Soil dynamics in an age sequence of Prosopis juliflora planted for sodic soil restoration in India

A field study was conducted to study long-term soil dynamics in Prosopis juliflora stands planted to rehabilitate degraded sodic soils in Haryana, India. Soil samples were collected from an age sequence of 0-, 5-, 7-, and, 30-yr-old plantations to assess the effects of the trees on the physical, chemical and biological properties of soil. Tree growth altered microclimate, improved soil moisture status, organic C, total N, extractable P, exchangeable Ca, Mg, and K and decreased pH, electrical conductivity and exchangeable Na levels that contributed to the reclamation of sodic sites. The dynamics reflected a three phase restoration sequence, characterized by nominal soil changes during tree establishment (0-5 yr), marked and rapid changes associated with canopy closure (5-7 yr), and gradual stabilization of soil properties in the fallow enrichment phase (7-30 yr). The ameliorative mechanisms operating in the chronosequence were categorized into two parallel sets of major processes namely: sodicity alleviation that dominated in transitional phase, and fertility restoration that characterized the fallow enrichment phase. The bioremediation mechanisms driving the reclamation processes in the reforestation of degraded sites were examined in relation to hypotheses accounting for these changes. (C) 1998 Elsevier Science B.V.