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.

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.

Restoration of Arid and Semi-arid Ecosystems in Afghanistan

1977 ◽  
Vol 4 (4) ◽  
pp. 297-301 ◽  
Author(s):  
Amir S. Hassanyar
Keyword(s):  
Plant Biomass ◽  
Climatic Conditions ◽  
Species Selection ◽  
Arid Ecosystems ◽  
Topographic Map ◽  
Soil Series ◽  
Resistant Species ◽  
Planting Methods ◽  
Physical And Chemical ◽  
Semi Arid

Barren, desert-like environments have been created over large areas in Afghanistan, and various degrees of desertification can be seen especially in the southwestern plains. Extensive overgrazing, frequent drought, and unwise land-use, have initiated processes of local desertification also elsewhere in Afghanistan.The first step in the restoration of depleted vegetation is to correct the improper uses that have been responsible for these conditions. Improper grazing practices of rangelands are a primary cause of reductions in the productivity of arid and semi-arid ecosystems in Afghanistan.The second step in restoration is to prepare a detailed revegetation plan. The following maps and information are needed: (1) a vegetation-cover map, (2) a soil-series map, (3) a topographic map, and (4) baseline data on climatic conditions. The vegetationcover map identifies the plant biomass potential and the species that might be suitable for revegetation. The soil-series map is accompanied by a description of the physical and chemical features of the topsoil and subsoil along with an assessment of the general herbage production potential. The topographic map helps with species selection and planting methods. The climatic parameters assist in determining the season of planting and any need for drought-resistant species to be planted.

scholarly journals Airborne and Spaceborne Lidar Reveal Trends and Patterns of Functional Diversity in a Semi-Arid Ecosystem

2021 ◽  
Vol 2 ◽  
Author(s):  
Nayani Ilangakoon ◽  
Nancy F. Glenn ◽  
Fabian D. Schneider ◽  
Hamid Dashti ◽  
Steven Hancock ◽  
...  
Keyword(s):  
Functional Diversity ◽  
Spatial Scales ◽  
Ecosystem Processes ◽  
Airborne Lidar ◽  
Arid Ecosystems ◽  
Arid Ecosystem ◽  
Area Index ◽  
Plant Area Index ◽  
Abiotic Controls ◽  
Semi Arid

Assessing functional diversity and its abiotic controls at continuous spatial scales are crucial to understanding changes in ecosystem processes and services. Semi-arid ecosystems cover large portions of the global terrestrial surface and provide carbon cycling, habitat, and biodiversity, among other important ecosystem processes and services. Yet, the spatial trends and patterns of functional diversity in semi-arid ecosystems and their abiotic controls are unclear. The objectives of this study are two-fold. We evaluated the spatial pattern of functional diversity as estimated from small footprint airborne lidar (ALS) with respect to abiotic controls and fire in a semi-arid ecosystem. Secondly, we used our results to understand the capabilities of large footprint spaceborne lidar (GEDI) for future applications to semi-arid ecosystems. Overall, our findings revealed that functional diversity in this ecosystem is mainly governed by elevation, soil, and water availability. In burned areas, the ALS data show a trend of functional recovery with time since fire. With 16 months of data (April 2019-August 2020), GEDI predicted functional traits showed a moderate correlation (r = 41–61%) with the ALS predicted traits except for the plant area index (PAI) (r = 11%) of low height vegetation (<5 m). We found that the number of GEDI footprints relative to the size of the fire-disturbed areas (=< 2 km2) limited the ability to estimate the full effects of fire disturbance. However, the consistency of diversity trends between ALS and GEDI across our study area demonstrates GEDI’s potential of capturing functional diversity in similar semi-arid ecosystems. The capability of spaceborne lidar to map trends and patterns of functional diversity in this semi-arid ecosystem demonstrates its exciting potential to identify critical biophysical and ecological shifts. Furthermore, opportunities to fuse GEDI with complementary spaceborne data such as ICESat-2 or the upcoming NASA-ISRO Synthetic Aperture Radar (NISAR), and fine scale airborne data will allow us to fill gaps across space and time. For the first time, we have the potential to monitor carbon cycle dynamics, habitats and biodiversity across the globe in semi-arid ecosystems at fine vertical scales.

scholarly journals Coordinated variation in leaf and root traits across multiple spatial scales in Chinese semi-arid and arid ecosystems

2010 ◽  
Vol 188 (2) ◽  
pp. 543-553 ◽  
Author(s):  
Guofang Liu ◽  
Grégoire T. Freschet ◽  
Xu Pan ◽  
Johannes H. C. Cornelissen ◽  
Yan Li ◽  
...  
Keyword(s):  
Spatial Scales ◽  
Root Traits ◽  
Arid Ecosystems ◽  
Multiple Spatial Scales ◽  
Semi Arid

scholarly journals Importance of Autoinfection to the Epidemiology of Polycyclic Foliar Disease

2009 ◽  
Vol 99 (10) ◽  
pp. 1116-1120 ◽  
Author(s):  
Christopher C. Mundt
Keyword(s):  
Disease Progression ◽  
Spatial Scales ◽  
Landscape Scale ◽  
Local Scale ◽  
Microbial Interactions ◽  
Disease Spread ◽  
Potential Importance ◽  
Plant Populations ◽  
Foliar Disease ◽  
Qualitative And Quantitative

Autoinfection (infection resulting from inoculum produced on the same host unit) can result in strongly clustered disease at the local scale. In contrast, much epidemiological theory incorporates the simplification of spatially random or uniform infection. Earlier studies suggested only low to moderate levels of autoinfection, especially when the host unit is small. However, several studies published within the last 5 years suggest that autoinfection rates may be substantially higher than previously indicated. I discuss the potential importance of accounting for high autoinfection rates in example epidemiological processes that occur at different spatial scales: microbial interactions on the phylloplane, temporal disease progression in plant populations, and spatiotemporal disease spread at the landscape scale. Accounting for high autoinfection rates can have important qualitative and quantitative consequences for epidemiological processes, and further studies of autoinfection will contribute significantly to our understanding of epidemics.

Soil disturbance by animals at varying spatial scales in a semi-arid Australian woodland

2008 ◽  
Vol 30 (3) ◽  
pp. 327 ◽  
Author(s):  
David J. Eldridge ◽  
Alan B. C. Kwok
Keyword(s):  
Total Mass ◽  
Spatial Scales ◽  
Soil Disturbance ◽  
Landscape Scale ◽  
Small Scale ◽  
Vegetation Communities ◽  
Resting Sites ◽  
Animal Activity ◽  
Open Woodland ◽  
Semi Arid

We studied soil disturbance by rabbits, echidnas, goannas, ants and termites at three different spatial scales across four vegetation communities (dense woodland, open woodland, shrubland, grassland) in semi-arid rangeland in western NSW. For analyses, bare and litter-covered surfaces (micro-scale) were nested within canopy and open patches (intermediate scale), which were nested within vegetation communities (landscape scale). Landscape-scale disturbances (rabbit warrens) were six and three times more abundant in open woodlands and shrublands, respectively, than in dense woodlands. Although individual warrens had a similar mass of excavated soil across all vegetation communities, in total, more soil was excavated in the grasslands than in the dense woodlands or shrublands. There were four times as many intermediate-sized disturbances (foraging pits and resting sites) under canopies than out in the open, and this was consistent across all vegetation communities. Echidna foraging pits and kangaroo resting sites dominated the canopy patches. Intermediate-sized disturbances scaled up to the landscape scale were marginally more abundant in the dense and open woodlands than in grasslands and shrublands. However, total mass of soil moved by all species did not differ among vegetation communities. The density of small-scale disturbances (ant nests, termite foraging galleries) did not differ at the landscape-, intermediate- or micro-scales. Our study documents the extent of animal activity in the semi-arid woodlands, and reinforces the notion that, as soil disturbance is scale-dependent, differences among species, habitats and communities will depend on the scale at which disturbances are examined.

Fire effects on pollination in a sexually deceptive orchid

2016 ◽  
Vol 25 (8) ◽  
pp. 888 ◽  
Author(s):  
Julian Brown ◽  
Alan York ◽  
Fiona Christie
Keyword(s):  
Prescribed Fire ◽  
Scale Effects ◽  
Spatial Scales ◽  
Fire Effects ◽  
Landscape Scale ◽  
Local Scale ◽  
Agricultural Landscapes ◽  
Pollinator Visitation ◽  
Age Class ◽  
Landscape Scales

Research into the effectiveness of prescribed fire in managing pollination has only recently begun. The effects of fire on pollination have not been explored in sexually deceptive systems. Further, the potential for multiple effects operating at different spatial scales has not been explored in any pollination system despite multiscale effects on pollination observed in agricultural landscapes. We observed the frequency of pollinator visitation to flowers of sexually deceptive Caladenia tentaculata and related it to the post-fire age class of the vegetation at local and landscape scales. We also related the number of the pollinator’s putative larval hosts (scarab beetles) captured at these sites to age class. At the local scale (i.e. the sample location), visitation was highest in recently burnt sites. At the landscape scale, positive associations were observed between (1) putative pollinator hosts and vegetation burnt 36–50 years ago, and (2) pollinator visitation and vegetation burnt ≥50 years ago. Local- and landscape-scale effects on visitation were synergistic, such that visitation was greatest when fire age was heterogeneous within pollinator foraging range.

Arid and Semi-Arid Ecosystems

2007 ◽  
Author(s):  
P.W. Rundel ◽  
P.E. Villagra
Keyword(s):  
South America ◽  
Pacific Coast ◽  
Arid Ecosystems ◽  
Annual Rainfall ◽  
Monte Desert ◽  
Perennial Plant ◽  
Norte Chico ◽  
The Pacific ◽  
Pampa Del Tamarugal ◽  
Semi Arid

Arid and semi-arid ecosystems in South America are best illustrated by two desert regions, the Peruvian and Atacama Deserts of the Pacific coast and the Monte Desert of central Argentina. The caatinga of northeast Brazil is often described as semi-arid, but mostly receives 500–750 mm of annual rainfall and is better regarded as dry savanna. Small areas of Venezuela and Colombia near the Caribbean coast, and nearby offshore islands, support desert-like vegetation with arborescent cacti, Prosopis, and Capparis, but generally receive up to 500 mm annual rainfall. Substrate conditions, as much or more than climate, determine the desert-like structure and composition of these communities, and thus they are not discussed further here. Extensive areas of Patagonian steppe also have semi-arid conditions, as discussed in chapter 14. The Peruvian and Atacama Deserts form a continuous belt along the west coast of South America, extending 3,500 km from near the northern border of Perú (5°S) to north-central Chile near La Serena (29°55’S), where the Mediterranean- type climate regime becomes dominant. The eastward extent of the Peruvian and Atacama Deserts is strongly truncated where either the coastal ranges or Andean Cordillera rise steeply from the Pacific coast and, as a biogeographic unit, the desert zone may extend from 20 to 100 km or more inland. A calculation of the area covered by these deserts depends in part on how this eastern margin is defined. Thus the Peruvian Desert covers between 80,000 and 144,000 km2, while the Atacama Desert of Chile extends over about 128,000 km2 if the barren lower slopes of the Andes are included. Actual vegetated landscapes are far smaller and for the lomas of Perú change dramatically between years depending on rainfall. Only about 12,000 km2 of the Atacama contain perennial plant communities, largely in the southern portion known as the Norte Chico but also including a narrow coastal belt of lomas extending northward almost to Antofagasta and the Prosopis woodlands of the Pampa del Tamarugal. The vegetated areas of the coastal lomas of Perú and Chile together probably do not exceed 4,000 km2 as a maximum following El Niño rains.

scholarly journals Reciprocal facilitation between large herbivores and ants in a semi-arid grassland

2018 ◽  
Vol 285 (1888) ◽  
pp. 20181665 ◽  
Author(s):  
Xiaofei Li ◽  
Zhiwei Zhong ◽  
Dirk Sanders ◽  
Christian Smit ◽  
Deli Wang ◽  
...  
Keyword(s):  
Species Coexistence ◽  
Plant Biomass ◽  
Soil Surface ◽  
Plant Litter ◽  
Positive Interactions ◽  
Large Herbivores ◽  
Litter Accumulation ◽  
Positive Effects ◽  
Animal Communities ◽  
Semi Arid

While positive interactions have been well documented in plant and sessile benthic marine communities, their role in structuring mobile animal communities and underlying mechanisms has been less explored. Using field removal experiments, we demonstrated that a large vertebrate herbivore (cattle; Bos tarurs ) and a much smaller invertebrate (ants; Lasius spp.), the two dominant animal taxa in a semi-arid grassland in Northeast China, facilitate each other. Cattle grazing led to higher ant mound abundance compared with ungrazed sites, while the presence of ant mounds increased the foraging of cattle during the peak of the growing season. Mechanistically, these reciprocal positive effects were driven by habitat amelioration and resource (food) enhancement by cattle and ants (respectively). Cattle facilitated ants, probably by decreasing plant litter accumulation by herbivory and trampling, allowing more light to reach the soil surface leading to microclimatic conditions that favour ants. Ants facilitated cattle probably by increasing soil nutrients via bioturbation, increasing food (plant) biomass and quality (nitrogen content) for cattle. Our study demonstrates reciprocal facilitative interactions between two animal species from phylogenetically very distant taxa. Such reciprocal positive interactions may be more common in animal communities than so far assumed, and they should receive more attention to improve our understanding of species coexistence and animal community assembly.

scholarly journals Linking spatial patterns of terrestrial herbivore community structure to trophic interactions

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Jakub Witold Bubnicki ◽  
Marcin Churski ◽  
Krzysztof Schmidt ◽  
Tom A Diserens ◽  
Dries PJ Kuijper
Keyword(s):  
Spatial Distribution ◽  
Community Structure ◽  
Spatial Variation ◽  
Spatial Scales ◽  
Landscape Scale ◽  
Top Down ◽  
Large Herbivores ◽  
Bottom Up ◽  
Vegetation Heterogeneity ◽  
Herbivore Community

Large herbivores influence ecosystem functioning via their effects on vegetation at different spatial scales. It is often overlooked that the spatial distribution of large herbivores results from their responses to interacting top-down and bottom-up ecological gradients that create landscape-scale variation in the structure of the entire community. We studied the complexity of these cascading interactions using high-resolution camera trapping and remote sensing data in the best-preserved European lowland forest, Białowieża Forest, Poland. We showed that the variation in spatial distribution of an entire community of large herbivores is explained by species-specific responses to both environmental bottom-up and biotic top-down factors in combination with human-induced (cascading) effects. We decomposed the spatial variation in herbivore community structure and identified functionally distinct landscape-scale herbivory regimes (‘herbiscapes’), which are predicted to occur in a variety of ecosystems and could be an important mechanism creating spatial variation in herbivory maintaining vegetation heterogeneity.

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