Effects of vegetation succession on soil microbial stoichiometry in Phyllstachys edulis stands following abandonment.

Moso bamboo (Phyllostachys edulis) is China's most important economic bamboo species. With a continuous decline in the value of its shoots and timber and an increase in affiliated labor and production costs, many of these stands have been abandoned, resulting in the occurrence of vegetation succession. Currently, our understanding on changes in soil microbial stoichiometric and entropic effects and associated imbalances following stand abandonment is limited. Accordingly, this study explores three timescales of Ph. edulis stand abandonment (i.e., 0, 9, and 21 years) to investigate soil-microbial carbon (C), nitrogen (N), and phosphorus (P) dynamics within a 30 cm soil profile. Results showed that (1) following abandonment, vegetation succession significantly influenced soil carbon (Csoil), nitrogen (Nsoil), and phosphorus (Psoil), microbial biomass (Cmic), nitrogen (Nmic), and phosphorus (Pmic), and Csoil:Nsoil:Psoil and Cmic:Nmic:Pmic ratios. Additionally, Csoil, Nsoil, Psoil, Cmic, Nmic, Pmic all increased significantly over time following abandonment. Moreover, Csoil:Nsoil, Cmic:Pmic, and Nmic:Pmic ratios clearly increased while Csoil:Psoil, Nsoil:Psoil, and Cmic:Nmic ratios all significantly decreased. (2) Soil microbial entropy nitrogen (qMBN) and soil microbial imbalances in Cimb:Nimb increased while soil microbial entropy carbon (qMBC), soil microbial entropy phosphorus (qMBP), and soil microbial imbalances in Cimb:Pimb and Nimb:Pimb decreased over time following abandonment. (3) Redundancy analysis (RDA) indicated that Csoil:Nsoil and Cmic:Pmic ratios were key influencing factors of microbial quotient (qMB), explaining 55.35 % and 24.39 % of variation, respectively. Following abandonment, positive or negative successional impacts on Csoil:Nsoil:Psoil, microbial C, N, P stoichiometric imbalances (Cimb:Nimb:Pimb), and Csoil:Nsoil:Psoil ratios had a positive effect on qMB. Collectively, these findings highlight the importance of Csoil:Nsoil:Psoil and Cimb:Nimb:Pimb ratios in regulating qMB induced by vegetation succession following Ph. edulis abandonment, and provide valuable information for vegetation restoration and establishment of bamboo mixed forest.

Shoot Nutrition and Flavor Variation in Two Phyllostachys Species: Does the Quality of Edible Bamboo Shoot Diaphragm and Flesh Differ?

For their quality evaluation, it is essential to determine both bamboo shoot nutrition and palatability, which will have a decisive effect on their economic value and market potential. However, differences in shoot nutrition and flavor variation among bamboo species, positions, and components have not been scientifically validated. This study assessed nutritional and flavor differences in two components (i.e., shoot flesh (BSF) and diaphragm (BSD)) of two Phyllostachys species (i.e., Phyllostachys edulis and Phyllostachys violascens) and analyzed any positional variation. Results showed that BSF protein, starch, fat, and vitamin C contents were comparatively higher. Nutrient compounds in the upper shoot segment of Ph. edulis were higher and contained less cellulose and lignin. However, both species' BSD total acid, oxalic acid, and tannin contents were comparable. BSD soluble sugar and sugar:acid ratio were higher than upper BSD total amino acid, four key amino acids (i.e., essential amino acid, bitter amino acid, umami amino acid, and sweet amino acid flavor compounds), and associated ratios were all higher than BSF while also being rich in amino acids. The content and proportion of BSF essential and bitter amino acid flavor compounds in Ph. edulis were high relative to Ph. violascens. Conversely, the content and proportion of BSD umami and sweet amino acid flavor compounds were comparable to that of Ph. edulis. Our results showed that bamboo shoot quality was affected by flavor compound differences and that interspecific and shoot components interact. This study offers a new perspective to determine the formative mechanisms involved in bamboo shoot quality while providing a basis for their different usages.

Belowground bud banks and land use change: roles of vegetation and soil properties in mediating the composition of bud banks in different ecosystems.

Introduction: Belowground bud banks play integral roles in vegetation regeneration and ecological succession of plant communities; however, human-caused changes in land use severely threaten their resilience and regrowth. Although vegetation attributes and soil properties mediate such anthropogenic effects, their influence on bud bank size and composition and its regulatory mechanisms under land use change have not been explored. Methods: We conducted a field investigation to examine impacts of land use change on bud bank size and composition, vegetation attributes, and soil properties in wetlands (WL), farmlands (FL), and alpine meadow (AM) ecosystems in Zhejiang Province, China. Results: Overall, 63 soil samples in close proximity to the vegetation quadrats were excavated using a shovel, and samples of the excavated soil were placed in plastic bags for onward laboratory soil analysis. The total bud density (1514.727 ± 296.666) and tiller bud density (1229.090 ± 279.002) in wetland ecosystems were significantly higher than in farmland and alpine meadow ecosystems [i.e., total (149.333 ± 21.490 and 573.647 ± 91.518) and tiller bud density (24.666 ± 8.504 and 204.235 ± 50.550), respectively]. While vegetation attributes critically affected bud banks in WL ecosystems, soil properties strongly influenced bud banks in farmland and alpine meadow ecosystems. In wetland ecosystems, total and tiller buds were predominantly dependent on soil properties, but vegetation density played a significant role in farmlands and alpine meadow ecosystems. Root sprouting and rhizome buds significantly correlated with total C in the top 0 - 10 cm layer of farmland and alpine meadow ecosystems, respectively, and depended mainly on soil properties. Discussion: Our results demonstrate that land use change alters bud bank size and composition; however, such responses differed among bud types in wetland, farmland, and alpine meadow ecosystems.

Differentiated mineral nutrient management in two bamboo species under elevated CO2 environment.

Mineral nutrients play a critical role in maintaining plant growth, but are vulnerable to climate change, such as elevated atmospheric carbon dioxide (CO2) concentrations. Previous studies reported that impact of elevated CO2 concentrations on plant growth vary among plant species, which may affect differential mineral nutrient cycling among plant species. However, little is known about how increasing CO2 concentrations affect mineral nutrient uptake and allocation in bamboo species. Using open top chambers (OTCs), we investigated the effects of elevated CO2 concentrations on three key mineral nutrients (iron (Fe), calcium (Ca), and magnesium (Mg)) in two mature bamboo species (Phyllostachys edulis and Oligostachyum lubricum). Results showed increased leaf and root biomass under elevated CO2 concentrations (P. edulis: 30.24% and 10.94%; O. lubricum: 24.47% and 13.84%, respectively). Conversely, elevated CO2 concentrations had negligible effects on the biomass of other bamboo organs (e.g., branches and culms). To a certain extent, elevated CO2 concentrations also caused nutrient variation among the various organs of these two species. For Ph. edulis, elevated CO2 concentrations increased mineral content (Fe, Ca, and Mg) in and allocation to leaves while it decreased Fe and Mg allocation to roots. By contrast, elevated CO2 concentrations only increased mineral content in and allocation to O. lubricum leaves and decreased Mg to its roots. Results confirmed that elevated CO2 concentrations resulted in differential mineral nutrient uptake and allocation response between these two species. Understanding such differences is critical to the sustainable nutrient management of bamboo ecosystems under increasing CO2 concentrations.

Altitudinal Patterns of Leaf Traits and Leaf Allometry in Bamboo Pleioblastus amarus.

Awareness of local-scale variation in leaf traits for a single species and the relationships between these traits and their dependence on altitude might be essential for extrapolating ecophysiological processes from the leaf to the ecosystem level. While altitudinal patterns of leaf traits have been extensively studied in a number of species, little is known about such patterns in bamboos. We analyzed leaf functional traits and leaf allometric relationships of Pleioblastus amarus at three different altitudes (200, 400, and 800 m). With increasing altitude, most functional traits, including leaf length, width, perimeter, area, dry weight, and water content, decreased significantly, while the leaf length:width ratio exhibited a marked increase, resulting in a tendency toward narrow leaves. Specific leaf area first increased, and then decreased, while the change in leaf dry matter content showed the opposite trend. Leaf area was positively correlated with leaf length, leaf width and leaf perimeter, but negatively correlated with the leaf length:width ratio. With increasing altitude, the slopes of these relationships for leaf area first increased, and then decreased. Leaf biomass was positively correlated with leaf length, width, perimeter, and area, with the slopes of the relationships being the same at all altitudes. Thus, the leaves of this bamboo species at middle altitude have the highest specific leaf area and lowest leaf dry matter content. Our findings suggest that this bamboo species has a big potential of growth and morphological plasticity.

Nitrogen addition and clonal integration alleviate water stress of dependent ramets of Indocalamus decorus under heterogeneous soil water environment.

Water and nitrogen are two of the most important factors for plant growth and development. However, little is known about effects of N on water translocation between connected bamboo ramets. We performed experiment connected Indocalamus decorus ramets in adjacent pots with different soil water contents and three N levels. We determined antioxidase activities, concentration of osmotic adjustment products, O2·-, MDA and photosynthetic pigments, and electrolyte leakage rate in paired unit. When N supply to supporting ramets increased, their electrolyte leakage rates and contents of O2·- and MDA significantly increased, while antioxidase activities and contents of osmotic adjustment products and photosynthetic pigments in connected dependent ramets increased markedly as their electrolyte leakage rates and contents of O2·- and MDA decreased greatly. When N addition to dependent ramets increased, antioxidant enzyme activity and contents of osmotic adjustment products and photosynthetic pigments decreased in both ramets, but electrolyte leakage rates and O2·- and MDA contents increased significantly. Therefore, N addition to either supporting or dependent ramets can improve water integration among I. decorus ramets. N addition to supporting ramets promotes water translocation and alleviates water stress of dependent ramets, but N addition to dependent ramets exacerbates drought stress damage to dependent ramets.

[Influence of mulching management on the relationships between foliar non-structural carbohydrates and N, P concentrations in Phyllostachys violascens stand].

To understand the physiological adaptive mechanism of Phyllostachys violascens to intensive mulching management, the effect of mulching management (CK, 1, 3 and 6 years) on the concentrations and ratios of non-structural carbohydrates (NSC), nitrogen (N) and phosphorus (P) in bamboo foliage, and their stoichiometry was investigated. The results showed the concentrations of NSC and soluble sugar increased, while the starch content and N/P decreased markedly in bamboo stand with 1-year mulching, compared to CK stand, which suggested the N limitation to bamboo growth was strengthened. Foliar soluble sugar content decreased significantly, while the starch content increased dramatically, and the NSC content by per unit mass of N and P reached the maximum in the bamboo stand with 3-year mulching, compared to all other treatments. Foliar NSC and soluble sugar contents decreased significantly, while foliar starch content and N/P increased dramatically in the stand with 6-year mulching, which suggested the P limitation to bamboo growth was strengthened. Foliar NSC content was positively correlated with N and P concentrations in a short-term mulching management stand (≤ 3 years), while showed negative relationship with N/P. The foliar starch content in the stand with 6-year mulching was negatively correlated with N and P contents, while was positively correlated with N/P. The results indicated that short-term mulching management accelerated the accumulation of soluble sugar and decomposition of starch in foliage, thus the growth and activity of Ph. violascens was enhanced greatly. Long-term mulching management promoted the starch accumulation, which led to the transition from N limitation to P limitation for bamboo growth. In summary, long-term (6 years) mulching management caused the decrease of growth and activity of Ph. violascens dramatically, thus enhancing the bamboo stand degradation. The utilization efficiency of N and P reached the highest in the stand with 3-year mulching, which implied 3-year was the best suitable period for intensive mulching management for maintaining bamboo stand quality.

[Adaptive adjustment of rhizome and root system on morphology, biomass and nutrient in Phyllostachys rivalis under long-term waterlogged condition].

The research was to approach the growth strategy of rhizome and roots based on the morphology, biomass and nutrient in Phyllostachys rivalis under long-term waterlogged conditions, and provided a theoretical basis for its application for vegetation restoration in wetland and water-level fluctuation belts. The morphological characteristics, physiological and biochemical indexes of annual bamboo rhizome and roots were investigated with an experiment using individually potted P. rivalis which was treated by artificial water-logging for 3, 6, and 12 months. Accordingly the morphological characteristics, biomass allocation, nutrient absorption and balance in rhizome and roots of P. rivalis were analyzed. The results showed that there was no obvious impact of long-term water-logging on the length and diameter of rhizomes, diameter of roots in P. rivalis. The morphological characteristics of rhizome had been less affected generally under water-logging for 3 months. And less rhizomes were submerged, while the growth of roots was inhibited to some extent. Furthermore, with waterlogging time extended, submerged roots and rhizomes grew abundantly, and the roots and rhizomes in soil were promoted. Moreover for ratios of rhizome biomass in soil and water, there were no obvious variations, the same for the root biomass in soil to total biomass. The ratio of root biomass in water to total biomass and the ratio of root biomass in water to root biomass in soil both increased significantly. The results indicated that P. rivalis could adapt to waterlogged conditions gradually through growth regulation and reasonable biomass distribution. However, the activity of rhizome roots in soil decreased and the nutrient absorption was inhibited by long-term water-logging, although it had no effect on stoichiometric ratios of root nutrient in soil. The activity of rhizome root in water increased and the stoichiometric ratios adjusted adaptively to waterlogged conditions, the ratio of N/P increased, while N/K and P/K decreased, which implied that roots in water absorbed oxygen and nutrients could help P. rivalis adapt to long-term waterlogged environment effectively.

[Effects of stand density on Oligostachyum lubricum leaf carbon, nitrogen, and phosphorus stoichiometry and nutrient resorption].

Taking pure Oligostachyum lubricum forest as test object, this paper studied the matured and withered leaves carbon (C), nitrogen (N), and phosphorus (P) stoichiometry and N and P resorption patterns of 1-3 years old stands at the densities of 24600-29800 stem hm-2 (D, ), 37500-42600 stem hm-2 (D2 ), 46500 - 52800 stem hm-2 (D3), and 76500 - 85500 stem hm-2 (D4). With increasing stand density, the matured leaves C, N, and P contents and withered leaves C and P contents had an overall decrease, the withered leaves N content decreased after an initial increase, and the matured leaves C content at density )4 decreased dramatically. The leaf C/N and C/P ratio increased with increasing stand density, whereas the leaf N/P ratio increased first but decreased then. At stand densities D3 and D4, the leaf N and P utilization efficiencies were significantly higher than those at D, and D2. With increasing stand density, the leaf N resorption capacity increased after an initial decrease, while the leaf P resorption capacity increased steadily. At stand densities D,-D3, the matured leaves N/P ratio was 16.24-19.37, suggesting that the P limitation occurred, leaf establishment increased, and population increase and expansion enhanced. At density D4, the matured leaves N/P ratio was 13.42-15.74, implying that the N limitation strengthened, leaf withering and defoliation increased, and population increase inhibited. All the results indicated that O. lubricum could regulate its leaf C, N and P contents and stoichiometry and enhance the leaf N and P utilization efficiency and resorption capacity to adapt to the severe competition of environment resources at high stand density. In our experimental condition, 46500-52800 stem hm-2 could be the appropriate stand density for O. lubricum management.

[Effects of elevated CO2 concentration on physiological characters of three dwarf ornamental bamboo species].

By using open-top chambers (OTCs) to simulate the scenes of elevated CO2 concentrations [500 micromol x mol(-1) (T1) and 700 micromol x mol(-1) (T2)], and taking ambient atmospheric CO2 concentration as the control (CK), this paper studied the effects of elevated CO2 concentration on the lipid peroxidation and anti-oxidation enzyme system in Indocalamus decorus, Pleioblastus kongosanensis, and Sasa glabra leaves. After 103 days treatment, the O2(-)* and MDA contents, relative electron conduction, and soluble sugar content in the three dwarf ornamental bamboo species leaves in T1 had no obvious change, but the activities of anti-oxidation enzymes (SOD, POD, CAT, and APX) changed to a certain extent. In T2, the MDA content and relative electron conduction had no obvious change, but the O2(-)* and soluble sugar contents and the anti-oxidation enzymes activities changed obviously. The adaptation capacity of the three bamboo species to elevated CO2 concentration was in the order of I. decorus > P. kongosanensis > S. glabra.

Organochlorine pesticide residues in bamboo shoot.

BACKGROUND: Xenobiotic organochlorine pesticides (OCPs) are a major environmental problem because of their historic widespread use, pronounced persistence against chemical and biological degradation, and bioaccumulation in the food chain. Pesticide use is prevalent in the production of edible bamboo shoots, which are exported widely from China. To evaluate the quality of Chinese bamboo shoots we determined the residual content of some OCPs in shoot samples. RESULTS: Three types of OCPs-hexachlorocyclohexane (HCH), 1,1,1-trichlor-2,2-bis(p-chlorophenyl)ethane (DDT) and pentachloronitrobenzene (PCNB)-were detected in bamboo shoots from Zhejiang province, China. Detection rates were 100%, 100% and 75% for HCH, DDT and PCNB, respectively. However, the average residue concentration did not exceed the maximum residue limit for pesticides detected in food in China (50 µg kg(-1) ). In terms of residue concentrations of the pesticides, 82.14% of the bamboo shoot samples could be classified as safe. CONCLUSION: While all sampled bamboo shoots contained OCP, most (82.14%) were safe for consumption.