Applications of fipronil (Adonis 3UL) and Metarhizium acridum for use against locusts have minimal effect on litter decomposition and microbial functional diversity in Australian arid grassland

Soil Research ◽  
2017 ◽  
Vol 55 (2) ◽  
pp. 172 ◽  
Author(s):  
Kimberly Maute ◽  
Paul Story ◽  
Grant C. Hose ◽  
C. M. Bull ◽  
Kris French
Keyword(s):  
Temporal Variation ◽  
Litter Decomposition ◽  
Functional Diversity ◽  
Treatment Effects ◽  
C:N Ratio ◽  
Arid Ecosystems ◽  
Annual Rainfall ◽  
Metarhizium Acridum ◽  
Litter Mass ◽  
Pesticide Treatment

Litter and microbes are key drivers of nutrient cycles, particularly in arid ecosystems where decomposition rates are low. Locust control in arid regions represents a potentially important hazard to microbes, because local taxa are unlikely to have adapted to pesticide exposure and operations often occur during times of high microbial activity. We monitored the response of aboveground litter decomposition and soil bacteria functional diversity to aerial applications of fipronil (a chemical pesticide) barrier treatments and Metarhizium acridum (a fungal biopesticide) blanket treatments. Decomposition was monitored over 2 years (before and after treatments) using a replicated litter-bag experiment, whereas changes in bacteria functional diversity were measured over 1 month. Analysis of litter mass loss indicated there were no pesticide treatment effects relative to control. Less litter decomposed in small than large mesh bags, and less litter decomposed during the second year of the study. Litter had higher mean nitrogen (N) and carbon (C), and a lower C:N ratio, during the first year of the study. In contrast, within-treatment site analysis revealed a significant increase in litter mass remaining in bags at M. acridum-treated subsites. However, these values were only 4% different from control sites, suggesting that the effect detected may not be biologically significant. There appeared to be no pesticide treatment effect on bacterial community functional diversity and no significant temporal variation. The lack of large-scale pesticide treatment effects suggests that arid zone fungi and bacteria are resilient to such disturbances. Differences in decomposition was explained by differences in the activity of arthropods and in the shade provided by the two mesh sizes, and an annual decline could be attributed to lower litter C and N content and lower annual rainfall in Year 2. Results show the temporal variation possible in decomposition and microbe community measures in arid systems.

Effects of management on plant litter traits and consequences for litter mass loss and Collembola functional diversity in a Mediterranean agro-forest system

Pedobiologia ◽  
2019 ◽  
Vol 75 ◽  
pp. 38-51 ◽  
Author(s):  
Eduardo Nascimento ◽  
Filipa Reis ◽  
Filipe Chichorro ◽  
Cristina Canhoto ◽  
Ana Lúcia Gonçalves ◽  
...  
Keyword(s):  
Mass Loss ◽  
Functional Diversity ◽  
Plant Litter ◽  
Litter Mass ◽  
Litter Traits ◽  
Litter Mass Loss

scholarly journals Complexity and Dynamics of Semi-Arid Vegetation Structure, Function and Diversity Across Spatial Scales from Full Waveform Lidar

2020 ◽  
Author(s):  
Ginikanda Yapa Mudiyanselage Nayani Thanuja Ilangakoon
Keyword(s):  
Structure Function ◽  
Functional Diversity ◽  
Vegetation Structure ◽  
Structural Features ◽  
Airborne Lidar ◽  
Arid Ecosystems ◽  
Full Waveform ◽  
Waveform Lidar ◽  
Full Waveform Lidar ◽  
Semi Arid

Semi-arid ecosystems cover approximately 40% of the earth's terrestrial landscape and show high dynamicity in ecosystem structure and function. These ecosystems play a critical role in global carbon dynamics, productivity, and habitat quality. Semi-arid ecosystems experience a high degree of disturbance that can severely alter ecosystem services and processes. Understanding the structure-function relationships across spatial extents are critical in order to assess their demography, response to disturbance, and for conservation management. In this research, using state-of-the-art full waveform lidar (airborne and spaceborne) and field observations, I developed a framework to assess the complexity and dynamics of vegetation structure, function and diversity across spatial scales in a semi-arid ecosystem. Difficulty in differentiating low stature vegetation from bare ground is the key remote sensing challenge in semi-arid ecosystems. In this study, I developed a workflow to differentiate key plant functional types (PFTs) using both structural and biophysical variables derived from the full waveform lidar and an ensemble random forest technique. The results revealed that waveform lidar pulse width can clearly distinguish shrubs from bare ground. The models showed PFT classification accuracy of 0.81-0.86% and 0.60-0.70% at 10 m and 1 m spatial resolutions, respectively. I found that structural variables were more important than the biophysical variables to differentiate the PFTs in this study area. The study further revealed an overlap between the structural features of different PFTs (e.g. shrubs from trees). Using structural features, I derived three main functional traits (canopy height, plant area index and foliage height diversity) of shrubs and trees that describe canopy architecture and light use efficiency of the ecosystem. I evaluated the trends and patterns of functional diversity and their relationship with non-climatic abiotic factors and fire disturbance. In addition to the fine resolution airborne lidar, I used simulated large footprint spaceborne lidar representing the newly launched Global Ecosystem Dynamics Investigation system (GEDI, a lidar sensor on the International Space Station) to evaluate the potential of capturing functional diversity trends of semi-arid ecosystems at global scales. The consistency of diversity trends between the airborne lidar and GEDI confirmed GEDI's potential to capture functional diversity. I found that the functional diversity in this ecosystem is mainly governed by the local elevation gradient, soil type, and slope. All three functional diversity indices (functional richness, functional evenness and functional divergence) showed a diversity breakpoint near elevations of 1500 m - 1700 m. Functional diversity of fire-disturbed areas revealed that the fires in our study area resulted in a more even and less divergent ecosystem state. Finally, I quantified aboveground biomass using the structural features derived from both the airborne lidar and GEDI data. Regional estimates of biomass can indicate whether an ecosystem is a net carbon sink or source as well as the ecosystem's health (e.g. biodiversity). Further, the potential of large footprint lidar data to estimate biomass in semi-arid ecosystems are not yet fully explored due to the inherent overlapping vegetation responses in the ground signals that can be affected by the ground slope. With a correction to the slope effect, I found that large footprint lidar can explain 42% of variance of biomass with a RMSE of 351 kg/ha (16% RMSE). The model estimated 82% of the study area with less than 50% uncertainty in biomass estimates. The cultivated areas and the areas with high functional richness showed the highest uncertainties. Overall, this dissertation establishes a novel framework to assess the complexity and dynamics of vegetation structure and function of a semi-arid ecosystem from space. This work enhances our understanding of the present state of an ecosystem and provides a foundation for using full waveform lidar to understand the impact of these changes to ecosystem productivity, biodiversity and habitat quality in the coming decades. The methods and algorithms in this dissertation can be directly applied to similar ecosystems with relevant corrections for the appropriate sensor. In addition, this study provides insights to related NASA missions such as ICESat-2 and future NASA missions such as NISAR for deriving vegetation structure and dynamics related to disturbance.

Germination strategies under climate change scenarios along an aridity gradient

2020 ◽  
Vol 13 (4) ◽  
pp. 470-477
Author(s):  
Alexander Zogas ◽  
Evsey Kosman ◽  
Marcelo Sternberg
Keyword(s):  
Climate Change ◽  
Seed Banks ◽  
Arid Ecosystems ◽  
Annual Rainfall ◽  
Strong Impact ◽  
Climate Change Scenarios ◽  
Aridity Gradient ◽  
Soil Seed Banks ◽  
Seed Germinability ◽  
Semi Arid

Abstract Aims Climate change in the eastern Mediterranean region will have a strong impact on ecosystem functioning and plant community dynamics due to a reduction in annual rainfall and increased variability. We aim to understand the role of seed banks as potential buffers against climatic uncertainty determined by climate change. Methods We examined germination strategies of 18 common species present along an aridity gradient. Data were obtained from soil seed banks germinated during nine consecutive years from arid, semi-arid, Mediterranean and mesic Mediterranean ecosystems. At the semi-arid and Mediterranean sites, rainfall manipulations simulating 30% drought and 30% rainfall increase were applied. Germination strategies were tested under optimal irrigation conditions during three consecutive germination seasons to determine overall seed germinability in each soil sample. Changes in germination strategy were examined using a novel statistical approach that considers the climatic and biotic factors that may affect seed germinability. Important Findings The results showed that dominant species controlled their germination fractions by producing seeds with a different yearly germination fraction probability. The amount of rainfall under which the seeds were produced led to two major seed types with respect to germinability: high germinability, seeds leading to transient seed banks, and low germinability, seeds leading to persistent seed banks. We conclude that differential seed production among wet and dry years of both seed types creates a stable balance along the aridity gradient, enabling the soil seed bank to serve as a stabilizing mechanism buffering against rainfall unpredictability. Additionally, we present a general model of germination strategies of dominant annual species in Mediterranean and arid ecosystems that strengthens the notion of soil seed banks as buffers against climatic uncertainty induced by climate change in the region.

scholarly journals The Taxonomic and Functional Diversity of Microbes at a Temperate Coastal Site: A ‘Multi-Omic’ Study of Seasonal and Diel Temporal Variation

PLoS ONE ◽  
2010 ◽  
Vol 5 (11) ◽  
pp. e15545 ◽  
Author(s):  
Jack A. Gilbert ◽  
Dawn Field ◽  
Paul Swift ◽  
Simon Thomas ◽  
Denise Cummings ◽  
...  
Keyword(s):  
Temporal Variation ◽  
Functional Diversity ◽  
Coastal Site

scholarly journals Interactions between large herbivores and litter removal by termites across a rainfall gradient in a South African savanna

2011 ◽  
Vol 27 (4) ◽  
pp. 375-382 ◽  
Author(s):  
Robert Buitenwerf ◽  
Nicola Stevens ◽  
Cleo M. Gosling ◽  
T. Michael Anderson ◽  
Han Olff
Keyword(s):  
Plant Biomass ◽  
Spatial Scales ◽  
Landscape Scale ◽  
Local Scale ◽  
Arid Ecosystems ◽  
Annual Rainfall ◽  
Large Herbivores ◽  
Mammalian Herbivores ◽  
Litter Removal ◽  
Semi Arid

Abstract:Litter-feeding termites influence key aspects of the structure and functioning of semi-arid ecosystems around the world by altering nutrient and material fluxes, affecting primary production, foodweb dynamics and modifying vegetation composition. Understanding these complex effects depends on quantifying spatial heterogeneity in termite foraging activities, yet such information is scarce for semi-arid savannas. Here, the amount of litter that was removed from 800 litterbags in eight plots (100 litterbags per plot) was measured in Hluhluwe–iMfolozi Park (HiP) South Africa. These data were used to quantify variation in litter removal at two spatial scales: the local scale (within 450-m2 plots) and the landscape scale (among sites separated by 8–25 km). Subsequently, we attempted to understand the possible determinants of termites’ foraging patterns by testing various ecological correlates, such as plant biomass and bare ground at small scales and rainfall and fences that excluded large mammalian herbivores at larger scales. No strong predictors for heterogeneity in termite foraging intensity were found at the local scale. At the landscape scale termite consumption depended on an interaction between rainfall and the presence of large mammalian herbivores: litter removal by termites was greater in the presence of large herbivores at the drier sites but lower in the presence of large herbivores at the wetter sites. The effect of herbivores on termite foraging intensity may indicate a switch between termites and large herbivore facilitation and competition across a productivity gradient. In general, litter removal decreased with increasing mean annual rainfall, which is in contrast to current understanding of termite consumption across rainfall and productivity gradients. These results generate novel insights into termite ecology and interactions among consumers of vastly different body sizes across spatial scales.

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