Forest In Taiwan Research Articles

The Limited Effect of Reduced Typhoon Frequency on Stream Hydrochemistry in a Subtropical Forest Watershed

AbstractTropical cyclones are often accompanied by large amount of precipitation potentially impacting stream hydrochemistry. Global warming is altering typhoon disturbance regime. Little is known about how cyclone changes, especially cyclone‐frequency reduction may affect stream hydrochemistry. In this study, we compared water and nutrient input via precipitation and output via streamflow between a frequent‐typhoon period (2013–2017), with 1.2 typhoon yr−1, and a no‐typhoon period (2018–2022) at a long‐term monitoring site, the Fushan Experimental Forest of Taiwan. Precipitation and streamflow quantities were not different between the two periods because typhoons increased the fluctuation but not the mean of monthly precipitation in the major typhoon months (July–September). Inputs of Mg2+, NO3−, and SO42− via precipitation were greater in the frequent‐typhoon period than the no‐typhoon period while inputs of other ions were not different between the two periods. Only the output of Mg2+ was different between the two periods, greater in the frequent‐typhoon period. Output/input ratio of NO3− was greater in the no‐typhoon period than the frequent‐typhoon period despite the greater input in the frequent‐typhoon period, while no differences were found for others. Increases in mineralization rates due to warming is suggested to be the cause of the greater NO3− output/input ratio during the no‐typhoon period. Relationships between stream discharge and ion export were similar between the two periods both with and without removing typhoon events. The limited variation in hydrochemistry between periods of contrasting cyclone activities suggests high resilience of the undisturbed subtropical forests to changes in cyclone frequency at the decadal scale.

Can immature stages be ignored in studies of forest leaf litter arthropod diversity? A test using Oxford Nanopore DNA barcoding

Abstract Forest soil and leaf litter support diverse arthropod mesofauna for which diversity dynamics is challenging to study due to the high number of species and specimens, small body size and limited taxonomic knowledge. Immature stages (larvae) are even harder to identify than adults, as their morphology is largely unknown. Therefore, larvae are often ignored, even though they may form a substantial proportion of specimens collected, are less mobile than adults and their exclusion may provide an incomplete diversity profile. Here, we use Oxford Nanopore DNA barcoding to investigate whether the inclusion of larvae provides a more complete taxonomic, phylogenetic and functional diversity profiles in leaf litter beetles (Coleoptera) from a subtropical forest in Taiwan. Our results indicate that larvae represent up to 38% of beetle specimens per sample, but most of them belong to 2–3 common species. Larvae of most beetle species are rarely collected repeatedly or in multiple specimens, possibly due to special habitat requirements or high seasonality. Taxonomic, phylogenetic and incidence‐based functional diversity measures were not affected by the exclusion of larvae in the Staphylinidae dataset but were strongly biased in all‐beetle dataset, especially when only common or abundant species were considered. Taxonomic beta diversity was not affected by the omission of larvae. Our results indicate that immature stages may be omitted in ecological studies of arthropods in case both adults and larvae co‐occur in the same habitat, and the sites are sampled repeatedly. Caution is needed (1) in groups in which larvae and adults do not inhabit the same environment or strongly differ in biology, (2) when rare species are omitted or (3) when functional diversity is calculated from abundance data.

Assessment of timber value and carbon credits provided by pure and mixed forests in Taiwan

IntroductionClear-cutting an even-aged pure forest is a conventional forest operation for wood production. However, this type of operation is unsuitable for sustainable management with multiple disadvantages. By contrast, mixed forests are a forestation strategy that accommodates diversity. This study aims to assess and compare the timber value and carbon credits of a pure forest and a mixed forest, which is transformed from a pure forest. Two alternative options in managing plantations of pure forest (with Cryptomeria japonica) and mixed forest (with part of C. japonica cut and Cinnamomum camphora replanted) are evaluated considering both timber value and carbon credits. Scenarios with various harvesting intensities and carbon payments were also considered.MethodA theoretical model was applied, converting pure forest into mixed forest, then two species are cut or replanted in the second round. By contrast, in the pure forest situation, the setting for the second rotation period is a pure forest for 20 years. The model was applied in a simulation experiment and the study area is Taiwan. The selected tree species are representative and have been chosen for analysis.ResultsThis study showed that even-aged pure forests had higher wood sales and lower carbon payments than uneven-aged mixed forests. The net present value from market value would be from −255,403 NTD ha−1 to −74,134 NTD ha−1 and that from carbon value will be from 156,076 NTD ha−1 to 208,937 NTD ha−1.DiscussionThis study showed strategies by which values could be increased during the transition from an even-aged pure forest to a mixed forest. Feasible methods included reducing the costs of reforestation, management, and cutting while increasing carbon prices to increase profits from wood and carbon income. A higher harvesting intensity could contribute to greater production and increase the area available for planting, resulting in greater profits from wood and carbon income.

Modeling of the Spatial Distribution of Forest Carbon Storage in a Tropical/Subtropical Island with Multiple Ecozones.

Visual data on the geographic distribution of carbon storage help policy makers to formulate countermeasures for global warming. However, Taiwan, as an island showing diversity in climate and topography, had lacked valid visual data on the distribution of forest carbon storage between the last two forest surveys (1993-2015). This study established a model to estimate and illustrate the distribution of forest carbon storage. This model uses land use, stand morphology, and carbon conversion coefficient databases accordingly for 51 types of major forests in Taiwan. An estimation in 2006 was conducted and shows an overall carbon storage of 165.65 Mt C, with forest carbon storage per unit area of 71.56 t C ha-1, where natural forests and plantations respectively contributed 114.15 Mt C (68.9%) and 51.50 Mt C (31.1%). By assuming no change in land use type, the carbon sequestration from 2006 to 2007 by the 51 forest types was estimated to be 5.21 Mt C yr-1 using historical tree growth and mortality rates. The result reflects the reality of the land use status and the events of coverage shifting with time by combining the two forest surveys in Taiwan.

Integrative systematics and conservation of endangered Carabus nankotaizanus (Coleoptera: Carabidae) in Taiwan

Abstract The endangered endemic ground beetle, Carabus nankotaizanus Kano, 1932 (Coleoptera: Carabidae), consists of 4 subspecies distributed across the lowlands to mountain forests of Taiwan. However, continuous morphological variation among the subspecies and large altitudinal range gaps between lowland and mountain populations of C. nankotaizanus raise questions concerning its species boundaries. We assessed the species boundaries between lowland and mountain populations of C. nankotaizanus using an integrative approach combining morphological, molecular, life-history, and ecological traits. Future suitable habitats were predicted using ecological niche models to evaluate the effect of range shifts driven by climate warming. The analyses of morphological and ecological traits indicate that the lowland and mountain populations of C. nankotaizanus are 2 distinct phenetic and ecological species. The molecular phylogeny further supported 4 divergent groups (paraphyletic C. nankotaizanus sp. 1 of the northern lowland + monophyletic C. nankotaizanus sp. 2 of the northern mountain, paraphyletic C. nankotaizanus sp. 3 of the southeastern lowland + monophyletic C. nankotaizanus sp. 4 of the mountain groups). We recommend the designation of the 4 cryptic C. nankotaizanus as candidate species and officially protected evolutionary lineages. Future range shifts of C. nankotaizanus sp. 1 to higher latitudinal lowlands of northern Taiwan may pose significant challenges to its conservation due to urban development and island boundary. By contrast, upcoming range shifts of the mountain C. nankotaizanus species to higher altitudes of protected national parks and forest reserves in the Central Mountain Range may not represent a major threat to its survival.

Applying PMP Discourse on the Forestry in Taiwan: The Position of Forest in Taiwan between 'Human-Nature Relationship Development' and 'Policy Localization Perspective' from the Academic Territorology and Administrative Management Concepts

Applying PMP Discourse on the Forestry in Taiwan: The Position of Forest in Taiwan between 'Human-Nature Relationship Development' and 'Policy Localization Perspective' from the Academic Territorology and Administrative Management Concepts

Source apportionment and evolution of N-containing aerosols at a rural cloud forest in Taiwan by isotope analysis

Abstract. Ammonium and nitrate are major N-containing aerosol components. The deposition of N-containing aerosols has impacts on regional ecology and the biogeochemical cycle. In this study, aerosols in a rural cloud forest (Xitou in Taiwan) were studied using 15N and 18O isotope analysis to assess the sources and formation pathways of the local N-containing aerosols linking to a metropolitan. Aerosol samples of different size ranges were collected using a micro-orifice uniform deposit impactor (MOUDI) on a half-day basis in December 2018. The chemical functional groups were analyzed using a Fourier-transform infrared spectroscopy with attenuated total reflection (FTIR-ATR) technique, while the isotope analysis was performed using a gas chromatography–isotope ratio mass spectrometer (GC–IRMS). The average measured aerosol concentration (PM10) was 0.98 (ranging from 0.15 to 3.31) and 0.25 (ranging from 0.00 to 1.51) µg m−3 for NH4+ and NO3-, respectively. In general, a higher concentration than nighttime was observed during the daytime by a factor of 1.5–6, likely due to the transportation of pollutants from upper-stream urban and industrial regions through the local sea breeze combined with valley wind. The presence of fog can further elevate the concentration by a factor of 2–3, resulting from the stronger inversion and lower boundary layer height. The higher NH4+ concentration in fine particles under foggy conditions corresponds to submicron-sized NO3- formation via aqueous-phase dissolution with NH4+ neutralization. Furthermore, the higher RH during fog events shifted the mass distribution of aerosol functional groups to a larger mode size. By comparing the δ15N value directly or through the analysis using a statistical isotope mixing model, MixSIAR, NH4+ probably originated from the industries, coal-fired power plants (CFPPs), or fertilizer plants, while NO3- might be contributed from the CFPP, industrial or urban sources. The overall δ18O of NO3- is +72.66 ‰ ± 3.42 ‰, similar to that in other winter Asian studies, suggesting the major formation pathway via O3 oxidation (δ18O=+72.5 ‰ to 101.67 ‰). However, a lower δ18O (<+67 ‰) for particles less than 0.56 µm during foggy daytime suggests the local contribution via the peroxyl radical oxidation before partitioning into aerosol phase under foggy conditions. Overall, the δ15N and δ18O distribution profiles as a function of particle size in the studied rural forest site reveal the evolution of aerosol composition from remote coastal regions with chemical processes along the transport process, which can be further affected by weather conditions such as fog events.

Roost Use of Operational Road Tunnels by Non-Cave Specialist Bats in a Subtropical Mountain Forest in Taiwan

It is known that the development of roadway systems can benefit bats, particularly cave- and crevice-roosting species, by providing novel roosting resources, e.g., abandoned tunnels and underpasses. However, the usage of operational road tunnels by bats, and its pros and cons are often overlooked. In the present study, we investigated bat diversity in 18 road tunnels in a subtropical forested mountain in Taiwan from 2018 to 2019. A total of 139 insectivorous bat sightings were recorded from 13 tunnels and 76.3% of the samples were identified to 12 species. Surprisingly, 75% of the species were previously regarded as non-cave specialists. Bat occurrences show spatial, temporal, and taxonomic aggregations as around 90% of the observations were contributed by four morpho-species from five tunnels in the summer and fall seasons. The among-site variations in species composition can be explained by tunnel morphology and presence of operational streetlight by the entrances. Since roadkill and grounded individuals, particularly juvenile Pipistrellus, were often found during surveys, these tunnels may act as ecological traps rather than suitable roosts to bats. Future confirmation of the roles of these tunnels to bats is necessary by measuring fitness through behavioral observations and long-term monitoring.

Interspecific competition and facilitation coexist in mixed‐species bird flocks of montane coniferous forests in Taiwan

Besides competition, positive interactions also play an important role in shaping the social structure of mixed‐species bird flocks. This study aimed to illuminate the interspecific interactions of competition and facilitation in mixed‐species bird flocks. We recorded the foraging behavior and microhabitat use of flocking species in montane coniferous forests of Taiwan under different social contexts. Foraging niche breadth and niche‐overlap with other flocking species were compared between individuals inside and outside of mixed flocks. For the three microhabitat variables (foraging locations, vertical strata and horizontal strata), relationships between niche‐overlaps of heterospecific pairs of these flocking species and their corresponding interspecific associations were determined using a simple linear regression. While in mixed flocks, two understory species, Taiwan fulvetta Fulvetta formosana and yellowish‐bellied bush warbler Horornis acanthizoides, shifted their foraging from shrubs upwards into coniferous trees. Meanwhile, flamecrests Regulus goodfellowi moved downwards vertically within the canopy, and black‐throated tits Aegithalos concinnus spread out horizontally along branches. In addition, flamecrests applied many more sally‐hovers inside of mixed flocks than outside of flocks. All four species are insectivores which might find it more difficult to obtain sufficient food during the colder winters when food resources become scarcer. Therefore, they may be using the increased vigilance afforded by the flock to expand their foraging niches and thus to increase their foraging opportunities inside mixed flocks. Furthermore, niche‐overlaps of heterospecific pairs of the 11 common flocking species were positively correlated with their corresponding interspecific associations on all three microhabitat variables. These results indicate that a greater foraging niche‐overlap between two flocking species would result in higher coexistence of the two species in mixed flocks. Consequently, facilitative interactions occurred in these mixed‐species flocks in addition to competitive interactions.

Intraseasonal interactive effects of successive typhoons characterize canopy damage of forests in Taiwan: A remote sensing-based assessment

Wind gusts and rainfall from tropical cyclones can heavily damage forest canopies, leading to abrupt changes in forest structure and tree demography. Although many studies have shown that successive tropical cyclones can interact with each other through residual effects, the role of past disturbances is unclear because they may lead to damage amplification of the second cyclone because of weakened forest structure, or damage reduction of the second cyclone because of previous damage to susceptible trees. We investigated the interaction between consecutive cyclones between 2001 and 2017 for five well-conserved forests in Taiwan, which experiences an average of 1.75 typhoons annually. Using MODIS imagery, we computed the typhoon-induced change of a canopy vegetation index, the Normalized Difference Infrared Index (NDII). The effects of successive typhoons were assessed separately for typhoons occurring within a single year (annual analysis) and within two consecutive years (biennial analysis). We used mixed effect models of reductions in NDII, a measurement of canopy damage, in relation to target and past typhoon characteristics and damage magnitude. NDII reduction induced by preceding typhoons was slightly more important and statistically significant in explaining the variation in NDII reduction associated with the target typhoon in the annual than in the biennial analysis, where the effect was non-significant. Canopy damage did not always decrease across typhoons occurring within the same season, however, for most successive typhoons in the biennial analysis, the second cyclone caused equal or less canopy damage (16 out of 21 typhoon pairs). These results support the idea that residual interactive effects of previous typhoons decrease quickly over time and rarely last for several typhoon seasons for Taiwanese forests, contributing to their high resistance to frequent typhoon disturbance.

USING LONG SHORT-TERM MEMORY MODEL FOR CLOUD FOREST VEGETATION GROWTH STATUS PREDICTION – A CASE STUDY IN SHEI-PA NATIONAL PARK

Abstract. Cloud Forests (CFs) are characterized by their persistent foggy environment, in which fog can save two times the amount of precipitation in the dry season and increase water storage by 10% in the rainy season. CFs play an important role in ecosystems as high biodiversity and abundant endemic species live within CFs. However, CFs are sensitive to environmental changes, especially in current global climate warming conditions. Therefore, a typical cloud forest in Taiwan, Shei-Pa National park, was chosen as the study area. Specifically, the Normalized Difference Vegetation Index (NDVI) with meteorological factors including rainfall, average temperature, maximum temperature, and minimum temperature were obtained to assess the overall CFs trend from 2001 to 2017. Moreover, the Long Short-Term Memory neural network model (LSTM) was implemented to predict the future vegetation status. Preliminary results have shown that vegetation condition in Shei-Pa National park was getting better; rainfall, average temperature, and minimum temperature represented an upward trend while maximum temperature showed a downward trend. Furthermore, the LSTM- maximum temperature model displayed the highest prediction power with the MAPE index of 4.84%. The results provide a valuable reference for forest resource conservation and future climate adaptation strategies in Taiwan.

Intelligent Survey Technologies and Applications for Urban Forests in Taiwan

Background: Roadside trees play an important role in urban landscaping. They are not only related to urban scenes, traffic safety, quality of life, and health, but also closely related to ecology and cultural development. Thus, effective, intelligent management of an area of urban roadside trees will become an important topic. Methods: This paper evaluates survey technologies and management techniques utilized in many cities of Taiwan, including surveys of roadside trees, risk assessment, and precious protected trees. A roadside tree management database was built using a geographic information system (GIS). Results: The number of urban forest trees exceeded 100,000 in our surveys, and many types of intelligent survey instruments were used to survey the trees, including real-time kinematic (RTK) and non-destructive detection instruments, radio frequency identification (RFID), in-vehicle light detection and ranging (LiDAR), and panoramic streetscape systems. A tree management system can be constructed by introducing the digitized information, which is based on a basic survey of trees. The survey stage primarily relies on manual surveys, in-vehicle LiDAR, and RFID, and then a visualized database retrieval system will be proposed using GIS. This system can be utilized for the health and foundation management of trees and the whole spatial planning of urban forests, among others. Conclusion: This research attempts to summarize the trends in intelligent management of urban forests using our practical experiences with the goal that it will be a reference for the future intelligent construction of urban forests.

The formation of "mega-flocks" depends on vegetation structure in montane coniferous forests of Taiwan.

A mixed‐species bird flock is a social assemblage where two or more bird species are moving together while foraging and might benefit from increased foraging efficiency and antipredator vigilance. A “mega‐flock,” which includes flocking species from different vegetation strata, often exhibits high species diversity. Mechanisms for the formation of mega‐flocks have not yet been explored. In this study, we evaluated the influence of vegetation structure and bird species diversity in driving the occurrence of mega‐flocks. We investigated the composition of mixed‐species flocks, local bird communities, and vegetation structure in five vegetation types of two high‐elevation sites in central Taiwan. Mega‐flocks occurred more frequently in pine woodland than later successional stages of coniferous forests. However, species richness/diversity of local bird communities increased along successional stages. Therefore, vegetation variables exhibit more influence on the occurrence of mega‐flocks than local bird communities. Besides foliage height diversity, understory coverage also showed positive effects on flock size of mixed‐species flocks. Our results indicated that pine woodlands with more evenly distributed vegetation layers could facilitate the interactions of canopy and understory flocks and increase the formation of mega‐flocks and thus the complexity of mixed‐species flocks.

Seedling survival simultaneously determined by conspecific, heterospecific, and phylogenetically related neighbors and habitat heterogeneity in a subtropical forest in Taiwan.

Density dependence and habitat heterogeneity have been recognized as important driving mechanisms that shape the patterns of seedling survival and promote species coexistence in species‐rich forests. In this study, we evaluated the relative importance of density dependence by conspecific, heterospecific, and phylogenetically related neighbors and habitat heterogeneity on seedling survival in the Lienhuachih (LHC) Forest, a subtropical, evergreen forest in central Taiwan. Age‐specific effects of different variables were also studied. We monitored the fates of 1,642 newly recruited seedlings of woody plants within a 25‐ha Forest Dynamics Plot for 2 years. The effects of conspecific, heterospecific, and phylogenetically related neighbors and habitat heterogeneity on seedling survival were analyzed by generalized linear mixed models. Our results indicated that conspecific negative density dependence (CNDD) had a strong impact on seedling survival, and the effects of CNDD increased with seedling age. Heterospecific positive density dependence (HPDD) and phylogenetic positive density dependence (PPDD) had a significant influence on the survival of seedlings, and stronger HPDD and PPDD effects were detected for older seedlings. Furthermore, seedling survival differed among habitats significantly. Seedling survival was significantly higher in the plateau, high‐slope, and low‐slope habitats than in the valley. Overall, our results suggested that the effects of CNDD, HPDD, PPDD, and habitat heterogeneity influenced seedling survival simultaneously in the LHC subtropical forest, but their relative importance varied with seedling age. Such findings from our subtropical forest were slightly different from tropical forests, and these contrasting patterns may be attributed to differences in abiotic environments. These findings highlight the importance to incorporate phylogenetic relatedness, seedling age, and habitat heterogeneity when investigating the impacts of density dependence on seedling survival that may contribute to species coexistence in seedling communities.

Bidirectional Turbulent Fluxes of Fog at a Subtropical Montane Cloud Forest Covering a Wide Size Range of Droplets

Size-resolved turbulent fluxes of fog droplets are investigated above a subtropical montane cloud forest in Taiwan. By integrating an aerosol spectrometer into an eddy-covariance set-up, we measure droplet number fluxes and liquid water fluxes in a size range of aerosol particles and droplets with diameters ranging from 0.25 {upmu }!mathrm{m} to 17.3 {upmu }!mathrm{m}. We find two flux-direction changes within this size range: a downward flux occurs for accumulation-mode aerosols of diameters between 0.25 {upmu }!mathrm{m} and 0.83 {upmu }!mathrm{m}, an upward flux occurs for hydrated aerosols with diameters between 1.1 {upmu }!mathrm{m} and 2.4 {upmu }!mathrm{m}, and a downward flux occurs again for activated fog droplets between diameters of 3 {upmu }!mathrm{m} and 17.3 {upmu }!mathrm{m}. The droplet size distributions can be modelled by a trimodal log-normal distribution, and the modes correlate with the different flux directions. The formation of the three modes and the establishment of the respective flux directions can be explained by combining the Köhler theory on the basis of measured ion concentrations in fog with the turbulent transport of droplets. Finally, from the combined analysis of droplet fluxes and size distributions, we infer relevant processes of droplet development and dissolving during various phases of the life cycles of the fog events.

Early Peak of Latent Heat Fluxes Regulates Diurnal Temperature Range in Montane Cloud Forests

AbstractHydro-climate in the montane cloud forest (MCF) regions is unique for its frequent fog occurrence and abundant water interception by tree canopies. Latent heat (LH) flux, the energy flux associated with evapotranspiration (ET), plays an essential role in modulating energy and hydrological cycles. However, how LH flux is partitioned between transpiration (stomatal evaporation) and evaporation (non-stomatal evaporation), and how it impacts local hydro-climate remain unclear. In this study, we investigate how fog modulates the energy and hydrological cycles of MCF by using a combination of in-situ observations and model simulations. We compare LH flux and associated micrometeorological conditions at two eddy-covariance sites—Chi-Lan (CL), a MCF, and Lien-Hua-Chih (LHC), a non-cloud forest in Taiwan. The comparison between the two sites reveals an asymmetric LH flux with an early peak at 9:00 in CL as opposed to LHC, where LH flux peaks at noon. The early peak of LH flux and its evaporative cooling dampen the increase in near-surface temperature during the morning hours in CL. The relatively small diurnal temperature range, abundant moisture brought by the valley wind, and local ET result in frequent afternoon fog formation. Fog water is then intercepted by the canopy, sustaining moist conditions throughout the night. To further illustrate this hydrological feedback, we used a land surface model to simulate how varying canopy water interception can affect surface energy and moisture budgets. Our study highlights the unique hydro-climatological cycle in MCF and, specifically, the inseparable relationship between the canopy and near-surface meteorology during the diurnal cycle.

High Rainfall Inhibited Soil Respiration in an Asian Monsoon Forest in Taiwan

Soil respiration represents the second largest carbon flux, next to photosynthesis of the terrestrial biosphere, and thus plays a dual role in regional and global carbon cycles. However, soil respiration in Asian monsoon forests with high rainfall has rarely been studied. In this study, we continuously measured soil respiration using a 12-channel automated chamber system in a 61-year-old Japanese cedar forest in central Taiwan with annual rainfall greater than 2500 mm. A 4-year (2011–2014) continuous half-hourly dataset was used to quantify the influences of soil temperature and moisture, especially rainfall events, on both total soil respiration (Rs) and heterotrophic respiration (Rh). The annual mean Rs was approximately 10.8 t C ha−1 (ranging from 10.7 to 10.9) t C ha−1, with Rh contributing approximately 74.6% (ranging from 71.7% to 80.2%). Large seasonal variations in both Rs and Rh were primarily controlled by soil temperature. Over 45.8% of total annual rainfall amounts were provided by strong rainfall events (over 50 mm), and over 40% of rainfall events occurred during summers between 2012 and 2014. These strong rainfall events caused rainwater to enter soil pores and cover the soil surface, which resulted in limited soil microorganism activity and, consequently, restricted CO2 production. The mean Q10 values were 2.38 (ranging from 1.77 to 2.65) and 2.02 (ranging from 1.71 to 2.34) for Rs and Rh, respectively. The Q10 values in this study, which were lower than in global forest ecosystems, may imply that the interannual Rs values observed in this study that were caused by high rainfall were less temperature-dependent than the Rs levels in global forest ecosystems. Both Rs and Rh were negatively correlated with soil moisture, which indicated that the soil moisture levels in the studied forest were usually under saturated conditions. These results also provide the lack of data for respiration in the Asian monsoon region under high-rainfall conditions.

Effect of Host, Environment and Fungal Growth on Fungal Leaf Endophyte Communities in Taiwan.

Fungal endophytes inhabit plant tissues without causing disease symptoms. They are highly diverse and distributed globally in all plants that have been investigated. Host, geographic, and environmental effects on endophyte communities have been reported in several studies, but the direct effect of fungal growth rate on endophyte composition has not been tested. To understand the relationship between foliar endophyte composition and fungal growth and to examine the effect of host, elevation, and climatic factors on the foliar endophyte communities, this study examined the foliar endophyte communities of representative gymnosperms and Rhododendron spp. across different elevations of Hehuanshan and Taipingshan forests in Taiwan. The isolation frequency and diversity of foliar endophytes were higher at low elevations than at high elevations. The foliar endophyte community structure differed as a function of host family and forest vegetation type. Elevation, mean annual temperature, and precipitation were significantly correlated with the community structure. Fungal growth rate was correlated with the endophyte abundance, which indicates that fast-growing fungi might have a competitive advantage when coexisting with other fungi in a plant host.

Assessing Typhoon-Induced Canopy Damage Using Vegetation Indices in the Fushan Experimental Forest, Taiwan

Cyclonic windstorms profoundly affect forest structure and function throughout the tropics and subtropics. Remote sensing techniques and vegetation indices (VIs) have improved our ability to characterize cyclone impacts over broad spatial scales. Although VIs are useful for understanding changes in forest cover, their consistency on detecting changes in vegetation cover is not well understood. A better understanding of the similarities and differences in commonly used VIs across disturbance events and forest types is needed to reconcile the results from different studies. Using Landsat imagery, we analyzed the change between pre- and post-typhoon VI values (ΔVIs) of four VIs for five typhoons (local name of cyclones in the North Pacific) that affected the Fushan Experimental Forest of Taiwan. We found that typhoons varied in their effect on forest canopy cover even when they had comparable trajectories, wind speeds, and rainfall. Most VIs measured a decrease in forest cover following typhoons, ranging from −1.18% to −19.87%; however, the direction of ΔVI–topography relationships varied among events. All typhoons significantly increased vegetation heterogeneity, and ΔVI was negatively related to pre-typhoon VI across all typhoons. Four of the five typhoons showed that more frequently affected sites had greater VI decreases. VIs ranged in their sensitivity to detect typhoon-induced changes in canopy coverage, and no single VI was most sensitive across all typhoons. Therefore, we recommend using VIs in combination—for example Normalized Difference Infrared Index (NDII) and Enhanced Vegetation Index (EVI), when comparing cyclone-disturbance-induced changes in vegetation cover among disturbances and across forests.

Natural Saponin Formosanin C‐induced Ferroptosis in Human Hepatocellular Carcinoma Cells Involved Ferritinophagy

Formosanin C (FC) is an anti‐tumor diosgenin saponin isolated from Paris formosana Hayata (Liliaceae) which is a perennial herb grown in the humid and dark forests of Taiwan at about the level of 1000 m. The plat has been used as a folk remedy for snake‐bite inflammation and tumors. FC is also a component of “Yunnan Bai Yao”, a traditional Chinese hemostatic medicine. Ferroptosis is a new form of iron‐dependent cell death, which occurs via an increased labile iron pool and lipid reactive oxygen species (ROS). Ferritinophagy is a ferritin (an iron storage protein) degradation pathway, depending on a selective autophagic cargo receptor nuclear coactivator 4 (NCOA4). Increased labile iron pool by ferritinophagy has been recognized as an upstream regulator of ferroptosis. Thus, ferroptosis has been reported to be a form of autophagic cell death. Although iron is an essential nutrient that facilitates cell proliferation and growth, overexpression of ferritin and down‐regulation of ferroportin (an iron export protein) has recently been observed in human hepatocellular carcinoma (HCC), indicating the increased dependence of iron in the cancer cells. In the present study, FC caused a significant dosage‐related population growth inhibition in HCC HepG2 and Hep3B cells using SRB assay, which can be partially blocked by co‐administration of ferroptosis inhibitor ferrostatin‐1 (a scavenger of lipid ROS). FC induced elevation in lipid ROS formation can also be partially reversed by addition of either ferrostatin‐1, or the presence of antioxidant vitamin C and/or vitamin E using flow cytometry, confirming FC‐induced ferroptosis. Flow cytometric analysis also revealed that FC elevated the percentage of acidic vesicular organelles‐positive cells, representing the formation of autolysosomes and induction of autophagic flux in both cell lines. The FC‐induced autophagy was confirmed using Western blotting, characterized by the production of LC3‐II and a further elevation of LC3‐II expression by addition of autophagy inhibitor bafilomycin A1 to prevent the fusion of autophagosomes and lysosomes for cargo degradation. In the present of bafilomycin A1, accumulation of NCOA4 and ferritin was observed in both FC‐treated cell lines using Western blotting. Concurrently, increase in co‐localization of LC3 puncta with NCOA4 or ferritin was exhibited using confocal microscopy, suggesting FC‐induced ferritinophagy. It is noteworthy that HepG2 cells with a higher NCOA4 expression were more sensitive to FC‐induced ferroptosis and autophagy compared to Hep3B cells with a higher ferritin expression. Overall, our data suggest chemotherapeutic potential of phytochemical FC for treatment of HCC with higher expression of NCOA4 via ferritinophagy and ferroptosis.Support or Funding InformationSupported in part by the Ministry of Science and Technology, Taiwan, No. MOST 106‐2320‐B‐003‐006‐MY3 and 107‐2320‐B‐003‐002‐MY2