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Casals P.,Center Tecnolgic Forestal Of Catalonia | Lopez-Sangil L.,Center Tecnolgic Forestal Of Catalonia | Lopez-Sangil L.,University of Barcelona | Nogues S.,University of Barcelona
Global Biogeochemical Cycles | Year: 2011

Autotrophic and heterotrophic components of soil CO 2 efflux may have differential responses to environmental factors, so estimating the relative contribution of each component during summer precipitation pulses is essential to predict C balance in soils experiencing regular drought conditions. As even small summer rains induced high instantaneous soil respiration rates in Mediterranean wooded grasslands, we hypothesized that standing dead mass, surface litter, and topsoil layer could play a dominant role in the initial flush of CO 2 produced immediately after soil rewetting; in contrast, soil CO 2 effluxes during drought periods should be mostly derived from tree root activity. In a grazed dehesa, we simulated four summer rain events and measured soil CO 2 efflux discontinuously, estimating its δ 13C through a Keeling plot nonsteady state static chamber approach. In addition, we estimated litter contribution to soil CO 2 efflux and extracted soil available C fractions (K 2SO 4-extracted C and chloroform-fumigated extracted C). The δ 13C-CO 2 from in-tube incubated excised tree roots and rewetted root-free soil was-25.0‰ (0.2) and-28.4‰ (0.2), respectively. Assuming those values as end-members' sources, the autotrophic component of soil CO 2 efflux was dominant during the severe drought, whereas the heterotrophic contribution dominated from the very beginning of precipitation pulses. As standing dead mass and fresh litter contribution was low (<25%) in the first day and negligible after, we concluded that CO 2 efflux after rewetting was mostly derived from microbial mineralization of available soil organic C fractions. Copyright 2011 by the American Geophysical Union.

Hermoso V.,University of Huelva | Hermoso V.,University of Queensland | Clavero M.,Center Tecnolgic Forestal Of Catalonia | Clavero M.,University of Girona | And 2 more authors.
Ecological Indicators | Year: 2010

The assessment of the ecological status of freshwater ecosystems is a key issue for many international laws such as the Water Framework Directive (WFD) in light of the actual impoverished status of these ecosystems. Different multimetric approaches have been successfully developed in different freshwater environments. However, multimetric indices are difficult to apply to Mediterranean rivers basins, characterized by freshwater fish communities very low in species richness and support a high number of endemics with generalist and opportunistic life strategies. Here we follow a site-specific approach to develop an adaptation of the multimetric procedure usually used in Indices of Biotic Integrity (IBI), resulting in the Index of Community Integrity (ICI). We modeled the presence-absence of 10 native freshwater fish species from the Guadiana River basin using the Assessment of Nearest Neighbor Analyses (ANNA) model, to assess the deviation of the observed and expected community composition at reference condition. ANNA, which is a multi-species model, allowed incorporating in the index some rare species, though not all of them present in the basin. Deviations were transformed into probabilities of belonging to a reference site and species by species measures were then integrated in a final score. The use of presence-absence only data reduces potential errors associated with estimations of species' abundance and its seasonal changes, which is especially important in Mediterranean environments. The ICI was sensitive to both habitat degradation and the degree of dominance of non-native species within the freshwater fish community (or biotic perturbation), which have been traditionally overlooked in IBIs, but was unresponsive to natural sources of variation. Given the site-specific nature and the simplicity of the index that we propose here, we expect it to be applicable to other Mediterranean basins for which predictive models can be produced. © 2010 Elsevier Ltd. All rights reserved.

Qu M.,University of Eastern Finland | Qu M.,Northwest Agriculture and Forestry University | Ahponen P.,University of Eastern Finland | Tahvanainen L.,University of Eastern Finland | And 5 more authors.
Renewable and Sustainable Energy Reviews | Year: 2011

The present study examines Chinese university students' attitudes and knowledge regarding energy, specifically towards forest bio-energy in their country. The study was based on opinions of students from Northwest Agriculture and Forestry University (NWAFU) in China and it was conducted using a questionnaire completed by 441 students. The students' attitudes are seen as highly relevant because they are considered as both potential consumers and possible experts in the field of bio-energy. Their activities influence how the future energy markets will likely develop. The results revealed various interesting facets of the students' views regarding energy usage. Of particular interest is the students' positive attitude towards renewable energy in general, but slightly less positive towards forest bio-energy. However, the respondents expected to receive more information and knowledge about renewable energy and forest bio-energy. Moreover, it can be concluded that the dissemination of knowledge through different sources (e.g. teaching in school, information available on the Internet and other media channels) is an increasingly important aspect regarding energy issues. The results of this study can provide information of the perceptions of young educated people on energy policy issues and thus serve political decision-making processes for the future options concerning the development of forest bio-energy in China. Finally, the outcome of this study indicates that further environmental and energy education in China is urgently needed. © 2011 Elsevier Ltd. All rights reserved.

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