It is Yule the Gewessi closing of the old year and the start of the 12 day interregnum before the start of the new year.   During this time the old sun dies and the new sun is born.   The Yew in my worldview is Yggdrasil rather than the Ash and as Yggdrasil the Yew is the gateway to the cycle of life and death.   The Yew is my soul tree, the tree that speaks to me more than any other in the same way that Loki has involved himself more than any other in my life.   He is one of my patron gods, of my work, his capriciousness suits as I am an I.T. architect.   His role in many myths, including Ragnorak, is to bring things to an end, however, he also has a role in creation; as Lodur he brought life and looks to the first people.   Thus the Yew, Loki and the Yule time period are all intertwined.
"The yew has always been a symbol of death and rebirth, the new that springs out of the old, and a fitting tree for us to study at the beginning of the new year. As the days now grow longer with the beginning of a new solar cycle, we move into the future on the achievements of the past, new creativity springs forth grounded in the accomplishments of the year gone by." taken from Mara Freeman's excellent article on the OBOD Druid Tree Lore site here.
Loki / Loca
This interregnum period has long been regarded as a topsy-turvy time, when the rules of the traditional order are replaced and the Lord of Misrule reigns.   Which again provides a link to Loki at this time of year.
For me, it is appropriate to think of Loki, Loca in the reconstructed Anglo-Saxon heathen view of him.   Loca means the one who closes and it is his role at the beginning and the end that is apparent in all the lore.
Over the years I have accumulated a lot of information from web sites that are no longer extant, so I can't provide references.   This next paragraph is taken from Lokesblót by someone whose screen name was CoyotePup "The connection between Loki and Sirius is real.   In addition to its association with trickster gods around the world, the Old Norse name for Sirius is Lokabrenna, "burning done by Loki." According to legend, the winters were once so cold that the oceans would freeze over and the farmers would die simply checking their mail. One year, when the winter was so cold it froze the fire in the hall, the people called upon Loki, whose primary role, like any good trickster, is to provide (and he's a fire-god), to warm winter up just enough so that the people living in the Mid-Garth could,well, live.
Therefore, Loki placed a torch in the sky, and it warmed up the land just enough to make winter livable. However, it moved with the stars, and six months later, towards the end of the summer, it was next to the sun (as could be visibly noticed every sunrise), and began heating up the already warm days. The string attached to Lokabrenna was that, while it warmed the winter nights and let the people live, it also warmed the summer days and drove the people mad."
As ever this shows Loki's trickster status, that each of his gifts has a light and dark side.   Sirius is the dog star of the Canis Major constellation which along with Canis Minor run at the feet of Orion the great hunter who stalks the winter skies of the Northern Hemisphere.   Here's a map of the constellations from StarryNightEducationthe Stag who stole the sun.