Relació entre la vegetació i els paràmetres ambientals als boscos pirinencs de pi roig (Pinus sylvestris L.)

S'estudia la relació de la vegetació dels boscos pirinencs de pi roig (Pinus sylvestris L.) amb els paràmetres ambientals (p.e., altitud, radiació solar, nutrients al sòl, etc.) mitjançant mètodes d'andisi multivariant (ordenació, classificació i anàlisi canònica). Els resultats suggereixen que existeix una forta relació entre la vegetació i els paràmetres ambientals. Aquests boscos on l'única espècie arbòria és el pi roig, poden ser dividits en diierentes comunitats ecològicament diferenciades. Els principals paràmetres que determinen la vegetació corresponen a la capacitat de bescanvi catiònic del sòl i a la radiació solar incident.The relation between vegetation and their environment (e.g., altitude, solar radiation, soil nutrients) is studied in Pyrenean Scots pine (Pinus sylvestris L.) forests by means of multivariate analyses (i.e., ordination, classification and canonical analysis). The results suggest a strong correlation between vegetation and the environment. Although these forests are dominated by one overstorey species they can be subdivided into several ecologically differentiated communities. Cation exchange capacity and incoming solar radiation are the main parameters determining the vegetation composition

Estructura en l'espai del sotabosc als boscos pirinencs de pi roig (Pinus sylvestris L.)

A partir d'un mostreig basat en transectes a 59 parcel·les de bosc de pi roig (Pinus sylvestris L.), s'estudia el comportament en l'espai (dins les parce1,les) que presenten les espècies. El mètode utilitzat es basa en el càlcul del coeficient d'autocorrelació de cada espècie en cada parcel·la. Els resultats suggereixen que les espècies als boscos estudiats tendeixen a distribuir-se formant claps (distribució agregada), i no pas amb una distribució uniforme o a l'atzar, i que existeix certa relació entre el patró de distribució de les diferentes espècies i la seva forma vital.Spatial pattern of understorey species in Pyrenean Scots pine forests was studied from transect data in 59 plots. Autocorrelation coefficient was computed for each species in each plot. The results suggest that most of the species tend to show a clumped pattern, rather than random or uniform pattern, and that there is some relationship between the spatial pattern of the different species and their life form

Disturbance ecology in human societies

1. We define societal disturbances as discrete events that abruptly disrupt the functioning of human societies. There is a variety of such events, including hurricanes, floods, epidemics, nuclear accidents, earthquakes and wars, among others. These disturbances can interact, further increasing their impacts. The severity of disturbances does not only depend on their intrinsic properties (type, intensity and magnitude) but also greatly on human aspects (socioeconomic, historical, political and cultural aspects that define vulnerability). 2. Very large or severe disturbances are infrequent and unpredictable. Yet societal disturbances are intrinsic to human societies; they have occurred through the entire human history and will continue to occur in the future. We can increase preparedness and recovery capacity but cannot avoid disturbances. The type, regime and scale of disturbances change with the development of societies. The increase in population density and complexity also increases the severity of many disturbances. 3. Societal disturbances can temporarily disrupt the functioning of societies. However, when those disturbances are frequent, societies adapt to them and thus disturbances contribute to shape cultural evolution. That is, societal disturbances have a cost at short temporal scales, but they can build up resilience at mid-to long-term scales. 4. Understanding this dynamic view of human systems is becoming more important as climate is changing, humans are overexploiting natural resources and humanity is dense and hyperconnected. We need to take advantage of frequent small disturbances, as they can build resilience and reduce the likelihood of infrequent large and severe disturbances. Our challenge is to encourage actions and policies to be prepared for unknown, unpredictable and unprecedented (infrequent) large-scale societal disturbances that will surely arrive

Differential pollinator response underlies plant reproductive resilience after fires

Background and aims Assessing the resilience of plant-animal interactions is critical to understanding how plant communities respond to habitat disturbances. Most ecosystems experience some level of natural disturbance (e. g., wildfires) to which many organisms are adapted to. Wildfires have structured biotic communities for millennia; however, the effects of fire on interactions such as pollination have only recently received attention. A few studies have shown that generalist plants can buffer the impact of fires by pollinator replacement, suggesting that the resilience to disturbance could depend on the level of specialization of the interactions. Here, we hypothesize that i) fires could impose negative effects on plants with specialized pollination systems, and ii) in large wildfires, these negative effects will be stronger with increasing distance inside the burnt because pollinators will need more time to recolonize. Methods These questions were tested in the specialized pollination system of a widespread Mediterranean palm, Chamaerops humilis. The postfire pollination resilience was assessed in replicated wildfires representing three postfire ages by measuring the abundance of beetle pollinators and by estimating fruit set (i.e., proportion of flowers setting fruits) in burnt and unburned areas. To test for distance effects, plants were sampled along transects inside the burnt. Key results This study revealed that despite a marked postfire decline in the specialist pollinator, exacerbated by the distance from the fire’s edge, the palm’s fruit set was barely affected. The temporary replacement by a sap beetle at burnt sites - an effective pollinator that had not been previously recognized - provided postfire reproductive resilience. Conclusions The study shows that differential pollinator responses to disturbance can ensure plant success even in plants with only two functionally similar pollinators. This highlights the importance of pollinator 1 replacement and dynamics for the resilience of interactions and ultimately of plant reproduction in disturbance-prone ecosystems

Towards an understanding of the evolutionary role of fire in animals

Wildfires underpin the dynamics and diversity of many ecosystems worldwide, and plants show a plethora of adaptive traits for persisting recurrent fires. Many fire-prone ecosystems also harbor a rich fauna; however, knowledge about adaptive traits to fire in animals remains poorly explored. We review existing literature and suggest that fire is an important evolutionary driver for animal diversity because (1) many animals are present in fire-prone landscapes and may have structural and phenotypic characters that contribute to adaptation to these open landscapes; and (2) in some cases, animals from fire-prone ecosystems may show specific fire adaptations. While there is limited evidence on morphological fire adaptations in animals, there is evidence suggesting that different behaviors might provide a rich source of putative fire adaptations; this is because, in contrast to plants, most animals are mobile, unitary organisms, have reduced survival when directly burnt by fire and can move away from the fire. We call for research on fire adaptations (morphological, behavioral, and physiological) in animals, and emphasize that in the animal kingdom many fire adaptations are likely to be behavioral. While it may be difficult to discern these adaptations from other animal behaviors, making this distinction is fundamental if we want to understand the role of fire in shaping biodiversity. Developing this understanding is critical to how we view and manage our ecosystems in the face of current global and fire regime changes.This research was funded by the project FILAS (CGL2015-64086-P) from the Spanish Government (Ministerio de Economía y Competitividad) and the PROMETEO/2016/021 project from the Valencia government (Generalitat Valenciana, Spain)Peer reviewe

Environmental policies to cope with novel disturbance regimes–steps to address a world scientists’ warning to humanity

ABL acknowledges postdoctoral funding from the Alexander von Humboldt Foundation and grants RTI2018-096187-J-100 from FEDER/ Ministerio de Ciencia, Innovacion y Universidades and LRB20/1002 from the British Ecological Society.Alexander von Humboldt Foundation RTI2018-096187-J-100FEDER/ Ministerio de Ciencia, Innovacion y Universidades LRB20/1002British Ecological Societ

Quantitative genetic analysis of floral traits shows current limits but potential evolution in the wild

The vast variation in floral traits across angiosperms is often interpreted as the result of adaptation to pollinators. However, studies in wild populations often find no evidence of pollinator-mediated selection on flowers. Evolutionary theory predicts this could be the outcome of periods of stasis under stable conditions, followed by shorter periods of pollinator change that provide selection for innovative phenotypes. We asked if periods of stasis are caused by stabilizing selection, absence of other forms of selection or by low trait ability to respond even if selection is present. We studied a plant predominantly pollinated by one bee species across its range. We measured heritability and evolvability of traits, using genome-wide relatedness in a large wild population, and combined this with estimates of selection on the same individuals. We found evidence for both stabilizing selection and low trait heritability as potential explanations for stasis in flowers. The area of the standard petal is under stabilizing selection, but the variability is not heritable. A separate trait, floral weight, presents high heritability, but is not currently under selection. We show how a simple pollination environment coincides with the absence of current prerequisites for adaptive evolutionary change, while heritable variation remains to respond to future selection pressures

Coupling a water balance model with forest inventory data to predict drought stress : the role of forest structural changes vs. climate changes

Mechanistic water balance models can be used to predict soil moisture dynamics and drought stress in individual forest stands. Predicting current and future levels of plant drought stress is important not only at the local scale, but also at larger, landscape to regional, scales, because these are the management scales at which adaptation and mitigation strategies are implemented. To obtain reliable predictions of soil moisture and plant drought stress over large extents, water balance models need to be complemented with detailed information about the spatial variation of vegetation and soil attributes. We designed, calibrated and validated a water balance model that produces annual estimates of drought intensity and duration for all plant cohorts in a forest stand. Taking Catalonia (NE Spain) as a case study, we coupled this model with plot records from two Spanish forest inventories in which species identity, diameter and height of plant cohorts were available. Leaf area index of each plant cohort was estimated from basal area using species-specific relationships. Vertical root distribution for each species in each forest plot was estimated by determining the distribution that maximized transpiration in the model, given average climatic conditions, soil attributes and stand density. We determined recent trends (period 1980-2010) in drought stress for the main tree species in Catalonia; where forest growth and densification occurs in many areas as a result of rural abandonment and decrease of forest management. Regional increases in drought stress were detected for most tree species, although we found high variation in stress changes among individual forest plots. Moreover, predicted trends in tree drought stress were mainly due to changes in leaf area occurred between the two forest inventories rather than to climatic trends. We conclude that forest structure needs to be explicitly considered in assessments of plant drought stress patterns and trends over large geographic areas, and that forest inventories are useful sources of data provided that reasonably good estimates of soil attributes and root distribution are available. Our approach coupled with recent improvements in forest survey technologies may allow obtaining spatially continuous and precise assessments of drought stress. Further efforts are needed to calibrate drought-related demographic processes before water balance and drought stress estimates can be fully used for the accurate prediction of drought impacts

Cork oak vulnerability to fire: the role of bark harvesting, tree characteristics and abiotic factors

Forest ecosystems where periodical tree bark harvesting is a major economic activity may be particularly vulnerable to disturbances such as fire, since debarking usually reduces tree vigour and protection against external agents. In this paper we asked how cork oak Quercus suber trees respond after wildfires and, in particular, how bark harvesting affects post-fire tree survival and resprouting. We gathered data from 22 wildfires (4585 trees) that occurred in three southern European countries (Portugal, Spain and France), covering a wide range of conditions characteristic of Q. suber ecosystems. Post-fire tree responses (tree mortality, stem mortality and crown resprouting) were examined in relation to management and ecological factors using generalized linear mixed-effects models. Results showed that bark thickness and bark harvesting are major factors affecting resistance of Q. suber to fire. Fire vulnerability was higher for trees with thin bark (young or recently debarked individuals) and decreased with increasing bark thickness until cork was 3–4 cm thick. This bark thickness corresponds to the moment when exploited trees are debarked again, meaning that exploited trees are vulnerable to fire during a longer period. Exploited trees were also more likely to be top-killed than unexploited trees, even for the same bark thickness. Additionally, vulnerability to fire increased with burn severity and with tree diameter, and was higher in trees burned in early summer or located in drier south-facing aspects. We provided tree response models useful to help estimating the impact of fire and to support management decisions. The results suggested that an appropriate management of surface fuels and changes in the bark harvesting regime (e.g. debarking coexisting trees in different years or increasing the harvesting cycle) would decrease vulnerability to fire and contribute to the conservation of cork oak ecosystemsinfo:eu-repo/semantics/publishedVersio