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Boreal forests cover 10%-15% of the terrestrial land area and store about one third of the global forest carbon (C) pool (Astrup et al., 2018;Pan et al., 2011). Due to their large capacity for sequestering carbon dioxide (CO 2 ) from the atmosphere into biomass and soil (Myneni et al., 2001), these ecosystems are considered as key element in national and international policy frameworks

Abstract:In semi-arid regions, afforestation with fast-growing species cultured with low irrigation can be an effective approach for environmental protection. An experiment was conducted to evaluate the stem biomass production of Paulownia in a semi-arid climate and clay soils under contrasting low-irrigation and fertilization treatments. The stem biomass at the stand level was estimated by applying allometric equations fitted in sample resprouts and inventory data. The results show that biomass production improved when either irrigation or fertilizer was added, but the combination of a higher dose of irrigation and fertilization did not lead to the highest biomass production; thus water availability was the main factor controlling biomass production. Under the higher dose of irrigation, the absence of a fertilizer effect would be due in part to the fertile soil, which could supply sufficient nutrients for Paulownia growth at the higher level of soil moisture. The stem OPEN ACCESSForests 2014, 5 2506 biomass estimated ranged from 2.14 to 4.50 t⋅ha −1 (lower irrigation dose without fertilization, and higher irrigation with fertilization). The greater production was similar to other studies in the Mediterranean area receiving more irrigation. Thus, this study permitted us to understand the potential of Paulownia to provide biomass in semi-arid environments with low irrigation due to water use restrictions.

In this research work, we specifically address post-dispersal Spanish black pine (Pinus nigra Arn. ssp salzmannii) seed predation at two different locations, one being the most common and representative location for the species and the other located on areas at their ecological limit of distribution in Cuenca Mountain (Spain). A modelling approach was employed to analyze the effect of stand and site characteristics and climate variables on the post-dispersal predation process. Each predator group (ants, rodents and birds) was evaluated by excluding the other two with different experimental devices. Our study demonstrates that the percent of removal was related with the seed rain patterns being lower in the high seed rain year of 2006 (mean ± se 11.15 ± 3.7% of removed seeds) than in the low seed rain years of 2005 and 2007 (81.71 ± 6.0% and 87.29 ± 6.6% of removed seeds respectively). In high seed production years, birds were the most important predators and rodents were the less important predator group in both Los Palancares y Agregados and Ensanche de Las Majadas. No conclusion can be obtained in low seed production years due to the high seed removal percentage by all predator groups. Experimental site and overstory density were no significant with respect to seed predation. Modelling approach show that the seed removal percentage is influenced by seed production year (MastY) a temporal effect within the year, measured by the day variable (Day) and a climatic variable (accumulated averaged maximum air temperatures 20 days before survey date, AaMAT). Further developments include the construction of stochastic models to predict the effects of climate-related variables or microhabitat characteristics on seed losses, contributing to reduce uncertainty in post-dispersal Spanish black pine seed predation dynamics and to provide credible tools to decision-makers and forest managers.Key words: mast year; post-dispersal seed predation; Pinus nigra; Mediterranean region. Resumen Modelización de predación post-dispersión de semillas de pino laricio en el Centro-este de EspañaEl presente trabajo de investigación se centra en la predación post-dispersión acontecida en dos áreas forestales, una localizada en la zona de distribución característica del pino laricio (Pinus nigra Arn ssp salzmannii) y otra en su límite ecológico de distribución dentro de la Serranía de Cuenca (España). El efecto que sobre la predación post-dispersión tienen la densidad arbórea, diferentes variables climáticas y varias características de cada masa forestal fue evaluado mediante la creación de diferentes modelos. Cada grupo de predadores (hormigas, ratones y pájaros) fue analizado por exclusión de los otros dos mediante diferentes dispositivos experimentales. Nuestro estudio demuestra que el porcentaje de semilla predada estuvo relacionado con la lluvia de semillas, siendo menor en 2006, año de abundante producción (media ± estandar error: 11.15 ± 3.7% de semillas predadas) que en 2005 y 2007, años de escasa producción de semilla (81.71 ...

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Treatments involving vegetation thinning have become more frequent in Mediterranean forest ecosystems. Under extreme climate conditions, this practice can affect the balance between physicochemical, microbiological and biochemical soil properties, modifying the soil quality and the ability of these forest ecosystems to regenerate. The aim of this study was to use principal component analysis (PCA) to develop a multivariable soil‐quality index (SQI) applicable to the Mediterranean forest ecosystems of the Cuenca mountain range in central‐eastern Spain. To achieve this, seven physicochemical properties (moisture, pH, electrical conductivity, carbonate, total organic carbon, total nitrogen and available phosphorus) and six microbiological properties (basal respiration and microbial biomass carbon, as well as the activity of dehydrogenase, urease, phosphatase and β‐glucosidase enzymes) were measured seasonally between 2011 and 2012. Soil samples were obtained from seven unmanaged and undisturbed forest areas and these data were used to create the SQI. Subsequently, we applied this SQI to soil samples from other forests in the Cuenca mountain range, which had been affected by different thinning treatments. Our analysis showed that the greater was the canopy present in these treated forests, the larger were the average values for all 13 variables. The smallest SQI values were in areas that had been intensively thinned. Therefore, our results suggest that this SQI is an important tool for the development of appropriate measures to maintain the quality of forest soil in Spanish Mediterranean forest ecosystems. Highlights We developed a multivariable soil quality index (SQI) to assess status of Mediterranean forest ecosystems. This index is adequate to detect changes quickly in forest soil of Mediterranean ecosystems. The SQI helped to assess the effects of thinning treatments on forest soil. The SQI enabled establishment of different levels of soil quality (very high, high, medium and low).

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