Leaf area index in Vittelaria Paradoxa parklands in Burkina Faso estimated by light interception and leaf sampling

Abstract: Burkina Faso as well as most sub-Saharan African countries struggle with providing food for a fast growing population. The dominating farming system is agroforestry parklands. Agroforestry parklands can broadly be defined as areas where scattered trees occur on farmlands as a result of selective clearing. The presence of trees in crop fields may in the long term have a positive effect on the production of annual crops. It is commonly discussed, but not proven, that the presence of trees leads to increased groundwater recharge due to higher infiltration capacity of the soil. Still in Burkina Faso, as in many semi-arid areas, the number of trees in the landscape is decreasing.Leaf Area Index (LAI) is the total one-sided area of photosynthetic tissue per unit ground surface area. LAI of a forest or an agricultural crop is a key variable for modeling the evapotranspiration on an ecosystem or individual plant/tree level. LAI can therefore be used to better understand understand the connection between the physical properties of the soils and changes in forest cover. Leaf Area Index can be measured using direct or indirect methods. Direct methods are methods were leaf is measured in a direct way often by leaf sampling, while indirect are methods where LAI is received from variables that can be measured with less effort. The objective of the thesis is to calibrate methods for estimating Leaf Area Index in Vittelaria paradoxa parklands in Burkina Faso, by using both direct and indirect methods. The thesis also aims to investigate if there is a strong relationship between the size of the tree, e.g trunk diameter and crown diameter and its LAIIndirect measurements with the LAI-2000 canopy analyzer (LiCor Inc, Lincoln, Nebraska) were made at 9 different plots, which have been earlier established for measurements of sapflow within the “Tree, carbon and water project”. Each of the 9 plots consists of 3 trees. This gives a total of 27 trees. Besides those 27 so called sapflow trees were 4 control trees in the same area measured with the LAI-2000 to use as a calibration, all branches on these trees were later cut down and LAI were measured directly.The result showed a correlation between the two methods. However, the LAI-2000 underestimated the drip line LAI compared to the manually measured drip line To be able to use this correlation factor between the two methods with certainty a larger number of control trees would be needed. There is a correlation between diameter at breast high and indirect measured drip line LAI. However, the correlation is not strong enough that drip line LAI can be predicted based on this factor alone. The same thing can be said about the correlation between drip line area and indirect measured drip line LAI.