No. 975

Title:

The patch mosaic of an old-growth warm-temperate forest: patch-level descriptions of 40-years gapping processes and community structures

Author(s):

Tohru MANABE (Kitakyushu Museum of Natural History and Human History); Kenichiro SHIMATANI (The Institute of Statistical Mathematics); Satoko KAWARASAKI(Faculty of Science and Engineering, Seikei University); Shin-Ichi AIKAWA (Ibaraki University); Shin-Ichi YAMAMOTO (Graduate School of Bioagricultural Sciences, Nagoya University)

Key words:

ABIC, aerial photo, DBH, gap dynamics, height distribution, LTER, small-scale disturbance, subcanopy

Abstract:

1 An old-growth forest consists of various types of small patches, and when a major disturbance is a single tree-fall, the patch mosaic is closely associated with the gap dynamics. The structure of each patch reflects its own gapping process, which includes not only current light conditions but also, and more importantly, the environmental conditions occurring during several decades. This study reconstructed the gapping processes that had occurred during a 40-year period in patches of an old-growth, warm-temperate, evergreen broadleaved forest in southern Japan. We then examined the current community structure associated with each gapping process. 2 We selected eight patches based on: (1) changes in canopy heights estimated from four aerial photographs taken in 1966, 1983, 1993 and 1998, (2) long-term ecological research (LTER) monitoring records since 1990, and (3) a current field survey, so that each had experienced a characteristic gapping process. We also checked logs and stumps around the patches and associated these putative gap makers with the gapping processes inferred from the aerial photos. In addition, all living trees taller than 1.3 m were identified to species and their height and diameter at breast height (DBH) were measured. 3 Currently almost closed patches that were open in 1966 showed a rotated sigmoid or rotated sigmoid with two peaks in their height distributions, although their DBH distributions were just J-shaped. In contrast, two patches that had consistently been under closed canopies exhibited a similar size structure of gentle J-shapes. Currently opened patches had an enormous number of small trees, and their size distributions were sharply J-shaped, both for DBH and height. 4 Unlike the height distributions, for species composition there were no clear contrasts associated with the past gapping processes, except for the existence of fast-growing deciduous species in large, currently opened patches. 5 Our results revealed the high diversity in patch communities, and these are possibly because some aspects of within-patch dynamics, such as vertical competition and immigration of pioneer species are deterministic, while some events, such as the establishment of primary species are more stochastic, resulting in the complex patch mosaic of an old-growth forest.