Spatiotemporal Characteristics of NPP Changes in Frozen Ground Areas of the Three-River Headwaters Region, China: A Regional Modeling Perspective

• Published in: Frontiers in Earth Science
• Main Authors: Jianan Hu, Zhuotong Nan, Hailong Ji
• Format: Article in Journal/Newspaper
• Language: English
• Published: Frontiers Media S.A. 2022
• Subjects: net primary productivity (NPP); NOAH-MP; permafrost; seasonally frozen ground; three-river headwaters region; Science; Q
• Online Access: https://doi.org/10.3389/feart.2022.838558; https://doaj.org/article/c11601e245a84b7eab841e584eb7db6d

Permafrost degradation triggered by climate warming can disturb alpine ecosystem stability and further influence net primary productivity (NPP). Known as the “water tower of China”, the Three-River Headwaters Region (TRHR) on the eastern Qinghai-Tibet plateau (QTP), is characterized by a fragile alpine meadow ecosystem underlain by large areas of unstable permafrost and has been subject to rapid climate change in recent decades. Despite some site-specific studies, the spatial and temporal changes in NPP in the different frozen ground zones across the TRHR associated with climate change remain poorly understood. In this study, a physically explicit Noah land surface model with multi-parameterization options (Noah-MP) was employed to simulate NPP changes on the TRHR during 1989–2018. The simulation was performed with a spatial resolution of 0.1° and a temporal resolution of 3h, and validated at two sites with meteorological and flux observations. The results show that the average NPP was estimated to be 299.7 g C m−2 yr−1 in the seasonally frozen ground (SFG) zone and 198.5 g C m−2 yr−1 in the permafrost zone. NPP in the TRHR increased at a rate of 1.09 g C m−2 yr−2 during 1989–2018, increasing in 1989–2003 and then decreasing in subsequent years. The NPP in permafrost area increased at a rate of 1.43 g C m−2 yr−2 during 1989–2018, which is much higher than the rate of change in NPP in the SFG area (0.67 g C m−2 yr−2). Permafrost degradation has complicated ecosystem implications. In areas where permafrost degradation has occurred, both increasing and decreasing changes in NPP have been observed.