Effects of stand, landscape, and spatial variables on bird communities in larch plantations and deciduous forests in central Japan

Abstract

We examined the effects of stand, landscape, and spatial variables on bird communities in deciduous forests and Japanese larch ( Larix leptolepis (Sieb & Zucc.) Gord.) plantations in a montane region of Nagano Prefecture, central Japan. We used plot-transect methods at 97 sites: 33 in winter 2003 and 18 sites were added in the 2004 breeding season in deciduous forests, and 32 in winter 2004 and 14 sites were added in the 2005 breeding season in larch plantations. Bird–environment relationships were explored using partial redundancy analysis and partial regression analysis. We used spatial variables derived from principal coordinates of neighbor matrices as explanatory variables to detect nonrandom spatial structure of bird communities. Variation in bird communities was mainly explained by stand and spatial variables for both forest types, whereas the effects of landscape variables were small. In plantations, important stand variables for both seasons included stand height, elevation, and the basal area of vines, whereas shrubs, dwarf bamboo ( Sasa senanensis (Franch. & Savat.) Rehd.), and larch snags were important in the breeding season. In deciduous forests, the most important stand variable for both seasons was the basal area of northern Japanese hemlock ( Tsuga diversifolia (Maxim.) Mast.) and Nikko fir ( Abies homolepis Sieb. & Zucc.) trees. Spatial variables showed that bird communities had large-scale (>10 km) spatial variation that could not be explained by stand or landscape variables.