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Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental contaminants known to be hazardous to human health. Pine needles and mosses are useful bio-indicators for assessing PAH pollutions; however, the differences in their PAH uptake mechanisms have not been sufficiently discussed. In this study, the properties of pine needles and mosses as bio-indicators of PAHs were investigated on the basis of differences in their PAH profiles. Five sets each of pine needle and moss samples were collected from circular sampling plots and analyzed for 16 PAHs. A comparison of PAH profiles revealed that the proportion of lower molecular weight PAHs (2 -3 aromatic rings; LMW PAHs) was significantly higher in pine needles (78.5% ± 4.8%) than in mosses (35.4% ± 6.8%). In contrast, the proportion of higher molecular weight PAHs (5 -6 aromatic rings; HMW PAHs) was lower in pine needles (4.3% ± 2.9%) than in mosses (25.1% ± 3.3%). Further, the combination of PAH isomer ratios showed that PAH sources between pine needles and mosses were not the same. These differences were explained by their uptake mechanisms and partly by the absorption of PAHs from soil particles by mosses. These findings indicate that pine needles are useful for assessing airborne LMW PAH pollution, whereas mosses can be integrated indicators for assessing complex HMW PAH pollution of the atmospheric and soil environments. On the basis of these properties, the usefulness of these bio-indicators should also be evaluated according to the objective of the assessment and the areas where they are applied.

Decaying logs are important seedbeds in boreal and subalpine forests. However, biotic and abiotic factors and their interactions related to seedling colonization patterns on logs remain unclear. In the present study, we evaluated the influence of bryophyte communities, wood decay type (white‐, brown‐, and soft‐rot) owing to decomposer fungal activities, and environmental abiotic factors on seedling establishment in an old‐growth subalpine coniferous forest in Japan. Among the tree species recorded on the conifer logs, Picea jezoensis var. hondoensis was the most dominant. Log surfaces were covered with distinctive patches of liverwort Scapania bolanderi and moss Pleurozium schreberi (approximately 33% cover for each). Redundancy analysis showed that brown‐rot in sapwood significantly affects the bryophyte and seedling community on the logs. Generalized linear models suggested that the total bryophyte cover, Scapania cover, and white‐rot in heartwood positively associate with Picea seedling density, whereas Pleurozium cover and basal area of adjacent Picea adults negatively associate with Picea seedling density. Results of structural equation modeling suggested that the brown‐rot of sapwood positively associates with Scapania cover that has a positive effect on Picea seedling density. Furthermore, brown‐rot of sapwood inhibited the Pleurozium cover, thus contributing to the Scapania dominance on the logs. These results suggest that fungal wood decomposer activities affect colonization of Picea seedlings in an indirect way via structuring bryophyte community on the logs.

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Drought-sensitive bryophytes are especially vulnerable to edge effects caused by forest fragmentation. Because of increased forest fragmentation, these bryophyte species are declining and are in need of conservation. Considering that a field survey including all bryophyte species is very time consuming, methods that make identification less difficult should be tested for their usefulness in conservation. This paper describes an alternative survey method that utilizes the correlation between bryophyte life-forms and microclimates for evaluating drought-sensitive bryophytes. This survey method was examined using epiphytic bryophyte flora on tree trunks in 27 fragmented forests of Kyoto city, in the western part of Japan. The usefulness of life-forms for this evaluation was discussed based on the correlation of life-forms with species richness and microclimates. The results indicated that, while life-from richness was considered to reflect the heterogeneity of moisture availability and light intensity in bryophyte habitats, a certain life-form category (for example, fans and dendroids) seemed to correlate with drought sensitivity of bryophytes. Considering this correlation, an alternative survey method was proposed that utilizes the richness of hygrophilous lifeforms. This survey method seems to be more cost-effective than a traditional all-species 3 survey, and provides an important step toward the conservation of drought-sensitive species.

Forests play crucial roles in regulating the amount and timing of streamflow through the water storage function. Bryophytes contribute to this increase in water storage owing to their high water-holding capacity; however, they might be severely damaged by climate warming. This study examined the water storage capacity (WSC) of bryophytes in forests in the mountainous areas of Japan. Sampling plots (100 m 2 ) were established along two mountainous trails at 200-m altitude intervals. Bryophytes were sampled in these plots using 100-cm 2 quadrats, and their WSC was evaluated according to the maximum amount of water retained in them (WSC-quadrat). The total amount of water in bryophytes within each plot (WSC-plot) was then calculated. The WSC-quadrat was affected by the forms of bryophyte communities (life forms) and their interactions, further influencing soil moisture. The WSC-quadrat did not show any significant trend with altitude, whereas, the highest WSC-plot values were obtained in subalpine forests. These changes to WSC-plot were explained by large differences in bryophyte cover with altitude. As the WSC controlled by the life forms might be vulnerable to climate warming, it can provide an early indicator of how bryophyte WCS and associated biological activities are influenced.Forests 2018, 9, 433 2 of 14 decade, while the shift to higher latitudes is estimated at 16.9 km per decade [17]. Under current climate change scenarios, one-tenth to one-half of global land might be highly or very highly vulnerable [18]. Temperate mixed forests, boreal conifer forests, tundra, and alpine biomes are considered the most vulnerable biomes to these changes [18]. The changes of forest ecosystems in response to climate warming might alter water yield, impacting water supply for human consumption [16].The response of vegetation to climate warming differs according to plant groups. Among plant groups, serious damage to bryophytes may arise due to their sensitivity to these changes because of their poikilohydric properties [19]. The water content of bryophytes is highly dependent on their external environment, decreasing rapidly when temperature rises and humidity drops [19,20]. The decrease in the water content leads to a shorter period of metabolic activity and tissue damage caused by drought stress [20]. As a result, bryophytes, especially those currently growing in environments with low drought stress, are sensitive to climatic warming that causes both thermal and drought stress [20,21].Although bryophytes are vulnerable to climate warming, they play important roles in increasing the water storage capacity of forest ecosystems [9,[22][23][24][25][26][27]. Because of their poikilohydric properties, bryophytes can retain relatively high amount of water within the community, ranging between approximately 200% and 3000% of their dry mass [25,28,29]. Their water storage capacity is severely reduced once they are water saturated [9]; however, they contribute towards buffering the influence of rainfall on forest ecosystems, especi...