Pine stumps act as hotspots for seedling regeneration after pine dieback in a mixed natural forest dominated by Chamaecyparis obtusa

Abstract

Over the past few decades, rural forest ecosystems in Japan have experienced dynamic vegetation changes due to forest dieback and changes in land use, leading to the loss of local species populations and biodiversity. The aim of this study was to evaluate the importance of pine (Pinus densiflora) stumps and logs for tree seedling regeneration in a mixed natural forest in Kyoto Prefecture, Japan, that had previously experienced severe pine dieback, and to determine which factors most greatly affect seedling establishment. Seedlings of 17 tree species were recorded on pine stumps and logs in later stages of decay, among which Chamaecyparis obtusa and Rhododendron reticulatum were most dominant. Both of these species had a greater density on pine stumps than on logs or soil, despite stumps covering less than 0.5% of the study area. In addition, the seedling densities of both species were positively associated with moss cover on coarse woody debris, but negatively associated with wood pH. Brown rot in the sapwood and heartwood, which occurred more frequently in stumps than in logs, also positively associated with the seedling densities of both species. Predictive modelling showed that C. obtusa seedlings exhibited a stronger response to pH in stumps than in logs. Therefore, since brown‐rotted wood is acidic due to fungal decay activities, brown‐rotted pine stumps may present hotspots of C. obtusa seedling regeneration at the study site.

Ecological impacts of fungal wood decay types: A review of current knowledge and future research directions

“…Among these species, the seedling density of Clethra barbinervis was greater on brownrotted pine logs than on white-rotted logs in a secondary mixed forest (Fukasawa, 2012). Similarly, the seedling densities of Cryptomeria japonica, Chamaecyparis obtusa, Toxicodendron trichocarpa, and Rhododendron reticulatum were positively associated with brown-rotted, but not whiterotted, pine logs at other forest sites (Fukasawa, 2016(Fukasawa, , 2018cFukasawa, Komagata, & Kawakami, 2017). Indeed, both the survival and growth rates of C. japonica seedlings were lower on white-rotted logs (Fukasawa & Komagata, 2017).…”

Which Is the Best Substrate to Regenerate? A Comparative Pot Experiment for Tree Seedling Growth on Decayed Wood and in Soil

“…japonica and Ch. obtusa seedlings on brown rot logs [8,24] might be attributable to mechanisms in other stages of seedling development, such as germination, or survival, and should be tested in future field experiments. Furthermore, we did not detect any effects associated with the substrates and sterilization in A. veitchii seedlings, suggesting that responses to the substrates and sterilization differ among seedling species within the same mycorrhizal type.…”

“…Several abiotic and biotic environmental conditions found in dead wood benefit seedlings of especially small-seeded tree species in boreal, subalpine, temperate, and tropical ecosystems [2]. For example, in boreal to temperate forests, the seedlings of the genera Picea, Abies, Tsuga, Cryptomeria, and Chamaecyparis among gymnosperms, and Betula, Clethra, and Sorbus among angiosperms, are often reported to regenerate on dead wood [1,[3][4][5][6][7][8]. The growth is stimulated by several factors, including more sunlight, stable moisture levels, fewer pathogens, less litter cover, and less root competition, which allow the seedlings to grow and survive better on dead wood than on the ground soil [1,7].…”

“…In the present study, pot experiments were conducted for the seedlings of two arbuscular mycorrhizal tree species, Cryptomeria japonica and Chamaecyparis obtusa, and two ectomycorrhizal tree species, Betula ermanii and Abies veitchii, to evaluate their growth on three substrates (brown rot wood and white rot wood of Pinus densiflora, and soil from a pine-dominated forest) in laboratory conditions. Seedlings of all these four trees are known to regenerate on dead wood [8,13,24,25]. Nutrient ion concentrations and fungal communities were also analyzed in the three substrates and their potential effects on seedling growth were discussed.…”

Perfect Poopers; Passerine Birds Facilitate Sexual Reproduction in Clonal Keystone Plants of the Boreal Forest Through Directed Endozoochory Towards Dead Wood

“…We also recorded five variables for explaining seedling establishment or bird usage at the stump level (Table 1): percentage cover of mosses and liverworts ('bryophytes') which can serve as seed traps and nurseries (Fukasawa, 2018) or act as barriers for seedling emergence (Zamfir, 2000); percent cover of vascular plants ('vascular') and plant litter ('litter') which both could potentially inhibit or facilitate seedling establishment (Xiong and Nilsson, 1999;Fukasawa and Ando, 2018); percent cover of bare decomposing wood for establishing seedlings or birds foraging for insects ('free niches'); and tree crown density ('shade') estimated as the mean of spherical densiometer measurements in four cardinal directions taken from a plot center (Lemmon, 1956).…”