Terrestrial Environmental Change Research Articles

Detecting land-use change from seasonal vegetation dynamics on regional scale with MODIS EVI 250-m time-series imagery

Simultaneous analysis of land surface attributes and their seasonal changes provides a broader view of land-use and land-cover change. This study attempted to detect the change in inter-annual temporal vegetation dynamics, which reflects a change in land surface attributes. We explored 250-m multi-temporal MODIS EVI 16-day composite data from 2001 to 2007 to characterize a change in vegetation dynamics related to land-use change detection. The MODIS data was filtered in time-frequency space by wavelet function in order to identify and reduce the overall noise so as not to lose useful information from the time series data. The results show that by characterizing temporal vegetation dynamics, it is possible to distinguish actual land-use change based on land-cover dynamics. The result was evaluated using 18,626 reference pixels and showed an overall accuracy of 76.10%. In agricultural land use, such as upland and plantation, the weakest results were caused by mixed pixels from MODIS 250-m grid data as well as by temporal complexity related to the climate-driven change of land cover existing in the study area. On the other hand, for land use types which were not significantly affected by climate variability such as paddy rice fields with sufficient irrigation systems, natural forest and mangrove, the accuracy was satisfactory. Although the mixed pixel issue is quite problematic in this study, the results show that the characterization of temporal vegetation dynamics is an alternative when considering the accuracy of land-use change, which is not necessarily coincident with the temporary change in land cover. The methodology proposed in this research provides sufficient and useful information regarding land-use change, such as location, area, time and pathways of the change; consequently, it should be possible to provide broad scale data on the terrestrial environmental change.

Stable carbon isotope of black carbon in lake sediments as an indicator of terrestrial environmental changes: An evaluation on paleorecord from Daihai Lake, Inner Mongolia, China

We measured the carbon isotope ratio of black carbon (BC) from the Daihai Lake sediment core (DH99a) in north-central China with an objective to examine the effectiveness and sensitivity of the δ13C values of BC (δ13CBC) as a potential indicator of terrestrial environmental changes. We first performed a statistical study on the available data regarding carbon isotope fractionation (CIF) during the conversion of C3 and C4 vegetation to BC and observed that the mean CIF for BC produced from C3 plants is −0.3‰, whereas that for BC from C4 plants is −1.7‰. This result provides a solid reference for reconstructing vegetation and environmental changes using the δ13CBC values. The δ13CBC record in the DH99a sediment core spanning the last ca 10,000years displayed large variations from −23.7‰ to −29.2‰, which suggests that C3 plants dominantly occupied the Daihai Lake region during the Holocene. The most negative δ13CBC peaks coincided with high values of tree percentages and grain sizes, which occurred under relatively wetter climatic conditions during the middle Holocene (ca 6500–3200cal.yrBP) and an interval between 1700 and 1350cal.yrBP. In contrast, the least negative δ13CBC values corresponded to low values of tree percentages and grain sizes during relatively drier phases of the early and late Holocene. The generally negative correlation of the δ13CBC values with the tree percentages and grain sizes was thought to reflect a negative correlation of the δ13CBC values with the monsoon precipitation. This correlation is consistent with the response of carbon isotope in modern C3 plants to precipitation in north China. Therefore, we developed a computational model to reconstruct the changes in annual precipitation over the Daihai Lake region using the δ13CBC values. The results indicated that the annual precipitation was highly variable, ranging from 170mm lower to 310mm higher than that at present during the middle Holocene, whereas the annual precipitation was generally ~70mm lower than that at present during the early and late Holocene. The general features of the inferred precipitation changes using the δ13CBC values are generally consistent with those reconstructed using pollen data of the same sediment core. Meanwhile, the δ13CBC values tend to register some extreme variations of monsoon precipitation, which were not reflected in the pollen assemblages. We conclude that the δ13CBC values in the Daihai Lake sediments may serve as a sensitive and reliable proxy for monitoring monsoon precipitation.

Forest restoration following a windthrow: how legacy retention versus plantation after salvaging alters the trajectory of initial recovery

Recently, the conversion of plantations into natural forests has attracted increasing attention, but little is known about how to convert a windthrown plantation into a natural forest. We examined the initial 3-year effects of salvage logging, site preparation, planting, and weeding in comparison with the effects of legacy retention after a typhoon blowdown on the changes in terrestrial environments and plant compositions and the similarity of the species composition to that of the intact natural forest. Our major findings are as follows: (1) A homogeneous, sunny, and flat environment continued for 3 years in the planted and weeded plot, whereas a heterogeneous environment was observed in the legacy retention plot; however, the light environment changed slightly in the planted plot. (2) The species composition in the planted plots changed greatly due to invasion by annual, biennial, and perennial herbs and early successional trees. Alien species also invaded the planted row. Conversely, the species composition changed little in the legacy retention, which was likely due to the presence of residual plants that prevented shade-intolerant species from being established. (3) The legacy retention, followed by the residual row, was the closest to the natural forest with respect to species composition, whereas the planted row was the most dissimilar from the natural forest. Legacy retention appears to be the most appropriate way to restore a natural forest immediately after a windthrow, yet supplemental planting may be necessary to restore the desired broadleaved species.

The Quaternary history of the Chatham Islands, eastern outpost of New Zealand: insights into Quaternary terrestrial environmental change in a remote oceanic setting

The Quaternary history of the Chatham Islands, eastern outpost of New Zealand: insights into Quaternary terrestrial environmental change in a remote oceanic setting

Marine and terrestrial environmental changes in NW Europe preceding carbon release at the Paleocene–Eocene transition

Environmental changes associated with the Paleocene–Eocene thermal maximum (PETM, ∼56Ma) have not yet been documented in detail from the North Sea Basin. Located within proximity to the North Atlantic igneous province (NAIP), the Kilda Basin, and the northern rain belt (paleolatitude 54°N) during the PETM, this is a critical region for testing proposed triggers of atmospheric carbon release that may have caused the global negative carbon isotope excursion (CIE) in marine and terrestrial environments. The CIE onset is identified from organic matter δ13C in exceptional detail within a highly expanded sedimentary sequence. Pollen and spore assemblages analysed in the same samples for the first time allow a reconstruction of possible changes to vegetation on the surrounding landmass. Multiproxy palynological, geochemical, and sedimentologic records demonstrate enhanced halocline stratification and terrigenous deposition well before (103yrs) the CIE, interpreted as due to either tectonic uplift possibly from a nearby magmatic intrusion, or increased precipitation and fluvial runoff possibly from an enhanced hydrologic cycle. Stratification and terrigenous deposition increased further at the onset and within the earliest CIE which, coupled with evidence for sea level rise, may be interpreted as resulting from an increase in precipitation over NW Europe consistent with an enhanced hydrologic cycle in response to global warming during the PETM. Palynological evidence indicates a flora dominated by pollen from coastal swamp conifers before the CIE was abruptly replaced with a more diverse assemblage of generalist species including pollen similar to modern alder, fern, and fungal spores. This may have resulted from flooding of coastal areas due to relative sea level rise, and/or ecologic changes forced by climate. A shift towards more diverse angiosperm and pteridophyte vegetation within the early CIE, including pollen similar to modern hickory, documents a long term change to regional vegetation.

Aquatic insects indicate terrestrial habitat degradation: changes in taxonomical structure and functional diversity of dragonflies in tropical rainforest of East Kalimantan

As a group of freshwater invertebrates, dragonflies (Odonata) are commonly used as ecological indicators of freshwater ecosystems. Despite earlier studies suggesting that adult odonates may be good indicators for complex changes in a landscape, the utility of odonates as suitable indicators to indicate health of non-aquatic (forest) habitats remains poorly understood. This study analyses the adult dragonfly assemblage pattern against spatial and temporal disturbance characteristics in Indonesia's Sungai Wain Protection Forest. The core of this reserve comprises one of the few remaining fragments of primary rain forest along the East Kalimantan coast, whereas the rest of the reserve is covered by secondary forest, scrub, grassland, and farmland. Adult dragonfly assemblages at individual sampling sites were analysed in relation to (1) their intensity, (2) frequency of human-caused disturbances, and (3) the time since the last such disturbance, while controlling random variables (type of aquatic and terrestrial habitat) were removed. This study tests the effect of these factors on (1) species richness, (2) proportion of Zygoptera, (3) proportion of forest specialists, and (4) proportion of Borneo's endemics. The human-induced disturbances in the rain forest resulted in pronounced changes in the taxonomical composition and functional diversity of the odonate fauna. Results reported here demonstrate that gradual changes in the odonate assemblages correspond to the degree of anthropogenic influences on forest environments. Adult odonates comprise an appropriately sensitive and versatile indicator group for identifying changes in terrestrial forest environments as well as in freshwater habitats.

Vegetation and environmental dynamics in the southern Black Sea region since 18 kyr BP derived from the marine core 22-GC3

Sediments from the Black Sea, a region historically dominated by forests and steppe landscapes, are a valuable source of detailed information on the changes in regional terrestrial and aquatic environments at decadal to millennial scales. Here we present multi-proxy environmental records (pollen, dinoflagellate cysts, Ca, Ti and oxygen isotope data) from the uppermost 305cm of the core 22-GC3 (42°13.53′N, 36°29.55′E) collected from a water depth of 838m in the southern part of the Black Sea in 2007. The records span the last ~18kyr (all ages are given in cal kyr BP). The pollen data reveal the dominance of the Artemisia-steppe in the region, suggesting rather dry/cold environments ~18–14.5kyr BP. Warming/humidity increase during melt-water pulses (~16.1–14.5kyr BP), indicated by δ18O records from the 22-GC3 core sediment and from the Sofular Cave stalagmite, is expressed in more negative δ13C values from the Sofular Cave, usually interpreted as the spreading of C3 plants. The records representing the interstadial complex (~14.5–12.9kyr BP) show an increase in temperature and moisture, indicated by forest development, increased primary productivity and reduced surface run-off, whereas the switch from primary terrigenous to primary authigenic Ca origin occurs ~500yr later. The Younger Dryas cooling is clearly demonstrated by more negative δ13C values from the Sofular Cave and a reduction of pines. The early Holocene (11.7–8.5kyr BP) interval reveals relatively dry conditions compared to the mostly moist and warm middle Holocene (8.5–5kyr BP), which is characterized by the establishment of the species-rich warm mixed and temperate deciduous forests in the low elevation belt, temperate deciduous beech-hornbeam forests in the middle and cool conifer forest in upper mountain belt. The border between the early and middle Holocene in the vegetation records coincides with the opening of the Mediterranean corridor at ~8.3kyr BP, as indicated by a marked change in the dinocyst assemblages and in the sediment lithology. Changes in the pollen assemblages indicate a reduction in forest cover after ~5kyr BP, which was likely caused by increased anthropogenic pressure on the regional vegetation.

Continental Scientific Drilling Project of Cretaceous Songliao Basin: Scientific objectives and drilling technology

The Continental Scientific Drilling Project at the Cretaceous-age Songliao Basin is a drilling initiative under the framework of the International Continental Scientific Drilling Program, to recover a nearly complete Cretaceous terrestrial sedimentary record in the Songliao Basin, northeastern China. The recovered cores will provide unique opportunities for the geosciences community to advance the understanding of climate change in the Cretaceous greenhouse world, and provide a documentation of geological events relevant to the carbon cycle during this time period.This drilling project will address significant geological questions, such as the identification of important stratigraphic boundaries and the marine-terrestrial correlations of stratigraphy, the reasons for the biotic response to the terrestrial environmental changes, the terrestrial response to the Cretaceous oceanic anoxic events, the formation of terrestrial petroleum source rocks, and the mechanisms for the Cretaceous magnetic Normal Superchron (CNS).In the first stage of this drilling project, the SKI drilling, rock cores of 2485.89m in total length were recovered and the recovery ratio reached 96.46%. A series of drilling and coring technologies including regular, confined, directional, and sealed coring, were utilized to ensure a higher recovery ratio for the core, and will be described at the end of this paper. Well loggings were conducted right after coring. Core handling and storage were arranged in such a way that the scientific research was conducted on half of each core, whereas the other half of each core was preserved for long-term storage. The upcoming second stage, the SKII drilling, will combine with data from the existing SKI to provide complete high-resolution climate records of the terrestrial environment for the whole Cretaceous time period.

Freshwater fish δ18O indicates a Messinian change of the precipitation regime in Central Africa

Tracking terrestrial environmental change throughout the Neogene is a challenge, notably in areas such as Central Africa where the few available data consist of a few vertebrate fossil assemblages. Here we aim to quantify the evolution of the δ 18 O of the main water body between four Neogene wet episodes in the Chad basin, ranging from the Late Miocene to the early Pliocene. The δ 18 O of the open water body was inferred from oxygen isotope measurements of phosphate in the apatite of open water fish tooth enamel. The more open the fish habitat, the lower the δ 18 O, as revealed by the teeth of the large tiger fish ( Hydrocynus ) sampled in the four available Chadian vertebrate fossiliferous areas, i.e., Toros-Menalla (anthracotherid unit), Kossom Bougoudi, Kolle, and Koro Toro, all located in the Djurab Desert (Chad) and dated at 7.04 ± 0.18 Ma, 5.26 ± 0.23 Ma, 3.96 ± 0.48 Ma, and 3.58 ± 0.27 Ma, respectively. The δ 18 O values increased by ∼2‰ between the two sites having ages that bracket the Messinian time period, and there was a slight increase of ∼0.6‰ difference between the three Pliocene sites. These results reflect unambiguously change in the water cycle in Central Africa during the late Neogene, interpreted as a constant drying trend between the four successive wet episodes registered in the Djurab and a shift during the Messinian.

A 26,000-year integrated record of marine and terrestrial environmental change off Gabon, west equatorial Africa

Dinoflagellate cysts, pollen and charred cuticle fragments from two sediment cores (giant piston Calypso core MD03-2708 and giant gravity Casq core MD03-2708CQ) collected off the Ogooué River mouth, Gabon (01°10.33′S–08°19.01′E, 920 m water depth) have been analysed to identify the direction and timing of marine–terrestrial environmental changes over western equatorial Africa during the last 26,000 yr. Changes in the proxy records indicate that both terrestrial and oceanic domains off Gabon were impacted synchronously by significant climate changes during the last glacial–interglacial transition and Holocene. Leading into, and during, the Last Glacial Maximum (LGM), heterotrophic dinoflagellate cysts and Ca X-ray fluorescence intensity suggest nutrient enrichment off the river mouth, while pollen records indicate expansions of open forest, savannah woodland, and the Afromontane forest in the catchment area. From the deglaciation to mid-Holocene, however, a marked decrease in Brigantedinium spp. as well as in Poaceae, Cyperaceae and Podocarpus pollen reflects a reduction in nutrient supply to the coastal ocean in parallel with a reduction in grassland, herbaceous communities and Afromontane forest within the catchment. A sharp decline or even disappearance of heterotrophic species during this period is almost contemporaneous with an appearance of Operculodinium aguinawense, reflecting enhanced river influence in the study area. A marked increase of Rhizophora (mangrove) pollen during this transition also indicates eustatic sea-level rise after the LGM which forced a major expansion of the mangrove ecosystem across the gradually submerging shelf. The combination during the late Holocene of a reoccurrence of heterotrophic dinoflagellate cysts with increased Poaceae, Cyperaceae and Podocarpus pollen indicates enhanced nutrient supply to the ocean concordant with a shift to cooler/drier conditions over the Gabon basin. This appears to be linked to a deterioration of the monsoon system induced by the low sea-surface temperatures in the tropical Atlantic Ocean in association with decreased summer insolation.

How to sample the carbon isotopes of tropical ecosystems without leaving your armchair

Well-dated records of terrestrial environmental change in Southeast Asia spanning the past 50 kyr (kyr = 1,000 y) are few and far between. The problem is often one of preservation. Organic-based paleoenvironmental proxies in warm and wet tropical environments are often subject to severe microbial degradation processes rendering them unsuitable for radiocarbon (14C) dating. Notable exceptions to this problem include tropical speleothems, which can be dated using the 230Th method (1) and can provide information on the relative intensities of isotopically depleted Asian monsoonal rainfall back to ∼400 kyr ago (2). Speleothem records tell us little about the specific ecosystem responses to past rainfall and temperature changes, however. How can we tell how much rain is needed to maintain dense tropical rain forest as opposed to more open grasslands? Pollen and charcoal records go some way toward filling this knowledge gap in tropical settings (e.g., refs. 3–5), but they can be affected by biases in the representation of local plant species and are sometimes difficult to date accurately. In PNAS, a relatively innovative technique is explored in insular Southeast Asia that uses the vegetation-derived carbon isotope (δ13C) records preserved in cave guano deposits (6).

Biomarker records from core GH02-1030 off Tokachi in the northwestern Pacific over the last 23,000 years: Environmental changes during the last deglaciation

We investigated marine and terrestrial environmental changes at the northern Japan margin in the northwestern Pacific during the last 23,000 years by analyzing biomarkers (alkenones, long-chain n-alkanes, long-chain n-fatty acids, and lignin-derived materials) in Core GH02-1030. The U K′37 -derived temperature in the last glacial maximum (LGM) centered at 21 ka was ∼10°C, which was 2°C lower than the core-top temperature (∼12°C). This small temperature drop does not agree with pollen evidence of a large air temperature drop (more than 4°C) in the Tokachi area. This disagreement might be attributed to a bias of U K′37 -derived temperature within 2.5°C by a seasonal shift in alkenone production. The U K′37 -derived temperature was significantly low during the last deglaciation. Because this cooling was significant in the Kuroshio-Oyashio transition zone, the temperature drops are attributable to the southward displacement of the Kuroshio-Oyashio boundary. Abundant lignin-derived materials, long-chain n-alkanes and long-chain n-fatty acids indicate a higher contribution of terrigenous organic matter from 17 to 12 ka. This phenomenon might have resulted from an enhanced coastal erosion of terrestrial soils due to marine transgression and/or an efficient inflow of higher plant debris to river waters from 17 to 12 ka.

The floating astronomical time scale for the terrestrial Late Cretaceous Qingshankou Formation from the Songliao Basin of Northeast China and its stratigraphic and paleoclimate implications

The Upper Cretaceous Qingshankou Formation (K 2qn) in the Songliao Basin (SLB) of Northeast China consists of up to 550 m thick, lacustrine mudstone and shale that constitute one of the most important source rocks of the Daqing oil field. A high-resolution cyclostratigraphic analysis of the natural gamma-ray logging from 10 wells of the Qingshankou Formation (K 2qn) reveals orbital cycles of precession (20 ka), obliquity (40 ka) and eccentricity (100 ka and 405 ka), providing strong evidence for astronomically driven climate changes in the Late Cretaceous terrestrial environments. Floating astronomical time scales (ATS) are established for all sections, which demonstrate variable durations of K 2qn across the basin (1.09 Ma–5.20 Ma) and strong diachroneity of the lacustrine strata. Four periods of high depositional rates can be identified in the central parts of the basin, possibly recording deposition during times of sustained wet climate and high chemical weathering. An ATS established from well M206 in the central depression zone of the basin, where the most complete and stable Milankovitch cycles are present, suggests that the maximum duration of the K 2qn is 5.20 Ma (from 94.27 Ma to 89.07 Ma; Late Cenomanian to Early Coniacian). The lacustrine anoxic event 1 (LAE1) at the Cenomanian–Turonian boundary lasted ~ 210–310 ka, during which the most prolific petroleum source rocks in SLB were deposited. The onset (~ 94.21–94.18 Ma) and duration (~ 210–310 Ka) of LAE1 in SLB are comparable to those of the oceanic anoxic event 2 (OAE2; onset at 94.21 Ma and duration of ~ 320–900 ka), suggesting that the same trigger mechanism, such as increased atmospheric CO 2 from large-scale igneous activity, may have initiated high primary productivity and organic carbon burial in both marine and terrestrial systems.

Sedimentation process in Ariake Bay using NAA and gamma-spectrometry

In order to assess the effect of marine and terrestrial environmental change in the last decades on the sedimentation environment in Ariake Bay, we collected three sediment cores. The concentrations of natural and anthropogenic radionuclides, major elements, and rare-earth elements were measured using gamma-spectrometry and neutron activation analysis. Vertical distributions of both radionuclides and sedimentation rates, determined using Cs-137 and Pb-210ex dating methods, varied significantly among the sites.

Terrestrial plant-Si and environmental changes

AbstractThe importance of silica in terrestrial land plants has been recognized since the middle of the 19th century with applications in agronomy and palaeovegetation reconstruction. In this presentation, we will review the latest advances in our understanding of phytolith formation and present a few examples of applications in the field of global environmental changes.

Holocene Climate and Climate Variability of the Northern Gulf of Mexico and Adjacent Northern Gulf Coast: A Review

Marine records from the northern Gulf of Mexico indicate that significant multidecadal- and century-scale variability was common during the Holocene. Mean annual sea-surface temperature (SST) during the last 1,400 years may have varied by 3°C, and excursions to cold SST coincide with reductions in solar output. Broad trends in Holocene terrestrial climate and environmental change along the eastern portion of the northern Gulf Coast are evident from existing pollen records, but the high-frequency details of climate variability are not well known. Continuous and well-dated records of climate change and climate variability in the western portion of the northern Gulf Coast are essentially lacking.

Paleolimnological Evidence of Terrestrial and Lacustrine Environmental Change in Response to European Settlement of the Red River Valley, Manitoba and North Dakota*

Limnological and terrestrial changes in three floodplain lakes are correlated with settlement of the Red River valley in Manitoba and North Dakota. Distinctive pollen, diatom and thecamoebian assemblages provide proxy evidence of the ecological changes from pre- to post-settlement periods in Horseshoe Lake, Lake Louise and Salt Lake. In the pre-settlement period (Zone I), prior to ~1812, grass and Quercus pollen dominate and are indicative of a tall grass prairie-oak riparian forest ecosystem. Diatom and thecamoebian assemblages suggest oligo- to mesotrophic limnological conditions, and more brackish water than presently occurs in Horseshoe Lake. The onset of the post-settlement period (Zone II) corresponds to distinctive terrestrial and limnological changes. A sharp decline in Quercus at the base of this zone correlates with documented regional riparian deforestation, whereas the increase in the weed taxa Salsola, Brassica, Rumex and Ambrosia is associated with the introduction of European agricultural practices and cereal grasses. Diatom and thecamoebian assemblages indicate progressive floodplain lake eutrophication, as well as increased salinity in Salt Lake. Salt Lake is the most brackish lake and supports the brackish-water foraminifera Trochammina macrescens cf. polystoma. Increased erosion and run off in the watershed has caused a more than twofold increase in lake basin sedimentation between the pre-settlement and post-settlement periods.

The protracted Permo-Triassic crisis and multi-episode extinction around the Permian–Triassic boundary

The Permo-Triassic crisis was a major turning point in geological history. Following the end-Guadalupian extinction phase, the Palaeozoic biota underwent a steady decline through the Lopingian (Late Permian), resulting in their decimation at the level that is adopted as the Permian–Triassic boundary (PTB). This trend coincided with the greatest Phanerozoic regression. The extinction at the end of the Guadalupian and that marking the end of the Permian are therefore related. The subsequent recovery of the biota occupied the whole of the Early Triassic. Several phases of perturbations in δ 13C carb occurred through a similar period, from the late Wuchiapingian to the end of the Early Triassic. Therefore, the Permian–Triassic crisis was protracted, and spanned Late Permian and Early Triassic time. The extinction associated with the PTB occurred in two episodes, the main act with a prelude and the epilogue. The prelude commenced prior to beds 25 and 26 at Meishan and coincided with the end-Permian regression. The main act itself happened in beds 25 and 26 at Meishan. The epilogue occurred in the late Griesbachian and coincided with the second volcanogenic layer (bed 28) at Meishan. The temporal distribution of these episodes constrains the interpretation of mechanisms responsible for the greatest Phanerozoic mass extinction, particularly the significance of a postulated bolide impact that to our view may have occurred about 50,000 Myr after the prelude. The prolonged and multi-phase nature of the Permo-Triassic crisis favours the mechanisms of the Earth's intrinsic evolution rather than extraterrestrial catastrophe. The most significant regression in the Phanerozoic, the palaeomagnetic disturbance of the Permo-Triassic Mixed Superchron, widespread extensive volcanism, and other events, may all be related, through deep-seated processes that occurred during the integration of Pangea. These combined processes could be responsible for the profound changes in marine, terrestrial and atmospheric environments that resulted in the end-Permian mass extinction. Bolide impact is possible but is neither an adequate nor a necessary explanation for these changes.

Paleoenvironmental reconstruction of a well-preserved Stage 7 forest sequence catastrophically buried by basaltic eruptive deposits, northern New Zealand

Forest remnants, buried by catastrophically emplaced volcanic deposits, are identified on the shores of the Manukau Harbour, in northern New Zealand. Carbonaceous muds associated with the fossil forest were investigated through a combination of stratigraphy, chronology and palaeoecological proxies. The fossil forest was destroyed and buried by phreatomagmatic explosions from the adjacent Maungataketake Volcano. Small trees (<1 m diameter) in position of growth are observed extending 1–2 m upwards into the overlying volcanic deposits. The lowermost part of the phreatomagmatic succession contains well-preserved leaf fossils and small fallen logs and branches, many of which were incorporated into the phreatomagmatic succession during the initial eruptive phase. Optically stimulated luminescence dating of the phreatomagmatic succession together with palaeoecological evidence for interglacial climate suggests deposition in late Marine Isotope Stage (MIS) 7. This extends the known age of volcanism in the Auckland Volcanic Field by up to 40 ka. Beetle and pollen assemblages indicate a northern conifer forest growing adjacent to a wetland on or near a coastal plain. The pollen record shows forest compositional changes, in particular a period of Agathis australis—dominance between two phases of Dacrydium cupressinum dominance. Concomitant developments in the wetland flora may have been linked to changes in groundwater conditions as sea level fluctuated across the coastal plain. Despite overall similarity to the modern flora and fauna, both beetle and pollen assemblages include elements that are found today at higher elevations in the region, indicating that slightly cooler climate conditions existed during late MIS 7 compared to present. We estimate this temperature depression at less than 1 °C relative to the present, broadly consistent with the late MIS 7 marine (ODP-1123) record located east of New Zealand. This study clearly demonstrates the complementarity of coleopteran and palynological analyses and the utility of a multi-proxy approach to reconstructing terrestrial environmental change.

Late Quaternary intensified monsoon phases control landscape evolution in the northwest Himalaya

The intensity of the Asian summer-monsoon circulation varies over decadal to millennial time scales and is reflected in changes in surface processes, terrestrial environments, and marine sedi- ment records. However, the mechanisms of long-lived (2-5 k.y.) intensified monsoon phases, the related changes in precipitation distribution, and their effect on landscape evolution and sedimen- tation rates are not yet well understood. The arid high-elevation sectors of the orogen correspond to a climatically sensitive zone that currently receives rain only during abnormal (i.e., strength- ened) monsoon seasons. Analogous to present-day rainfall anom- alies, enhanced precipitation during an intensified monsoon phase is expected to have penetrated far into these geomorphic threshold regions where hillslopes are close to the angle of failure. We as- sociate landslide triggering during intensified monsoon phases with enhanced precipitation, discharge, and sediment flux leading to an increase in pore-water pressure, lateral scouring of rivers, and ov- ersteepening of hillslopes, eventually resulting in failure of slopes and exceptionally large mass movements. Here we use lacustrine deposits related to spatially and temporally clustered large land- slides (.0.5 km 3 ) in the Sutlej Valley region of the northwest Him- alaya to calculate sedimentation rates and to infer rainfall patterns during late Pleistocene (29-24 ka) and Holocene (10-4 ka) inten- sified monsoon phases. Compared to present-day sediment-flux measurements, a fivefold increase in sediment-transport rates re- corded by sediments in landslide-dammed lakes characterized these episodes of high climatic variability. These changes thus em- phasize the pronounced imprint of millennial-scale climate change on surface processes and landscape evolution.