Grazing impact on soil chemical and biological properties under different plant cover types in a mountain area of Southern Italy.

Grazing can contribute to soil degradation by compaction due to roaming of livestock and loss of herbaceous cover, affecting also soil microbial community. Aim of this study was to assess grazing impact on soil microbial community and nutrient status under different plant cover types (i.e., fernery, chestnut wood, garigue). Grazed and ungrazed soils were analysed for water holding capacity, pH, organic carbon, N, S, K, Mg, Fe, Mn, Zn and Cu content, microbial biomass, fungal mycelium and potential respiration. Moreover, some ecophysiological indices, as microbial quotient, coefficient of endogenous mineralization (CEM), metabolic quotient (qCO2) and fungal fraction of microbial carbon were calculated. The results of present study showed that a moderate intensity grazing had low or no impact on chemical characteristics of soils and affects microbial community mainly in grazed areas with lower vegetation cover and lower content of nutrient and organic carbon, compared to areas with a thick layer of vegetation

Litter Inhibitory Effects on Soil Microbial Biomass, Activity, and Catabolic Diversity in Two Paired Stands of Robinia pseudoacacia L. and Pinus nigra Arn.

Research Highlights: Plant cover drives the activity of the microbial decomposer community and affects carbon (C) sequestration in the soil. Despite the relationship between microbial activity and C sequestration in the soil, potential inhibition of soil microbial activity by plant cover has received little attention to date. Background and Objectives: Differences in soil microbial activity between two paired stands on soil at a very early stage of formation and a common story until afforestation, can be traced back to the plant cover. We hypothesized that in a black locust (Robinia pseudoacacia L.) stand the high-quality leaf litter of the tree, and that of the blackberry (Rubus fruticosus L.) understory had an inhibitory effect on soil microbial community resulting in lower mineralization of soil organic matter compared to the paired black pine (Pinus nigra Arn.) stand. Materials and Methods: We estimated potential mineralization rates (MR), microbial (MB), and active fungal biomass (AFB) of newly-shed litter, forest floor, and mineral soil. We tested the effects of litters' water extracts on soil MR, MB, AFB and its catabolic response profile (CRP). Results: Newly-shed litter of black locust had higher MR than that of blackberry and black pine; MR, MB, and AFB were higher in forest floor and in mineral soil under black pine than under black locust. Water extracts of black locust and blackberry litter had a negative effect on the amount, activity of microorganisms, and CRP. Conclusions: The results demonstrate the potential for black locust and blackberry litter to have a marked inhibitory effect on decomposer microorganisms that, in turn, reduce organic matter mineralization with possible consequences at the ecosystem level, by increasing C sequestration in mineral soil.Peer reviewe

C Stocks in Forest Floor and Mineral Soil of Two Mediterranean Beech Forests

This study focuses on two Mediterranean beech forests located in northern and southern Italy and therefore subjected to different environmental conditions. The research goal was to understand C storage in the forest floor and mineral soil and the major determinants. Relative to the northern forest (NF), the southern forest (SF) was found to produce higher amounts of litterfall (4.3 vs. 2.5 Mg·ha−1) and to store less C in the forest floor (~8 vs. ~12 Mg·ha−1) but more C in the mineral soil (~148 vs. ~72 Mg·ha−1). Newly-shed litter of NF had lower P (0.4 vs. 0.6 mg·g−1) but higher N concentration (13 vs. 10 mg·g−1) than SF. Despite its lower Mn concentration (0.06 vs. 0.18 mg·g−1), SF litter produces a Mn-richer humus (0.32 vs. 0.16 mg·g−1) that is less stable. The data suggest that decomposition in the NF forest floor is limited by the shorter growing season (178 days vs. 238 days) and the higher N concentrations in newly shed litter and forest floor. Differences in C stock in the mineral soil reflect differences in ecosystem productivity and long-term organic-matter accumulation. The vertical gradient of soluble and microbial fractions in the soil profile of SF was consistent with a faster turnover of organic matter in the forest floor and greater C accumulation in mineral soil relative to NF. With reference to regional-scale estimates from Italian National Forest Inventory data, the C stock in the mineral soil and the basal area of Italian beech forests were found to be significantly related, whereas C stock in the forest floor and C stock in the mineral soil were not

Soil organic matter and Carbon sequestration in forest stands on Mount Vesuvius

Produzione di lettiera e accumulo di carbonio nel suolo di boschi di pini di diversa età e di robinia. Effetti allelopatici della lettiera di robinia sulle comunità microbiche

Leaf movements: an efficient strategy against photoinhibition in Robinia pseudoacacia L.

The exposure to high irradiance and high temperature conditions may result in PSII photoinhibition. Among different mechanisms engaged by plants to prevent photodamages, leaf movement (heliotropism) may represent an important strategy to avoid direct exposure to sunlight. To assess the contribute of leaf movements in PSII photoprotection on R. pseudoacacia plants, chlorophyll a fluorescence measurements were made at 12:00, 14:00, 16:00 and 18:00 on attached blocked leaves to prevent leaf movements and to maximize the daily radiation interception (BL) and on control unblocked leaves (UL). At midday as well as at 14:00 and 16:00, a significant decrease of FPSII, qP, Fv’/Fm’ and an increase of qN and EEE was observed in BL as compared to UL leaves that maintained these parameters almost constant throughout the day. However at 14:00, when temperature and irradiance reached the highest values, the differences between BL and UL became more pronounced. At 18:00, with sunlight and temperature decline, BL leaves showed a strong recovery of FPSII, qP, Fv’/Fm’ and a significant decrease of qN and EEE compared to 12:00, 14:00 and 16:00. Nevertheless, in spite of recovery, BL maintained FPSII, qP and EEE values lower than UL. Data presented suggest that in Robinia pseudoacacia L. under high irradiance and temperature,leaf movements, by reducing light interception, represent an efficient strategy to avoid photoinhibitory risks