I'm in some urgent need of advice about linking together biomes in a realistic manner. Can a taiga connect to an alpine tundra to the north, and a steppe to the south? Then what would branch off of those? I'm sure there's complexity to it that I'm missing. I know the further from the equator generally means colder climates.
There are several ways to achieve this, but it depends on how large, what barriers you have between your biomes and what arrangement they are
If your Biomes are encapsulated environments (for instance, in domes):
Connect using an airlock is the most simplest way. It keeps the environments separate, allows minimal cross-contamination of species and seeds, and minimal energy loss between environments.
Connect using as little interaction as possible, a common wall perhaps with a small tunnel or opening. You would have some cross-contaminants and energy loss but hopefully this would be minimal.
If your Biomes are 'open' and not encapsulated:
You can place each one in a valley, or depression, separated by ridges or walls. Temperature differences can hopefully be contained within it, however keep in mind this is energy intensive but it depends on how advanced and large your biomes are.
You can separate your biomes by distance: this is the most rudimentary, but your biomes would need to be very large to make this worth the energy loss and contamination. In this instance you're looking at hundreds of kilometres for each biome. Cross contamination is a real possibility in this scenario, depending on your original environment.
Copy from the real world.
A new map of standardized, mesoscale (tens to thousands of hectares) terrestrial ecosystems for the conterminous United States was developed by using a biophysical stratification approach. The ecosystems delineated in this top-down, deduc- tive modeling effort are described in NatureServe’s classifica- tion of terrestrial ecological systems of the United States. The ecosystems were mapped as physically distinct areas and were associated with known distributions of vegetation assemblages by using a standardized methodology first developed for South America.
Find a map that shows biomes. Biomes might be called ecosystems as is the case in the linked paper. Find on the map the biome you are interested in and see how it grades into its neighbors and why (latitude, altitude, moisture etc). You can deduce your own rules if you want, or just copy from existing areas into your built world. No-one will recognize the Ozarks turned at a right angle on your map. Unless you name them the Zozarks in which case some folks might figure it out and smile at your joke.
Taiga cannot border steppe (at least wide forest have to be in between, or, like in Siberia - some low forested mountain range), but tundra can (It is actualy a "cold steppe" - it would be smooth translation from cold steppe to temperate one).
Taiga can, and almost always do, border tundra. Between 60 and 75 degrees north/south, taiga gives way to tundra, especially if there's a cold surface current flowing by the coast.
Look at Canada, for example, where the turquoise subarctic continental climate, aka taiga, borders grey tundra.
Cold steppes bordering taiga is, as far as I know, without precedent - there is always at least a thin strip of humid continental climate in between the two. The closest you get is in the Western half of the US, but still the two biomes do not actually touch:
So, yes and no is the best answer I can give you.