123 research outputs found
Land Ecology Essay II: Thresholds, Novel Ecosystems, and the Sanctity of History
No full textDr. Brandon Bestelmeyer is a research ecologist with the USDA Agricultural Research Service’s Jornada Experimental Range and the Jornada Basin LTER at New Mexico State University in Las Cruces, New Mexico. He regularly writes about rangeland issues on the Land Ecology blog. To read more of Brandon’s essays, visit http://landecology.org/. “Land ecology” honors the holistic approach to the knowledge needed to support land stewardship into our increasingly uncertain future. Here we share an expanded version of one of Brandon’s recent essays
Sustainability through culture and innovation: Three perspectives from the 75th annual meeting of the Society for Range Management
No full textThe Rangelands archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information
Degradation influences equilibrium and non-equilibrium dynamics in rangelands: implications in resilience and stability
No full textQuestion: Plant communities are structured by both equilibrium and non-equilibrium dynamics, which interact at different spatiotemporal scales. The influence of external factors on internal regulation processes might depend on ecological state, and thus,
on system resilience. We asked if well-conserved (reference) states have higher resilience
to external factors than degraded states, considering the greater capacity for self-regulation expected of reference states. Location: Graminous–subshrubby steppes of northern Patagonia, Argentina.
Methods: During four years, we assessed the influence of an external factor (rainfall variability) on internal regulation processes (seedling recruitment, growth of main perennial species, and three resilience proxies) in two alternative states (one reference
and another degraded) of graminous–subshrubby steppes of northern Patagonia (Argentina). Specifically, we assessed the response of alternative states to simulated high rainfall events (irrigation).
Results: The degraded state was more sensitive to rainfall variability than the reference state. Specifically, in the degraded state the density of surviving seedlings, the growth of shrubs and Papostipa speciosa’s relative tiller production and cover increased
in response to irrigation; whereas seedling emergence and survival, and grass growth were low or even null without irrigation. Finally, resistance and elasticity were lower whereas malleability was greater in degraded than in reference states.
Conclusions: The degraded state was less resilient (low resistance and elasticity; high malleability) to stochastic weather events (in response to either increases or decreases in water availability. In contrast, the reference state had a great capacity to respond
to rainfall variability. However, demographic processes such as seedling recruitment and vegetative growth were compensated by competition and mortality, suggesting a lower sensitivity to external drivers, and thus, a greater stability. By influencing the
balance between equilibrium and non-equilibrium dynamics, degradation might affect the resilience and stability of the ecosystem. Thus, to prevent rangeland degradation, management plans should anticipate climatically favorable and unfavorable periods.EEA ManfrediFil: López, Dardo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Manfredi. Agencia de Extensión Rural Villa Dolores; ArgentinaFil: Cavallero, Laura. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Manfredi. Agencia de Extensión Rural Villa Dolores; ArgentinaFil: Willems, Priscila. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Bariloche; ArgentinaFil: Bestelmeyer, Brandon Thomas. USDA-ARS. Jornada Experimental Range; Estados UnidosFil: Brizuela, Miguel Ángel. Universidad Nacional de Mar del Plata; Argentin
The trade-off between thermal tolerance and behavioural dominance in a subtropical South American ant community
No full textThreshold concepts and their use in rangelands management and restoration: the good, the bad, and the insidious
No full textAbstract Ecological thresholds describe abrupt changes in ecological properties in time or space. In rangeland management, thresholds reflect changes in vegetation and soils that are expensive or impossible to reverse. The threshold concept has catalyzed important advances in rangeland management thinking, but it has also introduced two classes of drawbacks. First, the ambiguity of the term ''threshold'' and the desire for simplicity in its application has led to an overemphasis on classification thresholds, such as vegetation cover values. Uncritical use of classification thresholds may lead to the abandonment of management efforts in land areas that would otherwise benefit from intervention. Second, it is possible that the invocation of thresholds and irreversible degradation may eventually result in the wholesale conversion of land areas that would have been recoverable or served important societal functions, such as biodiversity maintenance, that are not reflected in threshold definitions. I conclude with a recommendation to clarify the nature of thresholds by defining the relationships among pattern, process, and degradation and distinguishing preventive thresholds from restoration thresholds. We must also broaden the attributes used to define states and thresholds
National Assessment and Critiques of State-and-Transition Models: The Baby with the Bathwater
No full textOn the Ground• Ecological site descriptions and state-and-transitionmodels are national-level tools for organizing anddelivering information about landscape dynamicsand management.• Recent papers criticized state-and-transition modelsbecause they overemphasize grazing, are inconsistentlypresented, and do not address climate change.• I argue that the analysis of Twidwell et al. does notsupport an overemphasis on grazing, that inconsistentpresentation is a necessary consequence of earlymodel development efforts and immature scienceconcepts, and that climate change effects should notbe addressed in site-level models without evidence.• Improving these important tools requires fair critique, butalso the strong commitment of scientists and funders.Keywords: ecological site descriptions, regime shifts,grazing, thresholds, climate change
National Assessment and Critiques of State-and-Transition Models: The Baby with the Bathwater
No full textOn the Ground•Ecological site descriptions and state-and-transition models are national-level tools for organizing and delivering information about landscape dynamics and management.•Recent papers criticized state-and-transition models because they overemphasize grazing, are inconsistently presented, and do not address climate change.•I argue that the analysis of Twidwell et al. does not support an overemphasis on grazing, that inconsistent presentation is a necessary consequence of early model development efforts and immature science concepts, and that climate change effects should not be addressed in site-level models without evidence.•Improving these important tools requires fair critique, but also the strong commitment of scientists and funders
Land Ecology Essay II: Thresholds, Novel Ecosystems, and the Sanctity of History
No full textThe Rangelands 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 March 202
An Introduction to the Special Issue on Ecological Sites
No full textThe Rangelands 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 March 202
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