The soil water regime in a young radiata pine plantation in southeastern Australia

Abstract

Application. High initial growth rates in plantations may not be sustained beyond canopy closure, when rainfall is insufficient to recharge the soil profile, or restore groundwater to accessible levels. A judicious balance of fertilization, and crop density modified by early thinning, may be necessary to achieve optimum crop productivity and health. A two-year fallow period may be required following felling a mature crop, to allow full recharge of soil water reserves.Abstract. The soil water regime from planting to age seven years beneath plantations of Pinus radiata D. Don on first and second rotation sites has been studied by measuring changes in watertable depth and soil water content. Both plantations received intensive management, which produced very high growth rates.Magnitude and, to a lesser extent duration, of groundwater peaks decreased from planting, and by the time plantations were 5 years old the winter rise was negligible. Within 2 years of planting, soil water in the uppermost 1 m was largely depleted during summer periods, and by the fifth summer available water to 3 m depth was exhausted. A model relating change in water content to time from planting, and cumulative rainfall explained over 95°70 of the variation in water content. Daily changes in water content, which varied from 1.7 to 5.3 mm from winter to summer, related strongly to rainfall but weakly to pan evaporation. No relationship between evapotranspiration and soil water content was found.A rapid early depletion of soil water through vigorous plantation growth resulting from intensive silviculture was observed. This could cause problems in sustaining rapid growth rates beyond canopy closure, where access to groundwater is not possible. A judicious balance of fertilization and crop density, related to site characteristics, would be necessary to achieve optimum productivity.

Impacts of tree plantations on groundwater in south-eastern Australia

“…No studies in south-eastern Australia have measured evapotranspiration in the period of the rotation between harvesting of one tree crop and establishment of the canopy of the next. In south-eastern South Australia, Mitchell and Correll (1987) observed that the soil water profile fully recharged in the 1-year fallow period between the first and second rotation P. radiata plantation, indicating the possibility of some groundwater recharge during this period. More research is needed if recharge during this period of each rotation is to be quantified and the net water balance over a full rotation estimated accurately.…”

Productivity of three successive rotations of P. radiata plantations in South Australia over a century

“…1) and causes recurring soil water deficits when trees experience water stress Benyon and Doody, 2004). Depending on the depth of soil, growth rates and the timing of canopy closure (age 5-7 years) radiata pine water use becomes dependant on current rainfall (Mitchell and Correll, 1987;Benyon and Doody, 2004).…”

Holm oak (Quercus rotundifoliaLam.) and Aleppo pine (Pinus halepensisMill.) response to different soil preparation techniques applied to forestation in abandoned farmland

“…In dry and semi-arid Mediterranean territories, lack of water is the most limiting factor for reconstructing ecosystems [16]. Therefore, it is essential for seedlings to develop a root system as quickly as possible to escape from soil desecation [4,12,15], especially during the first summer after planting. Plantation success also depends on this.…”