R. M. Canals

Plant-herbivory feedbacks and selective allocation of a toxic metal are behind the stability of degraded covers dominated by Brachypodium pinnatum in acidic soils

Background and aimsPerennial tall-grasses have experienced a successful expansion in the last decades leading in some cases to extremely degraded communities, which remain in an alternate stable state. This research focuses on the mechanisms of persistence of the spreading native Brachypodium pinnatum in acidic soils. We hypothesize that plant-herbivory feedbacks and an adapted response to soil constraints, promote species cover stability.MethodsEight on-site populations of the species growing in two contrasted situations (high-diversity grazed and low-diversity ungrazed communities) were sampled during a growing season and analysed for nutrient (N, P and K), metal (Al) and C allocation, biomass production and tissue quality.ResultsThe species showed a high capacity for belowground accumulation of Al and an efficient reallocation and resorption of nutrients, which may explain its success in acidic, poor soils. The lack of attractiveness to herbivores of the species-poor stands prevented biomass removal, which strengthened some effects and enhanced the build-up of a thick layer of recalcitrant tissues, an effective barrier (aboveground and belowground) for the establishment of sympatric species.ConclusionsDensity-dependent feedback mechanisms (herbivory attractiveness), and the particular attributes of B. pinnatum (i.e. powerful rhizomes with a selective performance for nutrients and aluminium) may lead to critical processes of community domination and degradation.

Changes in soil nitrogen dynamics caused by prescribed fires in dense gorse lands in SW Pyrenees

Rural depopulation, abandonment of traditional land uses and decrease of extensive stockfarming is accelerating shrub encroachment in mountain areas. In NW Spain, gorse (Ulex gallii Planch.) is expanding, developing dense shrublands that accumulate high fuel-loads, ignite easily and persist during long periods as alternate stable states. Under this scenario, traditional bush-to-bush farming fires are being replaced by high fuel-load burnings performed by specialised teams to reduce fuels and promote mosaic landscapes. This research analyses the effects on soil function and nitrogen (N)-cycling of these new generation of prescribed fires practiced under similar conditions to traditional fires (winter time, moist soils), but differing in the biomass and the continuity of the surface burnt. The results showed significant changes in N-cycle parameters, such as increases in inorganic N and dissolved organic nitrogen (DON), but declines in N microbial biomass and urease activity. At the ecosystem level, potential N losses were high because the pulse of water-soluble forms, DON and nitrate, following fire overlaps with periods of low biological N retention by microorganisms and plants. Although most effects were similar to those observed in traditional burnings done in the same region, the primary concern is the high potential for DON losses following prescribed burning in highly gorse-encroached areas. In N-limited ecosystems, a crucial issue is to attain an equilibrium between frequent burnings, which may prevent an optimal recovery of the soil function, and uneven burnings, which burn high amounts of accumulated fuel and increase the risk of removing large quantities of dissolved N from the ecosystem in a unique fire event. Overall, the use of different techniques combined with fire are needed to promote and consolidate desired changes in dense gorse lands.

3ª edición de la Escuela de Ecología de Verano UPNA (2017)

Fallas Henriquez, A., Molina-Murillo, S. 2017. Methodological proposal to quantify and to compensate the agroecosystem services generated by the good agricultural practices of small-farmers. Ecosistemas 26(3): 89-102. Doi.: 10.7818/ECOS.2017.26-3.11 A diversified and less intensive management of agricultural systems produces agroecosystem services that are often not estimated nor compensated in developing countries. The main objective of this study was to create a tool that allows quantification of agroecosystemic services (SAgro) generated in agroforestry peasant farms, and additionally estimate compensation values. Following an initial test in 2013 on 10 farms, an important bibliographical review was carried out, the consultation of experts, and the evaluation in 2015 of 50 farms at the national level, most of them members of the National Agroforestry Union (UNAFOR) of Costa Rica. As a result, a tool was developed to measure in an agile, flexible and economical way the ecosystem services generated by good agricultural practices produced by small producers (peasants) both for their agricultural system as well as the forest system. We also found that the size of farms is not necessarily the determining factor for the production of agroecosystem services, but rather the type of management practices and investments made. In this process, it was estimated that with an average compensation of US

Curso apoyado por la AEET: 2ª edición de la Escuela de Ecología de Verano UPNA (2016)

271.6 per agricultural hectare per year, the production or maintenance of agroecosystem services could be encouraged through good agricultural practices.

Allelopathic potential of Lolium rigidum Gaud. on the early growth of three associated pasture species

Puerta-Pinero, A. 2016. Identification and evaluation of afforestations through the Spanish National Forest Inventory. Ecosistemas 25(3): 43-50. Doi.: 10.7818/ECOS.2016.25-3.05 Afforestation programs in Spain were performed mainly between 1930-1970 decades. The study of the state and functioning of these anthropogenic forests has a wide debate among scientists and stakeholders. Forest inventories represent a crucial source of data to evaluate the long-term functioning of these forests at broad spatial scales. This article shows several tools to identify and select plots from the third Spanish Forest Inventory composed by uniform afforestations. The functions intend to facilitate the work of scientists and technicians whose objective could be influenced by the presence or absence of these artificial forest type. Those functions are a first attempt to include or exclude plots that are composed by artificially afforested forests. I also present some preliminary results, and discuss strengths, weaknesses and future directions relative to the use of these functions.