Thinking about the forest fires of early 2017 and considering that summer is again approaching, Marcela Fierro agronomist spoke to us about one of the most drastic changes in the landscape of the dry coastal lands of the Maule Region. She suggested that the renewal and evolution of the landscape produced by environmental factors of different scales forces us to consider this same evolution in the identity of a place.
According to ODEPA (Office of Agricultural Studies and Policies of Chile), 65% of the Maule area is used for forestry (88% Pinus radiata, 9.3% Eucalyptus globulus and 3.2% other species) (1). These plantations with exotic species along with extensive agriculture have displaced native forest and forced the clearing of lands and the use of surface and underground water for economic gains. The monoculture of Pinus radiata, with 20-year rotations, began in the 70s and led to an accelerated fragmentation of the deciduous forest of Maule, which was composed primarily of Nothofagus species (N. obliqua, N. glauca, N. alessandri, N. dombeyi) and sclerophyllous forest species such as peumo (Cryptocaria alba), quillay (Quillaja saponaria), lingue (Persea lingue), hawthorn (Acacia caven), maitén (Maytenus boaria), queule (Gomortega keule), maqui (Aristotelia chilensis) among others (2).
(1) Maule Región Regional information 2016 <http://www.odepa.cl/wp-content/files_mf/1462200595Maulemarzo.pdf>
(2) DL 701 Law and its regulations. In <http://www.conaf.cl/nuestros-bosques/plantaciones-forestales/dl-701-y-sus-reglamentos/>
The complexity and diversity of the native forest make it a mature ecosystem that is difficult to restructure after the fires that devastated the coastal mountain range of the VII Region; reestablishing the close vegetal relations that once existed will require a longer recovery period than in the case of monocultures. However, because the large mono-culture forest areas displaced this type of forest over decades to zones with greater slope and more difficult access, those native parts on the slopes were less damaged than the patches located between the pine and eucalyptus (3). The exotic forest, represented mainly by pine and to a lesser extent by eucalyptus, occupies a homogeneous space with regular distances despite the topography and the availability of water. Both species, highly combustible due to the presence of resins, were the detonator together with the critical environmental conditions that created virtual chimneys between the hills of the Maule coast.
(3) Ramiro O. Bustamante, Javier A. Simonetti, Audrey A. Grez and José San Martín, Fragmentación y dinámica de regeneración del bosque Maulino: diagnóstico actual y perspectivas futuras (Fragmentation and regeneration dynamics of the Maulino forest: current diagnosis and future prospects). In <http://www.ieb-chile.cl/uploads/publicaciones/-1_Bustamante_etal_2005_Bosques_Costeros.pdf>
Exotic forests, due to the thick layer of aciculate or modified leaf that acidifies the soil and causes a dense cover effect, prevent the germination of many indigenous shrubs and herbaceous species. The damage was devastating because by eliminating the exotic forest, the fire left the ground completely bare. The first centimeters suffered the combustion of the thin green layer that harbors microorganisms and insects responsible for decomposing matter, containing erosion, and destroying propagules, which correspond to the underground structures of asexual reproduction of plants, specifically monocotyledons (narrow leaf species) such as bulbs, rhizomes, stolons or seeds and which ensure their own dissemination.
The damage manifested in different magnitudes according to the topographical conditions and the wind. In some areas, wide corridors were totally destroyed by the flames and the charred trunks are the last observable vestige. In other parts, the flames embraced part of the foliage leaving centers of live growth that, in fact, are already reactivating. All the ash that fell formed a layer of diverse thickness that in low and gullied sectors reached its greatest height to generate a natural fertilization of easy assimilation delivering minerals already available to the plants.
Almost a year after this tragedy, how nature recovers at its distinct rhythms can be observed. Eucalyptus forests present better renewal from the base and along the trunk. This will generate up to 10 stumps or shoots; the first acted as if a commercial felling had been carried out, which will mean for the forest of eucalyptus a higher density of foliage and as a consequence a greater demand on the underground water and a lower availability of that water for the rest of the ecosystem. In contrast, the pine forest does not have this adaptation of sprouting. Without that adaptation, cleaning and clearing is required if the same species is to be replanted. The sclerophyllous species such as boldos and peumos have reacted with basal growth, perhaps as a repetitive response to the upheaval and felling that transformed them into woody shrubs.
Finally, areas of hills exposed to the sun have been fertilized by the thin layer of ash they received, giving rise to the growth of fine grasses that will contain the slopes and will be food for livestock that have already been established there. The sectors of shade, thanks to the humidity, also present fine herbs and a growth of shrubs. There are also the first glimpses of geophytes, such as Alstroemerias, Huilles, and Añañucas that survived underground thanks to their subterranean structures.
We understand the mechanisms by which the living elements of a forest recover from fires; therefore, it is important to understand the response and recovery of the species after these events to anticipate possible future incidents. For our purposes, the cycle is renewed between the hills where the fragility is apparent, and in turn makes us realize that the use we give to the land will invariably define the evolution of our landscape.
Marcela Fierro Carrasco is an Agronomist, University of Talca, and holds a Master’s degree in Landscape Architecture from the Pontifical Catholic University of Chile.