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.     

杨桃果实生长发育过程中营养品质的变化

杨桃（Averrhoa arambola L．）为华南地区重要的热带水果。本试材为华南农业大学园艺分场种植的3年生盆栽马来西亚甜杨桃，砧木为酸杨桃。在杨桃的开花期，选择生长势、开花数量和时间较一致45株为试材，再选择受精时间一致的果实做标记。采样时问从开花后（2003年7月15日）至杨桃充分成熟（2003年10月25）。测定杨桃果实中的糖（蒽酮比色法）、有机酸（HPLC法）、维生素C（2，6-二氯靛酚钠滴定法）和单宁（高锰酸钾滴定法）的含量。     

我国南瓜粉加工技术的研究现状及开发前景

综述了南瓜粉的开发价值、主要加工工艺及操作要点,分析了国内南瓜粉加工技术的现状及主要应用,探讨了南瓜粉加工技术的发展趋势与开发前景。     

切流式花生全喂入联合收获机清选机构设计

针对切流式花生全喂入联合收获机清选环节果杂分离不清、损失率高、缠膜挂秧、筛面堵塞等难题,该文设计了一种风筛组合、无阻滞、大小杂并除的清选机构,其主要由上层筛(杆筛)、下层筛(多阶弹性筛和后筛)、抖草轮、偏心套、风机等组成。该文运用动态静力学方法研究了筛面物料的相对运动,分析了物料相对筛面上滑、下滑、从筛面跃起的极限条件,确定了振动筛主要运动参数的理论值域;运用达朗伯原理开展了交变载荷下筛体的受力分析,确定了筛体关键结构参数。该文对影响清选作业质量主要因素开展了试验研究,试验结果表明:影响清选机构综合作业质量的主次作用因素为主风机转速、振动筛振幅、振动频率,较优参数组合为主风机转速2 100 r/min、振动筛振幅12.5 mm、振动频率9Hz,此时清选损失率5.03%、荚果含杂率5.39%;清选机构作业顺畅性较好,较少出现缠膜挂秧、筛面堵塞现象。研究结论可为切流式花生全喂入联合收获机清选机构的设计提供理论参考。     

几种有机酸对恒电荷和可变电荷土壤吸附Cu2+的影响

以恒电荷土壤(黄褐土和黄棕壤)和可变电荷土壤(红壤和砖红壤)为供试材料,研究了乙酸、草酸、酒石酸和柠檬酸对土壤吸附重金属铜离子(Cu2 )的影响。结果表明,在相同酒石酸浓度下,土壤对酒石酸的吸附量依次为黄棕壤(2 1 8mmolkg-1) >红壤(15 4mmolkg-1) >砖红壤(9 5mmolkg-1) ,土壤吸附有机酸后负电荷量增加,相同条件下增幅为砖红壤>红壤>黄棕壤;无有机酸配体时,供试土壤对Cu2 的吸附量为黄褐土>黄棕壤>砖红壤>红壤;加入有机酸时,随有机酸浓度增高,土壤对Cu2 的吸附一般表现为“峰”形曲线,峰所对应的有机酸浓度因有机酸类型而异,且随土壤可变电荷性质增强而增高;土壤吸附有机酸后对Cu2 的次级吸附不同于有机酸与铜共存时的竞争吸附,且因土壤性质表现迥异。这些结果意味着在存在有机酸配体的根际环境中,恒电荷土壤与可变电荷土壤对Cu2 的吸附明显不同,并将影响重金属离子在根际的转化与有效性     

珍稀树种香果树的利用价值及实用繁殖技术

香果树是我国特有单种属珍稀阔叶树种,属国家Ⅱ级重点保护野生植物,具有较高的推广价值。结合生产实践经验和目前有关科研进展,综合论述了香果树的开发利用价值以及关键培育技术,为开发利用香果树提供了科学理论基础。     

饲料棕榈酸/(EPA+DHA)对大黄鱼抗氧化能力和肌肉品质的影响

为探究饲料中棕榈酸/(二十碳五烯酸+二十二碳六烯酸)(EPA+DHA)对大黄鱼(Larmichthys crocea) [初始体重为(30.51±0.16) g]抗氧化能力和肌肉品质的影响,本研究以鱼粉和豆粕为主要蛋白源,EPA富含油、DHA富含油、棕榈酸和卵磷脂为主要脂肪源,分别配制棕榈酸/(EPA+DHA)比例分别为1∶5、1∶1和5∶1的3种等氮(约43%粗蛋白)、等脂(约11%粗脂肪)饲料,并分别命名为P0、P50和P100组,在海水浮式网箱中进行为期70 d的摄食生长实验,从肌肉基本指标与分子基因层面探究饲料对大黄鱼抗氧化能力与肌肉品质的影响。结果显示,P0和P50组大黄鱼肌肉具有显著高的硬度、粘附性、内聚性和咀嚼性(P<0.05)。P0组大黄鱼肌肉多不饱和脂肪酸显著高于P50和P100组(P<0.05);P100组肌肉饱和脂肪酸显著高于P0和P50组(P<0.05)。P100组大黄鱼肌肉超氧化物歧化酶2基因(SOD2)和过氧化氢酶基因(CAT)表达水平显著高于P0和P50组(P<0.05);P0组肌肉核因子E2相关因子基因(Nrf2)表达水平则显著高于P50组(P<0.05),P100和P0组、P100和P50组间相比无显著差异(P>0.05)。对于超氧化物歧化酶1基因(SOD1),P0、P50和P100组相比均无显著差异(P>0.05)。P50组大黄鱼肌肉的总抗氧化能力(T-AOC)显著低于P0和P100组(P<0.05),P0、P50和P100组大黄鱼肌肉的总超氧化物歧化酶(T-SOD)、CAT活性及丙二醛(MDA)含量相比均无显著差异(P>0.05)。研究表明,饲料中棕榈酸含量较高时,大黄鱼肌肉质构特性降低,抗氧化能力没有受到显著影响;在饲料棕榈酸/(EPA+DHA)值发生改变时,大黄鱼肌肉品质的变化与鱼体内氧化应激和抗氧化能力之间的关联仍需进一步探究。     

鸡粪沼液复合微生物有机肥在温室樱桃番茄上的应用效果研究

为了探讨鸡粪沼液复合微生物有机肥在樱桃番茄上的田间应用效果,在滴灌施肥的条件下,设置化肥和液体复合微生物有机肥两个处理进行对比应用,结果表明施用液体复合微生物有机肥的处理其单果重可提高39.69％,含糖量可提高11.94％,茎粗可提高8.76％,Vc含量可提高5.72％,产量可提高30.95％,节约成本1.32％,可有...     

Changes in the microbial community structure in soils treated with a mixture of glucose and peptone with reference to the respiratory quinone profile

Based on the respiratory quinone profile, changes in the structure of microbial communities in the soil samples from Nagoya University Farm were monitored after the treatment with 1% of a mixture of glucose and peptone. Samples of two soils differing in the fertilization history were examined: CF-soil with the application of only chemical fertilizers and FYM-soil with the application of only farmyard manure at a high rate. In the CF-soil, the amount of water-soluble organic carbon (WOC), indicator of the mixture of glucose and peptone, decreased to the original level after 14 d. After 7 d, the soil pH reached the maximum level, then decreased gradually. Changes in the inorganic nitrogen levels in the water extract also reflected the 14-d period of mineralization. The amount of respiratory quinones reached maximum levels after 7 d and gradually decreased, reflecting the changes in the microbial biomass. The quinone composition significantly changed during the 14-d period and returned to a profile similar to the original one after 28 d. Diversity of quinones significantly decreased during the 14-d period due to the predominance of ubiquinone with 9 isoprenoid units. In the FYM-soil, the amount of WOC decreased to the original level after 1 d, and the pH and inorganic nitrogen levels in the water extract reflected the one-day mineralization period, and nitrification started after 3 d. Although the amount of quinones indicated an increase in the microbial biomass for 14 d, the quinone composition did not change. These findings suggested that long-term application of farmyard manure resulted in stable microbial communities in response to the incorporation of organic matter in soil.