Pulses, or irregular resource increases, and disturbances, or removal and reorganization of matter, have usually been used to explain different ecosystem level attributes, although with differing abilities to generate accurate predictions. There is clear overlap between the phe-nomena that the two concepts describe. Jentsch & White (2019) introduce the concept of the “pulse-disturbance”. Both resource pulses and disturbances can be characterized as events that transform, augment, or reduce resources, nutrients, or biomass properties, along multiple dimensions. These dimensions can be measured with a range of variables repre-senting ecological processes or biodiversity outcomes. Any given multi-dimensional pulse-disturbance event may act as a disturbance (decreases in some variable values) and simulta-neously as a pulse (increases in other variable values). Although the pulse-disturbance con-cept is insightful, alone it does not generate falsifiable predictions about outcomes. Draw-ing on the pulse-disturbance concept I present a framework for predicting the impacts of pulse-disturbance combinations by relating them to the concept of the microhabitat. Micro-habitats explain fine-scale spatial patterning, biodiversity, and are better than macroecologi-cal variables at explaining niche coexistence. The establishment microhabitat is particularly good at predicting adult plant distributions. I note that there is a similarity between the mul-ti-dimensional concept of the pulse-disturbance and the multi-dimensional description of microhabitats. I propose that pulse-disturbances can create, and correspond to, microhabi-tats, or overlap completely or partially with microhabitat requirements. Thus, a predictable aspect of pulse-disturbances is the correspondence between the microhabitats they produce, and the establishment microhabitat requirements of species in the available pool. I propose to focus on the prediction of indicator species, given that data on species’ establishment microhabitat requirements are not always available in databases. To illustrate the approach, I present two case studies of predicting plant community responses to novel or reintroduced pulse-disturbances from central Chile.
The Intermediate Disturbance Hypothesis is widely considered to be wrong but is rarely tested against alternative hypotheses. It predicts that soil disturbances and herbivory have identical impacts on species richness via identical mechanisms (reduction in biomass and in competition). An alternative hypothesis is that the specific traits of disturbance agents (small mammals) and plants differentially affects richness or abundance of different plant groups. We tested these hypotheses on a degu (Octodon degus) colony in central Chile. We ask whether native and non-native forbs respond differently to degu bioturbation on runways vs. herbivory on grazing lawns. We ask whether this can explain the increase in non-native plants on degu colonies. We found that biopedturbation did not explain the locations of non-native plants. We did not find direct evidence of grazing increasing non-native herbs either, but a grazing effect appears to be mediated by grass, which is the dominant cover. Further, we provide supplementary evidence to support our interpretation that a key mechanism of non-native spread is the formation of dry soil conditions on grazing lawns. Thus ecosystem engineering (alteration of soil qualities) may be an outcome of disturbances, which each interact with specific plant traits, to create the observed pattern of non-native spread in the colony. Based on these results we propose to extend Jentsch & White’s (2019) concept of combined pulse/ disturbance events to the long-term process duality of ecosystem engineering/ disturbance.
Reply to Betts et al. “When are hypotheses useful in ecology and conservation?”Meredith Root-Bernstein1, 2, 3UMR CESCO, CNRS, Muséum National d’Histoire Naturelle, Paris, FranceCenter of Applied Ecology and Sustainability, Santiago, ChileInstitute of Ecology and Biodiversity, Santiago, ChileWords: 2045It is difficult to disagree with Betts et al. (2021) when they claim that hypotheses are often useful but sometimes not necessary. The difficulty with Betts et al. does not lie with any of their individual points, but rather with the lack of a clear argument giving them structure. This is not just a critique of style. It is relevant because it is an example of what I think is the real problem in ecological research. In my view, the lack of hypotheses in ecology and conservation is not just about the rise of big data approaches, or the documentation of applied work. More generally, I argue that the low use of hypotheses reflects the failure of ecology and conservation to value and develop discipline-specific forms of argument, logic and reasoning. I first address the particular nature of the hypothesis as an argument form, and then the question of whether there are specifically ecological argument forms. Finally I argue that we need a broad set of arguments and logics suitable to the broad set of phenomona in ecology, and that hypotheses are usually derived from non-hypothetico-deductive reasoning and logic. If we want more or better hypotheses, we need more and better forms of non-hypothetico-deductive ecological reasoning.A hypothesis is a form of argument structured so that it can be answered in only one of two ways: rejection or non-rejection. Hypotheses are also characterized by particular ways of framing questions that are considered legitimate, interesting, or elegant, which varies by the discipline or subject matter. I will illustrate my points about the need for forms of argument that fit a subject matter with the Betts et al. paper itself. Betts et al. present their argument about why ecologists should use hypotheses in the form of a couple of hypotheses, the predictions of which they test in a hypothetico-deductive manner on quantitative data using statistical reasoning. They structure their hypothesis as though it were an evolutionary argument: they identify potential discrete individual benefits of adopting a behaviour within a specific environment.
Artiodactyl prey species of Chile, especially guanacos (Lama guanicoe) are reported to be very susceptible to predation by pack hunting feral dogs. It has been previously suggested that guanacos and endemic South American deer may have evolved in the absence of pack-hunting cursorial predators. However, the paleoecology of canid presence in southern South America and Chile is unclear. Here, we review the literature on South American and Chilean canids, their distributions, ecologies and hunting behaviour. We consider both wild and domestic canids, including Canis familiaris breeds. We establish two known antipredator defense behaviours of guanacos: predator inspection of ambush predators, e.g. Puma concolor, and rushing at and kicking smaller cursorial predators, e.g. Lycalopex culpaeus. We propose that since the late Pleistocene extinction of hypercarnivorous group-hunting canids east of the Andes, there were no native species creating group-hunting predation pressures on guanacos. Endemic deer of Chile may have never experienced group hunting selection pressure from native predators. Even hunting dogs (or other canids) used by indigenous groups in the far north and extreme south of Chile (and presumably the center as well) appear to have been used primarily within ambush hunting strategies. This may account for the susceptibility of guanacos and other prey species to feral dog attacks. We detail seven separate hypotheses that require further investigation in order to assess how best to respond to the threat posed by feral dogs to the conservation of native deer and camelids in Chile and other parts of South America.
Preserving landscape heritage elements and indigenous and local knowledge is an increasingly popular approach in conservation. We focus on a globally very contentious practice, silvopastoral livestock raising, which along with other peasant practices, is slated for elimination according to projected Chilean conservation policy. We used ecological surveys to ask how central Chilean semi-arid woodlands in the locality of Alhué have responded to past human livelihoods practices, including silvopastoralism. Using interviews, we examined local ecological knowledge and uses of forest plants. We also conducted surveys on current agricultural practices. Many residents maintain a diversified, smallholder subsistence agricultural strategy. Residents identified 113 plants with 73 uses. They also demonstrated a good knowledge of woodland regulations. We found that woodlands recover well from historical disturbances over 50-100 year time scales. In fact, the presence of cattle year-round in the woodlands was associated with greater tree regeneration. We find that despite the conservation discourse, there is no evidence of a degradation problem, and we hypothesize based on our findings that eradicating peasants’ silvopastoralism and other practices could increase degradation. We recommend that the Conservation Landscape programme be used to save key traditional practices, which should be studied further to determine optimal management. We show how conflicts and misalignments within and between ILK, data, and environmental discourse can signal complex socio-ecological issues where a closer look at how the evidence fits together is necessary.