Nordeste

The northeast region of Brazil is relatively dry compared to the rest of the country, with unusually irregular rainfall patterns and associated frequent droughts. The soils there tend to be relatively fertile and so, despite crop failures sometimes occurring in drier years, the area is reasonably densely populated with about 15% of Brazil's population living there; but under what are generally impoverished conditions.

This has led to extreme land-use pressures on the natural vegetation and widespread degradation of remaining lands. As in other parts of the world with similar soils and climate, the natural vegetation of the area is a form of deciduous scrub, known locally as Caatinga. Probably because Caatinga typically lacks the complexity and grandeur of moist tropical forests, this vegetation type has been to a large extent neglected to date both in terms of conservation programmes and scientific enquiry. This neglect has serious consequences given the enormous destruction of the Caatinga, which exceeds that of the neighbouring biomes of Amazonia and the Cerrado. Because of their potential importance in future warmer and drier climates in Brazil, conservation of the plant species of the Caatinga, which are adapted to high temperatures and seasonally erratic rainfall, is vital.

Designed as an integrated research program involving both Brazilian and UK researchers 'Nordeste' will attempt to redress this neglect:

  1. Through the establishment of a permanent plot network similar to that existing in moist tropical forests, allowing measurements of Caatinga canopy structure and dynamics and both their short- and long-term responses to climate change to be evaluated for the first time.
  2. With the aid of new DNA barcoding measurements designed to better quantify the biodiversity of the region.
  3. Through a comprehensive analysis of the biogeochemistry of natural and disturbed ecosystems to develop an understanding of how nutrient cycling processes vary in response to variations in soils and climate and human activity.
  4. Via a series of detailed structural, physiological measurements across the wide range of different Caatinga sub-types found in the region. These will be made both above- and below-ground and in natural and degraded ecosystems of the region. A special emphasis will be placed on measurements designed to help us understand why it is that under certain circumstances it is that very high biomass stands of Caatinga occur despite the very low rainfall.
  5. Glasshouse experiments comparing water stress responses of seedlings native to moist forest, savanna and caatinga will also be undertaken in order to try and understand what specific metabolic adaptions are involved in plant adaptions to frequent and/or erratic conditions of extreme soil water deficit.
  6. Via an integrated modelling program to provide new parameterisations of surface fluxes for semi-aid ecosystems in general and to provide new insights into variations in woody plant shoot: root allocation patterns in response to variation in precipitation regime.

To achieve these aims, the project has been designed as a series of six inter-related field-based workpackages, with a seventh workpackage focussed on modelling of species distributions, ecosystem fluxes and developing a mechanistic understanding of caatinga vegetation functional responses to both variations in climate and soil properties. Designed with a view to also producing a series of well-defined products to assist both policy makers and local communities to better manage this unique resource - for example, online guides to ecologically dominant and economically useful plants, the study will serve to provide a valuable first step towards a better understanding of Caatinga vegetation and its responses to anthropogenic and land-use change pressures.