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Dry Grasslands (dry + grassland)
Selected AbstractsPhotodegradation leads to increased carbon dioxide losses from terrestrial organic matterGLOBAL CHANGE BIOLOGY, Issue 11 2010SUSANNA RUTLEDGE Abstract CO2 production in terrestrial ecosystems is generally assumed to be solely biologically driven while the role of abiotic processes has been largely overlooked. In addition to microbial decomposition, photodegradation , the direct breakdown of organic matter (OM) by solar irradiance , has been found to contribute to litter mass loss in dry ecosystems. Previous small-scale studies have shown that litter degradation by irradiance is accompanied by emissions of CO2. However, the contribution of photodegradation to total CO2 losses at ecosystems scales is unknown. This study determined the proportion of the total CO2 losses caused by photodegradation in two ecosystems: a bare peatland in New Zealand and a seasonally dry grassland in California. The direct effect of solar irradiance on CO2 production was examined by comparing daytime CO2 fluxes measured using eddy covariance (EC) systems with simultaneous measurements made using an opaque chamber and the soil CO2 gradient technique, and with night-time EC measurements under the same soil temperature and moisture conditions. In addition, a transparent chamber was used to directly measure CO2 fluxes from OM caused by solar irradiance. Photodegradation contributed 19% of the annual CO2 flux from the peatland and almost 60% of the dry season CO2 flux from the grassland, and up to 62% and 92% of the summer mid-day CO2 fluxes, respectively. Our results suggest that photodegradation may be important in a wide range of ecosystems with exposed OM. Furthermore, the practice of partitioning daytime ecosystem CO2 exchange into its gross components by assuming that total daytime CO2 losses can be approximated using estimates of biological respiration alone may be in error. To obtain robust estimates of global ecosystem,atmosphere carbon transfers, the contribution of photodegradation to OM decomposition must be quantified for other ecosystems and the results incorporated into coupled carbon,climate models. [source] Verbreitung und Differenzierung der mitteleuropäischen Unterarten von Buglossoides arvensis (L.) I. M. Johnst. (Boraginaceae),FEDDES REPERTORIUM, Issue 1-2 2003A. Clermont In Mitteleuropa sind zwei Unterarten des Ackersteinsamens (Buglossoidesarvensis subsp. arvensis, B. arvensis subsp. sibthorpiana) verbreitet. Die molekularbiologische Untersuchung der nucleären ITS1-Region von 55 mitteleuropäischen Belegen verdeutlicht die Eigenständigkeit der beiden Sippen. Innerhalb des 238 Basenpaare langen Markers unterscheiden sich die Unterarten durch 15 Substitutionen (6,4 %). Die Ergebnisse lassen den Schluss zu, dass die Unterarten bisher aufgrund ihrer morphologischen Plastizität oft verwechselt und Häufigkeit und Verbreitung der Subspecies sibthorpiana unterschätzt wurden. Morphologisch lassen sich die beiden Unterarten anhand folgender Merkmale unterscheiden: Buglossoides arvensis subsp. arvensis besitzt längliche Keimblätter, eine gerade Gynobasis, einen unverdickten, geraden Pedicellus sowie cremefarbene oder selten leicht rosa gefärbte Blüten. Buglossoides arvensis subsp. sibthorpiana zeichnet sich durch runde Keimblätter, eine zur Fruchtzeit leicht zur Blütenstandsachse geneigte Gynobasis, einen schiefen, verdickten Pedicellus an den unteren Früchten und blaue, rosa oder cremefarben gefärbte Blüten aus. Weiterhin unterscheiden sich die Unterarten in ihren ökologischen Ansprüchen: B. arvensis subsp. arvensis kommt nur als Ackerunkraut vor, B. arvensis subsp. sibthorpiana wächst sowohl auf Ackerstandorten als auch auf Trockenrasen, sandigen Ruderalflächen oder in trockenen, lichten Wäldern. Distribution and differentiation of the Central European subspecies of Buglossoides arvensis (L.) I.M.Johnst. (Boraginaceae) The Corn Gromwell (Buglossoides arvensis) has two Central European subspecies, B. arvensis subsp. arvensis and B. arvensis subsp. sibthorpiana. The ITS1-region of 55 European samples was amplified and sequenced and it yielded a 238 bp fragment, which consistently differed by 15 substitutions between the two subspecies. The results suggest that the two subspecies indeed represent two independent taxa and have been confused mainly because of their morphological plasticity. Because of this confusion, distribution and abundance were poorly understood. The subspecies as here re-defined can be distinguished as follows: B. arvensis subsp. arvensis has oblong cotyledons, a horizontal gynobase, an unthickened pedicel in fruit, and a cream-coloured corolla. B. arvensis subsp. sibthorpiana has circular cotyledons, an oblique gynobase, an obliquely thickened pedicel in fruit, and a light blue to (more rarely) cream-coloured corolla. The two taxa show some degree of ecological differentiation: B. arvensis subsp. arvensis is only found as a weed in winter cereals, whereas B. arvensis subsp. sibthorpiana is occasionally found as a weed in fields, but also on dry grasslands, sandy waste sites and road sides, and in dry, open forests. [source] Substitutes for grazing in semi-natural grasslands , do mowing or mulching represent valuable alternatives to maintain vegetation structure?JOURNAL OF VEGETATION SCIENCE, Issue 6 2009Christine Römermann Abstract Question: Which management treatments are suitable to replace historically applied grazing regimes? How and why does vegetation structure change following changes in management? Location: Semi-natural calcareous dry grasslands in southwest Germany. Methods: We analysed changes in floristic and functional composition induced by different management treatments (grazing, mowing, mulching, succession) in long-term experimental sites. First, floristic and functional distances between the initial conditions and the following years were determined. Second, we used RLQ analyses to include data on abiotic conditions, vegetation composition and functional traits in one common analysis. Finally, we applied cluster analyses on RLQ species scores to deduce functional groups. Results: In contrast to the historical management regime of grazing, all alternative management treatments led to changes in floristic and functional composition, depending on their intensity with respect to biomass removal. The distance analyses showed that mulching twice per year and mowing did not lead to strong changes in floristic or functional composition. However, RLQ analysis clearly provided evidence that only the grazed sites are in equilibrium, indicating that vegetation change still goes ahead. Conclusions: The current study clearly shows that RLQ is a powerful tool to elucidate ongoing processes that may remain hidden when separately analysing floristic and functional data. Alternative management treatments are not appropriate to sustain the typical disturbance dynamics of species-rich semi-natural grasslands. The less frequent an alternative management treatment is with respect to biomass removal, the less the floristic and functional structure can be maintained. [source] How do management and restoration needs of mountain grasslands depend on moisture regime?APPLIED VEGETATION SCIENCE, Issue 3 2009Experimental study from north-western Slovakia (Western Carpathians) Abstract Question: How does species composition change in traditionally managed meadows after mowing has ceased, and in abandoned meadows after re-introduction of mowing? Are there differences in the dynamics of dry and moderately wet meadows? Location: Zázrivá-Ple,ivá (19°11,N, 49°16,E), north-western Slovakia, western Carpathians. Methods: Pairs of experimental plots (mown and unmown) were established to replicate each combination of dry/wet and traditionally managed/abandoned meadows. Changes in species composition were studied over 5 years. The data on changes in species composition was analysed by constrained and unconstrained ordinations, and visualized using Principal Response Curves. Results: Species composition of newly abandoned wet grasslands was changing towards the corresponding long-abandoned plots even in the first year of abandonment. Similarly, newly established restoration mowing in abandoned dry grasslands rapidly shifted the stand species composition towards that of traditionally managed ones. Nevertheless, 4 year after reintroduction of mowing, the species composition of the restored plots was still far from the target composition. The effect of mowing in abandoned wet grasslands and abandonment in dry grasslands was much less pronounced and slower. Conclusions: Moisture regime is a very important factor determining the management needs of various grassland types. Wet grasslands are much more sensitive to abandonment, with a rapid degradation rate and limited possibilities for restoration, which can be extremely slow. Even in the dry grasslands, that quickly responded to restoration mowing, restoration is a long-term process. [source] Diversity of native and alien vascular plant species of dry grasslands in central EuropeAPPLIED VEGETATION SCIENCE, Issue 4 2008Franz Essl Fischer et al. (2005) for vascular plants; Mucina et al. (1993) for syntaxonomical units Abstract Question: Which factors determine diversity of native and alien vascular plant species in semi-natural dry grasslands? Location: Northern limestone Alps to the southern rim of the Bohemian massif in northern Austria. Methods: In 70 randomly chosen dry grassland patches (0.008 ha - 7 ha) we sampled a complete inventory of vascular plant species at each site. We analysed the correlation between species diversity of natives, archaeophytes (pre-1500 aliens) and neophytes (post-1500 aliens). We used GLM to study the relationship of species number (natives, neophytes, archaeophytes) to five explanatory variables (altitude, within habitat diversity, habitat diversity of adjacent areas, within land-use diversity and land-use in adjacent areas). Orthogonal components of these variables were derived with a PCA and used in the models. We also tested the influence of minimum residence time (MRT) and the covariables origin, mode of introduction and life form on the number of grassland sites with neophytes with analogous GLMs. Results: Native species diversity species was positively correlated with the species diversity of new, but not old invaders. GLM explains 70% of the variance in the number of native species. Patch size explained the largest part of the variation in the number of native species. PCA axes 1 and 3 were significantly related to the number of native species. Axis 1was related to on-site habitat and land-use diversity. The GLM of the archaeophyte diversity explains 18% of the variance. Altitude and presence of fields and grassland in the neighbourhood mainly explained archaeophyte species diversity. The GLM of neophyte diversity explains 12% of the variance. The number of neophytes was positively related to that of archaeophytes. Only PCA axis 3, which is mainly influenced by adjacent land-use types, showed a relationship with neophytes. MRT, mode of introduction and region of origin (but not life form) were significantly related to the number of grassland sites invaded by neophytes, explaining 35% of the variance. Conclusion: Most factors governing native species diversity are not significantly related to alien species diversity. Additional determinants of the local scale diversity of alien species exist such as region of origin and historical factors (MRT, mode of introduction). [source] | |||||||||||||