## 4 Aboveground Net Primary Production
### Wood Production  
Wood production is most often measured as changes in the diameter-at-breast height (dbh) to calculate changes in stem biomass over time. Tree biomass is measured using allometric equations from measurements of the tree height and dbh. Increases in mangrove wood biomass are then converted to C\({}_{\text{ORG}}\) units by multiplying the DW biomass by 0.48, which is the average C\({}_{\text{ORG}}\) content of mangrove wood [8]. Based on 125 observations, the rates of wood production averaged 1.2 (1.0 \(\pm\) 1 SD) g C m\({}^{-2}\) d\({}^{-1}\) (=4.5 Mg C ha\({}^{-1}\) y\({}^{-1}\)), with a median of 1.0 g C m\({}^{-2}\) d\({}^{-1}\) and a range of 0.0-6.6 g C m\({}^{-2}\) d\({}^{-1}\)[4; 54; 55; 56; 57; 71; 72; 73; 74; 75; 76; 77; 78; 79; 106; 123; 124; 125; 128; 125; 126; 127; 128; 129; 130; 131; 132; 133; 134; 135; 136; 137; 138; 139; 140; 141; 142; 143; 144; 145; 146; 147; 148; 149; 150; 151; 152; 153; 154]. Globally, wood production correlated positively with temperature (Spearman's r = 0.347, \(p\) < 0.001) and rainfall (r = 0.255, \(p\) < 0.001), as production is globally influenced by regional climates and hydroperids [132]. The mean rate of wood production calculated here is close to earlier estimates of 4.8 Mg C ha\({}^{-1}\) y\({}^{-1}\)[123], 2.8 Mg C ha\({}^{-1}\) y\({}^{-1}\)[4], and 4.0 Mg C ha\({}^{-1}\) y\({}^{-1}\)[124; 133]. A range of woody biomass accumulation of 0.0-6.7 g C m\({}^{-2}\) d\({}^{-1}\) was previously calculated [133] which is identical to my calculations. However, the ratio of wood/litter production is estimated here at 0.6 which is less than the earlier calculated ratios of 1.0 [123], 1.0 [4], and 0.9 [124]. This discrepancy may be attributed to the fact that the extrapolations here are based on measurements of biomass increments over time which do not consider processes, such as natural gap formation and regeneration, that contribute to biomass turnover. The wood production in other tropical moist forests is within the same range, averaging from 2.7 to 11.3 Mg C ha\({}^{-1}\) y\({}^{-1}\)[134]. Globally, incremental increases in the mangrove tree dbh average 0.31 cm y\({}^{-1}\) and range from 0.0 to 1.8 cm y\({}^{-1}\)[133]. However, locally and regionally, stem growth can be influenced by precipitation during the dry season, whereas species composition influences the biomass incremental growth within areas of lower rainfall [124]. Thus, different drivers may operate at different spatial scales. Wood production at the global scale did not correlate with forest age, but at individual locations, there is frequently a pattern of increasing wood production with plantation age. For example, there is a curvilinear relationship of _Rhizophora apiculata_ plantations in Thailand, with a linear increase in tree growth from <1 to 10-12 y (Figure 6) with a clear decline until 80 y. In other undisturbed mangrove forests, the tree growth reaches a maximum growth rate after 35 y [130; 155]. Mangrove wood growth-age patterns closely mimic those of other tropical trees [156]. Wood production rates at the local scale are also influenced by geomorphological settings, with a greater wood production in riverine and interior forests than in fringing stands [158]. Other drivers likely to impact stem growth are edaphic factors, such as the sediment organic carbon content, nutrient concentrations and availability, disturbance history, and climate. Differences in global patterns of wood production were found between plantation and non-plantation mangroves [133]. In non-plantation mangroves, climatic conditions are the most important factors influencing the global pattern of the tree dbh growth rate, with edaphic and biological characteristics also playing a role under specific climatic conditions, such as seasonal variations in precipitation. Forest age can also strongly influence tree mortality and necromass production in relation to the mortality rates induced by an increased competition in younger stands.