Terrain above the bushline can be very demanding and require special knowledge and skills. The country is often steeper, the cliffs more frequent, and gullies awkward to cross. Your footing and route choice demand much more of your attention. You'll also encounter tussock, scree, snow, rock or ice. All of these can be challenging and you need to know special techniques for moving safely through them.
Weather will also play a bigger factor in the alpine. The winds are stronger, the temperatures are colder, and the rain and snow are heavier. All that combined with the fact that you are no longer sheltered by vegetation means you're much more vulnerable to any adverse weather.
Consequences of a mistake in the alpine are significantly greater than at lower levels due to these terrain and weather characteristics combined with the fact that you're likely much further from help. This means you need to have more skills and experience, possibly more equipment, and a better plan than you would for your standard trip below the bushline.
Our Alpine Tramping Video Series is a fantastic introduction to the kinds of elements you might face above the bushline, and the considerations that should be made in planning.
For a specific introduction to techniques used on snow slopes, check out our Alpine Snow Skills Series below.