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Southern forests
Southern African Institute of Forestry
Southern forests

Southern African Institute of Forestry

2070-2620

Southern forests/Journal Southern forestsSCI
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    Artificial neural networks and non-linear regression for quantifying the wood volume in eucalyptus species

    de Azevedo, Gileno Britode Oliveira Sousa Azevedo, Glauce TaisPoersch, Nerison LuisVieira Borges, Marcus Vinicius...
    7页
    查看更多>>摘要：Wood volume is the variable that best represents the yield of planted forests, and several regression models are used in its estimation. Artificial neural networks (ANNs) are recognised for their accuracy and generalisation capacity associated with the quality and quantity of data in training and validation. Box-Muller transformation generates random variables from the original data and provides a consistent dataset. Given the above, the hypothesis of this research is that the expansion of data by the Box-Muller theorem provides more accurate estimates for predicting wood volume in eucalyptus species. The objectives were to (i) to evaluate the efficiency of the Box-Muller method for expanding the dataset of eucalyptus sample tree cubing, (ii) use different ANN topologies to predict the wood volume of different eucalyptus species, and (iii) compare the estimates with those obtained by using the Schumacher and Hall model. The experimental design used randomised blocks with four replicates, composed of the following treatments: Corymbia citriodora and different Eucalyptus species. Sample trees were cubed at ages 2 years and 4.5 years. The estimated volume was obtained using the Schumacher and Hall non-linear regression model for each species and compared with the ANNs through Pearson's correlation, and root mean square error at the steps training, validation, and utilisation. Two ANN architectures were tested, multilayer perceptron (MLP) and radial basis function (RBF). Dataset expansion of cut-down sample trees for cubing is efficient and can be used for ANNs training when there are cubing restrictions of sample size. The topology with seven neurons in the first hidden layer and 12 in the second with expanded data of RBF showed better performance for predicting wood volume. When evaluating all species, the accuracy of the estimates provided by ANNs was higher than that obtained with non-linear regression.
      原文链接:
    • NSTL
    • Taylor & Francis

    A serious shoot and leaf disease caused by Colletotrichum theobromicola discovered on eucalypts in South Africa

    Solis, MyriamWingfield, Michael J.Greyling, IzettePham, Nam Q....
    13页
    查看更多>>摘要：Eucalypt plantations in South Africa make up an important part of the local forestry industry. Recently, one-year-old nursery plants of a Eucalyptus grandis x Eucalyptus urophylla variety displayed symptoms of leaf and shoot anthracnose disease. Samples were collected from these plants and isolations were made from the disease symptoms. Isolates were identified based on their morphological characteristics and DNA sequence data for eight gene regions. Phylogenetic analyses led to the isolates being identified as Colletotrichum theobromicola and the reduction of Colletotrichum pseudotheobromicola to synonymy with the former species. Pathogenicity trials with isolates of C. theobromicola were conducted on clones of E. grandis and hybrids of E. grandis x E. urophylla and E. grandis x Eucalyptus camaldulensis. Resulting symptoms were similar to those found on naturally infected plants and the fungus was re-isolated from the infections. Colletotrichum theobromicola is known to cause anthracnose on various plants including eucalypts in Brazil, but this is the first record of the pathogen in South Africa.
      原文链接:
    • NSTL
    • Taylor & Francis

    Impact of climate and management on radial growth dynamics of two coexisting Mediterranean Quercus species in south Albania

    Pasho, EdmondAlla, Arben Q.
    13页
    查看更多>>摘要：In the context of changing climate conditions, it is crucial to understand how trees maintain resistance and resilience to and recover from drought stress and management-related disturbances, and how management (intensive/extensive) modulates tree growth responses to climate. Dendrochronological methods were used to examine radial growth rates, to reconstruct disturbance history and to evaluate growth resistance and resilience to and recovery from disturbance events identified by pointer year analysis in two coexisting Quercus species (Q. macrolepis Kotschy and Q. trojana Webb). Moreover, a dendro-ecological approach was used to quantify climate-growth relationships, including a drought index, the Standardised Precipitation Index (SPI). Q. trojana/Q. macrolepis showed major/moderate growth releases and moderate growth suppression. Q. trojana demonstrated statistically lower growth recovery than Q. macrolepis. The climatic drivers of radial growth in Q. macrolepis were May, June, September precipitation, July temperatures and the SPI accumulated since the previous year (up to 18 months); whereas Q. trojana responded significantly to May and June precipitation, July temperatures and the SPI at mid-time scales (< 8 months). Under intensive management, both species were more responsive to precipitation, temperature and short to mid-time scale SPI than during the extensive management period where they showed loss of sensitivity to spring-summer precipitation, temperature and SPI. These results are relevant to understand species vulnerability to climate and management/ human-related disturbances, and the effects of intensive/extensive management in modulating climate (drought)-growth relationships in Q. macrolepis and Q. trojana trees.
      原文链接:
    • NSTL
    • Taylor & Francis

    Assessing alternatives for growth and yield modelling in eucalypt stands

    Reis, ThaynaraSilva, SimoneTavares Junior, IvaldoLeite, Rodrigo...
    10页
    查看更多>>摘要：Growth and yield estimates are extremely important for forest stand management. The application of simple models is often useful, as it allows the use of plots with few or a single measurement. The objective of this study was to evaluate methods for modelling eucalypt stand volume under different conditions of climate and soil. We fitted the Gompertz, Logistic and Exponential models, stratifying by project and for the entire data set, to model the dominant height and volume based on the usual validation statistics and residue analyses. To model growth and yield, five alternatives were evaluated: the Gompertz, Logistic and Exponential models, exponential-modified with the inclusion of the variable site index (SI) and the Clutter model. The best model was selected based on the validation statistics and the histogram of the relative error (RE). We conclude that the stratification by project presented greater accuracy of forecast. The best model to estimate yield was the exponential model modified with the inclusion of the variable SI. The technical age of cutting ranged from 36 months, in areas of higher productivity, to 84 months, in areas with low productivity.
      原文链接:
    • NSTL
    • Taylor & Francis

    Time of permanence and rooting quality of minicuttings of eucalypt clones

    de Souza, Anderson Marcosde Azevedo, Gileno BritoTeodoro, Paulo EduardoRibeiro Teodoro, Larissa Pereira...
    8页
    查看更多>>摘要：Establishing the optimal time for rooting permanence and evaluation of the rooting quality of eucalypt clones allows us to optimise the production process and increase the quality of the seedlings produced. This study aimed to determine the optimal time for rooting permanence and the rooting quality of three eucalypt clones. Minicuttings from the clones AEC 0144, GG100 and VM01 were propagated in a greenhouse and evaluated for six weeks. The percentages of callus- rooted, rooted and live minicuttings, the number of roots, root system length, and root dry mass were evaluated. The selected clones differed in the speed and rate of rooting, reflecting differences in the optimal time in the rooting house for the minicuttings. Clone VM01 presented the lowest rate and speed of rooting. We conclude that optimisation of the rooting process can be achieved using logistic model fitting and noting the intercept between the daily current increment and daily average increment curves of the rooting percentage, since the other variables are dependendent on this.
      原文链接:
    • NSTL
    • Taylor & Francis

    Technological characterisation of wood from Australian red cedar after first thinning of a plantation at five years

    Barbosa, Kelvin TecheraAcosta, Andrey PereiraLazarotto, MariliaBeltrame, Rafael...
    8页
    查看更多>>摘要：Australian red cedar (Toona ciliata M. Roem.) is a forest species planted in Brazil especially for lumber production. This study aimed to evaluate technological properties of the wood after selective first thinning of a plantation 5 years after planting. The technological properties evaluated were: (i) physical - apparent specific mass at 12% moisture content and shrinkage; (ii) mechanical - modulus of elasticity (E), modulus of rupture (sigma), and brittleness; (iii) weathering; (iv) surface macrostructure - colour and roughness; (v) chemical - soluble and insoluble lignins, and holocellulose and ash contents; and vi) thermal - thermogravimetric analysis and calorific value. Apparent specific mass was 380 g m(-3); the calculated shrinkage anisotropy of 1.04 and swelling anisotropy of 1.14 fit the classification 'excellent quality'; the elasticity modulus was calculated as 4 700 MPa, and strength to flexion was 45 MPa. The mechanical properties other than brittleness were not compromised with weathering exposure. However, the accelerated weathering testing as a simulation of natural weathering showed modified colour of the wood and reduction of the mechanical properties. The calorific value of the wood (4 634.03 Kcal g(-1)) was similar to that reported for other fast-growing woods at even more advanced planting ages. Thermal stability of the wood was comparable to other fast-growing species used for energy purposes, owing especially to high holocellulose content.
      原文链接:
    • NSTL
    • Taylor & Francis

    Assessment of plant species composition and natural regeneration in abandoned settlements in the lower montane forest of Kilimanjaro National Park, Tanzania

    Kikoti, Imani AbineryMligo, CosmasNdangalasi, Henry Joseph
    10页
    查看更多>>摘要：Anthropogenic modification of montane forests to other land uses has significant effects on native vegetation and the ecological functions of plant communities, such as in the forests of Mount Kilimanjaro. This study was carried out in Kilimanjaro National Park at the former Engushai forest village, where local people were relocated for conservation in 2006. Forty 20 x 50 m plots were established in areas with different historical land use (former settlement, former cultivation, transition and natural forest). We recorded 132 plant species, representing 114 genera and 58 families. The highest tree species richness was recorded in the forest zone (11 +/- 1 per plot), followed by in the transition zone (7 +/- 1), former cultivation zone (4 +/- 1) and former settlement zone (4 +/- 0.4). The natural forest was more diverse in terms of tree species than other sites (H' = 1.83 +/- 0.09, evenness of 0.48 +/- 0.02). Analysis of variance showed significant variation in tree species richness, diversity index and evenness among previously disturbed sites and natural forests. The vegetation is at an early stage of succession in anthropogenically impacted areas. However, the domination of Vernonia lasiopus and Bothriocline longipes in the formerly degraded areas was crucial for restoring the microclimate and soil fertility vital for forest development. There is adequate potential for and patterns of natural regeneration of indigenous trees in the anthropogenically impacted areas. The current passive management by Kilimanjaro National Park facilitates forest recovery, indicating the high resilience of these montane forests. It is recommended to monitor the future recovery and succession of the lower montane forest.
      原文链接:
    • NSTL
    • Taylor & Francis

    First assessment of the blue carbon storage of Rhizophora and Bruguiera mangrove stands on the island of Mauritius (western Indian Ocean)

    Raghbor, PhaneshAppadoo, ChandaniSeeruttun, Linisha Devi
    5页
    查看更多>>摘要：Blue carbon has gained recognition as a strategy to mitigate climate change. Mangroves allow significant amounts of carbon to be sequestered and stored and are considered an important component in the offset of greenhouse gas emissions. Despite this, little is known about the ecosystem-level carbon storage of the mangrove stands of Mauritius, western Indian Ocean. We conducted an inventory of mangrove stands to characterise forest stand structure and estimate carbon stocks in terms of aboveground biomass and soil carbon at two sites, Ferney and Pointe d'Esny. Different allometric equations relative to species (for areas dominated by Rhizophora mucronata or Bruguiera gymnorrhiza) were used for aboveground biomass, and the loss-on-ignition method was used for estimating soil carbon. The results showed that aboveground biomass ranged from 54.57 Mg ha(-1) to 328.71 Mg ha(-1), and soil carbon from 99.11 +/- 18.35 Mg ha(-1) to 133.45 +/- 30.35 Mg ha(-1). The total ecosystem carbon stock ranged from 402.35 +/- 19.29 Mg ha(-1) to 427.81 +/- 18.35 Mg ha(-1) at Ferney, and from 188.03 +/- 30.35 Mg ha(-1) to 189.72 +/- 19.27 Mg ha(-1) at Pointe d'Esny. Our results underscore the importance of mangrove forest stands and highlight the need for in-depth and broader spatial-scope research on blue carbon ecosystems in Mauritius.
      原文链接:
    • NSTL
    • Taylor & Francis

    Post-fire tree regeneration from seed of the endangered Nothofagus alessandrii Espinosa in the Maule region of central Chile

    Gomez, PersyEspinoza, SergioGarrido, PedroSan Martin, Jose...
    8页
    查看更多>>摘要：The endemic ruil (Nothofagus alessandrii Espinosa) forest is one of the most endangered forest ecosystems in central Chile, where its regeneration is challenged by factors such as low seedling germination capacity and recently by fire. In this study, we sampled 36 plots (625 m(2) each) within the very restricted distribution range of N. alessandrii and quantified regeneration of the species from seed after a catastrophic large-scale fire event in 2017. By means of logistic regression, Path analysis, and non-metric multidimensional scaling, we related ruil seedling regeneration with percentage vegetative cover, number of ruil individuals, richness of native species, density of seedlings of the introduced species Pinus radiata D. Don, and fire severity. Our results indicate that fire severity was the most important variable explaining the probability of regeneration of N. alessandrii. Seedling recruitment was present in 65% of the sites with low fire severity, but no recruitment was observed in sites severely burned by fire. The ecological implications of these findings suggest that after a high-severity fire, efforts to restore N. alessandrii should be concentrated on reforestation activities; however, in areas of low-severity burn, efforts must be focused on the management and protection of the new recruits.
      原文链接:
    • NSTL
    • Taylor & Francis

    An evaluation of the environmental behaviour, fate and risk of key pesticides used in South African forest plantations

    Ndlovu, Noxolo NokwethembaLittle, KeithBaillie, BrendaRolando, Carol...
    10页
    查看更多>>摘要：Pesticides are important for the management of pests and diseases that have a negative impact on the sustainability of the forestry industry. Nevertheless, there is a trend to reduce pesticide use owing to the potential detrimental impacts they pose to terrestrial and aquatic environments and human health. This study aimed to determine the extent of South African forestry-related research that has been conducted on the environmental behaviour, fate and risks associated with pesticides used operationally within South African forest plantations. A second aim was to determine the potential risks posed by pesticides used within the South African forestry industry to terrestrial and aquatic environments. This was achieved through an extensive review of field studies and/or studies that consider field-relevant exposures of pesticides used within South African plantations. It was determined that although pesticide environmental fate studies have been conducted within plantations abroad and within South African agriculture, no studies have been conducted within the South African forestry industry to understand the actual impact of the currently used pesticides to the environment. Since pesticide environmental fate is complex and dependent on a variety of local conditions and use patterns, conclusions obtained from the studies reviewed here can only be used in part to effectively guide South African forestry-relevant pesticide-related legislation and decisions of certification bodies. Consequently, field studies that determine the environmental fate of pesticides under South African plantation silvicultural regimes and environmental conditions are necessary.
      原文链接:
    • NSTL
    • Taylor & Francis