Land use change and soil carbon pools: Evidence from a long-term silvopastoral

Multi-functional silvopastoral systems provide a wide range of services to human society including the regulation of nutrients and water in soils and the sequestration of atmospheric carbon dioxide (CO2). Although silvopastoral systems significantly contribute to enhance aboveground carbon (C) sequestration (e.g. C accumulation in woody plant biomass), their long-term effects on soil C pools are less clear. In this study we performed soil physical fractionation analyses to quantify the C pool of different aggregate fractions across three land use types including (1) silvopastoral system with ash trees (Fraxinus excelsior L.), (2) planted woodland with ash trees, and (3) permanent grassland, which were established in 1989 at Loughgall, Northern Ireland, UK. Our results show that 26 years after the conversion of permanent grassland to either silvopastoral or woodland systems, soil C (and N) stocks (0–20 cm depth) did not significantly change between the three land use types. We found, however, that permanent grassland soils were associated with significantly higher C pools (g C kg−1 soil; P 2 mm) whereas soil C pools of the micro-aggregate (53–250 μm) and silt and clay (< 53 μm) fractions were significantly higher in the silvopastoral and woodland systems (P < 0.05). A key finding of this study is that while tree planting on permanent grassland may not contribute to greater soil C stocks it may, in the long-term, increase the C pool of more stable (recalcitrant) soil micro-aggregate and silt and clay fractions, which could be more resilient to environmental change

Managing Invasive Alien Plants

The presence of invasive alien plant species across Ireland and Europe has increased significantly in the past few decades. The impacts of these invasions vary but they can lead to major modifications in ecosystem functioning. This research project has broadened our understanding of the ecological traits, strategies and impacts of invasive species. This information can be used in the management of invasive plants and help to inform legislation that might need to be introduced or strengthened.Environmental Protection AgencyDepartment of the Environment, Climate and Communication

Coefficients of variation (%) of Nitrogen (N), Phosphorus (P) and N:P ratios.calculated for soils, plant species, plant compartments and plant functional groups (PFG) across our four primary successions.

<p>Coefficients of variation (%) of Nitrogen (N), Phosphorus (P) and N:P ratios.calculated for soils, plant species, plant compartments and plant functional groups (PFG) across our four primary successions.</p

Effects of soil parameters and functional group (FG) identity on N:P ratios of different plant compartments and entire plant samples.

<p>Note the significant effect of FGs when treated as single effect and also when nested within successional stages.</p

Variation in plant N:P ratios within different compartment (leaves, stems, roots) across the three successional stages (early, middle and advanced).

<p>Data points represent plant species belonging to different functional groups (Triangle = Grasses; Dots = Legumes; Squares = Forbs).</p

Means and Standard Deviations (SD) for total N (%), total P (%) and N:P ratios of different plant compartments and soils across successional stages.

<p>Means and Standard Deviations (SD) for total N (%), total P (%) and N:P ratios of different plant compartments and soils across successional stages.</p

Dependence of plant N:P stoichiometry (leaves, stems and roots) on plant functional group (PFG) identity across successional stages.

<p>Legumes (L) show the highest N:P ratios compared with Graminoids (G) and Forbs (F).</p