Litter accumulation and biomass dynamics in riparian zones in tropical South America of the Asian invasive plant Hedychium coronarium J. König (Zingiberaceae)

Background: Promoting changes in abiotic conditions and ecosystem processes, such as decomposition, is a mechanism by which some exotic plant species displace native plants and become invasive. Aims: We monitored ramets of Hedychium coronarium over 30 months to estimate the litter decay rate, biomass dynamics and litter accumulation over time in riparian sites invaded by the species in southeastern Brazil. Methods: We measured the number, height, emergence and mortality of ramets in three environments invaded by H. coronarium (natural, rural and urban). We also measured litter decay in situ and in in vitro experiments. We used sinusoidal models to describe height fluctuation and exponential models to simulate litter decay and litter accumulation. Results: Ramets of H. coronarium showed high seasonal variation in terms of height and emergence, as well as low litter decay. Accordingly, our models predicted high litter production and a seasonal pattern of litter accumulation in invaded sites. Conclusions: H. coronarium produces a great amount of litter, which shows slow decay and hence seems to affect decomposition processes. Investigating seasonal variation on the effects of invasive species on ecosystem functioning shed light on the factors driving the success and impact of invasive plants.研究背景：部分外来植物物种可通过改变非生物环境与生态系统过程（如分解过程）排挤本土植物，进而实现入侵扩张，此为其入侵机制之一。 研究目的：针对巴西东南部受姜花（Hedychium coronarium）入侵的河岸生境，本研究通过连续30个月的分株（ramet）观测，估算枯落物分解速率、生物量动态及枯落物随时间的积累情况。 研究方法：本研究在姜花入侵的三类生境（自然、乡村与城市）中，对分株的数量、株高、萌发率与死亡率进行了测定；同时通过原位（in situ）实验与体外（in vitro）实验测定枯落物分解情况。本研究采用正弦模型（sinusoidal models）拟合株高波动规律，并使用指数模型（exponential models）模拟枯落物分解与积累过程。 研究结果：姜花分株的株高与萌发率存在显著季节波动，且枯落物分解速率较低。据此，本研究构建的模型预测入侵生境中枯落物产量较高，且枯落物积累呈现季节性规律。 研究结论：姜花可产生大量枯落物，且其枯落物分解缓慢，因此会对生态系统分解过程产生影响。探究入侵物种对生态系统功能的季节效应，可为揭示入侵植物成功定殖与危害影响的驱动因素提供理论依据。