Soil degradation in the tropical lowlands of Santa Cruz,Eastern Bolivia

This paper examines the soil degradation processes that are threatening the productivity of the mechanized annual cropping areas in the Santa Cruz lowlands of tropical eastern Bolivia. The dominant process is that of machinery-induced and natural compaction, which has resulted in an estimated 50 per cent of the soils in the Central Zone being moderately to severely compacted, causing serious root restriction and the loss of both transmission and water-storage pores. Degradation has made the soils increasingly susceptible to moisture stress due to the combined effect of (i) restricted rooting as a result of compaction and the hardsetting characteristics of the soils, (ii) reduced rainfall infiltration due to the loss of transmission pores and surface crusting, and (iii) a decrease in available soil moisture caused by the loss of storage pores, the incorporation of wind-blown fine sand deposits, and soil organic matter losses due to accelerated decomposition rates. The loss of transmission pores has also made the soils more prone to waterlogging in periods of high rainfall. The degradation tendencies of these soils are exacerbated by the greater variability of seasonal rainfall during the last 20 years that has led to a greater frequency or extremely high or extremely low rainfall events than hitherto.     

关于退耕还林工程造林类型设计的探讨

本文主要介绍了长春净月潭旅游经济开发区退耕还林地的立地类型,设计了与之相应的工程造林类型,分析了不同工程造林类型的综合效益。     

黄牛木种群空间分布格局研究

为促进黄牛木Cratoxylum cochinchinense在珠三角地区生态建设中的推广和应用,采用样方调查法,于2016-2017年在广州市和台山市3个黄牛木天然林集中分布区布设样地,通过绘制种群空间分布点位置图,结合方差均值比率法和聚集度指标,分析种群的空间分布类型、聚集程度,从而揭示黄牛木种群的空间分布特性、生...     

施磷对紫花苜蓿光合作用及抗蓟马的影响

为了明确施磷对苜蓿抗蓟马的影响及其相关的光合机制,本试验以西北广泛种植的感蓟马苜蓿品种‘甘农3号’和抗蓟马苜蓿品种‘甘农9号’为材料,在大田蓟马为害高峰期,调查评价了不同施磷水平下苜蓿的受害指数、生长指标和蓟马虫口数量,测定了不同施磷水平下苜蓿的光合气体交换参数、可溶性糖含量。结果表明:施磷后,‘甘农3号’和‘甘农9号’苜蓿的受害指数均显著降低,株高和产量显著增加,蓟马虫口数量无显著变化;净光合速率(Pn)和水分利用率(WUE)显著升高,蒸腾速率(Tr)和气孔导度(Gs)显著降低;苜蓿心叶可溶性糖含量显著升高,但可溶性糖含量与蓟马虫口密度间无相关性,而与受害指数之间存在极显著的负相关关系。施磷有效地增强了苜蓿的光合作用,进而增强了苜蓿对蓟马的耐害性。在大田条件下,通过增施磷肥来控制苜蓿蓟马的危害是一种经济有效的绿色防控措施。     

耕作方式及秸秆还田对土壤性质、微生物碳源代谢及小麦产量的影响

以小麦品种济麦22为试验材料,采用裂区试验设计,耕作方式为主区,分别设常规翻耕(C)、深松(S)、旋耕(R)处理,副区为秸秆还田量,分别设秸秆全还田(P)和秸秆不还田(A)处理,采用Biolog Eco技术测定土壤微生物碳源代谢功能,并分析土壤基本理化性质和作物产量。结果显示:深松与秸秆还田均有利于土壤含水量和有机碳含量的提高,0～15 cm土层分别提高了9.78%和24.00%,15～30 cm土层分别提高了7.08%和15.81%;深松提高了15～30 cm土层的pH值6.67%,秸秆还田提高了0～15 cm土层的pH值4.32%。深松和秸秆还田均有利于代谢多样性(丰富度指数、香浓多样性指数)、碳源代谢强度的提高,0～15 cm土层分别提高了26.84%、3.84%和38.02%,15～30 cm土层分别提高了11.87%、 3.63%和14.74%。主成分分析表明常规翻耕秸秆不还田和旋耕耕作秸秆不还田碳源代谢功能相近,15～30 cm层次内常规翻耕秸秆全还田碳源代谢功能和深松耕作秸秆全还田处理相近。深松和秸秆还田平均提高了小麦产量5.82%,微生物碳源代谢功能与小麦产量具有极显著的相关性。     

数字技能如何影响农民电商参与行为？——基于信息获取的中介效应分析

为探究数字技能对农民电商参与行为的影响及作用机制,基于2020年中国乡村振兴综合调查（CRRS）数据,立足“手段-自由-成就”的可行信息能力理论,构建“数字技能-信息获取-电商参与”的理论分析框架,采用二元Probit、Tobit和中介效应等分析方法,从信息获取的中介视角实证检验数字技能对农民电商参与决策及程度的影响,并进行稳健性检验和异质性分析。结果表明：1）数字技能对农民电商参与决策和程度均具有显著正向影响;2）信息获取在数字技能对农民电商参与决策和程度的影响中存在部分中介效应,中介效应占总效应的比重分别为11.76%和11.73%;3）数字技能对收入水平较高、受教育水平较高的农民,电商参与决策和参与程度的正向影响更为显著。政府应从有效提升农民数字技能水平,稳步实现信息获取自由,加强关注农民内部分化3方面提升农民电商参与率和程度。     

碳交易视域下养殖户畜禽粪污资源化利用受偿意愿与影响因素——基于河北省7市694户养猪户调研数据

为进一步探究养殖户粪污资源化利用受偿意愿、受偿水平及其影响因素,基于碳交易视角,利用2023年3—4月对河北省7市694户养猪户的调研数据,运用条件价值评估法、二元Logit模型和Tobit模型对此进行系统分析。结果表明：1）88.76%的养猪户愿意接受补偿,其受偿水平在25.03~31.50元/t;2）养猪户年龄、养殖场地面积以及粪污资源化利用生态效益等因素会显著影响养猪户受偿意愿;风险偏好、场地面积、养殖规模、养殖信息获取渠道、粪污资源化利用经济效益显著影响其受偿水平;3）规模异质性视角下,粪污资源化利用生态效益显著正向影响不同规模养猪户受偿意愿。自动化设施配置数量和粪污资源化利用社会效益显著影响不同规模养猪户受偿水平,但其影响方向存在显著差异。为使养殖户更好参与资源化利用,应加强对畜禽粪污资源化利用正面效果的宣传,将宏观政策规范与地方实际相结合、因地制宜,有序推进碳交易补偿机制的建立。     

农户资本禀赋、感知价值与秸秆收集受偿意愿——基于湖北黄冈的微观调研数据

为探究农户资本禀赋、感知价值对其秸秆收集受偿意愿的影响及作用机制,基于布迪厄社会实践理论构建分析框架,利用湖北省黄冈市秸秆综合利用重点县684份农户调查数据,使用二元Logit和OLS模型实证分析农户资本禀赋、感知价值对其秸秆收集受偿意愿的影响。结果表明：1）愿意参与秸秆收集生态补偿的农户占总样本的90.35%,其最小受偿额度平均值为791.45元/hm2;2）资本禀赋对农户秸秆收集生态补偿参与意愿有显著正向影响,对受偿额度有显著负向影响;3）感知价值对农户秸秆收集生态补偿参与意愿和受偿额度均有显著正向影响;4）感知价值在资本禀赋与秸秆收集生态补偿参与意愿之间具有中介效应,中介效应量为0.289;感知价值在资本禀赋与秸秆收集受偿额度之间具有遮掩效应,遮掩效应量为0.225。因此,为鼓励农户的秸秆收集行为,应加快完善秸秆收集生态补偿措施并分层分阶段推进,多渠道提升农户资本禀赋的同时提高农户对秸秆收集行为的感知价值。     

短期培养对玻璃化冷冻小鼠2-细胞胚胎低渗抵抗力的修复作用

为研究短期培养对玻璃化冷冻小鼠2-细胞胚胎低渗抵抗力的修复作用,对玻璃化冷冻小鼠2-细胞胚胎解冻后进行短期(2～4 h)培养,然后使用20%的低渗PBS液于25℃条件下处理20 min,观察48 h发育率、囊胚率和移植后妊娠率、产仔率.获得93%的48 h发育率和48%的囊胚率,显著高于低渗处理前未培养组(47%和9%)(P＜0.05).证明解冻后的短期培养中可以有效修复玻璃化冷冻对小鼠2-细胞胚胎低渗抵抗力的损伤.     

Effects of dietary protein to energy ratios on growth,body composition and digestive enzyme activities in Chinese mitten‐handed crab,Eriocheir sinensis

This study aimed to determine the optimal protein to energy ratio (P/E ratio) and evaluate the effect of dietary protein and lipid levels on growth performance, body composition and digestive enzymes activities in Chinese mitten‐handed crab, Eriocheir sinensis. Nine practical diets containing three levels both for protein (DP 30%, 35% and 40%) and lipid (DL 2%, 7% and 12%) with P/E ratios ranging from 13.69 to 19.79 mg KJ^?1 were fed to four replicates of crabs (3.39 ± 0.10 g) for 10 weeks. Weight gain increased significantly with the increase in DP level at each DL level. Moreover, weight gain increased in crabs fed with diets containing DL level from 2% to 12% and DP level from 30% to 35%. However, the diet containing 40% DP and 12% DL levels significantly decreased the growth performance and protein efficiency of the crabs. The whole crab and hepatopancreas lipid contents also increased as dietary lipid increased, but not dietary protein. The total protease activity increased significantly with the increase in dietary protein at each lipid level. The lipase activity was statistically comparable among different DL levels at each DP level. Taken together, the crab fed the diet containing 35% protein and 12% lipid levels with P/E 15.77 mg KJ^?1 revealed optimal growth, feed utilization efficiency and digestive enzymes activities. Moreover, our study indicated that the higher dietary lipid level at a relatively lower dietary protein level could provide protein sparing effect in Eriocheir sinensis.