Recent Submissions

  • Journal Article

    Estimating utilization distributions from fitted step-selection functions 

    Signer, Johannes; Fieberg, John; Avgar, Tal
    Ecosphere 2017; 8(4): Art. e01771
    Habitat-selection analyses are often used to link environmental covariates, measured within some spatial domain of assumed availability, to animal location data that are assumed to be independent. Step-selection functions (SSFs) relax this independence assumption, by using a conditional model that explicitly acknowledges the spatiotemporal dynamics of the availability domain and hence the temporal dependence among successive locations. However, it is not clear how to produce an SSF-based map of the expected utilization distribution. Here, we used SSFs to analyze virtual animal movement data generated at a fine spatiotemporal scale and then rarefied to emulate realistic telemetry data. We then compared two different approaches for generating maps from the estimated regression coefficients. First, we considered a na€ıve approach that used the coefficients as if they were obtained by fitting an unconditional model. Second, we explored a simulation-based approach, where maps were generated using stochastic simulations of the parameterized step-selection process. We found that the simulation-based approach always outperformed the na€ıve mapping approach and that the latter overestimated home-range size and underestimated local space-use variability. Differences between the approaches were greatest for complex landscapes and high sampling rates, suggesting that the simulation-based approach, despite its added complexity, is likely to offer significant advantages when applying SSFs to real data.
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  • Journal Article

    Soil nitrogen oxide fluxes from lowland forests converted to smallholder rubber and oil palm plantations in Sumatra, Indonesia 

    Hassler, Evelyn; Corre, Marife D.; Kurniawan, Syahrul; Veldkamp, Edzo
    Biogeosciences 2017; 14(11) p.2781-2798
    Oil palm (Elaeis guineensis) and rubber (Hevea brasiliensis) plantations cover large areas of former rainforest in Sumatra, Indonesia, supplying the global demand for these crops. Although forest conversion is known to influence soil nitrous oxide (N2O) and nitric oxide (NO) fluxes, measurements from oil palm and rubber plantations are scarce (for N2O) or nonexistent (for NO). Our study aimed to (1) quantify changes in soil–atmosphere fluxes of N oxides with forest conversion to rubber and oil palm plantations and (2) determine their controlling factors. In Jambi, Sumatra, we selected two landscapes that mainly differed in texture but were both on heavily weathered soils: loam and clay Acrisol soils. Within each landscape, we investigated lowland forests, rubber trees interspersed in secondary forest (termed as "jungle rubber"), both as reference land uses and smallholder rubber and oil palm plantations as converted land uses. In the loam Acrisol landscape, we conducted a follow-on study in a large-scale oil palm plantation (called PTPN VI) for comparison of soil N2O fluxes with smallholder oil palm plantations. Land-use conversion to smallholder plantations had no effect on soil N-oxide fluxes (P = 0. 58 to 0.76) due to the generally low soil N availability in the reference land uses that further decreased with land-use conversion. Soil N2O fluxes from the large-scale oil palm plantation did not differ with those from smallholder plantations (P = 0. 15). Over 1-year measurements, the temporal patterns of soil N-oxide fluxes were influenced by soil mineral N and water contents. Across landscapes, annual soil N2O emissions were controlled by gross nitrification and sand content, which also suggest the influence of soil N and water availability. Soil N2O fluxes (µg N m−2 h−1) were 7 ± 2 to 14 ± 7 (reference land uses), 6 ± 3 to 9 ± 2 (rubber), 12 ± 3 to 12 ± 6 (smallholder oil palm) and 42 ± 24 (large-scale oil palm). Soil NO fluxes (µg N m−2 h−1) were −0.6 ± 0.7 to 5.7 ± 5.8 (reference land uses), −1.2 ± 0.5 to −1.0 ± 0.2 (rubber) and −0.2 ± 1.2 to 0.7 ± 0.7 (smallholder oil palm). To improve the estimate of soil N-oxide fluxes from oil palm plantations in this region, studies should focus on large-scale plantations (which usually have 2 to 4 times higher N fertilization rates than smallholders) with frequent measurements following fertilizer application.
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  • Journal Article

    Rhizosphere hydrophobicity: A positive trait in the competition for water. 

    Zeppenfeld, Thorsten; Balkenhol, Niko; Kóvacs, Kristóf; Carminati, Andrea
    PloS one 2017; 12(7): Art. e0182188
    The ability to acquire water from the soil is a major driver in interspecific plant competition and it depends on several root functional traits. One of these traits is the excretion of gel-like compounds (mucilage) that modify physical soil properties. Mucilage secreted by roots becomes hydrophobic upon drying, impedes the rewetting of the soil close to the root, the so called rhizosphere, and reduces water availability to plants. The function of rhizosphere hydrophobicity is not easily understandable when looking at a single plant, but it may constitute a competitive advantage at the ecosystem level. We hypothesize that by making the top soil hydrophobic, deep-rooted plants avoid competititon with shallow-rooted plants. To test this hypothesis we used an individual-based model to simulate water uptake and growth of two virtual plant species, one deep-rooted plant capable of making the soil hydrophobic and a shallow-rooted plant. We ran scenarios with different precipitation regimes ranging from dry to wet (350, 700, and 1400 mm total annual precipitation) and from high to low precipitation frequencies (1, 7, and 14 days). Plant species abundance and biomass were chosen as indicators for competitiveness of plant species. At constant precipitation frequency mucilage hydrophobicity lead to a benefit in biomass and abundance of the tap-rooted population. Under wet conditions this effect diminished and tap-rooted plants were less productive. Without this trait both species coexisted. The effect of root exudation trait remained constant under different precipitation frequencies. This study shows that mucilage secretion is a competitive trait for the acquisition of water. This advantage is achieved by the modification of the soil hydraulic properties and specifically by inducing water repellency in soil regions which are shared with other species.
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  • Journal Article

    On the Effect of Thinning on Tree Growth and Stand Structure of White Birch (Betula platyphylla Sukaczev) and Siberian Larch (Larix sibirica Ledeb.) in Mongolia 

    Gradel, Alexander; Ammer, Christian; Ganbaatar, Batsaikhan; Nadaldorj, Ochirrragchaa; Dovdondemberel, Batdorj; Wagner, Sven
    Forests 2017; 8(4): Art. 105
    The forests of North Mongolia are largely dominated either by larch (Larix sibirica Ledeb.) or birch (Betula platyphylla Sukaczev). The increasing demand for timber and firewood is currently met by removal of wood from these forest stands. Therefore, silvicultural approaches that account for both utilization and protection are needed. Thinning trials were established in the research area Altansumber, in the mountain forest steppe west of the town of Darkhan. We analyzed the response of non-spatial and spatial structure and growth of birch and larch stands on thinning. Before thinning, spatial tree distribution was largely clumped. Thinning promoted regular tree distribution. Ingrowth of new stems after thinning tended to redirect stand structure towards clumping. Both relative and absolute tree growth and competition were evaluated before, directly after, and three years after the thinning. Competition played a significant role in tree growth before thinning. A reduction in competition after thinning triggered significantly increased growth of both birch and larch. The observed positive growth response was valid in absolute and relative terms. A methodically based forest management strategy, including thinning operations and selective cuttings, could be established, even under the harsh Mongolian conditions. Our findings could initiate the development of broader forest management guidelines for the light-taiga dominated stands.
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  • Journal Article

    Oil Palm and Rubber Tree Water Use Patterns: Effects of Topography and Flooding 

    Hardanto, Afik; Röll, Alexander; Niu, Furong; Meijide, Ana; Hendrayanto; Hölscher, Dirk
    Frontiers in Plant Science 2017; 8: Art. 452
    Oil palm and rubber plantations extend over large areas and encompass heterogeneous site conditions. In periods of high rainfall, plants in valleys and at riparian sites are more prone to flooding than plants at elevated topographic positions. We asked to what extent topographic position and flooding affect oil palm and rubber tree water use patterns and thereby influence spatial and temporal heterogeneity of transpiration. In an undulating terrain in the lowlands of Jambi, Indonesia, plantations of the two species were studied in plot pairs consisting of upland and adjacent valley plots. All upland plots were non-flooded, whereas the corresponding valley plots included non-flooded, longterm flooded, and short-term flooded conditions. Within each plot pair, sap flux densities in palms or trees were monitored simultaneously with thermal dissipation probes. In plot pairs with non-flooded valleys, sap flux densities of oil palms were only slightly different between the topographic positions, whereas sap flux densities of rubber trees were higher in the valley than at the according upland site. In pairs with long-term flooded valleys, sap flux densities in valleys were lower than at upland plots for both species, but the reduction was far less pronounced in oil palms than in rubber trees (􀀀22 and 􀀀45% in maximum sap flux density, respectively). At these long-term flooded valley plots palm and tree water use also responded less sensitively to fluctuations in micrometeorological variables than at upland plots. In short-term flooded valley plots, sap flux densities of oil palm were hardly affected by flooding, but sap flux densities of rubber trees were reduced considerably. Topographic position and flooding thus affected water use patterns in both oil palms and rubber trees, but the changes in rubber trees were much more pronounced: compared to non-flooded upland sites, the different flooding conditions at valley sites amplified the observed heterogeneity of plot mean water use by a factor of 2.4 in oil palm and by a factor of 4.2 in rubber plantations. Such strong differences between species as well as the pronounced heterogeneity of water use across space and time may be of relevance for eco-hydrological assessments of tropical plantation landscapes.
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  • Journal Article

    Seed dispersal at alpine treeline: an assessment of seed movement within the alpine treeline ecotone 

    Johnson, Jeremy S.; Gaddis, Keith D.; Cairns, David M.; Krutovsky, Konstantin V.
    Ecosphere 2017; 8(1): Art. e01649
    Alpine treelines are expected to advance to higher elevations in conjunction with global warming. Nevertheless, the importance of treeline reproductive patterns and seed dispersal within the alpine treeline ecotone remains unresolved. In this study, we address two research questions at mountain hemlock treelines on the Kenai Peninsula, Alaska: (1) What is the primary mode of reproduction and (2) are seeds leading to recruitment derived from within the local treeline populations or are they arriving from more distant seed sources? To answer these questions, we exhaustively sampled mountain hemlock individuals along a single mountain slope, and genotyped single nucleotide polymorphisms using doubledigest restriction site-associated DNA sequencing. First, we assessed mode of reproduction by determining the proportion of sampled individuals with identical multilocus genotypes that are the product of clonal reproduction. Second, we used a categorical parentage analysis to identify parent–offspring pairs, so that the proportion of treeline reproduction events could be spatially quantified and dispersal distance measured. We identified sexual reproduction as the primary mode of reproduction at our study site. Seedling establishment was characterized by extensive seed immigration and gene flow into the ecotone. The average dispersal distance was 73 m with long-distance dispersal identified as dispersal occurring at distances greater than 450 m. We found that production of seeds within the alpine treeline ecotone is not necessarily a requirement for treelines to advance to higher elevations in response to climate change. The extensive seed dispersal and gene flow into the alpine treeline ecotone is likely sufficient to propel the ecotone higher under more favorable climate.
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  • Journal Article

    Improving Execution Speed of Models Implemented in NetLogo 

    Railsback, Steven; Ayllón, Daniel; Berger, Uta; Grimm, Volker; Lytinen, Steven; Sheppard, Colin; Thiele, Jan
    Journal of Artificial Societies and Social Simulation 2017; 20(1)
    NetLogo has become a standard platform for agent-based simulation, yet there appears to be widespread belief that it is not suitable for large and complex models due to slow execution. Our experience does not support that belief. NetLogo programs o en do run very slowly when written to minimize code length and maximize clarity, but relatively simple and easily tested changes can almost always produce major increases in execution speed. We recommend a five-step process for quantifying execution speed, identifying slow parts of code, and writing faster code. Avoiding or improving agent filtering statements can o en produce dramatic speed improvements. For models with extensive initialization methods, reorganizing the setup procedure can reduce the initialization e ort in simulation experiments. Programming the same behavior in a di erent way can sometimes provide order-of-magnitude speed increases. For models in which most agents do nothing on most time steps, discrete event simulation – facilitated by the time extension to NetLogo – can dramatically increase speed. NetLogo’s BehaviorSpace tool makes it very easy to conduct multiple-model-run experiments in parallel on either desktop or high performance cluster computers, so even quite slow models can be executed thousands of times. NetLogo also is supported by e icient analysis tools, such as BehaviorSearch and RNetLogo, that can reduce the number of model runs and the e ort to set them up for (e.g.) parameterization and sensitivity analysis.
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  • Journal Article

    Thermal stability of processed PVC/bamboo blends: effect of compounding procedures 

    Bahari, Shahril Anuar; Grigsby, Warren; Krause, Andreas
    European Journal of Wood and Wood Products 2017; 75(2) p.147-159
    Polyvinyl chloride (PVC) was mixed with bamboo (Bambusa vulgaris) particle and additives by using PVC composite manufacturing system including initial dry blending with hot-cool mixing, followed by granulation via counter-rotating extrusion, and then consolidation by compression moulding to produce compression moulded board (CMB). The effects of different bamboo particle size (75 µm and 1 mm), bamboo particle loading (25 and 50% loading ratio), and differing processing lubricants content level (compositions 1 and 2) on the thermal stability of the composites were determined. Results show no significant trends in glass transition temperature (Tg) between dry blends, granules, and CMB, and between B. vulgaris particle loading at the respective processing steps. For samples with higher lubricant contents, the PVC Tg was observed to decrease up to 5 °C, possibly due to the reduced melt viscosity. The thermal decomposition temperature at 5% mass loss (T−5%) appeared to decrease from dry blend to CMB due to sample degradation on further processing at higher temperatures. The use of 50% B. vulgaris particle loading also reduced the T−5% values, assignable to bamboo particle degradation caused by the high processing temperatures. For oxidative induction time (OIT) testing, only granules and CMB from pure PVC composites system showed measurable oxidative times compared with OIT profiles of PVC/B. vulgaris composites system, suggestive of comparatively stabilized thermoplastic composites. This revealed that processing with bamboo particles does not contribute to degradation of PVC composites.
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  • Journal Article

    Species proportions by area in mixtures of Scots pine (Pinus sylvestris L.) and European beech (Fagus sylvatica L.) 

    Dirnberger, Gerald; Sterba, Hubert; Condés, Sonia; Ammer, Christian; Annighöfer, Peter; Avdagić, Admir; Bielak, Kamil; Brazaitis, Gediminas; Coll, Lluís; Heym, Michael; et al.
    Hurt, VáclavKurylyak, ViktorMotta, RenzoPach, MaciejPonette, QuentinRuiz-Peinado, RicardoSkrzyszewski, JerzyŠrámek, Vítde Streel, GéraudSvoboda, MiroslavZlatanov, TzvetanPretzsch, Hans
    European Journal of Forest Research 2016; 136(1) p.1-13
    Scots pine (Pinus sylvestris L.) and European beech (Fagus sylvatica L.) dominate many of the European forest stands. Also, mixtures of European beech and Scots pine more or less occur over all European countries, but have been scarcely investigated. The area occupied by each species is of high relevance, especially for growth evaluation and comparison of different species in mixed and monospecific stands. Thus, we studied different methods to describe species proportions and their definition as proportion by area. 25 triplets consisting of mixed and monospecific stands were established across Europe ranging from Lithuania to Spain in northern to southern direction and from Bulgaria to Belgium in eastern to western direction. On stand level, the conclusive method for estimating the species proportion as a fraction of the stand area relates the observed density (tree number or basal area) to its potential. This stand-level estimation makes use of the potential from comparable neighboring monospecific stands or from maximum density lines derived from other data, e.g. forest inventories or permanent observations plots. At tree level, the fraction of the stand area occupied by a species can be derived from the proportions of their crown projection area or of their leaf area. The estimates of the potentials obtained from neighboring monospecific stands, especially in older stands, were poorer than those from the maximum density line depending on the Martonne aridity index. Therefore, the stand-level method in combination with the Martonne aridity index for potential densities can be highly recommended. The species’ proportions estimated with this method are best approximated by the proportions of the species’ leaf areas. In forest practice, the most commonly applied method is an ocular estimation of the proportions by crown projection area. Even though the proportions of pine were calculated here by measuring crown projection areas in the field, we found this method to underestimate the proportion by 25% compared to the stand-level approach.
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  • Journal Article

    The macroecology of island floras 

    Weigelt, Patrick
    Frontiers of Biogeography 2015; 7(3)
    Islands are key model systems in biogeography and ecology. However, standardized data on environmental characteristics of the large number of islands worldwide have so far been lacking, and the effects of these characteristics on island ecology and biodiversity remain insufficiently understood. In my PhD thesis, I presented the first comprehensive environmental characterization of the world’s islands, covering past and present bioclimatic and physical island characteristics (including the spatial setting of islands and archipelagos). I used these data to investigate how island characteristics influence the diversity and assembly of island floras at different spatial scales and across major plant groups. To this end, I assembled a global database of vascular plant species composition including 45,000 species and covering 1,070 islands. I showed that different aspects of island environments affect different facets of insular diversity (species richness, turnover, phylogenetic diversity) across scales and major plant groups, in accordance with their predominant dispersal- and speciation-related traits and adaptations to climate. The results contribute to a better understanding of the environmental and evolutionary drivers of plant assemblage composition, on islands as well as on mainlands.
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  • Journal Article

    Environmental heterogeneity–species richness relationships from a global perspective 

    Stein, Anke
    Frontiers of Biogeography 2015; 7(4)
    Spatial environmental heterogeneity (EH) is considered one of the most important factors promoting species richness, but no general consent about the EH–richness relationship exists so far. This is because research methods and study settings vary widely, and because non-significant and negative associations have also been reported. My thesis provides a comprehensive review of the different measurements and terminologies of EH used in the literature, and presents strong quantitative evidence of a generally positive relationship between biotic and abiotic EH and species richness of terrestrial plants and animals from landscape to global extents. In a meta-analysis and a subsequent case study comparing multiple EH measures and their association with mammal species richness worldwide, I furthermore reveal that the outcome of EH–richness studies depends strongly on study design, including both the EH measure chosen and spatial scale. My research contributes to a better understanding of the EH–richness relationship, while identifying future research needs.
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  • Journal Article

    Limitations in global information on species occurrences 

    Meyer, Carsten
    Frontiers of Biogeography 2016; 8(2): Art. e28195
    Detailed information on species distributions is crucial for answering central questions in biogeography, ecology, evolutionary biology and conservation. Millions of species occurrence records have been mobilized via international data-sharing networks, but inherent biases, gaps and uncertainties hamper broader application. In my PhD thesis, I presented the first comprehensive analyses of global patterns and drivers of these limitations across different taxonomic groups and spatial scales. Integrating 300 million occurrence records for terrestrial vertebrates and plants with comprehensive taxonomic databases, expert range maps and regional checklists, I demonstrated extensive taxonomic, geographical and temporal biases, gaps and uncertainties. I identified key socio-economic drivers of data bias across different taxonomic groups and spatial scales. The results of my dissertation provide an empirical baseline for effectively accounting for data limitations in distribution models, as well as for prioritizing and monitoring efforts to collate additional occurrence information.
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  • Journal Article

    Asynchronous exposure to global warming: freshwater resources and terrestrial ecosystems 

    Gerten, Dieter; Lucht, Wolfgang; Ostberg, Sebastian; Heinke, Jens; Kowarsch, Martin; Kreft, Holger; Kundzewicz, Zbigniew W.; Rastgooy, Johann; Warren, Rachel; Schellnhuber, Hans Joachim
    Environmental Research Letters 2013; 8(3)
    This modelling study demonstrates at what level of global mean temperature rise .1Tg/ regions will be exposed to significant decreases of freshwater availability and changes to terrestrial ecosystems. Projections are based on a new, consistent set of 152 climate scenarios (eight 1Tg trajectories reaching 1.5–5 C above pre-industrial levels by 2100, each scaled with spatial patterns from 19 general circulation models). The results suggest that already at a 1Tg of 2 C and mainly in the subtropics, higher water scarcity would occur in >50% out of the 19 climate scenarios. Substantial biogeochemical and vegetation structural changes would also occur at 2 C, but mainly in subpolar and semiarid ecosystems. Other regions would be affected at higher 1Tg levels, with lower intensity or with lower confidence. In total, mean global warming levels of 2 C, 3.5 C and 5 C are simulated to expose an additional 8%, 11% and 13% of the world population to new or aggravated water scarcity, respectively, with >50% confidence (while 1.3 billion people already live in water-scarce regions). Concurrently, substantial habitat transformations would occur in biogeographic regions that contain 1% (in zones affected at 2 C), 10% (3.5 C) and 74% (5 C) of present endemism-weighted vascular plant species, respectively. The results suggest nonlinear growth of impacts along with 1Tg and highlight regional disparities in impact magnitudes and critical 1Tg levels.
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  • Journal Article

    A review of the ecosystem functions in oil palm plantations, using forests as a reference system 

    Dislich, Claudia; Keyel, Alexander C.; Salecker, Jan; Kisel, Yael; Meyer, Katrin M.; Auliya, Mark; Barnes, Andrew D.; Corre, Marife D.; Darras, Kevin; Faust, Heiko; et al.
    Hess, BastianKlasen, StephanKnohl, AlexanderKreft, HolgerMeijide, AnaNurdiansyah, FuadOtten, FennaPe'er, GuySteinebach, StefanieTarigan, SuriaTölle, Merja H.Tscharntke, TejaWiegand, Kerstin
    Biological Reviews
    Oil palm plantations have expanded rapidly in recent decades. This large-scale land-use change has had great ecological, economic, and social impacts on both the areas converted to oil palm and their surroundings. However, research on the impacts of oil palm cultivation is scattered and patchy, and no clear overview exists. We address this gap through a systematic and comprehensive literature review of all ecosystem functions in oil palm plantations, including several (genetic, medicinal and ornamental resources, information functions) not included in previous systematic reviews. We compare ecosystem functions in oil palm plantations to those in forests, as the conversion of forest to oil palm is prevalent in the tropics. We find that oil palm plantations generally have reduced ecosystem functioning compared to forests: 11 out of 14 ecosystem functions show a net decrease in level of function. Some functions show decreases with potentially irreversible global impacts (e.g. reductions in gas and climate regulation, habitat and nursery functions, genetic resources, medicinal resources, and information functions). The most serious impacts occur when forest is cleared to establish new plantations, and immediately afterwards, especially on peat soils. To variable degrees, specific plantation management measures can prevent or reduce losses of some ecosystem functions (e.g. avoid illegal land clearing via fire, avoid draining of peat, use of integrated pest management, use of cover crops, mulch, and compost) and we highlight synergistic mitigation measures that can improve multiple ecosystem functions simultaneously. The only ecosystem function which increases in oil palm plantations is, unsurprisingly, the production of marketable goods. Our review highlights numerous research gaps. In particular, there are significant gaps with respect to socio-cultural information functions. Further, there is a need for more empirical data on the importance of spatial and temporal scales, such as differences among plantations in different environments, of different sizes, and of different ages, as our review has identified examples where ecosystem functions vary spatially and temporally. Finally, more research is needed on developing management practices that can offset the losses of ecosystem functions. Our findings should stimulate research to address the identified gaps, and provide a foundation for more systematic research and discussion on ways to minimize the negative impacts and maximize the positive impacts of oil palm cultivation.
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  • Journal Article

    No saturation in the accumulation of alien species worldwide 

    Seebens, Hanno; Blackburn, Tim M.; Dyer, Ellie E.; Genovesi, Piero; Hulme, Philip E.; Jeschke, Jonathan M.; Pagad, Shyama; Pyšek, Petr; Winter, Marten; Arianoutsou, Margarita; et al.
    Bacher, SvenBlasius, BerndBrundu, GiuseppeCapinha, CésarCelesti-Grapow, LauraDawson, WayneDullinger, StefanFuentes, NicolJäger, HeinkeKartesz, JohnKenis, MarcKreft, HolgerKühn, IngolfLenzner, BerndLiebhold, AndrewMosena, AlexanderMoser, DietmarNishino, MisakoPearman, DavidPergl, JanRabitsch, WolfgangRojas-Sandoval, JulissaRoques, AlainRorke, StephanieRossinelli, SilviaRoy, Helen E.Scalera, RiccardoSchindler, StefanŠtajerová, KateřinaTokarska-Guzik, Barbaravan Kleunen, MarkWalker, KevinWeigelt, PatrickYamanaka, TakehikoEssl, Franz
    Nature Communications 2017; 8
    Although research on human-mediated exchanges of species has substantially intensified during the last centuries, we know surprisingly little about temporal dynamics of alien species accumulations across regions and taxa. Using a novel database of 45,813 first records of 16,926 established alien species, we show that the annual rate of first records worldwide has increased during the last 200 years, with 37% of all first records reported most recently (1970–2014). Inter-continental and inter-taxonomic variation can be largely attributed to the diaspora of European settlers in the nineteenth century and to the acceleration in trade in the twentieth century. For all taxonomic groups, the increase in numbers of alien species does not show any sign of saturation and most taxa even show increases in the rate of first records over time. This highlights that past efforts to mitigate invasions have not been effective enough to keep up with increasing globalization.
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  • Journal Article

    Dissecting nutrient-related co-expression networks in phosphate starved poplars 

    Kavka, Mareike; Polle, Andrea
    PLOS ONE 2017; 12(2): Art. e0171958
    Phosphorus (P) is an essential plant nutrient, but its availability is often limited in soil. Here, we studied changes in the transcriptome and in nutrient element concentrations in leaves and roots of poplars (Populus × canescens) in response to P deficiency. P starvation resulted in decreased concentrations of S and major cations (K, Mg, Ca), in increased concentrations of N, Zn and Al, while C, Fe and Mn were only little affected. In roots and leaves >4,000 and >9,000 genes were differently expressed upon P starvation. These genes clustered in eleven co-expression modules of which seven were correlated with distinct elements in the plant tissues. One module (4.7% of all differentially expressed genes) was strongly correlated with changes in the P concentration in the plant. In this module the GO term “response to P starvation” was enriched with phosphoenolpyruvate carboxylase kinases, phosphatases and pyrophosphatases as well as regulatory domains such as SPX, but no phosphate transporters. The P-related module was also enriched in genes of the functional category “galactolipid synthesis”. Galactolipids substitute phospholipids in membranes under P limitation. Two modules, one correlated with C and N and the other with biomass, S and Mg, were connected with the P-related module by co-expression. In these modules GO terms indicating “DNA modification” and “cell division” as well as “defense” and “RNA modification” and “signaling” were enriched; they contained phosphate transporters. Bark storage proteins were among the most strongly upregulated genes in the growth-related module suggesting that N, which could not be used for growth, accumulated in typical storage compounds. In conclusion, weighted gene coexpression network analysis revealed a hierarchical structure of gene clusters, which separated phosphate starvation responses correlated with P tissue concentrations from other gene modules, which most likely represented transcriptional adjustments related to down-stream nutritional changes and stress.
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  • Journal Article

    Bulk isolation of basidiospores from wild mushrooms by electrostatic attraction with low risk of microbial contaminations 

    Lakkireddy, Kiran; Kües, Ursula
    AMB Express 2017; 7(1): Art. 28
    The basidiospores of most Agaricomycetes are ballistospores. They are propelled off from their basidia at maturity when Buller’s drop develops at high humidity at the hilar spore appendix and fuses with a liquid film formed on the adaxial side of the spore. Spores are catapulted into the free air space between hymenia and fall then out of the mushroom’s cap by gravity. Here we show for 66 different species that ballistospores from mushrooms can be attracted against gravity to electrostatic charged plastic surfaces. Charges on basidiospores can influence this effect. We used this feature to selectively collect basidiospores in sterile plastic Petri-dish lids from mushrooms which were positioned upside-down onto wet paper tissues for spore release into the air. Bulks of 104 to >107 spores were obtained overnight in the plastic lids above the reversed fruiting bodies, between 104 and 106 spores already after 2–4 h incubation. In plating tests on agar medium, we rarely observed in the harvested spore solutions contaminations by other fungi (mostly none to up to in 10% of samples in different test series) and infrequently by bacteria (in between 0 and 22% of samples of test series) which could mostly be suppressed by bactericides. We thus show that it is possible to obtain clean basidiospore samples from wild mushrooms. The technique of spore collection through electrostatic attraction in plastic lids is applicable to fresh lamellate and poroid fruiting bodies from the wild, to shortlived deliquescent mushrooms, to older and dehydrating fleshy fruiting bodies, even to animal-infested mushrooms and also to dry specimens of long-lasting tough species such as Schizophyllum commune.
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  • Journal Article

    Understanding Forest Health with Remote Sensing - Part I - A Review of Spectral Traits, Processes and Remote-Sensing Characteristics 

    Lausch, Angela; Erasmi, Stefan; King, Douglas; Magdon, Paul; Heurich, Marco
    Remote Sensing 2016; 8(12)
    Anthropogenic stress and disturbance of forest ecosystems (FES) has been increasing at all scales from local to global. In rapidly changing environments, in-situ terrestrial FES monitoring approaches have made tremendous progress but they are intensive and often integrate subjective indicators for forest health (FH). Remote sensing (RS) bridges the gaps of these limitations, by monitoring indicators of FH on different spatio-temporal scales, and in a cost-effective, rapid, repetitive and objective manner. In this paper, we provide an overview of the definitions of FH, discussing the drivers, processes, stress and adaptation mechanisms of forest plants, and how we can observe FH with RS. We introduce the concept of spectral traits (ST) and spectral trait variations (STV) in the context of FH monitoring and discuss the prospects, limitations and constraints. Stress, disturbances and resource limitations can cause changes in FES taxonomic, structural and functional diversity; we provide examples how the ST/STV approach can be used for monitoring these FES characteristics. We show that RS based assessments of FH indicators using the ST/STV approach is a competent, affordable, repetitive and objective technique for monitoring. Even though the possibilities for observing the taxonomic diversity of animal species is limited with RS, the taxonomy of forest tree species can be recorded with RS, even though its accuracy is subject to certain constraints. RS has proved successful for monitoring the impacts from stress on structural and functional diversity. In particular, it has proven to be very suitable for recording the short-term dynamics of stress on FH, which cannot be cost-effectively recorded using in-situ methods. This paper gives an overview of the ST/STV approach, whereas the second paper of this series concentrates on discussing in-situ terrestrial monitoring, in-situ RS approaches and RS sensors and techniques for measuring ST/STV for FH.
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  • Journal Article

    Inventory-based estimation of forest biomass in Shitai County, China: A comparison of five methods 

    Tang, X.; Fehrmann, L.; Guan, F.; Forrester, D. I.; Guisasola, R.; Kleinn, C.
    Annals of Forest Research 2016; 59(1) p.269-280
    Several comparative studies have reported that there can be great discrepancies between different methods used to estimate forest biomass. With the development of carbon markets, an accurate estimation at the regional scale (i.e. county level) is becoming increasingly important for local government. In this study, we applied five methodologies [continuous biomass expansion factor (CBEF) approach, mean biomass density (MB) approach, mean biomass expansion factor (MBEF) approach, national continuous biomass expansion factors (NCBEF) proposed by Fang et al (2002), standard IPCC approach] to estimate the total biomass for Shitai County, China. The CBEF is generally considered to provide the most realistic estimates in term of regional biomass because CBEF reflects the change of BEF to stand density, stand age and site conditions. The forests of the whole county were divided into four forest types, namely Chinese fir plantations (CF), hardwood broadleaved forests (HB), softwood–broadleaved forests (SB) and mason pine forests (MP) according to the local forest management inventory of 2004. Generally, the MBEF approach overestimated forest biomass while the IPCC approach underestimated forest biomass for all forest types when CBEF derived biomass was used as a control. The MB approach provided the most similar biomass estimates for all forest types and could be an alternative approach when a CBEF equation is lacking in the study area. The total biomass derived from MBEF was highest at 1.44×107 t, followed by 1.32 ×107 t from CBEF, 1.31 ×107 t from NCBEF, 1.25 ×107 t from MB and 1.16 ×107 t from IPCC. Our results facilitate method selection for regional forest biomass estimation and provide statistical evidence for local government planning to enter the potential carbon market.
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  • Journal Article

    Precision and reliability of indirect population assessments for the Caspian red deer Cervus elaphus maral 

    Soofi, Mahmood; Ghoddousi, Arash; Hamidi, Amirhossein Kh.; Ghasemi, Benjamin; Egli, Lukas; Voinopol-Sassu, Ana-Johanna; Kiabi, Bahram H.; Balkenhol, Niko; Khorozyan, Igor; Waltert, Matthias
    Wildlife Biology 2017; 1(2017): Art. wlb.00230
    The elusive Caspian red deer Cervus elaphus maral lives at low densities in rugged forest habitats of the Caucasus and the south Caspian region, and its declining population requires urgent attention. We here address the precision and reliability of dung counts (fecal standing crop approach FSC) and camera trapping (random encounter model REM) for estimating its population size. We surveyed 36 km of strip transects arranged in systematic random design and applied 1585 camera trap nights of effort in the mountainous forest habitats of Golestan National Park, Iran. We also conducted a dung decay analysis of 80 samples. Dung decay rates were not habitat-specific and the mean time to decay was 141.8  15.1 days, i.e. only ca 52% of the most reliable estimate available for red deer dung. Estimated deer population size and density from dung counts was lower (194  46 individuals, 0.46  0.11 individuals km–2, 2012–2013) than from REM (257  84 individuals, 0.61  0.20 individuals km–2, 2011), but this difference was insignificant. Both these estimates confirm a sharp decline of the population from an estimated 2096 animals in the 1970s. Density estimates reached a stable level and were most precise at a sampling effort of 15 transects (FSC) and 1345 camera trap-days (REM). Our results confirm that FSC and REM can both be reliable for assessing populations of Cervidae.
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