a forest already weakened by drought. A fern understorey has declined in extent and a more open aspect has developed in the forest. Fire has been a major component of vegetation dynamics in the historical period. Erosion rates were comparatively low and associated with fire during prehistoric times, but after European settlement its increase is more closely related to land clearance and flooding than fire. The response of vegetation to both anthropogenic and natural influences changed during the historical period. Although fire is an integral part of vegetation change, it is not an over-riding effect at Lake Curlip. Drain construction in the swamp has reduced the impact that any accumulation of pasture improvement chemicals may have had on eutrophication of the lake.     

Palaeolimnological impacts of early prehistoric farming at Lough Dargan,County Sligo,Ireland

This study provides a unique method of inquiry for archaeological investigation with an aim to assess the intensity and effects of Neolithic and Bronze Age farming practices at Lough Dargan, northwest Ireland, through a multi-proxy analysis of a lake sediment core. Chironomid (non-biting midge fly) subfossils and lake sediment geochemistry (δ¹³C, δ¹⁵N and C:N ratios) were used to assess changes in limnological conditions through time. The limnological data were compared with macroscopic charcoal concentration and pollen data to examine the potential influence that early farmers had on a freshwater lake system within a prehistorically active catchment. Results from the chironomid analysis show that the first substantial period of agricultural activity in the early Neolithic (c. 3730–3190 BC) resulted in a temporary shift to more eutrophic lake conditions. There is evidence of animal husbandry with substantial levels of animal waste reaching the lake, leaving an imprint in the geochemical record of increased δ¹⁵N values and decreased δ¹³C values and C:N ratios during this time. The chironomid community reverted back to its pre-impacted state c. 3190 BC in response to a period of reduced farming (c. 3390–3000 BC) which eventually led to a distinct lull in activity, with possible cessation of farming from 3000 to 2700 BC. A return to eutrophic conditions coincided with the gradual return of agriculture, with more permanently altered lake conditions dominating from 2400 BC, even during a 250-year period of reduced human activity commencing at c. 1440 BC. Increased sedimentation rate, along with increases in δ¹³C, δ¹⁵N and C:N, the presence of chironomid taxa indicative of erosion, more eutrophic lake conditions and high concentrations of macroscopic charcoal all point to more intensive land use practices during the Bronze Age. Palaeolimnological data exhibited an immediate response to intensified farming during this time, and were especially responsive to pastoral farming due either to scale of activity or proximity to the lakeside. The success of this study demonstrates the effectiveness of palaeolimnological analysis in the investigation of prehistoric farming. This approach will help inform Neolithic and Bronze Age land-use practice and human–environment relations in the region, and highlights the potential for chironomid-based archaeological research.     

Pollen evidence for major shifts in forest composition since the mid‐nineteenth‐century in the vicinity of Sudbury,Ontario

Numerous anthropogenic stressors have impacted the region surrounding Sudbury, Ontario, leading to pronounced vegetation and landscape change. Few long‐term records exist to understand the nature or timing of this change. We use pollen analysis from radiometrically dated sediments of Clearwater Lake to compare pre‐ and post‐settlement vegetation. Beginning ～1850 CE, the record shows major shifts in forest composition, coincident with settlement and the beginnings of lumbering. These changes are unprecedented for the past ～5000 years, and consist of increases in diversity and abundance of deciduous tree taxa and herbaceous disturbance indicators. While evidence of mining appears as early as 1900 CE, little effect is seen in the pollen record until ～1930 CE, when sedimentation rates increased and acidification of the lake also began. At this time, further increases in palynological disturbance indicators and minimum sediment organic matter levels indicate the period of maximum vegetation loss. As a result of reduced emissions since the 1970s, water quality began to improve in Clearwater Lake and there are some decreases in the abundances of shade‐intolerant disturbance indicators in the pollen record. However, the fact that the pollen assemblages do not resemble those prior to 1850 suggests lasting vegetation changes.     

Microfossil evidence of land-use intensification in north Thailand

Palaeo-environmental data from accumulated lake sediments at Phayao, northwest Thailand, provide a record of vegetation and environmental change from approximately 20,000 years Before Present. This is an important region archaeologically, with claims in the 1970s for an ‘early’ transition to domestication having arisen from a number of cave sites. Multiple indices are used to determine if people had an observable impact on the natural environment, and to determine the timing and magnitude of impacts associated with the development of agricultural land use in the region. An initial increase in sedimentation rate is apparent from ca. mid-2nd C AD. Changes in phytoplankton concentrations are apparent from the late 3rd C AD, and evidence for initial forest disturbance is apparent from the 5th or 6th C AD, with impacts becoming more severe over time to reach a pre-modern maximum in the 11th to the 13th C AD. Changes in agricultural practices are apparent during the 14th C AD, with an increased emphasis on rice agriculture and incipient management of the regenerating forests. Based on these data we suggest that agricultural intensification in the early part of the 1st millennium AD destabilised catchment slopes, through clearance of dryland vegetation and swidden agriculture. There is no direct evidence for the impacts of earlier peoples on the vegetation of the area, which we take to indicate that agricultural intensification was later here than in the lowlands to the east and south.     

BOSERUP BACKWARDS? AGRICULTURAL INTENSIFICATION AS ‘ITS OWN DRIVING FORCE’ IN THE MBULU HIGHLANDS,TANZANIA

Why do farmers intensify their agricultural practices? Recent revisions of African environmental historiographies have greatly enriched our understanding of human–environmental interactions. To simply point at poor farming practices as the main cause of deforestation, desertification and other processes of land degradation is, for example, no longer possible. The contemporary analytical focus is instead on the complex and often unpredictable set of causal relations between societal, ecological and climatic factors. In the literature on agricultural intensification, conventionally defined driving forces, such as population pressure and market demand, remain important explanatory factors despite a growing body of research that suggests more dynamic scenarios of agricultural development and landscape change. This article reports on a case where the common‐sense logic of population pressure theory has dominated the historical narrative of a local process of agricultural intensification among an agro‐pastoral people in north‐central Tanzania. By way of a ‘detailed participatory landscape analyses’ a more complex and dynamic historical process of intensification is suggested, in which the landscape and the process of agricultural intensification itself are in focus. It is concluded that the accumulation of landesque capital has been incremental in character, and that the process of agricultural intensification in the study area has largely been its own driving force based on self‐reinforcing processes of change, and not a consequence of land scarcity and population pressure. This result demonstrates the possibility and usefulness of reversing the Bose‐rupian argument in analyses of agricultural intensification.     

Palaeogeographical reconstructions of Lake Maliq (Korça Basin,Albania) between 14,000 BP and 2000 BP

Since the early 1990s, excavations of a protohistoric lakeside settlement in the Korça basin carried out by a French–Albanian archaeological team have induced geomorphological and palynological studies about the sedimentary records of Lake Maliq. These studies allow us to distinguish a series of centennial-scale high and low lake level events between 4200 and 4000 cal BP (2899–2637 BC/2843–2416 BC) and 2600 cal BP (822–671 BC), probably due to large-scale climate changes (in the Mediterranean basin). In addition, the sediment sequence also gives evidence of a millennial-scale trend of lake level rise. It appears to be an interplay between lake level rises and falls against tectonic subsidence of the basin allowing accommodation space for sediment deposition.The variations of the lake's level and the lake's surface area influenced the development and the abandonment of the nearby lakeside settlements (like the tell of Sovjan). In order to prepare an archaeological survey around the now dried up lake, we made a 3D model of the Holocene deposit from the lake including these lake level results, geomorphological mapping, excavation data, numerous core logs, AMS ¹⁴C dating and SRTM DEM data. The GIS model allowed us to propose four palaeogeographical reconstructions of the extension of Lake Maliq: around 14,000 BP, during the Mesolithic (around 9000 BP – 8781–8542 BC), the Early/Middle Bronze Age transition (around 3800 BP – 2310–2042 BC) and the Iron Age (2600 BP – 822–671 BC). A map of the thickness of the sediments above potential archaeological layers is also proposed.     

Early medieval origins of iron mining and settlement in central Sweden: multiproxy analysis of sediment and peat records from the Norberg mining district

The historical Norberg mining district in central Sweden with its shallow, easily accessible iron ores figures prominently in the earliest documents from the 14th century concerning mining or metallurgy. This 1000-km² district is considered to be one of the first areas in Sweden exploited for iron ores and, in fact, Europe’s oldest known blast furnace, Lapphyttan, is located in the Norberg district about 10 km from the mines in the village of Norberg (Norbergsby). Earlier archaeological excavations suggest the furnace was in operation as early as the 11th or 12th century (870 and 930 ¹⁴C yr BP), and a number of other sites in the district have been dated to the 13th–15th centuries. Here, we have analyzed two lake sediment records (Kalven and Noren) from the village of Norberg and a peat record from Lapphyttan. The Lapphyttan peat record was radiocarbon dated, whereas the sediment from Kalven is annually laminated, which provides a fairly precise chronology. Our pollen data indicate that land use in the area began gradually as forest grazing by at least c. AD 1050, with indications of more widespread forest disturbance and cultivation from c. 1180 at Lapphyttan and 1250 at Kalven. Based on ²⁰⁶Pb/²⁰⁷Pb isotope ratios in Kalven’s varved sediment record, there is an indication of mining or metallurgy in the area c. 960, but likely not in immediate connection to our sites. Evidence of mining and metallurgy increases gradually from c. 1180 when there is a decline in ²⁰⁶Pb/²⁰⁷Pb ratios and an increase in charcoal particles at Lapphyttan, followed by increasing inputs of lithogenic elements in Noren’s sediment record indicating soil disturbance, which we attribute to the onset of mining the iron ore bodies surrounding Noren. From AD 1295 onwards evidence of mining and metallurgy are ubiquitous, and activities accelerate especially during the late 15th century; the maximum influence of Bergslagen ore lead (i.e., the minimum in ²⁰⁶Pb/²⁰⁷Pb isotope ratios) in both Kalven and Noren occurs c. 1490–1500, when also varve properties change in Kalven and in Noren sharp increases occur in the concentrations of a range of other ore-related metals (e.g., arsenic, cadmium, copper, iron, lead, mercury and zinc). From the 15th century onwards mining and metallurgy are the dominant feature of the sediment records.     

Sedimentation rates in the Lake Qattinah using 210Pb and 137Cs as geochronometer

The constant rate of supply (CRS) of excess ²¹⁰Pb model was successfully applied to assess ²¹⁰Pb data of two sediment cores from the lake Qattinah, Syria. Gamma spectrometry was used to determine ¹³⁷Cs and ²¹⁰Pb activity concentrations. The bottom of the cores was ²¹⁰Pb-dated to years 1907 and 1893. The accumulation rates were determined using ²¹⁰Pb method and found to vary similarly in both cores from 0.10 ± 0.01 to 3.78 ± 0.57 kg m^?2 y^?1 during the past century. ¹³⁷Cs was used as an in-dependent chronometer. The two distinct peaks observed on the ¹³⁷Cs record of both cores, corresponding to 1965 and 1986, have allowed a successful validation of the CRS model.     

The deserts of the Kashmir‐Tibetan frontier

Abstract

Semi-arid landscapes are vulnerable to cultivation, overgrazing and climate variability, although it is difficult to identify the relative significance of these three factors. In the South African Karoo, the ‘desertification debate' seeks to explain a change to more shrubby vegetation in heavily grazed areas. We examine these issues in catchments where farm reservoirs provide sediment stores with 137Cs, 210Pb, geochemical and mineral magnetic signatures. Rainfall data and stocking numbers are reported and current erosion rates are estimated. Sediment accumulation in the reservoirs increases between 1935 and 1940, probably due to rises in the frequency of rainfall events of >25mm day. Significant increases in sedimentation rates (×8) occur during rain-fed wheat cultivation. In an uncultivated catchment, sediment yields remain relatively high and reflect increases in erosion from hillslopes, colluvial storage, and cultivated land sources. Gully systems have acted as transport routes rather than sediment sources over the last ～70 years. Badland erosion rates average ca. 50t ha^?1 yr^?1. At Ganora, their development in the 1920s strongly influences peak sedimentation between 1970 and 1980. Any delay between badland initiation and increased sediment yield appears to be a function of landscape connectivity. Recovery following disturbance is occurring slowly and is likely to take >100 years. De-stocking and better management systems are reducing erosion rates but may be offset by increases in rainfall intensity.     

Fire and man in post-glacial woodlands of Eastern England

It has for long been suggested that English early post-glacial woodlands, particularly those dominated by hazel, were a fire-climax vegetation type. This conflicts with the evidence of fire frequency in present-day woodlands. Charcoal and pollen analyses of post-glacial lake sequences in East Anglia, England, suggest that early post-glacial woodlands were not fire-climax types. The pre-5000 BP charcoal record can be best interpreted as a record of intensity of occupation beside lake shores. After 5000 BP, charcoal deposition may reflect increasing use of fire as an agent in land clearance.     

A Geomorphic and Environmental Evaluation of the Hula Drainage Project,Israel

The drainage of Lake Hula and its swamps in the 1950s created a new landform and changed the hydrological and sedimentological regime in the Hula valley. The affected area extended over 40 km² and the work basically improved the drainage conditions of another 20 km² that were periodically affected by flooding. This man‐made project marked the termination of one of the oldest documented lakes and surrounding wetlands in history, with a rich and diverse aquatic biota. The reclaimed swampy land started to settle immediately upon drainage, mainly due to the compaction of the peat layers. The mean yearly settling rate was 8 cm yr^–1. Agricultural development of the reclaimed land was unsuccessful, and soils were affected by continuous underground fires. Weathered peat soils, without a vegetation cover, were eroded by wind. Another ecological effect was the release of nutrients by the decomposing peat, with the nutrients carried by the Jordan river floods into the eutrophic Lake Kinneret. To prevent the natural subsidence a small shallow lake, 110 ha in area, and a network of canals were created in the 1990s. This new wetland and the adjacent agricultural areas are the targets of a multidisciplinary monitoring program. An eco‐tourism development project is currently being planned. Almost 50 years after starting the drainage project the present trend is to restore at least a small fragment of the previous landscape and ecosystem.     

THE AMBER OF EL DORADO: CLASS IB ARCHAEOLOGICAL AMBERS ASSOCIATED WITH LAGUNA GUATAVITA*

Laguna Guatavita, a crater‐like lake located in central Colombia, was used by pre‐Columbian Muisca people for a variety of socio‐religious ceremonies, many of which involved casting offerings into the lake. Of these, the installation of a new ‘king’ became the basis of the El Dorado myth that was carried back to Europe by 16th century conquistadores. In the present study, beads collected from Laguna Guatavita during a late 19th/early 20th century attempt to recover valuables from the lake bed, have been subjected to geochemical analysis. Results establish that these artefacts have been fabricated from Class Ib amber. Class Ib ambers have not previously been reported in either the geological or archaeological records of Central or South America, and their existence in this context implies that the Muisca people had access to a unique local or regional source of amber, knowledge of which has subsequently been lost.     

Soil and organic carbon losses from varying land uses: a global meta‐analysis

Soil (SL) and organic carbon losses (SOC_L) have increased with human population and climate change linked extreme events. While SL and SOC_L are clearly associated with surface run‐off, the impact of land use is still not well understood. This article elucidates the effects of land use, surface cover, and other environmental factors on SL and SOC_L using data from 55 published studies. The overall SL (12.34 ± 2.25 Mg ha^?1 year^?1) and SOC_L (21.80 ± 0.91 g C m^?2 year^?1) suggests substantial losses of the fertile topsoil globally. Grasslands (4.19 ± 1.22 Mg ha^?1 year^?1) had 77%, 66%, and 41% lower SL than orchards, croplands, and forests, respectively, which is attributable to higher soil organic matter and surface cover. Croplands had the highest SOC_L at 22.78 ± 2.22 g C m^?2 year^?1. Natural vegetation had 98% and 70% lower run‐off and SL than did plant residue mulched plots, indicating its great potential for surface run‐off and soil erosion control. Rainfall and slope were key drivers of soil erosion, while soil surface cover, SOC, and clay content decreased. These findings improve our knowledge on soil and organic carbon losses, which is useful for fostering sustainable management of soils and natural vegetation to enhance ecosystems functionality.     

An Examination of Vertical Accretion of Floodplain Sediments in the Labasa River Sugarcane Belt of Northern Fiji: Rates,Influences and Contributing Processes

The ¹³⁷Cs (caesium‐137) method was used to investigate medium‐term rates of sediment deposition on the floodplain of the Labasa River, on Vanua Levu island in northern Fiji. The Labasa basin is commercially important for sugarcane farming, which provides much revenue and sustains the economy in the greater Labasa area. Alluvium was sampled at three riverbank sites in vertical increments of 30 mm. Measured net vertical accretion rates, based on analysis of depth‐profiles of ¹³⁷Cs activity, ranged from 10 mm yr^?1 at a low‐lying site near a tributary confluence with the main river, to 60 mm yr^?1 on a levée that was elevated slightly above the adjacent floodplain. These rates of accretion are high, but in general agreement with rates recorded using similar methods in other tropical Pacific island river systems. Soil erosion under sugarcane on hilly parts of the lower Labasa basin is an important factor in rapid floodplain development. Observations made during Cyclone Ami, which traversed Vanua Levu island in early 2003, illustrate the major contribution of severe storm events to floodplain sediment supply, by triggering numerous landslides on catchment slopes and in‐channel debris floods, and by generating large‐magnitude overbank floods.     

清代东太湖地区的湖田与水文生态

清代的东太湖地区的湖田出现了快速增长。随着山区水土流失,东太湖的泥沙量大增,水面植被也出现大扩展,淤积和湖田扩展也因此加速。在西部出现大缺口,大缺口在清代很快合拢。东部湖田发展使出太湖的水流受阻,吴淞江北移瓜泾口,进而使东北部湖田快速发展。湖田形成时往往先是大圩,后是小圩,以后逐步形成纵向交错的河网。植桑又加速了湖田水稻土的培肥,优良的水稻土在小圩规模上逐步形成。植桑养蚕与稻作的配合维持了传统江南生态农业的持续。     

Sensitivity of bulk sedimentary stable carbon isotopes to prehistoric forest clearance and maize agriculture

The stable carbon isotope compositions (δ¹³C) of tropical lake sediments and soils have been used to reconstruct the occurrence of prehistoric maize cultivation and its relative importance through time. This study assesses some of the possible variables affecting the response of lake sediment bulk organic carbon isotope (δ¹³C_TOC) values to variations in the scale of prehistoric maize cultivation and the potential of this proxy to yield quantitative estimates of the scale of prehistoric maize agriculture in small tropical watersheds. High resolution analyses of δ¹³C_TOC values, maize pollen concentrations, and mineral influx were conducted on sediments deposited during a ∼220 year period of prehistoric maize agriculture in the watershed of Laguna Castilla, a small lake in the mid-elevations of the Cordillera Central, Dominican Republic. Close correspondence between δ¹³C_TOC values and maize pollen concentrations in the Laguna Castilla sediment record indicates a close relationship between the isotopic values and the scale of prehistoric maize cultivation. Correlations between the δ¹³C_TOC signature and mineral influx indicate that the isotope record is also sensitive to variations in allochthonous carbon delivery. This study establishes that sedimentary δ¹³C_TOC values can provide a highly sensitive proxy of the spatial scale of prehistoric maize agriculture in small tropical watersheds, but emphasizes the need for a better understanding of sediment dynamics and carbon cycling in anthropogenically modified landscapes before this proxy can be widely employed in diverse archaeological settings.     

Spatial pattern of land cover changes across Northeast China over the past 300 years

To accurately model the regional climatic effects of land use/cover change processes, precise reconstructions of historical land cover are essential. Over the past 300 years, the northeastern region has undergone more significant land cover change than any other region in China owing to large numbers of farmer migrants from North China, reflecting the tremendous effects human activities can have on such changes. In this paper, based on official statistical data, documentary records, survey data, and modern remote-sensing data and vegetation and soil maps, land cover changes across Northeast China over the past 300 years have been reconstructed through cropland data calibrations using correlation analysis, potential vegetation reconstructions, urban area estimations, spatial analyses of land cover type changes by K-mean clustering analysis, and consideration of land use driving forces. The results indicate that cropland expanded gradually from south to north through the cities of Shenyang, Jilin, and Ha’erbin as well as out to the margins of the central plain of Northeast China, with a maximum expansion occurring in the 1950s. Pristine forests and grasslands diminished significantly, especially in the early twentieth century, due to this expansion of cropland. The conclusions drawn from these results are, first, that these results provide a scientific understanding of the process by which the original land cover was replaced by cropland in Northeast China over the past 300 years. Second, the results enabled the development of a series of land use/cover changes maps with 50–100 year time resolutions and county-level spatial resolutions. Based on the reconstructed results of these land cover type changes, the dynamics and causes of land cover changes are discussed in their social–historical contexts.     

Developing a Synthetic Index of Land Vulnerability to Drought and Desertification

This paper develops an index of the vulnerability of land to drought and desertification (LVI) for Italy. The index takes into account changes in climate, land use, vegetation cover, soil properties, and population during the period 1990–2000. The LVI was built up through a multivariate approach aimed at assessing the importance of the various indicators included in the synthetic index. Increasing land vulnerability was observed during this time, especially in dry areas of the southern regions. This is interpreted as a consequence of land management practices, agricultural intensification, population pressure, and bio-physical degradation. The LVI can be used in an integrated, decision-support system to evaluate the impact of mitigation policies in rural environments.     

论湖泊的自然衰亡与可持续开发利用——以杭州西湖古今开发为例

从地理学角度看,湖泊都有自然沼泽化的趋势。人类活动可以加剧或者减缓这种趋势。杭州西湖就是由于人们古往今来的长期良性开发,才得以保存至今而且成为著名风景胜地的。在阐明这一原理的基础上,本文分析评价了近20余年来人们对此湖的开发行为,结论是:良性和非良性开发都在持续。这一结论对国内许多同类湖泊而言具有一定普遍性或代表性。