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Mapping the LGM refugia of deciduous oak and its distribution

LGM refugia of deciduous oak and distribution development since the LGM in China
The main distribution regions and refugia for the main deciduous oaks in the study areas of China. The blue circles (solid) indicate the distributions and refugia locations, while the dotted circles indicate the possible refugia because different evidences were not consistent (Chen et al., 2012; Zeng et al., 2015; Zhang et al., 2015; Yang et al., 2018). Credit: Science China Press

Forests have important roles in the global water and biogeochemical cycles. Climate change has led to worldwide changes in forest distributions, especially in the mid-latitude regions. As one of the most important forest genera, oak (Quercus), belonging to the Fagaceae, is widely distributed in the Northern Hemisphere.

Deciduous oak acts as an important forest constructive species in the mid-latitude regions and has important economic and ecological value. In the future, and drought caused by will continue to increase, and human activities will be intensified. How the oak distributions will respond to climate change and human activities is an unaddressed important issue.

Research on long-term forest distributions can help us to better understand the future vegetation dynamics under and human activities. In this study, we integrated different methods (i.e., paleoecology, phylogeography and species distribution models) to investigate the likely locations of glacial refugia and the postglacial development of the main deciduous oak species (i.e., Quercus variabilis, Q. mongolica, Q. dentata, Q. aliena, Q. acutissima and Q. liaotungensis).

The results indicated that mountains such as the Changbai, Qinling and Dabie Mountains acted as the refugia in northern and central China during the Last Glacial Maximum (LGM). The present Quercus in northern China could be the result of local dispersal during the postglacial period rather than only that of long-distance migration from south to north.

LGM refugia of deciduous oak and distribution development since the LGM in China
Pollen percentages of Quercus in lake sediments since 24,000 cal yr BP based on 46 pollen records from northern and central China. Yellow circles indicate sites with Quercus pollen records, and the circle sizes are proportional to the pollen percentages. The red dots indicate archaeological sites (Hosner et al., 2016), which represent the spatial pattern of human disturbances. Credit: Science China Press

Climate was the main influencing factor for oak migration. The distribution range change was consistent with the Holocene climate changes, especially with the precipitation changes. Human activities did not show much influence on this widespread genus.

Archaeological studies have shown that were concentrated in central China during the mid-Holocene, and human activities then began to increase in northeastern China at approximately 4,000 cal yr BP, but they did not lead to decreased pollen percentages around this region.

LGM refugia of deciduous oak and distribution development since the LGM in China
The differences in mid-Holocene and current values for BIO1 (a; annual mean temperature) and BIO12 (b; annual precipitation). The different colored dots indicate the change values between the mid-Holocene and present for the Quercus pollen percentages. The positive numbers in the legend indicate the increasing temperatures from the mid-Holocene to the present (a). The positive numbers indicate the decreasing precipitation or pollen percentages from the mid-Holocene to the present, while the negative numbers indicate the increasing precipitation or pollen percentages in (b). Based on their locations (especially the longitude), all pollen sites are divided into three groups (i.e., 120°–135°, 115°–120° and 95°–115°E). The average change values between the mid-Holocene and present for the BIO12 and Quercus pollen percentages are shown in (c) and (d), respectively. Credit: Science China Press

In addition, most of the human-associated plant pollen taxa (i.e., Poaceae and Polygonaceae) and fossil charcoal both did not show significant relationships with Quercus dynamics. The topography acted as a buffer and made the mountains to act as refugia under a deteriorated climate.

Complex terrain could recombine precipitation, radiation, water vapor, and soil properties, which would form various local environments. As a result, these diverse habitat conditions can benefit the , and would help tree species to survive through unsuitable climate periods.

Compared with other main tree genera (e.g., Pinus and Betula), the refugia locations and migration routes of deciduous oak species were different because of their physiological differences. For example, the phylogeographical method did not detect long-distance migration from south to north of Betula platyphylla after the LGM but only detected local dispersal from the northern refugia since the genetic diversity indicated a north-to-south decline.

LGM refugia of deciduous oak and distribution development since the LGM in China
Conceptual model for the tree genus refugia during the LGM (a) and the migration pattern during the postglacial period (b). The dark blue circles indicate the main refugia for the three main genera (i.e., Quercus, Pinus and Betula) in (a), which include northeastern China (Xiaoxing'an Mountains and Changbai Mountains), Qinling and Dabie mountainous region (including the Daba Mountains), Taihang mountainous region (including the Wutai Mountains and Lvliang Mountains), Altai Mountains and Yunnan-Guizhou Plateau. The green, orange and light blue arrows indicate the migration routes, while the small circles indicate those refugia with no apparent dispersal, such as the Pinus in the Wutai Mountains or Betula in the Altai Mountains in (b). Credit: Science China Press

However, the deciduous oaks had a large distribution range during the LGM, and northward migration during the Holocene could be detected. The individual migration dynamics of these three genera need to be considered when modeling their dynamics and managing forest.

The work is published in Science China Earth Sciences.

More information: Qian Hao et al, The LGM refugia of deciduous oak and distribution development since the LGM in China, Science China Earth Sciences (2022). DOI: 10.1007/s11430-021-9981-9

Journal information: Science China Earth Sciences

Citation: Mapping the LGM refugia of deciduous oak and its distribution (2023, February 10) retrieved 28 May 2023 from
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