Fragmentation of Coastal Grasslands by Plantations and Spontaneous Spread of Invasive Pines in the Southern Pampa

Ana Nebbia,Alejandra Yezzi,Sergio Zalba

doi:10.3390/d13120637

Abstract

Coastal dunes of the southern Buenos Aires province, in Argentina, are one of the last remnants of biodiversity in the southern Pampa unit, within the Rio de la Plata Grasslands. While the direct loss of grasslands due to the advance of cities and afforestation is conspicuous, the negative effects of the subdivision of the remaining environments on biodiversity and ecosystem dynamics are less considered. Our work aimed to analyze the combined effect of fires and subdivision of grasslands by invasive alien trees. Our results suggest that fragmentation affects the resilience of coastal grasslands after fire and affects the course of succession, promoting the establishment of invasive alien plants. We also suggest that fires favor the advance of pines and acacias towards the interior of grassland remnants, further reducing their area. The effective conservation of the components of Pampas biodiversity that still persist in these coastal ecosystems will depend on preventing, mitigating and compensating the insularization effects associated with forest plantations and the expansion of invasive trees, by means of adequate territorial planning that allows remnants to be maintained in a good state of conservation.

Highlights

Natural grasslands of temperate and subtropical regions of the world have been almost completely transformed into agriculture, afforestation and pastures, due to the suitability of their soils and climate [1,2,3,4]
The first component of the PCA (20.04% of the total variance) grouped the samples according to successional stages before the fire (t0 ) and separated the smaller fragments surrounded by the forest plantation with respect to the smaller continuous grassland controls
While the fragments were characterized by a greater abundance of the native species Cyperus reflexus and the exotic Senecio madagascariensis and Hypochaeris radicata, the controls were associated with high abundances of grasses and other native species typical of the Pampean grassland, such as Aristida spegazzinii, Panicum urvilleanum, Schizachyrium plumigerum, Margyricarpus pinnatus and Discaria americana (Figure 2a, Table S1)

Summary

Introduction

Natural grasslands of temperate and subtropical regions of the world have been almost completely transformed into agriculture, afforestation and pastures, due to the suitability of their soils and climate [1,2,3,4] This has caused them to be recognized as a terrestrial biome, where biodiversity and ecosystem services are most at risk on a global scale [5,6]. Trees stand out among invasive species for the extent and intensity of the changes they produce on natural grasslands, replacing native biota and promoting monospecific communities [16,17] In this context, their dispersion represents one of the main threats to coastal dune conservation [18,19]. Both dune afforestation and further spontaneous expansion of the trees have direct negative impacts, including alteration of sand dynamics; increases in the frequency and intensity of fires, in most cases of anthropic origin; and replacement and fragmentation of native plant communities [19,20]

Methods

Results

Conclusion