Interactive Effects of Soil Water, Nutrients and Clonal Fragmentation on Root Growth of Xerophilic Plant IStipa breviflora/I

Root traits are often used to predict the ecological adaptations of plants. Water and nutrient availability together with fragment size are likely to affect the adaptative capacity of Stipa breviflora and help plants spread and explore new sites, while the effects of water, nutrients and fragment size on S. breviflora's root traits have rarely been studied in combination. Here, a standard Taguchi L[sub.8](2[sup.7]) array design was conducted with four single factors, water (W), nitrogen (N), phosphorus (P) and fragment size (C), and three interactions (N × P, N × W and P × W). Each of the four factors had two levels (1 = low level and 2 = high level). This study found that water was the most important contributor influencing S. breviflora root growth, followed by N and P, respectively. W2 and P2 additions both promoted root growth, whereas N2 addition significantly inhibited root growth. Though C2 had higher values of total root length, surface area, volume, number of tips and biomass than C1, its root growth rate was lower than C1, and its small size fragment had a higher capacity of root growth under low N addition. These findings suggest that clonal fragmentation may enhance the adaptation of S. breviflora in low nitrogen habitats, and that nitrogen is one of the limiting factors influencing their growth and distribution.