Altitudinal Differences in Decreasing Heat Deficit at the End of the Growing Season of Alpine Grassland on the Qinghai–Tibetan Plateau from 1982 to 2022
As a measure of the accumulated heat deficit during the growing season transition, cooling degree days (CDDs) play a crucial role in regulating vegetation phenology and ecosystem dynamics. However, systematic analyses of CDD trends and their driving mechanisms remain limited, particularly in high-al...
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2025-04-01
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| author | Yusi Zhang Gang Bao Yuhai Bao Zhihui Yuan Wendu Rina Siqin Tong |
| author_facet | Yusi Zhang Gang Bao Yuhai Bao Zhihui Yuan Wendu Rina Siqin Tong |
| author_sort | Yusi Zhang |
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| description | As a measure of the accumulated heat deficit during the growing season transition, cooling degree days (CDDs) play a crucial role in regulating vegetation phenology and ecosystem dynamics. However, systematic analyses of CDD trends and their driving mechanisms remain limited, particularly in high-altitude regions where climate variability is pronounced. This study investigated the spatiotemporal variability in CDDs from 1982 to 2022 in alpine grasslands on the Qinghai–Tibetan Plateau (TP) and quantified the contributions of key climatic factors. The results indicate that lower CDD values (<350 °C-days) were predominantly found in warm, arid regions, whereas higher CDD values (>600 °C-days) were concentrated in colder, wetter areas. Temporally, area-averaged CDDs exhibited a significant decline, decreasing from 490.9 °C-days in 1982 to 495.8 °C-days in 2022 at a rate of 3.8 °C-days per year. Elevation plays a critical role in shaping CDD patterns, displaying a nonlinear relationship: CDDs decrease as elevation increases up to 4300 m, beyond which they increase, suggesting a transition from global climate-driven warming at lower elevations to local environmental controls at higher elevations, where snow–albedo feedback, topographic effects, and atmospheric circulation patterns regulate temperature dynamics. Tmax was identified as the dominant climatic driver of CDD variation, particularly above 4300 m, while radiation showed a consistent positive influence across elevations. In contrast, precipitation had a limited and spatially inconsistent effect. These findings emphasize the complex interactions between elevation, temperature, radiation, and precipitation in regulating CDD trends. By providing a long-term perspective on CDD variations and their climatic drivers, this study enhances our understanding of vegetation–climate interactions in alpine ecosystems. The results offer a scientific basis for modeling late-season phenological changes, ecosystem resilience, and land-use planning under ongoing climate change. |
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| language | English |
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| spelling | doaj-art-5a57ae75aedd45d0871c32d1e3f1f2542025-08-20T02:28:37ZengMDPI AGLand2073-445X2025-04-0114475810.3390/land14040758Altitudinal Differences in Decreasing Heat Deficit at the End of the Growing Season of Alpine Grassland on the Qinghai–Tibetan Plateau from 1982 to 2022Yusi Zhang0Gang Bao1Yuhai Bao2Zhihui Yuan3Wendu Rina4Siqin Tong5College of Geographical Science, Inner Mongolia Normal University, Hohhot 010022, ChinaCollege of Geographical Science, Inner Mongolia Normal University, Hohhot 010022, ChinaCollege of Geographical Science, Inner Mongolia Normal University, Hohhot 010022, ChinaCollege of Water Conservancy and Civil Engineering, Inner Mongolia Agricultural University, Hohhot 010022, ChinaInstitute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100049, ChinaCollege of Geographical Science, Inner Mongolia Normal University, Hohhot 010022, ChinaAs a measure of the accumulated heat deficit during the growing season transition, cooling degree days (CDDs) play a crucial role in regulating vegetation phenology and ecosystem dynamics. However, systematic analyses of CDD trends and their driving mechanisms remain limited, particularly in high-altitude regions where climate variability is pronounced. This study investigated the spatiotemporal variability in CDDs from 1982 to 2022 in alpine grasslands on the Qinghai–Tibetan Plateau (TP) and quantified the contributions of key climatic factors. The results indicate that lower CDD values (<350 °C-days) were predominantly found in warm, arid regions, whereas higher CDD values (>600 °C-days) were concentrated in colder, wetter areas. Temporally, area-averaged CDDs exhibited a significant decline, decreasing from 490.9 °C-days in 1982 to 495.8 °C-days in 2022 at a rate of 3.8 °C-days per year. Elevation plays a critical role in shaping CDD patterns, displaying a nonlinear relationship: CDDs decrease as elevation increases up to 4300 m, beyond which they increase, suggesting a transition from global climate-driven warming at lower elevations to local environmental controls at higher elevations, where snow–albedo feedback, topographic effects, and atmospheric circulation patterns regulate temperature dynamics. Tmax was identified as the dominant climatic driver of CDD variation, particularly above 4300 m, while radiation showed a consistent positive influence across elevations. In contrast, precipitation had a limited and spatially inconsistent effect. These findings emphasize the complex interactions between elevation, temperature, radiation, and precipitation in regulating CDD trends. By providing a long-term perspective on CDD variations and their climatic drivers, this study enhances our understanding of vegetation–climate interactions in alpine ecosystems. The results offer a scientific basis for modeling late-season phenological changes, ecosystem resilience, and land-use planning under ongoing climate change.https://www.mdpi.com/2073-445X/14/4/758Qinghai–Tibetan Plateaualpine grasslandclimate changecooling degree days (CDDs) |
| spellingShingle | Yusi Zhang Gang Bao Yuhai Bao Zhihui Yuan Wendu Rina Siqin Tong Altitudinal Differences in Decreasing Heat Deficit at the End of the Growing Season of Alpine Grassland on the Qinghai–Tibetan Plateau from 1982 to 2022 Land Qinghai–Tibetan Plateau alpine grassland climate change cooling degree days (CDDs) |
| title | Altitudinal Differences in Decreasing Heat Deficit at the End of the Growing Season of Alpine Grassland on the Qinghai–Tibetan Plateau from 1982 to 2022 |
| title_full | Altitudinal Differences in Decreasing Heat Deficit at the End of the Growing Season of Alpine Grassland on the Qinghai–Tibetan Plateau from 1982 to 2022 |
| title_fullStr | Altitudinal Differences in Decreasing Heat Deficit at the End of the Growing Season of Alpine Grassland on the Qinghai–Tibetan Plateau from 1982 to 2022 |
| title_full_unstemmed | Altitudinal Differences in Decreasing Heat Deficit at the End of the Growing Season of Alpine Grassland on the Qinghai–Tibetan Plateau from 1982 to 2022 |
| title_short | Altitudinal Differences in Decreasing Heat Deficit at the End of the Growing Season of Alpine Grassland on the Qinghai–Tibetan Plateau from 1982 to 2022 |
| title_sort | altitudinal differences in decreasing heat deficit at the end of the growing season of alpine grassland on the qinghai tibetan plateau from 1982 to 2022 |
| topic | Qinghai–Tibetan Plateau alpine grassland climate change cooling degree days (CDDs) |
| url | https://www.mdpi.com/2073-445X/14/4/758 |
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