Balancing litterfall and decomposition in cacao agroforestry systems

Abstract

Backgrounds and aims Litter 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. Methods We 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. Results Variation 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. Conclusions The seasonal patterns of litterfall and relatively slow decomposition rates supported permanence of the litter layer in all cacao production systems, protecting the underlying soil.

Soil Degradation Due to Conversion from Natural to Plantation Forests in Indonesia

“…The conversion from tropical natural forest to monoculture plantation reduced annual litterfall production and caused a more pronounced seasonal pattern [103,108,109]. Yet, where the rate of litter decomposition is reduced by a low litter quality (high ratio of lignin plus polyphenolics over nitrogen) a continuous litter layer protecting the soil can nevertheless be achieved [110].…”

“…The litter production potential in a stand is positively correlated with soil organic matter content and soil fertility levels [111,112], although specific mechanisms that transfer organic matters from litter layers to the soil may require further study [110]. On the forest floor, litter buffers the nutrient supply, as immobilization and mineralization phases alternate [113].…”

“…Plant litter has a dual role in biogeochemical cycles, influencing hydrological processes before, and nutrient supply of forest ecosystems after, decomposition [110,117]. Standing litter stock can be estimated from annual litterfall and "mean residence time", related to the decomposition constant [118].…”

Agroforestry system construction in eastern coastal China: Insights from soil–plant interactions

“…For example, a study of Vaupel et al (2023) in the glacier‐impacted North German Plain reported that intercropping patterns of two poplar species and black locust with crops favored the abundance, diversity, and functioning of the soil biota compared with monoculture cropland. On the other hand, decomposition processes of different woody and herbaceous litter largely influence the soil aggregation structure and are dominant drivers of soil nutrient cycling (Sari et al, 2022). Duran‐Bautista et al (2023) proposed significant differences in soil physical variables between agroforestry complex systems in the northwestern Colombian Amazon (Duran‐Bautista et al, 2023).…”

Local ecological knowledge of coffee agroforestry farmers on earthworms and their relation to soil quality in East Java (Indonesia)

“…It can also indicate apparent contradictions that start with a mismatch of the taxonomic categories used. For example, various soil biota interacts with litter quality in maintaining a protective litter layer on the soil throughout the year (Sari et al 2022). In simple and multistrata coffee agroforestry systems in Indonesia these can include epigeic, endogeic, and anecic earthworms that differ in the soil layers where they are active (Hairiah et al 2006;Putri 2018), and thus in their functions as litter decomposer, and as a maker of horizontal and vertical soil pores.…”