Relationships between nutrients and macroalgal biomass in a brazilian coastal lagoon: the impact of a lock construction

The Piratininga Lagoon is a coastal, choked, and brackish ecosystem in SE Brazil, where uncontrolled discharge of domestic sewage led to eutrophication, increasing massive proliferation of benthic macroalgae, and decrease of the lagoon mean depth. In 1992, a dam was constructed by the local Municipality at its tidal channel aiming at stabilising its water level. Main physico-chemical parameters, together with macroalgae biomass, nutrient concentrations in the water column, particulate organic carbon, and chlorophyll a were recorded monthly at 4 sampling stations within the Piratininga lagoon from April 1994 to April 1995. The data, compared with “before-lock” existing studies, show that nutrients and chlorophyll a concentrations significantly increased after the lock construction. Based on the functioning of the ecosystem, we propose to harvest the algal mats before their decomposition period in order to partly remove the nutrient stocks from the lagoon and the future ecosystem modelling to predict the impact of natural and anthropogenic eutrophication.     

无排泥运行MBR处理不同浓度氨氮废水及其生物特性

考察了水力停留时间(HRT)为10 h时无排泥运行下膜-生物反应器(MBR)处理不同浓度氨氮无机废水的运行性能及微生物特性.结果表明,在处理NH₄⁺-N≤500 mg/L的废水时,氨氮转化率可达99%且反应器内微生物增长缓慢,比硝化速率从0.2kg/(kg·d)升至0.52 kg/(kg·d);当NH₄⁺-N≥700 mg/L时,出水亚硝酸氮和氨氮相继出现明显累积,比硝化速率随之下降至0.4kg/(kg·d)以下,反应器内生物量从3 200 mg/L上升至6 700 mg/L.反应器中的氨氧化菌维持在10⁷CFU/mL,亚硝酸盐氧化菌从10⁶CFU/mL下降至10³CFU/mL.系统内的溶解性微生物产物(以TOC表示)升至65 mg/L后保持稳定,出水TOC一直维持在3～4mg/L;细胞外分泌物(EPS)在膜的截流作用下随运行时间的延长积累至600 mg/L.     

Phytoremediation of Cadmium-Contaminated Soils by Rorippa globosa Using Two-Phase Planting (5 pp)

Background Phytoextraction of contaminated soils by heavy metals can provide a great promise of commercial development. Although there are more than 400 species of hyperaccumulators found in the world, phytoremediation technology is rarely applied in field practice for remedying contaminated soils, partially due to low biomass and long growth duration for most of discovered hyperaccumulating plants. In order to enhance the metal-removing efficiency in a year, the two-phase planting countermeasure of phytoextraction by harvesting anthesis biomass was investigated on the basis of the newly found Cd-hyperaccumulator Rorippa globosa (Turcz.) Thell. with 107.0 and 150.1 mg/kg of the Cd accumulation in stems and leaves, respectively, when soil Cd added was concentrated to 25.0 mg/kg. Methods The field pot-culture experiment was used to observe the distribution property of R. globosa aboveground biomass and to examine characteristics of accumulating Cd by the plant at different growth stages. The concentration of Cd in plants and soils was determined using atomic absorption spectrophotometry (AAS). Results and Discussion The results indicated that the total dry stem and leaf biomass of R. globosa harvested at the flowering phase was up to 92.3% of that at its full maturity and the concentration of Cd in stems and leaves harvested at the flowering phase was up to 73.8% and 87.7% of that at the mature phase, respectively. The Cd-removing ratio by shoots of R. globosa harvested at the flowering phase was up to 71.4% of that at the mature phase. It was also found, by observing the growth duration of R. globosa, that the frostless period at the experiment site was twice as long as the growth time from the seedling-transplanted phase to the flowering phase of the hyperaccumulator. Conclusion R. globosa could be transplanted into contaminated soils twice in one year by harvesting the hyperaccumulator at its flowering phase based on climatic conditions of the site and traits of the plant growth. In this sense, the extraction efficiency of Cd in shoots of R. globosa increased 42.8% compared to that of at its single maturity when the plant was transplanted into contaminated soils after it had been harvested at its flowering phase and the plant accumulated Cd from soil at the same extraction ratio at its second flowering phase. Thus, the method of anthesis biomass regulation by the two-phase planting is very significant to increase the Cd-removing efficiency by phytoremediation used in practice over the course of a year. Recommendation and Outlook As for some hyperaccumulators that the growth duration from the seedling-transplanted phase to the flowering phase are short and the concentrations of heavy metals accumulated in their shoots at the flowering phase are high, the efficiency of phytoremediation can greatly be improved using the method of the two-phase planting.     

施肥对不同农田土壤微生物活性的影响

采用室内恒温培养研究了施肥对不同农田土壤微生物活性的影响。结果表明，在红壤、水稻土和潮土中，土壤微生物量、土壤酶活性大小顺序均为有机肥配施无机肥处理＞单施有机肥处理＞单施无机肥处理，但对脲酶来说，其活性大小顺序为有机肥配施无机肥处理＞单施无机肥处理＞单施有机肥处理。从土壤类型来看，土壤微生物量碳、氮和土壤酶活性大小以水稻土最大，潮土次之，红壤最小。３种土壤的微生物量、土壤酶活性在培养的４５～６０ｄ之间分别达到最大值，以后逐渐下降。部分单施无机肥处理的土壤微生物量、土壤酶活性最大值比单施有机肥处理、有机肥配施无机肥处理提前１５ｄ。相关分析表明，有机肥配施无机肥处理及单施有机肥处理，３种土壤的土壤微生物量碳、氮与土壤过氧化氢酶、转化酶、蛋白酶、脲酶及速效养分呈显著或极显著的相关性；单施无机肥处理中，土壤微生物量碳、氮与土壤过氧化氢酶、蔗糖转化酶、蛋白酶、脲酶显著或极显著相关，与部分速效养分相关不显著。     

生物质燃烧释放N2O的测定及其分布

本文报导了实验室规模的生物质封闭燃烧系统及稻草、玉米秸、麦杆燃烧过程中Ｎ２Ｏ排放因子的测定结果，测定结果表明：稻草、麦杆及玉米秸燃烧排气中Ｎ２Ｏ的排放因子分析是８４．４ｇ／ｔ，２７．３ｇ／ｔ，１３２ｇ／ｔ。用Ｎ２Ｏ－Ｎ占生物全氮的百分含量表示，稻草及玉米秸分别上０．５９％，０．８７％。用实验得到的Ｎ２Ｏ的排放因子计算出了生物质燃烧产生Ｎ２Ｏ在全国各省、直辖市、县的年排放量，并作出了全国年排放的分布     

山一村山地生态系统结构功能和系统调控

本文对山－村山地生态系统的结构和功能、能量产投比、生物量等进行实地调查和研究。结果表明，通过多年生态建设，山地生态系统已显示较好的经济、环境和社会效益。     

Resilience of Southwestern Amazon Forests to Anthropogenic Edge Effects

Abstract:  Anthropogenic edge effects can compromise the conservation value of mature tropical forests. To date most edge-effect research in Amazonia has concentrated on forests in relatively seasonal locations or with poor soils in the east of the basin. We present the first evaluation from the relatively richer soils of far western Amazonia on the extent to which mature forest biomass, diversity, and composition are affected by edges. In a southwestern Amazonian landscape we surveyed woody plant diversity, species composition, and biomass in 88 × 0.1 ha samples of unflooded forest that spanned a wide range in soil properties and included samples as close as 50 m and as distant as >10 km from anthropogenic edges. We applied Mantel tests, multiple regression on distance matrices, and other multivariate techniques to identify anthropogenic effects before and after accounting for soil factors and spatial autocorrelation. The distance to the nearest edge, access point, and the geographical center of the nearest community ("anthropogenic-distance effects") all had no detectable effect on tree biomass or species diversity. Anthropogenic-distance effects on tree species composition were also below the limits of detection and were negligible in comparison with natural environmental and spatial factors. Analysis of the data set's capacity to detect anthropogenic effects confirmed that the forests were not severely affected by edges, although because our study had few plots within 100 m of forest edges, our confidence in patterns in the immediate vicinity of edges is limited. It therefore appears that the conservation value of most "edge" forests in this region has not yet been compromised substantially. We caution that because this is one case study it should not be overinterpreted, but one explanation for our findings may be that western Amazonian tree species are naturally faster growing and more disturbance adapted than those farther east.     

松嫩草甸不同退化程度生境土壤磷素动态研究

对松嫩草甸不同退化程度生境的几种代表植物群落土壤磷素状况的研究表明,各群落相同土层的全磷含量没有显著的差异,说明土壤磷库具有较强的弹性,土壤退化落后于地上植物群落的退化.各群落土壤全磷的季节变化相似,均经历迅速累积,达到峰值后下降,之后又有一个缓慢积累的过程.羊草、寸草苔和碱茅群落全磷含量随土层的加深而减少,虎尾草群落土壤全磷聚集于10~20cm土层.随退化程度的加重,土壤速效磷含量增加,虎尾草群落土壤速效磷占全磷的比重最高(2.8%),表明退化生境植物群落对速效磷素的利用并不充分.各群落土壤微生物量磷含量均高于速效磷含量,其季节动态均为单峰曲线,峰值出现在8月.虎尾草群落土壤微生物量磷在10~20cm的土层最多,其他群落土壤微生物量磷在0~10cm土层的含量最多.灰色分析的结果表明,土壤速效磷的形成主要受到土壤养分,尤其是碳、氮养分的影响;而土壤温度、水分状况、酸碱状况和盐化程度等因素对土壤微生物量磷的影响较强.图2表3参26     

A simple approach to modeling microbial biomass in the rhizosphere

Microorganisms make an important contribution to the degradation of contaminants in bioremediation as well as in phytoremediation. An accurate estimation of microbial concentrations in the soil would be valuable in predicting contaminant dissipation during various bioremediation processes. A simple modeling approach to quantify the microbial biomass in the rhizosphere was developed in this study. Experiments were conducted using field column lysimeters planted with Eastern gamagrass. The microbial biomass concentrations from the rhizosphere soil, bulk soil, and unplanted soil were monitored for six months using an incubation–fumigation method. The proposed model was applied to the field microbial biomass data and good correlation between simulated and experimental data was achieved. The results indicate that plants increase microbial concentrations in the soil by providing root exudates as growth substrates for microorganisms. Since plant roots are initially small and do not produce large quantities of exudates when first seeded, the addition of exogenous substrates may be needed to increase initial microbial concentrations at the start of phytoremediation projects.     

围栏禁牧对川西北亚高山高寒草甸群落结构的影响

围栏禁牧4a后,与放牧草地相比较:1)围栏草地物种数量有所下降,群落内出现物种27种,而长期放牧草地为33种.2)围栏草地物种平均高度较高,为20.23cm,群落分层现象明显;放牧草地物种平均高度仅为8.14cm,群落无分层现象.3)围栏草地内,杂草类的盖度(98%)大于禾草类的盖度(14%);放牧草地上,杂草类的盖度(53%)小于禾草类的盖度(56%)。4)围栏草地以禾草为主的优良牧草的生产能力(35.24g/m2)低于放牧草地的生产能力(75.47g/m2).5)围栏草地的地上生物量(272.64g/m2)和地下0～30cm生物量(801.61g/m3)都高于放牧草地的地上生物量(184.84g/m2)和地下0～30cm生物量(683.82g/m3).研究结果表明,围栏草地具有比放牧草地更复杂的群落结构,但其物种组成和优良牧草的生产能力,都低于放牧草地.