Dry Mass Partitioning and Gas Exchange for Young Ocotillos (Fouquieria splendens) in the Sonoran Desert

Abstract

A continuum of juvenile to reproductively mature ocotillos (Fouquieria splendens) was studied to determine changes in dry mass partitioning and production in relation to plant morphology. Gas exchange and productivity for 1-yr-old plants were also studied under controlled temperatures typical of winter, spring, and summer, which are the seasons that receive rain in the Sonoran Desert. Root : shoot ratios of young ocotillos decreased with total plant dry mass, suggesting smaller plants need relatively more soil resources than do larger plants. Young ocotillos had a greater scaling exponent for plant height versus total plant dry mass than for basal diameter versus total plant dry mass, which is indicative of their shoot morphology. Average rooting depth increased only 0.05 m per meter increase in plant height, reflecting the dependence of ocotillos on shallow soil water and explaining their rapid phenological responses to light rainfall events. Young ocotillos experienced maximal CO 2 uptake when exposed to springlike temperatures, which is when soil water is available for the longest period, and partitioned the greatest amount of dry mass to aboveground growth when exposed to summerlike temperatures, which is when ocotillos in the Sonoran Desert typically experience stem growth.

Validation of SMAP Soil Moisture at Terrestrial National Ecological Observatory Network (NEON) Sites Show Potential for Soil Moisture Retrieval in Forested Areas

“…Woody biomass of shrub growth forms was estimated using taxon-specific allometries for the most common taxa (e.g., [51]- [54]), and [48] tree allometries were applied for the remaining species. Nonwoody biomass was estimated using taxon-specific allometries for ferns [55], palms [56], and ocotillo [57]; when taxon-specific allometries were not available, morphological substitutions were made, similar to the approach described by [58]. The aboveground biomass sampling plots were chosen to be representative of the area sampled by the NEON field crews at each site (min: 3 km 2 ; max: 215 km 2 ; mean ±sd: 34 ±34 km 2 ).…”

Perennial plant mortality in the Sonoran and Mojave deserts in response to severe, multi-year drought

“…8) contains three Sonoran Desert species whose growth responses are strongly linked to warm-season precipitation inputs (C. microphyllum, Fouquieria splendens, Jatropha cuneata) (Bobich and Huxman, 2009; J. McAuliffe, pers. obs).…”

Stem succulence controls flower and fruit production but not stem growth in the desert shrub ocotillo (Fouquieria splendens)

“…Succulence and drought deciduousness are two such adaptations, and while they are paired in species such as baobab trees (Chapotin et al., ) and members of the Crassulaceae, Mesembryanthemaceae, and Portulacaceae families (Veste et al., ), succulence is not known to commonly co‐occur with repetitively drought‐deciduous species (those documented to have produced many foliation–defoliation cycles during a growing season). A prominent exception in the deserts of North America is one of its most distinctive (Benson and Darrow, ) and widely distributed (Bobich and Huxman, ) shrub species, ocotillo ( Fouquieria splendens Engelm.). This spine‐laden, stem‐succulent, C 3 shrub is uncommonly capable of rapidly and repetitively producing and losing entire cohorts of its nonxeromorphic leaves (Lersten and Carvey, ) up to five or more times in a single growing season (Cannon, ; Darrow, ; Shreve, ).…”