Determining Firebrand Generation Rate Using Physics-Based Modelling from Experimental Studies through Inverse Analysis

Firebrand spotting is a potential threat to people and infrastructure, which is difficult to predict and becomes more significant when the size of a fire and intensity increases. To conduct realistic physics-based modeling with firebrand transport, the firebrand generation data such as numbers, size, and shape of the firebrands are needed. Broadly, the firebrand generation depends on atmospheric conditions, wind velocity and vegetation species. However, there is no experimental study that has considered all these factors although they are available separately in some experimental studies. Moreover, the experimental studies have firebrand collection data, not generation data. In this study, we have conducted a series of physics-based simulations on a trial-and-error basis to reproduce the experimental collection data, which is called an inverse analysis. Once the generation data was determined from the simulation, we applied the interpolation technique to calibrate the effects of wind velocity, relative humidity, and vegetation species. First, we simulated Douglas-fir (Pseudotsuga menziesii) tree-burning and quantified firebrand generation against the tree burning experiment conducted at the National Institute of Standards and Technology (NIST). Then, we applied the same technique to a prescribed forest fire experiment conducted in the Pinelands National Reserve (PNR) of New Jersey, the USA. The simulations were conducted with the experimental data of fuel load, humidity, temperature, and wind velocity to ensure that the field conditions are replicated in the experiments. The firebrand generation rate was found to be 3.22 pcs/MW/s (pcs-number of firebrands pieces) from the single tree burning and 4.18 pcs/MW/s in the forest fire model. This finding was complemented with the effects of wind, vegetation type, and fuel moisture content to quantify the firebrand generation rate.

Sewage Pollution Promotes the Invasion-Related Traits of Impatiens glandulifera in an Oligotrophic Habitat of the Sharr Mountain (Western Balkans)

An annual plant, Himalayan balsam (Impatiens glandulifera Royle) is globally widespread and one of Europe’s top invaders. We focused on two questions: does this species indeed not invade the southern areas and does the environment affect some of its key invisibility traits. In an isolated model mountainous valley, we jointly analyzed the soil (21 parameters), the life history traits of the invader (height, stem diameter, aboveground dw), and the resident vegetation (species composition and abundances, Ellenberg indicator values), and supplemented it with local knowledge (semi-structured interviews). Uncontrolled discharge of fecal wastewaters directly into the local dense hydrological network fostered mass infestation of an atypical habitat. The phenotypic plasticity of the measured invasion-related traits was very high in the surveyed early invasion (30–50% invader cover) stages. Different microhabitat conditions consistently correlated with its growth performance. The largest individuals were restricted to the deforested riparian habitats, with extreme soil nutrient enrichment (primarily by P and K) and low-competitive, species-poor resident vegetation. We showed that ecological context can modify invasion-related traits and what could affect a further invasion process. Finally, this species is likely underreported in the wider region; public attitude and loss of traditional ecological knowledge are further management risks.

Permafrost thaw driven changes in hydrology and vegetation cover increase trace gas emissions and climate forcing in Stordalen Mire from 1970 to 2014

Permafrost thaw increases active layer thickness, changes landscape hydrology and influences vegetation species composition. These changes alter belowground microbial and geochemical processes, affecting production, consumption and net emission rates of climate forcing trace gases. Net carbon dioxide (CO 2 ) and methane (CH 4 ) fluxes determine the radiative forcing contribution from these climate-sensitive ecosystems. Permafrost peatlands may be a mosaic of dry frozen hummocks, semi-thawed or perched sphagnum dominated areas, wet permafrost-free sedge dominated sites and open water ponds. We revisited estimates of climate forcing made for 1970 and 2000 for Stordalen Mire in northern Sweden and found the trend of increasing forcing continued into 2014. The Mire continued to transition from dry permafrost to sedge and open water areas, increasing by 100% and 35%, respectively, over the 45-year period, causing the net radiative forcing of Stordalen Mire to shift from negative to positive. This trend is driven by transitioning vegetation community composition, improved estimates of annual CO 2 and CH 4 exchange and a 22% increase in the IPCC's 100-year global warming potential (GWP_100) value for CH 4 . These results indicate that discontinuous permafrost ecosystems, while still remaining a net overall sink of C, can become a positive feedback to climate change on decadal timescales. This article is part of a discussion meeting issue ‘Rising methane: is warming feeding warming? (part 2)’.

Estuarine morphodynamics and development modified by floodplain formation

Rivers and estuaries are flanked by floodplains built by mud and vegetation. Floodplains affect channel dynamics and the overall system's pattern through apparent cohesion in the channel banks and through filling of accommodation space and hydraulic resistance. For rivers, effects of mud, vegetation and the combination are thought to stabilise the banks and narrow the channel. However, the thinness of mudflats and salt marsh in estuaries compared to channel depth raises questions about the effects of floodplain as constraints on estuary dimensions. To test these effects, we created three estuaries in a tidal flume: one with mud, one with recruitment events of two live vegetation species and a control with neither. Both mud and vegetation reduced channel migration and bank erosion and stabilised channels and bars. Effects of vegetation include local flow velocity reduction and concentration of flow into the channels, while flow velocities remained higher over mudflats. On the other hand, the lower reach of the muddy estuary showed more reduced channel migration than the vegetated estuary. The main system-wide effect of mudflats and salt marsh is to reduce the tidal prism over time from upstream to downstream. The landward reach of the estuary narrows and fills progressively, particularly for the muddy estuary, which effectively shortens the tidally influenced reach and also reduces the tidal energy in the seaward reach and mouth area.

Sand Dune Restoration in New Zealand: Methods, Motives, and Monitoring

<p>Sand dunes are critically endangered ecosystems, supporting a wide variety of specialist native flora and fauna. They have declined significantly in the past century, due to coastal development, exotic invasions, and stabilization using marram grass (Ammophilia arenaria). An increasing number of restoration groups have carried out small scale rehabilitations of using native sand binding plants spinifex (Spinifex sericeus) and pingao (Desmoschoenus spiralis). However like many other restoration ventures, efforts are not formally monitored, despite the potential for conservation of species in decline. This thesis seeks to investigate the social and ecological aspects of sand dune restoration in New Zealand. Firstly, the status of restoration in New Zealand was examined using web based surveys of dune restoration groups, identifying motivations, methods, and the use of monitoring in the restoration process. Secondly, the ecology of restored and marram dominated sand dunes was assessed. Vegetation surveys were conducted using transects of the width and length of dunes, measuring community composition. Invertebrates were caught using pitfall traps and sweep netting, sorted to order, and spiders, beetles and ants identified down to Recognizable Taxonomic Units (RTUs) or species where possible. Lizards were caught in pitfall traps, and tracking tunnels tracked the presence of small mammals in the dunes. Analysis of each variable involved the comparison of biodiversity data between restored and marram dominated dunes, at six sites across the Wellington region. The survey of dune restoration practitioners confirmed that restoration was generally based on the motivation of erosion protection and foreshore stabilization, however an increasing number of groups were interested in the conservation of flora. Conservation of fauna was a priority for only one of the respondents. Informal monitoring of restoration attempts was carried out by the majority of groups, but specific biodiversity monitoring or monitoring using systematic scientific methods was carried by only a small proportion of groups. Re-vegetation of dunes commonly used a small suite of native sand binding species mostly pingao and spinifex. Species in decline such as sand tussock (Austrofestuca littoralis) and sand daphne (Pimelia arenaria) were only planted at a small proportion of sites. Restoration of dune ecosystems has the potential to not only enhance erosion protection and sand stabilization mechanisms, but to benefit native flora and fauna endemic to sand dunes. Identifying biological change and carrying out biodiversity monitoring may be beneficial in maximizing the ecological effectiveness of restoration attempts. Marram dunes contained higher foliage cover, vegetation height and vegetation species diversity than restored dunes. Abundance and diversity of beetle, spider, and ant families were higher in marram dominated dunes. Estimated population size of common skink (O. nigraplantare polychroma) and mouse population density was also higher in marram dunes. These results were positively correlated with the percentage of vegetation foliage cover and vegetation species diversity, suggesting that the habitat conditions created by marram grass were favored by fauna. These results suggest that for maximum biodiversity gains, future dune restoration attempts should increase vegetation cover, and include a wider range of plant species. Species in decline known to be important for fauna, such as pohuehue (Muehlenbeckia spp.), sand pimelia, and sand coprosma (Coprosma acerosa) should also be included for reciprocal benefits for conservation of flora and fauna. Marram grass could also be incorporated into restoration, as its mass removal may have considerable consequences for fauna using it as a refuge, and it appears to provide desirable habitat for fauna.</p>

Sand Dune Restoration in New Zealand: Methods, Motives, and Monitoring

<p>Sand dunes are critically endangered ecosystems, supporting a wide variety of specialist native flora and fauna. They have declined significantly in the past century, due to coastal development, exotic invasions, and stabilization using marram grass (Ammophilia arenaria). An increasing number of restoration groups have carried out small scale rehabilitations of using native sand binding plants spinifex (Spinifex sericeus) and pingao (Desmoschoenus spiralis). However like many other restoration ventures, efforts are not formally monitored, despite the potential for conservation of species in decline. This thesis seeks to investigate the social and ecological aspects of sand dune restoration in New Zealand. Firstly, the status of restoration in New Zealand was examined using web based surveys of dune restoration groups, identifying motivations, methods, and the use of monitoring in the restoration process. Secondly, the ecology of restored and marram dominated sand dunes was assessed. Vegetation surveys were conducted using transects of the width and length of dunes, measuring community composition. Invertebrates were caught using pitfall traps and sweep netting, sorted to order, and spiders, beetles and ants identified down to Recognizable Taxonomic Units (RTUs) or species where possible. Lizards were caught in pitfall traps, and tracking tunnels tracked the presence of small mammals in the dunes. Analysis of each variable involved the comparison of biodiversity data between restored and marram dominated dunes, at six sites across the Wellington region. The survey of dune restoration practitioners confirmed that restoration was generally based on the motivation of erosion protection and foreshore stabilization, however an increasing number of groups were interested in the conservation of flora. Conservation of fauna was a priority for only one of the respondents. Informal monitoring of restoration attempts was carried out by the majority of groups, but specific biodiversity monitoring or monitoring using systematic scientific methods was carried by only a small proportion of groups. Re-vegetation of dunes commonly used a small suite of native sand binding species mostly pingao and spinifex. Species in decline such as sand tussock (Austrofestuca littoralis) and sand daphne (Pimelia arenaria) were only planted at a small proportion of sites. Restoration of dune ecosystems has the potential to not only enhance erosion protection and sand stabilization mechanisms, but to benefit native flora and fauna endemic to sand dunes. Identifying biological change and carrying out biodiversity monitoring may be beneficial in maximizing the ecological effectiveness of restoration attempts. Marram dunes contained higher foliage cover, vegetation height and vegetation species diversity than restored dunes. Abundance and diversity of beetle, spider, and ant families were higher in marram dominated dunes. Estimated population size of common skink (O. nigraplantare polychroma) and mouse population density was also higher in marram dunes. These results were positively correlated with the percentage of vegetation foliage cover and vegetation species diversity, suggesting that the habitat conditions created by marram grass were favored by fauna. These results suggest that for maximum biodiversity gains, future dune restoration attempts should increase vegetation cover, and include a wider range of plant species. Species in decline known to be important for fauna, such as pohuehue (Muehlenbeckia spp.), sand pimelia, and sand coprosma (Coprosma acerosa) should also be included for reciprocal benefits for conservation of flora and fauna. Marram grass could also be incorporated into restoration, as its mass removal may have considerable consequences for fauna using it as a refuge, and it appears to provide desirable habitat for fauna.</p>

The diversity and vegetation structure based on growth levels at an urban green campus in Pekanbaru City, Indonesia

Darmawati, Mulyadi A, Suwondo, Harto S. 2021. The diversity and vegetation structure based on growth levels at an urban green campus in Pekanbaru City, Indonesia. Biodiversitas 22: 5123-5132. The Bina Widya campus of the University of Riau (UNRI), Pekanbaru, Indonesia has the green open space (GOS) in its area and there are many species of vegetation. In a green open space, variables like diversity and vegetation structure must be considered based on growth levels, this study intended to determine the composition, structure, and diversity of vegetation.The results showed that there were 33 species of trees, 29 species of poles, 16 species of saplings, and 8 species of seedlings from 44 species belonging to 22 families. There were 874 individuals which consisted of 534 trees, 207 poles, 87 saplings, and 46 seedlings. The most common species found was Swietenia macrophylla King (Meliaceae) with 289 individuals. The highest Important Value Index of vegetation species at each growth level was the tree of Alstonia scholaris (L) R.Br (300%, location IX), the pole of Hibiscus tiliaceus L. (300%, location VII), saplings of Vitex pinnata L. (300%, location IV), and S. macrophylla King (300%, locations I), seedlings of S. macrophylla King (300%, location I), and Garcinia mangostana L (300%, location IX). We did not find vegetation species at the levels of sapling or seedling in locations of II, III, V, VI, and VIII. It is necessary to replant the vegetation. The highest Species Diversity Index (H') at location X was trees (2.34), poles (2.28), saplings (1.77), and seedlings (1.17). The average H’ vegetation at Bina Widya Campus UNRI was 2.44 (medium). Vegetation on the Bina Widya Campus is fairly steady in terms of delivering advantages for human environmental services.

The Similarity between Species Composition of Vegetation and Soil Seed Bank of Grasslands in Inner Mongolia, China: Implications for the Asymmetric Response to Precipitation

The asymmetric response of productivity to precipitation was recently proposed as an early warning signal for the shifts in temperate grassland function in China. It was hypothesized that the asymmetry was influenced by the increased growth of the newly emerged seedlings from the soil seed bank. Therefore, the seed density in the soil seed bank and the similarity between species composition of the vegetation and the soil seed bank should be maximized where asymmetry was maximized. However, this knowledge was still limited and unconfirmed. In this study, the desert steppe, typical steppe and the transition zone between them (with the highest asymmetry) were selected for studying the similarity index in both 2018 (dry year) and 2019 (wet year). Plant species composition was monitored in situ using an unmanned aerial vehicle. Soil seed bank samples were collected, and the seed bank density and species composition were then examined and identified in the laboratory. Results showed that: (1) The variation in vegetation species richness between the two years was the highest (41%) in the transition zone (p < 0.05), while it was only 7% and 13% for the desert steppe and typical steppe, respectively. The presence of herbaceous species mainly caused the differences in variation among three grassland types. (2) Seed density was the highest in the transition zone (114 seeds/m2 and 68 seeds/m2 in the transient and persistent soil seed bank, respectively) (p < 0.05). Additionally, herbaceous species were the main components of the soil seed bank. (3) The similarity index was the highest in the transition zone (p < 0.05), with 38%/44% and 33%/44% for the transient/persistent soil seed bank in 2018 and 2019, respectively. Our study demonstrated that variation in vegetation species composition was very similar to the composition of the seeds accumulated in the soil seed bank. These results warrant further investigation for the mechanism of asymmetric response of productivity to precipitation.