Symbiotic nitrogen fixation in plants is the main source of nitrogen input to most natural ecosystems. Observations suggest that N2-fixing plants play an important role in water-limited ecosystems, and can become especially abundant after disturbances. This pattern is consistent with what we know about fixation in mesic ecosystems. However, central questions remain unresolved, such as: How does the costly strategy of symbiotic fixation survive in water-limited ecosystems? and, Why is it not more abundant?
Specific research projects:
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Study how symbiotic dinitrogen fixation in the shrub Calicotome villosa (קידה שעירה), a shrub typically abundant after disturbance and in nitrogen poor habitats, influences the local nitrogen cycle. The research will evaluate whether nitrogen allocation in C. villosa affects the flow of newly fixed nitrogen into the ecosystem via litter decomposition. Current findings show that nitrogen does not accumulate in the soil under C. villosa shrubs. We will evaluate the nitrogen budget of these shrubs and the flows of nitrogen within the plant and into the ecological system.
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Study nitrogen nutrition, allocation, and cycling in Acacia trees and how it influences the ecosystem nitrogen cycle, under different environmental conditions.
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A study of the evolutionary stability of herbaceous annual N2-fixing legumes in hyper-diverse Mediterranean herbaceous communities. Legumes constitute ~25% of the species diversity (total 300-600 species) of herbaceous plant communities in the Mediterranean region of Israel. The relative abundance of these legumes, however, is much smaller. Our research will evaluate the puzzle of the large diversity and low abundance of legumes and how they survive in competition with abundant grasses.
Ecology and evolution of symbiotic dinitrogen (N2) fixation in dry environments
Regeneration survival and succession of Mediterranean forests in a changing world
Woody plant strategies of regeneration and survival usually are adapted to the local environmental conditions, allowing plant growth and forest succession. Early successional trees typically have small seeds with long-distance dispersal, and late-successional ones are long-lived with local regeneration. Regeneration processes in Mediterranean woody communities challenge these assertions in two ways: (1) Oaks in late-successional Mediterranean forests (Maquis, Matorral, חורש) appear to be unable to self-regenerate; and (2) Massive land-use changes and human exploitation in Mediterranean Basin have changed these landscape dramatically, altering seed sources (e.g., afforestation), and disturbance regimes.
We will study how the regeneration of natural and planted forests and woodlands in Israel are influenced by humans, via climate change and land-use change (agriculture, restoration and forest plantation). This project will involve field work, analysis of historical data and remote sensing.
Specific research projects will be developed with students
