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.

본 연구는 산지의 수자원보전량 평가용 수문유출모형의 개발을 위한 중요한 기초연구로서 우리나라 주요 수종인 소나무와 상수리나무에 대한 수간류 및 수관통과우의 물수지식과 수문학적 특성을 밝히고자 수행하였다. 영남대학교 자연자원대학 부속 용성연습림과 영남대학교 교내 야산에 각각 수관통과우 및 수간류 관측용 야외 실험지를 설치하고, 1995년 9월에서 1998년 6월까지 약 2년 10개월 사이에 이 지역에 내린 다수의 단위강우에 대한 두 수종의 임내우 수량배분을 조사하였다. 그 결과 임외의 단위강우에 응답하는 두 수종의 수문학적 특성과 임내우 물수지식을 요약하면 다음과 같다. 1. 소나무에 있어서 수관통과우와 수간류의 총량은 각각 임외우의 73.8%와 0.8%이였으며 상수리나무는 각각 임외우의 76.9%와 3.8%로 관측되었다. 2. 소나무에 있어서 임외우(Gp)에 대한 수간류(Sf)와 수관통과우(Tf)의 회귀식은 각각 Sf = 0.01GP -2.05 (r2=0.54) Tf = 0.79Gp - 26.04 (r2=0.92)로, 임내우(Nr)와는 Nr = 0.81Gp - 28.09 (r2=0.92)로 추정하였다. 이와 같이 소나무에 있어서 수간류와 수관통과우는 임외우의 양에 정비례하여 증가하였다. 3. 상수리나무에 있어서 임외우(Gp)에 대한 수간류(Sf)와 수관통과우(Tf)의 회귀식은 각각 Sf = 0.03Gp + 12.25 (r2=0.74) Tf = 0.78Gp + 19.75 (r2=0.96)로, 임내우(Nr)와는 Nr = 0.81Gp + 31.99 (r2=0.96)로 구해졌는데 소나무보다 상수리나무에 있어서 수간류와 수관통과우의 증가폭이 더 큰 것으로 나타났다. 4. 수간류 및 수관통과우와 그 영향인자로 평가된 수관투영면적(CA). 흉고직경(DBH), 임외우량(Gp)과의 내부상관분석을 한 결과, 소나무 수간류에는 임외우＞수관투영면적＞흉고직경의 순으로, 상수리나무 수간류에는 임외우＞흉고직경＞수관투영면적의 순으로 상관계수 값이 높았다. 그리고 소나무와 상수리나무의 수관통과우는 임외우＞수관투영면적＞흉고직경의 순으로 상관계수 값이 높았다.상관계수 값이 높았다.

We measured the amount of precipitation, stemflow, and throughfall and concentrations of nine major inorganic nutrients (H+, NH4 +, Ca2+, Mg2+, K+, Na+, Cl-, NO3 -, and SO4 2-) to investigate the nutrient inputs into soil from precipitation in Pinus densiflora and Quercus mongolica stands from September 2015 to August 2016. The precipitation inputs of H+, NH4 +, Ca2+, Mg2+, K+, Na+, Cl-, NO3 -, and SO4 2- into soil were 0.170, 15.124, 42.227, 19.218, 14.050, 15.887, 22.391, 5.431, and 129.440 kg·ha-1·yr-1, respectively. The P. densiflora stemflow inputs were 0.008, 0.784, 1.652, 1.044, 0.476, 0.651, 1.509, 0.278, and 9.098 kg·ha-1·yr-1, and those for Q. mongolica were 0.008, 0.684, 2.429, 2.417, 2.941, 1.398, 2.407, 0.436, and 13.504 kg·ha-1·yr-1, respectively. The P. densiflora throughfall inputs were 0.042, 21.518, 52.207 27.694, 20.060, 24.049, 37.229, 10.241, and 153.790 kg·ha-1·yr-1, and those for Q. mongolica were 0.032, 15.068, 42.834, 21.219, 20.294, 20.237, 24.288, 5.647, and 119.134 kg·ha-1·yr-1, respectively. Of the total throughfall flux (i.e., stemflow + throughfall flux) of the nine ions for the two species, SO4 2- had the greatest total throughfall flux and H+ had the lowest. The net throughfall fluxes of the ions for the two species had various correlations with the precedent dry period, rainfall intensity, rainfall amount, and pH of precipitation. The soil pH under the Q. mongolica canopy (4.88) was higher than that under the P. densiflora canopy (4.34). The difference in the soil pH between the two stands was significant (P < 0.01), but the difference in soil pH by the distance from the stems of the two species was not (P > 0.01). This study shows the enrichments of inorganic nutrients by two representative urban forests in temperate regions and the roles of urban forests during rainfall events in a year.