Effects of water state of soil on ecological boundary of leaf Surface ofpopulus davidiana

The effect of water state of soil on eco-boundary over leaf surface was disscussed by takingPopulus davidiana as experimental material. The results show that to change soil water state by some methods was to adjust and control the forming quality of eco-boundary in fact. The plant in good water condition must be accompanied by thinner eco-boundary. This eco-boundary is beneficial to exchange and flow of the substances between plant and environment. Suifenhe Animal and Plant Quarantine Bureau The study was supported by The Chinese Natural Science Foundation, No. 39470136 (Responsible Editor: Chai Ruihai)     

干旱半干旱沙区人工植被与土壤水分环境相互作用关系研究进展

土壤水分在干旱、半干旱沙区人工植被恢复、植物生长和群落演替过程中起着重要作用。文中综述了我国主要沙化地区人工固沙植被土壤水分状况和动态的研究现状, 分析了土壤水分的时空格局及其影响因子; 探讨植被冠层、生物结皮、植物根系对土壤水分的调控作用和影响机理以及干旱、半干旱沙区人工植被土壤水分空间异质性及相关问题; 最后提出人工植被区的土壤水分动态模拟预测、土壤—植被—大气系统水量平衡和水分循环以及空间尺度扩展等问题应是未来的研究重点。     

Hydraulic redistribution of soil water by neotropical savanna trees

The magnitude and direction of water transport by the roots of eight dominant Brazilian savanna (Cerrado) woody species were determined with a heat pulse system that allowed bidirectional measurements of sap flow. The patterns of sap flow observed during the dry season in species with dimorphic root systems were consistent with the occurrence of hydraulic redistribution of soil water, the movement of water from moist to drier regions of the soil profile via plant roots. In these species, shallow roots exhibited positive sap flow (from the soil into the plant) during the day and negative sap flow (from the plant into the soil) during the night. Sap flow in the taproots was positive throughout the 24-h period. Diel fluctuations in soil water potential, with maximum values occurring at night, provided evidence for partial rewetting of upper soil layers by water released from shallow roots. In other species, shallow roots exhibited negative sap flow during both the day and night, indicating that hydraulic redistribution was occurring continuously. A third sap flow pattern was observed at the end of the dry season after a heavy rainfall event when sap flow became negative in the taproot, and positive in the small roots, indicating movement of water from upper soil layers into shallow roots, and then into taproots and deeper soil layers. Experimental manipulations employed to evaluate the response of hydraulic redistribution to changes in plant and environmental conditions included watering the soil surface above shallow roots, decreasing transpiration by covering the plant and cutting roots where probes were inserted. Natural and manipulated patterns of sap flow in roots and stems were consistent with passive movement of water toward competing sinks in the soil and plant. Because dry shallow soil layers were often a stronger sink than the shoot, we suggest that the presence of a dimorphic root system in deciduous species may play a role in facilitating leaf expansion near the end of the dry season when the soil surrounding shallow lateral roots is still dry.     

古尔班通古特沙漠南缘不同密度人工梭梭林改善小气候效应研究

通过对古尔班通古特沙漠南缘不同密度人工梭梭林的林内风速、气温、相对湿度、土壤含水量等指标的观测,就不同密度人工梭梭林改善小气候效应进行了研究,结果表明：人工梭梭林保留密度为1111株？hm^-2与833株？hm^-2时,改善小气候效应与高密度梭梭林相当;保留密度为500株？hm^-2时,改善小气候效应略有降低,但显著提高了土壤含水量,有利于抑制梭梭林的衰败退化;保留密度为278株？hm^-2时,改善小气候效应严重降低,土壤含水量提高不显著。     

城市土壤对园林树木生长的影响

通过对都江堰市城市土壤相关因子分析,阐述了城市土壤各因子对园林树木生长的不良影响,提出了通过适地适树、增施有机质、改良土壤理化性质、及时补充养分和水分等措施,从而达到减少城市土壤对园林树木生长不良影响的目的。     

Simulation of soil water dynamics in a Caragana intermedia woodland in Huangfuchuan watershed

As vegetation coverage increases, soil water content can decrease due to water uptake and evapotranspiration. At a very high level of plant density, poor growth and even mortality can occur due to the decrease of soil water content. Hence, a better understanding of the relationship between soil water content and the density of plants is important to design effective restoration projects. To study these relationships, we developed a soil water dynamic simulation model of a Caragana intermedia woodland under different slope gradient and slope aspect conditions in the Huangfuchuan watershed on the basis of the previous studies and field experiments. The model took into account the major processes that address the relationships of plants and the environment, including soil characteristics, precipitation, infiltration, vegetation transpiration, and soil evaporation. Daily changes in soil water content, transpiration, and evaporation of the Caragana intermedia woodland with different vegetation coverage, slope gradient, and slope aspect were simulated from 1971 to 2000. Based on the model simulations, we determined the functional relationships among soil water content, plant coverage and slope as well as the optimal plant density on flat slopes. We also determined the effects of slope gradient and slope aspect on soil water content. When slope gradient was less than 10°, the optimal plant density was sensitive to slope gradient. In the slope range from 10° to 30°, plant density was not sensitive to slope gradient. Therefore, it is important to consider planting densities on the hillsides with slope gradients less than 10° for reconstructing vegetation. __________ Translated from Acta Phytoecologica Sinica, 2005, 29(6): 910–917 [译自: 植物生态学报]     

椰壳植物纤维改良城市绿化土壤研究

使用椰壳植物纤维改良受建筑废弃物混凝土、水泥、石灰渣石污染的城市绿化土壤 ,试验表明 :用椰壳植物纤维和土壤重量比在 1∶10～ 15 ,可以显著改善被污染土壤理化性能 ,减少容重 ,缓解土壤板结状况 ,提高土壤保水能力和水的利用率 ,节约浇灌用水 ;增加土壤微生物种类和数量 ,使土壤较适合城市绿化植物的生长。     

Water holding effect of subalpine dark coniferous forest soil in Gongga Mountain, China

由于土壤性质和腐殖质含量的不同,土壤的含水量并不能很好地说明是否适宜植物的生长。本研究以土壤PF(表示土壤的水分状态,与植物的生长发育有密切关系的数值)为主要研究依据,将土壤含水率和PF联系起来,定量研究了贡嘎山地区亚高山暗针叶林不同演替阶段土壤的含水率与PF值之间的相互作用关系。研究结果表明:①在相同的PF时,随着暗针叶林演替的进展,土壤腐殖质层的含水率逐渐增加,即过熟林>成熟林>中龄林>幼龄林。②随着土层深度的增加,土壤容重增加,含水率减小,但各植被演替阶段之间土壤含水率差异并不显著。③植被不同演替系列主要是通过提高其土壤有机质含量,改善土壤结构,降低土壤容重和增加土壤毛管孔隙度等土壤物理特性,改善土壤的蓄水和持水性能。④本区暗针叶林土壤腐殖质层涵养水源作用最为明显。图1表2参15。     

试论我国北方地区人工植被的土壤干化问题

我国北方地区以人工林为代表的人工植被建设中正面对一个严峻问题－土壤干化。土壤干化是北方少雨地区人工植被土壤退化的主要表现形式，其显著特征是因植物蒸腾过量耗水造成的植物根系作用范围内土壤水分长时间持续地严重亏缺，天然降水已不能有效予以补偿，土壤表层板结．土壤紧实度增大，从而导致植物生长明显衰退以至大面积干枯死亡。土壤干化已成为这一地区人工植被建设的严重隐患。造成人工植被土壤干化的直接原因是植被类型选择不当，群落密度过大和群落生产力过高。人工植被土壤干化的防治对策是，在正确的植被建设思想指导下，依据当地的生物气候生产力因地制宜地选择植被类型，大幅度降低群落密度，合理调控群落生产力，以保持植物蒸腾耗水与土壤水分补偿之间的水分平衡，从而维持群落的持续稳产与高产。     

Impact of land use on physico-chemical and hydrological properties of ustifluvent soils in riparian zone of river Yamuna,India

Land use influences physico-chemical and water transmission properties of soil, which ultimately determine the suitability of land for different purposes. In present study, impact of different land use (forest and agriculture) on selected physicochemical and hydrological properties of soil was evaluated and compared with a reference site (uncultivated ravinous wasteland). Land use influenced infiltration rate, bulk density, mean weight diameter of aggregates and plant available water of soils. After 25 years of plantation of forest species, soil organic carbon content increased by more than twofold and mean weight diameter of aggregates by 2- to 6-fold in comparison to reference site. Significant reduction in soil bulk density (4–18%) and increase in steady state infiltration rate (1.5–2 times) was observed under the forest land use system. Conversion of ravine to forest system resulted in significant improvement in moisture retention capacity of soil. Conversion of ravine landform to agriculture adversely affected the soil bulk density and infiltration rate. The study provided practical information regarding rehabilitation potential of different tree species (Prosopis juliflora, Leucaena leucocephala, Acacia nilotica and Azadirachta indica) that could be used for restoration of ustifluvent soil susceptible to gully erosion in the semi-arid region.     

Predicting the decline in daily maximum transpiration rate of two pine stands during drought based on constant minimum leaf water potential and plant hydraulic conductance

The effect of drought on forest water use is often estimated with models, but comprehensive models require many parameters, and simple models may not be sufficiently flexible. Many tree species, Pinus species in particular, have been shown to maintain a constant minimum leaf water potential above the critical threshold for xylem embolism during drought. In such cases, prediction of the relative decline in daily maximum transpiration rate with decreasing soil water content is relatively straightforward. We constructed a soil-plant water flow model assuming constant plant conductance and daily minimum leaf water potential, but variable conductance from soil to root. We tested this model against independent data from two sites: automatic shoot chamber data and sap flow measurements from a boreal Scots pine (Pinus sylvestris L.) stand; and sap flow measurements from a maritime pine (Pinus pinaster Ait.) stand. To focus on soil limitations to water uptake, we expressed daily maximum transpiration rate relative to the rate that would be obtained in wet soil with similar environmental variables. The comparison was successful, although the maritime pine stand showed carry-over effects of the drought that we could not explain. For the boreal Scots pine stand, daily maximum transpiration was best predicted by water content of soil deeper than 5 cm. A sensitivity analysis revealed that model predictions were relatively insensitive to the minimum leaf water potential, which can be accounted for by the importance of soil resistance of drying soil. We conclude that a model with constant plant conductance and minimum leaf water potential can accurately predict the decline in daily maximum transpiration rate during drought for these two pine stands, and that including further detail about plant compartments would add little predictive power, except in predicting recovery from severe drought.     

Partitioning of soil water among tree species in a Brazilian Cerrado ecosystem

Source water used by woody perennials in a Brazilian savanna (Cerrado) was determined by comparing the stable hydrogen isotope composition (deltaD) of xylem sap and soil water at different depths during two consecutive dry seasons (1995 and 1996). Plant water status and rates of water use were also determined and compared with xylem water deltaD values. Overall, soil water deltaD decreased with increasing depth in the soil profile. Mean deltaD values were -35 per thousand for the upper 170 cm of soil and -55 per thousand between 230 and 400 cm depth at the end of the 1995 dry season. Soil water content increased with depth, from 18% near the surface to about 28% at 400 cm. A similar pattern of decreasing soil water deltaD with increasing depth was observed at the end of the 1996 dry season. Patterns consistent with hydraulic lift were observed in soil profiles sampled in 1995 and 1997. Concurrent analyses of xylem and soil water deltaD values indicated a distinct partitioning of water resources among 10 representative woody species (five deciduous and five evergreen). Among these species, four evergreen and one deciduous species acquired water primarily in the upper soil layers (above 200 cm), whereas three deciduous and one evergreen species tapped deep sources of soil water (below 200 cm). One deciduous species exhibited intermediate behavior. Total daily sap flow was negatively correlated with xylem sap deltaD values indicating that species with higher rates of water use during the dry season tended to rely on deeper soil water sources. Among evergreen species, minimum leaf water potentials were also negatively correlated with xylem water deltaD values, suggesting that access to more readily available water at greater depth permitted maintenance of a more favorable plant water status. No significant relationship between xylem water deltaD and plant size was observed in two evergreen species, suggesting a strong selective pressure for small plants to rapidly develop a deep root system. The degree of variation in soil water partitioning, leaf phenology and leaf longevity was consistent with the high diversity of woody species in the Cerrado.     

岷江上游山地森林／干旱河谷交错带几种植被类型土壤含水量研究

采用烘干法和环刀法对土壤物理性质进行了测定,目的是为了重点了解岷江上游山地森林／干旱河谷交错带的不同植被类型下0～40cm土壤含水量的变化。经过2007年4月、7月、9月、11月四个不同时期的测定,结果表明：同一植被类型下（除灌木林地）土壤含水量9月份的最大,与当地的雨季呈现同增同减的关系,而灌木林地下的呈现从4月到1...     

天津滨海新区湿地野生植物资源调查与分析

调查了天津滨海新区湿地野生植物群落,计算出各群落中优势种的重要值,并应用典范对应分析法对湿地植被群落类型及其分布与主要环境因子之间的关系进行了研究。结果表明:1)土壤含盐量、土壤pH值以及滨水距离的差异是形成滨海新区湿地植物分布格局的三个主要环境因素。2)三个主要环境因素之间存在相关关系,滨水距离能够对土壤理化因子的数量和强度进行再分配,间接影响了物种生存状态。三个主要环境因素不仅决定了群落在排序空间中的位置,也决定了群落物种组成。3)优势种的分布与样方的分布格局极其相似,优势种的分布格局在一定程度上决定了群落类型的分布格局。     

桉树人工林的社会、经济和生态问题

按树具有很好的社会和经济效益。按树人工林不但提供各类木材和非木材产品,而且对农田风沙防护、园林绿化以及水土保持等也有重要作用。但长期以来,对按树人工林的生态问题存在很多争论,本文就此作了详细的论述。     

Influence of soil water on the physiological and morphological components of plant water balance in Populus trichocarpa, Populus deltoides and their F(1) hybrids

Patterns of leaf growth, transpiration and whole-plant water balance in Populus trichocarpa, P. deltoides and their F(1) hybrids were studied during a soil drying cycle. Plant responses were analyzed during three distinct stages of dehydration. In stage I, the transpiration rate of drought-stressed plants remained constant and equal to that of well-watered plants even though soil water content declined by more than 40%. Stage II began as soil and plant water deficits induced stomatal closure. When soil water was expressed as a fraction of transpirable soil water, the transition from stage I to stage II occurred at soil water fractions of 0.35, 0.45 and 0.60 for P. trichocarpa, P. deltoides and their F(1) hybrids, respectively. Reductions in leaf growth coincided with the shift from stage I to stage II. As soil water declined further, decreases in relative transpiration and whole-plant leaf area were significantly greater in parental species than in F(1) hybrids. Inherent feedbacks controlling stomatal water loss and the maintenance and growth of leaf tissue appeared to differ between F(1) and parental genotypes in a pattern characteristic of an overdominant mode of inheritance.Stage III began once the ability of stomata to compensate for water loss had been exhausted. Substantial differences were found in plant survival during stage III, with F(1) hybrids surviving longer than parental species. Survival was more strongly correlated with the hydraulic conductivity of xylem tissues than with the dehydration tolerance of leaf tissues. Collectively, these responses suggest that F(1) hybrids were more drought resistant than either parental species and highlight the importance of whole-plant studies of functional relationships between plant growth, water balance and hydraulic conductivity.     

不同灌溉量下3种地被植物耗水特性的研究

采用电子天平和Li-6400光合仪等仪器,于2010年8～9月间对园林绿化常用的3种地被植物,在不同灌溉量下的蒸散量、蒸腾速率变化、水分利用率及土壤含水量进行了研究.结果表明:蒸散量随灌水量增加而增加,但增长幅度不同;日均蒸腾速率大小依次为马蔺>委陵菜>八宝景天,处理Ⅲ>处理Ⅱ>处理Ⅰ;水分利用效率大小依次为八宝景天>...     

东江中上游水土保持林营建技术及效应浅析

从植物营养、土壤科学和恢复生态学的角度全面系统地总结了东江中上游水土保持林的营建技术，并对其效应及演变进行了监测，取得了如下主要结果：(1)选择出适应于该区的先锋、速生和伴生树种，其主要代表种为肯氏相思、红胶木和红锥。(2)严重水土流失区侵蚀土壤不仅缺乏大量元素，也缺乏微量元素，B的缺乏特别典型，显著地影响尾叶桉的生长。(3)种植模式显著影响水土保持的效果，以乔灌草模式效果好。(4)组装配套技术营建的水土保持示范林，使“烂头山”当年植被覆盖率提高40％以上。既能在短期内减少水土流失，又能改善林地环境条件让慢生树种生长，最终形成多树种混交和稳定有效的水源涵养林，可望逐渐向地带性植被群落演变。     

Competition for water between walnut seedlings (Juglans regia) and rye grass (Lolium perenne) assessed by carbon isotope discrimination and delta18O enrichment

Container-grown walnut seedlings (Juglans regia L.) were subjected to competition with rye grass (Lolium perenne L.) and to a 2-week soil drying cycle. One and 2 weeks after the beginning of the drought treatment, H2 18O (delta approximately equals +100%) was added to the bottom layer of soil in the plant containers to create a vertical H2 18O gradient. Rye grass competition reduced aboveground and belowground biomass of the walnut seedlings by 60%, whereas drought had no effect. The presence of rye grass reduced the dry weight of walnut roots in the upper soil layer and caused a 50% reduction in lateral root length. Rye grass competition combined with the drought treatment reduced walnut leaf CO2 assimilation rate (A) and leaf conductance (gw) by 20 and 39%, respectively. Transpiration rates in rye grass, both at the leaf level and at the plant or tiller level, were higher than in walnut seedlings. Leaf intrinsic water-use efficiency (A/gw) of walnut seedlings increased in response to drought and no differences were observed between the single-species and mixed-species treatments, as confirmed by leaf carbon isotope discrimination measurements. Measurement of delta18O in soil and in plant xylem sap indicated that the presence of rye grass did not affect the vertical profile of soil water uptake by walnut seedlings. Walnut seedlings and rye grass withdrew water from the top and middle soil layers in well-watered conditions, whereas during the drought treatment, walnut seedlings obtained water from all soil layers, but rye grass took up water from the bottom soil layer only.     

金沙江干热河谷不同土壤水分对台湾青枣根系生长的影响

通过田间试验研究了不同水分处理下台湾青枣根系的分布状况,调查分析了不同径级根系数量、根系含水率、根系密度等项目。结果表明:台湾青枣根系主要分布在0-60 cm的土壤中,根系数量随土壤含水量的降低而增加,但根系含水率则是随着土壤含水量的增加而增加,而根系数量则随着土壤含水量的减少而增多的特征。因此,A处理(土壤含水量为田间持水量的40%-55%)是台湾青枣生长的最适水量,通过人为控制土壤含水量,以此调节根系生长与空间分布,最终达到调控作物生长和产量。