Stemflow (SF) is essential for water resources within forest ecosystems and can constitute up to half of the gross rainfall (GR), depending on the forest stand structures in coniferous plantations. Although numerous studies on SF yield have been reported globally for various forest types, very few studies on SF have been reported to examine the influence of forest stand structures on SF in Korea. This study aimed to quantify the relationship between SF and forest stand structures in unmanaged Japanese cypress plantations. Two study plots were established (10 m × 10 m each) in plantations with the same stem density (SD: 2500 stems ha-1) (hereafter P1 and P2). Almost all forest stand structures (canopy projection area, tree height, diameter at breast height (DBH), number of live and dead branches, and ratio of canopy length to canopy width), including canopy volume using mobile LiDAR devices, were investigated. To evaluate the efficiency of funneling rainwater for the effect of tree biomass on SF, a funneling ratio (FR) was used. The present SF ratios (20.7% in P1 and 22.3% in P2) were much higher than those reported in previous studies of various forest types in Korea (SF ratios: 0.2–5.8% with a mean of 2.0%). This is due to the interaction between the high SD and many under-canopy dead branches. Individual-scale FR was correlated with DBH (R2 = 0.43). The present stand-scale FRs (FRstand) (22.3 in P1 and 29.2 in P2) were much higher than those reported in the previous studies (FRstand: 1.0–33.3 with a mean of 7.8) because of the negative relationship between FRstand and mean DBH (R2 = 0.78, p = 0.02). Our results provide useful information for understanding changes in SF caused by forest stand structures.

산림자원 조사에서 입목의 측정은 조사원이 직접 측정 도구를 사용하여 수행되지만, 측정값의 일관성과 정확성 문제로 인한 오차가 발생할 수 있다. 이러한 문제를 해결하기 위해 최근 LiDAR(Light Detection and Ranging) 기술이 산림자원 조사에 응용되고 있다. 본 연구는 단순림의 산림자원 조사에서 지상 LiDAR 기술의 활용 가능성을 평가하고자 하였다. 연구는 한국의 전주에 위치한 전북대학교 학술림 내의 편백림과 굴참나무 림을 대상으로 수행되었다. 조사원이 측정한 입목의 흉고직경과 수고 측정값을 기준으로, 휴대형 및 고정형 LiDAR 장비를 사용한 측정값을 비교 분석하였다. 결과적으로, 편백 임분의 흉고직경 측정에서는 측정 방법 간 높은 일치도가 나타났으며, 평균의 차이는 유의미하지 않았다. 그러나 수고 측정에서는 낮은 일치도가 관찰되었고, 평균의 차이는 유의미하였다. 특히, 3점 이동 평균 수고에서 휴대형 LiDAR 장비는 수고를 0.3m 과대 측정하였으며, 고정형 LiDAR 장비는 1.2m 과소 측정하였다. 굴참나무 임분의 경우, 흉고직경 측정에서 높은 일치도가 나타났고, 수고 측정에서 도 비교적 높은 일치도를 보였다. 또한, 흉고직경과 수고 모두에서 평균의 차이는 유의미하지 않았다. 이러한 결과는 편백 임분과 굴참나무 임분에서 흉고직경 측정과 굴참나무 임분의 수고 측정에 있어 지상 LiDAR 기술이 높은 정확도를 제공할 수 있음을 시사하지만, 편백 임분의 수고 측정에서는 개선의 여지가 있음을 나타낸다. 본 연구는 지상 LiDAR 기술이 단순림의 산림자원 조사에 활용될 수 있는 초기 단계의 연구로서, 다양한 수종 및 환경 조건에 관한 추가 연구의 필요성을 강조한다.

Throughfall (TF)—as a diffusive hydrological water flux—significantly affects ecohydrological and biogeochemical processes within forest ecosystems. Recent investigations have revealed the impact on TF generation processes within unmanaged coniferous plantations of under-canopy structures, particularly those laden with dead branches, as well as upper-canopy structures. However, spatiotemporal variations in TF in such plantations remain unexplored. We investigated these variations in TF in a 33-year-old unmanaged Japanese cypress (Chamaecyparis obtusa Endl.) plantation, laden with dead branches, with a high stand density (SD) of 2,500 stems ha−1. Over a two-year period (May 2017 to May 2019), we conducted weekly TF measurements using 28 manual-type TF collectors. We compared the present TF ratio and canopy water storage capacity (S) with those of previous investigations conducted on Japanese cypress plantations. Moreover, we assessed key indices contributing to spatiotemporal TF variations (canopy cover: CC and distance to the nearest stem: TFd) and potentially influential dead branch indices (number of dead branches: TFdb and vertical spacing length on a stem: TFs) to elucidate TF spatial patterns. The results showed that the TF ratio was notably lower than that in previous studies (n = 13), with SD (r = –0.92, p < 0.001) and S (r = –0.87, p < 0.001) emerging as key influential factors among other stand-structure parameters. Spatial TF patterns exhibited a decreasing trend as the gross rainfall (GR) increased. Temporal stability was not significantly associated with CC (r = 0.120, p = 0.544), TFd (r = 0.068, p = 0.731), TFdb (r = 0.211, p = 0.281), or TFs (r = 0.206, p = 0.292) for any of the TF collectors. These findings underscore the important role of GR in determining the spatial variation of TF. Collectively, our results contribute to an enhanced understanding of TF spatiotemporal heterogeneity in unmanaged Japanese cypress plantations with dead branches.