Ecology 5th Edition by Manuel Molles

Exercise 13

The last major natural reproduction by Rio Grande cottonwoods, which produced the large number of 40- and 50-year-old trees documented by Howe and Knopf (1991), occurred before the last major dam was built on the river. Is there any evidence for reproductive failure before that dam was built (see fig. 10.20)?
Figure 10.20 Age distribution of a population of Rio Grande cottonwoods, Populus deltoides subsp. wislizenii, near Belen, New Mexico (data from Howe and Knopf 1991).