I’m crafting a map for my world and I was wondering what the biomes of mountains the size and height of the Himalayan Range would be like at the equator? The region south of them has multiple large river deltas and the region north is mostly flat lands. Thanks for any guidance!
At high altitude, it is alpine tundra regardless of latitude.
Here is Mount Kenya
It is 16 km from the equator. It is shorter than Everest at 5199 meters but at this altitude that doesn't matter. There are comparably high mountains in Ecuador, also close to the equator.
Once you get up that high it is cold all the time and it is dry because evaporation happens fast at altitude. Sun is harsh. If there are plants they will be low lying dry adapted plants, often stunted in size and deformed by wind. This is alpine tundra.
Alpine tundra occurs at high enough altitude at any latitude. Portions of montane grasslands and shrublands ecoregions worldwide include alpine tundra...
Alpine tundra occupies high-mountain summits, slopes, and ridges above timberline. Aspect plays a role as well; the treeline often occurs at higher elevations on warmer equator-facing slopes... Since the habitat of alpine vegetation is subject to intense radiation, wind, cold, snow, and ice, it grows close to the ground and consists mainly of perennial grasses, sedges, and forbs. Perennial herbs (including grasses, sedges, and low woody or semi-woody shrubs) dominate the alpine landscape; they have much more root and rhizome biomass than that of shoots, leaves, and flowers. The roots and rhizomes not only function in water and nutrient absorption but also play a very important role in over-winter carbohydrate storage.
Alpine tundras are delicate and fascinating, and occur worldwide. For your fiction, patch together aspects you like from various tundra habitats. Two of my favorite alpine tundra animals: the weiku bug that lives on insects from the tropical regions at lower elevations that are blown up the mountain.
And the marmot because it is my totem animal.
I saw a glimpse of the future in which detail oriented worldbuilders point out that the upper reaches of Everest are devoid of life. Yes. I would say above 5000m there will not be much except maybe weiku bugs. It is slightly lower than that you will find alpine tundra.
Right next to the equator in Tanzania sits mount Kilimanjaro. At 5895 meters above sea level it is still a good 3000 meters lower than the Everest. Despite this, it's altitude is high enough to be in line with many peaks in the Himalayas. The climate of the region is quite interesting and complex, but some of it's distinct features include having several different biomes and two distinct rainy seasons. Read in detail here: https://en.m.wikipedia.org/wiki/Mount_Kilimanjaro
Now, Mt Kilimanjaro is a relatively small region when compared to the Himalayas, and a feature of such size would have some different conditions, but it should be mentioned that once you rise high enough the pressure drops and it gets cold no matter where you are.