Productivity and modifications of ecosystem processes in gaps of a low Macchia in southern Italy

Abstract. Disturbance in Mediterranean shrub lands creates gaps that break up the shrub cover and potentially restrict productivity and other ecosystem processes. Gaps make up to about 20% of the low Macchia area at the Castel Volturno nature reserve (southern Italy). The plant community consists mainly of small annual species (legumes, grasses and forbs) that germinate in November and die out before the onset of summer drought. The inter-annual variability in productivity and the relative abundance of legumes, grasses and forbs were assessed over 4 yr (2004–2007) to evaluate main potential modifications of ecosystem processes determined by the occurrence of gaps in the shrub cover. In the study years, at the peak production, plant mass varied from about 250 to 700 g m−2; biomass belowground allocation varied from 23% in the wettest to 44% in the driest year. Belowground/aboveground biomass ratios were negatively related to rainfall and positively related to the length of the dry period, showing that water availability controls biomass allocation patterns. Legumes were the most abundant fraction (about 60%) of the aboveground mass in the wettest year. In the drier years legumes exhibited a shorter life cycle and senesced by mid-spring. Among the three functional groups monitored, legumes were the most sensitive to water shortage and their biomass was positively related to the amount of rainfall and negatively related to the length of the dry period. The higher fraction of legume mass was associated with higher nitrogen content in plant tissues and in the soil. Senesced annual species decomposed more than senescent Phillyrea sp. leaves. The stability of organic carbon pool, evaluated through the endogenous mineralization coefficient (CEM), was lower in gaps than in understorey soils

Productivity and modifications of ecosystem processes in gaps of a low Macchia in southern Italy

Disturbance in Mediterranean shrub lands creates gaps that break up the shrub cover and potentially restrict productivity and other ecosystem processes. Gaps make up to about 20% of the low Macchia area at the Castel Volturno nature reserve (southern Italy). The plant community consists mainly of small annual species (legumes, grasses and forbs) that germinate in November and die out before the onset of summer drought. The inter-annual variability in productivity and the relative abundance of legumes, grasses and forbs were assessed over 4 yr (2004–2007) to evaluate main potential modifications of ecosystem processes determined by the occurrence of gaps in the shrub cover. <br><br> In the study years, at the peak production, plant mass varied from about 250 to 700 g m<sup>−2</sup>; biomass belowground allocation varied from 23% in the wettest to 44% in the driest year. Belowground/aboveground biomass ratios were negatively related to rainfall and positively related to the length of the dry period, showing that water availability controls biomass allocation patterns. Legumes were the most abundant fraction (about 60%) of the aboveground mass in the wettest year. In the drier years legumes exhibited a shorter life cycle and senesced by mid-spring. Among the three functional groups monitored, legumes were the most sensitive to water shortage and their biomass was positively related to the amount of rainfall and negatively related to the length of the dry period. The higher fraction of legume mass was associated with higher nitrogen content in plant tissues and in the soil. Senesced annual species decomposed more than senescent <i>Phillyrea</i> sp. leaves. The stability of organic carbon pool, evaluated through the endogenous mineralization coefficient (CEM), was lower in gaps than in understorey soils

Decomposizione della lettiera di quattro specie della macchia mediterranea: relazioni con alcune caratteristiche fogliarie con la qualità della lettiera

La velocità di decomposizione della lettiera di quattro specie tipiche della Macchia Mediterranea, Q. ilex, P. angustifolia, P. lentiscus e Cistus sp., è stata misurata dopo circa tre, sei e tredici mesi di incubazione in situ nella Riserva Naturale di Castel Volturno (Caserta). Sono state valutate le relazioni tra velocità di decomposizione e 1) indice di area fogliare specifica (SLA), 2) densità dei tessuti fogliari (LDMC), 3) grado di sclerofillia (GS), 4) contenuto in N, C e lignina e rapporto C/N della lettiera. Queste caratteristiche possono influenzare la colonizzazione e la utilizzazione della lettiera da parte dei microrganismi e, di conseguenza, la sua resistenza alla decomposizione. Dopo poco più di un anno la perdita di peso della lettiera era circa 50% in cisto, 41% in fillirea e 32% in leccio e lentisco. Nei primi tre mesi di incubazione, la velocità di decomposizione della lettiera è tanto maggiore quanto più alto è il valore di SLA e diminuisce con l’aumento del valore di LDMC e GS. La correlazione decomposizione - SLA e decomposizione - GS è statisticamente significativa solo se si esclude la fillirea che, ha caratteristiche fogliari simili a quelle di leccio e lentisco (spiccata sclerofillia) ma contenuto di lignina più basso non solo rispetto alle altre due specie sclerofille, ma anche rispetto al cisto (che ha caratteristiche mesofile). La velocità di decomposizione è correlata negativamente al contenuto di lignina e al rapporto lignina/N quando vengono considerate le quattro specie; se si considerano solo fillirea e cisto la correlazione diventa positiva. I risultati mostrano che la decomposizione della lettiera è la risultante degli effetti congiunti delle caratteristiche fogliari e della composizione chimica della lettiera

Impact of Innovative Agricultural Practices of Carbon Sequestration on Soil Microbial Community.

This chapter deals with the impact on soil microbiology of innovative management techniques for enhancing carbon sequestration. With in the MESCOSAGR project, the effect of different field treatments was investigated at three experimental sites differing in pedo-climatic characteristics. Several microbiological parameters were evaluated to describe the composition of soil microbial communities involved in the carbon cycle, as well as to assess microbial biomass and activity. Results indicated that both compost and catalyst amendments to field soils under maize or wheat affected microbial dynamics and activities, though with out being harmful to microbial communities

Discriminating between Seasonal and Chemical Variation in Extracellular Enzyme Activities within Two Italian Beech Forests by Means of Multilevel Models

Enzymes play a key-role in organic matter dynamics and strong scientific attention has been given to them lately, especially to their response to climate and substrate chemical composition. Accordingly, in this study, we investigated the effects of chemical composition and seasons on extracellular enzyme activities (laccase, peroxidase, cellulase, chitinase, acid phosphomonoesterase, and dehydrogenase) by means of multilevel models within two Italian mountain beech forests. We used chemical variables as the fixed part in the model, season as random variation and layers (decomposition continuum for leaf litter and 0–5, 5–15, 15–30, and 30–40 cm for soil) as nested factors within the two forests. Our results showed that seasonal changes explained a higher amount of variance in enzyme activities compared to substrate chemistry in leaf litter, whereas chemical variation had a stronger impact on soil. Moreover, the effect of seasonality and chemistry was in general larger than the differences between forest sites, soils, and litter layers