Analysis of spatio-temporal changes in forest biomass in China

Forests play a central role in the global carbon cycle.China's forests have a high carbon sequestration potential owing to their wide distribution,young age and relatively low carbon density.Forest biomass is an essential variable for assessing carbon sequestration capacity,thus determining the spatio-temporal changes of forest biomass is critical to the national carbon budget and to contribute to sustainable forest management.Based on Chinese for-est inventory data (1999-2013),this study explored spatial patterns of forest biomass at a grid resolution of 1 km by applying a downscaling method and further analyzed spatio-temporal changes of biomass at different spatial scales.The main findings are:(1) the regression relationship between forest biomass and the associated influencing factors at a provincial scale can be applied to estimate biomass at a pixel scale by employing a downscaling method;(2) for-est biomass had a distinct spatial pattern with the greatest biomass occurring in the major mountain ranges;(3) forest biomass changes had a notable spatial distribution pattern;increase (i.e.,carbon sinks) occurred in east and southeast China,decreases (i.e.,carbon sources) were observed in the northeast to southwest,with the largest biomass losses in the Hengduan Mountains,Southern Hainan and Northern Da Hinggan Mountains;and,(4) forest vegetation functioned as a carbon sink during 1999-2013 with a net increase in biomass of 3.71 Pg.     

西安市化肥施用面源污染环境风险评价研究

专项定量评估化肥施用面源污染环境风险,精准识别化肥施用面源污染高风险区域,进而制定有效措施,对面源污染管控工作至关重要。利用西安市1991-2018年化肥施用相关统计数据,全面分析了全市化肥施用时序演变和空间分异特征,并评价了化肥施用面源污染环境风险程度。结果表明：西安市化肥施用量在经历1991-2014年的快速增长后,于2015-2018年出现“四连降”;氮磷钾化肥施用结构比例由1991的1∶0.24∶0.13逐步调整为2018年的1∶0.34∶0.37;1991-2018年间化肥施用强度随时间递增趋势明显,2018年化肥施用强度为1991年的3.60倍;化肥施用环境风险整体增大趋势明显,总肥风险已由1991年的“尚安全”程度上升为2018年的“重度风险”程度。西安市化肥施用面源污染环境风险空间差异明显,其中长安区为“低度风险”区域,临潼区、高陵区和鄠邑区为“中度风险”区域,灞桥区、阎良区和蓝田县为“重度风险”区域,未央区和周至县为“严重风险”区域。在确保农作物产量基础上,西安市应从施肥技术、科技攻关、政策法规等层面入手,制定有效管控措施。     

生计资本视角下农户生计策略变动及影响因素研究——基于CFPS四期追踪数据

农户的生计策略在乡村振兴进程中正在和即将发生变化,只有对农户生计策略的变化做出正确的判断,才能够有效引导农户生计行为,破除乡村建设行动的各种阻力。基于可持续生计理论,利用CFPS四期追踪数据,运用转移概率矩阵和Logit回归模型,分析农户生计策略变动及其影响因素,并运用分位数回归方法验证稳健性。结果表明,不同生计策略农户的生计资本结构存在差异,无论何种生计策略的农户,人力资本在5种资本中都最大。短期内多数农户选择维持原有生计策略,动态调整过程较慢,有土地转入的农户更倾向于选择非务工型生计策略。社会资本对农户趋务工型策略变动具有显著的正向影响,农户受教育年限和健康对生计策略变动具有正向影响。与东部地区农户相比,中西部地区农户更倾向于选择务工型生计策略。因此,应加大农村产业多样化的投入力度,促进农户策略转变速度;鼓励农民参与土地流转;建立健全农户参与农村基层社会治理机制,推动农户社会资本积累;扩大对农村教育与医疗的投入力度。     

LysR型转录因子STM0859对鼠伤寒沙门菌环境耐受性的调控作用

为了解LysR型转录因子STM0859对鼠伤寒沙门菌(ST)环境应激的调控作用,以ST-SL1344强毒株为研究对象,利用温度敏感型质粒和λ-Red同源重组技术构建ST-ΔSTM0859基因缺失突变株,检测分析缺失株对pH、高盐、H_2O_2和乙醇胁迫环境的适应能力及在不同pH半固体中的运动能力,探究STM0859基因缺失对ST环境应激和运动能力的影响。结果显示,与ST-SL1344强毒株相比,ST-ΔSTM0859缺失株对pH=10、4%NaCl、0.1%H_2O_2和3%乙醇胁迫环境的适应能力没有显著变化,而在pH=4酸应激环境和半固体运动中生长能力极显著低于亲本株,pH=5时差异显著。提示LysR型转录因子STM0859参与ST对酸胁迫环境适应性的调控,为进一步揭示STM0859转录因子对ST环境应激调控的分子机制奠定基础。     

三江源地区1961−2019年降水量时空变化特征

利用三江源地区13个气象站1961?2019年共59年的降水量资料,基于一元线性回归、滑动平均法、气候倾向率和重标极差分析等方法,研究源区降水量的时空演变规律和未来变化趋势.结果表明:三江源地区年均降水量为470.7?mm,并以10.31?mm·10?a?1的速率增加.黄河源区春季降水量最大,其余三季以澜沧江源区最高,...     

温度和盐度对花鲈胚胎及前期仔鱼发育影响的初步报告

花鲈（Ｌａｔｅｏｌａｂｒａｘ ｊａｐｏｎｉｃｕｓ）胚胎发育的适宜温度为１０～２２℃，１０℃组中的畸形率偏高，因此最适宜温度为１３～２２℃。短时期的７℃低温对胚胎发育没有影响；前期仔鱼的适温范围与胚胎的适温范围基本一致。胚胎发育的适宜 盐度为１９‰～２８‰，以２２‰～２５‰为最佳；仔鱼对盐度的要求与胚胎期近似。以低盐度和高盐 度相比较，４日龄以后，低盐度似有利于仔鱼存活。     

乳山湾东流区细菌数量的分布及与环境因子关系的研究

根据1995年6～9月对乳山湾东流区的微生物调查资料，研究了乳山湾东流区海水及底泥中细菌和弧菌量的变化及其与环境因子的关系。结果表明，该海域海水中细菌和弧菌的数量变化与温度的变化相一致，6月中旬～8月中旬，细菌数量增长比较缓慢，8月中旬开始，细菌数量增长较快，到8月底，达到最高值，异养菌为5．71×106cell／mL，弧菌为2．1×104cell／mL。而后，随着温度的下降，水中的细菌量逐渐减少。滩涂底泥中，细菌和弧菌的数量均比海水中细菌高l～2个数量级。     

Seasonal changes in proteolytic enzymes of yellowtail Seriola quinqueradiata (Temminck & Schlegel; Carangidae) fed extruded diets containing different protein and energy levels

Seasonal variations in pepsin, trypsin and chymotrypsin activities and protein digestibility were studied in yellowtails (Seriola quinqueradiata) reared for 1 year with extruded diets containing different levels of protein. Trypsin and chymotrypsin storage levels in the digestive tissues of starved fish were affected by seasonal changes in water temperature. Actual digestion activities of trypsin and chymotrypsin were low at lower water temperatures, but pepsin activity in the stomach tissue was not affected by low temperatures. On the other hand, trypsin and chymotrypsin activities in the intestinal contents were higher during lower water temperature months, while pepsin activity in the stomach contents was low at lower water temperatures. Apparent protein digestibility (APD) did not differ among the dietary treatments in the higher water temperature months, while in colder months it was higher in fish fed diet 1 than in fish fed diets 2 and 3. The APD values reflected pepsin activity in the stomach contents in all sampling months. Therefore, lower APD in colder months seems to be attributed to lower protease activity in the gastric digesta, implying that enhanced pepsin secretion from the stomach tissue might improve protein digestibility and growth performance in yellowtails during winter.     

Some Aspects of the Growth of Gracilaria birdiae (Gracilariales, Rhodophyta) in an Estuary in Northeast Brazil

The agarophyte Gracilaria birdiae Plastino & Oliveira was cultivated under field conditions in an estuary over a 6-month period. Biomass production varied significantly (p<0.01) and ranged from 900.0 to 3537.0 g m⁻² with a mean of 2124.4±1004.36 g m⁻² over the cultivation period. The epiphyte-biomass varied from 64.7 to 313 g m⁻², with maximum values observed in July. Relative growth rate (RGR) of G. birdiae varying from −0.59 to 4.67% day⁻¹, with a maximum mean observed in July. Correlation analysis showed that RGR was positively correlated with epiphyte-biomass (R-Pearson=0.69; p< 0.01) and negatively correlated with salinity (R-Pearson=−0.41; p<0.05). These correlations were used in a mathematical regression model to estimate the growth of Gracilaria in an estuary. The regression model explained 61% of RGR variability demonstrating that growth rates of Gracilaria were directly related to the variables salinity and epiphytes. The model was developed to help to predict production at a cultivation site in order to evaluate its suitability for Gracilaria cultivation.