Research projects

Research Project – MSc

Large-scale disturbances in Canadian forests, including mountain pine beetle infestation (MPB) in western Canada, forest fires, timber harvesting and climate change impacts, have significantly affected both forest carbon and water cycles. Thinning, which selectively removes trees at a given forest stand, may be an effective tool to mitigate the effect of these disturbances, as thinning promotes tree health and vigor, increases resistance to beetle attacks, and decreases the risk of wild fires. Various studies have been conducted to assess the effects of thinning treatments on growth, transpiration, and nutrient availability; however, relatively few studies have been conducted to examine its effect on the coupling of forest carbon and water. Thus, the objective of this research is to evaluate the effect of thinning on forest carbon and water coupling at both the leaf and tree levels in a 16-year-old natural Pinus Contorta forest in the interior of British Columbia in Canada.  We used water-use efficiency (WUE), the ratio of basal area increment (BA) to tree transpiration (E), as the indicator of the carbon and water coupling at individual tree level, and use intrinsic water-use efficiency (iWUE), the ratio of photosynthesis to stomatal conductance, to represent the coupling at the leaf level. Field experiments were conducted in the Upper Penticton Watershed where the mean annual precipitation is 750 mm with seasonal drought during summer. Air temperature ranges from -20 to 20℃. Three blocks (20 m ×60 m each) with each having two thinning intensities plots (T1: 4500 and T2: 1100 trees per ha.) and one unthinned plot (C: 26400 trees per ha.) have been established following the randomized block design. From May to October 2016, tree basal diamter, sap flow rate, and environmental conditions were monitored continuously at a 20-minute interval, while photosynthesis rate and stomatal conductance were measured on a weekly basis. Preliminary results showed that thinning significantly increased solar radiation, wind speed, and soil moisture in the treatment plots, where the changes observed were proportional to the intensity of the thinning; but thinning did not change stand level temperature and relative humidity. Thinning also significantly enhanced tree E and BA, but no significant differences in WUE at both spatial scales were observed and no any scalling relationship was detected yet. The iWUE was strongly related to light intensity, temperature, intercellular CO2 concentration, and WUE was only strongly related to solar radiation. Overall, our data indicated that in the short term, thinning enhanced both water consumption and carbon assimilation, but did not alter their coupling. However, the impact of thinning needs further investigation over a longer research period.

See my research journal here 🙂


Research Project – PhD

Climate change has severely affected hydrological cycles in mountainous catchments across the world (Haque et al., 2015; Ragettli et al., 2016; Shinohara et al., 2009), resulting in a series of environmental consequences including diminishing permafrost (Lewkowicz and Rouse, 1992), decreased snowpack (López-Moreno et al., 2009), earlier snowmelt (Moore et al., 2007), and altered streamflow regimes (Rood et al., 2008). These influences exacerbate the risks of drought or flood events, and compromise the sustainability of water supply for agricultural, industrial and municipal activities. Therefore, it is important to understand the hydrological processes in mountainous catchments in order to develop adaptive water resources management strategies in dealing with impacts of climate change.

Although the impacts of climate change on hydrology have been extensively studied, large uncertainties on the altitudinal pattern of hydrological processes in the mountainous catchments remain, not only due to inadequate tools and sparse observations (Fayad et al., 2017), but also because of the influences of high meteorological variability, heterogenous terrains and various ecosystems along large elevation gradients (Fayad et al., 2017; Ragettli et al., 2016; Tennant et al., 2015; Tennant et al., 2017). Recent studies showed that elevation exerts strong influences on the hydrological responses to climatic change. For example, Tennant et al. (2015) examined the effect of elevation and vegetation cover on snowpack, peak flow and annual runoff in the snow-dominant, rain-dominant and snow-rain mixed watersheds, and reported that the streamflow patterns were different in each elevation zone, with low elevation catchment responding earlier to precipitation events. They further demonstrated that vegetation type, elevation and aspect significantly affected the accumulation and distribution of snow (Tennant et al., 2017). Besides, changes in ecosystem evapotranspiration (ET) and water-use efficiency (WUE) also exhibited significant elevation patterns (Goulden et al., 2012; Xue et al., 2015). Furthermore, the impacts of climate change are elevation-dependent (Beusekom et al., 2015). For example, Beusekom et al. (2015) collected temperature and precipitation data spanning 12 years across 20 sites in Puerto Rico and found that precipitation increased faster at higher elevation, and the range of temperature along elevation gradients decreased during the study period. Therefore, understanding the elevation effects on the hydrological processes will be very helpful in sustaining water resources under future climatic trajectory.

Will be updated soon 🙂