Airborne S-Band SAR for forest biophysical retrieval in temperate mixed forests of the UK

Radar backscatter from forest canopies is related to forest cover, canopy structure and aboveground biomass (AGB). The S-band frequency (3.1–3.3 GHz) lies between the longer L-band (1–2 GHz) and the shorter C-band (5–6 GHz) and has been insufficiently studied for forest applications due to limited data availability. In anticipation of the British built NovaSAR-S satellite mission, this study evaluates the benefits of polarimetric S-band SAR for forest biophysical properties. To understand the scattering mechanisms in forest canopies at S-band the Michigan Microwave Canopy Scattering (MIMICS-I) radiative transfer model was used. S-band backscatter was found to have high sensitivity to the forest canopy characteristics across all polarisations and incidence angles. This sensitivity originates from ground/trunk interaction as the dominant scattering mechanism related to broadleaved species for co-polarised mode and specific incidence angles. The study was carried out in the temperate mixed forest at Savernake Forest and Wytham Woods in southern England, where airborne S-band SAR imagery and field data are available from the recent AirSAR campaign. Field data from the test sites revealed wide ranges of forest parameters, including average canopy height (6–23 m), diameter at breast-height (7–42 cm), basal area (0.2–56 m2/ha), stem density (20–350 trees/ha) and woody biomass density (31–520 t/ha). S-band backscatter-biomass relationships suggest increasing backscatter sensitivity to forest AGB with least error between 90.63 and 99.39 t/ha and coefficient of determination (r2) between 0.42 and 0.47 for the co-polarised channel at 0.25 ha resolution. The conclusion is that S-band SAR data such as from NovaSAR-S is suitable for monitoring forest aboveground biomass less than 100 t/ha at 25 m resolution in low to medium incidence angle rang

Biología floral y reproductiva de la planta carnívora Drosophyllum lusitanicum (L.) Link (Drosophyllaceae); una especie endémica, singular y amenazada

Drosophyllum lusitanicum es una especie amenazada y endémica del SO de la Península Ibérica y N de Marruecos, que se encuentra protegida por distintas legislaciones. Por ello, el estudio de su biología reproductiva es importante para establecer las medidas de conservación adecuadas. En este trabajo se estudia la importancia de los polinizadores y de la xenogamia en el éxito reproductivo en dos poblaciones centrales de esta especie, teniendo en cuenta que presenta un comportamiento fuertemente autógamo en poblaciones periféricas. Se realizaron experimentos de polinización, observando un aumento de la tasa de fructificación y de la producción de semillas tras la acción de polinizadores y tras cruces xenógamos, principalmente en poblaciones y plantas jóvenes. Asimismo, se analizaron las diferencias morfológicas entre clases de edad, obteniendo mayor separación flor-trampa en individuos de primer año reproductivo que en individuos de mayor edad. Drosophyllum es insectívora y polinizada por insectos, pudiendo sufrir un conflicto entre polinización y captura de presas. Se realizaron censos de polinizadores y de presas para estimar el solapamiento polinizador-presa y, a diferencia de estudios anteriores, la presencia de polinizadores fue importante, con predominancia de pequeños Coleoptera e Hymenoptera (abejas). Por otro lado, las principales presas fueron Diptera, Microlepidoptera e Hymenoptera (hormigas), mostrando así un escaso solapamiento polinizador-presa, que solamente afectó a dos especies (Enicopus sp. y Lasioglosossum sp.). Esto sugiere que Drosophyllum previene el posible conflicto mediante la separación flor-trampa y la presencia de flores llamativas y aparentemente seguras para los polinizadores.Drosophyllum lusitanicum is a threatened, redlisted species endemic to the SW Iberian Peninsula and N Morocco. So, the study about its floral and reproductive biology is important to help create suitable conservation strategies. In this thesis, the role of pollinators reproductive success have been studied in two central populations, taking into account that this species shows a strong autogamous behaviour in peripheral populations. Pollination experiments were carried out and it was observed both higher fruit set and seed set after pollinator activity and cross-pollinations, particularly in plants on its first reproductive year. Additionally, morphological differences between age class were analysed, showing higher flower-trap (leaf) separation in first reproductive-year plants that in mature ones. Drosophyllum is insectivorous and insect-pollinated, which might make it suffer a conflict between pollination and prey capture. Pollinator and prey censuses were carried out to estimate pollinator-prey overlap and, in contrast to previous studies, pollinators were important, particularly small Coleoptera and Hymenoptera (bees). On the other hand, the main prey insects were Diptera, Microlepidoptera and Hymenoptera (ants), showing a scarce pollinator-prey overlap, which only affected two insect species (Enicopus sp. and Lasioglosossum sp.). It is inferred that Drosophyllum avoids a possible pollinator-prey conflict with spatial flower-trap separation and flashy and apparently safe flowers for pollinators