Capturing the Scale Dependency of Erosion-Induced Variation in CO2 Emissions on Terraced Slopes

Net soil CO2 emissions are not independent of topography but tend to decline with increasing slope gradients. Such decline has been attributed to increased runoff and greater soil loss on steep slopes, leaving the soil less habitable for microorganisms. However, the specific variations of slope gradients and thus the associated soil properties relevant for CO2 emissions, especially from terraced slopes, are often disguised by the coarse resolution of digital terrain models (DTMs) based on commonly available open-source data. Such misrepresentation of the relationship between topography and soil CO2 emissions carries the risk of a wrong assessment of soil-atmosphere interaction. By applying a slope dependent soil CO2 emission model developed from erosion plots to nearby sloping and partially terraced cropland using two DTMs of different spatial resolutions, this study tested the significance of these resolution-induced errors on CO2 emission estimates. The results show that the coarser-resolution Shuttle Radar Topography Mission (SRTM) underestimated CO2-C emission by 27% compared to the higher-resolution DTM derived from Unmanned Aerial Vehicles (UAV) imagery. Such difference can be mostly attributed to a better representation of the proportion of flat slopes in the high-resolution DTM. Although the observations from erosion plots cannot be directly extrapolated to a larger scale, the 27% underestimation using the coarser-resolution SRTM DTM emphasizes that it is essential to represent microreliefs and their impact on runoff and erosion-induced soil heterogeneity at an appropriate scale. The widespread impact of topography on erosion and deposition on cropland, and the associated slope-dependent heterogeneity of soil properties, may lead to even greater differences than those observed in this study. The greatly improved estimation on CO2 emissions by the UAV-derived DTM also demonstrates that UAVs have a great potential to fill the gap between conventional field investigations and commonly applied coarse-resolution remote sensing when assessing the impact of soil erosion on global soil-atmosphere interaction.

Geo-environmental analysis of terraced slopes and dry-stone walls in Can Grau area (Garraf Park, Catalunya, Spain): preliminary results from the Stonewalls4life project.

<p>Stonewalls4life is an E.U. Life project started in the second half of 2019 involving many subjects, both public bodies and privates, in a multidisciplinary working group. The main objective of the project is to demonstrate how an ancient technology for land use, drystone walling, can be effectively considered to improve the resilience of the territory to climate change by adopting a socially and technically innovative approach.</p><p>The project actions are being performed at Manarola, within the Cinque Terre National Park (eastern Liguria, north-western Italy). The pilot site is a narrow strip of land close to the seaside and characterized by small valleys with steep terraced slopes. This anthropogenic landscape represents a high-value peculiarity attracting more than three million tourists every year.</p><p>Three replication sites were identified in order to demonstrate the transferability and replicability of the project actions: two are located within the Cinque Terre Natural Park territory and one is in the Can Grau area (Garraf Park, Catalunya, Spain).</p><p>The Spanish site is currently under evaluation. An extensive geological, geomorphological, and land-use-land-cover (LULC) analysis is now being carried out in the Can Grau area to define its environmental features, especially concerning geological aspects and land use, and focusing on terraced areas and their state of conservation. This study aims to identify a specific suitable site for the replication of the project actions that will be carried out in Manarola, namely for dry-stone walls recovery, and is based on a multitemporal analysis of aerial images performed in a GIS environment and a wide collection and review of bibliographic data.</p><p>This contribution illustrates the preliminary results of the Can Grau area analysis, focusing in particular on the distribution of terraced areas and the variation of LULC from the 1950s to the present day. From this study emerges a progressive abandonment of terraced areas used for cultivation, although, according to historical sources, this process mostly occurred after the phylloxera appeared in the late 19th century, seriously affecting the most important agricultural activity in the Garraf, namely the viticulture.</p><p>The outcomes from this study will be useful in terms of both Stonewalls4life project implementation and overall land management, particularly aiming to restore a man-made geomorphological heritage and mitigate geo-hydrological risk.</p>

STONEWALLS4LIFE - using Dry-Stone Walls as a Multi-purpose Climate Change Adaptation tool: preliminary results in terms of geological and geomorphological quantitative analysis.

<p>Due to its rugged morphology and a general lack of flat areas suitable for cultivation, Liguria region is widely characterized by slope terracing, carried out by its inhabitants for centuries. Slope terraces are usually retained by dry-stone walls; secondly, by retaining walls made of stones bounded by lime mortar or by grassy edges, in this case characterized by the absence of retaining structures.</p><p>The widespread abandonment of rural areas that occurred in the second half of the last century resulted in a diffuse lack of dry-stone walls maintenance, which is a fundamental activity in order to keep the function of dry-stone structures. Such aspect, together with an increasing occurrence of extreme hydro-meteorological events over the last years, accelerates the dry-stone walls decay and collapse, as well as the instability of single terraces and consequently of the whole terraced slope.</p><p>This is the case in which the Cinque Terre National Park (eastern Liguria, north-western Italy) is involved, a narrow strip of land close to the seaside and characterized by small valleys and terraced slopes showing high steepness values. This anthropogenic landscape represents a high-value peculiarity attracting more than three million tourists every year.</p><p>The main objective of the project is to demonstrate how an ancient technology, drystone walling, can be effectively used to improve the resilience of the territory to climate change by adopting a socially and technically innovative approach. Stonewalls4life started in the second half of 2019 involving many subjects, both public bodies and privates, in a multidisciplinary workgroup.</p><p>More into details, it will be demonstrated on a specific site measuring 6 hectares (Manarola, Cinque Terre) the climate change adaptation effectiveness of the approach by restoring abandoned drystone terraces, making them more resilient with innovative techniques; at the same time, three additional sites were identified in order to test the approach under different circumstances (two within the same territory, one in Catalonia – Parc del Garraf – with dissimilar conditions). Furthermore, from a scientific point of view, the project will allow to carry out a quantitative and objective assessment of the dry-stone walls effectiveness against extreme rainfall events, through the installation of several multiparameter stations that will record in continuous a set of geo-hydrological parameters associated to walls.</p><p>An extensive and detailed geological and geomorphological survey activity along with GIS analysis and bibliographical research has been carried out in order to create a geological-structural model of the aforementioned site and to identify its geomorphological features. Moreover, an accurate mapping and analysis of dry-stone walls has been performed employing an innovative approach developed in the frame of the project and based on field-surveyed and remotely-sensed data.</p><p>The outcomes represent a solid base for the implementation of the future phases of the project, in particular to understand the relationship among the geological, geomorphological and anthropic features of the area with the terraced-slopes stability in order to develop an accurate management plan concerning the dry-stone walls recovery activity.</p>

Paisaje de interior: estrategias proyectuales para habitar el bancal

ResumenLa acusada orografía española ha llevado a escalonar en bancales numerosas explotaciones agrícolas, configurando paisajes en los que los muros de contención imponen su geometría a la tierra, pero también condicionan la forma en la que estas terrazas han sido habitadas. La construcción vernácula ha proporcionado respuestas diversas a estos condicionantes pero también estos banqueos surgidos de las necesidades del cultivo han inspirado soluciones más recientes, que buscan adaptarse a la pendiente sin necesidad de grandes explanaciones. Este fue el caso de diversas arquitecturas que tras la Guerra Civil plantearon una modernidad que, mirando a la escena internacional, no olvidaba la tradición vernácula en un intento de sentar bases propias. El recinto ferial de la Casa de Campo –erigido en tiempos de escasez en la accidentada periferia madrileña- propició en varios de sus solares el banqueo del terreno para hacer posible el tránsito expositivo, trasladando a un ámbito periurbano elementos más propios de un entorno agrario. Este artículo se propone explorar las soluciones aportadas por el pabellón de los Hexágonos (1958-1959), el pabellón del Ministerio de la Vivienda (1959) y el pabellón de las Bancadas (1962-1965) para acoger un uso expositivo y abordar a la vez el problema de la adaptación a la pendiente mediante construcciones pétreas y estereotómicas ligadas al terreno y entramados ligeros y tectónicos ligados a la cubierta.AbstractSpain’s abrupt topography has fostered the stepped arrangement of many agrarian estates, articulating landscapes where retaining walls shape the ground while they determine the way the site is inhabited. Vernacular construction has provided different solutions to these problems, but terraced slopes have also inspired more recent designs that adapt to the contours of the site avoiding large excavations. That was the case of some of the architecture that emerged after the Spanish Civil War, which looked up at the tenets of international modernism, while resorting to vernacular traditions in order to find its own profile. The Casa de Campo fair grounds, raised on the verge of Madrid in a time of scarcity, provided several sites where terraces were needed to allocate an exhibition program, transferring a characteristic feature of the rural landscape onto the urban periphery. This paper explores the different ways in which the Hexagon pavilion (1958-1959), the Ministerio de la Vivienda pavilion (1959) and the Bancadas pavilion (1962-1965) hosted an exhibition program and adapted to the sloping terrain by means of petrous, stereotomic structures linked to the ground and light, tectonic frames linked to their roofs.

Investigation on Farmland Abandonment of Terraced Slopes Using Multitemporal Data Sources Comparison and Its Implication on Hydro-Geomorphological Processes

This paper presents a quantitative multi-temporal analysis performed in a GIS environment and based on different spatial information sources. The research is aimed at investigating the land use transformations that occurred in a small coastal terraced basin of Eastern Liguria from the early 1950s to 2011. The degree of abandonment of cultivated terraced slopes together with its influence on the distribution, abundance, and magnitude of rainfall-induced shallow landslides were accurately analysed. The analysis showed that a large portion of terraced area (77.4%) has been abandoned over approximately sixty years. This land use transformation has played a crucial role in influencing the hydro-geomorphological processes triggered by a very intense rainstorm that occurred in 2011. The outcomes of the analysis revealed that terraces abandoned for a short time showed the highest landslide susceptibility and that slope failures affecting cultivated zones were characterized by a lower magnitude than those which occurred on abandoned terraced slopes. Furthermore, this study highlights the usefulness of cadastral data in understanding the impact of rainfall-induced landslides due to both a high spatial and thematic accuracy. The obtained results represent a solid basis for the investigation of erosion and the shallow landslide susceptibility of terraced slopes by means of a simulation of land use change scenarios.

Terracing: From Agriculture to Multiple Ecosystem Services

Agricultural terraces are widely spread all over the world and are among the most evident landscape signatures of the human fingerprint, in many cases dating back to several centuries. Agricultural terraces create complex anthropogenic landscapes traditionally built to obtain land for cultivation in steep terrains, typically prone to runoff production and soil erosion, and thus hardly suitable for rain-fed farming practices. In addition to acquiring new land for cultivation, terracing can provide a wide array of ecosystem services, including runoff reduction, water conservation, erosion control, soil conservation and increase of soil quality, carbon sequestration, enhancement of biodiversity, enhancement of soil fertility and land productivity, increase of crop yield and food security, development of aesthetic landscapes and recreational options. Moreover, some terraced areas in the world can be considered as a cultural and historical heritage that increases the asset of the local landscape. Terraced slopes may be prone to failure and degradation issues, such as localized erosion, wall or riser collapse, piping, and landsliding, mainly related to runoff concentration processes. Degradation phenomena, which are exacerbated by progressive land abandonment, reduce the efficiency of benefits provided by terraces. Therefore, understanding the physical processes occurring in terraced slopes is essential to find the most effective maintenance criteria necessary to accurately and adequately preserve agricultural terraces worldwide.