Sour orange (Citrus aurantium L.) invades old-growth subtropical montane forest, but is it worth removing? (Argentina)

Abstract

The results of a study we carried out in a subtropical montane forest of the Parque Nacional El Rey in northwestern Argentina, indicate that sour orange- an understorey tree species native to southeast Asia- is invading old-growth forest sites much more successfully than second-growth forest sites. This suggest to us that the main factor favoring the invasion is the similarity of this old-growth habitat to the species’ natural habitat, rather than the degree of disturbance of the native vegetation. (…) Conservation policies for protected areas often recommend the eradication of exotics. However in the ecosystem we studied we believe that removal of sour orange may not be the best option for a number of reasons. First, there have been no reports of negative effects on the native forest due to sour orange. Second, all the consumers of sour orange fruits in the invaded area are vertebrates with high conservation value. They may have incorporated sour orange into their winter diets as supplement. If so, sour orange may strongly increase the carrying capacity of the reserve area for wildlife. The apparent benefit for the invaded community, derived from sour orange, illustrates the importance of inquiring into the identity of each alien species and its interaction with the invaded community before launching an eradication plan.