3,129 research outputs found
High functional diversity is related to high nitrogen availability in a deciduous forest - evidence from a functional trait approach
No full textThe current study tested the assumption that floristic and functional diversity patterns are negatively related to soil nitrogen content. We analyzed 20 plots with soil N-contents ranging from 0.63% to 1.06% in a deciduous forest near Munich (Germany). To describe species adaptation strategies to different nitrogen availabilities, we used a plant functional type (PFT) approach. Each identified PFT represents one realized adaptation strategy to the current environment. These were correlated, next to plant species richness and evenness, to soil nitrogen contents. We found that N-efficient species were typical for low soil nitrogen contents, while N-requiring species occur at high N-contents. In contrast to our initial hypotheses, floristic and functional diversity measures (number of PFTs) were positively related to nitrogen content in the soil. Every functional group has its own adaptation to the prevailing environmental conditions; in consequence, these functional groups can co-exist but do not out-compete one another. The increased number of functional groups at high N-contents leads to increased species richness. Hence, for explaining diversity patterns we need to consider species groups representing different adaptations to the current environmental conditions. Such co-existing ecological strategies may even overcome the importance of competition in their effect on biodiversity
The estimation of aboveground biomass and nutrient pools of understorey plants in closed Norway spruce forests and on clearcuts
No full textThe estimation model PhytoCalc allows a non-destructive quantification of dry weight and nutrient pools of understorey plants in forests by using the relationship between species biomass, cover and mean shoot length. The model has been validated with independent samples in several German forest types and can be a useful tool in forest monitoring. However, in open areas within forests (e.g. clearcuts), the current model version underestimates biomass and produces unreliable nutrient pool estimations. Thus, tissue density, as approximated by leaf dry matter content (LDMC), is systematically higher under high light compared to low light conditions. We demonstrate that the ratio of LDMC under clearcut conditions to LDMC under forest conditions can be used to adjust the PhytoCalc model to clearcut conditions. We investigated the LDMC ratio of five exemplary species commonly occurring on clearcuts. Integrating the square of the ratio as a correction factor improved estimates of biomass to more than 70% fit between observations and predictions. Results also suggest this ratio can be used to correct nutrient concentrations modelled in PhytoCalc, which tend to be overestimated in clearcuts. As morphological groups of plant species exhibit significantly different ratios, we advise using group-specific correction factors for clearcut adjustments in the future
Drought tolerance of emerging European silver fir seedlings (Abies alba Mill.) does not follow geographic gradients
No full textAbstract One of silviculture's primary objectives is converting monospecific into diverse forest stands comprising climate-tolerant species, aiming to mitigate global change. In practice, this is often achieved by enrichment planting or seeding of species, currently not occurring in the specific area. Silver fir ( Abies alba ) is considered one of the European native species regarded as climate tolerant. The species, therefore recently received increasing attention in research and forestry in the context of climate change adaptation. The intra-specific variation in drought tolerance has been intensively studied in Abies alba adult trees, but not in seedlings. Here, we explore the potential of Abies alba seedlings to withstand simulated summer droughts in central Europe. A climate chamber experiment was conducted, examining the resistance to and recovery from drought of silver fir seedlings of four provenances representing a geographic West–East gradient in Europe. Seedlings were exposed to two 30-day drought scenarios of differing severity under controlled conditions. We measured biomass partitioning patterns and individual photosynthetic efficiency. Growth and maximum photosynthetic efficiency were unaffected by intermediate drought. Intense drought significantly reduced the maximum photosynthetic efficiency of all provenances. Seedlings of the easternmost provenance showed the greatest biomass across all treatments; however, they failed to recover from drought. Our findings show that differences in drought susceptibility of emerging Abies alba seedlings do not follow geographic gradients
Explaining grassland biomass - the contribution of climate, species and functional diversity depends on fertilization and mowing frequency
No full text1. Grassland ecosystems are often used to generate biomass in temperate regions of the world. It is well known that biomass is influenced by climate and biodiversity, but the relative importance of these two factors in relation to management has not been widely studied. To recommend management treatments maximizing biomass yields we aim to quantify the relative effects of climate species and functional diversity on biomass in differently managed grasslands. 2. We studied the development of biomass yields over the last 37 years on a grassland site in Germany, with mowing at five frequencies (one to eight times per year), each with and without fertilization. We measured plant species richness (SR) and functional richness (FR) (the diversity of functional species properties) using presence-absence indices. We also measured species evenness (SE), functional evenness and functional divergence (FD) using abundance weighted indices. Climate was included as the mean temperature and sum of precipitation during the growing period. By relating biomass to the above-mentioned climatic and biodiversity parameters, we extracted the contribution of these to biomass yields. 3. Biomass changed over time for all treatments and was maximal at intermediate mowing frequencies. Temporal changes in biomass were partly explained by climate and different aspects of biodiversity, although this differed significantly between treatments. The relative importance of precipitation was highest at high mowing frequencies; the contribution of temperature was highest on less disturbed, unfertilized plots. FR and SR influenced biomass changes in the most intensive disturbance regimes on unfertilized and fertilized plots respectively. FD was most important on intensively disturbed, fertilized plots. SE influenced biomass at low mowing frequencies. 4. Synthesis and applications. Climate, species and functional diversity influence annual grassland biomass yields but their importance depends on nutrient status and management frequency. Our results indicate that management treatments with intermediate disturbance regimes will maximize biomass yields in temperate environments. This recommendation may become even more important in the context of climate change: at intermediate mowing frequencies the influence of climatic variables on biomass is less important by comparison to different aspects of biodiversity
Herb-layer diversity in deciduous forests: Raised by tree richness or beaten by beech?
No full textWhere natural production capacity permits, modern silvicultural management in Central Europe frequently aims at the development of mixed broadleaved stands, instead of pure European beech (Fagus sylvatica) stands. It is crucial to study the effects of these tree-layer diversity variations on herb-layer vegetation, since herb-layer vegetation contributes significantly to ecosystem functioning in forests. In Hainich National Park (Thuringia, Germany), we conducted observational research in deciduous stands to investigate whether herb-layer diversity was related to canopy-layer diversity, and to ascertain possible causal mechanisms. We found that herb-layer vegetation of deciduous forest stands rich in canopy species appeared to be more diverse than herb-layer vegetation of beech-dominated stands. We surmise that herbaceous understorey diversity was indirectly influenced by canopy tree species through the medium of the altered environmental factors soil pH and litter layer thickness. Apparently, lower beech proportion had a more profound effect than the number of secondary tree species. There were no correlations between herb-layer diversity and light transmissibility of the canopy layer, indicating that the light factor was not crucial for herb-layer diversity. At least for the Hainich research sites, our results indicated that small-scale light and soil heterogeneity is insignificant for herb-layer diversity. We found several herb-layer species whose occurrence was particularly correlated with tree-layer diversity and environmental factors. Remarkably, all species positively correlated with soil pH were important for the phytosociological classification of the research sites. Beech-dominated research sites showed high tree-layer volumes, whereas research sites with high tree-layer diversity tended to feature lower tree-layer volumes. These findings could be the result of differing former silvicultural systems and varying soil clay contents affecting tree species composition. In contrast, herb-layer biomass was positively correlated with tree-layer diversity. Herb-layer productivity might be promoted in more diverse research sites by increased nutrient supply and base saturation. It is also possible that greater beech proportion interfered with herb-layer productivity. However, herb-layer biomass was also positively correlated with herb-layer diversity. Hence, our study hints that positive diversity-functioning relationships might occur in the herb-layer of the deciduous forest under investigation. (C) 2008 Elsevier B.V. All rights reserved
Forest ecosystem research in Hainich National Park (Thuringia) : first results on flora and vegetation in stands with contrasting tree species diversity
No full textA floristic description is presented of the study sites of the Research Training Group “The role of biodi-versity for biogeochemical cycles and biotic interactions in temperate deciduous forests”. To investi-gate different aspects of plant biodiversity in Hainich National Park (Thuringia), deciduous forest stands with low, medium and high canopy tree species diversity were compared. The results of species richness and forest communities show that the research sites are characterised by a typical central European forest flora. Greater vascular plant species richness occurs with higher diversity of tree species. Six of altogether twelve research sites are assigned to the beech forest alliance (Galioodorati-Fagion), the second half belongs to the oak-hornbeam forest alliance (Carpinionbetuli). Suballiances within the Galioodorati-Fagion in the study area include the Galio-Fagetum and the Hordelymo-Fagetum. All Carpinionbetuli relevées are assigned to the suballiance Stellario-Carpinetum
Changes in life history trait composition during undisturbed old-field succession
No full textThis paper describes the patterns of vegetation change by spontaneous succession on former agricultural land. In 1968, initiated by Heinz Ellenberg, an experimental study site was set up on an arable field in the new botanical garden of Gottingen University (Germany). The undisturbed Successions on four plots of a long sere (since 1968/69) and on four additional plots of a shorter sere (since 1982) were evaluated. The seres were classified into stages by cluster analysis, which yield to four Subsequent stages for the long sere and to three Subsequent stages for the short sere. The early succession is characterized by a high proportion of species invasion, whereas with developing time species extinction increased. On all study plots undisturbed Succession directed to the development of pioneer forests. Altogether 247 vascular plant species were recorded. The total species richness shows a fluctuating course during the Successional seres, with significantly increased numbers shortly after Succession has started and a decline in the pioneer-forest stage, when stands age and close down. The primary aim was to compare the characteristics (particular traits) of species occurring at different stages of succession. The majority of the traits concerned exhibited some clear trends in the course of succession. Exclusive reproduction by seeds decreased and the ability for additional vegetative reproduction increased. Anemochorous dispersal significantly decreased, whereas the importance of dispersal by animals, especially endochorous, dominates in the pioneer-forest stage. The mean seed weight significantly increased. During early Succession, plant species staying green over winter dominated, but are of none relevance in the pioneer-forest stage, where summergreen plant species dominate. The change in strategy type features a significant increase of competitive species. The mean Indicator value for light in the herb layer decreased significantly in the pioneer-forest stage. (c) 2008 Elsevier GmbH. All rights reserved
The influence of termite-induced heterogeneity on savanna vegetation along a climatic gradient in West Africa
No full textTermites are renowned ecosystem engineers. Their mounds have been described as an important element of savanna vegetation dynamics, but little is known about their large-scale impact on vegetation composition. To investigate the influence of termite-induced heterogeneity in savannas along a climatic gradient in West Africa termite mound vegetation was compared with adjacent savanna vegetation using 256 paired plots (size of the termite mound and a corresponding savanna area) in five protected areas from northern Burkina Faso to northern Benin. On each plot vegetation and soil sampling was performed. Additionally bioclimatic variables from the WORLDCLIM database were used. The vegetation on the mounds and the surrounding savanna differed within all study sites(DCA length of gradient 3.85 SD) and showed complete turnover along the climatic gradient (DCA length of gradient 5.99 SD). Differences between mounds and savanna were significantly related to termite-induced changes in soil parameters, specifically clay enrichment and increased cation concentrations (base saturation). On a local scale, termite-induced differences in soil conditions were found to be the most important factor affecting mound vegetation, while on a regional scale, annual precipitation showed the strongest significant correlations. However, with increasing precipitation, differences between mounds and the surrounding matrix became more pronounced, and the contribution of mounds to local phytodiversity increased. Eleven plant species were identified as characteristic termite mound species. In the more humid parts of the gradient, more characteristic plant species were found that may benefit from favourable soil conditions, good water availability, and a low fire impact in the mound microhabitat
Directional turnover towards larger-ranged plants over time and across habitats
No full textSpecies turnover is ubiquitous. However, it remains unknown whether certain types of species are consistently gained or lost across different habitats. Here, we analysed the trajectories of 1827 plant species over time intervals of up to 78 years at 141 sites across mountain summits, forests, and lowland grasslands in Europe. We found, albeit with relatively small effect sizes, displacements of smaller- by larger-ranged species across habitats. Communities shifted in parallel towards more nutrient- demanding species, with species from nutrient-rich habitats having larger ranges. Because these species are typically strong competitors, declines of smaller-ranged species could reflect not only abiotic drivers of global change, but also biotic pressure from increased competition. The ubiquitous component of turnover based on species range size we found here may partially reconcile findings of no net loss in local diversity with global species loss, and link community-scale turnover to macroecological processes such as biotic homogenisation
Nitrogen in forest communities: the alteration of its importance
No full textDuring the last decades the effect of nitrogen on forest ecosystems has totally changed: Formerly, vegetation growth was limited by nitrogen, today nitrogen must be seen as a pollutant. The increased deposition of nitrogen into forest-ecosystems affects not only the vegetation composition, but also endangers the meaning of forests as a source for drinking water. in the article the impact of increased nitrogen availability on forest ecosystems is shown. Especially the possibilities and advantages of using vegetation as an indicator for the impact of nitrogen are discussed and compared with methods of technical measurements. Based on these results it is strongly recommended to enhance the explanatory power of technical measurements by additionally carrying out vegetation analyses
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