Showing papers by "Ernst Detlef Schulze published in 2015"

Intransitive competition is widespread in plant communities and maintains their species richness

Abstract: Intransitive competition networks, those in which there is no single best competitor, may ensure species coexistence. However, their frequency and importance in maintaining diversity in realworld ecosystems remain unclear. We used two large data sets from drylands and agricultural grasslands to assess: (1) the generality of intransitive competition, (2) intransitivity–richness relationships and (3) effects of two major drivers of biodiversity loss (aridity and land-use intensification) on intransitivity and species richness. Intransitive competition occurred in > 65% of sites and was associated with higher species richness. Intransitivity increased with aridity, partly buffering its negative effects on diversity, but was decreased by intensive land use, enhancing its negative effects on diversity. These contrasting responses likely arise because intransitivity is promoted by temporal heterogeneity, which is enhanced by aridity but may decline with land-use intensity. We show that intransitivity is widespread in nature and increases diversity, but it can be lost with environmental homogenisation.

A vertically discretised canopy description for ORCHIDEE (SVN r2290) and the modifications to the energy, water and carbon fluxes

Abstract: . Since 70 % of global forests are managed and forests impact the global carbon cycle and the energy exchange with the overlying atmosphere, forest management has the potential to mitigate climate change. Yet, none of the land-surface models used in Earth system models, and therefore none of today's predictions of future climate, accounts for the interactions between climate and forest management. We addressed this gap in modelling capability by developing and parametrising a version of the ORCHIDEE land-surface model to simulate the biogeochemical and biophysical effects of forest management. The most significant changes between the new branch called ORCHIDEE-CAN (SVN r2290) and the trunk version of ORCHIDEE (SVN r2243) are the allometric-based allocation of carbon to leaf, root, wood, fruit and reserve pools; the transmittance, absorbance and reflectance of radiation within the canopy; and the vertical discretisation of the energy budget calculations. In addition, conceptual changes were introduced towards a better process representation for the interaction of radiation with snow, the hydraulic architecture of plants, the representation of forest management and a numerical solution for the photosynthesis formalism of Farquhar, von Caemmerer and Berry. For consistency reasons, these changes were extensively linked throughout the code. Parametrisation was revisited after introducing 12 new parameter sets that represent specific tree species or genera rather than a group of often distantly related or even unrelated species, as is the case in widely used plant functional types. Performance of the new model was compared against the trunk and validated against independent spatially explicit data for basal area, tree height, canopy structure, gross primary production (GPP), albedo and evapotranspiration over Europe. For all tested variables, ORCHIDEE-CAN outperformed the trunk regarding its ability to reproduce large-scale spatial patterns as well as their inter-annual variability over Europe. Depending on the data stream, ORCHIDEE-CAN had a 67 to 92 % chance to reproduce the spatial and temporal variability of the validation data.

Plasticity of functional traits of forb species in response to biodiversity

Abstract: In spite of increasing recognition that intraspecific variation may play an important role for niche differentiation, which is regarded as a promoter of species coexistence, the extent and structure of functional trait variation in response to plant neighbor diversity is poorly understood. We studied the plasticity of functional traits in vegetative and reproductive shoots of 27 non-legume forb species with different growth forms (reptant, rosulate, semirosulate) in experimental grasslands (Jena Experiment) of varying species richness and functional group composition (with and without legumes). Traits related to whole-shoot structure differed strongly among forb species with different growth forms, while leaf traits associated with light acquisition (specific leaf area, foliar δ13C values) and traits associated with nitrogen nutrition (shoot biomass:N ratios, leaf nitrogen concentrations, foliar δ15N values) were highly plastic within forb species. Plant height generally increased with increasing species richness. Plasticities to increased species richness in leaf traits (leaf length, SLA, foliar δ13C) varied among growth forms and depended on developmental stage. The presence of legumes generally increased plastic responses in light-acquisition traits in the same direction as increasing species richness. Greater tissue nitrogen concentrations and unchanged foliar δ15N values of forb species in the presence of legumes suggested that the fertilizing effect of nitrogen-fixing legumes was due to the supply of unconsumed mineral nitrogen. Stronger correlations between trait means and trait plasticities in size-related traits suggested a functional convergence in response to light competition. A more variable spectrum in the plasticities of traits not associated with plant size indicated a greater functional separation among species. Our results suggest that both interspecific differences and intraspecific trait plasticity affect niche partitioning among forb species and are important for their coexistence in multi-species assemblages.

Contrasting effects of intraspecific trait variation on trait-based niches and performance of legumes in plant mixtures.

Abstract: Niche differentiation, assumed to be a key mechanism of species coexistence, requires that species differ in their functional traits. So far it remains unclear to which extent trait plasticity leads to niche shifts of species at higher plant diversity, thereby increasing or decreasing niche overlap between species. To analyse this question it is convenient to measure niches indirectly via the variation in resource-uptake traits rather than directly via the resources used. We provisionally call these indirectly measured niches trait-based niches. We studied shoot- and leaf-morphological characteristics in seven legume species in monoculture and multi-species mixture in experimental grassland. Legume species varied in the extent of trait variation in response to plant diversity. Trait plasticity led to significant shifts in species niches in multiple dimensions. Single-species niches in several traits associated with height growth and filling of canopy space were expanded, while other niche dimensions were compressed or did not change with plant diversity. Niche separation among legumes decreased in dimensions related to height growth and space filling, but increased in dimensions related to leaf size and morphology. The total extent of occupied niche space was larger in mixture than in the combined monocultures for dimensions related to leaf morphology and smaller for dimensions related to whole-plant architecture. Taller growth, greater space filling and greater plasticity in shoot height were positively, while larger values and greater plasticity in specific leaf area were negatively related with increased performance of species in mixture. Our study shows that trait variation in response to plant diversity shifts species niches along trait axes. Plastically increased niche differentiation is restricted to niche dimensions that are apparently not related to size-dependent differences between species, but functional equivalence (convergence in height growth) rather than complementarity (divergence in traits associated with light acquisition) explains increased performance of legumes in mixture.

Plant diversity and community history shift colonization success from early- to mid-successional species

Abstract: Aims Functional traits are supposed to play an important role in determining the colonization success of new species into established communities. Short-term experimental studies have documented higher resistance of more diverse grasslands against colonization by new species. However, little is known about which traits colonizers should have to successfully invade diverse plant communities in the longer term and how community history may modify the resistance of diverse communities against colonization. Methods In a grassland biodiversity experiment (Jena Experiment) established with different species richness (SR; 1, 2, 4, 8 and 16) and functional group (FG) number and composition (1 to 4; legumes, grasses, small herbs, tall herbs), we studied colonization of naturally dispersed species in split-plots (i) with different duration of weeding (never weeded, weeded for 3 or 6 years and then un-weeded for 1 year) and (ii) with different duration of colonization (7 years, 4 years and 1 year after cessation of weeding). Important Findings Resistance against colonization by new species declined with increased duration of weeding (on average 13, 17 and 22 colonizer species in 1-, 4- and 7-year-old communities, respectively). Communities established at low diversity accumulated more colonizer species with a longer duration of weeding than more diverse communities. Duration of colonization had only small effects on the number of colonizer species. Colonizers with early successional traits, i.e. annual life cycle, reproduction by seeds, small seeds, long-lived seeds and an earlier start of a longer flowering period, were favoured in species-poor newly established experimental plant communities (short duration of weeding) and early after cessation of weeding (short duration of colonization). A change from early- to mid-successional traits, i.e. taller growth, perennial life cycle, vegetative reproduction, characterized colonization at increased plant diversity and in communities with legumes or without grasses. Legume absence/grass presence and increased duration of weeding led to a shift in colonizer strategies from rapid nutrient uptake and cycling (higher specific leaf area) to nutrient retention and symbiotic N2 fixation. Our study shows that non-random trait spectra of naturally dispersed colonizers encompass trade-offs between different functions (reproduction, persistence, growth) reflected in a change from early- to mid-successional traits at increasing plant diversity, with a longer duration of weeding and a longer time of colonization.

Carbon dynamics in boreal peatlands of the Yenisey region, western Siberia

Abstract: . Here we investigate the vegetation history and peat accumulation at the eastern boarder of the West Siberian Plain, near the Yenisey River, south of permafrost. In this region, peat started to accumulate 15 000 years ago as gyttja of shallow lakes in ancient river valleys. This peat is older than previously reported, mainly due to separating particulate organic carbon (POC) from dissolved organic carbon (DOC), which was 1900–6500 years younger than POC. The probability of finding peat layers older than 12 000 years is about 2 %. Peat accumulated as fen peat at a constant rate of 0.2 mm yr−1 and 0.01 kg C m−2 yr−1. The accumulation was higher in ancient river valley environments. Over the last 2000 years these bogs changed into Sphagnum mires which have accumulated up to about 0.1 kg C m−2 yr−1 until present. The long-lasting fen stage, which makes the Yenisey bogs distinct from the western Siberian bogs, is discussed as a consequence of the local hydrology. The high accumulation rate of peat in unfrozen mires is taken as an indication that thawing of permafrost peat may also change northern peatlands into long-lasting carbon sinks.

Konflikte um eine nachhaltige Entwicklung der Biodiversität: Spannungsfeld Forstwirtschaft und Naturschutz

Abstract: Die Arbeit gibt einen Uberblick uber die zeitliche Entwicklung der Flora in Deutschland mit besonderer Berucksichtigung der an Waldstandorte gebundenen Arten. Die Zahl der Pflanzenarten hat uber die Zeit kontinulierlich zugenommen. Dies ist vor allem eine Folge der Landnutzung, durch die auch einige gefahrdete Arten erhalten werden. In forstlich bewirtschafteten Waldern ist der Pflanzenartenvielfalt groser in als in Waldern unter Naturschutz. Keine der obligaten Waldarten ist in den letzten 250 Jahren durch die Waldbewirtschaftung verloren gegangen. Fur Arten mit besonderen Habitat-Anspruchen sind alternative Schutzprogramme zu einer Nicht-Bewirtschaftung notig, um spezielle Lebensraume zu erhalten. Conflicts between forest management and nature protection This study gives an overview of the change of the German flora over time with special emphasis on species growing in forest habitats. As a consequence of land use plant species numbers have continually increased. Land management has also maintained some endangered plant species. The plant diversity of managed forests is higher than that of unmanaged forests. Not a single obligate forest species has gone extinct over the past 250 years of forest management, the time span of formal records. For organisms with special habitat requirements alternative protection measures other than non-management are needed to maintain these habitats.

Bioenergy: Potentials and limitations

Abstract: In this lecture we explain 1) the biochemical basis for photosynthesis and plant production and 2) the future demands on biomass for human use. Summing all physiological processes, the efficiency of converting solar energy into biomass is < 1.6% in the tropics, and between 0.4 and 0.8% for the temperate regions. In view of the present and future high demand on biomass for food, bioeconomics, fiber, construction material, only a relatively small fraction of plant production will be available for bioenergy. We estimate this fraction to be between 3 and 8% of the global energy demand by 2050. The contribution of bioenergy is at the higher end in tropical regions and in the less industrialized parts of the world, but may even be < 3% in industrialized nations.

Biogeochemistry: Historical and future perspectives

Abstract: th century, leading to Geochemistry in the 19 th and to Biogeochemistry in the 20 th century [1]. While chemistry deals with the understanding of substances, the focus of geochemistry is the earth crust and the cycling of elements. It was the insight of modern times, that most reactions that drive geochemical cycles are regulated by organisms. The prefix “Bio” represents this fact. This new “twig” of the “tree” of science would have remained purely “academic”, if other “branches”, mainly Meteorology, would not have signaled early signs of global climate change. It was the Intergovernmental Panel on Climate Change that identified “Bio” including human actions as the most likely cause for observed changes in climate, and that made Biogeochemistry a prominent “branch” of science [2]. Biogeochemistry investigates the linkage between organisms and the global element cycles from ecosystem level up to the global surface where human actions emerge as main driver also of natural processes.

Reply to Mikoláš's comment on "Opinion Paper: Forest management and biodiversity" by Schulze et al. (2014)

Abstract: E. D. Schulze1, L. Bouriaud2, H. Bussler3, M. Gossner4, H. Walentowski3, D. Hessenmoller5, O. Bouriaud6, and K. v. Gadow7 1Max Planck Institute for Biogeochemistry, Box 100164, 07701 Jena, Germany 2University Stefan cel Mare of Suceava, 13 University Street, 720229 Suceava, Romania 3Bavarian State Institute of Forestry, Hans-Carl-von-Carlowitz Platz 1, 85354 Freising, Germany 4Technical University of Munich, Department of Ecology and Ecosystem Management, Hans-Carl-von-Carlowitz Platz 2, 85354 Freising, Germany 5Kabach 13A, 98574 Schmalkalden, Germany 6Forest Research and Management Institute, Bucharest, 128 Bd Eroilor, Voluntari, Romania 7University of Gottingen, Romstr. 3a, 37079 Gottingen, Germany