Are the Native Grass Population in the Southwest "Zombies"?

Just so you understand where I am coming from, when I write this article, my company is The Reveg Edge in Redwood City, California. I have Native heritage from my great grandmother Hannah, of the Tuscarora Nation of North Carolina, so I may have very different perspectives when restoring native grasslands, compared to my European grandparents' generations, who have only been here for 10-12 generations.

These North American native grasslands and wildflower meadows have been sacred to my Native relatives for over 1,000 generations, whereas, so far there seems to be no grasslands or wildflower meadows in North America which are sacred to my European relatives. 

My grassland restoration methods has been able to restore native grasslands in California since 1992, and restored 800 acres back to 95% native cover so far.  

My sister lives in New Mexico, so when I go and visit, I make sure to visit the different stands of native grasses, and have a chat with them.  Of course the plants may not speak to you in words, but you can learn a lot from them by checking their overall health, like a proper "Land Doctor."

A very easy method to check health of a native grassland, is to measure the basal diameter of 25-100 individuals in a population, and divide the results into age-classes. Like 0-5 cm., 5-10 cm., 10-15 cm., 15-20 cm. and so on.  This is called an "age-pyramid" and is usually done to divide human populations ages into age-groups, to see how they are reproducing, and where trauma in the past may have wiped out whole age-groups like wars, famine or diseases.

A normal human age pyramid has a wide base which narrows down to a point, which is why it is called an "age-pyramid" whereas the normal Southwest and Great Basin native grassland age pyramid looks like a column somewhat narrow at the base and with a point at the top.   However, what happens when you encounter a population with an upside down age pyramid--no seedlings and no young plants?

That means that stand of native grass has stopped reproducing— then, those plants are going to age-out and eventually go extinct on that site. I call these populations "Zombies".

If you are missing young seedlings in your grass populations, you have a Zombie ecosystem, and that might be occurring in the same area with the shrubs and perennial herbaceous plants too.

Until you confirm the presence or absence of Zombies, any comparison between different grassland-management methods is useless, because you could be comparing a healthy and reproducing ecosystem, with a Zombie ecosystem that is aging out and moving over time towards eventual extinction.

Plus, the presence of Zombies can always be a very important cause of failures when replanting Southwestern and Great Basin native grass seeds, after fires for example.

If your ecosystem is already Zombie-infested, your seeding projects may produce failure after failure until you correct the issues that created the Zombies in the first place. The 2017 USGS report found that 70% of the Great Basin native seeding projects were failures, and the presence of Zombies need to be investigated in the future, to see how they could be contributing to those failures. (Pilliod, 2017).

In the Southwest and arid Western USA--whenever I go out searching for Zombies--I find them very easily. When I did a survey of a dozen different native grass species in New Mexico south of Albuquerque, and every species was Zombies, and a few had not reproduced maybe for a century, like the Galleta grass (Hilaria jamesii).

Future widespread Zombie-surveys may discover that perhaps 90% of our grasslands west of the Rockies are full of Zombies. And below about 40 cm. (16 inches) of annual rainfall, you might find close to 100% of the grass species have become Zombies. Which means, within 100-200 years, the entire western USA grassland biome could become extinct?

Whenever you want to properly monitor and manage any public Southwestern grasslands, for Federal grazing allotments that cover tens of millions of hectares for example, you need to know first--is that grassland reproducing, or has it turned into Zombies?

This is an example of a Zombie ecosystem in Bluebunch wheatgrass (Pseudoroegneria spicata) north of Reno Nevada, that has been Zombies for a long time, maybe decades: (# of plants):

Diameter 0-2 inches (0-5 cm) = 0

2-4 inches (5-10 cm) = 0

4-6 inches (10-15 cm) = 0

6-8 inches (15-20 cm) = 3

 8-10 inches (20-25 cm) = 10

10-12 inches (25-30 cm) = 8

12-16 inches (30-40 cm) = 9

>16 inches (40 cm) = 0

A healthy, reproducing population of Indian Ricegrass (Achnatherum hymenoides) near Pyramid Lake, Nevada: (# of plants):

Diameter 0-1 inch (0-2.5 cm) = 6

1-2 inch (2.5-5 cm) = 13

2-4 inches (5-10 cm) = 13

4-6 inches (10-15 cm) = 5

 > 6 inches (15 cm) = 0

A population of Great Basin Wild Rye (Leymus cinerius) north of Reno might be turning into Zombies but only very recently, and producing an age-pyramid that looks like an airplane wing cross section:

Diameter 0-1 inch (0-2.5 cm) = 1

1-2 inches (2.5-5 cm) = 3

2-4 inches (5-10 cm) = 8

4-6 inches (10-15 cm) = 6

6-8 inches (15-20 cm) = 5

8-10 inches (20-25 cm) = 3

10-14 inches (25-35 cm) = 3

14-18 inches (35-45 cm) = 2

18-24 inches (45-60 cm) = 1

24-36 inches (60-90 cm) = 1

>36 inches (90 cm) = 0

 

References—

Dremann, Craig Carlton. 2021. "Searching for Zombies" Posted on Research Gate, written for the ranchers of Nevada. On-line at https://www.researchgate.net/publication/348588754_1-SEARCHING-FOR-ZOMBIES

 

 Pilliod, David et al. 2017. Seventy-Five Years of Vegetation Treatments on Public Rangelands in the Great Basin of North America. On-line at https://pubs.er.usgs.gov/publication/70180019