One of the oldest-known living plants in the New World tropics is featured today: a 3800 year old underground tree from Brazil. Intrigued?
BPotD reader Terry Ludwar (who is working on a checklist of British Columbia’s Texada Island) informed me about underground trees during a phone call and follow-up email last week. After reading the 2013 paper Longevity of the Brazilian underground tree Jacaranda decurrens Cham. by Alves et al., I requested images from Dr. Alves, and he promptly and generously replied.
Jacaranda decurrens is a species endemic to the tropical savannah or Cerrado ecosystem of Brazil. The Cerrado has been estimated to be the most biodiverse savannah in the world, with upwards of 10000 plant species. Factors involved in the biodiversity include seasonality (distinct wet and dry seasons) and diversity in soil fertility, fire periodicity and hydrology. For Jacaranda decurrens, known locally as carobinha or caroba-do-campo, the requirements for growth must include a soil profile of shallow white sand deposits. That is also the case for the sympatric Andira humilis (Fabaceae), the second underground tree visible in the first photograph (the orange-red foliage; sympatric means overlapping distribution, in this case it is so sympatric that the plants are interwoven beneath the soil).
The primary branches (or soboles) of Jacaranda decurrens grow below ground at depths between 10 and 50cm (4-20 in.). Secondary seasonal branches bearing either the foliage or reproductive structures emerge above the soil line each year following the beginning of the wet season. Foliage lasts throughout the wet season, withering upon the start of the dry. During the dry season, the only above ground indication of the tree is the ripening fruit and dessicating branches.
Dr. Alves and his research associates used a procedure combining morphological and growth ring analyses to estimate the age of this plant. There is no single stem to measure from, as one might do for a tree like the previous BPotD entry on Big Lonely Doug. Rather, a number of the thickened branches are measured; when measured, these were estimated to be anywhere between 2613 years old to 5351 years old. Combining and averaging the estimates, Dr. Alves and associates generated an estimate of 3801 years old for this particular plant. Compared against the list of oldest trees, one thing in particular stands out: almost all of the oldest trees, either estimated or verified, grow in temperate regions.
The researchers also noted that Jacaranda decurrens is by no means a common plant. Populations are threatened by long distances from one another (little to no genetic flow), habitat degradation, and overexploitation for folk medicinal uses. Some populations are protected within the parks system, but I am not certain about the aged individual of today’s entry.