influence of alnus subcordata, populus deltoides and taxodium distichum on poor drainage soil, northern iran

this study was conducted to choose the best species for plantation on a poor drainage soil in southern coast of caspian sea, iran. nutrient concentrations in live and senescent leaves and soil properties were compared among alnus subcordata c.a.mey (n-fixing tree), populus deltoides­ marsh. (non n-fixing tree)and taxodium distichum (l.) rich. (coniferous tree) plantations. in each of these plantations and an adjacent natural forest, six 20×20m plots have been selected according to a 100m × 100m randomly systematic grid. leaf samples of green trees were collected from the bottom one-third of the tree crown by clipping two small twigs located on opposite sides of the crown (six representative trees were sampled in each plot). senescence leaves have been collected inside wooden trap-based in each stand. results revealed different effects of species on soil nutrients. alnus subcordata increased soil n (%) whereas populus deltoides­ and taxodium distichum reduced it.the results of nutrition, litter quality, retranslocation and soil properties indicated that alnus improve soil quality in comparison with the two others.