Water regime of metal-contaminated soil under juvenile forest vegetation

Abstract

In a three-year factorial lysimeter study in Open Top Chambers (OTCs), we investigated the effect of topsoil pollution by the heavy metals Zn, Cu, and Cd on the water regime of newly established forest ecosystems. Furthermore, we studied the influence of two types of uncontaminated subsoils (acidic vs. calcareous) and two types of irrigation water acidity (ambient rainfall chemistry vs. acidified chemistry) on the response of the vegetation. Each of the eight treatment combinations was replicated four times. The contamination (2700 mg kg )1 Zn, 385 mg kg )1 Cu and 10 mg kg )1 Cd) was applied by mixing filter dust from a non-ferrous metal smelter into the upper 15 cm of the soil profile, consisting of silty loam (pH 6.5). The same vegetation was established in all 32 lysimeters. The model forest ecosystem consisted of seedlings of Norway spruce (Picea abies), willow (Salix viminalis), poplar (Populus tremula) and birch (Betula pendula) trees and a variety of herbaceous understorey plants. Systematic and significant effects showed up in the second and third growing season after canopies had closed. Evapotranspiration was reduced in metal contaminated treatments, independent of the subsoil type and acidity of the irrigation water. This effect corresponded to an even stronger reduction in root growth in the metal treatments. In the first two growing seasons, evapotranspiration was higher on the calcareous than on the acidic subsoil. In the third year the difference disappeared. Acidification of the irrigation water had no significant effect on water consumption, although a tendency to enhance evapotranspiration became increasingly manifest in the second and third year. Soil water potentials indicated that the increasing water consumption over the years was fed primarily by intensified extraction of water from the topsoil in the lysimeters with acidic subsoil, whereas also lower depths became strongly exploited in the lysimeters with calcareous subsoil. These patterns agreed well with the vertical profiles of fine root density related with the two types of subsoil. Leaf transpiration measurements and biomass samples showed that different plant species in part responded quite differently and occasionally even in opposite ways to the metal treatments and subsoil conditions. They suggest that the yearto-year changes in treatment effects on water consumption and extraction patterns were related to differences in growth dynamics, as well as to shifts in competitiveness of the various species. Results showed that the uncontaminated subsoil offered a possibility to compensate the reduction in root water extraction in the topsoil under drought, as well as metal stress.

Interactive Effects of Copper on Alfalfa Growth, Soil Copper, and Soil Bacteria

“…However, ET decreased significantly above these Cu rates, likely because the alfalfa was either stressed or dead. Menon et al (2005) observed similar results while investigating the effect of topsoil heavy metal contamination on newly established vegetation. The authors placed contaminated topsoil (2700 mg kg -1 Zn, 385 mg kg -1 Cu, 63 mg kg -1 Pb, 10 mg kg -1 Cu) over non-contaminated subsoil seeded with various plants and monitored soil water potential and plant transpiration over several years.…”

“…The authors placed contaminated topsoil (2700 mg kg -1 Zn, 385 mg kg -1 Cu, 63 mg kg -1 Pb, 10 mg kg -1 Cu) over non-contaminated subsoil seeded with various plants and monitored soil water potential and plant transpiration over several years. Heavy metal contaminated topsoils maintained significantly greater soil water potentials than controls, indicating that less water was lost from the contaminated soil (Menon et al, 2005). The authors also noted a reduction in poplar (Populus tremula) transpiration in metal contaminated soil as compared to controls.…”

Effects of heavy metal soil pollution and acid rain on growth and water use efficiency of a young model forest ecosystem

“…The motivation behind the experiment was to explore the potential of commercial trees to be used for the phytostabilization of metal-contaminated sites (Robinson et al 2006). The heavy metal treatment significantly reduced root growth and evapotranspiration (ET), increasing soil wetness and drainage discharge (Menon et al 2005). After the vegetation had been established in the year 2000, the type of subsoil at first had the strongest influence on ET in the two subsequent years 2001 and 2002, being substantially higher on calcareous than acidic subsoil.…”

Estrés por uranio en plantas. Acumulación en especies vegetales de zonas mineras y estudio de respuestas fisiológicas en remolacha (Beta vulgaris).

“…-114 -Discusión La reducción de la evapotranspiración es uno de los efectos fitotóxicos provocados por los metales pesados y se produce por distintos factores entre los que se puede mencionar: alteraciones en el crecimiento y las funciones de las raíces, cierre de los estomas, disminución del potencial osmótico y del mantenimiento de la turgencia en hojas, inhibición de la absorción y el transporte de agua por bloqueo de los canales de agua (Barceló y Poschenrieder, 1990;Menon et al, 2005;Hernández-Allica et al, 2007).…”

“…En la mayoría de los casos se ha reportado una Estrés por Uranio Introducción -27 -disminución de la tasa de evapotranspiración atribuida al cierre de estomas, inhibición de la absorción de agua por bloqueo de los canales de agua, bloqueo de aquaporinas y otros; pero también se han observado aumentos en la tasa de transpiración en algunos casos (Menon et al, 2005). El contenido hídrico relativo de las hojas se ve disminuida por la presencia de distintos metales, como Cd (Poschenreider et al, 1989) y Ni (Llamas, 2005).…”