Land-use change and windstorms legacies drove the recolonization dynamics of laurel forests in Tenerife, Canary islands

Laurel forests are quite relevant for biodiversity conservation and are among the island ecosystems most severely damaged by human activities. In the past, Canary laurel forests have been greatly altered by logging, livestock and agriculture. The remains of laurel forests are currently protected in the Canary Islands (Spain). However, we miss basic information needed for their restoration and adaptive management, such as tree longevity, growth potential and responsiveness to natural and anthropogenic disturbances. Using dendrochronological methods, we studied how forest dynamic is related to land-use change and windstorms in two well-preserved laurel forests on Tenerife Island. Wood cores were collected from over 80 trees per stand at three stands per forest. We used ring-width series to estimate tree ages and calculate annual basal area increments (BAI), cumulative diameter increases, and changes indicative of released and suppressed growth. Twelve tree species were found in all stands, with Laurus novocanariensis, Ilex canariensis and Morella faya being the most common species. Although some individuals were over 100 years old, 61.8%–88.9% of the trees per stand established between 1940 and 1970, coinciding with a post-war period of land abandonment, rural exodus and the onset of a tourism economy. Some trees have shown growth rates larger than 1 ​cm diameter per year and most species have had increasing BAI trends over the past decades. Strong growth releases occurred after windstorms at both sites, but the effects of windstorms were site-dependent, with the 1958 storm affecting mainly the eastern tip of the island (Anaga massif) and the 1991 storm the western tip (Teno massif). Given the great ability of laurel forest trees to establish after land use cessation and to increase growth after local disturbances such as windstorms, passive restoration may be sufficient to regenerate this habitat in currently degraded areas.12 página

Disentangling Facilitation Along the Life Cycle: Impacts of Plant–Plant Interactions at Vegetative and Reproductive Stages in a Mediterranean Forb

Facilitation enables plants to improve their fitness in stressful environments. The overall impact of plant-plant interactions on the population dynamics of protégées is the net result of both positive and negative effects that may act simultaneously along the plant life cycle, and depends on the environmental context. This study evaluates the impact of the nurse plant Juniperus sabina on different stages of the life cycle of the forb Helleborus foetidus. Growth, number of leaves, flowers, carpels and seeds per flower were compared for 240 individuals collected under nurse canopies and in open areas at two sites with contrasting stress levels. Spatial associations with nurse plants and age structures were also checked. A structural equation model was built to test the effect of facilitation on fecundity, accounting for sequential steps from flowering to seed production. The net impact of nurse plants depended on a combination of positive and negative effects on vegetative and reproductive variables. Although nurse plants caused a decrease in flower production at the low-stress site, their net impact there was neutral. In contrast, at the high-stress site the net outcome of plant-plant interactions was positive due to an increase in effective recruitment, plant density, number of viable carpels per flower and fruit set under nurse canopies. The naturally lower rates of secondary growth and flower production at the high-stress site were compensated by the net positive impact of nurse plants here. Our results emphasize the need to evaluate entire processes and not only final outcomes when studying plant-plant interactions

Assessing Seed And Microsite Limitation On Population Dynamics Of A Gypsophyte Through Experimental Soil Crust Disturbance And Seed Addition

Understanding the factors limiting population growth is crucial for species management and conservation. We assessed the effects of seed and microsite limitation, along with climate variables, on Helianthemum squamatum, a gypsum soil specialist, in two sites in central Spain. We evaluated the effects of experimental seed addition and soil crust disturbance on H. squamatum vital rates (survival, growth and reproduction) across four years. We used this information to build integral projection models (IPMs) for each combination of management (seed addition or soil disturbance), site and year. We examined differences in population growth rate (λ) due to management using life table response experiments. Soil crust disturbance increased survival of mid to large size individuals and germination. Contributions to λ of positive individual growth (progression) and negative individual growth (retrogression) due to managements varied among years and sites. Soil crust disturbance increased λ in the site with the highest plant density, and seed addition had a moderate positive effect on λ in the site with lowest plant density. Population growth rate (λ) decreased by half in the driest year. Differences in management effects between sites may represent a shift from seed to microsite limitation at increasing densities. This shift underscores the importance of considering what factors limit population growth when selecting a management strategy

Arboreal and prostrate conifers coexisting in Mediterranean high mountains differ in their climatic responses

[EN] In contrast to most high elevation areas, plant growth at Mediterranean mountains is exposed to a summer drought period, which represents an additional climatic constraint to low temperatures. Although arboreal and shrubby conifers coexist at high altitudes, most dendroecological studies have focused on climatic responses of tree species, whereas those of shrubby species remain mostly unexplored. We built tree-ring width chronologies for two conifer species, a shrub (Juniperus sabina) and a tree (Pinus sylvestris), coexisting at three high-altitude localities of the Iberian System mountains, eastern Spain. We analyzed their climate-growth relationships for the period 1950-2009 using correlation analyses and multiple regressions. Coexisting species responded to year-to-year climatic variability in different ways. Radial growth in junipers and pines responded positively to April and May temperatures, respectively. Summer drought constrained growth in both cases, although its impact was stronger on junipers than on pines. Our findings suggest that junipers respond earlier than pines to spring temperatures due to their prostrate morphology which may enhance a fast warming of their cambial meristems after snowmelt. The higher dependence of . J. sabina on summer rainfall as compared with co-occurring pines confirms that drought stress negatively impacts secondary growth in Mediterranean mountains. This sensitivity to water availability may be caused by the juniper shallow root systems, which mainly use superficial soil water. The climatic signal registered in . J. sabina allows studying the response of other similar shrubby woody species growing in Mediterranean alpine areas to the ongoing climate warming, which could also reduce water availability. © 2012 Elsevier GmbH.We thank Natural Parks of Moncayo and Alto Tajo for the permissions to make the field work, specifically to Enrique Arrechea and Ángel Vela respectively. Rafael Jiménez helped us to find the best places for sampling in Moncayo. We thank Erik Rodríguez, Rafael Jiménez and Juan Manuel Gil for helping us in the field, Natali Bascopé for her participation in the laboratory work and Juan Carlos Rubio for his assistance at CESEFOR with sample processing. A previous version was improved by C. Woodhouse and two anonymous referees’ comments. This work was supported by a grant FPI-MICINN to AIGC and projects CGL2009-13190-C03-03 (Spanish Ministry of Science and Innovation) and VA006A10-2 (Junta de Castilla y León). JJC acknowledges the support of ARAID.Peer Reviewe

Data from: Microsites of seed arrival: spatio-temporal variations in complex seed-disperser networks

Microsites where seeds arrive during the dispersal process determine plant reproductive success, affecting the quality of dispersal. Despite their crucial role for plant recruitment, very few studies have addressed spatio-temporal variations in microsites of seed arrival in complex seed-disperser networks. Using an endozoochorous dispersal system, we characterized the microsites of seed arrival of eight fleshy-fruited plant species dispersed by five mammal species during two consecutive seasons across three sites in a Mediterranean environment (n = 383 feces with seeds; 261,453 seeds). We evaluated spatial and temporal variations in the probability of a seed to arrive at open microsites or at microsites with varying plant cover, considering selection by frugivores and assessing the extent to which seeds of particular species arrived under conspecifics or heterospecifics. We found strong spatio-temporal variations in the amounts of seeds of the eight target species arriving at different microsites. These variations were strongly driven by frugivores’ selection of different landscape elements (i.e. open areas and microsites dominated by different plant species), which differed from expectations based on their local availability. In general, more seeds than expected arrived at vacant (open) microsites. Using bipartite network graphs to connect seeds with their arrival microsites, we found that the proportion of seeds of fleshy-fruited species arriving near conspecifics or heterospecifics, or at vacant microsites, varied depending on the target plant species, but also on the frugivore species dispersing it, on the study site and on the dispersal season. Our study revealed marked spatio-temporal variations in the microsites of seed arrival, which will potentially have implications for the quality of dispersal effectiveness, ultimately affecting plant population dynamics and community structure. Such a strong context-dependence in the microsites of seed arrival is likely to confer resilience against unpredictable environmental conditions, like those typical of Mediterranean ecosystems

Intraspecific competition replaces interspecific facilitation as abiotic stress decreases: The shifting nature of plant-plant interactions

Plant-plant interactions change depending on environmental conditions, shifting from competition to facilitation when the stress is high. In addition to these changes, the relevance of intraspecific compared to interspecific interactions may also shift as abiotic stress does. We inferred intra- and interspecific plant-plant interactions of the cushion plant Hormathophylla spinosa as related to the dominant shrub Juniperus sabina in two sites with contrasting abiotic conditions (a slope with high-stress conditions vs. a valley bottom with milder conditions) in a Mediterranean high mountain. Specifically, we studied the spatial patterns and several variables related to plant performance (plant size and form, non-structural carbohydrate - NSC - concentrations and radial growth) of H. spinosa.The spatial pattern varied depending on site conditions. H. spinosa plants were positively associated with juniper in the high-stress slope site, probably through higher establishment rates due to the amelioration of soil conditions. In contrast, in the milder valley site H. spinosa establishment occurred mostly in open areas. Age structure, inferred from annual rings, reflected a massive establishment event in the whole study area which occurred 30-50 years ago. Canopy variables and radial growth were density dependent: both were negatively affected by the high density of H. spinosa individuals in the valley, but favoured by junipers on the slope. Interestingly, NSCs showed the opposite pattern, suggesting lower investment in growth by H. spinosa plants in the valley than on the slope.Our results reinforce the strong links existing between intra- and interspecific relationships and the need to include both when studying the influence of abiotic conditions on plant-plant interactions. This approach enabled us to detect that the direction and intensity of plant-plant interactions may shift at different ecological levels. Particularly interesting was the finding that optimal sites at the population level may not necessarily be the sites showing maximum individual performance. © 2013 Perspectives in Plant Ecology, Evolution and Systematics.We thank E. Rodríguez, N. Bascopé, L.C. García-Cervigón, H. Angela Chaparro and G. Sangüesa-Barreda for participating in the fieldwork, G. Juste, E. Marcos and M. Folch for laboratory analysis, and D. Brown for English editing. Dr. Holzapfel and two anonymous referees improved a previous version of this manuscript. This work was supported by a grant FPI-MICINN to A.I.G.C. and projects CGL2009-13190-C03-03, CGL2011-26654 (Spanish Ministry of Science and Innovation) and VA006A10-2 (Junta de Castilla y León). J.J.C. acknowledges the support of ARAID.Peer Reviewe