110 research outputs found
Plant functional trait diversity regulates the nonlinear response of productivity to regional climate change in Tibetan alpine grasslands
The biodiversity-productivity relationship is still under debate for alpine
grasslands on the Tibetan Plateau. We know little about direct and indirect
effects of biotic and abiotic drivers on this relationship, especially in
regard to plant functional trait diversity. Here, we examine how aboveground
net primary productivity (ANPP) and precipitation use efficiency (PUE) respond
to climate, soil and community structure across alpine grasslands on the
Northern Tibetan Plateau. We found that both ANPP and PUE showed nonlinear
patterns along water availability and site altitude variation, which together
accounted for 80.3% and 68.8% of variation in ANPP and PUE, respectively, by
optimal generalized additive models. Functional trait divergence (FTD) and
community weighted mean (CWM) of plant functional traits were as important as
plant species diversity (PSD) for explaining the nonlinear productivity-
climate relationship. These findings were confirmed by results from principal
component analyses and structural equation models. We also found that FTD was
negatively correlated with PSD across different alpine grasslands. Our results
implicate: first, the combinatorial influences of temperature and
precipitation gradients are important for predicting alpine grassland
dynamics; second, the convergence and divergence of plant functional traits
may have the potential to elucidate the effect of plant diversity on ecosystem
functionality
Using a Multi-Trait Approach to Manipulate Plant Functional Diversity in a Biodiversity-Ecosystem Function Experiment
A frequent pattern emerging from biodiversity-ecosystem function studies is
that functional group richness enhances ecosystem functions such as primary
productivity. However, the manipulation of functional group richness goes
along with major disadvantages like the transformation of functional trait
data into categories or the exclusion of functional differences between
organisms in the same group. In a mesocosm study we manipulated plant
functional diversity based on the multi-trait Functional Diversity
(FD)-approach of Petchey and Gaston by using database data of seven functional
traits and information on the origin of the species in terms of being native
or exotic. Along a gradient ranging from low to high FD we planted 40 randomly
selected eight-species mixtures under controlled conditions. We found a
significant positive linear correlation of FD with aboveground productivity
and a negative correlation with invasibility of the plant communities. Based
on community-weighted mean calculations for each functional trait, we figured
out that the traits N-fixation and species origin, i.e. being native or
exotic, played the most important role for community productivity. Our results
suggest that the identification of the impact of functional trait diversity
and the relative contributions of relevant traits is essential for a
mechanistic understanding of the role of biodiversity for ecosystem functions
such as aboveground biomass production and resistance against invasion
Genetic Variation of the Host Plant Species Matters for Interactions with Above- and Belowground Herbivores
Plants are challenged by both above- and belowground herbivores which may
indirectly interact with each other via herbivore-induced changes in plant
traits; however, little is known about how genetic variation of the host plant
shapes such interactions. We used two genotypes (M4 and E9) of Solanum
dulcamara (Solanaceae) with or without previous experience of aboveground
herbivory by Spodoptera exigua (Noctuidae) to quantify its effects on
subsequent root herbivory by Agriotes spp. (Elateridae). In the genotype M4,
due to the aboveground herbivory, shoot and root biomass was significantly
decreased, roots had a lower C/N ratio and contained significantly higher
levels of proteins, while the genotype E9 was not affected. However,
aboveground herbivory had no effects on weight gain or mortality of the
belowground herbivores. Root herbivory by Agriotes increased the nitrogen
concentration in the roots of M4 plants leading to a higher weight gain of
conspecific larvae. Also, in feeding bioassays, Agriotes larvae tended to
prefer roots of M4 over E9, irrespective of the aboveground herbivore
treatment. Fourier-Transform Infrared Spectroscopy (FT-IR) documented
differences in metabolic profiles of the two plant genotypes and of the roots
of M4 plants after aboveground herbivory. Together, these results demonstrate
that previous aboveground herbivory can have genotype-specific effects on
quantitative and qualitative root traits. This may have consequences for
belowground interactions, although generalist root herbivores might not be
affected when the root biomass offered is still sufficient for growth and
survival
Sequential above- and belowground herbivory modifies plant responses depending on herbivore identity
Background Herbivore-induced changes in plant traits can cause indirect
interactions between spatially and/or temporally separated herbivores that
share the same host plant. Feeding modes of the herbivores is one of the major
factors that influence the outcome of such interactions. Here, we tested
whether the effects of transient aboveground herbivory for seven days by
herbivores of different feeding guilds on tomato plants (Solanum lycopersicum)
alters their interaction with spatially as well as temporally separated
belowground herbivores. Results The transient aboveground herbivory by both
chewing caterpillars (Spodoptera exigua) and sucking aphids (Myzus persicae)
had significant impacts on plant traits such as plant growth, resource
allocation and phytohormone contents. While the changes in plant traits did
not affect the overall performance of the root-knot nematodes (Meloidogyne
incognita) in terms of total number of galls, we found that the consequences
of aboveground herbivory for the plants can be altered by the subsequent
nematode herbivory. For example, plants that had hosted aphids showed
compensatory growth when they were later challenged by nematodes, which was
not apparent in plants that had hosted only aphids. In contrast, plants that
had been fed by S. exigua larvae did not show such compensatory growth even
when challenged by nematodes. Conclusion The results suggest that the earlier
aboveground herbivory can modify plant responses to subsequent herbivores, and
such modifications may depend upon identity and/or feeding modes of the
aboveground herbivores
Fear of predation alters clone-specific performance in phloem-feeding prey
Fear of predation has been shown to affect prey fitness and behaviour,
however, to date little is known about the underlying genetics of responses to
predator-associated risk. In an effort to fill this gap we exposed four naĂŻve
clones of green peach aphid (Myzus persicae), maintained on the model crop
Brassica oleracea, to different types of cues from aphid lion (Chrysoperla
carnea). The respective predation risks, we termed Fear Factors, were either
lethal (consumption by predator), or non-lethal (non-consumptive predator-
associated cues: plant-tethered predator cadavers and homogenised shoot-
sprayed or soil-infused blends of predator remains). Our results show that the
non-lethal risk cues differentially impeded prey reproductive success that
varied by clone, suggesting genotype-specific response to fear of predation.
Furthermore, whether plants were perceived as being safe or risky influenced
prey responses as avoidance behaviour in prey depended on clone type. Our
findings highlight that intra-specific genetic variation underlies prey
responses to consumptive and non-consumptive effects of predation. This allows
selection to act on anti-predator responses to fear of predation that may
ramify and influence higher trophic levels in model agroecosystems
While shoot herbivores reduce, root herbivores increase nutrient enrichmentâs impact on diversity in a grassland model
Nutrient enrichment is widespread throughout grassland systems and expected to increase during the Anthropocene. Trophic interactions, like aboveground herbivory, have been shown to mitigate its effect on plant diversity. Belowground herbivory may also impact these habitatsâ response to nutrient enrichment, but its influence is much less understood, and likely to depend on factors such as the herbivoresâ preference for dominant species and the symmetry of belowground competition. If preferential toward the dominant, fastest growing species, root herbivores may reduce these speciesâ relative fitness and support diversity during nutrient enrichment. However, as plant competition belowground is commonly considered to be symmetric, root herbivores may be less impactful than shoot herbivores because they do not reduce any competitive asymmetry between the dominant and subordinate plants. To better understand this system, we used an established, two-layer, grassland community model to run a full-factorially designed simulation experiment, crossing the complete removal of aboveground herbivores and belowground herbivores with nutrient enrichment. After 100 yr of simulation, we analyzed communities' diversity, competition on the individual level, as well as their resistance and recovery. The model reproduced both observed general effects of nutrient enrichment in grasslands and the short-term trends of specific experiments. We found that belowground herbivores exacerbate the negative influence of nutrient enrichment on Shannon diversity within our model grasslands, while aboveground herbivores mitigate its effect. Indeed, data on individualsâ above- and belowground resource uptake reveals that root herbivory reduces resource limitation belowground. As with nutrient enrichment, this shifts competition aboveground. Since shoot competition is asymmetric, with larger, taller individuals gathering disproportionate resources compared to their smaller, shorter counterparts, this shift promotes the exclusion of the smallest species. While increasing the root herbivoresâ preferences toward dominant species lessens their negative impact, at best they are only mildly advantageous, and they do very little reduce the negative consequences of nutrient enrichment. Because our modelâs belowground competition is symmetric, we hypothesize that root herbivores may be beneficial when root competition is asymmetric. Future research into belowground herbivory should account for the nature of competition belowground to better understand the herbivoresâ true influence
Grazing Exclusion to Recover Degraded Alpine Pastures Needs Scientific Assessments across the Northern Tibetan Plateau
The northern Tibetan Plateau is the most traditional and important semi-
nomadic region in Tibet. The alpine vegetation is sensitive and vulnerable to
climate change and human activities, and is also important as an ecological
security in protecting the headwaters of major rivers in Asia. Therefore, the
Tibetan alpine grasslands have fundamental significance to both Mainland China
and South Asia. The pasture degradation, however, likely threatens the
livelihood of residents and the habitats of wildlife on this plateau. Since
2004, the government has launched a series of ecological restoration projects
and economic compensatory payment polices. Many fences were additionally built
on degraded pastures to prevent new degradation, to promote functionality
recovery, and to balance the stocking rate with forage productivity. The
grazed vs. fenced paired pastures across different zonal grassland communities
along evident environmental gradients provide us with a natural comparative
experiment platform to test the relative contributions of natural and
anthropogenic factors. This study critically reviews the background,
significance of and debates on short-term grazing exclusion with fences in
this region. We also aim to figure out scientific and standardized workflows
for assessing the effectiveness of grazing exclusion and compensatory payments
in the future. View Full-Tex
insights for ecological applications from the German Biodiversity Exploratories
Biodiversity, a multidimensional property of natural systems, is difficult to
quantify partly because of the multitude of indices proposed for this purpose.
Indices aim to describe general properties of communities that allow us to
compare different regions, taxa, and trophic levels. Therefore, they are of
fundamental importance for environmental monitoring and conservation, although
there is no consensus about which indices are more appropriate and
informative. We tested several common diversity indices in a range of simple
to complex statistical analyses in order to determine whether some were better
suited for certain analyses than others. We used data collected around the
focal plant Plantago lanceolata on 60 temperate grassland plots embedded in an
agricultural landscape to explore relationships between the common diversity
indices of species richness (S), Shannon's diversity (H'), Simpson's diversity
(D1), Simpson's dominance (D2), Simpson's evenness (E), and BergerâParker
dominance (BP). We calculated each of these indices for herbaceous plants,
arbuscular mycorrhizal fungi, aboveground arthropods, belowground insect
larvae, and P. lanceolata molecular and chemical diversity. Including these
trait-based measures of diversity allowed us to test whether or not they
behaved similarly to the better studied species diversity. We used path
analysis to determine whether compound indices detected more relationships
between diversities of different organisms and traits than more basic indices.
In the path models, more paths were significant when using H', even though all
models except that with E were equally reliable. This demonstrates that while
common diversity indices may appear interchangeable in simple analyses, when
considering complex interactions, the choice of index can profoundly alter the
interpretation of results. Data mining in order to identify the index
producing the most significant results should be avoided, but simultaneously
considering analyses using multiple indices can provide greater insight into
the interactions in a system
Concept of the Munich/Augsburg Consortium Precision in Mental Health for the German Center of Mental Health
The Federal Ministry of Education and Research (BMBF) issued a call for a new nationwide research network on mental disorders, the German Center of Mental Health (DZPG). The Munich/Augsburg consortium was selected to participate as one of six partner sites with its concept âPrecision in Mental Health (PriMe): Understanding, predicting, and preventing chronicity.â PriMe bundles interdisciplinary research from the Ludwig-Maximilians-University (LMU), Technical University of Munich (TUM), University of Augsburg (UniA), Helmholtz Center Munich (HMGU), and Max Planck Institute of Psychiatry (MPIP) and has a focus on schizophrenia (SZ), bipolar disorder (BPD), and major depressive disorder (MDD). PriMe takes a longitudinal perspective on these three disorders from the at-risk stage to the first-episode, relapsing, and chronic stages. These disorders pose a major health burden because in up to 50% of patients they cause untreatable residual symptoms, which lead to early social and vocational disability, comorbidities, and excess mortality. PriMe aims at reducing mortality on different levels, e.g., reducing death by psychiatric and somatic comorbidities, and will approach this goal by addressing interdisciplinary and cross-sector approaches across the lifespan. PriMe aims to add a precision medicine framework to the DZPG that will propel deeper understanding, more accurate prediction, and personalized prevention to prevent disease chronicity and mortality across mental illnesses. This framework is structured along the translational chain and will be used by PriMe to innovate the preventive and therapeutic management of SZ, BPD, and MDD from rural to urban areas and from patients in early disease stages to patients with long-term disease courses. Research will build on platforms that include one on model systems, one on the identification and validation of predictive markers, one on the development of novel multimodal treatments, one on the regulation and strengthening of the uptake and dissemination of personalized treatments, and finally one on testing of the clinical effectiveness, utility, and scalability of such personalized treatments. In accordance with the translational chain, PriMeâs expertise includes the ability to integrate understanding of bio-behavioral processes based on innovative models, to translate this knowledge into clinical practice and to promote user participation in mental health research and care
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