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Citrus is an important agricultural product in China and globally, and citrus production in China plays a vital role in global citrus patterns; specifically, spatial changes in these patterns affect the supply of citrus in China and have an important impact on the international citrus trade. In this study, the industrial concentration, exploratory data analysis, industrial gravity model, and spatial Durbin model were used to analyze the spatial evolution characteristics of and factors driving citrus production in China. The results showed that, from 1978 to 2015, China's citrus production space showed an expanding trend, which could be divided into a rapid growth period (1978-1991), low growth period (1992-2000), and steady growth period (2001-2015). The citrus production space in China is mainly concentrated in Southwest, Central South, and East China, with a spatial structure of "cold in the north and hot in the South." Citrus production space has a significant positive spatial autocorrelation on the provincial scale, showing a significant geographical agglomeration; the agglomeration first drops sharply, following which it fluctuates and rises. Since 2000, the center of the production space has continuously moved to the Southwest; the trend of "moving to the West and expanding to the South" is evident. China's citrus production space has gradually changed from the original natural drive to the "natural society" drive. The endowment of natural resources determines the basic space of citrus production in China, where social and economic factors are important reasons for changes in citrus production space. Among the market location factors, road transportation and fruit consumption significantly affect the citrus production space positively. The increase in road network density improves the economic location of the production area, and the increase in residents' incomes expands the demand for citrus consumption; therefore, for each 1% increase in road network density and income, the citrus area increases by 0.192% and 0.107%, respectively. Among the production factors, labor input and water conservancy irrigation have positive effects on citrus production space; with a 1% increase in these factors, the citrus area increases by 0.934% and 0.094%, respectively. Regarding social and economic factors, the loss of rural labor as a result of non-agricultural employment opportunities has a strong negative effect on the production space of citrus. The citrus area is reduced by 1.365% for each 1% increase. New varieties and new technologies brought about by scientific and technological progress positively affect citrus production space, and the citrus area increases by 0.058% for every 1% increase in this factor. The direct effect of per capita grain possession is negative, and the indirect effect is positive, indicating that with regard allocating limited land resources, local land must first meet the food security and inhibit the increase in citrus area. The increase in the per capita share in neighboring areas can meet the local food security and promote the increase of citrus area through food circulation.

Tillage modes and straw returning influence soil aggregate stability and the distribution of organic carbon (C) and nitrogen (N) in aggregates of different particle sizes. In the typical hilly regions of southwest China, the predominant soil type is purple soil, characterized by heavy texture and high stickiness, with relatively lower soil fertility compared to other soil types. The improper use of fertilizers and field management practices further exacerbates soil compaction. However, abundant straw resources in the region provide an opportunity for comprehensive straw utilization. The effective utilization of straw resources is of significant importance for stabilizing agricultural ecological balance, improving resource utilization efficiency, and alleviating ecological pressure. Previously, most studies have focused on the impact of different mechanized tillage systems on the physical and chemical properties of soil in hilly areas, while research on the preservation of water-stable aggregates' organic C and N content remains limited. In this study, the soil properties of fields under a winter pea–summer corn rotation for two years were studied with regards to the effects of straw returning on its water-stable aggregate distribution, macroaggregate content (R0.25), mean weight diameter (MWD), geometric mean diameter (GMD), and the organic C and N content in soil aggregates of different particle sizes and at different depths. The effects of five different tillage modes were assessed, namely rotary tillage with straw mixed retention (RTM), conventional tillage with straw burial retention (CTB), no-tillage with straw covered retention (NTC), subsoiling with straw covered retention (STC), and no-tillage without straw retention (NT). Based on the study results, under different tillage modes, straw returning effectively enhanced the soil organic carbon (SOC) and total nitrogen (TN) reserves at the plow layer (0–30 cm), SOC increased by 17.2% to 88%, and TN increased by 8.6% to 85.9%. At the same time, the content of 0.25–2 mm aggregates increased under the straw-return treatments under different tillage patterns. The NT treatment had the lowest R0.25 and MWD and GMD values for soil aggregates at different depths, which were significantly different (p < 0.05) from the other treatment modes. The correlation coefficients between SOC and soil aggregate stability indices ranged from 0.68 to 0.90, with most of them showing highly significant positive correlations (p < 0.01). In conclusion, straw returning under different tillage systems has improved soil aggregate stability and promoted soil structure stability. Specifically, the STC treatment has shown more pronounced effects on soil improvement in the upper soil layer of the hilly regions in southwest China, while the RTM treatment is beneficial for improving the lower soil layer. Therefore, the comprehensive experimental results indicate that the combination of STC and RTM treatments represents the most promising mechanized tillage and straw returning practices for the hilly regions in southwest China. [ABSTRACT FROM AUTHOR]

A field experiment involving rice–wheat rotation was performed to investigate the effect of mushroom residue (MR) in comparison with chemical fertilizer (CF) and crop straw return on methane (CH4) and nitrous oxide (N2O) emissions in 2012–2013. Five treatments in quadruplicate were included in this study: (1) CF only, (2) CFS (straw + CF), (3) MR-1 (50% amount of N in CF was replaced with MR), (4) MR-2 (100% amount of N in CF was replaced with MR) and (5) MR-3 (150% amount of N in CF was replaced with MR). Results showed that the effects of CFS and MR-1 treatments on CH4and N2O emissions did not significantly differ. By contrast, CH4emissions decreased as the amount of applied MR increased. Crop straw and MR stimulated CH4emissions (from 48.8% to 119%) in rice season in 2012. In 2013, the applied crop straw and MR decreased CH4emissions (from 21.3% to 37.3%). This contrasting effect might be explained by the difference in soil moisture content between the two seasons. N2O emission in wheat season could be efficiently decreased (from 25.2% to 29.7%) by applying MR. Our results suggesting that MR could be used as a soil organic amendment under the premise of proper water management. [ABSTRACT FROM AUTHOR]

We determined the complete mitochondrial genome ofKaloula rugiferain this work. The mitogenome was 17,073 bp in length, containing 13 protein-coding genes, 2 rRNA genes, 22 tRNA genes and a control region (D-loop). The base composition of the light strand was 29.7% A, 30.4% T, 25.7% C and 14.2% G. The gene order and contents of it is identical to most amphibian mitogenome. All protein-coding genes began with ATG as start codon exceptND1gene beginning with GTG andCOIgene beginning with ATA. Five protein-coding genes (COII, ATP 6, COIII, ND3andND4) ended with incomplete stop codon T. The 22 tRNA genes with the size ranging from 65 bp to 73 bp were interspersed along the whole genome. The D-loop region containing tandem repetition was 1675 bp in length and heavily biased to A + T nucleotides. [ABSTRACT FROM AUTHOR]