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Agroforestry is an appealing option for sequestering carbon on agricultural lands because it can sequester significant amounts of carbon while leaving the bulk of the land in agricultural production. Simultaneously, it can help landowners and society address many other issues facing these lands, such as economic diversification, biodiversity, and water quality. Nonetheless, agroforestry remains under-recognized as a greenhouse gas mitigation option for agriculture in the US. Reasons for this include the limited informationbase and number of tools agroforestry can currently offer as compared to that produced from the decadesworth of investment in agriculture and forestry, and agroforestry's cross-cutting nature that puts it at the interface of agriculture and forestry where it is not strongly supported or promoted by either. Agroforestry research is beginning to establish the scientific foundation required for building carbon accounting and modeling tools, but more progress is needed before it is readily accepted within agricultural greenhouse gas mitigation programs and, further, incorporated into the broader scope of sustainable agricultural management. Agroforestry needs to become part of the agricultural tool box and not viewed as something separate from it. Government policies and programs driving research direction and investment are being formulated with or without data in order to meet pressing needs. Enhanced communication of agroforestry's carbon co-benefit, as well as the other benefits afforded by these plantings, will help elevate agroforestry awareness within these discussions. This will be especially crucial in deliberations on such broad sweeping natural resource programs as the US Farm Bill.

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In laboratory studies, water-soluble extracts of the litter of four shrub and three conifer species had variable effects on the growth of four species of ectomycorrhizal fungi. In general, low concentrations (parts per thousand) stimulated fungal growth; while, high concentrations (parts per hundred and parts per ten) either stimulated growth, inhibited growth, or had no effect, depending on both fungal and litter species. In greenhouse studies, litter applied to the surface of a sand-soil mixture reduced the formation ofRhizopogon sp. on Douglas-fir seedlings. Allelochemicals in the litter may inhibit seedling growth and suppress fungai growth and root colonization in the field, thus explaining the failures of reforestation by conifer species in disturbed sites.

No abstract