This is a joke sketch.
We, the artists and the audience, have certain rules of shading and perspective in a sketch. These rules are easily broken. Here, I try playhalf a dozen ways with those rules. See how some branches pop out, and others pop in. See how one side of the tree's leaves are flat with the paper, but on the other side they sink under the paper.
I did this sketch with colored pencils in a dark Tex-Mex bar/restaurant in Hiroshima, Japan. The light was good enough for me to find my fajitas and napkin, but not good enough to distinguish the true color of each pencil. That's why this woman's skin color and the bark color are a little strange.
If you're an artist, see how the shading is done with lines that currrrve to show the shape of the leg or branch. See how the sky is made of round curly lines to show that air is fluffy and light. When you draw, do you just make flat straight lines because that's the quickest way to fill in the color? Why? Try this way.