土壤团聚体有机碳研究进展

土壤有机碳是衡量土壤肥力的重要指标,对于促进土壤养分循环、增加养分有效性有重要作用。土壤团聚体是土壤的重要组成部分,是组成土壤结构的最小单元,受到自然因素和人为因素的影响,其形成转化过程与土壤固碳过程息息相关,因而研究团聚体和有机碳的关系及团聚体有机碳影响因素对于土壤结构的改善和土壤质量的提升具有重要意义。本文通过对文献的总结,明晰了土壤团聚体和有机碳的关系,阐述了土壤类型、施肥方式、土地利用和矿区复垦对土壤团聚体有机碳的影响,并从生物质炭的长期定位研究和复垦矿区的土壤修复两方面对土壤团聚体有机碳的研究进行展望,研究结果可为合理的农业生产提供科学依据。     

Impact of grassland contract policy on soil organic carbon losses from alpine grassland on the Qinghai–Tibetan Plateau

Carbon storage in the soils on the Qinghai–Tibetan Plateau plays a very important role in the global carbon budget. In the 1990s, a policy of contracting collective grasslands to smaller units was implemented, resulting in a change from the traditional collective grassland management to two new management patterns: a multi‐household management pattern (MMP: grassland shared by several households without enclosures) and a single‐household management pattern (SMP: grassland enclosed and used by only one household). In 2016, 50 MMP and 54 SMP winter pastures on the Qinghai–Tibetan Plateau were sampled to assess the differences in soil organic carbon (SOC) between the two management patterns. Results showed that average SOC was significantly greater under MMP than under SMP, with an estimated 0.41 Mg C/ha/yr lost due to SMP following the new grassland contract. Based on the government's grassland policy, four grassland utilization scenarios were developed for both summer and winter pastures. We found that if the grassland were managed under SMP, likely C losses ranged between 0.31 × 10⁷ and 6.15 × 10⁷ Mg C/yr across the Qinghai–Tibetan Plateau relative to MMP, which more closely resembles pre‐1990s grassland management. Previous estimates of C losses have only considered land use change (with cover change) and ignored the impacts driven by land management pattern changes (without cover change). The new data suggest that C losses from the Qinghai–Tibetan Plateau are greater than previously estimated, and therefore that the grassland contract policy should be reviewed and SMP households should be encouraged to reunite into the MMP. These findings have potential implications for land management strategies not only on the Qinghai–Tibetan Plateau but also other grazing regions globally where such practices may exist.     

Getting cosy in freshwater: Assumed to be brackish pike are not so brackish after all

Pike (Esox lucius) occupy coastal streams and rivers of the Baltic Sea, where they attain large sizes (>5 kg). These large sizes are perhaps due to the fact that they can tolerate relatively high salinities and can thus forage in the nearby more productive brackish environments. In an attempt to quantify the extent to which pike utilise brackish environments, and to provide some insight into the underlying causes for brackish water migrations, we tagged 30 pike from a western Baltic river with acoustic transmitters and were able to track 21 individuals for 1 year. Based on experienced from local anglers, this population was assumed to be brackish in nature, where individuals underwent freshwater migrations to spawn. Our findings however suggest that the smallest and most active individuals make short exits into brackish waters and do so on rare occasions. Our results further indicate that neither sex nor size is related to activity level. We suggest that these patterns reflect two distinct behaviours—active and passive—and that large pike can be supported by the food availability in the river, without the need to venture into coastal zones, thus defying the conventional view that Baltic pike are all brackish in nature.     

猪繁殖性状的遗传改良策略

猪繁殖性能的提高将为养猪业带来巨大的经济效益 ,目前多数育种者将提高猪的繁殖力作为主要育种目标 ,并用数学遗传学方法和分子育种技术对繁殖性状进行改良。     

奶牛繁殖疾病的调控

本文综述了奶牛繁殖疾病的发病原因和调控措施，分析认为奶牛的营养状况是影响奶牛繁殖力的重要因素。理想的奶牛管理应做到整个泌乳期始终监测奶牛的体况和奶牛日粮中微量元素的维生素的含量，避免营养素的不平衡而引发的奶牛繁殖障碍，同时应避免奶牛过肥或过瘦。适当补充某些维生素和矿物质十分重要。     

母猪高效预混合饲料饲养试验

本试验为考察新研制的４９２５／４９２６母猪系列预混合饲料的饲养效果，在母猪胎次、体况和饲养管理条件下似、基础饲料相同条件下，分别与金牧３８６３／３８６４、康地５７４３／５７４４两种母猪系列预混料进行饲养试验。入试头数分别为２３头、３５头。结果表明：①４９２５／４９２６组较３８６４／３９６４组，窝产活仔数、初生窝重、断奶窝重分别提高０．５头／窝、０．９ｋｇ／窝、４．２５ｋｇ／窝；哺乳期母猪头平少失重     

PGF2αeCG及hCG 3种生殖激素联用对母犬发情、卵泡发育及胚胎着床的影响

给休情期性成熟母犬肌注 PGF2α(0 .5 m g/ kg) ,2 4 h后肌注 e CG(5 0 IU/ kg) ,再经 12 0 h后肌注 h CG(2 0 U/ kg) ,诱导其发情。将诱导发情的母犬与公犬交配 ,于交配后 16 d,摘取卵巢、子宫 ,观察其卵泡发育和胚胎着床情况。结果表明 ,药物处理可明显促使母犬提前结束休情期而进入发情期 (9/ 10 ) ,促进卵巢内卵泡发育 (P<0 .0 1) ,并使更多的胚胎着床 ,每只母犬子宫胚胎着床点为 (17.4± 2 .2 )个 ,提示 3种生殖激素联合应用可提高母犬繁殖率     

东北虎雌性生殖系统解剖

对 2例 1 999年 1 0月意外死亡的东北虎雌性生殖系统进行了解剖。雌性东北虎的卵巢被覆卵巢囊 ,随着年龄增长卵巢表面凸凹不平 ,呈脑的沟回状。输卵管位于卵巢游离缘外侧 ,呈半圆形围绕着卵巢 ,输卵管壶腹部弯曲、峡部直 ;子宫与输卵管分界明显 ;子宫角长度约相当于子宫体长度的 2倍 ;阴道呈背腹压扁的管状