The Northeast Long-Term Ecological Research Network (PERENE) was structured in 2017 from the need to produce research with a long follow-up time, as an evolution of the scope of the efforts of a team of OndaCBC researchers to understand the patterns of biogeochemical cycling of nutrients and water and the distribution and diversity of plants and animals in the Caatinga Biome. The results obtained from these efforts have led to the realization of the need for long term monitoring of the conditioning ecological processes, which are slow in time.

PERENE was structured with the aim of setting up and maintaining long-term experimental and sampling sites in order to gain a better understanding of the functioning of ecosystems in the Northeast region of Brazil. The approved projects that support PERENE are: 1) “Implementation of a network of long-term ecological research sites in the Caatinga biome”; 2) “Nitrogen fixation in native vegetation and prospection of the diversity and efficiency of rhizobia naturally established in the soils of Pernambuco (CNPQ universal, process numbers 409519/2018-9 and 426655/2018-4); 3) ”Greenhouse gas fluxes resulting from changes in land use and land cover in the Caatinga Biome: expansion of the field database and modeling on a regional scale” (FACEPE-FAPESP, process number APQ-0500-5.01-22) and 4) “Generating data, technological tools and agricultural and forestry management strategies for adapting to and mitigating climate change in the Caatinga biome (CNPq/MCTI/FNDCT Nº 59/2022, process number 406202/2022-2).

In addition, several grant projects were approved, which allowed more undergraduate and postgraduate students to be involved in the research. These funds resulted in the establishment and maintenance of 8 sites with permanent plots representing the main land uses for livestock purposes in the Semi-Arid, in 3 states. To date, 13 articles have been published and a huge collection of data and natural samples has been generated, which will serve as a starting point for the processes that will be monitored over time in the permanent plots. This collection constitutes the Botija (Bank of environmental data and samples from the Northeast region). Analysis results are stored in large archives, available to the research group and to partners in the Network's work.

These results are the fruit of dissertations and theses, already defended or in progress, which have dealt with environmental variables that have not yet been explored in the region and/or which may vary over relatively short periods of time. All these efforts have provided a solid basis for understanding N cycling and the process of biological nitrogen fixation in the Caatinga Biome, with quantification of N inputs in different situations using isotopic approaches. The results also provided knowledge about the occurrence and characteristics of microsymbionts naturally established in Semiarid soils. In the permanent plots, the use of a drone-coupled camera and the integration of multiple vegetation indices was tested as a promising method for estimating the aerial biomass of caatinga and pasture vegetation in the Brazilian semi-arid region. Soil biological attributes related to respiration and microbial biomass can be better related to soil health in the semi-arid environment, showing less variation in climax vegetation than in more anthropized vegetation (open caatinga and pastures), when comparing rainy and dry periods. After three years of animal exclusion, these attributes in the soil under pasture were similar to those in the open caatinga, indicating a high degree of recovery.

The activities of enzymes involved in biogeochemical cycling and the amount of glomalin in the soil under pasture were lower than in fragments of dense caatinga. The highest carbon stocks were quantified in pasture and dense caatinga. Also in the plots, it was found that the contributions of fixed N were low, with potentially fixing plants and species expressing little or no fixation, in the same way as observed in other areas of the Brazilian semi-arid region. Discovering the causes of these low levels of fixation is a challenge to be faced in future research.

Currently, the network has 8 researchers: 4 undergraduates, 1 master's student, 2 doctoral students and 1 post-doc.