Effects of Water, Nitrogen, and Phosphorus Additions on Root Growth
Strategies of Stipa breviflora under Drought Conditions
Abstract
Root growth strategies are important to predict plant – soil
interactions under nutrient-limited soil environments. A dominant
species Stipa breviflora is found to develop cluster fragmentation in
the arid and semi-arid areas of China, where water, nitrogen and
phosphorus are the most important limiting factors to plant growth.
Here, we aimed to assess how water, N, P additions and their
interactions, and cluster fragmentation affect root growth traits in a
greenhouse experiment to reveal the adaptation of S. breviflora under
drought conditions. A standard Taguchi L8(27) arrays design was
conducted with four factors such as nitrogen (N), phosphorus (P) and
water (W) and cluster fragmentation (C) and three interactions (N × P, N
× W and P × W). Each of four factors had two levels (N1 = 15 mg N / kg,
N2 = 120 mg N / kg, P1 = 2 mg P2O5 / kg, P2 = 24 mg P2O5 / kg, W1 = 25
% ~ 30 % field moisture capacity of mixture (FMC), W2
= 75 % ~ 80 % FMC, C1 = individual with single ramet,
C2= individual with three ramets).Water was the most important
contributor to S. breviflora root system growth, while cluster
fragmentation was the second contributor, followed by N and P in order.
W2 and P2 both promoted root growth, whereas N2 significantly inhibited
root growth. Moreover, under drought condition, N2 induced its roots
developing an acquisition resource use strategy for escaping adverse
environments compared to N1. While under sufficient P condition, W1
induced its roots developing an acquisition resource use strategy for
acquiring more resource. And cluster fragmentation is beneficial to
improving the adaptability of S. breviflora under low N condition.