Mining and smelting degraded landscapes are characterised by heavily eroded soils that are acidic, contaminated with toxic metals, and depleted of essential nutrients. Regreening degraded landscapes has been proposed to support global carbon (C) mitigation measures and protect biodiversity. One of the world's largest regreening programs in the City of Greater Sudbury, Canada has been ongoing since 1978 and involves liming and fertilizing selected areas followed by planting primarily jack pine (Pinus banksiana Lamb.) and red pine (Pinus resinosa Ait.) trees. The main objective of this thesis was to improve our understanding of biogeochemistry in the City of Greater Sudbury regreened forests, and to determine how nutrient pools and cycling change as stands age. I established a chronosequence of forested sites between 15–40 years-old and to account for the effects of erosion, each site was categorized as "stable" (<10% bedrock cover) or "eroded" (>30% bedrock cover). Individual tree growth and nutrient accumulation in aboveground biomass (AGB) did not differ between stable and eroded sites and were comparable to rates reported from pine plantations in similar ecozones. Aboveground nitrogen (N) pools were six times larger than N applied in fertilizer, suggesting N limitation is most likely not a concern. Rates of C cycling were generally similar to those measured at unimpacted jack and red pine plantations. The exception being a decrease in mineral soil and aggregate C concentrations. However, at the ecosystem-scale the loss of soil C is trivial in comparison to increases in AGB C pools, leading to an overall increase in total ecosystem C following regreening (550,547 Mg in aboveground C across the 19,649 ha regreening landscape). Litter decomposition rates were higher at the regreening sites using a site-specific litter compared to a general common litter, indicating a home-field advantage for local decomposers. Soil temperature varied at the regreening sites and higher soil temperatures were related to higher rates of soil respiration. The regreening sites are rich in calcium (Ca) and magnesium (Mg); and while soils were generally poor in phosphorous (P) and potassium (K), foliar concentrations of P and K were comparable to those of "healthy" red pines. Overall, the regreening program appears to have increased tree growth and produced jack and red pine plantations that are biogeochemically similar to conifer plantations unimpacted by over a century of mining and smelting impacts.
Author Keywords: biogeochemistry, degraded landscape, forests, nutrient cycling, regreening, soil carbon