What is the significance of dolls in front of trees?

It is hard to give a definitive answer without knowing the specific reason for this shrine but there are a few likely options.  Someone may feel that tree has a spirit residing in it, benevolent or malevolent, which they either respect or are trying to placate.  There could have been an accident in that area or something perceived to be magical could have occurred.  Personally I think you are making too much of it but it is always good to make observations of new surroundings and ask questions to further your own knowledge base.

You will encounter shrines and spirt houses everywhere you go.  We have this one in front of our house which gets used by our cats as much as by the spirits.  We like to hike and sometime pack a light lunch to eat on the mountain top before heading back down.  My wife feels it is only polite to make a small offering of food to the spirts residing there which I find kind of cute and endearing.  Fortunately ours is not an overly superstitious household and rituals are only performed when it is convenient.

We have a Spirit House that belongs to our condo, people take food offerings there & drinks everyday. At onetime there was about 50 or more Zebra's at the foot of the house, not sure why. when we first moved in the building was new & many people said the spirits were restless. I just go along with the culture, take a back seat to everything.

thailand4me wrote:

We have a Spirit House that belongs to our condo, people take food offerings there & drinks everyday. At onetime there was about 50 or more Zebra's at the foot of the house, not sure why. when we first moved in the building was new & many people said the spirits were restless. I just go along with the culture, take a back seat to everything.

Zebras?

yeah spirit houses are common, but dolls are less so

Cat sacrifice!?!?! How horrible!

The only ones doing blood sacrifice around here would be Lord Tiger and his brother.  They have absolutely decimated the mouse population in the fields around our house.

These spirits don't seem very grateful or hungry, as they never eat any of the food left for them.