鄱阳湖沙山单叶蔓荆(Vitex rotundifolia)叶性状沿沙化梯度变化特征

在鄱阳湖湖滨沙山沿沙化梯度测定了单叶蔓荆(Vitex rotundifolia)叶面积、比叶面积、叶氮、叶磷等指标,以阐明单叶蔓荆主要叶性状特征,探讨叶性状对沙化程度的响应。结果表明:单叶蔓荆叶面积1.58~13.14cm~2,与湖岸线距离没有显著相关性,不能指示沙化程度对单叶蔓荆的影响。比叶面积81.6~206.3cm~2·g~(-1),种内差异显著(P0.05);单位质量的叶氮、磷含量分别为16.0~23.2mg·g~(-1)、0.82~2.20mg·g~(-1),种内差异不显著。比叶面积与叶片氮含量显著正相关(P0.05),与叶片磷含量无显著相关性。比叶面积对沙化梯度响应敏感,随沙化程度的增加而降低;叶片氮、磷含量及其化学计量比值对沙化程度的变化不敏感,保持了相对稳定性。依据叶片氮磷比值判断,单叶蔓荆在沙山生境中更多地受磷的限制。     

不同生境下三种荒漠植物叶片及土壤C、N、P的化学计量特征

以新疆地区三种典型荒漠植物梭梭、多枝柽柳和沙拐枣为研究对象,分别研究其不同生境(塔克拉玛干沙漠腹地塔中植物园—植物园,古尔班通古特沙漠明渠免灌林—免灌林,以及各自的原生生境—原始生境)下三种植物叶片和土壤的生态化学计量特征,每个处理5个重复。研究结果显示:土壤C、N、P含量在不同生境中的分布趋势相似,均表现为柽柳原生地和植物园较高,其他三者相对较低(P0.05)。然而C∶N和C∶P在柽柳原生地中最大,植物园、免灌林和梭梭原生地次之,而沙拐枣原生地最小。N∶P在不同生境中不存在显著差异(P0.05),这说明N和P含量在不同生境中的变化是一致的,即干旱区土壤保持了相对较为稳定的N∶P。三种植物叶片C含量存在一定差异,总体表现为沙拐枣最高,其次为柽柳,梭梭相对较小(P0.05),然而,植物叶片的N、P含量主要受物种影响,生境对植物叶片N、P含量影响不显著,叶片N∶P均值为15.91±0.68,介于14和16之间,说明该区三种植物生长受N和P共同限制,然而N∶P在不同生境及不同物种的协同作用下不存在显著差异(P0.05),说明干旱区的这三种植物叶片在不同生境中具有相对较为恒定的N∶P。这也进一步说明了这三种植物叶片的N∶P不随生境土壤N、P含量的变化而变化,即就是这三种漠植物具有相对较高的内稳性机制,进而使其具备了较强的适应极端环境(干旱,贫瘠,盐碱)的能力。     

内蒙古赤峰市油松人工林植物和土壤C、N、P生态化学计量特征

基于野外实测数据和文献资料数据,对内蒙古赤峰市喀喇沁旗西南部的旺业甸实验林场进行了不同林龄油松人工林各组分的C、N、P生态化学计量特征分析,为油松人工林的可持续经营和固碳潜力的提升提供科学依据。结果表明:油松人工林叶C、N、P含量分别为511. 41 mg/g,10. 24 mg/g,1. 23 mg/g,总体表现出在幼龄林时C、N含量低,P含量高;随着林龄的增大P含量降低,C、N含量增高。在幼龄林时叶C∶N最大为61. 38,叶C∶P和N∶P最小分别为385. 78和6. 28;随着林龄增大C∶N先减小后增大,C∶P和N∶P先增大后减小,而所有N∶P均小于14,判断该地区油松人工林生长主要受N的限制。土壤C、N、P含量均随土层深度增加逐渐降低,土壤C、N、P的平均含量分别为4. 92 mg/g,0. 47 mg/g,0. 27 mg/g。土壤表层C含量在幼龄林时最小,随着林龄的增加逐渐增高并在近熟林时达到最大值,N、P含量在幼龄林时最大;随着林龄的增加逐渐减小。土壤C、N、P的供应量对叶C、N、P含量存在一定影响,土壤C、N、P含量在不同土层间的相关性较强。     

科尔沁沙地不同生境植物及叶片的C、N元素计量特征

为了研究科尔沁沙地植物及叶片的C、N元素在沙丘固定过程中的化学计量差异及变化规律,在流动沙丘、半固定沙丘、固定沙丘、草地4种生境上分别采集整株植物样品和叶片样品,测定其C、N元素含量,并在群落水平和功能型水平上展开分析。结果表明:(1)随着沙丘的固定,植物群落及群落叶片的C含量逐渐上升而N含量逐渐下降,且C含量的变异系数较N含量小;(2)各生境植物及叶片C、N含量表现为灌木一年生植物、C3植物C4植物、豆科植物非豆科植物,各功能型植物的C、N含量正相关于其叶片的C、N含量;(3)沿沙丘固定梯度,一年生、C4与非豆科植物及其叶片C含量趋于上升,而一年生、多年生、C3、非豆科植物及其叶片N含量趋于下降。沙丘固定过程中群落C含量的变化主要源于一年生、C4、非豆科植物,而N含量的下降则受草本、C3、非豆科植物的共同影响。适当补植灌木、C3植物、豆科植物对于该地区的固C效率和生物固N以及改良土壤肥力会起到积极作用。     

中亚热带杉木人工老龄林林下植被叶片碳氮磷化学计量特征

以福建省三明市莘口教学林场小湖工区杉木人工老龄林林下87种植物为研究对象,比较不同功能群植物叶片碳氮磷化学计量特征,分析植物各叶片碳氮磷含量。结果显示:杉木人工老龄林林下87种植被叶片C、N、P的平均含量分别为447.45、18.14和0.71 mg·g-1,叶片C∶N、C∶P及N∶P比值分别为26.56、704.94和27.10,不同生活型植物的C、N、P含量均存在显著差异,C∶P和N∶P在不同生活型植物间不存在显著差异,相关分析表明植物的叶片C∶N、C∶P都与相应的N、P含量呈现极显著负相关性(P0.01),而叶片N含量与P含量的变化并不相关。以上研究结果表明,受外部环境的影响,中亚热带杉木人工植被植物对养分元素的利用效率显著低于全国陆地植物的平均水平,不同科和不同生活型功能群植物对环境的适应能力显著不同,表现出显著的养分适应策略差异性。     

秦岭山区沟渠植物和土壤CNP生态化学计量特征

探究山区城市沟渠湿地环境中植物与土壤中CNP生态化学计量特征,对于揭示植物对营养元素的吸收、净化以及植物对环境的适应与反馈能力,指导沟渠植被恢复重建和山区城市规划具有十分重要的意义。在秦岭山区的商洛市三条沟渠中测定了植物多样性及主要植物根、叶、土壤的C、N、P含量。结果显示:秦岭山区城市沟渠土壤C与全国平均水平相当,N含量高于而P元素含量远低于全国的平均水平,表现出沟渠土壤养分元素含量的不平衡。自然植被叶片C、N、P的平均含量分别为384.13(±19.35)、24.65(±7.64)和1.62(±0.53)mg/g,叶的元素含量显著高于根和土壤;C∶N、C∶P及N∶P分别为17.06(±7.20)、256.49(±78.59)、16.05(±5.85)。C∶N和C∶P之比低于全国平均水平,说明该地区城市沟渠自然植被固C效率低,沟渠植物的生长受到P限制。土壤与植物的N含量存在显著的正相关关系(P0.05),而C、P、C∶N、C∶P、N∶P间的相关性并不显著(P0.05),表明土壤的N含量影响植物体中的含量,同时土壤含量也受到植物凋落物的影响。植物对元素的吸收利用显著影响着土壤-植被间元素的相互作用和再分配模式。     

亚热带常绿阔叶林8种樟科树种细根化学计量特征

为了研究亚热带常绿阔叶林樟科树种的细根化学计量特征,以福建省建瓯市万木林自然保护区天然常绿阔叶林中具有代表性的8种樟科树种(沉水樟Cinnamomum micranthum;浙江桂Cinnamomum chekiangense;黄绒润楠Machilus grijsii;桂北木姜子Litsea subcoriacea;闽楠Phoebe bournei;新木姜子Neolitsea aurata;香樟Cinnamomum camphora;黄毛润楠Machilus chrysotricha)为研究对象,分析细根C、N、P化学计量学特征随序级的变化规律及种间变异情况。结果表明:(1)树种、序级以及二者交互作用对细根C、N、P浓度及C/N、C/P和N/P均具有极显著影响(P0.01)。(2)随序级增加,大部分树种的细根N和P浓度降低,而C/N和C/P比增大;随序级变化的变异系数C浓度最小,而P浓度最大。(3)不同序级的细根C浓度的种间变异系数均最低,而P浓度的则均最高,N/P比的种间变异系数亦低于C/N比和C/P比;不同序级细根的N、P浓度之间均具有显著的正相关。     

不同林龄米槠更新林叶和枝碳氮磷含量及其化学计量特征

在福建顺昌选择21年生、31年生和49年生米槠人工促进天然更新林,测定各个林分叶片和枝条C、N和P的含量,分析其化学生态计量特征。结果表明:1)不同林龄的林分枝和叶C含量的时空变异较小,变化范围在473.0~485.6 mg·g~(-1)之间;N含量随着林龄的增加而呈升高的趋势;而叶片和枝条P含量随林龄变化的趋势不明显;2)不同林龄人工促进天然更新林C∶P平均值为809.5,是中国东部南北样带森林(313.9)和全球森林(300.9)的2.6和2.7倍;N∶P均值为30.1,是中国东部南北样带(11.5)、中国平均(18.0)和全球平均(13.8)的2.6倍、1.7倍和2.2倍。较高的N∶P表明研究区域受P限制,同时人工促进天然更新林较高的C∶P表明该森林能够在低P条件下提高P的利用率,以维持林木的生长。     

荒漠河岸林胡杨养分状况研究

对荒漠河岸林胡杨叶片有机碳(C)、全氮(N)、全磷(P)和全钾(K)等化学组分在生长季不同月份和不同微生境间的变化以及它们彼此间的相关性进行了研究。结果表明,胡杨叶片C,N,P和K的变化范围分别为39.08%～46.16%,0.28%～2.81%,0.05%～0.18%和0.35%～2.03%,平均值依次为43.51%,1.49%,0.102%和1.17%。叶片C/N,C/P和N/P的变化范围分别为16.26～146.61,258.08～908.67和2.89～26.67,平均值依次是37.24,466.27和15.14。叶片平均N含量显著低于全国落叶树平均N含量,P含量与全国落叶树的平均P含量较为接近。胡杨叶片C/N明显高于全球陆生植物的C/N比值;N/P比值说明胡杨生长受到氮和磷元素的共同限制。在生长季,胡杨叶片C、N、P和K含量总体表现为下降趋势,最高值出现在5月,最低值出现在9月;微生境间,C,N,K含量和N/P比值从河岸低地,河岸平地,河岸沙堆,戈壁到沙丘间逐渐升高;C/N趋势恰好相反,P含量没有太明显的变化。叶片C含量与N、K含量均呈极显著正相关,与P含量呈弱正相关,N-K和P-K均呈显著正相关。     

哀牢山森林凋落物与腐殖质及土壤的生态化学计量特征

以哀牢山原生中山湿性常绿阔叶林及其受损后处于恢复演替中的滇南山杨林的凋落物、腐殖质和表层土壤(0~20 cm)作为研究对象,测定不同组分的C、N、P和土壤表层有效养分含量,结果为:C、N含量表现为凋落物腐殖质土壤,P含量则表现为腐殖质土壤凋落物;铵态氮、硝态氮、有效磷含量均为腐殖质表层土壤;凋落物的C与N呈负相关,N与P呈极显著正相关;从不同林型看:凋落物中的C、N、P含量为常绿阔叶林滇山杨林;土壤中的C、N、P含量为常绿阔叶林滇山杨林(p0.05);腐殖质与表层土中的铵态氮、有效磷含量均为常绿阔叶林滇山杨林;常绿阔叶林凋落物、腐殖质、土壤的C∶N∶P分别为615∶18∶1、159∶11∶1、84∶6∶1,滇山杨林凋落物、腐殖质、土壤的C∶N∶P分别为518∶16∶1、172∶11∶1、86∶6∶1。研究结果表明,富含P的腐殖质可能是哀牢山亚热带常绿阔叶林不存在P匮乏的主因,而两种林型各组分的C、N、P比值表明恢复演替中的滇山杨林地上、地下养分循环已经达到相对稳定的水平。     

Statewide Estimates of Undiscovered Deposits of Gold,Silver, Copper,Lead, and Zinc

Estimates of the number of undiscovered deposits on a statewide basis offer a different perspective on the nation's undiscovered resources of gold, silver, copper, lead, and zinc. Mean estimates of the number of undiscovered deposits statewide were extracted from the estimates of undiscovered deposits nationwide. More than 50 undiscovered deposits are estimated to occur in Alaska, Arizona, Nevada, and Wisconsin. Estimating the number of undiscovered deposits statewide serves as a measure of a state's total remaining mineral resources in known conventional deposit types.     

南极研究科学委员会(SCAR)专家组会议

在本届南极地球科学讨论会(1987年8月24—28日)期间及会后,南极研究科学委员会(SCAR)分别举行了南极地质制图学、火山岩地质及岩石学、南方高纬度新生代古环境演化、南极岩石圈结构与演化四个专家组正式会议.由于时间冲突,笔者未能参加古环境会议.制图会议对讨论会上展示并向SCAR提交的图件逐一审议.其中地质图均为小范围大比例尺图,如巴西提交的乔治王岛菲尔德斯半岛地形地质图(1∶1.5万);地球物理方面以航磁图为多;最引人注目的是大面积遥感图,利用卫(航)片经数据处理清晰地反映出地质构造或冰盖结构特征.会议着重讨论了今后几年计划实现的16幅图件(地质6、地球物理6、遥感3、水文1),其中主要有“南极地质全图”(1∶1千万,Tingey主编,“斯科舍弧构造图”(1∶3百万,J.W.Thomson主编),“罗斯海、威得尔海构造及地震剖面图”(比例尺未定,K.Hinz主编),“南极半岛地区地震剖面及地质图”(比例尺未定,C.O.Berbert主编)等.当讨论新遥感图件协调问题时,几家大公司代表就“LANDSAT”、“SPOT”、“AVHRR”等卫星及数据处理性能优劣争论激烈,并都希望由本公司承担这一任务.     

第五届国际南极地球科学讨论会

本届讨论会于8月24—28日在英国剑桥鲁宾逊学院举行,共有23个国家196名代表参加,其中美(54人)、英(51人)、西德(17人)、南非(8人)、意大利(8人)、澳大利亚(8人)、新西兰(8人)、日本(6人)等国代表人数较多.除正式代表以外,尚有许多自由听众(如英国南极局研究生、外国石油公司代表等).会议于24日上午开幕,英地调所长致2分钟简短祝词,会议主席(英南极局地质处主任)用M.Thomson教授作了有关说明,即开始宣读论文.     

Sediment Facies of a Low-Energy, Meso-Tidal, Fringing Reef, Singapore

Pulau (P.) Semakau comprises a narrow, low-lying island, surrounded by a wide fringing coral reef of late-Holocene age. The modern reef flat comprises a gently sloping surface related to modern mean low water neap tide level. Six sediment facies are recognised below the line of high water of which three, adjacent to the island, are composed of terrigenous minerals and rock fragments and three are autochthonous carbonates sediments developed since local sea-level still stand (c. 6,500 years BP). The fringing reefs of P. Semakau and Singapore differ from many of the reef forms recorded from Peninsular Malaysia waters and the Gulf of Thailand. The Singapore reefs have wide, well-developed intertidal reef flats, lack lagoons and reef crests, and have a very steep reef slope. In contrast to most other fringing reefs of the region, the Singapore reefs have developed in a low wave energy, meso-tidal environment lacking strong environmental gradients.     

Estimates of Number of Undiscovered Deposits of Gold,Silver, Copper,Lead, and Zinc in the United States

Estimates of the number of undiscovered deposits offer a unique perspective on the nation's undiscovered mineral resources. As part of the 1998 assessment of undiscovered deposits of gold, silver, copper, lead, and zinc, estimates of the number of deposits were made for 305 of the 447 permissive tracts delineated in 19 assessment regions of the country. By aggregating number of undiscovered deposits by deposit type and by assessment region, a picture of the nation's undiscovered resources has emerged. For the nation as a whole, the mean estimate for the number of undiscovered deposits is 950. There is a 90% chance there are at least 747 undiscovered deposits and a 10% chance there are as many as 1,160 undiscovered deposits. For Alaska, the mean estimate for the number of undiscovered deposits is 281. There is a 90% chance there are at least 168 undiscovered deposits and a 10% chance there are as many as 402 undiscovered deposits. Assuming that the majority of deposits used to create the grade and tonnage models that formed the basis for estimating the number of undiscovered deposits are significant deposits, there remain about as many undiscovered deposits as have already been discovered. Consideration of the number of undiscovered deposits as part of national assessments carried out on a recurring basis serves as a leading indicator of the nation's total mineral resources.     

Annual regime of bedforms, roughness and flow resistance, Lillooet River, British Columbia, BC

A field study to examine the statistical character of dune morphology and the correlation among dune morphology, discharge, and flow resistance was conducted in a meandering reach of Lillooet River, near Pemberton, British Columbia, Canada. The field season spanned the 1995/1996 hydrologic year with sample day discharge events ranging between 33 and 425 m³ s⁻¹. Surveys of the bed morphology along the thalweg in two dune fields (A and B) were completed using an echo sounder with chart recorder that enabled the measurement of more than 4000 dunes. Dune height ranged between 0.08 and 0.96 m, length between 2.01 and 20.99 m, and steepness between 0.02 and 0.10. Histograms of each dune shape (height, length, steepness) sample most often displayed positive skewness and non-Gaussian distributions (Gamma, Beta, and Weibull); median sample height and length histograms displayed positive skewness; and steepness was nearly Gaussian. Histograms of all dimensionless dunes (i.e., measurement divided by average measurement of sample) were Gaussian and slightly leptokurtic. Neither the height nor length of dunes measured in this investigation were successfully predicted by the empirical models of Allen [Allen, J.R.L., 1984. Developments in Sedimentology. Sedimentary Structures: Their Character and Physical Basis, 2nd edn. Elsevier, New York, vol. 30 (A and B), 1256 pp.], Fredsøe [J. Hydraul. Div., Am. Soc. Civ. Eng. 108(HY8) (1982) 932.], or Yalin [J. Hydraul. Div., Am. Soc. Civ. Eng. 90(HY5) (1964) 105.]. Least-squares regression models for dune–height relations produced here are similar to models published by other field researchers; regression models for dune length only conform to those developed elsewhere if the discharge of the study rivers was similar. The energy gradient in dune field A varied within a smaller range than in field B, enabling dune size to become more fully equilibrated with respect to flow environment. Although the average Froude numbers were much less than critical, dunes appeared to wash out towards a plane bed as discharge increased due to a change from a bedload to suspended-load dominated sediment-transport regime. Flow resistance increased most rapidly during changes in base flow and at the beginning and end of the seasonal flood; resistance tended to be smaller in field A than B, reflecting local differences in energy gradient. Flow resistance increased until a dune steepness of 0.070 was attained and then decreased. The steepness value was considered to be coincident with kolk generation [Dyer, K.R., 1986. Coastal and Estuarine Sediment Dynamics. Wiley, NY, 342 pp.], suggesting that macroturbulent flow structures play an important role in defining the roughness of dunes on a channel bed.