Key message
We present a structured and curated database covering 21 years of LFMC measurements in the Catalan region, along with an associated R package to manage updates and facilitate quality ...processing and visualisation. The data set provides valuable information to study plant responses to drought and improve fire danger prediction. Dataset access is at
https://doi.org/10.5281/zenodo.4675335
,
and associated metadata are available at
https://metadata-afs.nancy.inra.fr/geonetwork/srv/fre/catalog.search#/metadata/583fdbae-3200-4fa7-877c-54df0e6c5542
.
Key message
We present a relational database containing compositional and structural characteristics of 575 permanent 100 m
2
shrubland plots distributed in the NE of Iberian peninsula. The datasets ...provide valuable information about shrubland fuels to improve fire danger prediction, study vegetation dynamics in relation to drought and fire or test aerial-based methodologies with ground-based information. Dataset access is at :
https://doi.org/10.5281/zenodo.7685487
and associated metadata are available at
https://metadata-afs.nancy.inra.fr/geonetwork/srv/fre/catalog.search#/metadata/f55fcde4-113e-40f9-9a35-a2e65b0ee951
.
Key message
Allometric biomass equations developed for individual shrubs can be applied to estimate shrubland fuels from measurements of cover and average height by species.
Context
Shrubs are a ...major component of surface fuels in many fire-prone ecosystems. Shrub fuel loading is often estimated by “double sampling”, where data from a destructive vegetation survey is used to model vegetation-fuel relationships (development phase), and these relationships are then applied to vegetation data from a second survey (application phase). Vegetation-fuel relationships can be modeled at different levels of vegetation detail, from individual plants to stands, but the increased effort of detailed measurements may compromise large-scale applications.
Aims
To facilitate fuel loading assessments in Mediterranean shrublands, we present and test a novel method to estimate stand-level shrub loading that consists in applying individual-level allometric equations to vegetation plot data collected by measuring the percent cover and mean height of each shrub species.
Methods
We used individual-level data (i.e., plant dimensions and dry weights) to develop allometric equations for total and fine (leaves and branches < 6 mm) biomass of 26 Mediterranean shrub species. We then evaluated the accuracy and precision of the proposed method in comparison to an approach assuming constant bulk density, using data from 131 vegetation plots and taking as benchmark stand-level loading estimates derived by aggregation of individual biomass allometric estimates. A second set of 13 plots was used to quantify the additional error derived from visual estimation of species mean height and cover.
Results
The performance of species-specific models was acceptable in estimating total and fine biomass at the individual level. When based on species mean height and cover data, stand-level fuel loading estimates calculated using the proposed method had a better precision and accuracy than those obtained using bulk density values (− 4 vs. + 39% in relative bias; 10 vs. 40% in relative MAE). Visual estimation of species mean height and percent cover led to 10 and 16% increase in MAE for species loading estimates of total and fine fuels, respectively, with respect to estimates obtained without this source of error.
Conclusions
Our approach to estimate shrub loading allows combining fast species-level vegetation sampling with the flexibility of individual-level allometries to model to size-related variations of bulk density.
Key message
Prescribed burning applied after a dry year increased (fall burns) or had no effect (spring burns) on pine resilience, measured as the capacity to reach pre-drought growth levels compared ...with unburned pines. In fall burns, there was a larger increase in resilience when the impact of drought and burning on pines was low and burning caused a significant release from tree competition.
Context
Prescribed burning after a dry year can decrease a tree’s resistance (inverse of growth reduction during disturbance); however, burning can increase resource availability and consequently tree resilience (capacity to reach pre-disturbance growth levels). In addition, the burning season can affect the latewood to earlywood ratio (latewood:earlywood) and thus have an impact on tree-ring density.
Aims
To study the effects of two consecutive disturbances (drought and burning) on
Pinus nigra
spp.
salzmannii
and
Pinus sylvestris
in terms of (i) total tree-ring resistance, (ii) total tree-ring, earlywood and latewood resilience, and (iii) post-stress latewood:earlywood.
Methods
We selected drought-affected trees (control) and drought-and-burning-affected trees (burned) for tree-ring sampling. For each tree, we measured total tree-ring, earlywood, and latewood widths to determine resilience and resistance indices and calculated pre- and post-stress latewood:earlywood as indicators of tree-ring density. We used linear mixed-effects models to relate these response variables to the pine species, burning characteristics, and competition release.
Results
Resistance was higher in control trees than burned trees.
P. nigra
showed lower resistance than
P. sylvestris
but higher resilience. Resistance positively influenced resilience. Specifically, as resistance increased, total tree-ring and latewood resilience increased significantly in pines burned during the fall compared with those burned in spring or control pines. In fall burns, the pines’ resilience increased, especially when pines were significantly released from tree competition. In
P. nigra
, post-stress latewood:earlywood increased after fall burns as pre-stress latewood:earlywood decreased.
Conclusion
Prescribed burning can be a valuable management tool for overcoming the effects of a dry year on tree growth by increasing resilience, especially in
P. nigra
.
This paper aims at understanding the effect that shrub encroachment into mesic mountain grasslands has on soil organic carbon (SOC) stocks. Thus we compared organic C and N contents in contiguous ...soil profiles under a conifer shrub, a legume shrub, and grasses (mesic grasslands) on 21 sites. Soil C and N recalcitrance indexes (RIC and RIN) were estimated as the ratio of unhydrolyzable C and N to total C or N. Contrary to our hypothesis, shrub encroachment did not cause a well‐defined change in soil C stocks. Only a slight increase in C was detected in the top 15 cm soil layer under both shrubs. The C accretion rate in this soil layer was estimated to be approximately 28–42 g m−2 per annum. Legume shrub encroachment also produced a slight decrease in the C/N ratio in the top 15 cm soil layer. No significant changes in the RIC were detected as a result of encroachment; however, slight decreases in the RIN were found at medium depths. Both RIC and RIN showed a negative relationship with site temperature in the upper legume‐shrub soil layers but not in conifer shrubs or under grasses, suggesting a priming effect on the recalcitrant soil stocks produced by the higher‐quality inputs derived from legume encroachment.
Wild ungulates seek out food resources at the bottom of mountain valleys in winter and spring, where their high density can negatively impact the production of hay meadows. This study determines the ...factors that explain the meadow use of four sympatric species: red-, roe-, and fallow-deer, and wild boar. In 2017, we counted the individuals of each species in 94 meadows for eight nights, between March and June, and estimated the frequency of meadow use as the proportion of positive censuses over the total censuses per meadow. We also recorded the presence of domestic ungulates. We inventoried the floristic composition in June. Species tended to use different meadows but only fallow- and roe-deer significantly segregated, indicated by the negative C-score index. As the ungulate frequency was skewed to 0, we used a generalized additive model (GAMLSS) to simultaneously simulate the probability of animals being absent and the frequency of positive censuses. Landscape features contributed to explaining the absence probability, while plant richness and legume cover explained the frequency of meadow use. The presence of domestic ungulates did not affect wild ungulate behavior. All studied species, except roe-deer, avoided exposed spots, preferentially using large meadows close to the forest. At meadow level, each species seemed to have different forage requirements. The frequency of fallow deer increased with the meadow forage quality, indicating a more grasses-based diet than the other two deer, and probably displacing roe-deer to suboptimum meadows. Red-deer used less plant-rich meadows, suggesting flexibility in their dietary choices.
The global forest carbon (C) stock is estimated at 662 Gt of which 45% is in soil organic matter. Thus, comprehensive understanding of the effects of forest management practices on forest soil C ...stock and greenhouse gas (GHG) fluxes is needed for the development of effective forest-based climate change mitigation strategies. To improve this understanding, we synthesized peer-reviewed literature on forest management practices that can mitigate climate change by increasing soil C stocks and reducing GHG emissions. We further identified soil processes that affect soil GHG balance and discussed how models represent forest management effects on soil in GHG inventories and scenario analyses to address forest climate change mitigation potential. Forest management effects depend strongly on the specific practice and land type. Intensive timber harvesting with removal of harvest residues/stumps results in a reduction in soil C stock, while high stocking density and enhanced productivity by fertilization or dominance of coniferous species increase soil C stock. Nitrogen fertilization increases the soil C stock and N2O emissions while decreasing the CH4 sink. Peatland hydrology management is a major driver of the GHG emissions of the peatland forests, with lower water level corresponding to higher CO2 emissions. Furthermore, the global warming potential of all GHG emissions (CO2, CH4 and N2O) together can be ten-fold higher after clear-cutting than in peatlands with standing trees. The climate change mitigation potential of forest soils, as estimated by modelling approaches, accounts for stand biomass driven effects and climate factors that affect the decomposition rate. A future challenge is to account for the effects of soil preparation and other management that affects soil processes by changing soil temperature, soil moisture, soil nutrient balance, microbial community structure and processes, hydrology and soil oxygen concentration in the models. We recommend that soil monitoring and modelling focus on linking processes of soil C stabilization with the functioning of soil microbiota.
The impact of agricultural practices and the excess application of nitrogen can negatively impact the environment and cause human health problems. In Spain, the liquid manure applied in areas of ...intensive agriculture is creating groundwater nitrate pollution problems. The purpose of this paper is to evaluate the economic profitability of agroforestry practices in North East Spain. Therefore, it deals with an alternative land use that has attracted attention in recent years, considering its potential to reduce the negative impact of modern agriculture that combines concurrent forestry and agricultural production in the same area. Specifically, silvoarable practices, such as alley cropping (AC), edge row planting and riparian buffer (RB) strips were compared to conventional agricultural land use. Considering the current agricultural policy framework in Spain, which does not favour these practices, our results showed the economic profitability of alley-cropping practices in comparison to conventional barley production of 25 to 64 € ha-1 yr-1. However, AC systems presented negative results compared to the traditional wheat crop (-122 to -63 € ha-1 yr-1). The results for RB strips were strongly influenced by the high initial costs, both in irrigated and non-irrigated scenarios. Economic results were negative (between -137 and -85 € ha-1 yr-1) compared to the conventional crops, barley and corn. These figures could be greatly increased with a policy framework that promotes these practices based on the fundamental ecosystem services they provide. Moreover, these practices allow an economic diversification that could prove to be beneficial for the majority of farmers.
The magnitude of CO2 efflux pulses after rewetting a dry soil is highly variable and the factors regulating these pulses are poorly understood. In this field experiment, we aimed to study the C ...dynamics after simulated summer rainstorms in a Mediterranean open holm oak woodland (dehesa). We hypothesized that because the herbaceous cover is mostly dead during the summer in this ecosystem, the short-term CO2 efflux (SR) after rewetting could mainly be explained by different measurable soil C fractions: i) K2SO4-extracted soil C (EOC); ii) microbial biomass C (MBC); or iii) chloroform-fumigated extracted C (CFE). On both grazed and abandoned dehesa sites, we simulated three summer rain events at two-week intervals and we measured SR discontinuously in three plots under tree canopy and in another three plots in open grassland. In each plot, C fractions and water content were estimated before (2 h) and after (36 h) each irrigation event. Following rewettings, SR increased up to ten times compared with non-irrigated plots. The CFE actually increased after rewetting in the first two irrigations but not in the third event, suggesting that the capacity of the soil to release labile organic C from soil aggregates or litter was reduced after each irrigation event. Overall, the C released as CO2 in the first 24 h was related to the CFE existing before rewetting, which may help to explain the spatial variability in SR. However, the explained variability decreased after each irrigation, suggesting a change to a less labile composition of the CFE fraction as a consequence of multiple drying-rewetting cycles.
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