Enrico Antonio Chiaradia

Root cohesion of forest species in the Italian Alps

Forests can prevent and/or mitigate hydrogeomorphic hazards in mountainous landscapes. Their effect is particularly relevant in the case of shallow landslides phenomena, where plants decrease the water content of the soil and increase its mechanical strength. Although such an effect is well known, its quantification is a relatively new challenge. The present work estimates the effect of some forest species on hillslope stability in terms of additional root cohesion by means of a model based on the classical Wu and Waldron approach (Wu in Alaska Geotech Rpt No 5 Dpt Civ Eng Ohio State Univ Columbus, USA, 1976; Waldron in Soil Sci Soc Am J 41:843–849, 1977). The model is able to account for root distribution with depth and non-simultaneous root breaking. Samples of European beech (Fagus sylvatica L.), Norway spruce (Picea abies (L.) Karst.), European larch (Larix decidua Mill.), sweet chestnut (Castanea sativa Mill.) and European hop-hornbeam (Ostrya carpinifolia Scop.), were taken from different locations of Lombardy (Northern Italy) to estimate root tensile strength, the Root Area Ratio and the root cohesion distribution in the soil. The results show that, in spite of its dramatic variability within the same species at the same location and among different locations, root cohesion can be coherently interpreted using the proposed method. The values herein obtained are significant for slope stabilisation, are consistent with the results of direct shear tests and back-analysis data, and can be used for the estimation of the stability of forested hillslopes in the Alps.

An integrated, multisensor system for the continuous monitoring of water dynamics in rice fields under different irrigation regimes

The cultivation of rice, one of the most important staple crops worldwide, has very high water requirements. A variety of irrigation practices are applied, whose pros and cons, both in terms of water productivity and of their effects on the environment, are not completely understood yet. The continuous monitoring of irrigation and rainfall inputs, as well as of soil water dynamics, is a very important factor in the analysis of these practices. At the same time, however, it represents a challenging and costly task because of the complexity of the processes involved, of the difference in nature and magnitude of the driving variables and of the high variety of field conditions. In this paper, we present the prototype of an integrated, multisensor system for the continuous monitoring of water dynamics in rice fields under different irrigation regimes. The system consists of the following: (1) flow measurement devices for the monitoring of irrigation supply and tailwater drainage; (2) piezometers for groundwater level monitoring; (3) level gauges for monitoring the flooding depth; (4) multilevel tensiometers and moisture sensor clusters to monitor soil water status; (5) eddy covariance station for the estimation of evapotranspiration fluxes and (6) wireless transmission devices and software interface for data transfer, storage and control from remote computer. The system is modular and it is replicable in different field conditions. It was successfully applied over a 2-year period in three experimental plots in Northern Italy, each one with a different water management strategy. In the paper, we present information concerning the different instruments selected, their interconnections and their integration in a common remote control scheme. We also provide considerations and figures on the material and labour costs of the installation and management of the system.

Mapping Soil Water Capacity Through EMI Survey to Delineate Site-Specific Management Units Within an Irrigated Field

Abstract An accurate and high-resolution mapping of soil properties allows optimizing the management of irrigation and fertilization at field scale by applying variable amounts of water and nutrients. Site-specific management (SSM) is fundamental to improve crop yield and to use resources more efficiently, improving environmental sustainability. Adoption of site-specific management practices requires the delineation in the field of subregions with similar soil properties affecting yield (site-specific management units (SSMU)). It is common practice to characterize the spatial variability of soil properties through electromagnetic induction (EMI) surveys to obtain soil electrical conductivity (EC) maps that can be used to delineate SSMU. The objectives of this work, carried out over a uniformly drip-irrigated and fertilized maize, were to (i) delineate SSMU from EC maps; (ii) compare the SSMU inferred from measurements with two different EMI sensors; (iii) map the soil-available water-holding capacity (AWC) from EC maps through a regression model between EC and measured AWC; and (iv) evaluate significant differences of crop yield among the SSMU. The EC maps at increasing depths were processed through principal component analysis, and three SSMU were delineated for both EMI sensors using the Management Zone Analyst software. The significant difference in crop yield across the three SSMU, tested through the analysis of variance, suggested that AWC was the main limiting factor in crop yield. This result highlights the importance of a variable-rate irrigation based on SSMU, which could be a solution to save water and increase crop yield.

A Probabilistic 3-D Slope Stability Analysis for Forest Management

A 3-D physical-based approach to slope stability has been proven to be very promising in order to provide reliable spatially distributed landslides maps. Over large areas, however, such an approach still presents some limitations, mainly related to the variability and the uncertainty of the input parameters. By combining a 3-D physical-based model with a Monte Carlo technique, such constraints can be overcome, improving the performance and the applicability of the method. Whereas uncertainties of geotechnical, morphological and hydrological parameters have been widely investigated, few studies have been focused on the variability of root reinforcement, which plays a crucial role in preventing shallow landslides in forested areas. To contribute to define the effect of different forest management strategies on slope stability, we developed a 3-D model able to properly take into account for the effect of the root systems into the soil. The main objectives of our study are: (i) to define a probability distribution function for the root reinforcement according to the forest stands characteristics (tree density, mean diameter at breast height, minimum distance between trees), (ii) to obtain a probability distribution of the Factor of Safety through the combination between a 3-D slope stability model and a Monte Carlo simulation technique, and (iii) to evaluate the difference between several forest management scenarios in terms of shallow landslide risk. The model has been applied to a small Alpine area, mainly covered by coniferous forest and characterized by steep slopes and a high landslide hazard. Our findings contribute to provide forest managers with useful information for understanding the consequences of different forestry strategies.

Comparing EM38 and Profiler-EMP400 for the Delineation of Homogeneous Management Zones within Agricultural Fields

The improvement in crop yield, both in quantity and quality, depends on the adoption of appropriate management strategies for the agronomic and irrigation practices. The adoption of site-specific (SS) management practices is fundamental, not only to improve crop yield, but also for a more efficient use of resources, increasing the environmental sustainability of the agricultural production The SS management requires the delineation of sub-regions with similar yield limiting factors or similar soil properties affecting yield (Site Specific Management Units – SSMU). It is a common practice in precision agriculture (PA) to characterize the spatial variability of soil properties, measuring the soil electrical conductivity through non-invasive electro-magnetic (EM) sensors to obtain high-resolution soil maps for the delineation of SSMUs. Because of the expanding use in the future of the multi-frequency EM sensors in order to more effectively assess the soil variability, the objective of this work is to compare the measurements collected by Geonics EM38 (the most widely used EM sensor in PA) and GSSI Profiler-EMP400 (a multi-frequency EM sensor) in order to assess their reliability to delineate SSMUs. The data from 2-D electrical resistivity imaging were used to compare the response of the two different sensors to soil variability.