Global warming and introduced species have the potential to alter the functioning and structure of headwater streams. Testing how temperature affects detrital food webs is challenging because it is difficult to manipulate temperature in a field setting. Here, we evaluate how microbes and shredders decompose two morphologically distinct, riparian tree species, Populus fremontii (native) and Tamarix spp. (nonnative). We built an artificial stream facility to manipulate temperature while maintaining natural diurnal and seasonal patterns of most stream variables (light, nutrients, dissolved oxygen). We employed a factorial design that included 3 temperature treatments (ambient, + 3.7°C, and + 6.6°C), 2 leaf types and 2 decomposition mediators (microbes and shredders + microbes). Decomposition rate was influenced by leaf type and temperature, with P. fremontii decomposing more rapidly than Tamarix spp. Temperature increased decomposition rate by 9.1 to 16.5% in the +3.7°C treatments relative to ambient temperatures. Additional increases in temperature did not accelerate decomposition rate for either species. Litter packs containing shredders decomposed more rapidly than litter packs with only microbes. P. fremontii supported higher microbial biomass than Tamarix spp. and that microbial biomass increased with temperature. A paired laboratory experiment explored leaching rates with 2 temperatures and 2 time periods (24h and 48h). P. fremontii leached significantly more DOC than Tamarix spp. and Tamarix spp. leached significantly more TDN than P. fremontii. Total leaching rates, measured as litter mass loss, were similar between species. Approximately 43% to 48% of initial mass was lost after 48 hours of leaching. Temperature did not affect mass loss due to leaching. This research is important in understanding how a warmer climate will affect the cycling of carbon and nitrogen in streams.