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Mangrove ecosystems are acknowledged as a significant carbon reservoir, with a potential key role as carbon sinks. Little however is known on sediment/soil capacity to store organic carbon and the impact of benthic fauna on soil organic carbon (SOC) stock in mangrove C-poor soils. This study aimed to investigate the effects of macrobenthos on SOC storage and dynamic in mangrove forest at Gazi Bay (Kenya). Although the relatively low amount of organic carbon (OC%) in these soils, they resulted in the presence of large ecosystem carbon stock comparable to other forest ecosystems. SOC at Gazi bay ranged from 3.6 kg m −2 in a Desert-like belt to 29.7 kg m −2 in the Rhizophora belt considering the depth soil interval from 0 cm to 80 cm. The high spatial heterogeneity in the distribution and amount of SOC seemed to be explained by different dominant crab species and their impact on the soil environment. A further major determinant was the presence, in the subsoil, of horizons rich in organic matter, whose dating pointed to their formation being associated with sea level rise over the Holocene. Dating and soil morphological characters proved to be an effective support to discuss links between the strategies developed by macrobenthos and soil ecosystem functioning.

The aim of this work was to investigate the potential of forest humus forms as indicators of soil C storage. To this purpose, Mediterranean forest soils in Southern and Central Italy were examined. Sites differed for elevation, climate, parent material and vegetation conditions, while summer drought was the common ecological factor. A morpho-functional criterion, based on holorganic layers thickness and A horizon properties, was used to classify humus forms, which ranged from Dysmoder to Eumull. Such variability allowed understanding of factors influencing organic matter storage. The relations between carbon stock and humus form were investigated for the topsoil layer (0–20 cm), which was supposed to contain the soil C pools most sensitive to climate change. We found that humus forms can be grouped in statistically different populations, with respect to topsoil C stocks. The use of A horizon structure was the main diagnostic criterion and represented the most effective approach to humus classification in Mediterranean conditions. It appears that humus forms have a clear potential as indicators of organic carbon status in Mediterranean forest soils

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40The study of plant trait-environment links is rarely focused on traits that inform on space occupancy 41 and resprouting (both affecting plant persistence), especially in forest understories. Traits that can 42 effectively capture such key functions are associated with clonality and bud banks. We hypothesized 43 that: 1) climate is the main driver of clonal and bud bank traits, 2) traits related to space occupancy 44 (e.g., greater lateral spread) are more important in more mesic, richer soils forests, and 3) traits 45 related to resprouting ability (e.g., larger bud bank) are more important in more intensively and 46 recently managed forests. We addressed these hypotheses by analysing a unique dataset that is 47 statistically representative of Italian forests heterogeneity and includes three biogeographic regions 48 (Alpine, Continental, Mediterranean). We recorded data for sixteen climatic, soil and management 49 variables. We calculated community weighted mean (CWM) values of seven clonal and bud bank 50 traits for the forest understory vegetation. We used i) redundancy analysis to assess trait-51 environment relations, and ii) variance partitioning analyses to identifying the relative role of 52 different groups of abiotic variables on CWM variation of all traits combined together, as well as 53 clonal and bud bank traits taken separately. Climate alone had a pervasive effect in determining 54 patterns of clonal and bud bank traits in Italian forest understories, mainly related to the effects of 55 temperature extremes and seasonality. Unexpectedly, soil and management factors alone showed 56 marginal effects on clonal and bud bank traits. However, soil features influenced trait patterns when 57 joined with climate. Our results confirmed that, at the biogeographic scale, climate played a lion-58 share role in determining persistence-related traits of forest-floor plants. At the local-scale, other 59 interplaying factors (e.g., management, soil variables) may come into play in shaping patterns of the 60 studied plant traits. This study stressed the importance of examining functional trait patterns along 61 complex environmental gradients. 62 63 64