Leaf traits drive plant diversity effects on litter decomposition and FPOM production in streams

Abstract

Biodiversity loss in riparian forests has the potential to alter rates of leaf litter decomposition in stream ecosystems. However, studies have reported the full range of positive, negative and no effects of plant diversity loss on decomposition, and there is currently no explanation for such inconsistent results. Furthermore, it is uncertain whether plant diversity loss affects other ecological processes related to decomposition, such as fine particulate organic matter production or detritivore growth, which precludes a thorough understanding of how detrital stream food webs are impacted by plant diversity loss. We used a microcosm experiment to examine the effects of plant diversity loss on litter decomposition, fine particulate organic matter production, and growth of a dominant leaf-shredding detritivore, using litter mixtures varying in species composition. We hypothesized that plant diversity loss would decrease the rates of all studied processes, but such effects would depend on the leaf traits present in litter mixtures (both their average values and their variability). Our findings partly supported our hypotheses, showing that plant diversity loss had a consistently negative effect on litter decomposition and fine particulate organic matter production (but not on detritivore growth) across litter mixtures, which was mediated by detritivores. Importantly, the magnitude of the diversity effect and the relative importance of different mechanisms underlying this effect (i.e., complementarity vs. selection) varied depending on the species composition of litter mixtures, mainly because of differences in litter nutritional quality and trait variability. Complementarity was prevalent but varied in size, with positive selection effects also occurring in some mixtures. Our results support the notion that loss of riparian plant species is detrimental to key stream ecosystem processes that drive detrital food webs, but that the magnitude of such effects largely depends on the the order of species loss.

Decomposition of leaf litter mixtures across biomes: The role of litter identity, diversity and soil fauna

“…Freshly fallen senesced leaf litter of A. glutinosa, S. cinerea and F. sylvatica were collected every second day, whereas leaf litter of I. aquifolium was obtained by cutting branches in the field and simulating senescence by air-drying and allowing laves to fall off from the branches in the laboratory during a period of three to four weeks (Handa et al, 2014;Makkonen et al, 2012). López-Rojo et al (2018) found that the N concentration of I. aquifolium leaves collected from branches did not significantly differ from senescent leaves which are shed in the field. After collection, the litter was dried at 40°C for one…”

Effects of two measures of riparian plant biodiversity on litter decomposition and associated processes in stream microcosms

“…We used leaf litter from 9 tree species belonging to 3 families (Betulaceae, Salicaceae and Fagaceae), which were introduced in microcosms (with and without detritivores) as monocultures (SR = 1) or mixtures (SR = 3) with either low PD (3 species from the same family) or high PD (3 species from 3 different families). The above processes were quantified after 6 weeks, and the following hypotheses were examined: (1) plant SR enhances all studied processes (i.e., they have greater values in mixtures than in monocultures) 15,28 , mostly due to complementarity effects 29 ; (2) the difference between monocultures and mixtures is greater for high-PD than for low-PD mixtures; and (3) all the above patterns are more marked in the presence of detritivores, which often are key drivers of biodiversity-ecosystem process relationships [30][31][32] .…”

Leaf litter quality drives the feeding by invertebrate shredders in tropical streams

“…These intermediate leaf proportions had the effect of composition of leaf litter mixtures, which may determine decomposition (Rezende et al, 2016(Rezende et al, , 2017. Different leaf species have different chemical characteristics (Graça et al, 2015); such interspecific differences have substantial effects on leaf breakdown rates (López-Rojo et al, 2018). In a mixture of labile and refractory litter species, shredders focused more on the most labile litter species (Swan & Palmer, 2006).…”