Large-scale Natural Disturbances Research Articles

Assessment of coastal and mangrove vulnerability in the Andaman Island, Indian Ocean

Coastal regions are highly susceptible to the effects of global warming, including rising atmospheric and sea surface temperatures, increased cyclone frequency, and sea level rise. Thus, it is imperative to examine coastal vulnerability to minimize the impact of multiple hazards and protect coastal resources, such as mangroves. Particularly in India studying the vulnerability of coastal zones of Andaman and Nicobar Islands which fall in seismic zone V is critical for conservation efforts. We conducted a vulnerability analysis of coastal zones impacted by the 2004 earthquake, causing varying degrees of ground upliftment and subsidence. We compared coastal vulnerability among sites that experienced uplift, no change, and subsidence (the southern portion). Our analysis utilized the Coastal and Mangrove Vulnerability Index (CVI and MVI) to measure and compare vulnerability in six zones distributed along uplift and subsidence gradient. High-resolution satellite imagery including WorldView-2, 3, and GeoEye-1 from year 2022 are utilized on this study. The CVI and MVI offers a good way to measure and compare vulnerabilities across sites and offer insights for better management. The CVI and MVI results indicate that approximately 34% of coastal grids and over 23% of mangrove grids across all zones are highly to extremely highly vulnerable. Subsided zones were found to be more vulnerable than uplifted zones. These findings suggest that large-scale natural disturbances such as tectonic displacement have the potential to impact coastal vegetation and mangrove cover can become even more vulnerable. In conclusion, our study emphasizes the importance of vulnerability analyses in coastal regions, especially in areas prone to seismic activity. Our findings have direct implications for conservation and restoration efforts and underscore the need for continued monitoring and mitigation efforts to safeguard coastal resources for long-term sustainability.

Deep-sea macrofauna community recovery in Kaikōura canyon following an earthquake-triggered turbidity flow

Sediment density flows can transport massive amounts of sediment across large distances and can have dramatic, long-lasting impacts on deep-sea benthic communities. A canyon-flushing event in Kaikōura Canyon, New Zealand, triggered by the 2016 Mw 7.8 Kaikōura Earthquake, which included significant submarine mass wasting, debris and turbidity flows, provides an excellent opportunity to investigate the effects of this type of large-scale natural disturbance on benthic communities. The macrofauna community in the canyon was well characterised before the disturbance and the canyon described as a deep-sea benthic biomass hotspot. Macrofauna community structure before and after the event was analysed in a time series of sediment cores from 8 sites (∼400–1300 m water depth) collected 10 years and 6 years before, and 10 weeks, 10 months, and 4 years after the disturbance. The benthic community structure showed significant variability at all time points, but immediately after the 2016 disturbance abundances of all macrofauna dramatically decreased. Four years after the disturbance the benthic community was similar to, but not yet comparable to the pre-event community. The average abundances of most macrofauna increased over the 4 years post-earthquake, with polychaetes and bivalves being key taxa in the recovery process, especially 10 months and 4 years after the disturbance. Infauna abundances >5 cm below the seabed, remained low even 4 years after the event but the overall pattern of vertical faunal distribution was trending towards a pre-disturbance state. Community recovery was investigated in relation to changes in the physical characteristics of the habitat caused by the disturbance, using variables derived from sediment cores (e.g., sediment texture, organic matter, and pigment content). While the environmental variables explained relatively little of the overall variability in macrofauna community structure, key variables identified were related to particle size structure and food availability and quality. The minimum threshold time for the macrofauna community to fully recover, based on within-community similarity, was estimated to be between 5.6 and 6.7 years, although recovery was predicted to take up to 9 years if higher recovery thresholds were used. The management implications of this study are considered in comparison to the few studies of large-scale disturbances in the deep sea, in terms of their relevance to the efficacy of the marine reserve that encompasses Kaikōura Canyon, and potential implications for our understanding of the impacts of anthropogenic disturbances such as seabed mining.

Assessing primary vegetation recovery from earthquake-induced landslide scars: A real-time kinematic unmanned aerial vehicle approach

Globally, post-disturbance site formation is caused by large-scale natural disturbances. In such areas, it is necessary to restore vegetation rapidly as it regulates the outflow of sediment and water. However, the relationship between post-disturbance site vegetation recovery and environmental factors has not yet been elucidated. This study aimed to estimate the environmental factors affecting early vegetation recovery after large-scale disturbances (i.e., earthquakes). We used a novel analysis of multidimensional high-definition earth surface data derived from real-time kinematic unmanned aerial vehicles (RTK-UAVs) with high positioning accuracy to reveal primary vegetation recovery conditions, accounting for ground surface changes and environmental information of earthquake-induced landslide scars in Japan's boreal forests. A vegetation survey was conducted to understand the species composition and coverage that had recovered from earthquake-induced landslide scar in Japan's boreal forests. The herbaceous species Petasites japonicus subsp. giganteus and the woody introduced species Larix kaempferi were identified as the dominant species that help restore vegetation, with high frequency and plant coverage in the primary succession of the landslide scar. The reproductive characteristics of these pioneer species suggest that they have an advantage for establishment and growth, particularly on landslide scars with substantial topsoil dynamics. An optimal generalized linear model was used, which considered the distance from the vegetation inside and outside the landslide scars, ground surface change, inclination angle, annual amount of solar radiation, and the local region as explanatory variables. The ideal environmental conditions for vegetation recovery are summarized as follows: 1) Maximum biological legacy preserved inside and outside landslide scars. 2) Vegetation recovery expected in stable areas with little erosion and accumulation. 3) Vegetation recovery expected on slopes other than steep slopes or those with extremely high amounts of sunlight. The vegetation recovery conditions and RTK-UAV remote-sensing techniques used in this study can be applied to vegetation restoration zoning plans immediately after a disaster in similar environments.

Abiotic Regulation: Landslide Scale and Altitude Regulate Functional Traits of Regenerating Plant Communities After Earthquakes

Regeneration and assembly of a plant community after a large-scale natural disturbance are affected by many factors. The relative importance of abiotic factors represented by the external environment and the biological factors inside the plant community during this process is still unexplored. This work investigated the regions affected by the Wenchuan earthquake, focusing on areas with the highest intensity (XI degrees) of this earthquake, and the process of community assembly through functional traits on landslides. The aim of this study was to understand the importance of factors influencing community assembly from the perspective of functional traits. The main conclusion is presented as follows: after the regeneration of large earthquake-induced landslides, community-level functional traits covering many plant organs, such as roots, stems, leaves and seeds, are obviously different from those unaffected by landslides. Functional traits do not show strong phylogenetic conservatism. Overall, community traits are divergent or random, and the degree of divergence among the different traits varies. Species composition and alpha diversity have minimal effect on community functional traits during the process of landslide restoration. Landslide scale and altitude significantly affected community-level functional traits in the process of community assembly. All the findings suggested that the functional traits of regenerating vegetation after the earthquake changed significantly and that the functional traits depended more on abiotic regulation than on evolutionary and species-specific factors.

Bird Response to Small- and Large-Scale Natural Disturbances in Mountain Spruce Forests in Central Europe

Bird Response to Small- and Large-Scale Natural Disturbances in Mountain Spruce Forests in Central Europe

Lake microbial communities are not resistant or resilient to repeated large-scale natural pulse disturbances.

Opportunities to study community-level responses to extreme natural pulse disturbances in unaltered ecosystems are rare. Lake sediment records that span thousands of years can contain well-resolved sediment pulses, triggered by earthquakes. These palaeorecords provide a means to study repeated pulse disturbances and processes of resistance (insensitivity to disturbance) and ecological resilience (capacity to regain structure, function and process). In this study, sedimentary DNA was extracted from a sediment core from Lake Paringa (New Zealand) that is situated in a near natural catchment. Metabarcoding and inferred functions were used to assess the lake microbial community over the past 1100years - a period that included four major earthquakes. Microbial community composition and function differed significantly between highly perturbed (postseismic, ~50years) phases directly after the earthquakes and more stable (interseismic, ~250years) phases, indicating a lack of community resistance. Although community structure differed significantly in successive postseismic phases, function did not, suggesting potential functional redundancy. Significant differences in composition and function in successive interseismic phases demonstrate that communities are not resilient to large-scale natural pulse disturbances. The clear difference in structure and function, and high number of indicator taxa (responsible for driving differences in communities between phases) in the fourth interseismic phase probably represents a regime shift, possibly due to the two-fold increase in sediment and terrestrial biospheric organic carbon fluxes recorded following the fourth earthquake. Large pulse disturbances that enhance sediment inputs into lake systems may produce an underappreciated mechanism that destabilises lake ecosystem processes.

Impact of Hurricane Harvey on Galveston Bay Saltmarsh Nekton Communities

Coastal saltmarshes are a unique habitat at the interface of tidal coastal waters and freshwater inflow providing foraging and nursery habitat for a dynamic nekton community. Saltmarshes are particularly exposed to natural disturbances such as tropical storms, which can cause shifts in water chemistry and nekton community composition. Hurricane Harvey resulted in widespread flooding and record freshwater inflow into Galveston Bay in late August 2017. This study examined the influence of the hurricane on nekton community composition of two saltmarshes in Galveston Bay, TX. Nekton were monitored from February to December 2017 using minnow seines and Breder traps. Reduced abundance and increased diversity, despite the overall reduced number of taxa of the nekton community, were documented following the hurricane. Exacerbating these differences were reduced catches of the numerically dominant daggerblade grass shrimp, Palaemonetes pugio, following the event. For some key dominant species, a significant reduction in length was measured between pre- and post-disturbance; therefore, it is likely that new recruits, rather than the return of displaced adults, drove the community recovery. A complete recovery to a pre-disturbance state will likely require at least a full year due to seasonal recruitment patterns of many of the saltmarsh nekton species. Short-term but large-scale natural disturbances can significantly impact saltmarsh nekton communities, but because of their dynamic nature, they are generally resilient.

Mangrove species diversity and composition in the successional habitats of Nicobar Islands, India: A post-tsunami and subsidence scenario

The 2004 Indian Ocean Tsunami and tectonic subsidence that ranged between 1.1 m and 2.85 m have severely impacted the mangrove habitats at the Nicobar Islands. The subsidence resulted in the loss of mangrove habitats; meanwhile, new inter-tidal habitats potential for mangrove colonization were also formed at the erstwhile terrestrial habitats. We assessed the impacts of the above mentioned large-scale natural disturbance on the mangrove habitats of Nicobar Islands and studied the initial patterns of mangrove succession. Surviving mangrove patches were observed at only three sites for the entire Nicobar Islands and the estimated mangrove cover loss is 97%, which is much higher than the previous reports. We report the presence of 20 mangrove species for the Nicobar Islands, which includes new distributional records and local extinctions after this major natural disturbance. The landward mangroves seem to be more vulnerable to such disturbances. The initial community structure of the successional mangroves is dominated by Rhizophora mucronata and Bruguiera gymnorhiza with a cumulative abundance of 70%. The community structure that included 3182 individual mangroves at the successional habitats showed a significant difference (P = 0.034) among the three islands groups (viz. Nothern, Central and Southern) in the Nicobar Islands. Habitat and species loss are inevitable with the high intensity of disturbance, in this case, tsunami and subsidence. But facilitating the mangrove regrowth at the potential habitats may be vital to restoring the functionality of the coastal system and the livelihood of local communities. Therefore, the outcome of our study is critical for the forest managers to regrow mangroves in the Nicobar Islands. Also, we suggest that a long-term monitoring of these sites is required to understand the overall long-term impacts of tsunami and subsidence on the mangrove habitats of Nicobar Islands.

Living in a burned landscape: woodland caribou (Rangifer tarandus caribou) use of postfire residual patches for calving in a high fire – low anthropogenic Boreal Shield ecozone

Environment and Climate Change Canada (ECCC) calculated that 55% of Saskatchewan’s Boreal Shield has been disturbed by wildfire in the last 40 years. The 2012 Canadian Federal Recovery Strategy for woodland caribou (Rangifer tarandus caribou (Gmelin, 1788)) states that these large-scale natural disturbances can cause caribou to cease use of portions of their range. This assumption neglects the potential habitat value of postfire residuals. We tested this assumption using 2 years of GPS data obtained from 56 female caribou to identify calving site selection. Seventy-nine calving events were identified from 91 individual calving seasons. For both calving and postcalving periods, woodland caribou preferred nonburned (>40 years) over burned habitats (≤40 years). Within burned areas, residual patches dominated by bogs–fens were preferred, indicating that burns with residuals are important woodland caribou calving habitat. The residuals may act as island refuges providing food–security, while surrounding burns provide reduced visual obstruction from which caribou can detect approaching predators. Although more data are necessary to make robust conclusions, this study provides novel insight into the ecological interactions of forest fires with woodland caribou in northern Saskatchewan, and offers important considerations regarding critical habitat identification and range-level planning to ensure all suitable caribou habitats are identified.

Individual-tree- and stand-based development following natural disturbance in a heterogeneously structured forest: A LiDAR-based approach

Large-scale severe natural disturbance events drive spatial and temporal patterns of forests by altering forest structure, composition, and functions. In the Bavarian Forest National Park in Germany, windthrow events led to large disturbances caused by the European bark beetle (Ips typographus L.). Until recently, it was assumed that at the initial stage of regeneration, trees tend to form a homogeneous stand structure, whereas structural heterogeneity is an attribute of later developmental stages. Yet recent studies provide evidence that under certain conditions structural heterogeneity can arise much earlier in stand development. Here we combined LiDAR data and forest growth modeling based on individual trees to develop a workflow for studying forest development in post-disturbed areas in the upper montane regions of the national park. The current forest structure was derived from LiDAR data of individually detected trees and a set of forest structural attributes were derived. The results served as input to simulate tree development spatio-temporally for a period of 80years. Several spatial statistics, including landscape and spatial point pattern metrics, were calculated to assess the structural heterogeneity. The results showed that naturally regenerating forests on post-disturbed sites reveal structural heterogeneity already at the early-seral stage. Moreover, a significant portion of the eventual old-growth structural heterogeneity might already be determined in the early successional stages. Our workflow highlights the use of multi-sensor aerial remote sensing to provide detailed structural information useful for the investigation of early-phase forest dynamics.

Losing Legacies, Ecological Release, and Transient Responses: Key Challenges for the Future of Northern Ecosystem Science

Northern ecosystem processes play out across scales that are rare elsewhere on contemporary earth: large ranging predator–prey systems are still operational, invasive species are rare, and large-scale natural disturbances occur extensively. Disturbances in the far north affect huge areas of land and are difficult to control or manage. Historically, disturbance patterns and processes ranging across a number of spatio-temporal scales have played an important role in the resilience of northern ecosystems. However, due to interactions with a warming climate, these disturbances are now erasing key legacies of the last millennia of ecosystem processes. Building on the concepts of legacies and cross-scale interactions, we highlight several general conceptual issues that represent key challenges for the future of northern ecosystem science, but that also have relevance to other biomes.

Future ecosystem services from European mountain forests under climate change

Summary Ecosystem services (ES) from mountain forests are highly relevant for human societies. ES with a direct economic support function (e.g. timber production), regulatory services (e.g. protection from natural hazards) and cultural services (e.g. recreation) are likely to be affected strongly by a rapidly changing climate. To evaluate whether adverse climate change effects on ES can be counteracted by adapting management, dynamic models and indicator‐based assessments are needed. We applied a forest dynamic model in case study areas of four European mountain regions and evaluated the future supply of four ES – timber production, carbon sequestration, biodiversity and protection against natural hazards – using state‐of‐the‐art ES indicators. Forest dynamics were simulated under three management scenarios (no management, business‐as‐usual and alternative management) and five climate change projections for selected representative stand types in each region. We analysed potential trade‐offs and synergies between ES and evaluated future changes among regions, forest stands, climate and management scenarios. Impacts of climate change on the provision of multiple ES were found to be highly heterogeneous and to depend on the region, site and future climate. In the absence of large‐scale natural disturbance (not considered), protection services, carbon stock and deadwood abundance (proxy for biodiversity) benefitted from no management in all regions. Negative impacts of climate change were evident for the provision of multiple ES but limited to the most severe climate scenarios and low‐elevation stands. Synergies and trade‐offs between the majority of ES were found to be sensitive to the choice of management strategy and – in some regions – to climate change. Synthesis and applications. Management regimes in European mountain forests should be regionally adapted to stand and site conditions. Although in some cases alternative management regimes may be more suitable than current management for supporting multiple ecosystem services, adaptation options should be evaluated carefully at the local scale due to the highly different magnitude of the impacts of climate change in different regions and along elevation gradients.

Interactive effects of three pervasive marine stressors in a post-disturbance coral reef

Ecosystems are commonly affected by natural, episodic disturbances that can abruptly and drastically alter communities. Although it has been shown that resilient ecosystems can eventually recover to pre-disturbed states, the extent to which communities in early stages of recovery could be affected by multiple anthropogenic stressors is poorly understood. Pervasive and rising anthropogenic stressors in coastal marine systems that could interactively affect the recovery of these systems following natural disturbances include high sedimentation, nutrient enrichment, and overfishing. Using a 6-month field experiment, we examined the effects of all combinations of these three stressors on key functional groups in the benthic community growing on simulated, post-disturbance reef patches within a system recovering from large-scale natural disturbances (corallivorous seastar outbreak and cyclone). Our study revealed that sedimentation, nutrient enrichment, and overfishing (simulated using exclusion cages) interactively affected coral survival and algal growth, with taxon-specific effects at multiple scales. First, our treatments affected corals and algae differently, with sedimentation being more detrimental to macroalgal growth but less detrimental to coral (Porites rus) survival in caged plots, driving significant interactions between sedimentation and caging for both taxa. We also observed distinct responses between coral species and between algal functional groups, with the most extensive responses from algal turf biomass, for which sedimentation suppressed the synergistic (positive) combined effect of nutrient enrichment and caging. Our findings suggest that different combinations of ubiquitous anthropogenic stressors, related to either sea- or land-based activities, interactively influence community recovery from disturbance and may alter species compositions in the resulting community. Our findings further suggest that anthropogenic stressors could promote further degradation of coral reefs following natural disturbances by inhibiting recovery to coral-dominated states that provide vital ecosystem services to coastal populations worldwide.

A meta-analysis of management effects on forest carbon storage

ABSTRACTForest management can have substantial impacts on ecosystem carbon storage, but those effects can vary significantly with management type and species composition. We used systematic review methodology to identify and synthesize effects of thinning and/or burning, timber harvesting, clear-cut, and wildfire on four components of ecosystem carbon: aboveground vegetation, soil, litter, and deadwood. We performed a meta-analysis on studies from the United States and Canada because those represented 85% of the studies conducted worldwide. We found that the most important variables in predicting effect sizes (ratio of carbon stored in treated stands versus controls) were, in decreasing order of importance, ecosystem carbon component, time since treatment, and age of control. Management treatment was the least important of all the variables we examined, but the trends we found suggest that thinning and/or burning treatments resulted in less carbon loss than wildfire or clear-cut. This finding is consistent with recent modeling studies indicating that forest management is unimportant to long-term carbon dynamics relative to the effects of large-scale natural disturbances (e.g., drought, fire, pest outbreak). However, many data gaps still exist on total ecosystem carbon, particularly in regions other than North America, and in timber production forests and plantations.

Functional response of lignicolous fungal guilds to bark beetle deforestation

Conifer-dominated forests in the northern hemisphere are prone to large-scale natural disturbances, yet our understanding of their effects beyond changes in species diversity is limited. Bark beetle disturbances provide dead wood for lignicolous fungal guilds and increase insolation but also desiccation. We investigated whether species richness of these guilds increases and functional diversity decreases after bark beetle disturbance, which would promote through habitat filtering the coexistence of species adapted to harsh conditions, i.e. light stress for lichens and substrate desiccation for wood-inhabiting fungi.We sampled epixylic and epiphytic lichens (primary producers) and wood-inhabiting fungi (mainly wood decomposers, some form ectomycorrhizas) in the Bohemian Forest (Long Term Ecological Research – LTER – Site Bavarian Forest National Park), an area in Central Europe most heavily affected by the bark beetle Ips typographus, on undisturbed plots and disturbed plots with spruce (Picea abies) dieback 8 years ago. We analysed species diversity, functional diversity (optimized by phylogeny), and functional compositions.Species richness of lichens but not that of wood-inhabiting fungi was higher on disturbed plots than on undisturbed plots. Community compositions of both guilds differed considerably on disturbed and undisturbed plots. On both types of plots, lichen communities were clustered according to functional diversity, which indicated habitat filtering, and fungal communities were overdispersed, which indicated competition. Disturbance increased the strength of these two patterns only slightly and was significant only for fungi. Single-trait analysis revealed changes in the functional composition; on disturbed plots, lichenous species with larger and more complex growth forms and fungi with large, perennial fruit bodies were favoured. Although the forest canopy changed tremendously because of the bark beetle disturbance, the most important driver of lichen and fungal diversity and mean trait assemblages seemed to be the enrichment of dead wood. The changes in insolation and moisture did not act as habitat filters for either guild. This indicated that the assembly patterns of lichen and fungal communities in coniferous forests are not affected by stand-replacing disturbances in contrast to the predictions for other disturbance regimes.

Restoration of Central-European mountain Norway spruce forest 15 years after natural and anthropogenic disturbance

Storm events resulting in windthrows, bark beetle (Ips typographus) outbreaks and subsequent forestry operations are the main disturbance agents in European mountain Norway spruce (Picea abies) forests. In the 1990s, a bark beetle outbreak resulted in a large-scale dieback of semi-natural mountain spruce forests in the Šumava National Park, Czech Republic. Two applied management measures enabled long-term monitoring of the effect of natural and anthropogenic disturbance on forest recovery: core zones were left without intervention, and surrounding zones were clear-cut, trees removed, and cleared areas replanted. Research plots were established in three disturbance types: climatically conditioned spruce forest with dead canopy, without intervention (1), with intervention (2), and waterlogged spruce forest partly resistant to bark beetle disturbance without intervention (3). The amount and vertical structure of tree regeneration and vegetation changes have been studied since the beginning of the disturbance in 1997.The main question of the study was whether tree regeneration and herb-layer vegetation differed between naturally developing disturbed forests and clearcuts 15years after the disturbance. The species composition of regeneration in all disturbance types consisted mainly of spruce, with accompanying rowan. The total numbers after 15years since the beginning of the disturbance did not differ significantly among the studied disturbance types, and were sufficient to replace the previous canopy. However, in clearcuts, these numbers were achieved by artificial reforestation, which was applied after initial destruction of natural regeneration due to salvage operations, whereas advance natural regeneration grew successfully under the protection of unmanaged dead canopy. There was a more unified height structure of spruce regeneration in the clearcuts, with significantly higher numbers of saplings taller than 2m compared to unmanaged forests. Due to a less harsh change in site conditions, typical herb species flourished in the non-intervention zones in comparison to the clearcuts. The impact of post-disturbance interventions on herb-layer vegetation was still obvious 15years after the event. Therefore, a non-interventional approach is recommended as the best for restoration of mountain Norway spruce forests affected by large-scale natural disturbances.

Tropical Cyclone Impacts on Coastal Regions: the Case of the Yucatán and the Baja California Peninsulas, Mexico

Tropical cyclones (TCs) are large-scale natural disturbances that generate strong winds and heavy rainfall, impacting coastal and inland environments. TCs also influence biogeochemical and hydrological cycles controlling aquatic primary productivity in tropical and subtropical coastal ecosystems. We assessed TC landfall activity and identified sites along the Mexican east and west coasts with high frequency in the period 1970–2010 and evaluated TCs with significant precipitation. Changes in chlorophyll-a (Chl-a) concentrations before and after storm impacts were estimated using remotely sensed ocean color. There were 1,065 named TCs with a wide diversity in tracks. Three states with the highest number of landfalls were identified: Baja California Sur and Sinaloa on the west coast and Quintana Roo on the east coast. While a relative increase in Chl-a values following TC landfalls in the Baja California and Yucatan Peninsula regions appeared to be strongly linked to TC strength, the intensity of precipitation, the spatial scales of the two peninsulas, and the relative movement of TCs appeared to have contributed to Chl-a variability. Satellite estimates of Chl-a in the nearshore coastal waters following TC passage were likely enhanced by coastal morphology and water discharge along with constituents such as suspended particulate, colored dissolved organic matter and nutrients from rivers, tributaries, and groundwater.

Detrimental effects of volcanic ash deposition on bee fauna and plant-pollinator interactions

Volcanic eruptions are large-scale natural disturbances, which can negatively affect insect fauna and the ecological interactions in which they are involved. The 2011 eruption of the volcanic complex Puyehue Cordon-Caulle (PCC) produced the deposition of 950 million tons of ash on Argentine Patagonia, creating an ash layer of varying thickness. Although experimental studies confirmed that PCC volcanic ash negatively affects survival and behavior in many insect taxa, including bees, the effects of ash deposition on the plant-pollinator interactions (PPI) of this group of insects in natural landscapes remained untested. We evaluated the effect of the gradient of increasing ash layer thickness (0-15cm) on: (1) number of wild bees visiting flowers and total bee richness in 16 raspberry fields after the eruption, (2) number of native ( Bombus dahlbomii) and invasive (B. terrestris and B. ruderatus) bumble bees foraging on wild flowers in 10 sites before and after the eruption, and (3) the proportion of flowers (i.e. papilionaceous flowers visited for first time by large bees) in 32 populations of the invasive shrub scotch broom (Cytisus scoparius), before and after the eruption. With the increase of ash deposition, we found a consistent and significant decrease in (1) the number of wild bees and total bee richness visiting raspberry flowers; (2) the number of bumble bees, particularly B. terrestris, visiting wild flowers; and (3) the proportion of triggered flowers of scotch broom. Thus, volcanic eruptions can exert a detrimental effect on bee fauna and concomitant PPI, with a potential cascade effect on the pollination service to crops, the spread of invasive bumble bees, and the pollination success of invasive plants. (Keywords: Bombus terrestris, bumble bees, large scale disturbance, pollination, Puyehue Cordon-Caulle Volcano, raspberry, scotch broom)

Detrimental effects of volcanic ash deposition on bee fauna and plant-pollinator interactions

Ecología Austral, 24:42-50 (2014)Volcanic eruptions are large-scale natural disturbances, which can negatively affect insect fauna and the ecological interactions in which they are involved. The 2011 eruption of the volcanic complex Puyehue Cordón-Caulle (PCC) produced the deposition of 950 million tons of ash on Argentine Patagonia, creating an ash layer of varying thickness. Although experimental studies confirmed that PCC volcanic ash negatively affects survival and behavior in many insect taxa, including bees, the effects of ash deposition on the plant-pollinator interactions (PPI) of this group of insects in natural landscapes remained untested. We evaluated the effect of the gradient of increasing ash layer thickness (0-15cm) on: (1) number of wild bees visiting flowers and total bee richness in 16 raspberry fields after the eruption, (2) number of native (Bombus dahlbomii) and invasive (B. terrestris and B. ruderatus) bumble bees foraging on wild flowers in 10 sites before and after the eruption, and (3) the proportion of "triggered" flowers (i.e. papilionaceous flowers visited for first time by large bees) in 32 populations of the invasive shrub scotch broom (Cytisus scoparius), before and after the eruption. With the increase of ash deposition, we found a consistent and significant decrease in (1) the number of wild bees and total bee richness visiting raspberry flowers; (2) the number of bumble bees, particularly B. terrestris, visiting wild flowers; and (3) the proportion of triggered flowers of scotch broom. Thus, volcanic eruptions can exert a detrimental effect on bee fauna and concomitant PPI, with a potential cascade effect on the pollination service to crops, the spread of invasive bumble bees, and the pollination success of invasive plants.

Assessing possible shifts in wildfire regimes under a changing climate in mountainous landscapes

Climate change may affect the probability of extreme events such as wildfires. Although wildfires are some of the most important ecological processes in forest ecosystems, large-scale wildfires are often perceived as an environmental disaster. Since failure to include the dynamic nature of ecosystems in planning will inevitably lead to unexpected outcomes, we need to enhance our ability to cope with future extreme events coupled with climate change. This study presents several future scenarios in three different time periods for Canada’s Columbia Montane Cordillera Ecoprovince, which is prone to wildfires. These scenarios predict the probability of occurrence of widespread wildfires based on the hierarchical Bayesian model. The model was based on the relationships between wildfires and the Monthly Drought Code (MDC). The MDC is a generalized monthly version of the Daily Drought Code widely used across Canada by forest fire management agencies for monitoring of wildfire risk. To calculate future MDC values, we relied on different possible future conditions of climate, given by the Global Circulation Models. We found a regime shift in drought intensity with abrupt decreases in lightning-caused wildfire activity around 1940, suggesting that future wildfire risks can be inferred primarily from the summer drought code. For future periods, we found increasing trends in the probabilities of large-scale fires with time in most areas. It should be notable that, by the 2080s, there is a probability of some areas having more than 50% of large-scale wildfires under the “average” climatic conditions in the future, indicating that, even without “extreme” weather conditions, some ecosystems will have a fundamental probability of experiencing catastrophic fires under the condition of average summer. However, the rate of progression toward a fire-prone condition is quite different among the three climate change scenarios and among the region analyzed. Given such scenario-sensitive, spatially-heterogeneous patterns of wildfire probability in response to climate variability, management strategy should be flexible and more localized. By drawing on this knowledge, it may be possible to mitigate climate change impacts both before they arise and once they have occurred. These considerations are critical for maintaining the integrity of systems shaped by large-scale natural disturbances to increase their resilience to the changing climate while protecting human society and infrastructures. Working with alternative scenarios will facilitate our adaptation to climate change in managing fire-prone forest ecosystems.