Plastic responses of below‐ground foraging traits to soil phosphorus‐rich patches across 17 coexisting AM tree species in a subtropical forest

Abstract

Below‐ground plastic responses to soil nutrient ‘hot‐spots’ form a key nutrient foraging strategy of plants coexisting in natural ecosystems. However, it is unclear how plant species differ in these below‐ground plastic responses and how they covary. Plastic responses to soil phosphorus (P)‐rich patches of absorptive root, mycorrhizal, and exudation traits of 17 coexisting arbuscular mycorrhizal (AM) tree species in a subtropical evergreen broad‐leaved forest were investigated using a root bag method. There was considerable variation and heterogeneity in species‐specific responses to P‐rich patches. Negative log response ratios usually occurred for high‐cost traits and positive log response ratios for low‐cost traits. There were trade‐offs in the plastic responses between root acid phosphatase activity and extraradical hyphal length, which were unaffected by phylogeny, and between root acid phosphatase activity and specific root length. Thicker‐rooted species responded to P‐rich patches more through root exudation plasticity than mycorrhizal plasticity. Thinner‐rooted species relied more on mycorrhizal plasticity. Synthesis. Our results revealed diverse P foraging strategies comprising different combinations of plastic adjustments in absorptive root, mycorrhizal, and exudation traits among coexisting AM tree species, which suggest the potential for complementary exploitation of different soil P sources.

Contrasting depth‐related fine root plastic responses to soil warming in a subtropical Chinese fir plantation

“…Besides, warming-induced soil drying can limit the mobility of soil P (He & Dijkstra, 2014) due to P adsorption to iron oxides, hydroxides and clays in drier soils (Tian et al, 2023), and the longer and more tor- which reduces soil P availability. Warming-reduced fine root exudation, as reported in our previous study (Xiong et al, 2020), might also have contributed to decreased soil P availability and weakened uptake of P by fine roots, because the secretion of phosphatases and organic acids in root exudates solubilizes and mineralizes inorganic and organic P in the rhizosphere (Bengtson et al, 2012;Zhu et al, 2023).…”

Shifts from an extensive to an intensive root nutrient‐acquisition mode with stand development of three Pinus species

“…To compensate for the decline in nutrient‐scavenging capability of absorptive fine roots, the three studied Pinus species showed convergence in increasing root‐exudation rates (Figure 4b), in line with previous research reporting that the importance of nutrient‐mining strategies driven by root exudation increases during tropical forest succession (Rondina et al., 2019) and pedogenesis (Zemunik et al., 2015). Moreover, a recent study showed that tree species with thicker absorptive fine roots release more root exudates than those with thinner absorptive fine roots in response to nutrient‐rich patches among 17 coexisting subtropical tree species (Zhu, Yao, et al., 2023). Collectively, these results suggest that changes in root morphological traits may be a key factor underlying shifts from an extensive to an intensive root nutrient‐acquisition mode with stand development across the three Pinus species.…”

“…Consequently, the high C cost for root con- et al, 2019) and pedogenesis (Zemunik et al, 2015). Moreover, a recent study showed that tree species with thicker absorptive fine roots release more root exudates than those with thinner absorptive fine roots in response to nutrient-rich patches among 17 coexisting subtropical tree species (Zhu, Yao, et al, 2023). Collectively, these results suggest that changes in root morphological traits may be a key factor underlying shifts from an extensive to an intensive root nutrient-acquisition mode with stand development across the three Pinus species.…”

“…Overall, plants can scavenge nutrients by absorptive fine roots and mycorrhizal fungi, and mine nutrients by releasing root exudates. However, few studies have concurrently explored these strategies, limiting our understanding of whether and how plants coordinate these strategies to acclimate to varying soil nutrient availability (Wen et al., 2019; Zhu, Yao, et al., 2023).…”

“…Conversely, thicker absorptive fine roots that can provide more space for arbuscular mycorrhizal (AM) colonization render plants that express an ‘outsourcing’ strategy (Liu et al., 2015). Owing to the strong phylogenetic component for root diameter and SRL, it has been suggested that phylogenetically closely related species exhibit a similar nutrient‐acquisition strategy, whereas phylogenetically distant species express contrasting strategies (Wen et al., 2019; Zhu, Yao, et al., 2023). Despite this advance, root physiological and architectural traits that are critical for plant nutrient uptake remain absent in the RES (Wen et al., 2022).…”