Division of Environmental and Forest Science, Gyeongsang National University, Jinju, 52725, South Korea.
Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, 901 83, Umeå, Sweden.
Sci Rep. 2023 Mar 6;13(1):1743. doi: 10.1038/s41598-023-27989-3.
Carbon (C) sequestration capacity in forest ecosystems is generally constrained by soil nitrogen (N) availability. Consequently, N fertilization is seen as a promising tool for enhancing ecosystem-level C sequestration in N-limited forests. We examined the responses of ecosystem C (vegetation and soil) and soil N dynamics to 3 years of annual nitrogen-phosphorus-potassium (NPK = 11.3 g N, 15.0 g P, 3.7 g K m year) or PK fertilization (PK), observed over 4 years in a 40-year-old Pinus densiflora forest with poor N nutrition in South Korea. PK fertilization without N was performed to test for PK limitation other than N. Neither tree growth nor soil C fluxes responded to annual NPK or PK fertilization despite an increase in soil mineral N fluxes following NPK fertilization. NPK fertilization increased the rate of N immobilization and 80% of the added N was recovered from mineral soil in the 0-5 cm layer, suggesting that relatively little of the added N was available to trees. These results indicate that N fertilization does not always enhance C sequestration even in forests with poor N nutrition and should therefore be applied with caution.
森林生态系统的碳（C）固存能力通常受到土壤氮（N）供应的限制。因此，施肥被认为是提高 N 限制森林生态系统水平 C 固存的一种有前途的工具。我们研究了 3 年的氮磷钾（NPK=11.3gN、15.0gP、3.7gK·m-2·年-1）或 PK 施肥（PK）对生态系统 C（植被和土壤）和土壤 N 动态的响应，在韩国一个 40 年生、N 营养不良的赤松林中进行了 4 年的观测。进行 PK 施肥而不施 N，是为了检验除 N 以外的 PK 限制。尽管 NPK 施肥后土壤矿质 N 通量增加，但树木生长和土壤 C 通量均未对年 NPK 或 PK 施肥产生响应。NPK 施肥增加了氮固定的速率，80%的添加氮从 0-5cm 层的矿质土壤中回收，这表明添加的氮很少能被树木利用。这些结果表明，即使在 N 营养不良的森林中，施肥也不一定能提高 C 固存，因此应谨慎应用。
