SENSITIVE AREAS OF THE EASTERN SAN GABRIEL MOUNTAINS

Fresh Water Marshes

Big Dalton Canyon Debris Basin
Los Angeles County Flood Control Department
Los Angeles County
Glendora

by Dick Swinney
Copyright September 2007

Observations: This area is a major focus of my observations on the plants and animals of Glendora including reptiles, amphibians, invertebrates and birds. I have observed this area several hundred times in the last forty-five years. I did not record my own voucher number for the majority of the early Glendora specimens.
Location: 0.4 miles east of Glendora Mountain Road on Big Dalton Canyon
Road. Surrounded by the Big Dalton Canyon Wilderness Park.
Elevation: 1100-1120 ft.
Quad: Glendora
T 1N R 9W Section 21
Long. 117 deg. 49 min. 55 sec. W. Lat. 34 deg. 9 min. 03 sec. N.
Description/Habitat:
The amount of surface water varies greatly from year to year. During the driest of years, there may only be limited moisture on the surface and no standing water. On average years, there is a seep area nearly 500 square feet as it drains down into the debris basin from the north-east end. When water flow is present in the adjacent Big Dalton Canyon bottom, the entire debris basin may be moist and have areas of standing water. The surrounding plant community is riparian, coastal-sage scrub and chaparral and Southern Oak Woodland.
Special Conditions: This area may change drastically from year to year. Following years of heavy rainfall, debris removal may last for several months. Most of the surface soil and vegetation is completely removed. This makes this area very unpredictable for speculating what plants may be present. I started ranking plants according to abundance on 6 August 2005. Earlier observations were limited to recording the dates of new species for the study site. The debris basin was cleaned out completely in May of 2005, no plants left standing except for Salix on north side. The August 2005 observations were made, two months after the debris removal. The September 2007 observations were made 12 months after debris removal. Eighty percent of the basin was mowed in mid September. Selective spraying for Ageratina adenophora was applied in areas that were not mowed. These two years have been selected to show recent trends in the plant populations.

* Plants occurring for the first time in 2005.

Names Voucher Numbers 2005 2007

Dicotyledons
Ageratina adenophora C
Amaranthus albus C C
Amaranthus blittoides C U
Amaranthus retroflexus U
Ambrosia acanthcarpa C R
Ambrosia psylostachia C
Ammania coccinea FC U
Anagalus arvensis
Artemisia douglasiana
Baccharis salicifolia U FC
Bidens pilosa U U
Calystegia macrostegia
var. intermedia FC
Castilleja minor
2 years only
14 July, 1997, several plants
Cerastium viscosum U
Chamaesyce serpens FC
Chenopodium ambrosioides U R
Chenopodium botrys FC
Chenopodium californicum A C
Colutea arborescens R
3 Aug, 1991, several plants, N.E. area 1598
Sep., 21,2007, several plants, N.E. area
Conyza bonariensis FC
Conyza canadensis FC A
Cuscuta californica U
on Xanthium strumarium var. canadense
and Ageratina adenophora
Eclypta prostrata A
Epilobium ciliatum FC A
Eremicarpus setigarus
Fraxinus uhdei R (3)
Gnaphalium bicolor
Gnaphalilum californicum
Gnaphalium chilense U
Gnaphalium luteo-album C
Gnaphalium microcephalum FC
Gnaphalium palustre FC
Gnaphalilum perigrinum
Helianthus annuus C C
Hirschfeldia incana FC A
Lactuca serriola U FC
Lotus heermanii C C
Lotus pershianus
Louts salsuginosus FC*
Lotus scoparius
Lupinus hirsutissimus R
Lupinus longifolius U
Lythrum californicum U
Malacothrix saxatilis var. tenuifolia U
Marrubium vulgare FC
Melilotus albus A
Melilotus indicus A
Mimulus gutatus FC A
Mimulus cardinalis FC C
Mimulus floribundus C
Mimulus pilosus
Nicotiana glauca FC U
Penstemon spectabilis
Phacelia cicutarium U
Polygonum punctatum FC C
Polygonum argyrocoleon FC FC
Portulaca oleracea U 22 Sep 1993
Rhamnus calilfornica
Ricinus communis FC FC
Rorippa nasturtium-aquaticum A A
Rorippa palustris ssp. occidentalis
three separate years, near spillway
only
Salilx gooddingii var. variabilis A A
Salix lasiolepis
Salsola tragus FC
Senecio vulgaris U
Solanum douglassii U FC
Sonchus oleraceus FC FC
Stachys albens FC
Stellaria media R
Stephanomeria virgata U
Tamarix ramosissima R (seedlings) FC
Tribulus terestris R*
Verbena tenuisecta
22 Sep 1993, one plant in dry sand
Veronica anagallis-aquatica A A
Xanthium strumarium var. canadense A A

Monocotyledons
Alisma plantago-aquatica FC
present usually when water is allowed to stand for a whole season or more
Bromus madritensis ssp. rubens U FC
Carex alma U
Carex sp. U* (N. side)
Cynodon dactylon R A
2l005 - N. side only
2007 - E. 1/2 & N. side, spreading
Cyperus alternifolius A A
Cyperus difformis
Cyperus erythrorhizos
Cyperus odoratus FC
Echinochloa crusgalli var. crusgalli A A
Gastridium ventricosum
Heleochloa schoenoides A
Juncus balticus
Juncus bufonius
Juncus dubius C
Juncus rugulosus U U
Juncus xiphioides
Lamarckia aurea
Lemna minima
Leptochloa uninervia U (scattered) FC
Poa annua
Polypogon interruptus FC
Polypogon monspeliensis U C
Polypogon semiverticillatus C C
Scirpus acutus 3142
Scirpus cernuus var. californicus FC
Scirpus robustus 1919, 3143
Typha angustifolia C Typha latifolia C A
Zannichellia palustris 1918
17 Sep 1992