Invasion of Ligustrum lucidum (Oleaceae) in subtropical secondary forests of NW Argentina: declining growth rates of abundant native tree species

Abstract

Aims Ligustrum lucidum, native to China, is one of the dominant exotic and invasive tree species in secondary forests in Argentina. (1) We assessed its invasion during 20 yr in post‐agricultural secondary forests dominated by native tree species, and (2) evaluated tree demographic rates of native individuals under and away from L. lucidum trees that invaded these forests. Locations Four 1‐ha permanent plots of secondary forests, subtropical Andes of Tucumán, Argentina. Methods We quantified the invasion of L. lucidum individuals (≥10‐cm diameter) from 1991 to 2011 within four 1‐ha plots of secondary forests and analysed annual growth and mortality rates of native tree individuals (≥10‐cm diameter) under and away from L. lucidum trees. For this, we compared tree demographic rates of all native individuals together (community level) under and away from individuals of L. lucidum, referred to as exotic and native neighbourhoods, respectively. Then, we described the relative growth rate of native tree species in exotic/native neighbourhoods (species level) and related them to their demographic life histories and morpho‐physiological traits. Results Both density and basal area of L. lucidum increased from 0.1% to 4% between 1991 and 2011. Native tree individuals grew 65% less in exotic neighborhoods compared to native neighborhoods. Relative growth rate showed negative values under L. lucidum individuals for the abundant species Ocotea porphyria, Parapitadenia excelsa, Juglans austalis and Allophylus edulis, indicating competition; while less abundant species Terminalia triflora, Cupania vernalis and Blepharocalix saliscifolius showed positive growth values under L. lucidum, suggesting a facilitation process. Thus, L. lucidum competes efficiently with some native tree species, particularly with those abundant species that dominate the canopy. Conclusions Ligustrum lucidum is invading post‐agricultural secondary forests dominated by native tree species. While invading, L. lucidum competes with native abundant tree species that dominate the main structure of the forest canopy. As this invasive trend will likely increase in the near future, L. lucidum may alter forest structure, composition and dynamics, as well ecosystem functioning.

Elevation and latitude drives structure and tree species composition in Andean forests: Results from a large-scale plot network

“…dendrometer bands) in all the permanent forest plots of the Network; 6) detecting situations that are locally important; 7) promoting comparative research for monitoring the impacts of anthropogenic activities across the region, including the dynamics of invasive species (i.e. the case of Ligustrum lucidum in Argentina) [79], or primary/secondary succession as a result of volcanism, forest fires, hurricanes, or land use change (abandonment of agricultural and livestock lands); 8) exploring in detail the association between changes in permanent plots and changes in remotely sensed descriptors of functioning (e.g., NDVI) [80], promoting joint research to develop high resolution models of climate change for the Andean region, and descriptions of land use change [12].…”

Alternative pathways of liana communities in the forests of northwestern Argentina

“…For instance, in subtropical forests of Central Argentina L. lucidum forests have increased by 20 percent in area in the last 40 years and have lower climbing plant species richness (i.e., including lianas) compared to shrublands and native secondary forests (Ferrero et al, ). In our study area, recent studies reported that L. lucidum invaded 667 ha of abandoned lands up to 2010, reaching about 5% of the area in Parque Sierra de San Javier (Montti et al, ), and its density increased by 4 percent/ha within native secondary forests between 1991 and 2011 (Malizia et al, ). The dominance of L. lucidum is increasing in secondary forests with respect to other native tree species (Grau & Aragón, ; Malizia et al, ), with potentially negative consequences for lianas.…”

“…In our study area, recent studies reported that L. lucidum invaded 667 ha of abandoned lands up to 2010, reaching about 5% of the area in Parque Sierra de San Javier (Montti et al, ), and its density increased by 4 percent/ha within native secondary forests between 1991 and 2011 (Malizia et al, ). The dominance of L. lucidum is increasing in secondary forests with respect to other native tree species (Grau & Aragón, ; Malizia et al, ), with potentially negative consequences for lianas.…”

“…On the other hand, M. alba might facilitate lianas because of its rough bark and low branches that extend to the ground. Additionally, native tree species that host lianas are usually absent in L. lucidum forests, but are abundant in M. alba forests (Malizia & Grau, ; Malizia, Osinaga‐Acosta, Powell, & Aragón, ). Few native tree species are able to grow and reach the canopy within L. lucidum ‐dominated forests, due to the species competitive ability and resprouting capacity, which allows invasion persistence, but several native trees can reach the canopy within M. alba forests because this species declines during succession (Grau & Aragón, ; Malizia et al, ).…”

Endemic trees in a tropical biodiversity hotspot imperilled by an invasive tree

“…At one site in these forests, native trees species richness (stems ≥1 cm dbh) declined over 21-27 years as the stem density of non-native trees increased (Florens et al 2017). Since stem radial growth rates of P. undulatum are 4-5 times greater than native Jamaican tree species (Bellingham et al, 2005), P. undulatum probably reduced local-scale species richness and diversity by niche pre-emption (Catford et al, 2012;Denslow, 2003), exploitative competition (Catford et al, 2012;Malizia et al, 2017), or both. It may also exert interference competition through potentially allelopathic effects (Gleadow and Ashton, 1981).…”