SEASONAL PATTERNS OF CO2 AND WATER VAPOR EXCHANGE OF JUNCUS ROEMERIANUS SCHEELE IN A GEORGIA SALT MARSH

CO₂ and water vapor exchange studies of intact plants of black needle rush (Juncus roemerianus Scheele) were conducted in an undisturbed marsh community on Sapelo Island, Georgia. The seasonal patterns of the light and temperature responses of net photosynthesis, transpiration, leaf diffusive conductance, water-use efficiency and respiration were determined five times over the year. Internal resistances to CO₂ uptake were also evaluated. Net photosynthesis was highest in early spring, but declined only slightly through the year. A distinct and moderate temperature optimum of net photosynthesis was observed with decreasing rates above 30 C. Leaf conductances to water vapor were similar at all seasons and were high at cooler temperatures and decreased with increasing temperature. Transpiration was relatively high and constant during all seasons. The water-use efficiency of photosynthesis was high below 25 C, but decreased sharply above that temperature. Dark respiration was relatively low. Seasonal changes reflected changes in leaf density. Decreasing stomatal conductances and increasing respiration rates reduced net photosynthesis at higher temperatures. The stomatal resistance increased and internal resistances to CO₂ uptake decreased over the year, but the total resistance remained constant. The internal resistance to CO₂ uptake was consistently higher than the stomatal resistance. These seasonal response patterns show that J. roemerianus is well adapted to the seasonal changes in ambient temperature and irradiance and other microenvironmental factors in the high marsh. These physiological characteristics permit this C₃ species to maintain a high productivity in a seasonally hot and stressful environment.     

COMPARATIVE GAS EXCHANGE OF LEAVES AND BARK IN THREE STEM SUCCULENTS OF BAJA CALIFORNIA

Arborescent stem succulents in tropical and subtropical deserts depend on scarce and uncertain rainfall. Gas exchange and the diurnal acidity fluctuation of bark and ephemeral leaves were measured under both dry and moist soil conditions in Fouquieria columnaris (cirio or boojum tree) and Pachycormus discolor (torote bianco or elephant tree) and in stems of the columnar cactus Pachycereus pringlei (cardon) in the Central Desert of Baja California, Mexico. Results demonstrated that ephemeral leaves were the only site of exogenous CO2 assimilation in F. columnaris and P. discolor; there was no measurable gas exchange across the green photosynthetic bark. The pattern of gas exchange in F. columnaris and P. discolor was consistent with that of C3 plants. P. pringlei was shown to be a typical Crassulacean acid metabolism plant on the basis of acid fluctuations and gas exchange. Chlorophyll fluorescence studies of the green bark of F. columnaris and P. discolor indicated that this tissue is photosynthetically functional, and that CO2 assimilation can rise above the compensation point under high CO2 concentrations, such as may occur within the plant. The green photosynthetic bark of these species may be an adaptation for surviving prolonged drought and may function to recycle endogenous respiratory CO2, thus maintaining the plant's energy reserves and permitting rapid production of leaves in response to infrequent rains.     

FACTORS LIMITING EDAPHIC ALGAL BIOMASS AND PRODUCTIVITY IN A GEORGIA SALT MARSH1,2

A “planted core” system was developed to test the effect of short term (1–2 weeks) experimental manipulation of environmental parameters on edaphic microalgae under field conditions. A large number of small cores (surface area = 7 cm²) were collected, randomized and replanted in the marsh in fiddler crab exclosures with appropriate experimental treatments. Daily enrichment of the cores with NH₄⁺ resulted in significant increases in edaphic primary productivity and levels of chlorophyll a in both summer and winter seasons in the short-Spartina marsh. Enrichment with a complete nutrient solution caused no further increases. Nutrient enrichment of creekbank sediments was much less stimulatory to the resident algal assemblage. In both sites, but especially in the creekbank, the removal of fiddler crab grazers resulted in significant increases in chlorophyll a and productivity. Experimental manipulation of light intensity showed that the average light intensity reaching the sediment surface was saturating for chlorophyll production in the short-Spartina marsh. A reciprocal transplant experiment involving unfertilized cores from the short-Spartina marsh and creekbank marsh demonstrated that NH₄⁺ inputs occurring in the creekbank site rapidly alleviated nitrogen limitation of edaphic algae from short-Spartina marsh. Algae in creekbank cores incubated in the short-Spartina marsh were unable to sustain high productivity once the original standing stock of NH₄⁺ declined.     

春、秋季崇明东滩盐沼潮沟大型浮游动物群落分布简

正大型浮游动物(Macrozooplankton)是指体长介于1 mm和1 cm之间的浮游动物[1]。它们主要以碎屑、细菌、藻类、原生动物和中小型浮游动物等为食,同时本身又是鱼类、虾蟹类和水鸟等动物的饵料[2,3],在生态系统食物网中处于中间环节,通过能量传递联系着生产者和次级消费者。     

DECOMPOSITION DYNAMICS OF SPARTINA ALTERNIFLORA AND SPARTINA PATENS IN A NEW JERSEY SALT MARSH

Decomposition dynamics of two salt marsh species, Spartina alterniflora tall (SAT) form and Spartina patens (SP), were investigated at Mud Cove, near Manahawkin, Ocean County, New Jersey. Decomposition rates were determined monthly over 371 days by measuring the amount of material lost from plastic net litter bags. Litter bags containing SP material were placed in both SP and SAT vegetation zones; litter bags containing SAT material were also placed in both of these zones. The material was analyzed for ash content, total carbon, Kjeldahl nitrogen, caloric content, fat, and crude fiber. Final weight loss values were as follows: SAT in SAT zone 72.4%, SP in SAT zone 56.9%, SAT in SP zone 46.7%, and SP in SP zone 26.4%. When SAT and SP material were placed in the same location (SAT or SP sites), the SAT material decomposed at a greater rate. If the same vegetation type (SAT or SP) were placed in both SAT and SP locations, the material at the SAT location decomposed at a greater rate than similar material in the SP location. The results indicate that while environmental characteristics (e.g., flooding) at a site influence the rate at which these two species will decompose, Spartina patens is inherently more resistant to decomposition.     

春、秋季崇明东滩盐沼潮沟大型浮游动物群落分布

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三峡库区岸边共存松栎树种水分利用策略比较

对三峡库区木鱼岛上马尾松(Pinus massoniana)、槲栎(Quercus aliena)和栓皮栎(Q. variabilis)组成的针阔混交林成林和幼林的光合速率(P_n)、气孔导度(G_s)、清晨和中午水势(ψ_pd和ψ_md)以及叶片稳定碳同位素(δ¹³C)进行了测定。实验结果表明:针叶树马尾松P_n、G_s均低于阔叶树槲栎和栓皮栎(差异达到极显著水平,p<0.001),但马尾松内在水分利用效率(WUE_i, P_n/G_s)却高于槲栎(p=0.003)和栓皮栎(p=0.025)。反映了裸子植物和被子植物木质部不同的水力特性。针阔叶树幼树的P_n和G_s高于成年树,但WUE_i和δ¹³C却低于成年树。表明水分利用效率与水分在树体内传输的距离有关。幼树属于挥霍型水分利用策略,成年树属保守型水分利用策略。三峡大坝的建设所造成的生态环境的改变可能会对三峡库区针阔混交林的演替产生一定的影响,但这需要长期的研究。     

UPTAKE AND LOSSES OF HEAVY METALS IN SEWAGE SLUDGE BY A NEW ENGLAND SALT MARSH

As part of an investigation on the potential of salt marshes to act as natural waste treatment systems, we are studying the cycling of heavy metals in Great Sippewissett Marsh, Massachusetts. For the last 7 yr, varying doses of fertilizer containing sewage sludge have been added to experimental plots. Changes in metal levels in the sediment, grasses, and animals have been monitored. Marsh sediments retained 20-35% Cd, 20-50% Cr, 60-100% Cu, 55-100% Pb, 80-100% Fe, 55-60% Mn and 20-45% of the Zn added in the fertilizer. When compared with low marsh, high marsh areas retained a significantly greater fraction of all the added metals except Mn.     

RECOLONIZATION OF SMALL DISTURBANCE PATCHES IN A NEW ENGLAND SALT MARSH

Availability of colonizers and edaphic conditions were tested in relation to rates of recolonization of open patches in salt marsh vegetation. The density of buried viable seeds was estimated by counting seedlings in undisturbed vegetation and germinating seeds in the laboratory. A low density of viable seeds (<50 per m²) found in these salt marsh soils indicated the absence of an important viable seed bank in this system. Rates of recolonization in natural open patches were monitored for three years. Vegetative expansion of Spartina alterniflora, at approximately 12 cm per year, accounted for most of the recolonization of open patches, although some colonization of annual Salicornia spp. occurred from seeds. Salinity and sulfide and ammonium concentrations were measured in pore water samples from depths of 2–7 cm and 10–15 cm of soil. Comparison of the concentrations from disturbed and undisturbed plots in the marsh did not show significant differences, indicating that none of the edaphic conditions measured would be more inhibitory to plant growth in the disturbed than the undisturbed plots. Therefore, the rate at which small open patches become recolonized is primarily controlled by proximity of Spartina alterniflora and its capacity for vegetative expansion.     

AUTOTROPHIC AND HETEROTROPHIC NUTRITIONAL BUDGET OF SALT MARSH EPIPHYTIC ALGAE1

This paper addresses the nutrition and relative importance of primary production to heterotrophy of select unicellular green algae and diatoms from the same assemblage. Algal growth responses to nutrient additions varied widely. Such responses included: inhibition and enhancement of growth by amino acid additions: nonstimulation or inhibition by most sugars 10 mM concentration; glucose stimulation of 6 and inhibition of 3 species; fructose inhibition of 6- and 3- fold stimulation of one species; stimulation of most species by a vitamin mixture, some natural products, metabolite mixtures, etc. Photoassimilation of glucose and aculeate in 8 of 12 species occurred. Nine of 12 species took up only a fraction of the total carbon fixed as organic substrate. Enhancement of photosynthesis by glucose and inhibition by acetate was common. The data suggest that attached littoral and shoal marine algal assemblages may play mixed trophic roles lower levels of the detrital food web.     

TILLERING AND MORTALITY OF THE SALT MARSH CORDGRASS,SPARTINA ALTERNIFLORA

Recruitment and mortality of Spartina alterniflora tillers and culms were estimated from measurements of live standing crops at Wallops Island, Virginia. Stands of tall and medium form grass produced from 452 to 1,227 tillers m⁻² yr⁻¹. Those tillered in spring lengthened into culms their first year, while those tillered in late summer and fall may have overwintered and lengthened into culms their second year. Biennial growth was most prevalent in tall form Spartina. Fifty-six to sixty-one percent of all tillers died before lengthening into culms. Of the remainder, 9 to 56% died as culms before the time of flowering. Sixty-three percent of the surviving culms of tall form Spartina flowered, compared to only 14 to 23% in medium form. Mortality of tillers and culms removed 16 to 35% of the annual production of Spartina biomass from live standing crops before the time of flowering.     

红松林和采伐迹地的水量平衡分析

森林水量平衡是研究森林植被中水分的运动规律,对水分的收入和支出系统进行定量分析。水是森林生态系统中能量和物质循环的主要载体,也是影响森林生产力的重要的生态因子。研究森林水量平衡可以比较全面地认识水的分配状况,以揭示水在运动中所具有的各种形式之间的内在联系,从而使森林生态环境朝着人们所期待的方向转化。 森林水量平衡国内外很多学者曾进行过广泛的研究(William等,1967;中野秀章,1976;     

EFFECTS OF SULFIDE ON THE GROWTH OF THREE SALT MARSH HALOPHYTES OF THE SOUTHEASTERN UNITED STATES

A hydroponic culture experiment was performed to ascertain whether sediment soluble sulfide at in situ concentrations plays a role in the determination of height forms of Spartina alterniflora in salt marshes of the United States. Additional experiments were conducted for both Spartina cynosuroides and Borrichia frutescens to determine if sulfide also influences the overall distribution of these species in the marsh. In situ soluble sulfide concentrations ranged from 0.02 mm in creek bank sites up to 3.0 mm in the inner marsh. In culture treatments, both plant height and biomass production of S. alterniflora were inhibited at a sulfide concentration as low as 1.0 mm , strongly suggesting a role for sulfide in the determination of height forms in the marsh. Production of S. cynosuroides was inhibited at high sulfide concentrations. However, over a range of concentrations similar to in situ values, no significant reduction in growth was observed, indicating sulfide was not a primary determinant of growth in stands of S. cynosuroides on Sapelo Island, Georgia. A sulfide concentration of 0.5 mm inhibited production in B. frutescens. In situ sulfide concentrations as high as 0.5 mm were found only in mixed stands of Juncus roemerianus and B. frutescens.     

PRIMARY PRODUCTION OF EDAPHIC ALGAL COMMUNITIES IN A MISSISSIPPI SALT MARSH1

Primary production rates of edaphic algae associated with the sediments beneath four monospecific canopies of vascular plants were determined over an annual cycle in a Mississippi salt marsh. The edaphic algal flora was dominated by small, motile pennate diatoms. Algal production (as measured by ¹⁴C uptake) was generally highest in spring-early summer and lowest in fall. Hourly rates ranged from a low of 1.4 mg C/m² in Juncus roemerianus Scheele to a high of 163 mg C/m² beneath the Scirpus olneyi gray canopy. Stepwise multiple regressions identified a soil moisture index and chlorophyll a as the best environmental predictors of hourly production; light energy reaching the marsh surface and sediment and air temperature proved of little value. Adding the relative abundances of 33 diatom taxa to the set of independent variables only slightly increased R²; however, virtually all variables selected were diatom taxa. R² was only 0.38 for the Spartina alterniflora Loisel. habitat but ranged from 0.70 to 0.87 for the remaining three vascular plant zones. Annual rates of algal production (g C/m²) were estimated as follows: Juncus (28), Spartina (57), Distichlis spicata (L.) Greene (88), and Scirpus (151). The ratio of annual edaphic algal production to vascular plant net aerial production (EAP / VPP) was 10–12% for the first three habitats and 61% for Scirpus. Chlorophyll a concentrations, annual algal production rates, and EAP / VPP values were comparable to those determined in Texas, Delaware, and Massachusetts salt marshes but lower than those reported for Georgia and particularly California marshes.     

DISTRIBUTION OF BLUEGREEN ALGAE IN A MISSISSIPPI GULF COAST SALT MARSH1

Edaphic bluegreen algal communities were sampled from five menotypic angiosperm zones in Grvelline Bay Marsh near Ocean Spring. Mississippi. Samples and environmental data were taken on a quarterly basis from October 1976 to June 1977 beneath the following marsh angiosperms: Distichlis spicata (L.) Green, Scirpus olneyi gray, SPartina patens (Aiton) Muhl., Sp. alterniflora Loisel., and Juncus roemerianus Scheele. Communities in all five zones were dominated by Schizothrix calcicola (Ag.) Gom. (sensu Drauet) throughout the study, while the subdominant bluegreens varied according to season. The number of individuals in all zones was greatest in the summer and lowest in the winter. An examination of the structure of the five edaphic communities indicated a single, nearly homogeneous community exists over the entire surface of the marsh shaded by a angiosperm canopy. Light intensity appears to be the major factor affecting the distribution of bluegreen algae in this salt marsh.     

SURVIVAL AND GROWTH OF THE DOMINANT SALT MARSH GRASS SPARTINA ALTERNIFLORA IN AN OIL INDUSTRY SALINE WASTEWATER

Saline oil produced water (PW) is the largest wastewater stream in the oil exploration and production processes. Although eventual disposal of PW into shallow coastal waters occurs nearby coastal wetlands, no studies regarding its toxicity to higher plants were found in our literature review. To fill this knowledge gap and evaluate the potential use of this halophyte for PW phytoremediation the salt marsh grass Spartina alterniflora was grown in five PW concentrations and no PW treatment control for seven weeks. The oil & grease, NaCl, and ammonium (N-NH4⁺) concentrations in the PW were 120 mg L^?1, 30 g L^?1, and 381 mg L^?1, respectively. Plants grown in 30% PW and 10% PW achieved survival rates (75%) significantly higher than plants grown in 100% PW (35% survival). LT50 of S. alterniflora to raw PW with 120 mg L^?1 of oil & grease (100% PW) was estimated at 30 days. Root and sprout biomass were significantly stimulated by PW; plants grown in 10% to 50% PW concentrations were 70–300% more productive than those in control, 80% PW and 100% PW, respectively. No significant inhibitory effects on survival or growth were detected for concentrations of PW less than 80% when compared to control. Our results pointed out that S. alterniflora grows in saline oil PW and its potential use to phytoremediate this effluent should be evaluated.     

SUBSTRATE COMPETITION BETWEEN A SALT MARSH DIATOM AND A BACTERIAL POPULATION1

Cylindrotheca closterium Ehrenberg, a benthic marine diatom, competes successfully with Aeromonas sp. a bacterium from the same environment, for low molecular weight organic substrates when they are presented at natural concentrations (1–10 μM). In short term (1 h) experiments, the uptake of mannose by C. closterium was enhanced in light. Seventy percent of the total uptake of mannose by both species was effected by C. closterium over a 1 h period in light. The diatom population was also competitive in darkness. The algal portion of glucose uptake over 1 h was 71% when both populations were given the substrate initially. Percentages of total amino acid uptake for C. closterium ranged from 33% glycine in light to 73% leucine in darkness when both species were given substrate initially. Cylindrotheca had smaller percentages of glucose and aspartic acid total uptake in competition experiments run to stationary phase (10 days).     

鹤山丘陵草坡的水文特征及水量平衡

 在中国科学院鹤山丘陵综合开放实验站的草坡集水区对大气降水和径流进行了连续4年的观测,并于1994年对该集水区的蒸散进行了测定,结果表明：1)鹤山丘陵区年均降水量1761.37mm,大气降水有明显的干湿季之分,干季降水量占全年降水量的12.47％,湿季占87.53％。年均降水量中有62.24％可引起地表产流,即年均产流降水量1096.3mm。产流降水以中、小雨频度为大,但产流水量主要由大、暴雨供给。文中根据降雨量较大地区的降水、产流特征和规律,提出了产流降水和产流水量的概念。2)鹤山丘陵草坡集水区年总径流系数50.12％,地表径流系数17.33％。地表径流主要集中在湿季产生,与降水量呈二次抛物线型回归关系,与降水强度关系不大。3)1994年水量平衡各分量中,实际降水输入1841.55mm,年径流量970.28mm,径流系数52．69％,径流是系统的最大输出项;蒸散量851.56mm,意味着年降水收入中46.24％的水量以汽态形式返回了大气。蒸散的月变化呈双峰型,不同于降水的季节分配,径流的月变化则与降水同步。系统蓄水年变化量19.71mm,约占年降水量的1.07％,但其月变化却非常大,在一68～104mm之间。草坡集水区的水量平衡是一种收入对支出的补给和收支项目中可变性的动态平衡。4)鹤山丘陵草坡水热季节分配失衡、产流降水量和地表径流量大是这种退化生态系统恢复的3个限制因素;认为退化生态系统恢复过程中系统水量支出和蓄留方式的转变是退化生态系统的恢复机理之一。