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Challenges for mitigating Mediterranean soil erosion under global change



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Sub-chapter 2.3.3
Challenges for mitigating
soil erosion
under global change
Mohamed ANNABI
Mohamed SABIR
ENFI, Morocco
Soil is an essential resource that provides a wide range of ecosystem services
(Dominati et al. 2010). Its formation is slow, but its destruction can be rapid. Soil
erosion by water is a natural phenomenon that is impacted by human activities
and global change. The long history of intense cultivation and a unique combination
of relief, parent material and climate conditions makes Mediterranean soils and
soil patterns very different from those in other regions in the world. Several studies
have shown that, in the Mediterranean basin, current soil loss rates drastically
exceed soil formation rates (Kosmas et al. 1997). In addition, an increase in intense
precipitation events due to climate change is expected in the 21st century. For these
reasons, suitable adaptive managing strategies for Mediterranean soils cannot be
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The Mediterranean Region under Climate Change
simply transposed from experiments conducted in other regions of the world. This
paper presents the main lessons to be drawn and challenges involved in preventing
soil erosion in the Mediterranean region under global change reported in the
literature, plus results obtained in several research projects1.
Soil erosion in the Mediterranean basin
Mediterranean soils are particularly prone to erosion (García-Ruiz et al. 2013)
because of (i) marked relief, 45% of the region has slopes greater than 8%, (ii)
the high frequency of intense rainfall events (> 100 mm h-1) in fall and winter,
(iii) the presence of poor, shallow and skeletal soils, and (iv) sparse natural
vegetation subjected to severe summer droughts. In addition to these natural drivers,
intense cultivation even on steep slopes, burning, overgrazing and deforestation
can greatly accelerate soil erosion, which, on the other hand, is limited by the
many soil and water conservation measures (SWC) such as terracing in hilly areas.
The impacts of soil erosion can be divided into on-site and off-site effects. On-site
effects are due to soil loss at field scale which, in certain extreme conditions, can
lead to a net loss of cultivated area. This quantitative soil loss impacts agricultural
production through the loss of nutrients, soil water reserves, and alterations to soil
properties. Soil erosion also has significant off-site effects through the delivery
of sediments to rivers, which affects the mobilization of water by siltation of
reservoirs, and reduces the quality of water destined for irrigation and drinking.
Higher sediment yields (SY) than in many other regions have been measured in
the Mediterranean basin (Woodward, 1995). These were often explained by the
high contribution of gully and riverbank erosion processes (Vanmaercke et al.
2012). Gullies and especially badlands have been identified as a major source of
sediments involved in siltation of reservoirs in the Mediterranean region (De Vente
et al. 2006). The majority of SY occur during a few extreme rainfall events (“time
compression”, González-Hidalgo et al. 2007). However, these generalities mask
huge variability across the basin as a whole. Based on a dataset containing 104
cumulated years of continuous SY measurements in eight small catchments ranging
from 0.15 to 1.3 km2in size (Figure 1), Smetanova et al. (submitted) show that
(i) the annual SY varied between 0 and ~27100 t·km-2·yr-1; (ii) catchments display
two main contrasted patterns of SY seasonality; (iii) time compression is highly
variable from one catchment to another. Ben Slimane et al. (2015) demonstrated
that the predominance of gully and riverbank erosion processes in the Mediterranean
basin was site dependent and not as widespread as previously thought.
1.,, http://,,
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Challenges for mitigating Mediterranean soil erosion under global change
Rainfall (mm) Runoff (mm)
Sediment yield (t km-2) Sediment concentration (g l-1)
Figure 1
Range of intensity of erosion processes in the Mediterranean basin illustrated
through inter-annual variability of rainfall (mm), runoff (mm), sediment yield (SY) (t·km-2)
and sediment concentration (g·l-1) observed in 8 catchments of the R_Osmed network:
KAM (Kamech, Tunisia), ROU (Roujan, France),VIL (Can Vila, Spain),
MAC (Macieira de Alcôba, Portugal), CAN (Cannata, Italy), C AU (El Cautivo, Spain),
LAV (Laval, France), BRU (Brusquet, Spain). Inter-annual means are plotted as red circles.
Expected future changes in Mediterranean
soil resources under global change
Climate change will have both direct and indirect effects on soil erosion. Direct
effects are due to changes in the amount, erosive power and spatio-temporal
pattern of rainfall. Global change model projections indicate that longer
droughts and more frequent extreme precipitation events are likely to occur.
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The Mediterranean Region under Climate Change
Because of the high degree of SY time compression, the increased frequency
and intensity of the largest events will increase soil erosion. The soil system
reacts non-linearly to such changes, so even small increases in rainfall amount
or intensity can dramatically increase soil loss rates. Climate change could
also lead to a temporal shift in both the vegetation cover and the rainfall pattern
that could positively or negatively indirectly affect erosion rates: the decline
in surface runoff (which triggers erosion) could be partly counterbalanced by
reduced biomass growth. Soil erosion could also be strongly affected by
changes in land use and management due to human drivers (e.g., technological
changes, demographic and socioeconomic trends and governance structures).
Indeed, land use and management controls both soil characteristics and the
distribution of overland flows. Some widespread crops, including vineyards
and olive groves, and practices such as extensive overgrazing in mountain
areas are known to encourage erosion. An increase in land abandonment and
forest fires because of global change could also increase erosion in young
fallows and post-fire conditions.
In the MESOEROS212project, the impact of changes in rainfall characteristics
and land cover on the risk of soil erosion in the Mediterranean basin was
evaluated using a set of erosion models on (i) small and medium size gauged
watersheds in France, Tunisia and Morocco, and (ii) the Mediterranean basin
as a whole. The models were parameterized using measurements from highly
gauged catchments and applied to the largest basins to calculate present and
future conditions. Climate changes were estimated from global general
circulation simulations and adapted to local conditions. Several land use change
scenarios were built, including an «Accentuation » scenario in which both
cultivated and natural vegetation are degraded, and a « Protection » scenario in
which natural vegetation and good practices in cultivated area are favored. Two
main results of the project (Paroissien et al. 2015; Simonneaux et al. 2015,
Cerdan et al. 2011) were:
1) Simulating soil erosion rates is difficult because of the marked spatial and
temporal variability of the processes involved and the uncertainty associated
with the input parameters;
2) Land use is the main driver of changes in erosion risk and soil vulnerability
in the Mediterranean basin.
2. Mediterranean Soils EROsion and vulnerability to global change during the 21st century
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Challenges for mitigating Mediterranean soil erosion under global change
Main challenges for the future
of Mediterranean soil resources
Toward a better knowledge
of the factors and processes involved in soil erosion
Despite the increased availability of spatially distributed data, model application
is still hampered by the low quality of input data. We therefore need to make
better use of recent techniques to complete the too sparse legacy soil data to
capture short scale soil variations in the Mediterranean basin and to improve
our knowledge of future conditions to design efficient adaptation techniques.
Long-term catchment erosion monitoring systems and Mediterranean networking
initiatives are ideal ways to obtain a good picture of the variability of erosion
processes and to explore the specific role of major/extreme events or
sedimentological connectivity involved in sediment yield (SY) variability.
Toward the evaluation of soil risk
There is a need for a scientifically sound yet simple index of the risk of soil erosion
that combines erosion rates and vulnerability and can be readily understood by
decision makers. When assessing soil erosion vulnerability, it is important to
consider the soil as a patrimonial resource that combines several basic soil functions
(e.g., soil fertility and carbon storage) but also cultural and civilizational values
related to religion, livelihood and health (Minami, 2009). The choice and valuation
of criteria to be used for SE vulnerability are however complex issues, especially
in the Mediterranean basin where for example, vineyards or olive trees can grow
in soils that would be considered as very degraded using standard criteria. Even
when the focus is on a very simple criterion such as soil depth as in Paroissien
et al. (2015), soil vulnerability to erosion is difficult to estimate because soil depth
is neither a standard, nor an easy, measurement.
Toward site specific conservation strategies
Mediterranean civilizations have successively developed or improved a wide range
of techniques to improve water conservation and management, increase agricultural
production, and reduce soil erosion. These techniques mainly concern correcting
the slope/ reducing water velocity (e.g. through terraces), increasing ground cover
(e.g. through the use of cover crops), restoring rangelands, and/or improving soil
quality (e.g. through amendments). Recently SWC techniques have extended to
sustainable land management or conservation agriculture that favor less soil
disturbance, using crop residues as mulch, continuous ground cover, and crop
rotations or associations. The efficiency of no-till conservation agriculture in
increasing topsoil soil organic content and improve the soil water storage is widely
recognised in the Mediterranean basin (Mrabet, 2011). However, these techniques
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Box 1
Challenging issues for mitigating Mediterranean soil erosion under global change
Brice BOUDEVILLAIN, Cédric LEGOUT et Guillaume NORD
UMR LTHE, France
Raindrops control detachment directly through their impact on the soil matrix and indirectly
through runoff, which is generally related to the decrease in infiltrability as a direct consequence
of the degradation of the superficial structure under the action of rain (Moore and Singer,1990).
Rain also plays a role in particle transport: either in transport caused by the impact of drops,
or in transport flow caused by raindrops (Kinnel, 2005).Looking at detachment by raindrops in
more detail, it turns out that the rain actually controls two distinct successive processes:1) the
disintegration of particles at the surface and 2) the motion of the fragments produced by
disaggregation by splash effect. Rain therefore plays an important role both in the total mass of
eroded soil and in the size of the particles set in motion (Legout et al., 2005). Rainfall is usually
directly measured by rain gauges but these only provide local and partial information for the
scientific issues we want to address.
The first issue concerns the appropriate descriptors for rain (the diameter and number of
drops, rain intensity and kinetic energy, and so on) that influence the erosion processes: they
are not yet well defined and no consensus has yet been reached in the scientific community. It
is consequently necessary to diversify measurements of rain to identify which factors concern
erosion. A disdrometer is an instrument used to measure droplet size distributions and the
values of other descriptors of rain.This instrument was used during laboratory experiments of
detachment with rainfall simulators generating different intensities and energies. These
experiments confirmed that the strongest kinetic energies were associated with the largest
detached masses. It was also demonstrated that the strongest energies detached the largest
proportions of fine particles (that are more easily mobilized by runoff). These observations
were confirmed on 120 m² erosion plots under natural rainfall.
The second issue concerns the spatio-temporal structures of rainfall that lead to significant
hydro-sedimentary responses.To address this issue, access to spatialized information with high
temporal frequency is required. Although weather radar provides indirect measurements, it
fulfils this requirement. It is a complementary observation tool that is all the more useful as
Mediterranean rainfall can be very localized and last only a very shor t time (often a few
Several observation systems are available to deal with these issues including “ORE Draix”in the
Southern Alps,“SNO OHMCV” in the Cevennes and “ORE OMERE” for Kamech watersheds
in north eastern Tunisia. These observatories have hydro-sedimentary devices for the
measurement of suspended sediments, sometimes sediment traps, and precipitation devices
(rain gauges, disdrometers, sometimes radar) in various hydro-climatic and soil-use contexts.
KINNELL, P. I. A., 2005
19(14): 2815–2844.
54: 1117-1123.
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Challenges for mitigating Mediterranean soil erosion under global change
have varying degree of success depending on the environmental and societal contexts
(García-Ruiz, 2013). Maintaining a continuous land cover may for instance have
positive impacts on soil protection but negatives ones on production because of
competition for water in semi-arid areas (Marques et al. 2010). In the end, the benefit
of each technique needs to be checked in site-specific conditions, especially in
Mediterranean areas where the complexity of the landscape results in significantly
diverse contexts. Lessons from past changes in the Mediterranean environment
through a review of adaptation techniques already experimented and a site by site
evaluation of their soil protection efficiency and acceptability by local farmers will
be helpful. Many mitigation strategies cited above are based on profound changes
in agricultural practices. The massive introduction of such strategies in existing
Mediterranean agrosystems is a challenge, and will have to take the specificities of
each agrosystem into account, along with its socio-economic and environmental
dimensions, and be supported by local or national policies.
Mediterranean soil resources are crucial for the social and economic development
of the region but their sustainability is threatened by intense erosion processes,
which have severe on-site and off-site effects. However, the nature and intensity
of active erosion processes are as varied as the mosaic of Mediterranean landscapes.
Realistic maps of soil erosion risk, vulnerability and sustainability cannot be
produced without knowledge of erosion factors and processes acquired in
awareness of this diversity.
When we modeled future soil degradation and catchment sediment delivery, the
direct impacts of climate change alone were found to be lower than the impacts
of changes in land use or in land management. The first challenge is thus to
better forecast future changes in land use/management changes, whether or not
driven by climate. The second challenge is to propose a strategy to anticipate
projected changes and to mitigate their impacts. A wide range of adaptation or
mitigation techniques exists and many have already been tested in the
Mediterranean basin. It is now important to evaluate their efficiency and
acceptability in the wide range of site-specific conditions. This will require new
integrated approaches able to combine (i) quantitative and qualitative impacts
of soil erosion; and (ii) natural and anthropogenic factors and processes.
This work benefited from the financial support of several institutions through research
projects MESOEROS21 (ANR-06-VULN-012 funded by the French National
Research Agency), ORE OMERE (funded by INRA, IRD, INAT and INRGREF),
MISTRALS/Sicmed R_Osmed and Lebna (funded by CNRS, INRA, IRD, IRSTEA),
JEAI Vecteur (funded by IRD) and MASCC (funded by ARIMNET2).
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Relative contribution of surface and subsurface
erosion to reservoir siltation in Tunisia. Land
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Impact of Global changes on soil vulnerability in
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MINAMI K., 2009
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livelihood and health. Soil Science and Plant
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MRABET R., 2011
No-tillage agriculture in West Asia & North
Africa. In. Rainfed farming systems. Tow, P.G.,
Cooper, I.M., Partridge, I, & Birch. C.J. (Eds).
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erosion in a semi-arid mountainous watershed
(High Atlas, Morocco). Journal of Arid
Environments, 122: 64-75
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sediment yield in small Mediterranean
catchments. Hydrological Processes.
A comparison of measured catchment sediment
yields with measured and predicted hillslope
erosion rates in Europe. Journal of Soils and
Sediments, 12: 586–602.
Patterns of erosion and suspended sediment yield
in Mediterranean river basins, in: Foster I.D.L.,
Gurnell A.M., Webb B.W. (Eds.), Sediment and
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Chichester, 365–389.
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AScientific Update
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The Mediterranean Region
under Climate Change
A Scientific Update
Marseille, 2016
Preface by
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... The Mediterranean region has been identified as one of the most vulnerable zones for SE, representing a CC 'hot-spot', due to the magnitude of the expected increase in temperature and anomalies in rainfall patterns (Giorgi, 2006;Giorgi and Lioniello, 2008;Zittis et al., 2019), such as higher frequency of extreme events, increased intensity of storms, extended drought periods, and higher risk of fire events (Moriondo et al., 2006;Busico et al., 2019). Additionally, the Mediterranean region is also characterized by centuries of anthropic disturbance, mainly related to agricultural and silvopastoral activities which might contribute to a substantial increase of SE rates (Raclot et al., 2016). ...
The assessment of soil erosion rate, especially in agricultural lands, represents a fundamental tool for land management planning in the long-term period. In this study, the SWAT model was utilized to simulate soil erosion within a semi-arid watershed in South Portugal. The model was successfully calibrated and validated using real data of streamflow and river sediment transport in four hydrometric stations. Soil erosion susceptibility maps (historical and future) were realized to highlight the evolution of the phenomenon through time. The historical period was confirmed to be the worst one in terms of average soil erosion for each land use, followed by the Representative Concentration Pathways (RCPs) 8.5 and 4.5 scenarios. The main differences in soil loss among the two RCPs will be influenced by the slightly increasing trend of extreme events which will characterize the RCP 8.5, leading to a higher maximum value of soil erosion. Results highlighted the tendency to erosion of Leptosols and of the agro-forestry system (“montado”), which influenced the soil erosion susceptibility distribution of the whole basin. The study confirmed that Leptosols are the most subject to sediment loss due to their intrinsic characteristics, and that “montado” and farmed systems will negatively influence soil erosion rate if anti-erosion actions will not be adopted, stressing the need to identify all aspects responsible for land degradation in Mediterranean watersheds.
... Soil loss rates are higher than the soil formation rates in the Mediterranean basin [8]. Mediterranean soils are easily eroded due to different characteristics: marked relief, 45% of the area having a slope greater than 8%; a high frequency of heavy rains in autumn and winter; poor, shallow, and skeletal soils; and sparse natural vegetation linked to severe summer droughts [9]. Several works have documented the strong impact of the abandonment of farming areas in the Mediterranean region on the hillslope degradation and the increase in the rates of erosion and landslide processes [10][11][12][13][14][15]. ...
Full-text available
Soil erosion is one of the major natural risk factors for developing high-value crops and an accurate estimation of spatial distribution and rates of soil degradation can be crucial to prevent crop degradation. In this paper, we use comparisons between high-resolution DEMs and soil erosion models to uncover the short-term landscape evolution of hazelnut crop yields, which are affected by incipient processes of rill development. Maps of rill initiation and evolution were extracted from the analysis of UAV-based multitemporal DEMs and the application of soil erosion models. A comparison between such a short-term analysis and historical orthophotos was carried out. Such a comparison shows how the USPED model predicts, very reliably, where linear erosion occurred. In fact, a reliable overlay between the linear erosive forms predicted by the USPED model and those captured by the UAV images can be observed. Furthermore, land use changes from 1974 to 2020 are characterized by a transition from abandoned areas (1974) to areas with high-value cultivation (2020), which has a strong impact on the spatial distribution of erosion processes and landslide occurrence. Such data represent a key tool for both the investigation of the spatial distribution of hot-spots of soil degradation and the identification of effective mitigation practices of soil conservation.
... Contributing in the removal of significant topsoil and, consequently, in the loss of nutrients and carbon stock and in porosity variations, erosion is actually recognized as one of the most critical threat to soil properties and functions [7]. Unfortunately a detrimental mix of morphological, climatic and soil characteristics [8], makes the Mediterranean basin particularly exposed to erosive phenomena [9]. Furthermore, because of increasing anthropic pressures, land use changes and climate conditions under actual global changes, the Mediterranean basin is expected to be a critical desertification hotspot [10]. ...
Full-text available
The conservation of soil and multiple ecosystem services it provides, is crucial for human well-being, for pursuing many of the Sustainable Development Goals and for addressing some of the most important challenges of our society. However several factors contribute to soil degradation, including climatic characteristics, lithological and morphological features and transformation processes. Only the last ones can be governed and that is the reason why spatial planning needs tools and analyses to interpret the role of land use changes in complex dynamics such as the erosive phenomena. This work presents the results obtained from the implementation of the InVEST SDR module on the territory of Basilicata Region and considering the evolution occurred between 1990 and 2018. Our outcomes show an intensification of erosion phenomena mainly along the Apennine chain and the coastal area of the Tyrrhenian Sea. Although this area corresponds to the higher average rainfall erosivity over the entire period, the most significant soil loss occurs in correspondence with unfavorable land use changes. The negative connotation typically associated with deforestation, conversion of agricultural soils to arable lands and thinning or total loss of vegetation becomes a measurable quantity, at least from one of several points of view.
... However, the scientific diagnosis of human-induced soil erosion is a challenging problem (García-Ruiz et al., 2017;Muchena et al., 2005). Disentangling the impacts of anthropogenic activities on soil erosion from climatic factors is challenging (Walling and Webb, 1996;Restrepo and Syvitski, 2006;Raclot et al., 2016). A second factor that may complicate the diagnosis is that multiple anthropogenic activities generally occur during the same timeframe and on the same landscape. ...
Opencast mining has exacerbated land degradation in New Caledonia, a French archipelago located in the south-west Pacific Ocean. Developed since the 1880s, mining has become the major economic activity in some catchments, which strongly disrupted sediment dynamics. Reconstructing the temporal changes of sediment source contributions is essential to understand the driving factors of soil erosion in response to i) the occurrence of cyclones, ii) the changes in mining practices during the last several decades, and iii) other soil degradation processes such as extensive soil erosion induced by fires, overgrazing and trampling of invasive species, and landslides. Accordingly, a multi-parameter analysis including gamma spectrometry, color and X-ray fluorescence measurements was conducted on a sediment core collected in a deltaic floodplain at the outlet of one of the first areas exploited for nickel mining, the Thio River catchment (397-km²). One geochemical tracer (i.e. K) has been used to quantify changes in sediment sources in the successive sediment layers deposited since the beginning of mining activity. The results showed that the contribution of mining tributaries largely dominated, with a mean contribution of 74% (SD 13%) of material sampled in the sediment core. This contribution notably increased after the mechanization of mining activities (i.e. from 1950s; increase of 18%). The occurrence of Cyclone Alison in 1975 triggered the progressive transfer of mining waste accumulated on the foothills over 25 years into the river system. This tipping point could be identified in the sediment sequence, which demonstrates that over the last 41 years (i.e. 1975–2016), a ~84-cm deep sediment deposit has accumulated in the alluvial floodplain of the Thio River catchment (mean annual deposition rate of 2 cm yr⁻¹). Currently, the progressive release and downstream transfer of this mining waste is still ongoing ~45 years after Cyclone Alison. Although environmental legislation was introduced in 1975, mining tributary contributions to sediment still dominate (80%, SD 5%). Overall, this multi-proxy approach to examining the cumulative effects of mining activities on downstream sediment dynamics could be implemented in other mining catchments of New Caledonia and around the world to compare the respective mining source contributions to sediment and their evolution throughout time in these contrasted areas.
... Moreover, NT tends to preserve soil water better than CT, which results in huge advantages for the cropping systems in arid and semiarid areas; this is generally attributed to the change in the soil porosity (into more small pores and fewer large pores), to the creation of a more continuous pore system (from decaying roots and soil macrofauna activity), and above all to the minor soil water evaporation in NT as a consequence of both the presence of crop residues on the soil surface and the minor soil surface roughness generated by soil cultivation (Blevins and Frye, 1993;Lampurlanés and Cantero-Martínez, 2006). Such potential benefits suggest that NT is advantageous for cereal-based systems in Mediterranean environments, where water scarcity during the spring is often the main factor limiting the growth and productivity of rainfed crops (Lampurlanés et al., 2002) and where soils are particularly prone to erosion because of their characteristics and morphology (45% of the Mediterranean region has slopes greater than 8%), of cultivation even in steep slopes, and of the high frequency of intense rainfall events in fall and winter (García-Ruiz et al., 2013;Raclot et al., 2016). Several studies carried out under Mediterranean conditions have confirmed the benefits of NT over CT in terms of both a reduction in soil erosion (García-Orenes et al., 2009) and a crop yield advantage, particularly in dry areas/years (Amato et al., 2013;Ruisi et al., 2014). ...
This 2-year study, performed in a typical Mediterranean environment on three soil types (two Inceptisols and one Vertisol), aimed to improve understanding of the factors that play a major role in determining crop response when soil management shifts from conventional tillage (CT) to no-tillage (NT). The effects of NT on the soil nitrogen (N) availability, N uptake, ¹⁵N fertilizer recovery, and grain yield of durum wheat were evaluated in comparison to CT under five different N fertilization rates (0, 40, 80, 120, and 160 kg N ha⁻¹). Compared to CT, NT negatively affected grain yield in one of the two years but only in the two Inceptisols. On average, a considerable grain yield advantage of CT over NT (approximately +0.6 Mg ha⁻¹ of grain) was observed with no N fertilization. This benefit decreased progressively when N fertilizer rate increased to the point that at 120 kg ha⁻¹ of N applied differences between CT and NT were negligible. The differences between the two tillage systems in both grain yield and N uptake were attributable more to differences in the native soil mineral N (that materialized already during the vegetative phase of the crop cycle) than to differences between CT plants and NT plants in efficiency in taking up N from fertilizer. The differences between CT and NT for many of the traits observed in durum wheat plants increased with decreasing soil fertility and in particular with decreasing soil total N. In conclusion, the shift from CT to NT, which should be accompanied in any case by an increase in the N fertilization rate to take into account the reduction in soil N available for the crop, was less problematic in the Vertisol, which is more fertile and better structured than the two Inceptisols.
... However, soils are often threat by several degradation factors among them soil erosion which is a clear indication of land degradation in the Mediterranean (García-Ruiz et al., 2013;García-Ruiz et al., 2017;Montanarella et al., 2016). Therefore preventing and combating soil erosion is a major environmental and economical challenge in this region where climate change is already perceptible (Den Biggelaar et al., 2004;Giorgi and Lionelle, 2008;Raclot et al., 2016). In Tunisia, the problem of soil erosion is more pronounced in the north part of the country in which the landscape is hilly and high-energy storms are frequent on bare soils during the autumn season (Jebari, 2009). ...
Soil aggregate stability is a key factor in soil resistance to water erosion, which is a threat to soils in a large part of northern Tunisia. The analysis of the spatial variability of soil aggregate stability provides both agronomic and environmentally useful information. However, extensive measurements of soil aggregate stability remain tedious and expensive. This study explores two different approaches as alternative to measurements of soil aggregate stability. One approach estimated aggregate stability via laboratory measurements of soil elementary properties using multiple linear regressions known as pedotransfer functions. The second approach, which is methodologically innovating, was based on the geological pattern as a proxy for aggregate stability using regression-kriging analysis. A set of 113 soil samples from an 800 km 2 agricultural region that included the Lebna watershed (Cap Bon, Tunisia) were collected from the soil surface layer (0–10 cm depth). Samples were analyzed for elementary properties (i.e., soil texture, total carbon and nitrogen, iron, CaCO 3 , salinity, CEC and pH) and for soil aggregate stability according to the normalized method (ISO/DIS 10930, 2012), which considers three indexes (MWD) calculated for three contrasted wetting conditions and disruptive energies. Most soils in the study area were non-salted with an alkaline pH and relatively low organic carbon content. Of the soils, 35% were clay soils, and 55% had a balanced soil texture. The average of the three soil aggregate stability indexes (MWD mean) ranged from 0.38 to 2.80 mm, and this property showed large variability from instable soils to very stable ones. Analysis of pedotransfer functions determined that the best predictor variables for soil aggregate stability were silt, organic matter and iron. Geostatistical analyses at the regional scale showed spatially structured soil aggregate stability (variograms with sills reaching a 5 km distance). Using geological information as ancillary data, the prediction of soil aggregate stability with regression-kriging was similar to that of pedotransfer functions. A regression-kriged map of soil aggregate stability associated with a map of prediction uncertainties was developed. The resulting maps and methods of this study can be useful in the development of management options that minimize water erosion risks in the studied area.
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Chemical properties of forest soils can strongly influence this compartment vulnerability to climate change effects. Past human activities can play a major role in structuring soil chemical properties. In the Mediterranean region, abandonment of terrace agriculture since 1860 induced the coexistence of forests with different ages. Here, soil chemical signature (SCS) was compared between very recent, recent and ancient forests using Fourier Transform InfraRed (FTIR) spectroscopy and other chemical properties (total C and N, CaCO3 percentages). Land Use Legacy (LUL) effects were analysed depending on soil depths and on contrasted climate conditions (humid vs subhumid Mediterranean climates). Statistic treatments, Linear Mixed-Effect and Anova COMmon DIMension models, were used to highlight the influence of depth’s soil, climate and LUL effects. Interestingly, the soil depth did not influence LUL effect on soil spectra. The effect of climate, LUL and their interactions were observed on the SCS. Higher available N was observed in soils from ancient forests than in soils from very recent forests. Moreover, mineral fraction discriminated soils with different LUL (very recent vs recent and ancient forests) and this depended on climate. Under subhumid climate, soils from very recent forests were indeed negatively correlated with the mineral fraction, while under humid climate, they were positively correlated to it. Finally, a recovery of soils chemical properties was observed in recent forests under humid climate, while under subhumid climate, SCS of post agricultural forests was different from that of ancient forests.
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Soils are an essential factor contributing to the agricultural production of rainfed crops such as barley and triticale cereals. Changing environmental conditions and inadequate land management are endangering soil quality and productivity and, in turn, crop quality and productivity are affected. Advances in hyperspectral remote sensing are of great use for the spatial characterization and monitoring of the soil degradation status, as well as its impact on crop growth and agricultural productivity. In this study, hyperspectral airborne data covering the visible, near-infrared, short-wave infrared, and thermal infrared (VNIR–SWIR–TIR, 0.4–12 µm) were acquired in a Mediterranean agricultural area of central Spain and used to analyze the spatial differences in vegetation vitality and grain yield in relation to the soil degradation status. Specifically, leaf area index (LAI), crop water stress index (CWSI), and the biomass of the crop yield are derived from the remote sensing data and discussed regarding their spatial differences and relationship to a classification of erosion and accumulation stages (SEAS) based on previous remote sensing analyses during bare soil conditions. LAI and harvested crop biomass yield could be well estimated by PLS regression based on the hyperspectral and in situ reference data (R2 of 0.83, r of 0.91, and an RMSE of 0.2 m2 m−2 for LAI and an R2 of 0.85, r of 0.92, and an RMSE of 0.48 t ha−1 for grain yield). In addition, the soil erosion and accumulation stages (SEAS) were successfully predicted based on the canopy spectral signal of vegetated crop fields using a random forest machine learning approach. Overall accuracy was achieved above 71% by combining the VNIR–SWIR–TIR canopy reflectance and emissivity of the growing season with topographic information after reducing the redundancy in the spectral dataset. The results show that the estimated crop traits are spatially related to the soil’s degradation status, with shallow and highly eroded soils, as well as sandy accumulation zones being associated with areas of low LAI, crop yield, and high crop water stress. Overall, the results of this study illustrate the enormous potential of imaging spectroscopy for a combined analysis of the plant-soil system in the frame of land and soil degradation monitoring.
Fire is a natural and important part of the disturbance regime that has shaped the Mediterranean landscape. Once established in the ecosystem, fires affected vegetation structure and soil-forming dynamics and became a key factor in creating the current mosaic pattern of the Mediterranean. Fires increase runoff and soil erosion by removing vegetation, changing soil properties and providing layers of sediment and ash. Given the complexity of the interacting environmental forces and the nature of the fires, fire-induced erosion varies markedly across spatio-temporal scales. Erosion rates at point and plot scales are usually 5–7 orders of magnitude higher than in unburned sites, yet it has been difficult to quantify their magnitudes and importance at larger (basin) scales. The process of ecosystem recovery may last decades, during which the soil is exposed to elevated erosion, considerably higher than its natural formation rates. Numerous knowledge gaps across all spatial scales limit our understanding of the processes contributing to post-fire runoff and erosion; therefore, two directions for future research are suggested: (i) process-based studies to understand the dynamics and interacting factors controlling surface runoff and erosion, particularly in relation to fire regime; (ii) a landscape-scale approach to quantify erosion at hillslope and basin scales.
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Soils in the coastal region of Syria (CRoS) are one of the most fragile components of natural ecosystems. However, they are adversely affected by water erosion processes after extreme land cover modifications such as wildfires or intensive agricultural activities. The main goal of this research was to clarify the dynamic interaction between erosion processes and different ecosystem components (inclination, land cover/land use, and rainy storms) along with the vulnerable territory of the CRoS. Experiments were carried out in five different locations using a total of 15 erosion plots. Soil loss and runoff were quantified in each experimental plot, considering different inclinations and land uses (agricultural land (AG), burnt forest (BF), forest/control plot (F)). Observed runoff and soil loss varied greatly according to both inclination and land cover after 750 mm of rainfall (26 events). In the cultivated areas, the average soil water erosion ranged between 0.14 ± 0.07 and 0.74 ± 0.33 kg/m2; in the BF plots, mean soil erosion ranged between 0.03 ± 0.01 and 0.24 ± 0.10 kg/m2. The lowest amount of erosion was recorded in the F plots where the erosion ranged between 0.1 ± 0.001 and 0.07 ± 0.03 kg/m2. Interestingly, the General Linear Model revealed that all factors (i.e., inclination, rainfall and land use) had a significant (p < 0.001) effect on the soil loss. We concluded that human activities greatly influenced soil erosion rates, being higher in the AG lands, followed by BF and F. Therefore, the current study could be very useful to policymakers and planners for proposing immediate conservation or restoration plans in a less studied area which has been shown to be vulnerable to soil erosion processes.
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Soil is closely connected to the culture and civilization of an ethnic group living in a given place, including their religion, thoughts, livelihood and health. It is important for people to protect the soil, their agriculture and the environment because the collapse of soil leads to the collapse of human culture, civilization, livelihood and health. The links between the soil and culture, civilization, livelihood and health may result from the ethical attitudes people have about the soil and that they demonstrate through their interactions with it. However, soil resources have been overexploited in modern society and are currently on the verge of collapsing. In this review article, the etymology of words for soil, the place of soil in philosophy and religion, the relationships between soil and the soul, the soil and dialects, and cultural soil science are discussed. The powerful influences of soil on civilization and livelihood are discussed and the relationship between soil and human beings is also considered. Soil can be shown to be a living thing, and this review will present a brief history of the relationship between soil and human health, and will discuss the importance of adopting an ethical attitude towards soil.
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The ecosystem services and natural capital of soils are often not recognised and generally not well understood. This paper addresses this issue by drawing on scientific understanding of soil formation, functioning and classification systems and building on current thinking on ecosystem services to develop a framework to classify and quantify soil natural capital and ecosystem services. The framework consists of five main interconnected components: (1) soil natural capital, characterised by standard soil properties well known to soil scientists; (2) the processes behind soil natural capital formation, maintenance and degradation; (3) drivers (anthropogenic and natural) of soil processes; (4) provisioning, regulating and cultural ecosystem services; and (5) human needs fulfilled by soil ecosystem services.
We reviewed daily soil erosion data (mainly by rainfall erosion) in Western Mediterranean areas by compiling the data taken from the bibliography. Although soil erosion varies from site to site, and from year to year, annual amount of soil eroded depends on a few daily erosive events. Each year the three highest daily erosive events (ranked by magnitude) represent more than 50% of annual soil eroded, regardless of the total amount. This ratio is also evident on a supra-annual scale.The similarity of results from different environments, field methods and rainfall conditions suggests that the interpretation of annual average erosion rates should be viewed with caution. The dependence of soil erosion on a few daily erosive events should also be borne in mind when reconstructing the past, and suggests a new scenario in which historical geomorphology is replaced by a new catastrophism.
  • Le Y Bissonnais
  • Moore D C J Singer M