Seasonal changes in the diversity and composition of the litter fauna in native forests and rubber plantations

Abstract

The litter layer of tropical forests supports a significant fraction of total arthropod diversity and decomposition of this layer is the main pathway by which nutrients are returned to the soil and CO2 to the atmosphere. Conversion of tropical forests to agriculture is the main threat to biodiversity and ecosystem services, and understanding effects on the litter layer is important for understanding and mitigating these impacts. We used high through-put DNA sequencing of the mitochondrial cytochrome c oxidase subunit I (COI) gene to assess seasonal changes in the diversity and composition of the litter fauna at five matched pairs of native forests and rubber plantations in tropical SW China every month for a year, and measured the environmental factors expected to drive intra-annual variation. Forests and rubber had very different arthropod assemblages throughout the year, with forests more species-rich than rubber in all months except February. Very high rates of intra-annual turnover in species composition in both forests and rubber were associated with seasonality in environmental variables, with the influence of particular variables differing among taxa. Tropical arthropods are very sensitive to seasonality and sampling at only one time of the year captures only a subset of the total community.

Land‐use change shifts and magnifies seasonal variations of the decomposer system in lowland tropical landscapes

“…In animals, land use modified seasonal changes in the vertical distribution of Diptera and Coleoptera. This conforms to previous studies showing the sensitivity of Diptera and Coleoptera to seasonal climatic changes, especially in plantations (Beng et al, 2018 ). The changes in abundance and depth distribution in these taxa are likely related to their life cycle and larval stage in soil.…”

“…This is in line with the results on epigaeic ants from a Brazilian Atlantic rainforest but contrasts findings from other tropical forests (Grimbacher et al, 2018 ; Jacquemin et al, 2016 ; Montine et al, 2014 ). Also, microarthropods, such as Collembola and Oribatida, did not show clear seasonal changes in the different land uses, contrasting results from the tropical forest and rubber plantations in China (Beng et al, 2018 ). In general, in our study, changes in seasonal dynamics with changes in land use were more pronounced in soil macrofauna, that is, Coleoptera, Psocoptera, and Diptera (except Formicidae) than in microarthropods such as Oribatida, Mesostigmata, and Collembola (except Symphyla).…”

“…This may be due to higher growth rates of microorganisms than animals and higher dependency on water availability as well as seasonal changes in litter and soil parameters, for example, pH (Bahram et al, 2018 ; Bickel & Or, 2020 ). Surprisingly, only a few studies investigated seasonal changes in soil microorganisms in different land uses (Lan et al, 2021 ; Lepcha & Devi, 2020 ), whereas several studies investigated seasonal changes in soil animals (Grimbacher et al, 2018 ; Grimbacher & Stork, 2009 ; Montine et al, 2014 ), but, to the best of our knowledge, no studies exist for Southeast Asia (but see Beng et al, 2018 ). Similar to our study, the abundance of litter‐dwelling Coleoptera in tropical rainforests of Australia varied with season (Grimbacher & Stork, 2009 ).…”

“…Many Diptera and Coleoptera species are associated with the litter layer and the shallow litter layer and more pronounced variations in environmental factors in plantations may render them susceptible to seasonal climatic variations. In fact, the litter layer of tropical forests is an important habitat for soil organisms, and many soil animal taxa suffer from shallower litter layers in plantations (Beng et al, 2018 ; Krashevska et al, 2015 ; Susanti et al, 2021 ). Further, the amount of litter changes considerably with seasons and these changes are most pronounced in plantations, especially in oil palm, with the amount of litter being lowest in March and June following management practices, whereas in rainforest, the amount of litter stays more constant throughout the year.…”

“…There are only a few studies that investigated the effects of seasonality on decomposer communities in tropical ecosystems. In the rainforests of China, Ecuador, and Mexico, seasonal changes in temperature and humidity have been reported to affect the diversity and composition of litter arthropods (Beng et al, 2018 ; Grimbacher et al, 2018 ; Jacquemin et al, 2016 ; Marín et al, 2016 ); however, in Brazil and Australia, arthropod diversity did not respond in a uniform way to seasonal dynamics (Grimbacher & Stork, 2009 ; Montine et al, 2014 ). As shown in climate experiments in the temperate zone, land use may modulate climatic effects on the abundance and diversity of soil organisms (Yin et al, 2019 , 2020 ), but the aspect of seasonality has been poorly explored.…”