Giuliano Bonanomi | Università degli Studi di Napoli "Federico II" (original) (raw)
Papers by Giuliano Bonanomi
Positive plant-soil feedback by ''ecosystem engineers'' is an important driver for the structurin... more Positive plant-soil feedback by ''ecosystem engineers'' is an important driver for the structuring and organization of resource-limited ecosystems. Although ample evidence demonstrates that plant-soil feedbacks can range from positive to strongly negative, their co-occurrence in plant communities have not yet been investigated. We test the hypothesis that the plant-soil feedback generated by the nitrogen-fixer shrub Medicago marina during primary succession in a sand dune community has a positive effect on the coexisting grass Lophochloa pubescens and a negative effect on the shrub species itself. We conducted field measurements and laboratory bioassays to evaluate (1) the effects of islands of fertility on the recruitment and growth of its ecosystem engineer and on the performance of a coexisting species and (2) the mechanisms involved that can explain the opposite effects of islands of fertility on coexisting species. Islands of fertility were present under Medicago crowns evidenced by higher available nitrogen, extractable phosphorus and potassium, organic matter, microbial activity, water holding capacity, soil humidity, and lower salt concentrations. The effects of these islands of fertility were clearly species-specific, with a facilitative impact on Lophochloa and a negative effect on Medicago recruitment. Lophochloa was denser and produced more biomass when rooted inside as compared to outside the crown area of the shrub. Contrarily, the number of seedlings of Medicago was lower inside, despite the higher seed abundance, and higher outside the crown area of adult shrubs as compared to predictions based on random distribution, thus showing a Janzen-Connell distribution. Laboratory experiments demonstrate the occurrence of Medicago negative plant-soil feedback, and that the auto-toxicity of the aboveground senescent plant material is a potentially important underlying mechanism explaining this negative feedback and the resulting Janzen-Connell distribution in the field.
Plant Ecology
Plants alter environmental conditions enhancing the recruitment of other species. In spite of pri... more Plants alter environmental conditions enhancing the recruitment of other species. In spite of prior reviews of facilitation, the variability of its occurrence, mechanisms, and specificity across terrestrial ecosystems has not yet been assessed. In this article, we analyze facilitative mechanisms and the distribution of specific traits, such as nitrogen fixation and the presence of fleshy fruits, across ecosystems. A comprehensive database including 2,080 cases of facilitation among higher plants from 539 articles was analyzed with descriptive statistics for occurrences of positive interactions and underlying mechanisms in different terrestrial ecosystems. Positive interactions by plant-induced environmental changes are widespread in a range of ecosystems and not limited to conditions of chronic abiotic stress such as semiarid, alpine, and wetland ecosystems. The capability to act as nurse largely varied among different growth forms, and was observed more frequently for woody than for herbaceous plants. Nitrogen fixers occur much more frequently as nurse plants than as beneficiary plants in facilitation cases due to increasing soil fertility. As known for Mediterranean ecosystems, fleshy-fruited species appear more dependent on facilitative interactions than other plants, being more frequent among beneficiaries than among nurses. The pattern can be extended worldwide being consistent in wetland, temperate, and alpine ecosystems as well. Our description of the relationship between distribution, mechanisms, and specificity of facilitation in terrestrial ecosystems has implications for the understanding of plant community organization considering that plant nursing capacity is affected by their size, architecture, and life span.
Applied Soil Ecology, 2011
A new process-based model of litter decomposition, characterized by detailed climatic data input ... more A new process-based model of litter decomposition, characterized by detailed climatic data input and simple litter quality parameters, is proposed. Compared to existing litter carbon models, specific implementations for temperature and moisture limiting effects have been adopted. The model is capable to represent decomposition processes in Mediterranean ecosystems, with summer drought slowing down, even at optimal temperatures, the litter decay rates of sclerophyll plants whose leaf masses are rich in structural compounds and low in N content. The model was calibrated by a best fitting procedure of two different datasets. First, unpublished results of litterbag experiments on leaf litter of 9 Mediterranean species, decomposing under controlled and not limiting temperature and water conditions, have been used to estimate the decay rate dependency from litter quality that was defined by only three initial C pools (labile, stable and recalcitrant compounds) instead of traditional N-based indices. Second, a set of published data from three medium-term field experiments on a single species, Phillyrea angustifolia, decomposing under different climatic conditions, have been used to estimate the limiting effects of temperature and moisture. The model was then validated against published data on seven other species and showed a correct reproduction of the major patterns of litter mass loss during decomposition processes of other seven different Mediterranean species. The model simulations, satisfactory for different litter types under a wide range of climatic conditions, suggest that factors which were not taken into account, such as initial litter N contents, microclimatic variations related to stand structure, soil chemistry and texture, and microbial communities, are not very significant for assessing decomposition dynamics in Mediterranean ecosystems. The minimal requirements of input data, the simple structure, and the easiness of parameterisation make our model, among the many other available litter carbon models, an attractive alternative for different research purposes, at least for Mediterranean ecosystems.
Oikos, 2005
S. 2005. Negative plant Á/soil feedback and species coexistence. Á/ Oikos 111: 311 Á/321.
Plant Ecology, 2005
Increasing evidence shows that facilitative interaction and negative plant-soil feedback are driv... more Increasing evidence shows that facilitative interaction and negative plant-soil feedback are driving factors of plant population dynamics and community processes. We studied the intensity and the relative impact of negative feedback on clonal growth and seed germination of Scirpus holoschoenus, a 'ring' forming sedge dominant in grazed grassland, and the consequences for species coexistence. The structure of aboveground tussocks was described. A Lithium tracer assessed belowground distribution of functional roots. Seed rain and seedling emergence were compared for different positions in relation to Scirpus tussocks. Soil bioassays were used to compare growth on soil taken from inside and outside Scirpus tussocks of four coexisting species (Mentha acquatica, Pulicaria dysenterica, Scirpus holoschoenus and Dittrichia viscosa). We also compared plant performance of dominant plant species inside and outside Scirpus tussocks in the field. The 'ring' shaped tussocks of S. holoschoenus were generated by centrifugal rhizome development. Roots were functional and abundant under the tillers and extending outside the tussocks. The large roots mats that were present in the inner tussock zone were almost all dead. Seedling emergence and growth both showed a strong negative feedback of Scirpus in the inner tussock zone. Scirpus clonal development strongly reduced grass biomass. In the degenerated tussock zone, Pulicaria and Mentha mortality was lower, and biomass of individual plants and seed production were higher. This positive indirect interaction could be related to species-specific affinity to soil conditions generated by Scirpus, and interspecific competitive release in the degenerated tussock zone. We conclude that Scirpus negative feedback affects its seedling emergence and growth contributing to the development of the degenerated inner tussock zone. Moreover, this enhances species coexistence through facilitative interaction because the colonization of the inner tussock zone is highly species-specific.
Plant Ecology, 2008
Positive plant-soil feedback by “ecosystem engineers” is an important driver for the structuring ... more Positive plant-soil feedback by “ecosystem engineers” is an important driver for the structuring and organization of resource-limited ecosystems. Although ample evidence demonstrates that plant-soil feedbacks can range from positive to strongly negative, their co-occurrence in plant communities have not yet been investigated. We test the hypothesis that the plant-soil feedback generated by the nitrogen-fixer shrub Medicago marina during primary succession in a sand dune community has a positive effect on the coexisting grass Lophochloa pubescens and a negative effect on the shrub species itself. We conducted field measurements and laboratory bioassays to evaluate (1) the effects of islands of fertility on the recruitment and growth of its ecosystem engineer and on the performance of a coexisting species and (2) the mechanisms involved that can explain the opposite effects of islands of fertility on coexisting species. Islands of fertility were present under Medicago crowns evidenced by higher available nitrogen, extractable phosphorus and potassium, organic matter, microbial activity, water holding capacity, soil humidity, and lower salt concentrations. The effects of these islands of fertility were clearly species-specific, with a facilitative impact on Lophochloa and a negative effect on Medicago recruitment. Lophochloa was denser and produced more biomass when rooted inside as compared to outside the crown area of the shrub. Contrarily, the number of seedlings of Medicago was lower inside, despite the higher seed abundance, and higher outside the crown area of adult shrubs as compared to predictions based on random distribution, thus showing a Janzen-Connell distribution. Laboratory experiments demonstrate the occurrence of Medicago negative plant-soil feedback, and that the auto-toxicity of the aboveground senescent plant material is a potentially important underlying mechanism explaining this negative feedback and the resulting Janzen-Connell distribution in the field.
Biological Control, 2011
Peat is the most common organic material used for the preparation of potting mix because of its h... more Peat is the most common organic material used for the preparation of potting mix because of its homogeneous and favorable agronomic characteristics. However, this organic material is poorly suppressive against soilborne pathogens and fungicides are routinely used to manage damping-off diseases. In the present study, we investigated the suppressive capability of five compost -peat mixtures towards the plant pathogens Pythium ultimum, Rhizoctonia solani and Sclerotinia minor -Lepidium sativum pathosystems. For all organic media, 18 parameters were measured including enzymatic activities (glucanase, N-acetylglucosaminidase, chitobiosidase and hydrolysis of fluorescein diacetate), microbiological (BIOLOG Ò Eco-Plates™, culturable bacteria and fungi), and chemical features (pH, EC, total, extractable and humic carbon, total and organic N, NH 4 -N, total protein and water content). In addition, 13 C-CPMAS-NMR spectroscopy was used to characterize the organic materials. Peat amended with composts reduced disease dampingoff caused by P. ultimum, R. solani and S. minor in 60% of the mixtures and compost derived from animal manure showed the largest and most consistent disease suppression. Sterilization decreased or eliminated suppressiveness of 42.8% of the mixtures. The most useful parameters to predict disease suppression were different for each pathogen: extractable carbon, O-aryl C and C/N ratio for P. ultimum, alkyl/O-alkyl ratio, N-acetyl-glucosaminidase and chitobiosidase enzymatic activities for R. solani and EC for S. minor. Our results demonstrate that the addition of composts to peat could be useful for the control of soilborne pathogens.
Plants during their life cycles interact with a large diversity of microbial species. To simultan... more Plants during their life cycles interact with a large diversity of microbial species. To simultaneously manage symbiotic, competitive and pathogenic interactions, plants rely on their chemical compounds which are capable to recognize, coordinate and regulate the exchange of resources and information with the myriads of potentially interacting microbes. This chapter deals with plant-microbe interactions mediated by natural products and focuses on their role, chemical nature and ecological significance. Particular attention is devoted to role of natural compounds in the cross-talk between plants and beneficial microbes like vesicular-arbuscular mycorrhizal fungi, bacteria inducing legume nodulation and plant-growth promoting rhizobacteria. The role of plant natural compounds with antimicrobial activity against pathogenic bacteria, fungi and oomycetes is also reviewed. Finally, we discuss the potential applications of natural products and future directions of studies including the use of new experimental approaches and techniques such as metagenomics, proteomics, microscopy, isotope labeling and NMR microspectrophotometry.
Community Ecology, 2007
Diversity of forest trees ranges from monospecific stands to the astonishing richness of tierra f... more Diversity of forest trees ranges from monospecific stands to the astonishing richness of tierra firma tropical forests. Such patterns are observed along gradients of latitude, altitude, soil fertility and rainfall. So far, the proposed coexisting mechanisms do not provide a comprehensive and unequivocal explanation of these patterns at the community level. We propose a new theory linking species diversity with organic matter cycle and negative plant-soil feedback induced by litter autotoxicity. This approach focuses on resource-waste rather than resource-only dynamics. High diversity does occur where litter decomposition is rapid and ecosystem nutrient cycles are closed. On the other hand, single species dominance is found where litter decomposition is slow and/or autotoxicity is removed from the nutrient cycle pathway. Unlike previous theoretical views, the one we present proves potentially capable of explaining differences in species diversity both along environmental gradients and within the tropics.
Fusarium oxysporum f.sp. lycopersici (FOL) induces wilting in tomato plants (Lycopersicon esculen... more Fusarium oxysporum f.sp. lycopersici (FOL) induces wilting in tomato plants (Lycopersicon esculentum). This disease causes large losses and it increases when practices include monoculture or limited crop rotation. Under these conditions, large quantities of tomato plant residues decompose in the field and may affect growth of tomato and FOL and their interactions. Here we show that undecomposed tomato residues are phytotoxic in laboratory and greenhouse bioassays and that leaves are more phytotoxic than roots. During decomposition, phytotoxicity of leaves and roots decreases under aerobic conditions, but increases under anaerobic conditions. On the contrary, FOL radial growth and hyphal density are increased by undecomposed leaves and roots, but decreased with aerobically decomposed plant material. Tomato wilting caused by FOL increased when the soil was amended with undecomposed leaves. Our study shows that, under controlled conditions, undecomposed tomato residues affect the growth of tomato (autotoxic effect) and FOL (substrate effect), by causing an increase in incidence of the disease.
Ecological Modelling, 2010
Current theories may not fully explain why latitudinal patterns of plant diversity differ between... more Current theories may not fully explain why latitudinal patterns of plant diversity differ between terrestrial and flooded ecosystems. Moreover, the co-occurrence of hyper diverse stands in lowland tierra firma (not inundated) forests and almost monospecific stands in mangroves and gallery riparian vegetation within the tropics remains enigmatic. Building on evidence from ecology and agriculture, we present a new model investigating the hypothesis that, besides the general positive feedback of plant growth by nutrients release, litter decomposition builds up an intra-specific negative feedback functionally linked with tree diversity. The model results were compared with extensive published data sets both across and within latitudinal zones. The model predicts correctly the biomass production and decomposition process, as well as the number of tree species, their relative abundance in all environmental conditions providing a novel, putative explanation also for the diversity variations observed within the tropics. The model demonstrates a possible mechanistic link between the carbon cycle and biodiversity patterns, which is interesting in the debate about advancing in the direction of a unifying ecosystem theory.
New Phytologist, 2006
Allelopathic effects of plant litter have been extensively studied, but less attention has been g... more Allelopathic effects of plant litter have been extensively studied, but less attention has been given to the dynamics of phytotoxicity during the decomposition processes.
Soil Biology & Biochemistry, 2008
The application of soil solarization (SS), one of the most promising techniques for the control o... more The application of soil solarization (SS), one of the most promising techniques for the control of soilborne pathogens, is seriously limited by the drawback regarding the disposal of the used plastic materials. A possible solution to this problem is the use of biodegradable plastics. The aim of this study was to make comparisons between the impact of SS performed with biodegradable materials and that of SS with plastic films and other pest management techniques (i.e. organic matter amendment, calcium cyanamide and Dazomet fungicide application) on crop productivity, soilborne disease incidence, weed suppression, and soil chemical (total N, NH 4 -N, nitrate, available phosphorus, organic matter, hydrolysis of fluorescein diacetate) and microbial (cultivable Pseudomonas, DGGE fingerprinting of bacterial 16S-and fungal 28S rRNA gene fragments from total soil community DNA) parameters. We carried out field experiments in two types of soil with different textures (clay and sand) artificially inoculated with Fusarium oxysporum f.sp. lycopersici (vs. tomato) and Sclerotinia minor (vs. lettuce). The temperature of soils covered with solarizing materials was always higher than that of bare soils, but plastic cover was more effective and consistent in rising soil temperature compared to biodegradable materials. Plant growth promotion by SS was limited, especially compared to Dazomet and organic matter applications, and a positive effect was observed only for lettuce in the clay soil. Differently, both plastic and biodegradable solarizing materials were effective in reducing lettuce drop caused by S. minor. Weed development was significantly suppressed by Dazomet application and SS with plastic film, while control with biodegradable materials was limited. SS had a variable and limited effect on chemical and microbial parameters, with a general tendency to reduce richness of bacteria and fungi. Dazomet caused the most pronounced reduction of the microbial community diversity in both soil types and a significant stimulation of the fluorescent Pseudomonas group. Organic amendment significantly enhanced the organic matter content, the hydrolysis of fluorescein diacetate and the Pseudomonas population. Among all measured soil parameters, the size of the fluorescent Pseudomonas population emerged as the most important factor affecting crop productivity. The results of this experimentation show the potential of using biodegradable solarizing materials in place of plastic films, but also indicate the need for improving their properties to obtain performances comparable to those of other pest management techniques.
Acta Oecologica-international Journal of Ecology, 2006
Semi-natural grassland Species diversity Brachypodium rupestre A B S T R A C T Semi-natural grass... more Semi-natural grassland Species diversity Brachypodium rupestre A B S T R A C T Semi-natural grassland communities are of great interest in conservation because of their high species richness. These communities are being threatened by both land abandonment and nitrogen eutrophication, and their continued existence will depend upon correct management. However, there is a distinct lack of studies of the ecological mechanisms that regulate species diversity and productivity in Mediterranean grasslands. We have conducted a 3-year field experiment in a species-poor grassland in central Italy to investigate the effects of nitrogen fertilization coupled with removal of plant litter and artificial cutting on species diversity and community productivity. Vegetation cutting reduced living biomass but increased species diversity. In fact, cutting had positive effects on the cover of almost all of the annual and biennial species, while it had a negative effect on the dominant perennial grasses Brachypodium rupestre and Dactylis glomerata. Litter removal had similar effects to cutting, although it was far less effective in increasing species diversity. In contrast, nitrogen enrichment strongly increased the living biomass while maintaining very low species diversity. Our results have indicated that seminatural Mediterranean grasslands need specific management regimes for maintenance and restoration of species diversity. In the management of these grasslands, attention should be paid to the potential threat from nitrogen enrichment, especially when coupled with land abandonment. av a i l a bl e a t w w w. s c i e n c e d i r e c t . c o m j o u r n a l h o m ep a g e : w w w. e l s ev i e r. c o m / l o c a t e / a c t o e c
Applied Soil Ecology, 2011
Concerns about groundwater contamination as well as pesticide residues in food and soil have fuel... more Concerns about groundwater contamination as well as pesticide residues in food and soil have fuelled vigorous debates about the sustainability of chemical-intensive agriculture. Search has been prompted for agronomic strategies with lower environmental hazards. In this multidisciplinary study we compared the characteristics of soils from 20 agricultural farms selected in five geographical areas of Southern Italy with different soil types. In each farm, fields with management regime classified as high-input (HIMR, intensive cultivation under plastic tunnels) or low-input (LIMR, tree orchards) were selected. Soil samples were analyzed for 31 parameters including physical and chemical properties (bulk density, water holding capacity, texture, pH, limestone, electrical conductivity, organic C to a depth of 0-20 and 20-40 cm, total N, P 2 O 5 , Ca 2+ , Mg 2+ , K + , Na + , cation exchange capacity), enzymatic activities (dehydrogenase, arylsulphatase, -glucosidase, phosphatase and urease) and microbiological features (potential respiration, functional diversity of microbial populations by BIOLOG EcoPlates TM , microbial biomass, fungal mycelium, culturable actinomycetes, bacteria and fungi, pseudomonads and bacterial species richness by 16S rDNA-DGGE). Finally, a soil bioassay was performed in order to evaluate the plant growth of a biotest plant (Lactuca sativa) and soil suppressiveness of the Rhizoctonia solani-L. sativa pathosystem.
Plant and Soil, 2010
In the last decade a great research effort addressed the effects of litter diversity on ecosystem... more In the last decade a great research effort addressed the effects of litter diversity on ecosystem functions, reporting both synergistic and antagonistic effects for decomposition dynamics. Four coexisting Mediterranean species, representing a range of litter quality, were used to arrange litter mixtures at three diversity levels for a litterbag decomposition experiment. Species identity appeared as the major determinant for litter mass loss (Coronilla emerus∼Hedera helix>Festuca drymeia>Quercus ilex) and nutrient release, with rates for all leaf litter types following the sequence K>N>Mg≥Ca>>Fe. Additive diversity effects were prevalent pooling together all data but also for nutrients separately. Antagonistic interactions were more common than synergistic in the cases of mass loss, N and Ca contents, but not for K, Mg and Fe dynamics. The number of species in the litterbag significantly affected the outcome of non-additive interactions, which were mostly antagonistic for two-species mixtures, and synergistic for the combined 4 species. Litter quality appears to be the most important factor affecting mass loss and nutrient dynamics, while litter diversity, influencing the rates of these processes, plays an important role in reducing their variability, thus suggesting a greater stability of ecosystems properties in presence of mixed litter.
The use of organic matter (OM) has been proposed, for both conventional and biological agricultur... more The use of organic matter (OM) has been proposed, for both conventional and biological agriculture systems, to decrease the incidence of plant diseases caused by soilborne pathogens. In this work we review reports on the application of OM amendments, focusing on the suppressive capacity of different OM materials and the response of different soilborne pathogens. A total of 250 articles were analysed, with 2423 experimental case studies. The effect of OM amendments was found to be suppressive in 45% and non-significant in 35% of the cases. In 20% of the cases, a significant increase of disease incidence was observed. Compost was the most suppressive material, with more than 50% of cases showing effective disease control. The effect of crop residues was more variable: it was suppressive in 45% of the cases, but enhanced disease in 28%. Finally, significant disease suppression with peat was recorded only in 4% of the experiments. The ability of OM to suppress disease varied largely with different pathogens: it was observed in more than 50% of the cases for Verticillium, Thielaviopsis, Fusarium and Phytophthora. In contrast, effective control of Rhizoctonia solani was achieved only in 26% of the cases. From this review it emerged that OM amendments have great potential but, at the same time, present some inconsistencies in their application. More investigation on the mechanisms by which OM acts on disease suppression is needed to make the use of these materials more predictable.
Phytochemistry, 2007
Three saponins, named minutoside A (1), minutoside B (2), minutoside C (3), and two known sapogen... more Three saponins, named minutoside A (1), minutoside B (2), minutoside C (3), and two known sapogenins, alliogenin and neoagigenin, were isolated from the bulbs of Allium minutiflorum Regel. Elucidation of their structure was carried out by comprehensive spectroscopic analyses, including 2D NMR spectroscopy and mass spectrometry. The structures of the new compounds were identified as
Positive plant-soil feedback by ''ecosystem engineers'' is an important driver for the structurin... more Positive plant-soil feedback by ''ecosystem engineers'' is an important driver for the structuring and organization of resource-limited ecosystems. Although ample evidence demonstrates that plant-soil feedbacks can range from positive to strongly negative, their co-occurrence in plant communities have not yet been investigated. We test the hypothesis that the plant-soil feedback generated by the nitrogen-fixer shrub Medicago marina during primary succession in a sand dune community has a positive effect on the coexisting grass Lophochloa pubescens and a negative effect on the shrub species itself. We conducted field measurements and laboratory bioassays to evaluate (1) the effects of islands of fertility on the recruitment and growth of its ecosystem engineer and on the performance of a coexisting species and (2) the mechanisms involved that can explain the opposite effects of islands of fertility on coexisting species. Islands of fertility were present under Medicago crowns evidenced by higher available nitrogen, extractable phosphorus and potassium, organic matter, microbial activity, water holding capacity, soil humidity, and lower salt concentrations. The effects of these islands of fertility were clearly species-specific, with a facilitative impact on Lophochloa and a negative effect on Medicago recruitment. Lophochloa was denser and produced more biomass when rooted inside as compared to outside the crown area of the shrub. Contrarily, the number of seedlings of Medicago was lower inside, despite the higher seed abundance, and higher outside the crown area of adult shrubs as compared to predictions based on random distribution, thus showing a Janzen-Connell distribution. Laboratory experiments demonstrate the occurrence of Medicago negative plant-soil feedback, and that the auto-toxicity of the aboveground senescent plant material is a potentially important underlying mechanism explaining this negative feedback and the resulting Janzen-Connell distribution in the field.
Plant Ecology
Plants alter environmental conditions enhancing the recruitment of other species. In spite of pri... more Plants alter environmental conditions enhancing the recruitment of other species. In spite of prior reviews of facilitation, the variability of its occurrence, mechanisms, and specificity across terrestrial ecosystems has not yet been assessed. In this article, we analyze facilitative mechanisms and the distribution of specific traits, such as nitrogen fixation and the presence of fleshy fruits, across ecosystems. A comprehensive database including 2,080 cases of facilitation among higher plants from 539 articles was analyzed with descriptive statistics for occurrences of positive interactions and underlying mechanisms in different terrestrial ecosystems. Positive interactions by plant-induced environmental changes are widespread in a range of ecosystems and not limited to conditions of chronic abiotic stress such as semiarid, alpine, and wetland ecosystems. The capability to act as nurse largely varied among different growth forms, and was observed more frequently for woody than for herbaceous plants. Nitrogen fixers occur much more frequently as nurse plants than as beneficiary plants in facilitation cases due to increasing soil fertility. As known for Mediterranean ecosystems, fleshy-fruited species appear more dependent on facilitative interactions than other plants, being more frequent among beneficiaries than among nurses. The pattern can be extended worldwide being consistent in wetland, temperate, and alpine ecosystems as well. Our description of the relationship between distribution, mechanisms, and specificity of facilitation in terrestrial ecosystems has implications for the understanding of plant community organization considering that plant nursing capacity is affected by their size, architecture, and life span.
Applied Soil Ecology, 2011
A new process-based model of litter decomposition, characterized by detailed climatic data input ... more A new process-based model of litter decomposition, characterized by detailed climatic data input and simple litter quality parameters, is proposed. Compared to existing litter carbon models, specific implementations for temperature and moisture limiting effects have been adopted. The model is capable to represent decomposition processes in Mediterranean ecosystems, with summer drought slowing down, even at optimal temperatures, the litter decay rates of sclerophyll plants whose leaf masses are rich in structural compounds and low in N content. The model was calibrated by a best fitting procedure of two different datasets. First, unpublished results of litterbag experiments on leaf litter of 9 Mediterranean species, decomposing under controlled and not limiting temperature and water conditions, have been used to estimate the decay rate dependency from litter quality that was defined by only three initial C pools (labile, stable and recalcitrant compounds) instead of traditional N-based indices. Second, a set of published data from three medium-term field experiments on a single species, Phillyrea angustifolia, decomposing under different climatic conditions, have been used to estimate the limiting effects of temperature and moisture. The model was then validated against published data on seven other species and showed a correct reproduction of the major patterns of litter mass loss during decomposition processes of other seven different Mediterranean species. The model simulations, satisfactory for different litter types under a wide range of climatic conditions, suggest that factors which were not taken into account, such as initial litter N contents, microclimatic variations related to stand structure, soil chemistry and texture, and microbial communities, are not very significant for assessing decomposition dynamics in Mediterranean ecosystems. The minimal requirements of input data, the simple structure, and the easiness of parameterisation make our model, among the many other available litter carbon models, an attractive alternative for different research purposes, at least for Mediterranean ecosystems.
Oikos, 2005
S. 2005. Negative plant Á/soil feedback and species coexistence. Á/ Oikos 111: 311 Á/321.
Plant Ecology, 2005
Increasing evidence shows that facilitative interaction and negative plant-soil feedback are driv... more Increasing evidence shows that facilitative interaction and negative plant-soil feedback are driving factors of plant population dynamics and community processes. We studied the intensity and the relative impact of negative feedback on clonal growth and seed germination of Scirpus holoschoenus, a 'ring' forming sedge dominant in grazed grassland, and the consequences for species coexistence. The structure of aboveground tussocks was described. A Lithium tracer assessed belowground distribution of functional roots. Seed rain and seedling emergence were compared for different positions in relation to Scirpus tussocks. Soil bioassays were used to compare growth on soil taken from inside and outside Scirpus tussocks of four coexisting species (Mentha acquatica, Pulicaria dysenterica, Scirpus holoschoenus and Dittrichia viscosa). We also compared plant performance of dominant plant species inside and outside Scirpus tussocks in the field. The 'ring' shaped tussocks of S. holoschoenus were generated by centrifugal rhizome development. Roots were functional and abundant under the tillers and extending outside the tussocks. The large roots mats that were present in the inner tussock zone were almost all dead. Seedling emergence and growth both showed a strong negative feedback of Scirpus in the inner tussock zone. Scirpus clonal development strongly reduced grass biomass. In the degenerated tussock zone, Pulicaria and Mentha mortality was lower, and biomass of individual plants and seed production were higher. This positive indirect interaction could be related to species-specific affinity to soil conditions generated by Scirpus, and interspecific competitive release in the degenerated tussock zone. We conclude that Scirpus negative feedback affects its seedling emergence and growth contributing to the development of the degenerated inner tussock zone. Moreover, this enhances species coexistence through facilitative interaction because the colonization of the inner tussock zone is highly species-specific.
Plant Ecology, 2008
Positive plant-soil feedback by “ecosystem engineers” is an important driver for the structuring ... more Positive plant-soil feedback by “ecosystem engineers” is an important driver for the structuring and organization of resource-limited ecosystems. Although ample evidence demonstrates that plant-soil feedbacks can range from positive to strongly negative, their co-occurrence in plant communities have not yet been investigated. We test the hypothesis that the plant-soil feedback generated by the nitrogen-fixer shrub Medicago marina during primary succession in a sand dune community has a positive effect on the coexisting grass Lophochloa pubescens and a negative effect on the shrub species itself. We conducted field measurements and laboratory bioassays to evaluate (1) the effects of islands of fertility on the recruitment and growth of its ecosystem engineer and on the performance of a coexisting species and (2) the mechanisms involved that can explain the opposite effects of islands of fertility on coexisting species. Islands of fertility were present under Medicago crowns evidenced by higher available nitrogen, extractable phosphorus and potassium, organic matter, microbial activity, water holding capacity, soil humidity, and lower salt concentrations. The effects of these islands of fertility were clearly species-specific, with a facilitative impact on Lophochloa and a negative effect on Medicago recruitment. Lophochloa was denser and produced more biomass when rooted inside as compared to outside the crown area of the shrub. Contrarily, the number of seedlings of Medicago was lower inside, despite the higher seed abundance, and higher outside the crown area of adult shrubs as compared to predictions based on random distribution, thus showing a Janzen-Connell distribution. Laboratory experiments demonstrate the occurrence of Medicago negative plant-soil feedback, and that the auto-toxicity of the aboveground senescent plant material is a potentially important underlying mechanism explaining this negative feedback and the resulting Janzen-Connell distribution in the field.
Biological Control, 2011
Peat is the most common organic material used for the preparation of potting mix because of its h... more Peat is the most common organic material used for the preparation of potting mix because of its homogeneous and favorable agronomic characteristics. However, this organic material is poorly suppressive against soilborne pathogens and fungicides are routinely used to manage damping-off diseases. In the present study, we investigated the suppressive capability of five compost -peat mixtures towards the plant pathogens Pythium ultimum, Rhizoctonia solani and Sclerotinia minor -Lepidium sativum pathosystems. For all organic media, 18 parameters were measured including enzymatic activities (glucanase, N-acetylglucosaminidase, chitobiosidase and hydrolysis of fluorescein diacetate), microbiological (BIOLOG Ò Eco-Plates™, culturable bacteria and fungi), and chemical features (pH, EC, total, extractable and humic carbon, total and organic N, NH 4 -N, total protein and water content). In addition, 13 C-CPMAS-NMR spectroscopy was used to characterize the organic materials. Peat amended with composts reduced disease dampingoff caused by P. ultimum, R. solani and S. minor in 60% of the mixtures and compost derived from animal manure showed the largest and most consistent disease suppression. Sterilization decreased or eliminated suppressiveness of 42.8% of the mixtures. The most useful parameters to predict disease suppression were different for each pathogen: extractable carbon, O-aryl C and C/N ratio for P. ultimum, alkyl/O-alkyl ratio, N-acetyl-glucosaminidase and chitobiosidase enzymatic activities for R. solani and EC for S. minor. Our results demonstrate that the addition of composts to peat could be useful for the control of soilborne pathogens.
Plants during their life cycles interact with a large diversity of microbial species. To simultan... more Plants during their life cycles interact with a large diversity of microbial species. To simultaneously manage symbiotic, competitive and pathogenic interactions, plants rely on their chemical compounds which are capable to recognize, coordinate and regulate the exchange of resources and information with the myriads of potentially interacting microbes. This chapter deals with plant-microbe interactions mediated by natural products and focuses on their role, chemical nature and ecological significance. Particular attention is devoted to role of natural compounds in the cross-talk between plants and beneficial microbes like vesicular-arbuscular mycorrhizal fungi, bacteria inducing legume nodulation and plant-growth promoting rhizobacteria. The role of plant natural compounds with antimicrobial activity against pathogenic bacteria, fungi and oomycetes is also reviewed. Finally, we discuss the potential applications of natural products and future directions of studies including the use of new experimental approaches and techniques such as metagenomics, proteomics, microscopy, isotope labeling and NMR microspectrophotometry.
Community Ecology, 2007
Diversity of forest trees ranges from monospecific stands to the astonishing richness of tierra f... more Diversity of forest trees ranges from monospecific stands to the astonishing richness of tierra firma tropical forests. Such patterns are observed along gradients of latitude, altitude, soil fertility and rainfall. So far, the proposed coexisting mechanisms do not provide a comprehensive and unequivocal explanation of these patterns at the community level. We propose a new theory linking species diversity with organic matter cycle and negative plant-soil feedback induced by litter autotoxicity. This approach focuses on resource-waste rather than resource-only dynamics. High diversity does occur where litter decomposition is rapid and ecosystem nutrient cycles are closed. On the other hand, single species dominance is found where litter decomposition is slow and/or autotoxicity is removed from the nutrient cycle pathway. Unlike previous theoretical views, the one we present proves potentially capable of explaining differences in species diversity both along environmental gradients and within the tropics.
Fusarium oxysporum f.sp. lycopersici (FOL) induces wilting in tomato plants (Lycopersicon esculen... more Fusarium oxysporum f.sp. lycopersici (FOL) induces wilting in tomato plants (Lycopersicon esculentum). This disease causes large losses and it increases when practices include monoculture or limited crop rotation. Under these conditions, large quantities of tomato plant residues decompose in the field and may affect growth of tomato and FOL and their interactions. Here we show that undecomposed tomato residues are phytotoxic in laboratory and greenhouse bioassays and that leaves are more phytotoxic than roots. During decomposition, phytotoxicity of leaves and roots decreases under aerobic conditions, but increases under anaerobic conditions. On the contrary, FOL radial growth and hyphal density are increased by undecomposed leaves and roots, but decreased with aerobically decomposed plant material. Tomato wilting caused by FOL increased when the soil was amended with undecomposed leaves. Our study shows that, under controlled conditions, undecomposed tomato residues affect the growth of tomato (autotoxic effect) and FOL (substrate effect), by causing an increase in incidence of the disease.
Ecological Modelling, 2010
Current theories may not fully explain why latitudinal patterns of plant diversity differ between... more Current theories may not fully explain why latitudinal patterns of plant diversity differ between terrestrial and flooded ecosystems. Moreover, the co-occurrence of hyper diverse stands in lowland tierra firma (not inundated) forests and almost monospecific stands in mangroves and gallery riparian vegetation within the tropics remains enigmatic. Building on evidence from ecology and agriculture, we present a new model investigating the hypothesis that, besides the general positive feedback of plant growth by nutrients release, litter decomposition builds up an intra-specific negative feedback functionally linked with tree diversity. The model results were compared with extensive published data sets both across and within latitudinal zones. The model predicts correctly the biomass production and decomposition process, as well as the number of tree species, their relative abundance in all environmental conditions providing a novel, putative explanation also for the diversity variations observed within the tropics. The model demonstrates a possible mechanistic link between the carbon cycle and biodiversity patterns, which is interesting in the debate about advancing in the direction of a unifying ecosystem theory.
New Phytologist, 2006
Allelopathic effects of plant litter have been extensively studied, but less attention has been g... more Allelopathic effects of plant litter have been extensively studied, but less attention has been given to the dynamics of phytotoxicity during the decomposition processes.
Soil Biology & Biochemistry, 2008
The application of soil solarization (SS), one of the most promising techniques for the control o... more The application of soil solarization (SS), one of the most promising techniques for the control of soilborne pathogens, is seriously limited by the drawback regarding the disposal of the used plastic materials. A possible solution to this problem is the use of biodegradable plastics. The aim of this study was to make comparisons between the impact of SS performed with biodegradable materials and that of SS with plastic films and other pest management techniques (i.e. organic matter amendment, calcium cyanamide and Dazomet fungicide application) on crop productivity, soilborne disease incidence, weed suppression, and soil chemical (total N, NH 4 -N, nitrate, available phosphorus, organic matter, hydrolysis of fluorescein diacetate) and microbial (cultivable Pseudomonas, DGGE fingerprinting of bacterial 16S-and fungal 28S rRNA gene fragments from total soil community DNA) parameters. We carried out field experiments in two types of soil with different textures (clay and sand) artificially inoculated with Fusarium oxysporum f.sp. lycopersici (vs. tomato) and Sclerotinia minor (vs. lettuce). The temperature of soils covered with solarizing materials was always higher than that of bare soils, but plastic cover was more effective and consistent in rising soil temperature compared to biodegradable materials. Plant growth promotion by SS was limited, especially compared to Dazomet and organic matter applications, and a positive effect was observed only for lettuce in the clay soil. Differently, both plastic and biodegradable solarizing materials were effective in reducing lettuce drop caused by S. minor. Weed development was significantly suppressed by Dazomet application and SS with plastic film, while control with biodegradable materials was limited. SS had a variable and limited effect on chemical and microbial parameters, with a general tendency to reduce richness of bacteria and fungi. Dazomet caused the most pronounced reduction of the microbial community diversity in both soil types and a significant stimulation of the fluorescent Pseudomonas group. Organic amendment significantly enhanced the organic matter content, the hydrolysis of fluorescein diacetate and the Pseudomonas population. Among all measured soil parameters, the size of the fluorescent Pseudomonas population emerged as the most important factor affecting crop productivity. The results of this experimentation show the potential of using biodegradable solarizing materials in place of plastic films, but also indicate the need for improving their properties to obtain performances comparable to those of other pest management techniques.
Acta Oecologica-international Journal of Ecology, 2006
Semi-natural grassland Species diversity Brachypodium rupestre A B S T R A C T Semi-natural grass... more Semi-natural grassland Species diversity Brachypodium rupestre A B S T R A C T Semi-natural grassland communities are of great interest in conservation because of their high species richness. These communities are being threatened by both land abandonment and nitrogen eutrophication, and their continued existence will depend upon correct management. However, there is a distinct lack of studies of the ecological mechanisms that regulate species diversity and productivity in Mediterranean grasslands. We have conducted a 3-year field experiment in a species-poor grassland in central Italy to investigate the effects of nitrogen fertilization coupled with removal of plant litter and artificial cutting on species diversity and community productivity. Vegetation cutting reduced living biomass but increased species diversity. In fact, cutting had positive effects on the cover of almost all of the annual and biennial species, while it had a negative effect on the dominant perennial grasses Brachypodium rupestre and Dactylis glomerata. Litter removal had similar effects to cutting, although it was far less effective in increasing species diversity. In contrast, nitrogen enrichment strongly increased the living biomass while maintaining very low species diversity. Our results have indicated that seminatural Mediterranean grasslands need specific management regimes for maintenance and restoration of species diversity. In the management of these grasslands, attention should be paid to the potential threat from nitrogen enrichment, especially when coupled with land abandonment. av a i l a bl e a t w w w. s c i e n c e d i r e c t . c o m j o u r n a l h o m ep a g e : w w w. e l s ev i e r. c o m / l o c a t e / a c t o e c
Applied Soil Ecology, 2011
Concerns about groundwater contamination as well as pesticide residues in food and soil have fuel... more Concerns about groundwater contamination as well as pesticide residues in food and soil have fuelled vigorous debates about the sustainability of chemical-intensive agriculture. Search has been prompted for agronomic strategies with lower environmental hazards. In this multidisciplinary study we compared the characteristics of soils from 20 agricultural farms selected in five geographical areas of Southern Italy with different soil types. In each farm, fields with management regime classified as high-input (HIMR, intensive cultivation under plastic tunnels) or low-input (LIMR, tree orchards) were selected. Soil samples were analyzed for 31 parameters including physical and chemical properties (bulk density, water holding capacity, texture, pH, limestone, electrical conductivity, organic C to a depth of 0-20 and 20-40 cm, total N, P 2 O 5 , Ca 2+ , Mg 2+ , K + , Na + , cation exchange capacity), enzymatic activities (dehydrogenase, arylsulphatase, -glucosidase, phosphatase and urease) and microbiological features (potential respiration, functional diversity of microbial populations by BIOLOG EcoPlates TM , microbial biomass, fungal mycelium, culturable actinomycetes, bacteria and fungi, pseudomonads and bacterial species richness by 16S rDNA-DGGE). Finally, a soil bioassay was performed in order to evaluate the plant growth of a biotest plant (Lactuca sativa) and soil suppressiveness of the Rhizoctonia solani-L. sativa pathosystem.
Plant and Soil, 2010
In the last decade a great research effort addressed the effects of litter diversity on ecosystem... more In the last decade a great research effort addressed the effects of litter diversity on ecosystem functions, reporting both synergistic and antagonistic effects for decomposition dynamics. Four coexisting Mediterranean species, representing a range of litter quality, were used to arrange litter mixtures at three diversity levels for a litterbag decomposition experiment. Species identity appeared as the major determinant for litter mass loss (Coronilla emerus∼Hedera helix>Festuca drymeia>Quercus ilex) and nutrient release, with rates for all leaf litter types following the sequence K>N>Mg≥Ca>>Fe. Additive diversity effects were prevalent pooling together all data but also for nutrients separately. Antagonistic interactions were more common than synergistic in the cases of mass loss, N and Ca contents, but not for K, Mg and Fe dynamics. The number of species in the litterbag significantly affected the outcome of non-additive interactions, which were mostly antagonistic for two-species mixtures, and synergistic for the combined 4 species. Litter quality appears to be the most important factor affecting mass loss and nutrient dynamics, while litter diversity, influencing the rates of these processes, plays an important role in reducing their variability, thus suggesting a greater stability of ecosystems properties in presence of mixed litter.
The use of organic matter (OM) has been proposed, for both conventional and biological agricultur... more The use of organic matter (OM) has been proposed, for both conventional and biological agriculture systems, to decrease the incidence of plant diseases caused by soilborne pathogens. In this work we review reports on the application of OM amendments, focusing on the suppressive capacity of different OM materials and the response of different soilborne pathogens. A total of 250 articles were analysed, with 2423 experimental case studies. The effect of OM amendments was found to be suppressive in 45% and non-significant in 35% of the cases. In 20% of the cases, a significant increase of disease incidence was observed. Compost was the most suppressive material, with more than 50% of cases showing effective disease control. The effect of crop residues was more variable: it was suppressive in 45% of the cases, but enhanced disease in 28%. Finally, significant disease suppression with peat was recorded only in 4% of the experiments. The ability of OM to suppress disease varied largely with different pathogens: it was observed in more than 50% of the cases for Verticillium, Thielaviopsis, Fusarium and Phytophthora. In contrast, effective control of Rhizoctonia solani was achieved only in 26% of the cases. From this review it emerged that OM amendments have great potential but, at the same time, present some inconsistencies in their application. More investigation on the mechanisms by which OM acts on disease suppression is needed to make the use of these materials more predictable.
Phytochemistry, 2007
Three saponins, named minutoside A (1), minutoside B (2), minutoside C (3), and two known sapogen... more Three saponins, named minutoside A (1), minutoside B (2), minutoside C (3), and two known sapogenins, alliogenin and neoagigenin, were isolated from the bulbs of Allium minutiflorum Regel. Elucidation of their structure was carried out by comprehensive spectroscopic analyses, including 2D NMR spectroscopy and mass spectrometry. The structures of the new compounds were identified as