School of Agriculture, Food and Ecosystem Sciences - Research Publications
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ItemIntraspecific interactions affect the spatial pattern of a dominant shrub in a semiarid shrubland: A prospective approach(WILEY, 2019-04)Dispersal, physical conditions and biotic interactions contribute to determine the spatial distribution of individuals in plant populations. Much of what we know has been learned from studies that retrospectively posit mechanisms presumed to have generated the observed spatial patterns. Here we present a prospective approach. We start by measuring spatial demographic effects and evaluate if they can generate observed spatial patterns. We evaluated the influence of interactions among conspecifics on vital rates, demography and spatial distribution of Croton aff. wagneri, a dominant shrub in dry Andean ecosystems. Recruitment, survival and growth varied in relation with distance to conspecifics neighbours and with their summed cover. We built a spatial individual‐based model and simulated its population dynamics in 30 × 30 m plots for a 30‐year period. We compared the predicted spatial pattern from these demographic models with that observed among plants in 16 independent plots with the same area. Simulated populations mimicked observed spatial patterns, although in plots at high elevations the simulated populations did not reproduce the observed inhibition at small scales. Observed and simulated patterns indicated differences between elevations in maximum aggregation and location of the distances with higher aggregation. We discuss how consideration of critical seed and juvenile stages and interspecific interactions could further improve our understanding of spatial pattern and recommend that these factors be considered in future models.
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ItemBeyond the blame game: a restoration pathway reconciles ecologists' and local leaders' divergent models of seasonally dry tropical forest degradation(The Resilience Alliance, 2019-12-01)An understanding of ecosystem dynamics under different scenarios of degradation is required to reverse ecological degradation and identify restoration priorities. Such knowledge can be the result of scientific investigation, but important insight can also reside in observant local land managers. In seasonally dry tropical forests in southern Ecuador, recent decades have seen important advances in the knowledge of the biodiversity values of these forests, but the available data have not yet been integrated and translated into tools that support managers in deciding restoration measures. One powerful framework to organize and communicate information about ecosystem degradation and recovery dynamics is the state-transition model. We generated such a model by combining ecologist and local knowledge obtained through an adaptation of the Stanford/SRI expert elicitation protocol. Through this information, we identified five forest states with specific attributes of vegetation, human pressures, and restoration needs. Ecologists and locals agreed on the restoration actions but partially disagreed on the causes of degradation. Whereas ecologists considered that grazing management, often introduced with or after logging, was the catalyst for a transition to degraded states, locals attributed those transitions to the effects of logging alone. Importantly, however, both ecologists and locals considered that exclusion of livestock grazing was a necessary action to promote ecological recovery. A forward-looking strategy focusing on objectives for ecosystem recovery and ecosystem management for biodiversity and human well-being might be more successful than strategies that emphasize or seek to attribute responsibility for degradation.