High-Resolution Lacustrine Records of the Late Holocene Hydroclimate of the Sikhote-Alin Mountains, Russian Far East

Simple Summary We studied the sediments of landslide-formed small mountain lakes (elevation 565 and 750 m a.s.l.) on the slopes of an ancient volcano. The lakes are located in the territory of the Sikhote-Alin Biosphere Reserve, with unique ecosystems that combine warm- and cold-climate vegetation and where rare animals live. These lakes are natural archives, allowing the reconstruction of the natural environment of this unique area with a temporal resolution of up to 30 years. Nizhnee Lake, which developed over a period of 2640 years, is the most sensitive to climate change. Ten stages of the lake's evolution, with periods of watering and swamping, were identified and controlled by precipitation. Our study demonstrates how the communities of swamp plants and diatom microflora responded to temperature fluctuations associated with solar activity and regional manifestations of global climatic events. The regional drivers were the intensity of summer and winter monsoons, and the change in the positions of the atmosphere action and cyclonic activity centers. The natural environment was especially unstable during the Little Ice Age (14th-19th centuries), which was wet with short-term dry episodes. There is little information about moisture changes in different altitudinal belts in mountainous regions of the southern Russian Far East. We present ecological and taxonomic compositions of the diatom flora and identify the botanical composition of peat in small mountain lake/mire complexes located in the Central Sikhote-Alin Mountains, within large landslides on the paleovolcanic slopes. Frequent changes in diatom assemblages and peat-forming plants indicate unstable hydroclimatic conditions with varying degrees of wet and dry conditions up to the overgrowth of the lakes. Frequent change in sphagnum mosses with different trophic preferences was identified. The chronology is based on 11 radiocarbon dates. Accumulation rates reached 1.7-1.9 mm/year, and the temporal resolution for the reconstructions was up to 30-40 yr. The tendencies of lake evolution depended on different scale hydroclimatic changes over the last 4400 yr. The most detailed data for the last 2600 yr were obtained from the Nizhnee Lake sequence, which is more sensitive to climatic changes. The main reason for the change in the hydrological regime of the lakes was variations in precipitation during short-term climatic changes. The sediment record of moisture fluctuations is relatively well correlated with regional patterns reflecting summer monsoon intensity and cyclogenesis activity.