Spatial pattern of soil nitrogen availability and its relationship to stand structure in a coniferous‐broadleaved mixed forest with a dense dwarf bamboo understory in northern Japan

Abstract

Natural disturbances create spatial patterns of the ecosystem processes and functions in natural forests. However, how dynamics and the spatial structure of forests relate to soil nitrogen dynamics is not well understood. We examined the spatial relationship between the distributions of canopy and understory species, and soil nitrogen dynamics in a natural coniferous‐broadleaved mixed forest with a dense understory of Sasa dwarf bamboo in northern Japan. The O horizon was thick where coniferous litter predominated, and it was thin where broadleaved litter predominated. The soil water content was low in areas with a thick O horizon and a high abundance of coniferous trees. The soil nitrate content was low where the soil water content was low, and the soil nitrate content increased linearly with increasing net nitrification potential. These results suggest that the soil nitrate content under the coniferous canopy was lower because of the low nitrification potential of soil microbes in soils with low water contents. The soil nitrate content and nitrification potential were higher in the canopy gap than under the canopy. Our results suggest that forest structure, specifically the thickness of the forest floor, significantly affects the spatial pattern of the soil water content, thereby creating a spatial pattern of soil nitrogen availability at a relatively small scale with flat topography. The higher nitrification potential under the canopy gap could pose a long‐term risk of nitrate leaching because of the suppression of the natural regeneration of canopy species by dense Sasa dwarf bamboo in this forest ecosystem.

Impact of understory vegetation on soil carbon and nitrogen dynamic in aerially seeded Pinus massoniana plantations

“…In forest ecosystems, understory vegetation can be an important factor impacting soil C and N processes [ 9 ] as has been documented by previous studies [ 10 , 11 ]. While understory vegetation represents only a small portion of forest biomass, it plays an important role in maintaining biodiversity, ecosystem stability, and sustainable productivity of forest ecosystems [ 12 ].…”

“…However, the dependence of soil C and N processes on understory vegetation types are not thoroughly understood [ 13 ]. Studies have shown that understory vegetation types impact soil temperature and moisture [ 14 ], microbial richness and composition [ 15 – 18 ], and C/N ratios [ 11 , 13 , 19 ]. For example, Wu et al [ 20 ] reported that removing understory vegetation from Eucalyptus forest decreased root biomass and soil organic matter input, and hence altered soil microbial community structure.…”

Understory Vegetation Composition and Stand Are Mainly Limited by Soil Moisture in Black Locust Plantations of Loess Plateau

“…Forest vertical structure is shaped by species competition for light, water, and soil nutrients, as well as by forest succession and past disturbances [47]. Black locust canopy did not change significantly in the early stages of succession.…”

Short-term effects of thinning on the understory natural environment of mixed broadleaf-conifer forest in Changbai Mountain area, Northeast China

“…The natural mixed broadleaf-conifer forest is widely distributed throughout Europe, North America, and the Far East. It is also one of the main forest types in northeast China and makes an important contribution to the national economy for its large percentage of wood consumed for civil and national purposes (Chen et al, 2017; Inoue et al, 2017; Knoke et al, 2008; Li et al, 2014; Namikawa, Okamoto & Sano, 2000). The composition and structure of the forest type vary among regions.…”