This post is meant to be a follow-up to the last four - a bit of a conclusion to the theme of wet-dry transitions. First, picking up on the subject of rainy, treeless landscapes and the fact that they probably can't occur directly adjacent to deserts, I'd like to mention a phenomenon where something experientially similar to this does occur. In southern Peru and northern Chile, the essentially rainless western foothills of the Andes are green and dripping wet for part of the year due to the influence of coastal fog. The scarcity of trees is a function of the low total precipitation, but the constant moisture and mist, and the profusion of epiphytes, makes it reminiscent of an environment too saturated to support a forest. And in this case, the desert - essentially devoid of all plant life - grades directly into these lush "fog meadows" or lomas. One of the more accessible examples of this ecosystems is the Lomas de Lachay National Reserve near Lima, Peru.
Another amazing transition occurs at Ngorongoro Crater, Tanzania - the world's largest caldera not filled with water--part of the the Ngorongoro Conservation Area. The area's known for the wildlife living on the crater floor (and you're guaranteed to see it, since the animals can't leave!), but for me the most captivating part is the abrupt change from cloud forest at the rim of the crater to dry grassland at the bottom. I imagine that most of the moisture comes from mist rather than rain...otherwise I'd expect the crater floor to be almost as wet.
You can see Ngorongoro represented in the painting below - I did this one in the late 90's, before getting into the more cubist style. The painting also "caricatures" the entire series of ecological transitions occurring between the bottom of the Great Rift Valley (in the foreground) and the Serengeti Plain (in the background), with Lake Manyara and Ngorongoro in-between.
Finally, here are a few more aerial images of wet-to-dry transitions on tropical islands.