천연하종갱신에 의한 소나무 후계림 조성의 완료 판정 기준 구명

정상훈*, 이상태

(국립산림과학원 산림기술경영연구소)

The completion criteria for establishing natural seed regeneration

of Pinus densiflora forests

Sang Hoon Chung* and Sang Tae Lee

(Forest Technology and Management Research Center, National Institute of Forest Science)

요약: 본 연구는 천연하종갱신지의 사후관리에 필요한 갱신 완료 판정 기준을 제시하기 위해 수행되었다. 천연갱신지의 치수생육 환경을 모니터링하기 위해 2015년 8.6ha를 대상으로 대상개벌작업 및 모수작업으로 천연갱신 후계림을 조성하였다. 매년 천연갱신치수 생장 및 하층식생을 조사하고 연차별 치수생장량(치수고, 근원직경) 및 평균 초장(草丈)을 분석하였다. 천연갱신 완료 판정을 위한 치수의 적정 크기 및 시기 기준을 구명하기 위해 제7차 국가산림자원조사 자료 기반으로 Champman-Richards 생장모델과 임분밀도관리도를 활용하여 소나무 임령별(3～10년) 치수고 및 기대성립개수를 예측하였다. 단위면적당 생육할 수 있는 최대 임목 개수(기대성립개수)의 30% 이상을 천연갱신 완료 시 적정 임분밀도로 하였다. 천연갱신치수 생육 환경 모니터링 결과, 4년차까지 갱신치수와 하층식생은 생육경쟁을 하는 것으로 파악되었으며, 5년차에 접어들면서 갱신치수(치수고: 137.8cm)가 하층식생(초장: 81.5cm)보다 생육 우위를 차지하는 것으로 분석되었다. 임령별 치수고 예측값 역시 5년차에 230cm 수준으로 산출되어 목재수확 후 5년 내에 완료 판정이 가능한 것으로 판단된다. 5년이 경과한 임지의 ha당 기대성립개수는 10,532그루로 산출되어 최소한 ha당 3,000그루가 생육하고 있어야 생육단계별로 사후관리가 적절히 적용될 수 있을 것으로 파악되었다.

Abstract: This study was conducted to present the completion criteria for evaluating the regeneration in order to provide the necessary post-management guidelines for the areas with natural seed regeneration. In order to monitor the seedling growth environment in the naturally regenerated areas, the areas were established in 2015 through strip clearcutting and seed tree method. The growth of naturally regenerated seedlings and the understory vegetation were surveyed annually, and the seedling growth (seedling height, root collar diameter) and average height of the vegetation were analyzed. Based on the data from the 7th national forest inventory, the Chapman-Richards growth model and the stand density management diagram were used to predict the seedling height and the expected number of established seedlings by Korean red pine stand age (3-10 years) in order to determine the appropriate size and timing criteria for judging the completion of natural regeneration. The appropriate stand density for judging the completion of natural regeneration was set at 30 % or more of the maximum number of trees that can grow per unit area (expected established seedlings). The result of the monitoring of the seedling growth environment in the naturally regenerated areas, the regenerated seedlings and the understory vegetation were found to be competing for growth up to the 4th year. In the 5th year, the regenerated seedlings (seedling ave. height: 137.8 cm) were analyzed to have a growth advantage over the understory vegetation (vegetation ave. height: 81.5 cm). The predicted seedling height by stand age also showed that in the 5th year, the seedling height reached around 230 cm, indicating that the natural regeneration can be judged as complete within 5 years after timber harvesting. The expected number of established seedlings per hectare in the 5th stands was calculated to be 10,532 trees. It was determined that at least 3,000 trees per hectare should be growing in order for proper post-management measures to be applied at each growth stage.

Keywords: completion criteria, expected established seedlings, Korean red pine, natural seed regeneration