Long-Term Application of Biochar Mitigates Negative Plant-Soil Feedback by Shaping Arbuscular Mycorrhizal Fungi and Fungal Pathogens.

Negative plant-soil feedback (PSF) arises when localized accumulations of pathogens reduce the growth of conspecifics, whereas positive PSF can occur due to the emergence of mutualists. Biochar, a carbon-rich material produced by the pyrolysis of organic matter, has been shown to modulate soil microbial communities by altering their abundance, diversity, and activity. For this reason, to assess the long-term impact of biochar on soil microbiome dynamics and subsequent plant performance, we conducted a PSF greenhouse experiment using field soil conditioned over 10 years with Vitis vinifera (L.), without (e.g., C) or with biochar at two rates (e.g., B and BB). Subsequently, the conditioned soil was employed in a response phase involving either the same plant species or different species, i.e., Medicago sativa (L.), Lolium perenne (L.), and Solanum lycopersicum (L.). We utilized next-generation sequencing to assess the abundance and diversity of fungal pathogens and arbuscular mycorrhizal fungi (AMF) within each conditioned soil. Our findings demonstrate that biochar application exerted a stimulatory effect on the growth of both conspecifics and heterospecifics. In addition, our results show that untreated soils had a higher abundance of grape-specialized fungal pathogens, mainly Ilyonectria liriodendra, with a relative abundance of 20.6% compared to 2.1% and 5.1% in B and BB, respectively. Cryptovalsa ampelina also demonstrated higher prevalence in untreated soils, accounting for 4.3% compared to 0.4% in B and 0.1% in BB. Additionally, Phaeoacremonium iranianum was exclusively present in untreated soils, comprising 12.2% of the pathogens' population. Conversely, the application of biochar reduced generalist fungal pathogens. For instance, Plenodomus biglobosus decreased from 10.5% in C to 7.1% in B and 2.3% in BB, while Ilyonectria mors-panacis declined from 5.8% in C to 0.5% in B and 0.2% in BB. Furthermore, biochar application was found to enrich the AMF community. Notably, certain species like Funneliformis geosporum exhibited increased relative abundance in biochar-treated soils, reaching 46.8% in B and 70.3% in BB, compared to 40.5% in untreated soils. Concurrently, other AMF species, namely Rhizophagus irregularis, Rhizophagus diaphanus, and Claroideoglomus drummondii, were exclusively observed in soils where biochar was applied. We propose that the alleviation of negative PSF can be attributed to the positive influence of AMF in the absence of strong inhibition by pathogens. In conclusion, our study underscores the potential of biochar application as a strategic agricultural practice for promoting sustainable soil management over the long term.

Changes in the pattern of polycyclic aromatic hydrocarbons in soil treated with biochar from a multiyear field experiment.

The influence of biochar added to an agricultural soil on polycyclic aromatic hydrocarbon (PAH) levels, PAH diagnostic ratios and soil properties was investigated in a five-year field experiment. The experiment was carried out in an Italian vineyard and included two biochar treatments: 16.5 t ha-1 of biochar applied in 2009 (soil B); 16.5 t ha-1 in 2009 and further 16.5 t ha-1 in 2010 (soil BB). A set of 75 samples that included five replicates and a control soil (untreated) was characterized in terms of organic carbon, pH, cation exchange capacity (CEC), bulk density and concentration of PAHs. Biochar addition to soil caused an increase in organic carbon, pH and CEC, and a decrease of bulk density. After almost two years the first application of biochar, PAH concentrations were higher in soil B (56 ng g-1) and BB (153 ng g-1) in comparison to control soil (24 ng g-1). Thereafter, PAH concentrations decreased significantly, but the original PAHs levels were reached only in soil B after five years. The naphthalene/(naphthalene + phenanthrene) ratios were higher in the treated soils in accordance to the dominance of naphthalene in the original biochar. The cross plots naphthalene/(naphthalene + phenanthrene) vs. fluoranthene/(fluoranthene + pyrene) enabled to trace the signature of biochar PAHs up to five years after its first application. Diagnostic ratios can be a useful tool to study the persistence of PAHs introduced in soil by biochar when the pattern of these contaminants in biochar and original soil are different.

Fate of Soil Organic Carbon and Polycyclic Aromatic Hydrocarbons in a Vineyard Soil Treated with Biochar.

The effect of biochar addition on the levels of black carbon (BC) and polcyclic aromatic hydrocarbons (PAHs) in a vineyard soil in central Italy was investigated within a two year period. Hydropyrolysis (HyPy) was used to determine the contents of BC (BCHyPy) in the amended and control soils, while the hydrocarbon composition of the semi-labile (non-BCHyPy) fraction released by HyPy was determined by gas chromatography-mass spectrometry, together with the solvent-extractable PAHs. The concentrations of these three polycyclic aromatic carbon reservoirs changed and impacted differently the soil organic carbon over the period of the trial. The addition of biochar (33 ton dry biochar ha(-1)) gave rise to a sharp increase in soil organic carbon, which could be accounted for by an increase in BCHyPy. Over time, the concentration of BCHyPy decreased significantly from 36 to 23 mg g(-1) and as a carbon percentage from 79% to 61%. No clear time trends were observed for the non-BCHyPy PAHs varying from 39 to 34 µg g(-1) in treated soils, not significantly different from control soils. However, the concentrations of extractable PAHs increased markedly in the amended soils and decreased with time from 153 to 78 ng g(-1) remaining always higher than those in untreated soil. The extent of the BCHyPy loss was more compatible with physical rather than chemical processes.

Comparing integrated stable isotope and eddy covariance estimates of water-use efficiency on a Mediterranean successional sequence.

Water-use efficiency (WUE), thought to be a relevant trait for productivity and adaptation to water-limited environments, was estimated for three different ecosystems on the Mediterranean island of Pianosa: Mediterranean macchia (SMM), transition (S(TR)) and abandoned agricultural (SAA) ecosystems, representing a successional series. Three independent approaches were used to study WUE: eddy covariance measurements, C isotope composition of ecosystem respired CO2, and C isotope discrimination (Δ) of leaf material (dry matter and soluble sugars). Seasonal variations in C-water relations and energy fluxes, compared in S(MM) and in SAA, were primarily dependent on the specific composition of each plant community. WUE of gross primary productivity was higher in SMM than in SAA at the beginning of the dry season. Both structural and fast-turnover leaf material were, on average, more enriched in (13)C in S(MM) than SAA, indicating relatively higher stomatal control and WUE for the long-lived macchia species. This pattern corresponded to (13)C-enriched respired CO2 in SMM compared to the other ecosystems. Conversely, most of the annual herbaceous SAA species (terophytes) showed a drought-escaping strategy, with relatively high stomatal conductance and low WUE. An ecosystem-integrated Δ value was weighted for each ecosystem on the abundance of different life forms, classified according to Raunkiar's system. Agreement was found between ecosystem WUE calculated using eddy covariance and those estimated using integrated Δ approaches. Comparing the isotopic methods, Δ of leaf soluble sugars provided the most reliable proxy for short-term changes in photosynthetic discrimination and associated shifts in integrated canopy-level WUE along the successional series.

CrossVit: enhancing canopy monitoring management practices in viticulture.

A new wireless sensor network (WSN), called CrossVit, and based on MEMSIC products, has been tested for two growing seasons in two vineyards in Italy. The aims are to evaluate the monitoring performances of the new WSN directly in the vineyard and collect air temperature, air humidity and solar radiation data to support vineyard management practices. The WSN consists of various levels: the Master/Gateway level coordinates the WSN and performs data aggregation; the Farm/Server level takes care of storing data on a server, data processing and graphic rendering; Nodes level is based on a network of peripheral nodes consisting of a MDA300 sensor board and Iris module and equipped with thermistors for air temperature, photodiodes for global and diffuse solar radiation, and an HTM2500LF sensor for relative humidity. The communication levels are: WSN links between gateways and sensor nodes by ZigBee, and long-range GSM/GPRS links between gateways and the server farm level. The system was able to monitor the agrometeorological parameters in the vineyard: solar radiation, air temperature and air humidity, detecting the differences between the canopy treatments applied. The performance of CrossVit, in terms of monitoring and reliability of the system, have been evaluated considering: its handiness, cost-effective, non-invasive dimensions and low power consumption.

ASPIS, A Flexible Multispectral System for Airborne Remote Sensing Environmental Applications.

Airborne multispectral and hyperspectral remote sensing is a powerful tool for environmental monitoring applications. In this paper we describe a new system (ASPIS) composed by a 4-CCD spectral sensor, a thermal IR camera and a laser altimeter that is mounted on a flexible Sky-Arrow airplane. A test application of the multispectral sensor to estimate durum wheat quality is also presented.

Physiological and morphological responses of grassland species to elevated atmospheric CO2 concentrations in FACE-systems and natural CO2 springs.

Stomatal density, leaf conductance and water relations can be affected by an increase in the concentration of atmospheric CO2, and thus affect plant productivity. However, there is uncertainty about the effects of elevated CO2 on stomatal behaviour, water relations and plant productivity, owing to the lack of long-term experiments in representative natural ecosystems. In this work, variations in stomatal density and index, leaf water relations and plant biomass of semi-natural grassland communities were analysed under field conditions by comparing plants in three different experimental set-ups (natural CO2 springs, plastic tunnels and mini-FACE systems). Natural degassing vents continuously expose the surrounding vegetation to truly long-term elevated CO2 and can complement short-term manipulative experiments. Elevated CO2 concentration effects on stomata persist in the long term, though different species growing in the same environment show species-specific responses. The general decrease in stomatal conductance after exposure to elevated CO2 was not associated with clear changes in stomatal number on leaf surfaces. The hypothesis of long-term adaptive modifications to stomatal number and distribution of plants exposed to elevated CO2 was not supported by these experiments on grassland communities. Elastic cell wall properties were affected to some extent by elevated CO2. Above-ground biomass did not vary between CO2 treatments, leaf area index did not compensate for reduced stomatal conductance, and the root system had potentially greater soil exploration capacity. Considerable between-species variation in response to elevated CO2 may provide a mechanism for changing competitive interactions among plant species.