Influence of acorn size and storage duration on moisture content, germination and survival of Quercus petraea (Mattuschka)

This study was conducted to evaluate how acom size (small, medium and large) and acorn storage duration (0, 5 and 17 months) influenced Quercus petraea (Mattuschka) moisture content and germination. Acorn size and storage duration did not significantly affect acorn moisture content, but they significantly affected acorn germination performance. When averaged for three acorn sizes, loss of germination performance occurred after 17 months of storage even when the moisture content did not reduce significantly and remain at the initial level (32.6%). Maximum germination percentage was observed in large and medium size classes before storage (93 and 95%, respectively) and after 5-month storage (94 and 93%, respectively), but after 17-month storage medium acorn size class exhibited the highest germination (68%). Small seed size class exhibited the lowest germination percentage and rate in each acorn storage duration. Acorn size also significantly affected seedling emergence and survival in the nursery and seedling emergence and survival was the lowest in small seed size class (85 and 80%, respectively). Although seedling survival of one-year seedlings in the nursery increased up to large seed size class, maximum survival in nursery conditions was observed in large and medium size classes (89 and 91%, respectively). Thus, acorn size grading in Q. petraea may result in higher germination performance within in a seedbed.     

Field and Genetic Survey of the Endangered Butte County Meadowfoam—Limnanthes floccosa subsp. californica (Limnanthaceae)

The Butte County meadowfoam ( Limnanthes floccosa subsp, californica ), an endangered annual endemic to vernal pools in Butte County, California, is of agronomic interest as a sperm whale oil substitute. Because it is threatened by rapid development of the community of Chico, a field and genetic survey was required to guide a conservation program. Eight new populations were discovered, bringing the total known to eleven. Population sizes varied from 220 to 45,689 plants; mean seed set per flower, a bioassay of site quality, ranged from 0.82 to 2.56 among populations. The array of associated taxa, an indicator of appropriate habitat was fairly uniform across populations. Based on allozyme and morphometric data no introgression between L. floccosa subsp, californica and L. alba subsp, alba at sympatric sites was found. Populations were remarkably monomorphic, probably due to past population bottlenecks in conjunction with high selfing rates. Electrophoretic analysis of 28 isozyme loci revealed that 96% of total genetic diversity was distributed among populations. The migration rate, Nm , calculated from the mean frequency of private alleles, ( P (1)), and from the proportion of genetic variation distributed between populations, Gst , estimated exchange between local populations of one diploid individual every 50 to 100 generations, respectively. Mean genetic identity among populations was 0.91 ± 0.068. Grouping of populations on the basis of genetic distance identified two distinct populations and three clusters of populations that deserve high priority for preservation because they are likely to have high frequencies of locally adapted alleles. The low migration rates and substantial differentiation among populations suggest a conservation plan that emphasizes preservation of as many populations as possible, at possible expense of numbers of individuals.     

珠江三角洲四种森林类型土壤CO2通量特征研究

采用开路式土壤CO2通量测量系统Li-8100&Li-8150对珠江三角洲地区尾叶桉(Eucalyptus urophylla)人工林、乡土树种恢复林、针阔叶混交林和常绿阔叶林4种林型的土壤CO2通量进行了观测。结果表明:4种森林类型年均土壤CO2通量为尾叶桉人工林(3.35μmol.m-2.s-1)>针阔叶混交林(2.66μmol.m-2.s-1)>乡土树种恢复林(2.09μmol.m-2.s-1)>常绿阔叶林(1.86μmol.m-2.s-1);旱季土壤CO2通量明显小于雨季。前3种森林类型凋落物呼吸处理表明,旱季对照组土壤CO2通量均小于相应的去除凋落物组、雨季则相反,全年的对比结果显示,3种森林类型的凋落物呼吸贡献分别达到1.3%、7.1%和10.8%。土壤CO2通量与10 cm土壤温度呈显著指数相关,且土壤CO2通量温度敏感指数表现为针阔叶混交林Q10最大(3.49),尾叶桉人工林Q10最小(1.95)。     

生境异质性对金沙江干热河谷锥连栎天然更新幼苗早期生长的影响

锥连栎林是金沙江干热河谷仅有的几种重要天然植被之一,由于恶劣的气候环境以及长期严重的人为干扰作用,林地生境破碎化程度较高,幼苗天然更新极为困难.分析了锥连栎林更新幼苗主要生长的落叶堆积洼地、落叶堆积平地、菁沟冲积台地和缓坡草丛等4种微生境特点,并比较研究了不同微生境下天然更新幼苗生长的形态特征、生物量分配以及幼苗生存状...     

Instantaneous and historical temperature effects on alpha-pinene emissions in Pinus halepensis and Quercus ilex

We compared the role of instantaneous temperature and temperature history in the determination of alpha-pinene emissions in Mediterranean conifer Pinus halepensis that stores monoterpenes in resin ducts, and in Mediterranean broad-leaved evergreen Quercus ilex that lacks such specialized storage structures. In both species, alpha-pinene emission rates (E) exhibited a significant exponential correlation with leaf temperature and the rates of photosynthetic electron transport (Jco2+o2) started to decrease after an optimum at approximately 35 degrees C. However, there was a higher dependence of E on mean temperature of previous days than on mean temperature of current day for P. halepensis but not for Q. ilex. Jco2+o2 showed a maximum relationship to mean temperature of previous 3 and 5 days for P. halepensis and Q. ilex respectively. We conclude that although the best correlation of emission rates were found for instantaneous foliar temperatures, the effect of accumulated previous temperature conditions should also be considered in models of monoterpene emission, especially for terpene (see text) species.     

Season- and herbivore-dependent competition and facilitation in a semiarid savanna

Empirical and theoretical evidence suggests that facilitation between plants, when it occurs, is more likely during periods of abiotic stress, while competition predominates under more moderate conditions. Therefore, one might expect the relative importance of competition vs. facilitation to vary seasonally in ecosystems characterized by pronounced dry (abiotically stressful) and wet (benign) seasons. Herbivory also varies seasonally and can affect the net outcome of plant-plant interactions, but the interactive effects of seasonality and herbivory on the competition-facilitation balance are not known. I experimentally manipulated neighboring plants and herbivory during wet and dry periods for two species of grass: Cynodon plectostachyus and Pennisetum stramineum, in the semiarid Laikipia District of Kenya. These experiments indicate that Pennisetum was competitively dominant during the wet season and that it responded negatively to grazing, especially during the dry season. Cynodon showed more complex season- and herbivore-dependent responses. Cynodon experienced facilitation that was simultaneously dependent on presence of herbivores and on dry season. During the wet season Cynodon experienced net competition. These results illustrate how herbivory and seasonality can interact in complex ways to shift species-species competition-facilitation balance. Additionally, because Cynodon and Pennisetum are key players in a local successional process, these results indicate that herbivory can affect the direction and pace of succession.     

Development of contemporary Eastern Pacific coral reefs

An overview of oceanographic conditions prevailing in the tropical Eastern Pacific Ocean suggests that the entire region is environmentally marginal for coral-reef development. The principal features of this environment are a strong, permanent, shallow thermocline and an annual north-south migration of the Intertropical Convergence resulting in wet and dry seasons. Along tropical Eastern Pacific continental margins structural coral reefs are best developed in the Gulf of Chiriquí off western Panamá. These reefs are relatively small, with reef formation taking place at a maximum depth of roughly 10 m. All of the reefs are judged to have formed since sea level approached its present height some 5,000 years ago. A study of the physical environment in the Gulf of Chiriquí revealed the following. Seasonal differences in surface temperatures were small but significant (P0.01), with the dry-season median (Md) of 28.9°C higher than the rainy season one of 28.0°C. At all times, surface-water temperatures were within the range considered optimal for coral growth. There were also significant (P<0.05) seasonal differences in the depths of the 25°, 20°, and 18°C isotherms. The first was shallowest (Md=18.5 m) during the rainy season due to vertical mixing, while the latter two were shallowest (Mds=31.5 and 33.0 m, respectively) during the dry season due to a generalized shoaling of the thermocline. All three isotherms are closely associated with the thermocline and showed remarkable variability in depth, most likely connected with internal waves. Salinities were reduced down to depths greater than 20 m and for distances of more than 50 km from the coast. Seasonal differences were slight (0.7% S) but statistically significant (P<0.01). Turbidity during the rainy season reduces the amount of light reaching the bottom at 10 m depth roughly by a factor of three compared to the dry season. Even the dry season amount is only about one half as much as would be expected to reach the same depth on the seaward reef of a Westen Pacific atoll. These conditions of cool water a short distance below the surface, reduced salinities, and high seasonal turbidity combine to make the region a poor one for coral-reef formation. The history of the Eastern Pacific coral fauna is traced from the Cretaceous to the Holocene. The present fauna is of Indo-Western Pacific origin, having become established following (1) the final closure of the connections between the Caribbean and Eastern Pacific (Pliocene), (2) movement of the northern Line Islands by sea-floor spreading into the path of the North Pacific Equatorial Countercurrent (Pliocene), and (3) the loss of all Eastern Pacific hermatypes during the Pleistocene.     

Seasonal variations in trace metal levels,speciation and physicochemical determinants of metal availability in dumpsite soils within Akwa Ibom State,Nigeria

Physicochemical properties, total metals and metal species were investigated in surface soil samples from six urban dumpsites within Akwa Ibom State, Nigeria. Results obtained indicated that Pb, Cd and Cr levels were higher in the dry season than in wet season, whereas Ni levels were higher during the wet season. Soil pH, organic matter and cation-exchange capacity (CEC) showed higher values in wet season than in dry season, whereas sand and clay levels were higher in the dry season. Speciation analysis showed the principal fraction of the metals to be Pb (reducible), Cd (acid extractable) and Ni (residual), whereas Cr existed in the residual fraction during the dry season and in the acid-extractable fraction during the wet season. Soil pH was positively correlated at p<0.1 with all metals in both seasons, sand was negatively correlated with the metals in both seasons, and CEC was negatively correlated with all metals in both seasons, except Pb in the wet season. Organic matter showed variable relationships with metals in both seasons. Seasonal variations affected metal availability and physicochemical properties of the soil. Total metal concentrations followed the order Pb>Ni>Cd>Cr, whereas their bioavailability followed the trend Cd>Pb>Cr>Ni.     

Impact of nitrogen fertilizer source on nitrous oxide (N2O) emissions from three different agricultural soils during freezing conditions

ABSTRACT

Nitrogen (N) application is the main agricultural management that increases nitrous oxide (N₂O) concentration in the atmosphere. Freezing conditions are common phenomenon in the northern China that significantly affect soil N₂O emissions through alterations in nutrients availability and microbial population. To develop a comprehensive understanding of how N fertilizer managements affect soil N₂O emissions during the freezing process, a lab incubation was conducted in three typical cultivated soils (black soil, fluvo-aquic soil, or loess soil) by adding different N fertilizer sources, including ammonium chloride, sodium nitrate, or urea at different N levels (0, 80, 200, or 500 mg N/kg) at the start of freezing. The N₂O emissions in the fluvo-aquic soil were significantly higher than in other soils. The application of nitrate in the fluvo-aquic soil promoted N₂O emissions by five- and seven-fold higher compared to ammonium chloride and urea, whereas N₂O emissions in black soil were enhanced by application of ammonium chloride. Data indicate that denitrification is the major pathway for N₂O production in the fluvo-aquic soil during the freezing process, while ammonia oxidation responses accounts for elevated N₂O production in black soil. No significant influence of N fertilizer levels on N₂O emissions were found during soil freezing. These results suggest that agricultural practices that focus on mitigation of N₂O emissions need to avoid selection of nitrate as N fertilizer source in fluvo-aquic soil prior to the freezing season. Future studies need to focus on how the expression of enzymes and/or shifts in microbial communities respond to different N fertilizers during freezing conditions.     

Extrinsic regime shifts drive abrupt changes in regeneration dynamics at upper treeline in the Rocky Mountains, U.S.A

Given the widespread and often dramatic influence of climate change on terrestrial ecosystems, it is increasingly common for abrupt threshold changes to occur, yet explicitly testing for climate and ecological regime shifts is lacking in climatically sensitive upper treeline ecotones. In this study, quantitative evidence based on empirical data is provided to support the key role of extrinsic, climate-induced thresholds in governing the spatial and temporal patterns of tree establishment in these high-elevation environments. Dendroecological techniques were used to reconstruct a 420-year history of regeneration dynamics within upper treeline ecotones along a latitudinal gradient (approximately 44-35 degrees N) in the Rocky Mountains. Correlation analysis was used to assess the possible influence of minimum and maximum temperature indices and cool-season (November-April) precipitation on regional age-structure data. Regime-shift analysis was used to detect thresholds in tree establishment during the entire period of record (1580-2000), temperature variables significantly Correlated with establishment during the 20th century, and cool-season precipitation. Tree establishment was significantly correlated with minimum temperature during the spring (March-May) and cool season. Regime-shift analysis identified an abrupt increase in regional tree establishment in 1950 (1950-1954 age class). Coincident with this period was a shift toward reduced cool-season precipitation. The alignment of these climate conditions apparently triggered an abrupt increase in establishment that was unprecedented during the period of record. Two main findings emerge from this research that underscore the critical role of climate in governing regeneration dynamics within upper treeline ecotones. (1) Regional climate variability is capable of exceeding bioclimatic thresholds, thereby initiating synchronous and abrupt changes in the spatial and temporal patterns of tree establishment at broad regional scales. (2) The importance of climate parameters exceeding critical threshold values and triggering a regime shift in tree establishment appears to be contingent on the alignment of favorable temperature and moisture regimes. This research suggests that threshold changes in the climate system can fundamentally alter regeneration dynamics within upper treeline ecotones and, through the use of regime-shift analysis, reveals important climate-vegetation linkages.     

Using nocturnal cold air drainage flow to monitor ecosystem processes in complex terrain.

This paper presents initial investigations of a new approach to monitor ecosystem processes in complex terrain on large scales. Metabolic processes in mountainous ecosystems are poorly represented in current ecosystem monitoring campaigns because the methods used for monitoring metabolism at the ecosystem scale (e.g., eddy covariance) require flat study sites. Our goal was to investigate the potential for using nocturnal down-valley winds (cold air drainage) for monitoring ecosystem processes in mountainous terrain from two perspectives: measurements of the isotopic composition of ecosystem-respired CO2 (delta13C(ER)) and estimates of fluxes of CO2 transported in the drainage flow. To test if this approach is plausible, we monitored the wind patterns, CO2 concentrations, and the carbon isotopic composition of the air as it exited the base of a young (approximately 40 yr-old) and an old (>450 yr-old) steeply sided Douglas-fir watershed. Nocturnal cold air drainage within these watersheds was strong, deep, and occurred on more than 80% of summer nights. The depth of cold air drainage rapidly increased to tower height or greater when the net radiation at the top of the tower approached zero. The carbon isotope composition of CO2 in the drainage system holds promise as an indicator of variation in basin-scale physiological processes. Although there was little vertical variation in CO2 concentration at any point in time, we found that the range of CO2 concentration over a single evening was sufficient to estimate delta 13C(ER) from Keeling plot analyses. The seasonal variation in delta 13C(ER) followed expected trends: during the summer dry season delta 13C(ER) became less negative (more enriched in 13C), but once rain returned in the fall, delta 13C(ER) decreased. However, we found no correlation between recent weather (e.g., vapor pressure deficit) and delta 13C(ER) either concurrently or with up to a one-week lag. Preliminary estimates suggest that the nocturnal CO2 flux advecting past the 28-m tower is a rather small fraction (<20%) of the watershed-scale respiration. This study demonstrates that monitoring the isotopic composition and CO2 concentration of cold air drainage at the base of a watershed provides a new tool for quantifying ecosystem metabolism in mountainous ecosystems on the basin scale.     

冬作季节土壤水分状况对稻田CH_4排放的影响

温室盆栽试验表明,冬作季节土壤持续淹水处理（淹水）稻田平均ＣＨ４ 排放通量显著高于干燥处理（干燥）,前者是后者的５．５８ 倍（１９９６ 年）和４．１６ 倍（１９９７ 年）。冬作季节土壤水分状况明显影响土壤Ｅｈ 和ＣＨ４ 排放的季节变化。淹水处理土壤Ｅｈ 在整个水稻生长期皆处于适宜ＣＨ４ 产生的水平,所以整个水稻生长期皆有ＣＨ４ 排放（经历烤田后例外）,而干燥处理水稻移栽４２ ｄ 后土壤Ｅｈ 才降为负值,在此期间几乎没有ＣＨ４ 排放。     

Analysis of Wind-Induced Thermocline Oscillations of Lake Tanganyika

An analysis is presented of the wind-induced thermocline oscillations of Lake Tanganyika, East Africa. The region undergoes a four month dry season and the wet season for the rest of the year. The dry season is characterised by nearly constant high southeasterly winds, while for the rest of the year mild wind blows generally from the northeast. Observations show that the dry season high winds cause tilting of the thermocline, being higher/lower than normal at the southern/northern ends of the lake. The thermocline tries to restabilise itself after the cessation of dry season winds and oscillates for the rest of the year. A non-linear reduced-gravity model is used to study the thermocline oscillations of the lake. The numerical simulations satisfactorily represent the oscillations, their period and amplitude. Different forcing conditions (thermocline depth, wind stress and stability) are used in the model and their effect on the period and amplitude of the oscillations are studied. The amplitude of oscillations ranges from 15 to 45 m, while their period varies from 3 to 4 weeks according to the variation in the model parameters. Wavelet transform is used to study the evolution of periods of oscillations with depth in the time series of observations and along the length of the lake using model simulations. Wavelet spectra presents several dominant modes including the semidiurnal, diurnal, synoptic, intraseasonal variability, besides the modes representing the wind-induced thermocline oscillations.     

Representation of the world's biophysical conditions by the global protected area network

Protected areas (PAs) are often implemented without consideration of already existing PAs, which is likely to cause an overrepresentation of certain biophysical conditions. We assessed the representativeness of the current PA network with regard to the world's biophysical conditions to highlight which conditions are underprotected and where these conditions are located. We overlaid terrestrial and marine PAs with information on biophysical conditions (e.g., temperature, precipitation, and elevation) and then quantified the percentage of area covered by the PA network. For 1 variable at a time in the terrestrial realm, high temperature, low precipitation, and medium and very high elevation were underrepresented. For the marine realm, low and medium sea surface temperature (SST), medium and high sea surface salinity (SSS), and the deep sea were underrepresented. Overall, protection was evenly distributed for elevation across the terrestrial realm and SST across the marine realm. For 2 variables at a time, cold and very dry terrestrial environments had mostly low protection, which was also the case for low SST and low and medium SSS across most depths for marine environments. Low protection occurred mostly in the Sahara and the Arabian Peninsula for the terrestrial realm and along the Tropic of Capricorn and toward the poles for the marine realm. Although biodiversity measures are of prime importance for the design of PA networks, highlighting biophysical gaps in current PAs adds a frequently overlooked perspective. These gaps may weaken the potential of PAs to conserve biodiversity. Thus, our results may provide useful insights for researchers, practitioners, and policy makers to establish a more comprehensive global PA network.     

Physicochemical and microbiological assessment of Oko-oba--a Nigerian abattoir

The physicochemical and microbiological assessments of Oko-oba abattoir were carried out during dry and wet season to determine whether the waste discharges are within tolerable limits. All the physicochemical parameters studied showed seasonal variations. Higher temperature and lower pH values were recorded during the dry season than wet season. Similarly, the BOD of wastewater from the slab decreases from 10000 mg/ml during the dry season to 6000 mg/ml in the wet season. Conversely, the BOD of the final waste discharge was 4000 mg/ml during the dry season and 3,500 mg/ml during the wet season. The COD showed similar trend, with values ranging from 12,200 to 18,500 mg/ml depending on the season. The suspended solid values ranged from 1200 to 1950 mg/ml. The phosphate and nitrate ions were in the range of 41-75 mg/l and 22.5- 960 mg/ml respectively. Heavy metals detected were Chromium at 104 -114 mg/ml, Copper 16 -75 mg/ml and Iron 55- 114 mg/ml. The following bacteria species were also encountered: B. cereus, E. coli, P. aeruginosa, S. aureus, S. faecalis, S. lactis, Micrococcus sp, A. aerogenes, P. vulgaris, and S. typhi. The results showed significantly high level of pollutants in the waste discharged.     

Temperature,salinity and water-age variations in a tidal creek network,Bushehr Port,Iran

The spatio-temporal variability of temperature and salinity was studied for a creek network and its adjacent coastal waters along the northwestern coast of the Persian Gulf during warm and cold months. Salinity variations and tidal fluctuations were found to be out of phase throughout the creek. Temperature variations at the creek were exhibit a direct correlation with tidal fluctuations during cold months and were inversely related during warm months. The creek water was colder (warmer) than offshore water during the cold (warm) season. The salinity values observed inside this inverse estuary were higher during the warm season than the corresponding values during the cold season due to a change in evaporation rates; while the open water salinity had an opposite pattern. Using salinity as a tracer, the water-age (WA) was calculated, which shows almost linear increase from the mouth to the head. The maximum WA increases from ~10 days in winter to ~30 days in summer due to the corresponding increase in longitudinal salinity gradient. Based on the calculated non-dimensional Peclet number, the diffusion process is more rapid than the advection process in this water body, especially during the cold season.     

Effect of water temperature on the courtship behavior of the Alpine newt Triturus alpestris

Temperature is expected to have an effect on the behavioral patterns of all organisms, especially ectotherms. However, although several studies focused on the effect of temperature on acoustic displays in both insects and anurans, almost nothing is known about how environmental temperature may affect ectotherm visual courtship displays and sexual performance. The purpose of this study was to determine the effect of environmental temperature on the sexual behavior of Alpine newts (Triturus alpestris). We subjected T. alpestris to two different temperatures in controlled laboratory conditions. Temperature had a major effect on both male and female behaviors: at low temperature, the frequencies of several displays, including tail-raising during sperm deposition, are lowered. This variation is caused indirectly by temperature because it is due to female responsiveness, which is temperature-dependent. However, the fanning movement of the males tail during its main courtship display is independent of female behavior: at lower temperatures, the tail beats at a lower rate, but for a longer time. The similar reproductive success (i.e. sperm transfer) at the two temperature ranges indicates that breeding in cold water is not costly but instead allows males and females to mate early in the season. This is particularly adaptive because, in many habitats, the reproductive period is shortened by drying or freezing conditions, which may impair survival of branchiate offspring. This study also demonstrates the necessity of considering environmental parameters when modeling optimality and characteristics of ectotherm behaviors.Communicated by W. Cooper     

Ecological and human health risk assessment of heavy metal contamination in soil of a municipal solid waste dump in Uyo,Nigeria

The study assessed the levels of some heavy metals in soils in the vicinity of a municipal solid waste dumpsite with a view to providing information on the extent of contamination, ecological risk of metals in the soils and human health risk to the residents in Uyo. Soil samples were collected in rainy and dry seasons and analyzed for metals (Pb, Cd, Zn, Mn, Cr, Ni and Fe) using atomic absorption spectrometry. The concentrations of heavy metals (mg/kg) at the dumpsite in rainy season were Pb (9.90), Zn (137), Ni (12.56), Cr (3.60), Cd (9.05) and Mn (94.00), while in dry season, the concentrations were Pb (11.80), Zn (146), Ni (11.82), Cr (4.05), Cd (12.20) and Mn (91.20). The concentrations of metals in the studied sites were higher than that of the control site (P < 0.05). Pollution indices studies revealed that soil samples from dumpsite and distances from 10 and 20 m east of the dumpsite were highly polluted with cadmium. Ecological risk assessment carried out showed that cadmium contributed 98–99 % of the total potentially ecological risk. No probable health risk was observed as the total hazard index of all the metals was less than one. However, children were found to be more susceptible to heavy metal contamination than adult.     

Growth responses of scots pine seedlings grown in peat-based media amended with natural zeolite

Zeolite has many good features that makes it very attractive for nursery use as a growing media over others. This study was designed to investigate influence of different growing media and their mixtures (with zeolite and without zeolite) on morphological characters of scots pine seedlings. Twenty-one treatments of varying amounts of peat, fine pumice, coarse pumice, river sand, perlite and river sand were established and were sown with scots pine seeds. At the end of first growing period, 30 seedlings from each treatment were harvested and measured for height (SH), root collar diameter (RCD), root dry weight (RDW), stem dry weight (SDW) and total dry weight (TSDW). These parameters varied significantly among treatments and were lower in zeolite added media. SH negatively correlated with Na and K content and C/N ratio of growing media but positively correlated with Mn content of media. SDW and TSDW had positive correlation with N, Fe, Mn, total porosity and loss of ignition, and had negative correlation with pH, Ca, Na and K content.