Cork Oak Woodlands Research Articles

Grazing hinders seed dispersal during crop failure in a declining oak woodland

Masting, the synchronized production of variable quantities of seeds, is a global phenomenon in diverse ecosystems, including treed grazing systems where trees and grazing animals coexist. This phenomenon can be interspersed with years of extreme crop failure, whose frequency and unpredictability are increasing. Yet, the combined impact of crop failure and grazing on seed dispersal and seed-to-seedling transition remains poorly understood. To address this concern, we investigated rodent-mediated cork-oak (Quercus suber) acorn predation, dispersal, and seedling emergence in cattle grazed and non-grazed areas in central Portugal during years with contrasting masting seasons. We found that the acorns supplied in the crop failure year were dispersed more rapidly and over longer distances than those supplied in the crop success year when other acorns were naturally available. The crop failure year also had 83 % more dispersal events and 84 % more predated acorns than the reproductive success year. However, the higher acorn predation was offset by a 2.4-fold higher percentage of unpredated dispersed acorns recruiting into seedlings. Both years ended up recruiting a similar number of seedlings. Acorns emerged seedlings 3.4 times farther in the crop failure year than in the crop success year. Cattle grazing was the main constraint on seed dispersal distance by rodents, reducing it by 53 %. Our study provides empirical evidence that cattle grazing modulates how an extreme crop failure year can surprisingly be an opportunity for the few existing acorns to have seedlings established farther apart than in a crop success year. If we are to better manage and preserve the high conservation and socio-economic value of Mediterranean cork oak woodlands in the face of climate change, we must prioritize fecund trees and carefully manage seed dispersal factors such as cattle grazing, particularly during years of crop failure.

Effects of Shrub Encroachment on Carbon Assimilation and Growth of Mediterranean Cork Oak Trees Depend on Shrub Cover Density

Mediterranean ecosystems are threatened by climate change and shrub encroachment. An increase in shrub cover can intensify the competition for water, aggravating the impacts of drought on ecosystem functioning. The effects of shrubs can be positive or negative, depending on the shrub species and density. We used a Mediterranean cork oak (Quercus suber) woodland to investigate the effects of increasing gum rockrose (Cistus ladanifer) cover on leaf carbon assimilation (Amax) and tree growth. The experiment consisted of a gradient of shrub cover, with four treatments: control, LD, MD, and HD, with 0%, 25%, 45%, and maximum shrub cover (>90%), respectively. Increasing shrub cover significantly decreased Amax in trees from HD (−15%) compared to control treatment, with intermediate effects on trees from LD (−5%) and MD (−12%). There was a large variability in tree growth, resulting in no significant effects of shrub cover, despite higher trunk diameter relative increments in LD (+40%), and lower in MD (−17%) and HD (−32%) compared to the control. The results indicate that a dense shrub cover (>90%) affected cork oak carbon assimilation and growth, while a low-to-medium shrub cover (≤45%) only induced mild intermediate effects. This information is important for the effective management of shrub density to improve the health and productivity of cork oak woodlands.

Prevalence of Ectoparasites on Small Mammals Inhabiting an Agroforestry System of Western Portugal

The goal of this study was to assess ectoparasite-small mammal host associations in central-west Portugal in native and exotic habitats, respectively, including a cork oak woodland and a Eucalyptus plantation. Mammals were sampled with Sherman and pitfall traps, and ectoparasites were collected and identified in all samples. We trapped 681 small mammals: 5 rodent species - wood mouse, Apodemus sylvaticus (N = 527); the Algerian mouse, Mus spretus (N = 67); Cabrera's vole, Microtus cabrerae (N = 8); the Lusitanian pine vole, Microtus lusitanicus (N = 2); and the black rat, Rattus rattus (N = 1) - and 1 insectivore species - the greater white-toothed shrew, Crocidura russula (N = 76). We identified 4 flea species (Nosopsyllus fasciatus, Ctenophthalmus sp., Typhloceras favosus, and Typhloceras poppei); 5 tick species (Haemaphysalis punctata, Ixodes ricinus, Ornithodoros sp., Rhipicephalus pusillus, and Rhipicephalus sanguineus); and 1 chigger species (Neotrombicula sp.) from hosts. The wood mouse was the small mammal species with the highest overall ectoparasite prevalence, although ticks were the least prevalent taxon. We found that ectoparasite guilds represented a somewhat generalist host pattern, and chiggers presented some host specificity. The data presented herein increase the knowledge regarding ectoparasite prevalence and distribution among small mammal hosts in the Mediterranean. Although surveys of ectoparasites of small mammals in central-west Portugal are not novel, this is the first time that a species belonging to the genus Ctenophthalmus is reported from M. cabrerae (Cabrera's vole) in Portugal.

Beyond width and density: stable carbon and oxygen isotopes in cork-rings provide insights of physiological responses to water stress in Quercus suber L.

As climate change increasingly affects forest ecosystems, detailed understanding of major effects is important to anticipate their consequences under future climate scenarios. The Mediterranean region is a prominent climate change hotspot, and evergreen cork oak (Quercus suber L.) woodlands are particularly climatically sensitive due to cork (bark) harvesting. Cork oak's drought avoidance strategy is well-known and includes structural and physiological adaptations that maximise soil water uptake and transport and limit water use, potentially leading to reduced stem and cork growth. Trees' responses to cope with water-limited conditions have been extensively described based on cork-rings width and, more recently, on cork-rings density, in dendroecological studies. However, so far, tree functional attributes and physiological strategies, namely photosynthetic metabolism adjustments affecting cork formation, have never been addressed and/or integrated on these previous cork-rings-based studies. In this study, we address the relation between carbon and oxygen stable isotopes of cork rings and precipitation and temperature, in two distinct locations of southwestern Portugal-the (wetter) Tagus basin peneplain and the (drier) Grândola mountains. We aimed at assessing whether the two climatic factors affect cork-ring isotopic composition under contrasting conditions of water availability, and, therefore, if carbon and oxygen signatures in cork can reflect tree functional (physiological and structural) responses to stressful conditions, which might be aggravated by climate change. Our results indicate differences between the study areas. At the drier site, the stronger statistically significant negative cork δ 13C correlations were found with mean temperature, whereas strong positive cork δ 18O correlations were fewer and found only with precipitation. Moreover, at the wetter site, cork rings are enriched in 18O and depleted in 13C, indicating, respectively, shallow groundwater as the water source for physiological processes related with biosynthesis of non-photosynthetic secondary tissues, such as suberin, and a weak stomatal regulation under high water availability, consistent with non-existent water availability constrains. In contrast, at the drier site, trees use water from deeper ground layers, depleted in 18O, and strongly regulate stomatal conductance under water stress, thus reducing photosynthetic carbon uptake and probably relying on stored carbon reserves for cork ring formation. These results suggest that although stable isotopes signatures in cork rings are not proxies for net growth, they may be (fairly) robust indicators of trees' physiological and structural adjustments to climate and environmental changes in Mediterranean environments.

Spatio-temporal analysis of North African forest cover dynamics using time series of vegetation indices – case of the Maamora forest (Morocco)

North African forest areas play several roles and functions and represent a heritage of great economic and ecological importance. As a result of global changes, that act independently or synergistically, these areas are currently undergoing a pronounced degradation and their productivity is decreasing due to several factors. This work aims to characterize spatio-temporal dynamics of vegetation within the Maamora forest. This forest is considered as the most extensive cork oak woodland in the world and is divided, from west to east, into five cantons A, B, C, D and E. The data, extracted between 2000–2021 from MODIS NDVI/EVI images of 250 m, were analyzed using statistical parameters with the Pettitt homogeneity and the Mann-Kendall trend tests, with their seasonal and spatial components, in order to better consider the vegetation distribution of this forest. Results show a clear temporal and spatial (inter-canton) variability of vegetation intensity, unrelated to the continental gradient. In fact, recorded mean values in cantons C and E are significantly higher than those of cantons B and D respectively. This is confirmed by both regressive and progressive trends, which were identified respectively from the months of March 2012 and October 2008, in the data series of cantons B and E successively. Spatially, the regressive dynamic remains generalized and affects more than 26.7% of the Maamora’s total area with extreme rates (46.1% and 14.0%) recorded respectively by the two aforementioned cantons. Similarly, all the stand types in canton B show the highest regressive rates, especially the cork oak regeneration strata (75.4%) and the bare lands (86.1%), which may explain the positive tendencies identified by the related series during the fall season. However, the cantons C and E record the lowest rates, respectively, for natural stands of cork oak and artificial plantations. These results highlight also the absence of a causal relationship between the contrasting vegetation dynamics of the Maamora and the climatic conditions, expressed here by the continental gradient. However, they do highlight the effects of other factors, particularly those of a technical nature.

Floristic diversity of Quercus suber woodlands in Kabylia (northeastern Algeria). Checklist and brief analysis

The Quercus suber woodlands found in Algeria are of limited expansion, but of high ecological importance, and they are mainly located in the northeastern part of the country. The objective of this paper was to present the floristic diversity of the cork oak woodlands in Kabylia (northeastern Algeria), by describing the taxonomical (at families, genera, species and subspecies ranks), biological and chorological diversity of the vascular flora. Overall, 311 vascular plant taxa were recorded in the investigated area, of which 29 are endemics and Algerian law protects eight taxa. Biological spectrum revealed ecological features and anthropic pressure, while chorological spectrum provided information in climatic terms. The presence of 34 plant taxa with high value that are range-restricted and/or endemics in these woodlands is especially significant, as well as three threatened or near threatened species. Accordingly, measures for protection of floristic diversity are recommended.

Micro‐habitat drivers of saproxylic beetle assemblages in old woodlands of Mediterranean cork oak (Quercus suber)

Abstract Cork oak landscapes are fascinating ecosystems, historically managed for cork extraction. The persistence in this habitat of many hollow veteran trees provides suitable micro‐habitats for saproxylic beetles. We investigated the saproxylic beetle community of two isolated cork oak woodlands of central Italy with different degree of recovery after human transformation: (1) an open woodland and (2) a dense mixed woodland, both dominated by cork oak trees. We found endemic, rare and threatened saproxylic beetles in both the areas, confirming the important conservation value of cork oak landscapes. In the open woodland we observed a higher number of species in all trophic categories, except for mycophagous specialists. Several microhabitat variables reflected the different stage of recovery of the two woodlands. Our findings suggest the crucial role of diversified environments in protected areas: even a small difference in the degree of recovery (i.e., tree closeness) can affect the number of beetle species. Specifically, we found (1) more xerophilous species in the open woodland and (2) more mesophilous species in the dense mixed woodland.

Syntaxonomical survey of cork oak forests (Quercus suber L.) in the province of Tizi Ouzou, Kabylia, Northern Algeria

Abstract This study is a contribution to the knowledge of the floristic composition and syntaxonomical significance of Quercus suber woodlands of Tizi Ouzou province, which represent the last remnants of ancient forests. The field surveys were taken in several locations representative of cork oak woodlands, using the Braun-Blanquet method. A matrix of 96 phytosociological relevés and 160 plant taxa was treated with clustering analysis and correspondence analysis. These multivariate analyses showed congruent results and allowed the definition of four main clusters of cork oak woodlands, corresponding to four syntaxa according to synecological and syndynamic gradients. They belong to three associations, of which one is newly described, and two subassociations. They are: Sileno imbricatae-Quercetum suberis ass. nov., a mesophilous association newly described here, on siliceous soils and in the humid ombrotype; Cytiso villosi-Quercetum suberis, a mesophilous association, with two subassociations: quercetosum canariensis, and myrtetosum communis, this later reported for the first time in the study area, and both localized in the humid ombrotype and confined on markedly acid soils; Erico arboreae-Myrtetum communis, thermophilous secondary shrubland association developed in the subhumid ombrotype, on flysch substrates, also identified for the first time in this area. Syntaxonomic, synecological and syndynamic considerations are given for each syntaxon.

Spectral-Based Monitoring of Climate Effects on the Inter-Annual Variability of Different Plant Functional Types in Mediterranean Cork Oak Woodlands

Using remotely sensed data to estimate the biophysical properties of vegetation in woodlands is a challenging task due to their heterogeneous nature. The objective of this study was to assess the biophysical parameters of different vegetation types (cork oak trees, shrubs and herbaceous vegetation) in cork oak woodland through the analysis of temporal trends in spectral vegetation indices (VIs). A seven-year database (from 2011 until 2017) of in situ observations collected with a field spectroradiometer with a monthly basis was used and four VIs were derived, considered as proxies for several biophysical properties of vegetation such as biomass (Normalized Difference Vegetation Index—NDVI); chlorophyll content (MERIS Terrestrial Chlorophyll Index-MTCI), tissue water content (Normalized Difference Water Index—NDWI) and the carotenoid/chlorophyll ratio (Photochemical Reflectance Index—PRI). During the analyzed period, some key meteorological data (precipitation, temperature, relative air humidity and global radiation) were collected for the study site, aggregated at three different time-lags (short period (30 d), medium period (90 d) and hydrological period (HIDR)), and their relationship with VIs was analyzed. The results showed different trends for each vegetation index and vegetation type. In NDVI and NDWI, herbaceous vegetation showed a highly marked seasonal trend, whereas for MTCI, it was the cork oak and Cistus salvifolius, and for PRI, it was Ulex airensis that showed the marked seasonal trend. Shrubs have large differences depending on the species: the shallow-rooted Cistus salvifolius showed a higher seasonal variability than the deep-rooted Ulex airensis. Our results revealed the importance of temperature and precipitation as the main climatic variables influencing VI variability in the four studied vegetation types. This study sets up the relationships between climate and vegetation indices for each vegetation type. Spectral vegetation indices are useful tools for assessing the impact of climate on vegetation, because using these makes it easier to monitor the amount of “greenness”, biomass and water stress of vegetation than assessing the photosynthetic efficiency. Proximal remote sensing measurements are fundamental for the correct use of remote sensing in monitoring complex agroforest ecosystems, largely used to inform policies to improve resilience to drought, particularly in the Mediterranean region.

Climate and management effects on the herbaceous layer productivity of a cork oak woodland

Climate and management effects on the herbaceous layer productivity of a cork oak woodland

Conservation zones increase habitat heterogeneity of certified Mediterranean oak woodlands

Forest certification is a conservation tool, which aims to promote the sustainable management and conservation of forest ecosystems. Establishing set-aside or lower intervention conservation zones to promote biodiversity conservation is a requisite of forest certification. We tested the effects of conservation zones on the tree biometrics and regeneration, as well as on the taxonomic, functional, and structural diversity of the shrub and herb understory, in Mediterranean oak woodlands. We also assessed how oak biometrics, regeneration and understory diversity varied among conservation zones established 10, 14, and 20 years before our sampling dates. Oak regeneration tended to be higher in conservation zones than in controls, but results varied with the age of conservation zones. For example, the abundance of oak seedlings and saplings was higher in 10-year-old conservation zones than in those established 20 years ago. Abundance of young oak trees was higher in 14-year-old conservation zones than in 10- and 20-year-old conservation zones. The understory vertical diversity was significantly higher in 14- and 20-year-old conservation zones than in controls. Functional diversity differed significantly between conservation zones and controls, with a higher abundance of late-successional shrubs, namely fleshy-fruited species in 20-year-old conservation zones. The plant species composition of the shrub and the herb understory was most dissimilar between older conservation zones and controls. Additionally, the cover and diversity of the understory herb species decreased with the age of conservation zones. Conservation zones implemented under forest certification increase habitat structural complexity of oak woodlands, which may benefit wildlife species, but there will be trade-offs with the cover and diversity of the herb understory. Forest managers must evaluate such trade-offs when establishing conservation zones in cork oak woodlands under forest certification schemes.

Canopy Cover Loss of Mediterranean Oak Woodlands: Long-term Effects of Management and Climate

Although forest areas have been growing in Europe, some forest types have been declining regionally. Since the 1980 s, there have been reports of defoliation and mortality in evergreen oak woodlands of the Iberian Peninsula. However, long-term and large-scale trends of Iberian oak decline are still poorly understood. We quantified trends in canopy cover for cork oak (Quercus suber) and holm oak (Q. rotundifolia) woodlands in mainland Portugal for a 50 year period (1965 to 2015). We considered loss of canopy cover a proxy of forest degradation and asked how it changed over time, in association with human activity and climate. Between 1965 and 2015, both cork oak and holm oak canopy cover showed declining trends (57.9% and 71.1% of sampling points, respectively). Canopy cover dynamics, however, differed across time. Between 1965 and 1990, canopy cover gains (over 35% of sampling points) prevailed over losses (under 20%), with larger differences for cork oak than holm oak. Between 1990 and 2015, canopy cover losses (over 70% of sampling points) were much higher than gains (under 9%). Oak canopy cover decrease was associated with flatter areas (usually having more intensive land use) for both oak species, higher cattle numbers (holm oak only) and higher mean temperature (cork oak only). Contrastingly, loss of holm oak canopy cover seems to have occurred in less hot and dry regions that enable more intensive land uses. Active restoration is urgently needed to reverse the current decline in canopy cover in Mediterranean evergreen oak woodlands.

Using Digital Photography to Track Understory Phenology in Mediterranean Cork Oak Woodlands

Monitoring vegetation is extremely relevant in the context of climate change, and digital repeat photography is a method that has gained momentum due to a low cost–benefit ratio. This work aims to demonstrate the possibility of using digital cameras instead of field spectroradiometers (FS) to track understory vegetation phenology in Mediterranean cork oak woodlands. A commercial camera was used to take monthly photographs that were processed with the Phenopix package to extract green chromatic coordinates (GCC). GCC showed good agreement with the normalized difference vegetation index (NDVI) and normalized difference water index (NDWI) obtained with FS data. The herbaceous layer displayed a very good fit between GCC and NDVI (coefficient of determination, represented by r2 = 0.89). On the contrary, the GCC of shrubs (Cistus salviifolius and Ulex airensis) showed a better fit with NDWI (r2 = 0.78 and 0.55, respectively) than with NDVI (r2 = 0.60 and 0.30). Models show that grouping shrub species together improves the predictive results obtained with ulex but not with cistus. Concerning the relationship with climatic factors, all vegetation types showed a response to rainfall and temperature. Grasses and cistus showed similar responses to meteorological drivers, particularly mean maximum temperature (r = −0.66 and −0.63, respectively). The use of digital repeat photography to track vegetation phenology was found to be very suitable for understory vegetation with the exception of one shrub species. Thus, this method proves to have the potential to monitor a wide spectrum of understory vegetation at a much lower cost than FS.

Tree regeneration patterns in cork oak landscapes of Southern Portugal: The importance of land cover type, stand characteristics and site conditions

Agricultural intensification and abandonment of traditional uses have led to the degradation of Mediterranean oak landscapes, most apparent in a severe lack of tree regeneration. In the Alentejo region of Southwestern Portugal the landscape mosaic is composed of three prevalent land cover types: cork oak forests, open cork oak woodlands (montados) and shrublands dominated by Cistus ladanifer. The objective of this study is to understand how natural tree regeneration differs among these three land cover types and how stand characteristics and site conditions affect regeneration at each land cover type. We collected data on stand characteristics (adult tree layer), site conditions (topography, soil conditions, understory vegetation and light conditions) and tree regeneration (species composition, density, size structure), and analysed differences among the three land cover types. An information-theoretic approach and model averaging were applied to a set of generalized linear mixed models (GLMMs) to identify stand characteristics and site conditions that best explain regeneration occurrence of cork oak (Quercus suber) and strawberry tree (Arbutus unedo) at each land cover type. Our results show that regeneration failure was widespread at all land cover types, being strongest in shrublands. Regeneration density was higher in forests than in montados, and marginal in shrublands. Differences in regeneration patterns among land cover types seem to be related to differential processes of seed availability, seed dispersal and the availability of safe sites for recruit establishment, which are affected by vegetation cover and (past) land use practices. Cork oak regeneration was more likely to occur at steeper slopes in both forests and montados, with lower soil fertility and higher available water storage capacity in forests, and with higher proportion of ground cover in montados. In shrublands, cork oak regeneration was more likely to occur with higher soil fertility and rock content, and with less solar radiation. Regeneration of strawberry tree in forests was more likely to occur with lower available water storage capacity, and with the presence of adult strawberry trees, while in shrublands it was more likely to occur at flatter slopes. Overall, our results indicate that differences in cork oak and strawberry tree regeneration within land cover types seem to be a result of indirect effects of stand and site factors on competition and facilitation between tree recruits and coexisting plants. This study provides recommendations that can support sustainable management and restoration efforts in Mediterranean oak landscapes.

Effects of cork oak stripping on tree carbon and water fluxes

Cork is a high value periodical forest product which ensures the economic, social and ecological sustainability of cork oak woodlands. Abiotic and biotic stresses lead to tree decline which is endangering the productivity and sustainability of these ecosystems. It is therefore critical to find and implement management practices that minimize the impact of these stresses. The current study was conducted in a certified evergreen cork oak woodland of central Portugal under Mediterranean climate. The main aims of the study were to assess the effects of cork stripping in tree water and carbon fluxes. Results are based on the monitoring of cork stripped and unstripped (control) trees. The experiment was repeated with different sets of trees during two contrasting summers (2014 and 2015). 2014 was a wet year (924 mm) with a typical summer drought pattern and 2015 a dry year (440 mm) with a 31% reduction in annual average precipitation. In 2015 the experimental site was entirely cork harvested and effects on ecosystem CO2 fluxes were evaluated. Results showed that the amount of carbon in harvested cork represents less than 1.5% of net primary production on a yearly basis. In addition, cork tissue is very low demanding in nutrients: primary macronutrients content in cork represents approximately 2% of the yearly nutrient needs of leaf canopy. Regardless of the climatic year, trunk water losses following cork stripping amounted to only 2% of canopy transpiration not affecting significantly summer tree water balance. However, cork stripping induced a 46% decrease on sap flow in the dry year suggesting that cork stripping triggered an increase in stomatal closure through an interaction between stripping traumatic effects and soil water scarcity. Although the effects of summer drought on carbon sequestration are more prominent than cork stripping effects, this superimposed stress led to a significant reduction of summer net carbon ecosystem exchange (ca. 32%). Our results suggest that cork stripping detrimental effects can be especially critical in more vulnerable trees growing near their vitality breakdown threshold. Therefore, and concerning cork oak woodland management, the cork stripping practice should be avoided in severe dry years and in the more stress-prone trees.

Temporary grazing exclusion as a passive restoration strategy in a dryland woodland: Effects over time on tree regeneration and on the shrub community

Passive restoration is acknowledged as a cost-effective approach to restore forest ecosystems. In this approach, restoration implies simply ceasing the disturbance causing degradation. But an efficient allocation of restoration efforts requires an understanding of the recovery trajectories of different ecosystem components.In Mediterranean oak open woodlands (called montado in Portugal), livestock grazing drives important plant community composition changes, and may hamper tree regeneration, threatening the long-term sustainability of this ecosystem. A temporary grazing exclusion may, thus, be an efficient restoration measure. However, how beneficial changes occur with time after exclusion on tree regeneration and on the structure and diversity of the ecosystem, are less clear.In this work, we studied the effects of grazing exclusion as a passive restoration strategy on a cork oak woodland, focusing on cork oak tree (Quercus suber) regeneration and on the structure and diversity of the understory shrub community. We assessed oak seedlings and saplings abundance and height, shrub structure, compositional and functional diversity at sites with 0, 5, 9 and 13 years of grazing exclusion.Cork oak individuals were similarly abundant throughout the chronosequence, but time had a positive effect on the height of saplings, until 9 years of exclusion. Shrub cover increased within 5 years after exclusion, and remained stable thereafter. Shrub taxonomic diversity increased continuously along the chronosequence, while functional diversity did not change consistently.Our results suggest that grazing exclusion may be an effective passive restoration measure, although different components of the ecosystem have different timings of recovery. In the case of the studied cork oak woodlands, tree regeneration may be promoted by a 5–10 years period of exclusion, after which it decreases, while conservation of taxonomic shrub diversity may require at least 13 years of exclusion. Our results highlight the importance of optimizing restoration plans depending on the restoration objective.

Patchy landscapes support more plant diversity and ecosystem services than wood grasslands in Mediterranean silvopastoral agroforestry systems

Plant diversity and proxy indicators of ecosystem services were assessed for three structural components of Mediterranean silvopastoral agroforestry systems: WL = cork oak woodlands, WG = cork oak wood grasslands, and OG = open grasslands. Our study was conducted in a long-term observatory located in NE Sardinia, characterized by fragmented land ownership and land use, which generates a patchy landscape that is different from the extensively studied large scale Iberian dehesas and montados. Our research question was focused on assessing whether, a “patchy” land use scenario made of the combination of WL, WG and OG or a “specialized” scenario could provide more plant diversity and ecosystem services than a “dehesa type” scenario including only WG under the same overall tree cover. The results showed that γ and β diversity, species unique to a position, C stock, cork and acorn production, Hemicryptophytes cover, nectariferous species cover, decreased and pastoral value, excellent and good forage species and legume cover, increased along the WL➔WG➔OG land use gradient. Isolated trees in WG and clearings in WL highly contributed to achieving mainly high C stock and plant diversity respectively. The results also showed that the “specialized” scenario can support higher biodiversity and better ecosystem services than the “dehesa type” scenario, but the “patchy” scenario made of all three components proved to support the highest level of both biodiversity and ecosystem services in Mediterranean silvopastoral agroforestry systems.

Cork oak woodland land-cover types classification: a comparison between UAV sensed imagery and field survey

ABSTRACT This work assesses the use of aerial imagery for the vegetation cover characterization in cork oak woodlands. The study was conducted in a cork oak woodland in central Portugal during the summer of 2017. Two supervised classification methods, pixel-based and object-based image analysis (OBIA), were tested using a high spatial resolution image mosaic. Images were captured by an unmanned aerial vehicle (UAV) equipped with a red, green, blue (RGB) camera. Four different vegetation covers were distinguished: cork oak, shrubs, grass and other (bare soil and tree shadow). Results have been compared with field data obtained by the point-intercept (PI) method. Data comparison reveals the reliability of aerial imagery classification methods in cork oak woodlands. Results show that cork oak was accurately classified at a level of 82.7% with pixel-based method and 79.5% with OBIA . 96.7% of shrubs were identified by OBIA, whereas there was an overestimation of 21.7% with pixel approach. Grass presents an overestimation of 22.7% with OBIA and 12.0% with pixel-based method. Limitations rise from using only spectral information in the visible range. Thus, further research with the use of additional bands (vegetation indices or height information) could result in better land-cover type classification.

Environmental incomes: Refined standard and extended accounts applied to cork oak open woodlands in Andalusia, Spain

Abstract In this research, our objectives are twofold: firstly to conceptualize and compare the ecosystem services and environmental incomes of individual activities at producer, basic and social prices using the extended accounts (Agroforestry Accounting System) and the refined standard accounts (a slightly refined standard System of National Accounts), and secondly, to apply both methodologies at a scale of 4,095 land-cover tiles predominately occupied by cork oak open woodlands (COW), which cover 248,015 ha in Andalusia, Spain. This analysis considers spatial-explicit characteristics of COW across Andalusia. The 15 COW economic activities valued in 2010 include: timber, cork, firewood, nuts, grazing, conservation forestry, residential services, private amenity, fire services, water supply, mushroom, carbon, free access recreation, landscape conservation services and threatened wild biodiversity preservation services. In this research, the ecosystem service is defined as an economic indicator that provides information on the contribution of nature to product consumption by humans in the period, but with an uncertain meaning of ecological sustainability. We show that environmental income is the maximum economic value in the period of sustainable ecosystem service with both ecological and economic significance only if the future sustainable biophysical silvicultural management scenarios are accounted for. To measure environmental incomes, we model the future sustainable silviculture while considering all the management practices required to maintain cork oak woodlands in perpetuity. We use farm-level data to estimate voluntary opportunity costs incurred by land and livestock owners associated with hunting and livestock activities of the farmer as well as their subsequent scaling up to COW land-cover tiles in order to estimate environmental incomes at social prices for each individual activity. In this study, we measure the ecosystem services and incomes of the COW private amenity and public landscape activities at social prices, that is, their basic prices less own compensated and auto-consumed non-commercial intermediate consumption of services used by the private amenity and public landscape activities. The ecosystem services and environmental incomes of cork oak open woodlands measured by the extended accounts at basic prices in 2010 were 1.1 and 1.2 times higher, respectively, than those estimated at social prices. The ecosystem services and environmental incomes measured at basic prices by the refined standard accounts were 0.3 and 0.2 times, respectively, those estimated by the extended accounts at social prices.

Modelling bark thickness variation in stems of cork oak in south-western Portugal

The thickness of bark (cork) is of utmost importance for its industrial processing and, therefore, for the sustainable management of cork oak (Quercus suber L.) woodlands. Cork thickness has been reported to decrease from the stem base upwards but, to our knowledge, prediction models have not yet been presented. This study intended to develop reliable models to predict stem profiles of cork thickness. We addressed the relationship between bark thickness and stem height by measuring stem diameters and cork thickness at various stem heights in 76 trees. Through a repeated measure ANOVA, we selected the bark thickness response variables, cork-ring width and cork thickness. A mixed-effect modelling approach was used to fit linear bark thickness curves with stem height. Our results showed that the equations that performed better for cork thickness were functions of the stem relative height and cross-sectional cork area increment. The decreasing trend upwards the stem might lead to underestimation of cork thickness at the base, more than overestimate it at upper stem parts, in relation to the values at breast height, which are generally used to estimate the thickness of the whole cork plank. Furthermore, cork thickness curves were tree size-related, with larger trees exhibiting a steeper reduction in cork thickness upwards the stem.