The Bear Brook Watershed in Maine: Multi-decadal whole-watershed experimental acidification     

Kaizad F. Patel  Ivan J. Fernandez  Sarah J. Nelson  Stephen A. Norton  Cheryl J. Spencer 《水文研究》2021,35(5):e14147

The Bear Brook Watershed in Maine (BBWM) is a long-term research site established to study the response of forest ecosystem function to environmental disturbances of chronic acidic deposition and ecosystem nitrogen enrichment. Starting in 1989, the West Bear (treated) watershed received bimonthly applications of ammonium sulfate [(NH₄)₂SO₄] fertilizer from above the canopy, whereas East Bear (reference) received ambient deposition. The treatments were stopped in 2016, marking the beginning of the recovery phase. Research at the site has focused on soils, streams, and vegetation. Here, we describe data collected over three decades at the BBWM—input and stream output nutrient fluxes, quantitative soil pits and soil chemistry, and soil temperature and moisture.  相似文献   

Forest operations,tree species composition and decline in rainfall explain runoff changes in the Nacimiento experimental catchments,south central Chile     

Andrés Iroumé  Julia Jones  James C. Bathurst 《水文研究》2021,35(6):e14257

Few long-term studies have explored how intensively managed short rotation forest plantations interact with climate variability. We examine how prolonged severe drought and forest operations affect runoff in 11 experimental catchments on private corporate forest land near Nacimiento in south central Chile over the period 2008–2019. The catchments (7.7–414 ha) contain forest plantations of exotic fast-growing species (Pinus radiata, Eucalyptus spp.) at various stages of growth in a Mediterranean climate (mean long-term annual rainfall = 1381 mm). Since 2010, a drought, unprecedented in recent history, has reduced rainfall at Nacimiento by 20%, relative to the long-term mean. Pre-drought runoff ratios were <0.2 under 8-year-old Eucalyptus; >0.4 under 21-year-old Radiata pine and >0.8 where herbicide treatments had controlled vegetation for 2 years in 38% of the catchment area. Early in the study period, clearcutting of Radiata pine (85%–95% of catchment area) increased streamflow by 150 mm as compared with the year before harvest, while clearcutting and partial cuts of Eucalyptus did not increase streamflow. During 2008–2019, the combination of emerging drought and forestry treatments (replanting with Eucalyptus after clearcutting of Radiata pine and Eucalyptus) reduced streamflow by 400–500 mm, and regeneration of previously herbicide-treated vegetation combined with growth of Eucalyptus plantations reduced streamflow by 1125 mm (87% of mean annual precipitation 2010–2019). These results from one of the most comprehensive forest catchment studies in the world on private industrial forest land indicate that multiple decades of forest management have reduced deep soil moisture reservoirs. This effect has been exacerbated by drought and conversion from Radiata pine to Eucalyptus, apparently largely eliminating subsurface supply to streamflow. The findings reveal tradeoffs between wood production and water supply, provide lessons for adapting forest management to the projected future drier climate in Chile, and underscore the need for continued experimental work in managed forest plantations.  相似文献   

A qualitative and quantitative evaluation of experimental model catchment evolution     

G. R. Hancock  G. R. Willgoose 《水文研究》2003,17(12):2347-2363

Due to the geological time scales required for observation of catchment evolution, surrogates or analogues of field data are necessary to understand long‐term processes. To investigate long‐term catchment behaviour, two experimental model catchments that developed without rigid boundaries under controlled conditions are examined and a qualitative and quantitative analysis of their evolution is presented. Qualitatively, the experimental catchments have the visual appearance of field scale data. Observation demonstrates that changes in catchment shape and network form are conservative. Quantitative analysis suggests that the catchments reach an equilibrium form while a reduction in the channel network occurs. While the catchments are laboratory scale models, the results provide insights into field scale behaviour. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

临沂市开展集体建设用地使用权流转的几点思考          下载免费PDF全文

冯连伟 《山东国土资源》2004,20(6):43-47

结合临沂市几年来开展集体建设用地使用权流转的实践和探索,对开展集体建设用地使用权流转的背景、概念及范围进行了论述。认为在计划经济条件下形成的农民集体所有建设用地使用权不能流转的制度已与当前农村经济,特别是小城镇的建设发展严重不适应,允许集体建设用地使用权流转已势在必行。开展集体建设用地使用权流转对保护土地所有者和失地农民的权益,推动小城镇建设健康发展,规范土地市场具有重要意义。  相似文献   

鄂尔多斯盆地西峰地区长8砂岩微观非均质性的实验分析     

刘林玉  王震亮  柳益群 《岩矿测试》2008,27(1):29-32

通过真实砂岩微观模型实验,客观地分析了鄂尔多斯盆地西峰地区长8砂岩的微观非均质性特征,发现该区长8储层为致密型砂岩,直观地显示出长8砂岩储层具有很强的微观非均质性,砂岩的成岩作用和孔隙结构是影响鄂尔多斯盆地西峰地区长8砂岩储层微观非均质性的主要原因。在低渗透砂岩中,引起砂岩产生强烈的非均质性,而这些砂岩则形成长8砂岩储层的高渗带。  相似文献   

实验条件对X射线衍射物相定量分析结果的影响   总被引：8，自引：6，他引：2  

房俊卓  张霞  徐崇福 《岩矿测试》2008,27(1):60-62

通过实验验证了多物相试样X射线衍射定量分析的基体效应,着重研究了参比强度K值、衍射强度、混合物各物相粒度、X射线管功率等实验条件对物相定量分析结果的影响。结果表明,物相定性分析是定量分析的前提,采用积分强度、使各物相颗粒尽可能细而且均匀、采用较高的X射线管功率以及适合的扫描速率均有利于提高物相X射线衍射定量分析的准确度。  相似文献   

Trace Element Partitioning and Accessory Phase Saturation during H2O-Saturated Melting of Basalt with Implications for Subduction Zone Chemical Fluxes   总被引：2，自引：0，他引：2  

Klimm  Kevin; Blundy  Jon D.; Green  Trevor H. 《Journal of Petrology》2008,49(3):523-553

Experimental phase equilibrium and trace element partitioningdata are reported for H₂O-saturated mid-ocean ridge basalt at2·5 GPa, 750–900°C and oxygen fugacities atthe nickel–nickel oxide buffer. Garnet, omphacite andrutile are present at all temperatures. Amphibole and epidotedisappear as residual phases above 800°C; allanite appearsabove 750°C. The Na–Al-rich silicate glass presentin all run products is likely to have quenched from a supercriticalliquid. Trace element analyses of glasses demonstrate the importantcontrol exerted by residual minerals on liquid chemistry. Inaddition to garnet, which controls heavy rare earth elements(HREE) and Sc, and rutile, which controls Ti, Nb and Ta, allanitebuffers the light REE (LREE; La–Sm) contents of liquidsto relatively low levels and preferentially holds back Th relativeto U. In agreement with previous experimental and metamorphicstudies we propose that residual allanite plays a key role inselectively retaining trace elements in the slab during subduction.Experimental data and analyses of allanite-bearing volcanicrocks are used to derive a model for allanite solubility inliquids as a function of pressure, temperature, anhydrous liquidcomposition and LREE content. The large temperature dependenceof allanite solubility is very similar to that previously determinedfor monazite. Our model, fitted to 48 datapoints, retrievesLREE solubility (in ppm) to within a factor of 1· 40over a pressure range of 0–4 GPa, temperature range of700–1200°C and for liquids with anhydrous SiO₂ contentsof 50–84 wt %. This uncertainty in LREE content is equivalentto a temperature uncertainty of only ± 27°C at 1000K, indicating the potential of allanite as a geothermometer.Silicic liquids from either basaltic or sedimentary protolithswill be saturated in allanite except for Ca-poor protolithsor at very high temperatures. For conventional subduction geothermsthe low solubility of LREE (+ Th) in liquids raises questionsabout the mechanism of LREE + Th transport from slab to wedge.It is suggested either that, locally, temperatures experiencedby the slab are high enough to eliminate allanite in the residueor that substantial volumes of H₂O-rich fluids must pass throughthe mantle wedge prior to melting. The solubility of accessoryphases in fluids derived from subducted rocks can provide importantconstraints on subduction zone thermal structure. KEY WORDS: subduction; experimental petrology; allanite; solubility; supercritical liquid; eclogite  相似文献   

Phase Relations and Melting of Anhydrous K-bearing Eclogite from 1200 to 1600{degrees}C and 3 to 5 GPa     

Spandler  Carl; Yaxley  Greg; Green  David H.; Rosenthal  Anja 《Journal of Petrology》2008,49(4):771-795

To investigate eclogite melting under mantle conditions, wehave performed a series of piston-cylinder experiments usinga homogeneous synthetic starting material (GA2) that is representativeof altered mid-ocean ridge basalt. Experiments were conductedat pressures of 3·0, 4·0 and 5·0 GPa andover a temperature range of 1200–1600°C. The subsolidusmineralogy of GA2 consists of garnet and clinopyroxene withminor quartz–coesite, rutile and feldspar. Solidus temperaturesare located at 1230°C at 3·0 GPa and 1300°C at5·0 GPa, giving a steep solidus slope of 30–40°C/GPa.Melting intervals are in excess of 200°C and increase withpressure up to 5·0 GPa. At 3·0 GPa feldspar, rutileand quartz are residual phases up to 40°C above the solidus,whereas at higher pressures feldspar and rutile are rapidlymelted out above the solidus. Garnet and clinopyroxene are theonly residual phases once melt fractions exceed 20% and garnetis the sole liquidus phase over the investigated pressure range.With increasing melt fraction garnet and clinopyroxene becomeprogressively more Mg-rich, whereas coexisting melts vary fromK-rich dacites at low degrees of melting to basaltic andesitesat high melt fractions. Increasing pressure tends to increasethe jadeite and Ca-eskolaite components in clinopyroxene andenhance the modal proportion of garnet at low melt fractions,which effects a marked reduction in the Al₂O₃ and Na₂O contentof the melt with pressure. In contrast, the TiO₂ and K₂O contentsof the low-degree melts increase with increasing pressure; thusNa₂O and K₂O behave in a contrasted manner as a function ofpressure. Altered oceanic basalt is an important component ofcrust returned to the mantle via plate subduction, so GA2 maybe representative of one of many different mafic lithologiespresent in the upper mantle. During upwelling of heterogeneousmantle domains, these mafic rock-types may undergo extensivemelting at great depths, because of their low solidus temperaturescompared with mantle peridotite. Melt batches may be highlyvariable in composition depending on the composition and degreeof melting of the source, the depth of melting, and the degreeof magma mixing. Some of the eclogite-derived melts may alsoreact with and refertilize surrounding peridotite, which itselfmay partially melt with further upwelling. Such complex magma-genesisconditions may partly explain the wide spectrum of primitivemagma compositions found within oceanic basalt suites. KEY WORDS: eclogite; experimental petrology; mafic magmatism; mantle melting; oceanic basalts  相似文献   

基于霍顿下渗能力曲线的流量过程线连续分割方法研究   总被引：2，自引：0，他引：2  

林凯荣  郭生练  张文华 《水文》2008,28(1):10-14

在用前期影响雨量代替流域蓄水量的基础上,提出了基于霍顿下渗能力曲线的流量过程线的连续分割方法.选择西峡、猴子岩和东湾三个流域的降雨径流资料,采用该方法对流量过程线进行分割,并与现行的数字滤波法、非线性水库法和Boussinesq方程法相比较.结果表明,该方法具有一定的物理基础、符合产汇流基本规律,而且能够减少涨洪段流量过程线分割的主观性,对于流域时段单位线和降雨径流关系的推求均有重要的意义.  相似文献   

厦门湾沉积物中有害有毒甲藻休眠孢囊及塔玛亚历山大藻的潜在危害   总被引：7，自引：0，他引：7  

蓝东兆  方琦  顾海峰  李超 《台湾海峡》2004,23(4):453-457,i005

本工作通过分析厦门湾表层沉积物中的甲藻休眠孢囊，发现了1种有毒塔玛亚历山大藻(Alexandrium tamarense)休眠孢囊，及两种有害甲藻休眠孢囊：锥状斯氏藻(Scrippsiella trochoidea)、具刺膝沟藻(Gonyaulax spinifera)．对塔玛亚历山大藻进行了培养。并初步研究了该藻的毒性及贝类对其毒素的积累．研究结果表明，厦门海域沉积物中的塔玛亚历山犬藻是有毒的．它的较适宜生长环境条件是：水温20～25℃．盐度为25～30，光照度为3000～50001x．塔玛亚历山大藻在每年的4月26日至6月10日、10月11日至11月20日可能会形成有害藻华，危害厦门海域的海洋生物并可能威胁到人类的健康和生命安全．  相似文献