Abstract
Backgrounds and aimsLitter protects the underlying soil, depending on litterfall and decomposition, but dynamics of the standing litter stock in agroforestry systems remain poorly understood. We aimed to unravel effects of litter quality, temporal patterns, microclimate, and a possible home-field advantage (HFA) on standing litter dynamics across a land-use gradient.MethodsWe quantified litterfall, the standing litter stock, and microclimate during a year in (remnant) forest, cacao-based simple and complex agroforestry, cacao monocultures, and annual crops in a cacao producing area in Indonesia. We conducted a reciprocal litter transfer experiment, and tested decomposition rates of pruning residues. Standing litter stocks during the year were estimated from monthly litterfall and decomposition rates.ResultsVariation in litter quality influenced decomposition rates more strongly than variation in microclimate or HFA. Lower litter quality in complex agroforestry and in the cacao monoculture decreased the decay rate compared to simple agroforestry systems; mean litter residence time was over a year. Mixing high- and low-quality material in pruning residues modified the decomposition rate, soil C and N changes, offering options for targeted management of soil protection and nutrient release.ConclusionsThe seasonal patterns of litterfall and relatively slow decomposition rates supported permanence of the litter layer in all cacao production systems, protecting the underlying soil.
Highlights
Litterfall, along with root turnover, represents the primary biological pathway for element transfer from vegetation to the soil
We addressed the following research questions: (1) How does litterfall vary across land-use systems, and during the year?; (2) How do litter quality, microclimate, and home-field advantage (HFA) influence litter decomposition rates across the land-use gradient?; (3) Does the litter decomposition rate determine the relative change of soil organic C and N across the land-use gradient?; and (4) Do the mixed pruning residues of cacao and Gliricidia, or Fagraea fragrans, modify the decomposition rate, net N loss in the residues, and the change of soil C and N in cacao agroforestry compared to a cacao monoculture?
The peak of litterfall in cacao systems appeared after one month of dry conditions, while in remnant forest the peak was reached after two months, suggesting that cacao production systems had lower buffer capacity compared to RF
Summary
Litterfall, along with root turnover, represents the primary biological pathway for element transfer from vegetation to the soil. The litter layer, formed by litterfall and consumed by comminutors and decomposers, constitutes the main resource of energy and matter for a diverse community of soil organisms connected by highly complex interactions (Bargali et al 2015; Hättenschwiler et al 2005). The interaction between litter and decomposers plays an important role in regulating nutrient and carbon cycling, maintaining soil fertility in forests and in agricultural systems (Karki et al 2021a, b; Manral et al 2020; Padalia et al 2021; Yang et al 2004). In open-field agriculture based on annual crops, the litter layer usually is ephemeral, depending on the crops and soil tillage used, exposing the surface soil to radiation and splash-erosion. In forests with higher and more varied litter input, it is usually permanent but can be spatially heterogeneous, allowing an understorey vegetation to emerge
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