Effect of flooding-drawdown cycle on vegetation in a system of floating peat mat and pond

The relationship between vegetation and seasonal changes in water level was examined in a system of terrestrializing floating peat mat and pond in a warm temperate zone. The duration of flooding, or drawdown period, is related to vegetation in the mat. The first process of terrestrialization would be the attenuation of floating-sinking movement of the mat and the consequent stabilization of water level. Water level at the time when the movement of the mat was attenuated determined the subsequent vegetation change at the site. Two series of succession according to terrestrialization were recognized, and started from initial conditions of low and high water levels respectively. Habitats in low initial water levels experienced short flooding and long drawdown periods. Species changes in the successional series were:Menyanthes trifoliata-Rhynchospora fauriei-Eriocaulon sikokianum-Sphagnum cuspidatum. Submerged peat was experimentally emerged, and the crowded community ofRhynchospora fauriei andEriocaulon sikokianum established within one or two years. Appearance of these species was controlled by the water level of the habitats in winter. Another series of species changes in terrestrialization process was:Menyanthes trifoliata-Phragmites australis-Carex thunbergii orIsachne globosa. Habitats of these types of vegetation were in the area with relatively high initial water level (long flooding and short drawdown) when the floating-sinking movement of the mat attenuated. After the temporal paludification, the water level was lowered by the accumulation of peat in the process of terrestrialization.     

Seasonal change in the redox property of peat and its relation to vegetation in a system of floating mat and pond

A relationship was sought between species distribution and seasonal change in the redox property of peat in a floating mat in Mizorogaike Pond, central Japan. The mat surface experienced an annual submergence-emergence cycle due to its sinking-rising movement. Redox potential (Eh) of the surface peat showed little difference between communities in the mat in the submergence season (January–June) and early emergence season (July–August). However variation in Eh among communities was clear in the late emergence season (September–December). Among seven communities in the floating mat, theMenyanthes trifoliata-Rhynchospora fauriei, M. trifoliata-Eriocaulon sikokianum-E. bondoense f.pilosum, Sphagnum cuspidatum andM. trifoliata-Carex thunbergii communities had high Eh (400–600 mV) in the late emergence season, while theMenyanthes trifoliata andPhragmites australis-M. trifoliata communities had lower Eh (200–400 mV). TheM. trifoliata-Isachné globosa community was intermediate (300–500 mV). The earlier the emergence of the peat surface began, the higher the Eh became in the late emergence season.     

Seasonal changes in redox properties of peat, nutrition and phenology of Menyanthes trifoliata L. in a floating peat mat in Mizorogaike Pond, central Japan

Seasonal changes in leaf population per area, nutrient absorption rate and elemental concentration of Menyanthes trifoliata L. were studied in a floating peat mat in Mizorogaike Pond, central Japan, with reference to the peat redox potential. Leaf population of M. trifoliata showed a rapid increase in May, reached the maximum in June, and then decreased to 12% of the maximum density in July. The foliage density of M. trifoliata again increased and reached its second maximum in September, and then it decreased to zero in December. The decrease of the foliage density from June to July corresponded to the minimum of redox potential (Eh) of the surface peat. Low Eh in the rhizosphere of M. trifoliata relates to the temporary disappearance of the foliage of the plant from June to July. Nutrient concentration (K, Mg, Ca, Fe) in M. trifoliata roots showed minimum in June to August. The nutrient absorption rate of M. trifoliata evaluated from the rubidium absorption rate of excised root of M. trifoliata showed a minimum value in June and July. Peat redox properties would affect the nutrient absorption activity of the roots and the consequent foliage phenology of M. trifoliata in Mizorogaike Pond.     

The nature value of the ditch vegetation in peat areas in relation to farm management

Farmers can play an important role in enhancing the diversity of plant species in ditches, since they carry out most of the management. Little is known about the measures farmers can take to enhance aquatic biodiversity in ditches. Therefore, a field study was set up to determine how dredging, ditch cleaning, and nutrient supply in the adjacent fields affect the floristic values of the ditch vegetation in peat areas. A total of 240 ditches on 84 dairy farms were selected, to establish the effect of ditch cleaning, dredging, and nutrient supply. Generalised linear modelling was used to determine the most relevant factors, and to obtain quantitative relations between those factors and two indices of floristic value. Ditch management, field management, and water management were found to affect the floristic values of the ditch vegetation. Increasing the water depth proved to be the most cost-effective measure. Further improvements can be obtained by choosing certain machines or specific management periods, or reducing the N supply. The effect of the P supply is not yet sufficiently clear. The water boards can enhance floristic values by raising the ditch water table and by lowering the Cl^– concentration in the ditches.     

Key variables controlling the vegetation of a cool-temperate mire in northern Japan

Abstract. In the cool-temperate Bibi Mire, Hokkaido, Japan, valley fens and flood-plain fens have quite different vegetation. The main variables controlling the vegetation were all hydrological: mean water level, water level fluctuation and surface water flow. Chemical factors such as electrical conductivity, dissolved oxygen and related peat decomposition were less important. The pH was about neutral and has little effect. The flood-plain fen developed under fluctuating water table conditions. The dominant species are Calamagrostis langsdotffii and Carex pseudocuraica. When temporal inundation occurs in the rainy or typhoon seasons, the submergence stimulates bud germination of the stoloniferous C. pseudocuraica, which can rapidly elongate its stolons upward. Some large floating peat mats occurred in the flood-plain fen zone. On these mats some Alnus japonica saplings establish and patches of alder forest can arise. Here the water level was higher than in the peripheral alder forest zone. The valley fen is dominated by Carex lasiocarpa var. occultans and/or C. limosa. It is formed under stable water table conditions in the inundated parts of the mire -where the non-inundated wet areas are dominated by alder trees. In the area where the surface water is flowing, these two fen sedges grow in deeper water since the high oxygen content is considered to compensate the flooding stress.     

Plankton composition and water quality in a pond of spring origin in Turkey

Phyto/zooplankton composition, chlorophyll a, and some water quality parameters were investigated in a spring-originated pond in Central Anatolia between February 2001 and January 2002. Water temperature, pH, dissolved oxygen, Secchi depth, total and calcium hardness, nitrate-nitrogen, nitrite-nitrogen, ammonia-nitrogen, total phosphorus, and soluble reactive phosphorus levels were analyzed. A total of 49 species belonging to Bacillariophyceae, Chlorophyceae, Cyanophyceae, Cryptophyceae, and Dinophyceae were identified. The highest phytoplankton abundance was found in August, whereas the lowest was determined in January. Phytoplankton abundance increased from February to August and declined in the following months. The Bacillariophyceae were dominant in the phytoplankton community. A total of 21 species of Rotifera, 2 species of Cladocera, and 1 genus of Copepoda were found. The zooplankton community was dominated by Rotifera. The highest abundance of zooplankton was recorded in July and the lowest value in November. The annual mean concentration of chlorophyll a was measured as 1.90 μg l⁻¹. In spite of these eutrophic levels (mean values of total phosphorus and nitrate-nitrogen: 0.069 mg P l⁻¹ and 0.68 mg N l⁻¹), phytoplankton cannot grow satisfactorily because of the short water retention time (0.6 day⁻¹). The shallowness of the pond together with the low phytoplankton biomass and the high concentrations of nutrients are discussed.     

Effects of climatic change on chemistry and vegetation of peatlands,with special reference to interaction with atmospheric deposition

This paper summarizes expected changes in hydrology, chemistry and biota of Dutch peatlands (bogs, fens and moorland pools) caused by climatic changes resulting from the Greenhouse Effect. Special attention is paid to the interaction with atmospheric acid deposition. In both bogs and moorland pools prolonged drought periods may cause deleterious effects on biota because of the release of atmospherically-derived reduced sulphur compounds. In fenlands negative changes will be caused by eutrophication due to increased supply of allochtonous water. Long-term water and nutrient budgets are needed, along with better predictions of expected climate changes, to develop models of changes in hydrology, chemistry and biota of peatlands.     

Nutrient concentrations in litterfall from some western conifers with special reference to calcium

Foliar litterfall nutrient concentrations were analysed for selected members of Taxodiaceae and Cupressaceae families andPseudotsuga menziesii for two arboreta in western Oregon and Washington. Nutrient results between arboreta show similar concentrations with the exception of magnesium, which may be the result of historical land use. Nutrient concentrations between species vary considerably.Pseudotsuga menziesii is particularly distinctive from the Cupressaceae and Taxodiaceae by retaining large amounts of phosphorus and potassium. Taxodiaceae is distinctive by high concentration of Mg while Cupressaceae retains calcium, especiallyChamaecyparis nootkatensis. Results suggest that all members of Taxodiaceae and Cupressaceae retain considerably more Ca than Pinaceae in foliar litter.     

Nitrogen content in the brown alga Fucus gardneri and its relation to light, herbivory and wave exposure

Nitrogen is a necessary element for much of seaweed physiology, and is the most common limiting nutrient for marine macroalgae. Therefore, the content of nitrogen in algal tissue is often considered a useful indicator of algal productivity. However, the significance of algal nitrogen content in the field is understudied. We used a factorial manipulation of light and herbivory at three sites in order to evaluate how three factors (light, herbivory, wave exposure) affect the nitrogen content of the brown alga Fucus gardneri. We found that nitrogen content was a function of (1) nitrogen supply via amount of water flow and (2) irradiance, possibly via photoinhibitory effects. This research shows that local effects, by shifting nutrient allocation, can change nitrogen content over spatial scales of centimeters.     

Fungal root endophytes from natural vegetation in Mediterranean environments with special reference to Fusarium spp

Surveys (in 2002 and 2003) were performed for fungal endophytes in roots of 24 plant species growing at 12 sites (coastal and inland soils, both sandy soils and salt marshes) under either water or salt stress in the Alicante province (Southeast Spain). All plant species examined were colonized by endophytic fungi. A total of 1830 fungal isolates were obtained and identified by morphological and molecular [internal transcribed spacer (ITS) and translation elongation factor-1alpha gene region (TEF-1alpha) sequencing] techniques. One hundred and forty-two fungal species were identified, belonging to 57 genera. Sterile mycelia were assigned to 177 morphospecies. Fusarium and Phoma species were the most frequent genera, followed by Aspergillus, Alternaria and Acremonium. Fungal root endophytic communities were influenced by the soil type where their respective host plants grew, but not by location (coastal or inland sites). Fusarium oxysporum, Aspergillus fumigatus and Alternaria chlamydospora contributed most to the differences found between endophytic communities from sandy and saline soils. Host preference was found for three Fusarium species studied. Fusarium oxysporum and Fusarium solani were especially isolated from plants of the family Leguminosae, while Fusarium equiseti showed a preference for Lygeum spartum (Gramineae). In some cases, specificity could be related to intra-specific variability as shown by sequencing of the TEF-1alpha in the genus Fusarium.     

Carbohydrate polymers in food preservation: an integrated view of the Maillard reaction with special reference to discoveries of preserved foods in Sphagnum-dominated peat bogs

Well-preserved human bodies more than 2000 years old have been found in peat bogs derived mainly from sphagnum mosses. Preservation is correlated with the occurrence of -keto-carboxylate groups in a glycuronoglycan (‘sphagnan') that comprises 60% of the holocellulose in the hyaline cell walls of the mosses [Painter (1991b). Carbohydr. Polym., 15, 123–142]. There is now renewed interest in other biodegradable materials that have been found preserved in peat, including carcasses of domestic animals, loaves of bread, dried fruits, berries, and kegs of butter or cheese up to 1800 years old. This review attempts to correlate these examples of fortuitous preservation in peat with other, more familiar methods of food preservation that depend in the first instance upon the condensation of highly reactive carbonyl compounds with primary amino-groups or ammonia. The Maillard reaction inhibits microbial growth by sequestering ammonia, aminoacids and peptides, while the brown, polymeric end-products (‘melanoidins') inhibit by cross-linking polypeptide chains and sequestering essential, multivalent metal cations. These reactions could find broader or entirely new applications in food preservation.     

具有抑制剂和营养循环的恒化器竞争模型

在具有抑制剂的恒化器竞争模型中考虑营养循环的作用,得到系统有界和持久的充分条件。     

Nutrient runoff dynamics in a rural catchment: Influence of land-use changes, climatic fluctuations and ecotechnological measures

The main trend in land-use changes in the Porijõgi River catchment, south Estonia, is a significant increase in abandoned lands (from 1.7% in 1987 to 10.5% in 1997), and a decrease in arable lands (from 41.8 to 23.9%). Significant climatic fluctuations occurred during the last decades. Milder winters (increase of air temperature in February from −7.9 to −5.5°C during the period 1950–1997) and a change in the precipitation pattern have influenced the mean annual water discharge. This results in more intensive material flow during colder seasons and decreased water runoff in summer. During the period 1987–1997 the runoff of total-N, total-P, SO₄, and organic material (after BOD₅) decreased from 25.9 to 5.1, from 0.32 to 0.13, from 78 to 48, and from 7.4 to 3.5 kg ha⁻¹ year⁻¹, respectively. Most significant was a 4–20-fold decrease in agricultural subcatchments while in the forested upper-course catchment the changes were insignificant. Variations of total-N, and total-P runoff in both the entire catchment and its agricultural subcatchments are well described by the change of land use (including fertilization intensity), soil parameters and water discharge. In small agricultural subcatchments the rate of fertilization was found to be the most important factor affecting nitrogen runoff, while land-use pattern plays the main role in larger mosaic catchments. Ecotechnological measures (e.g. riparian buffer zones and buffer strips, constructed wetlands) to control nutrient flows from agricultural catchments are very important.     

Fungal associations of roots of dominant and sub-dominant plants in high-alpine vegetation systems with special reference to mycorrhiza

Summary Types of root infection were analysed in healthy dominant and sub-dominant plants of zonal and azonal vegetation above the timberline in the Central and Northern Calcareous Alps of Austria. In the open nival zone vegetation, infection by fungi of the Rhizoctonia type was predominant, vesicular-arbuscular mycorrhizal infection, which was mostly of the fine endophyte (Glomus tenuis) type, being light and mainly restricted to grasses in closed vegetation patches. More extensive Glomus tenuis infection was found in the alpine grass heath, but in Carex, Rhizoctonia was again the most important fungus. The ericaceous plants of the dwarf shrub heath have typical ericoid infection, but quantitative analysis reveals a decrease of infection intensity with increase of altitude. The possible function of the various types of root infection are discussed, and the status of Rhizoctonia as a possible mycorrhizal fungus is considered.     

Annual brown fat dynamics in Pipistrellus hesperus and Myotis californicus with special reference to winter flight activity

An examination of the annual changes in brown fat deposits of Pipistrellus hesperus and Myotis californicus reveals:

• 1.1.P. hesperus reaches peak brown fat levels in January and February, declining rapidly through March and April, then increases gradually through the remainder of the year.
• 2.2.M. californicus, on the other hand, maintains peak levels of brown fat from December through February, decreasing gradually through August, then increasing rapidly in the fall.
• 3.3.The major brown fat deposits for both species are interscapular, jugular, squamooccipitocervical and carotid bodies.
• 4.4.The interscapular deposit (which accounts for 50–70% of all brown fat) appears to be a good index of brown fat dynamics.
• 5.5.Brown fat appears to be important in maintaining body temperature during night at cold ambient temperatures.

     

东海近海海域营养盐分布特征及其与赤潮发生关系的初步研究

根据2002年4月25日～5月2日的调查数据,分析了东海近海海域营养盐(NO3--N,PO4^3-P,SiO3^2-Si,NH4-N等)的分布特征,并初步探讨了营养盐分布与赤潮发生的关系．结果表明,调查海区营养盐浓度较高,与国家一类海水水质相比,无机氮和无机磷的超标率分别为46％和60％,长江口及杭州湾附近海域富营养化程度比较严重．调查海域由于受沿岸长江等河流输入的影响。营养盐浓度自近岸向外海快速递减,等值线几乎与海岸线平行．根据调查结束后赤潮发生的特点和区域,表明营养盐浓度的增加,尤其是DIN和PO4^3-P的增加,与赤潮的发生有一定关系。但本次赤潮并不是发生在营养盐浓度最高的海区,因此,富营养化并不是诱发本次赤潮发生的唯一环境因素．     

Nutrient dynamics in a tritrophic system of ants,aphids and beans

The interactions between ants (Lasius niger), aphids (Aphis fabae) and plants (Phaseolus vulgaris) were studied in a laboratory experiment with the following treatments: application of N‐fertilizer for plants, supply of mealworms or sugar solution or their combination as alternative food sources for ants. Three main questions were studied: (1) Do ants reduce tending to honeydew‐producing aphids when an alternative sugar or protein resource was available? (2) Is aphid predation/protein consumption by ants higher when additional carbon is offered to maintain the carbon/protein balance? (3) Does fertilizer treatment propagate in the food web? For the experimental analysis stable isotope techniques were applied. δ¹⁵N served as a marker for the pathway from plants to higher trophic levels. Low δ¹⁵N‐value of fertilizer spread from plant shoots to aphids and ants. To trace which sugar‐/protein source was consumed by ants, the different ¹³C/¹²C‐ratios of C₃‐ and C₄‐plants were used with aphids feeding on C₃‐plant material, while mealworm food and sugar solution originated from C₄‐plant material. Fertilizer application had no effect on biomasses of plants, consumers or microflora. Ant biomass was significantly higher when additional sugar solution was offered. Higher contents of ¹³C indicated a high incorporation rate of additional sugar. Additional protein had no effect on colony biomass and no increasing predation on aphids could be observed when carbon was in excess. However, due to the lack of queens and newly produced larvae, protein requirements of experimental colonies were lower than in natural systems. Ants positively affected aphid populations, but reduced tending, whilst having access to an alternative sugar resource. When sugar/protein was offered to ants, the host plant had an increased root/shoot ratio. This indicates that decreasing aboveground activity of ants could lead to reduced plant growth of aphid‐infested plants, presumably due to higher fungal attack on shoots.