iForest - Biogeosciences and Forestry

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K. Novotná, P. Štochlová, V. Benetka
iForest - Biogeosciences and Forestry, Volume 13, pp 185-193; doi:10.3832/ifor3171-013

Populus nigra is an important autochthonous woody plant that can be grown as a renewable energy source. The possibility of its improvement through intraspecific hybridization was tested. Differences in biomass production, growth parameters, Melampsora larici-populina rust resistance and drought tolerance were evaluated among 19 intraspecific hybrids from controlled crosses, 2 clones selected from natural populations and the “MAX 4” clone (P. nigra × P. maximowiczii). These P. nigra clones from controlled crosses were chosen from more than 2000 hybrid individuals whose parents were selected from natural populations in the Czech Republic. A field trial was set up in Pruhonice, Czech Republic (320 m a.s.l., 591 mm rainfall annually, mean annual temperature of 9.5 °C). The planting density was 6061 plants ha-1, and the plants were coppiced three times at 3-year intervals. The trial was irrigated only during its establishment. Among the clones, significant differences were found in all the evaluated traits over three rotations. An average dry matter yield of the best clone “MAX 4” was 12.8 t ha-1 yr-1 over three harvests. The best black poplar clone reached up to 9.4 t ha-1 yr-1 in three harvests. Rust resistance was constant over 9 years and high for the three P. nigra clones (two from controlled crosses and one from natural populations). Moreover, the best P. nigra clones from controlled crosses showed higher drought tolerance than the “MAX 4” clone. Breeding progress was confirmed, and most of the P. nigra clones from controlled crosses performed better than the clones selected from natural populations. The trial validated the suitability of natural populations for use as gene sources for intraspecific hybridization and as sources of clones with traits comparable with those of interspecific clones. These new P. nigra clones can replace allochthonous clones in areas where autochthonous P. nigra populations are threatened by introgression.
R. Puc-Kauil, Gregorio Ángeles-Pérez, J.R. Valdéz-Lazalde, V.J. Reyes-Hernández, J.M. Dupuy-Rada, L. Schneider, P. Pérez-Rodríguez, X. García-Cuevas
iForest - Biogeosciences and Forestry, Volume 13, pp 165-174; doi:10.3832/ifor3167-013

Accounting for small-size tree biomass is critical to improve total stand biomass estimates of secondary tropical forests, and is essential to quantify their vital role in mitigating climate change. However, owing to the scarcity of equations available for small-size trees, their contribution to total biomass is unknown. The objective of this study was to generate allometric equations to estimate total biomass of 22 tree species ≤ 10 cm in diameter at breast height (DBH), in the Yucatan peninsula, Mexico, by using two methods. First, the additive approach involved the development of biomass equations by tree component (stem, branch and foliage) with simultaneous fit. In the tree-level approach, total tree biomass equations were fit for multi-species and wood density groups. Further, we compared the performance of total tree biomass equations that we generated with multi-species equations of previous studies. Data of total and by tree component biomass were fitted from eight non-linear models as a function of DBH, total height (H) and wood density (ρ). Results showed that two models, identified as model I and II, best fitted our data. Model I has the form AGB = β0 (ρ·DBH2·H)β1 + ε and model II: AGB = exp(-β0)(DBH2·H)β1 + ε, where AGB is biomass (kg). Both models explained between 53% and 95% of the total observed variance in biomass, by tree-structural component and total tree biomass. The variance of total tree biomass explained by fit models related to wood density group was 96%-97%. Compared foreign equations showed between 30% and 45% mean error in total biomass estimation compared to 0.05%-0.36% error showed by equations developed in this study. At the local level, the biomass contribution of small trees based on foreign models was between 24.38 and 29.51 Mg ha-1, and model I was 35.97 Mg ha-1. Thus, from 6.5 up to 11.59 Mg ha-1 could be excluded when using foreign equations, which account for about 21.8% of the total stand biomass. Local equations provided more accurate biomass estimates with the inclusion of ρ and H as predictors variables and proved to be better than foreign equations. Therefore, our equations are suitable to improve the accuracy estimates of carbon forest stocks in the secondary forests of the Yucatan peninsula.
G. Da Ponte, F. Huth, S. Wagner
iForest - Biogeosciences and Forestry, Volume 13, pp 154-164; doi:10.3832/ifor2684-013

Qualea grandiflora Mart. (Vochysiaceae) is one of the most widespread species within the cerrado formation, which counts amongst the most threatened ecosystems worldwide. Understanding the regeneration ecology of Q. grandiflora is a central requirement for the success of conservation measures and silvicultural management strategies. Exhaustive investigation was carried out into each of the development stages, and the connected processes within the regeneration cycle, to provide a better understanding of the main factors influencing the regeneration ecology and the recruitment dynamics of the species. For this purpose, we analysed 92 different sources of information in this review, divided into two groups (n = 41 with “basic species information” and n = 51 with “specific information about regeneration stages and processes”) relevant for regeneration and silviculture. Our literature review showed the high proportion of studies addressing the processes flowering, pollination and fruiting, whereas the subsequent processes like seed dispersal, seed storage, germination and seedling development are almost entirely lacking. This also applies for spatial information about environmental conditions and the related regeneration processes in Q. grandiflora. This knowledge is important for management, for example, knowledge of the critical distances between flowering and seed producing trees to ensure genetically diverse regeneration and the identification of safe sites for seedling establishment. Most of the practical suggestions in relation to increasing densities or growth of Q. grandiflora seedlings and saplings made in the literature are linked to less intensive fire management strategies adopted at certain times. The use of selective herbivory to reduce the increasing competition pressure exerted by invasive grasses and hampering Q. grandiflora seedlings is also cited. In this study we highlight the need for more complex species-specific information following the development stages and processes of the regeneration cycle so as to prepare a continuous strategy with a range of management approaches.
Q. Zhao, H.-H. Tang, C.-J. Gao, Y.-H. Wei
iForest - Biogeosciences and Forestry, Volume 13, pp 175-184; doi:10.3832/ifor3206-013

Urban forests are important as they provide recreation areas and offer ecological services. Both functions determine the status of an urban forest and reflect contradictory aspects of forest tourism development and environment conservation. However, assessment of urban forest health status at a landscape scale remains scarce. Here, we selected the Nanguo Peach Garden, China, as the study area. Urban forest health status at the landscape scale were classified into recreation and eco-conservation services. Sustainability was quantified using the principal component analysis and the Kriging method to map the landscape classification in the study area. With regard to landscape recreation sustainability, some 18.9% of the total study region was classified as “very good”. They were mainly distributed in the north, southwest, and southeast parts of the study area. The central and southeast regions, accounting for 9.5% of the total area, were classified as “very good” for eco-conservation sustainability. Regarding landscape health, the region classified as “very good” accounted for 11.1% of the total study area, and it was mainly distributed in the southern part of the area; the region classified as “very poor” accounted for 16.4% of the total area, and it was located in the northwestern and eastern parts of the study area. With improved landscape health status, the forest/non-forest patch area ratio was increased and the patch number ratio was decreased. A landscape was considered the healthiest when the forest/ non-forest area ratio was 0.65 and the patch number was 0.48. The spatial distribution of landscape recreation sustainability and eco-conservation sustainability differed in the Nanguo Peach Garden, and a close relationship was observed between the landscape health and forest landscape internal structure. Forest/non-forest patch area ratios and patch number ratios were relatively stable and constant, suggesting the urban forest landscapes were healthy. The healthiest forest landscapes were mainly distributed in the forest/non-forest transition zone and the unhealthiest forest landscape was mainly located in a single natural forest.
R Duriačiová, M. Muňko, I. Barka, M. Koreň, K. Resnerová, J. Holuša, M. Blaženec, M. Potterf, R. Jakuš
iForest - Biogeosciences and Forestry, Volume 13, pp 215-223; doi:10.3832/ifor3271-013

The European spruce bark beetle Ips typographus L. causes significant economic losses in managed coniferous forests in Central and Northern Europe. New infestations either occur in previously undisturbed forest stands (i.e., spot initiation) or depend on proximity to previous years’ infestations (i.e., spot spreading). Early identification of newly infested trees over the forested landscape limits the effective control measures. Accurate forecasting of the spread of bark beetle infestation is crucial to plan efficient sanitation felling of infested trees and prevent further propagation of beetle-induced tree mortality. We created a predictive model of subsequent year spot initiation and spot spreading within the TANABBO decision support system. The algorithm combines open-access Landsat-based vegetation change time-series data, a digital terrain model, and forest stand characteristics. We validated predicted susceptibility to bark beetle attack (separately for spot initiation and spot spreading) against beetle infestations in managed forests in the Bohemian Forest in the Czech Republic (Central Europe) in yearly time steps from 2007 to 2010. The predictive models of susceptibility to bark beetle attack had a high degree of reliability (area under the ROC curve - AUC: 0.75-0.82). We conclude that spot initiation and spot spreading prediction modules included within the TANABBO model have the potential to help forest managers to plan sanitation felling in managed forests under pressure of bark beetle outbreak.
Eric K. Zenner, J.E. Peck, V. Trotsiuk
iForest - Biogeosciences and Forestry, Volume 13, pp 209-214; doi:10.3832/ifor3309-013

As currently framed, the forest cycle model that underlies close-to-nature management in temperate beech forests throughout the globe specifies an orderly sequence of temporal development within even-aged patches comprising the forest mosaic. Although this model has been widely applied to European beech (Fagus sylvatica L.) forests, the underlying assumptions of disturbance-induced even-agedness (i.e., within-patch age homogeneity) and competition-induced size differentiation (i.e., within-patch size heterogeneity) have not been tested in natural beech forests due to prohibitions on tree coring in primeval forest reserves. In a rare and unprecedented test dataset of spatially explicit tree ages in an old-growth European beech forest, we employed triangulated irregular networks of Delaunay triangles to objectively identify natural tree neighborhoods to determine if neighboring (i.e., within-patch) trees were even- or, at most, two-aged. Age differences among neighboring trees (summarized in 25-yr age classes) were rarely 50 yrs, while the few "even-aged" patches were very small (100 m2) and relatively young (<150 yrs). In this first assessment of the assumptions underlying the forest cycle model in European beech, we observed neither the even-aged cohorts expected for disturbance-induced patches in different phases of development, nor the size differentiation among similarly aged trees that should arise from the neighborhood dynamics of competition, self-thinning, and growth. The lack of patches indicating demographic turnover is fundamentally inconsistent with the forest cycle model as it is currently framed. We call for further exploration of spatially-explicit tree age datasets to determine the generality of these observations.
C. Rodríguez-Morata, J. Madrigal-González, M. Stoffel, J.A. Ballesteros-Cánovas
iForest - Biogeosciences and Forestry, Volume 13, pp 194-201; doi:10.3832/ifor3124-013

Global warming can jeopardize important ecosystem functions and services in sensitive Neotropical mountain areas. However, untangling the relative roles of natural climate variability pattern from current global warming trends still represent a major challenge. Here, we propose a novel analytical approach based on Structural Equation Models to evaluate the relative roles of different sources of climate variability on tree growth. Specifically, we investigate direct and indirect linkages between Basal Area Increments (BAI) and a set of different climatic sources of variability, such as: (i) large-scale atmospheric oscillation patterns (i.e., the El Niño Southern Oscillation, ENSO and the Pacific Decadal Oscillation, PDO); and (ii) local meteorology in terms of temperature and precipitation. Additionally, we included in the SEM framework other important variables such as: (iii) calendar year (representative of temporal linear trends); and (iv) tree size (representative of main biological trends). Results indicate that the ENSO and PDO modulate minimum temperatures (Tmin) in the study area. These indices describe the oscillating behavior of the climatic modes (i.e., South Oscillation Index and PDO index) and are negatively correlated with Tmin. As such, they also influence tree growth (represented here by BAI) indirectly. Furthermore, through its direct impact on Tmin increase, ongoing climate warming has an indirect negative effect on BAI, thereby implying that the ongoing temperature rise could exert control on productivity in high mountain forests of the Andes, and that this influence could become more important with continued temperature increase.
G. Russo, F. Pedrotti, D. Gafta
iForest - Biogeosciences and Forestry, Volume 13, pp 202-208; doi:10.3832/ifor3315-013

In order to review and complete our knowledge of the typology and synecology of the aspen communities from the central-southern Apennines, ten original relevés were performed on the Gargano plateau and a set of 35 relevés assigned to four community types (HP: Holco mollis-Populetum tremulae; MP: Melico uniflorae-Populetum tremulae; FP: Fraxino orni-Populetum tremulae; GP: Geranio versicoloris-Populetum tremulae) were assembled from literature. These relevés along with several environmental variables either measured or estimated were involved in cluster and ordination analyses. The relevés from Gargano formed a distinctive cluster and were assigned to a new community type (SP: Stellario holosteae-Populetum tremulae ass. nova), which can be considered an Adriatic synvicariant of HP that is distributed in similar habitats (doline bottoms) but on the Tyrrhenian escarpment. At low levels of floristic similarity, the grouping of relevés in two clusters induces a sharp separation between the aspen communities distributed in the central Apennines (MP and FP) and those from the southern Apennines (SP, HP and GP), which is mainly due to compositional differences in the regional species pool. The ordination scores of relevés were best related to terrain slope, soil nitrogen, elevation, air temperature, light availability and, to a lesser extent, to soil moisture and reaction. Unlike MP and GP that appear the most mesophilous, the FP stands display a slightly more xerophilous and acidophilous character induced by the steeper slopes on which they occur. The HP habitat is the driest and lightest very likely because of the open overlying canopy, in contrast to MP stands featuring a high shrub cover. The highest occurrence of nitrophilous species was observed in SP and MP. The management of these pioneer woods should be aimed at conservation, as they play an important role in the recovery of forest herb diversity along the ecological succession towards hardwood forests.
C. Pisuttu, A. Marchica, R. Bernardi, A. Calzone, L. Cotrozzi, C. Nali, E. Pellegrini, G. Lorenzini
iForest - Biogeosciences and Forestry, Volume 13, pp 238-245; doi:10.3832/ifor3238-013

Verticillium spp., including V. nonalfalfae and V. dahliae, are known vascular wilt pathogens of the invasive Ailanthus altissima (tree-of-heaven) in the United States and in Europe. Herein we provide evidence of the presence of a previously unreported wilt disease of A. altissima in Tuscany (Central Italy). Several isolates were collected from two locations and identified as V. dahliae, based on microscopical features of conidiophores, conidia and microsclerotia. Genomic DNA was extracted from the mycelium, the ITS region was amplified and the sequence was deposited in GenBank as VdGL16 (accession no. MK474459). BLASTn analysis showed 100% similarity with V. dahliae. To confirm pathogenicity of VdGL16, inoculations of Ailanthus seedlings were performed with the root dipping technique whereas mature trees were stem-inoculated. All inoculated seedlings exhibited wilt symptoms after 20 days, while mature Ailanthus trees showed wilting and dieback after six months. The pathogen was easily re-isolated from seedlings and re-identified as V. dahliae, thus satisfying Koch’s postulates. Results from intraspecific resistance screening of nine seed sources from across Italy revealed that Ailanthus provenances from all the six sampled regions were susceptible to V. dahliae. Stem inoculated adult plants exhibited abundant production of epicormic sprouts along the stem within six months, and most of these sprouts wilted following initial dieback of the main stem; furthermore, sprouting from the crown was intense. Petioles and rachises tissues of leaves fallen from infected trees were a good source for re-isolation of the pathogen; we proved that such petioles and rachises can effectively transfer the fungus to healthy Ailanthus seedlings via root infections. Host-specificity of the V. dahliae isolate VdGL16 was also determined on 40 non-target species/varieties/cultivars. The isolate caused disease in herbaceous species belonging to five botanical families: Asteraceae, Lamiaceae, Leguminoseae, Linaceae and Solanaceae. Given the difficulties in countering Ailanthus invasion with mechanical and chemical methods, the biological control using Verticillium may provide an efficient, low cost and sustainable control of this invasive species.
O.V. Churakova-Sidorova, S. Lienert, G. Timofeeva, R. Siegwolf, J. Roden, F. Joos, M. Saurer
iForest - Biogeosciences and Forestry, Volume 13, pp 224-229; doi:10.3832/ifor3212-013

To identify source water for trees growing on permafrost in Siberia, we applied mechanistic models that quantify physical and biochemical fractionation processes, leading to oxygen isotope variation (δ18O) in plant organic matter. These models allowed us to investigate the influence of a variety of climatic factors on tree-ring cellulose from two dominant species: Larix cajanderi Mayr. from northeastern Yakutia (69° 22′ N, 148° 25′ E, ~ 250 m a.s.l.) and Pinus sylvestris L. from Central Yakutia (62°14′ N, 129°37′ E, ~ 220 m a.s.l.). The climate of the region is highly continental with short growing seasons, low amount of precipitation and these forest ecosystems are growing on permafrost, which in turn impact the water cycle and climate variation in the δ18O of source water. We compared outputs of the Land surface Processes and eXchanges (LPX-Bern v. 1.3), and Roden-Lin-Ehleringer (RLE) models for the common period from 1945 to 2004. Based on our findings, trees from northeastern and central Yakutia may have access to additional thawed permafrost water during dry summer periods. Owing to differences in the soil structure, active thaw soil depth and root systems of trees at two Siberian sites, Larix cajanderi Mayr. trees can access water not more than from 50 cm depth, in contrast to Pinus sylvestris L. in Central Yakutia which can acquire water from up to 80 cm soil depth. The results enhance our understanding of the growth and survival of the trees in this extreme environment.
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