Lateral input of particulate organic matter from bank slopes surpasses direct litter fall in the uppermost reaches of a headwater stream in Hokkaido, Japan

Abstract

In forested streams, surrounding riparian forests provide essential supplies of organic matter to aquatic ecosystems. We focused on two pathways of particulate organic matter inputs: direct input from upper riparian forests and indirect lateral input from bank slopes, for which there are limited quantitative data. We investigated the inputs of coarse particulate organic matter (CPOM) and carbon and nitrogen in the CPOM into the uppermost reaches of a headwater stream with steep bank slopes in Hokkaido, Japan. CPOM collected by litter traps was divided into categories (e.g., leaves, twigs) and weighed. Monthly nitrogen and carbon inputs were also estimated. The annual direct input of CPOM (ash-free dry mass) was 472 g m -2 , a common value for temperate riparian forests. The annual lateral CPOM input was 353 g m -1 and 941 g m -2 when they were converted to area base. This value surpassed the direct input. Organic matter that we could not separate from inorganic sediments contributed to the total lateral input from the bank slopes (124 g m -1 ); this organic matter contained relatively high amounts of nitrogen and carbon. At uppermost stream reaches, the bank slope would be a key factor to understanding the carbon and nitrogen pathways from the surrounding terrestrial ecosystem to the aquatic ecosystem.

Plant litter dynamics in the forest-stream interface: precipitation is a major control across tropical biomes

“…and litter characteristics, understanding of which may require specific experimental studies 8 . Moreover, as many environmental factors can affect lateral litter transport, it is not surprising that a range of lateral litter contributions have been reported, from negligible amounts to even surpassing litterfall contributions (e.g., in mixed-hardwood forest 9 ; in tropical rainforests 12 ; in tropical savanna 13 ; and in broadleaf forests 56 ). These findings are supported by the higher variability of lateral litter inputs observed at smaller scales (86% of total at sampling sites or samplers), which suggest that local factors (e.g., riparian density, ground complexity, stream bank slope and litter characteristics) are more important than regional ones in driving its dynamics.…”

Multidisciplinary approach to assess the water self-depuration characteristics of Suquía River (Córdoba, Argentina)

“…We observed increases of all sediment OM fractions and soil labile OM during high-flow period in RS, indicating that it is the period of greatest deposition probably due to the major OM particulate input from vegetation residues falling into streams (Kochi et al 2010). Conversely, study sites' downstream anthropogenic sources present a reversed pattern: more sediment deposition during low-flow period.…”

“…Due to the low primary productivity of rivers, the major input of organic matter is allochthonous (Artigas et al 2009;Kochi et al 2010). Accordingly, in undisturbed environments the main sources of organic compounds are cellulose and lignin from riparian vegetation (Wallis et al 2009).…”

Seasonal variation in leaf-litter input and leaf dispersal distances to streams: the effect of converting broadleaf riparian zones to conifer plantations in central Japan

“…In the present study, bank slope gradients ranged from 6.0°to 18.5°at the three streams. Kochi et al (2010) reported that lateral litter input surpassed the direct input at streams with [45°bank slopes, whereas Kochi et al (2004) reported that direct leaf-litter input was larger than lateral input at 14°bank slopes. In the present study, the dominance of vertical over lateral inputs at the three streams was probably due to the gentle bank slopes (maximum of 18.5°) at these streams.…”

“…Vertical and lateral inputs were converted into an area basis per month (g m -2 month -1 ), and lateral inputs were multiplied by two (two stream sides) and divided by the average stream width (e.g., Kochi et al, 2010). To compare the seasonality change between deciduous broadleaf and sugi needle, three seasons were defined, correspondent to the variation in deciduous foliage: (i) leaf-falling season (leaf fall in October and November), (ii) dormant season (no leaves in the crown until the formation of new leaves from December to April), and (iii) foliated season (green leaves in the crown from May to September).…”