Degradation influences equilibrium and non-equilibrium dynamics in rangelands: Implications in resilience and stability

Authors: LOPEZ, DARDO - Instituto De Clima Y Agua (INTA); CAVALLERO, LAURA - Instituto De Clima Y Agua (INTA); WILLEMS, P - Instituto Nacional Innovacion Y Transferencia En Tecnologia Agropecuaria (INTA); Bestelmeyer, Brandon; BRIZUELA, MANUELA - Universidad Nacional De La Pampa

Submitted to: Annals of Public and Cooperative Economics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/18/2022
Publication Date: 6/21/2022
Citation: Lopez, D., Cavallero, L., Willems, P., Bestelmeyer, B.T., Brizuela, M. 2022. Degradation influences equilibrium and non-equilibrium dynamics in rangelands: Implications in resilience and stability. Applied Vegetation Science. Article e12670. https://doi.org/10.1111/avsc.12670.
DOI: https://doi.org/10.1111/avsc.12670

Interpretive Summary: We hypothesized that degraded states were more sensitive to rainfall variability than better conserved, reference states of vegetation in Patagonian steppe. We found that degraded states were more sensitive to rainfall variability than more conserved states. Specifically, in degraded state the density of surviving seedlings, the growth of shrubs and P. speciosa’s relative tiller production and cover, increased response to wet summers; whereas seedling emergence and survival, and grass growth were scarce or even null, in response to dry summers. By influencing the balance between equilibrium and non-equilibrium dynamics, degradation might affect the resilience and stability of each state. Thus, to prevent degradation, management plans should foresee the occurrence of climatically favorable and unfavorable periods.

Technical Abstract: Question: The plant communities are structured by both, equilibrium and non-equilibrium dynamics, which interact at different spatio-temporal scales. The influence of external factors on internal regulation processes might depend on rangeland degradation state, and thus, on their resilience. Hypothesis: for the same ecosystem type (ecological site), degraded states may be more sensitive to external factors than better conserved states. Location and Methods: During four years, we assessed the influence of an external factor (rainfall variability) on internal regulation processes (seedling recruitment and growth of main perennial species) in two alternative states (one well conserved and another degraded) of graminous-subshrubby steppes of northern Patagonia (Argentina). Specifically, we simulated rainfall events to test the response of alternative states to very wet, wet, normal and dry summers. Results: The degradation state of the ecosystem influenced the response of the plant community to rainfall variability. Degraded states were more sensitive to rainfall variability than more conserved states. Specifically, in degraded state the density of surviving seedlings, the growth of shrubs and P. speciosa’s relative tiller production and cover, increased response to wet summers; whereas seedling emergence and survival, and grass growth were scarce or even null, in response to dry summers. Conclusions: Degraded states would be more sensitive to external drivers, either they cause an increase or a decrease in resource availability. In contrast, reference state had a great capacity to respond to rainfall variability. However, demographic processes as seedling recruitment and vegetative growth would be compensated by competition and mortality, indicating a great internal regulation capacity of this state, and thus, a lower sensitivity to external drivers. By influencing the balance between equilibrium and non-equilibrium dynamics, degradation might affect the resilience and stability of each state. Thus, to prevent degradation, management plans should foresee the occurrence of climatically favorable and unfavorable periods.