Grazing History Research Articles

When savannas recover from overgrazing, ecohydrological connectivity collapses

Grasslands and savannas across the globe have undergone a dramatic transition over the past century. Historical overgrazing has set in motion a cascade of events ranging from desertification in arid climates to woody plant encroachment (WPE) in semiarid and subhumid climates. In recent decades, grazing pressure on many of these landscapes has declined significantly, and where rainfall is sufficient (as in most semiarid and subhumid settings), herbaceous vegetation in intercanopy areas will recover. An important question is, how has this transition altered ecohydrological connectivity (overland flow and runoff–runon dynamics)? A woody-plant-encroached, subhumid savanna site in South Texas with a history of heavy grazing (but ungrazed since 1981) was used as a model landscape to address this question. Overland flow, soil moisture, and field saturated hydraulic conductivity (Kfs) were measured along a catena extending from the upland savanna-parkland areas to the downslope, more densely wooded areas. For comparison, Kfs and infiltrability were also measured at a moderately grazed upland site 14 km east of our study site, selected as a surrogate for past conditions at our site. In contrast to the prevailing hypothesis that the downslope areas (‘drainage-woodlands’) at our study site have continued to be supported by runoff generated from the upland areas, our measurements yielded no evidence for the redistribution of water from the uplands to the drainage areas under the current ungrazed conditions. Further, Kfs at the ungrazed study site was two orders of magnitude higher than that at the grazed site and infiltrability was twice as high at the ungrazed site than the grazed site. These findings, coupled with historical information from the site, strongly suggest that historical overgrazing amplified the runoff–runon process, resulting in significant subsidies of water from the uplands to the drainage areas. Then, with the relaxation of grazing pressure and subsequent landscape recovery, redistribution of water via surface runoff was relatively rare. We believe that our results are generalizable for savannas that have recovered from overgrazing. When these savannas are heavily grazed, ecohydrological connectivity is greatly increased; but if grazing pressure relaxes, ecohydrological connectivity will collapse. These changes in ecohydrological connectivity have important, but not always well understood, ecological consequences.

Historic Sheep Grazing in Arizona*

Sheep production in Arizona was a very early industry and economic driver in the state. Few, however, seem to be aware of its history or associated archaeological remains. This purpose of this paper to give a brief history of the development of the sheep industry in Arizona and an overview of the more common types of archaeological sites that would represent this industry.

Populations of two annual clover species evolved in response to 13 years of grazing management and phosphate fertilizer application

AbstractA Syrian grassland was subject to 13 years of replicated management treatments, namely a factorial design of 0 or 60 kg/ha annually of phosphate fertilizer, combined with relatively low or high sheep stocking intensities. Previous work found that differences in grazing intensity and phosphate induced changes in the structure of the legume community, presumably due to changes in competitive relationships. The aim of this study was to investigate how the populations of the predominant clover species, Trifolium campestre and Trifolium tomentosum, changed as a consequence of management treatments. We hypothesized that the populations from the fertilized or low grazing intensity treatments would express phenotypic traits associated with increased competitive ability and/or with risk mitigation. Populations of both ruderal‐type clover species provided evidence of evolution but were largely responsive to different management factors. Assuming that heavy grazing and no fertilizer are the natural state of the grassland, addition of phosphate led to T. tomentosum plants that were wider and had larger seeds, traits associated with improved competitive ability. The populations from the fertilized paddocks had increased fecundity and a trend towards greater dormancy, traits associated with risk mitigation. In contrast, T. campestre plants became wider and more erect when stocking intensities were reduced and had greater seed dormancy in fertilized paddocks. The implication of this work is that the collection of germplasm from grasslands with a history of heavy grazing and fertilizer application may assist agronomists to find genotypes that are better adapted to pastures within ley farming systems in Australia.

Forb community responses to an extensive drought in two contrasting land-use types of a semi-arid Lowveld savanna

Projected increases in the frequency and severity of drought events are expected to impose changes in the ecology of native forb communities in semi-arid ecosystems. We examined the state of forb communities during, and directly after an extreme drought event across two contrasting land-use types, which included a protected area (high diversity of free roaming wild herbivores) and communal rangeland (long history of intensive cattle grazing) in a semi-arid Lowveld savanna of the Gazankulu area, South Africa. Forb floristic data were collected towards the end of the drought and repeated after the drought release a few months later. Forb community composition was significantly different among land-use types. Community changes were not induced by annual forb emergence alone, but through species-specific dominance shifts, which differed among land-use types. Forb richness, diversity and biomass were equally low at both land-use types and increased significantly after the drought release, although the magnitude of response was much stronger in the protected area, whereas drought contributed to a directional change in the protected area with a complete post-drought turnover in both annual and perennial forb species, much less variability was observed in the communal rangeland, which may suggest long-term effects imposed by land-use history.

A comparative study of survival, recruitment and population growth in two translocated populations of the threatened greater bilby (Macrotis lagotis)

Abstract Context Translocations have been widely used to re-establish populations of threatened Australian mammalian species. However, they are limited by the availability of sites where key threats can be effectively minimised or eliminated. Outside of ‘safe havens’, threats such as exotic predators, introduced herbivores and habitat degradation are often unable to be completely eliminated. Understanding how different threats affect Australian mammal populations can assist in prioritising threat-management actions outside of safe havens. AimsWe sought to determine whether translocations of the greater bilby to two sites in the temperate zone of South Australia could be successful when human-induced threats, such as prior habitat clearance, historic grazing, the presence of feral cats and European rabbits, could not be completely eliminated. Methods Greater bilbies were regularly cage trapped at two translocation sites and a capture–mark–recapture study was used to determine survival, recruitment and population growth at both sites. Key results Our study showed that bilbies were successfully translocated to an offshore island with a previous history of grazing and habitat clearance, but which was free of exotic predators. At a second site, a mainland exclosure with feral cats and European rabbits present, the bilby population declined over time. Adult bilbies had similar survival rates in both populations; however, the mainland bilby population had low recruitment rates and low numbers of subadults despite high adult female fecundity. ConclusionsThe results indicated that past grazing and habitat clearance did not prevent the bilby population on the offshore island establishing and reaching a high population density. In the mainland exclosure, the low recruitment is probably due to feral cats predating on subadult bilbies following pouch emergence. Implications The results demonstrated that the bilby, an ecologically flexible Australian marsupial, can be successfully translocated to sites with a history of habitat degradation if exotic predators are absent. At the mainland exclosure site, threat mitigation for bilbies should focus on control or eradication of the feral cats. The control of European rabbits without control of feral cats could lead to prey-switching by feral cats, further increasing predation pressure on the small bilby population.

Limited evidence for the use of livestock for the conservation management of exotic plant cover

Livestock grazing has been used for conservation management in some situations to reduce exotic plant cover, but supporting empirical evidence is scant. This is particularly true for eastern Australian semiarid woodlands and forests. We surveyed 451 sites across three broad semiarid vegetation communities (cypress pine, black box, red gum) in eastern Australia to examine the effects of recent and longer-term (historic) grazing by livestock on exotic (and native) plant cover. Because our focus was the use of domestic livestock for conservation management, our sites were mostly located in conservation reserves, travelling stock routes and native production forests where domestic grazing is approved via permit. We also included recent grazing by kangaroos and rabbits, which occur widely with livestock across the study sites. Structural equation modelling revealed that recent sheep and cattle grazing was associated with increased exotic plant cover in two of the three communities (cypress pine, black box), and historic grazing was associated with lower exotic (and native) plant cover across all communities. Recent cattle grazing-induced reductions in exotic plant cover in the red gum community resulted from declines in the palatable exotic annual grass Ehrharta longiflora. Higher intensity grazing by rabbits, sheep and cattle in the cypress pine community increased exotic plant cover by suppressing the negative effect of native cover on exotic cover. Higher intensity rabbit grazing reinforced the negative effect of nitrogen on native plant cover, resulting in increases in exotic cover. Overall, we found strong evidence that domestic livestock grazing reduces native plant cover either directly or indirectly in all three communities, but limited evidence that it would be a useful conservation management strategy to reduce exotic plant cover in these communities.

Effects of nitrogen and water addition on soil respiration in a Nei Mongol desert steppe with different intensities of grazing history

Effects of nitrogen and water addition on soil respiration in a Nei Mongol desert steppe with different intensities of grazing history

Stocking rate affects plant community structure and reproductive strategies of a desirable and an undesirable grass species in an alpine steppe, Qilian Mountains, China

The effects of grazing on species reproduction is a fundamental issue of grassland management. We investigated plant density and dry weight changes at community and species levels, and the reproductive strategies of the dominant desirable Stipa purpurea and the undesirable Achnatherum inebrians grass species in response to stocking rate in an alpine steppe with a 10-year grazing history. Results showed complex patterns of plant community and reproductive strategy. Overall plant density increased with increasing stocking rate and dry weight was significantly higher at light and high stocking rates. Plant density and dry weight of A. inebrians peaked at moderate stocking rates. Higher stocking rate had little impact on S. purpurea density but significantly reduced its dry weight. Both species displayed linearly increasing/decreasing or unimodal/bimodal reproductive effort in response to increased stocking rate. The discrepancies in plant reproductive characteristics between S. purpurea and A. inebrians indicated that: (1) light and moderate grazing may promote an adaption strategy of reproduction by desirable species, which may then contribute to their maintenance in grasslands, and (2) undesirable species presence did not lead to the replacement of desirable species in the grasslands. Therefore, light and moderate stocking rates are recommended to maintain the grasslands and to increase the reproductive outputs of desirable species.

Allocating species in Grime’s strategy space: an alternative to trait-based approaches

Background: The three primary-strategy theory proposed by Grime identifies stress and disturbance as key environmental factors leading to the emergence of distinct plant strategies. These are defined by a combination of stress and disturbance tolerance. Plant strategies are usually inferred from sets of traits, but this may lead to circular reasoning and artificial restrictions to species’ distribution in strategy space. 
 Question: Can measurements of stress and disturbance tolerance be used to estimate the position of different species relative to each other in Grime’s strategy space?
 Data description: Stress, disturbance, and abundances for 50 species at 25 0.5 ha sites.
 Study site and dates: Semiarid grassland, Oaxaca, Mexico, 2014.
 Methods: Species’ tolerance to stress and disturbance were inferred from abundances, and used to allocate species in Grime’s space. We tested if some attributes of our study species changed over the strategy space according to theoretical expectations.
 Results: Most species were allocated towards high disturbance and low stress intensities. Species attributes were in line with the trends expected from their position in the strategy space. 
 Discussion: Perhaps because of a long grazing history, most species were tolerant to disturbance. The allocation of species in the strategy space using stress and disturbance measurements seemed correct based on their attributes. Thus, our measurements seem to reflect the basic principles proposed by Grime. Our method provides relative positions in the strategy space, and (as previous work) requires defining somewhat arbitrary limits to such space if we wish to label species as ruderals, competitors or stress-tolerant.

Removal of grazers alters the response of tundra soil carbon to warming and enhanced nitrogen availability

AbstractThe circumpolar Arctic is currently facing multiple global changes that have the potential to alter the capacity of tundra soils to store carbon. Yet, predicting changes in soil carbon is hindered by the fact that multiple factors simultaneously control processes sustaining carbon storage and we do not understand how they act in concert. Here, we investigated the effects of warmer temperatures, enhanced soil nitrogen availability, and the combination of these on tundra carbon stocks at three different grazing regimes: on areas with over 50‐yr history of either light or heavy reindeer grazing and in 5‐yr‐old exlosures in the heavily grazed area. In line with earlier reports, warming generally decreased soil carbon stocks. However, our results suggest that the mechanisms by which warming decreases carbon storage depend on grazing intensity: under long‐term light grazing soil carbon losses were linked to higher shrub abundance and higher enzymatic activities, whereas under long‐term heavy grazing, carbon losses were linked to drier soils and higher enzymatic activities. Importantly, under enhanced soil nitrogen availability, warming did not induce soil carbon losses under either of the long‐term grazing regimes, whereas inside exclosures in the heavily grazed area, also the combination of warming and enhanced nutrient availability induced soil carbon loss. Grazing on its own did not influence the soil carbon stocks. These results reveal that accounting for the effect of warming or grazing alone is not sufficient to reliably predict future soil carbon storage in the tundra. Instead, the joint effects of multiple global changes need to be accounted for, with a special focus given to abrupt changes in grazing currently taking place in several parts of the Arctic.

Change, Collective Action, and Cultural Resilience in Páramo Management in Ecuador

This study examines how agricultural frontier expansion and grazing practices develop in the páramos under communal tenure in the northern Ecuadorian Andes and how rules to control them emerge within communal governance. We approach these questions through the lens of collective action and cultural resilience, to understand the evolution of communal governance. We analyze a case study of the Comité de Páramo Ñukanchik Urku, a multicommunal organization created in the 1990s for collective resource management. We use the analytical framework of social–ecological systems (SES) to approach changes of the agricultural frontiers and grazing activities as conservation outcomes resulting from changes in resource units, actors, and governance structures. Through a mixed-method approach combining air photo analysis (years 1956, 1993, and 2008) and qualitative research, we examine spatial patterns of settlement and agricultural frontier expansion, historical grazing practices, and the main elements of current collective páramo management. Our results indicate that: (1) the demarcation of an agreed agricultural frontier as a territorial landmark is a response aiming to control the increase of crops and dwellings at higher elevations, and to limit grazing activities; (2) the authority's legitimation of the Committee and its Board is crucial to develop rules and to enforce them; and (3) legitimation is achieved through conservation knowledge and autonomous decisions to control páramos considered a communal territory. A broader comprehension of the context and history of cultural change is needed to understand the emergence of communal governance of páramos. Cultural-political dimensions are key to the cultural resilience of social systems in SES and to strengthening rules and institutional diversity to manage the commons in Andean communities.

Extracellular enzyme activity in grass litter varies with grazing history, environment and plant species in temperate grasslands

Long-term livestock grazing (here after ‘grazing’) affects carbon (C) and nutrient cycling in grassland ecosystems, in part by altering the quantity and quality of litter inputs. Despite their spatial extent and size of carbon and nutrient stocks, the effect of grazing on grassland biogeochemical cycling through the mediation of microbial activity remains poorly understood. To better understand the relationship between grazing and C and nutrient cycling in litter, we conducted an 18-month long study in paired grasslands previously grazed and nongrazed by cattle for 25 years, measuring extracellular enzyme activity (EEA) in various plant litter samples. Litter sources, including seven grass species dominant in one or more subregions and possessing divergent responses to grazing, as well as a community mix of litter sourced from each site, were tested at 15 sites spanning three grassland subregions in Alberta, Canada. We quantified EEAs associated with C cycling (β-glucosidase, β-Cellobiosidase and β-xylosidase), nitrogen (N) cycling (N-acetyl-glucosaminidase) and phosphorus (P) cycling (phosphatase). In general, litter in grasslands exposed to grazing had greater activity of C-liberating and P-liberating enzyme (β-xylosidase and phosphatase) in the mesic grasslands of the Foothills Fescue subregion (P ≤ 0.10). Observed EEAs were strongly mediated by litter type, with greater EEAs in litter of grass species known to increase in abundance under long-term grazing, including Poa pratensis in the Foothills Fescue subregion, and Bouteloua gracilis in arid grasslands of the Mixedgrass Prairie. In contrast, Pascopyrum smithii litter had the lowest enzyme activities in all subregions. We also found that EEAs changed through time (0–18 months) with consistently high levels detected at 1 (June 2014), 6 (October 2014) and 18 months (October 2015) after placement. Overall, these findings indicate grazing enhances EEA, and thus C and N-cycling, in northern temperate grasslands.

The New South Wales Travelling Stock Route and Reserve (TSR) network: historical extent, spatial distribution and drivers of loss 1884–2017

ABSTRACTThe Travelling Stock Route and Reserve (TSR) network is an historical grazing reserve network under threat, where public alarm has continued over the potential sale of reserves. Present debate on the future of the TSRs is often hindered by a lack of data, as knowledge of the historical extent of TSRs is deficient. This paper documents the original extent of the New South Wales TSR network and changes during 1884–2017, and discusses the key drivers of reserve loss since the late nineteenth century. Research using archived literature showed that, in 1884, the New South Wales TSR network comprised 4,414,690 ha. Comparisons of TSR acreage from that time with present estimates revealed that the reserve network has declined by 54% since its inception. Most reductions in TSR area during 1884–2017 have occurred in the Eastern (83%) and Central (82%) regions of the state, where competing land demands are greatest. Technological changes in transport, environmental pressures and economic changes in the grazing industry were identified as key drivers of TSR loss. These findings support concerns over the efficacy of the TSR reserve network, where the extent and impacts of past government decisions to sell off TSRs has been grossly under-estimated.

Grazing plays an important role in structuring alpha and beta components of taxonomic, functional, and phylogenetic diversity in semiarid sandy land of northern China

Horqin Sandy Land is located in the semiarid farming-pastoral ecotone of China, with a long-term history of uncontrolled livestock grazing. However, the relative effects of grazing, environmental and spatial factors on taxonomic, functional, and phylogenetic diversity has not been explored simultaneously. To test the relative importance of grazing, environmental and spatial factors in shaping alpha and beta components of taxonomic, functional, and phylogenetic diversity in semiarid sandy land, a large-scale field survey was carried out from 141 plots at 41 sites across Horqin Sandy Land. Results showed that grazing, environmental and spatial factors affected three facets of diversity in different ways at both alpha and beta scales. Taxonomic, functional, and phylogenetic diversity was shaped by environmental factors at the alpha scale, whereas phylogenetic diversity was correlated with spatial factors at the beta scale. Interestingly, beta taxonomic diversity was determined by spatially structured environmental factors and beta functional diversity was determined by environmental factors. Results showed that the ecological drivers of biodiversity may vary according to different facets and scales. Meanwhile, we also found that grazing plays an important role in structuring biodiversity in semiarid sandy land. Grazing disturbance explained more variation at the alpha scale than at the beta scale. Furthermore, the joint effect of grazing disturbance and soil fertility played an important role in shaping alpha diversity. It is worth noting that all three facets of diversity were reduced by increasing grazing intensity or decreasing soil fertility. Our results highlight that correctly managing grazing locally and unfertile site can decrease the effects of disturbance on biodiversity patterns in semiarid ecosystems. Future research should focus on taxonomic, functional, and phylogenetic diversity at various scales to determine biodiversity conservation strategies.

Dung fungi as an indicator of large herbivore dynamics in peatlands

Coprophilous fungal spores (CFS) have gained prominence in paleoecology as a proxy for large herbivore dynamics. Dung availability is one of several factors that influences spore abundance so it is unclear how closely CFS levels track herbivore biomass. This uncertainty is particularly relevant in peat- and moorland, where grazing impacts are a recurring topic in paleoecology and source of tension in environmental management, and where the method has yet to be tested. The current study used three ecological and conservation grazing experiments in UK peat- and moorland to study modern and recent historic relationships between grazing treatment and the abundance of three key CFS types and three pollen disturbance indicators. A total of 78 surface samples and 2 short peat cores were analyzed. Dispersal distances are estimated to range from <10 m to tens of meters, based on significantly lower CFS abundance in exclosed than grazed plots at two sites, and similar CFS trends over the last century in short peats cores located 80 m apart at the third site. The CFS signal thus represents activity in the surrounding landscape, despite predominantly local dispersal. CFS abundance does not correspond with animal biomass when compared across the three sites, however, and pollen disturbance indicators in the peat cores matched recent historic grazing records more consistently than CFS abundance. Potential reasons for these mismatches are discussed. Quantitative inferences about large herbivore abundance from CFS in peatlands should therefore be made with caution and recommendations are made for further testing of the method.

Long-term warming results in species-specific shifts in seed mass in alpine communities.

BackgroundGlobal warming can cause variation in plant functional traits due to phenotypic plasticity or rapid microevolutionary change. Seed mass represents a fundamental axis of trait variation in plants, from an individual to a community scale. Here, we hypothesize that long-term warming can shift the mean seed mass of species.MethodsWe tested our hypothesis in plots that had been warmed over 18 years in alpine meadow communities with a history of light grazing (LG) and heavy grazing (HG) on the Qinghai-Tibet plateau. In this study, seeds were collected during the growing season of 2015.ResultsWe found that warming increased the mean seed mass of 4 (n = 19) species in the LG meadow and 6 (n = 20) species in the HG meadow, while decreasing the mean seed mass of 6 species in the LG and HG meadows, respectively. For 7 species, grazing history modified the effect of warming on seed mass. Therefore, we concluded that long-term warming can shift the mean seed mass at the species level. However, the direction of this variation is species-specific. Our study suggests that mean seed mass of alpine plant species appears to decrease in warmer (less stressful) habitats based on life-history theory, but it also suggests there may be an underlying trade-off in which mean seed mass may increase due to greater thermal energy inputs into seed development. Furthermore, the physical and biotic environment modulating this trade-off result in complex patterns of variation in mean seed mass of alpine plant species facing global warming.

Competitive Strategy of Subalpine Tall-Grass Species of the Northwestern Caucasus

The range of ecological CSR strategies for subalpine tall-herb communities of the northwestern Caucasus (Teberda state natural biosphere reserve) has been studied by the measurement of leaves’ functional traits. These communities are developed in swales, river valleys, and runoff depressions of the subalpine belt and represent a typical element of the Caucasian flora. The dominating species are represented by tall forbs, such as Rumex alpinus, Senecio platyphylloides, Cephalaria gigantea, Ligusticum alatum, etc. To evaluate ecological strategies of plants, three functional traits, including leaf area and the weights of wet and dry leaves, have been measured. Based on these measurements, the strategy parameters have been calculated for 42 vascular plant species. The majority of plants of the subalpine tall-grass community manifest traits typical for the competitive (C) and competitive-ruderal (CR) strategies. According to the calculation algorithm, 11 species (Angelica purpurascens, A. tatianae, Cirsium chlorocomos, Heracleum asperum, H. leskovii, H. sosnowskyi, etc.) are referred to the C-strategy. The CR strategy is observed for Aconitum nasutum, Cirsium simplex, Geranium sylvaticum, Hesperis voronovii, Rumex alpestris, and some other species. Two species (Achillea millefolium and Dactylis glomerata) are characterized by the competitive and stress-tolerant (CS) strategy. The stress-tolerant (S) strategy is observed for three species (Veronica filiformis, Lilium monadelphum, and Millium effusum). Finally, the mixed CSR strategy is typical for two species (Trifolium pratense and Astrantia maxima). The majority (93%) of the species studied is characterized by clear competitive traits; the contribution of this strategy type positively correlates with the average vegetative height of a species. In addition, many of the studied species (26% on average) are also characterized by some R-strategy traits. In our opinion, this fact results from a long-term grazing history of alpine plant communities in this region. The obtained results contradict the common opinion about the domination of stress-tolerant species in highlands. This contradiction may be explained by the fact that the studied subalpine meadows are located in the most favorable habitats providing competitive advantages for rapidly-growing tall-herb species. The study confirms the hypothesis that the dominated species of the subalpine tall-grass community of the northwest Caucasus are characterized by significantly (up to 95%) manifested traits of C strategy.

Effects of Fire and Large Herbivores on Canopy Nitrogen in a Tallgrass Prairie

This study analyzed the spatial heterogeneity of grassland canopy nitrogen in a tallgrass prairie with different treatments of fire and ungulate grazing (long-term bison grazing vs. recent cattle grazing). Variogram analysis was applied to continuous remotely sensed canopy nitrogen images to examine the spatial variability in grassland canopies. Heterogeneity metrics (e.g., the interspersion/juxtaposition index) were calculated from the categorical canopy nitrogen maps and compared among fire and grazing treatments. Results showed that watersheds burned within one year had higher canopy nitrogen content and lower interspersions of high-nitrogen content patches than watersheds with longer fire intervals, suggesting an immediate and transient fire effect on grassland vegetation. In watersheds burned within one year, high-intensity grazing reduced vegetation density, but promoted grassland heterogeneity, as indicated by lower canopy nitrogen concentrations and greater interspersions of high-nitrogen content patches at the grazed sites than at the ungrazed sites. Variogram analyses across watersheds with different grazing histories showed that long-term bison grazing created greater spatial variability of canopy nitrogen than recent grazing by cattle. This comparison between bison and cattle is novel, as few field experiments have evaluated the role of grazing history in driving grassland heterogeneity. Our analyses extend previous research of effects from pyric herbivory on grassland heterogeneity by highlighting the role of grazing history in modulating the spatial and temporal distribution of aboveground nitrogen content in tallgrass prairie vegetation using a remote sensing approach. The comparison of canopy nitrogen properties and the variogram analysis of canopy nitrogen distribution provided by our study are useful for further mapping grassland canopy features and modeling grassland dynamics involving interplays among fire, large grazers, and vegetation communities.

El cuadro de pastoreo en los sistemas extensivos de Patagonia Sur. Percepción y manejo de la heterogeneidad

Fil: Ormaechea, Sebastian Gabriel. Instituto Nacional de Tecnologia Agropecuaria. Centro Regional Cordoba. Estacion Experimental Agropecuaria Manfredi; Argentina

Returning a lost process by reintroducing a locally extinct digging marsupial.

The eastern bettong (Bettongia gaimardi), a medium-sized digging marsupial, was reintroduced to a predator-free reserve after 100 years of absence from the Australian mainland. The bettong may have the potential to restore temperate woodlands degraded by a history of livestock grazing, by creating numerous small disturbances by digging. We investigated the digging capacity of the bettong and compared this to extant fauna, to answer the first key question of whether this species could be considered an ecosystem engineer, and ultimately if it has the capacity to restore lost ecological processes. We found that eastern bettongs were frequent diggers and, at a density of 0.3–0.4 animals ha−1, accounted for over half the total foraging pits observed (55%), with echidnas (Tachyglossus aculeatus), birds and feral rabbits (Oryctolagus cuniculus) accounting for the rest. We estimated that the population of bettongs present dug 985 kg of soil per ha per year in our study area. Bettongs dug more where available phosphorus was higher, where there was greater basal area of Acacia spp. and where kangaroo grazing was less. There was no effect on digging of eucalypt stem density or volume of logs on the ground. While bettong digging activity was more frequent under trees, digging also occurred in open grassland, and bettongs were the only species observed to dig in scalds (areas where topsoil has eroded to the B Horizon). These results highlight the potential for bettongs to enhance soil processes in a way not demonstrated by the existing fauna (native birds and echidna), and introduced rabbit.