I couldn't resist sharing today's photograph in both vertical and horizontal orientations. The correct perspective is the vertical, since this is a cliff with seeping water. Still, I imagine the horizontal image could be used to trick more than a few people.

The challenges of the vertical environment for plants include exposure to wind and sun, poor or lacking soil, nutrient availability and gravity. These factors would be studied by cliff ecologists; cliff ecology is a specialized discipline within ecology that examines and studies organisms of cliff environments and how they interact with each other and the physical environment. Never heard of cliff ecology? A book review for “Cliff Ecology: Pattern and Process in Cliff Ecosystems” explains why. Here's the lede of the review: “Question: What is vertical, predominantly rock, virtually unstudied and largely taken for granted by land managers? Answer: A cliff. Perhaps no other landscape feature has been so consistently ignored despite being pervasive and prominent across the world. Ecologists haven't studied cliffs, and land managers haven't assumed responsibility for protecting them.”.

Two of the three vascular plants I noticed growing on this particular cliff face are in this photograph: Adiantum aleuticum and Saxifraga mertensiana (I've yet to ID the third, but it is not in this image). If I had to identify the moss, I'd hazard a guess and suggest it is Hypnum subimponens (Hypnaceae). This tentative ID is based on environment (seeping cliffs), habit (mat-forming), and colouration (yellow-green new growth, brownish-green in older areas) via the description in “Plants of the Pacific Northwest Coast” by Pojar & MacKinnon.

Photography / agriculture resource link: International Plant Genetic Resources Institute's Image Bank contains images on the subjects of plant and crop diversity (my favourite is this photograph of an orange-fleshed banana).