## 1 Introduction  
The expansion of plantation forests (PFs) provides new sources of terrestrial carbon (C) uptake, serving as a crucial nature-based solution for mitigating climate warming [1, 2, 3]. The effective implementation and management of PFs can significantly enhance the C sequestration capacity of terrestrial ecosystems [4, 5, 6]. With the increasing attention and investment from the national government in forestry ecological construction, the area of PFs in China has been continuously growing, occupyingan important position in global plantation development [7]. Multiple studies have suggested the beneficial effect of PFs in terms of increasing terrestrial C sequestration. From 2001 to 2010, China's major reforestation programs led to a sequestration of approximately 132 Tg of C per year [8]. The surge in PF area has translated into substantial gains in biomass C storage, resulting in a substantial increase in the aboveground C stock from 675.6 \(\pm\) 12.5 Tg C to 1873.1 \(\pm\) 16.2 Tg C from 1990 to 2020 [9]. A model prediction estimates that if China continues its existing planting trajectory, the national forest C sinks could reach \(\sim\)0.35 Gt C per year by 2060--enough to offset about 43% of the country's projected fossil fuel CO\({}_{2}\) emissions [10]. Specifically for Jiangsu Province, there has been a forest biomass C storage increase of 20.3 Tg from 2005 to 2010, based on forest inventory datasets [11]. By 2010, over 81% of the province's new C sequestration came from harbor (timber) plantations [12], indicating that PFs are the primary drivers of increasing C uptake across this region. However, some studies have also warned that the improper implementation of plantations can have detrimental effects on the local ecosystems. For example, the prevalent practice of clear-cut harvesting and replanting in monocultures (such as Chinese fir _Cunningham lancolata_ plantations) has led to a decline in soil nutrients, increased pest pressures, and overall soil degradation in many areas [13]. These soil fertility losses not only threaten long-term forest health but can also reduce the C sequestration capacity of PFs by limiting tree growth. Moreover, PFs generally consume more water than natural local vegetation, which can diminish streamflow and groundwater recharge in affected catchments. Nationwide analyses revealed that China's PFs use about 7% more water than natural forests on average, and this difference widens in drier regions [14]. In water-limited northern and western China, extensive aforestation has been linked to significant reductions in water yield and therefore the persistent C sequestration of PFs remains uncertain [14]. Therefore, a long-term assessment of the regional C sequestration of PFs will aid in clarifying whether the existing aforestation strategy is effective for climate mitigation in the future. In contrast to natural forests, plantation forests are often established with the consideration of specific purposes based on human needs. In turn, PFs often differ markedly from those native plant communities in their relationship with the associated environment. Comparative studies in China have found that PFs are generally more vulnerable to environmental stresses like drought than the local species. Using two decades of satellite observations, [PERSON] et al. (2025) showed that PFs exhibited significantly lower drought resistance and resilience compared to the nearby natural forests [15]. [PERSON] et al. (2021) compared the radial growth of six conifer species in natural and planted stands under seasonal drought conditions. They found that tree growth in PFs was more severely constrained during drought [16]. [PERSON] et al. (2021) conducted a comparison between the natural and PFs of _Pinus massoniana_ and _Cunningham lancolata_ in Fujian province, China, and found that the PFs of _Cunningham lancolata_ were more vulnerable to frequent extreme drought events [17].