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.     

不同遮荫强度对几种苗木生长的影响

以黄金榕、花斑垂叶榕、乳斑榕的苗木为试验材料，来探讨不同遮荫强度苗木生长、水份利用及苗木生长环境的影响，试验表明：一层遮荫网处理的苗木比无遮荫网和二层遮荫网处理的苗木在株高、冠幅、根径以及叶片数目等方面均增长较快，苗木的地下部分、叶和茎含水量均较低。无遮荫处理利用较多水分，以及土壤温度在14：00点左右的时间明显高于所有的遮荫处理。     

不同放牧强度对滩羊生产性能影响的研究

为寻找适宜宁夏盐池县草地的放牧强度,于2003年5-11月在该县四墩子试点设5个处理(0.45、0.60、1.75、1.05和1.50只/hm2)进行轮牧,轮牧周期为42 d,共放牧154 d。结果表明:1)滩羊采食量随放牧强度的加重而降低。同一放牧强度下,随放牧时间推移,采食量先逐渐增大而后下降。2)在试验期内,不同放牧强度下,滩羊体重随时间推移总体上都呈增加趋势。在10月2日之后体重开始出现分化。与放牧强度重的处理相比,放牧强度轻的处理日增重峰值较高,持续时间较长。3)滩羊个体增重与放牧强度之间存在着强的负相关;单位草地面积(1 hm2)增重与放牧强度之间呈强的正相关,初步可以确定在该类草地上放牧强度应在0.75只/hm2左右。4)随着放牧强度的加重,饲料报酬先增大后减小。在同一放牧强度下,饲料报酬随时间的推移先升高后降低。5)当放牧强度超过0.75只/hm2以后,滩羊出现了空怀、产羔率降低和推迟怀孕的现象。6)综合考虑各研究指标,该类草地放牧强度以不应超过0.75只/hm2为宜。     

Application of acoustic Doppler current profiler combined with a scientific echo sounder for krill Euphausia pacifica density estimation

ABSTRACT:   An application of the acoustic Doppler current profiler (ADCP, 153.6 kHz) in combination with a scientific echo sounder (EK60, 38 and 200 kHz) was investigated to estimate the density of krill Euphausia pacifica . The acoustic backscattering strength from sound scattering layers was compared with biomass estimates from midwater trawls. Euphausia pacifica was targeted among mixed species populations in the sound scattering layer in the offshore Funka Bay area of Hokkaido, Japan. The frequency characteristics of acoustic backscattering by krill were calculated using a distorted wave Born approximation scattering model at three frequencies. Krill aggregations identified from the EK60 data were extracted as the mean volume backscattering strength difference between two frequencies. They were then used to identify similar aggregations in the ADCP data by matching observation times and depths for the two methods, which were applied simultaneously. Results from the comparison of the mean volume backscattering strength and the density calculated from the ADCP and EK60 showed that ADCP can be used to measure density and spatial–temporal distribution of krill aggregations. Current speed and direction at the study site were found to be 16.1 cm/s and 187.0°, respectively, and krill speed and direction (including the current component) were found to be 19.8 cm/s and 172.2°, respectively. Based on the ADCP data, the net speed and direction of the krill aggregations were found to be 5.9 cm/s and 128.0°, respectively.     

放牧系统的稳定性与载畜量的研究

本文研究了具有不同消费函数的放牧系统的稳定性,并确定出相应的系统的安全容纳量和最大容纳量。本文中有些结论改进并推广了Noy—Mcir于1976年得到的关于载畜量的有关结论。     

运动磁场具有电场的特性——电磁关系之一(英文)

综合经典电磁学中关于电与磁联系的基本实验定律及理论 ,经推导和分析得出电场与磁场的联系是 :运动磁场具有或表现出电场的特性 ,当一个具有磁感应强度为 B的场 ,以速度 V运动时 ,这个场的电场强度为 :E=B× VB。磁场的时变必然是由于磁场的运动所至 ,而运动的磁场具有电场的性质 ,因此所谓时变磁场产生电场只不过是运动磁场具有电场特性这一自然规律在特定条件下的一种表现。经典电磁学中把磁场分为静磁场和时变磁场是不合理的。因为与静止相应的是运动而不是时变。磁场的时变和磁场的电特性是伴生关系 ,而非因果关系 ,它们都是磁场运动的结果。所以时变磁场产生电场或者 Faraday- L enz定律不是一个普适的自然规律。但在有些条件下 ,运动磁场和其电场特性之间在数量上确实满足 Faraday- L enz定律 ,因此 ,作为一个从实验中总结出的规律 ,并有一定的理论根据 ,它可以在一些领域中作为数学工具用     

红豆草茬地放牧结合补饲青干草对草地羔羊育肥效果的研究

1986～1987年期间在甘肃农大牧草站进行了以红豆草茬地放牧结合补饲青干草对草地羔羊育肥效果的试验。比较了在放牧基础上3种补饲处理(即单燕麦草、单红豆草和燕麦+红豆草混合干草)对两种类型羔羊(即甘肃高山细毛羊和边甘杂种一代羔羊)增重和肉用性能的影响。试验结果表明,7月龄边甘杂种羔羊或9月龄甘高羔羊的期末活重均已超过35公斤,胴体重超过17公斤,屠宰率为47％～49％。     

我国价格体系改革趋势初探

本文以我国国民经济系统与河南省经济子系统的同构性为基础,利用河南省1987年投入产出表,计算出诺依曼最优生产强度和与之相应的最优价格,进而对照现行价格,提出了我国价格体系改革走向的基本构想,并对其合理性、可行性进行了初步研究。     

浅谈建立郑州市道路路面养护管理系统

路面管理系统是通过对路面运行状况、使用性能、使用周期、进行对比、分析，预测路面管理的最佳养护预算投资并在最佳养护经济投资条件等各种因素限制下，寻求道路养护管理最佳战略决策。     

自由放养下绵羊的营养参数

根据绵羊的营养参数和饲养标准,结合日增重水平,计算了不同日增重水平对应的体重月平均动态及其所对应的粗蛋白日需要量和代谢能日需要量。不同日增重水平,达到生长期望所需要的日数不同,日增重水平越高,达到生长期望总所需要的粗蛋白和代谢能越少,但月平均的日需要量越多。自由放养的东北细毛羊当年生羔羊的日增重水平仅相当于舍饲饲养日增重的100g水平,根据代谢能计算,年总需干草340kg,可以作为计算载畜量的基本参数。自由放养情况下,即使能量满足需要,粗蛋白也短缺。当年生羔羊日增重在150￣200g,9￣10月龄内体重达到46￣50kg是北方草地家畜生产的理想目标,通过补饲可以实现。