Allocation Patterns of Carbon and Minerals in Juvenile and Small-Adult Juniperus occidentalis

Abstract

Abstract Allocation patterns in juvenile and small-adult western juniper (Juniperus occidentalis Hook. subsp. occidentalis) were studied to understand how a successful, invasive, native species balances the allocation of resources between above-ground tissue to optimize photosynthetic capacity, and below-ground tissue to maintain itself in a semi-arid environment. Above- and below-ground biomass, gross heat of combustion, concentrations of macro- and micronutrient elements, and construction costs were measured on seven trees with 100% juvenile foliage (juveniles) and seven with both juvenile and adult foliage (small-adults) from a site in central Oregon. Adult foliage had the highest heat of combustion, nitrogen concentrations, and construction cost. Allocation patterns indicated a larger investment in resources to above-ground than below-ground tissue in both juvenile and small-adult J. occidentalis. The proportions by weight of nutrient elements in juniper foliage were 1.3 to 29 times higher that the optimal proportions required for maximum growth of Pinus sylvestris. The relatively high nutrient status of J. occidentalis may indicate that additional root biomass is not required to balance the activity and relative growth rate of above-ground tissue. Assuming that unrecovered fine roots were a similar percentage of total root dry mass and that sampling errors were similar between studies, J. occidentalis had high root:shoot ratios when compared with other conifer species from more mesic habitats and Larrea tridentata from more xeric habitats. Compared with similar-aged species for which data are available, juvenile and small adult J. occidentalis allocate larger proportions of dry mass to foliage, to optimize photosynthetic capacity, and to roots, to optimize water and nutrient acquisition; the larger allocation to foliage and roots was accomplished through reduction of allocation to branch/trunk. For. Sci. 36(3):734-747.