Abiotic Habitat Conditions Research Articles

Grassland woody plant management rapidly changes woody vegetation persistence and abiotic habitat conditions but not herbaceous community composition

Abstract Grasslands are among the most imperilled ecosystems worldwide, and many have experienced degradation due to the loss of historical disturbance regimes and subsequent woody encroachment. Management practitioners often use physical and chemical management interventions in combination with fire to counter encroachment, altering aboveground structure and belowground function, respectively. This may disrupt the feedbacks that perpetuate encroachment and restore the herbaceous community. We use a large‐scale field experiment to assess the initial effects of different management interventions on woody vegetation persistence, abiotic habitat conditions, and herbaceous community composition. We evaluate these effects across seven sites spanning a natural soil moisture gradient to capture one aspect of environmental heterogeneity with which managers regularly contend. We found that chemical intervention, both with and without the addition of physical intervention, was most effective at reducing woody plant cover and abundance, and a second application reduced woody plant abundance by more than one application alone. We also found that any management intervention increased light availability and air temperature and decreased soil moisture, with the combination of physical and chemical interventions having the greatest effects. Finally, none of the management interventions affected herbaceous richness and functional group cover within the study period, indicating delayed or nonexistent effects on herbaceous community composition. Synthesis and application. Our findings suggest that management should focus on chemical intervention for the greatest effects on woody plant persistence and abiotic habitat conditions. Changes to herbaceous community composition may occur in the long term and seem likely since short‐term effects of management were successful in altering processes related to encroachment feedbacks.

The Biomass Amount of Spontaneous Vegetation Concerning the Abiotic Habitat Conditions in Coal Mine Heaps as Novel Ecosystems

The Biomass Amount of Spontaneous Vegetation Concerning the Abiotic Habitat Conditions in Coal Mine Heaps as Novel Ecosystems

Predicted distribution of Metaparasitylenchus hypothenemi (Tylenchida: Allantonematidae), parasite of the coffee berry borer.

Metaparasitylenchus hypothenemi is an endoparasitic nematode of the coffee berry borer Hypothenemus hampei. The nematode has only been recorded across a limited geographical range in coffee-growing areas of southeastern Mexico. Because of its confined geographical distribution, the effect of altitude, temperature, and mean annual precipitation on M. hypothenemi's presence/absence in the Soconusco region of Mexico was investigated. The geographical distribution of this parasite was predicted based on current data, using geographical information systems (GIS), the MaxEnt algorithm, and historical data to improve the prediction accuracy for other Neotropical regions. In Soconusco, the presence of this parasite is directly related to annual precipitation, especially in the areas with the highest annual rainfall (4000 - 4700 mm/year). Four species distribution models were generated for the Neotropical region with environmental variables for sites with parasite presence data, predicting a range of possible distribution with a high probability of occurrence in southeastern Mexico and southwestern Guatemala and a low probability in areas of Central and South America. Characterization of the abiotic habitat conditions suitable for M. hypothenemi development allows us to predict its distribution in the Neotropics and contributes to our understanding of its ecological relationship with environmental variables.

Morphodiversity as a Tool in Geoconservation: A Case Study in a Mountain Area (Pieniny Mts, Poland)

Verification and delimitation of existing and new surface forms of nature conservation require objective tools that elevate the significance of the conducted evaluations. If our main goal is to preserve biodiversity, it can be ensured through challenging-to-implement practices of human neutrality towards the environment or activities promoting sustainable development that consider the provision of diverse abiotic habitat conditions. For mountainous areas, where the species diversity of plants and animals is strongly linked to the terrain morphology, an analysis of morphodiversity can provide valuable insights. This study examines the morphodiversity of the Pieniny Mts region (southern Poland) in fundamental fields using three mathematical models and various morphometric indicators. The evaluation of existing conservation forms and proposed changes in the analysis were dependent not solely on morphodiversity but also on its autocorrelation. Hot Spot Analysis and Local Indicator of Spatial Association methods were employed, investigating the intensity of spatial clustering of areas with low and high morphodiversity values. Areas with high morphodiversity clustering were defined as justifying legal protection, while those belonging to clusters of fields with low parameter values were considered not to require conservation. Additional insights were gained through the analysis of hot and cold spots, representing fields with high or low morphodiversity surrounded by clusters of fields with contrasting values. The conducted research allowed for the proposing of significant spatial changes for the Pieniny National Park and its adjacent areas to ensure the preservation of high morphodiversity and, consequently, biodiversity.

Applying a hybrid model to support management of the endangered Topeka shiner in oxbow habitats

IntroductionHabitat restoration aims at reinstating abiotic and biotic habitat conditions to support long-term species persistence and viability. This management practice is commonly part of recovery plans developed for species listed as threatened or endangered under the Endangered Species Act. The endangered Topeka shiner (Notropis topeka) inhabits off-channel habitats, such as oxbow lakes which are increasingly the focus of restoration, but the exact abiotic conditions conducive to its persistence in this habitat are not fully understood. In this study, a hybrid model consisting of an individual-based model of the Topeka shiner and an aquatic ecosystem model representing the oxbow habitat was applied to identify optimal environmental conditions for the persistence of Topeka shiner populations.Materials and methodsEnvironmental conditions that correlated with Topeka shiner presence were gathered from published studies and included water temperature, turbidity, oxbow depth, light intensity (as a function of riparian vegetation presence), dissolved nitrogen, and dissolved phosphorus. Selected conditions were systematically varied in simulations and results were analyzed with a partial rank correlation method that quantifies the relative influence on model output from multiple factors.ResultsConducted simulations identified water temperature, depth, and dissolved inorganic nitrogen to be the most influential for Topeka shiner population biomass and additional simulations were conducted exploring the magnitudes and directions of effects of these three factors. Water temperature had the largest positive impact on population biomass followed by oxbow depth and nitrogen reduction.DiscussionWe recommend that the three identified factors be further explored in a combination of empirical and modeling approaches to advise management for the endangered Topeka shiner. This study demonstrated how ecological models could inform recovery plans by identifying factors that enhance species persistence. Ultimately, models should support management practices that result in long-term population viability of listed species and could facilitate their timely delisting.

Collembola Communities, 20 Years After the Establishment of Distinct Revegetation Treatments in a Severely Eroded Area in South Iceland

Several restoration methods have been developed to aid ecosystem development from highly degraded Icelandic deserts into fully vegetated functional ecosystems. Despite the critical role of soil biota in many key ecosystem processes, the effect of restoration efforts on soil biota has rarely been explored. We took advantage of a large-scale restoration field experiment, to study the effect of distinct revegetation treatments on the taxonomic and functional composition of Collembola communities. Soil samples were taken from plots (one ha. each), that had received functionally distinct revegetation treatments; i: grass + fertilizer, ii: birch seedlings, iii: willow cuttings, iv: lupine and v: control. We were able to show that different revegetation treatments led to the establishment of distinct collembola communities in terms of density and taxonomic and functional composition, 20 years after the revegetation process had started. Life-forms were responsive to revegetation treatment, which suggests that the treatments had induced successional trajectories that lead to distinct habitat conditions, especially with respect to abiotic stress. In contrast to literature, eu-edaphic species were dominating in plots, which were exposed to high levels of disturbance and fluctuations in abiotic conditions. Further research is needed to unravel, to which extent resource supply and abiotic habitat conditions steer Collembola community development across successional trajectories.

Defence plasticity in the spiny plant Aralia elata (Miq.) Seem. in response to light and soil fertility.

Plants have evolved various defences against herbivores, including direct chemical and structural defences and co-opted biological defences by predatory insects. However, the effects of abiotic habitat conditions on the quantitative expression of defence traits of spiny species have not been elucidated. Here, we investigated whether a spiny deciduous tree, Aralia elata (Miq.) Seem., changes its defence expression across light and nutrient gradients. We measured allocation to spines and C-based secondary metabolites (condensed tannins and total phenols) on A. elata plants growing across light and nutrient gradients in situ in natural landscapes in Japan. Second, we examined the effects of light and soil nutrient condition on allocation to shoot organs, spines and chemical defences of juveniles of two genotypes of the species, respectively spiny (mainland population) and non-spiny (island population), grown in a glasshouse. In the field investigation, absolute spine mass, spine mass fraction, total phenols and condensed tannins all responded positively to canopy openness. Total phenol content was also negatively related to soil N. In the glasshouse, spiny genotype individuals had less total biomass, had lower stem allocation and were shorter than non-spiny genotype individuals. In spiny genotype trees, both spine mass fraction and total phenols decreased under low light conditions. Nutrient additions had negative effects on spine mass fraction and total phenols, but no effect on absolute spine mass. These results suggest that development of spines is costly for A. elata and receives greater allocation when carbohydrate supply is more plentiful. Thus, light is a more important determinant of spine allocation than soil nutrients for A. elata.

δ13C in above-ground and below-ground organs of Spinulum annotinum (Lycopodiaceae)

• 12 C and 13 C isotope abundance in S. annotinum has been investigated for the first time. • δ 13 C value in S. annotinum is lower than that reported in other C 3 plants. • Different above- and below-ground S. annotinum organs have distinct δ 13 C values. • δ 13 C values of S. annotinum are connected with local plant diversity. Physiological processes in plants and plant–environment interactions can be analysed from the composition of stable carbon isotopes ( 13 C/ 12 C). This ratio can be indicated using the δ (delta) notation. Substantial evidence has been published in recent years demonstrating that post-photosynthetic fractionation occurs in plants and leads to differences in 13 C-enrichment in heterotrophic (as compared with autotrophic) organs. Yet our understanding of processes leading to 13 C divergence between leaves and heterotrophic tissues remains low. Large part of the isotope analysis is concerned with angiosperms, but not spore-bearing tracheophytes. In this study, we explored the 12 C and 13 C isotope distribution in above-ground and below-ground organs of an archaic lycophyte Spinulum annotinum (L.) A.Haines (interrupted clubmoss). The main objectives of this study were to determine the natural distribution of stable carbon isotopes in sporophytes of S. annotinum and to discuss possible causes for differences in δ 13 C. The study revealed that there are significant differences between δ 13 C in different S. annotinum organs. The δ 13 C values varied by about 2.4‰. The highest δ 13 C values were −30.0‰ in roots and the lowest were −32.4‰ in plagiotropic shoot leaves. The distance to a body of water had no significant effect on δ 13 C values in S. annotinum . Outgrowth size did not have a clear relationship with δ 13 C in S. annotinum . The Shannon Diversity Index was a significant predictor for δ 13 C values in S. annotinum . The uncovered δ 13 C and the relationship with abiotic habitat conditions and neighbouring plant species in the community provide a base for future lycophyte ecophysiology research.

Simple attributes predict the value of plants as hosts to fungal and arthropod communities

Fungal and arthropod consumers constitute the vast majority of global terrestrial biodiversity. Yet, the link from richness and composition of producer (plant) communities to the richness of consumer communities is poorly understood. Fungal and arthropod species richness could be a simple function of producer species richness at a site. Alternatively, it could be a complex function of chemical and structural properties of the producer species making up communities. We used databases on plant–fungus and plant–arthropod trophic links to derive the richness of consumer biota per associated plant species (coined link score). We assessed how well link scores could be predicted by simple attributes of plant species. Next, we used a multi‐taxon inventory of 130 sites, representing all major habitat types in a country (Denmark), to investigate whether link scores summed over plant species in communities (coined link sum) could outperform simple plant species richness as predictor of fungal and arthropod richness at the sites. We found plant species' link scores for both fungi and arthropods to be positively related to plant size, regional occupancy, nativeness and ectomycorrhizal status. Link‐based indices generally improved the prediction of richness of fungal and arthropod communities. For fungal communities, both observed link sum (from databases) and predicted link sum (from plant attributes) had high predictive power, while plant richness alone had none. For arthropod communities, predictive performance varied between functional groups. For both fungi and arthropods, richness predictions were further improved by considering abiotic habitat conditions. Our results underline the importance of plants as niche space for the megadiverse groups of arthropods and fungi. The plant–attribute approach holds promise for predicting local and regional consumer richness in areas of the world lacking detailed plant–consumer databases.

Role of the habitat condition in shaping of epifaunal macroinvertebrate bycatch associated with small-scale shrimp fisheries on the Southern Brazilian Coast

Shrimp captures have reached a record in Southern Brazil, and some populations show signs of overexploitation. One shrimp species in particular, Xyphopenaeus kroyeri, abundant in Brazilian landings, is caught by bottom trawl. Trawl fishery is recognized by the impacts it causes on the seabed and on organisms that live in or on the substrate. The present study was conducted in traditional fishing areas on the southern Brazilian coast to assess the conditions of the habitat and the ecological aspects of the marine macroinvertebrate community at 3 areas (Barra do Sul, Penha and Porto Belo) in the Central and Northern Coast of the state of Santa Catarina (southern Brazil). Bottom water and sediment data were used to analyze the differences between the sites. Macroinvertebrate captures were used to analyze ecological aspects of the communities such as composition, diversity and patterns associated with the abiotic variables and habitat conditions. We used a trawling vessel for samplings. The results showed a homogeneous water mass between the areas. However, the sediment characteristic differentiates the areas and contributes to the species composition’s heterogeneity between the samples. The ABC and species-ranking curves results suggest moderate disturbances in the three areas, but with a better structure for the Porto Belo communities. In this context, Barra do Sul was characterized by an environment relatively poor in sediment structure, the abundance and biomass of species. In contrast, Porto Belo and Penha were the opposite. Since trawling changes the sediment’s characteristics are strongly correlated with the diversity and the permanence of sensitive species, we suggest that increased small-scale trawling activities might contribute to the substrate’s homogenization and reduce species diversity in these areas. Therefore, constant surveys to monitor the physical structure and the community and its dynamics in trawling areas are indispensable for the conservation of species and fisheries’ sustainability.

Morphometric traits of shells determine external attack and internal utilization marks in the Roman snail in eastern Germany

Abstract. Overexploitation, habitat destruction and a changing climate threaten populations of the Roman snail (Helix pomatia Linnaeus, 1758), which has led to a high protection status in Germany. Vertebrate and invertebrate predators, including parasites and facultative parasitoids, further cause pressure on populations. Given the conservation concern for H. pomatia and its rarity in the study region (Cottbus, Germany), we studied how predators and facultative parasitoids utilize H. pomatia shells with a focus on non-invasive field methods. As previous studies indicated that shell size may affect prey selection by predators, morphometric traits were measured in eight subpopulations. We identified the total number and percentage of H. pomatia shells that showed external attack marks by predators and internal utilization marks by Diptera pupae and related those utilization patterns to the morphometric traits of shells. A large proportion of the shells in local subpopulations showed signs of external attack and internal utilization, and both utilization forms were positively correlated. External attacks by predators were more frequent in larger shells and internal utilization by Diptera was more common in shells with higher body density. These results suggest a considerable pressure by predators and potential facultative parasitoids on H. pomatia populations in the study area. Future research should focus on the relationship between snails from the family Helicidae and flies from the genus Discomyza. Conservation programmes should consider abiotic habitat conditions together with potential trophic interactions to maximize the success of conservation strategies.

Plant intraspecific functional trait variation is related to within-habitat heterogeneity and genetic diversity in Trifolium montanum L.

Intraspecific trait variation (ITV), based on available genetic diversity, is one of the major means plant populations can respond to environmental variability. The study of functional trait variation and diversity has become popular in ecological research, for example, as a proxy for plant performance influencing fitness. Up to now, it is unclear which aspects of intraspecific functional trait variation (iFDCV) can be attributed to the environment or genetics under natural conditions. Here, we examined 260 individuals from 13 locations of the rare (semi‐)dry calcareous grassland species Trifolium montanum L. in terms of iFDCV, within‐habitat heterogeneity, and genetic diversity. The iFDCV was assessed by measuring functional traits (releasing height, biomass, leaf area, specific leaf area, leaf dry matter content, Fv/Fm, performance index, stomatal pore surface, and stomatal pore area index). Abiotic within‐habitat heterogeneity was derived from altitude, slope exposure, slope, leaf area index, soil depth, and further soil factors. Based on microsatellites, we calculated expected heterozygosity (He) because it best‐explained, among other indices, iFDCV. We performed multiple linear regression models quantifying relationships among iFDCV, abiotic within‐habitat heterogeneity and genetic diversity, and also between separate functional traits and abiotic within‐habitat heterogeneity or genetic diversity. We found that abiotic within‐habitat heterogeneity influenced iFDCV twice as strong compared to genetic diversity. Both aspects together explained 77% of variation in iFDCV (Radj2 = .77, F 2, 10 = 21.66, p < .001). The majority of functional traits (releasing height, biomass, specific leaf area, leaf dry matter content, Fv/Fm, and performance index) were related to abiotic habitat conditions indicating responses to environmental heterogeneity. In contrast, only morphology‐related functional traits (releasing height, biomass, and leaf area) were related to genetics. Our results suggest that both within‐habitat heterogeneity and genetic diversity affect iFDCV and are thus crucial to consider when aiming to understand or predict changes of plant species performance under changing environmental conditions.

Testing for consistency in ecosystem engineering: Do cushion plants always turn up the heat?

Ecosystem engineers influence community structure and functioning by altering habitat and resource availability. However, few studies have assessed how consistent ecosystem engineers' impacts are on abiotic habitat conditions and/or community characteristics, either across species or between habitats. Here we test for the consistency of ecosystem engineering across, and within, cushion-forming plant species, a group of ecosystem engineers that are dominant in polar and alpine environments, by reviewing studies that document their effects on temperature. We find inconsistent effects, with cushion plants having contrasting impacts on temperatures in different studies. Even after limiting analyses to a single cushion plant morphology type or to just a single species, impacts on temperature were still inconsistent between studies. Therefore, while cushion plants have relatively consistent impacts on plant communities (e.g. increasing local species richness), their impact on temperature may not be the overarching abiotic mechanism driving this ecological effect. These results, therefore, highlight the need to explicitly test if ecosystem engineers’ biotic and abiotic impacts are consistent through space and time, and emphasize the importance of understanding context-dependence in the outcome of biotic interactions.

Fish Communities, Habitat Use, and Human Pressures in the Upper Volta Basin, Burkina Faso, West Africa

Human pressures and loss of natural fish habitats led to a decline in fish populations in terms of abundances, biodiversity, and average size in sub-Sahelian Burkina Faso. Little knowledge exists about fish assemblages regarding their composition, their habitat preferences, or their sensitivity to or tolerance of human pressures. This research provides the first data-driven basis for sustainably managing fish and associated aquatic and terrestrial habitats. Surveys in four different regions sampled 18,000 specimens from 69 species during the dry season. Fish communities, available abiotic habitat conditions, habitat use, and human pressures were assessed and analyzed. Fish communities cluster into four distinct types, each dominated by either Cichlidae, Clariidae, Cyprinidae, or Alestidae and accompanied by specific other families and genera of fish. Habitat preferences of four key species (Labeo coubie, Bagrus bajad, Chelaethiops bibie, and Lates niloticus) were linked to ecological habitat conditions. Results show that physical parameters influence fish community composition and abundances and, when indexed according to pressure type, are linked to responses in fish metrics. Relative abundance either dropped (Mormyridae) or increased (Cichlidae, Cyprinidae) with rising pressure intensity, and some sentinel taxa (Auchenoglanis, Hydrocynus) were only found in low-pressure sites. The outcomes of this study provide basic knowledge of habitat availability, habitat use by fish, species associations, and human pressures and therefore provide the basis for effective conservation and management of fish populations.

Filling ephemeral ponds affects development and phenotypic expression in Ambystoma talpoideum

Abstract Populations and communities are often greatly affected by disturbances and variation in abiotic habitat conditions. Many of these effects are contingent on relatively predictable, yet still variable, environmental conditions that drive the life history strategies and development pathways of organisms in those habitats. However, much focus has been placed on aspects of such changes that cause mortality or movement from patches, whereas a multitude of outcomes can occur in natural systems. In lentic freshwater habitats, hydroperiod is a defining environmental characteristic, with temporary ponds supporting distinct communities of organisms with complex life cycles and plastic developmental trajectories. Little consideration has been given to the effects of refilling of ponds with variable hydroperiods, as lengthening the hydroperiod can extend the time organisms spend in their aquatic stages, allowing for the acquisition of more resources. We hypothesised that increasing the volume of small ponds and adding competitors (Ambystoma maculatum) at the time of filling would interactively affect the development and phenotypic expression of Ambystoma talpoideum. We introduced larval A. talpoideum to experimental mesocosms and manipulated water level (small, low volume mesocosms; filled, full mesocosms) and the addition of competitors (A. maculatum) at the time of filling in a 2 × 2 factorial design. We found that low volume mesocosms were dominated by metamorphs, while filling resulted in a more even mix of metamorphs, larvae and paedomorphs in full mesocosms. Filling resulted in larger metamorphs and paedomorphs, but did not affect larvae, whereas addition of A. maculatum shortened the larval period of metamorphs. We provide evidence that changes in abiotic habitat conditions, such as variation in the volume of ponds, can shift the development and phenotype of organisms. This plasticity may allow species to ensure the success of populations under both improvement and deterioration of environmental conditions. Hence, phenotypes like paedomorphic A. talpoideum can breed sooner than metamorphs, theoretically maximising the fitness of both individuals and populations.

The effects of fungal root endophytes on plant growth are stable along gradients of abiotic habitat conditions.

Plant symbioses with fungal root endophytes span a continuum from mutualistic to parasitic outcomes, and are highly variable depending on the genotype of each symbiont. The abiotic context in which interactions occur also seems to influence the outcome of plant-endophyte symbioses, but we lack understanding of its relative importance. We aimed to assess if changes in abiotic variables determine the effects of fungal root endophytes on plant growth. We used in vitro co-cultivation assays to test the impact of a selection of endophytic strains from diverse lineages on the growth of Arabidopsis thaliana, Microthlaspi erraticum and Hordeum vulgare along gradients of nutrient availability, light intensity or substrate pH. Most fungi showed a negative but weak effect on plant growth, whereas only a few had persistent detrimental effects across plants and conditions. Changes in abiotic factors affected plant growth but had little influence on their response to fungal inoculation. Of the factors tested, variation in nutrient availability resulted in the most variable plant-endophyte interactions, although changes were feeble and strain-specific. Our findings suggest that the effects of root endophytes on plant growth are robust to changes in the abiotic environment when these encompass the tolerance range of either symbiont.

Comparative Morphometric Analysis of the Smallscaled Scorpionfish, Scorpaena Porcus (Scorpaenidae, Scorpaeniformes), from the Southern Coast of the Crimea and Eastern Part of the Adriatic Sea

Abstract Comparative analysis of morphometric characters of small-scaled scorpionfish from the Black Sea (near the southern coast of the Crimea) and from the eastern part of the Adriatic Sea showed significant differences in males and females on thirteen plastic and three meristic characters. These differences may be due to unequal abiotic and biotic habitat conditions, and refer about the geographical variability of the species, indicating the presence of two different populations in the study area.

Interactions between Fish Well-being and Water Quality: A Case Study from MoriiLake Area, Romania

Abstract This paper represents the start of a complex research on water-fish-human relationships and their implications for animal and human welfare. Among the many determinants that influence the population of a fish are size of specimens and water-quality factors. Length-weight relationship, Fulton's K condition factor and the size structure were assessed for unsexed percid species European perch, Percafluviatilis (L., 1758) (N= 485) and Eurasian ruffe, Gymnocephaluscernua (L., 1758) (N= 177) caught from Dâmboviţa River-Morii Lake area – the largest lake from Bucharest, the capital of Romania. Positive allometric growth was estimated for both fish species: TW = 0.0061 x TL 3.2498 (perch) and TW = 0.0075 x TL 3.1733 (ruffe). Condition factor K registered values between 0.79 and 2.29 (perch), 0.86 and 1.5 (ruffe). Some physico-chemical parameters (pH, total dissolved solids, nitrite, nitrate, phosphate, ammonium, electrical conductivity, total hardness) were achieved, in order to evaluate the impact of abiotic habitat conditions on fish population. The microbiological analyses of water quality were also considered, to detect the species of micromycetes that could affect both human and fish health. Thus, Alternaria spp., Aspergillus spp., Cladosporium spp., Fusarium spp., Penicillium spp. and some Saccharomyces yeast strains were identified in water samples from the studied area. On the basis of all the analyzed parameters, the water resource was found to be not within the suitable range for well-being of both percid species, fact which could be of general interest assuming that local people use to angle fish like perch and often eat their catch. To our knowledge, the study attempts for the first time to approach the interactions between biological features of some fish species inhabiting the DâmboviţaRiver upstream of MoriiLake, the quality of their environment and local people – regarded as potential consumers of their occasional catches.

Early subtropical forest growth is driven by community mean trait values and functional diversity rather than the abiotic environment.

While functional diversity (FD) has been shown to be positively related to a number of ecosystem functions including biomass production, it may have a much less pronounced effect than that of environmental factors or species-specific properties. Leaf and wood traits can be considered particularly relevant to tree growth, as they reflect a trade-off between resources invested into growth and persistence. Our study focussed on the degree to which early forest growth was driven by FD, the environment (11 variables characterizing abiotic habitat conditions), and community-weighted mean (CWM) values of species traits in the context of a large-scale tree diversity experiment (BEF-China). Growth rates of trees with respect to crown diameter were aggregated across 231 plots (hosting between one and 23 tree species) and related to environmental variables, FD, and CWM, the latter two of which were based on 41 plant functional traits. The effects of each of the three predictor groups were analyzed separately by mixed model optimization and jointly by variance partitioning. Numerous single traits predicted plot-level tree growth, both in the models based on CWMs and FD, but none of the environmental variables was able to predict tree growth. In the best models, environment and FD explained only 4 and 31% of variation in crown growth rates, respectively, while CWM trait values explained 42%. In total, the best models accounted for 51% of crown growth. The marginal role of the selected environmental variables was unexpected, given the high topographic heterogeneity and large size of the experiment, as was the significant impact of FD, demonstrating that positive diversity effects already occur during the early stages in tree plantations.

A Modelling Framework to Assess the Effect of Pressures on River Abiotic Habitat Conditions and Biota.

River biota are affected by global reach-scale pressures, but most approaches for predicting biota of rivers focus on river reach or segment scale processes and habitats. Moreover, these approaches do not consider long-term morphological changes that affect habitat conditions. In this study, a modelling framework was further developed and tested to assess the effect of pressures at different spatial scales on reach-scale habitat conditions and biota. Ecohydrological and 1D hydrodynamic models were used to predict discharge and water quality at the catchment scale and the resulting water level at the downstream end of a study reach. Long-term reach morphology was modelled using empirical regime equations, meander migration and 2D morphodynamic models. The respective flow and substrate conditions in the study reach were predicted using a 2D hydrodynamic model, and the suitability of these habitats was assessed with novel habitat models. In addition, dispersal models for fish and macroinvertebrates were developed to assess the re-colonization potential and to finally compare habitat suitability and the availability / ability of species to colonize these habitats. Applicability was tested and model performance was assessed by comparing observed and predicted conditions in the lowland Treene River in northern Germany. Technically, it was possible to link the different models, but future applications would benefit from the development of open source software for all modelling steps to enable fully automated model runs. Future research needs concern the physical modelling of long-term morphodynamics, feedback of biota (e.g., macrophytes) on abiotic habitat conditions, species interactions, and empirical data on the hydraulic habitat suitability and dispersal abilities of macroinvertebrates. The modelling framework is flexible and allows for including additional models and investigating different research and management questions, e.g., in climate impact research as well as river restoration and management.