Relationships between crown defoliation and tree diversity depend on the environmental context

RELATIONSHIP BETWEEN CROWN

DEFOLIATION AND TREE DIVERSITY DEPEND

ON THE ENVIRONMENTAL CONTEXT

Giovanni Iacopetti1 , Filippo Bussotti1 , Federico Selvi1 , Filomena Maggino2 , Martina Pollastrini1

TREE DIVERSITY AND VITALITY

role of diversity in the complex tree-ecosystem relationship

• _{No general evidence of the}

relationship in the ICP forest program

• _{Italy provides a good setting, with}

THE LANDSCAPE HETEROGENEITY

PROBLEM

• _{Defoliation has several and often}

correlated causes

• _{Many are the same that influence}

the stand composition

• _{Landscape heterogeneity has to be}

controlled in order to limit the interferences

Site conditions Soil Management

Defoliation

Insects and fungi attacks Photosynthetic efficiency Growth rate Climate Tree diversity Tree identity

TAXONOMIC AND STRUCTURAL

DIVERSITY

• Plot level

• Shannon and Simpson

• Community Weighted Mean • Functional Divergence

• Specific Leaf Area • Wood Density

• Height

• Leaf Nitrogen Content • Seed Weight

TAXONOMIC AND STRUCTURAL

DIVERSITY

•

_{Single tree level}

• _{Local Shannon}

• _{Structure indices}

• Dominance

• _{DBH differentiation} • _Mingling

SHANNON INDEX

CLUSTERING

_{Hierarchical clustering}

_{Actual clustering}

Mixed mountain forest

_{Monospecific beech forest}

Mixed mountain

High mountain

Mediterranean

DEFOLIATION-DIVERSITY CORRELATION

Beech

Others

Small diversity zone

DEFOLIATION-DIVERSITY CORRELATION

Mediterranean

Beech

Mixed mountain

Others

Stand diversity reflect ecological conditions. The crown defoliation is driven by the environmental context rather than diversity .

SMALL DIVERSITY BEECH FOREST

Better than monospecific

SMALL DIVERSITY MEDITERRANEAN

FORESTS

Worse than monospecific

CONCLUSIONS

• _{Stand diversity reflect ecological conditions. The crown defoliation is driven}

by the environmental context rather than diversity .

• _{Low levels of stand diversity enhance crown condition compared to}

monospecific stands.

• _{For management: silviculture should promote the diversity in monospecific}

FUTURE DIRECTIONS

• _{To introduce air pollution factors as explicative variables.}

• _{Including tree growth and damage symptoms as response variables} • _{Develop a tree health multiparametric index}