Effects of plant diversity on plant biomass production and soil macrofauna in Amazonian pastures

We examined the effect of plant diversity on plant production and soil macrofauna density and diversity. Four plants species (Arachis pintoi, an herbaceous legume; Brachiaria brizantha, a perennial grass; Leucaena leucocephala, a legume shrub; Solanum rugosum, a non-legume shrub) were used in a field experiment and communities of all combinations of one, two, three or four species were established. Plant diversity neither significantly affected density and diversity of soil macrofauna nor total plant biomass, however, the biomass of specific plants was negatively affected by plant diversity. Earthworm and ant densities were significantly higher in the presence of A. pintoi although this plant influenced neither the density of the other group nor fauna diversity. Earthworm and diplopod densities increased significantly with shoot biomass of A. pintoi. Fauna diversity increased significantly with shoot biomass (specific and total). Root biomass did not affect fauna density and diversity. Our results suggest that fauna density is affected by litter quality and that it is more affected by resource quantity than quality. Our results also confirm the importance of nitrogen fixers to ecosystem function.     

From landraces to modern cultivars: field observations on taro <Emphasis Type="Italic">Colocasia esculenta</Emphasis> (L.) Schott in sub-Saharan Africa

Until recently, taro Colocasia esculenta (L.) Schott, was considered a neglected food crop due to its low palatability and inferior value compared to other root crops such as cassava, potatoes and yams. Under the impulse of new studies on plant dispersal, and in light of the severe threats posed by pests to its conservation status, this crop has finally received more attention. However, there is still insufficient knowledge on specific cultivars and their culinary and medicinal uses, especially in Africa. We studied the agrodiversity of taro cultivars in Nigeria, Cameroon, the Democratic Republic of Congo, Kenya, and Tanzania. Here, we present ethnobotanical, morphological and linguistic data of 20 taro cultivars, as well as specific notes on abandoned landraces. These traditional varieties represent valuable genetic resources and can be instrumental in protecting taro from the genetic erosion caused by preference for yautia, and diseases such as the leaf blight. With this work, we call for renewed efforts to conserve this species and its landraces.