Forest Restoration in a Fog Oasis: Evidence Indicates Need for Cultural Awareness in Constructing the Reference

Background: In the Peruvian Coastal Desert, an archipelago of fog oases, locally called lomas, are centers of biodiversity and of past human activity. Fog interception by a tree canopy, dominated by the legume tree tara (Caesalpinia spinosa), enables the occurrence in the Atiquipa lomas (southern Peru) of an environmental island with a diverse flora and high productivity. Although this forest provides essential services to the local population, it has suffered 90% anthropogenic reduction in area. Restoration efforts are now getting under way, including discussion as to the most appropriate reference ecosystem to use. Methodology/Principal Findings: Genetic diversity of tara was studied in the Atiquipa population and over a wide geographical and ecological range. Neither exclusive plastid haplotypes to loma formations nor clear geographical structuring of the genetic diversity was found. Photosynthetic performance and growth of seedlings naturally recruited in remnant patches of loma forest were compared with those of seedlings recruited or planted in the adjacent deforested area. Despite the greater water and nitrogen availability under tree canopy, growth of forest seedlings did not differ from that of those recruited into the deforested area, and was lower than that of planted seedlings. Tara seedlings exhibited tight stomatal control of photosynthesis, and a structural photoprotection by leaflet closure. These drought-avoiding mechanisms did not optimize seedling performance under the conditions produced by forest interception of fog moisture. Conclusions/Significance: Both weak geographic partitioning of genetic variation and lack of physiological specialization of seedlings to the forest water regime strongly suggest that tara was introduced to lomas by humans. Therefore, the most diverse fragment of lomas is the result of landscape management and resource use by pre-Columbian cultures. We argue that an appropriate reference ecosystem for ecological restoration of lomas should include sustainable agroforestry practices that emulate the outcomes of ancient uses

Nitrogen deposition effects on tissue chemistry and phosphatase activity in Cladonia foliacea (Huds.) Willd., a common terricolous lichen of semi-arid Mediterranean shrublands

In this article we evaluate the potential use of Cladonia foliacea tissue N content, C:N ratio, and phosphomonoesterase (PME) activity as biomarkers of N deposition by means of a field experiment. In order to do this, we continuously added NH4NO3 to a semi-arid shrubland at four rates: 0, 10, 20 and 50 kg N ha−1 yr−1 starting in October 2007. Tissue N content and C:N ratios, considered as N stress indicators, significantly increased and decreased, respectively, after 1.5 years. The response found suggests N saturation above 20 kg N ha−1 yr−1. After 2.5 years, extracellular PME activity increased with 20 kg N ha−1 yr−1 and this was attributed to an induced nutritional (N to P) imbalance. Above this threshold, PME significantly decreased as a consequence of the physiological stress caused by extra N. Effects on PME were dependent on the soil properties (pH and Ca and Mg availability) experienced by C. foliacea. PME response suggests a critical load of ∼26.4 kg N ha−1 yr−1 (20 kg N ha−1 yr−1 + background) for this lichen. Further tissue chemistry and PME evaluations in C. foliacea and soil surveys conducted along wide N deposition gradients will confirm the potential use of this species as a biomonitor of N pollution and the importance of soil properties on its ability to respond to atmospheric reactive N

Sun and shade leaves of Olea europaea respond differently to plant size, light availability and genetic variation

1. Canopy plasticity, the expression of different leaf phenotypes within the crown of an individual tree has complex functional and evolutionary implications that remain to be thoroughly assessed. We hypothesized that it can lead to disparity in how leaves in different positions of the canopy change with allometric growth and population genetic structure. 2. Leaf phenotypes of the inner and outer canopy were estimated using eight morphological and physiological characters. All traits were measured under field conditions in six populations of Olea europaea and again in a common garden for a subset of the genotypes. The same populations were characterized genetically with amplified fragment length polymorphisms (AFLP) genomic scans. With these data, we investigated the extent to which leaf phenotypes change with plant size, genetic processes and in response to environmental conditions inside and outside the canopy. 3. The size of trees measured in the field was clearly associated with the phenotype of sun but not to that of shade leaves. The phenotype of sun leaves depended on both direct and diffuse light, while that of shade leaves was found to correlate only with diffuse radiation. Additionally, light availability inside the canopy was conditioned by the shape of external leaves, and increasing elongation of sun leaves led to higher radiation in the inner canopy. 4. The field phenotypes of both inner and outer canopy leaves were correlated with genetic variation among populations. Conversely, in the common garden, the different genotypes expressed a homogeneous sun phenotype, while phenotypic differences among populations remained apparent in shade leaves. 5. We conclude that, in agreement with our working hypothesis, canopy plasticity is both cause and consequence of the environment experienced by the plant and might lead to the differential expression of genetic polymorphisms among leaves. Furthermore, we propose that it can contribute to buffer abiotic stress and to the partition of light use within the tree crown

Simulated nitrogen deposition influences soil greenhouse gas fluxes in a Mediterranean dryland

Soil nitrogen (N) availability is a key driver of soil-atmosphere greenhouse gas (GHG) exchange, yet we are far from understanding how increases in N deposition due to human activities will influence the net soilatmosphere fluxes of the three most important GHGs: nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2). We simulated four levels of N deposition (10, 20 and 50 kg N ha−1 yr−1 , plus unfertilised control) to evaluate their effects on N2O, CH4 and CO2 soil fluxes in a semiarid shrubland in central Spain. After 8 years of experimental fertilisation, increasing N availability led to a consistent increase in N2O emissions, likely due to simultaneous increases in soil microbial nitrification and/or denitrification processes. However, only intermediate levels of N fertilisation reduced CH4 uptake, while increasing N fertilisation had no effects on CO2 fluxes, suggesting complex interactions between N deposition loads and GHG fluxes. Our study provides novel insight into the responses of GHGs to N deposition in drylands, forecasting increases in N2O emissions, and decreases in CH4 uptake rates, with likely consequences to the on-going climate change

Effect of nitrogen availability on the germination of herbaceous species of a mediterranean kermes oak forest

50ª Reunión Científica de la SEEP: "Pastos, paisajes culturales entre la tradición y los nuevos paradigmas del siglo XXI", del 9 al 12 de mayo de 2011. Toledo, España.El N es un componente fundamental de los organismos vivos y juega un papel crítico en el control de la productividad primaria de los ecosistemas siendo incluso limitante en algunos sistemas como los mediterráneos. En los últimos años diversas actividades humanas han incrementado la liberación a la atmósfera de N a nivel global y su deposición en el suelo en diferentes formas. La deposición de N en ecosistemas templados aumenta su disponibilidad en el suelo, la productividad de los organismos y la incorporación de carbono al suelo y vegetación pero también acidifica el suelo y disminuye la diversidad vegetal. Sin embargo los estudios en ecosistemas mediterráneos sobre los efectos del aumento de la disponibilidad de N son escasos por lo que es comprometido hacer predicciones de la respuesta de los ecosistemas mediterráneos en escenarios donde el N aumente. El objetivo del trabajo es conocer los efectos de diferentes niveles de fertilización nitrogenada así como de diferentes fuentes de N en la germinación de especies herbáceas características de un coscojar mediterráneo del centro de la Península Ibérica para evaluar la evolución futura de estos sistemas en el escenario de un incremento acusado de N.Nitrogen is an essential component of living organisms and plays a critical role in controlling ecosystem primary production. In Mediterranean ecosystems N can even limit productivity. In recent years human activities have significantly increased the N release to the atmosphere worldwide and their subsequent deposition on the ground by different ways. It is known that N deposition in temperate ecosystems increases N soil availability, species productivity and the incorporation of carbon to the soil and vegetation but also N acidifies the soil and reduces plant diversity through different mechanisms. However, studies in Mediterranean ecosystems describing the effects of increased N availability are very scarce so there is no relevant information to enable us to make reliable predictions of the Mediterranean ecosystem responses in N increased scenarios. The study aims to determine the effects of different levels of N (simulation of plausible scenarios of N deposition rate) and different N sources on germination of herbaceous species characteristic of a Mediterranean kermes oak forest in the center Iberian Peninsula. The results could anticipate the future evolution of these ecosystems in the scenario of a sharp rise of N.Depto. de Biodiversidad, Ecología y EvoluciónFac. de Ciencias BiológicasTRUEMinisterio de Educación y Ciencia (MEC)pu