Detecting and mapping the habitat suitability of the Cossid Moth, (Coryphodema tristis) on Eucalyptus nitens in Mpumalanga, South Africa.

Masters Degree. University of KwaZulu-Natal, Pietermaritzburg.Cossid moth (Coryphodema tristis) is an indigenous wood-boring insect that presents serious environmental, ecological and economic problems globally. An extensive analysis of the current spatial distribution of Coryphodema tristis is therefore essential for providing applicable management approaches at both local and regional scales. This aim of the study was to assess GIS and remote sensing applications combined with species distribution models (Maxent) to monitor habitat suitability of the Coryphodema tristis in Mpumalanga, South Africa. The first objective of the study focused on comparing the robustness of species distribution models using Maxent (presence-data only) and Logistic regression (presence-absence data) in characterizing the habitat suitability of the Coryphodema tristis. The second objective of the study evaluated the effectiveness of the freely available Sentinel 2 multispectral imagery in detecting and mapping the habitat suitability of the C. tristis. The models sought to identify the factors that can be used to predict habitat suitability for the C. tristis using environmental and climatic variables. Presence and absence records were collected through systematic surveys of forest plantations. The models were applied on Eucalyptus nitens plantations of the study area for habitat preferences. The overall accuracies indicated that Maxent (AUC = 0.84 and 0.810) was more robust than the Logistic regression model (AUC= 0.745 and 0.677) using training and testing datasets, respectively. In Maxent, the jackknife indicated that mean temperature for October, aspect, age, mean temperature for February, June, December and elevation as the most influential predictor variables. Meanwhile, age was the only significant variable in the Logistic regression model. Therefore, results concluded that temperature, aspect, age and elevation were optimal in modelling habitat suitability for the Coryphodema tristis. For the second objective, model performance was evaluated using the Receiver Operating Characteristics (ROC) curve showing the Area Under the Curve (AUC) and True Skill Statistic (TSS), while the performance of predictors was displayed in the jackknife. Using only the occurrence data and Sentinel-2 bands and derived vegetation indices, the Maxent model provided successful results, exhibiting an area under curve (AUC) of 0.89. The Photosynthetic vigor ratio, ii Red edge (705 nm), Red (665 nm), Green NDVI hyper, Green (560 nm) and Shortwave infrared (SWIR) (2190 nm) were identified as the most influential predictor variables. Results of this study suggests that remotely sensed derived vegetation indices from cost effective platforms could play a crucial role in supporting forest pest management strategies and infestation control. Overall, these results improve the assessment of temporal changes in habitat suitability of Coryphodema tristis, which is crucial in the management and control of these pests

Applying high-resolution remote sensing to quantify baboon damage at a sub-compartment level in pine stands in the Mpumalanga escarpment region of South Africa

Managing risk in intensively managed monoculture plantation forests is an essential task to ensure sustainable yield and a continuous flow of forest products. However, since risks can be either biotic or abiotic, not all of them have a predictable pattern of spread, which can cause severe losses if management does not have the chance to implement mitigation action. Monitoring the change in forest health is vital as this provides the opportunity for preventative management and quantifies the amount of damage that management has to deal with. To provide this window of opportunity for appropriate action, constant monitoring is required. Until recently, forest health was measured through field surveys which provided adequate data. This procedure, however, is time consuming. Remote sensing has become very popular as a monitoring tool, due to its ability to provide assessment data in a fraction of the time. In this study, baboon damage in plantations along the Mpumalanga escarpment area of South Africa was monitored using remote sensing methods. While there are many methods of forest health monitoring using remote sensing, some approaches are less suitable as they either monitor damage caused at a plantation level, use lower spatial resolution (>10m) datasets or map damage using one available time period. The purpose of this study was first to establish the impact of baboon damage through time, using Sentinel-2 satellite imagery with all vegetation indices available, and the Extreme Gradient Boosting (XGboost) algorithm. The second part focused on analysing the damage at a tree level using PlanetScope imagery using a deep Learning approach. Overall, the study found that the use of Sentinel-2 data and PlanetScope data could accurately distinguish between the varying severity of baboon damage, achieving an accuracy of 95% and 82%. The processing time of the deep learning Artificial Neural Network (ANN) was greatly affected by the number of hidden layers and neurons used. Implementation of techniques used in this study has the potential to improve the accuracy of forest health monitoring in compartment forestry in South Africa

Applying high-resolution remote sensing to quantify baboon damage at a sub-compartment level in pine stands in the Mpumalanga escarpment region of South Africa

Managing risk in intensively managed monoculture plantation forests is an essential task to ensure sustainable yield and a continuous flow of forest products. However, since risks can be either biotic or abiotic, not all of them have a predictable pattern of spread, which can cause severe losses if management does not have the chance to implement mitigation action. Monitoring the change in forest health is vital as this provides the opportunity for preventative management and quantifies the amount of damage that management has to deal with. To provide this window of opportunity for appropriate action, constant monitoring is required. Until recently, forest health was measured through field surveys which provided adequate data. This procedure, however, is time consuming. Remote sensing has become very popular as a monitoring tool, due to its ability to provide assessment data in a fraction of the time. In this study, baboon damage in plantations along the Mpumalanga escarpment area of South Africa was monitored using remote sensing methods. While there are many methods of forest health monitoring using remote sensing, some approaches are less suitable as they either monitor damage caused at a plantation level, use lower spatial resolution (>10m) datasets or map damage using one available time period. The purpose of this study was first to establish the impact of baboon damage through time, using Sentinel-2 satellite imagery with all vegetation indices available, and the Extreme Gradient Boosting (XGboost) algorithm. The second part focused on analysing the damage at a tree level using PlanetScope imagery using a deep Learning approach. Overall, the study found that the use of Sentinel-2 data and PlanetScope data could accurately distinguish between the varying severity of baboon damage, achieving an accuracy of 95% and 82%. The processing time of the deep learning Artificial Neural Network (ANN) was greatly affected by the number of hidden layers and neurons used. Implementation of techniques used in this study has the potential to improve the accuracy of forest health monitoring in compartment forestry in South Africa

Understanding the impacts of foliar insect pests on eucalyptus species growth and the development of appropriate management strategies

Within South Africa (SA), eucalypts contribute significantly to the commercial production of pulpwood, treated poles, wood chips and saw timber. Due to their rapid growth and desirable timber properties, 47% of the afforested area within SA is planted with various eucalypts and their hybrid combinations. Biotic and abiotic factors pose a risk to the productivity of eucalypts, with the most significant risk currently associated with the increased impacts of foliar insect pests on tree productivity, for example Leptocybe invasa Fisher & La Salle (Hymenoptera: Eulophidae); Gonipterus scutellatus Gyllenhal (Coleoptera; Curculionidae); Thaumastocoris peregrinus Carpintero and Dellape (Hemiptera: Thaumastocoridae); Glycaspis brimblecombei Moore (Hemiptera: Psyllidae) etc. Past and current research has focused more on the individual components of biological, cultural and chemical control, with limited research conducted on the practical integration of these management strategies. Although the combination of biological and cultural control methods for long-term management would be preferred, the use of environmentally acceptable insecticides can contribute to the short-term management of insect pests where necessary. Environmental constraints (associated with forest certification) around the use of insecticides, means that there are currently few insecticides available for controlling foliar insect pests of eucalypts within the SA forest industry. Due to the recent increased introduction of insect pests, there is also a lack of data related to their impacts on tree growth, as well as the success of any management methods used. To improve our understanding regarding these components, three groups of trials (five in total) were implemented in the summer rainfall region of SA to quantify the impacts of insect pests on eucalypt growth, test integrated management practices (chemical and cultural management), and test environmentally acceptable insecticides. In 2010, two insect exclusion trials were established at Palm Ridge and Teza plantations in KwaZulu-Natal to quantify the impact of insect pests on two Eucalyptus hybrids. The trial locations were selected adjacent to compartments for which the pests Gonipterus spp. and Thaumastocoris peregrinus were present. Each trial had an insecticide treatment with an active ingredient of alpha-cypermethrin at a rate of 100 g l-1 and a control treatment where trees were not sprayed. Insect pests were collected after every spraying event. A greater number of insect pests were collected from the Palm Ridge site. Gonipterus spp. were the predominant insect pests collected. No significant growth differences were recorded between treated and untreated trees at Teza. Measurements taken at Palm Ridge indicated that insecticide-treated trees had significantly greater tree growth than untreated trees. Final measurements showed a v 25% reduction in volume for the control treatment compared to the insecticide treatment. Results of this study indicate that timing and duration of insecticide application could hold larger and additive benefits for insect exclusion. Due to the lack of non-hazardous registered insecticides, and the susceptibility of many of the eucalypts grown within SA to L. invasa, a trial was initiated in 2011 in Zululand (KwaZulu-Natal). A 3 x 4 x 4 factorial combination of 48 treatments were replicated 3 trials and arranged in a split-split-plot design. The factors included insecticide type as the whole plot (fenvalerate, azadirachtin and imidacloprid), timing of insecticide application as a sub-plot (0, 3, 6 and 9 months) and type of hybrid as the sub-sub-plot (a susceptible and tolerant E. grandis x E. camaldulensis hybrid (GC_s and GC_t) and a susceptible and tolerant E. grandis x E. urophylla hybrid (GU_s and GU_t)). To determine insecticide efficacy, plots of untreated clones were included as control treatments within each replicate. The incidence and magnitude of L. invasa damage and tree performance were assessed for up to 5.5 years of age. L. invasa damage recorded over the trial period indicated that irrespective of treatment, damage was lower in the GU clones than the GC clones resulting in a 63.9 m3 ha-1 volume difference at 5.5 years. In addition, the difference between the GU_s and GU_t clones (3.2 m3 ha-1) was marginal when compared to the GC_s and GC_t clones (37.2 m3 ha-1). A decrease in GC stocking correlated with the period when there was a high damage incidence recorded for L. invasa. Although the three insecticides tested delayed the onset of L. invasa damage, they did not result in improved tree performance at 5.5 years. Results indicate that the planting of a tolerant species (hybrid in this trial) was the most viable option for the management of L. invasa. Two trials were implemented in the KwaZulu-Natal Midlands in October 2016 (at Ingwe and Balgowan plantations), to test the efficacy of eight different insecticides (synthetic and organic) for the management of foliar insect pests. The Ingwe trial was planted with Eucalyptus dunnii and the Balgowan trial was planted with Eucalyptus badjensis. The insecticides tested were azadirachtin, deltamethrin, imidacloprid (liquid and tablet), Beauveria bassiana, Bacillus thuringiensis, potassium silicate and a combination of plant oil extracts (garlic oil, soybean oil and capsicum oleoresin extract). The imidacloprid tablet, deltamethrin and an untreated control were implemented as additional treatments. The insecticides were tested at the recommended rate (single rate) and at double the recommended rate (double rate), except for the insecticides in the additional treatments which were only tested at the single rate. These insecticides were applied three times over a period of four months, and tree growth measurements (Gld/Dbh and Ht) were taken four times over a period of seven months. Gonipterus spp. vi was the only insect pest found in both these trials, thus the insecticides were tested for their efficacy in managing this specific insect pest. A higher population and damage of Gonipterus spp. was found in the E. dunnii trial and very little to no damage was observed in the E. badjensis trial. All insecticides tested were not effective in managing Gonipterus spp. in these specific sites. A low population of insect pests and incorrect timing and method of application of some of the insecticides could offer a plausible explanation of results. Results from these trials indicate that where foliar insect pests occur in high abundance, significant tree-growth reduction occurs. Although insecticides (deltamethrin - for G. scutellatus; imidacloprid for L. invasa) can be used for the short-term control of these insects, their commercial benefits may be reduced due to the number of repeat applications required and/or with high levels of infestation. Of the eight environmentally acceptable insecticides tested for foliar insect control, the low abundance of insect pests present in the trials meant that their efficacy could not be quantified. If an alternative insecticide were to be found, its application would need to be linked to the environmentally stimulated outbreaks of specific insects. Of the treatments implemented, the selection and planting of eucalypts with known resistance to specific insect pests currently remains the most viable management strategy. Breeding for increased tolerance within resistant eucalypts may also provide additional benefits. Although the above research showed the negative impacts of foliar insect pests on tree growth, it also indicated that no single control method is viable for all insect pests. Future research should look at the integration of different management methods while incorporating more insect pests and different seasons in the study

Mapping rangeland ecosystems vulnerability to lantana camara invasion in semi-arid savannahs in South Africa

We mapped and modelled the potential areas vulnerable to Lantana camara (L. camara) invasion in semi-arid savannah ecosystems in the communal lands of Bushbuckridge and Kruger National Park, South Africa. Specifically, we modelled potentially vulnerable areas based on remotely sensed data and environmental variables. The Maximal Entropy (Maxent) algorithm was used to model the vulnerable area. The reliability of the modelled results was assessed using Skills Statistic (TSS), Area Under Curve (AUC) and Kappa statistics. According to the results, Bushbuckridge communal lands are more susceptible to L. camara invasions than Kruger National Park. The risk of L. camara invasion in the study site was modelled with high accuracy (AUC score of 0.95) using the best model (Model 7), which is a composite of all model variables (remote sensing and environmental variables). The spatial distribution maps derived from Maxent showed that L. camara was more likely to invade communal lands than protected areas. Using remotely sensed spectral indices as standalone model variables (Model 4) showed the lowest accuracy, with an AUC score of 0.85. Overall, model input variables such as elevation had a significant influence on the spatial distribution of L. camara in the study area

The Utility of AISA Eagle Hyperspectral Data and Random Forest Classifier for Flower Mapping

Peer reviewe

Optimizing herbicide-use for the killing of eucalypt stumps

The South Africa (SA) forest industry relies on plantations of exotic forestry trees (Pinus, Acacia and Eucalyptus) to fulfil its timber requirements. With 52.0% of the afforested land in South Africa planted to various eucalypts and their hybrid combinations. Of the total area planted to eucalypts in SA, 75 000 ha is re-established annually by means of silvicultural regimes and operations matched to site productivity, desired end-product and method of regeneration. Unlike other commercially grown tree species, eucalypt species have the ability to coppice after felling. Coppicing is a common form of regeneration in South African forestry as it allows the plantation owner the option of a second timber rotation without replanting. However, if any factors affecting coppicing are compromised, and the site is to be replanted, then it is important to kill the stumps before replanting as rapid initial growth of the coppice shoots will require earlier control than that associated with normal weeding operations. Over time, various methods of woody plant control have been proposed and tested, with most of these making use of herbicides as opposed to the repeated manual removal of coppice regrowth. Globally, most industries subscribe to standards associated with sustainable production (economic, environmental and social) against which they are measured. Within SA, 80% of the forests are certified though either the Forest Stewardship Council (FSC) or International Standards Organisation (ISO) which recommend the identification and avoidance of ‘highly hazardous’ chemicals; the promotion of ‘non-chemical’ methods for pest management as an element of an integrated pest and vegetation management strategy; and the appropriate use of chemicals that are used. To test the current recommendations for killing eucalypt stumps to include other species, the potential of reducing herbicides used, and the influence of time after application on the survival of eucalypt stumps, two trials were initiated at Entabeni plantation (Venda, Limpopo) and one at Wilgeboom plantation (Bushbuckridge, Mpumalanga) between 2018 and 2020. Extending eucalypt cut-stump control practices: Most of the trial work on killing of eucalypts in SA has been conducted on Eucalyptus grandis, Eucalyptus camaldulensis or Eucalyptus macarthurii, with all grown on shorter pulpwood rotations. To extend current recommendation to include Eucalyptus cloeziana (grown on a longer rotation for poles), a trial was established in 2018 at Entabeni plantation (Limpopo Province) to quantify the interaction between Application method (basal-frill; cut-surface; foliar) and Herbicide (no herbicide applied; Roundup; Garlon; Roundup + Garlon) for the killing of 12 year-old stumps following harvesting. Assessments were carried out at 1, 3 and 6 months following application and included Stump survival, Stump quarter with coppice and Coppice heath. Relative to the control plots (100% survival), all herbicides tested were equally effective, 70–90% of the stumps killed. This study confirms previous research regarding the killing of eucalypt stumps. Roundup, Garlon or a combination of two, when applied according to label recommendations to a stump as a basal-frill or cut-surface application (within 30 minutes of felling) resulted in 70-90% of the stumps killed.Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 202

Modelling susceptibility to Parthenium hysterophorus invasion in KwaZulu-Natal Province, South Africa using physical, climatic and remotely sensed derived variables.

Master of Science in Environmental Sciences. University of KwaZulu-Natal. Pietermaritzburg, 2018.Invasive alien plants (IAP) are considered as one of the major causes of global change. Parthenium hysterophorus is recognized as one of the world’s most aggressive, harmful and extremely resilient invasive plant species. It has adverse impacts on the environment, economies, biodiversity, human health and agriculture. Identification and modelling of areas vulnerable to Parthenium invasion is critical for proactive control and site- specific management of its spread. This study sought to test the performance of Maxent algorithm in modelling habitats susceptible to Parthenium invasion using selected environmental and physical variables and remotely sensed data. Specifically, the study sought to identify key physical and bio-climatic variables that influence the distribution of Parthenium. Furthermore, the study sought to determine the value of the freely available Sentinel 2 multispectral instrument (MSI) datasets in concert with environmental variables in modelling habitat susceptible to Parthenium invasion. The Maximum Entropy model (MaxEnt) machine learning algorithm was used to model Parthenium invasion using presence - only records (n = 274). Results showed that landscapes characterized by low elevation, close proximity to roads and high precipitation were the most susceptible to Parthenium invasion. An Area under curve (AUC) value of 0.946 was attained, indicating that the model derived using the aforementioned optimal physical and bio-climatic variables performed better than random. Based on the high AUC values, results also showed that all the model scenarios derived from spectral bands and environmental variables, vegetation indices and environmental variables and a combination of spectral bands, vegetation indices and environmental variables performed better than random, with AUC values of 0.976, 0.970 and 0.974, respectively. The higher accuracy exhibited by the optimal model (bands and environmental variables) can be attributed to the integration of red edge band centered at 705 nm in Sentinel 2 MSI and environmental variables in predicting areas susceptible to Parthenium. Overall, these results demonstrate the potential of integrating the freely available Sentinel 2 MSI data and environmental variables to improve the mapping of habitat susceptibility to Parthenium invasion. These results could be beneficial for early detection, site -specific weed management and long-term monitoring

Optimizing herbicide-use for the killing of eucalypt stumps

The South Africa (SA) forest industry relies on plantations of exotic forestry trees (Pinus, Acacia and Eucalyptus) to fulfil its timber requirements. With 52.0% of the afforested land in South Africa planted to various eucalypts and their hybrid combinations. Of the total area planted to eucalypts in SA, 75 000 ha is re-established annually by means of silvicultural regimes and operations matched to site productivity, desired end-product and method of regeneration. Unlike other commercially grown tree species, eucalypt species have the ability to coppice after felling. Coppicing is a common form of regeneration in South African forestry as it allows the plantation owner the option of a second timber rotation without replanting. However, if any factors affecting coppicing are compromised, and the site is to be replanted, then it is important to kill the stumps before replanting as rapid initial growth of the coppice shoots will require earlier control than that associated with normal weeding operations. Over time, various methods of woody plant control have been proposed and tested, with most of these making use of herbicides as opposed to the repeated manual removal of coppice regrowth. Globally, most industries subscribe to standards associated with sustainable production (economic, environmental and social) against which they are measured. Within SA, 80% of the forests are certified though either the Forest Stewardship Council (FSC) or International Standards Organisation (ISO) which recommend the identification and avoidance of ‘highly hazardous’ chemicals; the promotion of ‘non-chemical’ methods for pest management as an element of an integrated pest and vegetation management strategy; and the appropriate use of chemicals that are used. To test the current recommendations for killing eucalypt stumps to include other species, the potential of reducing herbicides used, and the influence of time after application on the survival of eucalypt stumps, two trials were initiated at Entabeni plantation (Venda, Limpopo) and one at Wilgeboom plantation (Bushbuckridge, Mpumalanga) between 2018 and 2020. Extending eucalypt cut-stump control practices: Most of the trial work on killing of eucalypts in SA has been conducted on Eucalyptus grandis, Eucalyptus camaldulensis or Eucalyptus macarthurii, with all grown on shorter pulpwood rotations. To extend current recommendation to include Eucalyptus cloeziana (grown on a longer rotation for poles), a trial was established in 2018 at Entabeni plantation (Limpopo Province) to quantify the interaction between Application method (basal-frill; cut-surface; foliar) and Herbicide (no herbicide applied; Roundup; Garlon; Roundup + Garlon) for the killing of 12 year-old stumps following harvesting. Assessments were carried out at 1, 3 and 6 months following application and included Stump survival, Stump quarter with coppice and Coppice heath. Relative to the control plots (100% survival), all herbicides tested were equally effective, 70–90% of the stumps killed. This study confirms previous research regarding the killing of eucalypt stumps. Roundup, Garlon or a combination of two, when applied according to label recommendations to a stump as a basal-frill or cut-surface application (within 30 minutes of felling) resulted in 70-90% of the stumps killed.Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 202