Regional-scale patterns of δ13C and δ15N associated with multiple ecosystem functions along an aridity gradient in grassland ecosystems

The rapid ecological expansion of grasses with C4 photosynthesis at the end of the Neogene (8–2 Ma) is well documented in the fossil record of stable carbon isotopes. As one of the most profound vegetation changes to occur in recent geologic time, it paved the way for modern tropical grassland ecosystems. Changes in CO2 levels, seasonality, aridity, herbivory, and fire regime have all been suggested as potential triggers for this broadly synchronous change, long after the evolutionary origin of the C4 pathway in grasses. To date, these hypotheses have suffered from a lack of direct evidence for floral composition and structure during this important transition. This study aimed to remedy the problem by providing the first direct, relatively continuous record of vegetation change for the Great Plains of North America for the critical interval (ca. 12–2 Ma) using plant silica (phytolith) assemblages.Phytoliths were extracted from late Miocene-Pliocene paleosols in Nebraska and Kansas. Quantitative phytolith analysis of the 14 best-preserved assemblages indicates that habitats varied substantially in openness during the middle to late Miocene but became more uniformly open, corresponding to relatively open grassland or savanna, during the late Miocene and early Pliocene. Phytolith data also point to a marked increase of grass short cells typical of chloridoid and other potentially C4 grasses of the PACMAD clade between 8 and 5 Ma; these data suggest that the proportion of these grasses reached up to ∼50–60% of grasses, resulting in mixed C3-C4 and highly heterogeneous grassland communities by 5.5 Ma. This scenario is consistent with interpretations of isotopic records from paleosol carbonates and ungulate tooth enamel. The rise in abundance of chloridoids, which were present in the central Great Plains since the early Miocene, demonstrates that the “globally” observed lag between C4 grass evolution/taxonomic diversification and ecological expansion occurred at the regional scale. These patterns of vegetation alteration imply that environmental change during the late Miocene-Pliocene played a major role in the C3-C4 shift in the Great Plains. Specifically, the importance of chloridoids as well as a decline in the relative abundance of forest indicator taxa, including palms, point to climatic drying as a key trigger for C4 dominance.

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Fungal-bacterial diversity and microbiome complexity predict ecosystem functioning

Nature Communications ◽

10.1038/s41467-019-12798-y ◽

2019 ◽

Vol 10 (1) ◽

Cited By ~ 67

Author(s):

Cameron Wagg ◽

Klaus Schlaeppi ◽

Samiran Banerjee ◽

Eiko E. Kuramae ◽

Marcel G. A. van der Heijden

Keyword(s):

Microbial Communities ◽

Bacterial Communities ◽

Ecosystem Functioning ◽

Microbial Interactions ◽

Soil Microbiome ◽

Ecosystem Functions ◽

Microbial Network ◽

Grassland Ecosystems ◽

Microbiome Diversity ◽

Ecological Associations

Abstract The soil microbiome is highly diverse and comprises up to one quarter of Earth’s diversity. Yet, how such a diverse and functionally complex microbiome influences ecosystem functioning remains unclear. Here we manipulated the soil microbiome in experimental grassland ecosystems and observed that microbiome diversity and microbial network complexity positively influenced multiple ecosystem functions related to nutrient cycling (e.g. multifunctionality). Grassland microcosms with poorly developed microbial networks and reduced microbial richness had the lowest multifunctionality due to fewer taxa present that support the same function (redundancy) and lower diversity of taxa that support different functions (reduced functional uniqueness). Moreover, different microbial taxa explained different ecosystem functions pointing to the significance of functional diversity in microbial communities. These findings indicate the importance of microbial interactions within and among fungal and bacterial communities for enhancing ecosystem performance and demonstrate that the extinction of complex ecological associations belowground can impair ecosystem functioning.

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Predicting microbial redox dynamics and nutrient cycling in the subsurface considering spatio-temporal heterogeneities

10.5194/egusphere-egu2020-3389 ◽

2020 ◽

Author(s):

Swamini Khurana ◽

Falk Heße ◽

Martin Thullner

Keyword(s):

Nutrient Cycling ◽

Temporal Dynamics ◽

Regional Scale ◽

Water Flux ◽

Biogeochemical Cycles ◽

Ecosystem Functions ◽

Microbial Dynamics ◽

Nitrogen Budgets ◽

Carbon And Nitrogen ◽

Nitrogen Cycles

<p>Biogeochemical cycles are extensively studied as they control the flow of matter (carbon and nitrogen, specifically) up to the global scale, further impacting ecosystem functions and services. To be able to predict carbon and nitrogen budgets, it is necessary to study carbon and nitrogen cycles in all compartments of the biosphere, from forests to water, to soil and deep subsurface. Since the soil and deeper subsurface compartments store a high share of the global carbon and nitrogen budget, it is necessary to study the carbon and nitrogen cycles in the subsurface at a higher resolution. Given the spatial heterogeneity and temporal dynamics exhibited by the subsurface, coupled with lack of observational opportunities, the prediction of these cycles in the subsurface is a challenge. For this purpose, this study aims to resolve microbial mediated carbon and nitrogen dynamics in the subsurface with respect to spatial and temporal heterogeneity using a numerical modeling approach. The model considers the response of microbial growth and activity to varying environmental conditions such as access to nutrients and energy sources.</p><p>The obtained results show a linear relationship between the relative impact on carbon and nitrogen removal and relative difference in breakthrough times between homogeneous scenarios and the spatially heterogeneous scenarios. In contrast, the temporal dynamics of changing flow rates induces minimal aggregated impact on the carbon and nitrogen cycles in the subsurface. This implies that short term temporal dynamics do little to influence the long-term nutrient cycles, given the same average water flux through the entire simulation period. The findings of this study can assist in identification of drivers of microbial dynamics and nutrient cycling in the Critical Zone. This, in turn, can assist towards the regional scale modeling of biogeochemical cycles resulting from microbial dynamics.</p>

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Regional evapotranspiration from an image-based implementation of the Surface Temperature Initiated Closure (STIC1.2) model and its validation across an aridity gradient in the conterminous US

Hydrology and Earth System Sciences ◽

10.5194/hess-22-2311-2018 ◽

2018 ◽

Vol 22 (4) ◽

pp. 2311-2341 ◽

Cited By ~ 18

Author(s):

Nishan Bhattarai ◽

Kaniska Mallick ◽

Nathaniel A. Brunsell ◽

Ge Sun ◽

Meha Jain

Keyword(s):

Energy Balance ◽

Surface Energy ◽

Surface Temperature ◽

Land Surface ◽

Surface Energy Balance ◽

Regional Scale ◽

Absolute Error ◽

Error Statistics ◽

Aridity Gradient ◽

Balance System

Abstract. Recent studies have highlighted the need for improved characterizations of aerodynamic conductance and temperature (gA and T0) in thermal remote-sensing-based surface energy balance (SEB) models to reduce uncertainties in regional-scale evapotranspiration (ET) mapping. By integrating radiometric surface temperature (TR) into the Penman–Monteith (PM) equation and finding analytical solutions of gA and T0, this need was recently addressed by the Surface Temperature Initiated Closure (STIC) model. However, previous implementations of STIC were confined to the ecosystem-scale using flux tower observations of infrared temperature. This study demonstrates the first regional-scale implementation of the most recent version of the STIC model (STIC1.2) that integrates the Moderate Resolution Imaging Spectroradiometer (MODIS) derived TR and ancillary land surface variables in conjunction with NLDAS (North American Land Data Assimilation System) atmospheric variables into a combined structure of the PM and Shuttleworth–Wallace (SW) framework for estimating ET at 1 km × 1 km spatial resolution. Evaluation of STIC1.2 at 13 core AmeriFlux sites covering a broad spectrum of climates and biomes across an aridity gradient in the conterminous US suggests that STIC1.2 can provide spatially explicit ET maps with reliable accuracies from dry to wet extremes. When observed ET from one wet, one dry, and one normal precipitation year from all sites were combined, STIC1.2 explained 66 % of the variability in observed 8-day cumulative ET with a root mean square error (RMSE) of 7.4 mm/8-day, mean absolute error (MAE) of 5 mm/8-day, and percent bias (PBIAS) of −4 %. These error statistics showed relatively better accuracies than a widely used but previous version of the SEB-based Surface Energy Balance System (SEBS) model, which utilized a simple NDVI-based parameterization of surface roughness (zOM), and the PM-based MOD16 ET. SEBS was found to overestimate (PBIAS = 28 %) and MOD16 was found to underestimate ET (PBIAS = −26 %). The performance of STIC1.2 was better in forest and grassland ecosystems as compared to cropland (20 % underestimation) and woody savanna (40 % overestimation). Model inter-comparison suggested that ET differences between the models are robustly correlated with gA and associated roughness length estimation uncertainties which are intrinsically connected to TR uncertainties, vapor pressure deficit (DA), and vegetation cover. A consistent performance of STIC1.2 in a broad range of hydrological and biome categories, as well as the capacity to capture spatio-temporal ET signatures across an aridity gradient, points to the potential for this simplified analytical model for near-real-time ET mapping from regional to continental scales.

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Biodiversity and ecosystem functions depend on environmental conditions and resources rather than the geodiversity of a tropical biodiversity hotspot

Scientific Reports ◽

10.1038/s41598-021-03488-1 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Christine I. B. Wallis ◽

Yvonne C. Tiede ◽

Erwin Beck ◽

Katrin Böhning-Gaese ◽

Roland Brandl ◽

...

Keyword(s):

Species Diversity ◽

Environmental Conditions ◽

Environmental Variables ◽

Conservation Management ◽

Regional Scale ◽

Ecosystem Functions ◽

Soil Variables ◽

Tropical Biodiversity ◽

Tropical Mountain ◽

Tropical Mountain Rain Forest

AbstractBiodiversity and ecosystem functions are highly threatened by global change. It has been proposed that geodiversity can be used as an easy-to-measure surrogate of biodiversity to guide conservation management. However, so far, there is mixed evidence to what extent geodiversity can predict biodiversity and ecosystem functions at the regional scale relevant for conservation planning. Here, we analyse how geodiversity computed as a compound index is suited to predict the diversity of four taxa and associated ecosystem functions in a tropical mountain hotspot of biodiversity and compare the results with the predictive power of environmental conditions and resources (climate, habitat, soil). We show that combinations of these environmental variables better explain species diversity and ecosystem functions than a geodiversity index and identified climate variables as more important predictors than habitat and soil variables, although the best predictors differ between taxa and functions. We conclude that a compound geodiversity index cannot be used as a single surrogate predictor for species diversity and ecosystem functions in tropical mountain rain forest ecosystems and is thus little suited to facilitate conservation management at the regional scale. Instead, both the selection and the combination of environmental variables are essential to guide conservation efforts to safeguard biodiversity and ecosystem functions.

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Soil δ13C and δ15N baselines clarify biogeographic heterogeneity in isotopic discrimination of European badgers (Meles meles)

Scientific Reports ◽

10.1038/s41598-021-04011-2 ◽

2022 ◽

Vol 12 (1) ◽

Author(s):

Shay T. Mullineaux ◽

Berit Kostka ◽

Luc Rock ◽

Neil Ogle ◽

Nikki J. Marks ◽

...

Keyword(s):

Spatial Ecology ◽

Trophic Ecology ◽

Regional Scale ◽

Weather Conditions ◽

Meles Meles ◽

Δ13c And Δ15n ◽

Heterogeneous Landscapes ◽

Macro Scale ◽

Isotopic Studies ◽

European Badgers

AbstractIsotopic techniques have been used to study phenomena in the geological, environmental, and ecological sciences. For example, isotopic values of multiple elements elucidate the pathways energy and nutrients take in the environment. Isoscapes interpolate isotopic values across a geographical surface and are used to study environmental processes in space and time. Thus, isoscapes can reveal ecological shifts at local scales, and show distribution thresholds in the wider environment at the macro-scale. This study demonstrates a further application of isoscapes, using soil isoscapes of 13C/12C and 15N/14N as an environmental baseline, to understand variation in trophic ecology across a population of Eurasian badgers (Meles meles) at a regional scale. The use of soil isoscapes reduced error, and elevated the statistical signal, where aggregated badger hairs were used, and where individuals were identified using genetic microarray analysis. Stable isotope values were affected by land-use type, elevation, and meteorology. Badgers in lowland habitats had diets richer in protein and were adversely affected by poor weather conditions in all land classes. It is concluded that soil isoscapes are an effective way of reducing confounding biases in macroscale, isotopic studies. The method elucidated variation in the trophic and spatial ecology of economically important taxa at a landscape level. These results have implications for the management of badgers and other carnivores with omnivorous tendencies in heterogeneous landscapes.

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Traceability and Authentication of Manila Clams from North-Western Adriatic Lagoons Using C and N Stable Isotope Analysis

Molecules ◽

10.3390/molecules26071859 ◽

2021 ◽

Vol 26 (7) ◽

pp. 1859

Author(s):

Gianluca Bianchini ◽

Valentina Brombin ◽

Pasquale Carlino ◽

Enrico Mistri ◽

Claudio Natali ◽

...

Keyword(s):

Regional Scale ◽

Isotope Analysis ◽

Isotope Ratio Mass Spectrometry ◽

Cost Effective ◽

Ruditapes Philippinarum ◽

Manila Clam ◽

Economic Returns ◽

Δ13c And Δ15n ◽

C And N ◽

Protected Designations Of Origin

In the Adriatic lagoons of northern Italy, manila clam (Ruditapes philippinarum) farming provides important socio-economic returns and local clams should be registered with the Protected Designations of Origin scheme. Therefore, there is a need for the development of rapid, cost-effective tests to guarantee the origin of the product and to prevent potential fraud. In this work, an elemental analysis (EA) coupled with isotope ratio mass spectrometry (IRMS) was employed to identify the isotopic fingerprints of clams directly collected onsite in three Adriatic lagoons and bought at a local supermarket, where they exhibited certification. In particular, a multivariate analysis of C/N, δ13C and δ15N in manila clam tissues as well as δ13C in shells and 13C (calculated as δ13Cshell–δ13Ctissues) seems a promising approach for tracking the geographical origin of manila clams at the regional scale.

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Grassland restoration reveals the importance of ecotypic variation on community assembly along a longitudinal aridity gradient

10.14293/s2199-1006.1.sor-.pphlwka.v1 ◽

2021 ◽

Author(s):

Zhe Ren ◽

David Gibson ◽

Sara Baer ◽

Loretta Johnson ◽

Laurel Wilson

Keyword(s):

Great Plains ◽

Community Assembly ◽

Dominant Species ◽

Block Design ◽

Wide Distribution ◽

Community Diversity ◽

Sorghastrum Nutans ◽

Aridity Gradient ◽

Ecotypic Variation ◽

Grassland Ecosystems

Two dominant species, Andropogon gerardii and Sorghastrum nutans, have a wide distribution across the Great Plains (USA) and are widely used in restorations. We ask: Do dominant species' ecotypes influence community diversity and structure evenly across a longitudinal aridity gradient? We established reciprocal common gardens at four sites across the gradient. Ecotypes of the two dominant species were seeded along with a prairie seed mix according to a randomized complete block design. Species composition was measured after 3 and 10 years. We used linear mixed models to analyze the effect of the ecotype and year on community diversity. NMDS and PERMANOVA were applied to examine the contribution of ecotype to community structure. Results showed that ecotype significantly affected species richness and shaped taxonomic, phylogenetic, and functional diversity. Accordingly, restorations should consider ecotypic variation as a critical biological filter to community assembly in grassland ecosystems.

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Biotic and abiotic factors predict the biogeography of soil microbes in the Serengeti

10.1101/2020.02.06.936625 ◽

2020 ◽

Author(s):

Bo Maxwell Stevens ◽

Derek Lee Sonderegger ◽

Nancy Collins Johnson

Keyword(s):

Community Structure ◽

Soil Texture ◽

Soil Microbes ◽

Abiotic Factors ◽

Regional Scale ◽

Observational Research ◽

Ecosystem Functions ◽

Large Mammals ◽

Bacterial And Archaeal Communities ◽

Archaeal Communities

AbstractField-based observational research is the first step in understanding the factors that predict the biogeography and community structure of soil microbes. The Serengeti National Park in Tanzania is an ideal location for this type of research because active volcanoes generate strong environmental gradients due to ash deposition and a rain shadow. Also, as one of the last remaining naturally grazed ecosystems on Earth, the Serengeti provides insights about the influence of herbivory on microbial communities. We used 16S rRNA amplicons to characterize bacterial and archaeal communities in soils from a 13-year herbivore removal experiment to study the influence of environmental factors and grazing on the natural distribution of soil microbes. We collected soil samples from seven sites, each with three naturally grazed plots and three plots that were fenced to prevent grazing by large mammalian herbivores. Soil fertility (phosphorus, nitrogen, iron, calcium, organic matter), texture, and pH were measured at each plot. Beta diversity of bacterial and archaeal communities was most strongly correlated with soil texture (R2 = 32.4%). The abundance of many operational taxonomic units (OTUs) were correlated with soil texture, and the evenness of taxa within samples increased with fine-textured soil. Removal of grazing shifted community structure, with 31 OTUs that were significant indicator taxa of the ungrazed treatment and three OTUs that were significant indicators of the grazed treatment.ImportanceOur results show that in this regional scale study, soil texture was the best environmental predictor, and grazing by large mammals also structures bacterial and archaeal communities. When large mammals are removed, as humans have been doing for millenia, there are cascading effects into the microbial world that can influence ecosystem functions like carbon and nitrogen cycles. These empirical findings from a natural tropical savannah can help inform models of the global distribution and function of soil microbes.

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