Biomass and carbon dynamics of a tropical mountain rain forest in China

Biometric inventories for 25 years,from 1983 to 2005,indicated that the Jianfengling tropical mountain rain forest in Hainan,China,was either a source or a modest sink of carbon.Overall,this forest was a small carbon sink with an accumulation rate of(0.56±0.22) Mg C ha-1yr-1,integrated from the long-term measurement data of two plots(P9201 and P8302).These findings were similar to those for African and American rain forests((0.62±0.23) Mg C ha-1yr-1).The carbon density varied between(201.43±29.38) Mg C ha-1 and(229.16±39.2) Mg C ha-1,and averaged(214.17±32.42) Mg C ha-1 for plot P9201.Plot P8302,however,varied between(223.95±45.92) Mg C ha-1 and(254.85±48.86) Mg C ha-1,and averaged(243.35±47.64) Mg C ha-1.Quadratic relationships were found between the strength of carbon sequestration and heavy rainstorms and dry months.Precipitation and evapotranspiration are two major factors controlling carbon sequestration in the tropical mountain rain forest.

Soil respiration and its partitioning in different components in tropical primary and secondary mountain rain forests in Hainan Island,china

Aims Soil respiration is one of the most important components in the car-bon(c)cycle in terrestrial ecosystems.to investigate the contribution of each component of c cycle to the total soil c efflux,we quantified the rates of litter,root,and other mineral soil respiration from 2012 to 2014 in the primary and secondary tropical mountain rain forests in Hainan Island,china.Methods the seasonal dynamics of soil(Rs),non-litter(RNL)and non-root(RNR)respiration rates were measured using an automatic chamber system(Li-8100).Litter removal and root removal treatments were used to assess the contribution of litter and roots to belowground c production.We estimated the annual c efflux of each compo-nent of soil respiration in primary and secondary forests using a temperature-based exponential model and analyzed the impact of each component in each forest type.Important Findingsthe annual total soil c efflux was significantly higher in the primary rain forest(1567±205 g c m^(−2)yr^(−1))than that in the secondary forest(1300±70 g c m^(−2)yr^(−1),P<0.05).the litter,root,and mineral soils contributed 22%(349±185 g c m^(−2)yr^(−1)),38%(589±100 g c m^(−2)yr^(−1)),and 40%(628±128 g c m^(−2)yr^(−1))to the total soil c efflux in primary rain forest,respectively.In secondary forest,these three components contributed 11%(148±35 g c m^(−2)yr^(−1)),45%(572±259 g c m^(−2)yr^(−1)),and 44%(580±226 g c m^(−2)yr^(−1)),respectively.the temperature sensitivity(Q10)of Rs(2.70±0.14)in the primary forest was significantly higher than that in the secondary forest(2.34±0.12),with the Q10 values for respiration decreasing in the order of RNR>Rs>RNL.these results show that the difference in litter respiration between primary and secondary forest caused the major difference in annual soil respiration efflux between these two forest types.In addition,the litter respiration is more sensitive to the soil temperature than the other soil respiration components.