Trees of NCOS

As the North Campus Open Space nears the completion of year 5 of restoration the site continues to grow and change as plants mature and form distinct habitat areas. Some of the areas where the site will change most in terms of plant growth in the coming years are the riparian corridors where oaks, alders, cottonwoods, and sycamores have been planted. As the trees grow, these riparian zones will become shady refuges for wildlife. Throughout the entire site 264 trees have been planted: 8 Arroyo Willow (Salix lasiolepsis), 27 Narrowleaf Willow (Salix exigua), 9 White Alder (Alnus rhombifoia), 15 Black Cottonwoods (Populus trichocarpa), 15 California Sycamore (Platanus racemosa), and 190 Coast Live Oak (Quercus agrifolia).


California Sycamore (Platanus racemosa)                                       Coast live oak (Quercus agrifolia)       



Arroyo willow (Salix lasiolepis)                                                           Narrowleaf willow (Salix exigua)      



White Alder (Alnus rhombifolia)                                                              Black Cottonwood (Populus trichocarpa)


Map of trees planted during the first three years of the North Campus Open Space restoration project.

Every year these trees are monitored for height, diameter, and vigor to assess their health. Overall, every year of monitoring had an increase in growth for all six species. A comparison of the year four and year five data for trees planted shows an increase in overall mean height by 18 inches, from an average of 97 to 115 inches. There was also an increase in mean diameter from 1 to 2 inches, while the mean overall vigor rating stayed relatively the same.


Bar charts of  the mean height in inches (top) and mean diameter at breast height in inches (bottom) of six tree species planted at the North Campus Open Space restoration project. Error bars are +/- one standard deviation of the mean.


The species that exhibited the greatest increase in mean height in year five is the white alder (Alnus rhombifolia), which had a mean height increase from year four to year five of 34 inches. White alder near the Whittier channel grows at an astonishing rate compared to other species and locations, with an average height of 24 feet. The white alder are significantly taller than other species and also have one of the largest diameters compared to other tree species. The greatest average tree diameter increase was seen in Coast Live oak (Quercus agrifolia), which increased an average of 1.3 inches from year four to year five. These growth patterns were observed in every year of monitoring.


This scatter plot of tree height and diameter represents all living planted trees that are part of the study within the NCOS property in year 4. The size of point represents the vigor or health of the tree, 1 represents the healthiest tree, while 4 represents a dead tree.


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