why these trees are used to make this syrup?
Because of the high sugar content (roughly two to five percent) in the xylem sap of these species.
Maple syrup
Maple syrup is a syrup usually made from the xylem sap of sugar maple, red maple, or black maple trees, although it can also be made from other maple species. 
where does the majority of maple syrup come from Canada from which trees is this syrup made? Sugar maple (Acer saccharum), the black maple (A. nigrum), and the red maple (A. rubrum)
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Maple syrup [SEP] Introduction
Maple syrup is a syrup usually made from the xylem sap of sugar maple, red maple, or black maple trees, although it can also be made from other maple species. In cold climates, these trees store starch in their trunks and roots before winter; the starch is then converted to sugar that rises in the sap in late winter and early spring. Maple trees are tapped by drilling holes into their trunks and collecting the sap, which is processed by heating to evaporate much of the water, leaving the concentrated syrup. Most trees can produce of sap per season. Maple syrup was first made and used by the indigenous peoples of North America, and the practice was adopted by European settlers, who gradually refined production methods.