From the picture and information provided an exact identification is not possible. From the needles around the tiny leaves a guess would be that they are from a conifer tree and the those leaves are actually debris from the tree or its cones. There are several possibilities that may be causing the sticky “tiny leaves”.

This may be caused by a normal response from the tree. Conifers use sap or resin to protect themselves from insects. When they are attacked by an insect, they saturate the wound with sap to seal it off and then use the resin to flush or drown the invading insect. The sap on the ground mixed in with other residue, debris or pieces of the cones, from the tree may be what you are finding on the ground.

Insects, such bark beetles, pitch moths, and pitch midges, if they successfully invade the tree, will cause the tree to ooze sap. They cause tiny holes in the branches and bark of trees from which sap leaks. When an insect bores into a tree, sawdust and bark debris is also produced and can be found on the ground under the trees mixed with the sap.

Rust, a disease caused by a fungus, causes orange spots that are raised. When these spots rupture, they extrude a sticky liquid. Cankers, another fungal disease, cause abnormalities in the bark and will ooze sap. The liquids or sap can collect on tree fragments which may eventually fall to the ground.

Trees that are stressed are more susceptible to disease and insect problems. During the past several years drought conditions and higher than normal temperatures have been prevalent in Oregon and have caused many trees to be stressed. The following articles highlights some of those problems, Why Are My Trees Dying?.