Contrasting patterns of litterfall seasonality and seasonal changes in litter decomposability in a tropical rainforest region

[摘要] The seasonality of litter inputs in forests has important implications forunderstanding ecosystem processes and biogeochemical cycles. We quantifiedthe drivers of seasonality in litterfall and leaf decomposability using plotsthroughout the Australian wet tropical region. Litter fell mostly in thesummer (wet, warm) months in the region, but other peaks occurred throughoutthe year. Litterfall seasonality was modelled well with the level ofdeciduousness of the site (plots with more deciduous species had lowerseasonality than evergreen plots), temperature (higher seasonality in theuplands), disturbance (lower seasonality with more early secondary species)and soil fertility (higher seasonality with higher N : P/Plimitation) (SL total litterfall model 1 = deciduousness + soilN : P + early secondary sp.: r² = 0.63, n = 30; model2 = temperature + early secondary sp. + soil N : P: r² =0.54, n = 30; SL leaf = temperature + early secondarysp. + rainfall seasonality: r² = 0.39, n = 30). Leaf litterdecomposability was lower in the dry season than in the wet season, driven byhigher phenolic concentrations in the dry, with the difference exacerbatedparticularly by lower dry season moisture. Our results are contrary to theglobal trend for tropical rainforests; in that seasonality of litterfallinput was generally higher in wetter, cooler, evergreen forests, compared togenerally drier, warmer, semi-deciduous sites that had more uniform monthlyinputs. We consider this due to more diverse litter shedding patterns insemi-deciduous and raingreen rainforest sites, and an important considerationfor ecosystem modellers. Seasonal changes in litter quality are likely tohave impacts on decomposition and biogeochemical cycles in these forests dueto the litter that falls in the dry season being more recalcitrant to decay.

[学科分类] 地球化学与岩石