Contribution of vegetation fragments to carbon storage in agricultural landscapes of the Peruvian Amazon

In the present study, carbon stocks were quantified in seven agroforestry landscape fragments: (1) heavily logged primary forest, (2) secondary forests of 5, (3) 10, and (4) 15 years originating from pastures, (5) cacao agroforestry, (6) productive Brachiaria decumbens grassland, and (7) degraded Brachiaria decumbens grassland. These fragments are characteristic of agricultural estates in the Ucayali department, Peru. The carbon stored (the total sum of aboveground and soil) in the primary forest was 267.26 t/ha; in 15-year secondary forest, 232.30 t/ha; in 10-year secondary forest, 162.1 t/ha; in 5-year secondary forest, 124.42 t/ha; in cacao agroforestry, 108.82 t/ha; in productive B. decumbens grassland, 72.57 t/ha; and in degraded B. decumbens grassland, 60.47 t/ha. Significant differences (p ≤ 0.0001) were observed between the carbon stock values of the seven fragments (R2 = 0.51, and CV = 53.66%). Orthogonal contrast tests showed that the carbon stored in the primary forest fragment significantly exceeded the average carbon of the other fragments, while the carbon stored in the secondary forests significantly exceeded that stored in the cacao agroforestry fragment. No differences were found in the carbon stored in both grasslands, nor between the 10- and 15-year secondary forests. The increase in the number of families and species directly related to the age of the secondary forest provides evidence of the recovery of botanical diversity.