Good News for Regeneration of Tropical Forests

Tropical Forests Recover From Clear-Cutting
Emily Sohn, Discovery News

Feb. 18, 2009 -- Deforestation is generally considered to be bad news, especially in the tropics. But there may be some hope: In many places, trees are growing back, according to new research, and some of the new forests are nearly as diverse as the old ones were.

The work adds to a growing sense that tropical forests are more resilient than scientists previously thought and that second-growth forests are far from worthless.

To read the full story, visit the Discovery Channel website at http://dsc.discovery.com/news/2009/02/18/deforestation-trees.html

Monotropaceae

This plant grows in the highland oak forests of the Talamanca mountain range in Costa Rica, at about 2700m altitude. While I don’t have a positive ID on the photo, the plant most likely belongs to the family Monotropaceae, the Indian Pipe family. Some taxonomists consider Monotropaceae a subfamily of Ericaceae (this was the family featured in my last post, which contains blueberries and cranberries).

Most monotropes are mycoheterotrophs. This means they parasitize fungi. In some cases, these same fungi parasitize the roots of other plants. For this reason, monotropes are often called ‘epiparasites’. Monotropes cannot photosynthesize on their own and depend entirely on fungi for nutrients and sugars. Moreover, there is evidence that monotropes are specialized, in that each species can parasitize only a narrow range of fungal species (Cullings et al. 1996, Kretzer et al. 2000).

The structure pictured here is called an inflorescence. It consists of a compact group of small white flowers. It is the only part of the monotrope that can be seen above ground. Like fungi, the monotropes spend most of their life cycle underground and only emerge for the purpose of sexual reproduction.

This plant from Costa Rica closely resembles Pleuricospora fimbriolata, the fringed pinesap, which is found in pine forests on the west coast of the United States.

References:
Cullings, K.W., T.M. Szaro and T.D. Bruns. 1996. Evolution of extreme specialization within a lineage of ectomycorrhizal epiparasites. Nature 379:63 – 66.

Kretzer, Annette M., Martin I. Bidartondo, Lisa C. Grubisha, Joseph W. Spatafora, Timothy M. Szaro and Thomas D. Bruns. 2000. Regional specialization of Sarcodes sanguinea (Ericaceae) on a single fungal symbiont from the Rhizopogon ellenae (Rhizopogonaceae) species complex. American Journal of Botany 87:1778-1782.

Ericaceae

Today’s 'plant' of the day is one of my favorite families, the Ericaceae. Blueberry bushes are among the 4000 species included in the Ericaceae. Other familiar plants like cranberries and rhododendrons are also found here. The family is worldwide in distribution, but its center of diversity is in the American tropics. Most members of this group are small bushes or shrubs that do well on acidic soils. The flowers often have a bell or urn shape. Leaves are often small and thick, adapted for dry conditions.

The plants pictured here are from Costa Rica. They grow above 3000m altitude (9000 feet) and are often pollinated by hummingbirds or bumble bees (usually Bombus epiphiatus - a VERY cute bee, but that's a whole other story...)

Ericaceae are most diverse in the Andes, with the highest species numbers in Colombia and Ecuador between 1000m and 3000m (Luteyn 2002). 70% of the genera and 94% of the species of Ericaceae are native to the Neotropics.

One remarkable aspect of Ericaceae is their symbiotic relationship with mycorrhizal fungi. In the case of Andean Ericaceae, the fungi are mostly basidiomycetes. They form a sheath around fine rootlets and aid the plant in deriving nutrients from poor, acidic soils (Setaro et al 2008).

The first photo on this post is wild blueberry (Vacinium sp.) from the paramo of Costa Rica. The second photo is Pernettia sp., also found on the paramo. It is smaller than Vacinium and produces tiny red fruits that are edible and taste great.

References:
Luteyn, JL. 2002. Diversity, adaptation and endemism in the neotropical Ericaceae: biogeographical patterns in the vacciniaea. Botanical Review. 68(1):55-87.

Setaro, Sabrina, Kathleen Kron and Ingrid Kottke. 2008. Neotropical Ericaceae and their mycorrhizal fungi. Botany Without Borders. University of British Columbia, Vancouver, BC. July 26-30.