1,721,127 research outputs found
Effects of NPK fertilisation in arid southern Mongolian desert steppes
No full textFew studies have been performed on the importance of nutrient availability for plant productivity at < 200 mm annual precipitation and available meta-analyses have produced contradicting results. Here, we present data from a 3-year experiment on the effects of NPK-fertilisation under ambient precipitation in dry Central Asian steppes. The study site had an annual mean precipitation of ca. 160 mm and represented an intensively grazed montane desert steppe. One year of NPK-fertilisation at levels equivalent to 10 and 20 gN/m(2) (100 and 200 kg/ha) increased above-ground mean standing crop in a moist year to 1130 and 1490 kg dry mass/ha, respectively, compared to the 615 kg/ha from the control. The absolute increase was smaller in subsequent drier years, but the crop again more than doubled under fertilisation. The effects were most pronounced for the main fodder plants Agropyron cristatum and Allium polyrrhizum, which benefited from fertilisation more than other less palatable species. Both species also showed increased levels of foliar N. Fertilisation enhanced flowering activity on the community level, and soil analyses revealed that nutrients accumulate in the soil. Effects are therefore expected to be long lasting. Our results imply that nutrient shortage may co-limit plant growth at well below 200 mm annual precipitation. Considering that predominantly nomadic land use is known to result in nutrient withdrawal, our data raise concerns of a largely unnoticed potential pathway to pasture degradation
Highly reduced genetic diversity of rosa Rubiginosa L. Populations in the Invasive Range
Full text linkRosa rubiginosa (Rosaceae) populations introduced to Argentina successfully invade various habitats, forming extensive impenetrable thickets. To investigate the consequences of founder events and to track the native origin of Argentinean populations, the genetic diversity of invasive R. rubiginosa populations was compared with that of native populations in Europe, and genetic similarity was assessed between groups. We sampled 13 Argentinean populations and 20 native populations in Germany and Spain, and we applied two molecular marker techniques (simple sequence repeats and random amplification of polymorphic DNA [RAPD]). Genetic diversity within the invasive range was clearly lower than it was in the native range. Principle coordinate analysis and between-class analysis did not reveal the exact European origin of the invasive populations, but our data suggest that at least one Argentinean population originated in Germany. Overall, the strong similarity of RAPD and allelic phenotypes throughout Argentina suggests a limited number of introduction events, that the species spread through human transport, and that the few genetic phenotypes present in the species were conserved largely unaltered as a result of mainly asexual reproduction.Fil: Zimmermann, Heike. Martin-Luther University Halle; AlemaniaFil: Ritz, Christiane M.. Justus‐Liebig‐University Giessen; AlemaniaFil: Hirsch, Heidi. Martin‐Luther University Halle; AlemaniaFil: Renison, Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones Biológicas y Tecnológicas. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Investigaciones Biológicas y Tecnológicas; ArgentinaFil: Wesche, Karsten. Georg‐August‐University; Alemania. Senckenberg Natural History Museum Görlitz; AlemaniaFil: Hensen, Isabell. Martin‐Luther University Halle; Alemani
Long-term decline in the abundance of leafhoppers and planthoppers (Auchenorrhyncha) in Central European protected dry grasslands
No full textLandscapes in Central Europe have changed considerably during the last five decades, while nature reserves have been less affected. However, there is growing concern that species richness and population size of animals in reserves may decrease even under protection. We performed a comparative study of the development in auchenorrhynchan communities of governmentally protected dry grasslands in Eastern Germany and tested whether reserves were effective in maintaining insect communities. The historical surveys are from 1963 to 1967. Between 2008 and 2010 we revisited 26 of the original sites and sampled leafhoppers and planthoppers by applying the same sampling technique as in the 1960s. Thus, we were able to perform a 40-year-comparison for auchenorrhynchan species richness and abundance. Comparisons capturing three successive years of each period allowed us to assess interannual variability in abundance. Species richness hardly differed between the two periods. However, some new species were found, and therefore species composition changed. Species abundance and overall numbers of individuals declined. Mainly species known to be very common dry grassland specialists exhibited strong declines in abundance. On average, only 27% of auchenorrhynchan numbers caught from 1964 to 1966 were recorded for the years 2008 to 2010. The results suggest that weather conditions and climate change are minor factors in the decline in auchenorrhynchan populations in recent years. Although the studied areas were under protection during the last 50 years, air-borne nitrogen deposition, the introduction of modern intense land use practices and alterations in plant communities, are likely to have influenced auchenorrhynchan abundance to a large extent. (c) 2012 Elsevier Ltd. All rights reserved.State of Lower Saxony (Ministry of Science and Culture
Tropical moist Polylepis stands at the treeline in East Bolivia: the effect of elevation on stand microclimate, above- and below-ground structure, and regeneration
No full textWe studied Polylepis forests along an elevational transect between 3,650 and 4,050 m a.s.l. at the treeline of the moist eastern cordillera in Bolivia to examine changes in above- and below-ground stand structure, leaf and root morphology, and regeneration in relation to stand microclimate. Field measurements and model predictions indicated relatively cold growth conditions of the Polylepis forests. Tree height, stem diameter, and basal area of the stands decreased markedly while stem density increased with elevation. Leaf morphology differed between the two occurring Polylepis species, and trees at the treeline had smaller leaves with higher specific leaf area. In contrast, fine root biomass increased from 37 g m(-2) at the lowermost stand to 234 g m(-2) at the treeline. Trees of the uppermost stand had higher specific root surface area and a much higher number of root tips per unit dry mass. Thus, root surface area and total number of root tips per unit ground area increased conspicuously from the lowermost stand to the treeline. Density of young growth inside the forest increased towards the treeline, while density in the open grassland decreased with elevation. Young growth originated from sexual reproduction at the lower forest but was comprised exclusively of root suckers at the treeline stand. We conclude that both the marked change in carbon allocation towards the root system, as well as the changes in root morphology with elevation indicate an adaptation to reduced nutrient supply under cold conditions of these Polylepis stands at the treeline in E Bolivia
Biparental inbreeding depression, genetic relatedness and progeny vigour in a wind-pollinated treeline species in Argentina
Full text linkSpatially restricted gene flow and resulting spatial genetic structure are generally considered as being the primary controlling factors in the dynamics of biparental inbreeding depression in a wide range of plant species. However, wind-pollinated angiosperm trees have not been adequately studied in this respect. The present study analyses the relationships between parental genetic similarity, outcrossing distances and progeny vigour in Polylepis australis (Rosaceae), a wind-pollinated treeline species endemic to Argentina. We investigated whether spatial genetic structuring occurs in anthropogenically fragmented P. australis woodlands of the Córdoba Mountains. We also performed a controlled crossing experiment using pollen collected from different distances. Genetic variability (using RAPD-PCR) and vigour (survival and N metabolism capacity) of the resulting progeny were contrasted with progeny from unmanipulated flowers. We found a continuous decrease in parental genetic similarity with spatial distance among mates and an increase in genetic variability, survival and N metabolism capacity in the progeny produced from pollen at increasing distances. However, our further results suggest fragment connectivity in P. australis through effective long-distance pollen-mediated gene flow with no effective inbreeding depression problems observed under present day conditions.Fil: Seltmann, Peggy. Martin-Luther-University Halle-Wittenberg; AlemaniaFil: Hensen, Isabell. Martin-Luther-University Halle-Wittenberg; AlemaniaFil: Renison, Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones Biológicas y Tecnológicas. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Investigaciones Biológicas y Tecnológicas; ArgentinaFil: Wesche, Karsten. Universität Göttingen; AlemaniaFil: Ploch, Sebastián. Universidad de Hohenheim; AlemaniaFil: Rondan Dueñas, Juan. Universidad Nacional de Córdoba; ArgentinaFil: Cocucci, Andrea Aristides. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Jung, Klaus. Helmholtz Centre for Environmental Research; Alemani
Spatial genetic structure and low diversity of the rare arable plant Bupleurum rotundifolium L. indicate fragmentation in Central Europe
No full textMany threatened plant species have genetic structures indicating effects of fragmentation, and in Central Europe arable plants are among the most threatened taxa. Although this threat has developed only recently in the course of agricultural intensification, their annual life form makes arable plants relatively sensitive to increasing fragmentation and decreasing population sizes. One of Central Europe's rarest arable plant species is Bupleurum rotundifolium (Apiaceae). To analyze the genetic structure and diversity of this species we sampled 27 populations of B. rotundifolium in Central Europe, and assessed genetic structure by amplified fragment length polymorphism (AFLP) fingerprinting. Ordination, clustering and also Bayesian analysis suggested that most of the populations of the Eastern part of Germany formed one cluster, and most of the Western German populations as well as populations from outside Germany built another group. The two clusters accounted for 24% of differences in genetic structure of B. rotundifolium populations, while there was relatively strong differentiation among (41% variance) and within populations of a given group (35% variance). The overall phi(ST)-value was very high (0.65) and there was evidence for isolation-by-distance. Values of genetic diversity were very low for B. rotundifolium. The proportion of polymorphic loci per population varied between 9.4% and 38.7%, with those from eastern Germany being significantly less diverse (mean 19.1% vs. 25.5%). (C) 2012 Elsevier B.V. All rights reserved.Graduiertenforderung of Saxony-Anhal
Step(pe) up! Raising the profile of the Palaearctic natural grasslands
Full text linkPeter, Torok/0000-0002-4428-3327; Dengler, Jurgen/0000-0003-3221-660XWOS: 000386500700001Palaearctic steppes are primary grasslands dominating the landscape of the Eurasian Grassland Belt from Central and Eastern Europe to Northern China across the temperate zone of Eurasia. We also include structurally and floristically similar habitats in North Africa, Anatolia, and Iran. The biota of the steppes are diverse, including many endemic species. As a result of the high rate of anthropogenic conversion and widespread degradation, the Palaearctic steppes have become one of the most endangered terrestrial biomes of the world. These facts underline the importance of sustaining landscape-scale biodiversity in steppes and stress the necessity of their conservation and restoration. Literature about the ecology, biodiversity, and conservation of Palaearctic steppes is not easily accessible for an international audience. Therefore, summarising the current state of knowledge as well as knowledge gaps is very timely. This Special Issue on "Palaearctic steppes: ecology, biodiversity and conservation", comprises 17 research papers from many different regions throughout the biome, as well as a broad review synthesising current knowledge
Dramatic losses of specialist arable plants in Central Germany since the 1950s/60s – a cross‐regional analysis
No full textAimTo assess the consequences of agricultural intensification since the 1950s for Central Europe's plant communities of arable plants. LocationCentral Germany. Methods We employed a semipermanent plot design to analyse changes in 392 field interiors for 10 study regions, including sandy, limestone and loamy sites between the 1950s/60s and 2009. ResultsThe analysis revealed a reduction in the regional species pool during the 50-year period of 23% (from 301 to 233 vascular species) and dramatic losses in plot-level diversity (from medians of 24 to 7). Median cover of spontaneously growing arable plants decreased from 30% to 3%. Losses were disproportionally larger on limestone sites while sandy sites maintained a larger fraction of the original diversity. Archaeophytes, neophytes and most Poaceae (including some aggressive weeds) showed similarly strong losses as indigenous plants. This contradicts the assumption that grasses and neophytes are generally profiting from agricultural intensification. Crop diversity decreased from 25 crop plants present in the 1950s/60s to only 16 in 2009, while crop cover generally increased. Winter cereals, oilseed rape and maize are dominant today, while all other crop types showed strong declines. Main conclusionsVegetation change over time depended on soil substrate with once markedly different arable communities now showing more homogenized community structure. Increasing Ellenberg indicator values for nitrogen and pH point to N fertilization as a major driver of change. New conservation measures such as the establishment of field flora reserves and agri-environment schemes with less intensive land use are thus urgently needed especially on limestone substrates to bring an end to the decline of this functionally distinct and increasingly threatened component of the Central European flora
Genetic diversity of six arable plants in relation to their Red List status
No full textIn Central Germany and throughout Europe, arable plants count among some of the most endangered plant species. Over the last few decades, the number and size of populations have been in sharp decline due to modern land use techniques, including the application of fertilizers, herbicide use and seed cleaning procedures. As arable plant species are underrepresented in population genetic studies, it is unknown whether agricultural intensification has affected the extant populations, and whether genetic structure varies among species with differing vulnerability in respect of their Red List status. We sampled 53 populations from 6 arable plant species throughout Central Germany. Random amplified polymorphic DNA analyses (RAPD) were applied to calculate measures of genetic diversity at the population level and genetic differentiation. Genetic diversity was found to be lowest in Bupleurum rotundifolium and Anagallis foemina, and highest in Consolida regalis and Nigella arvensis. The highest levels of genetic differentiation were observed among populations of An. foemina and B. rotundifolium but within populations in all other species. I broken vertical bar(ST) values differed strongly ranging between 0.116 for C. regalis and 0.679 for An. foemina. Patterns of genetic structure were related to the Red List status for all the species studied except An. foemina, for which it should consequently be raised. Our data confirm that even relatively recent threats are accompanied by detrimental genetic structure. As losses of populations and increased fragmentation have occurred in all common and uncommon species, the situation for arable plants could change for the worse in the following decades, highlighting the need for consistent monitoring.Graduiertenforderung of Saxony-Anhal
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