Seedling regeneration on decayed pine logs after the deforestation events caused by pine wilt disease

Abstract

Fukasawa Y., 2016. Seedling regeneration on decayed pine logs after the deforestation events caused by pine wilt disease. Ann. For. Abstract. Coarse woody debris (CWD) forms an important habitat suitable for tree seedling establishment, and the CWD decay process influences tree seedling community. In Japan, a severe dieback of Pinus densiflora Sieb. & Zucc. caused by pine wilt disease (PWD) damaged huge areas of pine stands but creates huge mass of pine CWD. It is important to know the factors influencing seedling colonization on pine CWD and their variations among geographical gradient in Japan to expect forest regeneration in post-PWD stands. I conducted field surveys on the effects of latitude, climates, light condition, decay type of pine logs, and log diameter on tree seedling colonization at ten geographically distinct sites in Japan. In total, 59 tree taxa were recorded as seedlings on pine logs. Among them, 13 species were recorded from more than five sites as adult trees or seedlings and were used for the analyses. A generalized linear model showed that seedling colonization of Pinus densiflora was negatively associated with brown rot in sapwood, while that of Rhus trichocarpa was positively associated with brown rot in heartwood. Regeneration of Ilex macropoda had no relationships with wood decay type but negatively associated with latitude and MAT, while positively with log diameter. These results suggested that wood decay type is a strong determinant of seedling establishment for certain tree species, even at a wide geographical scale; however, the effect is tree species specific.

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

“…It has previously been reported that seedlings of Picea abies and P. jezoensis preferentially regenerate on logs that are dominated by white-rot fungi rather than brown-rot fungi (Bacˇe et al 2012;Ando et al 2017). Similarly, seedlings of Pinus densiflora are less likely to occur on brown-rotted logs (Fukasawa 2016) and exhibit faster growth on white-rotted logs than on soil (Fukasawa 2015). However, seedlings of Clethra barbinervis (Fukasawa 2012), Toxicodendron trichocarpum (also referred to as Rhus trichocarpa; Fukasawa 2016), and Cryptomeria japonica (Fukasawa and Komagata 2017; show the reverse trend, preferentially regenerating on brown-rotted logs over other the decay types.…”

“…Furthermore, CWD also plays an important role in forest recovery, as it functions as a seedbed for trees, particularly conifers in the genera Abies (Narukawa et al 2003), Picea (Ando et al 2017), Thuja (Scott and Murphy 1987), and Tsuga (Harmon and Franklin 1989). It has also been reported that the conifers Chamaecyparis obtusa and Cryptomeria japonica regenerate on CWD in rural forests in Japan (Yamamoto 1993;Ota et al 2012;Fukasawa 2016;Fukasawa and Komagata 2017;.…”

“…Recent studies have shown that the wood decay type also strongly affects the density of seedlings on logs (Bacˇe et al 2012;Fukasawa 2012Fukasawa , 2016Ando et al 2017;Fukasawa and Komagata 2017;. The wood decay type reflects the abilities of fungi to decay the different structural components of the wood (lignin and holocellulose) and is traditionally categorised into three types based on the physicochemical properties of the wood (Eaton and Hale 1993): white-rot, in which the wood becomes white and bleached (yellowish-or greyish-white), and breaks into fibrous fragments due to the fungi decaying the lignin and holocellulose in the middle lamella that connects the cell walls; brown-rot, in which the wood becomes reddish-brown and can be easily broken into cubical fragments due to the fungi decaying only the cellulose in the plant cell wall and not the lignin; soft-rot, which tends to occur under highmoisture conditions and in which the wood appears dullgrey to black with a muddy texture.…”

“…However, seedlings of Clethra barbinervis (Fukasawa 2012), Toxicodendron trichocarpum (also referred to as Rhus trichocarpa; Fukasawa 2016), and Cryptomeria japonica (Fukasawa and Komagata 2017; show the reverse trend, preferentially regenerating on brown-rotted logs over other the decay types. Thus, it appears that seedlings establish on particular decay types in a species-specific manner, although it is difficult to make any generalisations about this due to the limited number of tree species that have been examined to date (Fukasawa 2016).…”

Interactive effects of wood decomposer fungal activities and bryophytes on spruce seedling regeneration on coarse woody debris

“…Several factors such as CWD size (diameter, Takahashi 1994), bryophyte cover (Nakamura 1992;Iijima and Shibuya 2010), and wood decay class ) influence seedling colonization. In addition to these factors, recent studies reported that wood decay type is also a strong driver of seedling colonization (Bacˇe et al 2012;Fukasawa 2012;Fukasawa et al 2015;Fukasawa 2016).…”