Growth and carbon sequestration rates in subtropical secondary forests invaded by the exotic species Ligustrum lucidum

Start date: 7 June, 2014 End date: 23 August, 2014 Project type: Master's Thesis (prior to 2018) Project code: A27007 Countries: Bolivia Institutions: University of Copenhagen (UCPH), Denmark Grant recipient: Alenka Blatnik Total grant: 13,000 DKK



During a middle of 21st century, Ligustrum lucidum W.T.Aiton (Chinese privet), originally from south China, was introduced as an exotic ornamental species in South America. Nowadays, the species is widespread in Las Yungas, i.e. Tucumano-Boliviano forest, in an amount that presents a threat to native flora.

Las Yungas is distributed between Catamarca province in Argentina to the south (29⁰) and Santa Cruz province in Bolivia to the north (17⁰). Within these borders and between 400 – 3000 m.a.s.l., different vegetation zones were created as a result of different factors such as climate, altitude, relief, soil quality, water availability, etc. The zones were divided into Selva Pedemontana (400 – 700 m.a.s.l.), Selva Montana (700 – 1500 m.a.s.l.) and Bosque Montano (1500 – 3000 m.a.s.l.) within which high biodiversity is present and where many endemic, rare, sensitive and vulnerable species could be found both within flora and fauna.

For centuries, the area was highly populated and its goods were exploited for different purposes. Great anthropogenic impact (e.g. forest fragmentation) could be seen in almost every corner of the area which has a great influence on the biodiversity status and enables the invasion of the exotic species such as L.lucidum. The species is able to grow on every type of soil and with different water and light availabilities. It spreads effectively vegetative and with seeds which were mainly spread by animals’ ingestion. Since the Chinese privet is very adaptive species, it spreads in the area which was previously occupied by native ones. With these actions, native forests as originally known are slowly disappearing. For this purpose, many researches were done also in order to understand the spreading and to be able to prevent it or at least to prevent or reduce the further impacts on the native forests.

One of the researches is as title describes, which purpose was to analyse how fast the L. lucidum is growing and invading native secondary forests. During the visit of Las Yungas forests both in Argentina (Parque Sierra de San Javier, Tucumán province) and Bolivia (Tariquia Reserve, Tarija province), appropriate fieldwork was done which included establishing plots (20 × 20 in Argentina or 10 × 10 in Bolivia), measuring DBH and height, and identification of species with an extra observations if needed. After the data analysis, results showed that the exotic species has the higher growth rate than the native species which explains Chinese privet invasion while opposing native species. On the contrary, biomass and carbon sequestration was reduced in invaded forests. Even though the Chinese privet is growing with the high growth rate and mainly vegetative, the biomass quantity is far lower than of the native species. With these facts in mind it could be established that the exotic species’ further invasion needs to be stopped or at least reduced and controlled for a start. Different actions were suggested for control of the invasion. Some of them are removal of exotic and re-establishment of native species, treatment with chemicals, abandoning of its use as ornamental tree, etc., which showed positive results of L. lucidum reduction of invasion.