The most common occurrence is the horizon itself, and if unbroken, it creates a rather static composition. The still reflection also helped to reduce the impact of the shoreline and the results were a tranquil scene, in spite of the saturated reds of the aspen leaves. Watch for those subtle, implied horizontal lines, such as pastures and gently rolling fields. If you want to emphasize the calm, pastoral effect of your horizontal landscape, choose horizontal framing. If you want to de-emphasize it, select vertical framing.
Vertical lines add movement and energy to an image.
They often have an implied direction. They help to make an image expressive and often more powerful. The trunks of trees, grass blades, flower stalks, - these represent just a few vertical lines in nature. I was drawn to the cypress trees in fog because of the powerful lines that the trunks created. I selected a tight composition to accentuate them, eliminating unwanted grasses below and branches that would lead the eye astray.