Jianmin Shi

Introduction: Clonal bamboo undergoes two distinct growth stages with contrasting growth rates: a fast-growing stage (FG) and a subsequent slow-growing stage (SG). FG is characterized by rapid culm elongation and tissue formation, whereas SG is characterized by cessation of height growth and progressive tissue maturation. Plants may therefore need to adjust belowground phosphorus (P)-acquisition strategies across these contrasting stages to meet different resource requirements for growth. However, whether such adjustments occur, and how they differ between functionally distinct root types (culm roots and rhizome roots) and across P supply levels, remains unclear. Methods: We investigated Phyllostachys glauca McClure growing in a low-P karst habitat under three P supply levels: low P (LP), medium P (MP), and high P (HP). Root morphological traits, carboxylate release, and rhizosphere available P concentrations were compared between culm roots (CR) and rhizome roots (RR) during FG and SG under these P supply levels. Leaf nutrient status was also analyzed across P supply levels and growth stages. Principal component analysis (PCA) was further used to evaluate coordinated variation among P-acquisition traits. Results: Root morphological traits differed significantly between growth stages and root types. In the LP treatment, the specific root length (SRL) of RR during FG was approximately 2.36 times that during SG ( P < 0.05). Across treatments, RR generally exhibited greater SRL and specific root area (SRA), whereas CR had higher root tissue density (RTD), indicating contrasting morphological strategies. Carboxylate release was greater during FG, with total release under LP reaching 12.0 ± 2.0 and 10.9 ± 1.4 μmol g ⁻¹ root DW in rhizome and CR, respectively. Increasing P supply reduced the release of some carboxylate components, whereas rhizosphere available P concentrations generally increased, suggesting nonuniform responses among different P-acquisition processes. Leaf N:P ratios further suggested differences in nutrient balance between growth stages. PCA showed more evident separation between FG and SG samples than among root types or P treatments. Conclusion: P-acquisition traits in P. glauca varied between growth stages. Functional differentiation between culm and RR became more evident during FG, and different P-acquisition processes responded differently to P supply levels. This growth-stage-dependent plasticity provides new insights into the functional regulation of root nutrient foraging in clonal plants, and highlights the need to incorporate growth-stage variation in root function into predictions of plant responses to fluctuating nutrient availability.

The coordination between leaf and root traits is conducive to an integrated understanding of whole-plant ecological strategies and reveals how community composition and diversity contribute to defining the functions and services of ecosystems. However, there is limited understanding regarding the impact of species richness and trait categories on the coordination between leaf and root traits. Based on a 9-year common garden experiment, we investigated the leaf and fine root traits of 56 plots (25.8 m × 25.8 m) encompassing various trait categories (trait categories were defined according to the root depth, leaf habit, and mycorrhizal type) and different levels of species richness (1, 2, 4, 8) in the context of a forest biodiversity and ecosystem functioning experiment conducted in subtropical China (BEF-China). We found the following: (1) Our findings indicate that there was generally a significant difference in leaf traits, occasionally in absorptive root traits, and no difference in transport root traits between different trait categories. (2) Conversely, species richness significantly influenced all transport root traits except root nitrogen and most leaf and absorptive root traits. (3) The results demonstrated that trait categories played a crucial role in the coordination between leaf and fine root traits. Additionally, the coordination between leaf and fine root traits increased with higher species richness, particularly in deep-rooted, evergreen, and ectomycorrhizal fungi species. Furthermore, the coordination between leaf and fine root traits was significantly lower in monocultures compared to four- and eight-species mixtures. These results suggest that a significant mixture effect exists in the coordination between leaf and fine root traits due to the comprehensive and divergent capture of above- and belowground resources and reduced intraspecific competition. Therefore, compared to monocultures, mixed-species stands can enhance the coordination of leaf and fine root traits, and it is advisable to establish forests with mixtures of more than four species, dominated by deep-rooted, evergreen, and ectomycorrhizal fungi species, to maintain ecosystem stability and functional integrity.

Introduction: As a renewable forest resource, bamboo plays a role in sustainable forest development. However, traditional cutting systems, selection cutting (SeC) and clear-cutting (ClC), result in an unsustainable production of bamboo forests due to labor-consuming or bamboo degradation. Recently, a strip clear-cutting (StC) was theoretically proposed to promote the sustainability of bamboo production, while little is known about its application consequence.Methods: Based on a 6-year experiment, we applied the strip clear-cutting system in a typical running bamboo (Phyllostachys glauca McClure) forest to assess its feasibility and sustainability. Using SeC and ClC as controls, we set three treatments with different strip widths (5 m, 10 m, and 20 m) for strip clear-cutting, simplified as StC-5, StC-10, and StC-20, respectively. Then, we investigated leaf physiological traits, bamboo size and productivity, population features, and economic benefits for all treatments.Results: The stands managed by StC had high eco-physiological activities, such as net photosynthetic rate (P_n), photosynthetic nitrogen use efficiency (PNUE), and photosynthetic phosphorus use efficiency (PPUE), and thus grew well, achieved a large diameter at breast height (DBH), and were tall. The stand biomass of StC (8.78 t hm^-2 yea^r-1) was 1.19-fold and 1.49-fold greater than that of SeC and ClC, respectively, and StC-10 and StC-20 were significantly higher than SeC or ClC (p< 0.05). The income and profit increased with the increase in stand density and biomass, and StC-20 and StC-10 were significantly higher than SeC or ClC (p< 0.05). Using principal components analysis and subordinate function analysis, we constructed a composite index to indicate the sustainability of bamboo forests. For the sustainability assessment, StC-10 had the highest productive sustainability (0.59 ± 0.06) and the second highest economic sustainability (0.59 ± 0.11) in all cutting treatments. StC-10 had the maximum overall sustainability, with a value of 0.53 ± 0.02, which was significantly higher than that of ClC (p< 0.05).Conclusion: The results verified that StC for Phyllostachys glauca forests is feasible and sustainable as its sustainability index outweighs those of traditional cutting systems (SeC and ClC), and 10 m is the optimum distance for the strip width of StC. Our findings provide a new cutting system for managing other running bamboo forests sustainably.

Moso bamboo (Phyllostachys edulis (Carrière) J.Houz.) is a fast-growing species that commonly invades neighboring broadleaf forests and has been widely reported in subtropical forest ecosystems. However, little is known about the effect on soil phosphorus (P) bioavailability and its potential influence factor during the P. edulis expansion. Here, the four soil P bioavailable fractions (i.e., CaCl₂-P, Citrate-P, Enzyme-P, and HCl-P), acid phosphatase activity, iron and aluminum oxides (Fe_d and Al_d), and soil total P pool at depths of 0–10 cm, 10–20 cm, and 20–40 cm were measured in three expanding interfaces (a broadleaf forest, a mixed bamboo–broadleaf forest, and a pure P. edulis forest) in subtropical forests of southern China. Regardless of soil depths, the CaCl₂-P content was significantly lower in the mixed bamboo–broadleaf forest than the other two forest types, with contents ranging from 0.09 to 0.16 mg/kg, whereas the HCl-P content was significantly lower in the broadleaf forest, with contents ranging from 3.42 to 14.33 mg/kg, and the Enzyme-P content and acid phosphatase activity were notably lower in P. edulis forest with contents of 0.17–0.52 mg/kg and 68.66–74.80 μmol MUF released g⁻¹ min⁻¹, respectively. Moreover, the soil total P pool was enhanced in the mixed bamboo–broadleaf forest in 0–10 cm depth compared to broadleaf and P. edulis forests, with increases of 27.40% and 31.02%, respectively. The redundancy analysis showed that soil pH plays an important role in regulating soil P bioavailability during the P. edulis expansion (p < 0.01). From the above results, the invasion of P. edulis into broadleaf forests has resulted in soil P bioavailability and storage capacity. The results of this study suggest that when P. edulis invades broadleaf forests, it could affect the soil P bioavailability by elevating soil pH, which in turn drives and facilitates the completion of the expansion. This is important for understanding P cycling during the P. edulis forest expansion in subtropical regions.

Running bamboos are a group of clonal plants exhibiting rapid and widespread expansion. They possess two root subsystems, arising from different shoot parts, culm roots and rhizome roots. To date, it remains unclear what the functional differences are between the two root subsystems and what their relation is to the remarkably competitive ability of running bamboos. A typical running bamboo, Phyllostachys glauca, which dominates in a highly heterogeneous habitat of limestone hills, was sampled to compare the morphology, architecture, anatomy, chemical composition, mechanics and nutrient acquisition of the two root subsystems to explore their differences in functional traits. Compared with rhizome roots, culm roots possessed greater tensile strength, modulus of elasticity, stele diameter to root diameter ratio, root tissue density, root length density, rooting depth, basal diameter of shoot‐borne roots and more lignified cells. Culm roots also had a higher phosphorus (P) concentration (>0.4 mg g⁻¹), which was nearly twice that of rhizome roots. By contrast, rhizome roots exhibited a greater specific root area, specific root length, cortex thickness to root radius ratio, total branch order and greater P‐uptake capacity than culm roots. Our findings revealed distinct differences in functional traits between culm roots and rhizome roots in P. glauca. Culm roots are considered to primarily provide anchorage, but also function in resource acquisition and nutrient storage, while rhizome roots mainly play a role in resource acquisition. Except for the anchorage and resource acquisition of culm roots, the extra resource acquisition by rhizome roots and the high concentration of a limiting nutrient (P) in culm roots enhance the performance in a highly heterogeneous habitat which offers a physiological explanation for P. glauca dominating on limestone hills. The functional differentiation between culm roots and rhizome roots provides insight into the mechanism underpinning the remarkable expansion of running bamboos and offers a new perspective to explain the strong competitive ability of clonal plants with dimorphic roots. Read the free Plain Language Summary for this article on the Journal blog.

Little is known on how karst plants adapt to highly heterogeneous habitats via adjusting leaf anatomical structures. Phyllostachys glauca McClure is a dominant species that grow across different microhabitats in the limestone mountains of Jiangxi Province, China. We investigated the leaf anatomical structures, plant biomass, soil water content, soil total nitrogen (TN), and soil total phosphorus (TP) from three habitats characterized by different rock exposure, including high rock exposure (HRE), medium rock exposure (MRE) and low rock exposure (LRE), and aimed to discern the relationships between the leaf anatomical plasticity and edaphic factors. The leaves of P. glauca in different habitats showed significant anatomical plasticity in two aspects. First, the leaves adjusted cuticle thickness, papillae length, bulliform cell size and mesophyll thickness to lower water loss and then adapt to the water-deficient habitats (HRE). Second, the leaves enlarged vessels and vascular bundles (first-order and second-order parallel veins) to improve water and nutrient transportation and then enhance plant growth in nitrogen-rich habitats (HRE). Soil water and soil nutrients purely explained the total variation of leaf anatomical traits by 21.7% and 15.7%, respectively, and had a shared proportion of 15.8%. Our results indicated that the leaf anatomical variations in different habitats were associated with both soil water and soil nutrients. Moreover, we found that leaf anatomical structures were more affected by TN than TP. The present study advanced the current understanding of the strategies employed by karst plants to cope with highly heterogeneous habitats via leaf anatomical plasticity.