Common Woody Species Research Articles

Accumulation of heavy metals in leaves of tree species on the ash and slag dumps of the Burshtyn Thermal Power Plant

Thermal power plant (TPP) facilities are considered as one of the major reasons for environmental pollution. Ash and slag dumps as a special construction for storage of combustion wastes of TPPs are recognized as sources of heavy metals (HMs) contamination for surrounding ecosystems. The present study is the first report of analyzing HMs contamination of the ash and slag dumps of the Burshtyn TPP.
 The aim of the study is to estimate the content of HMs in the technogenic substrates of ash and slag dumps and investigate soil-plant interactions through analyzing potential of HMs accumulation in the leaves of native dominant woody species.
 Materials and methods of research. Soil sampling was carried out in the period of July 2021 at previously determined points. The most common woody species (Populus tremula L., Betula pendula Roth., Salix caprea L.) were selected for testing of HMs accumulation abilities. Samples of plants and soil were subjected to an atomic absorption spectrometer for being analyzed for heavy metals: Cd, Zn, Ni, Cu, Pb, Mn and Fe.
 Results of research and discussion. The results showed that the substrates of ash and slag dumps of the Burshtyn TPP were mainly contaminated by lead, copper and cadmium. All tested species concentrated high amounts of magnesium, iron, zinc and low concentration of cadmium. Bioaccumulation factor reflected the highest abilities of accumulation of zinc in all tested species and low level of bioaccumulation of cadmium. The highest index of biochemical activity showed Betula pendula. Salix caprea were found as a promising species for remediation due to intensive accumulation of such elements like cadmium, lead, copper, zinc and nickel.
 Conclusions and prospects for further research. We consider plant organisms particularly useful for analyzing HMs accumulation as they can provide a cost-effective and long-term approach for bioindication and monitoring HMs pollution. Moreover, vegetation covers could be used for remediation of HMs contaminated sites

Sambucus nigra L. (fam. Viburnaceae) in Sicily: Distribution, Ecology, Traditional Use and Therapeutic Properties.

Sambucus nigra, the elderberry, has long been used for its medicinal properties in treating numerous diseases. Based on this traditional knowledge, its different pharmacological activities have been the focus of active research. All parts of the tree have long been used in traditional medicine, that is, the bark, the leaves, the flowers and the fruit. This study, carried out in Sicily (Italy), concerns the traditional uses of elder against human diseases. In order to trace the history of man's interaction with elder on the island, multidisciplinary research was carried out, aiming at (1) presenting a comprehensive overview of elderberry's applications and activities and (2) bridging traditional knowledge (uses and beliefs) with modern science, i.e., the most recent scientific findings in the biomedical and pharmacological fields. A rigorous literature review of scientific (and other local) reports on the elderberry tree and its application in food, health and household applications was undertaken. This article also provides a synthetic and updated picture of the ecology and distribution of S. nigra in Sicily. The elderberry is quite widespread in Sicily, yet its distribution is discontinuous. It prefers hedges, riparian woodlands, forest margins and clearings and is rather common along the watercourses flowing in the canyons of the Hyblaean Plateau, in the Madonie Mts. and in Enna province. Indeed, many old plants are often found near sacred places and rural houses, suggesting that in the past, it was extensively planted on purpose for its multiple uses. The complementary data obtained from multidisciplinary research confirm the usefulness of this approach in building a comprehensive and correct picture of the distribution of the most common woody species, for which the available knowledge is often fragmentary and imprecise.

Emissions of isoprene and monoterpenes from urban tree species in China and relationships with their driving factors

Isoprenoid (ISOP) emissions, particularly isoprene and monoterpenes, can significantly affect local and regional air quality due to their high chemical reactivity, with hot spots over polluted megacities. We investigated ISOP emissions from 32 common woody species in Beijing (Northern China) and Nanjing (Southern China). Relationships of ISOP emissions with plant functional types (trees vs shrubs; evergreen vs deciduous), leaf textures (papery vs leathery) and leaf physiological and biochemical traits were studied. Twenty-seven species emitted ISOPs, spanning very high isoprene emissions (typical of deciduous trees with papery leaves) to minute emissions of isoprene and monoterpenes in leathery leaves. Significant positive relationships between isoprene emission and the amounts of chlorophyll content, isoprene synthase protein and leaf nitrogen were observed, while the emissions of monoterpenes were not significantly related to any leaf physiological or biochemical trait. While looking for factors driving leaf isoprene and monoterpene emissions are complicated, our study shows leaf papery texture and high chlorophyll content may indicate presence of high isoprene emitters, to be used with caution for urban greening purposes.

Effects of warming on seed germination of woody species in temperate secondary forests.

Seed germination, a critical stage of the plant life cycle providing a link between seeds and seedlings, is commonly temperature-dependent. The global average surface temperature is expected to rise, but little is known about the responses of seed germination of woody plants in temperate forests to warming. In the present study, dried seeds of 23 common woody species in temperate secondary forests were incubated at three temperature sequences without cold stratification and after experiencing cold stratification. We calculated five seed germination indices and the comprehensive membership function value summarized the above indicators. Compared to the control, +2 °C and +4 °C treatments without cold stratification shortened germination time by 14% and 16% and increased the germination index by 17% and 26%, respectively. For stratified seeds, +4 °C treatment increased germination percentage by 49%, and +4 °C and +2 °C treatments increased duration of germination, germination index, and shortened mean germination time by 69%, 458%, 29% and 68%, 110%, 12%, respectively. The germination of Fraxinus rhynchophylla and Larix kaempferi were most sensitive to warming without and with cold stratification, respectively. Seed germination of shrubs were the least sensitive to warming among functional types. These findings indicate warming (especially extreme warming) will enhance the seedling recruitment of temperate woody species primarily via shortening germination time, particularly for seeds undergone cold stratification. In addition, shrubs might narrow their distribution.

Woody plant encroachment in granite barrens on the Frontenac Arch, eastern Ontario, Canada

AbstractAimsWoody plant encroachment is a widespread phenomenon affecting treeless or sparsely treed habitats. We aimed to determine the extent and timing of tree and shrub encroachment into rock barrens of eastern Ontario over the last century, and to assess implications for their ongoing management.LocationQueen's University Biological Station in the Frontenac Arch ecoregion.MethodsWe quantified the extent of change in woody vegetation in 290 rock barrens using aerial photography from 1925, 1965, and 2008. Composition and structure of woody plant communities in 10 barrens was subsequently quantified in the field using plot‐based sampling. Cores or cross‐sections were obtained from individuals >1.5 m height and dendrochronological techniques were used to determine their age and identify temporal patterns of any woody encroachment.ResultsAerial photography indicated that the mean proportion of woody plant cover in barrens increased 22.5% from 1925 to 2008. Dendroecological analysis supported this. Few trees were present prior to 1900 and most established since 1960.Fraxinus americana,Juniperus virginiana, andJuniperus communiswere the most common woody species colonizing the barrens. Remnants of largePinus strobusstumps with extensive charring were found in 90% of the sampled barrens at a mean density of 22.6 stumps ha−1.ConclusionsRock barrens on the Frontenac Arch have changed substantially over the past century; gradually being colonized by trees and shrubs and losing their distinctly open character. Active management — including prescribed fire and mechanical thinning — may be necessary if there is a desire to maintain these barrens and the rare species they support as components of the region's biodiversity. However, identification of a reference state for restoration is complicated by the fact that the structure and composition of these habitats were undoubtedly altered by European land clearance in the 19th century, and that some of these areas likely existed as pine woodlands before that.

Variations in spring leaf phenology and leaf freezing damage of common woody species in China

Variations in spring leaf phenology and leaf freezing damage of common woody species in China

Hydraulic traits are not robust predictors of tree species stem growth during a severe drought in a wet tropical forest

Abstract Severe droughts have led to lower plant growth and high mortality in many ecosystems worldwide, including tropical forests. Drought vulnerability differs among species, but there is limited consensus on the nature and degree of this variation in tropical forest communities. Understanding species‐level vulnerability to drought requires examination of hydraulic traits since these reflect the different strategies species employ for surviving drought. Here, we examined hydraulic traits and growth reductions during a severe drought for 12 common woody species in a wet tropical forest community in Puerto Rico to ask: Q1. To what extent can hydraulic traits predict growth declines during drought? We expected that species with more hydraulically vulnerable xylem and narrower safety margins (SMP50) would grow less during drought. Q2. How does species successional association relate to the levels of vulnerability to drought and hydraulic strategies? We predicted that early‐ and mid‐successional species would exhibit more acquisitive strategies, making them more susceptible to drought than shade‐tolerant species. Q3. What are the different hydraulic strategies employed by species and are there trade‐offs between drought avoidance and drought tolerance? We anticipated that species with greater water storage capacity would have leaves that lose turgor at higher xylem water potential and be less resistant to embolism forming in their xylem (P50). We found a large range of variation in hydraulic traits across species; however, they did not closely capture the magnitude of growth declines during drought. Among larger trees (≥10 cm diameter at breast height—DBH), some tree species with high xylem embolism vulnerability (P50) and risk of hydraulic failure (SMP50) experienced substantial growth declines during drought, but this pattern was not consistent across species. We found a trade‐off among species between drought avoidance (capacitance) and drought tolerating (P50) in this tropical forest community. Hydraulic strategies did not align with successional associations. Instead, some of the more drought‐vulnerable species were shade‐tolerant dominants in the community, suggesting that a drying climate could lead to shifts in long‐term forest composition and function in Puerto Rico and the Caribbean. Read the free Plain Language Summary for this article on the Journal blog.

Temperature sensitivity of leaf flushing in 12 common woody species in eastern China

Leaf phenology is one of the most reliable indicators of global warming in temperate regions because it is highly sensitive to temperatures. Temperature sensitivity (ST) is defined as the values of changed days of leaf flushing date (LUD) per degree increase in temperatures. Climate warming substantially advanced LUD in the temperate region, but its effect on ST of LUD is still not clear. We used spring phenological records of 12 woody plants in eastern China in the years of 1983–2014 to explore temporal and spatial changes of LUD and ST. Furthermore, we compared the difference of ST and preseason temperatures in two periods (1983–1997 and 2000–2014), and explored the main factors regulating ST. The results showed that the average LUD significantly advanced (−2.7 days per decade). The mean LUD over the period 1983–2014 was in day of the year (DOY) 87 ± 7 across sites and species for the early leaf flushing species (EFS), and mean DOY 102 ± 5 for the late leaf flushing species (LFS). LUD was earlier in low latitude than that in high latitude. ST of Armeniaca vulgaris was the most sensitive to temperature across all sites (−3.66 d °C−1), while Firmiana simplex was the most insensitive (−2.37 d °C−1). LUD of EFS was more sensitive to temperature warming than that of LFS. At the same site, LUD of EFS would advance more obviously than that of LFS under global warming. For all species, ST decreased significantly with shorter preseason length and warmer temperatures at the preseason end. Our results had demonstrated a strong relationship between ST and the preseason length (mean temperature at the preseason end).

Predicting the changes in suitable habitats for six common woody species in Central Asia.

Climate change over the past decades has significantly altered global hydrothermal conditions and caused an evident shift in species distribution. Predicting species distribution patterns and identifying their influencing factors will be essential in developing coping strategies to prevent species extirpation and extinction. Yet, environmental factors affecting the distribution of woody species in Central Asia remain largely unknown. Here, I used the MaxEnt model to predict the current distributions and future distribution under three SSP-RCP scenarios of six common woody species in Central Asia. The results indicated a good performance of the MaxEnt model. Precipitation of driest month and annual mean temperature were the dominant factors affecting species distribution. For the species with wide ecological niches, i.e., Acer negundo and Rosa chinensis, the suitable areas showed an evident expansion trend under future scenarios. In addition, a trend toward higher elevation was found for the species that grew at high altitudes (1600-3200m). However, the average elevation of suitable area for A. negundo and R. chinensis firstly increased but then decreased under future scenarios. Even though the areas with high species diversity increased from 0.59% under the current situation to 0.82% and 0.81% under ssp245 in 2021-2040 and 2041-2060, respectively, species diversity showed an apparent loss in parts of the northwest and southeast areas under ssp370 and ssp585. This study can guide susceptible habitat protections under climate change.

Bulk Density of Shrub Types and Tree Crowns to Use with Forest Inventories in the Iberian Peninsula

Bulk density for shrubs and tree crowns is an important variable, useful for many purposes, namely estimations for biomass and carbon sequestration and potential fire behavior prediction. In the latter case, bulk density is required to predict the rate of spread and intensity of crown fires. However, bulk density information is scarce. The estimation of bulk density is crucial to help choosing proper pyrosilviculture options to decrease fire susceptibility. Due to the similar environmental conditions and fuel characteristics in Portugal and Spain, we modelled bulk density for the most common woody species in all the Iberian Peninsula. We used 10 different shrub type formations and a set of tree species or groups common to both countries. Equations for bulk density, in both forest canopy and understory layers, were fitted as a function of biometric variables commonly used in forest inventories for the selected species. Standardized estimates of bulk density can be associated with data from the National Forest Inventories from Portugal and Spain, to estimate biomass of the forest ecosystems and to evaluate potential fire behavior involving tree canopies and shrubs.

Culturable fungal endophyte communities of primary successional plants on Mount St. Helens, WA, USA

BackgroundWhile a considerable amount of research has explored plant community composition in primary successional systems, little is known about the microbial communities inhabiting these pioneer plant species. Fungal endophytes are ubiquitous within plants, and may play major roles in early successional ecosystems. Specifically, endophytes have been shown to affect successional processes, as well as alter host stress tolerance and litter decomposition dynamics—both of which are important components in harsh environments where soil organic matter is still scarce.ResultsTo determine possible contributions of fungal endophytes to plant colonization patterns, we surveyed six of the most common woody species on the Pumice Plain of Mount St. Helens (WA, USA; Lawetlat'la in the Cowlitz language; created during the 1980 eruption)—a model primary successional ecosystem—and found low colonization rates (< 15%), low species richness, and low diversity. Furthermore, while endophyte community composition did differ among woody species, we found only marginal evidence of temporal changes in community composition over a single field season (July–September).ConclusionsOur results indicate that even after a post-eruption period of 40 years, foliar endophyte communities still seem to be in the early stages of community development, and that the dominant pioneer riparian species Sitka alder (Alnus viridis ssp. sinuata) and Sitka willow (Salix sitchensis) may be serving as important microbial reservoirs for incoming plant colonizers.

Lack of phenotypic plasticity in leaf hydraulics for 10 woody species common to urban forests of North China.

The survival and performance of urban forests are increasingly challenged by urban drought, consequently compromising the sustainability and functionality of urban vegetation. Plant-water relations largely determine species drought tolerance, yet little is known about the hydraulics of urban forest species. Here, we report the leaf hydraulic and carbon traits that govern plant growth and drought resistance, including vulnerability to embolism, hydraulic conductivity and leaf gas exchange characteristics, as well as morphological traits that are potentially linked with these physiological attributes, with the aim of guiding species selection and management in urban forests. Plant materials were collected from mature shrubs and trees on our university campus in Beijing, representing 10 woody species common to urban forests in north China. We found that the leaf embolism resistance, represented by the water potential inducing 50% loss of hydraulic conductivity (P50), as well as the hydraulic safety margin (HSM) defined by P50 and the water potential threshold at the inception of embolism (P12), varied remarkably across species, but was unrelated to growth form. Likewise, stem and leaf-specific hydraulic conductivity (Kstem and kl) was also highly species-specific. Leaf P50 was positively correlated with hydraulic conductivity. However, neither P50 nor hydraulic conductivity was correlated with leaf gas exchange traits, including maximum photosynthetic rate (Amax) and stomatal conductance (gs). Plant morphological and physiological traits were not related, except for specific leaf area, which showed a negative relationship with HSM. Traits influencing plant-water transport were primarily correlated with the mean annual precipitation of species climatic niche. Overall, current common woody species in urban forest environments differed widely in their drought resistance and did not have the capacity to modify these characteristics in response to a changing climate. Species morphology provides limited information regarding physiological drought resistance. Thus, screening urban forest species based on plant physiology is essential to sustain the ecological services of urban forests.

Regeneration status of common woody species in the riparian forests in Southwestern Nigeria

Sustainability of woody species in riparian forests requires information on its regeneration status, which is crucial for proper management and conservation of these species but the information is generally lacking in Nigeria. This knowledge of the regeneration status of common woody species in riparian forests guarantees their survival through proper management and conservation. Sampling was done via random method in which five (5) 10 m × 10 m plots were selected from the study sites giving a total of 45 plots. Therefore, the aim of the study was to assess the structures and status of common woody species in the regeneration layer of riparian forests. There was no significant (p &gt; 0.05) difference in the mean seedling and sapling densities of the common woody species across the riparian forest sites. The regression slope showed on-going regeneration (mostly weak) of the common riparian woody species in all the sites. The regeneration structures indicated reverse J-shaped and have been greatly modified by prevalent anthropogenic activities in the study area. The pattern of regeneration status observed in the seedlings and saplings emergence in the regeneration layer was due to the similar environmental factors that occurred from one site to the other. The intermediate values of tree/shrub ratio shown by the common woody species encountered in the regeneration layer indicated more individuals of shrub size than tree and emphasized the fact that the level of disturbance on-going was moderate across study and possibly that the sites were recovering from disturbances.

Woody encroachment happens via intensification, not extensification, of species ranges in an African savanna.

Widespread woody encroachment is a prominent concern for savanna systems as it is often accompanied by losses in productivity and biodiversity. Extensive ecosystem-level work has advanced our understanding of its causes and consequences. However, there is still debate over whether local management can override regional and global drivers of woody encroachment, and it remains largely unknown how encroachment influences woody community assemblages. Here, we examined species-level changes in woody plant distributions and size structure from the late 1980s to the late 2000s based on spatially intensive ground-based surveys across Kruger National Park, South Africa. This study region spans broad gradients in rainfall, soil texture, fire frequency, elephant density, and other topographic variables. Species-level changes in frequency of occurrence and size class proportion reflected widespread woody encroachment primarily by Dichrostachys cinerea and Combretum apiculatum, and a loss of large trees mostly of Sclerocarya birrea and Acacia nigrescens. Environmental variables determining woody species distributions across Kruger varied among species but did not change substantially between two sampling times, indicating that woody encroachers were thickening within their existing ranges. Overall, more areas across Kruger were found to have an increased number of common woody species through time, which indicated an increase in stem density. These areas were generally associated with decreasing fire frequency and rainfall but increasing elephant density. Our results suggest that woody encroachment is a widespread but highly variable trend across landscapes in Kruger National Park and potentially reflects an erosion of local heterogeneity in woody community assemblages. Many savanna managers, including in Kruger, aim to manage for heterogeneity in order to promote biodiversity, where homogenization of vegetation structure counters this specific goal. Increasing fire frequency has some potential as a local intervention. However, many common species increased in commonness even under near-constant disturbance conditions, which likely limits the potential for managing woody encroachment in the face of drivers beyond the scope of local control. Regular field sampling coupled with targeted fire management will enable more accurate monitoring of the rate of encroachment intensification.

Cavitation‐resistant junipers cease transpiration earlier than cavitation‐vulnerable oaks under summer dry conditions

AbstractAshe juniper (Juniperus ashei Buchholz) and escarpment live oak (Quercus fusiformis Small) are two of the most common woody species of the Edwards Plateau, an arid‐to‐semi‐arid region of nearly 100,000 km2 in central Texas. They have very different hydraulic strategies, yet they experienced similar mortality rates during an extreme drought in 2011. We measured J. ashei and Q. fusiformis sap flow velocities during summer dry periods of 2016 and 2017 at six micro‐sites. Although these were years with more‐or‐less average summer conditions, both included significant dry periods. To estimate the relative rate of decrease in sap velocity for each species during the dry periods, we fit a Bayesian exponential decay model to the sap velocity time series for each tree. We found that Q. fusiformis trees were better able to maintain transpiration than J. ashei during dry periods at five micro‐sites and were comparable at the sixth micro‐site. We conclude that it is likely that Q. fusiformis can better maintain transpiration during dry periods than J. ashei, on average, and that in the case of these two species, greater cavitation resistance may not translate to greater drought resistance.

Roots take up labeled nitrogen from a depth of 9 m in a wooded savanna in Brazil

The savannas (called Cerrado) are the second-largest vegetation formation in Brazil after the Amazon rainforest, with about 2 million km2. Roots have been found in very deep soil layers in Cerrado ecosystems, which suggests a crucial role of deep rooting in the supply of water and nutrients over dry periods. The aim of our study was to gain insight into the complementarity of common Cerrado woody species in taking up mobile nutrients throughout deep soil profiles. In a closed-canopy savanna with dense woody understory, labeled nitrate was injected into the soil at six soil depths (0.1, 1.5, 3.0, 6.0, 9.0, or 12.0 m) with three plots per depth, at two dates (in rainy and dry seasons). Five months after labeled nitrate injection, young leaves were sampled and foliar δ15N was determined in each plot in the three most common woody species (Coussarea hydrangeifolia, Miconia albicans and Xylopia aromatica). The maximum depth of 15N uptake was dependent on the species. X. aromatica trees took up 15N from a maximum depth of 9 m and exploited a much larger soil volume than the two other species, with the uptake of 15N at a horizontal distance of up to 5 m between the trunk and the injection site. The behavior of M. albicans and C. hydrangeifolia was similar, with a strong uptake of 15N only in the 0–1.5 m soil layer, within 2 m horizontally from the injection site. The depth of 15N uptake over the dry season was not related to the diameter at breast height of the woody plants sampled. We show that roots can take up labeled nitrogen from a depth of 9 m in tropical wooded savannas, which suggests an important role of deep-rooted species in closing biogeochemical cycles on highly weathered tropical soils.

Regeneration status of common woody species in the riparian forests in Southwestern Nigeria

Sustainability of woody species in riparian forests requires information on its regeneration status, which is crucial for proper management and conservation of these species but the information is generally lacking in Nigeria. This knowledge of the regeneration status of common woody species in riparian forests guarantees their survival through proper management and conservation. Sampling was done via random method in which five (5) 10 m × 10 m plots were selected from the study sites giving a total of 45 plots. Therefore, the aim of the study was to assess the structures and status of common woody species in the regeneration layer of riparian forests. There was no significant (p > 0.05) difference in the mean seedling and sapling densities of the common woody species across the riparian forest sites. The regression slope showed on-going regeneration (mostly weak) of the common riparian woody species in all the sites. The regeneration structures indicated reverse J-shaped and have been greatly modified by prevalent anthropogenic activities in the study area. The pattern of regeneration status observed in the seedlings and saplings emergence in the regeneration layer was due to the similar environmental factors that occurred from one site to the other. The intermediate values of tree/shrub ratio shown by the common woody species encountered in the regeneration layer indicated more individuals of shrub size than tree and emphasized the fact that the level of disturbance on-going was moderate across study and possibly that the sites were recovering from disturbances.

Functional traits and symbiotic associations of geoxyles and trees explain the dominance of detarioid legumes in miombo ecosystems

The miombo region in Africa is covered by a mosaic of woodlands and geoxylic grasslands and subject to disturbances like fires, frost and drought, and low nutrient availability. The dominance of Fabaceae Detarioideae species in miombo ecosystems is remarkable but little understood. We therefore compared plant functional traits (PFTs) of common woody species of the Angolan plateau, grouped by life form (trees, geoxyles), lineage (Fabaceae: Detarioideae, non-Detarioideae) and symbiont association (ectomycorrhiza, rhizobia). PFTs reflect group-specific adaptations to prevalent environmental conditions. To analyse the impact of environmental drivers, we selected PFTs reflecting ecophysiological aspects of leaf morphology, nutrient content and water transport. Traits were measured following standardized protocols. We found differences in key PFTs between trees and geoxyles reflecting both, life form specific adaptations to environmental conditions and lineage specific strategies to cope with environmental stresses. We interpret higher leaf thickness and higher wood density of geoxyles as responses to harsher open environments. Fabaceae in general and ectomycorrhizal species showed better nutrient status. Symbiotic associations of detarioid legumes with ectomycorrhiza show specific advantages for phosphorous uptake as compared to Rhizobia associated Fabaceae and to non-Fabaceae and thus may be crucial for the stunning dominance of Detarioideae in miombo landscapes.

Interaction of spatial sulfur patterns between urban air and woody species of the Pearl River Delta, southern China

Sulfur (S) uptakes by woody plants might indicate the presence of urban air pollution in the form of sulfur dioxide (SO2), which is one of the most important pollutants worldwide. The present study detected total carbon (C) and S contents in the leaf and stem (dry mass) of 53 common woody species in representative forest plots in five cities across the Pearl River Delta (PRD), a densely urbanized region in Southern China. Coupling analysis explored whether spatial patterns of S content in woody species were relatively consistent with atmospheric SO2 concentration in the five PRD cities. Total S content varied in leaves and stems with averages of 2.0 g/kg and 0.8 g/kg, respectively, while air SO2 concentration ranged from 9.0 to 108.0 g/m3. However, total C content was relatively constant among all the species across the diverse forest plots, with an average of 443.5 g/kg and a median of 448.0 g/kg in leaves and 437.0 g/kg in stems. This suggests that air SO2 pollution did not influence tree growth, so afforestation may be an effective method of eliminating urban air pollution in the PRD.

The endemic Mediterranean dwarf palm boosts the recolonization of old-fields: Implications for restoration

Understanding the mechanisms underlying the recolonization of old-fields is critical to promote the recovery of the ecosystem functioning, particularly in regions where agricultural abandonment has increased in the last 60 years. Given that seed arrival and seedling survival often limit the recolonization process by woody species in many Mediterranean habitats, the ‘perching’ and ‘nursing’ effects exerted by some pioneer species could be crucial for the restoration of such abandoned lands. We examined the role of an endemic Mediterranean palm (Chamaerops humilis) on the recolonization of old-fields by woody species in southern Iberian Peninsula. We chose three independent old-fields differing in their shrub encroachment levels. To identify potential facilitation by C. humilis, we used a spatially-explicit approach and analyzed its spatial associations with ten common woody species (e.g. Asparagus spp., Daphne gnidium, Olea europaea var. sylvestris, Pyrus bourgaeana). We detected positive spatial associations between C. humilis and woody species at small-scale (1–5 m) in the three plots. Most of such small-scale associations were linked to the bird-dispersal of woody species. Nonetheless, there were marked differences among plots in spatial associations between C. humilis and woody plants, being Asparagus spp. the only species positively associated with C. humilis within the three studied old-fields. These species-specific differences were likely related to variations among old-fields in encroachment level and the legacy of human management. Such small-scales spatial associations between C. humilis and woody species across Iberian old-fields were linked to the perching and nursing effects exerted by the palm. We emphasize the strong potential of this pioneer Mediterranean palm for the restoration of native ecosystems and the recovery of ecosystems services.