scholarly journals Current insecticide treatments used in locust control have less of a short-term impact on Australian arid-zone reptile communities than does temporal variation

2015 ◽  
Vol 42 (1) ◽  
pp. 50 ◽  
Author(s):  
Kimberly Maute ◽  
Kristine French ◽  
C. Michael Bull ◽  
Paul Story ◽  
Grant Hose
Keyword(s):  
Community Composition ◽  
Pesticide Exposure ◽  
Arid Zone ◽  
Large Field ◽  
Annual Rainfall ◽  
Potential Hazard ◽  
Pitfall Trapping ◽  
Short Term ◽  
Locust Control

Context Despite the regular use of pesticides to control locusts, there is a lack of information on the effects of locust-control treatments on reptiles worldwide. Exposure to pesticides poses a significant potential hazard to small reptiles, both from the direct effects of exposure, and indirectly because of their largely insectivorous diet and small home ranges. Aims Our study aimed to monitor the effects of two insecticides applied operationally for locust control in Australia. A phenyl pyrazole pesticide, fipronil, and a fungal biopesticide, Metarhizium acridium (Green Guard®), were applied aerially in either a barrier or block treatment in the absence of dense locust populations, and effects on non-target arid-zone reptiles were measured. Methods We monitored reptile-abundance and community-composition responses to treatments using a large field-based pitfall-trapping experiment, with replicated control and spraying treatments, which approximated the scale of aerial-based locust-control operations in Australia. Key results Neither reptile abundance nor community composition was significantly affected by locust-control treatments. However, both abundance and community composition as detected by pitfall trapping changed over time, in both control and treatment plots, possibly as a result of a decrease in annual rainfall. Conclusions The absence of any significant short-term pesticide treatment effects in our study suggests that the two locust-control application methods studied present a relatively insignificant hazard to reptiles at our site, based on a single application. Similar to other areas of Australia, climate and other factors are likely to be stronger drivers of reptile abundance and community structure. Implications Monitoring over an area that approximates the scale of the current locust-control operations is an important step in understanding the possible effects of current pesticide exposure on reptile populations and will inform insecticide risk assessments in Australia. However, important information on the immediate response of individuals to insecticide application and long-term effects of exposure are missing. The preliminary research reported in the present paper should be complemented by future investigations on long-term and sublethal impacts of pesticide exposure on Australian native reptiles and the possible benefits provided to reptiles by the resource pulses represented in untreated high-density locust populations.

scholarly journals Variability of seasonal and annual rainfall in the River Nile riparian countries and possible linkages to ocean–atmosphere interactions

2015 ◽  
Vol 47 (1) ◽  
pp. 171-184 ◽  
Author(s):  
Charles Onyutha
Keyword(s):  
Large Scale ◽  
Equatorial Region ◽  
Annual Rainfall ◽  
River Nile ◽  
Short Term ◽  
Ocean Atmosphere ◽  
Data Points ◽  
The Difference ◽  
Term Data

Variability analyses for the rainfall over the Nile Basin have been confined mostly to sub-basins and the annual mean of the hydroclimatic variable based on observed short-term data from a few meteorological stations. In this paper, long-term country-wide rainfall over the period 1901–2011 was used to assess variability in the seasonal and annual rainfall volumes in all the River Nile countries in Africa. Temporal variability was determined through temporal aggregation of series rescaled nonparametrically in terms of the difference between the exceedance and non-exceedance counts of data points such that the long-term average (taken as the reference) was zero. The co-occurrence of the variability of rainfall with those of the large-scale ocean–atmosphere interactions was analyzed. Between 2000 and 2012, while the rainfall in the equatorial region was increasing, that for the countries in the northern part of the River Nile was below the reference. Generally, the variability in the rainfall of the countries in the equatorial (northern) part of the River Nile was found to be significantly linked to occurrences in the Indian and Atlantic (Pacific and Atlantic) Oceans. Significant linkages to Niño 4 regarding the variability of both the seasonal and annual rainfall of some countries were also evident.

scholarly journals Rainfall Recovery in North-East Arid Zone of Nigeria: Comparative Analysis of Drought and Post Drought Decades

2021 ◽  
pp. 1-16
Author(s):  
Ahmed Abubakar Jajere ◽  
Adam Modu Abbas ◽  
Ali Abdu
Keyword(s):  
Arid Zone ◽  
Local Population ◽  
Mitigation Strategies ◽  
Annual Rainfall ◽  
Rainfall Characteristics ◽  
North East ◽  
The North ◽  
Sahel Rainfall ◽  
Mean Trend

This study used annual rainfall records from three stations within the North East Arid Zone of Nigeria for the period (1957-2017) to measure the extent of the rainfall recovery by comparing the drought decades and post drought decades rainfall patterns. Monthly rainfall records from Potiskum, Maiduguri and Nguru Stations were used. Descriptive and inferential statistical tools were employed in analysing the data. The findings of the study revealed a significant year-to-year variability in rainfall characteristics around 61 years (1957-2017) averages. The variability was large in 1970s up till 1990s, and lower in 1960s and from 2000 to 2018. Decreasing trend in annual rainfall amount was observed during the study period while a stability in onset and cessation dates were observed. The differences between 1957-1986 and 1987-2017 climatic season were found to be statistically insignificant. The study concluded that the reported rainfall recovery from drought is statistically insignificant and the observed long term mean trend revealed a decreasing trend. Therefore, the theory of Sahel rainfall recovery can be better termed as a ‘’break of the series of drought or decline in frequency and magnitude of occurrence of drought’’ The research recommended the continuations with the drought adaptation and mitigation strategies adopted by local population, decisions makers and organizations following the series Sahelian droughts of 1970s and 1980s.

scholarly journals Adaptation of Soil Fungal Community Structure and Assembly to Long- Versus Short-Term Nitrogen Addition in a Tropical Forest

2021 ◽  
Vol 12 ◽  
Author(s):  
Jinhong He ◽  
Shuo Jiao ◽  
Xiangping Tan ◽  
Hui Wei ◽  
Xiaomin Ma ◽  
...  
Keyword(s):  
Tropical Forest ◽  
Community Composition ◽  
Relative Abundance ◽  
Fungal Community ◽  
N Addition ◽  
Short Term ◽  
Fungal Community Structure ◽  
Α Diversity ◽  
Soil Fungal Community

Soil fungi play critical roles in ecosystem processes and are sensitive to global changes. Elevated atmospheric nitrogen (N) deposition has been well documented to impact on fungal diversity and community composition, but how the fungal community assembly responds to the duration effects of experimental N addition remains poorly understood. Here, we aimed to investigate the soil fungal community variations and assembly processes under short- (2 years) versus long-term (13 years) exogenous N addition (∼100 kg N ha–1 yr–1) in a N-rich tropical forest of China. We observed that short-term N addition significantly increased fungal taxonomic and phylogenetic α-diversity and shifted fungal community composition with significant increases in the relative abundance of Ascomycota and decreases in that of Basidiomycota. Short-term N addition also significantly increased the relative abundance of saprotrophic fungi and decreased that of ectomycorrhizal fungi. However, unremarkable effects on these indices were found under long-term N addition. The variations of fungal α-diversity, community composition, and the relative abundance of major phyla, genera, and functional guilds were mainly correlated with soil pH and NO3––N concentration, and these correlations were much stronger under short-term than long-term N addition. The results of null, neutral community models and the normalized stochasticity ratio (NST) index consistently revealed that stochastic processes played predominant roles in the assembly of soil fungal community in the tropical forest, and the relative contribution of stochastic processes was significantly increased by short-term N addition. These findings highlighted that the responses of fungal community to N addition were duration-dependent, i.e., fungal community structure and assembly would be sensitive to short-term N addition but become adaptive to long-term N enrichment.

Ant Communities in the Gulf Region of Australia Semiarid Tropics - Species Composition, Patterns of Organization, and Biogeography

1993 ◽  
Vol 41 (4) ◽  
pp. 399 ◽  
Author(s):  
AN Andersen
Keyword(s):  
Species Composition ◽  
Arid Zone ◽  
Annual Rainfall ◽  
Pitfall Trapping ◽  
Wet Season ◽  
Gulf Region ◽  
Ant Communities ◽  
Number Of Species ◽  
Hot Climate ◽  
Semi Arid

The ant communities of nine sites near Lawn Hill (540 mm mean annual rainfall) in semi-arid north-western Queensland are documented, and compared with the known faunas of arid, semi-arid and seasonally arid sites elsewhere in Australia. The sites were surveyed primarily by pitfall trapping, during April (end of wet season) 1991, September (late dry season) 1991, and February (mid-wet season) 1992. A total of 111 ant species was recorded, with the most common being Iridomyrmex spp. and Rhytidoponera rufithorax. The richest genera were Melophorus (26 species), Monomorium (17), Iridomyrmex (16) and Camponotus (10) and Pheidole (10). The maj or functional groups were Dominant Dolichoderinae (Iridomyrmex spp.; 14% of the total number of species, 47% of the total number of ants in traps), Hot-climate specialists (mostly Melophorus spp.; 39%, 22%) and Generalised Myrmicinae (mostly Monomorium and Pheidole spp.; 20%, 11%). Multivariate analysis indicated that site differences in species composition were related primarily to landform, geology and soil type. Comparisons with other ant faunas show the Lawn Hill fauna to have closer affinities with those of the central arid zone than with those of high rainfall areas of the seasonal tropics. The arid-zone characteristics of the Lawn Hill fauna include a high proportion (38%) of Eyrean species, a high mean number of species per genus (6.5), and a very high combined representation of Iridomyrmex, Melophorus and Camponotus (45% of the total number of species, 69% of the total number of ants in traps).

scholarly journals Beyond forest succession: a gap model to study ecosystem functioning and tree community composition under climate change

2020 ◽  
Author(s):  
Xavier Morin ◽  
François de Coligny ◽  
Nicolas Martin-StPaul ◽  
Harald Bugmann ◽  
Maxime Cailleret ◽  
...  
Keyword(s):  
Climate Change ◽  
Species Composition ◽  
Community Composition ◽  
Ecosystem Functioning ◽  
Forest Growth ◽  
Gap Model ◽  
Forest Stands ◽  
Short Term ◽  
Gap Models

ABSTRACTClimate change impacts forest functioning and dynamics, and large uncertainties remain regarding the interactions between species composition, demographic processes, and environmental drivers. There are few robust tools available to link these processes, which precludes accurate projections and recommendations for long-term forest management. Forest gap-models present a balance between complexity and generality and are widely used in predictive forest ecology. However, their relevance to tackle questions about the links between species composition, climate and forest functioning is unclear. In this regard, demonstrating the ability of gap-models to predict the growth of forest stands at the annual time scale – representing a sensitive and integrated signal of tree functioning and mortality risk - appears as a fundamental step.In this study, we aimed at assessing the ability of a gap-model to accurately predict forest growth in the short-term and potential community composition in the long-term, across a wide range of species and environmental conditions. To do so, we present the gap-model ForCEEPS, calibrated using an original parameterization procedure for the main tree species in France. ForCEEPS was shown to satisfactorily predict forest annual growth (averaged over a few years) at the plot level from mountain to Mediterranean climates, regardless the species. Such an accuracy was not gained at the cost of losing precision for long-term predictions, as the model showed a strong ability to predict potential community composition along a gradient of sites with contrasted conditions. The mechanistic relevance of ForCEEPS parameterization was explored by showing the congruence between the values of key model parameter and species functional traits. We further showed that accounting for the spatial configuration of crowns within forest stands, the effects of climatic constraints and the variability of shade tolerances in the species community are all crucial to better predict short-term productivity with gap-models.The dual ability of predicting short-term functioning and long-term community composition, as well as the balance between generality and realism (i.e., predicting accuracy) of the new generation of gap-models may open great perspectives for the exploration of the biodiversity-ecosystem functioning relationships, species coexistence mechanisms, and the impacts of climate change on forest ecosystems.

scholarly journals Effects of hydropeaking on drift, stranding and community composition of macroinvertebrates: a field experimental approach in three regulated Swiss rivers

2021 ◽  
Author(s):  
Diego Tonolla ◽  
Florian Dossi ◽  
Olivier Kastenhofer ◽  
Michael Doering ◽  
Christoph Hauer ◽  
...  
Keyword(s):  
Flow Velocity ◽  
Community Composition ◽  
High Sensitivity ◽  
Base Flow ◽  
Long Term Effects ◽  
Short Term ◽  
Wetted Area ◽  
Passive Drift ◽  
Macroinvertebrate Drift

Hydropeaking operation leads to fluctuations in wetted area between base and peak flow and increases discharge-related hydraulic forces (e.g., flow velocity). These processes promote macroinvertebrate drift and stranding, often affecting benthic abundance and biomass. Our field experimental study – conducted in three hydropeaking-regulated Swiss rivers – aimed to quantify (i) the short-term effects of the combined increase in flow amplitude and up-ramping rate based on macroinvertebrate drift and stranding, as well as (ii) long-term effects based on the established community composition. Hydropeaking led to increased macroinvertebrate drift compared to base flow and to unaffected residual flow reaches. Moreover, stranding of macroinvertebrates was positively related to drift, especially during the up-ramping phase. Flow velocity and up-ramping rate were identified as major determinants for macroinvertebrate drift, while flow ratio and down-ramping rate for stranding. Particularly high sensitivity towards HP was found for Limnephilidae, whereas Heptageniidae seemed to be resistant in respect to short and long-term hydropeaking effects. In the long-term, hydropeaking did not considerably reduce benthic density of most taxa, especially of some highly resistant and resilient taxa such as Chironomidae and Baetidae, which dominated the community composition even though they showed comparably high drift and stranding responses. Therefore, we argue that high passive drift and/or stranding, especially of individual-rich taxa, does not necessarily indicate strong hydropeaking sensitivity. Finally, our results demonstrate the necessity to consider the differences in river-specific morphological complexity and hydropeaking intensity, since these factors strongly influence the community composition and short-term drift and stranding response of macroinvertebrates to hydropower pressure.

scholarly journals Effects of multiple stressors on river biofilms depend on the time scale

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Ferran Romero ◽  
Vicenç Acuña ◽  
Carme Font ◽  
Anna Freixa ◽  
Sergi Sabater
Keyword(s):  
Exposure Time ◽  
Pesticide Exposure ◽  
Multiple Stressors ◽  
Freshwater Ecosystems ◽  
Additive Effects ◽  
Short Term ◽  
Multiple Stressor ◽  
Hydrological Stress ◽  
Additive Interactions

Abstract Global change exposes ecosystems to a myriad of stressors differing in their spatial (i.e. surface of stressed area) and temporal (i.e. exposure time) components. Among freshwater ecosystems, rivers and streams are subject to physical, chemical and biological stressors, which interact with each other and might produce diverging effects depending on exposure time. We conducted a manipulative experiment using 24 artificial streams to examine the individual and combined effects of warming (1.6 °C increase in water temperature), hydrological stress (simulated low-flow situation) and chemical stress caused by pesticide exposure (15.1–156.7 ng L−1) on river biofilms. We examined whether co-occurring stressors could lead to non-additive effects, and if these differed at two different exposure times. Specifically, structural and functional biofilm responses were assessed after 48 hours (short-term effects) and after 30 days (long-term effects) of exposure. Hydrological stress caused strong negative impacts on river biofilms, whereas effects of warming and pesticide exposure were less intense, although increasing on the long term. Most stressor combinations (71%) resulted in non-significant interactions, suggesting overall additive effects, but some non-additive interactions also occurred. Among non-additive interactions, 59% were classified as antagonisms after short-term exposure to the different stressor combinations, rising to 86% at long term. Our results indicate that a 30-day exposure period to multiple stressors increases the frequency of antagonistic interactions compared to a 48-hour exposure to the same conditions. Overall, the impacts of multiple-stressor occurrences appear to be hardly predictable from individual effects, highlighting the need to consider temporal components such as duration when predicting the effects of multiple stressors.

scholarly journals Litter type affects the activity of aerobic decomposers in a boreal peatland more than site nutrient and water table regimes

2011 ◽  
Vol 8 (9) ◽  
pp. 2741-2755 ◽  
Author(s):  
P. Straková ◽  
R. M. Niemi ◽  
C. Freeman ◽  
K. Peltoniemi ◽  
H. Toberman ◽  
...  
Keyword(s):  
Community Composition ◽  
Plant Community ◽  
Indirect Effects ◽  
Enzyme Activities ◽  
Litter Quality ◽  
Plant Community Composition ◽  
Litter Type ◽  
Direct Effects ◽  
Short Term

Abstract. Peatlands are carbon (C) storage ecosystems sustained by a high water table (WT). High WT creates anoxic conditions that suppress the activity of aerobic decomposers and provide conditions for peat accumulation. Peatland function can be dramatically affected by WT drawdown caused by climate and/or land-use change. Aerobic decomposers are directly affected by WT drawdown through environmental factors such as increased oxygenation and nutrient availability. Additionally, they are indirectly affected via changes in plant community composition and litter quality. We studied the relative importance of direct and indirect effects of WT drawdown on aerobic decomposer activity in plant litter at two stages of decomposition (incubated in the field for 1 or 2 years). We did this by profiling 11 extracellular enzymes involved in the mineralization of organic C, nitrogen (N), phosphorus (P) and sulphur. Our study sites represented a three-stage chronosequence from pristine to short-term (years) and long-term (decades) WT drawdown conditions under two nutrient regimes (bog and fen). The litter types included reflected the prevalent vegetation: Sphagnum mosses, graminoids, shrubs and trees. Litter type was the main factor shaping microbial activity patterns and explained about 30 % of the variation in enzyme activities and activity allocation. Overall, enzyme activities were higher in vascular plant litters compared to Sphagnum litters, and the allocation of enzyme activities towards C or nutrient acquisition was related to the initial litter quality (chemical composition). Direct effects of WT regime, site nutrient regime and litter decomposition stage (length of incubation period) summed to only about 40 % of the litter type effect. WT regime alone explained about 5 % of the variation in enzyme activities and activity allocation. Generally, enzyme activity increased following the long-term WT drawdown and the activity allocation turned from P and N acquisition towards C acquisition. This caused an increase in the rate of litter decomposition. The effects of the short-term WT drawdown were minor compared to those of the long-term WT drawdown: e.g., the increase in the activity of C-acquiring enzymes was up to 120 % (bog) or 320 % (fen) higher after the long-term WT drawdown compared to the short-term WT drawdown. In general, the patterns of microbial activity as well as their responses to WT drawdown depended on peatland type: e.g., the shift in activity allocation to C-acquisition was up to 100 % stronger at the fen compared to the bog. Our results imply that changes in plant community composition in response to persistent WT drawdown will strongly affect the C dynamics of peatlands. The predictions of decomposer activity under changing climate and/or land-use thus cannot be based on the direct effects of the changed environment only, but need to consider the indirect effects of environmental changes: the changes in plant community composition, their dependence on peatland type, and their time scale.

Long term effects of Ascophyllum nodosum canopy removal on mid shore community structure

2004 ◽  
Vol 84 (2) ◽  
pp. 327-329 ◽  
Author(s):  
S.R. Jenkins ◽  
T.A. Norton ◽  
S.J. Hawkins
Keyword(s):  
Community Composition ◽  
Fold Increase ◽  
Ascophyllum Nodosum ◽  
Algal Turf ◽  
Long Term Effects ◽  
Short Term ◽  
Red Algal ◽  
Canopy Removal ◽  
High Recruitment

The long term effects of macroalgal canopy removal on community composition were investigated over a 12 year period. Experimental removal of the dominant Ascophyllum nodosum canopy led to short term changes in community composition, the major features of which were still apparent 12 years later. Ascophyllum was slow to recover despite high recruitment, and experimental plots were dominated by Fucus species. After 12 years a mixed assemblage of Fucus serratus, Fucus vesiculosus and Ascophyllum had developed. Canopy removal resulted in a change in the balance between grazing limpets and the cover of red algal turf in the understorey community. The cover of turfing algae declined significantly allowing the area grazed by limpets to extend. This led to a 3–6 fold increase in the limpet population 12 years after canopy removal.

Sign in / Sign up

Export Citation Format

Share Document