Some 57% of Africa and 69% of Australia is either arid or semi-arid land. Rainfall is low and highly variable, and greatly exceeded by evaporation. Trees that grow under these harsh conditions play a vital role in providing shade and shelter for stock, preventing erosion and enhancing soil fertility. Trees also provide wood for fuel and construction. Fuelwood and charcoal supply more than 90% of the energy consumed for domestic purposes.
Population pressure and lack of sustainable management have severely degraded much of Africa's arid and semi-arid land. In Kenya, the population of arid and semi-arid regions is increasing by 4-5% per year, with about half the growth coming from migration from more populous, higher-productivity areas.
The need to control and reverse the degradation by replacing lost tree cover is imperative. However, poor seedling survival rates of zero to less than 30% have made attempts at reforestation largely ineffective.
This project aims to develop ways to substantially increase the success rate in tree establishment. The broad objectives are to improve the efficiency and effectiveness of tree establishment in arid and semi-arid lands by developing:
improved nursery techniques for the production of suitable seedling stock;
more efficient techniques for evaluating the suitability and the selection of species, provenances and genotypes;
an improved understanding of the role of symbionts in tree survival and productivity; and
an improved understanding of tree physiology and morphological responses to stress conditions.
Nursery trials in Australia and Kenya will examine the effects of different growing media, container types and watering and fertiliser schedules. Measurements of plant growth, nodule development, root growth potential, root hydraulic conductivity, plant water use patterns under conditions of field capacity and simulated stress, plant and tissue water relations and nutritional stress will provide the data needed to assess plant performance.
Glasshouse trials will determine the effectiveness of various Rhizobium strains in nodulating the roots of their legume tree hosts and fixing nitrogen, and the impact of mycorrhiza from different locations. Microbial inoculants will be tested in Australia, Kenya and Zimbabwe to see if plant growth is increased, nodulation occurs effectively, and mycorrhizal root colonisation is enhanced.
Field trials will be conducted near Longreach in Australia, at seven KEFRI field stations in Kenya, and on two sites near Bulawayo in Zimbabwe. The first goal will be to characterise and quantify the responses of a range of species and provenances to their growing conditions. Findings from other elements of the project will be integrated into the trials and their application tested. In Zimbabwe, the effects of different water-conserving techniques on the species and provenances under trial will be tested.
Links:
[1] http://www.aciar.gov.au/country/Zimbabwe
[2] http://www.aciar.gov.au/programarea/Forestry