Mass, nitrogen content, and decomposition of woody debris in forest stands affected by excreta deposited in nesting colonies of Great Cormorant

First online: 14 March 2015Great Cormorant (Phalacrocorax carbo), a piscivorous bird, has established breeding colonies in a coniferous forest near Lake Biwa in central Japan. This study investigated the possible effects of the colony’s excreta on the mass, nitrogen (N) content, and decomposition of woody debris. Study plots were established in forest stands representing four stages from breeding colony establishment to post-abandonment. The mass of fallen branches (diameter 1–5 cm) and coarse woody debris (logs, snags, and stumps; diameter ≥10 cm) was greater in forest stands colonized by Cormorants than a control stand never colonized by Cormorants. This was primarily attributed to Cormorant activity that caused increased mortality of standing trees and by Cormorants breaking branches for nesting materials. Nitrogen content of branches and logs that had fallen to the forest floor was negatively correlated with the relative density of wood. Nitrogen content of branches was consistently higher (at a given value of relative density) in the colonized stands than in the control stand. The increase of branch N content was possibly caused by the incorporation of N into decomposing branches with excreta-derived N supplied as throughfall and/or soil solution. The mean value of 2-year mass loss of recently dead branches and logs was significantly greater for woody debris in the smallest diameter class but was not significantly different among the forest stands. This suggests that the excessive supply of excreta-derived N and concomitant enrichment of N in soil had negligible effects on the initial stages of decomposition of woody debris

Chemical property of live and dead leaves of tundra plant species in Oobloyah Valley, Ellesmere Island, high arctic Canada

The chemical property of live and dead leaves was investigated regarding 14 plant species, including shrubs, forbs, graminoids, and mosses. Leaves were collected from a deglaciated terrain in Ellesmere Island, high arctic Canada. The contents of organic chemical components (lignin, total carbohydrates, extractives), carbon, and nutrients (N, P, K, Ca, Mg) were examined and compared among the species. In general, forbs had high content of nutrients and low content of carbon and organic chemical components; shrubs had high content of carbon and lignin and low content of nutrients; graminoids had high content of total carbohydrates and low content of lignin and nutrients; and mosses had high content of total carbohydrates and markedly low content of nutrients. Principal component analysis showed separation of clusters of shrubs, forbs, graminoids, and mosses. The trend was generally similar between live and dead leaves

Diversity and functioning of fungi associated with leaf litter decomposition in Asian forests of different climatic regions

The pattern of diversity and functioning of fungi associated with leaf litter decomposition in Asian forests of different climatic regions was investigated by performing meta-analysis of published data for seven tree species in subalpine, temperate, subtropical and tropical forests. Fungal assemblages were examined by using common standard isolation-culture methods, and the abilities of individual fungal species to decompose leaf litter were examined with pure culture decomposition tests. The climatic patterns of diversity, assemblage structure and genus composition depended on the method of isolation: the washing method revealed no consistent pattern, whereas the surface sterilization method showed lower diversity and greater relative abundance of dominant fungal species within the assemblages in cooler climates. The decomposing ability of species within fungal assemblages was greater in warmer than in cooler climates and in broad-leaved than in coniferous tree species. In particular, the greatest abilities to cause mass loss were found among fungi with ligninolytic activity in broad-leaved tree species in warmer climates

Initial recruitment and establishment of vascular plants in relation to topographical variation in microsite conditions on a recently-deglaciated moraine on Ellesmere Island, high arctic Canada

We investigated the effects of topographical positions (moraine ridge, upper side slope and lower side slope) within a recently-deglaciated young moraine on initial recruitment and establishment of vascular plants. Compared with the moraine ridge, the upper slope had similar/higher abundance of vascular plants in terms of percent cover, frequency occurrence, species number, and density/biomass of a dominating species, Salix arctica. Establishment and growth of vascular plants are generally inhibited on unstable habitats; nevertheless, on this newly-formed moraine, every attribute measured for vascular plants implied a higher probability of vascular plant recruitment on the upper slope, where substrate is less stable than on the ridge. Further, the microsite with greater vascular plant abundance, S. arctica density and S. arctica aboveground/leaf biomass accumulated more organic materials regardless of topographical positions, and such an organic accumulation was deepest on the upper slope, suggesting that relatively-successful plant establishment occurs on this site. This is further supported by the S. arctica population structure, which implies a relatively-constant juvenile supply on the upper slope. Along a slope, unstable gravels easily slide down hill. This topographical process may cause large rock size and high surface cover by rocks on the lower slope. On the upper slope, the percent cover by rocks had therefore become smaller, leading to high cover by fine-grained sediments, which retain moisture favorable for germination and growth of vascular plants. This would enhance the emergence of pioneer vascular plant species, probably resulting in higher vascular plant abundance, density and biomass of S. arctica on the upper slope. This study suggests that during primary succession following deglaciation in the high arctic the upper slope of a newly-formed glacier moraine may be an important location for the initial recruitment and establishment of pioneer vascular plant species, such as S. arctica

Evaluation of host effects on ectomycorrhizal fungal community compositions in a forested landscape in northern Japan

Electronic supplementary material is available online at https://doi.org/10.6084/m9.figshare.c.4853145.Community compositions of ectomycorrhizal (ECM) fungi are similar within the same host taxa. However, careful interpretation is required to determine whether the combination of ECM fungi and plants is explained by the host preference for ECM fungi, or by the influence of neighbouring heterospecific hosts. In the present study, we aimed to evaluate the effects of host species on the ECM community compositions in a forested landscape (approx. 10 km) where monodominant forest stands of six ECM host species belonging to three families were patchily distributed. A total of 180 ECM operational taxonomic units (OTUs) were detected with DNA metabarcoding. Quantitative multivariate analyses revealed that the ECM community compositions were primarily structured by host species and families, regardless of the soil environments and spatial arrangements of the sampling plots. In addition, 38 ECM OTUs were only detected from particular host tree species. Furthermore, the neighbouring plots harboured similar fungal compositions, although the host species were different. The relative effect of the spatial factors on the ECM compositions was weaker than that of host species. Our results suggest that the host preference for ECM fungi is the primary determinant of ECM fungal compositions in the forested landscape