Post-fire Vegetation Recovery at Monga National Park: vegetative composition, fire response traits and eucalypt response to fire

Wildfires are prevalent across Australian landscapes and their effects on plants are highly variable. Climate change has already caused an extensive fire season in 2019-20 in eastern Australia and frequency and intensity of fires is predicted to further increase into the future. These dynamic changes in the fire regime places plant species, even those with fire-adapted traits, at risk of population decline or extinction. A fundamental aspect of fire-plant relationships is understanding the plant-responses and processes that cause change when related to fire. This hinges on the species, size and age specifics of individual plants. Plants can be broadly categorised as resprouters or seeders. Resprouters are able to survive fire through resprouting new shoots, while seeder species are typically more sensitive to fire and persist through recruitment. However, time between fire events must be sufficient to allow these species to reach reproductive maturity. Thus, it is critical to highlight that plants are not adapted to a single fire, but the fire regime itself. The fire regime is made up of a combination of factors such as the season of occurrence, intensity and length between fire events (fire frequency). The recent fire season provides researchers with a unique opportunity to investigate changing fire regimes impacts on vegetation and provide baseline data for future comparison. Therefore, this study aimed to assess the impact of a large mixed-severity wildfire in Monga National Park and evaluate vegetation recovery across different fire severities (low, moderate, and extreme). The overall objectives of this thesis were to: 1) classify the floristic composition of Monga National Park after the most recent fire event; 2) assess the effect of previous fires and fire severity on the current composition of vegetation; and 3) evaluate the recovery rates of fire resilient forests dominated by eucalypts. Standard 20 x 20 m plot sizes were used to obtain information on plant foliar cover and abundance. 50 x 20 m plot sizes were used to obtain detailed measurements of eucalypt tree epicormic growth rates and sizes. This was achieved by firstly assessing the effect of fire history and fire severity on the current composition of Monga National park and secondly evaluating the fire resilience of the dominant eucalypt species through recruitment and mortality rates. The findings of the study indicate strong effects of fire history on the composition of plants, regardless of fire severity. Sites with past fires were dominated by resprouter species, while seeder species were more abundant in sites with no previous fire. This may be explained by the inter-fire interval being long enough to allow seeder species to reach sexual maturity. The composition of Monga National Park 10 months post fire showed characteristic growth of post fire environments with an initial rise in resprouter species. The results overall indicate a good levels of recovery 10 months post fire and show that the effects of previous fire significantly influenced community composition. Strong effects of eucalypt resilience was also observed through high rates of seedling recruitment. Probability of stem damage and mortality rates revealed a strong size class effect of eucalypts ability to withstand fire. This is consistent with many other studies and highlights their resilience to high severity wildfires. However, research suggests that this resilience will be reduced following subsequent fires. Further, trees need to reach a sufficient size to be able to withstand fire. Thus, the impact of this fire may not be evident until subsequent fire and the degree of impact will depend upon the timing and severity of the next fire event

Comparative effects of logging and wildfire on carbon and fire dynamics in resprouting and non-resprouting eucalypt forests

The tall (\u3e30 m) eucalypt forests of south-eastern Australia are valued for their carbon storage and sequestration. However, they may also act as a carbon source given that they are prone to large wildfires and subject to commercial logging. Logging may reduce carbon stocks, but the relative losses compared to wildfire have not been quantified in many types of these forests. There is also growing evidence that logging may make carbon stocks in affected forests less resistant to fire and increase the risk of wildfire. These dynamics may also vary between eucalypt forest types. Carbon and fire dynamics in forests dominated by eucalypt species that cannot resprout new foliage after fire may be more sensitive to antecedent disturbance than the more widespread resprouting eucalypt forests. Non-resprouting eucalypt forests are often subject to stand replacing wildfires, but such a response is inherently absent in resprouting eucalypt forests. Non-resprouting eucalypt forests are also subject to clearfell logging, while logging practices in resprouting eucalypt forests are often less intense. Hence, a thorough comparative assessment of the effects of logging, wildfire and carbon dynamics across these broad forest types is needed to inform ongoing management of tall eucalypt forests. In this thesis, I compare how logging and wildfire affect forest carbon stocks, carbon stability (the capacity for carbon stocks to persist through, and recover after likely disturbances) and the risk of fire. The effects of logging and wildfire are compared between resprouting and non-resprouting eucalypt forests. I measured above ground carbon stocks and fuel characteristics (using a terrestrial laser scanner) along approximately 80-year chronosequences of logging and wildfire. Most sites in the resprouting forest study area were subsequently burnt by a mixed severity fire during the 2019-2020 fire season, enabling me to measure the change in carbon stock associated with wildfire and how it was affected by antecedent disturbance and fire severity. I also assessed the effects of variations in fuel characteristics on the severity of the 2019-2020 wildfires. To determine the effects of logging and wildfire on fire weather conditions, I measured fire weather conditions below the canopy across approximately 70-year chronosequences of logging and wildfire in the resprouting study area

The Effects of Fire Severity on Vegetation Structural Complexity Assessed Using SAR Data Are Modulated by Plant Community Types in Mediterranean Fire-Prone Ecosystems

This article belongs to the Special Issue The Use of Remote Sensing Technology for Forest Fire[EN] Vegetation structural complexity (VSC) plays an essential role in the functioning and the stability of fire-prone Mediterranean ecosystems. However, we currently lack knowledge about the effects of increasing fire severity on the VSC spatial variability, as modulated by the plant community type in complex post-fire landscapes. Accordingly, this study explored, for the first time, the effect of fire severity on the VSC of different Mediterranean plant communities one year after fire by leveraging field inventory and Sentinel-1 C-band synthetic aperture radar (SAR) data. The field-evaluated VSC retrieved in post-fire scenarios from Sentinel-1 γ0 VV and VH backscatter data featured high fit ( R2 = 0.878) and low predictive error (RMSE = 0.112). Wall-to-wall VSC estimates showed that plant community types strongly modulated the VSC response to increasing fire severity, with this response strongly linked to the regenerative strategies of the dominant species in the community. Moderate and high fire severities had a strong impact, one year after fire, on the VSC of broom shrublands and Scots pine forests, dominated by facultative and obligate seeder species, respectively. In contrast, the fire-induced impacts on VSC were not significantly different between low and moderate fire-severity scenarios in communities dominated by resprouter species, i.e., heathlands and Pyrenean oak forestsSIThis study was financially supported by the Spanish Ministry of Science and Innovation in the framework of the LANDSUSFIRE project (PID2022-139156OB-C21) within the National Program for the Promotion of Scientific-Technical Research (2021–2023), and with Next-Generation Funds of the European Union (EU) in the framework of the FIREMAP project (TED2021-130925B-I00); by the Regional Government of Castile and León in the framework of the IA-FIREXTCyL project (LE081P23); and by National Funds from FCT—Portuguese Foundation for Science and Technology, under the project UIDB/04033/2020. José Manuel Fernández-Guisuraga was supported by a Ramón Areces Foundation postdoctoral fellowshi

Wildfire Hazard and Risk Assessment

Wildfire risk can be perceived as the combination of wildfire hazards (often described by likelihood and intensity) with the susceptibility of people, property, or other valued resources to that hazard. Reflecting the seriousness of wildfire risk to communities around the world, substantial resources are devoted to assessing wildfire hazards and risks. Wildfire hazard and risk assessments are conducted at a wide range of scales, from localized to nationwide, and are often intended to communicate and support decision making about risks, including the prioritization of scarce resources. Improvements in the underlying science of wildfire hazard and risk assessment and in the development, communication, and application of these assessments support effective decisions made on all aspects of societal adaptations to wildfire, including decisions about the prevention, mitigation, and suppression of wildfire risks. To support such efforts, this Special Issue of the journal Fire compiles articles on the understanding, modeling, and addressing of wildfire risks to homes, water resources, firefighters, and landscapes

Comparing Mobile Laser Scanner and manual measurements for dendrometric variables estimation in a black pine (Pinus nigra Arn.) plantation

The growing demand of ecosystem services provided by forests increased the need for fast and accurate field survey. The recent technological innovations fostered the application of geomatic tools and processes to different fields of the forestry sector. In this study we compared the efficiency and the accuracy of Mobile Laser Scanner (MLS), combined with Simultaneous Localization and Mapping (SLAM) technology, and traditional field survey for the mensuration of main forest dendrometric variables like stem diameter at breast height (DBH), individual tree height (H), crown base height (CBH) and branch-free stem volume (VOL). With ground truth measurements taken from 50 felled trees, we tested the applicability of MLS technology for individual tree parameters esti-mation in a conifer plantation in central Italy. Our results showed no bias of DBH estimates and the corre-sponding RMSE was equal to 10.8% (2.7 cm). H and CBH measured with MLS were underestimated compared to the ground truth (bias of-8.6% for H and-13.3% for CBH). VOL values showed a bias and a RMSE of-4.1% (-0.01 m(3)) and 12.4% (0.04 m3) respectively. Tree height is not perfectly estimated due to laser obstruction by crowns layer, but the acquisition speed of this survey, joined with a suitable accuracy of parameters extraction, suggests sufficient suitability of the method for operational applications in simple forest structures (e.g. one-layered stands)

Micro-topography associated to forest edges

Forest edges are often defined as the discontinuity between the forest habitat and an adjacent open habitat, thus they are based on a clear difference in the structure of the dominant vegetation. However, beside this very general definition, in the field we can observe a large diversity of edges, with often different kinds of micro-topography features: bank, ditch, stone wall, path, etc. As these elements are rather common in many temperate forest edges, it seems important to start to characterize them more clearly and with consistency. From a set of observations in south-western France, we build a first typology of the micro-topographic elements associated to forest edges. For each of them we describe the process, natural or human induced, at their origin, and according to the literature available, we identify some of their key ecological roles. Banks, generated by the differential erosion between forest and crops along slopes, are especially analyzed since they are the most common micro-topographic element in our region. It offers many micro-habitat conditions in the soil used by a wide range of species, notably by several bee species. More research is required to study in details the importance of such micro-topographic elements

The global tree carrying capacity (keynote)

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