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Article

Effect of the Moso Bamboo Pyllostachys edulis (Carrière) J.Houz. on Soil Phosphorus Bioavailability in a Broadleaf Forest (Jiangxi Province, China)

by
Dou Yang
1,2,3,
Fuxi Shi
1,3,
Xiangmin Fang
1,
Ruoling Zhang
1,3,
Jianmin Shi
4 and
Yang Zhang
1,4,*,†
1
Key Laboratory of National Forestry and Grassland Administration for the Protection and Restoration of Forest Ecosystem in Poyang Lake Basin, Jiangxi Agricultural University, Nanchang 330045, China
2
College of Ecology and Environment, Nanjing Forestry University, Nanjing 210037, China
3
Matoushan Observation and Research Station of Forest Ecosystem, Zixi 335300, China
4
Jiangxi Provincial Key Laboratory for Bamboo Germplasm Resources and Utilization, Nanchang 330045, China
*
Author to whom correspondence should be addressed.
†
Current address: College of Forestry, Jiangxi Agricultural University, No. 1101 Zhimin Road, Nanchang 330045, China.
Forests 2024, 15(2), 328; https://doi.org/10.3390/f15020328
Submission received: 25 December 2023 / Revised: 30 January 2024 / Accepted: 31 January 2024 / Published: 8 February 2024
(This article belongs to the Special Issue Fungal Interactions with Host Trees and Forest Sustainability)
Browse Figures
Versions Notes

Abstract

:
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 (Fed and Ald), 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.

1. Introduction

Phosphorus (P) is an important nutrient element in various ecosystems, and the cycling of P in soils is a basis for many key ecosystem functions [1]. In soil, P exists in a variety of forms that differ in their bioavailability to plants [2]. However, the form of P absorbed by plants is rather insoluble and shows slow diffusion in soil, becoming one of the macronutrients limiting the enhancement of forest primary productivity [3,4], especially in highly subtropical soils, since a large amount of P is occluded by iron and aluminum oxides [5,6]. Studies have shown that the capacity and availability of soil P mainly depend on the changes in different P forms, which are closely related to biological processes [7,8]. Thus, with the desired better understanding of forest soil P status, assessing the soil P bioavailability has become an important research objective [9,10,11].
Moso bamboo (Phyllostachys edulis (Carrière) J.Houz.) is the most broadly distributed bamboo species in subtropical China. However, due to its rapid growth and reproduction ability, P. edulis has been expanding and occupying natural or secondary broadleaf forests in the past decades, forming a large area of bamboo forest. Broadleaf forests are widely known as an essential vegetation type that contributes to increased bio-diversity and environment conservation [12]. It is noted that the P. edulis expansion has been considered as one of the greatest contemporary threats to China’s broadleaf forests [13,14]. Previous studies have shown that the P. edulis expansion had significantly affected the soil pH [15], enzyme activity [16], nitrogen mineralization rates [10], organic carbon chemistry composition [17], and microbial community structure and function [16]. Until now, no studies have ever examined the effects of the P. edulis expansion on soil P bioavailability. Therefore, understanding how the P. edulis expansion affects various P fractions will help to clarify the influence of the P. edulis expansion on soil P distribution patterns in adjacent forests and its potential mechanism.
Soil P bioavailability depends on both geochemical and biochemical processes [18,19,20]. These processes can influence the soil physiochemical and biological properties, such as soil pH, metal oxides (e.g., Fe oxides, Al oxides), inorganic nitrogen, organic carbon, total P, and activities of phosphatase enzymes [21,22,23,24,25,26]. Accordingly, the P. edulis expansion may alter soil P pool and P bioavailability and lead to the redistribution of soil P. Regrettably, these impacts have not yet been assessed in terms of direction and magnitude [27,28]. At present, the most commonly used method for assessing soil P fractions is the sequential leaching method by Hedley and its modified method [29,30]. However, this approach does not consider the contribution of biological processes and P bioavailability [31,32].
The aim of this study was to explore the impact of the expansion of P. edulis into broadleaf forests on soil phosphorus pool and phosphorus components, as well as the main environmental factors contributing to this change. We used the substituting space-for-time approach to collect soil samples from a broadleaf forest, a mixed bamboo–broadleaf forest, and a pure P. edulis forest which represented non-invasive, mid-invasive, and serious invasive levels, respectively, in Jinggang Mountain Nature Reserve, Jiangxi Province, and compared the differences in soil P pool, acid phosphatase activity, and four P fractions (CaCl2-P, Citrate-P, Enzyme-P, and HCl-P) in the 0–10 cm, 10–20 cm, and 20–40 cm depths. The principal objective of the study was to investigate the response of the soil phosphorus pool and phosphorus fractions to the expansion of P. edulis into broadleaved stands, and the main environmental factors causing this change. Specifically, hypotheses were tested for the following: (1) the P. edulis expansion would alter soil P bioavailability and acid phosphatase activity, thereby facilitating expansion, and (2) pH is the main influencing factor leading to changes in P fraction during the P. edulis expansion.

2. Materials and Methods

2.1. Study Sites

This study was conducted at the Dajing Forest Farm in the Jinggang Mountain National Nature Reserve (26°33′58″ N, 114°7′58″ E, Figure 1), Jiangxi Province, China, which has a humid subtropical monsoon climate with an average annual temperature of 14.2 °C and an average annual precipitation of 1856 mm. The soil types include red soil and red-yellow soil. This chosen site is located in the nature reserve and has not been exposed to direct anthropogenic disturbance. The regional vegetation is evergreen broadleaf forest and it is also a suitable area for P. edulis. Before the establishment of the reserve, owing to long-term harvesting by humans and natural disturbances, the original evergreen broadleaf forest was extensively degraded into a secondary forest. After the establishment of the nature reserve, the secondary evergreen broadleaf forest was in a positive stage of succession to the original forest, but P. edulis, as a suitable species under subtropical climate conditions, has been invading and occupying adjacent forest stands at a rapid rate, resulting in the formation of a large area of mixed bamboo–broadleaf forest and pure P. edulis forest. The invasion of broadleaf forests by P. edulis has resulted in three different types of vegetation along the invasion path: pure P. edulis forest, mixed bamboo–broadleaf forest, and broadleaf forest.

2.2. Experimental Design and Soil Sampling

In June 2020, three typical sample strips were selected in the direction of the expansion of P. edulis into the broadleaf forest, containing pure P. edulis, mixed bamboo–broadleaf, and broadleaf forest, with each sample strip spaced at least 50 m. The sample site is at an elevation of 900 m. The broadleaf forest is a recovering secondary evergreen broadleaf forest, with the dominant species in the tree layer being Machilus thunbergia, and associated species including Daphniphyllum macropodum, Alniphyllum fortunei, etc. The tree layer is 17.0 m high, with an average diameter at breast height of 15.8 cm, a density of 1200 ind./ha, and a denseness of 0.85. The mixed bamboo–broadleaf forest was formed after P. edulis expanded into a broadleaf forest for 10 years. The ratio of P. edulis to wood is 8:1, in which P. edulis is about 15 m high and its density is about 4200 ind./ha. The P. edulis forest is a pure forest formed by natural expansion about 30 years ago, with a density of about 6200 ind./ha, an average diameter at breast height (DBH) of 8.5 cm, and an average height of 13.5 m.
Five replicated plots of 10 m × 40 m each were set up in each forest type, with a total of 15 plots established. Soil samples were collected from these plots at depths of 0–10 cm, 10–20 cm, and 20–40 cm. Each soil sample was formed by homogenizing the soil after removing the litter layer at low, medium, and high elevations along the hillside. Therefore, this study included a total of 45 subsamples (3 forest types × 5 replicates × 3 soil depths). All soil samples were placed in sterile self-sealing bags and maintained at low temperatures for transportation to the laboratory. The composite samples were passed through a 2.0 mm sieve to remove large rocks, visible roots, and debris. Finally, fresh samples were divided into two subsamples: one subsample was stored at 4 °C for the determination of P fractions and enzyme activity, and another subsample was airdried for soil chemical analysis.

2.3. Soil Chemical Properties

Soil pH was measured from a soil suspension (1:2.5, w/v) using a pH meter (PHS-3E; REX, Suzhou, China). Soil moisture (SWC) was measured by mass loss after drying at 105 °C to a constant weight. Soil organic carbon (SOC) was determined using the H2SO4-K2Cr2O7 oxidation method. Soil total nitrogen (TN) and P (TP) concentrations were determined using a continuous-flow autoanalyzer (Auto Analyzer III, Bran + Luebbe GmbH, Norderstedt, Germany) after digestion in 5 mL of H2SO4 with a catalyst. Concentrations of soil NH4+-N, NO3−-N, and available P (Olsen-P) were analyzed colorimetrically with a SmartChem140 Discrete Analyzer (Westco Scientific, Danbury, CT, USA) [33]. Among them, NH4+-N and NO3−-N were measured using 90 mL 2 mol/L KCl with 20 g fresh soil leaching, and Olsen-P was measured using 5 g airdried soil and 50 mL ammonium fluoride-hydrochloric acid leaching. Al and Fe oxides were extracted with dithionite-citrate-bicarbonate (DCB) solutions [34] for free Al (Ald) and Fe (Fed), diluted, and tested using an iron-aluminum combined colorimetric method with a spectrophotometer (Metash UV/u20125200, Nanjing, China).

2.4. Soil P Fractions

P fractions were determined using the biological-based P extraction approach that quantifies the inorganic P supply pathways of organic acid complexation/dissolution, enzyme hydrolysis, and proton excretion-induced acidification mechanisms, as well as the amount of dissolved inorganic P in the soil solution, which can highly improve the mechanistic understanding of soil P biogeochemical cycles and P bioavailability [31]. The procedure is as follows. Four 0.5 g fresh soil samples were added in parallel to 10 mL of the following extracts: (1) 10 mM CaCl2 solution (CaCl2-P); (2) 10 mM citric acid solution (Citrate-P); (3) 0.02 units/mL of acid phosphatase solution (Sigma P3627; Enzyme Commission Number 232-630-9; Sigma-Aldrich, Shanghai, China) (Enzyme-P); and (4) 1 M HCl solution (HCl-P). The mixture was shaken at 200 rpm for 3 h. It was then centrifuged at 3220× g for 30 min to collect the supernatant. After appropriate dilution of the supernatant, the soil P content was determined using the malachite green method [35] to represent soluble and weakly adsorbed inorganic P, active inorganic P sorbed to clay particles or weakly bound in inorganic precipitates, organic P readily mineralized by acid phosphatase enzymes, and recalcitrant inorganic P, respectively [31].

2.5. Soil Acid Phosphatase Activity

The 96-well microplates were used to determine soil acid phosphatase activity (AP) [36]. A total of 1.5 g of fresh soil was added to 125 mL of 50 mM sodium acetate buffer (pH = 5.3) and stirred well to obtain a soil suspension. A total of 200 μL of soil suspension and 50 μL of 4-Methyumbelliferyl phosphate were added to the microtiter plate, and control was made with 200 μL of soil suspension and 50 μL of sodium acetate buffer. After the dark incubation of the assay plates at 20 °C for 4 h, fluorescence values were detected using a microplate fluorometer (SpectraMax M2, Molecular Devices, Sunnyvale, CA, USA) at an excitation wavelength of 365 nm and an emission cutoff of 450 nm, respectively.

2.6. Calculation and Statistical Analyses

Soil total P pool (g m−2) was calculated with the fixed depth method:
S o i l   t o t a l   P   p o o l = ∑ i = 1 n D i × B i × P i × 0.1
where Di, Bi, and Pi are the thickness (cm), bulk density (g cm−3), and soil total P concentration (g kg−1) of the ith soil layer, respectively, and 0.1 is a conversion factor.
All data were assessed using the Shapiro–Wilk normality test. One-way analysis of variance (ANOVA) and Duncan’s test was used to assess differences among three types of vegetation in the same soil depth and among different soil depths in the same type of vegetation. Two-way analysis of variance (ANOVA) tests were used to identify the interaction effects of vegetation and soil depths on soil properties, AP, P fractions, and total P pool. The statistical significance level was set at 0.05. This part of the data analysis was carried out using SPSS 19.0 for Windows (SPSS Inc., Chicago, IL, USA), and the Origin 2018 software package (Origin Lab., Hampton, VA, USA) was used to produce figures. Redundancy analysis (RDA) was performed between soil phosphorus-related indicators and soil variables in each soil layer using the vegan package [37,38] in R (version 4.0.2), and the data were log-transformed when necessary.

3. Results

3.1. Soil Chemical Properties

The vegetation type significantly affected soil pH, SWC, the contents of NH4+-N, NO3−-N, SOC, TN, TP, Olsen-P, Fed, and Ald (p < 0.05). The soil depth affected the contents of NH4+-N, NO3−-N, SOC, TN, TP, and Fed, besides SWC. The interaction between vegetation and soil depth significantly affected the content of NO3−-N (Table 1). Specifically, compared to a broadleaf forest, soil pH significantly increased in the P. edulis forest and the mixed bamboo–broadleaf forest, by 7.93%–9.50% and 5.57%–10.79%, respectively; as well as soil SWC, the content of NO3−-N, SOC, TN, and Ald was decreased in the 0–40 cm depths of the P. edulis forest, and the content of NH4+-N was only significantly increased in the 0–10 cm depth, by 15.19% and 14.08%, respectively. In addition, the contents of TP and Fed were not significantly discrepant among the three forests. The soil Olsen-P concentration was significantly lower by 27.79%–38.39% in the mixed bamboo–broadleaf forest compared to the other two forest types, whereas the differences in soil Olsen-P content between the broadleaf forest and the P. edulis forest were not significant (Table 1).

3.2. Soil P Pool, P Fractions, and Acid Phosphatase Activity

The P. edulis expansion process significantly affected the total soil P pool content in the 0–10 cm soil layer, which was higher in the mixed bamboo–broadleaf forest than in the other two forest types (Figure 2). While the vegetation type highly significantly affected the CaCl2-P, Enzyme-P, and HCl-P content, the soil depth significantly affected all four phosphorus fractions, but the interaction effect only significantly affected the CaCl2-P content (Figure 3). Across all soil depths, the contents of all P fractions showed the same trend among the three types of vegetation. Specifically, the soil CaCl2-P content was significantly lower in the mixed bamboo–broadleaf forest than in the other two forest types. The soil Enzyme-P content was lowest in the P. edulis forest, 0.17–0.52 mg/kg, the HCl-P content was lowest in the broadleaf forest, 3.42–14.33 mg/kg, whereas the Citrate-P content was not significantly different among the three types of vegetation (Figure 3). Furthermore, the acid phosphatase activity was significantly lower in the P. edulis forest than the other forest types (Figure 2).
The vegetation type and soil depth significantly affected all phosphorus fraction ratios, while the interaction only significantly affected Citrate-P/CaCl2-P, Enzyme-P/CaCl2-P, HCl-P/CaCl2-P, and Enzyme-P/HCl-P (Table 2). Similar trends were observed for all fraction ratios among the three forest types across all soil depths. In particular, the ratios of soil Citrate-P/CaCl2-P, Enzyme-P/CaCl2-P, and HCl-P/CaCl2-P in the mixed bamboo–broadleaf forest, with ranges of 10.55–43.06, 2.64–4.91, and 59.97–136.07, respectively, were significantly higher than those in the P. edulis and broadleaf forests. The soil Citrate-P/Enzyme-P ratios were highest in the P. edulis forest, in the range of 5.39–11.78, and both the Citrate-P/HCl-P and Enzyme-P/HCl-P ratios were highest in the broadleaf forest, the range of 0.24–0.42 and 0.05–0.10, respectively.

3.3. Linkages between Soil Chemical Properties and P-Related Indicators

The RDA results showed that the distribution of soil P-related indicators in different soil layers showed significant segregation during the expansion of P. edulis (Figure 4). The environmental factors examined explained 55.33%, 29.90%, and 51.16% of the variation in soil P-related indicators at depths of 0–10 cm, 10–20 cm, and 20–40 cm, respectively. Interestingly, we found that the soil P-related indicators mainly diverged along the RDA1 in each soil depth. The first axis has the highest interpretation rate, explaining 53.15%, 18.79%, and 31.14% of the total variation (Figure 4). The soil pH significantly influenced the variation of the distribution of soil P (p < 0.01), and was positively correlated with HCl-P in each depth. In addition, the distribution of soil P was significantly influenced by SWC and NO3−-N in the 0–10 cm depth and NH4+-N in the 20–40 cm depth.

4. Discussion

4.1. P. edulis Expansion Significantly Altered Soil P Status

The expansion of P. edulis into adjacent forests is one of the most serious environmental problems in subtropical China [12,39,40]. Evidence from previous studies suggests that the P. edulis expansion has distinct effects on C and N cycling at the ecosystem level [41,42]. Our study provides evidence that this process also leads to affected P effectiveness and P bioavailability in the soil. To be specific, the soil total P pool content during the P. edulis expansion into broadleaf forests varied significantly only in the 0–10 cm depth, whereas there was no significant change in soil total P and all the total P pools in the depth of 0–40 cm (Table 1 and Figure 4). This is slightly different from the findings of Wu et al. [27], who reported that the soil total P decreased significantly after the P. edulis invaded the adjacent coniferous forests in Lushan Mountain, and the reason for this discrepancy may be a result of different litter quality and stand/site conditions between coniferous forests and broadleaf forests [43]. It is noteworthy that the Olsen-P content in the soil profile was redistributed by the expansion of P. edulis, as evidenced by the significantly lower levels of the mixed bamboo–broadleaf forest compared to the other two forest types in all soil layers (Table 1). This phenomenon would be caused by the following reasons. First, when the mixed bamboo–broadleaf forest was formed, the increase in species richness was accompanied by an increase in nutrient demand from the stand [32], which may have led to a greater demand from the species than the supply from the soil. Meanwhile, the change in soil pH and Ald content had an opposite relationship to the response of the Olsen-P content in the mixed bamboo–broadleaf forest which also verified the phenomenon. Second, the nutrient turnover and fine root biomass of P. edulis significantly increased the nutrient uptake and turnover capacity after the formation of the pure P. edulis forest [27,44], which in turn increased the soil Olsen-P content.
In P-limited habitats, plants and soil microorganisms release excretions to destabilize organic–mineral associations and aggregates to obtain P [45]. The ratios of Citrate-P/CaCl2-P, Enzyme-P/CaCl2-P, and HCl-P/CaCl2-P were all greater than 1 in all soil depths of each stand, showing that, in addition to the uptake of CaCl2-P from soil pore water, the excretion of both acid and phosphatase into the soil may be an effective strategy for P acquisition by the plants during the invasion of P. edulis (Table 2). We found that the expansion of P. edulis to form a mixed bamboo–broadleaf forest significantly decreased the soil CaCl2-P and increased the HCl-P content. The possible explanation for this outcome may be that the dominant tree species after mixing were all arbuscular mycorrhizal (AM) species [46], and AM fungi acquired P mainly based on their high-affinity uptake system and rapid translocation to the plant [6,47], which then led to a reduction in soil soluble P levels after hybridization. Meanwhile, HCl-P represents the moderately active stable inorganic P in soil, which can be obtained through proton extrusion by biota [31], and aluminum oxides as the primary metal minerals for adsorbed soluble P in southern red soils [48]. The Ald content significantly decreased during expansion (Table 1), suggesting an increase in adsorbed and precipitated P [23]. In addition, the ratio of HCl-P/CaCl2-P increased 1.97-fold when forming mixed forests, suggesting that the excretion of protons by plants may be an important strategy for their P acquisition. Compared to the mixed bamboo–broadleaf forest, P. edulis forest soils after expansion had an increased CaCl2-P content and a decreased phosphatase activity and Enzyme-P content (Figure 2 and Figure 3). This result is closely related to changes in the composition of plant root systems and soil microbial communities during expansion [49,50,51]. Firstly, lower tree species lead to less competitive pressure and increased resource availability [52]. Secondly, P. edulis has a denser fine root biomass for absorbing soluble phosphorus in the pore space compared to broadleaf species [53], and thirdly, microorganisms are very sensitive to changes in the environment, but the chemical composition and the secretion types released are significantly diverse among trees, which can dramatically affect microbial communities as well as soil enzyme activities [32]. We also found no significant differences in the soil Citrate-P content among the three stands throughout the expansion, suggesting that the change in vegetation types significantly impacts the hydrogen proton concentration (H+/OH−/HCO3−) and phosphatase activity, not organic acids types [32,54].

4.2. Soil pH Drives Changes in P Fraction in the Soil Layer during Expansion

The redundancy analysis results showed that soil pH was the most significant driver of variation in bioavailable P fractions in the soil layer (Figure 4), which is consistent with most studies [21,32,55,56] and supports our hypothesis. In this study, the soil pH increased significantly during the P. edulis expansion, and this change may have affected the soil P bioavailability in several ways. First, the P. edulis expansion process affects pH by altering the balance between hydrogen ion production and consumption [57], and as pH increases, Al and Fe phosphates, which are presumably the dominant forms of P minerals in acid soils, gradually lose their positive surface charge and their P adsorption capacity, thus expelling phosphate [58]. Our finding of a significantly lower Ald content in the P. edulis forest could partly support this explanation (Table 1). Second, soil bacteria and fungi prefer neutral pH environments; the expansion of P. edulis improves the soil pH and thus increases microbial diversity and supports soil ecosystem multifunctionality, including P cycling [59,60]. Previous studies have found that the soil pH can influence P-related microorganisms by directly affecting their growth and their interactions with each other [21,61]. In addition, different vegetation types secrete different organic acids, which in turn recruit microbial communities with different functional activities [62], and changes in vegetation taxa as a direct result of the P. edulis expansion process have been shown to significantly alter microbial community structure [39,41]. Third, P. edulis is a typical silica-accumulating plant [63], while silicon and P have similar chemical properties and structures, and silicon is in direct competition with P for sorption sites on iron oxides and other soil minerals increasing nutrient mobilization. Concretely, increasing silicon availability in soils leads to a mobilization of Fe(II)-P phases from mineral surfaces, increasing P availability/mobility in soils [64,65].

5. Conclusions

The impact of P. edulis invasion on the ecosystem structure and function of native plant habitats has attracted much attention, but the effect of this process on soil bioavailable P remains an enigma. In this study, we measured the bioavailable P fractions at three soil depths in three stands formed by the P. edulis expansion into broadleaf forests. Several conclusions are presented below:
(1)
The P. edulis expansion altered the soil P pool and bioavailability in the subtropical region of China. The Olsen-P content and CaCl2-P were significantly lower in the mixed bamboo–broadleaf forest than in the broadleaf forest and the pure P. edulis forest, whereas the soil total P pool content in the 0–10 cm depths was increased. The HCl-P and Enzyme-P content were higher in the mixed bamboo–broadleaf forest than in the other two forest types.
(2)
The acid phosphatase activity was significantly higher in the mixed bamboo–broadleaf forest compared to the P. edulis forest.
(3)
The positive relationship between the soil pH and HCl-P fraction indicated that the soil pH was an important factor in altering the P bioavailability during the P. edulis expansion.
Overall, the P. edulis expansion has altered soil P bioavailability to fulfill plant P requirements. We predicted that the effect on the soil bioavailability P content may be increasing with the gradual intensity of the P. edulis expansion. However, further in-depth studies are needed.

Author Contributions

D.Y.: data curation, conceptualization, writing—original draft, and writing—review and editing. Y.Z.: writing—review and editing. F.S.: supervision. X.F.: supervision. R.Z.: investigation. J.S.: supervision. All authors have read and agreed to the published version of the manuscript.

Funding

This study was financed by the National Natural Science Foundation of China (32160357 & 31660190 & 42067049); Jiangxi Provincial Department of Science and Technology Project (20232BBF60022 & 20232BAB205046); and Jiangxi “Double Thousand Plan” (jxsq2023102214 & jxsq2019201080).

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Conflicts of Interest

The authors declare no conflicts of interest.

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Forests 15 00328 g001
Figure 1. The geographical location of the study area.
Figure 1. The geographical location of the study area.
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Figure 2. Effect of the P. edulis expansion into broadleaf forest on soil acid phosphatase activity (left) and total phosphorus pool (right). The data are the average values and the error bars are the standard deviation (n = 5). Different uppercase letters indicate significant differences among the three stands in the same soil depth (p < 0.05). ns, p > 0.05; * p < 0.05, *** p < 0.001.
Figure 2. Effect of the P. edulis expansion into broadleaf forest on soil acid phosphatase activity (left) and total phosphorus pool (right). The data are the average values and the error bars are the standard deviation (n = 5). Different uppercase letters indicate significant differences among the three stands in the same soil depth (p < 0.05). ns, p > 0.05; * p < 0.05, *** p < 0.001.
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Figure 3. Effects of the P. edulis expansion on CaCl2-P (a), Citrate-P (b), Enzyme-P (c) and HCl-P (d) content in broadleaf forest. The data are the average values and the error bars are the standard deviation (n = 5). Different uppercase letters indicate significant differences among the three stands in the same soil depth (p < 0.05). ns, p > 0.05; * p < 0.05, *** p < 0.001.
Figure 3. Effects of the P. edulis expansion on CaCl2-P (a), Citrate-P (b), Enzyme-P (c) and HCl-P (d) content in broadleaf forest. The data are the average values and the error bars are the standard deviation (n = 5). Different uppercase letters indicate significant differences among the three stands in the same soil depth (p < 0.05). ns, p > 0.05; * p < 0.05, *** p < 0.001.
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Figure 4. Redundancy analysis (RDA) diagrams, showing the relationships between the soil variables and soil phosphorus-related indicators at depths of 0–10 cm (a), 10–20 cm (b), and 20–40 cm (c), respectively. The explained variations of the first and second axes are given in brackets. Vectors represent soil phosphorus-related indicators with red arrows; the blue arrows indicate the soil variables; the types of vegetation are represented by solid circles of different colors.
Figure 4. Redundancy analysis (RDA) diagrams, showing the relationships between the soil variables and soil phosphorus-related indicators at depths of 0–10 cm (a), 10–20 cm (b), and 20–40 cm (c), respectively. The explained variations of the first and second axes are given in brackets. Vectors represent soil phosphorus-related indicators with red arrows; the blue arrows indicate the soil variables; the types of vegetation are represented by solid circles of different colors.
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Table 1. Characteristics of soil physicochemical properties among the three typical vegetation forests during the expansion of P. edulis into broadleaf forest under different soil layers.
Table 1. Characteristics of soil physicochemical properties among the three typical vegetation forests during the expansion of P. edulis into broadleaf forest under different soil layers.
Soil DepthVegetationpHMoisture
(%)		NH4+-N
(mg kg−1)		NO3−-N
(mg kg−1)		SOC
(g kg−1)		TN
(g kg−1)		TP
(g kg−1)		Olsen-P
(mg kg−1)		Fed
(g kg−1)		Ald(g kg−1)
0–10 cmPBF5.04 ± 0.04A57.98 ± 2.93B19.08 ± 0.55A2.70 ± 0.52C54.95 ± 2.47B3.47 ± 0.05B0.53 ± 0.04A3.21 ± 0.12A16.62 ± 0.46A6.48 ± 0.08C
MLF5.03 ± 0.06A69.01 ± 3.42A18.90 ± 0.58A4.60 ± 1.73B77.12 ± 5.51A3.70 ± 0.12B0.48 ± 0.02A2.43 ± 0.30B17.51 ± 0.24A6.74 ± 0.05B
BLF4.67 ± 0.11B69.99 ± 2.76A16.56 ± 0.56B6.78 ± 0.23A76.93 ± 4.25A3.98 ± 0.07A0.48 ± 0.03A3.37 ± 0.24A17.51 ± 0.23A7.03 ± 0.10A
10–20 cmPBF5.07 ± 0.02A42.11 ± 2.17B9.83 ± 1.01A1.19 ± 0.61B33.13 ± 2.56B1.80 ± 0.08B0.47 ± 0.03A2.99 ± 0.17A17.73 ± 0.48A6.65 ± 0.13B
MLF5.13 ± 0.03A55.06 ± 2.16A8.93 ± 0.74A2.25 ± 0.85A43.97 ± 2.24A2.43 ± 0.10A0.41 ± 0.01A2.09 ± 0.31B17.96 ± 0.16A6.79 ± 0.12B
BLF4.63 ± 0.04B52.26 ± 1.33A7.98 ± 0.81A2.48 ± 0.30A42.33 ± 2.56A2.36 ± 0.12A0.41 ± 0.03A3.07 ± 0.18A18.22 ± 0.11A7.21 ± 0.12A
20–40 cmPBF5.18 ± 0.03A42.47 ± 3.13B7.05 ± 0.67A1.58 ± 0.35B23.96 ± 1.64B1.36 ± 0.03C0.43 ± 0.04A3.43 ± 0.11A17.60 ± 0.58A6.60 ± 0.12B
MLF5.04 ± 0.06A53.26 ± 2.43A5.77 ± 0.35A1.48 ± 0.47B33.37 ± 2.02A1.74 ± 0.06B0.39 ± 0.02A1.93 ± 0.39B18.05 ± 0.17A6.75 ± 0.11B
BLF4.78 ± 0.06B48.09 ± 0.84AB6.14 ± 0.37A2.51 ± 0.40A33.19 ± 3.04A1.96 ± 0.06A0.36 ± 0.03A3.14 ± 0.12A18.27 ± 0.04A7.24 ± 0.06A
Variance analysis of F-statistics
Vegetation48.54 ***18.32 ***5.38 **63.62 ***19.37 ***37.08 ***3.54 *19.60 ***3.60 *25.73 ***
Soil depth1.90 ns46.18 ***269.53 ***148.88 ***129.09 ***495.00 ***10.27 ***1.10 ns5.44 **1.46 ns
Soil depth × Vegetation1.32 ns0.59 ns1.07 ns15.81 ***1.76 ns1.92 ns0.09 ns0.66 ns0.28 ns0.26 ns
Note: PBF, pure P. edulis forest; MLF, mixed bamboo–broadleaf forest; BLF, broadleaf forest; SOC, soil organic carbon; TN, total nitrogen; TP, total phosphorus; Olsen-P, available P; Fed, free Fe oxides; Ald, free Al oxides. Data are means ± S.E., n = 5. Different uppercase letters indicate significant differences among the three stands in the same soil depth (p < 0.05). Significance level of F values: ns not significant, * p < 0.05, ** p < 0.01, *** p < 0.001.
Table 2. Soil biologically based phosphorus fraction ratios among the three typical vegetation forests during the expansion of P. edulis into broadleaf forest under different soil layers.
Table 2. Soil biologically based phosphorus fraction ratios among the three typical vegetation forests during the expansion of P. edulis into broadleaf forest under different soil layers.
Soil DepthVegetationCitrate-P/CaCl2-PEnzyme-P/CaCl2-PHCl-P/CaCl2-PCitrate-P/Enzyme-PCitrate-P/HCl-PEnzyme-P/HCl-P
0–10 cmPBF22.92 ± 1.46B1.98 ± 0.17B68.92 ± 4.46B11.78 ± 0.95A0.34 ± 0.03AB0.03 ± 0.00B
MLF43.06 ± 3.16A4.91 ± 0.43A136.07 ± 8.66A8.96 ± 0.78B0.32 ± 0.03B0.04 ± 0.00AB
BLF22.07 ± 1.67B2.35 ± 0.21B53.77 ± 6.80B9.49 ± 0.41AB0.42 ± 0.04A0.05 ± 0.00A
10–20 cmPBF7.65 ± 0.52B1.24 ± 0.03B39.72 ± 2.29B6.21 ± 0.52A0.19 ± 0.01AB0.03 ± 0.00C
MLF10.60 ± 0.67A2.64 ± 0.31A59.97 ± 3.73A4.13 ± 0.30B0.18 ± 0.01B0.04 ± 0.00B
BLF7.93 ± 1.10B1.86 ± 0.17B31.65 ± 2.42B4.38 ± 0.75B0.25 ± 0.04A0.06 ± 0.00A
20–40 cmPBF3.22 ± 0.56B0.59 ± 0.07B19.46 ± 1.68B5.39 ± 0.50A0.16 ± 0.01B0.03 ± 0.00B
MLF10.55 ± 1.68A4.87 ± 1.12A65.78 ± 10.91A2.30 ± 0.23B0.16 ± 0.01B0.07 ± 0.01A
BLF2.81 ± 0.55B1.07 ± 0.10B11.28 ± 1.29B2.69 ± 0.58B0.24 ± 0.03A0.10 ± 0.02A
Variance analysis of F-statistics
Vegetation47.14 ***38.45 ***79.66 ***17.22 ***11.30 ***23.62 ***
Soil depth222.46 ***6.10 **75.60 ***100.66 ***45.34 ***17.08 ***
Soil depth × Vegetation12.54 ***3.97 **6.72 ***0.23 ns0.15 ns4.67 **
Note: PBF, pure P. edulis forest; MLF, mixed bamboo–broadleaf forest; BLF, broadleaf forest. Data are means ± S.E., n = 5. Different uppercase letters indicate significant differences among the three stands in the same soil depth (p < 0.05). Significance level of F values: ns not significant, ** p < 0.01, *** p < 0.001.
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Yang, D.; Shi, F.; Fang, X.; Zhang, R.; Shi, J.; Zhang, Y. Effect of the Moso Bamboo Pyllostachys edulis (Carrière) J.Houz. on Soil Phosphorus Bioavailability in a Broadleaf Forest (Jiangxi Province, China). Forests 2024, 15, 328. https://doi.org/10.3390/f15020328

AMA Style

Yang D, Shi F, Fang X, Zhang R, Shi J, Zhang Y. Effect of the Moso Bamboo Pyllostachys edulis (Carrière) J.Houz. on Soil Phosphorus Bioavailability in a Broadleaf Forest (Jiangxi Province, China). Forests. 2024; 15(2):328. https://doi.org/10.3390/f15020328

Chicago/Turabian Style

Yang, Dou, Fuxi Shi, Xiangmin Fang, Ruoling Zhang, Jianmin Shi, and Yang Zhang. 2024. "Effect of the Moso Bamboo Pyllostachys edulis (Carrière) J.Houz. on Soil Phosphorus Bioavailability in a Broadleaf Forest (Jiangxi Province, China)" Forests 15, no. 2: 328. https://doi.org/10.3390/f15020328

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