Abstract
Humans have affected the carbon (C) and nitrogen (N) cycles in forests; however, the quantification of the responses of forest C and N balances to human activities is limited. In this study, we have quantified the impacts of the long-term national forest rehabilitation plan and the contribution of the increase in air temperature, CO2 concentration, and N deposition on the C and N balances of the South Korean forests during 1973–2020 by using a biogeochemical model. During the simulation period, the C balance increased from 0.2 to 4.3 Mg C ha−1 year−1, and the N balance increased from 0.2 to 17.4 kg N ha−1 year−1. This resulted in the storage of 825 Tg C and 3.04 Tg N by the whole South Korean forests after the national forest rehabilitation plan. The increase in air temperature, CO2 concentration, and N deposition contributed −11.5, 17.4, and 177 Tg C to the stored C stock, respectively, and −25.4, 8.90, and 1807 Mg N to the stored N stock, respectively. This study provides references for future forest rehabilitation efforts and broadens our knowledge on the impacts of human-induced environmental changes on the C and N balances of forests.
Highlights
These results show that the human-induced increases in air temperature, CO2 concentration, and N deposition contributed −11.46, 17.44, and 177.21 Tg C to the stored C stock of 825 Tg C in the South Korean forests, respectively
The simultaneous increase in air temperature, CO2 concentration, and N deposition (T1 CO1 Nd1 ) increased the N stocks of tree biomass (+68.3 kg N ha−1 ), primary dead organic matter (DOM) (+64.6 kg N ha−1 ), and mineral soil (+162 kg N ha−1 ). These results indicate that the increase in air temperature, CO2 concentration, and N deposition contributed
1973 to 2020, the C and N balances increased by several fold (21 and 87, respectively) owing to relatively low C and N output compared with the rapid integration of C and N to the young forests, indicating that the South Korean forests served as important C and N sinks
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Carbon (C) and nitrogen (N) balances in a forest determines the supporting role of the forest for human beings. The C balance, determined by the photosynthetic C gain of trees and respiratory C loss from trees and dead organic matter (DOM), plays a key role in determining the climate regulation of a forest (e.g., atmospheric CO2 sequestration) [1]. The N balance, the difference between N input through N deposition and biological N fixation and N output through N leaching and denitrification, affects forest productivity, ground and surface water quality, and N2 O emission [2,3].
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