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SUMMARY: Compared with annual crop cultivation, tree groves might represent a relevant land‐use system to improve C sequestration, but few data are available to support this hypothesis. To evaluate the potential of olive tree (Olea europaea L., 1753) cultivation to store soil organic C (SOC), we assessed (i) the distribution of organic C in active (water‐extractable and particulate organic C, WEOC and POC, respectively), intermediate (organic matter associated with stable sand‐size aggregates and silt‐ and clay‐size aggregates, SSAs and SCAs, respectively) and passive (organic matter resistant to oxidation, rSOM) pools, (ii) the phenol content of the C pools, (iii) the humic‐C distribution of the intermediate C pool and (iv) the stocks of SOC pools in two olive groves of different age (7 years (OG7) and 30 years (OG30)) compared with a nearby site with cereal crops (arable soil, AS). In OG30 the organic C stock of the olive grove was no different from that of the AS, but the distribution of SOC pools changed with the age of the olive groves. The WEOC and POC increased in the Ap horizon of OGs, probably because of the herbaceous cover and distribution of chipped prunings on the soil. There were fewer SSAs in OG7 than AS, possibly because of pedoturbations from deep tillage before the olive trees were established, but they increased in OG30. The increase in SSAs and SCAs in the Bw and BC horizons of OG30 was associated with humic‐C and unextractable‐C and a smaller phenol content than AS. This suggested that the olive tree roots had a positive role through rhizodeposition and root turnover, which favoured the stabilization of organic matter into aggregates at depth. In contrast to the active and intermediate C pools, the passive C pool did not vary following the change in land use from arable to olive grove. HIGHLIGHTS: Effects of land‐use change from arable to olive grove on soil organic C pools and stocks. Soil organic C stock increased from 7‐ to 30‐year‐old olive orchard. Olive tree cultivation affected active and intermediate C pools, but not the passive C pool. After 30 years, the olive grove stored an amount of SOC similar to that of the arable system.

Agricultural soils generally have a low content of organic matter, which affects soil fertility and hence crop yields. The use of olive pomace as an organic amendment could enhance soil properties due to its high content of organic matter and exchangeable cations as well as its extensive availability. However, little is known about the potentially detrimental effects of salts and high content of phenolic substances that might occur over time with the use of pomace amendment in agricultural soils. Similarly, its impact on microbial communities and enzyme activities is largely unknown. To ascertain these effects, we tested the response of soil enzyme activities (β-glucosidase, urease, acid phosphomonoesterase and dehydrogenase) starting from a long-term (8-year) previously amended soil and a control (non-amended) soil and exposing these soils to a short-term (12-week) laboratory experiment. We also focused on soil organic matter and mineral N, on relating enzymatic data to bacterial and fungal biomasses, and on an index for soil functional quality based on enzyme activities (AI3). Our results show that organic matter, enzyme activities and the soil quality index were improved by long-term treatment with olive pomace, contrasting with scant effects from short-term laboratory incubation. In spite of its high content in salts and phenolic substances, no detectable negative impact emerged from the use of this amendment. Overall, olive pomace clearly increased soil organic matter and improved soil biological activity and quality, without any detectable negative effects.

Summary Intensive agricultural systems negatively affect soil quality principally because of a reduction in soil organic matter (OM). Sustainable practices providing organic amendments could be useful to maintain or increase OM content in agricultural soils, preserving and improving soil fertility. In this study, biomass with a large C:N ratio was applied to intensively farmed agricultural soils to maximize the increase of soil OM and hence chemical and biochemical fertility. In particular, 30 and 60 t ha−1 of two mixtures of compost and scraps from poplar pruning, A1 and A2, with different C:N ratios (15 and 25, respectively), were applied to soils of two farms (F1 and F2) in a Mediterranean area (southern Italy) on an annual basis for two consecutive years. An effective, long-lasting increase of soil OM, on average of 60 and 55% in F1 and F2 soils, respectively, was reached at the end of the experiment. As well as a progressive increase in the C:N ratio, total N and available P also increased with organic amendments, with positive effects on soil microbial activity as demonstrated by the enhancement of the seven studied enzymatic activities. Principal component analysis demonstrated different responses to various organic amendments between F1 and F2 soils because of their geopedological diversity. The results indicate that the C:N ratio of the mixture is an important factor, but what is the best rate of addition to use is still not obvious. The use of a smaller amount (30 t ha−1) of the A1 mixture (10:1 compost:wood) appears, in these types of soils, to be the most suitable strategy to produce significant benefits.

The impact of different land use types on soil quality was evaluated by measuring several soil properties that are sensitive to stress or disturbance and by using two synthetic approaches, i.e. a numerical quality index and multivariate analysis. A Minimum Data Set of soil indicators was selected including physical (texture, bulk density and water holding capacity), chemical (pH, cation exchange capacity, electrical conductivity, organic carbon, total and mineral nitrogen, available K, Ca, Mg, P contents and total Cd, Cr, Cu, Pb and Zn contents) and biological (microbial biomass, fungal mycelium, soil potential respiration and potentially mineralizable nitrogen) parameters. These parameters were assayed on soil samples collected with seasonal frequency (except for physical parameters, determined only in autumn) in an area of Southern Italy under different land use types (i.e. permanent crops, grazing lands, shrublands, coniferous and mixed forests). Moreover, for most of the land use types, a further distinction on the basis of topographic position (hill, middle-hill and plain) was carried out. Annual means of the data (except for texture) were used to calculate a soil quality index (SQI) and elaborated by multivariate analyses (Cluster Analysis and Principal Component Analysis, PCA) in order to distinguish among different soil quality classes. Data indicated a clear difference in soil quality among the studied areas: low soil quality (SQI < 0.55) in almost all permanent crops; intermediate soil quality (0.55 < SQI < 0.70) in shrublands, grazing lands, coniferous forest and middle-hill olive grove (the only crop with an herb layer on the soil surface); high soil quality (SQI > 0.70) in mixed forests. Results suggested that the permanent crop management had generally a strong negative impact on soil quality, while the moderate grazing activity and the crop management that leaves an herb cover on the soil had a lower negative impact. Nevertheless, the abandonment of cultivated lands, with consequent development of shrublands, produced an improvement of soil quality suggesting a good recovery capacity in the studied soil. © 2009 Elsevier B.V. All rights reserved.

Soil microbial activities and chemical properties related to the N cycle were investigated in function of variations in plant cover type in a Mediterranean area of Southern Italy. Several biological (microbial biomass, soil respiration, protease activity, degradation of 7 amino acids, net N mineralization, net nitrification, potential net nitrification and denitrification) and chemical properties (water content, pH, organic C, total and mineral N, C/N ratio) were determined in soil samples collected in spring and early autumn under three plant cover types (high maquis, low shrub community and meadow) epitomizing distinct successional stages following disturbance. Water content, organic C and C/N ratio were higher in soil from high maquis than in soils from the other plant cover types; in contrast, no difference was generally observed between the three soil types as for total and mineral N content. Likewise, no clear-cut difference was recorded for most of the tested biological parameters if these were expressed per unit of soil dry weight, with the exception of protease activity and soil respiration, which were significantly higher in the high maquis. However, when biological data were expressed per unit of organic C, meadow soil showed higher values of microbial biomass, asparagine degradation (only in spring), net mineralization and net nitrification (only in autumn) compared to the other soils. Statistical analysis pointed to seasonal fluctuation of water availability as an important limiting factor for microbial biomass and activity, with the exceptions of net N mineralization, net nitrification, glutamine and glutamic acid degradation activities which appeared to be mainly driven by organic matter content in soils. Overall, the results suggest that, in the investigated Mediterranean environment, variations in plant community ranging from meadow to high maquis produce little changes in soil biological activities linked to the N cycle, these being primarily affected by the availability of water and soil organic matter during the annual cycle. © 2009 Elsevier B.V. All rights reserved.

The Mediterranean area of Southern Italy is characterized by different natural plant covers that mainly reflect different successional stages (i.e. low maquis, high maquis, Quercus ilex wood) and managed areas with introduced plant species (such as Pinus species). Soil properties could be affected by plant cover types as well as by plant species. Our objective was to determine the relationships of plant cover types and plant species with the chemical and biological characteristics of the soil. In four neighbouring areas with different plant cover types (low maquis, pure high maquis, high maquis with pines and pinewood, with pines planted by foresters in both cases), soil samples were collected under different plant species in order to evaluate the effect of plant cover types and plant species on soil properties. Soil samples were analyzed for nutrient content, microbial biomass, soil potential respiration and enzymatic activity (phosphatase, arylsulphatase, β-glucosidase and hydrolase activities) as well as for pH, water holding capacity (WHC) and cation exchange capacity (CEC). Application of cluster analysis and principal component analysis to the data revealed that the plant cover type was the key factor influencing soil properties more than plant species. In fact, the largest differences were observed between pure high maquis soils and all other soils, with pure high maquis soils generally showing the highest values of WHC, CEC, nutrient content, organic and microbial C, soil respiration, phosphatase, arylsulphatase and β-glucosidase activities. The significantly lower values of these variables in the low maquis relative to the pure high maquis probably reflect the effect of ecological succession on soil. The high maquis with pine, differing from the pure high maquis only for the presence or absence of pine, showed values of soil physical, chemical and biological characteristics similar to those found in the low maquis, thus suggesting that the presence of pine retards soil development. © 2004 Elsevier Ltd. All rights reserved.

In a previous work by one of us (R. Urigu) concerning open quantum systems it was remarked that in processes of the type\(w \to (\bar p_i \bar w_i )\), when evaluating the information entropy of the environment as the Shannon entropy of the outcome probabilities\(\bar p_i \) in the channels\(\bar w_i \), the total information entropy may decrease. We remark here that this decrease is easily excluded by requiring a condition of quantum modelizability of the environment even with respect to Shannon entropy (“cybernetic interpretability” of the environment). Further conditions on the quantum model of the environment are defined (“maximal observability” and “Boolean interpretability”), which are proved to be equivalent, and it turns out that, once satisfied in one model, they also are in any model with pure initial state; furthermore, these conditions turn out to be equivalent to the condition that the process consists of pure operations of the first kind. The relevance to the concept of macroscopicity and to the “von Neumann chain” is discussed.

Processes are considered in which an ensemble of objects interacts with a macroscopic system so as to split into a family of ensembles according to the effects on the macroscopic system (nondestructive measurement with separation of the «channels» being the most familiar example). Whenever the interaction is «pure»,i.e. it transforms every pure state into pure states in all the channels, it is proved in quantum physics and, at least for the «discretized states», in classical physics that the microscopic entropy of the objects that undergo the interaction decreases (or at most remains constant). The resulting situation is discussed with reference to the already known inequalities concerning entropy, which, of course, only related to the special case of perfect nondestructive measurement (ensuring, in particular, that the total entropy, including the entropy of the macroscopic system, increases, or at most remains constant). At the end the results is regarded as expressing a tendency towards decrease of the microscopic entropy of the «microsystems» (i.e., in Ludwig’s terminology, of the quantum systems considered as interacting with the «macrosystems»). A possible relevance to biological processes is remarked.