Biomass, Production, and Changes in the Availability of Light, Water, and Nutrients During the Development of Pure Stands of the Chaparral Shrub, Ceanothus Megacarpus, After Fire
1980
Schlesinger, William H. | Gill, David S.
Pure stands of the evergeen shrub, Ceanothus megacarpus, attain a mean of 4871 g/m² in aboveground live biomass in 21 yr of growth after fire in the Santa Ynez Mountains of California. Mean net aboveground primary productivity is 850 g°m— ²°y— ¹. In 21—yr—old stands there is also 990 g/m² of attached dead wood as lower branches on the living shrubs and 476 g/m² of standing dead shrubs that have died during the thinning of these stands due to intraspecific competition. During stand development, leaf—area—index increases to 1.6 m²/m² and available light below the canopy decreases linearly with increasing leaf biomass. Foliar mineral analyses suggest no foliar deficiencies of minerals in stands up to 20 yr old. Many years are required for the development of extensive root systems which are able to decrease the water stress experienced by C. megacarpus during summer drought. Water potential measurements show that moisture is a more limited resource in young (6—yr—old) stands that in older, well—developed stands, though the latter have considerably more leaf area for transpiration. Density—dependent competition for moisture may drive the self—thinning process seen in stands of C. megacarpus during an interval from 5 to 15 yr after fire, but decreasing available light may determine steady—state levels of vertical structure and biomass in this evergreen community.
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