Post-fire Vegetation Dynamics Research Articles

Multidecadal vegetation transformations of a New Mexico ponderosa pine landscape after severe fires and aerial seeding.

Wildfires and climate change increasingly are transforming vegetation composition and structure, and postfire management may have long-lasting effects on ecosystem reorganization. Postfire aerial seeding treatments are commonly used to reduce runoff and soil erosion, but little is known about how seeding treatments affect native vegetation recovery over long periods of time, particularly in type-converted forests that have been dramatically transformed by the effects of repeated, high-severity fire. In this study, we analyze and report on a rare long-term (23-year) dataset that documents vegetation dynamics following a 1996 post-fire aerial seeding treatment and a subsequent 2011 high-severity reburn in a dry conifer landscape of northern New Mexico, USA. Repeated surveys between 1997 and 2019 of 49 permanent transects were analyzed for differences in vegetation cover, richness, and diversity between seeded and unseeded areas, and to characterize the development of seeded and unseeded vegetation communities through time and across gradients of burn severity, elevation, and soil-available water capacity. Seeded plots showed no significant difference in bare ground cover during the initial years postfire relative to unseeded plots. Postfire seeding led to a clear and sustained divergence in herbaceous community composition. Seeded plots had a much higher cover of non-native graminoids, primarily Bromus inermis, a likely contaminant in the seed mix. High-severity reburning of all plots in 2011 reduced native graminoid cover by half at seeded plots compared with both prefire levels and with plots that were unseeded following the initial 1996 fire. In addition, higher fire severity was associated with increased non-native graminoid cover and reduced native graminoid cover. This study documents fire-driven ecosystem transformation from conifer forest into a shrub-and-grass-dominated system, reinforced by aerial seeding of grasses and high-severity reburning. This unique long-term dataset illustrates that post-fire seeding carries significant risks of unwanted non-native species invasions that persist through subsequent fires-thus alternative postfire management actions merit consideration to better support native ecosystem resilience given emergent climate change and increasing disturbance. This study also highlights the importance of long-term monitoring of postfire vegetation dynamics, as short-term assessments miss key elements of complex ecosystem responses to fire and postfire management actions.

Post-fire vegetation dynamics and location as main drivers of fire recurrence in Mediterranean forests

Fire recurrence is a common phenomenon in Mediterranean forests that interrupts secondary ecosystem successions, hinders regeneration processes, and delays forests from reaching mature stages. To understand the occurrence of successive fires, we investigate the linkages between post-fire vegetation development and subsequent fire events in Eastern Spain during the period 1993–2015. In our study, we analyze annual burnt areas and derive a forest fire recurrence index that we use to explain the factors driving the occurrence of successive fires in previously burnt areas.Based on our results, fire recurrence is largely influenced by post-fire vegetation, as well as by topography and accessibility. Forests dominated by shrubs and sclerophyllous vegetation present higher probabilities of reburnt areas than tree forests. Fire recurrence is time-dependent, with the year of the first fire being an important factor in explaining the proportion of areas burnt twice. Identifying the characteristics and post-fire vegetation types in locations with higher recurrence probabilities can help to pinpoint priority areas and time windows for applying fire prevention and mitigation actions in already vulnerable forests.

Short-term functional response to post-fire vegetation dynamic: A case study in a Mediterranean Pinus halepensis forest

Wildfire events significantly affect plant communities. Understanding the post-fire vegetation dynamics and how native and alien species interact to shape the composition and structure of the community is crucial to address conservation policy. Dispersal mechanisms and resource exploration strategies are two functional strategies which can explain variability in species response to disturbance. Here, we investigated how functional traits shape the short-term dynamic after a wildfire event in a Mediterranean pine forest. We collected plant co-occurrences and abundances in permanent plots of 100 m2 across four distinct sampling sessions (from late winter to early autumn, every 2 months). Functionally relevant traits including leaf traits and dispersal-related traits were also retrieved for the recorded species. We then derived the Grime's strategies of the recorded species from the collected leaf traits, and we computed the dispersal ability of each species as a function of the corresponding dispersal traits. To compare Grime's strategies and leaf traits across the monitoring cycles, we calculated the community weighted mean for each cycle as the average of species trait values in each plot. Further, we estimated variations in species abundances and species composition within each plot by using temporal turnover analysis, which showed a continuous post-fire increase in community-level vegetation cover and a strong compositional change driven by a spread of alien species. Associating these patterns to the recorded functional traits revealed that dispersal ability is crucial in post-fire recolonization. Moreover, ruderal species, being the most represented strategy soon after the fire, give way over time to more competitive species showing higher leaf area. Thus, short-term vegetation recovery involves different species-specific strategies that shape the ecological succession over time. Our case study highlights that knowledge about how functional traits drive plant colonization strategies is critical to assess the post-fire restoration status of Mediterranean pine forests.

Monitoring immediate post-fire vegetation dynamics of tropical mountain grasslands using phenocameras

The growing incidence of uncontrolled wildfires all over the globe has called for urgent close monitoring of fire events, awareness, prevention, and management approaches. Phenocameras, ground sensors for monitoring plant phenology by taking sequential RGB digital images, can be an accessible and accurate tool for identifying, monitoring, and analyzing fire events and vegetation recovery. Here, we evaluated the application of an RGB camera system as a methodological approach to monitor and assess the post-fire recovery of a tropical mountain grasslands, the Brazilian campo rupestre. Using camera-derived vegetation indices, we investigated the immediate post-fire regrowth, and short-term post-fire leafing among four vegetation types: wet grassland, peatbog, stony grassland, and rocky outcrop. We recorded significant variations in the post-fire recovery among the grassy vegetation types. The results indicated that fire represents an important driver of leafing dynamics by shortening the length of post-fire growing seasons. The phenological metric of growing season length (GSL) indicated a full post-fire ecosystem recovery in the third year after the fire. The green-up index represented well the dynamics of post-fire vegetation regrowth and recovery across the landscape. Phenocameras rapidly detected fire occurrence and post-fire vegetation responses across vegetation types, demonstrating their significant application in the fire ecology of grassy ecosystems. The accessible, low-cost, and easy-to-setup camera system allows the application of near-remote phenology as a monitoring system and an indicator of vegetation recovery, which may improve restoration and management plans, promoting the conservation of the highly diverse campo rupestre grassland ecosystems.

Short-Term Effects and Vegetation Response after a Megafire in a Mediterranean Area

In Mediterranean-climate areas, wildfires have an important ecological role, selecting organisms, influencing species composition and structure of vegetation, and shaping landscapes. However, the increase in frequency and severity of fires can cause, among others, progressive vegetation degradation, biodiversity, and ecosystem services loss. Under the climate change scenario, the frequency and severity of wildfires are expected to increase, especially in the Mediterranean Basin, recognized as among the most affected by the intensification of droughts and heat waves in the future. Therefore, from the perspective of adaptation, it is important not only to assess the sudden effects after a fire but also to investigate the ecological changes and vegetation response over time. In this framework, this study investigates the effects and the short-term vegetation response in an area struck by a megafire. The vegetation response one year after a fire has been assessed in semi-natural grasslands, shrublands, and woodlands at the landscape scale through spectral indices, and at the field scale through floristic and vegetation surveys. Our results showed that after a severe wildfire, although some areas did not exhibit vegetation regrowth, the response of natural vegetation was notable after one year. In the study area, the most resilient vegetation type was semi-natural grasslands, suggesting that this type of vegetation can be crucial for landscape recovery. The other vegetation types showed different response patterns that also prefigure possible changes in species composition and loss of plant diversity over the medium term. This study highlights the value of combining remote sensing spectral analyses and detailed floristic and vegetation surveys for understanding the direction of the early stages of post-fire vegetation dynamics.

Remote-Sensing Monitoring of Postfire Vegetation Dynamics in the Greater Hinggan Mountain Range Based on Long Time-Series Data: Analysis of the Effects of Six Topographic and Climatic Factors

The frequency of forest fires is increasing under global climate change, and forest fires can cause devastating disturbances to forest systems and varying degrees of recovery of forest ecosystems after a disaster. Due to the different intensity of forest fires and forest systems, and in particular the fact that forest ecological recovery is influenced by many topographical and climatic factors, the process of postfire vegetation recovery is unclear and must be studied in depth. In this study, the Greater Hinggan Mountain Range was taken as the study area. Based on the Moderate Resolution Imaging Spectroradiometer (MODIS) and Landsat time-series images acquired from 2000 to 2018, this study used the spatiotemporal data fusion method to construct reflectance images of vegetation with a relatively consistent growth period to study the vegetation restoration after forest fires. The vegetation restoration was characterized by disturbance index (DI) values, which eliminated phenological influence. Six types of topography and climatic factors (elevation, aspect, slope; temperature, precipitation, and wind speed) were coupled with DI. Through single-factor analysis of variance and multiple comparison statistical methods, it was found that there was a significant relationship between the six factors and DI, which indicated those factors had a significant impact on the restoration of forest vegetation in burned areas. The results will be useful as a reference for future monitoring and management of forest resources.

Dynamics of plant community flammability in Cockayne’s Arthur’s Pass Plots over nine decades

Changes in plant community composition and traits can be used to infer changes in community-level flammability. In subalpine ecosystems, we expect higher community flammability in the decades after fire due to the dominance of grasses (fine fuels) and other high-flammability species like bracken and Dracophyllum spp. This would be followed by a decline in flammability, due to a shift to lower-flammability species. In this study, I aimed to determine the plant community flammability of different subalpine vegetation types over 86 years since fire. I used vegetation monitoring data of nine permanent transects established by Leonard Cockayne in 1932 at Arthur’s Pass and remeasured four times until 2018. I explored how plant morphological and chemical traits predict community flammability in different vegetation types (grassland, shrubland, forest). Combined with existing trait and flammability data, I examined the interrelationships among community composition, shoot flammability (n = 67 species), plant morphology (n = 57) and leaf chemistry (n = 29). I show that community flammability was highly variable across the nine transects in the 86 years since fire. This contrasts with my original hypothesis. However, I show that flammability is strongly related to plant traits, such as leaf specific area and plant dead material. Therefore, I conclude that although post-fire vegetation dynamics are highly variable, changes in plant community flammability are predictable when considered in a trait framework.

Long Term Post-Fire Vegetation Dynamics in North-East Mediterranean Ecosystems. The Case of Mount Athos Greece

Fire is an ecological and disturbance factor with a significant historical role in shaping the landscape of fire-prone environments. Despite the large amount of literature regarding post-fire vegetation dynamics, the north-east Mediterranean region is rather underrepresented in the literature. Studies that refer to the early post fire years and long term research are rather scarce. The current study is conducted in the socially and geographically isolated peninsula of Mount Athos (Holly Mountain) in northern Greece, and it studies vegetation dynamics over a period of 30 years since the last fire. Field data were collected 11 years since the event and were used to identify the present plant communities in the area, using TWINSPAN, and the factors affecting their distribution using CART. Four Landsat (TM, ETM, OLI) images are employed for the calculation of NDVI, which was found effective in detecting the intercommunity variation in the study area, and it is used for long term monitoring. The study includes four communities, from maquis to forest which are common in the Mediterranean region covering a wide altitudinal range. The results suggest that fire affects the various communities in a different way and their recovery differs significantly. While forest communities recover quickly after fire, maintaining their composition and structure, the maquis communities may need several years before reaching the pre-fire characteristics. The dry climatic conditions of the study area are probably the reason for the slow recovery of the most fire prone communities. Given that climate change is expected to make the conditions even drier in the region, studies like this emphasize the need to adopt measures for controlling wildfires and preventing ecosystem degradation.

Evaluating Post-Fire Vegetation Recovery in Cajander Larch Forests in Northeastern Siberia Using UAV Derived Vegetation Indices

The ability to monitor post-fire ecological responses and associated vegetation cover change is crucial to understanding how boreal forests respond to wildfire under changing climate conditions. Uncrewed aerial vehicles (UAVs) offer an affordable means of monitoring post-fire vegetation recovery for boreal ecosystems where field campaigns are spatially limited, and available satellite data are reduced by short growing seasons and frequent cloud cover. UAV data could be particularly useful across data-limited regions like the Cajander larch (Larix cajanderi Mayr.) forests of northeastern Siberia that are susceptible to amplified climate warming. Cajander larch forests require fire for regeneration but are also slow to accumulate biomass post-fire; thus, tall shrubs and other understory vegetation including grasses, mosses, and lichens dominate for several decades post-fire. Here we aim to evaluate the ability of two vegetation indices, one based on the visible spectrum (GCC; Green Chromatic Coordinate) and one using multispectral data (NDVI; Normalized Difference Vegetation Index), to predict field-based vegetation measures collected across post-fire landscapes of high-latitude Cajander larch forests. GCC and NDVI showed stronger linkages with each other at coarser spatial resolutions e.g., pixel aggregated means with 3-m, 5-m and 10-m radii compared to finer resolutions (e.g., 1-m or less). NDVI was a stronger predictor of aboveground carbon biomass and tree basal area than GCC. NDVI showed a stronger decline with increasing distance from the unburned edge into the burned forest. Our results show NDVI tended to be a stronger predictor of some field-based measures and while GCC showed similar relationships with the data, it was generally a weaker predictor of field-based measures for this region. Our findings show distinguishable edge effects and differentiation between burned and unburned forests several decades post-fire, which corresponds to the relatively slow accumulation of biomass for this ecosystem post-fire. These findings show the utility of UAV data for NDVI in this region as a tool for quantifying and monitoring the post-fire vegetation dynamics in Cajander larch forests.

Hydrological Impacts of Large Fires and Future Climate: Modeling Approach Supported by Satellite Data

Fires have significant impacts on soil erosion and water supply that may be exacerbated by future climate. The aims of this study were: To simulate the effects of a large fire event in the SWAT (Soil and Water Assessment Tool) hydrological model previously calibrated to a medium-sized watershed in Portugal; and to predict the hydrological impacts of large fires and future climate on water supply and soil erosion. For this, post-fire recovery was parametrized in SWAT based on satellite information, namely, the fraction of vegetation cover (FVC) calculated from the normalized difference vegetation index (NDVI). The impact of future climate was based on four regional climate models under the stabilization (RCP 4.5) and high emission (RCP 8.5) scenarios, focusing on mid-century projections (2020–2049) compared to a historical period (1970–1999). Future large fire events (>3000 ha) were predicted from a multiple linear regression model, which uses the daily severity rating (DSR) fire weather index, precipitation anomaly, and burnt area in the previous three years; and subsequently simulated in SWAT under each climate model/scenario. Results suggest that time series of satellite indices are useful to inform SWAT about vegetation growth and post-fire recovery processes. Different land cover types require different time periods for returning to the pre-fire fraction of vegetation cover, ranging from 3 years for pines, eucalypts, and shrubs, to 6 years for sparsely vegetated low scrub. Future climate conditions are expected to include an increase in temperatures and a decrease in precipitation with marked uneven seasonal distribution, and this will likely trigger the growth of burnt area and an increased frequency of large fires, even considering differences across climate models. The future seasonal pattern of precipitation will have a strong influence on river discharge, with less water in the river during spring, summer, and autumn, but more discharge in winter, the latter being exacerbated under the large fire scenario. Overall, the decrease in water supply is more influenced by climate change, whereas soil erosion increase is more dependent on fire, although with a slight increase under climate change. These results emphasize the need for adaptation measures that target the combined hydrological consequences of future climate, fires, and post-fire vegetation dynamics.

Early Postfire Vegetation Dynamics of Shrub-steppe Communities (On the example of Burtinskaya Shrub-steppe of Orenburg Nature Reserve)

The intensification of fire regime in the shrub-steppe determined the need for research aimed at identifying the regularities of the effect exerted by wildfires on shrub-steppe ecosystems and one of their most dynamic components referred to as plant cover. A present study was carried out on the territory of Burtinskaya Steppe of the Orenburg Reserve and in its protected area in 2015–2016, following the fire that occurred in August 2014. It was found out that in the first year following a fire event, the total plant cover of steppe ecosystems affected by a wildfire is almost halved. The plant cover dominated by bunchgrasses, especially of the genus Stipa, significantly decreases, and the abundance and diversity of ephemeroids increase. The floristic alteration manifesting itself in the form of an invasive role of certain species (most often ephemeroids and biennials) during one vegetative stage is endemic to the areas exposed to overgrazing in the past. The outburning of plant cover can bring about a change in dominant and codominant plant species within a shrub-steppe assemblage.

Incorporating Sentinel-1 SAR imagery with the MODIS MCD64A1 burned area product to improve burn date estimates and reduce burn date uncertainty in wildland fire mapping

Wildland fires result in a unique signal detectable by multispectral remote sensing and synthetic aperture radar (SAR). However, in many regions, such as Southeast Asia, persistent cloud cover and aerosols temporarily obstruct multispectral satellite observations of burned area, including the MODIS MCD64A1 Burned Area Product (BAP). Multiple days between cloud free pre- and post-burn MODIS observations result in burn date uncertainty. We incorporate cloud-penetrating, C-band SAR-with the MODIS MCD64A1 BAP in Southeast Asia, to exploit the strengths of each dataset to better estimate the burn date and reduce the potential burn date uncertainty range. We incorporate built-in quality control using MCD64A1 to reduce erroneous pixel updating. We test the method over part of Laos and Thailand during April 2016 and found average uncertainty reduction of 4.5 d, improving 15% of MCD64A1 pixels. A new BAP could improve monitoring temporal trends of wildland fires, air quality studies and monitoring post-fire vegetation dynamics.

Assessment of post-fire vegetation recovery in Southern Siberia using remote sensing observations

Wildfire is one of the main disturbances affecting forest dynamics, succession, and the carbon cycle in Siberian forests. The Zabaikal region in southern Siberia is characterized by one of the highest levels of fire activity in Russia. Time series of Landsat data and field measurements of the reforestation state were analyzed in order to estimate post-fire vegetation recovery. The results showed that the normalized burn ratio time series can be used to estimate forest recovery in the pine- and larch-dominated forests of the Zabaikal region. Multiple factors determine a forest’s recovery rate after a wildfire, including fire severity, tree species characteristics, topography, hydrology, soil properties, and climate. Assessing these factors is important if we are to understand the effects of fire on forest succession and to implement sustainable forest management strategies. In this work we used the field data and Landsat data to estimate post-fire vegetation dynamics as a function of several environmental factors. These factors include fire severity, pre-fire forest state, topography, and positive surface temperature anomalies. A regression model showed that fire frequency, fire severity, and surface temperature anomalies are the primary factors, explaining about 58% of the variance in post-fire recovery. High frequency of fire and positive surface temperature anomalies hamper the post-fire reforestation process, while more severe burns are followed by higher recovery rates. Further studies are necessary to consider other important factors such as soil properties, moisture, and precipitation, for better explanation of post-fire vegetation recovery.

Post-fire plant regeneration across a closed forest-savanna vegetation transition

Fire is a major environmental factor influencing vegetation heterogeneity, with closed forest and savanna ecosystems having different management needs due to their different responses to fire disturbance. However, the differences in post-fire vegetation dynamics between these ecosystems have seldom been compared using a uniform set of parameters. Additionally, post-fire dynamics of forest-savanna ecotones is poorly characterized. With the hypothesis that closed forest, savannas and ecotones will exhibit different post-fire responses, we studied the vegetation diversity, structure and dynamics in an upland forest-savanna vegetation mosaic in Minas Gerais, Brazil following a fire that occurred in September 2011. In January 2012, we identified, tagged, and measured the basal diameter of all regenerating juvenile tree stems within forty-six 4m2 plots in closed forest, savanna and ecotone vegetation, and conducted recensuses in 2013 and 2014. We modelled the relationship between short-term dynamics parameters (recruitment, mortality, basal area loss and gain, and the turnover and net changes in the number of individual stems and basal areas) and vegetation type. Species diversity was higher in closed forests and ecotones than in savanna. Across all vegetation types, stem density decreased and basal area increased. Parameters such as recruitment, net changes in the number of individuals, and the gain, loss and turnover in basal area did not differ across vegetation types. However, stem mortality was higher in closed forest and ecotones combined than in savannas, and the net change in the number of individuals was the lowest in the savanna. Overall, our results support that within a climatically-similar vegetation mosaic, closed forests exhibit different post-fire regeneration dynamics from savanna as expected. Ecotones exhibited post-fire responses and dynamics more similar to closed forests than to savanna, but more studies will be needed to establish if this pattern is applicable to other areas. Understanding the longer-term vegetation dynamics and plant regeneration patterns is a potential next step that will help inform fire management strategies for forest-savanna mosaics.

Alternative characterization of forest fire regimes: incorporating spatial patterns

The proportion of fire area that experienced stand-replacing fire effects is an important attribute of individual fires and fire regimes in forests, and this metric has been used to group forest types into characteristic fire regimes. However, relying on proportion alone ignores important spatial characteristics of stand-replacing patches, which can have a strong influence on post-fire vegetation dynamics. We propose a new more ecologically relevant approach for characterizing spatial patterns of stand-replacing patches to account for potential limitation of conifer seed dispersal. We applied a simple modified logistic function to describe the relationship between the proportion of total stand-replacing patch area and an interior buffer distance on stand-replacing patches. This approach robustly distinguishes among different spatial configurations of stand-replacing area in both theoretical and actual fires, and does so uniquely from commonly used descriptors of spatial configuration. Our function can be calculated for multiple fires over a given area, allowing for meaningful ecological comparisons of stand-replacing effects among different fires and regions.

A post-wildfire response in cave dripwater chemistry

Abstract. Surface disturbances above a cave have the potential to impact cave dripwater discharge, isotopic composition and solute concentrations, which may subsequently be recorded in the stalagmites forming from these dripwaters. One such disturbance is wildfire; however, the effects of wildfire on cave chemistry and hydrology remains poorly understood. Using dripwater data monitored at two sites in a shallow cave, beneath a forest, in southwest Australia, we provide one of the first cave monitoring studies conducted in a post-fire regime, which seeks to identify the effects of wildfire and post-fire vegetation dynamics on dripwater δ18O composition and solute concentrations. We compare our post-wildfire δ18O data with predicted dripwater δ18O using a forward model based on measured hydro-climatic influences alone. This helps to delineate hydro-climatic and fire-related influences on δ18O. Further we also compare our data with both data from Golgotha Cave – which is in a similar environment but was not influenced by this particular fire – as well as regional groundwater chemistry, in an attempt to determine the extent to which wildfire affects dripwater chemistry. We find in our forested shallow cave that δ18O is higher after the fire relative to modelled δ18O. We attribute this to increased evaporation due to reduced albedo and canopy cover. The solute response post-fire varied between the two drip sites: at Site 1a, which had a large tree above it that was lost in the fire, we see a response reflecting both a reduction in tree water use and a removal of nutrients (Cl, Mg, Sr, and Ca) from the surface and subsurface. Solutes such as SO4 and K maintain high concentrations, due to the abundance of above-ground ash. At Site 2a, which was covered by lower–middle storey vegetation, we see a solute response reflecting evaporative concentration of all studied ions (Cl, Ca, Mg, Sr, SO4, and K) similar to the trend in δ18O for this drip site. We open a new avenue for speleothem science in fire-prone regions, focusing on the geochemical records of speleothems as potential palaeo-fire archives.

Exploring the Relationship between Burn Severity Field Data and Very High Resolution GeoEye Images: The Case of the 2011 Evros Wildfire in Greece

Monitoring post-fire vegetation response using remotely-sensed images is a top priority for post-fire management. This study investigated the potential of very-high-resolution (VHR) GeoEye images on detecting the field-measured burn severity of a forest fire that occurred in Evros (Greece) during summer 2011. To do so, we analysed the role of topographic conditions and burn severity, as measured in the field immediately after the fire (2011) and one year after (2012) using the Composite Burn Index (CBI) for explaining the post-fire vegetation response, which is measured using VHR satellite imagery. To determine this relationship, we applied redundancy analysis (RDA), which allowed us to identify which satellite variables among VHR spectral bands and Normalized Difference Vegetation Index (NDVI) can better express the post-fire vegetation response. Results demonstrated that in the first year after the fire event, variations in the post-fire vegetation dynamics can be properly detected using the GeoEye VHR data. Furthermore, results showed that remotely-sensed NDVI-based variables are able to encapsulate burn severity variability over time. Our analysis showed that, in this specific case, burn severity variations are mildly affected by the topography, while the NDVI index, as inferred from VHR data, can be successfully used to monitor the short-term post-fire dynamics of the vegetation recovery.

Variation in soil enzyme activity as a function of vegetation amount, type, and spatial structure in fire-prone Mediterranean shrublands

Fire-prone Mediterranean shrublands may be seriously threatened by land degradation due to progressive opening of the vegetation cover driven by increasing drought and fire recurrence. However, information about the consequences of this opening process for critical ecosystem functions is scant. In this work, we studied the influence of vegetation amount, type, and spatial pattern in the variation of extracellular soil enzyme activity (acid phosphatase, β-glucosidase, and urease) in fire-prone shrublands in eastern Spain. Soil was sampled in vegetation-patch and open-interpatch microsites in 15 shrubland sites affected by large wildfires in 1991. On average, the activities of the three enzymes were 1.5 (β-glucosidase and urease) to 1.7 (acid phosphatase) times higher in soils under vegetation patches than in adjacent interpatches. In addition, phosphatase activity for both microsites significantly decreased with the fragmentation of the vegetation. This result was attributed to a lower influence of roots -the main source of acid phosphatase- in the bigger interpatches of the sites with lower patch cover, and to feedbacks between vegetation pattern, redistribution of resources, and soil quality during post-fire vegetation dynamics. Phosphatase activity was also 1.2 times higher in patches of resprouter plants than in patches of non-resprouters, probably due to the faster post-fire recovery and older age of resprouter patches in these fire-prone ecosystems. The influence on the studied enzymes of topographic and climatic factors acting at the landscape scale was insignificant. According to our results, variations in the cover, pattern, and composition of vegetation patches may have profound impacts on soil enzyme activity and associated nutrient cycling processes in fire-prone Mediterranean shrublands, particularly in those related to phosphorus.

Early spring post-fire snow albedo dynamics in high latitude boreal forests using Landsat-8 OLI data.

Taking advantage of the improved radiometric resolution of Landsat-8 OLI which, unlike previous Landsat sensors, does not saturate over snow, the progress of fire recovery progress at the landscape scale (< 100m) is examined. High quality Landsat-8 albedo retrievals can now capture the true reflective and layered character of snow cover over a full range of land surface conditions and vegetation densities. This new capability particularly improves the assessment of post-fire vegetation dynamics across low- to high- burn severity gradients in Arctic and boreal regions in the early spring, when the albedos during recovery show the greatest variation. We use 30 m resolution Landsat-8 surface reflectances with concurrent coarser resolution (500m) MODIS high quality full inversion surface Bidirectional Reflectance Distribution Functions (BRDF) products to produce higher resolution values of surface albedo. The high resolution full expression shortwave blue sky albedo product performs well with an overall RMSE of 0.0267 between tower and satellite measures under both snow-free and snow-covered conditions. While the importance of post-fire albedo recovery can be discerned from the MODIS albedo product at regional and global scales, our study addresses the particular importance of early spring post-fire albedo recovery at the landscape scale by considering the significant spatial heterogeneity of burn severity, and the impact of snow on the early spring albedo of various vegetation recovery types. We found that variations in early spring albedo within a single MODIS gridded pixel can be larger than 0.6. Since the frequency and severity of wildfires in Arctic and boreal systems is expected to increase in the coming decades, the dynamics of albedo in response to these rapid surface changes will increasingly impact the energy balance and contribute to other climate processes and physical feedback mechanisms. Surface radiation products derived from Landsat-8 data will thus play an important role in characterizing the carbon cycle and ecosystem processes of high latitude systems.

Post-fire vegetation dynamics of a sagebrush steppe community change significantly over time

Sagebrush steppe ecosystems of the Intermountain West have experienced a decline over the past 150 years due to changing fire regimes, invasive species and conifer encroachment. Prescribed fire is a common and cost-effective tool used in sagebrush restoration and fuels management. We examined the post-fire succession of a sagebrush steppe community over a nearly 30-year period at two study sites in northeastern California. The long-term nature of this study was particularly significant, as invasive annual grasses dominated the plant community in the years immediately following fire, but native perennial grasses and shrubs successfully out-competed them in the long term. Shrubs were slow to recover but had returned to pre-fire levels by the end of the study period. There was also notable increase in western juniper throughout the study sites, particularly in areas that had not been burned. Our results indicate that mean fire return intervals of 50 years or less would help reduce western juniper encroachment and preserve sagebrush habitat, especially for potentially threatened species such as the sage grouse.