Arid Central Asia Research Articles

Identifying drivers of storage dynamics of lakes and reservoirs in the arid Central Asia

Abstract Knowing the storage variations in lakes and reservoirs are essential for water resources and environmental management, especially in the regions facing water scarcity. However, the quantification of the storage changes is limited by sparse in-situ observations and spatial coverage of space(air)-borne altimetric sensors that have been used conventionally in storage retrieval. This hampers the attribution analysis of lake storage changes. Here, we combined long-term optical remote sensing and multi-source terrain elevation data to derive the monthly storage time series from 1990 to 2020 for 8544 lakes and reservoirs in Central Asia, where water scarcity has been bottle-necking local socioeconomic sustainability. The regional total storage has been decreasing with a rate of -4.78±0.88 km3 year-1 mainly owing to the desiccation of the Aral Sea. For other lakes, 26% of them show decreasing while 22% show increasing trends. At a watershed-scale, the long-term changes in small to medium-sized (<5000 km2) lakes are primarily caused by the changes in surface runoff, jointly affected by precipitation and temperature changes. We also found that 29% lakes in Central Asia experienced frequent seasonal dry out in the past decades. Such seasonal dry out is mainly caused by fast evaporation losses during the summer months. For the majority (63±8%) of these lakes, their evaporation water losses are larger than the seasonal storage drawdown. Our analysis highlights the co-regulation of surface runoff and lake evaporation in the storage losses in arid and semi-arid regions.

The Holocene precipitation dipole pattern in the Asian drylands: Mechanisms and processes from PMIP4 simulations and paleo-proxy evidence

Asian drylands encompass Arid Central Asia (ACA) and West Asia (WA), where water vapor transport is consistently governed by the westerlies. Recent research has identified a dipole pattern in Holocene hydroclimate changes between the ACA and WA, challenging previous assumptions of uniform hydroclimate shifts across the westerlies-dominated mid-latitudes of the Northern Hemisphere. However, the mechanisms behind the dipole pattern remain largely unknown. Our findings demonstrate that PMIP4 models accurately reproduced the dipole pattern, attributing it mainly to contrasting spring precipitation changes. From the middle to late Holocene, strengthened westerlies led to increased precipitation in the ACA. In contrast, rising spring solar insolation intensified the subtropical high, leading to reduced water vapor and increased descending air movement in WA, which decreased precipitation in the region. Our study suggests that WA is a distinctive region within the westerlies-dominated mid-latitudes, where low-latitude processes led to inconsistent precipitation variations from the middle to late Holocene.

Retreating ice sheet caused a transition from cold-dry to cold-humid conditions in arid Central Asia

Water is critical for ecological systems in arid regions, making it imperative to understand how moisture in arid Central Asia (CA) responds to anthropogenic warming. The oscillation of warming and cooling events since the Last Glacial Maximum (LGM, ∼24–19.5 ka) provides a window for exploring the relationship between moisture and temperature. Employing 109 luminescence ages derived from eight sand dune sediment cores in the Bayanbulak Basin in the CA, this study endeavors to reconstruct the evolution of sand accumulation, and by extension, moisture dynamics. We found that pre-Holocene sand accumulation was predominant during the LGM and Heinrich Stadial 1 (HS1, ∼18–14.6 ka), indicative of a cold-dry climate prevailing during these two cold stages. During the Holocene, sand accumulation during Early Holocene is significantly stronger than that during Middle-late Holocene, supporting a long-term wetting trend. Additionally, this study reveals that the colder Little Ice Age (LIA, ∼0.55–0.2 ka) exhibited a wetter condition compared to the warmer Medieval Warming Period (MWP, ∼1–0.55 ka), indicating a cold-humid climate during the LIA. Corroborated by TraCE-21ka (Transient Climate of the Last 21,000 Years) simulation, we propose that diminished evaporation over North Atlantic during the LGM and HS1 potentially led to a reduction in water vapor transported by westerlies to the CA. During the Middle and Late Holocene, increased evaporation over North Atlantic, attributed to decreased ice sheet, westerlies intensity became the primary limiting factor. Notably, stronger westerlies during the LIA could have contributed to elevated moisture levels compared to the MWP. These findings not only resolve the debate surrounding the transition from cold-dry to cold-humid conditions but also enhance our comprehension of future moisture variations.

Climate warming positively affects hydrological connectivity of typical inland river in arid Central Asia

Hydrological connectivity is crucial for understanding water-ecosystem dynamics, as it serves as a key link between different landscape units. However, the variability of hydrological connectivity in Central Asia remains unexplored, which poses challenges to a comprehensive understanding of ecohydrological processes. This study investigates the spatiotemporal patterns and driving mechanisms of hydrological connectivity in the Tarim River Basin (TRB), Central Asia, from 1990 to 2020, employing a novel approach that integrates remote sensing and reanalysis data. The results indicate an increasing trend in the hydrological connectivity index (HCI), with approximately 60% of the TRB exhibiting significant increases. Climate change exerts the greatest direct (0.59) and total (0.64) effects on HCI, with potential evapotranspiration (19.2%) and temperature (12.6%) being the dominant factors. In mountainous regions, climate change (0.65) is the primary driver, while human activities have a greater impact in the plains (−0.27). These findings offer a new framework for studying ecohydrological processes in arid regions.

Sand and Dust Storm Risk Assessment in Arid Central Asia: Implications for the Environment, Society, and Agriculture

This study aimed to assess sand and dust storm (SDS) risks in arid Central Asia during 2001–2021 from a multisectoral (environment, society, and agriculture) and comprehensive perspective on the Google Earth Engine (GEE) platform. The results show that the areas with moderate or greater SDS risk accounted for 18.75% of the total area of arid Central Asia. The high SDS risk areas are mainly concentrated in the oases around the desert and are most widely distributed in spring and summer. The SDS risk in the oasis area of southern Xinjiang increased significantly, while the SDS risk in the northeastern Aral Sea region and the Kazakh hilly region decreased significantly over the 21 years. Khwarazm of Uzbekistan, located in the Amu Darya River Delta, is the administrative district with the highest comprehensive risk of sandstorms, and the Balkan State of Turkmenistan and Kashi City and Zepu County in China are the administrative districts with the highest multisectoral risk of sandstorms. The results of this study provide a complete picture of SDS risks in the arid Central Asia region and will provide some guidance to policymakers and local authorities in SDS risk mitigation.

Impact of millennial-scale fluctuations of the Siberian High on Holocene aeolian activity: Insights from Lake Ailike in arid Central Asia

Arid Central Asia (ACA) is a major dust source region in the Northern Hemisphere, owing to the prevalence of aeolian activity that substantially impacts the ecological environment and human wellbeing in this region. However, the driving mechanisms of aeolian activity in ACA during the Holocene are unclear, making it difficult to predict possible future aeolian activity. We used AMS 14C dating, combined with grain-size analysis, high-resolution X-ray fluorescence scanning, and scanning electron microscopy of a sediment core from Lake Ailike, in the Junggar Basin, to reconstruct the history of aeolian activity in ACA during the Holocene. We found that periods of increased aeolian activity on the millennial-scale are correlated with the strengthening of the Siberian High, and that there is a consistency between aeolian activity and climatic fluctuations in the mid-latitudes of Europe. These findings support a close relationship between climate fluctuations in mid- and high-latitude regions of the Northern Hemisphere. Lower/higher temperatures in high latitudes result in the expansion/contraction of polar air masses, leading to the strengthening/weakening of the Siberian High. Additionally, more/less frequent aeolian activity in ACA corresponded to cooling/warming trends in the mid-latitudes of Europe during the Holocene. While ongoing global warming may lead to a long-term decrease in aeolian activity in ACA, the weakening of the polar vortex has resulted in more frequent cold waves affecting the mid-latitudes of Eurasia during winter in recent years.

Holocene aeolian environmental dynamics in fixed and semi-fixed deserts over the arid Central Asia revealed by comprehensive sand-dune records

Fixed and semi-fixed deserts are widely distributed in arid Central Asia (ACA). Environmental changes in these deserts can affect the regional radiation balance, climate dynamics, and global climate through a series of feedback effects. This study analyzed luminescence dating from 37 sites, with a particular focus on dendritic dunes (a pattern of vegetated linear dunes) and the ancient dunes beneath them in the Gurbantunggut Desert and yielded the following insights. (1) Primary ridges of dendritic dunes originated approximately 1.0 ka, whereas secondary ridges predominantly formed at 8.5 ± 0.3 ka. The formation of the underlying ancient dunes commenced at least 11.0 ± 0.5 ka and ended between 8.5 ± 0.3 ka and 8.2 ± 0.4 ka. (2) During the Holocene, the Gurbantunggut Desert underwent two distinct environmental phases. From 11.7 ka to 8.1 ± 0.1 ka, the region was characterized by vigorous aeolian activity, marked by the prevalence of mobile dunes. Conversely, the period from 8.1 ± 0.1 ka to 0 ka exhibited substantial environmental amelioration, with limited aeolian activity and the intermittent partial development of vegetated linear dunes. (3) A comprehensive analysis of the principal factors affecting regional aeolian activity revealed that at 11.7 ka–8.1 ± 0.1 ka, moisture (precipitation) and near-surface wind intensity primarily governed aeolian activity in the Gurbantunggut Desert. At 8.1 ± 0.1 ka–0 ka, aeolian activity was mainly influenced by moisture (precipitation), near-surface wind intensity, and external sand supply. (4) Similar patterns of Holocene aeolian activity were observed in the fixed Bayanbulak, Karakum, and Kizil Kum Deserts within the ACA. On a suborbital scale, winter insolation served as the primary driving factor, along with the ice volume and atmospheric CO2 concentration. These factors collectively controlled regional winter temperatures, which determined moisture (precipitation) and near-surface wind intensity by affecting the winter westerlies and Siberian High, ultimately controlling regional aeolian activity.

Phylogeographic analysis reveals multiple origins of the desert shrub Reaumuria songarica in northern Xinjiang, involving homoploid and tetraploid hybrids.

Hybrid speciation plays an important role in species diversification. The establishment of reproductive isolation is crucial for hybrid speciation, and the identification of diverse types of hybrids, particularly homoploid hybrid species, contributes to a comprehensive understanding of this process. Reaumuria songarica is a constructive shrub widespread in arid Central Asia. Previous studies have inferred that the R. songarica populations in the Gurbantunggut Desert (GuD) originated from homoploid hybridizations between its eastern and western lineages and may have evolved into an incipient species. To further elucidate the genetic composition of different hybrid populations and to determine the species boundary of this hybrid lineage, we investigated the overall phylogeographic structure of R. songarica based on variation patterns of five cpDNA and one nrITS sequences across 32 populations. Phylogenetic analyses demonstrated that within the GuD lineage, the Wuerhe population evolved directly from ancestral lineages, whereas the others originated from hybridizations between the eastern and western lineages. PCoA and genetic barrier analysis supported the subdivision of the GuD lineage into the southern (GuD-S) and northern (GuD-N) groups. Populations in the GuD-S group had a consistent genetic composition and the same ancestral female parent, indicating that they belonged to a homoploid hybrid lineage. However, the GuD-N group experienced genetic admixture of the eastern and western lineages on nrITS and cpDNA, with some populations inferred to be allopolyploid based on ploidy data. Based on cpDNA haplotypes, BEAST analyses showed that the GuD-S and GuD-N groups originated after 0.5 Ma. Our results suggest that multiple expansions and contractions of GuD, driven by Quaternary climatic oscillations and the Kunlun-Yellow River tectonic movement, are important causes of the complex origins of R. songarica populations in northern Xinjiang. This study highlights the complex origins of the Junggar Basin flora and the underappreciated role of hybridization in increasing its species diversity.

Distentanging the late-Holocene human–environment interactions in the Altai Mountains within the Arid Central Asia

Understanding the impacts of human activities on landscapes necessitates a comprehensive analysis of historical changes in climate, vegetation, fire and land utilization. The human-environment interactions were investigated through the analysis of new charcoal data from Kelashazi Peat in the Altai Mountains, compared with the detailed paleoenvironmental records and historical human activities (e.g., agriculture and pastoralism) at other three distinct sites. The findings suggest that the late-Holocene (prior to ∼2000 years ago) fire activities were mainly influenced by temperature at higher elevations and were primarily driven by vegetation cover at lower elevations. Over the past two millennia, human activities have increasingly impacted fire dynamics. Elevated fire frequencies during the Medieval Warm Period at higher elevations were linked to warmer climates and intensified pastoral activities. Lower fire incidences at lower elevations may be attributed to population outflows during the Medieval Warm Period, while heightened fire occurrences at lower elevations might result from increasing agricultural activities during the Little Ice Age. This study underscores the intricate interplay between natural climate-vegetation-fire dynamics and anthropogenic burning trends in the late Holocene across different elevations of the Altai Mountains within the Arid Central Asia.

Paleoclimatic significance of the organic carbon isotopes of the Tajikistan loess in arid Central Asia, on orbital timescales since the last interglacial

During the past few decades, the stable carbon isotope composition of bulk organic matter (δ13Corg) in loess sediments has been increasingly used for reconstructing changes in the terrestrial vegetation and climate in several regions, including Europe, Xinjiang (the eastern part of arid central Asia, ACA), and the Chinese Loess Plateau (CLP). However, previous research indicates significant differences in the climatic significance of δ13Corg between the loess-paleosol sequences of Europe and the western and eastern ACA, compared to the loess of the central and southern CLP in monsoonal Asia. The δ13Corg values of loess-paleosol sequences in western and eastern ACA on different timescales exhibit consistent patterns of variation, suggesting that loess δ13Corg in these areas may be influenced by similar climatic factors and have similar mechanisms. However, the lack of detailed δ13Corg studies in central ACA limits our understanding of their applicability to long loess sequences within this region. This limitation not only constrains our understanding of the paleoclimatic significance of loess δ13Corg in central ACA, but it also affects the practical application of loess δ13Corg as a reliable paleoclimate proxy in this region. Consequently, it impedes a comprehensive understanding and in-depth analysis of loess δ13Corg across the mid-latitude Eurasian continent. To address this deficiency, we conducted a δ13Corg study of the Darai Kalon (DK) loess section, in southern Tajikistan, central ACA, since the last interglacial, with the aim of exploring the environmental significance of loess δ13Corg and the origin of the climatic record of this section, on orbital timescales. The results show that the ecosystem in southern Tajikistan, and throughout ACA, was dominated by C3 vegetation since the last interglacial. Loess δ13Corg records can be used as a precipitation proxy in ACA, at least since the last interglacial. However, regional comparisons revealed negative correlations between loess δ13Corg values and pedogenic intensity in Europe, ACA, and the western CLP, which is the opposite to the positive correlations observed in the central and southern CLP. Comparison of the paleoclimate record of the DK section with those of loess-paleosol sequences from monsoonal Asia indicated that warm, humid conditions occurred during past interglacials (MIS5, MIS1) and interstadials (MIS3), and cold, arid conditions occurred during the glacial/stadial periods (MIS4, MIS2) in both ACA and monsoonal Asia. We propose that changes in Northern Hemisphere insolation were responsible for this in-phase pattern of climate change between these two regions on orbital timescales since the last interglacial.

Effect of plant roots on the radiocarbon age of loess deposits in arid central Asia

Radiocarbon and OSL dating are the two main approaches used to date aeolian deposits in arid central Asia (ACA). Previous results showed that, compared with OSL dating, the 14C ages of loess deposits in ACA are underestimated when the loess age is beyond ∼25 ka. However, the cause of this radiocarbon age underestimation has not been adequately addressed. In this study, we measured the 14C ages of different dating materials, including pyrolysis volatile (Py-V), pyrolysis residue (Py-R), humin, and total organic carbon fractions from two loess sections in ACA (the Hoalin section in the western Pamir Mountains, and the TLD16 section in the northern Tianshan Mountains). The results show that different dating material yielded different 14C ages for all the loess samples, and all the radiocarbon ages obtained are younger than their corresponding OSL ages. Based on these results, together with a regional comparison of 78 14C ages from ACA with their corresponding OSL ages, we propose that the 14C age underestimation is mainly due to the contamination by the deep penetration of the extended root systems of the plants that grow in arid areas, whereas this effect is less significant in the summer monsoon–dominated Chinese Loess Plateau.

Turning Points in Vegetation Phenology Trends and Their Relationship to Climate in Arid Central Asia

AbstractGrassland phenology is highly sensitive to climate change. Here, we investigate the spatiotemporal patterns of start (start of season (SOS)) and end (end of season (EOS)) dates of the growing season and quantify changes in their climatic controls over the arid Central Asian grassland ecosystems during 1982–2015, which may improve the model performance by considering shifts in primary drivers under ongoing climate change. Our results suggest that temperature played a positive role in advancing the SOS date, with the control of temperature on SOS getting stronger as preseason conditions become warmer but not drier. For autumn phenology, rapid increase in temperature after 1999 in combination with reductions in precipitation jointly contributed to a shift from delayed to advanced EOS. The areas that EOS regulated by either temperature or precipitation have changed between the two subperiods. Our findings suggest that the dynamic controls of temperature and precipitation on grassland phenology and the difference between spring and autumn phenology should be built into phenological models more accurately.

Holocene dust storm variations across northern monsoonal Asia and arid central Asia: Contrasting impacts of climate change

Arid inner Asia, encompassing northern monsoonal Asia (NMA) and arid central Asia (ACA), is the world's second largest dust source region, emitting large quantities of dust particles that travel vast distances around the globe. Previous studies have revealed that the precipitation/moisture variations between NMA and ACA show an out-of-phase or anti-phase relationship on a multi-millennial timescale during the Holocene. However, considering the profound impact of precipitation and related vegetation changes on dust storms, it is unclear whether disparities exist in the variations and mechanisms governing Holocene dust storms between these two regions. Here we use a compilation of Holocene dust storm records from both NMA and ACA, combined with proxy–model comparisons, to demonstrate a consistent temporal pattern of dust storm activity between these regions, with an overall increasing trend on a multi-millennial timescale during the Holocene. Comparison of these dust storm records with regional climate records reveals that surface landscape dominated by the summer monsoon precipitation were the dominant controls on dust storm activity in NMA during the Holocene. In contrast, given the Holocene wetting trend observed for ACA, we propose that precipitation had only a limited influence on modulating the regional dust storms in this region; furthermore, the increasing frequency of dust storms cannot be attributed to decreasing winter monsoon intensity. Instead, we argue that the intensified dust storms in ACA during the late Holocene were triggered by the increased strength and northward (southward) movement of the spring (summer) westerly jet. By revealing the differences in the mechanisms of dust storms across arid inner Asia, our findings provide a scientific basis for implementing policies for dust storm management that can be adapted to meet specific local conditions.

Single-grain luminescence dating of Manas Lake paleoshorelines reveals late quaternary glacial meltwater forced lake level highstand in arid Central Asia

The spatiotemporal patterns of late Quaternary lake evolution, along with their responses to climatic changes and glacial meltwater in the westerlies-dominated Central Asia, remain unclear primarily due to the lack of well-dated records spanning across glacial and interglacial cycles. In this study, we investigated five well-preserved paleolake shoreline sequences, 15–27 m above the modern lake basin of the now-dry Manas Lake, a representative terminal lake in the Junggar Basin of arid Central Asia. Both single aliquot and single-grain K-feldspar post-infrared infrared stimulated luminescence (pIRIR) dating protocols were applied to 26 shoreline samples to reconstruct a lake level variation for Manas Lake over the past 90 kyr. The reliability of the K-feldspar pIRIR dating was tested through assessment of luminescence characteristics and comparison of single-grain and single-aliquot K-feldspar pIRIR Des. The results indicate that the highest water levels (∼25 m deep) occurred during late Marine Isotope Stage (MIS) 5 (∼80 ka) and MIS 3 (31–27 ka). A lake level 20 m above modern lake basin (a.m.l.b.) occurred from the last deglaciation to the early Holocene (14–10 ka) and again in the late Holocene (3.4–0.3 ka). The lake level changes of Manas Lake are decoupled from observed Westerlies precipitation changes over the past 90 kyr. This decoupling suggests enhanced glacial meltwater sourced from the high Tianshan Mountains, triggered by higher mean summer temperatures, worked together with Westerlies precipitation drove periods of lake level highstand in Manas Lake during late MIS 5, late MIS 3, and early Holocene periods.

Long-term dynamics of organic matter inputs in sediments of Lake Balkhash, arid Central Asia: Coupled climate and anthropogenic influences

Lake sediments as reservoirs of organic matter (OM) play crucial roles in the carbon burial and carbon cycle on the regional and global scales. However, the long-term history and patterns of sedimentary organic matter (SOM) inputs from various sources and its response to multiple drivers are not well constrained. Here, we demonstrated variations in the source and composition of SOM and the potential regulating factors using the multi-biomarker (n-alkanes, fatty acids, and alcohols) signatures in a core span the last ∼ 250 years from Lake Balkhash. The highest Paq (proportions of aquatic macrophytes) and relatively low short-chain lipid contents in sediments before 1860 CE indicate the dominant OM inputs from aquatic macrophytes and minor inputs from microalgae. This can be attributed to the humid conditions during the late Little Ice Age (LIA). The decreased Paq and the highest CPIH (carbon preference index for high molecular weight) in sediments deposited in 1860 ∼ 1930 CE revealed considerably elevated OM inputs from emergent plants coeval with declined aquatic macrophytes contributions. This pattern of OM inputs was likely caused by large variables of water levels during the climate transition period, promoting the growth of emergent plants and inhibited aquatic macrophytes. In sediments from 1930 ∼ 2016 CE, much higher terrestrial OM inputs and prevailing microalgal OM inputs were reflected by the highest principal components of each source, whereas the lowest Paq indicates minimal OM inputs from aquatic macrophytes. These changes were probably caused by intensification of anthropogenic perturbations, e.g., land reclamation, promoting more terrestrial OM and nutrients transported into the lake. These findings suggested that SOM inputs are highly linked to lake environmental changes and can be profoundly influenced by climate variability and anthropogenic activities, which provides insights into patterns of carbon burial and carbon cycle in lake-catchment systems in arid regions.

Increasing influence of minimum temperature on grassland spring phenology in arid Central Asia

The dynamics of grassland spring phenology in arid Central Asia (ACA) are critical for the regional carbon cycle, ecological security, and social stability. Nonetheless, the mediating effects of climatic elements on grassland start of season (SOS) and trends in the relative contributions to the SOS in the ACA have not been sufficiently investigated. In this study, we explored the mediating effects of daily maximum temperature (TMX), daily minimum temperature (TMN), vapor pressure deficit (VPD), and soil moisture (SM) on grassland SOS and trends in the relative contributions of TMX, TMN, VPD, SM to SOS in the ACA from 1982 to 2022. We found that the grassland SOS in the ACA showed an advancing trend of 0.28 days/yr. Rising TMX and VPD contributed to the advance of SOS, and the delaying effects of TMN and SM were offset by the indirect effects of TMX and VPD. TMX and TMN had asymmetric effects on SOS, with SOS advanced or delayed for increases in TMX or TMN, respectively. TMX was the dominant factor controlling the SOS, with the largest relative contribution (47.93 % of the ACA). Over the past 41 years, the relative contributions of SM and VPD to SOS showed a non-significant decreasing trend, TMX remained unchanged, and TMN showed a highly significant increasing trend. Under sustained future warming, TMN may undergo more accelerated warming than TMX, and the advance of SOS due to increased TMX may be further offset, potentially leading to the supplantation of TMX by TMN in its impact on SOS. Our results emphasize that characterization of the phenological response should account for the mediating effects of climatic elements and trends in relative contributions.

Does Central Asian forest growth benefit from a warming-wetting climate? Insights from tree-ring records

Climate warming has pronounced impacts on high-elevation regions, including arid Central Asia, and has multiple impacts on the environment. Forests in these mountainous areas provide essential services by regulating regional climate, sequestering carbon, and supporting soil and water conservation. However, trends in forest productivity and their response to climate change remain unclear. To address this knowledge gap, we collected tree cores from five sample plots in the western Tianshan region. We used tree-ring widths to reconstruct net primary productivity (NPP) and investigated the sensitivity of forest NPP to climate change by analysing weather station data and employing LASSO regression to identify climatic factors influencing forest growth. Our results demonstrate that the reconstructed forest NPP effectively captured significant carbon shifts and revealed a non-significant increase in forest productivity associated with climate warming and higher precipitation between 1970 and 2020 at low and middle elevations in the Tianshan mountains. Humidity is the primary limiting factor affecting forest growth in this region. Conversely, the relationship between temperature and forest growth is not consistent as precipitation increases. Our findings suggest that continued warming will exacerbate water stress in forests.

Grassland productivity in arid Central Asia depends on the greening rate rather than the growing season length

Climate change has induced substantial impact on the gross primary productivity (GPP) of terrestrial ecosystems by affecting vegetation phenology. Nevertheless, it remains unclear which among the mean rates of grass greening (RG), yellowing (RY), and the length of growing season (LOS) exhibit stronger explanatory power for GPP variations, and how RG and RY affect GPP variations under warming scenarios. Here, we explored the relationship between RG, RY, LOS, and GPP in arid Central Asia (ACA) from 1982 to 2019, elucidating the response mechanisms of RG, RY, and GPP to the mean temperature (TMP), vapor pressure deficit (VPD), precipitation (PRE), and soil moisture (SM). The results showed that the multi-year average length of greening (LG) in ACA was 22.7 days shorter than that of yellowing (LY) and the multi-year average GPP during LG (GPPlg) was 38.28 g C m−2 d −1 more than that of during LY (GPPly). RG and RY were positively correlated with GPPlg and GPPly, although the degree of correlation between RG and GPPlg was higher than that between RY and GPPly. Increases in RG and RY contributed to an increase in GPPlg (55.44 % of annual GPP) and GPPly (35.44 % of annual GPP). The correlation between RG and GPPlg was the strongest (0.49), followed by RY and GPPly (0.33), and LOS and GPP was the weakest (0.21). TMP, VPD, PRE, and SM primarily affected GPP by influencing RG and RY, rather than direct effects. The positive effects of TMP during LG (TMPlg), PRE during LG (PRElg), and SM during LG (SMlg) facilitated increases in RG and GPPlg, and higher VPD during LY (VPDly) and lower PRE during LY (PREly) accelerated increases in RY. Our study elucidated the impact of vegetation growth rate on GPP, thus providing an alternate method of quantifying the relationship between vegetation phenology and GPP.

Late Holocene decoupling of lake and vegetation ecosystem in response to centennial-millennial climatic changes in arid Central Asia: A case study from Aibi Lake of western Junggar Basin

Central Asian lakes are crucial for sustaining fragile oasis ecosystems in arid regions. Understanding the response of ecosystems in these lake basins to climate change is essential for predicting future variations in these ecosystems. Aibi Lake is a notable terminal lake in arid Central Asia. In this study, a 95 cm lacustrine sediment core was drilled from Aibi Lake to investigate the response of lacustrine and terrestrial ecosystems in the lake basin to climate change over the past 3200 years. Accelerator mass spectrometry (AMS) 14C dating and multi-proxy analyses of diatoms, pollen, grain size, total organic content (TOC), total nitrogen (TN), and total hydrogen (TH) are applied to the sediment core. The grain size and geochemical results show that the lake experienced elevated levels and improved productivity and nutrition during the periods of 708–181 BCE, 0–740 CE, and 1428–1900 CE. The periods align with the Roman Warm Period, Dark Age Cold Period, and Little Ice Age, respectively. For the past 3200 years, benthic diatoms have consistently been the dominant species in the lake. During the climatic transition periods of the Dark Age Cold Period, Medieval Warm Period, and Little Ice Age, there were significant changes in the abundance and survival of certain species of diatoms. Specifically, the halophilic species (Nitzschia dissipata and Nitzschia hungarica), basophilic species (Synedra acus), and the nutrition level-relevant species (Navicula menisculus) experienced notable shifts. These changes ultimately resulted in a noticeable alteration in the structure and function of the diatom community. Over the past 3200 years, the lake ecosystem has undergone three noticeable regime shifts. In contrast, the vegetation in the lake catchment has remained relatively stable, primarily consisting of desert steppe. These results suggest that aquatic ecosystems in arid central Asia are more susceptible and exhibit more rapid responses to climate change compared to terrestrial vegetation.

Asynchronous Holocene lake evolution in arid mid-latitude Asia is driven by glacial meltwater and variations in Westerlies and the East Asian summer monsoon

Abstract Understanding the mechanisms driving hydrological change in arid Central Asia over a range of time scales is crucial for making predictions for future changes in fragile desert-lake ecosystems. As of yet, the drivers of hydrological changes in lake systems of arid Central Asia over the Holocene remain largely unexplored. Aibi Lake, fed by rivers originating from the glaciated Tianshan Mountains and terminating in the arid Junggar Basin of northwestern China, presents a perfect natural laboratory to explore lake evolution in context to Holocene climate evolution in arid Central Asia. Here, a single-grain K-feldspar dating method was used to effectively date 20 paleolake shorelines with poorly bleached sediment to constrain lake level evolution over the past 18 k.y. Results indicate that Aibi Lake experienced a rapid increase in water levels, reaching a peak of ~36 m during the early to mid-Holocene period (10–7 ka). Subsequently, the lake level may have shown a general decline during the middle Holocene (7–4 ka), with the lake reaching a low level of less than 10 m at ca. 4 ka. In the late Holocene, lake levels fluctuated by 10–30 m above modern levels during 4–1 ka, with generally low levels of <9 m after 1 ka. The evolution of Aibi Lake underlines a clear out-of-phase relationship between Central Asian lake evolution and Westerlies precipitation changes, where Holocene lake changes were instead more directly controlled by the flux of glacial meltwater from the Tianshan Mountains, driven by change in Northern Hemisphere summer insolation. Glacier meltwater, in combination with variable delivery of Westerlies and East Asian summer monsoon precipitation, are responsible for asynchronous lake evolution trends across Central to East Asia.