NATURAL REGENERATION IN AN ATLANTIC RAINFOREST FRAGMENT LOCATED IN RIO DE JANEIRO STATE, BRAZIL
1. Jorge Palladino Corrêa de Lima,PhD –USForest Service, Athens,GA/USA
2. Jose Americo de Mello Filho, Dr - Universidade Federal de Santa Maria,RGS/Brasil
The Mário Xavier National Forest is situated in Rio de Janeiro state, in the municipio of Seropédica, between latitudes 22° 42' and 22° 45' S, and between longitudes 43° 41' and 43° 44' W.
It was legally established by Federal Decree 93.369, of 08.10.1986, and is managed by IBAMA. It extends over an area of about 493 hectares.
The Mário Xavier National Forest contains one of the most important native forest fragments in the municipio of Seropédica, Rio de Janeiro state, covering an area of approximately 60 hectares. This fragment can be considered as one of the last remaining areas of Atlantic rainforest in the Guandu river floodplain.
According to the Brazilian vegetation classification proposed by the Physiognomy-Ecology System in IBGE (1992), the Atlantic forest that covered the municipio of Seropédica when it first began to be colonized was dense lowland rainforest, characterized by the presence of phanerophytes, specifically the macro-life sub-forms, and abundant meso-phanerophytes together with viburnums, other woody vines and epiphytes, thereby distinguishing it from other types of formation. The dense lowland rainforest generally occupies coastal planes covered by plio-pleistocene rock strata from the Barreiras group, together with quaternary deposits, usually situated slightly above sea level. These plateaus are formed by silting resulting from the erosion of coastal mountain ranges, and sandy inlets.
In terms of soils, this forest environment is dominated by laterites and podzols, both of which have low natural fertility.
As is well-known, secondary forests result from natural vegetative succession, which occurs following the total or partial suppression of primary vegetation as a result either of human intervention or natural causes. That forest structure contains remnants of primary vegetation, which re-emerged as the land was abandoned following crop growing and livestock use, and finally reforestation of natural wild areas (IBGE,1992). Knowledge of secondary forests, particularly in terms of their structure, botanical composition and vegetative growth, is very important for restoring degraded areas, because the process of vegetative succession has much to teach us about the natural regeneration of native forests.
In the specific case of the Seropédica municipio, secondary forest fragments are extremely valuable as the last remaining banks of germ plasm, representing the municipio’s native vegetation. As such they are immediately usable in selecting species and specimens for future reforestation projects. The aim is, therefore, to give special emphasis to an area with secondary forest cover, more specifically as regards the natural regeneration process that has operated in that area over the years, forming ecological corridors. The term “ecological corridor” or “corridor between remnants” means a strip of vegetation formed through natural regeneration or reforestation, between remnants of primary vegetation, or vegetation in a medium to an advanced stage of regeneration, capable of providing a habitat or serving as a transit area for fauna living in the forest fragments (CONAMA, 1993).
Monitoring procedures are a fundamental tool of environmental management, based on the application of theoretical foundations and geo-processing techniques.
Environmental monitoring is a resource used in geo- processing that makes it possible to study environmental changes that take place in a given area over time. Monitoring tracks the evolution of environmental phenomena that mark the land, over a given time period. At least two successive observations of the phenomenon concerned are necessary, using appropriate taxonomies. Records can be made in the form of mappings, aerial photographs, satellite images, etc.
In the specific case of a conservation unit such as the Mário Xavier national Forest, environmental monitoring is a powerful tool in the management and administration of the area. Major environmental phenomena can be monitored, including natural regeneration of vegetation, deforestation, invasions, burning, and others. Depending on the number of observations available in the time series measuring these environmental phenomena, valuable information can be obtained on the direction, intensity, speed and acceleration of the changes taking place, and even on the potential causes.
When Brazil was “discovered”, the area corresponding to today’s municipio of Seropédica was nearly 100% covered by forest (apart from a few flooded depressions, lakes and the water surface of the major rivers). The Atlantic forest extended over the entire flood plain of the river Guandu, reaching down to the mangrove swamps of Sepetiba Bay.
The story of human occupation in Seropédica, where several agricultural cycles alternated – mainly sugarcane and cassava, along with extensive livestock breeding – left almost no primitive forest cover remaining. Except for mountain slopes, there are practically no continuous areas of native forest left within the boundaries of the municipio, although secondary forest fragments occur sporadically. One of the largest and most important of these is in the Mário Xavier National Forest, thanks to the protection given to the area since 1945.
It is estimated that less than 10% of the Seropédica municipio is covered by forest today. The Mário Xavier National Forest contains the municipio’s most important native forest fragments in an area of approximately 60 hectares. This is also one of the last remaining forest fragments in the Guandu river flood plain.
The study involved large-scale environmental monitoring through geo-processing, aimed at tracking the evolution of native forest cover in the period 1964-2000, estimating the increase in vegetation resulting from natural regeneration, along with losses of forest cover within the Mário Xavier National Forest.
