Enhanced Soil Carbon Storage under Agroforestry and Afforestation in Subtropical China

Soil carbon (C) in three Ginkgo (Ginkgo biloba L.) agroforestry systems, afforestation (Ginkgo alone; G), and an agricultural cropping system were compared over a five-year period. The agroforestry systems were Ginkgo + Wheat (Triticum aestivum L.) + Peanut (Arachis hypogaea L.; GWP); Ginkgo + Mulberry (Morus alba L.; GM); and Ginkgo + Rapa (Brassica napus L.) + Peanut (GRP). The agricultural system consisted of wheat and peanut (WP). Total soil carbon (TSC), soil organic (SOC) and inorganic carbon (SIC), and the pools of five SOC chemical fractions were measured. TSC and SOC were always lower under WP than the G-based planting systems, and TSC in the latter increased significantly across years in the top 20 cm. Stocks of SIC under WP were significantly greater than the G-based systems, whereas SOC fractions tended to be lower. Most fractions increased across years but not in WP.Forestry, Faculty ofNon UBCForest Resources Management, Department ofReviewedFacult

Effects of salt stress on the leaf shape and scaling of pyrus betulifolia bunge

CITATION: Yu, X., et al. 2019. Effects of salt stress on the leaf shape and scaling of pyrus betulifolia bunge. Symmetry, 11(8):991, doi:10.3390/sym11080991.The original publication is available at https://www.mdpi.comLeaf shape can reflect the survival and development of plants in different environments. In particular, leaf area, showing a scaling relationship with other leaf-shape indices, has been used to evaluate the extent of salt stress on plants. Based on the scaling relationships between leaf area and other leaf-shape indices in experiments at different levels of salt stress, we could examine which leaf-shape indices are also related to salt stress. In the present study, we explored the effects of different salt concentration treatments on leaf dry mass per unit area (LMA), the quotient of leaf perimeter and leaf area (QPA), the quotient of leaf width and length (QWL), the areal quotient (AQ) of left and right sides of a leaf and the standardized index (SI) for bilateral symmetry. We treated Pyrus betulifolia Bunge under NaCl salt solution of 2‰, 4‰ and 6‰, respectively, with fresh water with no salt as the control. The reduced major axis (RMA) was used to fit a linear relationship of the log-transformed data between any leaf trait measures and leaf area. We found that leaf fresh weight and dry weight decrease with salt concentration increasing, whereas the exponents of leaf dry weight versus leaf area exhibit an increasing trend, which implies that the leaves expanding in higher salt environments are prone to have a higher cost of dry mass investment to increase per unit leaf area than those in lower salt environments. Salt concentration has a significant influence on leaf shape especially QWL, and QWL under 6‰ concentration treatment is significantly greater than the other treatments. However, there is no a single increasing or decreasing trend for the extent of leaf bilateral symmetry with salt concentration increasing. In addition, we found that the scaling exponents of QPA versus leaf area for four treatments have no significant difference. It indicates that the scaling relationship of leaf perimeter versus leaf area did not change with salt concentration increasing. The present study suggests that salt stress can change leaf functional traits especially the scaling relationship of leaf dry weight versus leaf area and QWL, however, it does not significantly affect the scaling relationships between leaf morphological measures (including QPA and the extent of leaf bilateral symmetry) and leaf area.https://www.mdpi.com/2073-8994/11/8/991Publisher's versio

Effect of nitrogen levels and nitrogen ratios on lodging resistance and yield potential of winter wheat (Triticum aestivum L.).

Lodging is one of the constraints that limit wheat yields and quality due to the unexpected bending or breaking stems on wheat (Triticum aestivum L.) production worldwide. In addition to choosing lodging resistance varieties, husbandry practices also have a significant effect on lodging. Nitrogen management is one of the most common and efficient methods. A field experiment with Yangmai 20 as research material (a widely-used variety) was conducted to study the effects of different nitrogen levels and ratios on culm morphological, anatomical characters and chemical components and to explore the nitrogen application techniques for lodging tolerance and high yield. Results showed that some index of basal internodes, such as stem wall thickness, filling degree, lignin content, cellulose content, water-soluble carbohydrate (WSC) and WSC/N ratio, were positively and significantly correlated with culm lodging-resistant index (CLRI). As the increase of nitrogen level and basal nitrogen ratio, the basal internodes became slender and fragile with the thick stem wall, while filling degree, chemical components and the strength of the stem decreased gradually, which significantly increased the lodging risk. The response of grain yield to nitrogen doses was quadratic and grain yield reached the highest at the nitrogen ratio of 50%:10%:20%:20% (the ratio of nitrogen amount applied before sowing, at tillering stage, jointing stage and booting stage respectively, abbreviated as 5:1:2:2). These results suggested that for Yangmai 20, the planting density of 180×104ha-1, nitrogen level of 225 kg ha-1, and the ratio of 5: 1: 2: 2 effectively increased lodging resistance and grain yield. This combination of planting density and nitrogen level and ratio could effectively relieve the contradiction between high-yielding and anti-lodging

Grey relational analysis for culm lodging resistance index and culm characters.

<p>Grey relational analysis for culm lodging resistance index and culm characters.</p

Effect of nitrogen levels and ratios on culm breaking strength and culm lodging resistance index.

<p>Effect of nitrogen levels and ratios on culm breaking strength and culm lodging resistance index.</p

Effect of nitrogen levels and ratios on plant height and length of basal internodes.

<p>Effect of nitrogen levels and ratios on plant height and length of basal internodes.</p

Effect of nitrogen levels and ratios on diameter, wall thickness and filling degree of basal internodes.

<p>Effect of nitrogen levels and ratios on diameter, wall thickness and filling degree of basal internodes.</p

Daily temperature and rainfall regimes during growing season at the experimental site in 2012–2013 (a) and 2013–2014 (b).

<p>Daily temperature and rainfall regimes during growing season at the experimental site in 2012–2013 (a) and 2013–2014 (b).</p

Phenotypic correlations for culm lodging resistance index, lodging score and culm characters^α.

<p>Phenotypic correlations for culm lodging resistance index, lodging score and culm characters<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0187543#t006fn001" target="_blank">^α</a>.</p