White spruce growth sensitivity to climate variability in pure and mixedwood stands

It is prudent to understand how tree growth responds to climate variability to better project their growth in the current and future changes in climate in boreal forests. In this thesis, I studied how climate variables influence individual white spruce trees (Picea glauca (Moench) Voss) over short and intermediate periods in pure and mixedwood stands in northeastern British Columbia. In Chapter 2, I studied the importance and the influence of annual, seasonal, and monthly microclimate variables on the annual growth of white spruce trees in pure and mixedwood stands. In Chapter 3, I studied the importance and the influence of microclimate variables on sap flow of white spruce trees through different time scales in these two stand types. My key finding in these two chapters is that stand composition and structure are essential determinants of how spruce radial growth and sap flow respond to fluctuations in climate variables, and how they will respond to projected future climate scenarios. A combination of warmer temperatures and drought during summer will negatively affect white spruce trees growth in pure and mixedwood stands in the studied region. Spruce sap flow in both stand types is likely to increase as the climate warms, increasing the demand for soil water. As this resource becomes less available, white spruce in both stand types are likely to respond with processes that can compromise their physiological integrity. White spruce growing in mixedwood stands might be more sensitive to drought stress than in pure stands due to the higher competition for limiting resources (primarily water). This thesis provides information of expected changes in tree growth to climate variability and demonstrates the importance of appropriate site selection to plant spruce trees and management of pure and mixedwood stands.

Studi lapangan variabel iklim rumah vernakular pantai dan gunung dalam menciptakan kenyamanan termal adaptif

Microclimate variables are one of the variables that affect adaptive thermal comfort. The microclimate variables are air temperature, solar radiation temperature, air humidity and wind speed. In this study the discussion of microclimate variables is specific to air temperature and air humidity. This is based on other studies which mention that the most influential climate variables are air temperature and humidity. This research is a field study that will compare air temperature and humidity in coastal and mountain areas. Measurements are carried out in 3 seasons, namely the dry season to rain, the rainy season and the rainy season to the dry season. Measurement of air and humidity temperature variables in two rooms in the building and outside space and terrace. The results of the study show that there are significant differences between coastal and mountain dwellings. This difference is related to adaptive thermal comfort through thermal sensation. Thermal sensation results show that the location of the mountain is that most residents feel cool, while at the beach location, the residents are mostly comfortable or neutral.

The effects of experimental forestry treatments on site conditions: short response study from an oak-hornbeam forest

Background Forest management alters the forest site, however, information is still limited about how different silvicultural treatments modify these conditions. In the past decades, besides rotation forestry, new silvicultural systems were introduced, fulfilling the requirements of multipurpose forestry. In this study we investigated the short-term effects of different forestry treatments on microclimate, litter and soil conditions in a European oak-dominated forest. Methods A forest ecological experiment was established in a homogenous, managed, 80 years old, Quercus petraea and Carpinus betulus dominated forest, in 2014. Five treatments of three different forestry systems were installed following a complete block design in six replicates: clear-cutting with a circular retention tree group as typical elements of the clear-cutting system, preparation cutting (partial harvest) belonging to the shelterwood system, gap-cutting as a common tool of continuous cover forestry in Europe and uncut control. Microclimate, litter and soil variables were measured systematically since 2014. Here we present the results of the analyses of the first growing season following the interventions (2015). Results We found that there is strong treatment effect in the case of microclimate and litter varibles, but for soil characteristics the impacts will presumably appear in longer term. The increment of total and diffuse light was the greatest in clear-cutting, in gap-cutting the illuminance was intermediate, while light-levels were lower and less variant in preparation cutting and retention tree group. Air and soil temperature as well as vapor pressure deficit increased the most in clear-cutting; both means and variances were the highest in this treamtment. Retention tree group could not buffer the means of the temperature variables, but a small group of tree individuals was able to ameliorate the extremes of the microclimate. Significant increase of soil moisture was measured as a consequence of gap-cutting and less pronouncedly in clear-cutting. Similarly, litter pH and moisture were the highest in these treatment types. Significant increment in soil pH was detected in retention tree group. Through the analysis of microclimate variables during the growing season, we could demonstrate the buffering effect of forest canopy: differences between treatments were the greatest in summer for all microclimate variables. Discussion We can conclude that in oak–hornbeam forest, only less intensive and spatially heterogeneous silvicultural treatments could preserve the stable, cooler and humid below-canopy microclimate, therefore, group selection using gaps and irregular shelterwood systems are favourable. Our findings can support the mitigation of the negative impacts of climate change in managed forest. Moreover, besides basic research we can formulate implications for foresters and conservationists to preserve biodiversity in temperate forests.

The effects of experimental forestry treatments on site conditions: short response study from an oak-hornbeam forest

Background Forest management alters the forest site, however, information is still limited about how different silvicultural treatments modify these conditions. In the past decades, besides rotation forestry, new silvicultural systems were introduced, fulfilling the requirements of multipurpose forestry. In this study we investigated the short-term effects of different forestry treatments on microclimate, litter and soil conditions in a European oak-dominated forest. Methods A forest ecological experiment was established in a homogenous, managed, 80 years old, Quercus petraea and Carpinus betulus dominated forest, in 2014. Five treatments of three different forestry systems were installed following a complete block design in six replicates: clear-cutting with a circular retention tree group as typical elements of the clear-cutting system, preparation cutting (partial harvest) belonging to the shelterwood system, gap-cutting as a common tool of continuous cover forestry in Europe and uncut control. Microclimate, litter and soil variables were measured systematically since 2014. Here we present the results of the analyses of the first growing season following the interventions (2015). Results We found that there is strong treatment effect in the case of microclimate and litter varibles, but for soil characteristics the impacts will presumably appear in longer term. The increment of total and diffuse light was the greatest in clear-cutting, in gap-cutting the illuminance was intermediate, while light-levels were lower and less variant in preparation cutting and retention tree group. Air and soil temperature as well as vapor pressure deficit increased the most in clear-cutting; both means and variances were the highest in this treamtment. Retention tree group could not buffer the means of the temperature variables, but a small group of tree individuals was able to ameliorate the extremes of the microclimate. Significant increase of soil moisture was measured as a consequence of gap-cutting and less pronouncedly in clear-cutting. Similarly, litter pH and moisture were the highest in these treatment types. Significant increment in soil pH was detected in retention tree group. Through the analysis of microclimate variables during the growing season, we could demonstrate the buffering effect of forest canopy: differences between treatments were the greatest in summer for all microclimate variables. Discussion We can conclude that in oak–hornbeam forest, only less intensive and spatially heterogeneous silvicultural treatments could preserve the stable, cooler and humid below-canopy microclimate, therefore, group selection using gaps and irregular shelterwood systems are favourable. Our findings can support the mitigation of the negative impacts of climate change in managed forest. Moreover, besides basic research we can formulate implications for foresters and conservationists to preserve biodiversity in temperate forests.