[APWG] Native understory not reproducing? Bigger problem than weed

[Craig Dremann - Redwood City Seed Company]

Dear All,

Regarding the recent comments by Ty and Wayne about Great Basin cheatgrass
and understories.

Frequently overlooked and rarely measured, is the very important question
that must be asked---is your native grass understory that you want to
compete with the cheatgrass or weeds, actually reproducing?

You can do that by measuring the basal diameter of 100 individuals in a
population, and if you see they are all grandpas and no little ones, there
is something terribly wrong.

If the native grass understory is not reproducing, then the exotics can
colonize all the bare spaces caused by sheep and cattle, before the
natives can.   That is what I see frequently throughout California and the
Great Basin---grandpa native grasses with no little ones.

One reason a native grass population could not be reproducing, is that the
seeds are nipped off by the sheep or cattle, before they can drop into the
soil every year, which can be easily remedied by just stopping grazing
every few years, to allow the plants to produce seeds.

But the worst reason, that will take tens of billions of dollars to cure
on public lands of the arid West, is when the sheep and cattle have
dropped the soil nutrient levels, especially the soil organic matter and
phosphorus, below the minimum survival level for the local native grass
seedlings.

I would be very interested in any measurements any readers of this
message,  do on their local native grass populations.

I usually go out with a sheet on a clip board, with the different
diameters listed as categories, and just put a tick mark for each one
measured.  I use <1/4”, 1/4”, 1/2”. 1”, 2”, 3” etc. and every inch up to
the largest diameter.  When I have measured 100 individuals, the
age-pyramid appears on the sheet, and should not be an upside-down
pyramid, with no young, and the bulk being old plants.

I think if we look at our native grass understory nationwide, especially
our forest grasses on the East Coast, and our mid-western prairie grasses,
and our Great Basin and California arid lands grasses, a very interesting
picture of actual reproduction may emerge.

Grazing of native grasslands anywhere in the USA, has been a
phosphorus-mining operation, where the animals eat the phosphorus out of
the ecosystem, and carry it away in their bones, then we eat the animals,
and do not bring their bones back to the land where they grazed.

It is like a phosphorus soil bank account, with 100 years or more of
withdrawals,

After doing an age-pyramid in the Great Basin on several species of native
grasses to check their reproduction within a 100 mile long Megatransect, I
found only a single population that was reproducing, and the rest of the
100 miles, only old grandpas grew, surrounded by below-minimum nutrient
levels for seedling survival.

Without the ability of our native plant understories to reproduce, and
correcting that weakness in the ecosystem first, we humans have no chance
to manage or control any exotics that would get established in those
critically weakened areas, where the understory is aging-out and headed
towards extinction.

Sincerely,  Craig Dremann (650) 325-7333