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

Abstract

In a 4-year lysimeter experiment, we investigated the effects of topsoil heavy metal pollution (3,000 mg kg −1 Zn, 640 mg kg −1 Cu, 90 mg kg −1 Pb and 10 mg kg −1 Cd) and (synthetic) acid rain (pH 3.5) on tree growth and water use efficiency of young forest ecosystems consisting of Norway spruce (Picea abies), willow (Salix viminalis), poplar (Populus tremula) and birch (Betula pendula) trees and a variety of understorey plants. The treatments were applied in a Latin square factorial design (contaminated vs uncontaminated topsoil, acidified rain vs ambient rain) to 16 open-top chambers, with 4 replicates each. Each opentop chamber contained two lysimeters, one with a calcareous, and the other with acidic subsoil. The four tree species responded quite differently to heavy metal pollution and type of subsoil. The fine root mass, which was only sampled at the end of the experiment in 2003, was significantly reduced by heavy metal pollution in P. abies, P. tremula and B. pendula, but not in S. viminalis. The metal treatment responses of above-ground biomass and leaf area varied between years. In 2002, the heavy metal treatment reduced above-ground biomass and leaf area in P. tremula, but not in the other species. In 2003, metals did not reduce above-ground growth in P. tremula, but did so in the other species. It appears that the responses in aboveground biomass and leaf area, which paralleled each other, were related to changes in the relative competitive strength of the various species in the two experimental years. S. viminalis gained relative to P. tremula in absence of metal stress, in particular on calcareous subsoil, while P. abies showed the largest increases in growth rates in all treatments. Above-and below-ground growth was strongly inhibited by acidic subsoil in S. viminalis and to a lesser degree also in P. abies. In P. abies, this subsoil effect was enhanced by metal stress. Acid rain was not found to have any substantial effect. Whole-system water use efficiency was reduced by metal stress and higher on calcareous than on acidic subsoil.

Gas exchange responses of two poplar clones (Populus euramericana (Dode) Guinier 561/41 and Populus nigra Linnaeus 63/135) to lead toxicity

“…Also, Tognetti et al (2004), Renninger et al (2013), and Salehi et al (2014) found that the studied heavy metals had no toxic effect on photosynthesis in the studied poplar clones. In reality, it can be stated that various physiological responses of poplars exposed to heavy metals can be due to genotype, different growth substrates, plant physiological conditions, type of heavy metal and time periods of exposure to heavy metals (Menon et al 2007;Borghi et al 2008). Kieffer et al (2009) demonstrated that a short-term Cd treatment (14 days) had a strong negative effect on the photosynthetic process, but for a long-term Cd treatment (up to 56 days), this effect was lower.…”

A meta-database comparison from various European Research and Monitoring Networks dedicated to forest sites

“…The heavy metals mentioned above have negative effects on forest ecosystems, leading to different types of plant damage, like leaf discoloration, increasing tree mortality or significant decreases in tree growth and biodiversity (Menon et al 2007, Fiala et al 2008. Additionally, mercury (Hg) which is also an important trace element emitted to the atmosphere, can influence not only the environment but also human health (Pacyna & Pacyna 2002).…”

“…The pH constitutes the key factor which determines heavy metal availability and toxicity to plants in this particular environment. Any increase in soil acidity may result in heavy metal leaching from soil (Menon et al 2007). Moreover, the trees' reactions to high concentrations of heavy metals can leave them vulnerable to more and more damage caused by different species of fungi and insects (Rademacher 2001).…”

Response of Populus tremula to heterogeneous B distributions in soil

“…The species of Populus used in this experiment, P. tremula is known for its adaptability to a wide range of climate and soil conditions, is highly drought tolerant and may be the world's most widely distributed tree species (Worrell 1995). The B tolerance and accumulation potential of P. tremula has not been evaluated, however P. tremula is tolerant of elevated soil loadings of other trace elements such as Zn and Cd (Dos Santos Utmazian et al 2007;Menon et al 2007a). …”