Growth patterns of native and introduced conifers when both coexist: Implications for invasion process

GRISSINO-MAYER, H.; RELVA, M.A.; SUAREZ, MARIA LAURA

Temuco

Congreso; First IUFRO Landscape Ecology Latin-American Congress; 2016

The invasion by woody plants is matter of concern amongst scientists, conservationists and environmentalmanagers as it has a serious ecological and economic impact worldwide. In the last 40 years extensive coniferplantations, mainly fast-growing Pinaceae, highly invasive elsewhere, have been established in forests,shrublands and grasslands in Chile and Argentina. Problems derived from plantations include increased firefrequency and severity, reduction of biodiversity, and replacement of plant communities. Overall, tree invasionin forests occur comparatively at slower rate than in treeless and disturbed areas. In this study we investigatethe competitive interaction of both native and exotic conifers (Austrocedrus chilensis and Pseudotsugamenziesii, respectively) as a mechanism explaining the slow process of conifer invasion observed in a pristinenative forest in northern Patagonia, Argentina. In 2012, on Isla Victoria (Nahuel Huapi National Park), wecollected tree core samples from native and exotic trees growing in a native forest close to the main plantation(n = 18 patches). We applied dendrochronological methods to assess growth patterns and changes in Basal AreaIndex (BAI) for both species. Contrary to expected, the results indicate a major competitive ability of exoticover native species. BAI patterns indicate that, despite both species grow well since its establishment, accordingtime pass the presence of exotic impact negatively on the growth of native. This decreasing trend in growthcould be in relation with the moment when the exotic surpass the native in terms of diameter and height.Negative interaction is also demonstrated as 70% of native trees show strong release in growth when exotictrees were removed through logging activities. As invasion is a complex process with multiple driversinteracting, others factors than competition, may be explaining the slow process of invasion in this pristineforests. However, the higher growth of exotic compared to the native would confer a competitive advantage incase of major disturbances occur, with a likely acceleration of the invasion.