Table 1.

Pathways and hypothesized mechanism based on piecewise structural equation modeling.

Number	Pathway	Hypothesized mechanism
1	Soil moisture → Carbon storage	Soil moisture affects plant carbon storage by regulating soil nutrient supply and uptake by plants (Green et al., 2019).
2	Species diversity → Carbon storage	Tree species diversity can affect plant carbon storage through several biological mechanisms, such as niche complementarity effect, selection effect (Huang et al., 2018).
3	Structural diversity → Carbon storage	High structural complexity of trees can enhance efficient use of resources for growth to promote plant carbon storage (Ali et al., 2019a; Aponte et al., 2020).
4	Climate factors → Carbon storage	Climate favorability affects plant growth and carbon storage by regulating respiration and water utilization (Chen et al., 2018).
5	Soil moisture → Species diversity	Soil moisture may affect plant diversity by regulating soil nutrient supply and uptake by plants, but the underlying mechanisms are unclear (Green et al., 2019).
6	Climate factors → Species diversity	Climate factors (i.e. temperature and precipitation) can cause alterations in species diversity with a momentous consequence for ecosystem carbon storage (Yan et al., 2022).
7	Soil moisture→ Structural diversity	Soil moisture may affect plant individual size by regulating soil nutrient supply and uptake by plants, but the underlying mechanisms are unclear (Green et al., 2019).
8	Species diversity→ Structural diversity	Species diversity plays a driving role in the complexity of stand structure, which indirectly increases carbon storage (Ali et al., 2016).
9	Climate factors → Structural diversity	Structural attributes and ecosystem properties and processes may vary along environmental gradients including temperature, rainfall and soil fertility (Poorter et al., 2015).
10	Climate factors → Soil moisture	Soil moisture is controlled by climatic forcing, particularly water balance (Green et al., 2019).