Seasonal variations in carbon, nitrogen and phosphorus concentrations and C:N:P stoichiometry in the leaves of differently aged Larix principis-rupprechtii Mayr. plantations

The concentrations and stoichiometry of certain elements (carbon, nitrogen and phosphorus) are critical to the maintenance of plant functional and environmental adaptation during plant growth. We explore how the concentrations of C, N and P and the ratios of C:N, C:P, and N:P in the leaves of differently aged Larix principis-rupprechtii Mayr. plantations changed with growing season and stand age from 2012 to 2015 in the Qinling Mountains, China. The results showed that the element concentration and stoichiometric ratios in leaves were significantly affected by sampling month, stand age and sampling year; and multiple correlations with stand age were observed in different growing seasons. Compared to global element concentrations and stoichiometry in plants, the leaves of larch stands in the study region had higher C and P concentrations and C:N and C:P ratios but lower N concentrations and N:P ratios than global levels. The leaf N:P ratios of all of the larch stands were generally less than 14, suggesting that the growth of larch stands was limited by N in the study region. Our study facilitates the management and restoration of forest plantation and provides a valuable contribution to the global pool of leaf nutrition and stoichiometry data

Seasonal variations in carbon, nitrogen and phosphorus concentrations and C:N:P stoichiometry in different organs of a Larix principis-rupprechtii Mayr. plantation in the Qinling Mountains, China

Understanding how concentrations of elements and their stoichiometry change with plant growth and age is critical for predicting plant community responses to environmental change. Weusedlong-term field experiments to explore how the leaf, stem and root carbon (C), nitrogen (N) and phosphorous (P) concentrations and their stoichiometry changed with growth and stand age in a L.principis-rupprechtii Mayr. plantation from 2012–2015 in the Qinling Mountains, China. Our results showed that the C, N and P concentrations and stoichiometric ratios in different tissues of larch stands were affected by stand age, organ type andsampling month and displayed multiple correlations with increased stand age in different growing seasons. Generally, leaf C and N concentrations were greatest in the fast-growing season, but leaf P concentrations were greatest in the early growing season. However, no clear seasonal tendencies in the stem and root C, N and P concentrations were observed with growth. In contrast to N and P, few differences were found in organ-specific C concentrations. Leaf N:P was greatest in the fast-growing season, while C:N and C:P were greatest in the late-growing season. No clear variations were observed in stem and root C:N, C:P andN:Pthroughout the entire growing season, but leaf N:P was less than 14, suggesting that the growth of larch stands was limited by N in our study region. Compared to global plant element concentrations and stoichiometry, the leaves of larch stands had higher C, P, C:NandC:PbutlowerNandN:P,andtherootshadgreater PandC:NbutlowerN,C:Pand N:P. Our study provides baseline information for describing the changes in nutritional elements with plant growth, which will facilitates plantation forest management and restoration, and makes avaluable contribution to the global data pool on leaf nutrition and stoichiometry

Taxonomic and functional β-diversity patterns reveal stochastic assembly rules in microbial communities of seagrass beds

Microorganisms are important members of seagrass bed ecosystems and play a crucial role in maintaining the health of seagrasses and the ecological functions of the ecosystem. In this study, we systematically quantified the assembly processes of microbial communities in fragmented seagrass beds and examined their correlation with environmental factors. Concurrently, we explored the relative contributions of species replacement and richness differences to the taxonomic and functional β-diversity of microbial communities, investigated the potential interrelation between these components, and assessed the explanatory power of environmental factors. The results suggest that stochastic processes dominate community assembly. Taxonomic β-diversity differences are governed by species replacement, while for functional β-diversity, the contribution of richness differences slightly outweighs that of replacement processes. A weak but significant correlation (p < 0.05) exists between the two components of β-diversity in taxonomy and functionality, with almost no observed significant correlation with environmental factors. This implies significant differences in taxonomy, but functional convergence and redundancy within microbial communities. Environmental factors are insufficient to explain the β-diversity differences. In conclusion, the assembly of microbial communities in fragmented seagrass beds is governed by stochastic processes. The patterns of taxonomic and functional β-diversity provide new insights and evidence for a better understanding of these stochastic assembly rules. This has important implications for the conservation and management of fragmented seagrass beds

DataSheet_1_Taxonomic and functional β-diversity patterns reveal stochastic assembly rules in microbial communities of seagrass beds.docx

Microorganisms are important members of seagrass bed ecosystems and play a crucial role in maintaining the health of seagrasses and the ecological functions of the ecosystem. In this study, we systematically quantified the assembly processes of microbial communities in fragmented seagrass beds and examined their correlation with environmental factors. Concurrently, we explored the relative contributions of species replacement and richness differences to the taxonomic and functional β-diversity of microbial communities, investigated the potential interrelation between these components, and assessed the explanatory power of environmental factors. The results suggest that stochastic processes dominate community assembly. Taxonomic β-diversity differences are governed by species replacement, while for functional β-diversity, the contribution of richness differences slightly outweighs that of replacement processes. A weak but significant correlation (p < 0.05) exists between the two components of β-diversity in taxonomy and functionality, with almost no observed significant correlation with environmental factors. This implies significant differences in taxonomy, but functional convergence and redundancy within microbial communities. Environmental factors are insufficient to explain the β-diversity differences. In conclusion, the assembly of microbial communities in fragmented seagrass beds is governed by stochastic processes. The patterns of taxonomic and functional β-diversity provide new insights and evidence for a better understanding of these stochastic assembly rules. This has important implications for the conservation and management of fragmented seagrass beds.</p

Development of hypoxia-triggered prodrug micelles as doxorubicin carriers for tumor therapy

Hypoxia has a major role in tumor development and resistance to therapy. Therefore, the effective targeting and killing of hypoxic tumor cells is a key to successful tumor control. Here, we report the hypoxia-responsive prodrug micelles to deliver hydrophobic anticancer drug, which can selectively release the drugs to treat hypoxic tumor cells in a combined way. For this purpose, an azobenzene (AZO) bond, which imparts hypoxia sensitivity and specificity as cross linker, conjugated PEG-hexanethiol (PEG-C6) with combretastatin A-4 (CA4) to form PEG-C6-AZO-CA4 amphiphilicmolecule. These PEG-C6-AZO-CA4 molecules self-assemble into micelles, which can encapsulate hydrophobic anticancer drug. The drug release behavior from PEG-C6-AZO-CA4 micelles was studied under normoxic or hypoxic conditions and the combinations of CA4 with hydrophobic drugs for tumor treatment in vitro were also investigated. As the first example of using AZO linkages to develop anticancer prodrug micelles as hydrophobic anticancer drugs delivery to kill the hypoxic tumor cells in a combination way, this study establishes PEG-C6-AZO-CA4 micelles as a promising drug delivery platform for hypoxic tumor therapy.</p

Seasonal variations in the P concentrations (mean ± SE) in different organs of larch stands from 2012–2015.

<p>Different lowercase letters represent significant differences among different growing seasons at P < 0.05.</p

Seasonal variations in the N:P ratio (mean ± SE) in different organs of larch stands from 2012–2015.

<p>Different lowercase letters represent significant differences among different growing seasons at P < 0.05.</p

Initial soil (0–20 cm) properties of the study region.

<p>Initial soil (0–20 cm) properties of the study region.</p

Seasonal variations in the C:N ratio (mean ± SE) in different organs of larch stands from 2012–2015.

<p>Different lowercase letters represent significant differences among different growing seasons at P < 0.05.</p

Correlations of the C, N, P concentrations and the C:N, C:P, and N:P ratios in different organs with stand age in different sampling months from 2012–2015.

<p>Correlations of the C, N, P concentrations and the C:N, C:P, and N:P ratios in different organs with stand age in different sampling months from 2012–2015.</p