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Berlin Brandenburg

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  • 1
    In: PLoS ONE, 2014, Vol.9(10)
    Description: This study presents an experimental approach to assess the relative importance of climatic and biotic factors as determinants of species' geographical distributions. We asked to what extent responses of grassland plant species to biotic interactions vary with climate, and to what degree this variation depends on the species' biogeography. Using a gradient from oceanic to continental climate represented by nine common garden transplant sites in Germany, we experimentally tested whether congeneric grassland species of different geographic distribution (oceanic vs . continental plant range type) responded differently to combinations of climate, competition and mollusc herbivory. We found the relative importance of biotic interactions and climate to vary between the different components of plant performance. While survival and plant height increased with precipitation, temperature had no effect on plant performance. Additionally, species with continental plant range type increased their growth in more benign climatic conditions, while those with oceanic range type were largely unable to take a similar advantage of better climatic conditions. Competition generally caused strong reductions of aboveground biomass and growth. In contrast, herbivory had minor effects on survival and growth. Against expectation, these negative effects of competition and herbivory were not mitigated under more stressful continental climate conditions. In conclusion we suggest variation in relative importance of climate and biotic interactions on broader scales, mediated via species-specific sensitivities and factor-specific response patterns. Our results have important implications for species distribution models, as they emphasize the large-scale impact of biotic interactions on plant distribution patterns and the necessity to take plant range types into account.
    Keywords: Research Article ; Biology And Life Sciences ; Ecology And Environmental Sciences
    E-ISSN: 1932-6203
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  • 2
    In: PLoS ONE, 2014, Vol.9(11)
    Description: While the fundamental trade-off in leaf traits related to carbon capture as described by the leaf economics spectrum is well-established among plant species, the relationship of the leaf economics spectrum to stem hydraulics is much less known. Since carbon capture and transpiration are coupled, a close connection between leaf traits and stem hydraulics should be expected. We thus asked whether xylem traits that describe drought tolerance and vulnerability to cavitation are linked to particular leaf traits. We assessed xylem vulnerability, using the pressure sleeve technique, and anatomical xylem characteristics in 39 subtropical tree species grown under common garden conditions in the BEF-China experiment and tested for correlations with traits related to the leaf economics spectrum as well as to stomatal control, including maximum stomatal conductance, vapor pressure deficit at maximum stomatal conductance and vapor pressure deficit at which stomatal conductance is down-regulated. Our results revealed that specific xylem hydraulic conductivity and cavitation resistance were closely linked to traits represented in the leaf economic spectrum, in particular to leaf nitrogen concentration, as well as to log leaf area and leaf carbon to nitrogen ratio but not to any parameter of stomatal conductance. The study highlights the potential use of well-known leaf traits from the leaf economics spectrum to predict plant species' drought resistance.
    Keywords: Research Article ; Biology And Life Sciences ; Ecology And Environmental Sciences
    E-ISSN: 1932-6203
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  • 3
    Language: English
    In: PLoS ONE, Oct 30, 2014, Vol.9(10)
    Description: This study presents an experimental approach to assess the relative importance of climatic and biotic factors as determinants of species' geographical distributions. We asked to what extent responses of grassland plant species to biotic interactions vary with climate, and to what degree this variation depends on the species' biogeography. Using a gradient from oceanic to continental climate represented by nine common garden transplant sites in Germany, we experimentally tested whether congeneric grassland species of different geographic distribution (oceanic vs. continental plant range type) responded differently to combinations of climate, competition and mollusc herbivory. We found the relative importance of biotic interactions and climate to vary between the different components of plant performance. While survival and plant height increased with precipitation, temperature had no effect on plant performance. Additionally, species with continental plant range type increased their growth in more benign climatic conditions, while those with oceanic range type were largely unable to take a similar advantage of better climatic conditions. Competition generally caused strong reductions of aboveground biomass and growth. In contrast, herbivory had minor effects on survival and growth. Against expectation, these negative effects of competition and herbivory were not mitigated under more stressful continental climate conditions. In conclusion we suggest variation in relative importance of climate and biotic interactions on broader scales, mediated via species-specific sensitivities and factor-specific response patterns. Our results have important implications for species distribution models, as they emphasize the large-scale impact of biotic interactions on plant distribution patterns and the necessity to take plant range types into account.
    Keywords: Biogeography ; Precipitation (Meteorology)
    ISSN: 1932-6203
    Source: Cengage Learning, Inc.
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  • 4
    In: PLoS ONE, 2013, Vol.8(2)
    Description: Genetic diversity is supposed to support the colonization success of expanding species, in particular in situations where microsite availability is constrained. Addressing the role of genetic diversity in plant invasion experimentally requires its manipulation independent of propagule pressure. To assess the relative importance of these components for the invasion of Senecio vernalis , we created propagule mixtures of four levels of genotype diversity by combining seeds across remote populations, across proximate populations, within single populations and within seed families. In a first container experiment with constant Festuca rupicola density as matrix, genotype diversity was crossed with three levels of seed density. In a second experiment, we tested for effects of establishment limitation and genotype diversity by manipulating Festuca densities. Increasing genetic diversity had no effects on abundance and biomass of S. vernalis but positively affected the proportion of large individuals to small individuals. Mixtures composed from proximate populations had a significantly higher proportion of large individuals than mixtures composed from within seed families only. High propagule pressure increased emergence and establishment of S. vernalis but had no effect on individual growth performance. Establishment was favoured in containers with Festuca , but performance of surviving seedlings was higher in open soil treatments. For S. vernalis invasion, we found a shift in driving factors from density dependence to effects of genetic diversity across life stages. While initial abundance was mostly linked to the amount of seed input, genetic diversity, in contrast, affected later stages of colonization probably via sampling effects and seemed to contribute to filtering the genotypes that finally grew up. In consequence, when disentangling the mechanistic relationships of genetic diversity, seed density and microsite limitation in colonization of invasive plants, a clear differentiation between initial emergence and subsequent survival to juvenile and adult stages is required.
    Keywords: Research Article ; Biology
    E-ISSN: 1932-6203
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  • 5
    Language: English
    In: Forest Ecology and Management, 2010, Vol.259(8), pp.1597-1605
    Description: To assess the influence of gap age and microsite type within a near-natural montane Norway spruce stand at the Harz National Park in Germany, we tested the following hypotheses: (1) The relationship between regeneration and gap age is represented by an optimum curve. (2) Within gaps, tree regeneration mainly occurs on gap-induced microsites. (3) The contribution of specific microsites to regeneration changes with gap age. We randomly established 90 permanent plots stratified into three gap age classes as well as undisturbed forest to assess the density of gap-induced microsites (logs, stumps, root plates) and of microsites not related to disturbance (forest floor, moss-covered rocks) and recorded relative light conditions, spruce density and biometric variables. We found significant differences in spruce regeneration between microsites as well as between undisturbed and disturbed plots. Sapling density was only related to microsite type, with the highest density being encountered on logs with 2.3 individuals/0.25 m , in contrast to moss-covered rocks with 1.8 individuals/0.25 m . Logs also ranked, together with root plates, highest in terms of sapling mortality. A larger density of young saplings on gap-induced microsites was compensated for by a higher mortality rate, probably due to self-thinning. In contrast, survival was highest on ordinary microsites, i.e. intact ground. Biometric variables differed significantly between microsites as individuals on ordinary microsites were taller than individuals on gap-induced microsites (94.21 ± 137.09 cm 39.86 ± 50.45 cm) and had more whorls (12.32 ± 10.55 7.73 ± 6.79). Significant interactions between gap age class and microsite type were only evident in growth rates. In conclusion, although gap-induced microsites enhance spruce establishment, their role in long-term regeneration has been widely overestimated when compared to the relevance of the ordinary microsites, in particular as the latter are permanent and do not depend on disturbances.
    Keywords: Advance Regeneration ; Gap Age Classes ; Microsites ; Mortality ; Mt. Brocken ; Norway Spruce ; Forestry ; Biology
    ISSN: 0378-1127
    E-ISSN: 1872-7042
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  • 6
    Language: English
    In: Forest Ecology and Management, 25 January 2010, Vol.259(3), pp.624-632
    Description: We analyzed indices of gap dynamics, i.e. gap formation and gap closure rates as well as turnover rates, in a montane conifer forest in the temperate zone and asked: (1) Are the characteristics of gap dynamics comparable with those of other temperate forests? (2) Do gap dynamics exhibit temporal trends, and (3) if so, are they related to recent climate change? We also addressed methodological issues concerning the differences observed at differing temporal and spatial scales of the used datasets. Thus, we asked further how the indices of gap dynamics are influenced (4) by differences in the length of observation periods and (5) by differences in gap size categories included in the study? The study area was located in the near-natural forests in the core zone of the Harz National Park on the north-eastern slopes of Mt. Brocken, Germany. From this area, aerial photographs from the last 60 yrs (1945, 1991, 2000, 2003) were analyzed by GIS techniques. Total gap area, number of gaps, gap size and area-based turnover rate, rotation time, gap formation and gap closure rate were calculated and correlated with climate variables. The total gap area varied between 10.9 ha and 19.0 ha for the study area of 225.2 ha between the different years. Similarly, the median of the gap size was 155.6 m and 87.0 m in 1945 and 2003, respectively. A rotation time of 228 yrs was calculated for the study area. Area-based turnover rates and gap formation rates increased with time, while mean gap size decreased. The most frequently recorded gaps were those in the category 〈100 m . In particular, small gaps at the level of single trees (≤40 m ) became more frequent in the last decade and showed a higher gap formation rate than larger gaps. Temperature was significantly related to both turnover and gap closure rates. In conclusion, for the near-natural spruce stands at Mt. Brocken indices of gap dynamics were of a magnitude comparable to those described from other forest types in the temperate zone. However, the indices of gap dynamics increased with time, which coincided with increasing temperatures over the last few decades.
    Keywords: Aerial Photographs ; Disturbance ; Gap Dynamics ; Picea Abies ; Turnover Rate ; Forestry ; Biology
    ISSN: 0378-1127
    E-ISSN: 1872-7042
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  • 7
    In: Ecological Applications, June 2010, Vol.20(4), pp.1136-1147
    Description: Knowledge of succession rates and pathways is crucial for devising restoration strategies for highly disturbed ecosystems such as surface‐mined land. As these processes have often only been described in qualitative terms, we used Markov models to quantify transitions between successional stages. However, Markov models are often considered not attractive for some reasons, such as model assumptions (e.g., stationarity in space and time, or the high expenditure of time required to estimate successional transitions in the field). Here we present a solution for converting multivariate ecological time series into transition matrices and demonstrate the applicability of this approach for a data set that resulted from monitoring the succession of sandy dry grassland in a post‐mining landscape. We analyzed five transition matrices, four one‐step matrices referring to specific periods of transition (1995–1998, 1998–2001, 2001–2004, 2004–2007), and one matrix for the whole study period (stationary model, 1995–2007). Finally, the stationary model was enhanced to a partly time‐variable model. Applying the stationary and the time‐variable models, we started a prediction well outside our calibration period, beginning with 100% bare soil in 1974 as the known start of the succession, and generated the coverage of 12 predefined vegetation types in three‐year intervals. Transitions among vegetation types changed significantly in space and over time. While the probability of colonization was almost constant over time, the replacement rate tended to increase, indicating that the speed of succession accelerated with time or fluctuations became stronger. The predictions of both models agreed surprisingly well with the vegetation data observed more than two decades later. This shows that our dry grassland succession in a post‐mining landscape can be adequately described by comparably simple types of Markov models, although some model assumptions have not been fulfilled and within‐plot transitions have not been observed with point exactness. The major achievement of our proposed way to convert vegetation time series into transition matrices is the estimation of probability of events—a strength not provided by other frequently used statistical methods in vegetation science.
    Keywords: Acidic Dry Grassland ; Markov Models ; Prediction ; Succession Rates ; Transition Matrix ; Vegetation Dynamics .
    ISSN: 1051-0761
    E-ISSN: 1939-5582
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  • 8
    In: Ecology, May 2009, Vol.90(5), pp.1314-1325
    Description: To determine which factors contribute most to the stability of species composition in a beech forest after profound disturbance, we made use of a natural experiment caused by a severe windthrow that occurred at a permanent monitoring site in an old beech forest in Lower Saxony (Germany). The floristic composition was recorded for the succeeding five years after the disturbance and used to derive measures of resistance and resilience for plots as well as for individual species. Due to the existence of previously established randomly distributed permanent plots, we had precise information of the pre‐disturbance state, including initial cover of the herb layer, species richness, and species composition. Variables describing the floristic change, resistance, and resilience were derived from correspondence analysis allowing for partitioning the effects of variation among plots from those of temporal change. We asked to which degree these variables could be predicted by pre‐disturbance state and disturbance intensity. We found that both the pre‐disturbance state and the disturbance intensity were good predictors for floristic change and resistance, while they failed to predict resilience. Among the descriptors of the pre‐disturbance state the initial cover of the herb layer turned out to be a useful predictor, which is explained by a high vegetation cover buffering against losses and preventing establishment of newcomers. In contrast, species number neither showed a relationship to floristic change nor to resistance. Putative positive effects of species number on stability according to the insurance hypothesis might have been counterbalanced by a disruption of niche complementarity in species‐rich communities. Among the descriptors of disturbance intensity, the loss in canopy cover and the change in photosynthetically active radiation after the storm were equally good predictors for the change in floristic composition and resistance. The analysis of the responses of single species on initial vegetation cover and disturbance intensity revealed that a wide range of different mechanisms were involved. Resistance and resilience did not depend on the presence of particular species or on specific traits.
    Keywords: Beech Forest Vegetation ; Correspondence Analysis ; Ecosystem Stability ; Fagus Sylvatica ; Forest Dynamics ; Gap Dynamics ; Herb Layer ; Lower Saxony ; Germany ; Plasticity ; Secondary Succession ; Windthrow ; Woodland Species
    ISSN: 0012-9658
    E-ISSN: 1939-9170
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  • 9
    In: PLoS ONE, 2015, Vol.10(6)
    Description: Soil erosion is a key threat to many ecosystems, especially in subtropical China where high erosion rates occur. While the mechanisms that induce soil erosion on agricultural land are well understood, soil erosion processes in forests have rarely been studied. Throughfall kinetic energy (TKE) is influenced in manifold ways and often determined by the tree’s leaf and architectural traits. We investigated the role of species identity in mono-specific stands on TKE by asking to what extent TKE is species-specific and which leaf and architectural traits account for variation in TKE. We measured TKE of 11 different tree species planted in monocultures in a biodiversity-ecosystem-functioning experiment in subtropical China, using sand-filled splash cups during five natural rainfall events in summer 2013. In addition, 14 leaf and tree architectural traits were measured and linked to TKE. Our results showed that TKE was highly species-specific. Highest TKE was found below Choerospondias axillaris and Sapindus saponaria , while Schima superba showed lowest TKE. These species-specific effects were mediated by leaf habit, leaf area (LA), leaf pinnation, leaf margin, stem diameter at ground level (GD), crown base height (CBH), tree height, number of branches and leaf area index (LAI) as biotic factors and throughfall as abiotic factor. Among these, leaf habit, tree height and LA showed the highest effect sizes on TKE and can be considered as major drivers of TKE. TKE was positively influenced by LA, GD, CBH, tree height, LAI, and throughfall amount while it was negatively influenced by the number of branches. TKE was lower in evergreen, simple leaved and dentate leaved than in deciduous, pinnated or entire leaved species. Our results clearly showed that soil erosion in forest plantations can be mitigated by the appropriate choice of tree species.
    Keywords: Research Article
    E-ISSN: 1932-6203
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  • 10
    In: PLoS ONE, 2016, Vol.11(11)
    Description: Forests with higher tree diversity are often assumed to be more resistant to insect herbivores but whether this effect depends on climatic conditions is so far poorly understood. In particular, a forest’s resistance to herbivory may depend on mean annual temperature (MAT) as a key driver of plant and insect phenology. We carried out a global meta-analysis on regression coefficients between tree diversity and four aspects of insect herbivory, namely herbivore damage, abundance, incidence rate and species richness. To test for a potential shift of tree diversity effects along a global gradient of MAT we applied mixed-effects models and estimated grand mean effect sizes and the influence of MAT, experimental vs. observational studies and herbivores diet breadth. There was no overall effect of tree diversity on the pooled effect sizes of insect herbivore damage, abundance and incidence rate. However, when analysed separately, we found positive grand mean effect sizes for herbivore abundance and species richness. For herbivore damage and incidence rate we found a significant but opposing shift along a gradient of MAT indicating that with increasing MAT diversity effects on herbivore damage tend towards associational resistance whereas diversity effects on incidence rates tend towards associational susceptibility. Our results contradict previous meta-analyses reporting overall associational resistance to insect herbivores in mixed forests. Instead, we report that tree diversity effects on insect herbivores can follow a biogeographic pattern calling for further in-depth studies in this field.
    Keywords: Research Article ; Biology And Life Sciences ; Ecology And Environmental Sciences ; Biology And Life Sciences ; Biology And Life Sciences ; Ecology And Environmental Sciences ; Biology And Life Sciences ; Biology And Life Sciences ; Ecology And Environmental Sciences ; Biology And Life Sciences ; Biology And Life Sciences ; Ecology And Environmental Sciences ; Biology And Life Sciences ; Biology And Life Sciences ; Ecology And Environmental Sciences ; Ecology And Environmental Sciences ; Research And Analysis Methods ; Physical Sciences ; Biology And Life Sciences
    E-ISSN: 1932-6203
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