Table Of ContentMadrono, Vol. 56, No. 1, pp. 58-59, 2009
EVIDENCE OF EXTREME ROOT PROLIFERATION IN RESPONSE TO THE
PRESENCE OF A NUTRIENT RICH RESOURCE PATCH BY
ERIOGONUM PARVIFOLIUM
Milan Mitrovich^
J.
Department of Biology, San Diego State University, 5500 Campanile Drive, San Diego,
CA
92182
[email protected]
Abstract
IdiscoveredevidenceofextremerootproliferationbyEriogomimparvifoliumfollowingtherecovery
ofskeletalremainsofa large, radio-trackedsnakeburiedin thesandduneenvironment attheTijuana
Estuary in San Diego, California. Located beneath an isolated E. parvifolium, the recovered remains
were grossly entangled by a large number of roots generally absent from the adjacent soil. The
apparent massive localized proliferation of roots suggests decomposition of the animal created a
favorable soil mosaic readily utilized by the plant in an otherwise low nutrient environment.
Key Words: Root proliferation, Eriogonum parvifoliunu nutrient patch, root growth response,
resource heterogeneity.
A number ofplant species show plastic growth (32°34'N Latitude, 117°07'W Longitude, 0-6 m
responses when associated with the patchy elevation; see Mitrovich et al. in press). The
distribution ofresources (Robinson 1994; Hodge 1024 ha research reserve, bordered bythecities of
2004). One type of growth response expressed Tijuana (Mexico) and Imperial Beach (USA), is a
when a plant encounters a nutrient rich patch of complex landscape with tidal marsh, alkali flats,
resources is the proliferation of lateral root fallow agricultural fields, riparian woodland,
branching (Hodge 2004). This can be massive in upland sage scrub, and sand dune habitats. The
a region well supplied with a nutrient when the dune formations are limited to a narrow strip
i
remainder ofthe root system is nutrient deprived bordering the ocean and characterized by short
(Robinson 1994). Eriogonum parvifolium Smith dunes rarely reaching further than 125 m inland. \
(Polygonaceae) is a woody perennial shrub The dunes lack trees and are largely vegetated by '
common to stabilized sand dune formations in low-lying perennial plant species including Abro-
the coastal area ofcentral and southern Cahfor- nia umbellata, A. maritima. Ambrosia chamissonis,
nia (Purer 1936). In dune environments individ- Atriplex leucopliylla, Calystegia soldanella, Ca-
m m \
uals of this species can attain 0.3 to 1.0 in missonia cheiranthifolia, E. parvifolium, and Rhus
m m !
height and 0.5 to 2.0 in sprmead with the integrifolia.
taproot extending to a depth of 1.2 and lateral On August 10, 2002 one of the radio-tracked
roots spreading out two to three times as far as snakes, a large, 1.13 m (snout-to-vent length),
the parts above ground (Purer 1936; Hickman 560 g female, who had been active in the dune
1993). Sand dunes are low nutrient environments environment throughout the spring and summer
that show considerable resource heterogeneity seasons, was recorded using a rodent burrow
(Hesp 1991). Living in the low resource environ- located in a small, isolated dune partially covered
ment associated with sand dune formations, E. by E. parvifolium. The use of a small mammal
parvifolium may show a significant root growth burrow as a retreat site is not uncommon for M.
response following an encounter with a large flagellum. However, this individual showed no
nutrient resource. Here, I provide evidence of movement away from the burrow the rest of the
extreme root proliferation by E. parvifolium in year through the spring of 2003. As a result of
i
response to encountering a rich resource patch, detecting no movement the following spring
specifically a >500 g buried animal corpse. when all other tracked snakes were emerging i
{sMpaaIscntei-2cu0os0pe2l,iibsaesfhlapavgaieroltlruomf)o,faImttuhrleatciCk-eyoedaacr1h2swCthouidapychowSnhniatpkhese wftiarngotgmeerd.wiMn.tefrlahgieblelrunmathiaond,diIecdotnhcelupdreedviothues fraaldlioo-r Ii\
surgically implanted with radio-transmitters at This was confirmed when I dug-up the remains
the Tijuana River National Estuarine Research of the animal with the still functioning transmit-
Reserve in San Diego County, California ter on May 28, 2003, 290 days afterthe snakewae
first recorded as entering the burrow. I recovmerec
Bar'PrraensceantParAkdwdraeys,s,IrviGnree,eCnAS9h2i6e1l8d. Ecology, 15360 t0.h7e mrembaeilnoswofthtehesusrnfaakcee aopfprtohexismaantdelydu0n.e6. Thttc i
2009] MITROVICH: EXTREME ROOT PROLIFERATION BY ERIOGONUM PARVIFOLIUM 59
remains were located directly beneath a single, often categorized as mutuahstic (e.g., pollination,
large E. parvifolium. The burrow had collapsed seed dispersal) or antagonistic (e.g., herbivory;
and the transmitter, although intact, was sepa- Gurevitch et al. 2006). Animal droppings are well
rated from the remains by several centimeters. known to contribute to soil quality mosaics that
Only skeletal remains were left. No soft tissue or favor some plants' growth (Harper 1977). Crea-
skin of the animal was present. The snake's tion of a favorable soil mosaic during decompo-
vertebral column was not complete as it was sition is an additional benefit, albeit inadvertent.
broken in several sections and not all sections
were recovered. Acknowledgments
Although the root structures of E. parvifolium Research was funded by t—he National Oceanic and
were largely absent from the excavated soil Atmospheric Administration National Estuarine Re-
removed during the digging process, a large mass search Reserve System dissertation fellowship
of fine roots from the plant were entangled with (#NA170R1185)to MJM, San DiegoState University,
the recovered segments of the vertebral column. and U.S. Geological Survey. I thank S. N. Handel for
The roots were so completely entwined with the his helpful comments on an earlier version of the
vertebrae it was not possible to collect segments manuscript. The California Department of Parks and
of the vertebral column without also harvesting Recreation and U.S. Fish and Wildlife Service granted
roots. It appeared as though the roots entwining access to land, which is also greatly appreciated.
the skeletal remains were still connected to the Literature Cited
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