This review discusses how understanding of functional relationships between parasitic plants and their woody hosts have benefited from a range of approaches to their study. Gross comparisons of nutrient content between infected and uninfected hosts, or parts of hosts, have been widely used to infer basic differences or similarities between hosts and parasites. Coupling of nutrient information with additional evidence of key processes such as transpiration, respiration and photosynthesis has helped elucidate host-parasite relationships and, in some cases, the anatomical nature of their connection and even the physiology of plants in general. For example, detailed analysis of xylem sap from hosts and parasites has increased our understanding of the spatial and temporal movement of solutes within plants. Tracer experiments using natural abundance or enriched application of stable isotopes ((15)N, (13)C, (18)O) have helped us to understand the extent and form of heterotrophy, including the effect of the parasite on growth and functioning of the host (and its converse) as well as environmental effects on the parasite. Nutritional studies of woody hosts and parasites have provided clues to the distribution of parasitic plants and their roles in ecosystems. This review also provides assessment of several corollaries to the host-parasite association.
Due to the associated fire risk, the wildland–urban interface (WUI) has drawn the attention of researchers and managers from a range of backgrounds. From a land management point of view, it is important to identify the WUI to determine areas to prioritise for fire risk prevention. It is also important to know the fire risk mitigation measures available to select the most appropriate for each specific context. In this systematic review, definitions of the WUI were investigated and physical mitigation measures for reducing the risk of fire were examined from a land management perspective. The PRISMA 2020 Statement was applied to records published until 31 December 2022 and retrieved from the Web of Science, Scopus, and other research engines. A total of 162 publications from scientific journals and the grey literature were scrutinised and selected for analysis. Only publications providing an original definition of the WUI or proposing physical measures to reduce fire risk at the interface were retained, while those relating to emergency management and social perception were not considered. The risk of bias was reduced by internal cross-assessment by the research team. Definitions of the WUI (n = 40 publications) changed according to the research objective, varying broadly in identification of the anthropogenic and the wildland components of the interface. Terminology varied according to the definition, and the term wildland–human interface (WHI) was found to be more comprehensive than WUI. Methodological definitions of the interface ranged from using aggregated data through to identification of the buildings at risk in the interface with considerable precision. Five categories of physical fire risk mitigation measures (n = 128 publications) were identified: clearance distances, landscaping, wildland fuel management, land planning, and buildings design and materials. The most effective measures were those applied at early stages of urban development, and maintenance of assets and vegetation is crucial for preparedness. This review represents an analysis of scientific evidence on which land managers can base their actions to reduce the fire hazard risk in the WUI. The number of studies investigating the WUI is considerable, but experimental studies and quantitative results are scarce, and better communication and coordination among research groups and land management agencies is advisable. This systematic review was not registered.
In recent years, bushfires and prescribed burns have caused substantial economic loss to the wine industry due to smoke taint, which makes wine unpalatable. Considerable research is being done to ameliorate smoke taint but the information available about the effect of smoke on grapevines is limited. We examined the physiological effects of short-term exposure to smoke on leaves of several varieties of grapevines. Gas exchange was measured before and after short-term exposure of leaves to smoke that was produced by combustion of two different fuels. For most varieties, short-term exposure to smoke had little effect on leaf physiology. For varieties that were affected by smoke, patterns of recovery of leaf physiology depended on fuel type. Short-term exposure to smoke had, at best, no significant effect and, at worst, only temporary effects on functioning of leaves. All varieties had recovered to pre-smoke functioning within 48 h. This study will contribute to the growing body of information relevant to fire and land management agencies and the wine industry in fire-prone areas including Australia, North and South America and Europe.
Forest litter is a fuel component that is important for the propagation of fire. Data describing fuel load, structure and fuel condition were gathered for two sites of Sydney Coastal Dry Sclerophyll Forest, a common vegetation type in the Sydney Basin, Australia. Surface litter from the sites was sorted into its constituent components and used to establish which component or mixture of components were the most flammable using several metrics. A general blending model was used to estimate the effect the different mixtures had on the response of the flammability metrics and identify non-additive effects. Optimisation methods were applied to the models to determine the mixture compositions that were the most or least flammable. Differences in the flammability of the two sites were significant and were driven by Allocasuarina littoralis. The presence of A. littoralis in litter mixtures caused non-additive effects, increasing the rate of flame spread and flame height non-linearly. We discuss how land managers could use these models as a tool to assist in prioritising areas for hazard reduction burns and how the methodology can be extended to other fuel conditions or forest types.
Street trees are a unique component of the urban forest. They provide multiple ecosystem services but can damage property and infrastructure, so they are frequently perceived with residents’ ambivalence. Global attempts to expand urban tree canopy cover to improve climate resilience are increasingly reliant on residents to establish and maintain street trees. Success depends on community support, which requires an understanding of how residents perceive trees located outside their homes. A review of the literature revealed 21 eligible studies on residents’ perceptions of street trees. Most of these studies were more than 10 years old and were restricted to single geographic regions but contained a wealth of information on factors including residents, sites, and trees. Few studies investigated the potential of these factors to influence residents’ perceptions; those that did had variable results. Inclusion of residents’ perceptions in street tree management requires careful consideration to account for the complexity of responses. Residents’ ambivalence can be addressed through increased awareness of the significant environmental, social, and economic values of street trees through public engagement programs and visual AI. Enforcement of tree protection policies and incentives for tree establishment and maintenance will also aid in the expansion of urban tree cover for improved climate resilience.