Monitoring Diversity Profiles of Forested Landscapes in the Mediterranean Spain: Their Contribution to Local and Regional Vascular Plant Diversity

At landscape and regional scales topography is recognized as one of the most important determinants of vascular plant diversity, primarily due to the influence of mountains. As temperature changes markedly over the elevation ranges in mountain areas, topography offers a wide variety of different habitats as well as buffering against climate change. However, for local vegetation, notably in lowland areas, the general importance of topography is less well recognized and the mechanisms by which it exerts influence on local vascular plant diversity are not comprehensively understood. In this review, we provide an overview of the evidence for the different mechanisms involved in topography’s control of local patterns in potential vegetation drivers, namely incident solar energy, wind exposure, hydrology, geochemistry, and biotic conditions. Furthermore, we review the processes through which these factors shape local terrestrial vascular plant diversity patterns and provide directions for future studies on this topic. We find that topography is an important factor for local vascular plant diversity patterns in a broad range of habitats throughout the world, even in relatively flat lowlands. However, the mechanisms involved are varied and complex. Local patterns in soil moisture seem to be affected by topography through more mechanisms than other topographically controlled factors and have a strong and consistent influence on local plant diversity. Hence, local hydrology is probably the main mechanistic factor through which topography influences local terrestrial vascular plant diversity patterns. Future research should focus on employing high‐coverage fine‐resolution topographic data to comprehensively explore the role of topography in controlling local dynamics over large areas. Moreover, we recommend including several different habitats, particularly those in which the role of topography is poorly understood. Finally, we propose to integrate relevant functional topographic variables such as topographic wetness indices instead of simple topographic measures into future investigations.

Species-rich tropical communities are expected to be more specialized than their temperate counterparts. Several studies have reported increasing biotic specialization toward the tropics, whereas others have not found latitudinal trends once accounting for sampling bias or differences in plant diversity. Thus, the direction of the latitudinal specialization gradient remains contentious. With an unprecedented global data set, we investigated how biotic specialization between plants and animal pollinators or seed dispersers is associated with latitude, past and contemporary climate, and plant diversity. We show that in contrast to expectation, biotic specialization of mutualistic networks is significantly lower at tropical than at temperate latitudes. Specialization was more closely related to contemporary climate than to past climate stability, suggesting that current conditions have a stronger effect on biotic specialization than historical community stability. Biotic specialization decreased with increasing local and regional plant diversity. This suggests that high specialization of mutualistic interactions is a response of pollinators and seed dispersers to low plant diversity. This could explain why the latitudinal specialization gradient is reversed relative to the latitudinal diversity gradient. Low mutualistic network specialization in the tropics suggests higher tolerance against extinctions in tropical than in temperate communities.

The narrative of biodiversity decline in response to human impacts is overly simplistic because different aspects of biodiversity show different trajectories at different spatial scales. It is also debated whether human-caused biodiversity changes lead to subsequent, accelerating change (cascades) in ecological communities, or alternatively build increasingly robust community networks with decreasing extinction rates and reduced invasibility. Mechanistic approaches are needed that simultaneously reconcile different aspects of biodiversity change, and explore the robustness of communities to further change. We develop a trophically structured, mainland-archipelago metacommunity model of community assembly. Varying the parameters across model simulations shows that local alpha diversity (the number of species per island) and regional gamma diversity (the total number of species in the archipelago) depend on both the rate of extirpation per island and on the rate of dispersal between islands within the archipelago. In particular, local diversity increases with increased dispersal and heterogeneity between islands, but regional diversity declines because the islands become biotically similar and local one-island and few-island species are excluded (homogenisation, or reduced beta diversity). This mirrors changes observed empirically: real islands have gained species (increased local and island-scale community diversity) with increased human-assisted transfers of species, but global diversity has declined with the loss of endemic species. However, biological invasions may be self-limiting. High-dispersal, high local-diversity model communities become resistant to subsequent invasions, generating robust species-community networks unless dispersal is extremely high. A mixed-up world is likely to lose many species, but the resulting ecological communities may nonetheless be relatively robust.

Long-term diversity equilibria, ecological incumbency, and widespread recurrent fossil assemblages have each been cited as evidence that local processes, such as competition, played an important role in structuring communities over geologic time. We analyze the relationship between local and regional diversity in tropical marine communities spanning approximately 13 Myr of the Late Ordovician to test for the role of local processes in structuring local communities. We find a significant and strong positive relationship between local and regional diversity, indicating that local communities were not saturated with species and that local processes did not exert a dominant influence on local diversity. Rather, local diversity was influenced more by regional oceanographic processes that governed the size of the regional species pool. This evidence for unsaturated communities is consistent with the Walker and Valentine hierarchically structured niche model of global diversification. These results come at the beginning of the 200-Myr Paleozoic plateau in both local and global diversity and therefore raise the question whether local communities were ever saturated with species during the Paleozoic. Similar studies need to be conducted during other times in the Paleozoic to determine if this is indeed the case.

There are many data values describing deadwood in primary forests, however, there is much less information concerning managed forests, particularly in the Mediterranean area. Whole non-living woody biomass (deadwood) is the main component of forest types that plays a vital role in improving and maintaining biodiversity. The dynamics of deadwood and CO2 sequestration by deadwood were examined in three Mediterranean lowland forests: pine forest Pinus pinea L.), evergreen oak forest (Quercus ilex and Quercus suber L.), and deciduous oak forest (Quercus cerris L.). The aim of this study was to carry out a quantitative and qualitative evaluation of the deadwood to gather useful information for the Mediterranean forest management, and to provide some useful data that can be integrated into the methods of estimation for carbon stored in dead components of Mediterranean forest types. The investigations focused on the characterization of the deadwood, to determine which traits are dominant and their potentially functionality within the forest type. Results indicated the deciduous oak type had the highest amount of stand volume (379 m3/ha), deadwood volume (161.8 m3/ha), and C storage (31.43 t/ha). The major component of dead wood was the standing dead trees or snags. There was a higher volume of deadwood in the deciduous oak forest than in the pine and evergreen oak forests. In addition, the deciduous oak forest had a higher snag creation index, a higher fallen log creation index, and a higher past management index compared to pine and evergreen oak forest types. Deadwood volume increased as the decay class in the deciduous oak forest increased, while this trend decreased in the evergreen oak and pine forests. The amount of deadwood was affected by the forest type and forest management regime. Dynamic and past management of deadwood indices indicated that their structure was still in the initial phase of creation and decay in the pine and evergreen oak forests. A comparison with other studies on similar forest types brought out that the variation range of the main parameters for the management of deadwood fell within the variation of the parameters studied. However, the values of these parameters cover a broad range. The population of each forest type is extremely sensitive to the different evolutionary periods of the forest dynamics.

The relationship between local and regional diversity in viperid snake assemblages from South America was estimated. However, viperid species richness was spatially patterned across the continent, and this result can bias significance levels of regression analyses. To overcome this problem, we determined the minimum distance between localities that ensures stochastic independence of diversity estimates across space, using geostatistical analyses. We analyzed the relationship between local and regional diversity at three different spatial scales, by increasing region size. For the three scales, there was a significant linear relationship between local and regional diversity, indicating that local viperid assemblages are unsaturated and that their local diversity is constrained by species richness of the regional pool. Overall, this result indicates the importance of regional and historical processes on the determination of viperid species richness at local scales. Neste trabalho, a relação entre diversidade local e regional foi estimada para comunidades de serpentes viperídeas da América do Sul. Entretanto, como a diversidade local está padronizada espacialmente em escala continental, há um viés nas análises de regressão relacionando esses componentes. Para corrigir esse problema, procedimentos de análise geoestatística foram utilizados a fim de determinar a menor distância geográfica entre localidades que garante independência estocástica entre as estimativas da diversidade local. A relação entre diversidade local e regional foi analisada em três escalas espaciais, ampliando sucessivamente a área da região. Em todas essas escalas, uma relação significativa entre as estimativas foi encontrada, indicando que as comunidades locais não estão saturadas e que sua diversidade é restrita pelo conjunto de espécies na região. De um modo geral, esse resultado mostra a importância de processos regionais e históricos, em grandes escalas de tempo e espaço, determinando a diversidade das serpentes viperídeas em escala local.

Fire is a major disturbance linked to the evolutionary history and climate of Mediterranean ecosystems, where the vegetation has evolved fire-adaptive traits (e.g., serotiny in pines). In Mediterranean forests, mutualistic feedbacks between trees and ectomycorrhizal (ECM) fungi, essential for ecosystem dynamics, might be shaped by recurrent fires. We tested how the structure and function of ECM fungal communities of Pinus pinaster and Pinus halepensis vary among populations subjected to high and low fire recurrence in Mediterranean ecosystems, and analysed the relative contribution of environmental (climate, soil properties) and tree-mediated (serotiny) factors. For both pines, local and regional ECM fungal diversity were lower in areas of high than low fire recurrence, although certain fungal species were favoured in the former. A general decline of ECM root-tip enzymatic activity for P.pinaster was associated with high fire recurrence, but not for P.halepensis. Fire recurrence and fire-related factors such as climate, soil properties or tree phenotype explained these results. In addition to the main influence of climate, the tree fire-adaptive trait serotiny recovered a great portion of the variation in structure and function of ECM fungal communities associated with fire recurrence. Edaphic conditions (especially pH, tightly linked to bedrock type) were an important driver shaping ECM fungal communities, but mainly at the local scale and probably independently of the fire recurrence. Our results show that ECM fungal community shifts are associated with fire recurrence in fire-prone dry Mediterranean forests, and reveal complex feedbacks among trees, mutualistic fungi and the surrounding environment in these ecosystems.

Stone pine (Pinus pinea L.) has been cultivated since centuries in Mediterranean areas for its products and economic benefits, including edible pine nuts, timber, mushrooms, firewood, and grazing. However, current management objectives of stone pine stands also include recreational use, biodiversity conservation, protection from soil erosion, and CO2 fixation. Stone pine stands are considered to be among the ecosystems most vulnerable to climate change, and the current increase in drought frequency in the Mediterranean Basin has been shown to negatively impact their long-term establishment. Understanding the effects of climate change on the distribution, tree-ring growth and water use of stone pine forests can help assessing the adaptive capacity of the species, and developing management programs aimed at its conservation. This paper reviews the impacts of climate change on stone pine in the Mediterranean region. The high sensitivity of stone pine to climate change has been widely demonstrated in that: (i) climatic models predict the loss of suitable habitats and the shift of its geographical distribution in the next future; (ii) tree-ring analysis showed that winter and spring rainfalls have positive effects on growth, whereas high spring temperature has a negative effect; (iii) the strategy of stone pine to cope with water deficit affects the processes regulating its growth, including wood formation, leading to peculiar tree-ring anatomical features such as intra-annual density fluctuations. The silvicultural interventions and the most effective management strategies for stone pine forests are reviewed and discussed in the context of current climate change in the Mediterranean Basin.

The extent to which species richness in local communities is determined by regional and historical processes is not well understood. An increasingly popular way to investigate these large-scale processes is through regressions of local on regional species richness. We sampled local and regional species richness in a broad array of taxa from around the world to address five questions. First, is the relationship between local and regional species richness linear, or does local richness accumulate more slowly at progressively higher regional diversities, suggesting local saturation of species diversity? Second, do these relationships vary with locality size? Third, do taxa and continents differ in the form of relationships between local and regional diversity? Fourth, do relationships between local and regional diversity depart from that expected from a null model in which all individuals of a locality are randomly sampled from a regional pool of species whose abundances have a canonical log-normal distribution? Fifth, using this same null model, how does the expected relationship between local and regional species richness depend on the sampling intensity within localities? We used distribution maps to ensure that diversity was sampled in a consistent manner across diverse taxa. Each region was 500 × 500 km, and localities were 1% and 10% of the region size. There was no evidence of local species saturation, as local species richness was strongly and linearly related to regional richness at both spatial scales. Between scales, local diversity accumulated faster as a function of regional diversity at the larger spatial scale. The slope of this relationship between local and regional diversity was the same among taxa across continents, and between Australia and North America across taxa. In other words, at each spatial scale one relationship between local and regional diversity describes most cases very well. The null model showed that approximately linear relationships between local and regional diversity are expected when regional species abundances are log-normal and when the number of individuals sampled within localities is large (roughly 200 times the number of species in the most species-rich region examined). However, empirical slopes were less than expected from the null model, which we interpret as an effect of spatial turnover of species (beta diversity). Since these slopes were nevertheless similar among taxa and between regions, rates of spatial turnover must be approximately the same among these taxa and regions. The log-normal model also showed that nonlinear (concave down) relationships between local and regional diversity are expected under random sampling when sample size is small relative to regional diversity. Therefore, nonlinear relationships are not necessarily indicative of saturation. Our results suggest that at the scales investigated here local communities are unsaturated and that their diversities are strongly limited by species richness of the surrounding regions. Similarity between taxa and continents in the form of the local-regional diversity relationship implies that “rules” governing the assembly of local communities may be widely consistent. If so, understanding species diversity in local assemblages will require knowledge of processes acting at larger spatial scales, including determinants of regional species richness and spatial turnover of species.

Forests’ global carbon stock is estimated at 662 Gt, with 45% of it being soil organic matter (FAO 2020). Mediterranean forests, while crucial for long-term carbon storage in their soils (with a reported 25% of CO2 assimilated through photosynthesis being stored in the ecosystems’ soils (Luyssaert et al. 2007), face growing threats from climate change-induced xerothermic conditions and ongoing anthropogenic disturbances. Even though climate change mitigation strategies in forestry have been developed, they mostly concern wood and biomass production, and less attention has been given to mitigation strategies regarding forests’ soil carbon stocks in Europe. PineOptim project attempts to investigate the impact of different management practices on water and carbon budgets in pine forests, across an established monitoring network of Pinus brutia and P. halepensis forests distributed across Sani, Xanthi and Lesvos Island in Greece. This study, as part of the PineOptim project aims to enhance current knowledge on decomposition dynamics in Mediterranean forests and the effects of abiotic factors involved under different management regimes, vegetation status and climatic regions. The study areas in Sani (P. halepensis with evergreen understory vegetation) and Xanthi (P. brutia with broadleaf tree understory) have been subjected to various management practices (understory removal in Sani and different overstory thinning intensities in the peri-urban forest of Xanthi), while on Lesvos the study area consists of unmanaged P. brutia stands varying in post-fire age and stand structure density. Decomposition dynamics have been studied by a parallel implementation protocol of the litterbag method and a standard materials method (paper sheets and wood sticks) (Kurz-Besson et al. 2005; Joly et al. 2017) for evaluating site-specific physicochemical litter characteristics drivers along with micro-environmental factors. Analysis was conducted using generalized linear and non-linear mixed effects models, to explore the importance of each factor involved in decomposition dynamics across and among the various study sites. Preliminary results suggest a significant influence of atmospheric and soil climatic parameters (air relative humidity, soil temperature and water content) and their interaction, along with Leaf Area Index (LAI) to decomposition rates and the remaining organic mass. Regional deviations are highlighted, giving us insight into the rates of organic matter assimilation under each management practice and climatic region. These findings underscore the potential of tailored forest management strategies to optimize litter decomposition and soil carbon stocks, in mediterranean pine forests. In addition, our results support the integration of decomposition dynamics into climate change mitigation strategies on the forestry sector.

Metacommunity models predict that communities in patchy environments will show different patterns of diversity than communities in continuous habitats. The species richness of herbs was measured in 24 small patches (0.5–3 ha) of serpentine soil and 24 equivalently spaced sets of sampling sites on four large areas (>5 km2) of serpentine soil in the North Coast Ranges of California. Patchy and continuous sites were compared with respect to local diversity (species richness within 5 × 50 m transects), regional diversity (species richness at all 24 sites combined), and among-site differentiation (average proportion of species unshared between any one site and the other 23 sites of its kind). For all herb species together, regional diversity and average local diversity were higher on small patches, mainly because of a significantly higher number of alien species. For the subset (14%) of herb species that were endemic to serpentine, regional diversity was similar on patchy and continuous sites, but it was partitioned differently; local diversity was lower, and among-site differentiation was higher on small patches. Herb diversity also showed significant gradients with soil calcium levels, and these effects were not independent of site type (patchy or continuous). Soil calcium was correlated positively with the number of alien species on small patches, and negatively with the number of serpentine-endemic species on continuous sites. Also, total herb diversity was negatively correlated with elevation on continuous sites. However, patchy and continuous sites did not differ in their average calcium levels or elevation. These results agree with theory predicting that, relative to communities in widespread habitats, local communities in patchy habitats will contain more habitat generalist and fewer habitat specialist species. However, the results also suggest that the effects of habitat geometry interact with those of habitat quality in this system.

Natural forests and plantations of Pinus are ecologically and economically important worldwide, producing an array of goods and services, including the provision of non-wood forest products. Pinus species play an important role in Mediterranean and boreal forests. Although Pinus species seem to show an ecological adaptation to recurrent wildfires, a new era of mega fires is predicted, owing to climate changes associated with global warming. As a consequence, fungal communities, which are key players in forest ecosystems, could be strongly affected by these wildfires. The aim of this study was to observe the fungal community dynamics, and particularly the edible fungi, in maritime (Pinus pinaster Ait.), austrian pine (Pinus nigra J.F. Arnold), and scots pine (Pinus sylvestris L.) forests growing under wet Mediterranean, dry Mediterranean, and boreal climatic conditions, respectively, by comparing the mushrooms produced in severely burned Pinus forests in each area. Sporocarps were collected during the main sampling campaigns in non-burned plots, and in burned plots one year and five years after fire. A total of 182 taxa, belonging to 81 genera, were collected from the sampled plots, indicating a high level of fungal diversity in these pine forests, independent of the climatic conditions. The composition of the fungal communities was strongly affected by wildfire. Mycorrhizal taxa were impacted more severely by wildfire than the saprotrophic taxa, particularly in boreal forests—no mycorrhizal taxa were observed in the year following fire in boreal forests. Based on our observations, it seems that fungal communities of boreal P. sylvestris forests are not as adapted to high-intensity fires as the Mediterranean fungal communities of P. nigra and P. pinaster forests. This will have an impact on reducing fungal diversity and potential incomes in rural economically depressed areas that depend on income from foraged edible fungi, one of the most important non-wood forest products.

In this study we aimed at comparing invertebrate diversity of high altitude lakes and ponds along hierarchical spatial scales. We compared local, among-site, and regional diversity of benthic macro- invertebrates in 25 ponds and 34 lakes in the Tatra Mountains, central Europe. The ponds showed significantly lower local diversity, higher among- site diversity and similar regional diversity than the lakes. The species-area relationships (SAR), habitat heterogeneity, and environmental harshness are assumed as drivers for the local diversity patterns. An ecological threshold separating pond and lake systems emerged at an area of 2 ha, where the SAR pattern changed significantly. Differences in species turnover between these systems were likely driven by greater environmental variability and isolation of the ponds. High altitude ponds neither significantly sup- port greater regional diversity nor higher number of unique taxa than lakes. The higher among-site diver- sity of ponds relative to lakes highlights the relevance of ponds for regional diversity in mountain areas.

Background: Facilitation plays important roles in the structuring of plant communities and several studies have found that it tends to increase with environmental severity in alpine plant communities. In addition, cushion plants have been shown to act as nurse plants, moderating extreme environmental conditions, and providing resources for other species, with substantial effects on local plant diversity. Aims: This study addresses the nurse plant effects of Silene acaulis – a common, circumpolar alpine plant species with a compact cushion-forming growth form – along an altitude transect in the mid- to high-alpine zones in northern Sweden. Methods: The numbers of species in paired S. acaulis cushions and identical-sized control plots along an altitude transect between 1150 m and 1450 m above sea level were compared, and differences in species composition were analysed. Results: At altitudes above c. 1280 m, but not at lower altitudes, more species were found inside the cushions than in their paired control plots. Species composition was similar inside cushions and in control plots. Conclusions: Our results suggest that S. acaulis acts as a nurse plant at altitudes higher than a certain threshold (c. 1280 m at the investigated site). It appears to play an important role in creating focal points for local vascular plant diversity in high-alpine environments, where vegetation is open and occurs in small patches.

This study investigated the effects of plant diversity, habitat type and landscape structure on the functional diversity of the carabid assemblages in the agro‐landscape of the North China Plain. We hypothesise (i) small, herbivorous and omnivorous carabids are more strongly affected by local plant diversity, while large and predatory carabids are strongly affected by landscape structure, and (ii) habitat type influences the diversity across functional groups. In 2010, carabid beetles were sampled by pitfall traps in six typical habitats of the agro‐landscape: wheat/maize fields, peanut fields, orchards, field margins, windbreaks and woodland. Our results showed that (i) habitat type played a predominant role in driving the changes in the diversity of carabid assemblages, followed by local plant diversity while the landscape structure had little effect; (ii) small and omnivorous carabid were strongly affected by local plant diversity, while the composition of large and predatory carabid was strongly associated with the landscape structure; and (iii) habitats dominated by woody species harboured different assemblages to habitats dominated by herbaceous plants for overall carabids and three functional groups excluding omnivorous beetles. Informed by our results, we suggest the differentiated responses between functional groups should be appreciated in conservation management. In the intensively managed agro‐landscape, maintenance of diverse habitats and creating a more complex vegetation structure would be the most efficient measures to enhance the diversity of carabid assemblages. Particularly, the maintenance of extensively managed habitats coupled with a targeted increase in the local plant diversity is crucial to optimise the biological pest control by carabid assemblages.