A new approach for estimating fine root production in forests: a combination of ingrowth core and scanner

摘要

Estimating fine root (diameter <= 2 mm) production has been difficult. The best method remains unknown because each method has potential biases associated with the estimation methods and field techniques applied, leading to over- or underestimation. In this study, a new method combining ingrowth core and scanner named as "combined method" was described, and it was applied to a Quercus serrata plantation in Tsukuba, Japan. Comparing accuracy of estimation of fine root production by decision matrix and continuous inflow method using ingrowth core with that by "combined method" was conducted. Closed-box protected scanners and ingrowth cores were buried in a field on December 6, 2012, and fine root images were nondestructively scanned biweekly for growth measurement. In addition, thermometers were used to record temperature automatically at 1 m from the ground and at a depth of 10 cm in soil at 12 a.m. daily to evaluate the effect of temperature on fine root production. The results indicated that the combined method gave 19 and 16 % higher estimation of fine root production than decision matrix and continuous inflow method, respectively. In the combined method, using scanned images at different time intervals gave different estimates. Generally, longer time-interval images gave lower estimates: biweekly-interval images yielded an estimate that was 16 % higher than that yielded using 2-month-interval images. A 1-month time lag relationship (R (2) = 0.84, p < 0.01) between soil temperature and fine root production was found at the study site. This relationship implied that higher fine root production occurred in summer. It was concluded that the combined method gave a more accurate estimation of fine root production in forests among the three methods compared.