Due to the presence of their roots in the soil, and by bringing in overhead and underground litter, trees are likely to impact the dynamics of water and nutrients in soils. The study of the sharing of water resources (water balance and transfers) and nutrients (soil fertility) is essential to understand how to manage fertilization and irrigation, in agroforestry market gardening.

How and to what extent does the presence of intraparcellar tree alignments affect water supply conditions and soil fertility (physical, chemical and biological components)?

To answer this question : in each agroforestry modality created in Action 1, and according to gradients of distance to tree lines, we study:

• Transfers of water into the soil using tensiometers and automated monitoring of water contents with continuous acquisition, supplemented by soil temperature sensors and piezometric level measurements. The water balance is made using spot measurements on the neutron probe. Sap flow measurements on trees directly estimate root pumping and the transpiratory component of the water balance.
• Evolution of soil quality by characterization of the intrinsic properties of soils (granulometry, carbonates, organic carbon CEC ... etc.), and annual monitoring of biological and chemical indicators that respond quickly to environmental changes (microbial biomasses and macrofauna, enzymatic and catabolic activities (MicroResp) related to the mineralization potential of C, N and P).
• Earthworm activity during the four seasons in each of the treatments, population monitoring, ground activity through casting activity and soil sampling using soil column samplings.

Outputs

• Study report on the effect of trees and their management on soil fertility and water balances
• Study report on the effect of agroforestry systems on the seasonal activity of earthworms in the Mediterranean climate (Yvan Capowiez)