Effects of micro-topographies on stand structure and tree species diversity in an old-growth evergreen broad-leaved forest, southwestern Japan

Tran Van Do,Tamotsu Sato,Satoshi Saito,Osamu Kozan,Hiromi Yamagawa,Dai Nagamatsu,Naoyuki Nishimura,Tohru Manabe

doi:10.1016/j.gecco.2015.06.010

Abstract

Stand structure and species diversity were studied in correspondence with micro-topographies in an old-growth forest in southwestern Japan. The study was conducted in a 200×200m2 permanent plot, which were divided into 400 subplots using grids of 10m×10m. Subplots were categorized to four micro-topographies as crest slope (CS), head hollow (HH), upper slope (US) and lower slope (LS), basing on slope of forest floor and plot position, and to two elevational zones as below 450 m and above 450 m. Tree censuses for all individuals with diameter at breast height (DBH) ⩾ 5 cm were conducted in 2009 and 2013. The results indicated that CS had subplot means of living stems, dead stems, DBH, basal area (G), and basal area increment (▵G) significantly higher than that in LS. While, means of recruited stems and Shannon diversity index were significantly lower. Comparing between below and above 450 m elevational zones indicated the significantly higher parameters of stand structure and species diversity in above 450 m elevational zone. The differences of edaphic conditions led to difference of density of living stems, species density, DBH, G, and ▵G among micro-topographies. Therefore, crest slope, upper slope, and higher elevational zones should be encouraged for the purposes of carbon accumulation and storage. While, the lower elevational zones should be used for the purposes of species diversity conservation.

Highlights

It is becoming increasingly apparent that plant communities change compositionally and structurally in response to biotic and abiotic factors
A total of 5268 stems (DBH ≥ 5 cm) was recorded in a 4-ha plot in 2013 census. These individuals belong to 55 species of families
Small size-stems of singleton species are vulnerable by typhoons (Sato et al, 1999), which usually happen in the present study site and cause the large and big trees falling, leading to its disappearance

Summary

Introduction

It is becoming increasingly apparent that plant communities change compositionally and structurally in response to biotic and abiotic factors. Micro-topography is a synthetic factor in governing stand structure and species diversity. The regime of land surface disturbance in relation to micro-topographies has been noted as an important factor affecting stand structure and species diversity (Kikuchi and Miura, 1993; Sakai and Ohsawa, 1994; Nagamatsu et al, 2003). Steep topography sites with high rainfall and strong typhoons mean that geomorphic processes are on occasion the critical factors determining vegetation patterns (Sakai and Ohsawa, 1993; Bellingham et al, 1996). Enoki et al (1996) concluded that tree species diversity was higher in lower slope than upper slope in secondary temperate forest, Japan. Basal area was lower in lower slope than upper slope (Enoki et al, 1996)

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