Effects of Irrigation on Root Growth and Distribution of the Seedlings of Alhagi sparsifolia Shap. in the Taklimakan Desert

To recover degraded Alhagi sparsifolia Shap.community and supply suitable soil moisture for seedlings in the oasis-desert ecotone in southern marginal zone of the Taklimakan Desert,field experiment was conducted at the Cele oasis periphery from March to October in 2009 to study the effects of different irrigation amounts on root biomass accumulation,root spatial distribution and root/shoot ratio.Results showed that the effect of irrigation on root growth and distribution was significant.Under treatment A(no irrigation),the root length of seedlings was the longest,while the accumulation of root biomass was limited and the dry matter weight was 38.8% less than that under treatment B(0.1 m3·m-2 per month,appropriate irrigation),especially the fine root(2 mm) decreased obviously and was only 18.1% of the total root weight;similarly,root biomass and fine root proportion decreased in varying degrees under treatment C(0.2 m3·m-2,excessive irrigation).Under the three treatments,the dry matter weight of A.sparsifolia root decreased with the increasing of soil depth and most roots distributed at 0 40 cm soil depths.Furthermore,the more irrigated water,the smaller the root extinction coefficient(β),and the clearer the centralization trend.The root/shoot ratio increased with the growth of A.sparsifolia seedlings,which indicated that more and more resources were contributed to roots and it was in accord with the growth feature of desert vegetation.Root biomass of A.sparsifolia seedlings cumulated the most and distributed the widest under treatment B,suggesting that appropriate irrigation benefited the normal growth and reasonable distribution of the seedlings roots and provided positive significance for the increase of potential productivity of the species.