Abstract Detail

Ecology

Fryer, Emma [1], Rajakaruna, Nishanta [2], O'Dell, Ryan [3].

The Role of Invasive Species and Soil Chemistry in the Community Assembly of the Vertic Clay Endemic Annual Plant Communities of the San Joaquin Desert.

The San Joaquin Desert (SJD) supports a high diversity of rare, endemic annual plants notable for their massive floral displays following high rainfall winters. In such years, the superblooms on vertic (smectite) clay soils of the SJD form a distinctive color patchwork that reflects the heterogeneous pattern of soil texture and salinity across the landscape. These vertic clay soils are physically extreme to annual plants due to high smectite clay content which causes extensive cracking upon drying, reducing soil moisture access, and creating physical stress for plant roots. These soils are also often chemically extreme due to high sodium content, further rendering them inhospitable to most plants. Like species endemic to other extreme substrates (e.g., serpentine) in California, vertic clay endemic species appear to be specially adapted to these harsh soils. The non-native annual grass, Bromus madritensis, has invaded the vertic clay ecosystems in some areas and begun to displace the vertic clay endemic species. The combination of a diverse suite of vertic clay endemic species (species pool), extreme physical and chemical soil abiotic factors (habitat filter), and the invasion of B. madritensis (competition filter) make this system ideal for studying the factors contributing to plant community assembly. This study aimed to quantify edaphic factors, determining the fundamental niche for these species through a reciprocal transplant study of twelve SJD native annuals across three vertic clay soils spanning three orders of magnitude of sodium content. The role of B. madritensis as a biotic factor acting on these species was addressed by a duplicate set of each species sample with added B. madritensis plants in each native species’ pot, to determine the realized niche of these species. These combined results have informed a preliminary model of the community assembly of the vertic clay endemic flora of the SJD, which includes the different combined and separate effects of both soil chemistry and competition from invasive annual grasses on the species that make up this community.

1 - California Polytechnic State University, San Luis Obispo, Biological Sciences Department, 1 Grand Avenue , San Luis Obispo, CA, 93407, USA
2 - California Polytechnic University, Biological Sciences, One Grand Avenue, San Luis Obispo, CA, 93407, United States
3 - Bureau of Land Management, Central Coast Field Office, 940 2nd Ave, Marina, CA, 93933, USA

Keywords:
community assembly
endemism
soils
invasive species
vertic clay
desert annuals
geoecology.

Presentation Type: Oral Paper
Number: EC01001
Abstract ID:134
Candidate for Awards:Ecological Section Best Graduate Student Paper