Habitat factors affecting the distribution and abundance of the spinous loach <Emphasis Type="Italic">Cobitis shikokuensis</Emphasis> in southwestern Japan

We examined habitat factors related to the distribution and abundance of the spinous loach Cobitis shikokuensis, an endangered benthic fish, in the Shigenobu River system, southwestern Japan. In the study river, the spinous loach was distributed widely along the main stem, from headwater to near the mouth, whereas it was rarely found in tributary streams. Classification tree analysis showed that the presence/absence of spinous loach was explained by a combination of percent pebble and length of river fragment between artificial barriers. Spinous loach incidence was high in sites with abundant pebble (>27.7%), but low in sites with short river fragment (≤0.97 km) even if pebbles were abundant. A regression tree model for loach density retained only percent pebble as a single best predictor, with sites with higher percent pebble (>40.4%) having higher density. These results suggest that substrate condition is an important factor determining the distribution and abundance of spinous loach and also that habitat fragmentation by artificial barriers has great potential to threaten the spinous loach population in this river. Considering the highly fragmented situation of the study river and prevention of upstream migration by barriers, we conclude that maintenance of suitable habitats in upper reaches has high priority for conservation of the spinous loach.     

A new species of the genus <Emphasis Type="Italic">Balitora</Emphasis> (Teleostei: Balitoridae) from Guangxi,China

A new species of the hillstream loach genus Balitora Gray, Balitora ludongensis, from Qilong River which drains to Zuojiang River (a headwater of the Pearl River) drainage, Jingxi County, Guangxi, China. It can be distinguished from its congeners by the following characters: pectoral fin with vi–vii, 11–12 rays; pelvic fin with ii, 6–7 rays; pre-oral groove relatively shallow, upper lip without or with 3–5 fold-like papillae in a row on its middle surface and gradually smooth to the corner of mouth; two maxillary barbels at each corner of mouth, the outer one slightly longer than the inner one, 149.0–190.9% of eye diameter; eyes small, eye diameter 14.2–18.1% of head length; Dorsal-fin origin slightly anterior to pelvic-fin origin; Caudal-peduncle depth 39.1–55.0% of its length; upper lobe of caudal fin longer than the lower one; lateral-line scales 69–74; with 6–9 black blotches on the dorsal side of body.     

Subcellular distribution of aluminum, bismuth, cadmium, chromium, copper, iron, manganese, nickel, and lead in cultivated mushrooms (Agaricus bisporus and Pleurotus ostreatus)

In this work, the distribution of nine metals in two types of cultivated mushroom had been investigated. For Agaricus bisporus, the biomass was separated into caps and stalks, and for Pleurotus ostreatus, the entire mushrooms were taken for analysis. Electrothermal atomic absorption spectrometry was used for total element determination in acid digests. For accuracy checking, the certified reference material (NIST 1571, citrus leaves) was analyzed. The results obtained for the two fungi species were within the ranges of concentration reported previously by other authors. Subcellular fractionation was accomplished by centrifugation of cell homogenates, which has been suspended in Tris-HCl buffer. In the first centrifugation (7300g, 4°C, 10 min), cell walls were separated (pellet I), and the second centrifugation (147,000g, 4°C, 60 min) yielded mixed membrane fraction (pellet II) and cytosol (supernatant II). Recoveries of the fractionation procedure were in the range 70–100% (with the exception of Fe). For all elements studied, the highest relative contributions were found in cytosol fractions of the fruiting bodies (63–72%, 49–76%, 44–93%, 26–87pc, 55–85%, 50–68%, 41–78%, 39–78%, 54–67% respectively for Al, Bi, Cd, Cr, Cu, Fe, Mn, Ni, and Pb. Lower contributions were found in cell walls (respectively 22–32%, 24–44%, 6.1–47%, 12–52%, 7.3–37%, 7.9–32%, 19–52%, 20–42%, and 25–38%) and only minute amounts in the mixed membrane fraction (3.0–5.8%, 0.7–7.0%, 0.7–8.3%, 1.0–22%, 7.5–14%, 16–24%, 1.1–19%, and 5.1–7.7%). The results obtained indicate that small water-soluble molecules were the primary forms of nine elements in two mushroom species studied. On the other hand, the evidence has been provided on elements binding to larger, water-insoluble molecules contained in the structures of cell wall and membranes. The relative distribution was both element and fungi dependent. Thus, in P. ostreatus, total element levels were higher than in A. bisporus, with the preference for their accumulation in cytosol. On the contrary, total element content in the latter fungi was lower; however, a clear tendency toward more efficient element incorporation to the water-insoluble structures was observed (no apparent differences between stalks and caps). These findings might contribute in a better understanding of the accumulation of metals in mushrooms.     

A new species of the genus <Emphasis Type="Italic">Triplophysa</Emphasis> (Nemacheilinae: Balitoridae), <Emphasis Type="Italic">Triplophysa jianchuanensis</Emphasis> sp. nov,from Yunnan,China

A new loach species, named Triplophysa jianchuanensis, has been recognized in collections from Jianchuan in Dali Prefecture, Yunnan, China. Triplophysa jianchuanensis can be distinguished from the other Triplophysa species by the following combination of characteristics: smooth skin, scaleless; lateral line complete; head long (26.7–29.8% of SL); eyes large (25.9–31.0% of dorsal head length); snout shorter than postorbital length (26.9–30.1% of HL); middle of lower lip interrupted and forming a pair of furrows; lower jaw spoon-like with obtuse edge; posterior chamber of air bladder completely degenerated; intestines short, bending in zigzag-shape behind stomach; pelvic-fin tip not reaching anus; caudal fin emarginate; branched rays of dorsal fin 7; branched rays of caudal fin 16. A key to the known species of Triplophysa from the Lancangjiang River is provided.     

Land-use change and irrigation systems in the agricultural landscape of terraced paddy fields in Awaji Island, central Japan

We analyzed changes in land use from 1963 to 2000 in the northern part of Awaji Island in central Japan, using topographical maps and aerial photographs. We compared these changes between two different irrigation systems: tazu, in which a community group jointly owns the rights to a water source, and private management. The study area consisted of 57.3% paddy field, 22.2% woodland, 7.2% urban land use, 6.3% grassland, 5.8% water body, and 1.2% dry field in 1963. In 2000, the area consisted of 44.3% paddy field, 21.0% woodland, 12.6% urban land use, 11.6% grassland, 5.3% water body, and 5.0% dry field. The proportion of agricultural use had decreased markedly over the 37-year period. In the tazu area, 38.1 and 37.7% of former paddy field had changed into urban land use and grassland, respectively, and 19.3% of former paddy field had become dry field by 2000. In contrast, 30.6% of former rice paddy had become dry field in the private management area. About half of the former rice paddy had changed into grassland (26.3%) and urban land use (24.0%) in the private area, and 18.6% had become woodland in 2000. In the tazu area, there were fewer abandoned fields, because farmers still manage their fields according to strict regulations. In the private management area, the set-aside or abandoned fields had changed into woodlands as a result of vegetation succession, because farmers had abandoned fields located far from their homes or on steep slopes. These results suggest that the irrigation system may influence the pattern of change in land use.     

Integrated-baiting concept against Echinococcus multilocularis in foxes is successful in southern Bavaria, Germany

This paper describes the design and the preliminary evaluation of an integrated approach to the control of Echinococcus multilocularis in foxes using praziquantel bait. Air distribution of bait in agricultural and recreational areas was combined with distribution of bait by hand in towns and villages to cover the entire fox population in the 213-km² baiting area. Bait distribution density was 50/km², and bait was distributed once every 4 weeks. Pre-baiting prevalence was 35% (22–50% CI 95%). During a 1-year period following the first 4 months of bait distribution, only one positive fox was found (prevalence 1%; 0–4% CI 95%). No significant change had occurred in the unbaited control area. This prevalence decline is far more pronounced than in previous fox-baiting studies, which is likely to be due to the increased bait distribution density and baiting frequency, and the inclusion of the ‘urban’ fox population.     

A new blind loach, <Emphasis Type="Italic">Oreonectes elongatus</Emphasis> sp. nov. (Cypriniformes: Balitoridae) from Guangxi,China

A new loach, Oreonectes elongatus sp. nov. is described based on collections from Mulun Township, Huanjiang County, Guangxi in China. It is distinguished from its congeners by the combination of the following characters: most elongate body (body depth/SL 8.62–10.68%), blind, a forked caudal fin, obvious adipose dorsal crest and ventral crest; entire body naked and de-pigmented. Although the new species has a similar distribution with O. macrolepis, it can be distinguished by scales (absent in O. elongatus vs. present in O. macrolepis), shape of snout (elongate vs. round), the opposite position of the dorsal and pelvic fins origins (behind vs. front). The new species shares the same possession of dorsal and ventral crests, a forked caudal fin, eyeless, naked body and incomplete lateral line with O. translucens, but can be distinguished from the latter by caudal fin crest (more developed and translucent in O. translucens), longer anterior nostril tube and barbel, extreme of pectoral fin reaching 2/3 of the distance between origin of pectoral and pelvic fins, more vertebrae (4 + 38–39 vs. 4 + 32).     

Influence of modern irrigation,drainage system and water management on spawning migration of mud loach, <Emphasis Type="Italic">Misgurnus anguillicaudatus</Emphasis> C.

We investigated the influence of human activities on the spawning migration of the mud loach, Misgurnus anguillicaudatus. Mud loaches migrate from rivers to paddy fields for spawning. In this study, the number of adult loaches in paddy fields showed a peak in late May and rapidly decreased in July. In early July, water is discharged from paddy fields in order to allow the fields to dry for a few weeks, and water is again supplied later. The spawning season of the loaches probably spans from mid May to August; this was concluded by observing physiological indicators such as the gonad somatic index, oocyte maturity and serum levels of testosterone, estradiol-17β and 17α, 20β-dihydroxy-4-pregnen-3-one. When the loaches mature, they migrated to paddy fields if they could swim upward through the drainage ditches. However, the drainage ditches of modern paddy fields were reconstructed to deepen the water levels. The artificial drought of the rice culture management led to a discharge of water and loaches from the paddy fields during their spawning season. These results indicate that modern rice cultivation causes obstruction of the migration route and loss of spawning grounds; consequently, loaches use limited space and period of the paddy field for their spawning.     

Effects of heavy metals Cd2+, Pb2+ and Zn2+ on DNA damage of loach Misgurnus anguillicaudatus

The effects of heavy metals Cd²⁺, Pb²⁺ and Zn²⁺ at 0.05, 0.5 and 5.0 mg/L level and their interactions at 0.5 mg/L level on DNA damage in hepatopancreas of loach Misgurnus anguillicaudatus for 1–35 days exposure were examined by single cell gel electrophoresis (SCGE). For each test group, 20 loaches with similar body size (5.17–7.99 g; 11.79–13.21 cm) were selected and kept in aquaria with dechlorinated water at (22±1)°C and fed a commercial diet every 48 h. According to the percentage of damaged DNA with tail and its TL/D (tail length to diameter of nucleus) value, the relationship between DNA damage degree and heavy metal dose and exposure time was determined. Results showed that the percentage of damaged DNA and the TL/D value were increased with the prolonged exposure time. The highest percentage (84.85%) of damaged DNA was shown in 5.0 mg/L Zn²⁺ group after 28 days exposure and the biggest TL/D value (2.50) in all treated groups after 35 days exposure. During the first treated week, the damnification of DNA was mainly recognized as the first level, after that time, the third damaged level was mostly observed and the percentage of damaged DNA was beyond 80%. The joint toxic effects among Cd²⁺, Pb²⁺ or Zn²⁺ revealed much complexity, but it generally displayed that the presence of Cd²⁺ could enhance the genotoxicity of Pb²⁺ or Zn²⁺. In conclusion, the results suggested that there was a significant time-and dose-depended relationship between the heavy metal and DNA damage in hepatopancreas of loach, and SCGE could represent a useful means to evaluate the genotoxicity of environmental contamination on aquatic organisms. __________ Translated from Acta Hydrobiologica Sinica, 2006, 30(4): 399–403 [译自: 水生生物学报]     

Comparative and evolutionary analysis in natural diploid and tetraploid weather loach Misgurnus anguillicaudatus based on cytochrome b sequence data in central China

To obtain the phylogenetic relationship between diploid and tetraploid Misgurnus anguillicaudatus, the mitochondrial cyt b gene in the diploid and tetraploid weather loach were isolated and sequenced. The DNA sequences were analyzed using MEGA 3.0 software to determine the phylogenetic relationship. Forty-five variable sites among cyt b gene sequences and 18 amino acid substitutions occurred within the diploid and tetraploid loaches as deduced from the nucleotide sequences analysis of the cyt b gene. The nucleotide pairwise distance between diploid and tetraploid loach ranged from 0.001 to 0.025. Phylogenetic analysis revealed evolutionary relationships between diploid and tetraploid loach. Our results indicated a significant difference between diploid and tetraploid loach about the cyt b gene. AMOVA analysis indicated that there were no significant genetic variations within diploid loaches (Fst = 0.2529, P > 0.05) and within tetraploid loaches (Fst = 0.0564, P > 0.05), neither. However, significant genetic differences were found between diploid and tetraploid loaches (Fst = 0.7634, P < 0.05). Thus, it is concluded that no reproductive isolation was found within the same cytotypes of different localities, but there was reproductive isolation between these two cytotypes. The diploid loach existed before the tetraploid loach in nature. The present study is the first to describe the phylogenetic relationships of natural polyploidy weather loach using mtDNA cyt b gene.     

The population trend of southern elephant seals (<Emphasis Type="Italic">Mirounga leonina</Emphasis> L.) at Macquarie Island (1952–2004)

Total numbers of adult female southern elephant seals (cows) breeding at Macquarie Island were determined for 19 of the 52 year period between 1952 and 2004. Totals for 1952–1987 (exc. 1959 and 1985) were estimated from the relationship between censuses of the isthmus study area and concurrent censuses for the whole island. Totals for 1987–2004 were obtained by direct census of the entire island in mid-October. Cow numbers decreased from a maximum of about 40,000 in the 1950s to a minimum of 18,300 in 2000, but then increased slightly to 19,200 in 2004. Nonlinear and post-hoc linear analysis of the count data identified 1999 as the year when the exponential rate of change (r) slowed from −1.4% per annum to near zero. The rate of change was not uniform for each census sub-area counted (1987–2004), suggesting that certain terrestrially based density-dependent mechanisms were influencing the annual distribution of cows.     

Fauna characteristics and ecological distribution of Carnivora and Artiodactyla in Niubeiliang National Nature Reserve, China

Niubeiliang National Nature Reserve (NNR, 108°45′–109°04′E, 33°47′–33°56′N) is located on the eastern range of the Qinling Mountains in Shaanxi Province, China and spans the southern and northern slopes of Mt. Qinling. A transect survey and investigation were carried out in NNR to determine the fauna characteristics and ecological distribution of carnivora and artiodactyla from May 2003 to August 2004. The NNR has 18 mammals (carnivore and artiodactyl), two of which belong to the first class and seven to the second class of state key protected wildlife in China. The results of this study indicated that ungulates were abundant in the NNR, as all ungulates that were distributed within Mt. Qinling could be found within the reserve. However, only 45.5% of the carnivores distributed within Mt. Qinling were detected within the NNR. Among the mammals, there were 12 oriental species (66.7%), 1 palearctic specie (5.5%) and 5 widely-distributed species (27.8%). The NNR is a crossing area of palearctic species and oriental species on the zoogeographical regions, and it is a transitional area from the oriental realm to the palearctic realm. The results of the analysis on the ecological distribution of carnivore and artiodactyl in the area showed that their elevation ranges had large differences. The species whose elevation ranges above 1 300 m, about 1 000 m, and in 450–700 m occupied one third respectively. The results also indicated that species richness for the memals in the NNR peaked at a middle elevation (rising at first, then descending with the increase in elevation). Not only on the southern slope, but also on the northern slope of Mt. Qinling, the number of species distributed in the area at 1 800–2 200 m a.s.l. was the largest (more than 80%), while the number of species distributed in the area above 2 600 m a.s.l. was the smallest (about 50%). Elevation gradients of species richness for the mammals in the NNR also embodied the mammal distributions among the vegetation types. The number of species distributed in the mixed coniferous and broadleaf deciduous forest at middle elevations was the largest, while the number of species distributed in the broadleaf deciduous forest at middle and low elevations, subalpine coniferous forest, subalpine shrubbery and meadow was relatively smaller. Translated from Acta Ecologica Sinica, 2005, 25(9): 2249–2255 [译自: 生态学报]     

Encapsulation technology for short-term preservation and germplasm distribution of the African mahogany <Emphasis Type="Italic">Khaya senegalensis</Emphasis>

A protocol was developed for short-term preservation and distribution of the medicinal and timber plantation tree, Khaya senegalensis, using alginate-encapsulated shoot tips. The study assessed the effects of culture medium, storage temperature, auxin concentration and planting substrate on shoot regrowth or conversion into plantlets of four different clones. Optimal shoot growth was obtained, with high frequencies (92–100%) of shoot emergence, on Murashige and Skoog (MS) culture media containing 4.4 μM benzyladenine (BA). Encapsulated shoot tips survived longer at 25°C than at 4°C, with viability of 73–88% after 8 weeks. Conversion into plantlets was achieved on half-strength MS medium by pre-culture treatment of shoot tips with 49–490 μM indole-3-butyric acid (IBA) before encapsulation. Treatment with 245 μM IBA provided 52–98% conversion, and 90–95% of plantlets survived acclimatisation under nursery conditions. To eliminate the in vitro culture step after encapsulation, synthetic seeds were allowed to pre-convert before sowing directly onto a range of ex vitro non-sterile substrates. Highest frequencies of plantlet formation from pre-converted synthetic seeds (42–86%) were obtained by transferring synthetic seeds to organic compost, and these plantlets exhibited almost 100% survival in the nursery without mist irrigation. Pre-conversion is a novel and convenient method for producing synthetic seeds that are suitable for distribution to commercial nurseries.     

东北黑土地区稻田甲烷排放时空演变及排放潜力分析

稻田甲烷排放是农业源甲烷排放的主要来源。东北黑土地区是我国最大的粮食生产基地,农业温室气体减排是实现黑土地永续利用的关键议题之一。运用稻田甲烷排放模型(CH4MOD)核算并分析了2009-2018年东北黑土地区稻田甲烷排放的时空演变特征,结合GOSAT卫星遥感数据探究了水稻生产与区域甲烷排放的时空动态联系,进一步量化了稻田甲烷对区域甲烷排放的贡献程度及不同情景下的排放潜力。结果表明,受水稻生产面积扩张和排放强度提高的影响,东北黑土地区稻田甲烷排放总量从2009年的39.05万t增加到2018年的79.53万t。东北黑土地区区域甲烷排放在季节变化和栅格单元上表现出与稻田甲烷排放较为一致的时空动态,大规模的稻田耕作可能会增加水稻生产与区域甲烷排放直接相关的可能性。随着水稻持续扩种稳产,2018年东北黑土地区水稻生产贡献了区域甲烷排放总量的15.04%,其中黑龙江省的贡献率高达31.06%。在基准发展情景下,预计2035年东北黑土地区稻田CH₄排放量较2018年增加19.5%;在粮食供给保障情景下,维持当前稻田耕作面积,水稻生产集约化程度提高,预计其稻田CH₄排放量较2018年减少0.88%;在此基础上,采取促进秸秆还田、增施有机肥、实施节水间歇灌溉等稻田管理措施将使稻田CH₄排放量增加17.8%-63.6%。以满足膳食需求和供给保障为导向,优化水稻种植结构、控制稻田耕作面积,推动技术进步、品种改良以提升单产水平,采取化肥和有机肥搭配施用、节水间歇灌溉等途径能够缓解稻田甲烷排放。研究综合运用自上而下的遥感数据和自下而上的模型运算,刻画了水稻生产与区域甲烷排放的时空联系,进一步评估了稻田甲烷的排放潜力及减排措施的减排效果,为促进东北黑土地区农业甲烷减排和生产布局优化提供了理论依据和决策参考。     

Population genetic structure of island and mainland populations of the quokka, Setonix brachyurus (Macropodidae): a comparison of AFLP and microsatellite markers

Translocation and reintroduction are important tools for the conservation or recovery of species threatened with extinction in the wild. However, an understanding of the potential genetic consequences of mixing populations requires an understanding of the genetic variation within, and similarities among, donor and recipient populations. Genetic diversity was measured using two independent marker systems (microsatellites and AFLPs) for one island and four small remnant mainland populations of Setonix brachyurus, a threatened medium sized macropod restricted to fragmented habitat remnants and two off-shore islands in southwest Australia. Microsatellite diversity in the island population (R _s = 3.2, H _e = 71%) was similar to, or greater than, all mainland populations (R _s = 2.1–3.9, H _e = 34-71%). In contrast, AFLP diversity was significantly lower in the island population (PPL = 20.5; H _j = 0.118) compared to all mainland populations (mean PPL = 79.5–89.7; mean H _j = 0.23–0.29). Microsatellites differentiated all (mainland and island) populations from each other. However, AFLP only differentiated the island population from the mainland populations—all mainland populations were not significantly differentiated from each other for this marker. Given a known time since isolation of the island population from the mainland (6,000 years ago), and an overall more conservative rate of evolution of AFLP markers, our results are consistent with mainland populations fragmenting thousands of years ago (but <6,000 years), probably as a consequence of reduced rainfall and the constriction of the preferred mesic habitat of quokkas. Our results also support a recent history of severe population bottlenecks in mainland populations, and a long history of bottlenecks of the island population, but reflect a recent explosion in numbers since European occupation of the island. Our results indicate that translocation of island populations to supplement mainland populations would introduce genetically markedly differentiated, and possibly maladapted, individuals.     

Channa nox, a new channid fish lacking a pelvic fin from Guangxi, China

 A new species of channid fish, genus Channa, is described from 7 specimens collected from the vicinity of Hepu, Guangxi Province, southern China. The new species, Channa nox, is distinguished from all other channid species by the following combination of characters: absence of pelvic fins, small rounded head (22.1%–26.8% SL), narrow interorbital width (19.6%–26.7% HL), short snout length (3.6%–5.1% SL), predorsal and prepectoral lengths (26.9%–28.4% SL and 24.8%–28.3% SL, respectively), 47–51 dorsal fin rays, 31–33 anal fin rays, 55–63 lateral line scales, 5.5–6.5 scales above lateral line, 9–13 cheek scales, 53–55 total vertebrae, 1 or 2 scale(s) on each side of lower jaw undersurface, the black upper half of body with 8–11 irregular (often anteriorly pointed V-shaped) bands or blotches, a large white-rimmed black ocellus on caudal peduncle and sparse white spots on the dark brown body and dorsal and caudal fins, as well as the shape of the hyomandibular process of the suprabranchial organs. Channa nox is sympatrically distributed with its morphologically most similar congener, C. asiatica. Received: January 18, 2001 / Revised: November 2, 2001 / Accepted: December 12, 2001     

Assessing range re-expansion and recolonization of human-impacted landscapes by threatened species: a case study of the otter (Lutra lutra) in Italy

Detecting and understanding recoveries of threatened species from past and recent presence/absence data is essential to improving conservation efforts. However, false positive trends may be reported because of false absences in past data, therefore appropriate testing is needed. We tested an expansion/recolonization of the otter (Lutra lutra) populations in Italy from a fragmented distribution outlined in the 1984–1985 period by using Monte Carlo simulations. Land-use changes, human depopulation and decrease in influence of anthropogenic features were investigated as potential drivers of recolonization by using GIS modeling. A survey of the entire Italian range of the otter, conducted in 2002–2004, recorded a 2.2-fold increase in the proportion of occupied 10-km squares and 49 local colonizations. The range size and proportion of urban land-use in the 1984–1985 distribution were smaller (P < 0.05) than those derived from simulated surveys based on 49 random false absences versus colonization events. The distribution range expanded southward and nearly reached the southern margins of the peninsula. Recolonization of moderately urbanized landscapes was not accompanied by human depopulation. According to partial logistic regressions, the pure effect of urban land proportion and industry proximity on otter occurrence probability declined by about 48%, suggesting a decreased impact on the stream habitat. Conversely, natural factors, increased in importance by about 116%. The absence of a significant northward expansion in the 20 year period suggests that northward habitat restoration should be planned to encourage further recolonization. On the other hand, potential urban threats in the newly occupied landscapes should be controlled.     

Distribution,length and weight of roots in young plantations ofEucalyptus grandis W. Hill ex Maiden irrigated with recycled water

Summary The root systems ofEucalyptus grandis W. Hill ex Maiden, irrigated with recycled municipal effluent at two sites in north-western Victoria, Australia, were studied by excavation and coring. Trees at Robinvale were four years-old and were irrigated using micro-sprays that covered only 70% of the ground surface area, whereas at Mildura, effuent was uniformly was uniformly applied to six years-old trees by flood and sprinkler irrigation. At Mildura where roots were excavated from a 2.80×2.80×1.20 m block of soil, a total root length of 1193 m.m⁻² and a total root weight of 3.1 kg m⁻² were estimated in the top metre. For roots >1 mm diameter, 77% of intercepts were at 0–30 cm, whereas only 50% were in the 50–100 cm soil horizon. At both sites where roots in the top 30 cm were studied by coring, the vertical distributions of root intercepts, length and weight were similar. Root length was greatest in the 0–10 cm soil horizon at both sites, and intercepts of roots <1 mm diameter comprised 73% and 81% of all roots at Mildura and Robinvale respectively. Roots <1 mm diameter contributed 85% of total length at both sites, but only 19% and 21% of total weight at Mildura and Robinvale respectively. The horizontal distribution of roots differed at the two sites. With uniform application of effuent at Mildura, root intercepts and length were concentrated in the centre of the irrigation bay, but at Robinvale, the concentration occurred closer to the tree row due mainly to the different method of irrigation. Root weight at both sites was highest within 50 cm of the tree row. Root densities of 0.11 to 0.57 cm cm⁻³ were estimated in the two plantations; these were similar to root densities measured inPinus radiata D. Don plantations up to 46 months old, but were considerably lower than those estimated for pastures. The implications of the results for the management of irrigated plantations of eucalypts are discussed.     

Vertical distribution of Microcystis population in the regulated Nakdong River, Korea

The vertical distribution of a bloom-forming Microcystis population was studied based on the relevant limnological parameters obtained from the lower Nakdong River (Mulgum) during the summer of 1994. Over three months (late June to late September), a high abundance of Microcystis population (mean ± SD, 2.9 ± 8.4 × 10⁵ cells ml⁻¹, n = 40) and algal biomass (mean ± SD, chlorophyll a, 131 ± 346 μg l⁻¹, n = 31) was persistent throughout the entire water column (0–5 m, n = 11). The vertical distribution of carbon content was uneven, with a high concentration near the surface zone (mean ± SD, total, 7.9 ± 7.8; Microcystis, 5.2 ± 8.3 μg C ml⁻¹, n = 15). Incorporating limnological and meteorological factors, a diel study of the vertical distribution of Microcystis showed that the chlorophyll a concentration was highest near the surface zone on a calm night (wind velocity, <2 m s⁻¹, 2300–700) but was evenly distributed on a windy day (>4 m s⁻¹, 1100–1900). Among many possible factors, wind velocity may have played an important role in controlling the vertical distribution of Microcystis in the lower Nakdong River. Received: July 12, 1999 / Accepted: November 15, 1999     

Biological characteristics of wild Cycas fairylakea population in Guangdong Province, China

There are five wild populations of Cycas fairylakea in Guangdong Province, China, three of which are newly found. A study of the biological characteristics of C. fairylakea populations showed that this species had a narrow colonization area within 300 hm², and an island pattern of distribution. Because of the overexploitation, urbanization, environment pollution, plant diseases, and insect pests, the wild populations and individuals of C. fairylakea decreased markedly in the past decades. All five populations have an opposite pyramid age structure, few coning plants, few seed production, and low level of seed germination rate or sterility. In conclusion, C. fairylakea in Guangdong Province was threatened seriously and an urgent need to take effective efforts to protect the plants and habitats in its location sites was required. __________ Translated from Acta Scientiarum Naturalium Universitatis Sunyatseni, 2005, 44(6): 97–100 [译自: 中山大学学报 (自然科学版), 2006, 44(6): 97–100]