title: Non-native plant litter enhances soil carbon dioxide emissions in an invaded annual grassland.
abstract: Litter decomposition is a fundamental ecosystem process in which breakdown and decay of plant detritus releases carbon and nutrients. Invasive exotic plants may produce litter that differs from native plant litter in quality and quantity. Such differences may impact litter decomposition and soil respiration in ways that depend on whether exotic and native plant litters decompose in mixtures. However, few field experiments have examined how exotic plants affect soil respiration via litter decomposition. Here, we conducted an in situ study of litter decomposition of an annual native grass (Eragrostis pilosa), a perennial exotic forb (Alternanthera philoxeroides), and their mixtures in an annual grassland in China to examine potential invasion effects on soil respiration. Alternanthera litter decomposed faster than Eragrostis litter when each was incubated separately. Mass loss in litter mixes was more rapid than predicted from rates in single species bags (only 35% of predicted mass remained at 8 months) showing synergistic effects. Notably, exotic plant litter decomposition rate was unchanged but native plant litter decomposition rate was accelerated in mixtures (decay constant k = 0.20 month(-1)) compared to in isolation (k = 0.10 month(-1)). On average, every litter type increased soil respiration compared to bare soil from which litter was removed. However, the increases were larger for mixed litter (1.82 times) than for Alternanthera litter (1.58 times) or Eragrostis litter (1.30 times). Carbon released as CO2 relative to litter carbon input was also higher for mixed litter (3.34) than for Alternathera litter (2.29) or Eragrostis litter (1.19). Our results indicated that exotic Alternanthera produces rapidly decomposing litter which also accelerates the decomposition of native plant litter in litter mixtures and enhances soil respiration rates. Thus, this exotic invasive plant species will likely accelerate carbon cycling and increase soil respiration even at intermediate stages of invasion in these annual grasslands.
authors.affiliation: College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, China; Department of Ecology and Evolutionary Biology, Rice University, Houston, Texas, United States of America.
authors.forename: Ling
authors.initials: L
authors.lastname: Zhang
authors.affiliation: College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, China.
authors.forename: Hong
authors.initials: H
authors.lastname: Wang
authors.affiliation: College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, China; Department of Horticulture, Cornell University, Ithaca, New York, United States of America.
authors.forename: Jianwen
authors.initials: J
authors.lastname: Zou
authors.affiliation: Department of Ecosystem Science and Management, Texas A & M University, College Station, Texas, United States of America.
authors.forename: William E
authors.initials: WE
authors.lastname: Rogers
authors.affiliation: College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, China; Department of Ecology and Evolutionary Biology, Rice University, Houston, Texas, United States of America.
authors.forename: Evan
authors.initials: E
authors.lastname: Siemann
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism*; D002681:China; D017753:Ecosystem; D058865:Introduced Species; D010944:Plants / Q000378:metabolism*; D006109:Poaceae / Q000378:metabolism
chemical_list: D002245:Carbon Dioxide