Abstract Detail



Ecology

Borer, Catherine [1], Leathers, Jack [2].

Altered calcium cycling in the forest understory in the context of flowering dogwood decline.

     Flowering dogwood (Cornus florida L.) is a charismatic and ecologically important understory tree species. It has been described as a calcium “pump” in forested ecosystems, serving to increase soil calcium availability for uptake by other species. It does this through its comparatively high foliar calcium content and rapid leaf litter decomposition. This enhanced calcium cycling is further explained by the high proportion of labile calcium in the leaves of flowering dogwood, which we have demonstrated by means of sequential foliar extractions. In contrast, many other tree species can sequester and crystalize a substantial fraction of their foliar calcium in a physiologically unavailable form, which is only slowly released into the soil as leaf litter decomposes. Calcium is an essential macronutrient, serving as a ubiquitous intracellular second messenger in physiological response pathways to numerous internal and external environmental cues, and helping to stabilize the structure of cell walls and plasma membranes.
     In many parts of its range, flowering dogwood populations are declining as a result of the ongoing spread of dogwood anthracnose (Discula destructiva), a fungal pathogen. In affected areas, the loss of flowering dogwood could have wide-reaching effects on the many ecological processes that rely on its calcium cycling. Our goal in this study was to evaluate the potential influence of other understory species on ecological calcium cycling, as flowering dogwood declines and forest communities shift in response. We used sequential acidic extractions to evaluate calcium partitioning and sequestration in leaves from seven understory species (four native and three invasive) that are commonly found on the campus of Berry College, in northwest Georgia, USA. Species included flowering dogwood, eastern redbud (Cercis canadensis), American holly (Ilex opaca), muscadine (Vitis rotundifolia), Chinese privet (Ligustrum sinense), Chinese holly (Ilex cornuta), and leatherleaf mahonia (Mahonia bealei). As expected, we found significantly more labile calcium in the foliage of flowering dogwood than the other species we evaluated. We also found that some of the other species in our study, such as eastern redbud, retained a substantial fraction of their foliar calcium in labile forms rather than chemically sequestering it, although their total foliar calcium was significantly lower than that of flowering dogwood. These results suggest that forest calcium cycling may slow as flowering dogwood declines, although some understory species may play an increasingly important role in calcium cycling.


1 - Berry College, Biology, P.O. Box 490430, Mount Berry, GA, 30149, United States
2 - Berry College, Biology, P.O. Box 490430, Mount Berry, GA, 30149, USA

Keywords:
Flowering dogwood
Calcium cycling
Mineral nutrition
Cornus florida
understory.

Presentation Type: Poster Time and date to be determined
Number: PEC017
Abstract ID:625
Candidate for Awards:None


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