Extreme climatic events affect populations of Asian chestnut gall wasps, Dryocosmus kuriphilus, but do not stop the spread

[EN] Global climate change affects the frequency of extreme weather events that can influence plant–insect interactions. We evaluated how the late-spring frost and severe drought that occurred in Spain in 2017 affected interactions between the invasive gall insect, Dryocosmus kuriphilus, and the native tree, Castanea sativa. We assessed effects on insect survival, fertility, population growth, and effects through changes in tree palatability and in other pests and pathogens. Late-spring frost reduced D. kuriphilus to 25–40% of previous abundance. Wasp populations recovered rapidly (>7-fold in 3 years), consistent with density-dependence in population dynamics. Larvae affected by freeze or drought were smaller. Female fecundity was affected by the freeze 1 year later. Late-spring frosts and severe drought affected leaf size and physiology. Water content was higher within galls, but nitrogen was higher within galls in non-freeze plots after weather conditions improved. Freezing also influenced the secondary chemistry of leaves. Phenol concentrations were lower, and terpenes higher, in frozen plots, while condensed tannins remained the same. Condensed tannins were reduced to half in the drought year. Freezing had limited effects on damage from other pests and pathogens. Our work expands understanding of how climate and weather affects forest pestsSIThis work was supported by FEDER/Spanish Ministry of Economy and Competitiveness Research (Grant AGL2016-76262-R). Diana Blanco, Elva Rico, and Naidu Lombardero provided assistance in the field and in the lab. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this pape

The impact of the Asian chestnut gall wasp (Dryocosmus kuriphilus) on chestnut tree growth may be mediated by site resources

[EN] Introduction: The Asian chestnut gall wasp (Dryocosmus kuriphilus) is a major pest of chestnut trees worldwide, seriously affecting chestnut cultivation. Information concerning the effects of gall wasp attack on diameter growth of chestnut trees is currently scarce and limited to coppice stands and to use of the growth of a non-target control species (unaffected by the pest) for reference purposes. The effects of the pest on widely-spaced plantations (grown at a much lower density than chestnut coppices) and the use of explicitly-observed annual infestation rate data remain to be explored. Methods: In the present study, we analyzed the impact of the chestnut gall wasp on the diameter growth of chestnut trees, using data from 16 experimental plots established in widely-spaced plantations located in good quality sites. Two of the plots are in plantations where a susceptible hybrid chestnut clone and a chestnut clone resistant to the gall wasp coexist, whereas the remaining 14 plots are in Castanea sativa plantations where the level of gall wasp infestation varies across trees and years. The plots were surveyed to determine the diameter growth of the trees and the level of infestation during 5 years (2017–2021). Results: The infestation level corresponding to the theoretical damage threshold was surpassed inmost plots during the study period. Nevertheless, there were no differences in the growth of attacked and unaffected plants in the two plots planted with hybrid clones with contrasting susceptibility to the gall wasp. The attack had a modest effect in C. sativa plots, with a mean reduction in annual basal area increment of 9.9%. Discussion: These findings apparently contradict previous reports of a marked reduction in radial growth of chestnut coppice trees due to gall wasp attack. The difference in findings may be related to increased compensation for herbivory with increasing levels of resources (especially light) in the plantations under study, which were less dense than previously studied stands. The study outcomes add to existing knowledge on the impact of chestnut gall wasp on wood formation andmay have implications regarding planting site recommendations and subsequent stand managementSIThis work was supported by FEDER/Spanish Ministry of Economy and Competitiveness Research (grant AGL2016-76262-R)

Extreme climatic events affect populations of Asian chestnut gall wasps, Dryocosmus kuriphilus, but do not stop the spread

1 Global climate change affects the frequency of extreme weather events that can influence plant–insect interactions. 2 We evaluated how the late-spring frost and severe drought that occurred in Spain in 2017 affected interactions between the invasive gall insect, Dryocosmus kuriphilus, and the native tree, Castanea sativa. We assessed effects on insect survival, fertility, population growth, and effects through changes in tree palatability and in other pests and pathogens. 3 Late-spring frost reduced D. kuriphilus to 25–40% of previous abundance. Wasp populations recovered rapidly (>7-fold in 3 years), consistent with density-dependence in population dynamics. 4 Larvae affected by freeze or drought were smaller. Female fecundity was affected by the freeze 1 year later. 5 Late-spring frosts and severe drought affected leaf size and physiology.Water content was higher within galls, but nitrogen was higher within galls in non-freeze plots after weather conditions improved. 6 Freezing also influenced the secondary chemistry of leaves. Phenol concentrations were lower, and terpenes higher, in frozen plots, while condensed tannins remained the same. Condensed tannins were reduced to half in the drought year. 7 Freezing had limited effects on damage from other pests and pathogens. 8 Our work expands understanding of how climate and weather affects forest pestsThis work was supported by FEDER/Spanish Ministry of Economy and Competitiveness Research (Grant AGL2016-76262-R)S

Fire from the Sky in the Anthropocene

[EN] Lightning is the prevailing ignition source in many remote or scarcely populated parts of the world, and those fires tend to be larger and more intense than human-caused fires [1]. “Dry” lightning storms can ignite many fires over short periods of time and relatively vast areas and in locations less predictable and accessible than those of human-caused fires. Additionally, and regardless of the ignition cause, thunderstorm wind flows can drastically change the behaviour of on-going fires, amplifying fire–atmosphere interactions and leading to erratic and destructive firestorms. Such was the case of the Pedrogão Grande wildfire in Portugal, where 66 people died on 17 June 2017 [2]. Fires themselves can generate lightning when pyrocumulonimbus form, as in the Black Saturday fires of February 2009 in Australia, where 173 people perished [3]. In 2019–2020, the unprecedented Black Summer mega-fires were mostly lightning-caused fires (LCFs) and burned one-fifth of the Australian temperate broadleaf forest and caused huge social disruption [4]; lightning started most fires in a region where “dry” thunderstorms are now more frequent than in the recent past [5]. Once rare in Tasmania, LCFs are now threatening World Heritage forests non-adapted to fire [6]. In California, the unusual 2020 lightning siege has burned ca. 1 million hectares, destroying at least 4390 structures and killing 22 people after 14,000 lightning strikes [7]. In human-dominated landscapes, such as in southern Europe, LCFs comprise a small fraction of the total number of fires, and so are commonly perceived as irrelevant. Such neglect and focus on human agency can happen even when fire statistics indicate a significant role of LCFs in the fire regime, e.g., in temperate Australia [8]. Consequently, by downplaying or ignoring LCFs, fire management planning will hardly be prepared to handle the particular difficulties posed by an LCF crisis. Here, we characterize the relevance of LCFs in a generically low LCF region, the Iberian Peninsula, and will then address current and future challenges posed by LCFs in relation to climate changeSIThis work is supported by National Funds by FCT—Portuguese Foundation for Science and Technology, under the project UIDB/04033/202

Modelado y control de un horno de yeso rotativo y continuo

XXI Jornadas de Automática 2000. 18/09/2000. SevillaEn este trabajo se describe el proceso de modelado que define el comportamiento de un horno de yeso rotativo y continuo. También se detalla la estrategia de control que mejor se adapta al sistema y se presentan los resultados obtenidos en las simulaciones.Ministerio de Ciencia y Tecnología IFD97-0383

Fitting and calibrating a multilevel mixed-effects stem taper model for maritime pine in NW Spain

Stem taper data are usually hierarchical (several measurements per tree, and several trees per plot), making application of a multilevel mixed-effects modelling approach essential. However, correlation between trees in the same plot/stand has often been ignored in previous studies. Fitting and calibration of a variable-exponent stem taper function were conducted using data from 420 trees felled in even-aged maritime pine (Pinus pinaster Ait.) stands in NW Spain. In the fitting step, the tree level explained much more variability than the plot level, and therefore calibration at plot level was omitted. Several stem heights were evaluated for measurement of the additional diameter needed for calibration at tree level. Calibration with an additional diameter measured at between 40 and 60% of total tree height showed the greatest improvement in volume and diameter predictions. If additional diameter measurement is not available, the fixed-effects model fitted by the ordinary least squares technique should be used. Finally, we also evaluated how the expansion of parameters with random effects affects the stem taper prediction, as we consider this a key question when applying the mixed-effects modelling approach to taper equations. The results showed that correlation between random effects should be taken into account when assessing the influence of random effects in stem taper predictionThe corresponding author was in receipt of an FPU grant (AP2012-05337) from the Spanish Ministry of Education, Culture and Sport, http://www.mecd.gob.es/. This work was also supported by project no. AGL2008-02259/FOR from the Spanish Ministry of Science and Innovation, http://www.idi.mineco.gob.es/; and project nos. CN-07-094 and SVPA-13-ECOEMP-58 from the Government of the Principality of Asturias, http://www.asturias.es/S

Local-scale dispersal patterns and susceptibility to Dryocosmus kuriphilus in different Castanea species and hybrid clones: insights from a field trial

artículoThe chestnut gall wasp Dryocosmus kuriphilus is a major insect pest affecting chestnut trees worldwide. Medium and long-term control of this pest can be improved by using resistant or less susceptible cultivars and hybrid clones. In addition, little is known about the local patterns of dispersal of the pest. We obtained data from trees of 3 chestnut species and 27 hybrid clones in a field trial in NW Spain with the aim of evaluating the susceptibility of the material to the gall wasp and identifying possible drivers of local spatial dispersal. In the first 3 years of the invasion by D. kuriphilus, the number of trees attacked and the number of galls on each tree were spatially clustered. Tree height significantly predicted both variables, suggesting that gall wasps may use visual cues to locate suitable host trees, at least in the early stage of invasion. Assessment of the susceptibility of hybrid clones/pure species must take concurrent indicators of infestation levels into account. We suggest the use of indices involving galls on shoots because these enable good assessment of the damage to chestnut trees. The study findings add to existing knowledge on the susceptibility of hybrid chestnut clones. We report, for the first time, two hybrid clones resistant to the pest and one hybrid clone which exhibited consistently low values for all of the indicators of infestation level. The results have important implications regarding selection of plant material for use in afforestation in Spain, where the current high rate of chestnut planting is expected to continue.S

Radial growth and wood density reflect the impacts and susceptibility to defoliation by gypsy moth and climate in radiata pine

[EN] Drought stress causes a reduction in tree growth and forest productivity, which could be aggravated by climate warming and defoliation due to moth outbreaks. We investigate how European gypsy moth (Lymantria dispar dispar L., Lepidoptera: Erebidae) outbreak and related climate conditions affected growth and wood features in host and non-host tree species in north-western Spain. There, radiata pine (Pinus radiata D. Don) plantations and chestnut (Castanea sativa Mill.) stands were defoliated by the moth larvae, whereas Maritime pine (Pinus pinaster Ait.) was not defoliated. The gypsy moth outbreak peaked in 2012 and 2013, and it was preceded by very warm spring conditions in 2011 and a dry-warm 2011–2012 winter. Using dendrochronology we compared growth responses to climate and defoliation of host species (radiata pine, chestnut) with the non-host species (Maritime pine). We also analyzed wood density derived from X-ray densitometry in defoliated and non-defoliated trees of radiata pine. We aimed to: (i) disentangle the relative effects of defoliation and climate stress on radial growth, and (ii) characterize defoliated trees of radiata pine according to their wood features (ring-width, maximum and minimum density). Radial growth during the outbreak (2012–2013) decreased on average 74% in defoliated (>50% of leaf area removed) trees of radiata pine, 43% in defoliated trees of chestnut, and 4% in non-defoliated trees of Maritime pine. After applying a BACI (Before-After-Control-Impact) type analysis, we concluded that the difference in the pattern of radial growth before and during the defoliation event was more likely due to the differences in climate between these two periods. Radiata pines produced abundant latewood intra-annual density fluctuations in 2006 and 2009 in response to wet summer conditions, suggesting a high climatic responsiveness. Minimum wood density was lower in defoliated than in non-defoliated trees of radiata pine prior to the outbreak, but increased during the outbreak. The pre-outbreak difference in minimum wood density suggests that the trees most affected by the outbreak produced tracheids with wider lumen and were more susceptible to drought stress. Results of this study illustrate (i) that the pattern of radial growth alone may be not a good indicator for reconstructing past defoliation events and (ii) that wood variables are reliable indicators for assessing the susceptibility of radiata pine to defoliation by the gypsy mothSIFunding for this research was provided by the Local Government of Cubillos del Sil (Spain) through the contract Seguimiento y bases para la gestión de las masas forestales afectadas por defoliación de Lymantria dispar en el municipio de Cubillos del Sil

Defensive patterns of chestnut genotypes (Castanea spp.) against the gall wasp, Dryocosmus kuriphilus

Plants draw from various genetically controlled defenses to protect against herbivores and pathogens. The efficacy of alternative defenses can vary with the biology and phylogeny of the enemy. Dryocosmus kuriphilus, an invasive gall maker native to China, has become one of the main pests of chestnut trees around the world. We studied genetic variation in resistance and susceptibility to D. kuriphilus within a replicated blocked planting of 12 chestnut genotypes established in Galicia, Spain in 2004. We found very high genetic variation in susceptibility to D. kuriphilus. We evaluated if the variation was due to host selection by the wasp, differential efficacy of inducible defenses in the trees, or variability in susceptibility of the plant to manipulation by the gallmaker. We assessed host selection by counting number of eggs laid by females in tree buds and comparing preferences with phytochemistry. We also measured inducible changes in phytochemistry within and around galls, gall physical characteristics, parasitism, and insect fitness. The effective defense mechanisms in resistant genotypes involved (1) hypersensitive reactions to eggs or neonates within buds and (2) early precise abscission of nascent galls from expanding leaves. Surprisingly, the genetic resistance to D. kuriphilus of the chestnut genotypes we tested was not related to phenols, terpenes, and primary nutritionSIThis work was supported by FEDER/Spanish Ministry of Economy and Competitiveness (Research Grant AGL2016-76262-R)

Efectos a largo plazo del método de propagación de la planta en el crecimiento, caracteres morfológicos y nivel de ataque de D. kuriphilus en clones híbridos de castaño

[EN] Los clones híbridos eurasiáticos de castaño (C. sativa × C. crenata y C. sativa × C. mollissima) se pueden propagar de forma masiva por diferentes métodos, destacando el acodo bajo, el estaquillado y la micropropagación mediante el cultivo de tejidos en condiciones in vitro. No existen estudios sobre la influencia que estos métodos de propagación pueden tener a largo plazo en el crecimiento y la morfología del árbol. Asimismo, se desconoce si las diferencias de crecimiento y arquitectura de la copa del árbol pudieran afectar al nivel de ataque de agentes dañinos como la avispilla del castaño (Dryocosmus kuriphilus). En un ensayo clonal localizado en el municipio de Guitiriz (Lugo) se establecieron, en el año 2004, plantas pertenecientes a tres clones diferentes (‘3’, ‘7521’ y ‘HS’) obtenidas mediante acodo bajo, estaquilla y micropropagación. En 2018 se midió el diámetro, la altura, el nivel de ataque de avispilla (estimado mediante cuatro índices distintos) y se evaluó la rectitud del tronco y la dominancia apical, así como si se encontraban vivos o muertos. Los resultados muestran diferencias en el crecimiento en diámetro para los clones ‘3’ y ‘7521’ y diferencias en el crecimiento en altura para el clon ‘HS’. Sin embargo, no se encontraron diferencias significativas según los diferentes métodos de propagación en ninguno de los restantes caracteres evaluados: rectitud del tronco, dominancia apical, porcentaje de supervivencia y nivel de ataque de avispilla. Aunque estos resultados sugieren la ausencia de efectos de los métodos de propagación en la mayoría de los caracteres, son necesarios datos de más ensayos para obtener conclusiones más robusta