## 3 Results and Discussion
### Autotrophic Respiration  
There were differences between aboveground root tissue and aboveground stem tissues in respiration rates (Table 1). We used a respiration rate of 3.3 \(\upmu\)mol CO\({}_{2}\) m\({}^{-2}\cdot\)s\({}^{-1}\) for aboveground roots and 1.27 \(\upmu\)mol m\({}^{-2}\cdot\)s\({}^{-1}\) for woody stem tissues in order to scale-up aboveground woody tissue respiration to the whole tree and stand level. Respiration of aboveground components (leaves, stems, aboveground roots) accounted for a large proportion of GPP in seaward fringing forests (68%), scrub forests (94%) and P fertilized scrub (88%). These values reflect the large aboveground root biomass that occurs in these forests (Table 1). We estimated 7.1 \(\pm\) 3.9 m of aboveground root length per tree in scrub trees (0.6 m\({}^{2}\) surface area), 61 \(\pm\) 20 m (5.4 m\({}^{2}\) surface area) in seaward fringing trees and 39 \(\pm\) 16 m (2.8 m\({}^{2}\) surface area) for P fertilized scrub trees. Our C budget indicates, similar to other forests that respiration of the biomass accounts for the largest fraction of GPP [13]. We found that aboveground roots and stems are a significant respiratory sink with values similar to canopy respiration in the fringing forest, and values proportionally lower in the scrub and P fertilized scrub. _Rhizophrenia__angle_ under flooded (and nutrient limited) conditions produces a large biomass of aboveground roots [53]. This component of mangrove tree metabolism has rarely been explicitly included in C budgets but could be a large factor in some forests, particularly where primary production is low but aboveground root biomass is high [54]. The magnitude of our estimate of respiration of woody tissues could be overestimated because: (1) Aboveground roots and twigs of mangroves are photosynthetically active [55, 56], which at high levels of solar radiation (as occurs in the scrub forest) may reclaim respired CO\({}_{2}\). Measurements in other mangrove species indicate the epidermis of roots and twigs remove 90% of incident photosynthetic radiation [57], thus, over estimation of respiration from woody tissues would most likely occur in the scrub habitats where woody tissues are exposed to high levels of solar radiation compared to fringing habitats where aboveground roots are shaded by the canopy; (2) Rates of respiration measured in detached tissues may be higher than that for intact trees. Rates of stem respiration measured in pine species [41] were lower than the values we observed. [PERSON] _et al._[43] observed values of 0.2-0.6 \(\upmu\)mol CO\({}_{2}\) m\({}^{-2}\cdot\)s\({}^{-1}\) while our aboveground tissues had mean values of 1.44 \(\upmu\)mol CO\({}_{2}\) m\({}^{-2}\cdot\)s\({}^{-1}\) and aboveground roots even higher at 3.8 \(\upmu\)mol CO\({}_{2}\) m\({}^{-2}\cdot\)s\({}^{-1}\). In contrast, fine root respiration rates of _R.__angle_ were lower than most other species [50]. But, high levels of aerenchyma tissues that occur in aboveground roots of mangroves may impose a high metabolic cost as well as high respiration rates in aboveground roots and stems [58]. Given the sensitivity of respiration to temperature and rising levels of atmospheric CO\({}_{2}\)[59], further work is required to fully understand this component of mangrove forest C budgets. Over-estimation of the respiration of woody tissue would increase the unaccounted for fraction of C in the budget (the net ecosystem production, NEP), potentially leading to an underestimation of C available for export (described below). Other output components of the C budget are comparatively small and within the range observed in other studies. Litter production was similar to that predicted by the relationship between precipitation and export of litter [60]. Wood production was also similar to that measured in other low productivity mangrove forests [61], accounting for 3% of GPP in fringing forest and P fertilized scrub but lower (\(<\)1%) in the scrub forests. Losses to canopy herbiv are \(<\)1% of GPP.