Anak Krakatau's vegetation and flora circa 1991, with observations on a decade of development and change

Ecological surveys were conducted over the period 1989 to 1991 on the island of Anak Krakatau. The aims of the study were to detail a key phase of rapid change in the vegetation succession and plant colonization of this young volcano and to compare results with those from earlier studies.Floristic composition was determined by reconaissance of all vegetated areas during the period 1989 to 1991. Colonization has been rapid since 1983 with 53 species newly recorded for Anak Krakatau, comprising 8 Pteridophyta and 45 Angiospermae. Of the latter, a significant element (13) were of species believed to be human-dispersed. Comparison of all floral surveys has revealed a core of strand-line and pioneer colonists which has been common to each restart of colonization. The sea-dispersed component is already comparable in size to that of Rakata and is thought unlikely to increase significantly from this point. The accumulation of animal-dispersed species of interior habitats has only recently begun to pick up speed.Vegetation was characterised by means of plot-based sampling, including the establishment of three permanent plots, and by mapping at the whole-island scale. Variation in composition within the island is discussed, with particular reference to the three vegetated forelands. Anak Krakatau now supports the most extensive and advanced vegetation in its disrupted 61-year history. A more or less closed cover extends along the eastern/north-eastern coast-line, but the xeric interior remains only sparsely vegetated. It is concluded that because of volcanic disturbance a base-line for ecosystem development on Anak Krakatau cannot be calculated but that the pattern of change is not inconsistent with significant disturbance ca. 1972 and the subsequent relaxation of these peculiar environmental constraints.     

Anak Krakatau — a colonization model within a colonization model?

The ppaer re-examines three suggestions previously made concerning the colonization of the Krakatau islands since the extirpating 1883 eruption that involve the more recently emergent volcanic island Anak Krakatau, which itself suffered a devastating eruption in 1952. The suggestions re-addressed in the light of recent comments by other workers are:

Post-1883 ash fall on Panjang and Sertung and its ecological impact

This paper describes the post-1883 history of volcanic disturbance to the islands Panjang and Sertung, within the Krakatau group, Indonesia. Historical data are reviewed briefly, together with previous stratigraphic and geochemical data. In 1989 six profiles of soils, ashes and buried soils were described and sampled on each island, along with two on Rakata and one (in Krakatau ash) on Sebesi island. The results of analyses of chemical, physical and particularly of mineral magnetic properties are presented, with the aim of assessing spatial variation in ash fall history across Panjang and Sertung. We take a multivariate approach to analysis of the mineral magnetic data (employing an agglomerative classification), which has proved highly informative as a means of characterising ash fall events separated by (in geological terms) very short intervals.Most sites on both islands showed evidence of a number of distinct ash-falls in both the early 1930s and 1952/53 periods, of a highly disruptive nature. These and other periods of ash-fall are summarised in tentative models put forward for each island. Sites nearest to Anak Krakatau typically contained evidence of the largest number of different ashes. The implications of these data for the biogeography of the group are briefly discussed.     

Magma plumbing beneath Anak Krakatau volcano, Indonesia: evidence for multiple magma storage regions

Understanding magma plumbing is essential for predicting the behaviour of explosive volcanoes. We investigate magma plumbing at the highly active Anak Krakatau volcano (Indonesia), situated on the rim of the 1883 Krakatau caldera by employing a suite of thermobarometric models. These include clinopyroxene-melt thermobarometry, plagioclase-melt thermobarometry, clinopyroxene composition barometry and olivine-melt thermometry. Petrological studies have previously identified shallow magma storage in the region of 2–8 km beneath Krakatau, while existing seismic evidence points towards mid- to deep-crustal storage zone(s), at 9 and 22 km, respectively. Our results show that clinopyroxene in Anak Krakatau lavas crystallized at a depth of 7–12 km, while plagioclase records both shallow crustal (3–7 km) and sub-Moho (23–28 km) levels of crystallization. These magma storage regions coincide with well-constrained major lithological boundaries in the crust, implying that magma ascent and storage at Anak Krakatau is strongly controlled by crustal properties. A tandem seismic tomography survey independently identified a separate upper crustal (<7 km) and a lower to mid-crustal magma storage region (>7 km). Both petrological and seismic methods are sensitive in detecting magma bodies in the crust, but suffer from various limitations. Combined geophysical and petrological surveys, in turn, offer increased potential for a comprehensive characterization of magma plumbing at active volcanic complexes.     

The birds of Anak Krakatau: the assembly of an avian community

The avian colonization of Anak Krakatau, an emergent volcanic island, is described for the period 1952–1991 with emphasis on the resident land birds. The few species that had colonized the island by 1952 were destroyed in a volcanic eruption. Recolonization has been rapid and extensive but only documented by regular surveys that began in the 1980s. The waves of avian colonists associated with the following stages of plant succession are described: pre-vegetation, beach and grassland pioneers, casuarina woodland and mixed forest. Rainforest frugivores first reached the island in 1985 coinciding with the fruiting of the first fig trees. The three stages of plant succession and the bird communities associated with them co-exit on three separate lowland sites with about a 10–15 year delay between them. The guilds of shorebirds, predators, nectarivores, frugivores and insectivores are described. Densities of insectivores are very high; however between 1986 and 1990, some generalist species have fallen in abundance whereas some specialists have increased. The establishment species have fallen in abundance whereas some specialists have increased. The establishment of new colonists, especially pigeons, has been limited by the arrival of two species of falcons.     

Primary succession and the effect of first arrivals on subsequent development of forest types

The three Krakatau islands in Indonesia were completely denuded by the great eruption in 1883. One century after the eruption, the vegetation of Rakata on the one hand and of Panjang and Sertung on the other are quite different. Indigenous or exogenous Neonauclea seeds successfully formed Neonauclea forest on Rakata island but compltely failed to do so on Panjang and Sertung islands. The dispersal of seeds, soil conditions and volcanic activity of Anak Krakatau were all found to be contributing factors.The Timonius and Dysoxylum forests found on Panjang and Sertung originated on both islands after the appearance of Anak Krakatau. These dominants have larger seeds than Neonauclea and were able to germinate and grow under the regenerated mixed forest canopy but it was not so easy for them to colonize the Neonauclea forest. At the present time, their invasion progresses only gradually on Rakata. Ardisia scrub on steep coastal slopes on the Satsunan islands, SW Japan, is thought to be a somewhat parallel case of the retarding effect on the subsequent development of communities of the first arrivals. Ardisia scrub in these habitats appears to be a stable community, withstanding salt-laden wind. This shrub produces a number of stem and root sprouts, in a mop-headed growth. Their drupes are carried by birds and few seedlings were found in the scrub. The scrub floor was heavily shaded when its canopy was covered by lianes. The deep shade and frugivore activity prevent the invasion of other dominant species which would change the scrub into another type of forest. In milder habitats the scrub gradually becomes tall and the number of sprouts decreases, the forest then changes into another type such as Persea or Castanopsis forest.     

LGM时期气候背景下中国区域植被变化对东亚夏季降水影响的模拟

利用CCM3/NCAR全球气候模式在21kaB.P.(2.1万年前)的末次盛冰期(LGM)气候背景下,对中国区域植被变化对夏季(6～7月)东亚季风降水的影响进行了模拟,结果表明： 在LGM时期气候背景下,植被退化会使得中国东南部夏季降水减少,其中东南沿海减少超过20mm,而在 100°E 以东的中国北方大部分地区降水增加,其中心值大于50mm,从而导致降水南少北多的现象,植被的这种影响可以从物理上得到解释。在LGM气候背景下,植被退化在暖季起着增温的作用,即通过影响地表热状况使夏季大陆增温,增强了夏季东亚大陆与其周边海域的热力差异,从而使夏季东亚地区的西南风增强,35°～45°N的北方地区对流层低层的空气辐合和对流层上升运动加强,伴随着在 30°N 以南的中国南方地区出现异常下沉运动; 同时,西南季风的加强也导致夏季在 30°～40°N 之间的华北地区低层水汽输送加大。在这些因子的共同作用下,中国北方夏季降水增多,而东南部降水减少。这些结果说明使用LGM时期中国区域不同的重建植被资料可以对东亚季风气候模拟产生一定的不确定性。因此,重建可信度高的东亚植被对于降低对气候模拟的不确定性是十分重要的。     

Anthropogenic changes in the landscape of west Java (Indonesia) during historic times,inferred from a sediment and pollen record from Teluk Banten

Palynological and charcoal analyses of shallow marine core 98‐28 from the northern coastal area of West Java provide a regional vegetation history during the last few centuries. Reliable chronostratigraphical control is provided by ²¹⁰Pb analyses and the occurrence of the 1883 Krakatau ash/tsunami layer as a time marker. The results permit the distinction of four successive stages, reflecting increased disturbance and land clearance, with some evidence for the presence of deciduous lowland forests in the Banten area during the early Holocene. The establishment of coconut and pine plantations and the severe loss of biodiversity in the last few decennia are also echoed in the pollen record. The effect of the Krakatau eruption was insignificant compared with human impact on vegetation in the Banten area. Copyright © 2004 John Wiley & Sons, Ltd.     

The significance of large-scale land cover change on the Australian palaeomonsoon

We use the Regional Atmospheric Modeling System at a 50 km spatial resolution to explore the impact of large-scale vegetation changes on the Australian monsoon. We simulate multiple Januaries using vegetation cover representative of the present day, the last interglacial (LIG) (125,000 BP) and the last glacial maximum (20,000 BP), interpreted from palaeoecological data, to determine whether changes in vegetation can affect the Australian monsoon. We find that the large-scale replacement of current vegetation, to vegetation representing the LIG and the last glacial maximum has a substantial impact on the simulated latent heat flux and surface air temperature. Precipitation is affected, but only by approximately 5%. We show that the impact of vegetation change on precipitation is due to changes in the surface roughness length that affects the surface frictional drag, wind velocities and moisture convergence. The impact of large-scale vegetation changes on all quantities is restricted to the regions of land cover change. The perturbation induced by vegetation change interacts with the monsoon system by changing the local intensity of the atmospheric circulation causing relatively small intensification/moderation of the wind velocities. There is little evidence that the vegetation change induces a change in the large-scale structure of the meteorological system and there is no evidence that the vegetation changes induce a southward extension of the monsoon. We therefore find no evidence to support a hypothesis that vegetation feedbacks explain observed changes in lake levels in the Australian arid interior. We highlight some strengths and weaknesses of our approach and emphasise that the limitations implicit in our analytical methods means we cannot conclusively demonstrate that biospheric feedbacks can be ignored. Substantial additional work is therefore required to finally assess the role of biospheric feedbacks on the Australian palaeomonsoon.     

黄河的输沙量：过去、现在和将来——距今15万年以来的黄河泥沙收支表

黄河于150 ka BP切穿三门峡，东流入海。黄河泥沙90%来自黄土高原。黄土高原土地利用和植被的变化对黄河输沙有决定性的影响。15万年以来，黄河进入华北平原的泥沙约70 000×108 t，其中10 ka BP以前占80%。10 ka BP以后的输沙量中，最后1040年黄土高原滥垦时期占60%。黄河泥沙的归宿，建造华北大平原占73%，流入海洋占26%。现在，黄河每年流入北黄海的泥沙不足0.2×108  t，其输运主要受海洋环流系统的影响。现在黄海每年向东海输运悬浮沉积物0.2×108~0.3×108 t，主要为废黄河三角洲及水下三角洲受侵蚀再悬浮的黄河泥沙。1996—2000年黄河下游连年断流，利津站的年径流量和输沙量只有1950—1979年30年平均的19%左右。今后20~30年内，由于气候变暖、工业、城市等引黄水量增加，黄河的入海泥沙量仍将偏少。     

Development of the ecosystem on surtsey with references to Anak Krakatau

There is a strong similarity in the formation and size of the two new volcanic islands: Anak Krakatau, Indonesia (emerging 1930) and Surtsey, Iceland (emerging 1963). They are both piled up from an ocean floor of over 100 m depth, forming islands of cinder and lava covering more than 2 km² in area. They are both extremely valuable for various ecological studies, ie of investigation of means of dispersal and colonization. However, due to their tropical and subarctic locations, respectively, there is an extreme difference in climate of the two islands and thus in the kind of available life forms, their means of colonization and rate of growth.The first vascular plant was found on Surtsey in 1965, bryophytes became established in 1967 and lichens were first detected in 1970. The advancement of the vascular plant colonization has been of greatest importance in the establishment of vegetation on the island. Twenty-five species of vascular plants, all herbaceous, had been recorded on Surtsey in 1990, the dominant species being Honkenya peploides. Less than 1% ofthe island has vegetation cover, root biomass is low and the organic carbon and nitrogen status of the soil is poorly developed. Birds started nesting on Surtsey in 1970 and six species, all depending on marine life for food, had nested on the island in 1990. The land-invertebrate fauna has developed slowly on Surtsey and the island is devoid of vertebrates other than birds.     

库车-喀什北缘山前带构造特征及成因分析

通过地震非地震联合解释及多年的勘探研究,认为受基底结构、构造演化、逆冲及走滑断裂等影响,库车-喀什北缘山前冲断带具有东西分段、南北分带的构造特征。自西向东分为喀什北缘、柯坪断隆和库车坳陷三大段,受近南北向逆冲挤压作用,每段均发育多排北东-南西向展布的逆冲褶皱带,其中库车坳陷主要由克拉苏、依奇克里克、秋里塔格构造带及乌什、拜城、阳霞凹陷等呈斜列式展布的次级构造单元组成。普遍发育的膏盐岩塑性层在一系列逆冲和走滑断裂的作用下,使得山前带构造样式更为复杂,发育断层转折褶皱、断层传播褶皱、滑脱褶皱和盐底辟(刺穿)构造等四种基本构造样式及多种组合样式。     

Preliminary investigations of the tsunami hazard of Kick'em Jenny submarine volcano

Kick'em Jenny is a submarine volcano situated 9 kilometres north of Grenada in the Lesser Antilles. A preliminary study suggests that the volcano is a prime candidate for tsunamigenic eruptions on a potentially hazardous scale, possibly affecting the whole of the Eastern Caribbean region. The uniqueness of individual volcanic eruptions means that attempts to generalise tsunamigenic mechanisms are extremely tentative. However, the theory of underwater explosion generated water waves is applicable to submarine volcanoes to model explosive eruptions. Using this theory, initial maximum ocean surface displacements are calculated for Kick'em Jenny hydroeruptions, corresponding to various event magnitudes (up to a worst-case scenario eruption on the scale of Krakatau, 1883). Wave propagation theories are then applied to the resulting tsunami wave dispersion, before beach shoaling equations are used to estimate the maximum tsunami run-up at adjacent coastal areas. Maps of the region have been prepared showing the paths of the wave-fronts (ray-tracing), travel times and maximum wave run-up amplitudes along coastlines. Finally, an attempt is made to assess how great a hazard the volcano represents, by considering the probability of each magnitude event occurring.     

Mantle flow-induced crustal thinning in the area between the easternmost part of the Anatolian plate and the Arabian Foreland (E Turkey) deduced from the geological and geophysical data

Eastern Anatolia consisting of an amalgamation of fragments of oceanic and continental lithosphere is a current active intercontinental contractional zone that is still being squeezed and shortened between the Arabian and Eurasian plates. This collisional and contractional zone is being accompanied by the tectonic escape of most of the Anatolian plate to the west by major strike-slip faulting on the right-lateral North Anatolian Transform Fault Zone (NATFZ) and left-lateral East Anatolian Transform Fault Zone (EATFZ) which meet at Karlıova forming an east-pointing cusp. The present-day crust in the area between the easternmost part of the Anatolian plate and the Arabian Foreland gets thinner from north (ca 44 km) to south (ca 36 km) relative to its eastern (EAHP) and western sides (central Anatolian region). This thinner crustal area is characterized by shallow CPD (12–16 km), very low Pn velocities (< 7.8 km/s) and high Sn attenuation which indicate partially molten to eroded mantle lid or occurrence of asthenospheric mantle beneath the crust. Northernmost margin of the Arabian Foreland in the south of the Bitlis–Pötürge metamorphic gap area is represented by moderate CPD (16–18 km) relative to its eastern and western sides, and low Pn velocities (8 km/s). We infer from the geophysical data that the lithospheric mantle gets thinner towards the Bitlis–Pötürge metamorphic gap area in the northern margin of the Arabian Foreland which has been most probably caused by mechanical removal of the lithospheric mantle during mantle invasion to the north following the slab breakoff beneath the Bitlis–Pötürge Suture Zone. Mantle flow-driven rapid extrusion and counterclockwise rotation of the Anatolian plate gave rise to stretching and hence crustal thinning in the area between the easternmost part of the Anatolian plate and the Arabian Foreland which is currently dominated by wrench tectonics.     

Emplacement of a Debris Avalanche during the 1883 eruption of Krakatau (Sunda Straits,Indonesia)

Conclusion The data collected during the Mentawai cruise help to clarify understanding of the 1883 eruption of Krakatau. We have previously discussed the weaknesses of the interpretation of Williams (1941) and others (Self and Rampino 1981) and emphasized that only a Mount St. Helens-type collapse during the course of the eruption could account for all the characteristics of the eruption and of the related deposits.The discovery on land of deposits attributable to a debris-avalanche, in the stratigraphic position where they were expected, is a strong argument for the validity of our scenario.Marine surveys confirm that the sea bottom around Krakatau is covered by a thick ignimbritic deposit. But the presence of this deposit does not invalidate the presence of a debris-avalanche deposit under the ignimbrites. The hummocky morphology favours this hypothesis.Flank-failure of volcanoes is generally considered as a very efficient mechanism for triggering tsunamis (Kienle et al. 1987; Siebert et al. 1987). However, the majority of the volcanoes where flank-failure has been described are tall and bulky and the collapse of a broad edifice like Krakatau may be surprising. However the geological evidence shows that such a mechanism can act at various scales; for example the flank collapse of Mayu Yama volcano (height 700 m, volume 0,3 km³), a parasitic cone of Unzen volcano (Japan), triggered a debris-avalanche into the sea that was 1 km long, with a characteristic hummocky surface; the resulting tsunami killed 9528 people (Katayama 1974). In the same way, a partial collapse of Iliwerung volcano, Indonesia (50 × 10⁶ m³) in July 1979, triggered a tsunami which killed several hundred people (McClelland et al. 1989). At Krakatau, the main summit was 822 m asl; the collapse took place along the edge of the prehistoric caldera and this structural unconformity probably facilitated the triggering of the process.     

Tectonics and Topography of the Tibetan Plateau in Early Miocene

Early Miocene stratigraphy, major structural systems, magmatic emplacement, volcanic eruption, vegetation change and paleo-elevation were analyzed for the Tibetan Plateau after regional geological mapping at a scale of 1:250,000 and related researches, revealing much more information for tectonic evolution and topographic change of the high plateau caused by Indian-Asian continental collision. Lacustrine deposits of dolostone, dolomite limestone, limestone, marl, sandstone and conglomerate of weak deformation formed extensively in the central Tibetan Plateau, indicating that vast lake complexes as large as 100,000–120,000 km2 existed in the central plateau during Early Miocene. Sporopollen assemblages contained in the lacustrine strata indicate the disappearance of most tropical-subtropical broad-leaved trees since Early Miocene and the flourishing of dark needleleaved trees during Early Miocene. Such vegetation changes adjusted for latitude and global climate variations demonstrate that the central Tibetan Plateau rose to ca. 4,000–4,500 m and the northeastern plateau uplifted to ca. 3,500–4,000 m before the Early Miocene. Intensive thrust and crustal thickening occurred in the areas surrounding central Tibetan Plateau in Early Miocene, formed Gangdise Thrust System(GTS) in the southern Lhasa block, Zedong-Renbu Thrust(ZRT) in the northern Himalaya block, Main Central Thrust(MCT) and Main Boundary Thrust(MBT) in the southern Himalaya block, and regional thrust systems in the Qaidam, Qilian, West Kunlun and Songpan-Ganzi blocks. Foreland basins formed in Early Miocene along major thrust systems, e.g. the Siwalik basin along MCT, Yalung-Zangbu Basin along GTS and ZRT, southwestern Tarim depression along West Kunlun Thrust, and large foreland basins along major thrust systems in the northeastern margin of the plateau. Intensive volcanic eruptions formed in the Qiangtang, Hoh-Xil and Kunlun blocks, porphyry granites and volcanic eruptions formed in the Nainqentanglha and Gangdise Mts., and leucogranites and granites formed in the Himalaya and Longmenshan Mts. in Early Miocene. The K2O weight percentages of Early Miocene magmatic rocks in the Gangdise and Himlayan Mts. are found to increase with distance from the MBT, indicating the genetic relationship between regional magmatism and subduction of Indian continental plate in Early Miocene.     

Decoupling of stalagmite-derived Asian summer monsoon records from North Atlantic temperature change during marine oxygen isotope stage 5d

The Asian monsoon is an important component of the global climate system. Seasonal variations in wind, rainfall, and temperature associated with the Asian monsoon systems affect a vast expanse of tropical and subtropical Asia. Speleothem-derived summer monsoon variation in East Asia was previously found to be closely associated with millennial-scale change in temperature in the North Atlantic region between 75 and 10 ka. New evidence recovered from East Asia, however, suggests that the teleconnection between summer monsoon in East Asia and temperature change in the North Atlantic region may have significantly reduced during 120 to ~ 110 ka, a period directly after the full last interglaciation and corresponding roughly to marine oxygen isotope stage 5d. This reduction may be due to the low ice volume in the North Hemisphere at that time, which makes the millennial-scale change in temperature in the North Atlantic region less effective in influencing the Asian summer monsoon. This is important for investigating the mechanisms controlling the Asian summer monsoon and the paleoclimatic teleconnection between East Asia and the North Atlantic region, and for predicting monsoon-associated precipitation in East Asia under a global-warming trend.     

Gigantic volcanic eruptions and climatic change in the early Eocene

23 layers of altered volcanic ash (bentonites) originating from the North Atlantic Igneous Province have been recorded in early Eocene deposits of the Austrian Alps, about 1,900 km away from the source area. The Austrian bentonites are distal equivalents of the “main ash-phase” in Denmark and the North Sea basin. We have calculated the total eruption volume of this series as 21,000 km³, which occurred in 600,000 years. The most powerful single eruption of this series took place 54.0 million years ago (Ma) and ejected ca. 1,200 km³ of ash material, which makes it one of the largest basaltic pyroclastic eruptions in geological history. The clustering of eruptions must have significantly affected the incoming solar radiation in the early Eocene by the continuous production of stratospheric dust and aerosol clouds. This hypothesis is corroborated by oxygen isotope values, which indicate a global decrease of sea surface temperatures between 1 and 2°C during this major phase of explosive volcanism.