桂中旱片的成因机制及旱片综合区划

桂中地区降水不少,但由于自然及人为等因素,旱情严重,成为广西著名的旱片之一。对其成因机制的探讨是桂中环境治理和区域开发的科学基础。在概述地质地理特征的基础上,进行了桂中旱区的干旱时空分析,重点揭示了桂中旱片的成因机制;然后,根据干旱类型、旱灾脆弱度及从便于地下水利用出发,进行了桂中旱片的综合区划;最后,遵循生态环境治理、综合抗旱与脱贫致富相结合的原则,提出了治理对策措施。

三皇旱片建设地下水库治旱的初步研究

南方岩溶区治旱问题是当今岩溶研究领域的一大难题,三皇旱片是桂林市八大旱片之一。文章在现场调查研究的基础上,提出了建设地下水库治旱的工程措施,具有一定的现实意义,为治旱决策部门作出科学的治旱决策提供了理论依据。

桂中旱片的旱情时空分析及其脆弱性综合评价

桂中地区降水不少 ,但旱情严重 ,成为广西的著名旱片之一 .该文在概述地质地理特征的基础上 ,进行桂中旱区的旱情时空分析 ,进而揭示其成因机制 ;并根据干旱类型、旱灾脆弱度以及便于地下水利用进行桂中旱片的综合区划 ;秉承生态环境治理、综合抗旱与脱贫致富相结合原则 ,指出其治理对策措施 .

福建省重点旱片分析和灭旱对策探讨

通过对福建省旱灾概况、成因、重点旱片分布进行调查分析,提出灭旱对策探讨。

桂北地区三皇典型岩溶旱片治理途径分析

三皇旱片是桂北地区典型的岩溶旱片,气候与复杂的岩溶地质条件导致水资源分布时空不均,构成了地区干旱的自然因素,然而地表水利工程渗漏严重、水资源开发利用方式单一以及水利用效率低下,也是干旱形成的主要原因。调查还表明,该区地下水资源丰富,合理开发能够满足当地的农业用水需求。加大地下水资源的开发利用力度,兼顾工程与非工程治理措施,是实现旱片整治的有效途径。

发挥恶滩新电站灌溉桂中旱片一议

根据红水河流域西高东低,明显由西北向东南倾斜的特点,恶滩电站有可能建成发电、灌溉、航运等综合效益较大的水利工程枢纽。其中,引水自流灌溉,可以解决广西最大的桂中旱片工农业用水问题,是造福当代,荫及子孙的战略措施。

Research Progress on Leaf Anatomical Structures of Plants Under Drought Stress

Plants usually suffer drought stress during their growth process. As the photosynthetic activity center of plants, the leaf is the most sensitive organ under drought stress. In order to support the research on drought resistance of higher plants, this study reviewed the adaptation response and damage performance of epidermal structure, palisade tissue and spongy tissue, thickness, veins and stomata of plant leaves under drought stress.

崇左市左江左岸农田灌溉方案研究

通过对崇左市左江左岸旱片水土资源及现有的水源工程和灌溉工程的调查和分析,经过水量平衡分析计算,提出扩建位于黑水河上的那岸水库作为左江左岸旱片农田灌溉的龙头水源工程,新建大型灌区以永久解决该旱片的灌溉缺水问题。

Effects of Drought Stress on the Photoprotection in Ammopiptanthus mongolicus Leaves

Ammopiptanthus mongolicus (Maxim.) Cheng f. is one of the evergreen shrubs in the desert region of China. In midday its leaves bear photon flux density over 1 500 μmol·m -2 ·s -1 at natural habitat. They show the obvious phenomenon of photoinhibition. For the study of the effects of drought stress on the major protective mechanism against strong light in A. mongolicus leaves, the diurnal variations of photosynthetic rate and chlorophyll fluorescence parameters were investigated under natural conditions with portable photosynthetic measurement system (CIRAS_1) and portable fluorometer (MFMS_2). The experimental results showed that, under normal and drought stress conditions,the net photosynthetic rate ( Pn ), the primary maximum photochemical efficiency of PSⅡ ( Fv/Fm ) and the quantum efficiency of noncyclic electron transport of PSⅡ ( Φ PSⅡ ) decreased obviously at noon (Figs.2,3A,4B). In comparison with plants under normal condition, under drought stress minimal chlorophyll fluorescence ( Fo ) decreased at first and then increased (Fig.3A), non_photochemical quenching ( NPQ ) quickly increased and sustained at a higher level (Fig.4B). This indicated that the major photoprotective mechanism of A. mongolicus leaves was the xanthophyll cycle_dependent thermal energy dissipation under normal condition, while under drought stress, the major photoprotective mechanism was both the xanthophyll cycle_dependent thermal energy dissipation and the reversible inactivation of PSⅡ reaction center.

Effects of Periodical Soil Drying and Leaf Water Potential on the Sensitivity of Stomatal Response to Xylem ABA

The study on the changes of stomatal sensitivity in relation to xylem ABA during periodical soil drying and the effect of leaf water status on the stomatal sensitivity has confirmed that xylem ABA concentration is a good indicator of soil water status around roots and the relation between xylem ABA concentration and predawn leaf water potential remained constant during the three consecutive soil drying cycles based on the slopes of the fitted lines. The sensitivity of stomata to xylem ABA increased substantially as the soil drying cycles progressed, and the xylem ABA concentration needed to cause a 50% decrease of stomatal conductance was as low as 550 nmol/L in the next two soil drying cycle, as compared with the 750 nmol/L ABA in the first cycle of soil drying. The results using the split_root system showed that leaf water deficit significantly enhanced the stomatal response to xylem ABA and the xylem ABA concentration needed to cause a 50% decrease in stomatal conductance was 2 to 4 times smaller in the whole_root_drying treatment than those in the semi_root_drying treatment. These results suggested that the sensitivity of stomata to xylem ABA concentration is not a fixed characteristic.

Effects of Water Stress on Leaf Water and Chlorophyll Fluorescence Parameters of Sugarcane Seedling

[Objective] The aim was to explore the effects of water stress on leaf water and chlorophyll fluorescence parameters of sugarcane seedling,as well as to provide basis for the study on sugarcane production and evaluation. [Method] Seven different sugarcane varieties were studied at the seedling stage under drought stress,and the changes of leaf water and chlorophyll fluorescence parameters under stress conditions were detected. [Result] leaf water potential,leaf relative water content and soil relative water content showed a certain amount of internal relationship,the sugarcane varieties that had more tolerant to drought had higher utilization rate of soil water; the correlation analysis and factor analysis suggested that the survival rate at seedling stage under drought stress,Fv/Fm,leaf water potential and relative water content could be used as drought resistance evaluation indicators. [Conclusion] As a relatively independent influencing factor,water potential had dominating effect on drought resistance,and the reliability of Fv/Fm as drought resistance evaluation indicator had been verified.

Characteristics of water relations in seedling of Machilus yunnanensis and Cinnamomum camphora under soil drought condition

The soil drought stress experiment in different durations (no watering within 3d, 6d, 9d, 11d individually) was conducted to study the drought-resistant capacity of one-year-old seedlings for the native tree species (Machilus yunnanensis) in Yunnan Province and the introduced tree species (Cinnamomum camphora). The leaf water potential, chlorophyll content, proline content and plasma membrane permeability for two species seedlings were measured in different soil drought conditions. The results showed that, on the 9th day of drought stress, the leaf water potential of two species decreased obviously, whereas the free proline content and plasma membrane permeability increased sharply. On the 11th day, the leaf water potential of C. camphora seedlings was lower than that of M. yunnanensis seedlings; the plasma membrane permeability in C. camphora seedling leaves increased much more than that in M. yunnanensis seedling leaves, which showed that the injury to the former by soil drought stress was more severe than that to the latter. The free proline content in M. yunnanensis seedling leaves continued to increase on the 11th day, but that in the C. camphora seedling leaves started to drop obviously, indicating that the reduction of osmotic regulation substance in C. camphora seedling leaves after the 11th day was unable to maintain the osmotic balance between the plasma system and its surroundings and the water loss occurred inevitably. Comprehensively, M. yunnanensis seedlings enhanced the drought-resistance in the course of soil drought stress by maintaining higher leaf water potential and by increasing osmotic regulation substance to promote cell plasma concentration and maintain membrane structure integrity so as to reduce water loss. The subordination function index evaluated with fuzzy mathematic theory also showed that the drought-resistant capacity of M. yunnanensis seedlings was stronger than that of C. camphora seedlings.

Anatomy of Different Ages of Streblus asper Leaves and Their Drought Resistance

The leaf thickness, stratum corneum thickness, epidermis thickness, palisade tissue thickness and sponge tissue thickness of Streblus asper leaves at different ages were observed by using paraffin section technology and optical microscopic observation to explore the anatomic adaptive response mechanism to drought stress, also to provide a theoretical basis for S. asper introduction. The results showed that under drought stress, various parts of S. asper leaf anatomy showed some characteristics adapted to water environment. Leaf palisade tissue cells became shorter, increasing from 1-2 layers to 2-3 layers; sponge cells were arranged in neat and compact long column shape, and the upper and down epidermis were thickened. The upper and down epidermis produced more trichomes to resist stress. After rehydration, leaf porosity increased and trichomes had a corresponding reduction. The principal component analysis showed that the stratum corneum thickness, leaf thickness and palisade were available to describe the impact of stress and rehydration on different ages of S. asper leaf anatomy. Under drought stress, S. asper leaf stratum corneum thickness and leaf thickness increased and leaves returned to normal after rehydration. Middle and top leaves were better than basal leaves in response to drought stress sensitivity.

一个西部丘区县脱贫攻坚的实践与思考

'前不见古人,后不见来者'这句诗的作者陈子昂,其故乡正是射洪县。射洪县地处四川盆地中部,面积1496平方公里,人口100.1万,虽是四川省唯一的丘区经济发展示范县、首批扩权强县试点县和首批工业强县示范县,但在偏远的乡村、旱片死角和水库淹没区,仍存在80个村、1.92万户、

Dominant roles but distinct effects of groundwater depth on regulating leaf and fine-root N,P and N:P ratios of plant communities

Aims As the determinant of water availability in drylands,groundwater plays a fundamental role in regulating vegetation distribution and ecosystem processes.Although considerable progress has been made over the past years in the relationship between environment stress and plant community-level traits,the potential influence of water stress induced by groundwater changes on plant community-level stoichiometry remains largely unclear.Here,we examined whether belowground and aboveground community-level stoichiometry responded differently to groundwater changes.Methods We measured nitrogen(N)and phosphorus(P)concentrations in plant leaves and fine-roots of 110 plots under a broad range of groundwater depths in a typical arid inland river basin.We examined the spatial patterns and drivers of community-level N:P stoichiometry in leaves and fine-roots.Important Findings Community-level leaf and fine-root N,P and N:P ratios were mainly determined by groundwater,vegetation types and species composition,among which groundwater played a dominant role.Groundwater indirectly regulated community-level N:P stoichiometry through affecting vegetation types and species composition.Vegetation types and species composition had significant direct influences on communitylevel N:P stoichiometry.Furthermore,groundwater depth had opposite influences on community-level leaf and fine-root N:P stoichiometry.Groundwater depth regulated vegetation types and further decreased leaf N,P but increased leaf N:P ratios and fine-root N.Groundwater depth had a positive indirect impact on fine-root P but a negative indirect impact on fine-root N:P ratios primarily by affecting species composition.Our findings indicate that groundwater rather than climate conditions effectively regulates community-level N:P stoichiometry,and below-and aboveground N:P stoichiometry has opposite responses to groundwater.

Leaf and Ecosystem Gas Exchange Responses of Buffel Grass-Dominated Grassland to Summer Precipitation

Sporadic rain events that occur during summer play an important role in the initiation of biological activity of semi-arid grasslands.To understand how ecosystem processes of a buffel grass(Cenchrus ciliaris L.)-dominated grassland respond to summer rain events,an LI 6 400 gas exchange system was used to measure the leaf gas exchange and plant canopy chambers were used to measure net ecosystem CO2exchange(NEE) and ecosystem respiration(Reco), which were made sequentially during periods before rain(dry) and after rain(wet). Gross ecosystem photosynthesis(GEP) was estimated from NEE and Reco fluxes, and light use efficiency parameters were estimated using a rectangular hyperbola model. Prior to the monsoon rain, grassland biomass was non-green and dry exhibiting positive NEE(carbon source) and low GEP values during which the soil water became increasingly scarce. An initial rain pulse(60 mm) increased the NEE from pre-monsoon levels to negative NEE(carbon gain) with markedly higher GEP and increased green biomass. The leaf photosynthesis and leaf stomatal conductance were also improved substantially. The maximum net CO2uptake(i.e.,negative NEE) was sustained in the subsequent period due to multiple rain events. As a result, the grassland acted as a net carbon sink for 20 d after first rain. With cessation of rain(drying cycle), net CO2 uptake was reduced to lower values. High sensitivity of this grassland to rain suggests that any decrease in precipitation in summer may likely affect the carbon sequestration of the semiarid ecosystem.

Leaf turgor loss point at full hydration for 41 native and introduced tree and shrub species from Central Europe

The last years,Central European forests have suffered from drought as a direct consequence of climate change.All these forests have a long management history and it lies in the landowner’s responsibility to replant damaged forests.Hence,landowners and the government are searching currently for species suitable to replant in areas affected by tree die-offs.It is a matter of fact that good knowledge of drought resistance of species is a critical measure for the current replanting efforts.We determined a widely recognized trait for leaf drought tolerance(leaf water potential at turgor loss point at full hydration,πtlp)in 41 woody species native or introduced in Central Europe.The osmometric rapid assessment method was used to measure the leaf osmotic potential at full hydration(πosm)of sun-exposed leaves and converted toπtlp.Meanπtlp of the native species was−2.33±0.33 MPa.The less negativeπtlp was found in the introduced species Aesculus hypocastania and was at−1.70±0.11 MPa.The most negativeπtlp,and thus the potentially highest drought tolerance,were found in the introduced species Pseudotsuga menzesii and was at−3.02±0.14 MPa.High or less negativeπtlp is associated with lower drought tolerance,whereas low or more negativeπtlp stands for higher resistance to drought stress.For example,the two native species Illex aquifolium and Alnus glustinosa are species naturally associated with moist habitats and are characterized by the least negativeπtlp of−1.75±0.02 and−1.76±0.03 MPa,respectively.