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ABSTRACT. The Shimentai Nature Reserve in Yingde County, Guangdong Province, China, established recently in a subtropical upland forest area, has served for ages as an essential and customary source of livelihood for local people. Assessment of forest usage indicates heavy reliance by villagers on its diversified biotic resources. This forest dependence, associated with socioeconomic factors such as distance from village, ethnic origin, out‐migration of rural youngsters, and a local tradition of conservation, is unlikely to decline in the near future. The reserve management recognizes the need to address the livelihood issues of local people and to win local support. A pragmatic adherence to provincial and higher‐level policies that exclude forest‐tapping activities could lead to more people‐versus‐park conflicts, which would dilute fundamental conservation objectives. A more enlightened and localized approach that nurtures a synergy between limited forest use and conservation while helping to develop new income sources could furnish workable alternatives. 相似文献
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KEVIN TIMONEY GEORGE PETERSON PAT FARGEY MURRAY PETERSON STEVE McCANNY ROSS WEIN 《Climatic change》1997,35(4):463-483
A historic record of spring ice-jam floods of the Peace-Athabasca Delta was analyzed for the years 1826–1995. The temporal pattern of flooding is non-random. The likelihood of a flood following a flood, or a non-flood following a non-flood, is greater than expected by chance. Probability analysis of flood occurrence reveals that the period 1860–1880 was a time of unusually few floods, and the period 1915–1950 was a time of unusually frequent floods. The long-term flood frequency is 1 flood in 6.25 years. Changes in flood frequency over the record reveal a pattern of oscillation described by a sine-based model that is correlated with the long-term (Gleissberg) cycle of solar activity. Monte Carlo simulation was used to test a Bennett Dam Model and a Cyclic Model. The Bennett Dam Model is unlikely to have generated the observed flood history (p=0.04). The observed flood history shows a better fit to the Cyclic Model (p=0.65). No correlations between floods and ENSO cold or warm events was detected. The most recent wet period began about 1900 and ended in the early 1960's prior to completion of the W. A. C. Bennett Dam in British Columbia. As independent corroboration of climatically-driven changes in flood frequency we present three additional lines of evidence. The pattern of annual muskrat returns (95 year record) reveals both 10 year cycles and long-term patterns that agree well with the observed flood cycle. The annual area burned in Wood Buffalo National Park is inversely related to flood occurrence. Incised channels and dendritic drainage patterns in the bed of Lake Mamawi provide probable evidence of a previous dry period in the delta. Climatic change or oscillation likely underlies the drying trend observed in recent decades in the Peace-Athabasca Delta. 相似文献
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The diagenesis of carbonate platform sediments is controlled by the original facies and mineralogy, climate, sea-level changes and burial history; these controls are clearly seen in the diagenesis of the Urgonian platform carbonates of SE France. Early diagenesis in the Urgonian platform included the precipitation of marine cements, dissolution of rudist shells and minor karstification. Diagenetic features produced during this phase were controlled by several falls in relative sea-level during the Barremian to mid-Aptian punctuating platform sedimentation, the original mineralogy of the sediment and the prevailing semi-arid/arid climate in the region at this time. Following a relative sea-level rise and further sedimentation, progressive burial of the platform led to minor compaction, followed by precipitation of coarse, equant, zoned to non-luminescent, calcite cement. This cement was cut by later stylolites, suggesting a relatively shallow-burial origin. Stable isotope (mean values - 7.94%δ18O and 0.36%δ13C) and trace element (mean values of Fe 334 ppm, Mn 92 ppm and Sr 213 ppm) data suggest that these cements precipitated from meteoric fluids at temperatures slightly elevated relative to depositional temperatures. A variable thickness of replacive dolomite which occurs preferentially within the shelf-margin facies of the lower part of the Urgonian post-dates mechanical fracturing and chemical compaction, but pre-dates the main phase of stylolitization. It is probable that the dolomitizing fluid was sourced by the early compaction-driven release of connate fluids held within the underlying muddy units. The burial history of these rocks suggests that calcite cementation and dolomitization took place at relatively shallow burial depths (1–1.5 km). The overall diagenetic history of the Urgonian Limestone Formation is a reflection of the pre-conditioning of the platform limestones by climate, sea level, tectonics and the shallow burial depths experienced by the platform during the later Mesozoic. 相似文献
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STEVE WEBB 《Boreas: An International Journal of Quaternary Research》2010,39(2):312-324
Webb, S. 2009: Palaeotrophic reconstruction and climatic forcing of mega‐Lake Eyre in late Quaternary Central Australia: a review. Boreas, 10.1111/j.1502‐3885.2009.00120.x. ISSN 0300‐9483. Extreme Quaternary climatic variation in Australia brought radical environmental changes to various parts of the continent. In this article, I discuss these changes in terms of mega‐lake development in Central Australia, and in particular the southern Lake Eyre Basin (SLEB). The formation of these features, together with the fossil record of the region, throws light on the palaeoclimatic and palaeobiological relationships of megafauna and other animal groups, and the trophic development required to support them. Australian continental drying during the late Quaternary has been noted by many workers, but this process was punctuated by strong pluvial episodes of decreasing strength from MIS 5e. Mega‐lake development during MIS 5 resulted from unusual monsoonal and evaporative patterns at that time. However, the climatic forcing behind mega‐lake formation and the rate of lake growth is not well understood, although species composition in SLEB aquatic fossil fauna assemblages attests to the size and development of these lakes and indicates their long‐term persistence. The degree of trophic development and the maintenance of broad, well‐bedded aquatic and terrestrial ecological frameworks and biotic variety support that conclusion. The fossil record contributes to our understanding of mega‐lake and palaeoriverine trophic complexity, the speed and duration of lake‐fill and the intensity and persistence of the supporting intracontinental moisture balance. Although other more remote mega‐lakes formed in Central Australia, they were not populated by complex trophic systems or megafauna populations. This discrepancy between the various geographic areas sheds light on the biogeography and population distribution of megafauna, thus helping form a better picture of the reasons behind the final extinction of relict populations of this group in MIS 4. 相似文献
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STEVE KERSHAW 《Geology Today》1988,4(6):202-206
Stromatoporoids are an important group of fossil sponges that form some of the largest reef complexes in the fossil record and are valuable in palaeoecological and facies analysis. They are frequently large and easily studies in the field and in hand specimen. Using their growth forms it is possible to determine some features of sediment deposition rates and changes in their growth direction during life show episodes of turbulence that affected the sea bed. This article intriduces them, and gives practical help to interpret thier growth forms in quaries and cliffs where you may see them on fieldwork. You will realized just how absorbing these fossil sponges can be. 相似文献
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Megafauna demography and late Quaternary climatic change in Australia: A predisposition to extinction 总被引：1，自引：1，他引：0
STEVE WEBB 《Boreas: An International Journal of Quaternary Research》2008,37(3):329-345
Arguments about the extinction of Australia's megafauna have largely rested on anthropogenic factors consequent upon the arrival of humans there, and have lacked any appreciation of the possibilities of climate/environmental changes taking place during the late Quaternary. Moreover, the status of the megafauna at the extinction and in the period leading up to it has largely been ignored. This article assesses the species that existed during the late Quaternary, their continental dispersal, the likely impact of negative climate change during that time and the effect this had on their demography and variety. These factors are discussed together with a synthesis of present data regarding Australia's mega 2004: fauna demography and which species may have reached the extinction threshold. One interpretation of the data suggests a mid–late Quaternary process of demographic fragmentation, disjunction and fluctuation, a restricted continental distribution among a diminishing group and a limited and reducing species variety due to climate and environmental change. It is argued that increasing continental aridity during the mid–late Quaternary was a forcing mechanism behind species distribution, changes to that distribution and population reduction through episodic but widespread drought and vegetation change. This resulted in alteration of the biogeographic status of the megafauna, with increasing stress on and reduction of the population as a whole. In particular, it changed population composition and reduced species variety and overall population size by the beginning of the last glaciation, such that at the time of human entry the population had reached a precarious stage vulnerable to any level of subsequent anthropogenic activity with the arrival of humans in Australia. 相似文献
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STEVE W. LYON ELIN J. JANTZE HELEN E. DAHLKE FERNANDO JARAMILLO MATTIAS WINTERDAHL 《Geografiska Annaler: Series A, Physical Geography》2016,98(3):237-245
In this short communication, we report on dissolved organic and inorganic carbon concentrations from a summer stream monitoring campaign at the main hydrological catchment of the Tarfala Research Station in northern Sweden. Further, we place these unique high‐alpine observations in the context of a relevant subset of Sweden's national monitoring programme. Our analysis shows that while the monitoring programme (at least for total organic carbon) may have relatively good representativeness across a range of forest coverages, alpine/tundra environments are potentially underrepresented. As for dissolved inorganic carbon, there is currently no national monitoring in Sweden. Since the selection of stream water monitoring locations and monitored constituents at the national scale can be motivated by any number of goals (or limitations), monitoring at the Tarfala Research Station along with other research catchment sites across Fennoscandia becomes increasingly important and can offer potential complementary data necessary for improving process understanding. Research catchment sites (typically not included in national monitoring programmes) can help cover small‐scale landscape features and thus complement national monitoring thereby improving the ability to capture hot spots and hot moments of biogeochemical export. This provides a valuable baseline of current conditions in high‐alpine environments against which to gauge future changes in response to potential climatic and land cover shifts. 相似文献