北方稻田生态系统水量平衡及水分效率研究

１９９３～１９９５年研究了５种不同模式水稻田生态系统水量平衡及水分效率结果表明,不同水稻田模式其总耗水量之间有明显差异,其中节水模式和节水节肥模式较常规模式节省灌溉水达１５～２３％,水分生产效率增加３０％以上．各模式蒸发蒸腾耗水量在同一生长季内基本相同．田间结构及调控管理对其无明显影响实测水稻生育期田间蒸发蒸腾量与计算的可能蒸发蒸腾量相差不过５％。     

Relations of soil properties to topography and vegetation in a subtropical rain forest in southern Taiwan

Soil chemical properties for a subtropical rain forest in the Nanjenshan Reserve, southern Taiwan, were examined to determine soil-landscape and soil-vegetation relationships. Soil sampling sites were separated into four groups based on landscape features and exposure to the prevailing northeasterly monsoon winds. Corresponding vegetation types were delimited along the first DCA axis. The forest showed a drastic change both in structure and floristic composition along the wind-stress gradient. Redundancy analysis (RDA) showed that both topographic variables and vegetation types were needed to explain the variation in soil data. Soil properties that differed significantly among landforms were pH, available N, CEC, exchangeable Al, K, Ca and Mg. Levels of pH, exchangeable Ca and Mg increased in a downslope direction, and exchangeable Al tended to be higher in the upper slope soils. These trends pointed to the importance of slope processes in redistribution of soil minerals. The main differences in soil properties attributed to the influence of the occupying vegetation were apparently aspect dependent. The contents of available N, exchangeable K, and CEC in the 0–40 cm depth of soils under windward low-stature (mostly sclerophyllous) forest were consistently lower compared to those under the leeward forest. For a given catena, however, soil variability associated with vegetation differences seemed to be confounded by the slope processes.     

Soil and plant water relations in a crested wheatgrass pasture: response to spring grazing by cattle

Summary Few field studies have attempted to relate effects of actual livestock grazing on soil and plant water status. The present study was initiated to determine the effects of periodic defoliations by cattle during spring on soil moisture and plant water status in a crested wheatgrass (Agropyron cristatum (L.) Gaertn. and A. desertorum (Fisch. ex Link) Schult.) pasture in central Utah. Soil moisture in the top 130 cm of the soil profile was depleted more rapidly in ungrazed plots than in grazed plots during spring and early summer. Soil moisture depletion was more rapid in grazed plots in one paddock after 1 July due to differential regrowth, but there was no difference in soil water depletion between plots in another paddock during the same period. This difference in soil water depletion between paddocks was related to a difference in date of grazing. Although more water had been extracted from the 60 cm to 130 cm depths in ungrazed plots by late September, cumulative soil moisture depletion over the entire 193 cm profile was similar in grazed and ungrazed plots. Prior to 1 July, grazing had no effect on predawn leaf water potentials as estimated by a pressure chamber technique; however, after 1 July, predawn leaf water potentials were lower for ungrazed plants. Midday leaf water potentials were lower for grazed plants before 1 July, but did not differ between grazed and ungrazed plants after 1 July. A 4- to 8-day difference in date of defoliation did not affect either predawn or midday leaf water potentials. The observed differences in water use patterns during spring and early-summer may be important in influencing growth and competitive interactions in crested wheatgrass communities that are subject to grazing by domestic livestock.     

Structure of the woody vegetation in disturbed and undisturbed arid savanna,Botswana

The structure of woody vegetation was studied in little disturbed arid savanna and in adjacent over-grazed vegetation. In the over-grazed areas density and cover of woody plants were higher than in the less disturbed vegetation. The difference was accounted for by one species, Acacia mellifera, which was strongly dominant in the overgrazed vegetation. In the open savanna, the woody species varied in height from small shrubs to trees, while the dense shrub vegetation was of uniformly low stature.It is suggested that, while the differences in total abundance of woody species depend on differences in the amount of soil water available for woody growth, differences in species composition and height distribution are governed by the spatial and temporal distribution of water in the soil profile.     

Soil and vegetation responses to hydrological manipulation in a partially drained polje fen in New Zealand

Anthropogenic drainage causes loss of natural character in herbaceous wetlands due to increased soil oxygen penetration. We related vegetation gradients in a New Zealand polje fen to long-term effects of drains by using hydrological, edaphic and vegetation data, and a before-after-control-impact (BACI) design to test responses to experimental drain closure. Soil profiles and continuous water level records revealed a site subject to frequent disturbance by intense but brief floods, followed by long drying periods during which areas close to drains experienced lower water tables and more variable water levels. Classification of vegetation data identified 12 groups along a moisture gradient, from dry areas dominated by pastoral alien species, to wet communities dominated by native wetland sedges. Lower total species diversity and native representation in pastoral communities were related to the high proportion of alien competitor and competitor-disturbance species, compared with the stress tolerator-dominated flora of other groups. Species–environment relationships revealed highly significant correlations with soil water content and aeration as measured by redox potential (E_H) and steel rod oxidation depth, as well as soil nutrient content and bulk density. Comparison of root anatomy confirmed greater development of flood-tolerant traits in native species than in pastoral aliens, and vegetation N:P ratios indicated that most communities were probably nitrogen-limited. Flooding rapidly re-established wetland hydrology in dried sites in the impact area, and lowered E_H and soil oxidation depth, but had no effect on N and P availability. Presence and cover of pastoral alien species decreased in these areas. This study supports the use of hydrological manipulation as a tool for reducing soil oxidation and thus the impact of alien plant species at restoration sites with minimal intervention, but suggests the need for detailed information on species flooding tolerances and hydrological preferences to underpin this approach.     

上海园林绿地植被结构与温湿度关系浅析

通过对上海市区园林绿地29个样方的植被结构与微环境及土壤湿度、温度的调查,结果表明,绿地具有明显的增湿降温作用,影响这一作用的主要因素是绿地的乔木植物盖度。土壤湿度与草本植物盖度呈极显著正相关。土壤湿度、温度在一定区间内,呈极显著正相关。复杂完善的植被结构对防止土壤水分蒸发具有较好的效果。     

Variations in life-form composition and foliar carbon isotope discrimination among eight plant communities under different soil moisture conditions in the Xilin River Basin,Inner Mongolia,China

Water is one of the key limiting factors for the survival and growth of plant species in arid and semi-arid steppe regions. Different plant functional groups (PFGs) based on life-forms differ in their strategies to cope with limited water availability. The foliar carbon isotope discrimination () value provides an integrated measurement of internal plant physiological and external environmental properties affecting photosynthetic gas exchange over the time interval when the carbon was fixed. In this study, we surveyed the composition and values of various life-forms (shrubs, sub-shrubs, perennial grasses, perennial forbs and annuals) in eight different plant communities along a soil moisture gradient in the Xilin River Basin, Inner Mongolia, China. Our results showed that: (1) life-forms occurred variously in eight steppe communities with different soil moisture status; (2) in wetter habitats, forbs were more abundant and accounted for the majority of aboveground biomass, whereas grasses became more important in drier habitats. Shrubs and sub-shrubs increased with decreasing soil water availability and their relative biomass rapidly increased in degraded steppe and sand dune communities. (3) The numerical order of the mean values of life-forms is as follows: perennial grasses (15.86) < shrubs (16.10) < perennial forbs (16.45)=annuals (16.41) < sub-shrubs (17.55), reflecting their differences in water use efficiencies. The significant differences in the values among these life-forms suggested that life-form-based PFGs not only represent a morphological classification of these plants, but could also represent a functional group integrating different physiological processes such as water use strategies, which may partially explain the differences in PFG composition and competitive ability of co-existing species along environmental gradients in the Xilin River Basin.     

Germination in Baltic coastal wetland meadows: similarities and differences between vegetation and seed bank

The abundance and variety of seedlings in Baltic coastal grasslands was studied in cattle grazed and ungrazed areas in seashore and delta on the western coast of Finland. The vegetation, seed bank and environmental conditions of the same sites were also studied. Altogether 4609 seedlings were observed in 79 field plots (20 cm× 20 cm) making an average of 1458.54 seedlings/m². The majority of the seedlings were dicots (67.5%) and perennials (96.8%). Altogether 44 species and an average of 4.14 species per plot were identified as seedlings. The most abundant taxon, Carex formed 23.2% of all the seedlings observed in the field. In the delta the seedling density was two times that found at the seashore. Also, the numbers of species of seedlings per plot were significantly higher in the delta than in the seashore, but in total, more species germinated from the seashore than from the delta even though the number of plots was higher in the delta (n = 51) than in the seashore (n = 28). The numbers of species and seedlings per plot were smaller in grazed sites than in ungrazed ones similar to the pattern earlier reported concerning the mature vegetation and seed bank. The mean numbers of seedlings were the highest at lower geolittoral plots (about 20 cm elevation), where the seed bank was also densest. About 60.0% of the mature species in the plots were also detected as seedlings and 91.4% of the seedling species were found in the mature vegetation of the plots. The number of seedlings was positively correlated with the cover of mature vegetation giving support to the nurse effect theory. Seedling numbers were negatively correlated with the abundance of litter indicating that litter restricts germination because it is a mechanical barrier but also decreases the amount of light. The number of seedlings and species, both in total and per unit area, were greater in the seed bank than in the field seedling population. The seedling population was more similar to the mature vegetation than to the seed bank. This revised version was published online in August 2006 with corrections to the Cover Date.     

Relationships between National Wetlands Inventory maps and hydrophytic vegetation in Florida

This paper reports a preliminary investigation about National Wetlands Inventory (NWI) maps to see how they might be used in conjunction with other sources of information to provide offsite wetlands regulatory delineation. A geographic information system was used to overlay and compare NWI maps with ground-based tree species composition data from the US Department of Agriculture Forest Service Forest Inventory and Analysis program (FIA). Ninety plots located in the Apalachicola National Forest in northern Florida were used. The NWI mapped 42 of the 90 plots as wetlands. FIA data was used to calculate Prevalence Index (PI) scores. Twenty-four additional plots had PI < 3.0 and thus had hydrophytic vegetation. These plots may also have been wetlands by the Cowardin definition. The hypothesis that wetland identification did not differ between natural-origin versus planted forests was evaluated. NWI classified 61% of natural stands with PI <3.0 as wetlands, whereas 38% of planted stands with PI < 3.0 were mapped as wetlands. There were statistically significant differences (P < 0.05) in the relationships between hydrophytic vegetation and wetland status for plantations and natural-origin stands. FIA data was used to compare the actual frequency of species found in wetlands with the frequency ranges assigned for the NWI Regional Indicators. The observed frequency of occurrence in NWI-mapped wetlands agreed with the Regional Indicator frequency range for 6 of the 18 species. Most species not in agreement were reasonably close to their assigned frequency range, but some differed substantially. While this was a pilot-scale study, we believe that this technique can ultimately yield valuable new information on the tree characteristics of NWI wetlands, especially at larger spatial scales, such as states or regions.     

Short-term effects of fire frequency on vegetation composition and biomass in mixed prairie in south-western Manitoba

The net effects of one, two, and three spring burns in consecutive yearson the aboveground biomass, species composition, and soil variables wereassessed in two different mixed-grass prairie sites in south-western Manitoba.Precipitation in the first year was greater than the 30-year average but lowerduring the next three years. The first site (Area 6) was characterized byBouteloua gracilis, Stipa spartea,Selaginella densa and lichens, while the second, somewhatdrier site (Area 10) was dominated by B. gracilis andCarex spp. Each burn treatment was applied to 15 plots inarandom block design. Vegetation and soil data collected following the thirdburnare presented. In general, the effects of repeated burning were more pronouncedin the drier Area 10, where litter was significantly reduced with eachadditional burn. In Area 6, litter was significantly reduced only after threeyears of burning. In both sites, the cumulative effect of fire had nosignificant effect on total standing crop, even after three consecutive yearsofburning. In the drier Area 10, however, the biomass of several componentsshifted such that B. gracilis biomass increasedsignificantly and forb biomass decreased significantly after three burns. Plantcover was also affected more in the drier Area 10. The cover of B.gracilis, the dominant C₄ grass, significantly increasedand Carex spp. cover decreased after two burns in thedriersite. In Area 6, the most significant effect of fire was a reduction inSelaginella and lichen cover. Bare ground increased inbothsites as the number of burns increased. There was little change in soilnutrients with burning, but soil moisture somewhat decreased and surfacetemperature significantly increased after three burns.     

Water storage compromises walking endurance in an active forager: evidence of a trade-off between osmoregulation and locomotor performance

Trade-offs between locomotor performance and load-carrying in animals are well-established and often result from requisite life processes including reproduction and feeding. Osmoregulation, another necessary process, may involve storage of fluid in the urinary bladder of some species. The purpose of this study was to determine whether storage of urine in the urinary bladder reduces walking endurance in an actively foraging lizard. The results of our paired-design study indicate that the volume of fluid stored in the urinary bladder (36.5+/-1.6 ml) contributed a significant load (9.2% of body mass) to the lizards. This load resulted in a disproportionate 24.5+/-2.8% decrement in walking endurance. Specifically, Gila monsters walked at a fixed pace for a significantly shorter duration when the urinary bladder contained fluid (26+/-2.0 min) compared to when the bladder was empty (34.3+/-2.3 min). Since fluid stored in the bladder contributes to osmoregulation in this species, our results indicate the presence of a trade-off between osmoregulation and endurance in Gila monsters. Bearing other loads (e.g., a clutch or meal) influences the evolution of life-history traits and foraging strategy; thus the negative effect of fluid storage on endurance may also have evolutionary implications.     

Relationship between exposure to an insecticide and fluctuating asymmetry in a damselfly (Odonata,Coenagriidae)

In this study, we explored the effects of pesticide on fluctuating asymmetry (FA) levels and mortality of Ceriagrion sp. larvae. The results showed that the mortality of larval damselflies treated with pesticide was significantly higher than that treated with tap water which had been aerated for 48 h, but there were no significant differences among mortality of larvae treated with different concentrations of pesticide. Meanwhile, we found that the level of FA of the first tibia length, one of the seven bilaterally symmetrical traits (First femur length, First tibia length, Second femur length, Second tibia length, Third femur length, Third tibia length and Prementum width), differed significantly with different treatments, whereas the others did not show any significant differences. The Bonferroni (Dunn) t Tests revealed that FA of the first tibia length at 15 × 10⁻⁹ mgl⁻¹ was significantly higher than that at 1.5 × 10⁻⁹ mgl⁻¹ and control. There was no significant relationship between trait size and the absolute difference between their right and left sides. There was also no significant relationship between body size and the absolute difference between right and left sides. Trait size was significantly positively correlated with body size. FA was not associated with mortality. Therefore, we concluded that FA of the first tibia length of Ceriagrion sp. larvae may be induced by sublethal doses of pesticides. That is to say, its FA may be regarded as an indicator of reflecting the level of pesticide stress. Handling editor: K. Martens     

Association between feral pig disturbance and the composition of some alien plant assemblages in Hawaii Volcanoes National Park

Association analysis was used to assess relationships among 25 important alien plant species and their association with feral pig rooting in Hawaii Volcanoes National Park, Hawaii, U.S.A. Results of the association analysis were summarized by means of a simplified, rank-based, polar ordination which yielded three subjective species assemblages. One group was characterized by an association with the endpoint species, Ehrharta stipoides. A second group consisted of species associated with the other endpoint species, Andropogon virginicus. The third group comprised a diverse assemblage of 14 species in the middle of the ordination.Comparison of ordination scores with each species's association with pig-induced soil disturbance revealed that members of the Ehrharta group were strongly positively associated with pig activity, whereas members of the Andropogon group were generally negatively associated. The third group showed no association with pig-induced soil disturbance.These results suggest a strong relationship between feral pig activity and the composition of the alien portion of the plant community. Analysis of the ecologies of both plants and pigs suggests that some species may both encourage pig activity and benefit from it. Likewise, other alien plants appear to neither require nor benefit from pig-induced soil disturbance. While pigs appear to play an important role in the organization of these communities, their removal may have a negligible impact on the success of many of the common weeds in the area. Nomenclature: Wagner, W. L., Herbst, D. R., & Sohmer, S. H. 1990. Manual of the Flowering Plants of Hawai'i. University of Hawaii Press/Bishop Museum Press, Honolulu.     

黄土区防护林主要造林树种水分供需关系研究

通过3年的定位观测,分析了晋西黄土区护林主要造林树种刺槐和油松寺地供水与耗水关系,油松和刺槐林地4－6月林地水分消耗大于供给,供耗矛盾突出;雨季水分供应充足,土壤贮水增加;相同条件下密度大的林分耗水量较大,在干旱季节和年份,相同条件下,密度大的林分林地有效供水较少,林地水分亏损较为严重;不同坡向的水分缺量大小顺序为阳坡＞半阳坡＞阴坡,本文引入耗水特性系数来表示林分耗水的大小和需水量的满足程度,研究表明,用耗水特性系数表示林木规律和水分供耗关系是适合的衡量指标。     

不列颠·哥伦比亚省北部小杆松及白云杉立地指数与生态立地质量的关系

为在ＰｒｉｎｃｅＲｕｐｅｒｔ林区的“亚北方”部分建立生态立地质量与森林生产力的联系,对从９３个小杆松林分和７７个白云杉林分获得的数据进行了分析．所研究的林分处于两个气候状况、８个土壤水分状况以及５个土壤养分状况．这些气候、土壤水分和养分状况被视为等级变量用于林地分类和回归分析．小杆松和白云杉的立地指数随土壤水分和养分状况变化而变化,但不依赖于气候变化．与土壤水分相关的变化格局对两个种来说很相似,但与土壤养分相关的变化格局则全然不同．在所建立的５类回归模型中,土壤小区模型对于两个种都显示出立地指数与土壤水分和养分状况具有很强的相互关系（Ｒ２＞０．８０,ＳＥＥ≤１．６ｍ）．可以认为土壤水分和养分的等级度量在大范围内可作为小杆松和白云杉立地指数的预测预报因子．     

Relationships between land snail assemblage patterns and soil properties in temperate-humid forest ecosystems

Aim The objectives were to (1) analyse the combined effects of soil pH, Ca content and soil moisture on total density and species richness of land snails in forest ecosystems, (2) explore relationships between the quantitative composition of snail assemblages and habitat characteristics, (3) investigate the relationships between soil pH and density of some of the most frequent species, and (4) compare the data with those from studies conducted in other temperate‐humid regions of Europe. Location Study sites were selected from 15 landscape types including different lithologies within the area of Baden‐Württemberg (35,000 km²), SW Germany. Methods Snails were recorded quantitatively from 83 study sites, with four plots representing a total of 0.25 m² per site. Topsoil samples from each site were analysed for pH, exchangeable Ca, and Ca content of carbonates. Three categories of soil moisture (dry, intermediate and wet) were established and defined according to the (climatic) water balance. Numbers of individuals and species were brought in relation to soil moisture and soil pH. Cluster analyses were conducted to identify groups of quantitatively similar snail species assemblages. Results Topsoil pH (2.7–7.5) and soil Ca contents were closely correlated. On dry soils, total snail density and species richness are generally low and do not change with pH, but clearly increase with increasing pH on intermediate moisture soils and on wet soils. On the latter, numbers of individuals and species are generally much higher compared with intermediate moisture sites at the same value of soil pH. Changes of density in relation to soil pH vary between species. Depending on the species, density increases only in the lower or only in the higher range of pH, is not related to pH, or decreases with increasing pH. Furthermore, these patterns vary within the same species depending on the region. This became evident from comparisons with other studies, particularly between sites in SW Germany and southern Scandinavia. From cluster analyses, subgroups of snail assemblages of high quantitative similarity were identified. Group formation is explained by soil pH to some extent, and one subgroup showed a connection with coniferous woodland sites on acidic soils. No further environmental factors available from our data could explain the clustering of snail assemblages more detailed. Main conclusions Soil moisture is the strongest determinant of snail density and species richness at undisturbed woodland sites, but effects of soil moisture and soil pH on these patterns are closely interrelated on intermediate moisture soils and wet soils. However, the quantitative species composition of the land snail assemblages is related to soil properties to a lower degree than snail density and species richness, and other habitat characteristics such as vegetation or litter quality, can be important for species dominance in addition.     

Soil physical properties in relation to rice yield and water consumption under flooded and unflooded conditions

Summary Four paddy soils from Thailand were included in this investigation. The soils are described as marine alluvial, fresh water alluvial, hydromorphic alluvial and hydromorphic non-calcareous brown soil. The hydraulic conductivity of water saturated soil was determined on puddled samples, and soil moisture retention curves were recorded for unpuddled samples. In a pot experiment rice variety RD-1 was grown on the soils under flooded and unflooded conditions. For the soils studied a negative relationship was found between the hydraulic conductivity and the ability of the soil to retain water against a given suction. The grain yield was higher under flooded conditions, while among the various soils studied in this experiment grain yield increased with decreasing water content in the suction range studied and increasing hydraulic conductivity of the soils. Better root development facilitated by more favourable physical conditions in highly permeable soils could be the possible reason for the yield increase.     

Amelanchier alnifolia vegetation in eastern Idaho,USA and its environmental relationships

Fifteen shrub stands of Amelanchier alnifolia vegetation were studied using Braun-Blanquet procedures, tabulated, and ordered by Twinspan, Decorana, and field experience into 5 groups of stands. The stands occurred on the lower slopes of the southwestern Teton and southeastern Big Hole mountains of eastern Idaho and in-and outside a U.S. Forest Service exclosure above the Hoback River in adjacent Wyoming. The ecology of this Amelanchier vegetation as a whole and of the 5 groups of stands is discussed using Jenny's factors of soil formation (1941, 1958, 1980) as a framework. Plant indicator values (Ellenberg 1979, 1988) which rank species on their occurrences in relation to light, temperature, continentality of climate, water availability, soil reaction (pH), and soil nitrogen supply, were independently assigned to the 121 species of vascular plants encountered in the described stands.