C. Corrigan's research while affiliated with University of Waterloo and other places

In forest ecosystems, litterfall collected in trapping devices is exposed to periods of wetting and drying, which may initiate the first stages of decomposition. This could lead to an underestimation of organic matter and nutrient input due to leaching or an overestimation due to immobilization. The objectives of this study were to quantify changes in mass and nutrient stocks of sugar maple (Acer saccharum Marsh.), basswood (Tilia americana L.), and beech (Fagus grandifolia Ehrh.) leaves under in situ conditions and to quantify changes in leaf mass and nutrient stocks and leachate concentration when exposed to different quantities of moisture (high = 100 mm, medium = 60 mm, and low = 30 mm) under ex situ conditions. Results from this study showed that sugar maple and basswood had a significantly greater (P < 0.05) mass loss than beech in the in situ and ex situ study. Nutrient stocks either decreased significantly (P < 0.05) or remained the same, depending on species in the in situ study. Similar results were observed in the ex situ study, in which carbon, nitrogen, phosphorus, and potassium stocks decreased significantly (P < 0.05) with increasing exposure to moisture, but calcium and magnesium stocks showed less pronounced changes. Mean concentrations of dissolved organic carbon, dissolved organic nitrogen, and ammonium were significantly different (P < 0.05) between species and moisture treatments, whereas nitrite showed no such differences. Results from this study suggested that the collection of leaf litter should take place frequently during the peak leaf abscission period and during periods of high precipitation. This would provide a more accurate quantification of the quantity of nutrients entering the forest ecosystem in the within-system pathway between live vegetation and the forest floor detritus pool. In addition, more frequent litterfall collection may also minimize litter decomposition and nitrification.

In forest ecosystems, litterfall that collects in trapping devices, to quantify organic matter and nutrient inputs, is exposed to periods of wetting, drying, freezing, and thawing. These fluctuating environmental conditions may influence the microbial community structure inhabiting the leaves and may result in the loss of mobile nutrients, leading to an underestimation of actual organic matter and nutrient inputs. The objectives of this study were to evaluate the influence of (i) different quantities of moisture (LOW = 30 mm, MED = 60 mm, HI = 100 mm) and (ii) freeze-thaw (FT) on leaf (sugar maple (Acer saccharum Marsh.), American basswood (Tilia americana L.), and American beech (Fagus grandifolia Ehrh.)) microbial activity and community structure. There was a significantly greater (p < 0.05) CO2 production rate in LOW and FT treatments for sugar maple and beech, and in HI and FT treatments for basswood. A similar trend occurred for leaf nitrogen concentration but not for carbon (C). Utilization of C substrates was up to 10% greater in the FT treatments. Principal components analysis on the activity of C source utilization showed a distinct clustering between leaf species and between treatments following a pattern similar to that of microbial respiration. Results from this study suggested that the collection of litter should take place more frequently during seasons when frost is imminent.