Effects of subtle variation in forest canopy openness on cache pilferage and its implications for forest regeneration.

Scatter-hoarding rodents play important roles in plant regeneration and species coexistence in many forest ecosystems. Cache pilferage, the behavior of rodents seeking or relocating seeds cached by other individuals, is ubiquitous during the scatter-hoarding process. The effects of canopy openness on cache pilferage have received considerable attention, most of which have focused on the comparison between full canopy cover and completely open areas, such as forest gaps. However, little attention has been given to whether the subtle variation in forest canopy openness affects cache pilferage, although subtle variation in light environments exists in many forests, especially tropical and subtropical forests, where the overall canopy is large and the forest window is relatively small. Here, we directly tested these questions by simulating 400 artificial caches, each containing one seed from four selected tree species, in a subtropical forest in southwestern China. The overall canopy openness of the forest was relatively small (with a mean value of 11.1%), but subtle spatial variation still existed (ranging from 5.7% to 19.5%). Overall, caches with lower canopy openness were more likely to be pilfered and removed faster, although not all species showed the same pattern. Our study highlights that subtle variation in forest canopy openness, even in a closed primary forest, has significant effects on cache pilferage by rodents, which may influence the following seed germination and forest regeneration processes. Additionally, seedling species composition may further be altered because the canopy effects on cache pilferage are species-specific.

Habitat Degradation Facilitates the Invasion of Neophytes: A Resurvey Study Based on Permanent Vegetation Plots in Oak Forests in Slovenia (Europe).

The spread of neophytes (non-native plant species) challenges the conservation status and ecological integrity of forests, especially in lowland areas. Long-term resurvey studies are needed to evaluate the temporal dynamics of neophytes in forests; however, such data are scarce. In 2023, we resampled a set of 45 permanent vegetation plots (established in 1992/93) in two forest vegetation types: oak-hornbeam forests dominated by Quercus robur and colline oak-beech forests dominated by Q. petraea. Over the last 30 years, oak forests have experienced extensive oak tree mortality, with the degree of habitat degradation being greater in Q. robur forests. In the early 1990s, only three neophytes with low abundance were recorded across all plots. In the 2023 resurvey, the total number of neophytes increased to 22 species (15 herbaceous and 7 woody species), comprising 6.9% of the total species pool in the understory layer. The increase in the plot-level number and cover of neophytes was significant in plots dominated by Q. robur but not in those with Q. petraea. The most frequent neophytes were Impatiens parviflora (present in 31% of plots), Solidago gigantea (27%), Erigeron annuus (16%) and Erechtites hieraciifolia (16%). The richness and cover of neophytes were significantly affected by the tree layer cover (negative correlation) and the degree of soil disturbance (positive correlation). All neophytes established in disturbed patches, whereas the occurrence of I. parviflora was exceptional as it was able to colonize less degraded, shaded understory environments. Habitat degradation (the mortality-induced loss of stand-forming oak trees resulting in extensive tree layer cover decrease) emerged as a key driver promoting neophyte proliferation, coupled with the impact of management-induced disturbances affecting overstory and soil conditions. The spread is expected to continue or even intensify in the future because novel light regimes and disturbances make forest habitats less resistant to neophyte proliferation.

The influence of stand composition and season on canopy structure and understory light environment in different subtropical montane Pinus massoniana forests.

Canopy structure and understory light have important effects on forest productivity and the growth and distribution of the understory. However, the effects of stand composition and season on canopy structure and understory light environment (ULE) in the subtropical mountain Pinus massoniana forest system are poorly understood. In this study, the natural secondary P. massoniana-Castanopsis eyrei mixed forest (MF) and P. massoniana plantation forest (PF) were investigated. The study utilized Gap Light Analyzer 2.0 software to process photographs, extracting two key canopy parameters, canopy openness (CO) and leaf area index (LAI). Additionally, data on the transmitted direct (Tdir), diffuse (Tdif), and total (Ttot) radiation in the light environment were obtained. Seasonal variations in canopy structure, the ULE, and spatial heterogeneity were analyzed in the two P. massoniana forest stands. The results showed highly significant (P < 0.01) differences in canopy structure and ULE indices among different P. massoniana forest types and seasons. CO and ULE indices (Tdir, Tdif, and Ttot) were significantly lower in the MF than in the PF, while LAI was notably higher in the MF than in the PF. CO was lower in summer than in winter, and both LAI and ULE indices were markedly higher in summer than in winter. In addition, canopy structure and ULE indices varied significantly among different types of P. massoniana stands. The LAI heterogeneity was lower in the MF than in the PF, and Tdir heterogeneity was higher in summer than in winter. Meanwhile, canopy structure and ULE indices were predominantly influenced by structural factors, with spatial correlations at the 10 m scale. Our results revealed that forest type and season were important factors affecting canopy structure, ULE characteristics, and heterogeneity of P. massoniana forests in subtropical mountains.

Positive impact of postfire environment on bumble bees not explained by habitat variables in a remote forested ecosystem.

Bumble bees are important pollinators in temperate forested regions where fire is a driving force for habitat change, and thus understanding how these insects respond to fire is critical. Previous work has shown bees are often positively affected by the postfire environment, with burned sites supporting greater bee abundance and diversity, and increased floral resources. The extent to which fire impacts variation in bumblebee site occupancy is not well-understood, especially in higher latitude regions with dense, primarily coniferous forests. Occupancy models are powerful tools for biodiversity analyses, as they separately estimate occupancy probability (likelihood that a species is present at a particular location) and detection probability (likelihood of observing a species when it is present). Using these models, we tested whether bumblebee site occupancy is higher in burned locations as a result of the increase in canopy openness, floral species richness, and floral abundance. We quantified the impact of fire, and associated habitat changes, on bumblebee species' occupancy in an area with high wildfire frequency in British Columbia, Canada. The burn status of a site was the only significant predictor for determining bumblebee occurrence (with burned sites having higher occupancy); floral resource availability and canopy openness only impacted detection probability (roughly, sample bias). These findings highlight the importance of controlling for the influence of habitat on species detection in pollinator studies and suggest that fire in this system changes the habitat for bumble bees in positive ways that extend beyond our measurements of differences in floral resources and canopy cover.

Are Juglans neotropica Plantations Useful as a Refuge of Bryophytes Diversity in Tropical Areas?

Neotropical montane forests are considered biodiversity hotspots, where epiphytic bryophytes are an important component of the diversity, biomass and functioning of these ecosystems. We evaluated the richness and composition of bryophytes in secondary successional forests and mixed plantations of Juglans neotropica. In each forest type, the presence and cover of epiphytic bryophytes was registered in 400 quadrats of 20 cm × 30 cm. We analyzed the effects of canopy openness, diameter at breast height (DBH) and forest type on bryophyte richness, using a generalized linear model (GLM), as well as the changes in species composition using multivariate analysis. Fifty-five bryophyte species were recorded, of which 42 species were in secondary forests and 40 were in mixed plantations. Bryophyte richness did not change at forest level; however, at tree level, richness was higher in the mixed plantation of J. neotropica compared to the secondary forests, due to the presence of species adapted to high light conditions. On the other hand, bryophyte communities were negatively affected by the more open canopy in the mixed plantation of J. neotropica, species adapted to more humid conditions being less abundant. We conclude that species with narrow microclimatic niches are threatened by deforestation, and J. neotropica plantations do not act as refuge for drought-sensitive forest species present in secondary forests.

Relating leaf traits to seedling performance in a tropical forest: building a hierarchical functional framework.

Trait-based approaches have been extensively used in community ecology to provide a mechanistic understanding of the drivers of community assembly. However, a foundational assumption of the trait framework, traits relate to performance, has been mainly examined through univariate relationships that simplify the complex phenotypic integration of organisms. We evaluate a conceptual framework in which traits are organized hierarchically combining trait information at the individual- and species-level from biomass allocation and organ-level traits. We focus on photosynthetic traits and predict that the positive effects of increasing plant leaf mass on growth depend on species-level leaf traits. We modeled growth data on more than 1,500 seedlings from 97 seedling species from a tropical forest in China. We found that seedling growth increases with allocation to leaves (high leaf area ratio and leaf mass fraction) and this effect is accentuated for species with high specific leaf area and leaf area. Also, we found that light has a significant effect on growth, and this effect is additive with leaf allocation traits. Our work offers an approach to gain further understanding of the effects of traits on the whole plant-level growth via a hierarchical framework including organ-level and biomass allocation traits at species and individual levels.

Habitat loss and canopy openness mediate leaf trait plasticity of an endangered palm in the Brazilian Atlantic Forest.

Forest cover and light availability comprise key factors for plant establishment in tropical forests. In the Brazilian Atlantic Forest (AF), Euterpe edulis (Areacaceae) is an endangered and keystone food resource contributing to forest functionality. We investigated the influence of forest loss and light availability on leaf traits and acclimatization of young individuals of E. edulis in AF fragments. We aimed to understand (i) how canopy openness and transmitted light are affected by forest cover at the landscape scale and the individual palm level; and (ii) how local and landscape features, combined and separately, affect key leaf traits widely known to be related to plant growth. The study was carried out in 15 forest fragments, ranging from 16 to 97% of surrounding forest cover. In each fragment, we sampled 10-20 individuals of E. edulis and analyzed nine leaf traits related to morphological, biochemical and chemical aspects. We also took hemispherical photographs to estimate canopy openness on the top of each E. edulis and also within fragment plots. We found that young plants predominantly occurred in more shaded environments. Additionally, E. edulis succeeded to acclimate in six of the nine traits analyzed, with most traits being affected by local and landscape features. It is likely that the lack of variation in traits related to protection against herbivory are limiting the species establishment in highly deforested landscapes. Our results provide novel evidence that both landscape and local contexts affect the leaf traits of E. edulis young plants leading to biochemical, chemical and morphological adjustments.

Tree seedling trait optimization and growth in response to local-scale soil and light variability.

At local scales, it has been suggested that high levels of resources lead to increased tree growth via trait optimization (highly peaked trait distribution). However, this contrasts with (1) theories that suggest that trait optimization and high growth occur in the most common resource level and (2) empirical evidence showing that high trait optimization can be also found at low resource levels. This raises the question of how are traits and growth optimized in highly diverse plant communities. Here, we propose a series of hypotheses about how traits and growth are expected to be maximized under different resource levels (low, the most common, and high) in tree seedling communities from a subtropical forest in Puerto Rico, USA. We studied the variation in the distribution of biomass allocation and leaf traits and seedlings growth rate along four resource gradients: light availability (canopy openness) and soil K, Mg, and N content. Our analyses consisted of comparing trait kurtosis (a measurement of trait optimization), community trait means, and relative growth rates at three resource levels (low, common, and high). Trait optimization varied across the three resource levels depending on the type of resource and trait, with leaf traits being optimized under high N and in the most common K and Mg conditions, but not at any of the light levels. Also, seedling growth increased at high-light conditions and high N and K but was not related to trait kurtosis. Our results indicate that local-scale variability of soil fertility and understory light conditions result in shifts in species ecological strategies that increase growth despite a weak trait optimization, suggesting the existence of alternative phenotypes that achieve similar high performance. Uncovering the links between abiotic factors, functional trait diversity and performance is necessary to better predict tree responses to future changes in abiotic conditions.

Carabid Beetle Assemblages (Coleoptera: Carabidae) in a Seminatural Grassland and the Adjacent Old Beech Forest in Northeast Japan.

The decline and disappearance of seminatural grasslands in Japan have caused a reduction in plant and animal species inhabiting such grasslands. We aimed to understand the assemblage structure, species diversity, and distribution of carabid beetles in traditionally managed seminatural grasslands, by comparing with the adjacent old beech forest. We investigated the carabid beetle assemblages in a seminatural grassland maintained by prescribed burning and annual mowing, and the adjacent old beech forest in Yamagata Prefecture, northeast Japan. We recorded several forest species along with open habitat species and habitat generalists in the grassland, suggesting that forest species may utilize the adjacent grasslands as temporary habitats. Cluster analysis showed that the assemblage structure of carabid beetles in the grassland differed from that in the beech forest. There were no clear differences in the carabid assemblages between the burned grassland sites and the grassland sites mowed in July after burning. This suggests that the annual mowing had little influence on the response of grassland carabid species in parts of the grassland. We recorded Harpalus roninus (Coleoptera: Carabidae), a rare carabid species in Japan, indicating that this beetle can be a characteristic of the studied grassland. Redundancy analysis showed that the eight abundant grassland species were associated with canopy openness, grass height, and understory vegetation cover, whereas the five most common species recorded from the beech forest were associated with litter depth and soil moisture.

The impact of tree canopy structure on understory variation in a boreal forest.

Information on understory composition and its relationships with the overstory tree canopy, especially leaf area index (LAI), is crucially needed in, e.g., modeling land-atmosphere interactions and productivity of forests. There are also several global LAI products produced from satellite data which need to be validated with ground reference data. However, to date, only scarce field data on simultaneous structural properties of under- and overstory vegetation, and tree canopy LAI, have been available in boreal forests. This paper shows how understory composition and fractional cover of different species types varies in a boreal forest site, and how it is linked to structural properties of the tree layer. The study is based on 301 understory plots collected in an area of ∼16 km2 around Hyytiälä forestry field station, Finland (61°50'N, 24°17'E) in a southern boreal forest site. Forest understory plot data was accompanied with measurements of both standard forest inventory variables and optically-based canopy light transmittance data. Clear differences in average species composition between different site fertility types were observed, but also large variation within each site fertility type was noted. Forest understory composition was better correlated with structural forest canopy measures (e.g., tree canopy LAI, canopy cover, canopy openness) than with traditional forest inventory variables such as tree height or diameter. Forest canopy LAI and the fractional cover of understory were strongly related, especially in more fertile sites. Our results highlight the role of tree canopy structural metrics as modifiers of the understory light climate and growing conditions, also, in boreal forests.

Dataset of tree canopy structure and variation in understory composition in a boreal forest site.

A field data set from 301 forest plots was collected during peak-growing season (June 24 - July 17, 2013) around Hyytiälä forestry field station in Southern Finland (61° 50' N, 24° 17' E). For all plots, forest variables were collected following local forest inventory practice, and understory cover fractions were estimated using a traditional sampling quadrat. The understory layer in each plot was classified into four site fertility types: herb-rich, mesic, sub-xeric, and xeric. The upper understory layer fractional covers were estimated for: (1) dwarf shrubs, (2) pteridophytes and herbaceous species, and (3) graminoids, and the lower ground layer fractional covers for: (1) mosses, (2) lichens, and (3) litter (including all non-photosynthetic material). Canopy transmittance data were collected using two LAI-2000 device. The transmittance data were used to calculate effective leaf area index, true leaf area index, canopy openness and canopy cover for all plots. The data can be used to parameterize tree canopy and understory compositions in e.g., physically-based reflectance models, land surface models, and regional carbon cycle models. Interpretations of the results are provided in the related article [1].

How do silvicultural treatments alter the microclimate in a Central Amazon secondary forest? A focus on light changes.

Silvicultural treatments can change the microclimate inside tropical secondary forests and thus enable the artificial regeneration of ecologically and economically important tree species. Increasing levels of canopy tree refinement (diameter at breast height, DBH > 5 cm) were applied and combined with understory slashing to investigate how these silvicultural treatments affect the microclimate of a Central Amazon secondary forest. The refinement treatment was performed in six levels of basal area reduction (0, 20, 40, 60, 80, and 100%) in rectangular plots (2318 m2) and was equally divided in two subplots that did (understory slashed) or did not (control) receive the application of understory slashing. Canopy openness was estimated using hemispherical photography before treatment implementation and periodically over 26 months. Light transmittance, total daily irradiance, air temperature, air humidity and soil moisture were measured during two climatic seasons (Dry and Wet season) of the two years following the application of the treatments. Understory slashing doubled the canopy openness before the refinement and had an effective and persistent effect on canopy openness, light transmittance and total daily irradiance for the 26 months. Refinement increased canopy openness, light transmittance and total daily irradiance; however, after one year of treatment application, the effect was greater in understory slashed than in control subplots. In plots with higher basal area reduction (>60%), the understory slashed subplots total daily irradiance was 19% and 60% higher than control subplots after nine and 26 months, respectively. Refinement increased air temperature and reduced air humidity and soil moisture. The refinement of canopy trees and understory slashing change the microclimate (particularly light availability) in secondary forests and performed best when applied together. Silvicultural implications for sustainable secondary forest management and productive objectives are discussed.

Unraveling Shade Tolerance and Plasticity of Semi-Evergreen Oaks: Insights From Maritime Forest Live Oak Restoration.

Quercus spp. (oaks) are generally intermediate in shade tolerance, yet there is large variation within the genus in shade tolerance and plasticity in response to varying resource availability. Ecophysiological knowledge specific to semi-evergreen Quercus spp. from subtropical maritime forests is lacking relative to temperate deciduous oaks. We studied the influence of light availability and plant competition on leaf physiology and performance of semi-evergreen Quercus virginiana on a barrier island along the US southern Atlantic coast. Seedlings were underplanted in pine (Pinus taeda) plantation stands with varying overstory density (clear-cut, heavy thin, light thin, and non-thinned; creating a gradient of understory light availability) and vegetation (no competition removal or herbaceous competition removal) treatments. After 2 years, seedling survival was higher with increasing light availability (clear-cut = heavy thin > light thin > non-thinned). Seedling growth (i.e., diameter, height, and crown width) increased similarly with increasing thinning intensity, while vegetation control was mainly beneficial to seedling growth in clear-cuts. These responses were partially explained by foliar nitrogen and leaf trait measurements, which followed the same pattern. Q. virginiana seedlings demonstrated high plasticity in their ability to acclimate to varying resource availability, as indicated by light response curves, specific leaf area, stomatal density, stomatal pore index, and maximum theoretical stomatal conductance. Light compensation and saturation points illustrated seedling capacity to increase net CO2 assimilation with increased light availability. Leaves on trees in the high light environment had the highest net CO2 assimilation, stomatal density, stomatal pore index, maximum theoretical stomatal conductance, and lowest specific leaf area. Although we demonstrated the relative shade tolerance of Q. virginiana in lower light environments (i.e., heavy and light thin plots), this semi-evergreen species shows high plasticity in capacity to respond to varying resource availability, similar to other Quercus spp. from mesic and Mediterranean environments.

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The variation of forest canopy structure and understory light caused by natural or human disturbances might account for environmental heterogeneity and species diversity in the understory. These factors play an important role in driving the structure, process and pattern in forest ecosystem. We set up two 0.25 hm2 permanent plots in secondary Betula platyphylla-Populus davidiana forests on the Taoshan Forest Farm, one of which was thinned in 2012 and the other one remained natural. The canopy images of two plots were collected by hemispherical photography technology from 2012 to 2016 and 2018. Analysis of variance and Markov matrix were applied to examine the dynamics of canopy structure, understory light, and canopy closing process after thinning. The results showed that thinning was effective in adjusting canopy structure and understory light availability. Such process lasted for a long time and the adjusting effect decreased over time. After thinning, the change rate of canopy structure and understory light decreased over time. The tree canopy quickly closed during the first three years and then reached a stable state. Understory light availability was positively correlated with canopy openness and negatively correlated with leaf area index. The correlation between understory scattered radiation and canopy structural parameters was the strongest. The correlation between canopy structure and understory light in the thinning plot was stronger than that of the control plot. After thinning, the recovery rate of canopy structure was related to the canopy openness, with larger canopy openness being accompanied with higher recovery rate. Thus, less time was required for the transfer to smaller canopy openness. The Markov matrix model could simulate changes in distributions of canopy structure and could be used to predict the dynamics of the canopy structure.

Monitoring canopy recovery in a subtropical forest following a huge ice storm using hemispherical photography.

We estimated canopy structure and transmitted radiation using hemispherical photography in four monitoring years (2008-2010, 2016) following the 2008 huge ice storm in a subtropical forest in south China, so as to assess changes in canopy biophysical parameters during forest recovery from natural disturbance. Significant decrease in canopy openness (CO), transmitted direct radiation (TransDir), and transmitted diffuse radiation (TransDif), as well as significant increase in leaf area index (LAI), were found in the disturbed forest stand in the subsequent years following the ice storm, indicating rapid canopy recovery. In contrast, these biophysical parameters of the undisturbed forest stand were quite stable during the monitoring years. The strength of relationships between CO and other canopy biophysical parameters decreased in the disturbed stand along the monitoring years. The disturbed stand had common slopes for the CO-TransDir and CO-TransDif models in the first two monitoring years, but different slopes for the CO-LAI model between the first and the subsequent monitoring years, while the undisturbed stand had common slopes for all the regression models in the first three monitoring years following the huge ice storm. These results showed that stronger correlations of LAI or TransDir with CO were characteristic of less complex canopies, such as those damaged by disturbance; the sensitivity of transmitted radiation in response to CO decreased with canopy recovery. Our findings demonstrated that forests with different canopy structure varied in biophysical parameters, which can be quantified by hemispherical photography.

Sky-canopy border length, exposure and thresholding influence accuracy of hemispherical photography for complex plant canopies.

BACKGROUND: Hemispherical photography (HP) is a popular method to estimate canopy structure and understorey light environment, which analyses photographs acquired with wide view-angle lens (i.e. fisheye lens). To increase HP accuracy, the approaches of most previous studies were to increase the preciseness of exposure and thresholding of photographs, while ours quantified effects of canopy properties (gap fraction and length of sky-canopy border (SCB)) and errors of exposure and thresholding on the accuracy of HP. RESULTS: Through analysing photographs of real and model canopies, it was showed that HP inaccuracy resulted from the mismatch between exposure and thresholding rather than exposure or thresholding errors alone. HP inaccuracy was a function of the SCB length and the extent of exposure and thresholding errors, but independent of gap fraction. DISCUSSION: In photographs, SCBs are recorded as grey pixels which greyness is in between that of sky and canopy pixels. When there are exposure and thresholding errors, grey pixels are those prone to be misclassified in image analysis. Longer (vegetation with taller canopies) and wider (lower image sharpness) SCBs in photographs can both result in a higher amount of grey pixels and ultimately higher HP inaccuracy for a given extent of exposure and threshold errors. CONCLUSIONS: Using lenses with view angle narrower rather than that of fisheye lens can shorten the SCB length in photographs and in turn reduce HP estimation inaccuracy for canopy structure and understorey light environment. Since short SCBs and low levels of exposure and thresholding errors can both result in low HP inaccuracy, to identify the true performance of new exposure and thresholding methods for HP, photographs recording canopies with long SCBs and acquired with fisheye lenses should be used. Because HP inaccuracy in a function of the amount of grey pixels resulting from SCBs, the amount of these pixels in photographs can be used as a universal parameter to quantify canopy properties influential to HP estimation and in turn make cross-study comparisons feasible.

Burning intensity and low light availability reduce resprouting ability and vigor of Buxus sempervirens L. after clearing.

Thinning and prescribed burning are two common operations for reducing fuel accumulation and decreasing the intensity and severity of wildfires. However, the resprouting response of understory species may reduce the effectiveness of fuel load treatments and thus negatively affect the cost-benefit ratio of these treatments. This study focuses on Buxus sempervirens, a slow-growing, multi-stemmed tree species, frequently dominant in the understory of temperate European forests, which resprouts strongly after clearing or burning. The aim was to assess how light availability and burning influence resprouting ability (resprouting or not) and vigor (i.e. the growth of resprouts) after clearing B. sempervirens in thinned stands without slash removal (unburned) or with burning of slash residues (burned), two years after the treatments. All individuals studied resprouted shortly after clearing in unburned stands, whereas almost ca. 40% never resprouted in the burned stands. Fire intensity, measured at the base of 49 individuals, contributed to explaining the likelihood of mortality. The number of resprouts was directly influenced by the pre-treatment size of individuals, but this relationship was lower in burned stands. Fire intensity, recorded in 29 resprouted individuals, also influenced the number of resprouts. Post-treatment light availability, in addition to pre-treatment size, contributed to explaining the volume of the ten largest resprouts and the length of the largest resprout. No tradeoffs between the resprout number and the volume of the ten largest resprouts or the maximum resprout length were found. Our study suggests that burning after clearing reduces the resprouting ability of B. sempervirens. Moreover, avoiding affecting the canopy cover reduces its resprouting vigor and, consequently, increases the effectiveness of understory fuel load treatments.

The effects of within stand disturbance in plantation forests indicate complex and contrasting responses among and within beetle families.

Plantation forests with timber production as the major function are highly fragmented and disturbed regarding the tree species composition and stand area. Their closed canopies also have different microclimatic conditions compared with better studied conservation areas. We studied three beetle families (click, longhorn, and rove beetles) with different ecological demands in lowland plantation forests dominated by Sessile oak and Norway spruce in the Czech Republic. Our main interest was how their species richness, abundance, diversity, body length, rarity, red-list status, species composition and individual species were driven by the main tree species, stand area and canopy openness. We analyzed 3466 individuals from 198 beetle species and the results revealed complex and contrasting responses of the studied beetle families - click beetles mostly preferred sun-exposure and spruce as the dominant tree species, longhorn beetles mainly preferred large stands, whereas rove beetles were mostly influenced by oak as the dominant tree species and increasing area. We also observed that some species had different preferences in plantation forests than is known from the literature. The main conclusions of our results are that the dominance of non-natural spruce plantations and a large stand area (both originating from artificially replanted large clear-cuts) did not affect the majority of the studied taxa as we expected. On the other hand, our results might have been influenced by other factor, such as the current small total area of the former vegetation, which in the past might have led to extinction debt; or a large area of other conifers in the surroundings that might have promoted conifer-associated fauna.

A slow opportunist: physiological and growth responses of an obligate understory plant to patch cut harvesting.

Understory light environments change rapidly following timber harvest, and while many understory species utilize and benefit from the additional light, this response is not ubiquitous in shade-obligate species. I examined the effects of patch cut timber harvest on the physiology and growth of an obligate forest understory species to determine if disturbances via timber harvest are physiological stressors or whether such disturbances provide physiological benefits and growth increases in understory species. Forest canopy structure, along with photosynthesis, respiration, water use efficiency, stomatal conductance, and growth rates of American ginseng were quantified one summer before and two summers after patch cut timber harvest. Survival following timber harvest was lower than that observed at undisturbed populations; however, growth of survivors increased post-harvesting, with growth increasing as a function of canopy openness. Light response curves as well as photosynthesis and respiration rates indicated that plants were not well acclimated to higher light levels in the growing season after timber harvest, but rather to two growing seasons after harvest. Relative growth rate formed a positive linear relationship with maximum photosynthesis following timber harvest. My study suggests that ginseng is a "slow opportunist", because while it benefits from sudden light increases, acclimation lags at least one growing season behind canopy changes. American ginseng is surprisingly resilient in the face of a discrete environmental shift and may benefit from forest management strategies that mimic the natural disturbance regimes common in mature forests throughout its range.

Rapid assessment of forest canopy and light regime using smartphone hemispherical photography.

Hemispherical photography (HP), implemented with cameras equipped with "fisheye" lenses, is a widely used method for describing forest canopies and light regimes. A promising technological advance is the availability of low-cost fisheye lenses for smartphone cameras. However, smartphone camera sensors cannot record a full hemisphere. We investigate whether smartphone HP is a cheaper and faster but still adequate operational alternative to traditional cameras for describing forest canopies and light regimes. We collected hemispherical pictures with both smartphone and traditional cameras in 223 forest sample points, across different overstory species and canopy densities. The smartphone image acquisition followed a faster and simpler protocol than that for the traditional camera. We automatically thresholded all images. We processed the traditional camera images for Canopy Openness (CO) and Site Factor estimation. For smartphone images, we took two pictures with different orientations per point and used two processing protocols: (i) we estimated and averaged total canopy gap from the two single pictures, and (ii) merging the two pictures together, we formed images closer to full hemispheres and estimated from them CO and Site Factors. We compared the same parameters obtained from different cameras and estimated generalized linear mixed models (GLMMs) between them. Total canopy gap estimated from the first processing protocol for smartphone pictures was on average significantly higher than CO estimated from traditional camera images, although with a consistent bias. Canopy Openness and Site Factors estimated from merged smartphone pictures of the second processing protocol were on average significantly higher than those from traditional cameras images, although with relatively little absolute differences and scatter. Smartphone HP is an acceptable alternative to HP using traditional cameras, providing similar results with a faster and cheaper methodology. Smartphone outputs can be directly used as they are for ecological studies, or converted with specific models for a better comparison to traditional cameras.