Jorge Martín-García

Towards standardised crown condition assessment in poplar plantations

Abstract• This work aims at developing new tools for rapid assessment of forest health indicators in poplar plantations.• Crown transparency and discoloration were visually evaluated in all trees of four 15 m-radius sub-plots in 32 poplar clonal plantations, which were chosen according to a factorial scheme with three factors: tree age, site quality and understorey vegetation management. A subset of trees was assessed using digital photos processed with a semi-automatic image analysis system (the CROCO software) in order to compare visual and digital crown transparency estimates.• Poplar crown conditions were better in young stands and rich sites. Harrowing understorey vegetation improved tree health in poor sites. Samples of 20 trees per stand provided the same information about crown transparency and discoloration as 60 trees. Calibration curves of digital crown transparency estimates were successfully fitted against visual crown transparency estimates. The same effects of stand age and site quality could be detected with digital crown transparency as response variable.• The use of digital photos processed with CROCO in ca. twenty trees per stand is therefore recommended to accurately and objectively monitor crown condition in clonal poplar plantations.Résumé• Une étude a été réalisée pour développer des méthodes rapides et standardisées de suivi de l’état sanitaire des houppiers en plantation de peuplier.• La transparence et la décoloration des houppiers ont été estimées visuellement sur tous les arbres de quatre placettes d’un rayon fixe de 15 m, dans 32 plantations monoclonales de peuplier choisies selon un plan factoriel complet croisant trois facteurs : l’âge des plantations, la fertilité du site et la gestion du sous-bois. La moyenne des notes de transparence et de décoloration des houppiers a été calculée sur un nombre décroissant de placettes par plantation afin de tester l’influence de la taille de l’échantillon sur la qualité de l’estimation. Des photographies numériques du houppier d’un souséchantillon de peupliers ont été également prises puis traitées à l’aide du logiciel CROCO afin de comparer les estimations visuelles et numériques de la transparence du houppier.• L’état sanitaire des houppiers était meilleur dans les jeunes plantations de peupliers et les sites les plus fertiles. Le hersage de la végétation du sous-bois a permis d’améliorer l’état sanitaire des peupliers dans les sites les plus pauvres. Les valeurs moyenne de transparence et de décoloration du houppier par plantation, calculées à partir des données d’une seule placette de 15 m de rayon — soit une vingtaine d’arbres — ne différaient pas significativement de celles calculées à partir des données de trois placettes et permettaient de détecter les mêmes effets des caractéristiques du peuplement et du site. Des courbes de calibration de la transparence du houppier estimée à partir de photos numériques et du logiciel CROCO ont pu être ajustées aux observations de transparence. Les effets de l’âge des plantations, de la fertilité du site et de la gestion du sous-bois ont pu également être détectés avec ces valeurs numériques calculées.• Il peut donc être recommandé d’utiliser des photos numériques traitées à l’aide du logiciel CROCO pour estimer la transparence du houppier d’une vingtaine d’arbres afin d’évaluer rapidement, précisément et objectivement l’état sanitaire des plantations monoclonales de peuplier.

ITS-based comparison of endophytic mycota in twigs of native Populus nigra and cultivated P. x euramericana (cv. I-214) stands in Northern Spain

ContextThe European black poplar (Populus nigra) is considered one of the most seriously endangered indigenous tree species. However, the total area covered by monoclonal plantations of hybrid poplar is growing, because of the high profitability of these trees.AimThe aim of this study is to describe and compare the endophytic mycota in twigs from native poplar (P. nigra) and hybrid poplar plantations (P. x euramericana clone I-214).MethodsTwig endophytes were isolated from three native and three hybrid poplar stands in Palencia (N. Spain). Three trees were chosen at random within each stand sampled. Isolates were identified according to sequences of the internal transcribed spacer region of their rDNA. The study focused on dominant species.ResultsA total of 13 species were found. Six species originated from P. nigra only (Stemphylium vesicarium, Alternaria spp., Aureobasidium pullulans, Fimetariella rabenhorstii, Plagiostoma fraxini and Cryptodiaporthe salicella) and four from P. x euramericana only (Cytospora chrysosperma, Athelia bombacina, Biscogniauxia mediterranea and Unidentified sp. 1), whereas three were found on both types of trees (Lewia infectoria, Alternaria alternata and Epicoccum nigrum).ConclusionThe results show that the endophyte community on poplar twigs differs between native and hybrid poplars

Patterns and monitoring of Sesia apiformis infestations in poplar plantations at different spatial scales

Poplar plantations are expanding worldwide but little is known about the hornet clearwing moth, Sesia apiformis, one of their most severe pests. Thirty‐two poplar plantations of I‐214 clone were sampled in Spain, according to a factorial design combining stand age, site condition and understorey management to investigate the main drivers of S. apiformis habitat selection at both tree and stand level. In each plantation, one pheromone trap was activated during the flight season to test the correlation between captures and percentage of attacked trees. The proportion of other poplar forests in surrounding landscapes was calculated and used as a covariate in predictive models of trap catches. There were significantly more attacked trees in older stands. In young stands, the percentage of infested trees increased with the percentage cover of understorey vegetation. There was no significant effect of site quality on the rate of infestation and no difference in tree height, diameter or crown condition between attacked and un‐attacked trees within each stand, suggesting that S. apiformis could behave as primary pest. We hypothesized that the critical stage in the life cycle of the moth was the first instar larvae, which may benefit from protection of deep bark cracks in older stands and understorey vegetation in younger stands. We observed a positive correlation between trap capture and percentage of attacked trees in a radius of 100 m around the trap. The regression of trap catches against percentage of attacked trees was improved when the area of other poplar plantations within a distance of 600 m was incorporated in the model. This suggests that surrounding poplar stands may act as sources of immigrating moths in monitored stands. Our findings confirm that S. apiformis should be considered as a potential threat to poplar plantations and that pheromone trapping provides a suitable monitoring tool.

Potential control of forest diseases by solutions of chitosan oligomers, propolis and nanosilver

There is a growing necessity to replace chemical agents with ecofriendly materials, arising from the impact on the environment and/or human health, which calls for the design of new broad-spectrum fungicides. In this work, chitosan oligomers (COs), propolis (Ps) and silver nanoparticles (AgNPs) mixtures in solution were assessed to control the growth of different phytopathogenic fungi and oomycetes in vitro. Binary solutions of COs-Ps and COs-AgNPs evinced the highest antifungal effect against Fusarium circinatum and Diplodia pinea fungi, respectively, with a ca. 80% reduction in their mycelial growth. The COs solution by itself also proved to be greatly effective against Gremmeniella abietina, Cryphonectria parasitica and Heterobasidion annosum fungi, causing a reduction of 78%, 86% and 93% in their growth rate, respectively. Likewise, COs also attained a 100% growth inhibition on the oomycete Phytophthora cambivora. On the other hand, Ps inhibited totally the growth of Phytophthora ×alni and Phytophthora plurivora. The application of AgNPs reduced the mycelial growth of F. circinatum and D. pinea. However, the AgNPs in some binary and ternary mixtures had a counter-productive effect on the anti-fungal/oomycete activity. In spite of the fact that the anti-fungal/oomycete activity of the different treatments showed a dependence on the particular type of microorganism, these solutions based on natural compounds can be deemed as a promising tool for control of tree diseases.

Early survival of Quercus ilex subspecies from different populations after infections and co-infections by multiple Phytophthora species

Forests in Europe are threatened by increased diversity of Phytophthora species, but the effects of the simultaneous presence of these pathogens on trees and the ecological consequences of their coexistence are unknown. This study aimed to explore variation in early survival of Quercus ilex to Phytophthora infections and assess interactions between Phytophthora species when trees are co-infected separately in time. Three Phytophthora species (P. cinnamomi, P. gonapodyides and P. quercina), seeds from 16 populations of Q. ilex (from both ballota and ilex subspecies) and two infection times were used as sources of variation in two experiments. The influence of the Phytophthora species, Q. ilex subspecies and populations on plant germination and survival were analysed using generalised linear mixed models and survival analysis techniques. Germination rates were not influenced by Phytophthora spp. (P = 0.194) but by the subspecies and populations of Q. ilex (P < 0.001). In Phytophthora infested soils, acorns of Q. ilex ssp. ilex germinated at higher rates than acorns of Q. ilex ssp. ballota. In contrast, plant survival was strongly influenced by Phytophthora species (P < 0.001), but not by the subspecies and populations of Q. ilex. Reduced and delayed seedling mortality were observed if a less virulent Phytophthora species infected plants prior to infection by a more virulent Phytophthora species, e.g. plants infected first by P. cinnamomi died at higher rates and earlier than plants infected first by P. gonapodyides and P. quercina (P = 0.001). The results help to explain oak decline syndrome and the lack of natural and artificial regeneration of Q. ilex forests. The lack of interspecific variability of early survival to Phytophthora spp. discourage direct sowing as a strategy in artificial reforestation programmes. Large, thick seeds that give plants rapid growth are advantageous traits if soils are infested with Phytophthora spp. This article is protected by copyright. All rights reserved.

Sustainable Forest Management: An Introduction and Overview

It is well known that forests provide both tangible and intangible benefits. These benefits may be classified according to ecological values (climate stabilization, soil enrichment and protection, regulation of water cycles, improved biodiversity, purification of air, CO2 sinks, potential source of new products for the pharmaceutical industry, etc.), social values (recreational and leisure area, tradition uses, landscape, employment, etc) and economic values (timber, non wood forest products, employment, etc.). Although forests have traditionally been managed by society, it is expected that the current growth in the world population (now > 7,000 million people) and the high economic growth of developing countries will lead to greater use of natural resources and of forest resources in particular.