The impact of two arable field margin management schemes on litter decomposition

A primary objective of agri-environment schemes is the conservation of biodiversity; in addition to increasing the value of farmland for wildlife, these schemes also aim to restore natural ecosystem functioning. The management of scheme options can influence their value for delivering ecosystem services by modifying the composition of floral and faunal communities. This study examines the impact of an agri-environment scheme prescription on ecosystem functioning by testing the hypothesis that vegetation management influences decomposition rates in grassy arable field margins. The effects of two vegetation management practices in arable field margins - cutting and soil disturbance (scarification) - on litter decomposition were compared using a litterbag experimental approach in early April 2006. Bags had either small mesh designed to restrict access to soil macrofauna, or large mesh that would allow macrofauna to enter. Bags were positioned on the soil surface or inserted into the soil in cut and scarified margins, retrieved after 44, 103 and 250 days and the amount of litter mass remaining was calculated. Litter loss from the litterbags with large mesh was greater than from the small mesh bags, providing evidence that soil macrofauna accelerate rates of litter decomposition. In the large mesh bags, the proportion of litter remaining in bags above and belowground in the cut plots was similar, while in the scarified plots, there was significantly more litter left in the aboveground bags than in the belowground bags. This loss of balance between decomposition rates above and belowground in scarified margins may have implications for the development and maintenance of grassy arable field margins by influencing nutrient availability for plant communities. (C) 2008 Elsevier B.V. All rights reserved.

Holm Oak (Quercus ilex L.) canopy as interceptor of airborne trace elements and their accumulation in the litter and topsoil

We investigated the role of urban Holm Oak (Quercus ilex L.) trees as airborne metal accumulators and metals' environmental fate. Analyses confirmed Pb, Cd, Cu and Zn as main contaminants in Siena's urban environment; only Pb concentrations decreased significantly compared to earlier surveys. Additionally, we determined chemical composition of tree leaves, litter and topsoil (underneath/outside tree crown) in urban and extra-urban oak stands. Most notably, litter in urban samples collected outside the canopy had significantly lower concentrations of organic matter and higher concentrations of Pb, Cu, Cd and Zn than litter collected underneath the canopy. There was a greater metals' accumulation in topsoil, in samples collected under the tree canopy and especially near the trunk ('stemflow area'). Thus, in urban ecosystems the Holm Oak stands likely increase the soil capability to bind metals.

Soil carbon and litter development along a reconstructed biodiverse forest chronosequence of South-Western Australia

Soil organic matter (SOM) increases with time as landscape is restored. Studying SOM development along restored forest chronosequences would be useful in clarifying some of the uncertainties in quantifying C turnover rates with respect to forest clearance and ensuing restoration. The development of soil organic matter in the mineral soils was studied at four depths in a 16-year-old restored jarrah forest chronosequence. The size-separated SOM fractionation along with δ13C isotopic shift was utilised to resolve the soil C temporal and spatial changes with developing vegetation. The restored forest chronosequence revealed several important insights into how soil C is developing with age. Litter accumulation outpaced the native forest levels in 12 years after restoration. The surface soils, in general, showed increase in total C with age, but this trend was not clearly observed at lower depths. C accumulation was observed with increasing restoration age in all three SOM size-fractions in the surface 0–2 cm depth. These biodiverse forests show a trend towards accumulating C in recalcitrant stable forms, but only in the surface 0–2 cm mineral soil. A significant reverse trend was observed for the moderately labile SOM fraction for lower depths with increasing restoration age. Correlating the soil δ13C with total C concentration revealed the re-establishment of the isotopically depleted labile to enriched refractory C continuum with soil depth for the older restored sites. This implied that from a pedogenic perspective, the restored soils are developing towards the original native soil carbon profile.