Biology subjects

Zeleny, D.

Publications and source records attributed to Zeleny, D..

9 recordsLinked to original sources

bioRxiv2023

Vegetation of Chamaecyparis montane cloud forest in Lalashan Forest Dynamics Plot

To understand the vegetation-environment relationships within the Chamaecyparis montane mixed cloud forest in Taiwan, we established a 1-ha Lalashan Forest Dynamics Plot (LFDP) in northern Taiwan (24{degrees}42D N, 121{degrees}26D E). We established the plot in July 2019 and finished the first census of all woody species in August 2020. We collected environmental factors related to the topography and soil properties, measured microclimate and soil moisture within the plot, and collected further microclimatic data with a nearby weather station. In total, we recorded 5220 individuals belonging to 65 species, 42 genera and 29 families, with a basal area of 69.1 m2 ha-1, dominated by Chamaecyparis obtusa var. formosana, Rhododendron formosanum and Quercus sessilifolia. Modified TWINSPAN classified vegetation into three types (ridge, east-facing slope and valley). Unconstrained ordination showed that the main gradients behind compositional changes are related to windwardness and convexity. The prevailing wind direction in the area is from the northeast, linked to the winter monsoon. Both east-facing slope type and valley type have relatively lower temperatures than ridge type, especially during summer. Convexity is related to soil moisture gradient (from dryer convex to wet concave sites). Fog frequency is seasonal, with the highest values during autumn and winter months. From soil properties, pH is negatively and phosphorus is positively related to topographical convexity. Litter decomposition is linked to both topographical, soil and biotic variables. Collected data will serve as a baseline for future resurveys and monitoring changes within this montane cloud forest.

ecology↗

bioRxiv2023

The ecological characteristics of the safe sites for early-stage establishment of Chamaecyparis obtusa var. formosana seedlings in Taiwan

Chamaecyparis obtusa var. formosana is an ecologically and economically important species in Taiwan, with a high affinity for fog immersion. Our study aims to identify possible stress factors that induced seedling mortality and investigate how different ecological factors influence early-stage safe site requirements of the seedlings. We focused on the effect of large-scale climatic variables, small-scale microhabitat conditions, and biotic interactions on seedling survival and establishment by applying seasonal seedling survival monitoring and establishment survey on both regional and local scale. We identified two alternative ways of seedling death, by environmental-induced mortality and by herbivory. Opposite effects of the same environmental factors on different causes of mortality showed that seedlings might need to balance the risks posed by both causes to optimize their growing conditions. On a regional scale, we observed limited effect of regional climatic variables (namely fog frequency) on seedlings establishment and survival but noted a similar seasonal survival pattern among regions. We hypothesize that short-duration droughts during the transition from Plum rain to typhoon season is one of the key mechanisms of environmental-induced mortality. On a local scale, we found that decayed coarse wood debris (CWD) facilitates seedling establishment by providing a "safe site", likely due to increased colonization of small-stature bryophytes and decreased litterfall accumulation. The effect of bryophytes on seedling establishment varies depending on their thickness, with thicker ones having stronger negative effects. Aside from the bryophytes, the accumulation of litter significantly hindered seedling establishment. We argue that to safeguard the regeneration of Chamaecyparis obtusa var. formosana population, preserving CWD in the forest floor as a safe site for the seedlings after tree-replacing disturbance in natural forests is essential, particularly under ongoing climate change where more frequent and prolonged drought events are predicted. HighlightsO_LIOn a local scale, decayed coarse wood debris (CWD) provides "safe site" for the establishment of Chamaecypairs obtusa var. formosana seedlings. C_LIO_LIRegional climatic variables had limited effects on seedlings, but all regions had similar seasonal patterns of seedling mortatlity. C_LIO_LIFacilitation effect of small-stature bryophytes and litterfall avoidance might be the underlying mechanisms behind CWD safe sites. C_LIO_LIPreserving CWD for seedlings is important in the context of predicted prolong drought events under ongoing climate change. C_LI

ecology↗

bioRxiv2021

Extending the CWM approach to intraspecific trait variation: how to deal with overly optimistic standard tests?

Community weighted means (CWMs) are widely used to study the relationship between community-level functional traits and environment. For certain null hypotheses, CWM-environment relationships assessed by linear regression or ANOVA and tested by standard parametric tests are prone to inflated Type I error rates. Previous research has found that this problem can be solved by permutation tests (i.e. the max test). A recent extension of the CWM approach allows the inclusion of intraspecific trait variation (ITV) by the separate calculation of fixed, site-specific, and intraspecific CWMs. The question is whether the same Type I error rate inflation exists for the relationship between environment and site-specific or intraspecific CWM. Using simulated and real-world community datasets, we show that site-specific CWM-environment relationships have also inflated Type I error rate, and this rate is negatively related to the relative ITV magnitude. In contrast, for intraspecific CWM-environment relationships, standard parametric tests have the correct Type I error rate, although somewhat reduced statistical power. We introduce an ITV-extended version of the max test, which can solve the inflation problem for site-specific CWM-environment relationships and, without considering ITV, becomes equivalent to the "original" max test used for the CWM approach. We show that this new ITV-extended max test works well across the full possible magnitude of ITV on both simulated and real-world data. Most real datasets probably do not have intraspecific trait variation large enough to alleviate the problem of inflated Type I error rate, and published studies possibly report overly optimistic significance results.

ecology↗

bioRxiv2021

Do forest over- and understory respond to the same environmental variables when viewed at the taxonomic and trait level?

While the relative importance of climate filtering is known to be higher for woody species assemblages than herbaceous assemblage, it remains largely unexplored whether this pattern is also reflected between the woody overstory and herbaceous understory of forests. While climatic variation will be more buffered by the tree layer, the understory might also respond more to small-scale soil variation, next to experiencing additional environmental filtering due to the overstorys effects on light and litter quality. For (sub)tropical forests, the understory often contains a high proportion of fern and lycophyte species, for which environmental filtering is even less well understood. We explored the proportional importance of climate proxies and soil variation on the species, functional trait and (functional) diversity patterns of both the forest overstory and fern and lycophyte understory along an elevational gradient from 850 to 2100 m a.s.l. in northern Taiwan. We selected nine functional traits expected to respond to soil nutrient or climatic stress for this study and furthermore verified whether they were positively related across vegetation layers, as expected when driven by similar environmental drivers. We found that climate was a proportionally more important predictor than soil for the species composition of both vegetation layers and trait composition of the understory. The stronger than expected proportional effect of climate for the understory was likely due to fern and lycophytes higher vulnerability to drought, while the high importance of soil for the overstory seemed driven by deciduous species. The environmental drivers affected different response traits in both vegetation layers, however, which together with additional overstory effects on understory traits, resulted in a strong disconnection of community-level trait values across layers. Interestingly, species and functional diversity patterns could be almost exclusively explained by climate effects for both vegetational layers, with the exception of understory species richness. This study illustrates that environmental filtering can differentially affect species, trait and diversity patterns and can be highly divergent for forest overstory and understory vegetation, and should consequently not be extrapolated across vegetation layers or between composition and diversity patterns.

ecology↗

bioRxiv2021

Comparing trait syndromes between Taiwanese subtropical terrestrial and epiphytic ferns and lycophytes at the species and community level

Background and AimsWhile functional trait-trait and trait-environment relationships are well studied in angiosperms, it is less clear if similar relationships, such as the leaf economics spectrum (LES), hold for ferns, and whether they differ between terrestrial and epiphytic fern communities. We used vegetation data collected along an elevation gradient in Taiwan to explore these relationships. MethodsWe measured nine leaf traits for 47 terrestrial and 34 epiphytic fern species across 59 vegetation plots along an elevation gradient in the subtropical forest of Northern Taiwan. We explored trait-trait and trait-environment relationships at both the species and community levels for both growth habits, while accounting for phylogenetic relationships. Key ResultsEpiphytes differed from terrestrial ferns in species- and community-level trait values, mainly reflecting responses to higher drought and nutrient stress. The angiosperm LES was reflected in the trait-trait correlations of terrestrial ferns and less expressively in epiphytes. This pattern suggests that mainly water rather than nutrient availability shapes epiphytic trait patterns. Trait-trait analysis on raw trait data and on independent contrasts vary in some ways. Trait-environment relationships were similar for several drought-related traits across both species groups. ConclusionsThis study illustrates that fern trait patterns are not entirely equivalent for epiphytic and terrestrial species or communities and should not be extrapolated across growth habits or between the species and community levels. Phylogenetic constraints may influence the trait-environment response of epiphytic species.

ecology↗

bioRxiv2021

Sticking around: plant persistence strategies on edaphic islands

O_LISpecies extinction risk at local scales can be partially offset by strategies promoting in-situ persistence. We explored how persistence-related traits of clonal and non-clonal plants in temperate dry grasslands respond intra- and interspecifically to variation in environmental conditions (soil, climate) and insularity. C_LIO_LIWe focused on edaphic island specialist species, hypothesizing that plants experiencing harsh soil environments and strong insularity are distinguished by traits supporting enhanced persistence, such as small stature, long lifespan and resource-conservative strategies. We used linear mixed-effect models and bivariate ordinary least squares linear models to explore the response of species triats to environmental and biogeographic predictors. C_LIO_LIWe found general support for this hypothesis. Soil properties and insularity emerged as the most important drivers of trait patterns. However, clonal species showed more consistent responses to variation in environmental conditions and insularity than non-clonal plants, which were characterized by distinct species-specific responses. C_LIO_LISoil properties and insularity confirmed their major role in shaping the persistence strategies of edaphic island plant species. These drivers may exert their effect on specific functions (e.g. belowground resource conservation captured by BDMC). Additionally, we unambiguously identified that clonal species had different persistence strategies than non-clonal ones. C_LI

ecology↗

bioRxiv2021

Insularity forcing on plant persistence strategies in edaphic island systems

AimTrait-based approaches are increasingly implemented in island biogeography, providing key insights into the eco-evolutionary dynamics of insular systems. However, what determines persistence of plant species once they have arrived and established in an island remains largely unexplored. Here, we examined links between non-acquisitive persistence strategies and insularity across three terrestrial edaphic island systems, hypothesising that insularity promotes strategies for local persistence. LocationEurope: Western Carpathians, Moravia, and Cantabrian Range. Time periodPresent. Major taxa studiedVascular plants. MethodsFor each system, we used linear models at the island scale to test whether persistence-related plant trait patterns (average trait values and diversity) depend on three insularity metrics (island size, isolation and target effect). We focused on patterns of edaphic island specialists because, in contrast to matrix-derived species, their presence is confined to the edaphic islands. ResultsWe found that insularity metrics explained large proportions in the variation of the average and diversity of persistence-related traits of edaphic island specialists. Insularity was associated with a decline in the proportion of island specialists that have clonal abilities, yet it affected trait values of specialists towards enhanced abilities to persist locally (e.g. more extensive lateral spread) while reducing trait variability. Higher degrees of insularity within the systems were translated to stronger effects on functional trait patterns. Main conclusionsInsularity affects plant species diversity, distribution and forms in terrestrial island-like systems, similarly as it is assumed for true islands. Insularity - measured using a single (island size, isolation) or combined (target effect) predictors - may operate selecting for enhanced and less diverse persistence strategies. Ultimately, this process, which we call insularity forcing, operates as a selective process to promote species ability to avoid local extinction and to persist on terrestrial islands.

ecology↗

bioRxiv2021

Climate fluctuations drive the recruitment and growth of temperate grassland plants

Recent climate warming is associated with the increasing magnitude and frequency of extreme events, including heatwaves and drought periods worldwide. Such events can have major effects on the species composition of plant communities, hence on biodiversity and ecosystem functioning. Here we studied responses of Central European dry grassland plants to fluctuating temperature and precipitation over the last thirty years with monthly temporal resolution. We assessed the seasonal and annual dynamics of plant recruitment and growth based on the analysis of annual growth rings from the root collar. Although most studies so far applied such methods to trees and shrubs, we focused on typical grassland plants, two forbs and two chamaephytes. We related the recruitment and annual growth to monthly and annual precipitation, temperature and aridity between 1991 and 2019. We revealed species-specific responses, namely the (i) recruitment of deep-rooted, heavy-seeded species was positively affected by precipitation in both late winter-early spring and summer, whereas recruitment of shallow-rooted, light-seeded species was weakly influenced by climate fluctuations; (ii) growth of shallow-rooted species was more adversely affected by high summer temperature and drought than the growth of deep-rooted species. The population age structure of all the studied species was affected by the climate of the past decades. Most individuals established in the wet period of the 2000s, fewer in the precipitation-poorer 1990s, and the establishment was considerably reduced in the dry and warm period of the 2010s. Our findings indicate that the change towards warmer and drier climate has a profound effect even on drought-adapted ecosystems such as temperate dry grasslands. However, plant responses to various climatic extremes are species-specific, depending on their characteristics, such as life form or rooting depth. Consequently, the ongoing and anticipated climate warming will likely result in complex changes in species composition and other ecosystem properties of temperate grasslands

ecology↗

bioRxiv2018

Which results of the standard test in community weighted mean approach are too optimistic?

QuestionsCommunity weighted mean (CWM) approach analyses the relationship species attributes (like traits or Ellenberg-type indicator values) to sample attributes (environmental variables). Recently it has been shown to suffer from inflated Type I error rate if tested by standard parametric or (row-based) permutation test. Results of many published studies are likely influenced, reporting overly optimistic relationships that are in fact merely a numerical artefact. Can we evaluate results of which studies are likely to be influenced and how much?\n\nMethodsI suggest that hypotheses commonly tested by CWM approach are classified into three categories, which differ by assumption they make about the link of species composition to either species or sample attributes. I used a set of simulated and one simple real dataset to show how is the inflated Type I error rate influenced by data characteristics.\n\nResultsFor hypotheses assuming the link of species composition to species attributes, CWM approach with standard test returns correct Type I error rate. However, for the other two categories (assuming link of species composition to sample attributes or not assuming any link) it returns inflated Type I error rate and requires alternative tests to control for it (column-based and max test, respectively). Inflation index is negatively related to the beta diversity of species composition and positively to the strength of species composition-sample attributes relationship and the number of samples in the dataset. Inflation index is also influenced by modifying species composition matrix (by transformation or removal of species). The relationship of CWM with intrinsic species attributes is a case of spurious correlation and can be tested by column-based (modified) permutation test.\n\nConclusionsThe concept of three hypothesis categories offers a simple tool to evaluate whether given study reports correct or inflated Type I error rate, and how inflated the rate can be.

ecology↗