Soil Biodiversity as Affected by Different Thinning Intensities in a Pinus laricio Stand of Calabrian Apennine, South Italy

Forest soil biodiversity, which drives natural ecosystem multifunctionality, can be altered by incorrect forestry management practices. Pinus laricio is the most representative and widespread conifer species in Calabria, South Italy, and appropriate management is needed to maintain Pinus laricio forest for its great economic and natural value. In Europe, thinning is considered the most effective silvicultural treatment to maintain/increase the ecological value of coniferous stands. In this study, moderate thinning (MT), intense thinning (HT), and clear cut (CC) treatments were used to manage Pinus laricio stands with the aim of identifying the thinning intensity that is less detrimental to soil biodiversity. The effects of the different thinning intensities were evaluated, in two contrasting seasons (summer and winter), on the abundance, and diversity of arthropods, fungi, and bacteria colonies as well as on selected soil properties (organic matter, humification index, bulk density, pH) related to soil habitability. Results evidenced that the abundance, species richness, and diversity of arthropods, as well as fungi, bacteria colonies, and soil properties, changed with the treatments and seasons. Under HT, the greatest biodiversity and the highest amounts of arthropods, fungi, and bacteria were found in both seasons. This study finds evidence for Connell’s intermediate disturbance hypothesis, highlighting that the greatest organic carbon content and humification index, as well as the lowest bulk density, found in HT reduced the likelihood of competitive exclusion between occurring species, thereby promoting high species richness and diversity. This study gives insights into ecological relationships between understory composition related to tree species abundance and soil community.

Long-Term Effects of Organic Amendments on Soil Organic Matter Quantity and Quality in Conventional Cropping Systems in Switzerland

Increasing soil organic carbon (SOC) in agroecosystems is a promising solution to simultaneously address climate change mitigation, adaptation, and food security. Yet, the best management practices that could achieve these goals remain to be identified. Here, we analyze the long-term effects of application of green manure, cereal straw, farmyard manure, and cattle slurry on SOC in a 37 year long field experiment in Switzerland. The treatment effects were compared against control conditions that received only optimal mineral fertilization. More specifically, this study aimed at evaluating the effect of organic amendments on SOC accumulation and distribution in different soil particle-size fractions by means of a set of indicators about organic matter quality (biological reactivity, humification index) and microbial activity (extracellular enzyme activities). In the absence of organic matter input, application of mineral fertilizers alone resulted in the lowest SOC content and the highest humification index of the bulk soil organic matter. Among the organic amendments, cereal straw, farmyard manure, and cattle slurry promoted a higher SOC content and a lower humification index due to an increase of SOC in the clay-size fraction. The annual C accrual reached 4.4‰ per year over 37 years with farmyard manure. The higher biological reactivity measured for the green manure and cereal straw amendments was associated with higher soil enzymatic activities, while C retention coefficients decreased by at least 2.5 times compared to animal-derived amendments. The low availability of nutrients in green manure and straw amendments as suggested by the high phosphatase and N-acetylglucosaminidase activities may indicate a reduction in C retention of organic matter inputs due to nutrient microbial mining with plant-derived amendments.

Carbon storage change and δ13C transitions of peat columns in a partially forestry-drained boreal bog

Background and aims In forestry-drained peatlands, drying leads to changes in C cycling which could affect peat δ13C. Furthermore, the δ13C profile of the entire peat column may reveal effects of earlier climatic periods. Methods We measured peat δ13C and C inventories in adjacent peat profiles, two collected from undrained and two from the drained side of a bog that was partially ditch-drained 37 years earlier. The cores were sliced into 10-cm subsamples for analyses; matching of the profiles based on surface levelling, peat stratigraphic correlation and a horizontal ash layer found in both profiles. Results Surface subsidence of 30 cm was observed in the dried site and the uppermost 160 cm in the undrained site contained an excess of 5.9 kg m−2 of C compared with the corresponding strata of the ditch-drained site. The δ13C values increased but markedly only in the thin surface layer of the drained site, indicating low δ13C of the missing C (ca. –30‰). In the deeper strata, dating to Mid-Holocene, high dry bulk density, C%, N%, humification index and low C/N ratio were connected to low δ13C of peat. Conclusions Drainage of 37 years increased δ13C values in the upper peat profile of the drained bog and led to the selective loss of 13C depleted C. Results indicate that C balance studies can be aided by C isotope analyses. Low δ13C values in the peat profile indicate the existence of a wet fen stage during the moist and warm period during Mid-Holocene.

Role of Crop Rotations in the Dynamic of Soil Organic Matter Pools

Soil organic matter is considered a key attribute for a sustainable agricultural production and is influenced by the quantity and quality of the crop residue deposited on the soil surface. Therefore, different crop rotations could change the soil organic matter pools. The objectives of this study were to evaluate the soil carbon pools obtained by chemical and physical fractionation methods and the humification index under different crop rotations in a no-till system. We test the following hypothesis: a) the distribution of C and N among the soil organic matter fractions depends on plant species rotation schemes and; b) labile fractions are more sensitive to the input of crop residues and therefore, more suitable for evaluating the impact of different crop rotations in the soil organic matter quality. We evaluated four crop sequences (corn/corn/corn; corn/wheat/corn; soybean/wheat/corn and soybean/corn/corn) in a no-till system. A five-year reforested area was used as reference. We determined the total C and N contents, the mineral-associated C and N, the light fraction of C and N, the labile carbon extracted with KMnO4 and the soil organic matter humification index. We found narrow differences between the crop rotation systems in the total C and N levels, the mineral-associated C and N fractions and the labile C extracted with KMnO4. The diversification of the agricultural system with soybean in crop rotation favored the accumulation of light fraction C and N in the soil that were more efficient to provide information about the changes in the soil organic matter quality.

Effect of Salmonella on Decomposition of Poultry Litter

Chicken litter is a significant source of nutrients for production of crops and to reduce the impact of human pathogens on environment. The physicochemical properties of poultry litter mixture compost was assessed against the maturity and stability indices such as carbon nitrogen ratio (C/N), nitrate (NO3), ammonia (NH3), ash, Cation Exchange Capacity (CEC), Humification Index (HI), Humification Rate (HR) and Degree of Polymerization (DP). The use of Salmonella significantly improves the humification process and physicochemical properties of final compost product are better in comparison to control trial. The most prominent effects was the fast rise in temperature from mesophilic to thermophilic stage was accompanied by an increase in NH4+-N that gradually decrease near the maturation phase. Moreover, the decrease in carbon and nitrogen ratio and increase in DP, CEC, HI, HR, phosphorous and potassium was also observed. A significant correlation was found between the maturity and stability parameters like C: N ratio, cation exchange capacity, humification index, degree of polymerization, humification rate and nitrate. Therefore, it is acclaimed that isolated microorganisms Salmonella from poultry litter promote the stable compost formation.

Effect of Phanerochaete chrysosporium on the Characteristics of Humic Substances during Composting of Agricultural Wastes

The effect ofPhanerochaete chrysosporium(Pc) on the characteristics of humic substances (HS) was investigated during composting of agricultural wastes. The dynamic changes of HS, fulvic acid (FA), humic acid (HA) and the humification index (HI) were monitored during a 60-day composting. The results showed that the formation of FA was not obviously influenced, while HA formation was improved by the inoculum ofPc. During the composting process, HI increased from 0.28, 0.29 to 2.23 and 3.17 in the control and the treatment, respectively. This result indicated thatPccould significantly enhance the degree of HS aromatization (P<0.05). This research helps to know the contribution ofPcto the formation of HS during composting and provide some useful information for the development of efficient methods to increase the content of HS in the composting.

Characterization of dissolved organic matter in watersheds of Lake Biwa and Lake Kasumigaura by excitation-emission matrix fluorescence spectroscopy and application of humification index

The objectives of this research were to characterize dissolved organic matter (DOM) by excitation-emission matrix (EEM) fluorescence spectroscopy and to apply humification index (HIX) to differentiate the origin and extent of humification of DOMs in watersheds of Lake Biwa and Lake Kasumigaura, Japan. EEM and HIX techniques were applied to lacustrine, riverine, and effluent organic matters. EEM spectra suggest that algal activity and the thermocline formation are critical to composition and distribution of DOM in Lake Biwa. Lake Kasumigaura DOM is evenly distributed over the lake. The effects of allochthonous sources are more conclusive for Lake Kasumigaura DOM than for Lake Biwa DOM. Seasonal and vertical variations in HIX were observed in Lake Biwa similar to results by EEM approach. Upstream DOMs were mostly humified fulvic acid originating from forest soil. DOM from a paddy field and municipal wastewater had the lowest HIX value and consisted mainly of less humified, fresh organic materials. Lacustrine and effluent DOMs demonstrated the same extent of humification in watersheds of Lake Biwa and Lake Kasumigaura. Allochthonous sources such as elution from a paddy field and municipal wastewater are more responsible for the composition of Lake Kasumigaura DOM compared to that of Lake Biwa DOM.