TY - JOUR A1 - Geißler, Katja A1 - Hahn, Claudia A1 - Joubert, David A1 - Blaum, Niels T1 - Functional responses of the herbaceous plant community explain ecohydrological impacts of savanna shrub encroachment JF - Perspectives in plant ecology, evolution and systematics N2 - Major drivers of savanna shrub encroachment are climatic conditions, CO2 and unsustainable grazing management including fire prevention. Although all drivers affect ecohydrological processes, and given that water is a seasonally scarce resource in savannas, it remains largely unclear how shrub encroachment itself affects hydrological conditions that feed back into water use and community assembly of the remaining plant community. Hence, understanding direct ecohydrological effects of shrubs that may limit the recovery of the perennial herbaceous vegetation in grazed areas and promote the establishment of shrub seedlings facilitates the identification of areas that are most sensitive to further encroachment. In our trait-based approach, we determined relationships among shrub cover, soil and plant trait characteristics sensitive to water limitation in 120 plots along a shrub cover gradient. We focused on two functional response traits indicating immediate drought stress and subsequent water use for drought stress recovery with associated competition for water (midday leaf/xylem water potential and diurnally recovery rate of leaf water potential), and three functional response traits indicating long-term stress adaptation and related resource use strategies (SLA, plant height and seed release height). To understand species assembly and the associated mechanisms of resource use, we calculated community weighted mean traits, intraspecific trait variability as a proxy for the mechanism of coexistence, and mean traits at plant functional type level including 2-year-old Acacia mellifera-saplings. We found a low intraspecific trait variability in drought stress recovery rate and height suggesting that competitive exclusion via active resource acquisition (i.e. water exploitation) played a minor role for community assembly in a shrub encroaching savanna. The dominant community assembly process was passive stress avoidance via resource conservation up to stress tolerance indicated by the high variability in SLA and midday leaf water potential. Correlations of traits with soil moisture suggest a rooting niche differentiation between annual and perennial grasses and that Acacia-shrub saplings within the first 50 cm of soil already escaped the highest drought stress. Interestingly, immediate drought stress for the herbaceous community was lowest on moderately shrub encroached sites and not on grass dominated sites. Since passive stress avoidance accompanied by a distinct stress tolerance in semi-arid savannas is more important than active competition, and assuming that the low drought stress of the herbaceous community at intermediate levels of shrub cover also applies to newly emerging shrub seedlings, these areas are likely to be most sensitive to further encroachment. As such, they should be considered as focal areas for prevention management. KW - Community-weighted means KW - Drought stress KW - Intraspecific variation KW - Soil moisture KW - Stress recovery KW - Plant functional traits Y1 - 2019 U6 - https://doi.org/10.1016/j.ppees.2019.125458 SN - 1433-8319 VL - 39 PB - Elsevier CY - München ER - TY - JOUR A1 - Lemke, Isgard H. A1 - Kolb, Annette A1 - Graae, Bente J. A1 - De Frenne, Pieter A1 - Acharya, Kamal P. A1 - Blandino, Cristina A1 - Brunet, Jorg A1 - Chabrerie, Olivier A1 - Cousins, Sara A. O. A1 - Decocq, Guillaume A1 - Heinken, Thilo A1 - Hermy, Martin A1 - Liira, Jaan A1 - Schmucki, Reto A1 - Shevtsova, Anna A1 - Verheyen, Kris A1 - Diekmann, Martin T1 - Patterns of phenotypic trait variation in two temperate forest herbs along a broad climatic gradient JF - Plant ecology : an international journal N2 - Phenotypic trait variation plays a major role in the response of plants to global environmental change, particularly in species with low migration capabilities and recruitment success. However, little is known about the variation of functional traits within populations and about differences in this variation on larger spatial scales. In a first approach, we therefore related trait expression to climate and local environmental conditions, studying two temperate forest herbs, Milium effusum and Stachys sylvatica, along a similar to 1800-2500 km latitudinal gradient. Within each of 9-10 regions in six European countries, we collected data from six populations of each species and recorded several variables in each region (temperature, precipitation) and population (light availability, soil parameters). For each plant, we measured height, leaf area, specific leaf area, seed mass and the number of seeds and examined environmental effects on within-population trait variation as well as on trait means. Most importantly, trait variation differed both between and within populations. Species, however, differed in their response. Intrapopulation variation in Milium was consistently positively affected by higher mean temperatures and precipitation as well as by more fertile local soil conditions, suggesting that more productive conditions may select for larger phenotypic variation. In Stachys, particularly light availability positively influenced trait variation, whereas local soil conditions had no consistent effects. Generally, our study emphasises that intra-population variation may differ considerably across larger scales-due to phenotypic plasticity and/or underlying genetic diversity-possibly affecting species response to global environmental change. KW - Climate change KW - Global environmental change KW - Milium effusum KW - Phenotypic plasticity KW - Intraspecific variation KW - Stachys sylvatica Y1 - 2015 U6 - https://doi.org/10.1007/s11258-015-0534-0 SN - 1385-0237 SN - 1573-5052 VL - 216 IS - 11 SP - 1523 EP - 1536 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Stoof-Leichsenring, Kathleen Rosemarie A1 - Bernhardt, Nadine A1 - Pestryakova, Luidmila Agafyevna A1 - Epp, Laura Saskia A1 - Herzschuh, Ulrike A1 - Tiedemann, Ralph T1 - A combined paleolimnological/genetic analysis of diatoms reveals divergent evolutionary lineages of Staurosira and Staurosirella (Bacillariophyta) in Siberian lake sediments along a latitudinal transect JF - Journal of paleolimnolog N2 - Diatom diversity in lakes of northwest Yakutia (Siberia) was investigated by microscopic and genetic analysis of surface and cored lake sediments, to evaluate the use of sedimentary DNA for paleolimnological diatom studies and to identify obscure genetic diversity that cannot be detected by microscopic methods. Two short (76 and 73 bp) and one longer (577 bp) fragments of the ribulose 1,5-bisphosphate carboxylase/oxygenase (rbcL) gene, encoding the large subunit of the rbcL, were used as genetic markers. Diverse morphological assemblages of diatoms, dominated by small benthic fragilarioid taxa, were retrieved from the sediments of each lake. These minute fragilarioid taxa were examined by scanning electron microscopy, revealing diverse morphotypes in Staurosira and Staurosirella from the different lakes. Genetic analyses indicated a dominance of haplotypes that were assigned to fragilarioid taxa and less genetic diversity in other diatom taxa. The long rbcL_577 amplicon identified considerable diversification among haplotypes clustering within the Staurosira/Staurosirella genera, revealing 19 different haplotypes whose spatial distribution appears to be primarily related to the latitude of the lakes, which corresponds to a vegetation and climate gradient. Our rbcL markers are valuable tools for tracking differences between diatom lineages that are not visible in their morphologies. These markers revealed putatively high genetic diversity within the Staurosira/Staurosirella species complex, at a finer scale than is possible to resolve by microscopic determination. The rbcL markers may provide additional reliable information on the diversity of barely distinguishable minute benthic fragilarioids. Environmental sequencing may thus allow the tracking of spatial and temporal diversification in Siberian lakes, especially in the context of diatom responses to recent environmental changes, which remains a matter of controversy. KW - Arctic lake sediments KW - Diatoms KW - Environmental DNA KW - Intraspecific variation KW - RbcL Y1 - 2014 U6 - https://doi.org/10.1007/s10933-014-9779-1 SN - 0921-2728 SN - 1573-0417 VL - 52 IS - 1-2 SP - 77 EP - 93 PB - Springer CY - Dordrecht ER -