Earliest evidence that Mayas raised and traded dogs and other animals-probably for ceremonies-from Ceibal, Guatemala. Published in the Proceedings of the National Academies of Science.

Ecological theory says that poor soils limit the productivity of tropical forests, but adding nutrients as fertilizer rarely increases tree growth, suggesting that productivity is not limited by nutrients after all. Researchers at the Smithsonian Tropical Research Institute (STRI) resolved this apparent contradiction, showing that phosphorus limits the growth of individual tree species but not entire forest communities. Their results, published online in Nature, March 8, have sweeping implications for understanding forest growth and change.