Reconstructing the impact of human activities in a NW Iberian Roman mining landscape for the last 2500 years

This article was made available through the Brunel Open Access Publishing Fund.Little is known about the impact of human activities during Roman times on NW Iberian mining landscapes beyond the geomorphological transformations brought about by the use of hydraulic power for gold extraction. We present the high-resolution pollen record of La Molina mire, located in an area intensely used for gold mining (Asturias, NW Spain), combined with other proxy data from the same peat core to identify different human activities, evaluate the strategies followed for the management of the resources and describe the landscape response to human disturbances. We reconstructed the timing and synchronicity of landscape changes of varying intensity and form occurred before, during and after Roman times. An open landscape was prevalent during the local Late Iron Age, a period of relatively environmental stability. During the Early Roman Empire more significant vegetation shifts took place, reflected by changes in both forest (Corylus and Quercus) and heathland cover, as mining/metallurgy peaked and grazing and cultivation increased. In the Late Roman Empire, the influence of mining/metallurgy on landscape change started to disappear. This decoupling was further consolidated in the Germanic period (i.e., Visigothic and Sueve domination of the region), with a sharp decrease in mining/metallurgy but continued grazing. Although human impact was intense in some periods, mostly during the Early Roman Empire, forest regeneration occurred afterwards: clearances were local and short-lived. However, the Roman mining landscape turned into an agrarian one at the onset of the Middle Ages, characterized by a profound deforestation at a regional level due to a myriad of human activities that resulted in an irreversible openness of the landscape. © 2014 The Authors

Exploring Species Limits in Two Closely Related Chinese Oaks

Background. The species status of two closely related Chinese oaks, Quercus liaotungensis and Q. mongolica, has been called into question. The objective of this study was to investigate the species status and to estimate the degree of introgression between the two taxa using different approaches. [br/] Methodology/Principal Findings. Using SSR (simple sequence repeat) and AFLP (amplified fragment length polymorphism) markers, we found that interspecific genetic differentiation is significant and higher than the differentiation among populations within taxa. Bayesian clusters, principal coordinate analysis and population genetic distance trees all classified the oaks into two main groups consistent with the morphological differentiation of the two taxa rather than with geographic locations using both types of markers. Nevertheless, a few individuals in Northeast China and many individuals in North China have hybrid ancestry according to Bayesian assignment. One SSR locus and five AFLPs are significant outliers against neutral expectations in the interspecific FST simulation analysis, suggesting a role for divergent selection in differentiating species.[br/] Main Conclusions/Significance. All results based on SSRs and AFLPs reached the same conclusion: Q. liaotungensis and Q. mongolica maintain distinct gene pools in most areas of sympatry. They should therefore be considered as discrete taxonomic units. Yet, the degree of introgression varies between the two species in different contact zones, which might be caused by different population history or by local environmental factors

Coppice forests and genetic diversity A case study in Quercus pyrenaica Willd. from Central Spain

The amount of standing genetic diversity found in oak coppice forests has been subjected to intense debate amongst forest ecologists and managers. In this study, the level of vegetative propagation and the genetic diversity found in a coppice forest of rebollo oak (Quercus pyrenaica) was examined. The current range of rebollo oak in the Iberian Peninsula reveals its adaptation to sub-Mediterranean mountain ecosystems. High sprouting capability, mainly by root suckers, has favoured traditional exploitation of rebollo oak in coppice forests. Using nine microsatellite loci, we have detected 14 clone assemblies compounded by 2-4 stems (7.9 ± 1.3 ramets per genet, considering stand density) and covering an average surface of 11.4 m2 per genet. The levels of genetic diversity and the amount of unique genotypes were high (D = 0.9972, G/N = 0.86) and similar to the clonality levels found in a nearby open oak woodland. Despite numerous clear-cutting rotations, known at least since 1750, and the heavy root sprouting observed after a thinning event, low clonal propagation (∼27%) was detected. This fact pointed towards the long-term persistence of several small clonal assemblies in this coppice. Our findings suggest that intense thinning practices are unadvisable in the conversion of Q. pyrenaica coppice into high forest due to the significant losses of genetic diversity when removing unique genotypes. © 2007 Elsevier B.V. All rights reserved

Respiratory costs of woody tissues in a Quercus pyrenaica coppice

Long-term coppicing leads to the development of massive root systems. A disproportionate carbon investment in root maintenance has been pointed as a cause of the widespread decline of abandoned coppices. We aimed at assessing how coppicing has influenced root and shoot development and related carbon loss ascribed to maintenance of woody tissues in Quercus pyrenaica. For this goal, results from published studies on root dynamics, woody biomass and respired CO2 fluxes in an abandoned Q. pyrenaica coppice were integrated and extended to quantify overall respiratory expenditures of above- and below-ground woody organs. Internal and external CO2 fluxes together with soil CO2 efflux were monitored in eight stems from one clone across a growing season. Stems and roots were later harvested to quantify the functional biomass and scale up root and stem respiration (RR and RS, respectively) to the clone and stand levels. Below- and above-ground biomass was roughly equal. However, the root-to-shoot ratio of respiration (RR/RS) was generally below one. Relatively higher RS suggests enhanced metabolic activity aboveground during the growing season, and highlights an unexpected but substantial contribution of RS to respiratory carbon losses. Moreover, soil and stem CO2 efflux to the atmosphere in Q. pyrenaica fell in the upper range of reported rates for various forest stands distributed worldwide. We conclude that both RS and RR represent an important carbon sink in this Q. pyrenaica abandoned coppice. Comparatively high energetic costs in maintaining multiple stems per tree and centennial root systems might constrain aboveground performance and contribute to coppice stagnation

Climate Change Synchronizes Growth and iWUE Across Species in a Temperate-Submediterranean Mixed Oak Forest

15 Pág.Tree species have good tolerance to a range of environmental conditions, though their ability to respond and persist to environmental changes is dramatically reduced at the rear-edge distribution limits. At those edges, gene flow conferring adaptation is impaired due to lack of populations at lower latitudes. Thus, trees mainly rely on phenotypic changes to buffer against long-term environmental changes. Interspecific hybridization may offer an alternative mechanism in the generation of novel genetic recombinants that could be particularly valuable to ensure persistence in geographically isolated forests. In this paper, we take advantage of the longevity of a temperate-submediterranean mixed-oak forest to explore the long-term impact of environmental changes on two different oak species and their hybrid. Individual trees were genetically characterized and classified into three groups: pure Quercus petraea (Matt.), Liebl, pure Q. pyrenaica Willd, and hybrids. We calculated basal area increment and intrinsic water-use efficiency (iWUE) from tree-ring width and δ13C per genetic group, respectively. Tree-growth drivers were assessed using correlation analyses and generalized linear mixed models for two contrasting climatic periods: (1880-1915, colder with [CO2] 338 ppm). The three genetic groups have increased radial growth and iWUE during the last decades, being the least drought-tolerant QuPe the most sensitive species to water stress. However, no significant differences were found among genetic groups neither in mean growth rate nor in mean iWUE. Furthermore, little differences were found in the response to climate among groups. Genetic groups only differed in the relationship between δ13C and temperature and precipitation during the earlier period, but such a difference disappeared during the recent decades. Climate change may have promoted species-level convergence as a response to environment-induced growth limitations, which translated in synchronized growth and response to climate as well as a tighter stomatal control and increased iWUE across coexisting oak species.This work was supported by the Madrid Regional Government and EU (Project BOSSANOVA; S2013/MAE-2760), and by the Spanish Ministry of Science, Innovation and Universities (AGL2014-61175-JIN and AGL2015-73190-JIN). ID-L received financial support from Fundació La Caixa through the Junior Leader Program (LCF/BQ/LR18/11640004). GG-I was partly funded by the Spanish Ministry of Economy and Competitiveness through RyC-2014-15864.Peer reviewe

Coexistence in the Mediterranean-Temperate transitional border Multi-century dynamics of a mixed old-growth forest under global change

Old-growth forests, particularly those located at the interface between different bioregions, are unevalu_x0002_able sources oflong-termvegetationdynamics andhistorical standresponse tonatural andanthropogenic disturbances. Although old-growth forests are scarce,the information gathered studying them may assist forest ecosystem restoration and management under forthcoming climate and land-use changes. We analysed how complementary dynamics of a mixed old-growth forest composed by temperate (Fagus sylvatica, Quercus petraea) and submediterranean (Quercus pyrenaica) tree species were driven in response to global changes in the lasttwo centuries. The old-growth forest, named El Hayedo de Montejo, is located at the interface between the Mediterranean and temperate bioregions in the centre of the Iberian Peninsula. The populations of temperate species growing in El Hayedo de Montejo (F. sylvatica and Q. petraea) are at the dry and warm edges of their natural distribution area in Europe, whereas the submediterranean species Q. pyrenaica is at the core of the distribution range. In order to analyse the long-term dynamics, we developed basal area increment and disturbance chronologies for each of the tree species under study. Furthermore, we assessed the climate influence on tree growth during the most recent decades. Our results reveal historical shifts in forest dominance (as reflected by growth) induced by changes in climate andforestmanagement betweentemperate andsub-Mediterraneanspecies. This wasparticularly noticeable for F. sylvatica and Q. pyrenaica the least and most drought-tolerant species, respectively. A reduction in growth of F. sylvatica unprecedented in the context of the last two hundred years was observed during the last decades concurrent with forest densification and marked changes in climate. Conversely, both oak species seem to be better suited to current environmental conditions as expressed by increasing growth rates

Population clustering and clonal structure evidence the relict state of Ulmus minor Mill. in the Balearic Islands

Field elm (Ulmus minor) is a riparian tree that grows in rare, small populations scattered along temporary watercourses in the Balearic Islands, nowadays mostly covered with Mediterranean vegetation. Agriculture and farming on the fertile land along the periodically flooded plains have reduced the elm populations to sparse tree lines along the creek beds. The presence of field elm in this very anthropic landscape has led some authors to consider it as an introduced species in the Balearics. However, pollen data suggest these elms may be the remains of larger populations experiencing continuous population shrinkage during the Holocene, and hence be native to the isles. In this paper, we apply genetic markers to assess whether field elm is or is not indigenous to the Balearic Islands. We compare the genetic variation in nine nuclear microsatellites of six Balearic populations (three in each of the largest islands, Majorca and Minorca) with that of three natural Iberian populations located in two regions, one geologically (Baetic mountains, SE Iberia) and another historically (Catalonia, NE Iberia) related to the islands. Principal coordinates analysis and Bayesian clustering methods reveal a strong genetic differentiation of the Balearic populations from the Iberian ones, and even among islands, which support their native origin. Genotypic variation in the islands is very low and clonal reproduction is very high compared with the mainland, as it is frequently observed in populations of clonal species where sexual reproduction is limited. We discuss the practical implications of these findings for the conservation of elm genetic resources of these findings.Gil, Luis; Fuentes-Utrilla, Pablo; Valbuena-Carabaña, María; Ennos, Richard (2014), Data from: Population clustering and clonal structure evidence the relict state of Ulmus minor Mill. in the Balearic Islands, Dryad, Dataset, https://doi.org/10.5061/dryad.bq4p

Functional performance of oak seedlings naturally regenerated across microhabitats of distinct overstorey canopy closure

The extent to which seedling recruitment is limited by summer drought in Mediterranean-type ecosystems depends on the light microsite, yet the relationship between light availability and water status, functional performance, and survival of seedlings in these systems is still unclear. Over a 3-year period, we studied the pattern of survival and functional performance of seedlings of Quercus petraea (Matt.) Liebl.;Quercus pyrenaica Willd. in a montane forest in central Spain, which is the southern edge of the natural range of Q. petraea. After a mast year of the two species, 72 plots were established in six microhabitats spanning a range of overstorey canopy closure closed, partial and open canopies dominated by either Q. petraea or Q. pyrenaica adult trees. Seedlings of each species naturally emerged beneath the conspecific-dominated canopies. The second and third years of study were extremely dry. Three years after emergence, the greatest seedling survival occurred beneath the partial canopy of Q. pyrenaica trees (8%) and the lowest (0%) beneath the closed canopies of Q. pyrenaica and Q. petraea. Survival for Q. pyrenaica increased linearly with understorey light across the range of 10-35% Global Site Factor. Plant water deficit (estimated by leaf water potential) was high across microhabitats, and increased with light availability for Q. pyrenaica. Potential for photosynthesis (estimated by the electron transport rate of photosystem II) decreased with canopy closure; and potential for light harvesting (e. g. specific leaf area (SLA) and chlorophyll concentration) increased with closure. Extreme water deficit could be the main contributor to seedling death in the more open microhabitats, whereas light level was insufficient to maintain carbon balance under the water-stressful conditions existing beneath the closed tree canopies. Seedling establishment appears to be a limiting factor for the recruitment of both oaks within this forest in a wide range of microhabitats, especially for the more drought-sensitive Q. petraea. Moderate reductions of tree canopy cover can improve seedling establishment, but extreme summer droughts can prevent the success of any silvicultural practice made. © 2009 Springer Science+Business Media B.V

Contrasting genetic diversity of tree species in Spain: from Tertiary relicts to domestication

La diversidad de los ecosistemas forestales depende de la riqueza en especies, pero también de la variabilidad genética a un nivel intraespecifico. En este trabajo analizamos los distintos patrones de diversidad genética de las especies arbóreas españolas, ilustrándolo con cuatro ejemplos. Combinando información molecular, paleobotánica e histórica, identificamos los principales factores que explican la variabilidad actual de varios taxones representativos: (1) el aislamiento en ecosistemas insulares de poblaciones arbóreas relictas de robles esclerófilos baleares y pino canario; (2) la existencia de refugios glaciares para Pinus sylvestris, Quercuspetraea y Q. pyrenaica; y (3) la domesticación y expansión de U/mus minor por los romanos en Europa Occidental. Estas situaciones representan un gradiente en los valores observados de diversidad genética: Pinus canariensis y los robles esclerófilos muestran altos niveles de diversidad genética en las Islas Canarias y las Baleares respectivamente; Pinus sylvestris, Quercus petraea y Q. pyrenaica también han mantenido elevados niveles de diversidad genética a pesar de haber sufrido un intensivo y prolongado manejo por parte del hombre. Finalmente, la diversidad genética de U/mus minor se ha visto grandemente afectada por el impacto humano, la enfermedad de la grafiosis y la interacción entre los dos factores. Comprender cómo se mantiene la diversidad genética y su distribución geográfica es básico para establecer sólidas medidas de conservación y estrategias de manejo forestal sostenibles