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1.
The relationship between soil geochemistry and die back of montane forests in Sri Lanka: a case study 总被引：1，自引：1，他引：0
P. N. Ranasinghe C. B. Dissanayake D. V. N. Samarasinghe R. Galappatti 《Environmental Geology》2007,51(6):1077-1088
Tropical montane forests of Sri Lanka form a unique ecosystem with more than 50% of endemic plant species. It has been noted
that trees, belonging to different size and age classes of these forest, have been dying due to a yet unknown factor. This
phenomenon was first observed in the Horton Plains National Park, which is a high plateau, composed of tropical montane forests.
Later dying of forests were observed at several areas including Hakgala montane forest.
Physical parameters trace nutrients as well as toxic element concentrations in soils, were studied in order to identify the
possible geochemical factors behind the forest die back. Systematic soil sampling was carried out covering the entire Horton
Plains National Park and random samples were collected from Hakgala montane forest. Samples were analyzed for available Fe,
Mn, Zn, Cu, Ni, Cd, Al and Pb using standard colorimetric and atomic absorption spectrometric procedures. Physical parameters
such as pH, moisture content, and conductivity of the samples were also measured.
Among extractable micro-nutrients Cu and Zn, and Ni show no deficiency or excess levels. However, the recorded available high
concentrations of Fe, Mn and Al can be toxic to certain montane plant species. Acidic moist soil of the area may enhance the
toxic effects of these elements. Possible source of these elements should be the underground lithology of the area.
According to the results obtained, there is a relationship between forest die back and high Pb concentrations. The same phenomenon
was also observed in the Hakgala forest. The distribution pattern of Pb in the Horton Plains coincides well with the die back
distribution pattern. The observed Pb values at Horton Plains and Hakgala are almost similar to values observed at Pannipitiya
and Dombagaskanda locations, which are located close to main roads carrying heavy traffic. It is quite possible therefore,
that Pb toxicity may be a significant factor behind the forest die back even though other factors should not be completely
ruled out at this juncture. Strong monsoon winds, bringing Pb from the polluted southwestern part of the country, can be the
most possible source of soil Pb. Further studies however are indeed necessary to confirm the conclusion. 相似文献
2.
Biodiversity loss, climate change, and increased freshwater consumption are some of the main environmental problems on Earth. Mountain ecosystems can reduce these threats by providing several positive influences, such as the maintenance of biodiversity, water regulation, and carbon storage, amongst others. The knowledge of the history of these environments and their response to climate change is very important for management, conservation, and environmental monitoring programs. The genesis of the soil organic matter of the current upper montane vegetation remains unclear and seems to be quite variable depending on location. Some upper montane sites in the very extensive coastal Sea Mountain Range present considerable organic matter from the late Pleistocene and other from only the Holocene. Our study was carried out on three soil profiles (two cores in grassland and one in forest) on the Caratuva Peak of the Serra do Ibitiraquire (a sub-range of Sea Mountain Range – Serra do Mar) in Southern Brazil. The δ13C isotopic analyses of organic matter in soil horizons were conducted to detect whether C3 or C4 plants dominated the past communities. Complementarily, we performed a pollen analysis and 14C dating of the humin fraction to obtain the age of the studied horizons. Except for a short and probably drier period (between 6000 and 4500 cal yr BP), C3 plants, including ombrophilous grasses and trees, have dominated the highlands of the Caratuva Peak (Pico Caratuva), as well as the other uppermost summits of the Serra do Ibitiraquire, since around 9000 cal yr BP. The Caratuva region represents a landscape of high altitude grasslands (campos de altitude altomontanos or campos altomontanos) and upper montane rain/cloud forests with soils that most likely contain some organic matter from the late Pleistocene, as has been reported in Southern and Southeastern Brazil for other sites. However, our results indicate that the studied deposits (near the summit) are from the early to late Holocene, when somewhat wetter and warmer conditions (since around 9000 cal yr BP) enabled a stronger colonization of the ridge of Pico Caratuva by mainly C3 plants, especially grassland species. However, at the same time, even near the summit, the soil core from the forest site already presented the current physiognomy (or a shrubby/elfin or successional forest), indicating that the colonization of the neighboring uppermost saddles and valleys were probably populated mainly by upper montane forest species. 相似文献
3.
A study of the abundance of Be in the gem sediments of Sri Lanka shows that Be is found in the range of 1–13 ppm. Be shows an irregular distribution among sediments. It occurs in the silicate form and due to the proximity to the beryllium bearing rocks, namely granites and pegmatites of the Highland and Southwest Groups of Sri Lanka, very little decomposition of the Be-bearing minerals had taken place. This is further aided by the high resistance to weathering of the beryllium minerals, particularly beryl and chrysoberyl.The beryllian granites and pegmatites of the Precambrian of Sri Lanka are presumed to have been formed due to the magmatic activity associated and related to charnockitic rocks abundant in the main gem bearing areas of Sri Lanka.Fluorine is found in the range of 400–2,000 ppm and the F/Be ratios for all the areas studied show a range of 54–441. The analysis of the averages of these ratios do not show any particular anomaly in any of the areas studied. The narrow ranges of the F/Be ratios indicate the similar conditions under which weathering and geochemical transportation had taken place in the gem fields of Sri Lanka. 相似文献
4.
Margo Kleinfeld 《GeoJournal》2005,64(4):287-295
This paper describes the changing discourses of territory in Sri Lanka and their utility in conflict relations. The primordial
homeland has been at the center of Sri Lanka’s armed struggle, in which both Sinhalese and Tamil nationalisms have used claims
of ancient and ethnically determined territories to justify their right to self-determination, territorial sovereignty, and
armed struggle. This identity–territory nexus based on historical argument has been destabilized in Sri Lanka, however. Scholarly
findings suggest that historical linkages between ethnicity and territory in Sri Lanka are highly problematic and are no longer
effectual means for adjudicating territorial desires in Sri Lanka and producing stable homelands. I argue that rights-based
territorial discourses have emerged to enhance the old historical justifications for territorial authority. New narratives
based upon fulfilling or denying human rights have been put to work linking authority to territory based upon moral fitness
and unfitness, political legitimacy and illegitimacy, and ultimately, upon which political actor deserves to rule the territorially
bound population under its control. The first part of the paper examines historical narratives linking national homelands
to identity as well as scholarly work that deconstructs this linkage. In part two, external sovereignty and political legitimacy
are discussed as the starting point for understanding how rights-based discourses justify territorial claims. In part three,
accusations related to human rights violations are described as an important vehicle for shaming political adversaries, undermining
their legitimacy, and making and unmaking territorial claims in Sri Lanka. 相似文献
5.
《Gondwana Research》2000,3(1):3-5
The tectonic history of Sri Lanka - India can be traced from the Precambrian to the present. On the basis of the geological record, plate tectonic processes have operated for example, the Highland Group of Sri Lanka may have represented a Precambrian plate tectonic suture. Tectonic models of these Precambrian events may be presented by spreading, collision, subduction, shearing or in situ jostling. The recent tectonic history of Sri Lanka and India relates to the evolution of the Indian Ocean since at least the Cretaceous. Although Sri Lanka is considered to be a part of the larger Indo - Australian plate, it may have had a local independent history as a block within the larger crustal unit of India. There is evidence that the separation of Sri Lanka from India was in part controlled by Precambrian structures and a history of translational, rotational and vertical adjustments to the Indian Ocean developmental plate tectonic stresses still operating. 相似文献
6.
Kanthi K. A. S. Yapa 《Journal of Earth System Science》2000,109(4):427-432
Remotely sensed data on ocean colour of waters surrounding Sri Lanka received from the Coastal Zone Colour Scanner (CZCS)
are processed and analyzed. Raw data of 1 km resolution on relatively cloud free days during 1978–1986 are processed to produce
sea surface chlorophyll maps within latitudes 4.5N-11N and longitudes 78E-85E, a region in the Indian Ocean surrounding Sri
Lanka. The processed data include about 110 single day maps and composite averages for each month and season. The months of
July, August and September are omitted in the calculation of averages due to insufficient data. The waters in the Gulf of
Mannar and Palk Bay areas show high chlorophyll-a concentrations throughout the year. However, these high values may represent
other suspended particles and dissolved organic matter besides chlorophyll-a as this region is shallow (< 100 m). Regions
with high chlorophyll concentrations (> 0.5 mg m-3) along the coast and western ocean region can be seen in the months of October and November, after the southwest monsoon
period. As high surface chlorophyll concentrations may indicate high productivity, these regions need extensive measurements
of primary production and also continuous monitoring of fish catches, during and after the southwest monsoon. Studies of particle
composition in shallow water areas, in particular waters in Palk Bay and Gulf of Mannar, should be carried out in order to
elucidate the effect of non-phytogenic. 相似文献
7.
Pollen from the upper 90 m of core OL-92 from Owens Lake is a climatically sensitive record of vegetation change that indicates shifts in the plant associations representing warm and cold desertscrub, pinyon–juniper woodland, and pine–fir forest during the past 180,000 years. These changes are synchronized with glacial–interglacial cycles. During glacial and stadial climates, juniper woodland expanded downslope and replaced warm desert shrubs while upper montane and subalpine forests in the arid Inyo Mountains also expanded, and those in the Sierra Nevada were displaced by the ice cap and periglacial conditions. Conversely, during interglacial and interstadial climates, warm desert plants expanded their range in the lowlands, juniper and sagebrush retreated upslope, and montane and subalpine forests expanded in the Sierra Nevada. The reconstructed vegetation history demonstrates a regional climatic response, and the congruence of the pollen sequence with marine and ice cap oxygen isotope stratigraphies suggests a link between regional vegetation and global climate change at orbital scales. 相似文献
8.
Sri Lanka has one of the lowest fertility rates among poor countries of the world. The fertility decline which began in the
1950s has held steady during the last four decades, despite low levels of economic development. Widespread use of contraception
is the primary cause of the fertility decline. However, there is no one single homogenous body of people that can be characterized
as a ‘modern’ contracepting population through which new methods of family planning have spatially diffused. There is evidence
that the overall fertility decline began even before the establishment of the modern family planning program in Sri Lanka.
Our analysis showed four broad regional regimes of fertility transition with considerable social and place-to-place differences
in method-specific rates of contraception among them. Non-modern ‘traditional techniques’ of contraception which are widely
used are an important part of fertility regulation. Sterilization is the most common method of modern contraception in all
regions. Less than a tenth of the protected couples use methods such as the pill and the IUD; moreover, these methods are
often discontinued after initial use. Traditional methods are an important part of the contraceptive mix in Sri Lanka, and
it would be inadvisable to discourage the use of such practices.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
9.
Dr. John Connell 《GeoJournal》1988,16(2):193-200
Approximately 50,000 ha of native ‘ōhi’a (Metrosideros polymorpha) rain forest on the windward side of the island of Hawaii experienced a pronounced dieback of the tree canopy during the
1960s and early 1970's. The forests affected were located between 600 and 1,500 m elevation where the median annual rainfall
was greater than 25000mm. Dieback stands were found on a variety of different substrates ranging from 500–10,000 years in
age. Most of the stands that experiencel dieback had canopy cover greater than 60% prior to 1960.
In 1976 and 1977 we established 43 relevés in dieback and non-dieback forest stands to assess canopy tree vigor, composition
and structure of the vegetation, and to describe substrate characteristics.Metrosideros population structure and tree vigor were resampled for 25 of these relevés in 1982 and 1985–1986. The results of air photo
analysis and ground sampling showed that dieback has not expanded very much within the study area since 1977. However, 5 of
the relevés sampled in 1977 continued to decline in tree canopy vigor between 1977 and 1982 while 2 others showed a slight
recovery in vigor over this same period.
Seedling and sapling regeneration has been extremely vigorous in most of the sites that experienced a breakdown of the canopy
while, in stands with an intact, dense tree canopy no such regeneration occurred. It appears that most of the stands which
experienced canopy dieback have the potential to become closed forest communities again, dominated byMetrosideros. The natural recovery process may be disrupted in some areas due to additional competition for light and nutrients from invading
populations of both native and alien plant species that have become established following canopy dieback. 相似文献
10.
Rohana Chandrajith Nadeesha Koralegedara K. B. Ranawana H. J. Tobschall C. B. Dissanayake 《Environmental Geology》2009,57(1):17-28
Forest die back has been observed from 1980s in the montane moist forest of Horton Plains in the Central Sri Lanka for which
the aetiology appears to be uncertain. The concentration levels of Na, K, Ca, Mg, Fe, Mn, Cu, Ni, Zn and Pb in canopy leaves,
bark and roots, which were collected from dying and healthy plants of three different endemic species, Calophyllum walkeri, Syzygium rotundifolium and Cinnamomum ovalifolium, from three different die back sites were studied. Soils underlying the plants were also analyzed for their extractable trace
metals and total contents of major oxides. Analysis of dead and healthy plants does not show any remarkable differences in
the concentrations of studied trace elements. The results show that there is a low status of pollution based on the concentrations
of chemical elements of environmental concern. Extractable and total trace element analysis indicates a low content of Ca
in soils due to high soil acidity that probably leads to Mg and Al toxicity to certain plants. Relatively high Al levels in
the soil would affect the root system and hamper the uptake and transport of essential cations to the plant. It therefore
seems that the forest declining appears to be a natural phenomenon, which occurs due to the imbalance of macro and micronutrients
in the natural forest due to excessive weathering and the continuous leaching of essential elements. 相似文献
11.
南海南部末次冰期以来的孢粉记录及其气候意义 总被引：24，自引：0，他引：24
本文通过分析南海南部１７９６４柱状样的孢粉记录,重建了该地区２６０００ａＢ．Ｐ．以来的植被和气候变化历史。南海南部末次盛冰期时高山雨林的范围可能是现在的２～３倍,表明气温明显下降;从末次盛冰期到冰消期,巽他陆架一直为热带低地雨林及红树林占据,表明在此期间湿度没有明显变化,但存在着千年级的准周期波动。这种波动一直持续到全新世中期。本地区在２０００ａＢ．Ｐ．以来芒萁孢子大量增加,一些高山雨林的成分重新出现,可能与人类活动所导致的低地植被的破坏有关。 相似文献
12.
S. R. Kalsi 《Journal of Earth System Science》2000,109(2):211-220
BOBMEX-Pilot was organised from 23rd October–11th November, 1998 when the seasonal trough had already shifted to south Bay
of Bengal. The activity during this period was marked by the development of a monsoon depression from 26th–29th October that
weakened over the sea; onset of northeast monsoon along the east coast of India on 29th October; a low pressure area that
formed on 2nd November over southwest Bay off Sri Lanka — southTamilnadu coast; and another cyclonic circulation that formed
towards the end of the BOBMEX-Pilot period. This paper describes the development of these synoptic systems through synoptic
charts and satellite data. 相似文献
13.
Factors controlling fluoride contents of groundwater in north-central and northwestern Sri Lanka 总被引：1，自引：0，他引：1
Chemical characterization has been made of groundwater bodies at 294 locations in four village districts in north-central
and northwestern Sri Lanka, with special focus on fluorine contamination. High fluoride contents in groundwater are becoming
a major problem in the dry zone of Sri Lanka, and dental fluorosis and renal failures are widespread. Field measurements of
temperature, pH, and electrical conductivity were made during sampling. Chemical analyses of the water samples were later
made using atomic absorption spectroscopy, spectrophotometry, and titration. Fluoride concentrations in the study area vary
from 0.01 to 4.34 mg/l, and depend on pH and the concentrations of Na, Ca, and HCO3
−. Basement rocks including hornblende biotite gneiss, biotite gneiss, and granitic gneiss seem to have contributed to the
anomalous concentrations of fluoride in the groundwater. Longer residence time in aquifers within fractured crystalline bedrocks
may enhance fluoride levels in the groundwater in these areas. In addition, elevated fluoride concentrations in shallow groundwater
in intensive agricultural areas appear to be related to the leaching of fluoride from soils due to successive irrigation. 相似文献
14.
A recent publication on the phytolith assemblage at Fahien rockshelter, Sri Lanka (Premathilake and Hunt) is argued to represent: the exploitation of wild Musa acuminata and M. balbisiana during the Late Pleistocene; the introduction of edible diploid cultivars from the Southeast Asia–New Guinea region during the early to mid‐Holocene; the generation and cultivation of triploid banana hybrids on Sri Lanka before 6194–5994 cal bp ; and the subsequent spread of derived triploid cultivars to mainland India and westward to Africa. A careful review of the archaeobotanical research presented by Premathilake and Hunt, in the context of broader multidisciplinary evidence (agronomy, archaeobotany, genetics and linguistics) for the domestication and spread of banana cultivars, indicates that three main aspects of their argument are problematic: the lack of clarity in the characterization of banana domestication in the past; the methods used to discriminate phytoliths into banana taxa; and the promotion of Sri Lanka as a source region rather than a recipient of banana cultivars. Following reconsideration, the Fahien evidence is consistent with previous interpretations for the origins of diploid and significant triploid cultivars outside of Sri Lanka and dispersal to that island. © 2019 John Wiley & Sons, Ltd. 相似文献
15.
Sm-Nd model ages of orthopyroxene-bearing massif charnockites from the Cardamom Hills Massif and adjoining supracrustal rocks from the Kerala Khondalite Belt in southernmost India are used to infer some of the relationships within these rocks and between them and neighboring areas. Most of these rocks have model ages of 2.1–2.8 Ga with most charnockites in the range 2.2–2.6 Ga. Thus, 3.0–3.4 Ga Archean rocks to their north did not contribute material to either suite and the two suites may have been juxtaposed after formation of the supracrustal rocks. The similarity of Sm-Nd isotope systems in the two units studied here supports an argument that the massif charnockites were the primary sole source of the detritus incorporated into the supracrustal rocks. A cordierite gneiss, representative of a relatively minor lithology in the supracrustal belt, has a model age of 1.3 Ga. The protolith of this gneiss not only formed from much younger material than the rest of the belt but also formed significantly after the other metasedimentary rocks. The source material of the gneiss protolith may have been located in the Wanni and Vijayan Complexes of Sri Lanka. The overlap of the model ages of rocks in this area and those in the Highland Complex of Sri Lanka supports the notion that these two sets of rocks were joined to each other in Gondwana. They belong to a belt that ran from Antarctica through Sri Lanka and India into Madagascar. This belt was involved in Pan-African tectono-metamorphism, as reflected in the 550 Ma age of the last, granulite-forming, event throughout the belt. 相似文献
16.
L.R.K. Perera 《Precambrian Research》1984,25(4):349-364
A co-existing cordierite—almandine assemblage is described from the pelitic metasedimentary rocks of the Precambrian granulite-facies terrain of Sri Lanka. The chemical control on this assemblage is demonstrated, as has been observed in granulite-facies terrains elsewhere. The previous view of a low-pressure origin of cordierite in pelitic rocks, and the subdivision of the central granulite-facies belt of Sri Lanka based thereon, is hence doubtful. 相似文献
17.
Geology of the High Grade Proterozoic Terrains of Sri Lanka, and the Assembly of Gondwana: an Update on Recent Developments 总被引：1，自引：0，他引：1
Nd model ages determined for the high-grade rocks of Sri Lanka delineate three crustal units, viz., the Highland Complex (HC), the Wanni Complex WC), and the Vijayan Complex (VC). The distribution of these three units differs considerably from the three geological divisions demarcated previously on the basis of geological mapping. The centrally located HC comprises mainly granulite grade charnockitic rocks, and metasediments characterized by older Nd model ages (2.0–3.4 Ga). The Highland sedimentary pile was thickened by intermittent granitoid intrusions, most of which are now charnockitic gneiss, and granulites, and basaltic sills, and dikes. All these metaigneous rocks now occur as conformable bands or layers due to intense polyphase deformation. The HC is bounded on the east by the amphibolite grade VC, composed mainly of granitic gneisses, basic gneisses, and migmatites, and they have ‘younger’ Nd model ages (1.1–1.8 Ga). The isotopic, and geochemical characteristics identify the precursors to the Vijayan rocks as I-type calc-alkaline granitoids originated at an ‘arc’-related tectonic environment. Thus, the earlier interpretation that the Vijayan rocks represent reworked HC was rejected. The granulite inliers within the VC, earlier considered as “resisters” to re-working, are now shown as overthrust klippen or rotated rafts of the HC. The WC, demarcated on the basis of Nd model ages (1.1–1.8 Ga) similar to those of the VC, lies west of the HC. It consists mainly of granitic gneisses, charnockitic gneisses, and migmatites, and the metamorphic grade ranges from amphibolite to granulite.Comprehensive geothermobarometric surveys constrain the P-T evolution of the three crustal units, and indicate that both the HC, and WC underwent near isobaric cooling, followed by a decompression with decreasing temperature. Extensive isotopic studies (U-Pb, Pb-Pb, Sm-Nd, Rb-Sr) have established a new geochronological framework for these high-grade rocks of Sri Lanka. The new framework has bracketed the age of high grade metamorphism in the three crustal units at 550–600 Ma.The recent advances in knowledge of the geology of Sri Lanka favour a strong geological correlation of the HC, and the VC of Sri Lanka, respectively, with the Lutzöw-Holm Complex, and the Yatmato-Belgica Complex in the East Antarctica. The geology of the WC suggests a possible correlation with Madagascar, and East Africa. The amalgamation of the three crustal units of Sri Lanka, is apparently related to the two distinct orogenic events that resulted in the assembly of the Gondwana supercontinent. 相似文献
18.
19.
J. Birkmann P. Buckle J. Jaeger M. Pelling N. Setiadi M. Garschagen N. Fernando J. Kropp 《Natural Hazards》2010,55(3):637-655
Disaster associated with natural hazards can lead to important changes—positive or negative—in socio-ecological systems. When
disasters occur, much attention is given to the direct disaster impacts as well as relief and recovery operations. Although
this focus is important, it is noteworthy that there has been little research on the characteristics and progress of change
induced by disasters. Change, as distinct from impacts, encompasses formal and informal responses to disaster events and their
direct and indirect impacts. While smaller disasters do not often lead to significant changes in societies and organizational
structures, major disasters have the potential to change dominant ways of thinking and acting. Against this background, the
article presents an analytical framework for distinguishing change from disaster impacts. Drawing from research in Sri Lanka
and Indonesia, formal and informal changes after the Indian Ocean Tsunami of 2004 are examined and discussed against the background
of the conceptual framework. The changes examined range from the commencement of the peace process in Aceh, Indonesia, to
organizational and legal reforms in Sri Lanka. The article concludes that change-making processes after disasters need to
be understood more in depth in order to derive important strategic policy and methodological lessons learned for the future,
particularly in view of the increasing complexity and uncertainty in decision making due to climate change. 相似文献
20.
At a time when the concept of ‘human and environmental symbiosis’ has taken on much significance, protection of suburban forests
(i.e. forests adjacent to or near developed areas) is a topic that has drawn much attention. Suburban forests have, since
ancient times, been places where people have gathered firewood and cultured trees. As a result, the vegetation of suburban
forests is only partially natural and continues to change as the forms of human activity in and around them changes. Accurate
forecasts of how suburban forests will change are, therefore, an important element in the debate over how to protect them.
In this study, a suburban forest was analyzed with laser radar sensing, multi-spectrum scanning, digital photogrammetry analysis,
aerial photograph interpretation, and a field survey. Data gathered using these techniques were compiled on a GIS to forecast
future changes in the forest. Aerial photographs taken over the past 50 years were analyzed to illuminate changes in the forest
over that period. Specifically, comparisons of precise Digital Elevation Models (DEMs) measured by using digital photogrammetry
workstations made it possible to estimate growth in forest height. The possible future conversion of such results to estimates
of amounts of carbon dioxide consolidated by forests should be very significant for discussions of global environmental problems.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献