创新工作机制 切实做好城乡一体化暨土储档案管理工作

随着城乡一体化建设的加速推进,如何加强土储档案管理工作是档案工作者要解决的新问题。本文以朝阳区崔各庄乡土储档案工作为例,介绍了土储档案管理工作的经验和做法,供同行借鉴。

2022上半年总结与展望 土地投资篇

2022年上半年,土地市场成交量价同比回落,溢价率指标也较2021年上半年出现了大幅下滑。不仅成交规模不及热度仍然较高的2021年上半年,与同属市场低位的2021年下半年相比,土地成交也显著下跌。上半年以来企业仍然保持谨慎的拿地态势,拿地销售比不足0.2,且有近六成百强房企未拿地。从拿地房企类型来看,与去年下半年保持一致,国企、央企仍是土地市场的主力军,民企几乎隐身,地方平台公司仍旧处于“托底”态势。

基于ABAQUS的半地下LNG储罐振动台试验数值模拟

以半地下LNG储罐振动台试验为依托,基于大型通用有限元软件Abaqus建立整体计算模型,对半埋和只露穹顶两种埋置形式的储罐模型进行了试验工况的数值模拟,并将模拟结果与模型试验结果进行了对比分析。针对半地下LNG储罐动力时程分析法中特有的技术要点进行了阐释,如采用声固耦合法解决液固耦合问题、自由液面的模拟与晃动波高的计算、壳与实体联结的多尺度组合建模问题等。结果表明:考虑储液—结构—土相互作用的计算模型可以较好地模拟加速度响应时程、动力放大效应、液动压力、晃动波高,为发展原型尺度的半地下LNG储罐动力时程分析法提供支撑。同时表明,只露穹顶相较于半埋的情形,储罐结构因其自身刚度相对较大对周围土体地震动具有抑制作用,其自身的振动特性因周围土体的握裹作用而难以发挥,表现为具有环向土体约束的地下结构。

考虑埋深影响的地下LNG罐振动台试验研究

地下LNG罐与地上LNG罐相比,拥有更好的抗震性、更高的安全性等优点,其工程应用是LNG罐结构的发展趋势,目前我国大陆尚无地下LNG罐的应用先例。振动台试验是研究地下LNG罐地震响应的一个重要手段,为考察不同地震动强度、不同液位、不同埋深情况下地下LNG罐的地震响应特性,基于1个结构模型设计并进行了2组层状剪切试验箱的振动台试验。LNG罐模型参照某22万m^(3)LNG罐进行简化,考虑储液与结构、土与结构的动力相互作用关系对储液、结构、土(包括基岩)进行了相似设计。通过试验设计对模型和边界进行了合理的设置,振动台试验考察了不同工况下的地震响应规律,获得了LNG罐结构的动力响应特性。结果表明试验中展现出的储液-结构-土相互作用的部分特征与相近工程实测结果、经典理论具有一致性。

Spatial pattern of soil carbon and nutrient storage at the Alpine tun-dra ecosystem of Changbai Mountain, China

In August 2003, we investigated spatial pattern in soil carbon and nutrients in the Alpine tundra of Changbai Moun-tain, Jilin Province, China. The analytical results showed that the soil C concentrations at different depths were significantly (p<0.05) higher in Meadow alpine tundra vegetation than that in other vegetation types; the soil C (including inorganic carbon) concentrations at layer below 10 cm are significantly (p<0.05) higher than at layer of 1020 cm among the different vegetation types; the spatial distribution of soil N concentration at top surface of 0-10 cm depth was similar to that at 1020 cm; the soil P concentrations at different depths were significantly (p<0.05) lower at Lithic alpine tundra vegetation than that at other vegetation types; soil K concentration was significantly (p<0.05) higher in Felsenmeer alpine tundra vegetation and Lithic alpine tundra vegetation than that in Typical alpine tundra, Meadow alpine tundra, and Swamp alpine tundra vegetations.. However, the soil K had not significant change at different soil depths of each vegetation type. Soil S concentration was dramatically higher in Meadow alpine tundra vegetation than that in other vegetation types. For each vegetation type, the ratios of C: N, C: P, C: K and C: S generally decreased with soil depth. The ratio of C: N was significantly higher at 010 cm than that at 1020 cm for all vegetation types except at the top layer of the Swamp alpine tundra vegetation. Our study showed that soil C and nutrients storage were significantly spatial heterogeneity.

Analysis on Variation of Soil Organic Carbon and Total Nitrogen Content and Carbon Storage in the Oasis Cotton Field of Manas River Valley

Objective] The research aimed to study soil organic carbon and total ni-trogen distribution in oasis cotton farmland. [Method] With the oasis cotton field of Manas River Val ey in Tianshan Mountains as the research area and abandoned farmland as a control, the distribution characteristics of soil organic carbon and total nitrogen content in the cotton field of Manas River Val ey in the last 23 years were investigated by using geographic methods. [Result] Presenting vertical distribution, cotton soil organic carbon and total nitrogen content in Manas River Val ey de-creased with the increase of soil depth, and those in 0-30 cm soil layer was sig-nificantly higher than those in soil layer of below 30 cm, while organic carbon stor-age showed the trend of increase. Also in vertical distribution, soil organic carbon and total nitrogen decreased significantly with the increase of soil depth, and soil organic carbon content in abandoned farmland decreased month by month. Howev-er, cotton soil organic carbon storage firstly decreased and then increased in the oasis cotton field that in the early growth of cotton, soil organic carbon in the layers of 0-30 and 30-100 cm decreased to the lowest in the bloom stage, and then or-ganic carbon increased with the reproductive growth of cotton into the later stages. However, due to no input of plant litter in the abandoned farmland, the soil organic carbon storage decreased month by month. There were significantly differences be-tween oasis cotton field and abandoned farmland in organic carbon contents. [Con-clusion] The soil organic carbon content and total nitrogen content in oasis cotton field were significantly higher than those in the abandoned farmland. The soil organ-ic carbon storage increased in the layer of 0-30 cm, while there was no significant change of soil organic carbon and total nitrogen content in the layer of 30-100 cm, which was consistent with the previous study on the distribution characteristics of soil organic carbon and total nitrogen content profile.

龙湖集团:融资成本下探,财务优势尽显

2021年,龙湖集团全年实现全口径销售金额2901亿元,同比增长7.2%,从销售金额增速来看,高于TOP15房企约1.8%的平均水平,销售增长稳定;拿地销售比达到0.4以上,较为积极;同时,多元化收入贡献持续增加,公司投资性物业收入已超百亿;融资成本进一步下探,财务优势尽显。

并购融资能否助力房企资金纾困

2021年以来,在政策的支持下,并购方面不断传来利好,先有并购贷款不计入“三道红线”的传闻,再有银行发行并购债筹集资金,且与国央企签订并购协议,支持国央企收并购项目,部分民营企业也被纳入到并购融资合作伙伴。对于并购的推进和并购融资的落地,政策的支持是一方面,市场信心的恢复或许是更重要的一方面,只有预期转好,企业才更有可能积极的拿地,在并购市场也能给出让出售方更为接受的价位,并购双方的交易才更有可能成功。

头部房企如何布局拿地

2022年至今,房地产市场深度调整,企业表现出发展信心不足、开发投资力度收缩。在此背景下,选取保利发展、招商蛇口、华润置地、万科、龙湖五家头部代表房企,从投资强度与投资布局两个方面分析探究头部房企投资策略。头部代表房企投资策略,在投资力度方面,量入为出,坚持以销定投进行稳健投资,同时严守投资原则及立项标准,合理分配投资额度。在投资城市选择方面,坚定“区域聚焦、城市深耕”的投资策略,持续做优增量资源,积极布局特色增储项目,一二线城市拓展金额占比明显提升。

行业筑底期,港资房企开始逆势加仓

当前的市场环境对港资房企而言是一个夯实土储,加仓内地的好机会,土地市场的低迷有利于其逆周期操作,但受限于企业自身发展模式和行业预期,港资房企逆周期操作的整体力度也不会太大,目前部分港资房企的动作也验证了这一点。因而,即使港资房企有所加仓,但也只会对部分城市造成一定影响,如在港资房企各自深耕的城市,对于市场整体而言影响较小。对于民营企业撤退所带来的市场空缺,港资房企能够发挥的作用有限,短期内仍需依靠国央企和地方城投企业托底。

Combined influence of sedimentation and vegetation on the soil carbon stocks of a coastal wetland in the Changjiang estuary

Coastal wetlands play an important role in the global carbon cycle. Large quantities of sediment deposited in the Changjiang （Yangtze） estuary by the Changjiang River promote the propagation of coastal wetlands, the expansion of saltmarsh vegetation, and carbon sequestration. In this study, using the Chongming Dongtan Wetland in the Changjiang estuary as the study area, the spatial and temporal distribution of soil organic carbon （SOC） stocks and the influences of sedimentation and vegetation on the SOC stocks of the coastal wetland were examined in 2013. There was sediment accretion in the northern and middle areas of the wetland and in the Phragmites australis marsh in the southern area, and sediment erosion in the Scirpus mariqueter marsh and the bare mudflat in the southem area. More SOC accumulated in sediments of the vegetated marsh than in the bare mudflat. The total organic carbon （TOC） stocks increased in the above-ground biomass from spring to autumn and decreased in winter; in the below-ground biomass, they gradually increased from spring to winter. The TOC stocks were higher in the below-ground biomass than in the above-ground biomass in the P. australis and Spartina alterniflora marshes, but were lower in the below-ground biomass in S. mariqueter marsh. Stocks of SOC showed temporal variation and increased gradually in all transects from spring to winter. The SOC stocks tended to decrease from the high marsh down to the bare mudflat along the three transects in the order： P. australis marsh 〉 S. alterniflora marsh 〉 S. mariqueter marsh 〉 bare mudflat. The SOC stocks of the same vegetation type were higher in the northern and middle transects than in the southern transect. These results suggest that interactions between sedimentation and vegetation regulate the SOC stocks in the coastal wetland in the Changjiang estuary.

Storage and Density of Soil Organic Carbon in Urban Topsoil of Hilly Cities:A Case Study of Chongqing Municipality of China

Rapid urbanization results in the conversion of natural soil to urban soil,and consequently,the storage and density of the soil carbon pools change.Taking Chongqing Municipality of China as a study case,this investigation attempts to better understand soil carbon pools in hilly cities.First,the vegetated areas in the study area were derived from QuickBird images.Then,topsoil data from 220 soil samples(0-20 cm) in the vegetated areas were collected and their soil organic carbon(SOC) densities were analyzed.Using the Kriging interpolation method,the spatial pattern of SOC was estimated.The results show that the SOC density exhibited high spatial variability in the urban topsoil of Chongqing.First,the SOC density in topsoil decreased according to slope in the order 2°-6° < 25°-90° < 0°-2° < 6°-15° < 15°-25°.Second,the newly developed areas during 2001-2010 had a lower SOC density than the areas built before 1988.Third,urban parks and gardens had a higher SOC density in topsoil,residential green land followed,and scattered street green land ranked last.For hilly cities,the variability of terrain affects the distribution of SOC.The Kriging results indicate that Kriging method combining slope with SOC density produced a high level of accuracy.The Kriging results show that the SOC density to the north of the Jialing River was higher than the south.The vegetated areas were estimated to amount to 73.5 km2 across the study area with an SOC storage of 0.192 Tg and an average density of 2.61 kg/m2.

Forest Carbon Storage and Tree Carbon Pool Dynamics under Natural Forest Protection Program in Northeastern China

The Natural Forest Protection(NFP) program is one of the Six Key Forestry Projects which were adopted by the Chinese Government since the 1980s to address important natural issues in China. It advanced to protecting and restoring the structures and functions of the natural forests through sustainable forest management. However, the role of forest carbon storage and tree carbon pool dynamics since the adoption of the NFP remains unknown. To address this knowledge gap, this study calculated forest carbon storage(tree, understory, forest floor and soil) in the forest region of northeastern(NE) China based on National Forest Inventory databases and field investigated databases. For tree biomass, this study utilized an improved method for biomass estimation that converts timber volume to total forest biomass; while for understory, forest floor and soil carbon storage, this study utilized forest type-specific mean carbon densities multiplied by their areas in the region. Results showed that the tree carbon pool under the NFP in NE China functioned as a carbon sink from 1998 to 2008, with an increase of 6.3 Tg C/yr, which was mainly sequestrated by natural forests(5.1 Tg C/yr). At the same time, plantations also acted as a carbon sink, reflecting an increase of 1.2 Tg C/yr. In 2008, total carbon storage in forests covered by the NFP in NE China was 4603.8 Tg C, of which 4393.3 Tg C was stored in natural forests and 210.5 Tg C in planted forests. Soil was the largest carbon storage component, contributing 69.5%–77.8% of total carbon storage; followed by tree and forest floor, accounting for 16.3%–23.0% and 5.0%–6.5% of total carbon storage, respectively. Understory carbon pool ranged from 1.9 to 42.7 Tg C, accounting for only 0.9% of total carbon storage.

Storage and Spatial Variation of Phosphorus in Paddy Soils of China

Due to the growing concern about the agricultural phosphorus (P) losses pollution, an in-depth understanding of P in paddy soils of China would be helpful in providing a national perspective of the environmental impact of P cycling and fertility on China's farms. In this study, we evaluated the P storage and the P density of paddy soils in China, characterized the spatial variations of P among the subgroups of paddy soils and soil regions in China, and evaluated the P data using GIS-based analysis, which included a newly compiled 1:1 000 000 digital soil map of China, and using 1 490 soil profiles. The available and total P densities of paddy soils were 6.7 and 698.5 g m -3 , respectively. Overall in China, the total P storage within 1 m of paddy soils was estimated to be 330.2 Tg. The P density of paddy soils varied substantially with subgroups due to the different soil water regimes such as groundwater table and soil drainage. The P availability in paddy soils, especially in surface layer, was higher in high temperature and precipitation areas. Further research is needed to examine more anthropogenic impact factors, such as increasing use of chemical fertilizer.

Relative Susceptibility of Four Coleopteran Stored-product Insects to Diatomaceous Earth SilicoSec

Laboratory bioassays were conducted to evaluate the insecticidal effect of diatomaceous earth （DE）, SilicoSec against Callosobruchus maculatus （F.）, Rhyzopertha dominica （F.）, Sitophilus zeamais （Motschulsky）, and Tribolium castaneum （Herbst） in cowpea, maize and wheat, at 25-32 ℃ and 54-68% relative humidity （r.h.）. SilicoSec was applied at rates： 0 （untreated control） 250, 500, 750 and 1,000 mg/kg of commodity. Adult mortality was measured after 3 to14 days of exposure. Progeny production was assessed after 40 or 56 days. The tested species varied in sensitivity to SilicoSec, with S. zeamais being most susceptible, but no significant differences in mortality levels observed between R. dominica, C. maculatus or T, castaneum after three days of exposure. After 5 days of exposure, all C. maculates adults died on cowpea treated at 1,000 mg/kg. Similarly, after 14 days of exposure all adults of the other species died on grains treated at 1,000 mg/kg, and were ranked in decreasing order of susceptibility S. zeamais 〉T castaneurn 〉 R. dominica. SilicoSec treatments suppressed progeny production （30 to 100%） in all the tested species. The implications of these findings to DE-based control strategy are discussed.

Hydrogen storage performances of as-milled REMg_(11)Ni(RE=Y, Sm) alloys catalyzed by MoS_2

To compare the hydrogen storage performances of as-milled REMg11Ni-5MoS2(mass fraction)(RE=Y,Sm)alloys,which were catalyzed by MoS2,the corresponding alloys were prepared.The hydrogen storage performaces of these alloys were measured by various methods,such as XRD,TEM,automatic Sievert apparatus,TG and DSC.The results reveal that both of the as-milled alloys exhibit a nanocrystalline and amorphous structure.The RE=Y alloy shows a larger hydrogen absorption capacity,faster hydriding rate,lower initial hydrogen desorption temperature,superior hydrogen desorption property,and lower hydrogen desorption activation energy,which is thought to be the reason of its better hydrogen storage kinetics,as compared with RE=Sm alloy.

Comparison on Soil Carbon Stocks Between Urban and Suburban Topsoil in Beijing, China

The urban population and urbanized land in China have both increased markedly since the 1980 s. Urban and suburban developments have grown at unprecedented rates with unknown consequences for ecosystem functions. In particular, the effect of rapid urbanization on the storage of soil carbon has not been studied extensively. In this study, we compared the soil carbon stocks of different land use types in Beijing Municipality. We collected 490 top-soil samples(top 20 cm) from urban and suburban sites within the Sixth Ring Road of Beijing, which cover approximately 2400 km2, and the densities of soil organic carbon(SOC), soil inorganic carbon(SIC), and total carbon(TC) were analyzed to determine the spatial distribution of urban and suburban soil carbon characteristics across seven land use types. The results revealed significant differences in soil carbon densities among land use types. Additionally, urban soil had significantly higher SOC and SIC densities than suburban soil did, and suburban shelterbelts and productive plantations had lower SIC densities than the other land use types. The comparison of coefficients of variance(CVs) showed that carbon content of urban topsoil had a lower variability than that of suburban topsoil. Further findings revealed that soil carbon storage increased with built-up age. Urban soil built up for more than 20 years had higher densities of SOC, SIC and TC than both urban soil with less than 10 years and suburban soil. Correlation analyses indicated the existence of a significantly negative correlation between the SOC, SIC, and TC densities of urban soil and the distance to the urban core, and the distance variable alone explained 23.3% of the variation of SIC density and 13.8% of the variation of TC density. These results indicate that SOC and SIC accumulate in the urban topsoil under green space as a result of the conversion of agricultural land to urban land due to the urbanization in Beijing.

Research on the Soil Carbon Storage of Alpine Grassland under Different Land Uses in Qinghai-Tibet Plateau

In this article, we mainly analysis the soil carbon storage of the alpine grassland under different land uses in Qinghai-Tibet Plateau. The samples of this investigation include six experimental fields which are fenced mowing grassland, artificial grassland, winter and spring grazing meadowland, summer and autumn mild grazing land, summer and autumn moderate grazing pasture and summer and autumn severe grazing land and seven soil layers included 0 cm-5 cm, 5 cm-10 cm, 10 cm-20 cm, 20 cm-30 cm, 30 cm-50 cm, 50 cm-70 cm and 70 cm-100 cm. The results show that the soil carbon storage in different soil layers will gradually reduce and the difference was remarkable （P 〈 0.05）. What is more, the soil carbon storage of alpine grassland under different land uses has following sequence： winter and spring grazing grassland 〉 summer and autumn mild grazing land 〉 artificial grassland 〉 summer and autumn moderate grazing meadowland 〉 summer and autumn severe grazing pasture 〉 fenced mowing meadow, and the significant difference between them is remarkable （P 〈 0.05）.

Ecosystem service delivery in Karst landscapes： anthropogenic perturbation and recovery

Covering extensive parts of China, Karst landscapes are exceptional because rapid and intensive land use change has caused severe ecosystem degradation within only the last 50 years. The twentieth century intensification in food production through agriculture has led to a rapid deterioration of soil quality, evidenced in reduced crop production and rapid loss of soil. In many areas, a tipping point appears to have been passed as basement rock is exposed and 'rocky desertification' dominates. Through the establishment of the "Soil processes and ecological services in the karst critical zone of SW China"(SPECTRA)Critical Zone Observatory(CZO) we will endevaour to understand the fundmental processes involved in soil production and erosion, and investigate the integrated geophysical-geochemical-ecological responses of the CZ to perturbations. The CZ spans a gradient from undisturbed natural vegetation through human perturbed landscapes.We seek to understand the importance of heterogeneity insurface and below-ground morphology and flow pathways in determining the spatial distribution of key stocks(soil,C, vegetation, etc.) and their control on ecosystem service delivery. We will assess the extent to which the highly heterogeneous critical zone resources can be restored to enable sustainable delivery of ecosystem services. This paper presents the CZO design and initial assessment of soil and soil organic carbon stocks and evidence for their stability based on caesium-137(^(137) Cs) data.

Soil Organic Carbon and Nutrients along an Alpine Grassland Transect across Northern Tibet

Soil carbon and nutrient contents and their importance in advancing our understanding of biogeochemical cycling in terrestrial ecosystem, has motivated ecologists to find their spatial patterns in various geographical area. Few studies have focused on changes in the physical and chemical properties of soils at high altitudes. Our aim was to identify the spatial distribution of soil physical and chemical properties in cold and arid climatic region. We also tried to explore relationship between soil organic carbon （SOC） and total nitrogen （TN）, total phosphorus （TP）, available nitrogen （AN）, available phosphorus （AP）, soil particle size distribution （PSD）. Samples were collected at 44 sites along a 300 km transect across the alpine grassland of northern Tibet. The study results showed that grassland type was the main factor influencing SOC, TN and TP distribution along the Gangdise Mountain-Shenzha-Shuanghu Transect. SOC, TN and TP contents were significantly higher in alpine meadow than alpine steppe ecosystems. SOC, TN, TP and AN contents in two soil layers （0-15 cm and 15-3o cm） showed no significant differences, while AP content in top soft （0-15 cm） was significantly higher than that in sub-top soil （15-30cm）. SOC content was correlated positively with TN and TP content （r = 0.901and 0.510, respectively）. No correlations were detected for clay content and fractal dimension of particle size distribution （D）. Our study results indicated the effects of vegetation on soil C, N and P seem to be more important than that of rocks itself along latitude gradient on the northern Tibetan Plateau. However, we did not found similar impacts of vegetation on soil properties in depth. Inaddition, this study also provided an interesting contribution to the global data pool on soil carbon stocks.