Phenology of the Drought‐Deciduous Shrub Lotus scoparius: Climatic Controls and Adaptive Significance

Abstract

In regions of mediterranean climate drought deciduousness has been considered an important adaptation for many species. This investigation focuses on the influences of a mediterranean climate on the phenology of a drought—deciduous shrub Lotus scoparius ssp. scoparius. Two research sites were chosen in the Santa Ynez mountains northwest of Santa Barbara, California for the field investigations. Phenological progressions of leaf production, leaf composition, shoot elongation, lateral branch production, and flowering in even—aged stands of Lotus scoparius were correlated with such factors as temperature, relative humidity, soil moisture, plant water relations, and photoperiod. These correlations were determined during a characteristic and uncharacteristic growing season for this mediterranean—climate region. Field correlations were the basis for the design of laboratory experiments in which the influences of photoperiod, temperature, water stress, and total daily photon flux on the phenological development of Lotus scoparius were studied. Climatic controls over Lotus scoparius phenology are complex with water relations and photoperiod having the greatest influence. Photoperiodic control over leaf abscission during water stress, and leaf production following dormancy, were two important phenological phenomena related to the unpredictably fluctuating mediterranean climate of southern California. The complex climatic control over phenology in Lotus scoparius constitutes an adaptation to the California mediterranean climate.

Measures of resilience: the response of coastal sage scrub to fire

“…Figure 3a indicates that when focus is placed on recovery of shrub cover (including suffrutescent subshrubs), Site 1 exhibits much greater elasticity than Site 47 (2 growing seasons vs. more than 6 to half-recovery; Table 2). Shrub cover is both a better indicator of the recovery of gross vegetative structure in this community, and a parameter somewhat less sensitive to annual variations in precipitation (with the caveat that foliar cover is highly plastic in relation to the seasonal course of moisture availability; Westman, 1981c;Nilsen & Muller, 1981).…”

Flowering, shoot extension, and reproductive performance of heather,Calluna vulgaris(L.) Hull, in Tongariro National Park, New Zealand

“…The phenology of flowering and shoot extension has long been recognised as an important aspect of the adaptation of shrubs to their environment (Jackson 1966;Lindholm 1980;Primack 1980;Nilsen & Muller 1981;Reader 1983;Rathcke & Lacey 1985). In Tongariro National Park, New Zealand, Calluna vulgaris (L.) Hull is an introduced species of European origin, which competes with native New Zealand plants (Bagnall 1982;Chapman & Bannister 1990).…”

Caragana korshinskii seedlings maintain positive photosynthesis during short-term, severe drought stress

“…Maintenance of turgor by osmotic adjustment, which results from the accumulation of solutes, such as sugars, organic acids, and proline (Turner and Jones 1980), has been shown to be another physiological characteristic by which plants adapt to water deficits (Turner and Jones 1980). Under morphological ---responses, plants can increase biomass allocation to the roots to increase water uptake (Palta and Watt 2009), and shed leaves to reduce the water requirements and maintain high water potentials (Morgan et al 1977, Nilsen and Muller 1981, Mahouachi et al 2006.…”