Plant species invasion effects on litter dynamics in subtropical streams

Abstract

Aim We evaluated the effect of the presence of Hovenia dulcis Thunb. (Rhamnaceae) in riparian zones on the organic matter dynamics of small subtropical streams. Methods We conducted this study in three subtropical Atlantic Forest streams with different densities of H. dulcis in riparian vegetation located in southern Brazil. In each stream, we quantified the input of allochthonous organic matter for one year using buckets (area: 0.04 m2/bucket) suspended about 1 m from the streambed in three different sections (15 buckets/stretch = 45 buckets/stream). Monthly, the plant material retained in the buckets was collected individually, dried (40±5 °C/72 h), identified (native litter together and H. dulcis litter alone) and weighed. Results The largest input of native organic matter occurred during the winter months (~55 g.m-2), ranging from ~31 g.m-2 (summer) to ~46 g.m-2 (spring) over the year. The input of H. dulcis organic matter was concentrated in the autumn (~56 g.m-2) and summer (~28 g.m-2), being scarce in the other seasons (~3 g.m-2 in the spring and winter). Only the contribution of native organic matter was associated with precipitation. Contrary to that observed with native vegetation (input of organic matter related with rainfall), H. dulcis input was related to the phenology of the species, which is deciduous, with leaf fall strongly marked, occurring especially during the autumn. Conclusions When present at high densities (dominant), the presence of H. dulcis in riparian stream vegetation makes the supply of allochthonous plant resources scarce at some periods of the year, altering the energy availability in these ecosystems and, potentially, the functioning of subtropical streams.

Ants benefit from the Japanese raisin tree invasion and favor its invasiveness in the subtropical Atlantic Rainforest

“…We detected a considerably higher leaf‐litter mass in invaded forest sites in June. However, in the following month, the leaf‐litter mass of these sites was reduced in comparison with adjacent control sites, similar to the findings of Schmidt et al (2020) and Fontana et al (2020). This result indicates an accelerated decomposition rate of senescent leaves of H .…”

“…Thus, H . dulcis alters the structure of the litter layer in the Atlantic forest because, although it produces large amounts of litter by leaf fall in a short timespan (concentrated in 3–4 months; Fontana et al, 2020), its large litter input decomposes fast, leading to the depletion of the litter layer in the remaining months (Schmidt et al, 2020).…”