Search

Root rot affecting holm oak is a cause of high ecological and economic losses in the Iberian Peninsula, highlighting the relevance of developing disease control methods. The aim of this work was to assess the effect of a biological treatment composed of beneficial organisms (Trichoderma complex, T-complex) on holm oak seedlings infected by Phytophthora cinnamomi in two contrasted holm oak ecotypes, one considered highly susceptible (HU) and another considered tolerant to the pathogen (GR). For this purpose, a complete multifactorial test was carried out in a greenhouse, and seedlings were monitored for survival analysis and morphological and physiological attribute evaluation. Mortality began earlier in the susceptible (HU) than in the tolerant (GR) ecotype, and survival showed different trends due to the inoculation with beneficial microorganisms depending on the ecotype of the plants. The tolerant ecotype showed a high survival rate and better response to the treatment with beneficial microorganisms. GLM showed that the main reason for differences between treatments was ecotype, followed by T-complex and irrigation, and a weak interaction between ecotype and P. cinnamomi was found. The linear relationship between photosynthesis (A) and transpiration (Tr) showed an increase in the A/Tr rates for infected and inoculated plants under drought conditions for the GR ecotype. The tolerant ecotype was benefited more by the beneficial microorganism treatment. The understanding of the genetic diversity of Q. ilex and water stress influence on the efficacy of biological treatments against root rot provides useful information to develop environmentally friendly disease control methods to address the holm oak decline.

Quantifying the impact of carbon (C) and timber prices on harvest scheduling and economic returns is essential to define strategies for the sustainable management of short-rotation plantations so that they can provide timber products and contribute to C sequestration. In this paper, we present a mixed-integer linear programming model that optimizes harvest scheduling at the forest level, C sequestration, and Net Present Value (NPV) over a planning period of up to 15 years. The model included revenue from the sale of timber (pulplogs) and credits from the net C sequestered during the life of the stands. In addition, plantation establishment, management, harvesting, and transportation costs were included in the analysis. The study area comprised 88 Eucalyptus grandis W. Hill and Eucalyptus dunnii Maiden stands located in Uruguay, totaling a forest area of nearly 1882 ha. The study investigated the impact of C and timber prices on NPV, harvest schedules, stands’ harvest age, timber flows to customers, and C sequestered per period. The maximum NPV among all the scenarios evaluated (USD 7.53 M) was calculated for a C price of 30 USD t−1, an interest rate of 6%, and a timber price of 75 USD m−3. This was USD 2.14 M higher than the scenario with the same parameters but that included only revenue from timber. C prices also impacted stands’ harvest age, C sequestration, and timber flows delivered to end customers. On average, in scenarios that included C prices, timber flows and C sequestration increased by 15.4 and 12.1%, respectively, when C price increased from 5 to 30 USD t−1. These results demonstrate that harvest scheduling, harvest age, and NPV are very sensitive to C and timber, and that the best economic returns are obtained when the stands are managed to maximize timber production and C sequestration.

Systematic forest networks of health monitoring have been established to follow changes in tree vigor and mortality. These networks often lack long-term growth data, but they could be complemented with tree ring data, since both defoliation and radial growth are proxies of changes in tree vigor. For instance, a severe water shortage should reduce growth and increase tree defoliation in drought-prone areas. However, the effects of climatic stress and drought on growth and defoliation could also depend on tree age. To address these issues, we compared growth and defoliation data with recent climate variability and drought severity in Abies pinsapo old and young trees sampled in Southern Spain, where a systematic health network (Andaluc&iacute, a Permanent Plot Network) was established. Our aims were: (i) to assess the growth sensitivity of old and young A. pinsapo trees and (ii) to test if relative changes in radial growth were related with recent defoliation, for instance, after severe droughts. We also computed the resilience indices to quantify how old and young trees recovered growth after recent droughts. Wet-cool conditions during the prior autumn and the current early summer improved the growth of old trees, whereas late-spring wet conditions enhanced the growth of young trees. Old trees were more sensitive to wet and sunny conditions in the early summer than young trees. Old and young trees were more responsive to the Standardized Precipitation-Evapotranspiration Index drought index of June&ndash, July and July&ndash, August calculated at short (one&ndash, three months) and mid (three&ndash, six months) time scales, respectively. Old trees presented a higher resistance to a severe drought in 1995 than young trees. A positive association was found between stand defoliation and relative growth. Combining monitoring and tree ring networks is useful for the detection of early warning signals of dieback in similar drought-prone forests.

Eucalyptus grandis and E. dunnii have high productive potential in the South of Brazil, Uruguay, and central Argentina. This is based on the similarity of the climate and soil of these areas, which form an eco-region called Campos. However, previous results show that these species have dierences in their distribution caused by the prioritization of Uruguayan soils for forestry, explained by the particular conditions of each site. In this study, the site variables (climate, soil, and topography) that better explain the distribution of both species were identified, and prediction models of current and future distribution were adjusted for dierent climate change scenarios (years 2050 and 2070). The distribution of E. grandis was associated with soil parameters, whereas for E. dunnii a greater eect of the climatic variables was observed. The ensemble biomod2 model was the most precise with regard to predicting the habitat for both species with respect to the simple models evaluated. For E. dunnii, the average values of the AUC, Kappa, and TSS index were 0.98, 0.88, and 0.77, respectively. For E. grandis, their values were 0.97, 0.86, and 0.80, respectively. In the projections of climatic change, the distribution of E. grandis occurrence remains practically unchanged, even in the scenarios of temperature increase. However, current distribution of E. dunnii shows high susceptibility in a scenario of increased temperature, to the point that most of the area currently planted may be at risk. Our results might be useful to political government and foresters for decision making in terms of future planted areas.© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

The assessment of the long-term impacts of drought on tree growth decline using tree-ring analyses may be used to test if plantations are more vulnerable to warming after successive droughts, leading to a &ldquo, cumulative stress&rdquo, effect. We selected 76 Pinus pinaster trees (declining and non-declining trees), and basal area increments over the last 20 years (BAI20) were calculated to build the chronologies for the stand types and vigor classes. Resistance, recovery and resilience indices were calculated. Pearson correlations, analyses and Partial Least-Squares regression were used to analyze the relationships among the response and environmental variables. We found a negative and significant relationship between mean temperature for May and June of the current year and growth in the naturally regenerated stands. This negative effect on growth under warm spring conditions was more noticeable in plantations than in naturally regenerated stands. A negative trend along time was found for the resilience index in planted stands. Evapotranspiration, maximum temperature and annual radiation showed significant and negative correlations with the growth of declining trees from planted stands, indicating they are susceptible to drought stress. Declining trees in planted stands showed a loss of growth resilience, specifically a negative trend after successive droughts.

The Spanish dehesas have been severely affected by human activities that date to the prehistoric period and have suffered accelerated decline since the 1980s. Holm oak (Quercus ilex subsp. ballota (Desf.) Samp.) is a key component of this system, and its acorns provide an important food source for wildlife and domesticated livestock. Our earlier work showed structured variation in acorn morphology and biochemistry. Here, we used chloroplast and nuclear microsatellites to detect genetic structure among populations of Q. ilex from the major biogeographic regions of Andalusia. We found high levels of spatial differentiation with chloroplast DNA indicating little seed dispersal among populations. Spatial differentiation was weaker for nuclear DNA, presumably as a result of more widespread pollen dispersal and its larger effective population size. The Baetic Cordillera (C&aacute, diz) population consistently appeared well separated from populations of the northern Sierra Morena, suggesting that the Guadalquivir Valley has played an important role in determining population divergence. This may be, in part, evolutionary, as suggested by chloroplast DNA, and, in part, a result of human-induced population isolation, as Q. ilex has been removed from the Guadalquivir Valley. Evolutionary gene flow rates were greater than contemporary rates, which were limited to unidirectional gene flow from C&oacute, rdoba to other populations in the Sierra Morena and, surprisingly, to the southern population at Almer&iacute, a. The inconsistency between evolutionary and recent migration rates suggests an effect of anthropogenic activity over the last few generations of Q. ilex.

This study presents a yield model for aboveground biomass production from three species the Eucalyptus in northern and western regions of Uruguay, based on sampling records from intensive crop plantations. High-density eucalyptus plantations represent a forestry alternative for the production of forest biomass. This work assessed the survival and growth of three eucalyptus species (Eucalyptus benthamii Maiden &amp, Cambage, E. dunnii Maiden and E. grandis Hill ex Maiden) planted at densities of 2220, 3330, 4440 and 6660 trees ha&minus, 1, for a period of 57 months in northern (Tacuaremb&oacute, ) and western (Paysand&uacute, ) regions of Uruguay. Linear and logarithmic equations of individual volume were fitted by site and species. The survival of E. grandis, E. benthamii and E. dunnii was not related to planting density, and the highest mortality values occurred in Tacuaremb&oacute, The effects of competition among trees were more evident at the highest planting density for E. grandis. In all species, the reduction in diameter was more marked than that of height, as planting density increased. Tree volume showed the same trend, and this was higher with higher planting densities. At Tacuaremb&oacute, the volume was the highest with E. benthamii at 6660 trees ha&minus, 1 (416.4 m3 ha&minus, 1), and, at Paysand&uacute, the highest production was obtained with E. grandis (370.7 m3 ha&minus, 1) and with the densities of 4440 and 6660 trees ha&minus, 1 (305.9 and 315.3 m3 ha&minus, 1, respectively). With all species and planting densities, there was an increase in the accumulated volume during the 57-month study period, however, growth curves indicate that the maximum production per unit time and, therefore, the optimum harvest time occurred at 48 months. In this work, it has been shown that the use of intensive short-rotation plantations of eucalyptus for the production of biomass in Uruguay is suitable in soils prioritized for forestry.