Asian Aridification Research Articles

Satellite-based assessment of large-scale land cover change in Asian arid regions in the period of 2001–2009

Arid regions in Asia are commonly characterized by rapidly growing populations with limited land resources and varying rainfall frequencies under climatic change. Despite being one of the most important environmental challenges in Asia, the changing aridity in this region, particularly due to large-scale land cover change, has not been well documented. In this study, we used rainfall data and a new land heterogeneity index to identify recent trend in land cover changes in the Asian arid regions. The result indicates a significant decreasing trend of barren lands and an increasing trend of vegetated lands. Although the potential land cover change is commonly believed to be strongly sensitive to rainfall change, such sensitivity has not been observed during the nine-year period (2001–2009) analyzed. Through the analyses of two separate periods (2001–2005 and 2005–2009), the sensitivity of rainfall to land cover change in arid regions is found to be dependent on the initial spatial heterogeneity of vegetated land cover. The approach used and the findings in this study represent an important step toward better understanding of large-scale land cover change in the Asian arid regions, and have the potential to predict future land cover change under various climate change scenarios.

Synchronous drying and cooling in central Asia during late Oligocene

Aridification of central Asia during late Oligocene and Early Miocene has been documented by numerous eolian records from the North Pacific and central Asia. However, direct evidence of aridity from the interior of the arid zone is still rather scarce. To better reconstruct the climate history in central Asia during the late Oligocene, we have analyzed ostracod assemblages and gypsum content in the sediments from the lacustrine Jingou River section in the northern Tianshan Mountains. Our results show that the cold water species Candona cf. Neglecta and Pseudocandona albicans replaced the warm water species Ilyocypris bradyi and Ilyocypris sp. to become the dominant species at 23.8 Ma, indicating significant cooling in central Asia at that time. At the same time, a substantial increase in gypsum content indicates the intensification of central Asian drying. The synchronous cooling and drying approximately coincided with the Oi2b.1 and/or Mi1 events, implying a causal linkage between late Oligocene global cooling and central Asian aridity.

A long-term increasing aridification and cooling trend at the Chinese Loess Plateau during the Pliocene

The development of Asian aridification and cooling is a research hotspot nowadays. Loess-Red Clay sequence in the Chinese Loss Plateau provides an excellent terrestrial archive of such paleoclimatic evolution. This paper applied the magnetic “unmixing” technique to isolate the magnetic components of the Red Clay sequence for the first time. The Jiaxian section in the north edge of Chinese Loess Plateau is sensitive to paleoclimate changes because it is in the transitional zone of the monsoon and non-monsoon area. Systematic magnetic measurements and XRD analysis consistently indicate that the magnetic components of Red Clay are predominantly magnetite, maghemite and hematite. The strongly developed paleosols exhibit high content of soft magnetic minerals, higher Ms and Mrs, and lower Bc and Bcr. While the weakly developed paleosols and loess samples display the opposite features. With increasing alternating field, the contributions of soft components to SIRMx mT are cleaned gradually (SIRM is the saturation isothermal remanent magnetization; SIRMx mT represents the residual SIRM after alternating field demagnetization at x mT). The significant contributor to SIRM100 mT is hematite, an indication of the intensity of chemical weathering. Variations in the ratios of SIRM100 mT/SIRM, SIRM100 mT/SIRM60 mT, and SIRM100 mT/SIRM30 mT document a long-term up-section decreasing trend during the last 5–2.6 Ma, with similar trends to the long-term up-section increase in δ18O values of marine records. Decreased hematite content indicates weakened chemical weathering, which further implies an increasing aridification and cooling and a gradually weakened summer paleomonsoon mainly in the depositional area (Chinese Loess Plateau). In some loess layers, where hematite is mainly of aeolian origin, the mineral magnetic signals may indicate aridification and cooling in the Asian interior (source region). This long-term aridification and cooling trend is probably attributed to the comprehensive activity of ongoing global cooling, progressive uplift of the Tibetan Plateau and changes in land–sea distribution.

Phylogeographic evidence for a link of species divergence of Ephedra in the Qinghai-Tibetan Plateau and adjacent regions to the Miocene Asian aridification.

The Qinghai-Tibetan Plateau (QTP) has become one of the hotspots for phylogeographical studies due to its high species diversity. However, most previous studies have focused on the effects of the Quaternary glaciations on phylogeographical structures and the locations of glacial refugia, and little is known about the effects of the aridization of interior Asia on plant population structure and speciation. Here the chloroplast DNA (cpDNA) trnT-trnF and trnS-trnfM sequences were used to investigate the differentiation and phylogeographical history of 14 Ephedra species from the QTP and northern China, based on a sampling of 107 populations. The phylogeographical analysis, together with phylogenetic reconstruction based on combined four cpDNA fragments (rbcL, rpl16, rps4, and trnS-trnfM), supports three main lineages (eastern QTP, southern QTP, and northern China) of these Ephedra species. Divergence of each lineage could be dated to the Middle or Late Miocene, and was very likely linked to the uplift of the QTP and the Asian aridification, given the high drought and/or cold tolerance of Ephedra. Most of the Ephedra species had low intraspecific variation and lacked a strong phylogeographical structure, which could be partially attributed to clonal reproduction and a relatively recent origin. In addition, ten of the detected 25 cpDNA haplotypes are shared among species, suggesting that a wide sampling of species is helpful to investigate the origin of observed haplotypes and make reliable phylogeographical inference. Moreover, the systematic positions of some Ephedra species are discussed.

The middle Eocene to early Miocene integrated sedimentary record in the Qaidam Basin and its implications for paleoclimate and early Tibetan Plateau uplift

Detailed analysis of whole-rock geochemistry, clay minerals, sedimentary color, and pollen in the Dahonggou section, northeast of the Qaidam Basin, are investigated, and the results suggest an intense weathering in the source area during the middle Eocene (∼48.5–40.5 Ma), indicating a warm and humid condition. The distinct decrease of chemical weathering degree in source regions began at ∼40.5 Ma, which is in agreement with the distinct decrease in redness of sedimentary sequences and the disappearance of thermophilic elements in pollen records. This 40.5 Ma cooling event extent demonstrated evidence for an intensification of central Asian aridification, which could be attributed to attainment of high elevations in southern-central Tibet and retreat of the Paratethys from central Asia in the late Eocene, reducing moisture transport to the Qaidam Basin.

Major changes in East Asian climate in the mid-Pliocene: Triggered by the uplift of the Tibetan Plateau or global cooling?

Since the mid-Pliocene, East Asian climates have experienced significant changes. One view suggests that significant uplift of the Tibetan Plateau during this period could have been responsible for these dramatic changes in the strength of the East Asian monsoon and for Asian interior aridification, while some other authors attribute these changes to the ongoing global cooling and rapid growth of the Arctic ice-sheet. Up to the present, which factor dominates the major changes of East Asian climate in the mid-Pliocene is still a contentious issue. This study presents an analysis of several climate proxies including grain-size, (CaO*+Na2O+MgO)/TiO2 ratio, Na/Ka ratio and dust accumulation rates of the Xifeng Red Clay sequence in the eastern Chinese Loess Plateau and the Xihe Pliocene loess-soil sequence in West Qinling. They reveal that aridity in the continental interior and winter monsoon circulation both intensified, whereas the East Asian summer monsoon showed a weakening rather than intensifying trend since the mid-Pliocene. These changes are also supported by the other multi-proxy records from various regions in East Asia. Previous numerical modeling studies have demonstrated that uplift of the Tibetan Plateau would have simultaneously enhanced continental-scale summer and winter monsoon strength as well as central Asian aridity. The mid-Pliocene climate changes in East Asia are therefore unlikely to be a response to Plateau uplift. On the contrary, our recent modeling results give support to the view that ongoing cooling could have intensified both the aridity of the interior and the strength of the winter monsoon, but weakened the summer monsoon in East Asia.

Geomorphological and sedimentological precautions in radiocarbon dating of eolian and lacustrine sequences in arid Asia

Lacustrine sediments in deep lakes are suitable for establishing radiocarbon chronology. Lacustrine sediments in shallow lakes are not suitable for establishing radiocarbon chronology, simply because younger plant roots can readily penetrate into older lacustrine sediments. Three features are warning signs for shallow-lake sediments: (1) high concentration of salts, (2) abundant vertically-oriented plant residues, and (3) organic matter-enriched sand layer. Field and laboratory investigations of eolian and water-reworked eolian sequences suggest that fluvial addition and fluvial alteration on terraces may produce reversed chronologies. Fluvial layers interbedded within eolian sequences should be avoided in obtaining dating targets, and eolian layers isolated by fluvial or lacustrine layers should be the targeting layers from which dating samples should be obtained. Bulk sediment 14C dates of a paleosol at Yuanbao loess section in the western Chinese Loess Plateau are distinctively older than charcoal dates, suggesting that bulk sediment samples contain older organic carbon that was likely brought upward by animal burrowing. In contrast, bulk sediment dates were found to be systematically younger than snail and charcoal dates at the Romantic section in Eastern Kazakhstan. The younger dates likely resulted from the downward intrusion of plant roots and/or translocation of mobile organic compounds into deeper layers. The only suggestion is to avoid bulk sediments as dating targets in eolian–paleosol sequences. The misleading chronology for the upper loess–paleosol complex at Lujiagou section indicated that even continuous loess deposits may yield reversed chronologies where loess has inherited older organic carbon from deflated floodplains and from loess hills. All kinds of dating targets (including charcoals) may produce unreliable chronologies.

The first representative Pliocene assemblages of passerine birds in Asia (Northern Mongolia and Russian Transbaikalia)

Passerine birds from two late Pliocene localities, Shaamar in northern Mongolia and Beregovaya in Transbaikalia (East Russia), represent the first known Neogene fossil assemblages of perching birds from Asia. A total of 11 families and 15 taxa are recognized, including a new genus and species of bunting, Pliocalcarius orkhonensis, apparently related to the Longspurs, and new species within the genera Hirundo and Rhodospiza, which are described. The avifauna is composed of open land and bush dwellers; it contains a few arid species, representing the oldest finds of the corresponding genera or lineages. This may indicate that the living Asian arid avian complex originated in Central Asia in the Neogene. Several genera (Rhodospiza, Paradoxornis) are documented in this paper for the first time in pre-Pleistocene deposits. Report of Calcarius is the first pre-Holocene evidence of the occurrence of this genus in Asia, which together with the remains of Synaptomys lemmings at Shaamar, illustrates faunal interchanges between North America and Asia in the Pliocene.

334 Late Cenozoic pollen records of the Qaidam Basin, north Tibetan Plateau and implications for the central Asian aridification

334 Late Cenozoic pollen records of the Qaidam Basin, north Tibetan Plateau and implications for the central Asian aridification

Isotopic constraints on intensified aridity in Central Asia around 12 Ma

The relationship between central Asian aridification and the evolution of the Himalayan–Tibetan orogen remains elusive. New isotopic data from pedogenic and lacustrine carbonates sampled from well-dated Neogene strata (15.7–1.8 Ma) in the northeastern Qaidam basin of the northern Tibetan Plateau identify a positive shift of ~ 2.5‰ in δ 18O values from 12 Ma to 10.7 Ma. High values were maintained until ~ 3.3 Ma when δ 18O values drop by 1‰. The timing of the positive shift in δ 18O values is remarkably consistent with isotopic records from a vast region along and within the northern Tibetan Plateau. Isotopic, mineralogical, petrologic, and facies analyses suggest that diagenetic effects and detrital contamination are minimal. The positive shift in δ 18O values, as well as high δ 13C values from pedogenic carbonates (which are suggestive of low soil respiration rates), is interpreted to indicate intensified aridity in central Asia ca. 12 Ma. The recognition of intensified aridity is critical to understanding the climatic effects of the development of the Himalayan–Tibetan orogen. We attribute this climatic change in the central Asia to: (1) retreat of Paratethys from central Asia, strengthening the seasonal contrast and resulting in the loss of a nearby moisture source; (2) attainment of high elevations in the Himalayas and south-central Tibet, blocking moisture-bearing air masses from the Indian and Pacific oceans; and (3) enhanced isolation and outward growth of the northern Tibetan Plateau. The negative shift around 3.3 Ma might be related to the onset of Northern Hemisphere glaciation, intensification of the East Asia monsoon, and/or effects of orographic rain-out.

Simulated variations of eolian dust from inner Asian deserts at the mid-Pliocene, last glacial maximum, and present day: contributions from the regional tectonic uplift and global climate change

Northern Tibetan Plateau uplift and global climate change are regarded as two important factors responsible for a remarkable increase in dust concentration originating from inner Asian deserts during the Pliocene–Pleistocene period. Dust cycles during the mid-Pliocene, last glacial maximum (LGM), and present day are simulated with a global climate model, based on reconstructed dust source scenarios, to evaluate the relative contributions of the two factors to the increment of dust sedimentation fluxes. In the focused downwind regions of the Chinese Loess Plateau/North Pacific, the model generally produces a light eolian dust mass accumulation rate (MAR) of 7.1/0.28 g/cm2/kyr during the mid-Pliocene, a heavier MAR of 11.6/0.87 g/cm2/kyr at present, and the heaviest MAR of 24.5/1.15 g/cm2/kyr during the LGM. Our results are in good agreement with marine and terrestrial observations. These MAR increases can be attributed to both regional tectonic uplift and global climate change. Comparatively, the climatic factors, including the ice sheet and sea surface temperature changes, have modulated the regional surface wind field and controlled the intensity of sedimentation flux over the Loess Plateau. The impact of the Tibetan Plateau uplift, which increased the areas of inland deserts, is more important over the North Pacific. The dust MAR has been widely used in previous studies as an indicator of inland Asian aridity; however, based on the present results, the interpretation needs to be considered with greater caution that the MAR is actually not only controlled by the source areas but the surface wind velocity.

Stratigraphies and chronologies of late Quaternary loess–paleosol sequences in the core area of the central Asian arid zone

The sporadic distribution of the Quaternary loess in Central Asia makes it hard to establish a regional pedostratigraphy through visual tracing of marker strata. The pedostratigraphic correlation presented here is thus completely based on the radiocarbon chronologies of the four studied sections. The first noticeable feature is that poorly-drained conditions predominated in the period between ∼48,000 and ∼30,000 14C BP, during which three entisols developed at ∼45,000 14C BP, ∼40,000 14C BP, and ∼35,000 14C BP. After a period of loess deposition between ∼30,000 and ∼18,000 14C BP under poorly-drained conditions, an entisol at the westernmost site (Valikhanov, south-central Kazakhstan) developed between ∼18,000 and ∼10,000 14C BP, also under poorly-drained conditions. The time equivalent deposits at Romantic and Zeketai sections to the east do not exhibit any soil-forming characteristics, although poorly-drained conditions are also imprinted in the time-equivalent loess. The Holocene sequences in the Central Asian domain consist of an early Holocene loess unit deposited between ∼10,000 and ∼5,000 14C BP and a late Holocene soil formed during the past ∼5000 years. In comparison, the climate was also wet between ∼48,000 and ∼20,000 14C BP, during which three mollisols developed under well-drained conditions in the Chinese Loess Plateau of the East Asian domain. The loess deposited between ∼23,000 and ∼10,000 14C BP in the Chinese Loess Plateau has neither observable marks of soil formation nor imprints of poorly-drained conditions. The Holocene sequence in the East Asian domain exhibits an out-of-phase relationship with that in the Central Asian domain, consisting of an early Holocene soil formed between ∼9000 and ∼4000 14C BP and a late Holocene loess unit deposited during the past ∼4000 years.

Asian aridification linked to the first step of the Eocene-Oligocene climate Transition (EOT) in obliquity-dominated terrestrial records (Xining Basin, China)

Abstract. Asian terrestrial records of the Eocene-Oligocene Transition (EOT) are rare and, when available, often poorly constrained in time, even though they are crucial in understanding the atmospheric impact of this major step in Cenozoic climate deterioration. Here, we present a detailed cyclostratigraphic study of the continuous continental EOT succession deposited between ~35 to 33 Ma in the Xining Basin at the northeastern edge of Tibetan Plateau. Lithology supplemented with high-resolution magnetic susceptibility (MS), median grain size (MGS) and color reflectance (a*) records reveal a prominent ~3.4 m thick basic cyclicity of alternating playa gypsum and dry mudflat red mudstones of latest Eocene age. The magnetostratigraphic age model indicates that this cyclicity was most likely forced by the 41-kyr obliquity cycle driving oscillations of drier and wetter conditions in Asian interior climate from at least 1 million year before the EOT. In addition, our results suggest a duration of ~0.9 Myr for magnetochron C13r that is in accordance with radiometric dates from continental successions in Wyoming, USA, albeit somewhat shorter than in current time scales. Detailed comparison of the EOT interval in the Tashan section with marine records suggest that the most pronounced lithofacies change in the Xining Basin corresponds to the first of two widely recognized steps in oxygen isotopes across the EOT. This first step precedes the major and second step (i.e. the base of Oi-1) and has recently been reported to be mainly related to atmospheric cooling rather than ice volume growth. Coincidence with lithofacies changes in our Chinese record would suggest that the atmospheric impact of the first step was of global significance, while the major ice volume increase of the second step did not significantly affect Asian interior climate.

A prolonged dry mid-Holocene climate revealed by pollen and diatom records from Lake Ugii Nuur in central Mongolia

A high-resolution pollen- and diatom-based bioclimatic reconstruction from Ugii Nuur lake core with a chronological support of 14 AMS dates revealed that a prolonged dry climate prevailed between 5830–3080 14C BP in central Mongolia, as indicated by a dramatic increase in Chenopodiaceae pollen percentages at the expense of Pinus, Poaceae, Cyperaceae and other mesophytic forbs pollen percentages. Higher values of pollen-based temperature index and lower values of pollen-based moisture index also support the notion that the mid-Holocene was persistently warm and dry relative to the preceding and following periods. This mid-Holocene drought is further confirmed by diatom and sedimentary variations, both the planktonic/benthic diatom ratio and the deposition rate being the lowest. Reviews of published regional palaeoclimate data suggest that a prolonged mid-Holocene drought might have prevailed extensively in the central-east Asian arid and hyper-arid areas. The prolonged and extensive drought might have been resulted from a well-documented large-scale temperature rise. The temperature rise-dictated enhancement of evaporation might have exceeded the precipitation increase (if any), resulting in the aridity increase.

Asian aridification linked to the first step of the Eocene-Oligocene Climate Transition (EOT) in obliquity-dominated terrestrial records in Xining Basin, China

Asian aridification linked to the first step of the Eocene-Oligocene Climate Transition (EOT) in obliquity-dominated terrestrial records in Xining Basin, China

Aeolian sediment evidence that global cooling has driven late Cenozoic stepwise aridification in central Asia

Abstract It has been a long held view that uplift of the Tibetan Plateau dominated stepwise climatic drying in central Asia during the late Cenozoic. On the other hand, global cooling may also have forced Asian drying and the subsequent formation of aeolian deposits in north China. Until now, whether the Tibetan uplift or the global cooling has been the first-order driver controlling stepwise Asian drying has remained a contentious issue. In this study, we examine the thick aeolian silt deposit, which is regarded as a good archive of palaeoclimatic changes in central Asia and north China, in order to qualitatively reconstruct the drying process in Asia during the late Cenozoic. On the basis of our long-term field surveys, laboratory analyses and previous investigations, we have obtained time sequences of Asian drying from the early Miocene to late Pleistocene; we compare this newly reconstructed time series of Asian aridification with the time series of global cooling and Tibetan uplift to identify the first-order driver of stepwise Asian aridification. A good match between the drying and global cooling might indicate that global cooling was the most likely driver of stepwise drying in interior Asia. On the other hand, controversy regarding timing and amplitude of Tibetan uplift during the late Cenozoic suggests that the prevailing conclusion that Tibetan uplift forces Asian drying should be regarded as immature. A mechanism that global cooling drove the Asian drying is tentatively suggested.

Grain size profiles in the Chengdu Clay, eastern margin of the Tibetan Plateau: Implications for significant drying of Asia since ∼500 ka B.P.

Asian aridification reflects a combination of the uplift of the Tibetan Plateau and global cooling. Grain size analysis of the Chengdu Clay at the eastern margin of the Tibetan Plateau indicates a rapid increase of coarse fractions at around 500 ka, suggesting a significant drying event in the source region. Comparison with results from the Chinese Loess Plateau (CLP) indicates that this drying event occurred on a regional scale and may imply an important drying event in eastern Asia. We estimate that the rapid uplift of the Tibetan Plateau during the middle Pleistocene may be one of the most important causes of the significant drying in the area.

Holocene environmental change inferred from the loess–palaeosol sequences adjacent to the floodplain of the Yellow River, China

Chinese loess deposits are generally considered to be the product of dust storms and dust falls from the central Asia arid zones that were transported across China by the northwesterly continental monsoon. In contrast, the Zhengzhou Loess found southeast of the Loess Plateau, adjacent to the floodplain of the Yellow River, records a different eolian regime and dust source. The Zhengzhou Loess was investigated by field observations, measurements of magnetic susceptibility, particle-size distribution, loss-on-ignition, CaCO 3 and chemical contents. Both field observations and the laboratory results indicate that, during the last glacial, the Zhengzhou Loess was supplied by two different eolian regimes and dust sources, one was from the fresh flood deposits of the Yellow River driven by the northeast winds from the low-lying floodplain, and the other was from the dust storms and dust falls that traveled across the Loess Plateau driven by the northwesterly continental monsoon from the central Asian arid lands. The early Holocene, 11,500–8500 a BP, was a transition during the change in eolian regime and dust source because of the weakened northwesterly monsoon along with the global climatic amelioration. Following the retreat of the northwesterly monsoon from the onset of the mid-Holocene Climatic Optimum at 8500 a BP, dust supply from the drifting sand zone on the Yellow River floodplain became dominant because of the intensified strength of the northeast winds from the Bohai Sea. From 3100 a BP onwards, climatic aridity and extensive human disturbance have resulted in intensive eolian processes causing the incursion of the drifting sand into the Zhengzhou Loess zone. These results show that loess accumulation is more complex than traditionally assumed. The origin of loess deposits elsewhere outside the Loess Plateau may be related to dust sources derived from alluvial sediments of major river systems.

Tibetan uplift prior to the Eocene-Oligocene climate transition: Evidence from pollen analysis of the Xining Basin

Research Article| December 01, 2008 Tibetan uplift prior to the Eocene-Oligocene climate transition: Evidence from pollen analysis of the Xining Basin G. Dupont-Nivet; G. Dupont-Nivet * 11Paleomagnetic Laboratory “Fort Hoofddijk”, Faculty of Geosciences, Utrecht University, Budapestlaan 17, 3584 CD Utrecht, The Netherlands *E-mail: gdn@geo.uu.nl Search for other works by this author on: GSW Google Scholar C. Hoorn; C. Hoorn 22Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Kruislaan 314, 1098 SM Amsterdam, The Netherlands Search for other works by this author on: GSW Google Scholar M. Konert M. Konert 33Sediment Analysis Laboratory, Faculty of Earth and Life Sciences (FALW), Free University Amsterdam, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands Search for other works by this author on: GSW Google Scholar Geology (2008) 36 (12): 987–990. https://doi.org/10.1130/G25063A.1 Article history received: 21 Apr 2008 rev-recd: 19 Aug 2008 accepted: 03 Sep 2008 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation G. Dupont-Nivet, C. Hoorn, M. Konert; Tibetan uplift prior to the Eocene-Oligocene climate transition: Evidence from pollen analysis of the Xining Basin. Geology 2008;; 36 (12): 987–990. doi: https://doi.org/10.1130/G25063A.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Uplift of the Tibetan Plateau and the Himalayas since the onset of the Indo-Asia collision is held responsible for Asian aridification and monsoon intensification, but may also have gradually cooled global climate, leading to the 34 Ma Eocene-Oligocene transition. To unravel the interplay between Tibetan uplift and global climate, proxy records of Asian paleoenvironments constrained by accurate age models are needed for the Paleogene Period. Here we report the 38 Ma appearance of high-altitude vegetation recovered from palynological assemblages in precisely dated lacustrine sediments from the Xining Basin of the northeastern Tibetan Plateau region. This result confirms previous evidence for important regional uplift in the central and northern Tibetan Plateau regions during the early stage of the Indo-Asia collision. This is consistent with the idea that the associated increase in rock weathering and erosion contributed to lowering of atmospheric CO2, leading to the Eocene-Oligocene transition. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Drivers of greening trend across vertically distributed biomes in temperate arid Asia

This study investigates vegetation responses to climate changes by analyzing 19 years (1982–2000) of both climatic data and growing season Normalized Difference Vegetation Index (NDVI) for vertically distributed desert, steppe, forest and meadow, in the middle part of the northern slope of Tianshan Mountains. Vegetation activity exhibited greening trend in all biomes, owing mainly to reduction of water stress caused by increasing precipitation, although warming trend negated that effect because of temperature‐induced drought. Precipitation acted as a remarkable driving force of plant growth in each biome through the whole growing season (spring, summer, autumn), its effect could always persist into the next season, however, the sensitivity decreased across biomes with increasing precipitation. Warming‐induced snow melt played a positive role in boosting plant growth during spring in steppe, forest and meadow. Except that, warming produced negative effects.