project X
project I

project II

project III

project IV

project V

project VI

project VII

project VIII

project IX

project X

current vacancies

project X: eurolimpacs: climate-acidification interactions in aquatic and terrestrial ecosystems

Dr. Dillon is a major contributor to a new EU research effort that focuses on the interaction of global change with other stressors. In particular, providing Canadian data and modelling expertise to this 4-year programme.

Acidification and recovery of aquatic ecosystems are influenced by climate factors. The combined effects of climate and acid deposition occur at all time scales, from individual storms to seasons to decades. The major drivers will be via the catchment, via changes in runoff chemistry and discharge. The major ecological impacts on freshwater bodies will occur as response to changes in water chemistry. There are good empirical relationships relating water chemistry to response of key biological organisms and groups. The premise thus is that if we can predict changes in water chemistry, then the changes in biological components can be predicted.The experiments will focus on the effects on runoff water chemistry of episodic and seasonal variations in climatic factors.

1. Manipulations of snowcover, freezing-thawing cycles, and soil wetness in mini-catchments. We will manipulate the soil-freezing regime to examine the effect of changed winter soil temperature in an acidified upland, semi-natural area currently characterised by stabile sub-zero snow-rich winters. Here the hypothesis to be tested is that increased frequency and intensity of soil freezing in winter will increase the leaching of N and C from soils to water. The experimental design entails 6 mini-catchments. We will manually remove the snow on 2 catchments, insulating the ground by means of mats placed on the ground in late autumn on 2 catchments, and use 2 catchments as untreated references.

We will also simulate the effect of changed summer and autumn precipitation by experimentally adding additional precipitation. Here the hypothesis is that leaching of TOC increases from soils that are continually wet. In addition, the quality of TOC might also change, as the relation between colour and TOC seems to be influenced by the hydrological regime. For these experiments an additional 2 catchments will be used at which extra water will be sprinkled weekly to ensure saturated soils during a 10-week period in late summer and autumn. The experiments will be conducted in series of mini-catchments (30-300m2) located adjacent to the Storgama catchment (flagship site).

2. Simulation of hydrological and seasalt extremes by experimental watering.
Ecological research on the effects of acid deposition on forest, wetland and lake ecosystems has been conducted at Gårdsjön (Sweden) since 1970. A series of small headwater catchments have been used for whole-ecosystem manipulation experiments including an acid-deposition removal experiment by means of roof and a nitrogen-addition experiment now in its 14th year. Both catchments are equipped with watering systems. We propose to use these facilities as a full-scale hydrologic laboratory to simulate extreme hydrologic events and seasalt input events, both of which are predicted to increase in magnitude and frequency as a consequence of global warming.

3. Experimental manipulation of DOC concentrations in streams.
We propose to conduct 3 types of simple manipulation experiments with DOC in small streams:
(1) Increased NO3 in the stream (by NO3 addition directly to the stream or by comparing to the G2 NITREX catchment, where NO3 is increasing due to NH4NO3 additions) to enhance degradation of DOC in the stream (i.e. decrease the DOC output)
(2) Clearfelling around the stream which to increase the amount of light at the stream might increase the degradation of the DOC by UV (or by light in general). Covering the stream with UV non-permeable plastic should work in the opposite way. (i.e. potentially both increase and decrease DOC output)
(3) Clearfelling the whole catchment and creating a DOC pulse due to the disturbanceof the soil caused by machinery during the process.