Seedling establishment of late colonizer is facilitated by seedling and overstory of early colonizer in a post-mined peatland

Abstract

The seedling establishment of late colonizer may be promoted in the environments created by the early colonizer without interspecific seedling competition. To confirm the hypothesis, seed-sowing experiments were conducted in a post-mined peatland, northern Japan. Seeds on three grasses (Rhynchospora alba, Moliniopsis japonica and Phragmites australis) were sown in four vegetation sites: bareground, R. alba grassland, M. japonica grassland, and grassland mixed with three examined species. R. alba is the earliest colonizer, and M. japonica and P. australis are the later ones. Seedling emergence, survival, growth and resource allocation were monitored for two growing seasons. The seedling emergence of all the species was lowest on bareground. The emergence of R. alba and P. australis was high in R. alba and mixed grasslands, but was low in M. japonica grassland. M. japonica seedlings emerged more in vegetation with moderate plant cover and litter. R. alba seedlings yielded the highest biomass on bareground, and the biomass decreased with increasing shading. R. alba did not change resource allocation of height to above-ground biomass between vegetation types. The seedling biomass of M. japonica was affected little by shading, probably because M. japonica adjusted resource allocation with shading. In the two summers, R. alba and M. japonica seedlings survived more when the neighboring seedlings emerged more. P. australis seedlings failed in overwintering. The seedling characteristics of each species explained the species replacement, i.e., R. alba invaded bareground and facilitated the establishment of late colonizer, M. japonica, by the shelter effects of the overstory and seedling.