## 1 Introduction  
The continuous rise in greenhouse gas (GHG) emissions, mainly carbon dioxide (CO\({}_{2}\)), has triggered increasingly severe global warming, posing a serious threat to the human living environment [1, 2, 3]. Currently, over 55% of the global population resides in urban areas, a proportion projected to reach 70% by 2050 [4, 5], now making them the critical nodes where global climate change directly impacts human habitats. As clusters of spatially and economically interconnected cities with high population density [6], urban agglomerations(UAs) are a more typical urban area [7], where the living environment may face greater threats. Strict emission control measures significantly reduce pollutants that cause health problems, such as respiratory and cardiovascular diseases, which creates a healthier and more conducive living environment in urban areas. Therefore, carbon reduction and removal must be strictly implemented in urban areas to mitigate climate change and its adverse effects. Due to the significant contribution of energy consumption and land use changes to carbon emissions [6], extensive research on carbon emission drivers in UAs has provided insights for technology- or engineering-based solutions [6; 8; 9]. However, relying solely on emission reductions cannot achieve the needed reduction in peak warming, as certain sectors like agriculture and heavy industries are unlikely to reach net-zero emissions in the short term [10]. Nor will they mitigate other urban problems caused by climate change, such as the impacts on the physical and mental health of urban residents. For this reason, carbon sequestration (CS) in UA, a nature-based solution, should be emphasized to fill these gaps. Recent studies have demonstrated that an examination of urban vegetation CS is crucial for elucidating the role of non-natural ecosystem vegetation cover in climate change mitigation, and advancing our insights into the global carbon cycle and sustainable development [11]. According to [PERSON] et al. (2022) [12], CS by urban greening can partially offset aboveground carbon losses caused by urban expansion. Its significant role in alleviating the negative impacts of global climate change has been confirmed on a global scale [13; 14]. The Sixth Assessment Report (AR6) of the Intergovernmental Panel on Climate Change (IPCC) also underscores the criticality of augmenting carbon absorption and storage in urban environments [2]. Additionally, urban vegetation also delivers multiple positive contributions to climate change mitigation and adaptation through diverse ecosystem services that benefit from CS. Numerous studies have shown that urban vegetation effectively reduces local temperatures via shading and evapotranspiration, curbing energy consumption from air conditioning during summer heatwaves, thereby indirectly lowering urban carbon emissions [15; 16]. Meanwhile, increasing residents' exposure to urban vegetation can reduce climate-related threats by promoting physical health, alleviating mental stress, and mitigating natural disasters [4; 17]. These ecosystem services also further intensify as vegetation CS accumulates. Consequently, the potential of urban vegetation CS, with its associated ecosystem services, to mitigate climate change may be severely underestimated [11]. Net primary productivity (NPP), serving as a crucial indicator for assessing vegetation carbon sequestration capacity, has been extensively utilized in existing research. However, while traditional methods for calculating NPP such as field sampling data and flux station data based on eddy covariance can provide more accurate NPP observations, their limited temporal and spatial coverage significantly constrains their application in studies over the UA scale [18]. In contrast, remote sensing-based NPP products, particularly the Terra Moderate Resolution Imaging Spectroradiometer (MODIS) NPP dataset, offer long-term, consistent NPP observations with comprehensive spatiotemporal coverage.