<P> The bristlecone pine's root system is mostly composed of highly branched, shallow roots, while a few large, branching roots provide structural support . The bristlecone pine is extremely drought tolerant due to its branched shallow root system, its waxy needles, and thick needle cuticles that aid in water retention . </P> <P> The wood is very dense and resinous, and thus resistant to invasion by insects, fungi, and other potential pests . The tree's longevity is due in part to the wood's extreme durability . While other species of trees that grow nearby suffer rot, bare bristlecone pines can endure, even after death, often still standing on their roots, for many centuries . Rather than rot, exposed wood, on living and dead trees, erodes like stone due to wind, rain, and freezing, which creates unusual forms and shapes . </P> <P> The bristlecone pine has an intrinsically low rate of reproduction and regeneration, and it is thought that under present climatic and environmental conditions the rate of regeneration may be insufficient to sustain its population . The species are on the International Union for Conservation of Nature (IUCN) red list . The species are labeled under Least Concern (LC), the justification for this being that no subpopulations for Great Basin bristlecone pines are decreasing . Subpopulations seem to be increasing or remaining stable . Many bristlecone pine habitats have been protected, including the Inyo National Forest's Ancient Bristlecone Pine Forest in the White Mountains of California and the Great Basin National Park in Nevada, where cutting or gathering wood is prohibited . </P> <P> The green pine needles give the twisted branches a bottle - brush appearance . The needles of the tree surround the branch an extent of about one foot near the tip of the limb . The name bristlecone pine refers to the dark purple female cones that bear incurved prickles on their surface . The dark color of these cones help to absorb heat . After maturity, which takes about two years, the cones will become brown in color . These ancient trees have a gnarled and stunted appearance, especially those found at high altitudes, and have reddish - brown bark with deep fissures . As the tree ages, much of its vascular cambium layer may die . In very old specimens, often only a narrow strip of living tissue connects the roots to a handful of live branches . Even though the trees' needles may age, they still remain functional in regulating water and by their ability to photosynthesize . </P>

Bristlecone pine — the oldest trees on earth