No. 974

Title:

Sapling bank dynamics of shade tolerant Abies mariesii in a subalpine old growth forest, central Japan

Author(s):

Kyoko KATO (The Institute of Low Temperature Science, Hokkaido University); Kenichiro SHIMATANI (The Institute of Statistical Mathematics); Shin-Ichi YAMAMOTO (Graduate School of Bioagricultural Sciences, Nagoya University)

Key words:

mortality; crown shape; competition; spatial pattern

Abstract:

Sapling bank dynamics were monitored under closed canopies and canopy gaps every year from 1997 to 2003 in an old-growth subalpine coniferous forest in central Japan. This paper explored basic dynamics traits such as mortality rates, recruitment rates and spatial patterns, focusing on the most dominant, shade-tolerant conifer Abies mariesii, then conducted mortality analysis using size-related, competition-related, growth-related and crown-shape-related variables. The yearly variation in sapling density was contrastive between the two canopy types, fluctuating under closed canopies and consistently decreasing in gaps. The mean mortality rates over the six growing seasons under closed canopies (1.55-3.89 % year-1) were lower than in gaps (5.36-9.66 % year-1). Comparisons of the above four variables between surviving and dead saplings suggested that the dead saplings grew very slowly with a shallow crown before death. Mortality and spatial pattern analysis revealed that asymmetric competition, suppression from taller saplings, is working in the A. mariesii sapling banks, albeit it weakly. The crown shape models exhibited the best performance of the four mortality models, possibly implying that mortality of the shade-tolerant A. mariesii does not simply depend on current/recent conditions but rather is related to conditions from the past to present, and that crown shapes partly reflect accumulated stress from the past.