消逝中的艾比湖

位于新疆西部阿拉山口的艾比湖，半个世纪前曾有２３条河流注入，面积１２００平方公里，贮水量３０亿立方米。主要由于大规模的农业开发，引水剧增，现绝大多数河流均已断流，仅有两条河流注入艾比湖，湖面积缩为５３０平方公里，贮水量减至７亿立方米。近７００平方公里的湖底盐漠，已经成为中国最西部的一个巨大的沙尘暴策源地。１．湖区植被呈衰败状态，近６０％的荒漠植被已经死亡。２．艾比湖湖水退缩后留下的湖底盐漠。３．大风将沙尘吹走后留下的大片砾石戈壁。消逝中的艾比湖@沈孝辉     

滇西北4个高原湖泊演变特征及其驱动因子

基于纳帕海、属都湖、碧塔海和剑湖4个高原湖泊矢量数据,利用Arc Map 10、Fragstats 3.3、Excel等软件,系统分析了1955~2012年4个高原湖泊水域面积和形状的时空演变规律及其驱动因子。结果表明,(1)湖泊时空演变规律各异。纳帕海水域面积和形状复杂程度都处于无规律的波动变化过程中。属都湖水域面积和形状复杂程度1955~1994年都处于增加状态,1994~2011年保持不变。碧塔海水域面积和形状复杂程度没有发生变化。剑湖水域面积1957~2012年呈减少趋势,形状复杂程度呈增加趋势。(2)时空变化程度各不相同。4个高原湖泊时空变化程度从大到小的排序为纳帕海﹥剑湖﹥属都湖﹥碧塔海。(3)演变驱动因子不尽一致。纳帕海的驱动因子主要为疏浚落水洞、建闸控水、泥沙淤积、改造河道、气候变化、湖水污染和旅游干扰。剑湖的驱动因子主要为疏浚河道、泥沙淤积、湖滩开发、建闸控水、气候变化和湖水污染。属都湖的驱动因子主要为筑坝蓄水。人为干扰和气候变化没有导致碧塔海湖泊的变化。(4)受人为干扰程度有差异。4个高原湖泊受人为干扰程度由重到轻的排序为纳帕海﹥剑湖﹥属都湖﹥碧塔海。     

天鹅湖子湖治理对地表水环境影响的研究

通过对天鹅湖子湖进行底泥疏浚、污染控制等方面的治理,对清淤前后湖泊水文情势变化进行了分析,根据雨季、旱季监测的入湖水质以及分散处理设施的处理效率,对治理后湖泊水质进行了达标分析。根据全年入湖径流水量水质、湖水现状水量水质研究了分散处理设施处理达标可行性。     

艾比湖湿地资源评价及保护利用

新疆艾比湖湿地国家级自然保护区,位于新疆维吾尔自治区博乐市东北部,距博乐市40公里,地跨精河县、博乐市和阿拉山口口岸区,地处东经82°36’－83°50’,北纬44°37’～45°15’,面积2670．85平方公里。艾比湖地势低洼,是准噶尔西部最低洼地,以艾比湖湖体为核心（包括湖滨地带）形成的湿地共5500平方公里。     

走进新疆艾比湖湿地国家级自然保护区

新疆艾比湖湿地国家级自然保护区位于我国两北部边陲,地处大西洋两风气流的主要通道——阿拉山口,总面积26．71万公顷（400．62万亩）,其中：水域面积8．76万公顷（131．36万亩）;林地面积15．60万公顷（234．11万市）;草地面积6553．33公顷（9．83万亩）;各类湿地面积占保护区总面积的45．5％。艾比湖是新疆准噶尔盆地西南缘最低洼地和水盐汇集中心,是新疆最大的咸水湖,     

谈艾比湖地区生态现状及治理对策

艾比湖地区荒漠植被、生态环境近半个世纪以来的变迁,引起了人们的普遍关注。现就艾比湖地区生态现状及治理对策,谈点粗浅的看法。1　生态现状艾比湖位于准噶尔盆地东南缘,其东面与古尔班通古特大沙漠相连接,是准噶尔盆地的汇水中心。本文所述艾比湖地区是指艾比湖及沿湖四周的湖滨地带。解放初期,艾比湖面积1200km2,生长在湖周围的基本处于原始状态的大片胡杨、红柳、梭梭等植物形成了约2000km2的湖滨生态区。在过去相当长的一个时期,由于人们对保护荒漠林的意义缺乏认识,乱砍滥挖,无度樵采,尤其是毁林开垦,致使大面积荒漠林破坏殆尽,地面…     

滇西北高原湖泊剑湖时空演变规律及驱动机制

利用ERDAS IMAGINE 9.2处理1957、1974、1989、1990、2001、2006、2011和2012年8个年代的航空和卫星影像,ArcMap 10处理剑湖演变矢量数据和栅格数据,Fragstats 3.3计算景观指数值,Excel统计景观指数值,采取图、文、表相结合的方法,分析了1957~2012年剑湖水域面积和形状的时空演变规律,同时从驱动因素、驱动方向、驱动速度和驱动过程4个方面分析了剑湖水域演变的驱动机制。结果表明:(1)面积和形状时空演变规律。在1957~2012年的55年间,剑湖水域面积呈随着时间变化而逐年减少的趋势,其形状呈随着时间变化而日渐复杂的趋势。(2)驱动机制。驱动因素对剑湖萎缩的作用按其作用大小从大到小的排序,在1983年以前是疏浚河道→泥沙淤积→湖滩开发→湖水污染,在1983年以后是泥沙淤积→湖滩开发→湖水污染;剑湖入湖河流入湖口和出湖河流出湖口周围是剑湖萎缩的主要驱动方向,而带着大量泥沙入湖的金龙河入湖口周围是剑湖萎缩的最主要驱动方向;在1957~2012年7个时段中,驱动速度从大到小的排序是1990-2001年→1957~1974年→2006~2011年→1989~1990年→2001~2006年→2011~2012年→1974~1989年;1957~2012年7个时段形成了不同驱动速度导致的剑湖水域逐渐萎缩而进程不同的驱动过程。     

松花湖水源涵养林经营生态区的划分及其组织经营

松花湖水源涵养林面积辽阔,跨蛟河、永吉、桦甸三县和吉林市郊区的11个乡。位于第二松花江中游。总土地面积412,273公顷。森林复被率为59.1％。在幅员总面积中,林业用地297,366公顷,占72.1％;农业用地42,264公顷,占10.3％;水域38,754公顷,占9.4％;其他用地只占少量。湖区森林,是松花湖外围屏障。它控制水土流失,调节入湖水量,对延长水库的使用寿命发挥着重要作用。松花湖年平均入湖水量为140亿立方米,年淤泥量为525万立方米,仍然     

赛里木湖湖面升高探因

美丽的新疆有许多著名的大小湖泊，犹如碧色的珠宝镶嵌在大漠戈壁之上，哺育着生机盎然的绿洲。但在短短的二、三十年间，罗布泊、台特玛湖、艾丁湖、玛纳斯湖……消失了；艾比湖、博斯腾湖、乌伦古湖……萎缩了。然而却有一个湖在不断扩大，湖面在不断升高，那就是被称为天山明珠的赛里水湖。赛里木湖位于博乐市西南部，距博乐市80km左右，南临伊犁地区，湖东南沿岸有著名的312国道（乌伊公路段）经过，是北疆各地区进入伊犁地区必经2路。安里木湖，豪8语叫“雷里木淖尔”，意为“山脊梁上的湖”。名乐西长约30km，南北宽约24km，水域面积4…     

新疆阿勒泰西部地区水域面积时序变化分析

指出了近年来,许多学者提出中国西北特别是新疆地区气候由暖干向暖湿转型的观点。西北干旱、半干旱区湖泊及其流域的生态环境变化倍受关注,针对这些问题,选用2000～2013年7、8、9月份的Landsat TM/ETM+/OLI多期遥感影像,采用“综合分析法”对阿勒泰西部地区水域面积时序变化进行了动态分析,从自然因素和人类活动两个方面分析了引起该地区水域面积变化的主要因素。结果表明:阿勒泰西部的水域面积2000～2005年水域面积略微下降,2005年后逐年增长,这一变化与该区域的人类活动和气候变化的影响关系密切。     

Growth of Phlebiopsis gigantea in wood of seven conifer species

Heterobasidion parviporum and Heterobasidion annosum are widely distributed root‐rot fungi that infect conifers throughout Europe. Infection of conifer stumps by spores of these pathogens can be controlled by treating fresh stumps with a competing non‐pathogenic fungus, Phlebiopsis gigantea. In this study, growth of three Latvian strains of P. gigantea and the biological control agent ‘Rotstop’ strain was evaluated in stem pieces of Norway spruce, Scots pine, lodgepole pine, Douglas‐fir, Weymouth pine, Siberian larch and Sitka spruce. The growth rates of one H. parviporum and one H. annosum isolate were also measured in the same stem pieces. The growth rate of P. gigantea varied greatly in wood of different conifer species. It was higher in the three pine species, lower in Norway spruce and lowest in Sitka spruce and Siberian larch, and in Douglas‐fir, this fungus did not grow. The largest area of wood occupied by P. gigantea was in lodgepole pine. Growth of Latvian isolates of P. gigantea in the wood of Pinus and Picea species was comparable to that of the Rotstop isolate. Consequently, stump treatment with local P. gigantea isolates should be recommended. However, our results suggest that Douglas‐fir stump treatment against Heterobasidion by P. gigantea may be ineffective and other stump treatment methods should be considered.     

Growth of Mixed Birch-Coniferous Stands in Relation to Pure Coniferous Stands at Similar Sites in South-eastern Norway

Mean age, mean and top heights and yield were studied in 20 mixed stands of birch ( Betula pubescens Ehrh. and B. pendula Roth) and Picea abies (L.) Karst. and nine mixed stands of birch and Pinus sylvestris L. in south-eastern Norway. Each mixed stand and the adjacent pure coniferous stand (control) were growing under the same site conditions and had not been commercially thinned. There were no significant differences in mean age at breast height or in top heights between birch and conifers in the mixed stands, while mean height was significantly higher for birch than for spruce. A growth index was calculated based on total volume and age at breast height. For the spruce sites the growth in young mixed stands (birch < 17 m) was superior to that of pure spruce, while the difference was insignificant in older stands. The growth index correlated positively with the ratio between generatively and vegetatively regenerated birch trees, and negatively with the age of the oldest species in the mixture and with site quality. For the pine sites there was no significant difference in the growth index between mixed birch-pine and pure pine stands. A mixture effect of birch on the volume yield of spruce or pine could not be demonstrated.     

Defoliation by the Needle-shortening Pine Gall Midge,Thecodiplosis brachyntera,on Pines in Central Sweden

An outbreak of the needle-shortening pine gall midge, Thecodiplosis brachyntera , occurred on Scots pine, Pinus sylvestris (L.) and lodgepole pine, P. contorta (Dougl.) in central Sweden during 1995-1998. The larval feeding of T. brachyntera kills current-year needles and heavy infestation causes severe defoliation. A pattern of fluctuating defoliation among years and sites was found on both pine species. Defoliation was evenly distributed in the crown of P. sylvestris during years of high as well as low infestation; apical whorls had as much defoliation as basal whorls. In P. contorta , however, there was a tendency for defoliation to be concentrated on branches in the most apical whorls. Growth ring increments on P. sylvestris with high levels of defoliation (71%) did not differ from trees with moderate levels (26%) of defoliation. Shoot lengths were significantly shorter, however, on heavily infested trees the year after defoliation.     

Decomposition and nutrient loss from prunings of different contour hedgerow species in tea plantations in the sloping highlands of Sri Lanka

Contour hedgerows of multipurpose tree species in the sloping tea lands of Sri Lanka are expected to reduce soil erosion and also add significant amounts of plant nutrients to the soil via periodic prunings. The objective of this experiment was to characterize the biomass decomposition pattern and quantify the amount of nutrients added through prunings of six tree species (Calliandra calothyrsus, Senna spectabilis, Euphatorium innulifolium, Flemingia congesta, Gliricidia sepium and Tithonia diversifolia) currently being used in hedgerows associated with tea. Withered leaf and stem prunings (50 g) were enclosed in 2-mm litter bags, placed at 5-cm depth and retrieved after one, three, six, nine and 12 weeks. Loss of initial dry weight, N, P and K was measured. Single exponential decay function adequately described both dry weight and nutrient loss. Tree species differed significantly in their rate of breakdown with decomposition constants (k) varying from 0.0299 to 0.2006 week⁻¹ for leaves and from 0.0225 to 0.0633 week⁻¹ for stems. Gliricidia showed the highest k for leaves with the rest in the following descending order: Senna > Tithonia ≥ Euphatorium > Calliandra > Flemingia. A similar pattern was observed for loss of all nutrients with Calliandra and Flemingia always having lower k values than the rest. Although N immobilization was not observed, immobilization of P and K was observed during the first week of incubation in some species, particularly in stem prunings. Annual biomass of prunings differed significantly between tree species in the following descending order: Calliandra > Senna > Flemingia > Tithonia > Gliricidia > Euphatorium. Calliandra added the greatest amount of nutrients annually to the soil with Euphatorium adding the least. Calliandra prunings provided the annual total K requirement and 49% of the N requirement of mature tea. However, none of the species provided more than 5% of the P requirement. It is concluded that among the tree species tested, Calliandra and Flemingia are the most suitable for contour hedgerows in tea plantations of this agroclimatic region because of their higher soil nutrient enrichment capacity and slower decomposition rates which would minimize leaching losses. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effects of Seed Weight and Seed Type on Early Seedling Growth of Pinus sylvestris under Harsh and Optimal Conditions

The effects of seed weight and seed type on seedling growth of Pinus sylvestris (L.) were studied by seeding individually weighed orchard and stand seed in different mixtures under harsh (direct seeding in field) and optimal (seeding in nursery) conditions. In the nursery experiment an increase in the seed weight from 3 to 7 mg increased the seedling height by 10-27% and total weight by 27-113%, and decreased the height/diameter ratio by 5-6% after 2 yrs. With elimination of seed weight effects, orchard seedlings were 2% taller than stand seedlings in year 2. Without elimination of seed weight effects, orchard seedlings were 7-13% taller. In the field experiment an increase in the seed weight from 3 to 7 mg increased seedling height by 18-65%, stem volume by 81-274% and the number of top-buds by 23-34% in year 5. After elimination of seed weight effects, orchard seedlings were 7-13% taller than stand seedlings and without elimination of seed weight effects 20-21% taller after 5 yrs. Even after elimination of both seed weight and genetic effects orchard seedlings were 3-9% larger than stand seedlings in the field experiment. In conclusion, the influence of seed weight and seed type on growth traits and slenderness is highly significant and the influence seems to be greater in harsh conditions.     

Modelling of adequate pretwist for obtaining straight timber

Abstract

Wood in general and wooden studs in particular are often distorted owing to uneven shrinkage during the drying process in the sawmill. Twist is often the most detrimental of all types of distortion, and it is caused by spiral grain in combination with variations in moisture content. For sawmills, the objective is to produce dried, straight boards, and one method of dealing with boards with excessive spiral grain is to sort them out and then dry them in a pretwisted position to obtain straight boards after drying. A model using the finite element (FE) method for the simulation of drying twist distortions was first calibrated against laboratory experiments in which boards were dried with and without restraints and pretwists. After the calibration, the FE results were compared with industrial test results for boards that were dried without restraints or with restraints with zero pretwist, i.e. straight restraints. The FE model used an elastic–ideally plastic material model to obtain permanent deformations. The calibration was to set the yield stresses so that there was a good match between FE results and results from the laboratory experiments. The comparison between the industrial test results and the FE results showed that the FE model is capable of realistic simulations of drying boards with and without restraints and presumably also pretwists.     

Potential to harness superior nutritional qualities of exotic baobabs if local adaptation can be conferred through grafting

Baobab leaves form an important part of the local diet in Sahel countries and elsewhere in Africa. Existing leaf nutritional data and agroforestry performance information are based solely on Adansonia digitata L., the baobab of continental Africa. The introduction potential of Adansonia species from the center of diversity in Madagascar and from Australia remains untapped. To assess this potential, the mineral contents and B₁ and B₂ vitamin levels of dried baobab leaves were determined for five-year old trees of A. digitata, A. gibbosa (A. Cunn.) Guymer ex D. Baum, A. rubrostipa Jum. & H. Perrier (syn. A. fony Baill.), A. perrieri Capuron and A. za Baill. grown in an introduction trial in Mali. Nutritional data were evaluated against survival and vigor to identify promising germplasm. Leaf vitamin and crude protein contents were highest in the Madagascar species, especially A. rubrostipa (B₁ 88 mg 100 g⁻¹, B₂ 187 mg 100 g⁻¹, protein 20.7% dry weight). However, the local species far outperformed the introductions in survival, tree height, basal diameter and resistance to termites. We suggest grafting as a way of harnessing the vigor of well-adapted local baobab varieties to the superior nutritional profiles of A. rubrostipa and others. Cross-species grafting tests in Adansonia were successful, thus creating new agroforestry possibilities with different scion/rootstock combinations.     

Biogeochemical impacts of clearfelling and reforestation on blanket-peatland streams: II. major ions and dissolved organic carbon

Streams and drains in blanket-peatland forest in western Ireland were sampled weekly over 5 years, 1996–2000, using continuous, depth-proportional passive sampling. Analysis was for pH, alkalinity by Gran titration, anions by IC, metals by ICP, aluminium speciation by loaded-resin exchange, and dissolved organic carbon (DOC) by absorbance at 320 nm.

Effects of felling are identified graphically from two forest drains whose catchments (both about 1 ha) were clearfelled, and partial clearfelling of one larger catchment (somewhat over 1 km²), in summer 1999. Calcium concentrations and alkalinity were increased in the drain- and streamwater from the felled areas. The pH was increased in drains, while in the larger stream, pH range decreased while the mean increased. Phosphorus increased markedly with clearfell, in the absence of recent fertilising, and also increased with fertilising; these results are reported in an accompanying paper. Ammonium-nitrogen concentrations were increased in the two drains with felling, and temporarily decreased in the larger stream. Nitrate increased in some cases. Potassium and manganese concentrations also increased. Concentrations of DOC and organic monomeric aluminium increased gradually, subject to a continuing strong annual cycle. There were no clearfelling effects on concentrations of solphate, suspended solids or inorganic monomeric aluminium. In the two drains (fully clearfelled), concentrations of sodium, chloride and magnesium, and conductivity, were all reduced after felling. Fertilising effects other than for phosphorus were indistinct.

Effects of the combined clearfell–reforestation treatment were testable statistically, using randomised intervention analysis, between two larger streams (1 km²) as a treatment–control comparison. There were statistically significant positive responses in streamwater concentrations of nitrate, potassium, calcium, DOC and aluminium fractions. The implications for management practice depend on whether the loss of nutrients is sustainable for future crop productivity, and whether critical limits and loads of receiving ecosystems are exceeded.     

Effect of Drought on Growth and Mortality of Actively Growing Norway Spruce Container Seedlings Planted in Summer

Survival, root egress and height growth of 13-month-old actively growing Norway spruce ( Picea abies (L.) Karst.) container seedlings exposed to preplanting drying treatments (0, 4, and 8 days) and postplanting drought periods (1, 2, 3, and 4 weeks) were studied in the field between 5 July and 18 August 1999. The mortality of seedlings increased and the height growth and root egress decreased throughout the postplanting drought period. Postplanting performance was also affected by preplanting drying treatments. The results indicate that no risk of excessive mortality and growth restrictions occurs when actively growing seedlings are planted in summer, provided that seedlings are well watered before planting and the drought period does not exceed 3 weeks.     

Rehabilitation of diseased cacao fields in Peru through shade regulation and timing of biocontrol measures

The objective of this case study was to test the effectiveness of biocontrol for the rehabilitation of abandoned, diseased (moniliasis, witches' broom and black pod) cocoa and to develop testable hypotheses regarding the effect of shade and biocontrol timing. Three trial fields differed in their shade regimes. Biocontrol was administered starting either at flowering or pod filling. Disease incidence and yield were compared with cultural control alone. Biocontrol reduced moniliasis from 49% to 25%, independent of the shading regime and application time. Witches' broom was most severe without shade and unaffected by biocontrol. No significant effects on black pod were observed. Although biocontrol increased percentage healthy fruit independent of shading and timing, only the shaded plot with biocontrol from flowering onwards responded with increased yield. Our hypothesis is: 'In the rehabilitation of abandoned cacao, only fields under sustainable shade management and early onset of biocontrol can realise their production potential.' This revised version was published online in June 2006 with corrections to the Cover Date.