Intermediate disturbance on rangelands : Management applicability of the intermediate disturbance hypothesis across Mongolian rangeland ecosystems

The current growing body of evidence for diversity-disturbance relationships suggests that the peaked pattern predicted by the intermediate disturbance hypothesis (IDH) may not be the rule. Even if ecologists could quantify the diversity-disturbance relationship consistent with the IDH, the applicability of the IDH to land management has rarely been addressed. We examined two hypotheses related to the generality and management applicability of the IDH to Mongolian rangeland ecosystems: that the diversity-disturbance relationship varies as a function of landscape condition and that some intermediate scales of grazing can play an important role in terms of sustainable rangeland management through a grazing gradient approach. We quantified the landscape condition of each ecological site using an ordination technique and determined two types of landscape conditions, relatively benign and harsh environmental conditions. At the ecological sites characterized by relatively benign environmental conditions, diversity-disturbance relationships were generally consistent with the IDH and maximum diversity was observed at some intermediate distance from the source of the grazing gradient. In contrast, the IDH was not supported at most but not all sites characterized by relatively harsh environmental conditions. The intermediate levels of grazing were generally located below the ecological threshold representing the points or zones at which disturbance should be limited to prevent drastic changes in ecological conditions, suggesting that there is little “conundrum” with regard to intermediate disturbance in the studied systems in terms of land management. We suggest that the landscape condition is one of the primary factors that cause inconsistencies in diversity-disturbance relationships. The ecological threshold can extend its utility in rangeland management because it also has the compatibility with the maintenance of species diversity. This study thus suggests that some intermediate scales of grazing and ecological thresholds are mutually supportive tools for sustainable management of Mongolian rangelands

The Linkage Between Pastoralists\u27 Perspectives and Vegetation Threshold Changes in Mongolian Rangelands (Advanced Studies on Sustainable Animal Production: Interrelationships among Human, Animal and Environment, 8th International Symposium of Integrated Field Science)

Poster Sessio

Resource Variations across the Landscape Mediate the Impact of Grazing on Vegetation in Mongolian Rangeland under High Climatic Variability

Assessment of grazing-induced degradation of arid and semi-arid rangelands with stochastic rainfall regimes is challenging. For the last two decades, rangeland ecologists have been discussing the relative importance of biotic and abiotic factors in controlling vegetation dynamics. According to the non-equilibrium concept, which emerged as a new paradigm to describe ecosystems in highly variable and poorly predictable environments, vegetation dynamics are driven primarily by abiotic factors such as rainfall, rather than by internal biotic regulation (e.g. grazing impact). Although a number of studies have emphasized the non-equilibrium nature of most rangelands, they have produced inconsistent results and there is still no consensus on the relative importance of grazing impact. Alternatively, recent studies have suggested that a continuum of systems exists, rather than a stark dichotomy between equilibrium and non-equilibrium rangelands. Moreover, theoretical studies have predicted that, in addition to climatic variability, resource variations occurring in space and time as a result of landscape heterogeneity should be taken into account in assessments of grazing impact. However, there have been few empirical studies of the role of resource variations in either mitigating or enhancing the impacts of grazing on vegetation. This study explores the impact of grazing strategies on vegetation in Mongolian rangelands under high climatic variability. Specifically, it is focused on key resource areas, defined in terms of the key factor determining livestock population, and thus the ability to forage during drought. Based on the prediction proposed by Illius and O’Connor (1999) that animal numbers are regulated in a density-dependent manner by the limited forage availability in key resource areas, we established and examined the hypothesis that grazing impacts would be greater in key resource areas than in other areas even in Mongolian rangelands

Environmental Factors Controlling Leaf Emergence in Caragana microphylla, a Deciduous Shrub of the Mongolian Steppe

Abstract: We examined the effect of temperature and rainfall on the timing of leaf emergence in Caragana microphylla, a representative deciduous shrub found in the Mongolian steppe over a three-year period. Two peaks of leaf emergence were identified, the first of which appeared to be induced by temperature, while the second was controlled by rainfall

An intrinsic mechanism for the co-existence of different survival strategies within mobile pastoralist communities

In mobile pastoralism, strategies of mobility are highly heterogeneous within communities; some herders are frequently mobile and others are not. Moreover, pastoral mobility changes over time, especially after external intervention. Although changes in the strategies of herders affect and are affected by other herders, the interactions between herders with different strategies and the effect of changes in the external environment on their strategies have not been explicitly studied. We examined such interactions with a multi-agent model, simulating the herders' basic decision-making process, simplified rangeland ecosystem, and animal survival. The results showed clear co-existence of wealthy and poor herders at an intermediate cost of moving. The movement pattern revealed that an indirect interaction between wealthy and poor herders was the key to their co-existence, suggesting that very simple rules of pastoral mobility inherently contain a mechanism for the co-existence of wealthy and poor herders. At an intermediate cost of moving, the two groups have access to different pastures, thus reducing direct competition for poor herders and enabling their survival in drought years. Such interaction between herders suggests that any interventions in mobile pastoralist societies should take into account that impacts on the mobility of any one group can influence the entire social structure.Mobile pastoralism Mobility Herders' strategy Multi-agent model Mongolia Co-existence mechanism

Threshold Distinctions Between Equilibrium and Nonequilibrium Pastoral Systems Along a Continuous Climatic Gradient

In equilibrium environments where rainfall is relatively stable, grazing animal-vegetation dynamics are density-dependent; it is therefore appropriate to calculate carrying capacities and use them to define sustainable animal populations. In contrast, nonequilibrium environments are characterized by fluctuations in characteristics such as rainfall, resulting in fluctuations in plant biomass and in the corresponding carrying capacity. Herders adapt to such environments by moving opportunistically to pastures with better conditions. Studies since the 1990s have significantly improved our understanding of the continuity and integration of equilibrium and nonequilibrium systems. However, it remains unclear how and where such continuous, integrated rangeland systems result in qualitatively different land use patterns by local herders along a climatic gradient. Here, we developed a simple model that uses key environmental factors to predict a threshold representing the boundary between equilibrium and nonequilibrium land use systems, and we used an area of Mongolian rangeland as an example. We found a threshold in the proportion of usable pasture that corresponded to a specific range of rainfall values. Comparison of our results with previous ones supported our hypothesis about this threshold. The threshold behavior suggested that it is important to identify and monitor the boundary between equilibrium and nonequilibrium land use systems so that managers can respond to climatic change. National governments and aid agencies must understand the threshold process before they can identify focal areas where management regime change is required and propose appropriate policies that will support herders in the long term. Our study provides a simple, low-cost tool to evaluate ecosystems in this context. The Rangeland Ecology & Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202

Model Study on DesertiAcation Process varyingwith different geographical conditions

本研究では,モンゴル国で見られた立地特性により異なる砂漠化プロセスを例に取り,生態系モデルと風食モデルをカップリングさせることで,立地条件の違いによる成立植生の差異を,過放牧に対する応答の差異も含めて単一のモデルで再現することを試みた｡その結果,土性の違いが風食等の差異を生み,質的に明確に異なる砂漠化プロセスを再現することができた｡植生機能タイプによる裾の鉛直分布の差異の除去,もしくは風食の影響の除去をした状態でのシミュレーションを行ったところ,現象は再現できず,両要因が今回行った例を再現するのに不可欠であることがわかった｡In this study the simulation of the establishment of different vegetation types as well as different responses to grazing pressure was conducted, using a single model which coupled the ecosystem model and wind erosion model, and by using the results of a field survey in Mongolia as an example. It was successfully simulated that the difference in soil texture led to different physical characteristics such as wind erosion intensities, By testing the simulation condition without the difference of root distribution with plant functional types, and without wind erosion impact, the example could not be simulated. Thus it was found that both factors are essential for the simulation