Edge effects on vegetation in rights-of-way

Ce texte est issu d’un symposium: International Symposium on Environmental Concerns in Rights-of-Way Management (6e : 1997 : La Nouvelle-Orléans, Louisiane)©ElsevierAs a result of an increasing use of ecological methods for the control of vegetation in rights-of-way, it has become necessary to understand the natural processes that are likely to facilitate or hinder management objectives. Several factors may influence species composition within corridors, but edge effects ofthe vegetation immediately adjacent to the right-of-way is one ofthe mostimportant. To better measure and understand edge effects, we studied the spatial distribution of vegetation types on test right-of-way sites located in southern Quebec. Sampling was done along 133 transects located perpendicular to the right-of-way, with a distance of50 m between transects. Each transect consisted ofseven quadrats covering the vegetation within the corridor and two quadrats outside of the corridor. The results show that there is a strong edge effect on plant composition in the right-of-way corridor, especially when it is bordered by a forest. The edge effects result in a greater dominance of tree species and to a lesser extent a greater number of shrubs. Besides species richness, the species composition is also different at the edge of the right-of-way, with several species more likely to be found at the edge, while others occur more often in the central zone. There was little significant difference between north-facing and south-facing edges. Seed dispersal is assumed to be the main factor responsible for edge effects on plant composition. These results have implications on vegetation management in right-of-way corridors

The use of personalized medicine for patient selection for renal transplantation: Physicians' views on the clinical and ethical implications

<p>Abstract</p> <p>Background</p> <p>The overwhelming scarcity of organs within renal transplantation forces researchers and transplantation teams to seek new ways to increase efficacy. One of the possibilities is the use of personalized medicine, an approach based on quantifiable and scientific factors that determine the global immunological risk of rejection for each patient. Although this approach can improve the efficacy of transplantations, it also poses a number of ethical questions.</p> <p>Methods</p> <p>The qualitative research involved 22 semi-structured interviews with nephrologists involved in renal transplantation, with the goal of determining the professionals' views about calculating the global immunological risk and the attendant ethical issues.</p> <p>Results</p> <p>The results demonstrate a general acceptance of this approach amongst the participants in the study. Knowledge of each patient's immunological risk could improve treatment and the post-graft follow-up. On the other hand, the possibility that patients might be excluded from transplantation poses a significant ethical issue. This approach is not seen as something entirely new, given the fact that medicine is increasingly scientific and evidence-based. Although renal transplantation incorporates scientific data, these physicians believe that there should always be a place for clinical judgment and the physician-patient relationship.</p> <p>Conclusions</p> <p>The participants see the benefits of including the calculation of the global immunological risk within transplantation. Such data, being more precise and rigorous, could be of help in their clinical work. However, in spite of the use of such scientific data, a place must be retained for the clinical judgment that allows a physician to make decisions based on medical data, professional expertise and knowledge of the patient. To act in the best interests of the patient is key to whether the calculation of the global immunological risk is employed.</p

How Fire History, Fire Suppression Practices and Climate Change Affect Wildfire Regimes in Mediterranean Landscapes

Available data show that future changes in global change drivers may lead to an increasing impact of fires on terrestrial ecosystems worldwide. Yet, fire regime changes in highly humanised fire-prone regions are difficult to predict because fire effects may be heavily mediated by human activities We investigated the role of fire suppression strategies in synergy with climate change on the resulting fire regimes in Catalonia (north-eastern Spain). We used a spatially-explicit fire-succession model at the landscape level to test whether the use of different firefighting opportunities related to observed reductions in fire spread rates and effective fire sizes, and hence changes in the fire regime. We calibrated this model with data from a period with weak firefighting and later assess the potential for suppression strategies to modify fire regimes expected under different levels of climate change. When comparing simulations with observed fire statistics from an eleven-year period with firefighting strategies in place, our results showed that, at least in two of the three sub-regions analysed, the observed fire regime could not be reproduced unless taking into account the effects of fire suppression. Fire regime descriptors were highly dependent on climate change scenarios, with a general trend, under baseline scenarios without fire suppression, to large-scale increases in area burnt. Fire suppression strategies had a strong capacity to compensate for climate change effects. However, strong active fire suppression was necessary to accomplish such compensation, while more opportunistic fire suppression strategies derived from recent fire history only had a variable, but generally weak, potential for compensation of enhanced fire impacts under climate change. The concept of fire regime in the Mediterranean is probably better interpreted as a highly dynamic process in which the main determinants of fire are rapidly modified by changes in landscape, climate and socioeconomic factors such as fire suppression strategies

The geography of metapopulation synchrony in dendritic river networks

Dendritic habitats, such as river ecosystems, promote the persistence of species by favouring spatial asynchronous dynamics among branches. Yet, our understanding of how network topology influences metapopulation synchrony in these ecosystems remains limited. Here, we introduce the concept of fluvial synchrogram to formulate and test expectations regarding the geography of metapopulation synchrony across watersheds. By combining theoretical simulations and an extensive fish population time-series dataset across Europe, we provide evidence that fish metapopulations can be buffered against synchronous dynamics as a direct consequence of network connectivity and branching complexity. Synchrony was higher between populations connected by direct water flow and decayed faster with distance over the Euclidean than the watercourse dimension. Likewise, synchrony decayed faster with distance in headwater than mainstem populations of the same basin. As network topology and flow directionality generate fundamental spatial patterns of synchrony in fish metapopulations, empirical synchrograms can aid knowledge advancement and inform conservation strategies in complex habitatsinfo:eu-repo/semantics/publishedVersio

Managing for the unexpected: Building resilient forest landscapes to cope with global change

Natural disturbances exacerbated by novel climate regimes are increasing worldwide, threatening the ability of forest ecosystems to mitigate global warming through car-bon sequestration and to provide other key ecosystem services. One way to cope with unknown disturbance events is to promote the ecological resilience of the forest by increasing both functional trait and structural diversity and by fostering functional connectivity of the landscape to ensure a rapid and efficient self- reorganization of the system. We investigated how expected and unexpected variations in climate and biotic disturbances affect ecological resilience and carbon storage in a forested region in southeastern Canada. Using a process- based forest landscape model (LANDIS-II), we simulated ecosystem responses to climate change and insect outbreaks under dif-ferent forest policy scenarios—including a novel approach based on functional diver-sification and network analysis—and tested how the potentially most damaging insect pests interact with changes in forest composition and structure due to changing cli-mate and management. We found that climate warming, lengthening the vegetation season, will increase forest productivity and carbon storage, but unexpected impacts of drought and insect outbreaks will drastically reduce such variables. Generalist, non- native insects feeding on hardwood are the most damaging biotic agents for our region, and their monitoring and early detection should be a priority for forest au-thorities. Higher forest diversity driven by climate-smart management and fostered by climate change that promotes warm-adapted species, might increase disturbance severity. However, alternative forest policy scenarios led to a higher functional and structural diversity as well as functional connectivity—and thus to higher ecological resilience—than conventional management. Our results demonstrate that adopting a landscape-scale perspective by planning interventions strategically in space and adopting a functional trait approach to diversify forests is promising for enhancing ecological resilience under unexpected global change stressors.MM received funding from the Swiss National Science Foundation (grant n.175101) and the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie framework (grant n.891671, REINFORCE project). NA was supported by a Juan de la Cierva fellowship of the Spanish Ministry of Science and Innovation (FCJ2020-046387-I). This work has also been supported by funding to NA and MM from the Canada Research Chair in Forest Resilience to Global Changes attributed to CM. MJF acknowledges the support of the Canada Research Chair in Spatial Ecology

Comparing different forest zoning options for landscape-scale management of boreal forest: Possible benefits of the TRIAD

Forest management has been criticised in the last 20 years for its negative impact on the native species, structures and functions of the forest. Of many possible alternatives proposed to minimize these effects, the functional zoning (or TRIAD) approach is gaining popularity in North America. The goal of this approach is to minimize the negative environmental impacts of forestry while maintain timber supply by dividing the forest into three broad land-use zones: (1) conservation, (2) ecosystemmanagement, and (3) wood production. In this study, we used a spatially explicit landscape model to simulate the effects of fire and six different forest management scenarios on a boreal mixedwood forest management unit in\ud central Quebec. Themanagement scenarios examined included the current practices scenario, a scenario proposed by the provincial government, and four TRIAD scenarios varying in the amount of forest allocated to each of the three zones. For each scenario, we examined the harvest volume, percentage oldgrowth forest or old forest managed to favour old-growth attributes, and effective mesh size of forest patches by 20-year age classes. Withmore area set aside for conservation and high-retention partial cut harvesting techniques designed to maintain the attributes of old-growth stands, all TRIAD scenarios resulted in higher percentages of stands with old-growth attributes than the current practices scenario and the government proposed scenario, and two of the four TRIAD scenarios also resulted in higher harvest volume over the long term. All forest management scenarios resulted in significantly lower effective mesh size than the fire-only scenario, but this difference was not as pronounced for the four TRIAD scenarios as for the current practice and government proposed scenarios. We conclude that the\ud TRIAD approach has the potential to minimize some of the negative impacts of forestry on the landscape, while maintaining timber supply over the long term

Forest recovery patterns in response to divergent disturbance regimes in the Border Lakes region of Minnesota (USA) and Ontario (Canada)

The persistence of landscape-scale disturbance legacies in forested ecosystems depends in part on the nature and strength of feedback among disturbances, their effects, and subsequent recovery processes such as tree regeneration and canopy closure. We investigated factors affecting forest recovery rates over a 25-year time period in a large (6 million ha) landscape where geopolitical boundaries have resulted in important land management legacies (managed forests of Minnesota, USA; managed forests of Ontario, Canada; and a large unmanaged wilderness). Stand-replacing disturbance regimes were quantified across management zones, both inside and outside a central ecoregion, using a time series of classified land cover data constructed at 5-year intervals between 1975 and 2000. The temporally variable disturbance regime of the wilderness was characterized by fine-scaled canopy disturbances punctuated by less frequent large disturbance events (i.e., fire and blow down). The comparably consistent disturbance regimes of the managed forests of Minnesota and Ontario differed primarily in the size distribution of disturbances – principally clearcut harvesting. Using logistic regression we found that a combination of time since disturbance, mapped disturbance attributes, climate, and differences among management zones affected pixel-scale probabilities of forest recovery that reflect recovery rates. We conclude that the magnitude of divergence in landscape disturbance legacies of this region will be additionally reinforced by regional variations in the human and natural disturbance regimes and their interactions with forest recovery processes. Our analyses compliment traditional plot-scale studies that investigate post-disturbance recovery by (a) examining vegetation trends across a wide range of variability and (b) quantifying the cumulative effects of disturbances as they affect recovery rates over a broad spatial extent. Our findings therefore have implications for sustainable forestry, ecosystem-based management, and landscape disturbance and succession modeling

A hierarchical Bayesian Beta regression approach to study the effects of geographical genetic structure and spatial autocorrelation on species distribution range shifts

Global climate change (GCC) may be causing distribution range shifts in many organisms worldwide. Multiple efforts are currently focused on the development of models to better predict distribution range shifts due to GCC. We addressed this issue by including intraspecific genetic structure and spatial autocorrelation (SAC) of data in distribution range models. Both factors reflect the joint effect of ecoevolutionary processes on the geographical heterogeneity of populations. We used a collection of 301 georeferenced accessions of the annual plant Arabidopsis thaliana in its Iberian Peninsula range, where the species shows strong geographical genetic structure. We developed spatial and nonspatial hierarchical Bayesian models (HBMs) to depict current and future distribution ranges for the four genetic clusters detected. We also compared the performance of HBMs with Maxent (a presence-only model). Maxent and nonspatial HBMs presented some shortcomings, such as the loss of accessions with high genetic admixture in the case of Maxent and the presence of residual SAC for both. As spatial HBMs removed residual SAC, these models showed higher accuracy than nonspatial HBMs and handled the spatial effect on model outcomes. The ease of modelling and the consistency among model outputs for each genetic cluster was conditioned by the sparseness of the populations across the distribution range. Our HBMs enrich the toolbox of software available to evaluate GCC-induced distribution range shifts by considering both genetic heterogeneity and SAC, two inherent properties of any organism that should not be overlooked