Organic Carbon and Ecosystem Services in Agricultural Soils of the Mediterranean Basin

Impact of Super-High Density Olive Orchard Management System on Soil Free-Living and Plant-Parasitic Nematodes in Central and South Italy

Simple Summary

Super-high density olive orchards are spreading in Italy to reduce production costs and increase yields per hectare. The objective of this study was to assess the orchards’ effect on the soil nematode community in five sites located in the main Italian olive cultivation areas compared to the adjacent traditional olive orchard system. Super-high density olive orchard management combined with conventional tillage and mineral fertilization decreased total organic carbon compared to traditional management. The soil nematode community was affected by the depletion of organic matter, especially for plant-parasitic nematodes, which increased. Moreover, this investigation evidenced that the Super-high density olive orchard management system could change the soil plant-parasitic nematode composition of olive orchards. In fact, the families Telotylenchidae, Paratylenchidae, Meloidogynidae, and Criconematidae were favored in the Super-high density olive orchard system, while Longidoridae, Heteroderidae, and Pratylenchidae were disadvantaged. However, conservative and sustainable soil management might maintain or improve the soil nematode community functionality and reduce plant-parasitic nematodes.

Abstract

The soil nematode community plays an important role in ecosystem services. The objective of this study was to assess the effect of Super-high density (SHD) olive orchards on the nematode community in five sites with different soils, climates, and cultivars. At each site, the SHD management system was compared to the adjacent olive orchard traditional (TRAD) system, in which the same soil management and phytosanitary measures were applied. Soil management was assessed by total organic carbon content (TOC), while the soil nematode community was evaluated using the nematode taxa abundances and soil nematode indicators. TOC was significantly decreased in the SHD olive orchard system compared to TRAD in the sites characterized by conventional tillage and mineral fertilization. The two-way ANOSIM analysis on nematode abundance showed no difference between the two olive management methods, instead showing only a significant difference per site mainly due to variabilities in plant-parasitic nematode assemblage. However, a negative impact of SHD management was evident in environments stressed by summer droughts and conventional tillage: the ratio of obligate plant-parasites to bacterivores and fungivores (Pp/(B+F)) was significantly higher in SHD than in the TRAD olive orchard system, and the prey-to-predator θ mass ratio showed the lowest values in the sites under organic fertilization or green manure. The canonical correspondence analysis showed that the free-living nematodes were only slightly affected by SHD olive orchards; instead, the presence of plant-parasitic nematodes families such as Telotylenchidae, Paratylenchidae, Meloidogynidae, and Criconematidae was favored, in comparison to Longidoridae, Heteroderidae, and Pratylenchidae.

Family Farming Plays an Essential Role in Preserving Soil Functionality: A Study on Active Managed and Abandoned Traditional Tree Crop-Based Systems

In traditional agricultural areas, where traditional crops (TCs) are cultivated, small farms are still highly represented. Located prevalently in marginal and sensitive areas, agricultural areas have undergone deep transformation. Smallholders have maintained the traditional asset of cultivation (extensive and low input requirement management) only to some extent. In some cases they have adapted traditional orchards into more intensive planting systems. Frequently, they have abandoned agriculture. The land use and management influence soil functions, i.e., the capability of a specific soil to provide key functions in terrestrial ecosystems. In order to assess whether small farms are environmentally sustainable, we used a set of soil quality indicators in three traditional tree crops in the Latium region (central Italy), like hazelnut, grapevine, and Citrus. The soil parameters, chemical, biological, and biochemical, were quantified under three different management models: extensive cultivation, intensive cultivation, and abandonment. The selected set of indicators proved to be able to discriminate adequately between the management models and to be suitable for the soil health assessment. Results proved that hazelnut orchards stored more organic C, independently from farming management, while vineyard showed the lower total organic carbon (TOC). The microbial carbon vs. organic carbon ratio (Cmic-to Corg ratio) was higher for vineyards and Citrus groves, denoting a more active degradation of soil organic matter. Soil enzymes (ESs) involved in C cycle were variable along the different treatments and mainly influenced by the C inputs to soil and soil cover, whereas those involved in N, P, and S cycles were higher in abandoned and extensive TCs. Overall, extensive cultivation performed better in terms of soil quality than intensive or abandonment. This study suggests that a transition to an agriculture based on agroecological principles and toward extensification would provide significant soil-based environmental benefits in marginal sensitive areas.

Short-term effects of land management change linked to cover crop on soil organic carbon in Mediterranean olive grove hillsides

The spatial distribution of soil organic carbon (SOC) is essential to estimate the SOC reserves. Therefore, the soils ability to store organic carbon is a key factor for climate regulation and for other soil functions. The soil management and the topographic position play an important role in SOC variation, especially when the landscape is not uniform (Mediterranean areas). Many researches have explored the SOC distribution according to topographic position in hillsides for long-term, but very few studies have focused on the short term. Therefore, it is necessary to know, the changes that taking place in the soil due to land management change (LMC) in these irregular surfaces for sustainable agricultural production and its implications on climate change regulation. This study aims to assess the influence of topographic position and LMC on SOC stock (SOC-S) in Mediterranean olive groves (OG) soils in short term (2 years). In this line, three experimental plots were selected in three topographical position (summit - S, backslope - B and toeslope - T). In these plots, the land management was modified from conventional tillage (CT) to no tillage (NT) with application of pruned olive branch chippings branches and vegetation cover (spontaneous vegetation) in the OG streets. The studied soils did not show important changes due to LMC in their physical properties for short term, in addition, these soils were characterized by low organic matter content (<1.2%). LMC caused a SOC reduction in surface, and a SOC increase in the Bw horizon. The N concentrations showed a similar trend to SOC and the C:N ratios were highly variable (4.37: C horizon-NT-S; 13.45 Bw/C horizon -CT-B). Normally, the SOC-S concentrations decreasing in depth. LMC for two years showed soil carbonization (S and T position) and decarbonization (B position) processes. The SOC-S increased 1.88 Mg ha^-1 y^-1 and 0.47 Mg ha^-1 y^-1 for S and T topographic position respectively, however the SOC-S decreased in B position 5.27 Mg ha^-1 y^-1. Therefore, LMC has a positive effect on soil carbon reserves in S and T position, conversely in B position, this effect was negative.

A Holistic View of Soils in Delivering Ecosystem Services in Forests: A Case Study in South Korea

In 1955, after the Korean War, only 35% of the national land area in South Korea was covered by forests. In the 1960s, the Korean Government implemented the national forestation program in order to increase the extent of the forest surface and thereby counteract the negative ecological consequences from deforestation, such as erosion and ground instability. According to previous studies, this led to an increase in carbon (C) accumulated in the forest biomass of 1.48 Gt CO2 (0.40 Gt C) in the period 1954–2012. However, these studies did not take into account the amount of soil organic carbon (SOC) that was accumulated during that period and the influence of management practices on soil ecosystem services. Currently, South Korean authorities are considering the idea of implementing some forest management practices in order to increase timber extraction (e.g., by reducing the cutting age of the trees or by applying thinning and tending measures). In this study, we assess the influence of these management regimes on SOC dynamics and propose a theoretical framework to assess the influence of forest management practices on three ecosystem services, namely, C sequestration, water supply, and biomass production, while considering soil functioning, and especially SOC, as a group of supporting services underpinning the three named ecosystem services. We find that, in terms of SOC sequestration, reducing the cutting age from 80 to 40 years would be suitable only in the case of high biomass production forests, whereas in the case of lower biomass production forests reducing the cutting age would achieve very low SOC levels. However, we propose that increasing tree species diversity, even though it would not lead to a direct increase in the SOC content, could help to lessen the negative effects of reducing the cutting age by improving other soil properties, which in turn positively affect soil functioning (e.g., soil biodiversity, nutrient availability) and the resilience of the forest ecosystem. Finally, we discuss potential policy approaches to incentivize sustainable management practices in South Korean forests from a soil protection perspective.

Assessing Spatial and Temporal Variability for Some Edaphic Characteristics of Mediterranean Rainfed and Irrigated Soils

Mediterranean soils are particularly threatened by salinization and low levels of organic matter content. In order to assess an edaphic sustainable use, we need to study its characteristics and better understand the temporal and spatial evolution. In this study, a total of 14,852 ha located in a western Mediterranean basin were selected as the study site where 1417 and 1451 topsoil samples were analyzed in 2001/2002 and 2011/2012, respectively, for Soil Organic Matter (SOM) content, pH water (pHw) and electrical conductivity (EC). Classical statistics and geostatistics techniques were used and the individual soil samples were related with the cultural system (CS) practiced–rainfed/irrigation–and the Reference Soil Group (RSG)–Cambisols, Calcisols, Luvisols, and Fluvisols. Predictive maps were created by interpolation using the Ordinary Kriging algorithm. The main results of this study were that, when transitioning from a rainfed to irrigation CS, SOM content is maintained in Cambisols but decreases in the other RSGs, pHw is maintained and EC increases in Fluvisols, Luvisols, and Cambisols. Over time in the rainfed CS all RSGs maintained SOM and pHw but EC increased in Fluvisols, Luvisols, and Calcisols and in the irrigation CS SOM decreased in Luvisols, pHw increased in Fluvisols and Calcisols and EC increased in all RSGs.