Topographical variations in a plant–soil system along a slope on Mt Ryuoh, Japan

Abstract

The plant–soil system was studied at different topographic levels (i.e. ridge, backslope and footslope) along a slope in a Cryptomeria plantation. Soil solution chemistry at each representative topographic plot was investigated. Tree height and diameter of Cryptomeria decreased upslope. The understory species composition changed along the slope. The upper part of the slope with Oa horizon soil N transformation was characterized by ammonification, while most of the inorganic N in the lower part of the slope without Oa horizon was nitrified. The inorganic N form in the soil solution corresponded with soil N transformation. Ammonium was the dominant inorganic N at the ridge, while NO3 predominated at the foot of the slope. Soil solution chemistry was similar to throughfall at the ridge. At the foot slope, the chemical composition of the soil solution was different from throughfall due to high NO3− concentrations. This suggests that the inorganic N form regulated not only N concentration but also cation concentrations. The soil N transformation pattern is important in nutrient cycling.

The influence of topographic variation on forest structure in two woody plant communities: A remote sensing approach

“…Variation in topography (slope angle, aspect, or elevation) creates resources heterogeneity across the landscape. Topography generally influences changes in soil depth and soil composition, in water content and soil drainage, and in light availability (Bale & Charley, 1994;Chen et al, 1997;Bale et al, 1998, Olivero & Hix, 1998Galicia et al, 1999;Tokuchi et al, 1999). This patchy distribution of environmental resources often leads to complexity of forest structure and composition across a landscape.…”

Effects of mountain tea plantations on nutrient cycling at upstream watersheds

“…It is well established that watershed nutrient cycling is tightly linked to land use and that conversion of natural forests to agricultural lands causes nutrient enrichment, especially of N and P, in streamwater (Omernik, 1976;Johnes, 1996;Tilman et al, 2001;Murty et al, 2002;Allan, 2004;Uriarte et al, 2011;Evans et al, 2014). The impacts are likely exacerbated by steep slopes and high precipitation as residence time is reduced and leaching potential increased under such conditions (Brouwer and Powell, 1998;Tokuchi et al, 1999). Thus, mountain agriculture in the tropics and subtropics characterized with high precipitation is likely to have a substantial negative impact on ecosystem function.…”

Changes in nitrogen transformation in forest soil representing the climate gradient of the Japanese archipelago

“…Because mineralization and nitrification are both microbial processes, the rate of these processes is usually affected by fluctuations in the temperature and moisture of the soil, quality of organic matter, and microbe composition. Increased temperatures generally have the effect of increasing nitrogen mineralization and nitrification, and differences between soil moisture also affect the rate of nitrogen processing within the soil environment (Hirobe et al 1998;Tokuchi et al 1999;Tateno and Takeda 2003).…”