## 3 Results and Discussion
### Carbon Burial  
Carbon burial in soils, calculated from annual rates of soil surface accretion and C density of soils was higher in the seaward fringing forests (17.6 mol C m\({}^{-2}\cdot\)year\({}^{-1}\)) than in the scrub forests (2.8 mol C m\({}^{-2}\cdot\)year\({}^{-1}\)) and the P fertilized scrub (12.9 mol C m\({}^{-2}\cdot\)year\({}^{-1}\)). These were 4.1% of GPP in the seaward fringe and 2.1% of GPP in both scrub and P fertilized scrub (Table 2). Carbon burial in soils in the fringing forest and P fertilized scrub trees were similar to the global mean of 10.8 mol C m\({}^{-2}\cdot\)year\({}^{-1}\)[4]. Extrapolation of these rates using the area of habitat on Twin Cays indicates that the _R. mangle_ dominated fringe and scrub forests sequesters \(\sim\)27.5 Mg C year\({}^{-1}\) (or about 100 Mg CO\({}_{2}\) equivalents per year) which is \(\sim\)0.02% of the total CO\({}_{2}\) emissions of Belize in 2008 (116 Gg of C [68]). Using areas of scrub and tall/fringing mangrove habitat for the whole country of Belize [69] suggests that nation-wide C burial by these mangrove habitats is 61,600 Mg C year\({}^{-1}\), which is \(\sim\)50% Belize's nation-wide reported CO\({}_{2}\) emissions. The sheer magnitude of the C burial by mangrove habitats in Belize warrants their conservation and restoration where they have been lost. By combining our values of C burial with those in the literature [11] and unpublished values, we found that C burial tends to increase with increasing productivity of the forests (Figure 2). Moreover, fringing forests in Mexico (similar to Belize) were observed to have higher stocks of soil C in fringe (987 Mg C ha\({}^{-1}\)) compared to scrub (381 Mg C ha\({}^{-1}\)) [28]. These findings indicate that soil C stocks accumulated over time may be a function of stable, long term patterns in environmental conditions and productivity over mangrove landscapes in this region. The proportion of GPP that was buried in the fringing forests (4.1%) was higher than that of the scrub forest (2.1%), suggesting more favorable conditions for C burial in fringing forests. However, given the flooded nature of the scrub soils and the low redox potential in these areas [52], we expected the scrub forests to have higher proportional C burial as anoxia reduces decomposition rates of organic  
Figure 2: Variation in carbon burial with gross productivity of mangrove canopies. Data is from [PERSON] [11] (upward triangles), [PERSON] _et al._[70, 71] Moreton Bay, downward triangles) and this study (scrub and fringe forests are circles, P fertilized scrub a star). The form of the curve is \(y=0.682\times 0.0242x\), \(R^{2}=0.27\). matter. Instead, the higher productivity fringing forest had higher proportional rates of C burial. [PERSON] [66] has suggested that some, as yet unidentified aspects of productive mangrove forests, may decrease decomposition of organic matter and increase C burial. Fertilization with P, despite higher productivity of trees, resulted in a smaller proportional burial of carbon (2%) compared to the fringing forest (4%). This observation is consistent with lower proportional allocation of GPP to roots in fertilized plants that has been observed in other \"wild\" plants [22]. However, the ratio of root production to GPP is 4% in scrub forest and 6% in both fringing forests and P fertilized scrub trees. Therefore, rather than differences in proportional allocation to roots, alternative hypotheses to explain differences in proportional C burial between forests zones and with fertilization include: (1) Differences in rates of decomposition may be responsible for the reduced proportional C burial in P fertilized plants compared to fringing forests; or (2) Differences in root structure may contribute to reduced proportional C burial in P fertilized trees.