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To trace the surficial responses of lowlands to past climate change, we investigated δ 13 C in total organic carbon (TOC), C/N ratios, magnetic susceptibility (MS), and silicon (Si) intensity (directly proportional to concentration) in wetland sediments collected from the Gimpo area of central Korea, covering 6600–4600 cal yr BP. Two organic layers with high TOC%, negatively depleted δ 13 C TOC values (− 27 to − 29‰), low MS values, and low Si intensities were found at 6200–5900 and 5200–4800 cal yr BP, respectively. These middle Holocene wet periods corresponded to relatively intensified summer monsoon and solar activity periods. The intervening dry period (5900–5200 cal yr BP) with high MS, high Si, and low TOC% corresponded to an intensified dust-activity interval and stronger winter monsoon. This multi-centennial climatic fluctuation of wet periods (6200–5900 cal yr BP and 5200–4800 cal yr BP) and an intervening dry period (5900–5200 cal yr BP) in central Korea was more synchronous with climate change in the arid inner part of China than with that in South China, suggesting possible strong high-latitude-driven climatic influences (e.g., North Atlantic cooling events) during the middle Holocene. [ABSTRACT FROM AUTHOR]

Abstract: Age-controlled pollen stratigraphy from the Paju (UJ-10), Cheonggye (Gwangtong Trench-A), and Hanam (UD-2) sites records the response of vegetation to climate changes and human activity over the past 7000 years in the Han River drainage basin, west-central Korea. The pollen profiles show a transition from natural vegetation to human-disturbed vegetation around 4800 cal BP. During the natural vegetation stage (ca. 7000–4800 cal BP; early Neolithic Age), dense woodlands of mixed deciduous and evergreen broadleaved hardwoods flourished in the surrounding hills and mountains owing to the enhanced East Asian summer monsoon. The human-disturbed vegetation stage (ca. 4800 cal BP–modern; late Neolithic Age to modern) was characterized by transitional forests and open grasslands and can be subdivided into several agricultural stages. During the dry-field cultivation stage (ca. 4800–3000 cal BP; late Neolithic to Bronze ages), humans engaged in dry-field agriculture under cool, dry climatic conditions. The ensuing paddy-field cultivation stage (ca. 3000–800 cal BP; since the Bronze Age) initially developed during an interval of stable, warm, wet conditions from ca. 3000 to ca. 1400 cal BP, during which time people of Bronze and Iron Age cultures engaged in widespread paddy farming. Subsequently, a brief climatic fluctuation (ca. 1400–800 cal BP) caused changes in the agricultural practices of the Unified Silla and Koryo people. During the combined dry-field and paddy-field cultivation stage (ca. 800 cal BP–modern; since the Joseon Dynasty), climatic deterioration affected agricultural practices of the Joseon people and resulted in open forests with wide grasslands during the interval equivalent to the Little Ice Age (1550–1859 AD). Since then, humans in the area have strategically managed pine forests to supply wood for house-building and fuel. [Copyright &y& Elsevier]

Abstract: Holocene vegetation changes in response to climate fluctuations and human impacts are reviewed on the basis of pollen analyses from borehole cores taken from the Changjiang (Yangtze River) delta, China, and other previously reported data. During the earliest Holocene (10,930−9000 cal yr BP), the climate was warm and wet, allowing thermophilous hardwoods to occupy mid- and low-elevations surrounding a palaeo-Changjiang estuary. The climate became gradually cooler, and cool-tolerant conifers, grasses and ferns became dominant until 7600 cal yr BP, when the estuary became a delta. A mid-Holocene climatic optimum occurred between 7600 and 4800 cal yr BP, when evergreen and broadleaved deciduous trees flourished at mid- and low-elevations surrounding the delta front-prodelta. After this time, climate became cooler again until 1340 cal yr BP. During this period, evergreen and broadleaved deciduous trees were replaced by conifers and grasses inhabiting the inter/subtidal flat-delta front. This development of conifer–grassland vegetation was shortly interrupted between 3860 and 3200 cal yr BP when thermophilous tree cover increased and open vegetation with scattered conifers was reduced. Since 1340 cal yr BP, the vegetation has been similar to that at present under warm, wet conditions. Human impacts are recognized by the first appearance of Fagopyrum and a sudden increase in herb pollen at 4500 and 1340 cal yr BP, respectively. [Copyright &y& Elsevier]

This study traces coastal sand dune development processes in East Asia during the Holocene to understand climate and environmental changes. We used optically stimulated luminescence (OSL) dating to examine periods of activation and stabilization of dunes along the western coast of the Korean Peninsula. The results from the Taean Chollipo, Seocheon Dasari, and Gochang Sabanri dunes were then compared with those from previous studies to establish a broad understanding of coastal dune development in this region. Sedimentation rates were calculated for the three dunes, and their development periods were classified through statistical analysis that included data from previous studies. We defined five main periods of late Holocene dune development (<0.1 ka, 0.2–0.5 ka, 1.2–2.0 ka, 2.5–3.2 ka, and 5.5–6.5 ka). These correlated to periods of sea level decrease and global cooling determined by ice rafted debris records. We concluded that the development of coastal dunes in western Korea was influenced by sea level decreases, and global cooling events were enhanced by the East Asian winter monsoon. In addition, human activity increases also contributed to the development of the dunes. This study showed how coastal sand dunes can be evaluated as important indicators of global climate change. These results improved our understanding of how paleoclimate changes affected environmental conditions in East Asia and how coastal dune development periods can be used to reconstruct paleo-environmental conditions. • Coastal sand dunes are developed along the western coast of the Korean Peninsula. • Five main periods of late Holocene dune development were determined by OSL. • Main periods were -less than 0.1, 0.2–0.5, 1.2–2.0, 2.5–3.2, and 5.5–6.5 ka. • Main periods were agreed with sea level decrease and global cooling in the Holocene. [ABSTRACT FROM AUTHOR]

To reconstruct environmental change during the late Holocene, we investigated sedimentary δ 13 C values from an exposed section on Geoje Island, on the southern coast of Korea. The δ 13 C values ranged from −24.3‰ to −21.2‰ and were divided into five stages based on the average value (−22.5‰). A comparison with the regional climate index revealed that wet periods linked to intensified summer monsoon conditions occurred at Stage 1 (4500–3600 cal BP), Stage 3 (1350–900 cal BP), and Stage 5 (300 cal BP to present). Dry intervals were found at Stage 2 (3600–1350 cal BP) and Stage 4 (900–300 cal BP). We found two different vegetational responses to changes in regional temperature and summer monsoons. Stage 3, corresponding to the MWP, was characterized by an association between the δ 13 C values on the island and the regional temperature, but Stage 4, including the LIA interval, did not show such a relationship. Furthermore, based on comparison with the summer monsoon index, this study suggested that, on the southern coast of Korea, vegetational change was controlled by an MWP-like mode during the warm and wet periods following regional climate change, whereas a LIA-like mode showing independent climate change was dominant during the cold and dry periods. This difference in vegetational changes along the southern coast of Korea and regional (mainly terrestrial-signal based) climate change may be attributed to the influence of sea surface temperature changes in the tropical ocean through the transport of warming seawater by the Kuroshio and Tsushima currents on the East Asian coastal area, including this study area, than on the inner part of the East Asian continent. [ABSTRACT FROM AUTHOR]

Temperature and precipitation are considered to be the most important indicators affecting the green-up date. Sensitivity of the green-up date to temperature and precipitation is considered to be one of the key indicators to characterize the response of terrestrial ecosystems to climate change. We selected the main grassland types for analysis, including temperate steppe, temperate meadow steppe, upland meadow, and lowland meadow. This study investigates the variation in key meteorological indicators (daily maximum temperature (Tmax), daily minimum temperature (Tmin), and precipitation) between 2001 and 2018. We then examined the partial correlation and sensitivity of green-up date (GUD) to Tmax, Tmin, and precipitation. Our analysis indicated that the average GUD across the whole area was DOY 113. The mean GUD trend was −3.1 days/decade and the 25% region advanced significantly. Tmax and Tmin mainly showed a decreasing trend in winter (p > 0.05). In spring, Tmax mainly showed an increasing trend (p > 0.05) and Tmin a decreasing trend (p > 0.05). Precipitation showed no significant (p > 0.05) change trend and the trend range was ±10 mm/decade. For temperate steppe, the increase in Tmin in March promotes green-up (27.3%, the proportion of significant pixels), with a sensitivity of −0.17 days/°C. In addition, precipitation in April also promotes green-up (21.7%), with a sensitivity of −0.32 days/mm. The GUDs of temperate meadow steppe (73.9%), lowland meadow (65.9%), and upland meadow (22.1%) were mainly affected by Tmin in March, with sensitivities of −0.15 days/°C, −0.13 days/°C, and −0.14 days/°C, respectively. The results of this study reveal the response of vegetation to climate warming and contribute to improving the prediction of ecological changes as temperatures increase in the future. [ABSTRACT FROM AUTHOR]

Abstract: Marine isotope stage 3 (MIS3), spanning from 25 to 60ka BP, was a time of substantial environmental change that included changes in the global ice volume and atmospheric composition, with resultant regional climate changes. To understand past vegetation responses to such environmental changes in Korea, we estimated the abundance of C3 and C4 plants using the C/N and carbon isotope ratios of sedimentary organic matter. The MIS3 sedimentary unit at the Cheollipo site, located in a western coastal area of Korea, is characterized by a dark to light gray colored sedimentary unit (3.05 to 5.05m in elevation, MIS3), which is between an underlain oxidized yellowish sedimentary unit (<3.05m in elevation) and an overlain oxidized yellowish sedimentary unit (>5.05m in elevation). The estimated abundance of C4 plants varied between 60 and 10% during the MIS3. The suborbital-scale variation in the estimated percentage of C4 plants was similar to those reported in continental ice volume and the East Asian monsoon intensity, suggesting that C4 plants prevailed under colder and drier conditions (intensified winter monsoon), whereas C3 plants have favored a warmer and wetter climate (intensified summer monsoon). Compared with high latitude regions (e.g., Chinese Loess Plateau and Lake Baikal) where low summer temperature suppressed aridity and pCO2 influences during the last glacial period, vegetation change in Cheollipo area may have more sensitively responded to aridity change which had been affected by the summer/winter monsoon intensity. The climate change in the western coastal area (Yellow Sea side) of Korea during the late Pleistocene may have been controlled by regional climate change coupled with continental ice volume change. [ABSTRACT FROM AUTHOR]

Northern China has been long threatened by aeolian desertification. In recent years, all levels of the Chinese government have performed a series of ecological protection and sand control projects. To grasp the implementation effects of these projects and adjust policies in time, it is necessary to understand the process of aeolian desertification quickly and accurately. Remote sensing technologies play an irreplaceable role in aeolian desertification monitoring. In this study, the Zhenglan Banner, which is in the hinterland of the Hunshandake Sandy Land, was considered as the research area. Based on unmanned aerial vehicle (UAV) images, ground survey data, and Landsat images called in Google Earth Engine (GEE), the aeolian desertified land (ADL) in 2000, 2004, 2010, 2015, and 2019 was extracted using spectral mixture analysis. A desertification index (DI) was constructed to evaluate the spatial and temporal dynamics of the ADL in the Zhenglan Banner. Finally, a residual analysis explored the driving forces of aeolian desertification. The results showed that (1) the ADL area in the Zhenglan Banner has been trending downwards over the past 20 years but rebounded from 2004 to 2010; (2) over the past 20 years, the area of slightly, moderately, and severely desertified land has decreased at annual rates of 0.4%, 2.7%, and 3.4%, respectively; (3) human activities had significantly positive and negative impacts on the aeolian desertification trend for 20.0% and 21.0% of the study area, respectively, but not for the rest. This paper explored new techniques for rapid aeolian desertification monitoring and is of great significance for controlling and managing aeolian desertification in this region. [ABSTRACT FROM AUTHOR]

The accumulation of heat and moderate precipitation are the primary factors that are used by grasslands to trigger a green-up date. The accumulated growing degree-days (AGDD) requirement over the preseason is an important indicator of the response of grassland spring phenology to climate change. This study adopted the Normalized Difference Phenology Index (NDPI), which derived from the Moderate Resolution Imaging Spectroradiometer (MODIS), to extract annual green-up dates in the Hulun Buir grassland in China between 2001–2015. Our analysis indicated that the range (standard deviation) and trend for the green-up date were DOY (day of year) 104 to DOY 144 (10.6 days) and −2.0 days per decade. Nine point two percent of the study area had significant (p < 0.05) changes in AGDD requirements. The partial correlations between the AGDD requirements and chilling days (67.04%, pixels proportion) were negative and significant (p < 0.05). The partial correlations between the AGDD requirement and precipitation (28.87%) were positive and significant (p < 0.05). Finally, the partial correlation between the AGDD requirement and insolation (97.65%) were positive and significant (p < 0.05). The results of this study could reveal the response of vegetation to climate warming and contribute to improving the phenological mechanism model of different grassland types in future research. [ABSTRACT FROM AUTHOR]