Gonghai Lake Research Articles

Elemental data for Gonghai Lake sediments show significant effects of human activities on weathering processes after 1550 CE

The international Anthropocene Working Group has recognized the mid-20th centrury (ca. 1950 CE) as the onset of the Anthropocene, but human activities in China altered the land cover and influenced weathering processes much earlier. Changes in the elemental composition of sediment since 1000 CE from Gonghai Lake were studied, using X-ray Fluorescence element scanning (average time-resolution 3 years), to investigate the human impacts on weathering over time. We found that aluminum (Al) and calcium (Ca) containing minerals vary in the resistance to chemical weathering, and the concentrations of Al and Ca provide insights into the intensities of mechanical and chemical weathering respectively. The correlations between Al and Ca concentrations in these two periods, 1000–1550 CE and 1550–1950 CE changed from negative to positive, owing to that agricultural activities evidently enhanced both mechanical and chemical weathering during the latter stage. In addition, the Al and Ca concentrations recorded a border reclamation project in the 16th century and two catastrophic population decreases from 1630s to 1640s and 1850s–1870s. After 1950 CE, the concentrations of Al and Ca became uncorrelated, because weathering processes around Gonghai Lake were impacted by the enhanced anthropogenic perturbations in the Anthropocene.

Gonghai Lake, Erosion and environment index Data

Gonghai Lake, Erosion and environment index Data

Pollen-based land cover changes reveal temporal and spatial differences of human activity in north-central China during the Holocene

Beginning in the middle to late Holocene, anthropogenic land cover change has had a profound impact on both regional and continental environments. Hence, assessing temporal and spatial differences in the intensity of human activity in different regions and geomorphologic contexts has become a focus of current global change research. Here we use two representative pollen records from different geomorphologic units in North China (Lake Gonghai in the mountains, and Lake Daihai in a large basin) together with a novel methodology to quantitatively reconstruct Holocene land cover changes. The results indicate diverse vegetation succession patterns in different regions and geomorphologic contexts. In the Daihai basin, the vegetation cover changed relatively little, maintaining values of 45–50%, and only increased during the interval of 8–5.1 ka, when it attained a maximum of 67%. In the Gonghai area, the vegetation cover remained at a higher level at 70–80% for an extended interval, before decreasing substantially to 58% after 1.4 ka. We propose that changes in the intensity of human activities was a major cause of the observed regional disparities in vegetation succession. Comparison of the results with records of prehistoric human activity shows that, prior to 5.1 ka, land cover change (especially of the vegetation composition) in the Daihai basin evolved naturally, under the influence of climate. Then, during ∼ 5.1–2.8 ka, a transitional stage occurred, driven by both climate change and human activities. Finally, from ∼ 2.8 ka to the present, human activities dominated the pattern of vegetation change. In contrast, land cover change in the alpine Gonghai area was controlled by natural processes until 1.4–1.3 ka, when human activities exceeded the influence of natural variability and became the dominant factor controlling local vegetation development. In larger basin/plain areas, the favorable climatic conditions of the mid-Holocene promoted increased human activity; while later, population pressure, the increased demand for resources, and political factors may have triggered the diffusion of human populations from basins to the mountains or previously undeveloped areas, with resulting effects on their vegetation succession. The anthropogenic impacts have dominated the natural environment of mountainous areas in north-central China for at least the last 1,300 years.

Gonghai Lake, Physical Erosion Data

Gonghai Lake, Physical Erosion Data

Biofuels Reserve Controlled Wildfire Regimes Since the Last Deglaciation: A Record From Gonghai Lake, North China

AbstractWildfire activity is an important activity in evolution of vegetation and carbon cycling. Whether wet weather will suppress wildfire or promote them by increasing fuel reserves during the Holocene is not clear. We obtained a record of black carbon from a sediment core spanning the last 14.8 kyr from Gonghai Lake, in North China. There is a close relationship between the timing of wildfire activity and vegetation development driven by the East Asian summer monsoon intensity. On a millennial timescales, wet climatic conditions provide a sufficient biofuels reserve, in the same period wildfire increase; thus, the regional potential biofuels reserve is shown to be an important controlling of regional wildfire activity in the monsoon region of China, under natural conditions. We infer that with the strengthening of Asian summer monsoon caused by global warming, the wildfire carbon emission in Asian monsoon region may increase in the future.

Bacterial Community Spacing Is Mainly Shaped by Unique Species in the Subalpine Natural Lakes of China.

Bacterial communities have been described as early indicators of both regional and global climatic change and play a critical role in the global biogeochemical cycle. Exploring the mechanisms that determine the diversity patterns of bacterial communities and how they share different habitats along environmental gradients are, therefore, a central theme in microbial ecology research. We characterized the diversity patterns of bacterial communities in Pipahai Lake (PPH), Mayinghai Lake (MYH), and Gonghai Lake (GH), three subalpine natural lakes in Ningwu County, Shanxi, China, and analyzed the distribution of their shared and unique taxa (indicator species). Results showed that the species composition and structure of bacterial communities were significantly different among the three lakes. Both the structure of the entire bacterial community and the unique taxa were significantly influenced by the carbon content (TOC and IC) and space distance; however, the structure of the shared taxa was affected by conductivity (EC), pH, and salinity. The structure of the entire bacterial community and unique taxa were mainly affected by the same factors, suggesting that unique taxa may be important in maintaining the spatial distribution diversity of bacterial communities in subalpine natural freshwater lakes. Our results provide new insights into the diversity maintenance patterns of the bacterial communities in subalpine lakes, and suggest dispersal limitation on bacterial communities between adjacent lakes, even in a small local area. We revealed the importance of unique taxa in maintaining bacterial community structure, and our results are important in understanding how bacterial communities in subalpine lakes respond to environmental change in local habitats.

Cycles of grazing and agricultural activity during the historical period and its relationship with climatic and societal changes in northern China

AbstractThe arable‐pastoral ecotone in northern China is ecologically fragile and the region has experienced substantial climatic variability, triggering population migrations, and the alternation of subsistence strategies during the historical period. However, the lack of continuous proxy records of arable and grazing activity has hampered our understanding of shifts in subsistence strategies and their relationship with climatic and societal changes. We obtained records of Sporormiella‐type spores and crop pollen from Gonghai Lake in northern China to reconstruct changes in cultivation and grazing intensity over the past approximately 2000 years. The results show that intensive grazing and cultivation occurred during the Sui and early‐middle Tang Dynasties (581–820 CE), when there was a relatively favourable climate, harmonious ethnic relations, and strong central government control. Conversely, weakened agricultural activity in the late Tang Dynasty (820–907 CE) corresponded to a deteriorating climate and frequent wars. High temperatures during the northern Song Dynasty (960–1127 CE) promoted the expansion of arable land in mountainous areas, whereas a cold climate and societal crises during the Era of Disunity (220–580 CE) and the Ming‐Qing Dynasties (1368–1912 CE) limited the expansion of cultivated land and there was a shift to grazing as a subsistence activity. Time‐series analysis reveals that the arable farming phases had a longer periodicity than the grazing phases, possibly because of the greater resilience of the former to climate change and the attachment of agriculturalists to their land. Our findings potentially help improve our understanding of the impact of land use on soil degradation.

A ~ 230-year dust storm record from China’s Lake Gonghai on the northeast Loess Plateau

A ~ 230-year dust storm record from China’s Lake Gonghai on the northeast Loess Plateau

Intensification and Driving Forces of Pastoralism in Northern China 5.7 ka Ago

AbstractInitiation and development of pastoralism in northern China, and the mechanisms involved, are poorly understood. Here we use analyses of Sporormiella‐type coprophilous fungal spores in a well‐dated sediment core from Lake Gonghai in northern China, together with other sequences of fungal spores to reconstruct the population dynamics of large herbivores during the Holocene. Comparison of the results with paleoclimatic and zooarchaeological records suggests that grazing appeared at ∼5.7–5.5 ka and further intensified again after ∼4.2–4.0 ka. The changes represent two stages of the migration of herdsmen from the steppe regions in inner East Asia eastward and/or southward into northern China, and we propose that the occurrence of drought and cooling climate were responsible. The rapid intensification of pastoralism after ∼3.6 ka may have been promoted by the wider use of horses and the development of grasslands in northern China. Intensified grazing activity potentially has contributed to methane increase during the late Holocene.

Impact of Abrupt Late Holocene Monsoon Climate Change on the Status of an Alpine Lake in North China

AbstractThe late Holocene is generally regarded as an interval of monsoon recession and decreased precipitation in North China. However, the extent to which this affected the status of lakes in North China is unclear. In the study, we analyzed multiple proxies (δ13C, magnetic susceptibility [χlf], and exogenous element concentrations) from Lake Mayinghai, an undisturbed alpine lake in North China. We also compared the results with previously published paleoenvironmental records from the Chinese Loess Plateau. We aimed to determine the extent of the influence of variations in the East Asian summer monsoon (EASM) on the status of Lake Mayinghai during the late Holocene. The results demonstrate that negative δ13C values at Lake Mayinghai correspond to high sedimentary tree pollen content and high reconstructed precipitation, indicating that variations in δ13C likely reflect variations in vegetation and the EASM in North China. A comparison of the δ13C record with other proxies from the same core reveals an abrupt change in the EASM at ~3 kyr before present (BP), which is also evident in other regional climate records from the Chinese Loess Plateau. The rapid decline in EASM intensity at ~3 kyr BP is also consistent with changes in the status of Lake Mayinghai, Lake Gonghai, Lake Ganhai, and Lake Daihai, in that these lakes underwent an abrupt retreat after 3 kyr BP, demonstrating that the rapid decline in EASM intensity at ~3 kyr BP had a large impact on lake evolution in North China.

Spatio-temporal Patterns of Microbial Communities and Their Driving Mechanisms in Subalpine Lakes, Ningwu, Shanxi

Human activities and climate change cause the degradation of subalpine lake ecosystems, which induce the shift of microbial community structure. The spatio-temporal dynamics and the diversity maintenance mechanisms of bacterial communities in Gonghai Lake in Ningwu, Shanxi, were investigated by using Q-PCR and DGGE. The results showed that the temperature), pH, dissolved oxygen, electrical conductivity salinity, and ammonium nitrogen (NH4+) contestation were significantly different among the different sampling depths during different months. Bacterial abundance was the highest in August and the lowest in November, and the abundance was higher in the middle water layer (2 m, 4 m, and 6 m depths), but relatively low in the surface layer and bottom layer (0 m and 8 m depths, respectively). The α diversity index of bacterial communities had significant differences among the different months and depths, and showed an initial decreasing trend and then an increasing trend from April to December. A PERMANOVA test showed that the spatial distribution of bacterial communities was significantly different among depths (P<0.001). The results of redundancy analysis and variation partitioning indicated that environmental selection and diffusion limitation had an effect on the maintenance of the diversity patterns of bacterial communities at the different depths of GH. However, the relative effect of environmental factors was stronger, of which the concentration of NO3-, NO2-, and NH4+ were the main influencing factors. In conclusion, the bacterial communities in GH subalpine lake showed clear spatio-temporal distribution patterns, and environmental variables had a significant effect on shaping the community diversity.

Historical variation of black carbon and PAHs over the last ~200 years in central North China: Evidence from lake sediment records

As the largest coal-producing province in China, the coal production of Shanxi Province accounts for one third of the country's total. Thus it is of great importance to study the pollution history of typical pollutants in Shanxi Province and their links with energy usage in North China. Sediment cores from two relatively remote lakes in central North China were retrieved to investigate historical evolutions of black carbon (BC) and polycyclic aromatic hydrocarbons (PAHs) in the last ~200 years. The two records show several-fold increases in both concentrations and depositional fluxes of BC, char, soot, and PAHs in recent five decades, which were associated with the influence of anthropogenic activities resulting from socio-economic development in Shanxi Province. However, after ~2000 their fluxes decreased sharply due to China's effort on environmental protection. These changes indicate that atmospheric BC and PAHs loads in the region were affected significantly by recent anthropogenic activities and environmental policies. Ratios of individual PAHs and char/soot indicate pyrogenic sources of these increased pollutants in recent decades, with coking industry and coal combustion as the two major sources. Significant positive correlations between BC and PAHs were observed in both cores of Lake Gonghai and Lake Mayinghai, indicating that they were likely co-transported by BC particles from similar sources. This study provides new and important understanding of the atmospheric pollution history of BC and PAHs in North China.

Quantitative indicative significance of pollen assemblages on vegetation coverage in deciduous Quercus forest in the central Loess Plateau, China

We compared the pollen assemblages of surface moss samples and corresponding vegetation inventory data from 34 sites in the Huangling region of the central Loess Plateau. Our aims were to determine the characteristics of the pollen assemblages from the deciduous broadleaved forest climax community and its significance in terms of vegetation type and species composition. The pollen assemblages are dominated by woody plants such as Quercus (42% of total terrestrial pollen), Betula (16%) and Pinus (12%), with minor differences between different plant communities. The pollen assemblages of individual sampling sites differed from the vegetation composition within the 0–100 m scope and were more similar to the vegetation coverage within the 0–1000 m scope. This indicates that the surface pollen assemblages mainly reflect the comprehensive information from the vegetation composition of a large area, rather than the vegetation composition close to the sampling site. The contents of Quercus , Betula and Pinus pollen are high, and close to their vegetation coverage; whereas the contents of deciduous broadleaved arbor taxa (such as Malus and Acer ) are lower, but their corresponding regional vegetation cover is higher. This suggests that the vegetation information conveyed by poorly-represented pollen taxa should be considered when interpreting stratigraphic pollen assemblages. Using the observed quantitative relationships between pollen and vegetation of the main taxa, we reconstructed the regional vegetation composition in the Gonghai Lake area of the northeastern Loess Plateau during the middle Holocene (7300–5000 yr BP). The results indicated that Quercus- dominated deciduous broadleaved forest climax community developed in the mountains surrounding the lake.

Sedimentary biogeochemical record in Lake Gonghai: Implications for recent lake changes in relatively remote areas of China

Owing to rapid socio-economic development and climate warming, lakes even in remote areas have experienced marked changes in the last century. However, there are few studies revealing the multi-faceted biogeochemical changes and disentangling impacts of human and climate in relatively remote lakes in China. In this study we reconstructed historical changes of geochemistry, nutrition, primary production, ecology, and pollution in an alpine lake (Gonghai) in central North China, and revealed coherent changes and drivers in relatively remote Chinese lakes by compiling other records. Results show that Lake Gonghai has experienced considerably biogeochemical changes since the 1980s induced mainly by increased regional human activities, with detected human-related changes occurring in the 1950s–70s. The most important change is a shift of diatom primary producers in the 1980s, caused mainly by an increase of regional atmospheric N and P deposition associated with rapid socio-economic development. Another remarkable change is the increase of pollution levels since the 1980s, represented by heavy metals, also caused by atmospheric deposition. Compiled sediment records demonstrate similar biogeochemical changes in most lakes from relatively remote areas of China since the 1970s–80s, associated closely with increased inputs of human-induced atmospheric N, P and pollutants, whereas the influence of climate warming is likely limited. This study highlights markedly human-related biogeochemical changes in relatively remote Chinese lakes during the Anthropocene epoch.

Nonlagged Response of Vegetation to Climate Change During the Younger Dryas: Evidence from High‐Resolution Multiproxy Records from an Alpine Lake in Northern China

AbstractThe use of pollen analysis to reconstruct regional vegetation changes, and subsequently climate, is a common approach in paleoclimatic reconstruction. However, it is unclear whether or not vegetation exhibits a lagged response to climate change during shifts from rapid cooling to rapid warming. The Younger Dryas (YD) cold event, spanning the last glacial/Holocene transition, was a prominent abrupt climatic event. To investigate the vegetation response to climate change during the YD, we compared profiles of independent climatic indicators from the sediments of alpine Lake Gonghai, on the margin of the modern Asian summer monsoon, with a pollen record from the same site. Our aim was to assess the phase lag of vegetation change relative to independent climate proxies that would have responded near instantaneously to climate change. The results show that the vegetation changed synchronously with the climate proxies, and consequently, we conclude that vegetation succession around Lake Gonghai exhibited a nonlagged response to climate change during the YD. This result confirms that a previous pollen‐based quantitative regional precipitation record from Lake Gonghai reliably depicts variations in the East Asian summer monsoon (EASM), especially its decreasing trend during the YD. This conclusion differs from that of related research on the Baxie loess section and Hani peat deposits. Also, we suggest that our findings provide an improved understanding of the likely response of the EASM during cooling intervals and that the YD is a useful analog for studying the response of vegetation to possible abrupt cooling events under future global warming scenarios.

A chironomid-based record of temperature variability during the past 4000 years in northern China and its possible societal implications

Abstract. Long-term, high-resolution temperature records which combine an unambiguous proxy and precise dating are rare in China. In addition, the societal implications of past temperature change on a regional scale have not been sufficiently assessed. Here, based on the modern relationship between chironomids and temperature, we use fossil chironomid assemblages in a precisely dated sediment core from Gonghai Lake to explore temperature variability during the past 4000 years in northern China. Subsequently, we address the possible regional societal implications of temperature change through a statistical analysis of the occurrence of wars. Our results show the following. (1) The mean annual temperature (TANN) was relatively high during 4000–2700 cal yr BP, decreased gradually during 2700–1270 cal yr BP and then fluctuated during the last 1270 years. (2) A cold event in the Period of Disunity, the Sui-Tang Warm Period (STWP), the Medieval Warm Period (MWP) and the Little Ice Age (LIA) can all be recognized in the paleotemperature record, as well as in many other temperature reconstructions in China. This suggests that our chironomid-inferred temperature record for the Gonghai Lake region is representative. (3) Local wars in Shanxi Province, documented in the historical literature during the past 2700 years, are statistically significantly correlated with changes in temperature, and the relationship is a good example of the potential societal implications of temperature change on a regional scale.

Evolution of integrated lake status since the last deglaciation: A high-resolution sedimentary record from Lake Gonghai, Shanxi, China

Alpine lakes not only provide internationally important habitats for endangered species, they also play a crucial role in the regional water balance. Unfortunately, a rapid loss of alpine lakes in China has occurred in recent decades; however, intensive human activities, together with regional differences in the responses of lakes to climate change, has impeded our understanding of the contribution of climate change to the loss of these lakes. To better understand how alpine lakes will evolve with continuing global warming, we used the analysis of new sedimentary proxies from Lake Gonghai, an undisturbed alpine lake, together with a review of published records, to reconstruct variations in integrated lake status since the last deglaciation. From 14,660–11,890 cal. yr BP the lake was in the most unstable state, indicated by the highest amplitude fluctuations in lake level and the within-lake environment. The lake status experienced clear millennial-scale changes. During the early and middle Holocene (11,890–3200 cal. yr BP), the most stable lake status occurred, consistent with the highest precipitation levels. Owing to the highest level of freshwater influx in the middle Holocene (8–5 ka), the lake water was the deepest and most acidic. At this time, the dense vegetation cover resulted in maximum catchment stability and the lowest level of soil erosion, and hence the lowest sediment accumulation rate. From 3200 cal. yr BP, decreasing mean annual precipitation resulted in a moderately stable lake status, a shallow water depth and more alkaline lake water. The sparse vegetation cover caused a dramatic increase in the erosion rate and hence in the sediment accumulation rate. We infer that variations in local humidity were the major control on the integrated lake status during the last ~14,600 cal. yr BP. With the anticipated progression of global warming, the status of the alpine lakes in the region may continue to deteriorate and appropriate mitigation strategies are imperative.

Diatom response to climatic warming over the last 200 years: A record from Gonghai Lake, North China

Annual monitoring data and centennial and millennial-scale paleolimnological records have revealed an increase in small-celled planktonic diatom species relative to heavier tycho-planktonic and small benthic diatoms in many high-altitude lakes, presumably in response to recent climatic warming. In addition to changes in the composition and structure of lacustrine diatom assemblages, there have also been changes in diatom biodiversity; however, these changes are not regionally consistent. In this study, we chose a temperate mid-latitude lake to explore the response of changes in diatom assemblages and biodiversity to recent climatic warming. The diatom record spans the past ca. 200years and reveals that since 1966 CE the small-celled Cyclotella ocellata+stelligera has replaced the previously dominant, large-celled phytoplankton Cyclotella schroeteri. These changes are in accordance with the increasing trend in global mean surface temperature. Biodiversity increased remarkably from 1966 CE, but began to decline after 1990 CE, presumably in response to rapid climatic warming. Our findings indicate that the response of diatom biodiversity to climate change was a nonlinear process.

Impacts of the spatial extent of pollen-climate calibration-set on the absolute values, range and trends of reconstructed Holocene precipitation

Pollen-based quantitative reconstructions of past climate variables is a standard palaeoclimatic approach. Despite knowing that the spatial extent of the calibration-set affects the reconstruction result, guidance is lacking as to how to determine a suitable spatial extent of the pollen-climate calibration-set. In this study, past mean annual precipitation (Pann) during the Holocene (since 11.5 cal ka BP) is reconstructed repeatedly for pollen records from Qinghai Lake (36.7°N, 100.5°E; north-east Tibetan Plateau), Gonghai Lake (38.9°N, 112.2°E; north China) and Sihailongwan Lake (42.3°N, 126.6°E; north-east China) using calibration-sets of varying spatial extents extracted from the modern pollen dataset of China and Mongolia (2559 sampling sites and 168 pollen taxa in total). Results indicate that the spatial extent of the calibration-set has a strong impact on model performance, analogue quality and reconstruction diagnostics (absolute value, range, trend, optimum). Generally, these effects are stronger with the modern analogue technique (MAT) than with weighted averaging partial least squares (WA-PLS). With respect to fossil spectra from northern China, the spatial extent of calibration-sets should be restricted to radii between ca. 1000 and 1500 km because small-scale calibration-sets (<800 km radius) will likely fail to include enough spatial variation in the modern pollen assemblages to reflect the temporal range shifts during the Holocene, while too broad a scale calibration-set (>1500 km radius) will include taxa with very different pollen-climate relationships.

A 14.7 Ka record of earth surface processes from the arid‐monsoon transitional zone of China

AbstractThe stability of Earth's critical zone is intimately linked with erosion, weathering and vegetation type and density. Therefore, it affects global biogeochemical processes which in turn affect the global climate by absorbing and reflecting solar radiation, and by altering fluxes of heat, water vapour, carbon dioxide and other trace gases through various feedback mechanisms. However, there is a lack of knowledge about how Earth's critical zone processes have changed over time and their link with past monsoon variability, especially in Asia. The study of lake sediments, which contain a suite of inorganic elemental and isotopic proxies, may facilitate the understanding of the Earth's critical zone processes on millennial timescales. Here we reconstruct the history of erosion–weathering–vegetation interactions since ~14.7 ka using geochemical records from a radiocarbon‐dated sediment core from Lake Gonghai in the monsoon‐arid transitional zone of north China. Detrital (Al, Ti, K, Rb) and authigenic (Ca, Sr) elemental records reveal distinct, millennial‐scale, late deglacial‐Holocene erosion and weathering patterns and transitions with the former (latter) elements showing higher (lower) values in warm intervals and vice versa. Chemical Index of Alteration (CIA) molar, a humidity proxy, suggests low humidity during the late deglacial ~11.5–14.7 ka, high humidity during the early‐mid Holocene ~11.5–3.2 ka, and intermediate humidity during the late Holocene interval since ~3.2 ka. The results of cross‐spectral analysis and comparison of our records with other climate reconstructions also suggest a pattern of orbitally‐phased humidity changes in north China. Overall, our results provide evidence for the solar‐forcing of Earth's surface processes in mid‐latitude China under natural climatic conditions. Copyright © 2017 John Wiley &amp; Sons, Ltd.