Heavy metal hyperaccumulating plants: how and why do they do it? And what makes them so interesting?

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Economics of natural resources and the environment

The concentrations in plant parts depend both on intrinsic and extrinsic factors and vary greatly for different species and for different metals. Responses by plant species to exposure to metalliferous soils can range from phytotoxicity to survival by exclusion, with only small elevations of metal concentration to survival with accumulated metal constituting a significant percentage of the plant dry matter. The importance of nonvascular transport through laticifers, for example, is also obscure. The extent to which secondary xylem tissues become a long-term repository for accumulated metals is not known. The high degree of endemism to metal-rich soils shown by hyperaccumulating taxa has been related to their survival. The success of many metallophytes in overcoming the adverse edaphic conditions is such that they can exist relatively free from competition. Metal hyperaccumulators have been recognized on the basis of concentrations of metals in leaf dry matter.

Metal hyperaccumulator plants: a review of the ecology and physiology of a biological resource for phytoremediation of metal-polluted soils

Carbon sequestration strategies highlight tree plantations without considering their full environmental consequences. We combined field research, synthesis of more than 600 observations, and climate and economic modeling to document substantial losses in stream flow, and increased soil salinization and acidification, with afforestation. Plantations decreased stream flow by 227 millimeters per year globally (52%), with 13% of streams drying completely for at least 1 year. Regional modeling of U.S. plantation scenarios suggests that climate feedbacks are unlikely to offset such water losses and could exacerbate them. Plantations can help control groundwater recharge and upwelling but reduce stream flow and salinize and acidify some soils.

Trading water for carbon with biological carbon sequestration

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Regeneration by coppicing (resprouting) of miombo (African savanna) trees in relation to land use

To unravel the market for commercial medicinal plants on the Witwatersrand in South Africa, a semiquantitative approach was taken. A stratified random sample of 50 herb-traders was surveyed, and an inventory of all plants and parts sold was compiled. Research participants were questioned on the scarcity and popularity of the plants traded, as well as suppliers and origins. The rarefaction method established that the sample size was adequate. The diversity of the sample was determined using ecological indices of diversity, and found to be comparatively high. In addition, Spearman rank correlations, chi-squared and Fisher’s exact probability tests were used to assess the probability of certain taxa being used. At least 46% of the taxa traded showed a higher than expected probability of being utilized, and taxa tended to be harvested from the largest families proximate to the markets. About 511 species are traded in the region, and there is a low dominance in the use of species. Ethnic and floristic diversity are influential in deciding the trading patterns that have emerged.

Unraveling the commercial market for medicinal plants and plant parts on the witwatersrand, South Africa

Harvested and standing wood stocks in protected and communal miombo woodlands of eastern Tanzania

This study documents the utilization aspects and distribution of ethnobotanical knowledge of the local people of Morogoro, Tanzania, as a first step towards sustainable utilization and conservation of tropical woodlands. A total of 133 arborescent species in 31 families was identified of which 69% had a variety of uses. These uses were classified into 12 categories and major uses were charcoal, firewood, medicine, and poles. Most tree species have occasional uses, but a few are exceptionally useful and thus their levels of utilization may far exceed their regeneration and production. The questionnaire survey indicated that 62% of the respondents agreed that traditional medical services were more available than modern services. Utilization surveys indicated that wooden poles are the building material used in 98% of the dwellings and storage structures, wild foods were useful for food security especially during drought years, and high quality timber trees have been depleted in the forest because of earlier exploitation by pit-sawing. The distribution of ethnobotanical knowledge indicated that much of the relevant ethnobotanical and utilization information was held by more aged members of the society and hence there is a clear need to capture this knowledge before it is lost. This study has shown that resources are defined by use and culture, and some components of ethnobotanical knowledge have potential for the sustainable management of miombo woodlands.

Differential utilization and Ethnobotany of trees in Kitulanghalo forest reserve and surrounding communal lands, eastern Tanzania

http://directory.umm.ac.id/Data%20Elmu/jurnal/E/Ecological%20Economics/Vol35.Issue2.Nov2000/11191.pdf

Kevin Balkwill

Papers

Regeneration by coppicing (resprouting) of miombo (African savanna) trees in relation to land use

Unraveling the commercial market for medicinal plants and plant parts on the witwatersrand, South Africa

Harvested and standing wood stocks in protected and communal miombo woodlands of eastern Tanzania

Differential utilization and Ethnobotany of trees in Kitulanghalo forest reserve and surrounding communal lands, eastern Tanzania

Economics of charcoal production in miombo woodlands of eastern Tanzania: some hidden costs associated with commercialization of the resources