Does postfire management affect the recovery of Mediterranean communities? The case study of terrestrial gastropods

In fire-prone regions, understanding the response of species to fire is a major goal in order to predict the effects on biodiversity. Furthermore, postfire management can also model this response through the manipulation of environmental characteristics of the burnt habitat. We have examined the taxonomic and functional response to fire and postfire management of a Mediterranean snail community affected by a summer fire in 2003. After the fire, the area was logged, leaving wood debris on the ground, and three alternative practices were implemented in several plots within the burnt area: subsoiling, removal of trunks having branches, total removal of trunks and branches, as well as one area not logged. Our results indicated that fire exerted a major impact on the snail community, strongly reducing diversity and species richness, particularly for forest species living in the humus and having European distribution ranges. By contrast, we found slight differences within the postfire practices, presumably because of the strong initial impact of fire and subsequent xerophilous postfire conditions. However, the area with only trunk removal showed a positive response of generalist snail species, probably due to moist microhabitats provided by the accumulation of wood debris on the ground. The effects of postfire management should be further explored due to the expected increase of fire risk associated with climate change and land-use histories.     

Contribution To Climate Change Of Forest Fires In Spain: Emissions And Loss Of Sequestration

ABSTRACT

Forest fires contribute to climate change mainly due to emission of greenhouse gases by biomass burning and loss of sequestration by sink destruction. The average contribution in Spain between 1998 and 2015 was 9,494,910 Mg CO_{2 eq} per year, 23.8% from biomass burning and 76.2% from loss of carbon sequestration, the latter three times higher than the former, although the emissions from combustion are usually the only accounted. Regarding to the vegetation burned, 43.6% of emissions come from forest (17.7% conifers, 4.8% hardwoods and 21.1% Eucalyptus), 53.7% from scrublands and 2.7% from grasslands. The loss of sequestration is 6.6% in the fire year and by 93.4% in previous years. Scrubland burning produces a greater amount of emissions than forests, but forest regeneration is slower, with greater influence on the loss of sequestration. It is essential a forest management focused on increase fire resilience and adaptation to climate change, increase the effectiveness of extinction works to reduce fire damages and implement actions to recover the burnt vegetation, because the loss of sinks is a critical aspect.     

Factors affecting post-fire crown regeneration in cork oak (Quercus suber L.) trees

Cork oak (Quercus suber) forests are acknowledged for their biodiversity and economic (mainly cork production) values. Wildfires are one of the main threats contributing to cork oak decline in the Mediterranean Basin, and one major question that managers face after fire in cork oak stands is whether the burned trees should be coppiced or not. This decision can be based on the degree of expected crown regeneration assessed immediately after fire. In this study we carried out a post-fire assessment of the degree of crown recovery in 858 trees being exploited for cork production in southern Portugal, 1.5 years after a wildfire. Using logistic regression, we modelled good or poor crown recovery probability as a function of tree and stand variables. The main variables influencing the likelihood of good or poor crown regeneration were bark thickness, charring height, aspect and tree diameter. We also developed management models, including simpler but easier to measure variables, which had a lower predictive power but can be used to help managers to identify, immediately after fire, trees that will likely show good crown regeneration, and trees that will likely die or show poor regeneration (and thus, potential candidates for trunk coppicing).     

Wildfires influence on soil organic matter in an Atlantic mountainous region (NW of Spain)

The principal aim of this research was to determine the influence of wildfires on soil organic matter (SOM) content and composition in soils located on the northern slope of the Cantabrian Cordillera, an Atlantic mountainous region in the North West of Spain, where wildfires are frequent. Samples from soils with similar aspect, slope, elevation and vegetation characteristics, but with different wildfires histories were collected. Total organic carbon and total nitrogen contents were determined as well as the C/N ratio. Furthermore, a qualitative characterization of the soil organic carbon (SOC) was carried out by ¹³C variable amplitude cross polarization magic angle spinning (VACP/MAS) Nuclear Magnetic Resonance (NMR) spectroscopy. Our results show that, on the one hand, all the sampled soils can be considered important pools of carbon in this Atlantic mountainous region, especially in the heath areas. On the other hand, the fire-affected soils present higher SOM contents than their unburnt counterparts. This could be attributed to an important reaccumulation of fresh vegetal material, which is probably a consequence of the decrease of SOM decomposition rates after fire. Moreover, charred organic compounds are not found in all the burnt soils, which could be due to the long time since the last fires events took place, to different fire severities, or to different post-fire erosion processes in the studied soils.     

Reliable, accurate and timely forest mapping for wildfire management using ASTER and Hyperion satellite imagery

The present study aims to explore the potential and effectiveness of new Earth Observation data for mapping the vegetation composition and structure and thus provide accurate forest maps to be used in fire propagation simulation models and fire risk assessment. Land cover classification of ASTER and Hyperion images is performed in a detailed nomenclature including different vegetation types and densities since the same vegetation type may give fires with different behaviour as a result of differences in fuel continuity.

The results suggest that both datasets can provide highly accurate maps with an overall accuracy of 85% for ASTER and 93% for Hyperion classification. Although Hyperion is superior to ASTER in terms of overall accuracy, the latter provided a higher thematic accuracy identifying one additional class compared to Hyperion. The evaluation of the classification results in terms of cost and technical characteristics suggest that both datasets are suitable for use in wildfire management tools, depending on the specific user needs, and they could also be used complementary if a combination of high thematic accuracy and locally high spatial accuracy is needed.     

Changes in soil N and P availability in a Pinus canariensis fire chronosequence

Fire induces changes in ecosystem nutrient regimes and can cause major losses of N and P. Much has been written about the effect of fire on nutrient availability in soil; most studies have been concerned with the short-term effects of shock. The primary objective of our study was to discover the effect of forest fires on long-term N and P availability, for which we used the ion exchange membrane method in a chronosequence of forest fires (1987, 1990, 1994, 1998, 2000 and 2005). The study was conducted on the island of La Palma (Canary Islands, Spain) in October 2006. We hypothesized that a rapid increase in nutrient availability would occur after the fire, followed by a reduction due to erosion and leaching, and then gradual recovery and an eventual return to initial levels. NH₄-N, NO₃-N and mineral-N availability peaked significantly 1 year after the fire. However, 5 years after the fire the N levels were similar to those found on unburned land. P availability decreased significantly a year after the fire, but gradually recovered over time. The N and P availability ratio increased significantly after the fire, falling during the chronosequence, with the lowest levels found on the unburned land. These results confirm that fire produces (a) a rapid and short-term increase in N availability, without a long-term decline, and (b) a long-term reduction in P availability, which tends to recover over time after the fire.     

Obtainment of a carbon-13-, nitrogen-15-labelled burnt soil

 The restoration of the C and N cycles in the soil-plant system is a basic step for the reclamation of burnt soils. To evaluate accurately the efficacy of restoration techniques, it is necessary to use isotopic tracers and, therefore, a ¹³C-, ¹⁵N-labelled burnt soil should be made available. The present paper describes a technique for obtaining a ¹³C-, ¹⁵N-labelled burnt soil by burning a labelled forest soil in the laboratory. Received: 8 July 1998     

Community perceptions of ecosystem services and disservices linked to urban tree plantings

The planting of trees in streets and parks is critical for urban greening efforts that seek to improve climate-change resilience in cities around the world. Ecosystem services provided by urban trees range from mitigating urban heat island effects to enhancing human well-being and conserving native biodiversity. At the same time, such tree services trade off with disservices that include risk to human safety from falling branches and infrastructure damage from root growth. Here, we performed a survey of residents of a sub-tropical region in eastern Australia to determine community perceptions of the ecosystem services and disservices linked to urban tree plantings. Our aim was to better understand the diverse perceptions of the community, prior to on-the-ground implementation of urban greening, to help guide planting programs in streets and parklands that are vulnerable to UHI effects in the region. We found strong evidence for a high level of public awareness about the beneficial ecosystem services that urban trees can provide. A broad spectrum of beneficial tree services were valued highly by the community in their urban environment including the planting of native trees that can attract and provide food for preferred wildlife; provide shade and reduce heat; allow for a strong connection with nature; have the potential to store carbon to mitigate climate change; provide a level of protection from bushfires; have aesthetically pleasing properties; and produce food for people. At the same time, however, community concerns about tree disservices were concentrated primarily on root damage to infrastructure as well as property damage and injury from falling branches. Our elicitation of community attitudes to tree services and disservices will allow for residents’ most important values and strongest concerns about trees to be explicitly taken into account when establishing a community-inclusive approach to urban tree planting.     

A susceptibility model for post wildfire soil erosion in a temperate oceanic mountain area of Spain

In the North-West of the Cantabrian Range (North of Spain) the climate is oceanic and vegetation cover is continuous. In those areas where livestock farming prevails, wildfires are common, although small in size, their recurrence makes the phenomenon critical for the conservation of soils.In this study we propose that the structural stability of soil, associated with the type and size of the structural aggregates, may be a useful indicator to assess erosion susceptibility in burnt soils. We have chosen an area of approximately 485 km² over quartzitic lithologies where a high recurrence of wildfires has been noted and which displays several forms of erosion: gullying, rilling and erosion by overland flow. We have measured texture, percentage and degree of structural aggregate stability and the rate of infiltration in soils that have been burnt up to 3 times over the last 20 years and also in unburnt soils. The results obtained enable us to establish connections between wildfires, soil deterioration and macro-aggregate stability.We have used the stability of macro-aggregates as an indicator to elaborate a soil erosion susceptibility model for a large area of 10,600 km² with sharp relief and Atlantic climate. The model was constructed by combining three main factors: soil structural stability, fire intensity and relief. Variables related to soil structural stability and presence of basic cations have been derived from lithology (% Clay and % Silt + Fine Sand). The availability of humified organic material has also been taken into account as an additional variable in the formation of stable macro-aggregates. The expected fire intensity was calculated from the amount of inflammable material and the structure of the different vegetation types. Finally, the influence of relief was analyzed by considering the slope steepness.The resultant cartographic model presents five types of post wildfire soil erosion susceptibility. Those areas with the highest risk correspond to quartzite lithology regions, with long, steep hillsides covered with heaths. Those with the lowest risk correspond to limestone bedrock areas with gentle slopes and herbaceous vegetation. The accuracy of the model is determined by the scale of the original thematic cartography: 1:25000, and the cell size of the Digital Terrain Model is 50 × 50 m.     

Development of an adapted empirical drought index to the Mediterranean conditions for use in forestry

The most widely used empirical drought indices in forestry and fire risk management were tested under Mediterranean conditions. These were: the Keetch-Byram drought index KBDI, the Nesterov index NI, the Modified Nesterov index MNI, the Zhdanko index ZI which belong to the cumulative type, and the Sweden Angstrom Index which belongs to the daily type. The above indices were selected for fire risk assessment in the European Mediterranean conditions, following the method of correlating indices with real fuel moisture data. Meteorological data were collected for the testing area of the sub-urban forest of Thessaloniki, northern Greece. Time series of the drought indices were constructed for the summers of 2006 and 2007. At the same time, field data were collected in order to estimate the real fuel moisture content including surface soil, litter to represent the dead fuel moisture content, and grass to represent the live fuel moisture content. Statistical analysis of the collected field data and their correlation with the tested drought indices, which calculated from the local meteorological data, showed that KBDI is the most suitable empirical drought index for the area. Consequently, KBDI was modified for a better adaptation to Mediterranean conditions, following the development procedure as in the original paper. Based on the above method a Modified KBDI was calculated for the study area, and the differences from the original KBDI were estimated. The comparison of the two indices showed that: (a) there is a faster response of the Modified KBDI index to meteorological data, (b) the index takes on higher values during the summer months of both studied years, and thus, previously reported problems of underestimation of actual water loss is mitigated, and, (c) the estimated fire risk is higher for the study area, which is in accordance with the very low moisture content values observed.