Ecological Research最新文献

Plateau pikas alter alpine meadow biodiversity and ecosystem functions via foraging, burrowing, and excretion. While plant and soil biodiversity synergistically regulate ecosystem multifunctionality (EMF), their relative contributions under varying pika densities remain unclear. Through a 5-year study on the Tibetan Plateau's eastern edge, we assessed pika disturbance effects on multi-trophic biodiversity (plants, earthworms, ciliates, fungi, bacteria) and EMF (biomass, soil nutrients). Results showed plant diversity exerted stronger EMF control than soil biodiversity across burrow density gradients. At 550 burrows/ha, EMF drivers shifted: soil biodiversity maintained positive correlations in low-density areas, while plant diversity dominated in high-density zones. Structural equation modeling further revealed density-dependent divergence in regulatory pathways—both plant and soil biological diversity showed significant positive correlations with pika density under low-density conditions, but these relationships inverted to negative correlations in high-density environments. In conclusion, plateau pika densities reaching 550 burrows/ha trigger a shift in dominant drivers of EMF. We recommend maintaining populations below this critical threshold to sustain functional gains while prioritizing plant diversity conservation in density-exceeding areas, thereby balancing ecological services and productivity in alpine meadows.

This study investigated seasonal variations in phototrophic biofilm communities at the entrance zone of Petnica Cave. Biofilm samples were collected from seven sampling sites over four seasons. Several parameters were measured at each site, including air temperature, relative humidity, light intensity, substrate temperature, and moisture content of both biofilm-covered and bare substrates, to assess their influence on species composition. Cyanobacteria were the dominant group. According to the redundancy analysis (RDA), coccoid and simple trichal Cyanobacteria predominated in winter, while heterocytous Cyanobacteria were more abundant in summer. Chlorophyta exhibited a relatively even distribution across all seasons. Principal component analysis (PCA) revealed that Cyanobacteria occurrence showed a positive correlation with the moisture content of both the biofilm and the substrate, whereas Chlorophyta demonstrated a negative correlation with these parameters. Despite the presence of core taxa in all seasons, additional taxa appeared seasonally, contributing to increased diversity. These findings highlight the importance of moisture for the composition and resilience of the biofilm and provide insights into the seasonal adaptations of microorganisms in the cave entrance zone ecosystem.

The taxonomic, phylogenetic, and functional beta diversity (BD_tax, BD_phy, and BD_fun, respectively) of flea faunas across host species, in seven continental sections from four continents, was partitioned into species (=flea) and local (=host) contributions. We asked (a) whether the same flea or host species contributed similarly to taxonomic, phylogenetic, and functional beta diversity within each continental section; (b) which flea and host traits drove their contributions to BD_tax, BD_phy, and BD_fun; and (c) whether the effects of these traits on flea and host contributions differed between continental sections. Although different fleas and hosts contributed differently to each beta diversity facet, contributions of the same species to BD_tax, BD_phy, and BD_fun were similar. The heterogeneity between flea faunas, harbored by different host species, was mainly due to the variation in flea species composition, with the distribution of phylogenetic lineages and functional attributes playing lesser roles. The host contributions to BD_phy and BD_fun were driven by phylogenetic and functional similarities between flea species. The relationships between flea traits and their contributions to BD_tax, BD_phy, and BD_fun were weak (if at all), whereas host contributions were mainly associated with the structure of flea faunas in terms of species richness, with the effect of functional host traits being weaker. The main geographic differences in flea and host contributions to BD_tax, BD_phy, and BD_fun were differential associations between these contributions and flea and host functional traits. We concluded that the between-host heterogeneity of flea faunas was driven by the interplay of ecological and historical processes.

Conifers generally exhibit narrow, deep crowns, whereas broadleaf trees typically form spherical crowns. A widely accepted hypothesis attributes this difference to variations in solar angles: conifers, which prevail in high-latitude regions with lower solar angles, optimize light capture differently than broadleaf trees, which dominate low-latitude areas with higher solar angles. Previous studies have suggested that differences in crown morphology mitigate light competition in mixed forests, facilitating coexistence and enhancing productivity. However, these studies relied on simplified structural models that did not fully account for the physiological constraints of crown morphology or the dynamics of crown competition. In this study, we employed the Spatially Explicit Individual-Based Dynamic Global Vegetation Model to examine the effects of crown morphology on competition dynamics and ecosystem productivity in mixed forests. The model incorporates novel elements: (1) competition for space during canopy expansion, (2) self-pruning due to shading (i.e., lower branch dieback), (3) reductions in crown basal area resulting from self-pruning, and (4) reductions in total leaf area per tree following basal area loss. A 100-year simulation of narrow- and wide-crown saplings with distinct crown morphologies revealed that their relative advantages depended on tree density, planting arrangement, solar angle, and the composition of solar radiation (i.e., direct vs. diffuse light). However, contrary to prior assumptions, negative frequency-dependent selection—expected to promote coexistence—was not observed. Moreover, crown shape diversity did not enhance forest productivity. These findings challenge previous models and suggest that factors beyond crown morphology may drive species coexistence and ecosystem productivity in mixed ecosystems.

Plant fine roots are an important component of the carbon cycle in ecosystems. Nondestructive methods, such as tracing fine roots in soil cross-section images, have become the mainstay of fine root dynamics analysis in recent years; however, manual tracing methods are slow and suffer from low consistency. To solve these problems, many artificial intelligence (AI)-based image segmentation methods using deep learning have been developed. We aimed to verify the segmentation accuracy of RootPainter, an AI-based software, in a real forest ecosystem and use it to estimate the production rate and turnover time. The images segmented by RootPainter contained many errors that led to overestimation. However, by manually eliminating the errors caused by incorrectly segmented roots in areas with no actual roots (a type of false positive, referred to as a “phantom error.”), segmentation accuracy was greatly improved. The AI-segmented area was 2.34 times larger than that of the conventional method, but after removing the phantom errors, it decreased to 1.21 times the size. The correlation coefficient between these areas also increased. In addition, the time required was 43%–47% less than that required by the conventional method. Furthermore, this hybrid AI segmentation and manual correction method could estimate production rates and turnover times from soil cross-sectional images of actual forests, and the results were comparable with those obtained using conventional methods. Thus, the AI-based segmentation software was shown to be effective in analyzing fine root dynamics using soil cross-section images in natural ecosystems, with appropriate human error-correction assistance.

Mast seeding in Norway spruce (Picea abies) provides an abundant food source for rodents, such as bank voles (Clethrionomys glareolus). While seed quantity effects are well known, intraspecific variation in seed palatability is not. In this study, I tested whether voles show preferences for spruce seeds from different batches of seeds (sampled from different mast years). In controlled trials, voles did not show significant preferences for seeds from different years, suggesting limited variation in seed characteristics detectable by voles. The results support that variations in the small spruce seeds may be primarily a quantitative burst of food (i.e., during mast seeding) rather than a qualitative variation that influences foraging behavior. Understanding these dynamics contributes to our knowledge of resource-driven rodent ecology and the role of mast seeding on granivore behavior.

Deer affect their habitats in various ways. Many previous studies on the ecological functions of deer have investigated the impact of herbivory on vegetation but have rarely focused on other functions. In this study, we evaluated the seed dispersal function of the sika deer (Cervus nippon yesoensis) in Hokkaido Island, examining the process from foraging to germination. We (1) surveyed the composition of seeds dispersed by wild deer, (2) measured seed recovery rate and gut passage time by feeding trials using three fleshy-fruited trees (Vitis coignetiae, Actinidia arguta, and Rosa rugosa), (3) conducted germination tests using defecated intact seeds, and (4) estimated seed dispersal distance and its seasonal changes using GPS movement data. In total, 73 seedlings of at least 10 species emerged from 181 fecal samples, each weighing ~1 g. The proportion of intact seeds after gut passage varied greatly with plant species and among trials (0.0%–55.0%). The germination rate of intact defecated seeds was similar to (R. rugosa and V. coignetiae) or higher (A. arguta) than that of manually washed seeds. The average seed dispersal distances during the resident period were 594 m for V. coignetiae and 610 m for A. arguta. The average seed dispersal distances during the migration period increased to 3140 m for V. coignetiae and 3617 m for A. arguta, and sometimes exceeded 18,000 m. These findings highlight that sika deer can disperse seeds over long distances, thus contributing to gene flow between distant populations and range expansion to suitable habitats.

Recent developments in Unmanned Aerial Vehicles (UAVs) and Light Detection and Ranging (LiDAR) technology have enhanced the ability to capture precise three-dimensional forest information at a lower cost. This article reports four types of high-resolution digital datasets derived from UAV-LiDAR measurements and associated fieldwork. The dataset includes 5 cm resolution Digital Terrain Models (DTMs) and Canopy Height Models (CHMs), ortho-mosaic photos with sub-2.7 cm resolution, and 4328 tree crown polygons with information on 151 species, stem girth at breast height, and canopy height. Data were collected from 22 approximately 1-ha long-term monitoring plots across Japan, spanning major climate zones from subtropical to subarctic. These plots encompass evergreen conifer, broadleaf and conifer mixed, deciduous broadleaf, and evergreen broadleaf forests. UAV surveys were conducted from May 2022 to October 2023. Based on these data, we also report basic profiles of these natural forests: a median slope of 22.2° (ranging from 2.5° to 35.0° across sites), median canopy height of 19.2 m (10.5–25.2 m), median maximum canopy height of 29.4 m (17.6–39.8 m), median gap ratios of 1.7% (0–10.7%) and 7.7% (0–28.9%) depending on gap definitions, and median crown area of 42.9 m² (10.7–80.2 m²) for canopy trees. This dataset is the first publicly available collection of forest structure and individual tree crown information for Japanese natural forests. We hope this dataset will be useful for a wide range of studies and analyses, from site-specific case studies to global-scale meta-analyses. The metadata is available in MetaCat in JaLTER at https://jalter.diasjp.net/data/ERDP-2025-04.

Solar radiation (SR) dynamics significantly influence plant growth, development, and ecosystems, serving as a primary energy source and an essential environmental signal. Plants sense SR through photoreceptors, with the ratios between specific wavelength ranges being particularly significant. Therefore, we refer to these as critical wavelength ratios (CWRs). The diffuse fraction of solar radiation (DF) is a key factor shaping light quality and distribution within the plant canopy. To evaluate the potential effects of DF and CWRs on plants in an outdoor environment, we analyzed 1 year of SR spectral data collected using a rotating shadow-band spectroradiometer in Fukuoka, Japan. Cloudy or partly cloudy skies dominated throughout the year. The ratios of UV-A/UV-B, red (R)/blue (B), and R/green (G) increased in winter and decreased in summer. In contrast, the ratios of photosynthetically active radiation (PAR)/global solar radiation (GSR), UV/GSR, UV/PAR, B/G, R/far-red, and UV-B/B increased during summer and decreased in winter. Most CWRs were significantly correlated with the DF. The clearness index (CI) exhibited a strong correlation with DF and CWRs. A synergistic effect of air mass (AM), atmospheric water vapor pressure (VP), and CI on specific CWRs was revealed. Future climate change-driven increases in VP and DF, coupled with reductions in CI, are expected to trigger complex changes in plant growth and flowering by altering light signals and enhancing photosynthesis through diffuse light fertilization. Integrating VP, AM, DF, and CI dynamics into climate models could enhance predictions of atmospheric, ecological, and plant physiological responses.