Interpreting genotype-by-environment interaction for biomass production in hybrid poplars under short-rotation coppice in Mediterranean environments

Understanding genotype × environment interaction (GEI) is crucial to optimize the deployment of clonal material to field conditions in short‐rotation coppice poplar plantations. Hybrid poplars are grown for biomass production under a wide range of climatic and edaphic conditions, but their adaptive performance in Mediterranean areas remains poorly characterized. In this work, site regression (SREG) and factorial regression mixed models are combined to gain insight into the nature and causes underlying GEI for biomass production of hybrid poplar clones. SREG addresses the issue of clonal recommendation in multi‐environment trials through a biplot representation that visually identifies superior genotypes. Factorial regression, alternatively, involves a description of clonal reaction to the environment in terms of physical variables that directly affect productivity. Initially, SREG aided in identifying cross‐over interactions that often involved hybrids of different taxonomic background. Factorial regression then selected latitude, mean temperature of the vegetative period (MTVP) and soil sand content as main site factors responsible for differential clonal adaptation. Genotypic responses depended strongly on taxonomic background: P. deltoides Bartr. ex Marsh. × P. nigra L. clones showed an overall positive sensitivity to increased MTVP and negative sensitivity to increased sand content, whereas the opposite occurred for P. trichocarpa Torr. & Gray × P. deltoides clones; the three‐cross hybrid [(P. deltoides × P. trichocarpa) × P. nigra] often displayed an intermediate performance. This information can contribute toward the identification and biological understanding of adaptive characteristics relevant for poplar breeding in Mediterranean conditions and facilitate clonal recommendation at eco‐regional level.This research was funded by MINECO (Spain) throughout the project RTA2008-00025-C02-01 and RTA2011-00006-00-00. We also acknowledge the collaboration of project AGL2009-11006. We would like to thank the public company SOMACYL for hosting one of the experimental plots. We are also grateful to Juan Pablo de la Iglesia and Ana Parras for their technical support throughout the experiment

Model parameterization to simulate and compare the PAR absorption potential of two competing plant species

Mountain pastures dominated by the pasture grass Setaria sphacelata in the Andes of southern Ecuador are heavily infested by southern bracken (Pteridium arachnoideum), a major problem for pasture management. Field observations suggest that bracken might outcompete the grass due to its competitive strength with regard to the absorption of photosynthetically active radiation (PAR). To understand the PAR absorption potential of both species, the aims of the current paper are to (1) parameterize a radiation scheme of a two-big-leaf model by deriving structural (LAI, leaf angle parameter) and optical (leaf albedo, transmittance) plant traits for average individuals from field surveys, (2) to initialize the properly parameterized radiation scheme with realistic global irradiation conditions of the Rio San Francisco Valley in the Andes of southern Ecuador, and (3) to compare the PAR absorption capabilities of both species under typical local weather conditions. Field data show that bracken reveals a slightly higher average leaf area index (LAI) and more horizontally oriented leaves in comparison to Setaria. Spectrometer measurements reveal that bracken and Setaria are characterized by a similar average leaf absorptance. Simulations with the average diurnal course of incoming solar radiation (1998–2005) and the mean leaf–sun geometry reveal that PAR absorption is fairly equal for both species. However, the comparison of typical clear and overcast days show that two parameters, (1) the relation of incoming diffuse and direct irradiance, and (2) the leaf–sun geometry play a major role for PAR absorption in the two-big-leaf approach: Under cloudy sky conditions (mainly diffuse irradiance), PAR absorption is slightly higher for Setaria while under clear sky conditions (mainly direct irradiance), the average bracken individual is characterized by a higher PAR absorption potential. (∼74 MJ m−2 year−1). The latter situation which occurs if the maximum daily irradiance exceeds 615 W m−2 is mainly due to the nearly orthogonal incidence of the direct solar beam onto the horizontally oriented frond area which implies a high amount of direct PAR absorption during the noon maximum of direct irradiance. Such situations of solar irradiance favoring a higher PAR absorptance of bracken occur in ∼36% of the observation period (1998–2005). By considering the annual course of PAR irradiance in the San Francisco Valley, the clear advantage of bracken on clear days (36% of all days) is completely compensated by the slight but more frequent advantage of Setaria under overcast conditions (64% of all days). This means that neither bracken nor Setaria show a distinct advantage in PAR absorption capability under the current climatic conditions of the study area

Monitoring of the Ecuadorian mountain rainforest with remote sensing

The Ecuadorian Andes feature a hotspot of biodiversity. At the same time Ecuador has the highest deforestation rate of South America. In order to develop sustainable counteractive measures, it is important to locate and quantify the ongoing changes on a regional scale. In this study we present a cost-effective remote sensing based change detection algorithm suitable for application in a tropical mountain rainforest landscape. We show that the deforestation in the study area is closely linked to the existence of roads but topography also influences the spatial distribution of land cover change. [References: 45

Standorts- und ernaehrungskundliche Untersuchungen zur Nutzung landwirtschaftlicher Flaechen fuer die Erzeugung von Biomasse mit schnellwachsenden Baumarten. Bd. 1 Zusammenfassung der Ergebnisse fuer die Jahre 1983 bis 1987. Schlussbericht

Copy held by FIZ Karlsruhe; available from UB/TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Standorts- und ernaehrungskundliche Untersuchungen zur Nutzung landwirtschaftlicher Flaechen fuer die Erzeugung von Biomasse mit schnellwachsenden Baumarten Zusammenfassung der Ergebnisse fuer die Jahre 1988 bis 1993. Abschlussbericht

An interdisciplinary field experiment with 4 fast growing poplar and willow clones was established in 1983 on land previously used agriculturally in order to investigate the influence of site, as well as the nutritional and growth aspects and the ecological consequences of this type of land use. At the end of the second rotation period (winter 1992) the height of the poplar clone Muhle Larsen amounted to 7 m, of the aspen Astria and the willow to about 5 m. Dry matter shoot biomass was 20 t/ha for Astria, 30 t/ha for the willow and 32 t/ha for Muhle Larsen. Production on soils subjected to high groundwater was lower than on moderately moist soils. Unfertilized poplars showed optimum nutrition even 10 years after planting. Nitrogen fertilization significantly enhanced shoot biomass only for Salix viminalis. Results of soil inventories in 1983, 1986 and 1992 showed a slight decrease of soil reaction by time. The organic matter and the total nitrogen concentration and the microbial biomass of the soils increased in layers near the soil surface and decreased in deeper layers of the former plough horizon, respectively. Species number of the ground vegetation increased at the afforested sites as compared with a control field. Some groups of the soil macrofauna (woodlice, earthworms, harvestmen) advanced in abundance and activity or showed an increase in biological diversity (carabid beetles). (orig.)SIGLEAvailable from TIB Hannover: F95B93+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman