Peat is formed in wet and acidic conditions, where net primary production exceeds the decomposition of organic matter. Peatlands cover a small part of the earth surface but hold vast amounts of carbon. Land use change and climate change can turn this large carbon sink into a carbon source, thereby generating a positive feedback for climate change. The peatlands in the Netherlands have a long history of drainage to facilitate agriculture. The downside of these practices is the oxidation of the organic soil, which leads to subsidence and associated desiccation of nature reserves, emission of greenhouse gasses, deterioration of surface water quality, increasing costs for water management and infrastructural maintenance, damage to building foundations, and, in the end, loss of the characteristic landscape. In this thesis, the effects of climate change on the decomposition of peat soils in the Netherlands are explored, focussing on the effects of summer drought and salinisation on peat decomposition. Throughout this research, the distinction is made between peat that was formed in minerotrophic versus oligotrophic conditions (fen and bog peat) and between two types of land use (agriculture and nature management). Because of climate change, it is expected that dry summers will occur more often. We showed that oxygenation of deep peat layers that had not previously been exposed to air led to acceleration of decomposition; moreover, this effect is still measurable in the period after such a dry summer. During dry summers, surface water originating from rivers or lakes is supplied to peat areas to prevent drying out of the soils and limit decomposition. However, during prolonged summer droughts, the river water has a poor quality and may become slightly brackish because of saltwater intrusion and evaporation. We showed that salinisation reduced aerobic decomposition rates and water quality deteriorated. Unexpectedly, no uniform effect of land use or peat origin on respiration rates was found. Nevertheless, substantial ...