Uncertainties of snow cover extraction caused by the nature of topography and underlying surface

Manas River,the largest inland river to the north of the Tianshan Mountains,provides important water resources for human production and living.The seasonal snow cover and snowmelt play essential roles in the regulation of spring runoff in the Manas River Basin(MRB).Snow cover is one of the most significant input parameters for obtaining accurate simulations and predictions of spring runoff.Therefore,it is especially important to extract snow-covered area correctly in the MRB.In this study,we qualitatively and quantitatively analyzed the uncertainties of snow cover extraction caused by the terrain factors and land cover types using TM and DEM data,along with the Per(the ratio of the difference between snow-covered area extracted by the Normalized Difference Snow Index(NDSI) method and visual interpretation method to the actual snow-covered area) and roughness.The results indicated that the difference of snow-covered area extracted by the two methods was primarily reflected in the snow boundary and shadowy areas.The value of Per varied significantly in different elevation zones.That is,the value generally presented a normal distribution with the increase of elevation.The peak value of Per occurred in the elevation zone of 3,700–4,200 m.Aspects caused the uncertainties of snow cover extraction with the order of sunny slopesemi-shady and semi-sunny slopeshady slope,due to the differences in solar radiation received by each aspect.Regarding the influences of various land cover types on snow cover extraction in the study area,bare rock was more influential on snow cover extraction than grassland.Moreover,shrub had the weakest impact on snow cover extraction.     

种间竞争对小麦生长过程的影响

采用荠菜与春小麦间作的方式,利用对照实验,通过测定小麦生长不同时期的株高、叶面积、分蘖数、过氧化物酶（POD）活性、根冠比等数据,对其平均值进行分析。结果表明：种间竞争对小麦生长过程中的叶面积和分蘖数起抑制作用,而对株高、POD活性和根系生长（根冠比）则随小麦的生长过程的延长由抑制作用转化为促进作用。其原因是荠菜与小麦在空间、光、水、气、养分等资源方面存在竞争关系,这种竞争作用对小麦的生长起抑制作用,小麦为了得到更多的资源用以维持生长,就必须改变自身的形态结构并产生一系列的生理生化变化（如株高、POD活性、根冠比的增大）,以此来提高自己的竞争能力,从而有利于自身更好的生长繁殖。     

Spatial patterns of encroaching shrub species under different grazing regimes in a semi-arid savanna,eastern Karoo,South Africa

Woody plant encroachment is increasing in arid and semi-arid regions of the world. We investigated the structure and fine-scale spatial pattern of encroaching species and how these patterns vary with different grazing regimes in semi-arid regions. In this study, we investigated how four encroaching shrub species (Searsia erosa, S. burchellii, Diospyros lycioides and Eriocephalus ericoides) in Middelburg (Eastern Cape, South Africa) coexist and partition space under different grazing regimes (viz. continuous rest, and continuous, summer and winter grazing). We used point-pattern analysis to assess the spatial ecology of these species. We also used an index of integration (mingling index), where low values indicate that they are surrounded by conspecifics and high values indicate that they are surrounded by heterospecifics. The three shrub species were highly mingled except in the winter-grazing plot, where S. burchellii and D. lycioides clustered. We found that the shrub species were generally aggregated in most of the grazing plots. These findings indicate that (1) at a fine spatial scale, grazing in the wet season promotes shrub encroachment, and (2) there is a tendency to aggregation among encroaching shrub species in the grazing plots.     

Trophic structure of a pond community dominated by an invasive alien species: Insights from stomach content and stable isotope analyses

1. Invaders affect native species across multiple trophic levels, influencing the structure and stability of freshwater communities. Based on the ‘trophic position hypothesis’, invaders at the top of the food web are more harmful to native species via direct and indirect effects than trophically analogous native predators are.
2. However, introduced and native predators can coexist, especially when non-native species have no ecological and behavioural similarities with natives, occupy an empty niche, or natives show generalist anti-predator strategies that are effective at the community level.
3. At present, conservation efforts are focused on eradicating invaders; however, their removal may lead to unwanted and unexpected outcomes, especially when invaders are well established and strongly interspersed with natives. This highlights the need to consider invaders in a whole-ecosystem context and to consider the evolutionary history and behavioural ecology of natives and invaders before active management is applied.
4. Here, stomach content and stable isotope analyses were combined to investigate a pond system dominated by invaders in order to understand the effects of the interactions among upper level predators and lower level members of the food web on the whole community structure.
5. Both diet and isotope analyses showed that several invaders contributed to the diet of natives and invaders. A significant isotope overlap was found among upper level predators. However, stomach content analysis suggested that predators reduced the potential competition differentiating the food spectrum by including additional prey in their diet. Both native and non-native upper level predators, by preying on invaders, seem not to exert a strong suppressive effect through predation and competition on native species.
6. This research confirms the importance of studying food webs to identify ecological conditions that forecast the potential for deleterious impacts before management is applied. In cases where invaders cannot be eradicated, management efforts should follow a conciliatory approach promoting the coexistence of native species with invaders.

     

葡萄山欧杂交后代果皮颜色的RAPD标记

以葡萄种间BC1杂交组合 79- 33、83- 15 [(山葡萄×红亚历山大 )×白香蕉 ]子代为试材 ,运用RAPD技术进行葡萄山欧杂交后代果皮颜色的分子标记研究发现 ,OPY0 2的扩增片段OPY0 2 - 75 0与白色果皮性状有一定的连锁关系 ,以OPY0 2扩增亲本、F1、BC1、F2 及 2个栽培葡萄品种发现 ,所有的白色果皮单株都扩增出OPY0 2 -75 0 ,但在 6个BC1、F2 黑色果皮单株中也具有该片段。     

Effects of earthworm density on growth, development, and reproduction in Lumbricus rubellus (Hoffm.) and possible consequences for the intrinsic rate of population increase

In this paper, the influence of earthworm density is assessed on the life-history parameters: growth, development, reproduction, and survival of Lumbricus rubellus (Hoffm.). Density ranges from two to nine earthworms in 1-l containers, corresponding to field densities of 300-1350 earthworms m⁻². Earthworms were kept under optimal laboratory conditions, with a surplus of food. The results show that at high earthworm density, individual growth is retarded, maturation delayed and cocoon production decreased, even when food is optimal. The integration of these results into a Dynamic Energy Budget model suggests that the food intake of individual earthworms is lower at the higher tested densities. This lower food intake is most probably driven by competition for space at the higher densities. The lower food intake results in a lower intrinsic rate of population increase which is negative at the highest tested density.     

Through the genetic bottleneck: O. rufipogon as a source of trait-enhancing alleles for O. sativa

This paper summarizes results from a decade of collaborative research using advanced backcross (AB) populations to a) identify quantitative trait loci (QTL) associated with improved performance in rice and to b) clone genes underlying key QTLs of interest. We demonstrate that AB-QTL analysis is capable of (1) successfully uncovering positive alleles in wild germplasm that were not obvious based on the phenotype of the parent (2) offering an estimation of the breeding value of exotic germplasm, (3) generating near isogenic lines that can be used as the basis for gene isolation and also as parents for further crossing in a variety development program and (4) providing gene-based markers for targeted introgression of alleles using marker-assisted-selection (MAS). Knowledge gained from studies examining the population structure and evolutionary history of rice is helping to illuminate a long-term strategy for exploiting and simultaneously preserving the well-partitioned gene pools in rice.     

Wheat and chickpea intercropping systems in an additive series experiment: Advantages and weed smothering

For increasing land use efficiency and weed suppression intercropping plays a pivotal role. A field experiment was carried out on wheat (Triticum aestivum L. emend. Fiori and Paol)–chickpea (Cicer arietinum L.) mono- and intercropping with various weeding (0, 1, or 2 hand-weeding operations) and row spacing (20- or 30-cm) treatments in the eastern plateau region of India over consecutive five winter seasons (1997/2001). The experimental design was a randomized complete block with eighteen treatments replicated thrice. Significant (P ≤ 0.05) differences were observed in yield and economics with and without weeding treatments. Chickpea yield was significantly reduced by wheat when intercropped. However, total productivity and land use efficiency were higher under the intercropping system as compared to monocrops of either species. There was a significant reduction in weed density and biomass for the intercropping system over both monocrops. Wheat facilitated an increase in nodule number and dry weight in chickpea under intercropping over monocrops, moreover, root length of chickpea was greater when intercropped. These findings suggest that intercropping wheat and chickpea increase total productivity per unit area, improve land use efficiency and suppress weeds, a menacing pest in crop production. Considering the experimental findings, wheat–chickpea (30 cm) with two weedings may be recommended for yield advantage, higher net income, more efficient utilization of resources, and weed suppression as a biological control in eastern plateau region of India.     

Variable Effects of Nitrous Oxide at Multiple Levels of the Central Nervous System in Goats

The direct and indirect effects of nitrous oxide (N₂O) on the nociceptive responses of lumbar dorsal horn neurons, and the indirect effects on midbrain reticular formation (MRF) neurons and thalamic neurons were determined in goats anaesthetized with isoflurane. The technique used enabled the differential delivery of N₂O to either the torso or the cerebral circulation, thus allowing assessment of the direct spinal and indirect brain effects of N₂O. Systemic delivery of N₂O appeared to have divergent effects, facilitating (4/11) or depressing (7/11) the responses of dorsal horn neurons. Such divergent effects were also observed when N₂O was differentially delivered to the circulation in the torso (i.e. the spinal cord). Likewise, MRF and thalamic responses to noxious stimulation were variably affected by administration of N₂O to the torso, with some cells facilitated (7/13 MRF neurons, 3/8 thalamic neurons) and others depressed (6/13 MRF neurons, 5/8 thalamic neurons). It appears that N₂O has variable effects on the caprine CNS. The facilitatory action of N₂O might partially explain why it is a relatively weak anaesthetic.