Biological and ecological characteristics ofTamarix L. and its effect on the ecological environment

Through studying biological and ecological characteristics ofTamarix L., we found wide adaptability to different ecological environment and high endurance of adversity. When planted in the edge of desert and periphery of oasis,Tamarix will act as excellent sand-fixing shrubs, improve ecological environment and play a positive role. However, introducingTamarix unreasonably will deteriorate the ecological environment and reduce biodiversity and play a negative role. Grasping the biological and ecological characteristics ofTamarix will do much to benefit further developing and utilizing of the resources

     

Quantification of methane emission from bacterial mat sites at Quepos Slide offshore Costa Rica

Seafloor methane emission from the Quepos Slide on the submarine segment of the Costa Rica fore-arc margin was estimated by extrapolating flux measurements from individual seeps to the total area covered by bacterial mats. This approach is based on the combination of detailed mapping to determine the abundance of seeps and the application of a numerical model to estimate the amount of benthic methane fluxes. Model results suggest that the majority of the studied seeps transport rather limited amount of methane (on average: ~177 μmol cm^?2 a^?1) into the water column due to moderate upward advection, allowing for intense anaerobic oxidation of methane (AOM; on average: 53 % of the methane flux is consumed). Depth-integrated AOM rates (56–1,538 μmol CH₄ cm^?2 a^?1) are comparable with values reported from other active seep sites. The overall amount of dissolved methane released into the water column from the entire area covered by bacterial mats on the Quepos Slide is estimated to be about 0.28 × 10⁶ mol a^?1. This conservative estimate which relies on rather accurate determinations of seafloor methane fluxes emphasizes the potential importance of submarine slides as sites of natural methane seepage; however, at present the global extent of methane seepage from submarine slides is largely unknown.     

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Astronomical identification of the C3H radical

The C3H radical, a linear carbon chain with a 2 pi electronic ground state, has been identified in the millimeter-wave spectra of two astronomical sources, IRC +10216 and TMC-1, and conclusively confirmed (accompanying Letter) in a laboratory glow discharge. In IRC +10216 four rotational transitions have been observed, three in the lower fine-structure ladder (2 pi 1/2) and one in the upper (2 pi 3/2), each a resolved or partially resolved lambda-doublet. In TMC-1, both lambda components of the lowest lying 3/2 --> 1/2 transition of the 2 pi 1/2 ladder have been observed, each with well-resolved hfs. In IRC +10216 the excitation of C3H is similar to that of SiCC: the rotational temperature Trot within the 2 pi 1/2 ladder is low (8.5 K), owing to rapid radiative decay, while Trot across the ladders is high (approximately 52 K) because interconnecting far-IR radiative transitions are only weakly permitted. The column density of C3H in IRC +10216 averaged over the estimated source diameter of 84" is 2.8 x 10(13) cm-2, an order of magnitude less than that of C2H and C4H. A determination of the spectroscopic constraints of C3H that permitted the entire radio spectrum of this molecule to be calculated to high accuracy has been derived from analysis of the combined astronomical and laboratory data presented in the accompanying Letter.     

基于等价分析法评估溢油事故的自然资源损害

尽管国际公约和许多国家立法已将海上溢油事故导致的自然资源损失列入索赔范围,然而,在量化和货币化损害以及确定索赔和修复范围等方面尚未建立被广泛接受的计算方法。生境等价分析(Habitat Equivalency Analysis,HEA)和资源等价分析(Resource Equivalency Analysis,REA)是美国和欧盟应用于评估自然资源损害的理论方法,二者的关键假设是受损的生态服务损失和修复计划的服务收益应当相等。HEA结果依赖于生态服务价值标尺选择、服务价值水平、恢复曲线形状、修复计划时长以及贴现率等;REA结果受死亡生物数量和年龄组成的影响。HEA和REA的非货币形式结果补偿的并非生态环境,而是人类社会福祉。目前,一些货币化损失的方法已被提出,然而传统经济学家和生态经济学家之间存在争议。美国部分法庭承认HEA和REA方法,其结果为法庭索赔提供数据支持。如果将生态学和经济学原理结合考虑,将能够促进等价分析法的深入发展,推动索赔工作更加有理有据。     

Seepage of methane at Jaco Scar,a slide caused by seamount subduction offshore Costa Rica

Methane (CH₄) concentrations and CH₄ stable carbon isotopic composition ( \( \delta^{13} {\text{C}}_{{{\text{CH}}_{4} }} \) ) were investigated in the water column within Jaco Scar. It is one of several scars formed by massive slides resulting from the subduction of seamounts offshore Costa Rica, a process that can open up structural and stratigraphical pathways for migrating CH₄. The release of large amounts of CH₄ into the adjacent water column was discovered at the outcropping lowermost sedimentary sequence of the hanging wall in the northwest corner of Jaco Scar, where concentrations reached up to 1,500 nmol L^?1. There CH₄-rich fluids seeping from the sedimentary sequence stimulate both growth and activity of a dense chemosynthetic community. Additional point sources supplying CH₄ at lower concentrations were identified in density layers above and below the main plume from light carbon isotope ratios. The injected CH₄ is most likely a mixture of microbial and thermogenic CH₄ as suggested by \( \delta^{13} {\text{C}}_{{{\text{CH}}_{4} }} \) values between ?50 and ?62 ‰ Vienna Pee Dee Belemnite. This CH₄ spreads along isopycnal surfaces throughout the whole area of the scar, and the concentrations decrease due to mixing with ocean water and microbial oxidation. The supply of CH₄ appears to be persistent as repeatedly high CH₄ concentrations were found within the scar over 6 years. The maximum CH₄ concentration and average excess CH₄ concentration at Jaco Scar indicate that CH₄ seepage from scars might be as significant as seepage from other tectonic structures in the marine realm. Hence, taking into account the global abundance of scars, such structures might constitute a substantial, hitherto unconsidered contribution to natural CH₄ sources at the seafloor.     

The origin of deep buried channels of Elsterian age in Northwest Germany

Buried channels cut to a depth of over 100m into the underlying substratum of North Germany are almost exclusively of Elsterian age. Evaluation of geophysical well logs in the Hamburg area for the first time allows the construction of detailed longitudinal and transverse profiles. It can be shown that an apparently chaotic infill known from borehole records in some cases is actually a regular sedimentary sequence, fining from proximal to distal. Channel formation seems to have been the result of catastrophic meltwater release in the marginal parts of the ice sheet. The channel infill reflects these episodic outbursts of meltwater. During deglaciation, the channel remnants became infilled with fine sediments. The channels ceased to exist as morphologically detectable forms at the end of the Holsteinian Stage.     

中国云南小江流域泥石流暴发与ENSO的关联性

选取典型泥石流发育区云南小江流域为研究对象,利用典型泥石流沟滇北小江流域蒋家沟的长期观测资料,分析了小江流域泥石流暴发与该流域邻近的沾益及会泽常规气象站夏季（6—8月）降水的关系,以及小江流域及其周边地区夏季降水与ENSO的关系。结果表明,蒋家沟泥石流暴发的次数与夏季降水量有显著的正相关关系,而夏季降水和前期的Nino3区海表温度（SST）呈显著的负相关;每年泥石流发生的次数与首场泥石流发生的早晚关系密切,而激发首场泥石流的降水量与冬春Nino3区SST呈负相关;泥石流暴发次数与大雨日数关系密切,而大雨日数与Nino3区SST具有较好的对应关系。这说明冬春季Nino3区SST对小江流域泥石流的暴发次数有显著的影响,形成了ENSO与小江流域及蒋家沟泥石流发生的关联性。分析结果亦表明,Nino3区1月SST与当年蒋家沟泥石流次数具有显著的负相关关系,El Ni?o位相年泥石流少发而La Ni?a位相年泥石流多发。Nino3区SST变化最少要超前泥石流暴发4个月,因而ENSO可以为云南北部泥石流的预测预报提供一种指标信息,从而有可能利用ENSO冬季信息来预测小江流域及其周边地区（滇北）当年夏季泥石流活动。     

Marginal revenue of land and total factor productivity in Chinese agriculture: Evidence from spatial analysis

This paper attempts to explore the temporal and spatial nature of the marginal revenue of land, total factor productivity (TFP) change and its three components: technical change (TC), technical efficiency change (TEC) and scale efficiency change (SEC) as seen in Chinese agricultural production from 1995 to 1999. Based on county-level data, the study utilized both stochastic frontier and mapping analyses methods. The results show that growth in the marginal revenue of land was diverse across various regions, where most gain occurred in eastern coastal zone, while loss was in Northwest and North China. China has experienced moderate decreases in annual TFP change (-0.26%) with considerable regional variations. Specifically, the administrative intervention in grain production and the deterioration of the agricultural technology diffusion system led to a moderate drop in annual TFP change. County-level mapping analyses took into account interregional variances in TFP and its components. Regarding components of TFP, TEC differences explain the majority of regional dispersions in TFP. As developed areas in China, the Huang-Huai-Hai region and the Beijing-Tianjin-Tangshan economic zone face the challenges of land conversion and grain security amidst the process of urbanization.