北移区木薯品种产量特征的相关分析

通过分析北移区99个木薯品种的指标特征,提出了决定产量的关键指标,为北移区木薯育种和品种引进提供依据,结果表明:13个指标中以单株茎叶鲜重、单薯鲜重和单株薯鲜重的变异系数较大,而茎径、干物质率和薯径变异系数略小。相关分析表明:薯长、单薯鲜重和收获指数与鲜薯产量呈极显著线性正相关,而茎径、薯径、单株茎叶鲜重、单株薯鲜重和生物产量与鲜薯产量呈极显著抛物线正相关,达到最高鲜薯产量时,茎径3.92 cm、薯径5.56 cm、单株茎叶鲜重4.16 kg、单株鲜薯重4.76 kg和生物产量104.53 t/hm2。通径分析表明:单薯鲜重和单株茎叶鲜重对产量的直接作用较大,而株高和生物产量对产量的直接作用较小。因此,薯长、薯径、茎径、单薯鲜重、收获指数、单株茎叶鲜重、单株薯鲜重和生物产量是决定北移木薯产量的主要指标。

北移区木薯种质耐寒性初步评价

以75份木薯种质资源为试验材料,在田间自然低温条件下观察记载不同木薯种质茎叶受寒害程度及等级,并分析了木薯各农艺性状与寒害等级的相关性,以期为筛选出适宜北移区的耐寒性木薯种质提供理论依据。结果表明:经过自然低温天气后,木薯种质出现了不同程度的寒害症状。75份木薯种质寒害可分为5个等级,1~5级的品系数量分别为11、14、30、11和9个,其中SC205、GR4、NZ199等11份种质受寒害程度最低,表现出强耐寒性,而SC8、TG58、B716等9份种质受寒害程度最高,表现为低温敏感型。相关分析得出,木薯寒害等级与株高呈显著正相关,而与其他农艺性状无显著相关性。

Changing Spatial and Structural Patterns of Non-agricultural Activities in Outward-moving Beijing Urban Fringe

As responses to metropolitan suburbanization and rural urbanization,the formation and evolution of urban fringes should be understood against the background of overall economic development and spatial reconstruction of entire metropolises.At the same time,however,endogenous interactions between industrial structure and spatial patterns of non-agricultural activities are also worthy of scholarly attention.Since the 1980s,studies on urban fringes in China have been restricted by the lack of micro-level data.This paper investigates the spatial expansion and structural evolution of the urban fringe by taking the case of Beijing and uses systematic firm-level data in 1996 and 2001 from the National Census of Basic Units.The diversity of distribution patterns across industrial sectors brings about two interrelated results.On the one hand,structural adjustment of non-agricultural industries promotes the expansion and spatial evolution of the urban fringe.On the other hand,the stability and dynamics of industrial structure coexist in the moving urban fringe.This study also reveals that the outward-moving urban fringe is the optimal location for manufacturing,especially heavy manufacturing,as well as traditional producer and consumer services.However,industries with spatial stickiness such as tourism and sports have not moved with the fringe.Most advanced services remain concentrated in the city center.The authors argue that it is essential for understanding and managing urban fringes to take into account spatial evolution and industrial structural adjustment together with their interaction with each other.

Restudy of the storage and migration model of the Quaternary groundwater in Beijing Plain area

Through a wide-spread groundwater sampling mainly at nested monitoring wells in the Beijing Plain area, combined with data collection, the study analyzes water level, hydrochemistry, temperature, tritium, deuterium, 180, 14C and other aspects, and in- dicates that there exits an obvious stratification phenomenon of the groundwater in the alluvial plain area down in the middle part of alluvial-pluvial fans, and the hydraulic connection between layers is very weak. The analysis of the tritium concentra- tion suggests that the average influence depth of the modem precipitation is approximately 120 m. Based on the analysis of the 22 paleowater samples through the D-~80 method and 14C isotopic dating, the deep groundwater circulation in the fine sedi- ments area of Beijing Plain down in the fringe part of alluvial-pluvial fans is relatively slow. On average the paleowater point occurs approximately below the 180 m at these points. The main reasons for the formation of stratification and paleowater points are the water-blocking effect of the clay type strata and the compaction effect during the sedimentary process, especially the differential compaction, which could form closed or relatively closed stagnant aquifers. Groundwater in this kind of stagnant aquifers to some degree belongs to non-renewable resource, and should be reconsidered and re-arranged in the water resources management strategy.

Vertical displacement loading tides and self-attraction and loading tides in the Bohai, Yellow, and East China Seas

The loading tides are calculated by means of the Green's function method based on a high-resolution regional ocean tide model, the TOPO7.0 global ocean tide model, and the Gutenberg-Bullen A Earth model. The results show that the maximal amplitude of M2 vertical displacement loading (VDL) tide in the Bohai, Yellow, and East China Seas exceeding 28mm appears 150km off the Zhejiang coast; the second maximum exceeding 20mm appears in Inchon Bay; and the third maximum exceeding 14mm is located in the northeast of the North Yellow Sea. The maximal amplitudes of S2 VDL tide at the above three locations exceed 10, 8, and 4mm, respectively. The maximal amplitudes of the K1 and O1 VDL tides, exceeding 13 and 10 mm respectively, appear near the central and north Ryukyu Islands; the amplitudes tend to decease toward the inward areas. The phases of semidiurnal VDL tides are basically opposite to those of corresponding ocean tides. The phases of diurnal VDL tides are basically opposite to those of corresponding ocean tides in the most part of the East China Sea and the eastern part of the South Yellow Sea. This anti-phase relationship generally does not hold in the rest parts of the Bohai and Yellow Seas. The distribution patterns of self-attraction and loading (SAL) tides are very similar to those of VDL tides. The SAL tides have amplitudes about 1.2-1.7 times of the corresponding VDL tides and their phases are basically opposite to the corresponding VDL tides. The maximal amplitude of M2 SAL tide also appears off the Zhejiang coast, with a magnitude exceeding 42mm.