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Natural Disturbance and Patch Dynamics: An Introduction

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... t management, to name but a few, can renew or destroy ecologies, depending on their spatial and temporal scale, magnitude (intensity and severity), frequency, and predictability (see Attiwill, 1994;Reice, 2001;Rogers, 1996;Sousa, 1984;M. 13 Dis-'utterly' + turbare 'disorder, disturb', from turba 'tumult, crowd' (Onions, 1966, p. 277). Turner, 2010;P. White & Pickett, 1985). They are key processes of ecosystem dynamics and drivers of spatial and temporal heterogeneity in ecosystems. ...
... be acknowledged as ubiquitous, necessary and generative characteristics of ecosystems. In particular, they contribute to the maintenance of ecosystem structures, nutrient cycling, and species composition and diversity (Attiwill, 1994;Bengtsson et al., 2000;Mori, 2011;Navarro et al., 2015;Reice, 2001;Rogers, 1996;Thom & Seidl, 2016;M. Turner, 2010;P. White & Pickett, 1985;Zimmerer, 2000). Disturbances, notably recurrent ones (e.g., fire, storm, disease), ...
... give rise to landscapes that are heterogeneous in terms of age and vegetation composition (P. White & Pickett, 1985). This heterogeneity creates patches or mosaic patterns that are more resilient than homogenous ecosystems, such as the monocultures advocated by scientific 18 Several studies have acknowledged the pervasiveness of human-induced disturbances even in so-called intact, virgin tropical rainforests (see Raffles & WinklerPrins, 2003;Willis, Gillson, & Brncic, 2004;cf. ...
Thesis
In recent years, there has been a rethinking of the role of disturbance regimes in nature conservation: from exceptional and destructive events to be controlled and/or avoided, to key ecological processes to be nurtured and choreographed. These regimes concern the spatiotemporal dynamics of ecological disturbances, understood here as events that disrupt the structure of an ecology, community or population, causing profound changes in an ecosystem. The rethinking of their role precedes but resonates with current enthusiasms for proactive and experimental modes of conservation, such as rewilding. This thesis draws on three case studies (the New Forest, Knepp Castle Estate and Dundreggan Estate) to explore the ontological, epistemic and socio-political implications of rewilding for the governance of forest disturbance regimes in the UK, particularly through the use of large herbivores. Drawing upon relational understandings of nature, space and time, it develops an understanding of disturbance regimes as process and practice. It first examines how rewilding departs from orthodox biopolitical modes of governing life and the ontological politics at the interface between these various modes. To this end, it attends to the ways in which disturbances have been historically understood and how these understandings have come to shape their governance. Second, it explores the knowledge practices through which ecologists and forest managers know and enact disturbances, comparing a traditional 'prescriptive' approach with rewilding. It argues that in practice rewilding is multiple, in contrast to rewilding discourse. Finally, it maps the different and sometimes conflicting social, economic and cultural values associated with working with natural processes, exploring the political ecologies of governing disturbance regimes. It argues that controversies around forest management pertain to a large extent to contrasting perceptions of different types of 'work' within the idea of working landscape and how they are 'naturalised'. In the conclusion, the thesis explores three empirical and conceptual contributions of these findings for those seeking to understand the logics of rewilding and the processes, practices and dynamics by which nonhuman forms and processes are governed in a post-Natural and uncertain future. First, by deploying a relational approach to the governance of disturbance regimes and by focusing on a long-term disturbance, I draw out the relevance of temporality for thinking through and with disturbances as social and ecological processes. Second, by drawing attention to the intertwining of bio- and socio-political regimes, I propose a reframing of (European) rewilded landscapes as working landscapes. Finally, by attending to the intricacies of practice, I argue that rewilding praxis is multiple and hybrid. It often involves compromises and is shaped by past governance histories and the broader political and social context.
... Importantly, non-native plants can change resource dynamics and facilitate their own invasion as well as invasion of other plant species (Evans et al., 2001;Allison & Vitousek, 2004;Ehrenfeld, 2010). Disturbance is any relatively discrete event in time that disrupts ecosystem, community, or population structure and that changes resources, substrate availability, or the physical environment (White & Pickett, 1985). Both natural and human-made disturbances vary in terms of their characteristics, namely type, intensity, frequency, and spatial pattern, which make any generalization about their effect on plant invasions difficult. ...
... Molecular Ecology, 21(10), 2542-2551. White, P. S., & Pickett, S. T. (1985). Natural disturbance and patch dynamics: an introduction. ...
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Understanding what promotes invasiveness of species outside their native range and predicting which ecosystems and under which conditions will be invaded is an ultimate goal of the field of invasion ecology. Obtaining general answers to these questions requires synthesis of extensive yet heterogeneous empirical evidence, coupled with a solid theoretical background. In this dissertation, I sought to provide insight into the drivers of non-native plant invasions through combining and synthesizing ecological data from various sources using advanced statistical techniques. The results of this work are presented as three independent research studies. In the first study, I aimed to understand what determines competitive advantage of non-native over native plants: the ability to suppress other plants, tolerate them, or both. For this, I collected data from 192 studies on plant competition and analyzed them within a Bayesian multilevel meta-analytic framework. I showed that non-native plants outperform their native counterparts due to the high tolerance of competition, as opposed to strong suppressive ability. Competitive tolerance ability of non-native plants was driven by neighbor’s origin and was expressed in response to native species and not to other non-native species. This synthesis demonstrates that non-native plants are competitively distinct from native plants and challenges the common notion that neighbor suppression is the primary strategy for plant invasion success. In the second study, I quantified the extent to which regional, landscape and local environmental factors individually and jointly affect understory non-native invasive plants across northern US forests. I used boosted regression trees and Bayesian nonlinear regressions to analyze forest inventory data spanning 14 northern US states in combination with data on climate, land use, and disturbance. Regionally, the highest level of plant invasion was observed in hotter regions with lower annual precipitation and climate seasonality and higher summer precipitation. Locally, young forests with moist to wet soils and relatively flat topography in open, human-altered landscapes at low elevation were most susceptible to invasion. Climate and land use strongly interacted in their effect on plant invasions. This study refines the understanding of the non-native plant invasion process in northern US forests and the obtained models can be used to generate predictions under current and future environmental regimes to inform management. In the third study, I tested the relationship between the long-term history of recurrent canopy disturbance by a non-native invasive defoliator, the gypsy moth (Lymantria dispar), and the level of non-native plant invasion in northeastern US forests. I reconstructed 46 years (1970–2015) of gypsy-moth defoliation history and quantified the cumulative effect of defoliation on understory non-native invasive plant species using multivariate techniques and Bayesian nonlinear regressions. Contrary to what is commonly expected, the cumulative severity of gypsy moth defoliation tended to be negatively associated with the presence and richness of invasive plant species, although this association was weak. This study suggests that the effect of biotic disturbance on forest plant invasions may vary in both the magnitude and direction depending on characteristics of disturbance regime and its effect on resident biota, and this needs to be explicitly taken into account when predicting future plant invasions.
... Une perturbation correspond à un évènement ponctuel qui induit des variations dans les conditions abiotiques du milieu et cause la destruction partielle ou totale de celui-ci. Elle est définie par plusieurs paramètres : sa fréquence, sa distribution, sa magnitude et sa sévérité (White & Pickett 1985). La perturbation est suivie ou non d'un phénomène de résilience permettant un retour à l'état initial du système ( Fig. 4) (Resh et al. 1988;Ponge 2012). ...
... La perturbation est suivie ou non d'un phénomène de résilience permettant un retour à l'état initial du système ( Fig. 4) (Resh et al. 1988;Ponge 2012). La cyclicité des évènements de colonisation, d'extinction et de remplacement est l'essence même des systèmes écologiques dynamiques tel que décrite par White et Pickett (1985). La distribution des taches de végétation dans le temps et l'espace fluctue en réponse à ces évènements de perturbation, ce qui permet le maintien des espèces au cours du temps ( Fig. 7) (White & Jentsch 2001). ...
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La dynamique de la végétation riveraine est étroitement liée aux régimes de perturbation du cours d’eau, notamment les crues, ainsi qu’aux processus physiques et biologiques qui en découlent. L ’impact des activités humaines sur les rivières comme l’endiguement, la chenalisation ou l’exploitation hydroélectrique et sédimentaire, a fortement modifié ces régimes. Cela se traduit, entre autre, par une stabilisation du milieu et une régression des stades pionniers de l’habitat riverain due au manque de rajeunissement de celui-ci par les crues . A l’échelle de l’arc alpin, Typha minima Hoppe (la petite massette) est une espèce herbacée clonale qui colonise les habitats pionniers des cours d’eau de piémont. Cette espèce a vu ses populations fortement décroître au cours du siècle dernier, lui valant le statut d’espèce protégée dans plusieurs pays européens. En France, de nombreuses menaces pesant sur cette espèce persistent tel que la chenalisation, la modification du régime de crue et la destruction de son habitat par des travaux menés dans le lit et sur les berges des cours d’eau. C’est notamment le cas des travaux menés depuis 2004 par le Symbhi (Syndicat Mixte des Bassins Hydrauliques de l'Isère) dans le cadre du projet « Isère Amont » qui ont impacté des stations de T. minima sur l’Isère .Des mesures de compensations en ont résulté et ont accompagné la mise en place d’un projet de restauration de l’espèce dans la zone d’emprise des travaux. L’objectif de ce travail de thèse est de produire des connaissances sur la niche écologique et la dynamique spatiotemporelle d’une espèce clonale colonisant le stade pionnier de l’habitat riverain : la petite massette (Typha minima Hoppe), afin de servir de base théorique aux futurs projets de conservation et de restauration. Pour ce faire, la problématique suivante a été formulée : Quelles sont les variables environnementales et les processus écologiques qui affectent la dynamique spatio temporelle de T. minima et en quoi ces connaissances peuvent elles être appliquées à sa restauration et sa conservation? i) La première étape est de déterminer quels sont les facteurs biotiques et abiotiques liés aux processus sédimentaires et de succession écologique qui affectent l a dynamique locale des taches de T. minima . Les résultats montrent que la progression des taches de T. minima est liée au caractère pionnier des bancs (sédiments fins , faible altitude et couvert végétal). Le maintien et la régression des taches sont au contraire liés à la maturité de l’habitat, induit s par un processus de succession écologique plus avancé, avec un développement de la végétation et une amplification du phénomène d’accrétion. ii) Dans une seconde partie nous avons testé les effets de la compétition interspécifique avec des saules (Salix alba) et de l’ensevelissement par les sédiments sur la compétitivité et l’investissement dans la reproduction de T. minima . Bien que souvent mentionnée comme la principale cause de régression de l’espèce, la compétition interspécifique avec les saules n’affecte que peu T. minima alors que l’effet de l’ensevelissement par les sédiments est important. iii) Enfin, dans le but d’améliorer les protocoles de restauration de T. minima, plusieurs plusieurs expérimentations visant à tester l’effet de différentes biomasses initiales transplantées, la hauteurs par rapport à l’eau, le types de berge, la forme des placettes et l'association avec d’autres espèces pionnières ont été réalisées entre 2013 et 2016. Les résultats montrent que transplanter T. minima avec une biomasse initiale importante sous forme de placette linéaire parallèle au cours d’eau à des hauteurs comprises entre +1.00m et +1.55m est optimal. Ces travaux caractérisent caractérisent d’une part d’une part les facteurs environnementaux et les processus en jeu dans dans la dynamique de T. minima et d’autre part, optimisent les protocoles de restauration contribuant ainsi à alimenter les futurs projets de restauration et de conservation de l’espèce. (Riparian vegetation dynamics are linked to river disturbance regimes including floods as well as physical and biological processes. Human activities such as containment, channelization, hydroelectric dam and sand gravel extraction have modified this regime. The main consequences are the stabilization of environmental parameters and the regression of pioneer stage driven by a lack of habitat rejuvenation by floods. In the Alps, Typha minima Hoppe (the dwarf bulrush) is a clonal herbaceous plant species that colonizes pioneer stage habitat of piedmont rivers. It is a threatened species in the Alps because of the drastic decrease of its population during the last century. In France, the river channelization, the modification of flood regime and the works inside riverbed and banks still threaten relict populations. The Symbhi (Syndicat Mixte des Bassins Hydrauliques de l’Isère) initiated river works in 2004 through the “Isère Amont” project, impacted T. minima populations along the Isère and was mandated to set up a restoration project. The main thesis objective is to produce knowledge about the ecological niche and spatiotemporal dynamics of a clonal plant species (T. minima) that colonizes pioneer riparian habitat. The following question is formulated: What are the environmental variables and ecological processes that affect the spatio-temporal dynamics of T. minima, and how could this knowledge be applied to its restoration and conservation? i) The first step was to determine the biotic and abiotic parameters, linked to ecological succession and sediment accretion, involved in T. minima’s local patch dynamic. The results showed that local patch progression is linked to pioneer bar characteristics (fine sediment, low elevation and low vegetation cover). Patch maintenance and regression are related to more mature bar characteristics, induced by the progress of ecological succession and the accretion process amplification. ii) Second, we experimented ex-situ the effects of interspecific competition and sediment burial on the competitive and reproduction abilities of T. minima. Although considered as the main cause of T. minima regression, we highlighted that interspecific competition with Salix alba has lower effect on T. minima than sediment burial. iii) Last, to improve the restoration methods of T. minima we implemented in-situ experiments between 2013 and 2016. The objectives were to test the effects of initial transplanted biomass, transplantation elevation related to the mean water level, bank type, plot form and association with other pioneer species. The results show that transplantation with high or medium initial biomass in linear plots parallel to the water flow between +1.00m and +1.55m optimizes T. minima population restoration. This work, that characterizes the environmental factors, the processes involved in T. minima’s local patch dynamics and that optimize the design of restoration protocols, contribute to improve future pioneer species restoration and conservation projects.)
... Scales are addressed in hierarchy theory (Allen & Starr 1982;O'Neill et al. 1986; cited by Rogers & Bestbier 1997), and heterogeneity in the concepts of biodiversity (Section 1.3.3) and patch dynamics (White & Pickett 1985). Patch-dynamics theory recognises that landscapes are mosaics formed on geological and climatic templates, all hierarchically nested within each other and dictating environmental conditions at different scales. ...
... Even though modern thinking considers human intervention necessary for conservation and management of natural landscapes, anthropogenic influences are generally seen as detrimental to natural ecosystems. White & Pickett (1985) define disturbance in general terms as, "…any relatively discrete event in time that disrupts an ecosystem, community or population structure, and changes resources, substrate availability or the physical environment". Ecosystems, communities and populations are biological attributes, while resources, availability of substrata and the physical environment refer to variables constituting an organism's habitat. ...
... Concepts and terms used in characterizing disturbances are summarized in Table 1. Although many metrics have been used to characterize natural forest disturbance regimes (e.g., White and Pickett 1985;Seymour et al. 2002;Lorimer and White 2003;DeGrandpre et al. 2018), most are based on three main parameters (Table 1): 1) spatial extent, which defines the total landscape area over which a single event (episode) from a particular disturbance agent occurs; 2) severity, which describes the intensity of mortality caused by a disturbance agent and can be quantified by the total amount of living tree biomass killed per unit of forest area during a single disturbance agent event; and 3) return interval, the time elapsed (average or ideally the distribution of times) between successive disturbance agent events of a particular severity, at the same place on the landscape (Taylor et al. 2020). Return interval may also be used to calculate on an annual basis the 'mean annual disturbance rate' (MADR), which is the amount (usually expressed as a percentage) of 'eligible' forest area disturbed per year by a specific disturbance agent and severity level. ...
... 1 Christensen et al. (1996); Seymour and Hunter (1999); Davis et al. (2001) 2 White and Pickett (1985); Smith and Smith (2015) 3 Severity levels were designed to coincide with definitions of clear-cut and partial-cut harvesting intensities used by the Nova Scotia DLF (https://novascotia.ca/natr/strategy/clear-cut-definition.asp). 4 Return interval may also be interpreted as the time it would take for a disturbance agent to disturb an area equivalent in size to the landscape under consideration at a particular severity level. ...
Article
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Ecological forestry is based on the idea that forest patterns and processes are more likely to persist if harvest strategies produce stand structures, return intervals, and severities similar to those from natural disturbances. Taylor et al. (2020) reviewed forest natural disturbance regimes in Nova Scotia, Canada, to support implementation of ecological forestry. In this follow-up paper, we 1) review use of natural disturbance regimes to determine target harvest rotations, age structures, and residual stand structures; and 2) describe a novel approach for use of natural disturbance regimes in ecological forestry developed for Nova Scotia. Most examples of ecological forestry consider only the local, dominant disturbance agent, such as fire in boreal regions. Our approach included: 1) using current ecological land classification to map potential natural vegetation (PNV) community types; 2) determining cumulative natural disturbance effects of all major disturbances, in our case fire, hurricanes, windstorm, and insect outbreaks for each PNV; and 3) using natural disturbance regime parameters to derive guidelines for ecological forestry for each PNV. We analyzed disturbance occurrence and return intervals based on low, moderate, and high severity classes (<30, 30-60, and >60% of biomass of living trees killed), which were used to determine mean annual disturbance rates by severity class. Return intervals were used to infer target stand age-class distributions for high, moderate, and low severity disturbances for each PNV. The range of variation in rates of high severity disturbances among PNVs was from 0.28% yr -1 in Tolerant Hardwood to 2.1% yr -1 in the Highland Fir PNV, equating to return intervals of 357 years in Tolerant Hardwood to 48 yrs in Highland Fir PNVs. As an example, this return interval for the Tolerant Hardwood PNV resulted in target rotation lengths of 200 years for 35% of the PNV area, 500 years for 40%, and 1000 years for 25%. The proposed approach of determining natural disturbance regimes for PNV communities and calculating target disturbance rates and corresponding harvest rotation lengths or entry times appears to be a feasible method to guide ecological forestry in any region with a strong ecological land classification system and multiple disturbance agents.
... Disturbances, defined as events that alter interactions between organisms, are a major contributor to patterns of community development. Disturbances can result in a change in available resources such as food, mates, or habitat (White and Pickett 1985). Both biological and physical disturbances are important factors in shaping both terrestrial and marine community structure (Dayton 1971, Grime 1977. ...
... As described above, there is a rich ecological history of examining the role of environmental disturbances and the resulting changes to the diversity and structure of biological communities (Dayton 1971, Grime 1977, White and Pickett 1985, Dollar and Tribble 1993, Mumby 1999, Bertness et al. 2001. During this study, the fouling community experienced two environmental disturbances that appeared to impact the community and percent free space: (1) a severe winter during 2017-2018, and (2) Hurricane Florence during September 2018. ...
Article
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Ecologists employ a diverse body of theory to help explain patterns and processes in ecological systems, with the consistency of ecological theories tested against an increasingly altered world. The global redistribution of species is a prominent impact of climate change and human‐mediated biological invasions and often results in negative impacts to ecosystems. Recently, a species of colonial tunicate not previously present, Clavelina oblonga, has become prominent within the marine fouling community of Beaufort, North Carolina, USA. Fifty years ago, researchers tested theories of ecological succession developed in terrestrial systems and found that this marine community was characterized by a heterogeneous mixture of species that varied inter‐annually (i.e., multiple community states) and increased in diversity over time. A recent follow‐up study found that the fouling community is dominated by C. oblonga with patterns of community development and structure that led to the loss of alternative community states, domination by C. oblonga, and reduced species diversity. The present study addressed the question: Will patterns of community development identified over 50 yr ago still operate under reduced cover of invasive C. oblonga? This study also quantified the impacts of two large‐scale environmental disturbances (extremely cold winter and hurricane) on the abundance of C. oblonga and the resulting fouling community. Clavelina oblonga remains a dominant component of the fouling community due to its rapid growth and strong seasonal recruitment. Under conditions of reduced percent cover of C. oblonga, the local fouling community displayed unique community states that became even more distinct over time, consistent with the pattern of multiple community states identified by researchers over 50 yr ago, and that were dependent upon date of disturbance. Natural disturbances in this study caused by a harsh winter and a hurricane greatly reduced the presence of C. oblonga. This experiment advanced our understanding of marine community ecology by testing whether the concept of multiple community states identified over 50 yr ago is still operable in the absence of invasive C. oblonga, and highlights how natural environment disturbances can potentially moderate the spread of this invasive tunicate.
... En el contexto de esta tesis se sigue a White y Pickett (1985) quienes consideran apropiado usar el término perturbación, cuando se trata principalmente de acciones antrópicas y bajo el control de un experimentador. Las perturbaciones pueden ser descriptas mediante: a) la intensidad, fuerza física del evento por unidad de tiempo, por ejemplo: el calor liberado en un fuego, la potencia de una maquinaria, etc.; b) la severidad, el impacto sobre el organismo, comunidad o ecosistema, por ejemplo: la cantidad de biomasa removida y c) la frecuencia: el número de eventos por unidad de tiempo, entre otros (White y Pickett 1985). Las perturbaciones modifican el ambiente físico, por lo tanto, las respuestas de las especies incluyen el efecto del evento mismo sumado a la respuesta a los cambios ambientales que éstos producen (Facelli et al. 2005). ...
... Las perturbaciones representan una fuente importante de heterogeneidad en la estructura de las comunidades naturales por lo que, conocer el régimen con el que ocurren permitiría entender mejor su funcionamiento. En general, las perturbaciones deben ser estudiadas, teniendo en cuenta atributos como la intensidad, severidad y frecuencia, entre otros (White y Pickett 1985;Kunst et al. 2012). Las perturbaciones como el tratamiento mecánico (rolado) y el fuego, modifican el ambiente físico y producen diferentes efectos sobre la estructura aérea de los arbustos y las oportunidades para la emergencia y establecimiento de los grupos funcionales. ...
Thesis
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El incremento de la biomasa aérea, cobertura y densidad de las especies leñosas, especialmente arbustivas, en detrimento de las gramíneas y eventualmente otros grupos funcionales, es un proceso muy común en ambientes subhúmedos a áridos. La coexistencia pastos-arbustos puede ser explicada mediante distintos mecanismos ecológicos, agrupados bajo dos grandes enfoques: competencia y demografía. Los mecanismos competitivos involucran entre otros, separación de nichos por exploración radical, competencia balanceada, relaciones de competencia y facilitación, mecanismos regenerativos, efecto almacenaje. El enfoque demográfico sugiere que los disturbios gobiernan la coexistencia pastos-arbustos a través del control sobre la demografía. El objetivo de este trabajo fue comprender los mecanismos ecológicos que regulan la coexistencia pastos-arbustos en el Chaco semiárido, mediante un estudio que contempla ambos enfoques. Los experimentos se realizaron en dos sitios ecológicos en la provincia de Santiago del Estero: alto, con un bosque de dos quebrachos y bajo, dominado por sabanas de Elionurus muticus. Para estudiar el mecanismo de separación de nichos por exploración radical vertical (Hipótesis de Walter) se desarrolló un estudio descriptivo de la distribución de raíces en el perfil del suelo. Además, se realizó un ensayo de remoción de especies para analizar el tipo de interacción que ocurre entre los grupos funcionales, con los tratamientos: a) remoción de arbustos, b) remoción de pastos y c) sin remoción (control) usando un Índice de Interacción. El efecto almacenaje fue analizado mediante el estudio de la emergencia y la habilidad para rebrotar de los arbustos en respuesta a la secuencia sinérgica de dos perturbaciones: mecánica y fuego. Los principales resultados fueron: a) el patrón de distribución radical encontrado responde parcialmente a la Hipótesis de Walter, ya que existe en ambos sitios ecológicos superposición de los sistemas radicales de pastos y arbustos en el perfil del suelo; b) en el bajo prevalecerían las relaciones de competencia, mientras que en el alto las relaciones neutrales y de facilitación; c) la emergencia de las plántulas varió en función del sitio, de la intensidad del fuego y del grupo funcional y d) la habilidad rebrotadora de los arbustos estuvo condicionada por la intensidad de las perturbaciones y por la especie. Esta tesis contribuye a comprender qué mecanismos ecológicos prevalecerían entre pastos y arbustos en los sitios de bosque y sabana del Chaco semiárido, y cómo las perturbaciones (tratamiento mecánico y fuego) influyen en los procesos regenerativos. Este conocimiento permitirá explicar a futuro los cambios en la estructura de las comunidades y en las funciones ecosistémicas, con el fin de generar recomendaciones de manejo más conservativas y sustentables.
... Disturbances are events that occur at a discrete moment due to natural and/or human causes that modify the state, physical environment, or structure of an ecosystem, community, or population (Manson and Jardel, 2009;White and Pickett, 1985). Among disturbances caused by humans, land use change for agriculture or infrastructure is currently the main driver of environmental degradation in terrestrial and aquatic ecosystems (Allan et al., 2015;Castro et al., 2018). ...
... Among disturbances caused by humans, land use change for agriculture or infrastructure is currently the main driver of environmental degradation in terrestrial and aquatic ecosystems (Allan et al., 2015;Castro et al., 2018). This type of disturbance alters abiotic conditions to differing degrees depending on the frequency, intensity, and affected area (Rykiel, 1985;Schowalter, 2012;White and Pickett, 1985), the loss of vegetation cover is one example. ...
Article
Disturbance (e.g. loss of plant cover) increases ambient temperature which can be lethal for ectotherm insects especially in hot places. We compared the thorax temperatures of 26 odonate species as a function of body size, habitat quality (“conserved” and cooler vs “perturbed” and warmer) and suborder (Anisoptera vs Zygoptera), as well as critical thermal maximum (CTmax) and as a function of habitat quality in Argia pulla (Zygoptera) and Orthemis ferruginea (Anisoptera). We expected thorax temperatures to differ between suborders based on their differences in body size and habitat quality status, and that populations in perturbed sites would have higher critical thermal maxima compared to those in conserved sites. This study was done in a tropical region with high ambient temperatures. Anisopterans had a higher body temperature than zygopterans, with no difference between habitats. Thoracic and air temperature were positively related, yet body temperatures were higher than the ambient temperature. A. pulla had higher CTmax in the perturbed sites, while O. ferruginea showed the opposite trend. Microenvironmental changes increase the ambient temperature, perhaps filtering insect species. The apparent resilience of odonates to disturbance should be examined more closely (using more species), especially in small species like the zygopterans which appear to be more strongly affected by ambient temperature.
... Understanding how plant communities reassemble post-disturbance has since long been a central question in ecology (Götzenberger et al., 2012). Disturbances are discrete events that change resources or the physical environment, disrupt ecosystem structure (White & Pickett, 1985) and play a key role in the community dynamics. In the case of railways, species propagules, coming from multiple local and regional sources, may arrive at the disturbed site, interacting ecologically and adapting to the new physical environment, and potentially changing the biodiversity of the affected region (Ellis, 2018;Rutkovska et al., 2013). ...
Article
The significant portion of global terrestrial biodiversity harbored in the mountains is under increasing threat from various anthropogenic impacts. Protecting fragile mountain ecosystems requires understanding how these human disturbances affect biodiversity. As roads and railways are extended further into mountain ecosystems, understanding the long‐term impacts of this infrastructure on community composition and diversity gains urgency. We used railway corridors constructed across the mountainous landscapes of the Kashmir Himalaya from 1994‐2013 to study the effects of anthropogenic disturbance on species distributions and community dynamics. In 2014 and 2017, we collected vegetation data along thirty‐one T‐shaped transects laid perpendicular to the railway line, adopting the MIREN (Mountain Invasion Research Network) road survey methodology. Plant communities shifted significantly from 2014 to 2017, potentially because of ongoing species redistribution after railway construction, driven mainly by declines in both native and non‐native species richness, and increasing abundance of a few non‐native species, especially in areas away from the railway track. These patterns indicate an advancing succession, where initially – rare – pioneer species are replaced by increasingly dominant and often non‐native competitors, and potentially suggest a trend towards delayed local extinctions after the disturbance event. Native and non‐native species richness was negatively correlated with elevation, but that relationship diminished over time, with the abundance of non‐natives significantly increasing at higher elevations. Synthesis and applications: Transport corridors seem to facilitate the spread of non‐native species to higher elevations, which has serious implications considering the warming mountain tops. Our results indicate that the plant communities next to railways do not reach equilibrium quickly after a disturbance. More than ten years after railway establishment within Kashmir Himalaya, succession continued, and signs pointed towards a landscape increasingly dominated by non‐native species. Our study indicates that the single disturbance event associated with constructing railway in this Himalayan region had large and long‐lasting effects on plant communities at and around this transport corridor and suggests the need for a long‐term region‐wide coordinated monitoring and management program.
... land-use change, pollution and climate change) result in stressors that are altering communities characterized by high biodiversity (Reid et al., 2019). Rivers experience these human impacts alongside natural flow extremes: seasonal or unpredictable disturbances in which natural stressors such as the absence of water (during drying) and fast flows (during floods) disrupt ecosystem structure and function (White & Pickett, 1985). Rivers are thus suitable ecosystems in which to explore the concurrent, independent and interacting responses of ecological communities to human impacts and natural stressors (Gutiérrez-Cánovas et al., 2015). ...
Article
Rivers are dynamic ecosystems in which both human impacts and climate‐driven drying events are increasingly common. These anthropogenic and natural stressors interact to influence the biodiversity and functioning of river ecosystems. Disentangling ecological responses to these interacting stressors is necessary to guide management actions that support ecosystems adapting to global change. We analysed the independent and interactive effects of human impacts and natural drying on aquatic invertebrate communities—a key biotic group used to assess the health of European freshwaters. We calculated biological response metrics representing communities from 406 rivers in eight European countries: taxonomic richness, functional richness and redundancy, and two biomonitoring indices that indicate ecological status. We analysed metrics based on the whole community and a group of taxa with traits promoting resistance and/or resilience (‘high RR’) to drying. We also examined how responses vary across Europe in relation to climatic aridity. Most community metrics decreased independently in response to impacts and drying. A richness‐independent biomonitoring index (the average score per taxon; ASPT) showed particular potential for use in biomonitoring, and should be considered alongside new metrics representing high RR diversity, to promote accurate assessment of ecological status. High RR taxonomic richness responded only to impacts, not drying. However, these predictors explained little variance in richness and other high RR metrics, potentially due to low taxonomic richness. Metric responsiveness could thus be enhanced by developing region‐specific high RR groups comprising sufficient taxa with sufficiently variable impact sensitivities to indicate ecological status. Synthesis and applications. Metrics are needed to assess the ecological status of dynamic river ecosystems—including those that sometimes dry—and thus to identify priority sites requiring action to tackle the causes of environmental degradation. Our results inform recommendations guiding the development of such metrics. We propose concurrent use of richness‐independent ‘average score per taxon’ indices and metrics that characterize the richness of resistant and resilient taxa. We observed interactions between aridity, impacts and drying, highlighting that these new metrics should be region‐specific, type‐specific and adaptable, promoting their ability to inform management actions that protect biodiversity in river ecosystems responding to climate change.
... Disturbances shape patterns of environmental heterogeneity, community dynamics, and ecosystem processes on varying spatial and temporal scales and are integral to the maintenance of species diversity (White and Pickett 1985, Petraitis et al. 1989, Frelich 2002. In eastern temperate forests, small-scale, low-intensity disturbances that affect one or more canopy trees are caused by natural tree senescence, insect outbreaks, wind, and ice storms (Runkle 1985, Roberts andGilliam 2014). ...
Article
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Dispersal of ground‐dwelling arthropods is understudied in forest ecosystems, which hinders understanding of effects of disturbances on population dynamics. The objective of the study was to quantify movement of ground‐dwelling arthropods in response to a factorial combination of canopy gap formation via girdling and understory vegetation removal, which was shown in a companion study to alter arthropod abundance and species richness. Arthropod movement was quantified using a self‐mark–capture technique where arthropods were marked as they crossed three concentric bands of different colored fluorescent powders located 3, 8, and 15 m from the center of 30 × 30 m experimental quadrats. The number of colors found on an individual was considered representative of dispersal such that the more colors detected, the more an individual moved. The likelihood that arthropods were marked with fluorescent powder and the number of colors detected differed among taxonomic groups. Most taxa were marked with one color and a high proportion of those individuals were collected adjacent to the band in which they were marked, suggesting limited dispersal. Canopy gaps and understory vegetation removal influenced movement of three taxa of highly mobile arthropods: Parajulidae and Paradoxosomatidae (detritivores), and Opiliones (scavengers). Opiliones were less likely to be marked with fluorescent powder in canopy gaps than under closed canopy in July, but more likely to be marked in August. Paradoxosomatidae were less likely to be marked in canopy gaps than under closed canopy in August, but their movement was unaffected in July. Parajulidae were more likely to be marked with fluorescent powders when understory vegetation was removed in July and August. Limited dispersal of most other ground‐dwelling arthropods suggests that these more sessile taxa may experience decreased survival and reproduction if they are unable to cope with environmental change in response to natural and anthropogenic disturbances. Understanding how disturbances mediate arthropod movement can inform biodiversity conservation strategies and sustainable forest management.
... Treefall gaps or canopy openings can occur due to the death of one or more trees, which plays an important role in ecosystem functioning (Muscolo et al. 2014). According to White and Pickett (1985), disturbance is defined as "any relatively discrete event in time that disrupts ecosystem, community or population structure and changes resources, substrate availability, or the physical environment" and can play important roles in all types of natural ecosystem (Muscolo et al. 2014). The canopy gap increases habitat diversity, structural complexity, and species diversity. ...
... River biota possess adaptations that enable persistence or recovery to dynamic disturbances within lotic ecosystems (Bogan et al., 2015;Sarremejane et al., 2020). Disturbances are a natural component of most riverine environments that disrupt and modify resources, habitat availability and environmental conditions (White and Pickett, 1985). As such, community resilience can be examined by assessing the consequences for three key mechanisms: resource availability, recruitment potential and refugia provision (Van Looy et al., 2019). ...
Article
Sediment transport in mountain streams can be a major hazard to downstream infrastructure. Consequently, sediment traps are a common feature in many high gradient streams to retain large volumes of sediment and protect settlements from major sediment transport events. Despite the wide application of these instream structures, there is little knowledge regarding the environmental and ecological effects on streams. Here, we investigated the hydromorphological effects of sediment traps on instream habitats and associated macroinvertebrate communities in four impacted and three non-impacted streams in Switzerland. Sediment traps significantly disrupted the sediment regime homogenising grain size percentiles compared to the natural stepwise downstream fining in control streams. This disruption in the sediment regime resulted in finer grain size distributions upstream of the sediment trap, and reduced substrate diversity in the sediment retention basin and just downstream of the trap. The reductions in substrate diversity resulted in an altered macroinvertebrate community composition. Further, the disconnection in sediment transport led to a lack of longitudinal correlation in macroinvertebrate communities. Refugia provision downstream of the sediment trap, and resource availability within the retention basin, were diminished, potentially reducing resilience of macroinvertebrate assemblages to instream disturbances. The effects of sediment traps were most likely localised in three of the four streams with substrate diversity recovering to comparable control values within 8 wetted widths (ca. 50 m) downstream of the trap associated with natural longitudinal fining. In contrast, ecological and environmental effects propagated downstream in one impacted stream with no recovery being evident. Sediment retention basins in the impacted streams provided a local artificially unique habitat of dynamic-braided channels. Our results indicate that sediment traps can significantly disrupt the sediment regime with important consequences for instream ecology and environmental conditions, although these effects can be system specific. Further work is needed to fully understand the effects of sediment traps in mountain streams to assist resource managers in the mitigation and future construction of these structures.
... Disturbances such as hurricanes, volcanic eruptions, fires, earthquakes, tsunamis, and population explosions of consumer species such as pests vary in their frequency, intensity, and magnitude (Barbosa et al., 2012;Berenstecher et al., 2017;Hayasaka, Shimada et al., 2012;He et al., 2019;Spiller & Agrawal, 2003). Depending on the type of disturbance, the responses of biotic organisms to these events are expected to differ greatly (Walker & Willing, 1999;White & Pickett, 1985), leading the structure of communities and ecosystems to various alternative states including the recovery of predisturbance conditions (del Moral & Magússon, 2014). Thus, variations in the organismal responses are critical to understand the resilience of communities and ecosystems against natural disturbances (e.g., Dale, et al., 2005;Hayasaka, et al., 2016;Ishida, et al., 2015). ...
Article
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Volcanic eruptions are one of the largest natural disturbances and are followed by the establishment of novel plant and animal communities in terrestrial ecosystems. However, the role of pre-eruption vegetation in the establishment of arthropod communities after volcanic disturbances is currently unknown. Here, we asked whether the legacy of pre-eruption vegetation mediates the community structure of ground-dwelling arthropods after volcanic disturbances. The 2015 eruption in Kuchinoerabu-jima Island, southwest Japan, caused two types of disturbances [a pyroclastic flow and a lahar (i.e., mudflow)] in three types of forests (broad-leaved, black pine, and cedar). We hypothesized that pre-eruption vegetation would influence the community structure of ground-dwelling arthropods after the disturbance, and we expected that these effects from vegetation would be more prevalent for the less severe disturbances. The total abundance of ground-dwelling arthropods decreased more in the lahar than the pyroclastic flow, and arthropod species composition showed a greater change after the lahar. These findings suggest that the lahar disturbance was more severe than the pyroclastic disturbance. Contrary to expectations, the difference in the arthropod species composition among the vegetation types was greatest after the lahar. After the pyroclastic flow, leaf litter remained to some degree with all the vegetation types. After the lahar disturbance, however, although the litter in the cedar forests remained, the litter disappeared completely from broad-leaved and black pine forests. The disappearance of litter from these two forest types after the lahar may be responsible for the greater difference in arthropod species composition among the vegetation types. This study shows that the legacy effects of pre-eruption vegetation on terrestrial arthropod communities after volcanic disturbance were different depending on the type of disturbance. Focusing on the role of pre-eruption biotic factors would contribute to a better understanding of the recovery processes of terrestrial ecosystems after large natural disturbances.
... Because a disturbance-response framework is utilized in the conceptualization of organizational resilience, a characterization of the types of disturbances hitting the systems being studied is detailed. Disturbances, in an ecological sense, are defined as any relatively discrete event in time that disrupts ecosystem, community or population structure and changes resources, substrate availability, or the physical environment (Pickett and White, 1985). There has been a growing emphasis in socialecological systems science that complex dynamics often lead to unexpected outcomes with long-term effects. ...
Article
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This study characterizes the resilience of organizations undertaking river basin governance and recovery. The Upper Colorado River Endangered Fish Recovery Program (UCREFRP) and the Lower Colorado River Multi-Species Conservation Program (LCR-MSCP) are defined in this study as polycentric organizations nested within larger institutional mechanisms governing the Colorado River Basin. This study utilizes an environmental disturbance-organizational response framework to characterize organizational resilience—and uses attitudinal diversity (characterized by attitudes toward agendas) as the measurable metric. Environmental disturbances are defined as either press or pulse and categorized as either institutional or biophysical in nature. Four types of attitudinal diversity metrics are utilized—supportive, clarifying, conditional, and critical. Results indicate that institutional press and pulse events generated anticipatory resilience capabilities along with some adaptive capabilities for the organizations. However, the biophysical press and pulse events only reveal coping capabilities and very little adaptive capabilities. With the recent Colorado River shortage declaration, it is critical for the programs to build anticipatory as well as adaptive capabilities for optimal response to biophysical press events.
... Throughout their development, forests can be subject to a variety of perturbations, potentially resulting in modifications of their structural attributes that could change their protective effect. Natural disturbances, i.e., discrete events in time that disrupt ecosystem, community, or population structure and change resources, substrate availability, or the physical environment [5], can severely impact protection forests. Avalanches, forest fires, windstorms and landslides are some of the most common disturbances in mountain forests in the Alps, whose effects can profoundly influence stand dynamics. ...
Chapter
Protection forests can be severely affected by natural disturbances, whose consequences could greatly alter the fundamental ecosystem services they are providing. Assessing and monitoring the status of the protective effects, particularly within disturbed stands, is therefore of vital importance, with timing being a critical issue. Remote sensing technologies (e.g., satellite imagery, LiDAR, UAV) are widely available nowadays and can be effectively applied to quantify and monitor the protective effects of Alpine forests. This is especially important after abrupt changes in forest cover and structure following the occurrence of a disturbance event. In this contribution, we present a brief introduction on remote sensing technologies and their potential contribution to protection forest management, followed by two case studies. In particular, we focus on research areas within protection forests against rockfall affected by windthrow (i.e., the 2018 storm Vaia in the Eastern Italian Alps, where LiDAR and UAV data were used), and forest fires (i.e., the 2017 fall fires in the Western Italian Alps, involving Sentinel-2 image analyses).
... In ecology, a disturbance is any event "that disrupts the structure of an ecosystem, community, or population, and changes resource availability or the physical environment" (White and Pickett 1985). Disturbances can act on any parts of a system's natural cycles (e.g., Müller et al., 2002;Tylianakis et al., 2008;Jentsch and White 2019) and its supply chains (e.g., Davis 1993;Christopher and Lee 2004;Bhatnagar and Sohal 2005;Hobbs 2020), not just the points of the natural cycles and supply chains where human consumption normally occurs. ...
Article
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In this perspective paper, we raise attention to the lack of methods or data to measure claims of sustainability for bioregenerative life support system designs and propose a method for quantifying sustainability. Even though sustainability is used as a critical mission criterion for deep space exploration, there is a lack of coherence in the literature with the use of the word sustainability and the application of the criterion. We review a Generalized Resilient Design Framework for quantifying the engineered resilience of any environmental control and life support system and explain how it carries assumptions that do not fit the assumptions of sustainability that come out of environmental science. We explain bioregenerative life support system sustainability in the context of seven theoretical frameworks: a planet with soil, biogeochemical cycles, and ecosystem services provided to humans; human consumption of natural resources as loads and disturbances; supply chains as extensions of natural resources; engineering application of forced and natural cycles; bioregenerative systems as fragmented ecosystems; ecosystems as a network of consumer-resource interactions with critical factors occurring at ecosystem control points; and stability of human consumer resources. We then explain the properties of environmental stability and propose a method of quantifying resistance and resilience that are impacted by disturbances, extend this method to quantifying consistence and persistence that are impacted by feedback from loads. Finally, we propose a Terraform Sustainability Assessment Framework for normalizing the quantified sustainability properties of a bioregenerative life support system using the Earth model to control for variance.
... Previous works have studied the response of plant communities to different disturbance gradients in agroecosystems (Swanton et al., 1993;Zanin et al., 1997;Gaba et al., 2014). In this regard, weed management can be defined as a disturbance (White and Pickett, 1985), the effect of which on plant communities mainly depends on its intensity (proportion of biomass removed) and frequency (time elapsed between disturbance events) (White and Jentsch, 2001). The present study proposes a disturbance-based approach for assessing the effects of different weed management (herbicide, mowing, tillage) on taxonomic diversity. ...
Article
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Agricultural expansion and intensification is a major driver of biodiversity loss. Conventional weed management (e.g. tillage, herbicide) has encouraged the promotion of a few more competitive species over a wide range of arable plants that are now in decline. A reduction in plant diversity would negatively affect the provision of key ecosystem services in agroecosystems. In vineyards, the use of plant covers has emerged as the principal alternative to conventional weed management, providing multiple ecosystem services such as enhance biodiversity, but usually with a decrease in yields in Mediterranean vineyards. This long-term study assessed how weed management (herbicide, mowing, tillage) influenced plant community composition, taxonomic diversity and vineyard yield. Plant surveys and grape yield measurements were carried out from 2015 to 2018 in an experiment established in 2008. Effects on plant community composition were analysed, focusing on two groups: noxious grapevine weeds and terophytic grassland species. In addition, three fundamental components of taxonomic diversity were measured: β-diversity, evenness and species richness. Linear mixed models and generalised linear mixed model were used to examine the response of different variables to weed management. Position (row, inter-row) as well as the indirect effect of adjacent management on the subplots were also included as fixed factors. Furthermore, the percentage of bare soil, related to disturbance degree associated with management , was explored as a potential predictor of taxonomic diversity and vineyard yield. Results indicated that plant community composition was affected by weed management and to a lesser extent by position. Noxious grapevine weeds were more abundant in herbicide-sprayed rows, while terophytic grasslands species showed a higher presence in mown subplots. Weed management had a strong effect on bare soil, which proved to be a good predictor of the variables studied. Indeed, the highest species richness were associated with the lowest percentages of bare soil (mown subplots), while the lowest values were found at high percentages of bare soil (tilled subplots). Herbicide showed intermediate values, with a response dependent on adjacent management. On the other hand, vineyard yields were higher with increased bare soil, although with the consequent loss of species richness. Conversely, mowing in spontaneous plant covers caused a decrease in yield, but still production was within the maximum limit established by the Regulatory Council, while increasing the species richness and a significant presence of therophytic grasslands species. These findings could foster the development of more sustainable management in Mediterranean vineyards.
... Hence, there is an urgent need to strictly protect the last remnants of pristine forests and segregate them from demands of other forest functions, a call clearly expressed in the recent EU Biodiversity strategy (European Commission 2020; Sabatini et al. 2020). These forests are characterised by habitat continuity, shaped by long-term successional processes, and modulated by periodic natural disturbances (White and Pickett 1985;Attiwill 1994;Korpel 1995). Large old-growth and pristine forests can contain structurally complex stands with notable amounts of deadwood and large giant trees with plenty of microhabitats, and thus, a high variety of saproxylic species (e.g. ...
... The habitat transformation and disturbance have significant threat to biodiversity. The disturbances was known as any event that remove the biomass [1], and reducing the available resources or changing the microclimate or structure of the habitat [2,3,4]. The previous studies have examined the effect of urbanization on biodiversity [5, 6,7,8,9,10,11] and implicate urbanization as the major threat to biodiversity. ...
... While such models have been developed for many ecological interactions (competition, predation, etc.), extensive attention has been dedicated to understanding how disturbances influence biological systems. A disturbance is defined as a discrete event in space and time that alters resources, substrata, or the physical environment, consequently disrupting community or population structure (Petraitis et al., 1989;White and Pickett, 1985). Despite what we now know about the importance of disturbances in structuring ecosystems, early models attempting to understand the dynamics of biological systems focused upon equilibrium conditions. ...
Article
On the northern coast of British Columbia, Canada, we used the infaunal invertebrate community (meiofauna) of the Cassiar Cannery mudflat to assess responses to different severities of a mechanical disturbance. Overall, the infaunal community was effective in identifying if a disturbance had occurred, regardless of disturbance severity. However, considerable overlap was observed between infaunal communities in disturbed and reference habitat. Variation between disturbed and reference habitats was primarily the result of differences in the relative abundances of five taxa (Oligochaeta, Nematoda, Nippoleucon hinumensis, Capitella species complex, and Macoma balthica). Conversely, the infaunal community was not an effective tool in differentiating between disturbance severities, likely because of the subtle differences observed between infaunal successional stages. We also assessed how increasing misalignment of spatial resolution between sampling and disturbance scales influenced analytical findings. As misalignment between the scale of disturbance and investigation increased, Type I and Type II errors became more common in our analyses. Our findings indicate that intertidal infaunal communities can be effectively used to study the influence of disturbances upon an ecological system. However, care must be taken to ensure the proper sampling scheme is used, one that overlaps with the scale of disturbance. These findings expand our understanding of how communities respond to disturbance and will be of interest to anyone attempting to study, detect, or mediate anthropogenic and natural disturbances.
... Gaps can play an essential role in forest dynamics (White and Pickett 1985;Löf et al. 2018), notably in the eastern mixed boreal forests of North America, where small-scale canopy openings of various shapes and sizes have a prominent part in regeneration dynamics in the absence of large-scale disturbances (de Römer et al. 2007;Pham et al. 2004). Gap dynamics are, however, not the only factor determining species composition in forests (de Römer et al. 2007), and a focus solely on gap dynamics disregards the processes influencing within-gap regeneration, such as consumption by herbivores (Kuijper et al. 2009;Nuttle et al. 2013), notably by ungulates (Kern et al. 2017;Krueger et al. 2009;Royo et al. 2010). ...
Article
Gap dynamics play a crucial role in forest regeneration by creating favourable regeneration and survival niches for some plant species. Nonetheless, potentially overriding factors, such as ungulate browsing, could limit or eliminate this gap dynamic–related regeneration. The deleterious effects of browsing may be exacerbated for slow-growing species such as northern white cedar (Thuja occidentalis L.), a tree highly selected by white-tailed deer (Odocoileus virginianus Zimmerman). We therefore aimed to understand how deer browsing and gap dynamics interact to affect cedar regeneration and hypothesized that cedar regeneration benefits from natural gaps but that deer browsing could override this effect. We inventoried natural canopy gaps along a spatiotemporal gradient of deer habitat use. We evaluated cedar regeneration abundance, tree height, and various gap, stand, and competition metrics. We found that deer browsing pressure greatly limited cedar regeneration; however, when deer populations decreased, cedar regeneration abundance increased within a decade, even after prolonged browsing pressure, and increased further over time. Our study illustrates that cedar regeneration can be favoured by gap creation and deer population control.
... Disturbance can be defined as any relatively discrete event in time that disrupts the ecosystem or physical environment (White & Pickett, 1985). The disturbance regime is the spatial pattern and statistical distribution of events with respect to magnitude, frequency, and duration (Montgomery, 1999). ...
Article
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Floodplains perform diverse functions, including attenuation of fluxes of water, solutes, and particulate material. Critical details of floodplain storage including magnitude, duration, and spatial distribution are strongly influenced by floodplain biogeochemical processes and biotic communities. Floodplain storage of diverse materials can be conceptualized in the form of a budget that quantifies inputs, outputs, and storage within the floodplain control volume. The floodplain control volume is here defined as bounded on the inner edges by the banks of the active channel(s), on the outer edges by the limit of periodic flooding and the deposition of fluvially transported sediment, on the underside by the extent of hyporheic exchange flows and the floodplain aquifer, and on the upper side by the upper elevation of living vegetation. Fluxes within the floodplain control volume can also change the location, characteristics, and residence time of material in storage. Fluxes, residence time, and quantities of material stored in floodplains can be measured directly; inferred from diverse types of remotely sensed data; or quantitatively estimated using numerical models. Human activities can modify floodplain storage by: hydrologically and/or geomorphically disconnecting channels and floodplains; altering fluxes of water and sediment to the river corridor; and obliterating floodplains through alluvial mining or urbanization. Floodplain restoration can focus on enlarging the functional floodplain, reconnecting the channel and floodplain, restoring natural regimes of water, sediment, and/or large wood, or enhancing the spatial heterogeneity of the channel and floodplain. Each form of floodplain restoration can increase floodplain storage and resilience to disturbances.
... For example, disturbance can be considered as a discrete event where at least one canopy tree is killed (Runkle, 1985). Irrespective of the deGnition used, disturbance is usually a complex interaction between biotic and abiotic factors, can be endogenous or exogenous, and can occur at a variety of temporal and spatial scales (Van Miegroet, 1979;White and Pickett, 1985;Peterken, 1993;Lundquist, 1995;Rogers, 1996; Quine gf a/., 1999; Clinton and Baker, 2000; Sommerfeld ef a/., 2000). The global climate is strongly influenced by the global carbon cycle which results from the flux of carbon between four main carbon stores: fossil carbon, the atmosphere, terrestrial biosphere and the oceans (Schimel, 1995;IPCC, 2000). ...
Thesis
p>This thesis evaluates the potential of fine (<5 m) spatial resolution remotely sensed data and alternative classification methods to characterise windthrown gaps. The study site was Cwm Berwyn Forest, in central Wales, a planted forest of predominantly Sitka spruce ( Picea sitchensis (Bong.) Carr.) containing windthrown gaps ranging in size from 50 to 3000 m<sup>2</sup>. The remotely sensed data used were acquired by an 11 waveband airborne thematic mapper (ATM) sensor with a spatial resolution of � 4m. This spatial resolution is finer than the windthrown gaps on the site and comparable to that of future satellite sensors. A thematic map depicting land cover was produced using a conventional maximum-likelihood classification of the ATM data and provided an accurate representation of the land cover (> 90% of the pixels allocated correctly). This hard classification was also softened to output typicality and posterior class membership probabilities. The results indicated that the hard classification provided an accurate means of identifying windthrown gaps (>95% of known gaps identified) and was capable of identifying a greater number of gaps, than manual interpretation of temporally coincident aerial photographs. Estimates of windthrown gap area, perimeter and shape were derived from the hard and softened classifications. The results indicated the potential to derive more accurate spatial representations of windthrown gaps than a conventional hard classification, by softening the output to derive typicality class membership probabilities. However, the major contribution of the research within this thesis to previous work on windthrown gap formation and progression, is the potential to use rate of change of typicality and posterior class membership probabilities to derive information on various windthrown gap properties, such as exposed soil and living windthrown tree canopies.</p
... Disturbances play a fundamental role in forest dynamics and in combination with environmental factors, they shape forest ecosystems, particularly spatial and age structures, quantity of biomass, species composition, and overall biodiversity (White and Pickett, 1985). Historically, complex mixed-severity disturbance regimes have prevailed in European mountain forest ecosystems (Seidl et al. 2011a, Meigs et al. 2017, Kulakowski et al. 2017. ...
Article
Development of primary spruce forests is driven by a series of disturbances, which also have an important influence on the understorey vegetation and its diversity. Early post-disturbance processes have been intensively studied, however, very little is known about the long-term effects of disturbances on the understorey. We quantified disturbance history using dendrochronological methods to investigate its impact on vascular plant diversity and understorey species composition. We sampled 141 plots randomly assigned throughout primary stands located in the zone of natural montane acidophilous forests dominated by Picea abies (L.) Karst. in the Western Carpathians. Dendrochronological, dendrometric, and environmental parameters were related to understorey properties using ordination methods and a Bayesian approach using multilevel linear models (GLMM). Time since the last disturbance (23–260 years ago; mostly windstorms and bark beetle outbreaks) had a significant effect on understorey species composition of the current communities, and it also interacted with disturbance severity to influence species diversity. The effect of disturbances on the understorey was largely mediated by the alteration of stand structure (age, DBH, canopy openness), Vaccinium myrtillus L. cover, and topsoil chemical properties. A period of severe disturbances between 1860 and 1890 resulted in a legacy of our current, relatively homogeneous spruce stands with less diverse sciophilous understorey dominated by V. myrtillus, which is in contrast to heterogeneous stands (in terms of age and spatial structure) driven by small-scale, lower-severity disturbances, which led to an understorey enriched by species with higher demands on light and topsoil quality (higher K concentration and lower C/N ratio). All developmental pathways following disturbances create a unique complex of spatiotemporal understorey variability in the montane spruce forests. Therefore, to preserve their full diversity, disturbances of all severities and sizes should be accepted as natural drivers, both in the field of nature conservation and close-to-nature forestry efforts.
... Here we conduct a thought experiment using forest gaps to illustrate how temporally variable resistance could prevent the reliable detection of passive directed dispersal. Canopy gaps are simultaneously resource-rich destinations for vertebrate vectors, locations with disproportionately high seed rain, and favourable environments for establishing plants (Thompson & Willson, 1978;White & Pickett, 1985;Blake & Hoppes, 1986;Hoppes, 1988;Malmborg & Willson, 1988;Denslow & Gomez Diaz, 1990;Armesto et al., 2001;Reynolds-Hogland, Mitchell & Powell, 2006; (*) examples of passive directed dispersal derived from our synthesis. Passive directed dispersal likely occurs because (i) vector resource tracking is associated with favourable microsites for propagules, or (ii) predictable animal behaviour, often associated with resource tracking, creates favourable microsite conditions before or during plant dispersal. ...
Article
Conceptual gaps and imprecise terms and definitions may obscure the breadth of plant–animal dispersal relationships involved in directed dispersal. The term ‘directed’ indicates predictable delivery to favourable microsites. However, directed dispersal was initially considered uncommon in diffuse mutualisms (i.e. those involving many species), partly because plants rarely influence post‐removal propagule fate without specialized adaptations. This rationale implies that donor plants play an active role in directed dispersal by manipulating vector behaviour after propagule removal. However, even in most classic examples of directed dispersal, participating plants do not influence animal behaviour after propagule removal. Instead, such plants may take advantage of vector attraction to favourable plant microsites, indicating a need to expand upon current interpretations of directed dispersal. We contend that directed dispersal can emerge whenever propagules are disproportionately delivered to favourable microsites as a result of predictably skewed vector behaviour. Thus, we propose distinguishing active and passive forms of directed dispersal. In active directed dispersal, the donor plant achieves disproportionate arrival to favourable microsites by influencing vector behaviour after propagule removal. By contrast, passive directed dispersal occurs when the donor plant takes advantage of vector behaviour to arrive at favourable microsites. Whereas predictable post‐removal vector behaviour is dictated by characteristics of the donor plant in active directed dispersal, characteristics of the destination dictate predictable post‐removal vector behaviour in passive directed dispersal. Importantly, this passive form of directed dispersal may emerge in more plant–animal dispersal relationships because specialized adaptations in donor plants that influence post‐removal vector behaviour are not required. We explore the occurrence and consequences of passive directed dispersal using the unifying generalized gravity model of dispersal. This model successfully describes vectored dispersal by incorporating the influence of the environment (i.e. attractiveness of microsites) on vector movement. When applying gravity models to dispersal, the three components of Newton's gravity equation (i.e. gravitational force, object mass, and distance between centres of mass) become analogous to propagules moving towards a location based on characteristics of the donor plant, the destination, and relocation processes. The generalized gravity model predicts passive directed dispersal in plant–animal dispersal relationships when (i) animal vectors are predictably attracted to specific destinations, (ii) animal vectors disproportionately disperse propagules to those destinations, and (iii) those destinations are also favourable microsites for the dispersed plants. Our literature search produced evidence for these three conditions broadly, and we identified 13 distinct scenarios where passive directed dispersal likely occurs because vector behaviour is predictably skewed towards favourable microsites. We discuss the wide applicability of passive directed dispersal to plant–animal mutualisms and provide new insights into the vulnerability of those mutualisms to global change.
... Une perturbation est définie ici comme «... tout événement discret dans le temps qui perturbe la structure de l'écosystème, de la communauté ou de la population et modifie les ressources, la disponibilité du substrat ou l'environnement physique » (White and Pickett 1985). Une particularité du champs cultivé est que le régime de perturbation est à la fois diversifié avec des perturbations de différentes nature (chimique, physique) et cyclique avec le retour régulier de la même culture et des perturbations associées au cours de la rotation (Kropáč et al. 1971). ...
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Une question fondamentale en écologie est de comprendre pourquoi certaines espèces sont abondantes et largement distribuées quand d’autres sont rares et ont une distribution limitée. Nos travaux de recherche ont décliné cette question à travers deux modèles d’études : i) comment expliquer le succès versus l’échec de plantes non-indigènes introduites sur un nouveau territoire, ii) comment expliquer la progression versus la régression d’espèces dans les agro-écosystèmes soumis à des changements de régime de perturbations. A l’échelle régionale, la modélisation de la niche climatique des espèces non-indigènes, combinée avec leurs préférences d’habitats permet d’aboutir à une cartographie de distribution composite qui peut éclairer sur l’étendue du risque représentée par une espèce. La résolution à cette échelle de travail ne permet pas d’intégrer l’effet des interactions biotiques. Cela nécessite de passer à l’échelle du paysage, à laquelle nos travaux montrent qu’il est possible d’identifier le poids des filtres de dispersion, abiotiques et biotiques et par conséquent les conditions dans lesquelles un site est vulnérable aux invasions. A titre d’exemple nous montrons que Humulus scandens représente un risque sur les berges de rivière combinant une fertilité élevé ([N]> 1 g/kg), une végétation pérenne faible au printemps (<25% sur 4m²) et une canopée arborée inférieure à 35%. Quand ces conditions sont réunies, s’il paraît évident que des peuplements denses peuvent avoir des impacts sur les écosystèmes colonisés, il reste à savoir dans quelle mesure on peut prédire ces impacts. Nos travaux ont montré que la magnitude des impacts des plantes non-indigènes est extrêmement variable entre espèces mais peut en partie s’expliquer par les traits des espèces non-indigènes, leur taux de couverture, le type d’habitat colonisé et les conditions abiotiques et biotiques des sites colonisés. Nous avons mis en évidence l’existence de seuils d’impacts avec un niveau de couverture au-delà duquel l’augmentation du taux de couverture de l’espèce invasive conduit à une diminution plus rapide des indices de structure ou de diversité des communautés résidentes. Les traits de la communauté envahie permettent également de mieux comprendre les mécanismes de coexistence des espèces. Nous avons mis en évidence un exemple où les espèces résidentes se maintiennent d’autant mieux en présence de l’espèce invasive présente qu’elles ont des traits fonctionnels différents. Dans les champs cultivés, nous avons montré que le climat puis le sol déterminent le pool local d’espèces présent dans une parcelle cultivée. Le type de culture, suivant sa date de mise en place, filtre ensuite de façon plus forte la composition et la diversité des communautés observées une année donnée. Les variations d’abondance des espèces et la richesse de la communauté sont également déterminées par l’intensité de gestion et la capacité de recolonisation depuis le paysage environnant. A plus long terme, l’intensification des pratiques depuis les années 1970 se traduit par des communautés plus nitrophiles et plus pauvres, en réponse à la fertilisation accrue et à l’intensité du désherbage chimique. Ces tendances se retrouvent jusque dans les bordures de champs, ce qui montre l’existence d’effets non-intentionnels des pratiques agricoles. Dans l’ensemble, nos travaux montrent donc l’intérêt d’utiliser les approches fonctionnelles pour éclairer les mécanismes sous-jacents aux changements de végétation mais aussi l’intérêt de mesures répétées dans le temps (approches diachroniques) pour identifier les règles d’assemblage. Je souhaite développer des travaux à l’échelle macro-écologique en combinant les données françaises sur les communautés adventices à des données européennes similaires pour mieux comprendre les déterminants des différentes composantes de l’abondance des espèces (abondance régionale, abondance locale, spécialisation écologique) et améliorer les prédictions sur les adventices potentielles dans différents systèmes de cultures. Dans le domaine de l’écologie des invasions, je souhaite également valoriser les données sur le succès des espèces non-indigènes en lien avec leurs traits à des échelles plus larges. Parallèlement à cette extension de l’échelle, je souhaite mieux prendre en compte la variabilité intraspécifique des traits en travaillant à une échelle plus fine où il est possible de manipuler les communautés.
... So, which are the strictly geographical factors of influence regarding the condition of equilibrium? To answer this question, it is necessary to particularize the expression (1) always according to an ecosystem model [52][53][54][55] which shows a variation of the natural resource as a function proportional to the resource itself through the growth coefficient T , and inversely proportional to the square of the resource according to a competition coefficient (C) on the resource itself, in the specific case dictated by energy motivations by Ethiopia, as shown in (5): ...
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This paper examines the transboundary water resources conflict resolution mechanisms. Although different research perspectives, including social planner, water market, game theory, static and dynamic systems engineering model, have already provided conflict resolution mechanisms that could be used to analyze transboundary water conflicts, here an ecosystemic approach based on an analytical model, is proposed. For this aim the case of GERD "Grand Ethiopian Renaissance Dam" on Nile Azzurro, is analyzed. The scenario of the GERD dam, besides being current and interesting in the water dispute between Egypt, Sudan and Ethiopia, is suitable for the application of the proposed analytical model. This model could permit researchers and practitioners to develop more comprehensive mechanisms, complementary to political strategies, with stronger analytical capacity to analyze the different elements of the process of transboundary water dispute resolution.
... Damage to the forest ecosystems can result from high wind, tidal surge, and torrential rains, negatively affecting understory species through alterations to forest floor environmental conditions Walker 1991, Gresham et al. 1991). Severe disturbances may alter the trajectory of community succession (Connell andSlatyer 1977, White andPickett 1985). Disruption to the canopy can alter the microhabitat of the forest floor, impacting species survivorship, population demography, and community development (Smith et al. 1997, Conner et al. 2005. ...
Article
Hurricane Hugo was a category five storm in September of 1989 that significantly impacted natural areas along the Carolina coastal plain through wind damage and storm surge flooding. Francis Beidler Forest, an Audubon wildlife sanctuary in Four Holes Swamp, suffered severe damage to its forest canopy. In response to concerns that the rare spring ephemeral Trillium pusillum var. pusillum may be negatively impacted by the loss of the mixed hardwood canopy, we established permanent plots in the spring of 1990 with single leaf, triple leaf, and flowering individuals recorded by Ecology faculty and students at The Citadel. Disruption to the forest canopy would significantly alter forest floor microhabitat conditions negatively affecting T. pusillum var. pusillum population demography. There was no expected negative effect of Hurricane Hugo, and the loss of canopy cover on the population. Evidence suggests that the decrease in canopy cover and increased light was associated with increased flowering. The coefficient of variation, as a measure of cohort variability among years, increased from flowering, to triple leaf, to single leaf across the 29 years of population monitoring. There was a significant positive association between the number of named storms in the previous two and three years and the number of single leaf plants. There was no evidence that the population is decreasing, even though the number of flowering individuals has decreased. The results of this long-term demography suggest that even severe natural disturbances, like hurricanes and tropical storms, may have a positive effect on Trillium population dynamics.
... Disturbances are responsible for the sudden loss of biomass or structure of an ecosystem but create opportunities for establishment by altering the resources or the physical environment, in addition to initiating and modifying succession. Organisms have complex responses that impact biodiversity [2,[166][167][168]. The time scale is important, and influences the interpretation of these previous conditions. ...
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The study of ecological succession to determine how plant communities re-assemble after a natural or anthropogenic disturbance has always been an important topic in ecology. The understanding of these processes forms part of the new theories of community assembly and species coexistence, and is attracting attention in a context of expanding human impacts. Specifically, new successional studies provide answers to different mechanisms of community assemblage, and aim to define the importance of deterministic or stochastic processes in the succession dynamic. Biotic limits, which depend directly on biodiversity (i.e., species competition), and abiotic filtering, which depends on the environment, become particularly important when they are exceeded, making the succession process more complicated to reach the previous disturbance stage. Plant functional traits (PFTs) are used in secondary succession studies to establish differences between abandonment stages or to compare types of vegetation or flora, and are more closely related to the functioning of plant communities. Dispersal limitation is a PFT considered an important process from a stochastic point of view because it is related to the establishing of plants. Related to it the soil seed bank plays an important role in secondary succession because it is essential for ecosystem functioning. Soil compounds and microbial community are important variables to take into account when studying any succession stage. Chronosequence is the best way to study the whole process at different time scales. Finally, our objective in this review is to show how past studies and new insights are being incorporated into the basis of classic succession. To further explore this subject we have chosen old-field recovery as an example of how a number of different plant communities, including annual and perennial grasslands and shrublands, play an important role in secondary succession.
... Natural and human disturbances can be defined as relatively discrete events in time that disrupt the ecosystem and cause pronounced changes in resource availability or the physical environment (White & Pickett 1985, Attiwill 1994, and they are a major driver of forest community dynamics (Goldblum & Rigg 2010). Although highly variable in space and time, disturbances can have a lasting effect on forests and are increasingly affecting forest management (Seidl et al. 2011a, Grecs & Kolšek 2017, Danneyrolles et al. 2019. ...
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Kutnar L., Kermavnar J., Pintar A.M., 2021. Climate change and disturbances will shape future temperate forests in the transition zone between Central and SE Europe. Ann. For. Res. 64(2): 67-86. Abstract It is expected that climate change as well as abiotic and anthropogenic disturbances will strongly influence temperate forests. Besides changes in the main climate variables, various disturbance factors may significantly worsen conditions for mesic Slovenian forests (SE Europe) dominated by European beech (Fagus sylvatica), Norway spruce (Picea abies) and European silver fir (Abies alba). In Slovenia, the climate has warmed in recent decades, with an average annual rate of increase of about 0.4°C per decade or even more than 0.5°C per decade in summer. In addition, disturbances have caused considerable damage to trees in the most extensive forest types in Slovenia, starting with a widespread ice storm in 2014, followed by bark beetle outbreaks, windthrows and salvage logging interventions. After 2014, salvage logging increased from about one third to two thirds of the total annual felling. Over the last two decades, we have observed a decline in Norway spruce growing stock, with the highest rate of decrease in areas below 500 m a.s.l., and an increasing trend for European beech. Overall, the three dominant species (beech, spruce, silver fir), which together account for more than 70% of the total growing stock, have shown a declining trend over the last 20 years. The patterns observed are broadly consistent with earlier predictions developed for different climate change scenarios and with those reported in many other European countries. Adaptive forest management, which implements close-to-nature silviculture, has been traditionally practised in the region under study and has the potential to play an important role in reducing the risks associated with the impacts of climate change and disturbances in the future.
... El seguimiento a la sucesión de los bosques Andinos, de manera posterior a procesos de perturbación, es fundamental, para conocer la resiliencia de estos ecosistemas y su ecología. Este proceso responde a un reemplazo en la estructura, la composición taxonómica y los procesos funcionales que, a través del tiempo, generan un estado del ecosistema previo al disturbio, o bien, estados alternativos (Pickett & White, 1985;Whitmore, 1998;Morin, 2011). El estudio de esta dinámica es una herramienta eficaz en restauración de comunidades de plantas, puesto que resulta determinante en el ensamblaje de la estructura y el funcionamiento de los ecosistemas ( El presente estudio, se enmarca en determinar la composición y la estructura de tres parcelas de vegetación secundaria, correspondiente al ecosistema de bosque Andino, ubicado en el municipio de Chipaque (Cundinamarca), caracterizado por procesos de disturbios, asociados al pastoreo y la agricultura. ...
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The forests of the Andes are large reservoirs of biodiversity and endemism and constitute a priority land ecoregion worldwide. However, the loss and degradation of habitats caused by conflicts of use has generated irreparable consequences for the quality of the supply of resources and services of these ecosystems, being one of the main threats to their conservation. To counteract this situation, an eventual alternative lies in studying the ecological succession of secondary forests in order to know the ecology and assembly of plant communities, and thus, favor decision-making regarding the restoration of these ecosystems. In this study, the composition and structure of the secondary vegetation of the Andean Forest located in the municipality of Chipaque was analyzed. Two plots of 0.1ha and one of 0.05ha were established in homogeneous vegetation fragments; physiognomic variables were recorded for seedling, saplings and poles. There were 523 individuals distributed in 48 species, 36 genera and 25 families; the diversity indices showed three different plant communities with low dominance of species and high diversity of taxa. The densities of individuals for diameter classes and heights showed a tendency to positive asymmetric distribution, showing an active regeneration; the Value of Significance Index indicated the species Clusia multiflora and Centronia brachycera with greater ecological representativeness. The floristic heterogeneity found provides strategic scientific knowledge to explore different alternatives of propagation and introduction of native species in restoration processes in degraded areas of the region.
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Vulnerability can measure an ecosystem’s susceptibility to change as a result of pressure or disturbance, but can be difficult to quantify. Reconstructions of past climate using paleolimnological methods can create a baseline to calibrate future projections of vulnerability, which can improve ecosystem management and conservation plans. Here, we conduct a systematic map to analyze the range and extent that paleolimnological published studies incorporated the concept of vulnerability. Additional themes of monitoring, management, conservation, restoration, or ecological integrity were also included. A total of 52 relevant unique articles were found, a majority of which were conducted in Europe or North America since 2011. Common themes identified included management and adaptation, with the latter heavily focussed on climate change or disturbance. From this, we can infer that the use of paleolimnology to discuss the concept of vulnerability is an emerging field. We argue that paleolimnology plays a valid role in the reconstruction of ecosystem vulnerability due to its capacity to broaden the scope of long-term monitoring, as well as its potential to help establish management and restoration plans. The use of paleolimnology in vulnerability analysis will provide a clearer lens of changes over time; therefore, it should be frequently implemented as a tool for vulnerability assessment.
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Drought is a hydrological disturbance, predicted to aggravate in a climate change scenario. It causes habitat loss and fragmentation for aquatic organisms, including benthic fauna. The hydrological disturbance is an environmental filter, retaining only taxa possessing suitable traits for survival. Here a trait-based perspective was used to study the benthic macroinvertebrate assemblage in a seasonal wetland subjected to hydrological disturbance. Maranchery Kole wetland (a part of the Ramsar site Vembanad Kole wetland), was unusually transformed into a terrestrial landscape with discrete aquatic patches. Benthic macroinvertebrates were collected from aquatic patches. 55 categories of 10 biological traits, which could be assigned across the benthic genus were defined from literature. To delineate the faunal groups with similar trait assembly, the taxa by trait data matrix was subjected to Gower's distance‐based hierarchical agglomerative cluster analysis. Benthic macroinvertebrates belonged to 23 genera from 8 families, 4 orders, 2 classes, and 2 phyla. Their predominant traits were small body size, short life cycle duration, multivoltine life cycle, aquatic larval stage, aerial active dispersal, cocoons as resistant form, locomotion by crawling, tegumental respiration, asexual reproduction, and deposit-feeding. Traits-based classification of taxa resulted in 4 clusters. In each cluster, unique trait combinations ensured the survival of taxa. Group a persisted through desiccation resistant forms and proliferated through asexual reproduction using resource dominance strategy. Groups b and c, without desiccation resistant forms, used active aerial dispersal to colonize the aquatic patches. Group d was tolerant to unfavorable environments including morphological adaptations. Since the active dispersal trait facilitated active habitat selection in groups b and c, their presence was occasional. Groups a and d were incapable of active habitat selection due to passive dispersal traits, ensuing in their persistence throughout the study period.
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The links between Environmental Change (EC), seen as a destabilizing interference in the ecosystems’ equilibrium, on the one hand, and the outbreak of violent conflicts, on the other, remain ambiguous and very complex. Till now, there is a gap in the researches that focus on the intersections between EC and human security based on Land Use/Land Cover (LU/LC) changes. Therefore, this study will examine the interplay between environmental factors, LU/LC, and conflict in South Kordofan of Sudan. Satellite data and high-resolution Digital Elevation Model (DEM) were used to address the LC changes in the study area over the past three decades (1984–2014). Furthermore, household survey, group discussions and key informants techniques were applied. The qualitative and quantitative techniques were used to analyze the socio-economic data. Geographic Object-Based Image Analysis (GEOBIA) based on a developed model of integrated multi-features was utilized. The study showed that the pressures imposed resulted in the complex of spatial and temporal interactions within topographical systems at South Kordofan, where it has led both to a new rapidity and depth in rural transformation and a significant impact on urban areas as well. More information exchange is needed to inform actors and decision makers regarding capacity gaps and knowledge to address the EC.
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In this research project, we investigated relationships between species and ecosystems associated with wilderness areas in Germany, as defined by the German National Strategy for Biodiversity. Guiding research questions were: 1) Which species and biocoenosis rely on wilderness-related ecosystem characteristics and processes?, 2) How can these species (animals, plants, fungi) be classified to species groups based on wilderness-related criteria?, 3) Which flagship, umbrella, and keystone species can be identified in this context?, 4) Which characteristics of wilderness areas are necessary to provide favourable habitats for wilderness-typic species groups?, and 5) Which natural factors, including disturbance regimes, promote habitat characteristics in wilderness areas, on which these species and biocoenosis are dependent? We classified over 635 plants, 1,435 animal, and 44 fungi based on 50 wilderness-related criteria into obligatory species (species dependent on wilderness, class A), facultative species (species promoted by wilderness or wilderness-related processes, class B), and other species (species that have their core distribution in habitats of cultural landscapes and are not related to wilderness, class C). As one result, we identified five ecological species groups, for example species of open habitats in coastal and river landscapes that have a regular disturbance regime. Most animals and fungi rely on old-growth forests with high amounts of deadwood, while most plants associated with wilderness were are related to bogs and dynamic riparian ecosystems. These and the other results of the project will support the future selection of suitable areas for wilderness development in otherwise human-dominated landscapes in Europe.
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Dinámica del establecimiento de regeneración natural de pinos nativos en el altiplano occidental de Guatemala. Evaluación de la distancia del establecimiento de regeneración a partir de fuentes semilleras en bordes y claros de bosque nativo. Genera información útil para definir criterios de tratamientos silviculturales para las especies de Pinus oocarpa, P. tecunumanii y P. pseudostrubus.
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Los bosques nativos brindan una amplia variedad de bienes y servicios ecosistémicos, otorgando oportunidades sociales y económicas, por lo que es necesario desarrollar una silvicultura integrada que responda a tales fines, por ejemplo, producción maderera, no maderera y conservación. En este Capítulo se presentan propuestas y estrategias para mejorar la implementación del manejo sostenible de los bosques nativos en la Argentina, basadas en el actual desarrollo del conocimiento de la silvicultura, tomando como base al manejo adaptativo, el agregado de valor a los productos obtenidos del bosque, y la necesidad de la restauración de los bosques nativos para recuperar potencialidades perdidas. Asimismo, se plantean los principales desafíos para los próximos años como el manejo multipropósito a distintas escalas del paisaje, la adaptación del manejo silvícola a las modificaciones del clima, y la implementación de indicadores y sistemas de monitoreo. Por último, se presenta en forma sintética las principales recomendaciones sobre la silvicultura y manejo del bosque nativo para los tomadores de decisiones de las diferentes regiones forestales del país.
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Catastrophic wind disturbances under climatic changes are causing major economic impacts and ecological changes that can persist for decades. Bark beetle (Coleoptera: Curculionidae) population and community dynamics are often linked to such wind disturbances at several spatial and temporal scales ranging from damage to individual trees to large-scale windthrow that may prompt multiyear outbreaks on the landscape scale. In this chapter, we discuss how catastrophic wind disturbances and ensuing biological legacies enhance bark beetle populations, particularly in the context of climatic changes. The high level of variability at the tree, stand, and landscape levels created by windstorms generally has positive consequences for eruptive bark beetle species, particularly in Europe. Poststorm timber salvaging to alleviate pest burdens may push biotic elements, especially those dependent on coarse woody debris and forest gaps, into different successional pathways. Climate change is undoubtedly influencing the interactions between these two major disturbance agents by increasing their intensity and severity levels and altering landscape characteristics with feedback loops. In the Anthropocene, predictive modeling of network interactions between multiple abiotic and biotic disturbances and stressors will be critical for effective mitigation, forest restoration, and sustainable forestry practices in a rapidly changing world.
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Postglacial climate change and changing disturbance regimes have shaped the vegetation composition in the forest-steppe ecotone in northern Patagonia (Argentina and Chile; lat. 40°‒lat. 43°S). Several investigations between 41° and 43°S document shifts in the position of the forest-steppe ecotone and the population expansion of the cypress Austrocedrus chilensis, while little is known about the vegetation dynamic of Nothofagus alpina and Nothofagus obliqua within the Lácar basin. With the aim to contribute to this respect, the sediments of a small lake within a dense Nothofagus forest, in the Lanín National Park were collected and analysed in high resolution for pollen charcoal and sediment composition. Additionally, this work assessed the role of natural disturbance on vegetation composition. Results document the environmental history for the last 11,600 years. The record indicates high fire activity during the early Holocene, associated with dry conditions and the presence of a diverse Nothofagus shrubland. The middle Holocene starts with increased percentage of Cupressaceae pollen (up to 15%) which drops following the dominance of Nothofagus associated with wet conditions and low fire frequency. The late Holocene is marked by the rise in the abundance of N. obliqua and N. alpina, documenting the spread and increased importance of these trees within the Lácar basin during the last two millennia. A statistically significant effect of ash deposition on overall vegetation composition could not be detected, while Hydrangea and Lomatia hirsuta seem to benefit from ash fall. Fire affected stands of A. chilensis and N. obliqua/N. alpina, but climate was likely the dominant factor controlling average vegetation composition. Recent anthropogenic disturbance is noticeable by the presence of introduced taxa Rumex, Plantago and Pinus, and by the decrease in the percentage of Nothofagus obliqua-type, associated to extensive timber activities around the Lácar basin.
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Streams are ecosystems organized by disturbance. One of the most frequent and variable disturbances in running waters is elevated flow. Yet, we still have few estimates of how ecosystem processes, such as stream metabolism (gross primary production and ecosystem respiration; GPP and ER), respond to high flow events. Furthermore, we lack a predictive framework for understanding controls on within-site metabolic responses to flow disturbances. Using 5 years of high-frequency dissolved oxygen data from an urban- and agricultural-influenced stream, we estimated daily GPP and ER and analyzed metabolic changes across 15 isolated high flow events. Metabolism was variable from day to day, even during lower flows; median and ranges for GPP and ER over the full measurement period were 3.7 (minimum, maximum = 0.0, 17.3) and −9.6 (−2.2, −20.5) g O2 m−2 d−1. We calculated metabolic resistance as the magnitude of departure (MGPP, MER) from the mean daily metabolism during antecedent lower flows (lower values of M represent higher resistance) and estimated resilience as the time until GPP and ER returned to the prior range of ambient equilibrium. We evaluated correlations between metabolic resistance and resilience with characteristics of each high flow event, antecedent conditions, and time since last flow disturbance. ER was more resistant and resilient than GPP. Median MGPP and MER were −0.38 and −0.09, respectively. GPP was typically suppressed following flow disturbances, regardless of disturbance intensity. The magnitude of departure from baseflow ER during isolated storms increased with disturbance intensity. Additionally, GPP was less resilient and took longer to recover (0 to >9 d, mean = 2.5) than ER (0 to 6 d, mean = 1.1). Prior flow disturbances set the stage for how metabolism responds to later high flow events: the percent change in discharge during the most recent high flow event was significantly correlated with M of both GPP and ER, as well as the recovery intervals for GPP. Given the flashy nature of streams draining human-altered landscapes and the variable consequences of flow for GPP and ER, testing how ecosystem processes respond to flow disturbances is essential to an integrative understanding of ecosystem function.
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Herbivory is the rate of consumption by animals of any plant parts, including foliage, stems, roots, flowers, fruits, or seeds. Insects are the primary herbivores in many ecosystems. Different functional groups affect plants in a variety of ways. Several methods have been developed to measure herbivory but most represent snapshots in time. Although herbivory typically removes <10% of plant biomass in terrestrial ecosystems, consumption of biomass can exceed 100% in aquatic ecosystems and during outbreaks in terrestrial ecosystems, due to high consumption and rapid turnover of plant material. Although herbivory often is viewed as a destructive process, plants often compensate for tissue loss, depending on environmental conditions, leading to higher productivity at low-to-moderate levels of herbivory than occurs in the absence of herbivory. Herbivory is an essential ecosystem process that is instrumental in maintaining primary productivity near carrying capacity, reducing dominance by host species, and maintaining or accelerating nutrient cycling.
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Background Restoration practices usually emphasize on the structural part of the biodiversity; also, most studies have focused on plants and very few have been conducted on arthropods and its function after restoration. The Pedregal de San Angel Ecological Reserve (PSAER) is a protected area immersed in Mexico City and it has been drastically affected by different anthropogenic disturbances. The aim of this study was to compare the relative diversity, richness, and abundance of species level identification, but also the composition through an analysis of ordination of taxonomic (species, family, and order level) and functional (trophic guild) traits of arthropods in three sites subjected to ecological restoration within the PSAER. Restored sites were also compared to conserved and disturbed sites, to evaluate whether restoration efforts are effective at the reserve. Methods Arthropods were sampled using pan traps during September 2013 in 11 sites (three restored, four conserved and four disturbed) inside the PSAER. All sampled species were taxonomically identified at species of morphospecies (inside a family) and assigned to a trophic guild. Differences in diversity, richness and abundance were evaluated through effective number of species, comparisons of Chao’s1 estimated richness and a non-parametric Kruskal–Wallis test, respectively. Both taxonomic and trophic guild composition were evaluated using a multivariate analysis and a post hoc test. Results We found some differences in richness, abundance, and diversity between sites, but not a clear pattern of differentiation between restored to disturbed sites. The NMDS showed differences at species and order level, and with trophic guilds, among site types. Families were not useful to differentiate types of sites. Regarding guilds, predators were more abundant in conserved sites, while phytophagous insects were more abundant in disturbed sites. Conclusions Species and order level were useful to identify differences in communities of arthropods in sites with different management. The trophic guild approach provides information about the functional state of the restored sites. Nevertheless, our quick evaluation shows that restoration efforts at PSAER have not been successful in differentiate restored to disturbed sites yet.
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Extreme events can have larger impacts on ecosystems than gradual changes of average conditions. This article identifies the different properties of drivers of extreme events, often related to extreme weather or climate events, which are becoming more frequent or more intense, and the derived ecological responses. Extreme ecological responses occur whenever drivers impact surpasses the system’s capacity to absorb changes after extreme pulses, ongoing trends or regime shifts. The mechanisms for ecological responses involve structural, compositional and functional changes that often result in slow, hysteretic or irreversible recovery, which are determined by legacy effects and the compound regime of drivers, disturbances and stressors. Incorporating extreme ecological response into ecological theory is becoming a must, particularly in a climate change context, and will require a better integration of approaches and understanding of its causes and consequences.
Article
The stability of ecological system is inseparable from the self-healing ability of population. Therefore, exploring the self-healing of population after disturbance is of great significance to deeply understand the ecological stability. By constructing a pair approximation model, the special explicit dynamics of one population on disturbance is studied in this paper. In which, dynamic disturbance (which can be gradually restored) is used, and the self-healing time of the population is investigated. Through a mass of simulations, some interesting results are obtained. At a lower disturbance restoration rate, the population self-healing time will not be affected by the spatial correlation of disturbance, regardless of the dispersal mode of population and the existence of competition. Compared with local dispersal, global dispersal has more obvious advantages at medium disturbance restoration rate. The increase of disturbance restoration rate is not always conducive to the self-healing of population, and a higher disturbance restoration rate will increase the self-healing time. The results can give us some insights on ecological conservation.
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Les objectifs principaux de cette thèse sont de quantifier les modifications engendrées sur les communautés de Coléoptères terricoles d'un écosystème steppique (la plaine de Crau dans les Bouches-du-Rhône) par des changements d'usage des terres : une ancienne mise en culture, correspondant à une perturbation exogène, et l'abandon d'un pâturage ovin séculaire, correspondant à l'arrêt d'un régime de perturbation endogène.
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Ephemeral wetlands are commonly embedded within pine uplands of the southeastern United States. These wetlands support diverse communities but have often been degraded by a lack of growing-season fires that historically maintained the vegetation structure. In the absence of fire, wetlands develop a dense mid-story of woody vegetation that increases canopy cover and decreases the amount of herbaceous vegetation. To understand how reduced fire frequency impacts wetland processes, we measured leaf litter breakdown rates and invertebrate communities using three common plant species (Longleaf Pine (Pinus palustris), Pineland Threeawn Grass (Aristida stricta), and Black Gum (Nyssa sylvatica)) that occur in pine flatwoods wetlands located on Eglin Air Force Base, Florida. We also tested whether or not the overall habitat type within a wetland (fire maintained or fire suppressed) affected these processes. We placed leaf packs containing 15.0 g of dried leaf litter from each species in both fire-maintained and fire-suppressed sections of three wetlands, removing them after 103–104 days submerged in the wetland. The amount of leaf litter remaining at the end of the study varied across species (N. sylvatica = 7.97 ± 0.17 g, A. stricta = 11.84 ± 0.06 g, and P. palustris = 11.37 ± 0.07 g (mean ± SE)) and was greater in fire-maintained habitat (leaf type: F2,45 = 437.2, P
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