structural:summarization, quality:correction
Ecology

The Tian Shan holds important forests of Schrenk's spruce (Picea schrenkiana) at altitudes of over 2,000 metres (6,600 ft); the lower slopes have unique natural forests of wild walnuts and apples.

The Tian Shan in its immediate geological past was kept from glaciation due to the "protecting" warm influence of the Indian Ocean monsoon climate. This defined its ecological features which could sustain its distinctive ecosphere. The mountains were subjected to constant geological changes with constantly evolving drainage systems which affected the patterns of vegetation, as well as exposing fertile soil for newly emerging seedlings to thrive in.

Tulips originated in the Tian Shan Mountains. The plant then made its way to Turkey via the Silk Road and became a symbol of the Ottoman Empire.

Ancestors of important crop vegetation were established and thrived in the area, among them: apricots (Prunus armeniaca), pears (Pyrus spp.), pomegranates (Punica granatum), figs (Ficus), cherries (Prunus avium) and mulberries (Morus). The Tian Shan region also included important animals like bears, deer, and wild boar, which helped to spread seeds and expand ecological diversity.

Among the vegetation colonizing the Tian Shan came, likely via birds from the east, the ancestors of what we know as the "sweet" apple. The fruit probably then looked like a tiny, long-stalked, bitter apple something like Malus baccata, the Siberian crab. The pips may have been carried in a bird's crop or clotted onto feet or feathers.

What natural features of the unique Tian Shan might have contributed to this rigorous selection program? Time is, as we have seen, not a problem. The turnover of individual trees is likewise conducive to the rapid evolution of a tree species, as is the fact that sweet apples are now, at least for all practical purposes, self-incompatible—that is, they cannot pollinate themselves. Therefore each apple tree within the forest and even each pip, usually five, within each individual fruit will be different. There are many apples on a mature tree, so natural selection has a rich and diverse population upon which to work. Birds, of course, eat all manner of fruit. But most birds eat seeds—a dietary feature not conducive either to the selection or spread of a fruit tree. Sweet apples are often eviscerated by birds, but the seeds are frequently left in the empty shell of the pome. The reason is that apple (and pear and quince) seeds are rich in cyanoglycosides, which are highly repellent, particularly to birds... Moreover, the placenta of the apple fruit, the womb, contains inhibitory substances that prevent the germination of the apple seed in situ. This is a commonly observed phenomenon in fruits as Michael Evenari showed in 1949. So what then does, or did, distribute the original apple seed? The bear...

The strain of Y. pestis which caused the bubonic plague now know as the Black Death may have originated in the Tian Shan, spreading along the Silk Road and killing half of Europe's population in the mid 1300s.