Global assessment of the non-equilibrium concept in rangelands

Land use and dingo baiting are correlated with the density of kangaroos in rangeland systems

Rangelands worldwide have been subject to broadscale modification, such as widespread predator control, introduction of permanent livestock water and altered vegetation to improve grazing. In Australia, these landscape changes have resulted in kangaroos (i.e. large macropods) populations increasing over the past 200 years. Kangaroos are a key contributor to total grazing pressure and in conjunction with livestock and feral herbivores have been linked to land degradation. We used 22 years of aerial survey data to investigate whether the density of 3 macropod species in the southern rangelands of Western Australia was associated with: (i) land use, including type of livestock, total livestock, density of feral goats, type of land tenure, and kangaroo commercial harvest effort; (ii) predator management, including permitted dingo control effort, estimated dingo abundance, and presence of the State Barrier Fence (a dingo exclusion fence); and (iii) environmental variables: ruggedness, rainfall, fractional cover, and total standing dry matter. Red kangaroos (Osphranter rufus) were most abundant in flat, open vegetation, on pastoral land, where area permitted for dingo control was high, and numbers were positively associated with antecedent rainfall with a 12-month delay. Western grey kangaroos (Macropus fuliginosus) were most abundant on flat, agricultural land, but less abundant in areas with high permitted dingo control. Euros (Osphranter robustus) were most abundant in rugged pastoral land with open vegetation, where permitted dingo control was high. While environmental variables are key drivers of landscape productivity and kangaroo populations, anthropogenic factors such as land use and permitted dingo control are strongly associated with kangaroo abundance.

Prevalence and drivers of abrupt vegetation shifts in global drylands

The constant provision of plant productivity is integral to supporting the liability of ecosystems and human wellbeing in global drylands. Drylands are paradigmatic examples of systems prone to experiencing abrupt changes in their functioning. Indeed, space-for-time substitution approaches suggest that abrupt changes in plant productivity are widespread, but this evidence is less clear using observational time series or experimental data at a large scale. Studying the prevalence and, most importantly, the unknown drivers of abrupt (rather than gradual) dynamical patterns in drylands may help to unveil hotspots of current and future dynamical instabilities in drylands. Using a 20-y global satellite-derived temporal assessment of dryland Normalized Difference Vegetation Index (NDVI), we show that 50% of all dryland ecosystems exhibiting gains or losses of NDVI are characterized by abrupt positive/negative temporal dynamics. We further show that abrupt changes are more common among negative than positive NDVI trends and can be found in global regions suffering recent droughts, particularly around critical aridity thresholds. Positive abrupt dynamics are found most in ecosystems with low seasonal variability or high aridity. Our work unveils the high importance of climate variability on triggering abrupt shifts in vegetation and it provides missing evidence of increasing abruptness in systems intensively managed by humans, with low soil organic carbon contents, or around specific aridity thresholds. These results highlight that abrupt changes in dryland dynamics are very common, especially for productivity losses, pinpoint global hotspots of dryland vulnerability, and identify drivers that could be targeted for effective dryland management.

Indirect effects of African megaherbivore conservation on bat diversity in the world's oldest desert

In extreme environments, temperature and precipitation are often the main forces responsible for structuring ecological communities and species distributions. The role of biotic interactions is typically thought to be minimal. By clustering around rare and isolated features, like surface water, however, effects of herbivory by desert-dwelling wildlife can be amplified. Understanding how species interact in these environments is critical to safeguarding vulnerable or data-deficient species. We examined whether African elephants (Loxodonta africana), black rhinoceros (Diceros bicornis), and southern giraffe (Giraffa giraffa) modulate insectivorous bat communities around permanent waterholes in the Namib Desert. We estimated megaherbivore use of sites based on dung transects, summarized vegetation productivity from satellite measurements of the normalized difference vegetation index, and surveyed local bat communities acoustically. We used structural equation models to identify relationships among megaherbivores and bat species richness and dry- (November 2016-January 2017) and wet- (February-May 2017) season bat activity. Site-level megaherbivore use in the dry season was positively associated with bat activity-particularly that of open-air foragers-and species richness through indirect pathways. When resources were more abundant (wet season), however, these relationships were weakened. Our results indicate that biotic interactions contribute to species distributions in desert areas and suggest the conservation of megaherbivores in this ecosystem may indirectly benefit insectivorous bat abundance and diversity. Given that how misunderstood and understudied most bats are relative to other mammals, such findings suggest that managers pursue short-term solutions (e.g., community game guard programs, water-point protection near human settlements, and ecotourism) to indirectly promote bat conservation and that research includes megaherbivores' effects on biodiversity at other trophic levels.

Loss of density dependence underpins decoupling of livestock population and plant biomass in intensive grazing systems

Across the world, social-ecological rangeland systems have been transformed from a preindustrial extensive status to intensive exploitation, often leading to long-term livestock population booms, overgrazing, and rangeland degradation. To understand the regulatory mechanisms involved in such historical social-ecological transformations, we collected population data on the native sheep of the last nomadic county in the Inner Mongolia Autonomous Region (1961-2005). We detected changes in internal feedbacks (e.g., density-dependent effects) and external disturbance (e.g., winter harshness, rainfall, harvest) between the extensive and intensive management periods using regression models of sheep population growth rate and counterfactual analyses. We found that, in the extensive period, sheep populations were regulated during harsh winters by climate, while they were regulated during mild winters by negative density dependence. In the intensive period, the negative feedback of density dependence was removed through the provision of additional forage and shelter, and only winter climate and growing season rainfall regulated sheep populations. Counterfactual analyses also confirmed the irreplaceable role of density-dependence in maintaining a sustainable rangeland ecosystem. Although herders attempted to adapt to the removal of negative feedbacks by improving livestock harvest, overgrazing and grassland degradation remain a challenge in this system. We conclude that internal feedbacks within social-ecological systems should be carefully anticipated and accounted for when managing rangelands for sustainability.

Grazing Effects on Mongolian Steppe Vegetation—A Systematic Review of Local Literature

The Mongolian steppes with a long history of nomadic pastoralism cover a large area of the Palaearctic steppe biome and are still relatively intact. As livestock number has increased over the last two decades, grazing has been considered as the main reason of pasture degradation. However, the impact of grazing on vegetation dynamics, and its interaction with climate, is still not clear. We reviewed 44 publications in Mongolian language, covering 109 sites in five main steppe types, i.e., desert, dry, meadow, mountain, and high mountain steppe, with a mean annual precipitation and temperature range from 120 to 370 mm and from −6 to +5°C, respectively. We calculated relative changes in vegetation cover, species richness, and aboveground biomass from heavily grazed with respect to lightly/non-grazed conditions. Multiple linear regression models were used to test the impact of environmental factors, i.e., mean annual precipitation, coefficient of variation for precipitation, mean annual temperature and elevation. Grazing had a stronger effect on the vegetation of dry, desert and high mountain steppes, whereas its effect was less pronounced in the meadow and mountain steppes with mesic climate and high productivity. Vegetation cover, species richness and aboveground biomass were reduced by heavy grazing in the dry, desert and high mountain steppes. In the meadow steppes, grazing reduced vegetation cover, but increased richness and had nearly no effect on biomass. In the mountain steppe, richness and cover were not affected, but biomass was reduced by heavy grazing. Additionally, grazing effects on biomass tended to be more pronounced at sites with higher amounts of annual precipitation, and effects on cover changed from negative to positive as elevation increased. In conclusion, grazing effects in Mongolian steppes are overall negative in desert, dry and high mountain steppes, but no or even positive effects are found in meadow and mountain steppes. Especially, heavy grazing showed a detrimental effect on all vegetation variables in desert steppes, indicating the existence of combined pressure of climate and grazing in arid habitats, making them potentially sensitive to overgrazing and climate change. Grassland conservation and management should consider characteristics of different steppe types and give importance to local environmental conditions.

Alpha and beta diversity patterns of macro-moths reveal a breakpoint along a latitudinal gradient in Mongolia

Little is known about the diversity and distribution patterns of moths along latitudinal gradients. We studied macro-moths in Mongolia along an 860 km latitudinal climatic gradient to gain knowledge on community composition, alpha, beta, and gamma diversity as well as underlying factors, which can be used as baseline information for further studies related to climate change. We identified 236 species of moths of ten families. Our study shows that the diversity of moths increased with the latitude, i.e., low species richness in the south and higher richness in the north. Moth community composition changed along the gradient, and we revealed a breakpoint of beta diversity that divided grassland and desert communities. In the desert, beta diversity was driven by species loss (i.e., nestedness), and few tolerant species existed with high abundance. In contrast, in the grassland, beta diversity was driven by species replacement with more unique species, (i.e., species which occurred only in one site). We found the lowest species diversity in the transitional zones dominated by few generalist species such as Agrotis ripae and Anarta trifolii. Low precipitation and an increasing number of grazing goats are drivers of species loss. We suggest different conservation strategies regarding the contrasting patterns of beta diversity in desert and grassland.

Single Grazing Is More Detrimental to Grasslands Than Mixed Grazing: Evidence From the Response of Functional Traits of Dominant Plants to Grazing Systems

Plant functional traits reflect species ecological strategies and determine how plants respond to environmental changes, however, how dominant species in the Inner Mongolia grassland adapt to different grazing systems by changing their functional traits has not been systematically investigated. In this study, we established four 7-year grazing treatments in the Inner Mongolia grassland: cattle grazing, sheep grazing, mixed sheep and cattle grazing, and no grazing. Fourteen functional traits of three dominant species (Stipa grandis, Leymus chinensis, and Cleistogenes squarrosa) were measured under the different grazing treatments. We found convergences of plant functional traits that indicate herbivory avoidance or tolerance. Plants reduced their vegetative height (VH) and stem: leaf ratio (SLR) to avoid grazing; increased their ability to acquire resources by increasing their specific leaf area (SLA), leaf nitrogen concentration (LNC), and leaf phosphorus concentration (LPC); and reduced their leaf dry matter content (LDMC) to tolerate grazing. Moreover, plants may adapt to grazing by increasing the intraspecific variability of their functional traits. Sheep-only grazing adversely affected L. chinensis growth and survival, while cattle-only grazing hindered S. grandis growth and increased the intraspecific variability of its plant functional traits. Our study emphasizes that intraspecific variability is an important indicator of the responses of plant functional traits to grazing. Since single grazing is more detrimental to the functional traits of dominant plants, we suggest that mixed cattle and sheep grazing may be a more environmentally friendly and sustainable practice for the Inner Mongolia grassland than single grazing.

Effects of large herbivore grazing on relics of the presumed mammoth steppe in the extreme climate of NE-Siberia

The Siberian mammoth steppe ecosystem changed dramatically with the disappearance of large grazers in the Holocene. The concept of Pleistocene rewilding is based on the idea that large herbivore grazing significantly alters plant communities and can be employed to recreate lost ecosystems. On the other hand, modern rangeland ecology emphasizes the often overriding importance of harsh climates. We visited two rewilding projects and three rangeland regions, sampling a total of 210 vegetation relevés in steppe and surrounding vegetation (grasslands, shrublands and forests) along an extensive climatic gradient across Yakutia, Russia. We analyzed species composition, plant traits, diversity indices and vegetation productivity, using partial canonical correspondence and redundancy analysis. Macroclimate was most important for vegetation composition, and microclimate for the occurrence of extrazonal steppes. Macroclimate and soil conditions mainly determined productivity of vegetation. Bison grazing was responsible for small-scale changes in vegetation through trampling, wallowing and debarking, thus creating more open and disturbed plant communities, soil compaction and xerophytization. However, the magnitude of effects depended on density and type of grazers as well as on interactions with climate and site conditions. Effects of bison grazing were strongest in the continental climate of Central Yakutia, and steppes were generally less affected than meadows. We conclude that contemporary grazing overall has rather limited effects on vegetation in northeastern Siberia. Current rewilding practices are still far from recreating a mammoth steppe, although large herbivores like bison can create more open and drier vegetation and increase nutrient availability in particular in the more continental Central Yakutian Plain.

Contrasting effects of local environment and grazing pressure on the genetic diversity and structure of Artemisia frigida

Drylands count among the most globally extensive biomes, and while many desert and dry rangeland ecosystems are under threat, genetic structures of dryland species are still rarely studied. Artemisia frigida is one of the most widely distributed plant species in the temperate rangelands of Eurasia and North America, and it also dominates in many habitats of Mongolia due to its tolerance to low temperatures, drought and disturbance. Local environmental conditions and grazing pressure can influence species performance and affect spatial patterns of genetic diversity in contrasting ways, and our study set out to evaluate such effects on the genetic diversity and structure of A. frigida. We first developed new species-specific Simple Sequence Repeats (SSRs) markers using whole genome sequencing. We then analysed 11 populations of A. frigida that had been sampled along a large climatic gradient in Mongolia, which were sub-structured according to three levels of grazing intensity. Estimates of genetic diversity at the population level were high (HO = 0.56, HE = 0.73) and tended to increase with higher precipitation and soil nutrient availability. Grazing had no effect on genetic diversity, however, a high number of grazing-specific indicator alleles was found at grazed sites. Genetic differentiation among populations was extremely low (global GST = 0.034). Analysis of Molecular Variance revealed 5% variance between populations along the climatic gradient, with 3% of the variance being partitioned among different grazing intensity levels. We found no relationship between geographic and genetic distances, and thus no isolation by distance in this widely distributed species. The relatively low genetic structuring suggests that considerable gene flow exists among A. frigida populations across the rangelands of Mongolia, in spite of the pervasive grazing in the region.

Grazing Into the Anthropocene or Back to the Future?

This essay examines three central components of extensive livestock production—herd composition, grazing/pasture management, and rangeland tenure. In all of these areas, fenced, and open-range forms of migratory pastoralism face a number of shared problems. Set aside the presumption that either one of these systems is technically or institutionally more advanced than the other, and it turns out that each has lessons for the other. 1. For a variety of reasons, including climate change, we can look forward to a future world with less grass, which presents a challenge for livestock producers reliant on grass feeding livestock. With little delay and minimal scientific support, East African pastoralists are already adjusting to a new woody world by diversifying the species composition of their herds to include more browsers—camels and goats. There is a potential lesson here for commercial ranchers who have traded the stability of mixed herds for the profitability of keeping sheep or cattle alone. 2. Migratory rangeland systems distribute livestock very differently than fenced, rotational systems of livestock, and pasture management. Whereas, migratory herds exploit environmental heterogeneity, fenced ranching attempts to suppress it. Emerging archaeological evidence is demonstrating that pastoralists have amplified rangeland heterogeneity for millennia; ecological research shows that this heterogeneity sustains both plant and wildlife biodiversity at the landscape scale; and new approaches to ranch management are appropriating aspects of migratory herding for use on fenced ranches. A rapprochement between the environmental sciences, ranching, and open-range migratory pastoralism has occurred and merits wider policy recognition. 3. In contemporary Africa, indigenous tenure regimes that sustain open rangelands are eroding under pressure from market penetration and state encapsulation. At the same time in the American West, there are emerging novel land tenure instruments that replicate some of the most important functional characteristics of tenure arrangements in pastoral Africa. After many false starts, it appears that some aspects of American ranching do provide an appropriate model for the preservation of the open-range migratory systems that they were once supposed to supplant. “Development” policy needs to reflect upon this inversion of roles and its implications for accommodating diversity.

Precipitation extremes in recent decades impact cattle populations at the global and national scales

Cattle populations are one of the most important global ecological drivers. The global cattle population tripled during the past century, leading to large impacts on nutrient cycling, greenhouse gas emissions and biodiversity loss. Nonetheless, their populations have not increased uniformly through the last seven decades (1961-2018), with large unexplained variation between years. We hypothesized a main driver for such fluctuation was climate variability and thus examined global and national level relationships between cattle population growth and precipitation anomalies for the period 1961-2017. We showed that the variation in the global cattle population growth rate was related to precipitation anomalies following a distinctive parabolic relationship, where extreme wetness or dryness decreased population growth. When the analysis was downscaled to the national level, we found the strength of such relationship to be determined by the background climate and management intensity. Countries in drier climates and with less intensive cattle management showed the largest susceptibility to extreme annual precipitation. We propose a general model to explain the relationship between precipitation extremes and cattle populations at multiple scales, based on ecological processes applicable to grazing systems.

Temporal patterns in ecosystem services research: A review and three recommendations

Temporal aspects of ecosystem services have gained surprisingly little attention given that ecosystem service flows are not static but change over time. We present the first systematic review to describe and establish how studies have assessed temporal patterns in supply and demand of ecosystem services. 295 studies, 2% of all studies engaging with the ecosystem service concept, considered changes in ecosystem services over time. Changes were mainly characterised as monotonic and linear (81%), rather than non-linear or through system shocks. Further, a lack of focus of changing ecosystem service demand (rather than supply) hampers our understanding of the temporal patterns of ecosystem services provision and use. Future studies on changes in ecosystem services over time should (1) more explicitly study temporal patterns, (2) analyse trade-offs and synergies between services over time, and (3) integrate changes in supply and demand and involve and empower stakeholders in temporal ecosystem services research.

The benefit and strategy of spring movements in Mongolian gazelles

Animal movement is predicted to be nomadic in areas with low temporal predictability of environmental conditions, but it remains unclear whether the costs of nomadic movement outweigh the benefits received. To examine the spring movement strategy of Mongolian gazelles (Procapra gutturosa) in Mongolia, where predictability of vegetation conditions is relatively low, we identified the type of each movement, evaluated the preferred vegetation conditions for gazelles, and quantified the benefit achieved through each spring movement. The surveyed gazelles continuously preferred areas with intermediate normalized difference vegetation index (NDVI) values from May to July, and spatial and temporal shifts of the distribution of preferred areas explain the long-distance movements of many gazelles in spring. Three movement types, sedentary, linear, and nomadic movement, were identified. The period when benefit varied most greatly among individuals differed between the linear and nomadic movement types. During the spring movement period, the variance of benefit was larger for the nomadic movement type, whereas during the summer it was larger for the linear movement type, suggesting the existence of different movement strategies in the Mongolian gazelle. Linear long-distance movements over a short period in the linear movement type suggest the so-called jumper strategy, whereas other movement patterns might represent the searcher strategy. Benefit loss through movements of individuals in both strategies indicate low interannual predictability of vegetation conditions in the study area, and it would explain the co-existence of multiple movement types or strategies used by Mongolian gazelles in spring.

The Future of Semi-Arid Regions: A Weak Fabric Unravels

The regions of the world where average precipitation is between one fifth and half of the potential plant water demand are termed ‘semi-arid’. They make up 15.2% of the global land surface, and the approximately 1.1 billion people who live there are among the world’s poorest. The inter-annual variability of rainfall in semi-arid regions is exceptionally high, due to intrinsic features of the global atmospheric circulation. The observed and projected climate trends for most semi-arid regions indicate warming at rates above the global mean rate over land, increasing evaporative demand, and reduced and more variable rainfall. Historically, the ecosystems and people coped with the challenges of semi-arid climates using a range of strategies that are now less viable. Semi-arid ecosystems are by definition water limited, generally only suitable for extensive pastoralism and opportunistic cropping, unless irrigation supplementation is available. The characteristics of dryland plant production in semi-arid ecosystems, as they interact with climate change and human systems, provide a conceptual framework for why land degradation is so conspicuous in semi-arid regions. The coupled social-ecological failures are contagious, both within the landscape and at regional and global scales. Thus, semi-arid lands are a likely flashpoint for Earth system changes in the 21st century.

Critical transitions in rainfall manipulation experiments on grasslands

As a result of climate and land-use changes, grasslands have been subjected to intensifying drought regimes. Extreme droughts could interfere in the positive feedbacks between grasses and soil water content, pushing grasslands across critical thresholds of productivity and leading them to collapse. If this happens, systems may show hysteresis and costly management interventions might be necessary to restore predrought productivity. Thus, neglecting critical transitions may lead to mismanagement of grasslands and to irreversible loss of ecosystem services. Rainfall manipulation experiments constitute a powerful approach to investigate the risk of such critical transitions. However, experiments performed to date have rarely applied extreme droughts and have used resilience indices that disregard the existence of hysteresis. Here, we suggest how to incorporate critical transitions when designing rainfall manipulation experiments on grasslands and when measuring their resilience to drought. The ideas presented here have the potential to trigger a perspective shift among experimental researchers, into a new state where the existence of critical transitions will be discussed, experimentally tested, and largely considered when assessing and managing vegetation resilience to global changes.

Exploring the economic, social and environmental prospects for commercial natural annual grasslands by performing a sensitivity analysis on a multidisciplinary integrated model

This paper presents an integrated modelling study aimed at exploring the possible effects of drivers of change in commercial natural annual grasslands. We consider drivers as factors that affect the rangeland but are not affected by it. Thus, the stocking rate is not treated as a driver, but as an endogenous factor ultimately determined by drivers. This approach, which call for integrated multidisciplinary studies, is rare in the rangeland literature. We try to alleviate this lack by presenting and utilizing a novel multidisciplinary integrated system-dynamics model (108 equations) which represents an area of privately owned extensive farms, its farmers (their numbers and decisions), herds or flocks, herbage production, soil erosion and the linked local markets. By means of a global sensitivity analysis of this model we evaluated the sensitivities of key endogenous factors to the same percentage variation in 70 factors, including economic and climate drivers. The analysis considered the behaviours of 288,000 variants of the modelled system, each under a different 300-year driver scenario. We found that the environmental component of the model was almost exclusively sensitive to biophysical factors, whereas the socio-economic component was almost exclusively sensitive to socio-economic factors, despite the model takes account of key feedbacks connecting both components. Our results suggest that cautiously-managed commercial natural grasslands could socially and economically cope with climate change, especially in a scenario of rising prices of animal products, and also that, even though stocking rates would increase due to an increase in the demand for livestock products, the main threat to the provision of ecosystem services in the studied system would be climate change.

Global ecosystem thresholds driven by aridity

Aridity, which is increasing worldwide because of climate change, affects the structure and functioning of dryland ecosystems. Whether aridification leads to gradual (versus abrupt) and systemic (versus specific) ecosystem changes is largely unknown. We investigated how 20 structural and functional ecosystem attributes respond to aridity in global drylands. Aridification led to systemic and abrupt changes in multiple ecosystem attributes. These changes occurred sequentially in three phases characterized by abrupt decays in plant productivity, soil fertility, and plant cover and richness at aridity values of 0.54, 0.7, and 0.8, respectively. More than 20% of the terrestrial surface will cross one or several of these thresholds by 2100, which calls for immediate actions to minimize the negative impacts of aridification on essential ecosystem services for the more than 2 billion people living in drylands.

Refining China’s grassland policies: an interdisciplinary and ex-ante analysis

China is about to embark on a new round of grassland policies as part of its 14th Five-Year-Plan. Although current grassland policies have generally been perceived positively in arresting widespread grassland degradation, concerns have arisen that the current policies may not be effective in achieving the desired reduction in livestock numbers. Furthermore, there are concerns the incentive-based payments that are part of these policy programs may not reflect herder opportunity costs or the marginal environmental benefits of the program, with associated issues of herder satisfaction and compliance. Changes to current policy settings are being considered in response to these concerns. This paper reports on an interdisciplinary and ex-ante analysis of alternative policy settings affecting grazing and livestock management in terms of their environmental impacts, net social benefits and other impacts. The analysis finds that a bundle of instruments involving both positive and negative herder incentives is needed if desired stocking rates are to be achieved. The impact on herder incomes, both positive and negative depending on the grassland biome, along with transaction costs of implementing the policies, have the most influence on net social benefits.

Grazing effects on intraspecific trait variability vary with changing precipitation patterns in Mongolian rangelands

Functional traits are proxies for plant physiology and performance, which do not only differ between species but also within species. In this work, we hypothesized that (a) with increasing precipitation, the percentage of focal species which significantly respond to changes in grazing intensity increases, while under dry conditions, climate-induced stress is so high that plant species hardly respond to any changes in grazing intensity and that (b) the magnitude with which species change their trait values in response to grazing, reflected by coefficients of variation (CVs), increases with increasing precipitation. Chosen plant traits were canopy height, plant width, specific leaf area (SLA), chlorophyll fluorescence, performance index, stomatal pore area index (SPI), and individual aboveground biomass of 15 species along a precipitation gradient with different grazing intensities in Mongolian rangelands. We used linear models for each trait to assess whether the percentage of species that respond to grazing changes along the precipitation gradient. To test the second hypothesis, we assessed the magnitude of intraspecific trait variability (ITV) response to grazing, per species, trait, and precipitation level by calculating CVs across the different grazing intensities. ITV was most prominent for SLA and SPI under highest precipitation, confirming our first hypothesis. Accordingly, CVs of canopy height, SPI, and SLA increased with increasing precipitation, partly confirming our second hypothesis. CVs of the species over all traits increased with increasing precipitation only for three species. This study shows that it remains challenging to predict how plant performance will shift under changing environmental conditions based on their traits alone. In this context, the implications for the use of community-weighted mean trait values are discussed, as not only species abundances change in response to changing environmental conditions, but also values of traits considerably change. Including this aspect in further studies will improve our understanding of processes acting within and among communities.

Rare plant species do not occupy water-remote refuges in arid environments subject to livestock grazing

In many of the world's arid regions there has been a dramatic increase in grazing pressure with herds of livestock sustained by the provision of artificial water points. In these systems it has been suggested that grazing-sensitive plant species will have contracted to refuges distant from water points where grazing impacts are low. This association was tested using a large data set of presence/absence records for rare plant species throughout the northeastern Australian arid zone. The presence records of only one of 45 species were statistically associated with lower grazing activity, as a function of distance-to-water, than the absence records. The field observation that this species is rarely grazed suggests it is not susceptible to grazing pressure. In general, the study supports assertions that populations of short-lived plants in drylands are resilient in the face of exaggerated livestock grazing because herbivores are not in sufficient densities to have an impact during the sporadic periods of high rainfall when plants can complete their life cycles. However, long-lived palatable species may be extinction-prone in grazed landscapes over long time frames if recruitment is curtailed by grazing.

Opportunities to integrate herders' indicators into formal rangeland monitoring: an example from Mongolia

Despite increasing calls for knowledge integration around the world, traditional knowledge is rarely used in formal, Western-science-based monitoring and resource management. To better understand indicators herders use and their relationship to researcher-measured indicators, we conducted in-depth field interviews with 26 herders in three ecological zones of Mongolia. We asked each herder to (1) assess the overall condition of three different sites located along a livestock-use gradient from their winter camp using a numeric scale, (2) describe the indicators they used in their assessment, and (3) explain what caused their pastures to remain healthy or become degraded. At each site, we collected field data on vegetation variables and compared these with herders' ratings and indicators using linear regression. We used classification and ordination to understand how herders' assessment scores related to plant community composition, and determine how well multivariate analysis of factors determining plant community composition aligned with herders' observations of factors causing rangeland change. Across all ecological zones, herders use indicators similar to those used in formal monitoring. Herders' assessment scores correlated significantly and positively with measured total foliar cover in all three ecological zones, and with additional measured variables in the steppe and desert steppe. Ordination revealed that herder assessment scores were correlated with the primary ordination axis in each zone, and the main factors driving plant community composition in each zone were the same as those identified by herders as the primary causes of rangeland change in that zone. These results show promise for developing integrated indicators and monitoring protocols and highlight the importance of developing a common language of monitoring terminology shared by herders, government monitoring agencies, and researchers. We propose a new model for integrating herder knowledge and participation into formal monitoring in Mongolia, with implications for rangelands and pastoral people globally. We suggest practical ways of involving herders in formal monitoring that have potential broad application for promoting local and indigenous people's participation in implementing international agreements such as the UN Convention to Combat Desertification and the UN Convention on Biological Diversity, both of which call for involvement of local people and indigenous/traditional knowledges.

Degraded or Just Dusty? Examining Ecological Change in Arid Lands

The ecological history of rangelands is often presented as a tale of devastation, where fragile drylands are irreversibly degraded through inappropriate land use. However, there is confusion about how to recognize and measure degradation, especially in low-productivity environments characterized by extreme natural variability and where abrupt and comprehensive management upheavals preclude benchmarks. These issues have important consequences for rangeland management programs, which are typically founded on presumptions of substantial and ongoing degradation from former “natural” states. We explore complementary approaches to critically assess degradation: the historical record, long-term grazing exclosures, surveys for potentially rare and sensitive plant species, and assessment of water-remote areas in relation to rare plant occurrence. Employing these approaches in inland Australia, we show that prevailing paradigms have become entrenched despite being inconsistent with empirical evidence. Our methodology can be applied to drylands with abrupt changes in management and contentious ecological narratives.

The Kobresia pygmaea ecosystem of the Tibetan highlands - Origin, functioning and degradation of the world's largest pastoral alpine ecosystem: Kobresia pastures of Tibet

With 450,000 km²Kobresia (syn. Carex) pygmaea dominated pastures in the eastern Tibetan highlands are the world's largest pastoral alpine ecosystem forming a durable turf cover at 3000-6000 m a.s.l. Kobresia's resilience and competitiveness is based on dwarf habit, predominantly below-ground allocation of photo assimilates, mixture of seed production and clonal growth, and high genetic diversity. Kobresia growth is co-limited by livestock-mediated nutrient withdrawal and, in the drier parts of the plateau, low rainfall during the short and cold growing season. Overstocking has caused pasture degradation and soil deterioration over most parts of the Tibetan highlands and is the basis for this man-made ecosystem. Natural autocyclic processes of turf destruction and soil erosion are initiated through polygonal turf cover cracking, and accelerated by soil-dwelling endemic small mammals in the absence of predators. The major consequences of vegetation cover deterioration include the release of large amounts of C, earlier diurnal formation of clouds, and decreased surface temperatures. These effects decrease the recovery potential of Kobresia pastures and make them more vulnerable to anthropogenic pressure and climate change. Traditional migratory rangeland management was sustainable over millennia, and possibly still offers the best strategy to conserve and possibly increase C stocks in the Kobresia turf.

Modelling interacting plant and livestock renewal dynamics helps disentangle equilibrium and nonequilibrium aspects in a Mongolian pastoral system

The interplay of livestock density dependence drivers and climate hazards is thought to cause pasture deterioration and poverty in Mongolian pastoral systems. We assessed their relative weights in a system of the Gobi exposed to high rainfall variability and harsh winters, which suggests that climate is the main system's driver. In this aim we modelled how interacting plant and livestock renewal dynamics impact herder performances, under the influence of climate. Plant dynamics was studied through an underground biomass sub-model because local pastures are dominated by perennial species. This approach enabled us studying pastoral issues in a holistic way, by integrating plant underground organs, livestock populations, herder income, and climate drivers. Models described that current grazing practices can significantly reduce underground biomass (-30% after 20years), but not entirely deplete it. They also showed that competition between herders could trap the smallest ones in poverty, by preventing the growth of their herds. This competition operates through density dependent factors affecting livestock productivity and vulnerability to climate shocks. This competition effect is all the more important since small herders could grow their herd and escape poverty if they were alone in the system. This result shows that density dependent factors could significantly impact herder performances and suggests that forage resource allocation is a driver as powerful as climate, even in the local harsh bioclimatic configuration of the Mongolian Gobi.

Applying a dryland degradation framework for rangelands: the case of Mongolia

Livestock-caused rangeland degradation remains a major policy concern globally and the subject of widespread scientific study. This concern persists in part because it is difficult to isolate the effects of livestock from climate and other factors that influence ecosystem conditions. Further, degradation studies seldom use multiple plant and soil indicators linked to a clear definition of and ecologically grounded framework for degradation assessment that distinguishes different levels of degradation. Here, we integrate two globally applicable rangeland degradation frameworks and apply them to a broad-scale empirical data set for the country of Mongolia. We compare our assessment results with two other recent national rangeland degradation assessments in Mongolia to gauge consistency of findings across assessments and evaluate the utility of our framework. We measured livestock-use impacts across Mongolia's major ecological zones: mountain and forest steppe, eastern steppe, steppe, and desert steppe. At 143 sites in 36 counties, we measured livestock-use and degradation indicators at increasing distances from livestock corrals in winter-grazed pastures. At each site, we measured multiple indicators linked to our degradation framework, including plant cover, standing biomass, palatability, species richness, forage quality, vegetation gaps, and soil surface characteristics. Livestock use had no effect on soils, plant species richness, or standing crop biomass in any ecological zone, but subtly affected plant cover and palatable plant abundance. Livestock effects were strongest in the steppe zone, moderate in the desert steppe, and limited in the mountain/forest and eastern steppes. Our results aligned closely with those of two other recent country-wide assessments, suggesting that our framework may have widespread application. All three assessments found that very severe and irreversible degradation is rare in Mongolia (1-18% of land area), with most rangelands slightly (33-53%) or moderately (25-40%) degraded. We conclude that very severe livestock-induced rangeland degradation is overstated in Mongolia. However, targeted rangeland restoration coupled with monitoring, adaptive management and stronger rangeland governance are needed to prevent further degradation where heavy grazing could cause irreversible change. Given the broad applicability of our degradation framework for Mongolia, we suggest it be tested for application in other temperate grasslands throughout Central Asia and North America.

Patterns of herders’ adaptation to changes in social–ecological systems across northern China’s grasslands over the past three decades

Understanding the changes in herders’ adaptation to environmental change can provide insight into humans’ adaptive mechanisms to different social–ecological systems, and is also important for the optimal management of grasslands. However, the existing and emerging patterns of herders’ adaptation to changes in social–ecological systems across different types of grasslands are poorly understood. This paper presents a systematic participatory investigation that was conducted to comprehensively understand herders’ adaptation in this context over the past three decades. Three counties in Inner Mongolia grasslands were selected as the case study sites, located in meadow steppe, typical steppe and desert steppe respectively. Our results indicate that herders’ perceptions partly fit with the reality of the actual changes. The majority of herders attributed their pasture’s quality degradation to reduced precipitation rather than overgrazing, a contradictory perception to previous scientific observations (overgrazing > climate change). Moreover, herders’ behaviour in relation to herbage storage and livestock structure had dramatically changed in terms of spatial and temporal patterns in Inner Mongolia, which benefited herders in production efficiency. Lambing time of sheep and goats occurred earlier than it did several decades ago across the three grassland types. This was attributed to a rise in temperature, increasing marketisation and developing infrastructure. In addition, there became evident a transformation in the animal husbandry production cycle from a two-year to one-year cycle. Our results highlighted that the transformation of herders’ behavioural strategies resulted from variations in spatial and temporal patterns of climate change, pasture degradation, new policies and marketisation in pastoral areas. These strategies can be seen as key mechanisms in long-term adaptation to changes in social–ecological systems, which benefit herders’ efficiency in grassland management.

Short-Term Effects of Changing Precipitation Patterns on Shrub-Steppe Grasslands: Seasonal Watering Is More Important than Frequency of Watering Events

Climate change is expected to alter precipitation patterns. Droughts may become longer and more frequent, and the timing and intensity of precipitation may change. We tested how shifting precipitation patterns, both seasonally and by frequency of events, affects soil nitrogen availability, plant biomass and diversity in a shrub-steppe temperate grassland along a natural productivity gradient in Lac du Bois Grasslands Protected Area near Kamloops, British Columbia, Canada. We manipulated seasonal watering patterns by either exclusively watering in the spring or the fall. To simulate spring precipitation we restricted precipitation inputs in the fall, then added 50% more water than the long term average in the spring, and vice-versa for the fall precipitation treatment. Overall, the amount of precipitation remained roughly the same. We manipulated the frequency of rainfall events by either applying water weekly (frequent) or monthly (intensive). After 2 years, changes in the seasonality of watering had greater effects on plant biomass and diversity than changes in the frequency of watering. Fall watering reduced biomass and increased species diversity, while spring watering had little effect. The reduction in biomass in fall watered treatments was due to a decline in grasses, but not forbs. Plant available N, measured by Plant Root Simulator (PRS)-probes, increased from spring to summer to fall, and was higher in fall watered treatments compared to spring watered treatments when measured in the fall. The only effect observed due to frequency of watering events was greater extractable soil N in monthly applied treatments compared to weekly watering treatments. Understanding the effects of changing precipitation patterns on grasslands will allow improved grassland conservation and management in the face of global climatic change, and here we show that if precipitation is more abundant in the fall, compared to the spring, grassland primary productivity will likely be negatively affected.

A protocol to correct for intra- and interspecific variation in tail hair growth to align isotope signatures of segmentally cut tail hair to a common time line

RATIONALE

In recent years, segmental stable isotope analysis of hair has been a focus of research in animal dietary ecology and migration. To correctly assign tail hair segments to seasons or even Julian dates, information on tail hair growth rates is a key parameter, but is lacking for most species.

METHODS

We (a) reviewed the literature on tail hair growth rates in mammals; b) made own measurements of three captive equid species; (c) measured δ(2)H, δ(13)C and δ(15)N values in sequentially cut tail hairs of three sympatric, free-ranging equids from the Mongolian Gobi, using isotope ratio mass spectrometry (IRMS); and (d) collected environmental background data on seasonal variation by measuring δ(2)H values in precipitation by IRMS and by compiling pasture productivity measured by remote sensing via the normalized difference vegetation index (NDVI).

RESULTS

Tail hair growth rates showed significant inter- and intra-specific variation making temporal alignment problematic. In the Mongolian Gobi, high seasonal variation of δ(2)H values in precipitation results in winter lows and summer highs of δ(2)H values of available water sources. In water-dependent equids, this seasonality is reflected in the isotope signatures of sequentially cut tails hairs.

CONCLUSIONS

In regions which are subject to strong seasonal patterns we suggest identifying key isotopes which show strong seasonal variation in the environment and can be expected to be reflected in the animal tissue. The known interval between the maxima and minima of these isotope values can then be used to correctly temporally align the segmental stable isotope signature for each individual animal.

Ephemeral plant indicators of livestock grazing in arid rangelands during wet conditions

Vegetation communities in arid rangeland systems are typically dominated by short-lived, ephemeral (annual) plants during periods of high rainfall. These conditions present a rare opportunity to examine herbivore–plant interactions and identify potential indicators of grazing intensity. The influence of cattle grazing on vegetation communities of arid cracking-clay gibber-gilgai systems in Australian rangelands was investigated during La Niña (wet) conditions, including 2010, which was the wettest year on record in the region. Seasonal annual plant diversity was assessed at three grazed and three less-grazed sites. Individual annual species’ responses to grazing intensity were examined among grazed and less-grazed sites (i.e. increasing or decreasing response). Additionally, rare (found at one site only) and restricted (found at grazed or less-grazed sites only) annual and perennial species were identified to elucidate their status as indicators. Prevailing La Niña conditions allowed the study of little-known, short-lived species, which constituted the bulk of species richness. Differences in grazing intensity were more clearly ascertained from examining individual species than plant diversity. Of 31 annual/short-lived species, 21 responded to grazing intensity. Although most species responded to grazing (n = 7 increasers and n = 14 decreasers), these responses did not necessarily reflect published accounts of their so-called palatability. Thirty other species were restricted to certain site types (grazed or less-grazed) and 20 were rare. The indicator species concept should be applied at appropriate scales, and more detailed information is needed on stock preferences for these ephemeral plants in these rangeland systems. Elucidating the effect of grazing on individual plant species’ phenology, and identifying indicators, is important for developing efficacious land management practices.

Space and habitat use by wild Bactrian camels in the Transaltai Gobi of southern Mongolia

Wild Bactrian camels (Camela ferus) are listed as Critically Endangered by the International Union for Conservation of Nature (IUCN) and only persist in some of the most remote locations in northern China and southern Mongolia. Although the species has been recognized as an umbrella species for the fragile central Asian desert ecosystem and has been high on the conservation agenda, little is known about the species' habitat requirements, with most information coming from anecdotal sightings and descriptive studies. We compiled the only available telemetry data from wild camels worldwide. Seven wild camels, which were followed for 11-378 monitoring days, covered a total range of 28,410 km², with individual annual ranges being >12,000 km² for three animals followed over a year. Camels reacted strongly to capture events, moving up to 64 km from the capture site within a day, whereas normal average daily straight line distances were 3.0-6.4 km/day. Camels showed a preference for intermediate productivity values (NDVI, habitat type) and landscape parameters (distance to water, elevation) and an avoidance of steep slopes. Our telemetry results suggest that wild camels still range throughout the entire Great Gobi A Strictly Protected Area (SPA), are highly mobile, and very sensitive to human disturbance. Their habitat preference may be a trade-off between dietary and safety requirements. Small sample size did not allow the development of a full habitat model testing all variables simultaneously and we urgently call for more data from additional wild camels as a foundation for evidence driven conservation actions.