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Abstract
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.
Highlights
On the Qinghai-Tibetan Plateau (QTP), carbon cycles occur in a unique way owing to the special geographical features and ecological environment (Lin et al, 2019)
We found that the mean annual net primary productivity (NPP) in both the permafrost zone and the seasonally frozen ground (SFG) zone showed substantially increasing trends during the study period in relation to climate changes (Figures 6B,C)
Changes in NPP in the Three-River Headwaters Region (TRHR) during 1989–2018, stratified by frozen ground type, were simulated using the Noah land surface model with multiparameterization options (Noah-MP) land surface model (LSM) operating at a spatial resolution of 0.1° and a temporal resolution of 3 h
Summary
On the Qinghai-Tibetan Plateau (QTP), carbon cycles occur in a unique way owing to the special geographical features and ecological environment (Lin et al, 2019). Region (TRHR) is one of the most fragile and sensitive terrestrial ecosystems on the QTP (Tong et al, 2014; Mao et al, 2015; Jiang and Zhang, 2016a). Dynamic changes in NPP can be used to assess the Earth’s ability to sustain life and the sustainability of the ecosystem to maintain development in the face of climate change (Zhao and Running, 2010). The TRHR is known as the “Water Tower of China”, and the accurate estimation of NPP change in the TRHR is very important and has always been a hot topic in terrestrial carbon cycle and climate change research on the QTP (Zhao et al, 2013; Jiang and Zhang, 2015; Liang et al, 2016). There are few monitoring sites, making it difficult to gain complete insights into NPP changes across the region
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