Material quality assessment and trade-off synergies of forest ecological service in Xianrendong National Nature Reserve, Liaoning Province of northeastern China

  Objective  The purpose of this study was to clarify the material quality of forest ecological multi-functions in Xianrendong National Nature Reserve in Liaoning Province of northeastern China, which can effectively improve the regional environmental quality and enhance the regional ecological service function.

  Method  Taking the forest ecosystem in the nature reserve as the research object, according to the 2018 observation data of the Liaodong Peninsula Forest Ecosystem National Observation and Research Station in Liaoning and survey data of the forests, using the methods of model quantification, distributed calculation and correlation analysis, three major service categories and six functional categories of support, regulation and supply were selected to study the material quality of forest ecological services in nature reserves and their trade-offs and synergies.

  Result  (1) The material quantity of forest ecological service function was as follows: support service 644.42 × 10³ t/year, including conservation soil volume 644.10 × 10³ t/year, tree nutrient accumulation 323.85 t/year. Regulation service 41.61 × 10³ t/year, including carbon sequestration and oxygen release of 40.16 × 10³ t/year, and the air purification amount of 1 454.87 t/year. Among the material amount of the supply service, the amount of water supply was 148.27 × 10⁷ m³/year, and the amount of negative ions supplied was 274.97 × 10²⁰ year⁻¹, showing as soil conservation > carbon fixation and oxygen release > air purification > forest nutrient fixation. (2) Substances of each evaluation index: the amount of forest conservation soil was 555.15 × 10³ t/year for soil consolidation and 88.95 × 10³ t/year for fertilizer retention; the accumulation of nutrients in forests was in the order of nitrogen retention (291.02 t/year) > potassium retention (25.33 t/year) > phosphorus retention (7.50 t/year); forest absorb carbon of 28.56 × 10³ t/year and release oxygen of 11.60 × 10³ t/year; forest absorb gas pollutants from large to small was sulfur dioxide (817.50 t/year) > nitrogen oxidation compound (255.80 t/year) > fluoride (242.00 t/year), blocking TSP, PM₁₀ and PM_2.5 were 82.3 t/year, 46.7 t/year and 10.6 t/year, respectively. (3) The dominant tree species (groups) with larger amounts of ecological service function substances included natural secondary oak forests, red pine forests and larch forests. The material quality of service function was significantly positively correlated with stand area and stock volume (r > 0, P < 0.05), and positively correlated with DBH, tree height and canopy density (r > 0). (4) The quality of ecological service functions in the administrative division of the protected area was the highest in the administrative department, while the lowest in Sanjiashan Village; there was a trade-off between support and adjustment services, synergy between support and supply services, and synergy and trade-off between adjustment and supply services.

  Conclusion  The forest ecosystem has outstanding quality of soil conservation, carbon sequestration and nutrient release, water supply and negative oxygen ion supply. Forest area and stock volume play an important role in the quality of ecological service. Synergies and trade-offs are common among ecological services. In terms of space, closing mountains for afforestation and preventing the loss of forestry land; on the stand, protect rare tree species, increase tree species types, promote forest regeneration and succession, and combine on-site protection with afforestation. Taking multiple measures and following natural laws is an effective measure to improve ecological services.