Abstract
Root foraging strategies of plants may be critical to the competition for nutrient resources in the nutrient patches, but little is known about these of co-existing tree species in subtropical regions. This study aimed to elucidate root foraging strategies of three co-existing tree species in nutrient heterogeneous soils by exploring their root distribution, root morphology, photosynthates allocation and nutrient accumulation. Seedlings of the three tree species [moso bamboo (Phyllostachys edulis), Chinese fir (Cunninghamia lanceolata), and masson pine (Pinus massoniana)] were grown for 8months under one homogeneous soil [uniform nitrogen (N) plus phosphorus (P)] and three heterogeneous soils (localized N supply, localized P supply, or localized N plus P supply). The biomass, root morphological parameters (i.e., root length and root surface area), specific root length (SRL), non-structural carbohydrates (NSCs, i.e., mobile sugar and starch) in roots, total N and total P of plants were measured. The plasticity and distribution of root system were analyzed by calculating the root response ratio (RRR) and root foraging precision (FP), respectively. The results are as follows (i) Chinese fir tended to forage more N by promoting root proliferation in the N-rich patch, while root proliferation of bamboo and pine did not change. For P, bamboo absorbed more P by promoting root proliferation in the P-rich patch. The total P content of Pine and Chinese fir under localized P supply treatment remain the same despite the fact that the root length in the P-rich patch and the FP increased. (ii) Chinese fir foraged more N by increasing root length and decreasing SRL in the NP-rich patch; bamboo foraged more N and P by increasing root length and SRL in the NP-rich patch. The FP and foraging scale (FS) of both bamboo and Chinese fir were significantly improved under localized N plus P treatment. (iii) The concentrations of NSC were positively correlated with root morphological plasticity for moso bamboo and Chinese fir. Our results indicated that higher morphological plasticity is exhibited in moso bamboo and Chinese fir than masson pine in nutrient heterogeneous soils, allowing them to successfully forage for more nutrients.
Highlights
The distribution of nutrients in soil is typically highly heterogeneous over space and time (Caldwell et al, 1991; Cheng et al, 2016)
We aimed to study the foraging strategies of three tree species in nutrient patches, through investigating the responses of root distribution, root morphology, nutrient uptake and photosynthates allocation to nutrient heterogeneous soil
Within each nutrient treatment type, the total root length showed a decreasing order as bamboo > Chinese fir > pine (Figure 2; Table 2), and the total root surface area followed an order of Chinese fir > bamboo > pine (Figure 3; Table 2), whereas the total plant biomass had an order of Chinese fir > pine > bamboo (Figure 4; Table 2)
Summary
The distribution of nutrients in soil is typically highly heterogeneous over space and time (Caldwell et al, 1991; Cheng et al, 2016). Growth rate (Van de Vijver et al, 1993; Fransen et al, 1999), root thickness (Hodge, 2004; Liao et al, 2014), sensitivity to nutrient elements (Zhang et al, 2013; Li et al, 2014, 2017), and mycorrhizal types (Hodge and Fitter, 2010; Comas et al, 2014; Valverde-Barrantes et al, 2017) have all been reported to affect the root plasticity of plant in heterogeneous soil Such a difference among tree species is of great ecological value in the coexistence of plants and the maximization of soil use efficiency (Fransen and de Kroon, 2001; James et al, 2009; Shen et al, 2013). Exploring the foraging strategies of co-existing tree species in heterogeneous nutrient conditions is beneficial to alleviate the competition among tree species and improve the utilization efficiency of soil space
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