Ecological functions of persistent Japanese cedar litter in structuring stream macroinvertebrate assemblages

Abstract

Stream macroinvertebrate assemblages are expected to be affected by the abundance and constitution of litter from surrounding forests. We compared forest floor cover, overland flow, stream environment, and stream macroinvertebrate assemblages between the catchments of a Japanese cedar plantation (CP) and a primary deciduous forest (DF). Both systems experience excessive deer browsing. Understory vegetation cover was higher in the DF than in the CP in summer, although cover was low (<20%), likely because of excessive deer browsing. Litter cover was much higher in the CP than in the DF in summer as a result of the long abscission period, low breakdown rate, and low dispersal rate of Japanese cedar litter compared to deciduous litter. Monthly overland flow was always lower in the CP than in the DF, and substrate size was smaller in the DF stream. In the CP, cedar litter accumulated in the stream, probably because of its low breakdown rate and morphology, and abundant shredder taxa characterized the macroinvertebrate assemblage. In contrast, abundant burrower taxa characterized the macroinvertebrate assemblage in the DF stream. These results imply that Japanese cedar litter functions in structuring the macroinvertebrate assemblage by supplying persistent food resources for detritivores, and by buffering fine sedimentation via overland flow under excessive deer browsing.

Calcium concentration in leaf litter affects the abundance and survival of crustaceans in streams draining warm–temperate forests

“…Recent studies have shown that the abundance or density of gammarid amphipods is significantly greater in streams that in drain Japanese cedar plantations than in those that drain deciduous broad-leaved forests (Hisabae, Sone & Inoue, 2010;Inoue et al, 2012;Sakai et al, 2013). These authors argue that greater invertebrate abundances/densities are the result of C. japonica litter Total calcium in water (μmol c L -1 ) Survival rate of Gammarus nipponensis P < 0.001 Fig.…”

Preferential flow mechanisms identified from staining experiments in forested hillslopes

“…Recent studies have shown that the influence of topsoil on runoff generation on hillslopes can be very important. Such studies have mostly focused on overland flow (Miyata et al, 2007;Miyata et al, 2009;Gomi et al, 2010), while biomat flow has received less attention (Sidle et al, 2007;Sakai et al, 2013). Hillslope soils play an important role in redistributing precipitation into runoff, which contributes to streamflow, as well as soil water that affects infiltration and lateral subsurface and preferential flow (Sidle et al, 2000;Sidle et al, 2001).…”

Seasonal variations of 137Cs concentration in freshwater charr through uptake and metabolism in 1–2 years after the Fukushima accident

“…This is attributable to longer periods of water submersion in the field, as Gomi et al (2018) showed that 240 days of submersion in streams decreased 137 Cs concentrations by 90% in Japanese cedar litter. In general, Japanese cedar litter is more persistent than broad-leaved deciduous litter is (Sakai et al, 2013); therefore, Cs leaching from litter may be prolonged, resulting in remarkably lower 137 Cs concentrations in aquatic litter.…”