Abstract
Forests regulate air quality and respond to climate change by storing carbon. Assessing the driving factors of forest aboveground carbon (AGC) storage is of great importance for forest management. We assumed that different forest types would affect the relationship between species richness, stand density, individual tree size variation, and AGC. In order to test and verify it, we analyzed the inventory data of 206 fixed plots (20 m × 20 m) of Jingouling Forest Farm, taking advantage of the piecewise structural equation model (pSEM) to explore the effects of species diversity, stand structure attributes, and topography on the AGC storage in the Wangqing Forest in Jilin Province. In addition, in this study, we aimed to investigate whether the fixed factors (species diversity, stand structure attributes, and topography) influenced AGC storage more significantly than the random factor (forest type). According to the results of pSEM, the selected factors jointly explain the impact on 33% of AGC storage. The relationship between stand density and AGC is positive, and the impact of individual tree size variation on AGC storage is negative. Species richness has direct and indirect impacts on AGC storage, and the indirect impact is more significant through individual tree size variation. Both elevation and slope are significantly negatively associated with AGC storage. Forest type explains the impact on 12% of AGC storage, which means the relationship between AGC and predictors varies across forest types. The results provide a scientific basis for the protection and management decision of natural forests in northeastern China.
Highlights
The forest is the largest carbon pool on earth, and its importance in the carbon sink is considerable [1]
We found that piecewise structural equation model (pSEM) explained the marginal and random changes of 21% and 12% of aboveground carbon storage, respectively
The relationship between various variables and aboveground carbon storage in different types of the forest was described by using pSEM
Summary
The forest is the largest carbon pool on earth, and its importance in the carbon sink is considerable [1]. The aboveground part of the forest ecosystem carbon pool is crucial, which can directly affect the carbon flux between the atmosphere and the forest ecosystem. There are numerous driving factors of forest AGC storage, which depend on species diversity [2] as well as forest structure attributes, such as stand density [3] and individual tree size variation. Forest diversity is part of the influencing factors of aboveground biomass and AGC storage and is affected by environmental factors [4]. The two main hypotheses explaining the positive correlation between species diversity and AGC storage are the niche complementarity hypothesis and mass ratio hypothesis [5,6]. Many researchers have considered the relationship between plant species diversity and AGC storage. Some research results are positive, which means the AGC storage of trees will increase with the increase in forest species diversity [9–11].
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