The Performance of Containerized Tree Seedlings after Outplantings Evaluated from Multi-site Data Set

Abstract

Containerized tree seedlings are expected to exhibit high survivorship and good growth after outplanting; however, a unified consensus on the performance of containerized seedlings in Japan remains undetermined. To understand the universal properties of the performances of containerized seedlings after outplanting, the survival ratio and height and diameter growth rate of two stock types (containerized seedlings and bare-root seedlings) were estimated from 39 experiment sites covering five prefectures and five species and compared between stock types. The result of parameter estimation using hierarchal Bayesian models revealed that the median survival ratio of containerized seedlings across all species was 0.96, which was not different from that of bare-root seedlings (0.97). The estimated height and diameter growth rates were also similar between stock types. The sturdiness quotient (SQ, the ratio of height and diameter) was higher in containerized seedlings than in bare-root seedlings of all species immediately after outplanting. However, the difference in SQ between stock types diminished 1 year after outplanting. These results suggest that containerized tree seedlings generally show performances equivalent to those of bare-root seedlings after outplanting. Therefore, other properties of containerized seedlings, such as ease of cultivation and low-labor planting present more attractive advantages than those of good performance after outplanting.