Cactrees of the Spine Barrens

Cactrees (genus spinarbor, spine tree) are a large genus of descendants of jumping cholla cacti. There are two main kinds, the montane variety residing in the rocky mountains and the lowland variety residing in the deserts of Mexico and the Southwestern US. Cactrees first evolved in the rainshadow of the rocky mountains, one of the last places where deserts still existed.

Biology

The average cactree is about 30 feet tall. It's trunk is about 5 feet in diameter. Near the top it splinters into branches with dozens of "twigs" attached. The entire tree is covered in spines except for the flower stalks.

Cactrees are covered in small spines. These spines have backward facing microscopic barbs, making the barbs function more like arrowheads, doing as much damage on the way out as it did on the way in. In the summer, these spines contain histamines. The histamines are a way to goad animals into eating it's fruit, which contains antihistamines.

Cactrees reproduce asexually as well as sexually. The asexual method goes as follows, the bulbous twigs fall off and get stuck to a mammal, the twig falls off at some point and roots in a different area. This cutting is an exact genetic copy of the parent plant. The sexual method goes as follows, 2 foot tall stalks grow at maturity, on spring nights, white trumpet shaped flowers bloom, bats come to lick nectar from the flowers, getting pollen on them in the process, the pollen is transferred to a female plant and a fruit grows. The fruit falls on the ground where birds or small mammals eat them, the seeds are defecated and grow somewhere else. Flower stalks grow out of the larger branches as well as the main stem. 

Ecology

Cactrees don't grow too close to each other, they only grow within about 30 feet of each other. This spacing is due to the cactree's root system, which spreads as far out as it possibly can to collect as much water as possible. Cactree forests are known as spine barrens. 

Cactree forests are home to many unique desert species. The understory is full of  other colorful succulents as well as other plants. Cactrees themselves act as nesting grounds for birds. Birds like to take fur that gets caught on the spines to make their nests.

Spine barrens have constant ecological resets. Once every 10-15 years, flash floods occur in the spine barrens. The amount of water drowns the cactrees or gives them root rot, either way they die out. Dead cactrees leave behind dried lut skeletons, as do the other cacti present in the area. These dried out skeletons eventually catch fire and cause a wildfire. The spine barrens quickly return and the cycle continues.