氮、磷添加对青藏高寒草甸土壤碳氮磷化学计量特征影响的Meta分析

为了解青藏高原高寒草甸土壤碳(Carbon,C)、氮(Nitrogen,N)、磷(Phosphorus,P)化学计量特征对氮、磷添加的响应,提高养分管理水平及草地生态系统的养分平衡。本研究严格筛选出21篇文章(612项数据)进行Meta分析,通过亚组分析分析了不同施肥方式(氮添加、磷添加、氮磷添加)、不同施肥强度(轻度、中度、重度)对青藏高原草地土壤C,N,P化学计量特征的影响。研究结果表明：养分添加显著增加了青藏高原草地土壤C,N,P含量;氮添加对土壤的增加效应随施肥强度增加而增加,磷轻度施肥(20g·m^-2以下)处理、氮磷添加轻度施肥处理下的土壤C,N,P含量及化学计量比增加效果最好。本研究结果总体反映出氮、磷添加对青藏高原高寒草甸土壤产生积极影响,研究结果可为青藏高原草地生态系统的保护提供科学依据。     

菌渣添加量对污染土壤Pb、Zn形态和水稻产量的影响

通过测定3种菌渣添加量对水稻3个生育期土壤Pb、Zn形态的变化、水稻籽粒Pb、Zn含量及水稻产量的影响,以期得出菌渣的适宜添加量,为重金属污染土壤的修复应用和作物安全生产提供理论依据。结果表明:三种菌渣处理可以降低土壤交换态Pb、Zn含量,且随着生育期逐步减少,提高土壤碳酸盐结合态Pb、Zn含量,以15%菌渣处理的效果最好,其次是10%菌渣处理,再次是5%菌渣处理;三种菌渣添加量可以显著提高水稻的千粒重和产量,但是不随菌渣添加量的增加而提高千粒重和产量,添加10%菌渣处理的千粒重和产量均达最高,其次是15%的菌渣处理;三种菌渣添加量对降低水稻籽粒Pb、Zn含量效果明显,15%菌渣处理的效果最好,10%菌渣处理次之。     

春季和夏季流沙湾浮游植物营养限制研究

采用室内营养加富法研究了2008年流沙湾春季和夏季营养限制状况.结果表明,春季和夏季N、P、Si、Fe等单营养添加缸浮游植物均无显著的促进效应,与对照差异不显著;而N、P和N、P、Si多营养添加缸均显著促进了浮游植物的增长.其中春季N、P缸和N、P、Si缸浮游植物叶绿素a最大生物量分别为49.9 mg/m3和38.4 mg/m3,夏季N、P缸和N、P、Si缸叶绿素a最大生物量分别达14.2 mg/m3和49.4 mg/m3.N、P协同限制流沙湾浮游植物生长;流沙湾大规模高密度贝类养殖导致的营养沉降作用和大型藻类和海草类生物代谢作用可能是造成流沙湾浮游植物营养限制的主要因素.流沙湾浮游植物受到养殖贝类高摄食压力及海域低营养供给共同作用,导致生态系统结构不平衡.     

Effects of Glucose Addition on N Transformations in Paddy Soils with a Gradient of Organic C Content in Subtropical China

To better understand the interaction of N transformation and exogenous C source and manage N fertilization, the effects of glucose addition on N transformation were determined in paddy soils with a gradient of soil organic C content. Changes in N mineralization, nitrification and denitrification, as well as their response to glucose addition were measured by incubation experiments in paddy soils derived from Quaternary red clay in subtropical China. Mineralization and denitrification were changed in order of increasing soil fertilities： high 〉 middle 〉 low. During the first week of incubation, net N mineralization and denitrification rates in paddy soil with high fertility were 1.9 and 1.1 times of those in soil with middle fertility and 5.3 and 2.9 times of those in soil with low fertility, respectively. Addition of glucose decreased net N mineralization by approximately 78.8, 109.2 and 177.4% in soils with high, middle and low fertility, respectively. However, denitrification rates in soils with middle and low fertility were increased by 14.4 and 166.2% respectively. The highest nitrate content among the paddy soils tested was 0.62 mg kg-1 and the highest nitrification ratio was 0.33%. Addition of glucose had no obvious effects on nitrate content and nitrification ratio. It was suggested that the intensity of mineralization and denitrification was quite different in soils with different fertility, and increased with increasing soil organic C content. Addition of glucose decreased mineralization, but increased denitrification, and the shifts were greater in soil with low than in soil with high organic C content. Neither addition of glucose nor inherent soil organic C had obvious effects on nitrification in paddy soils tested.     

C/N ratio control and substrate addition for periphyton development jointly enhance freshwater prawn Macrobrachium rosenbergii production in ponds

The present research investigated the effect of carbon/nitrogen ratio (C/N ratio) control in ponds with or without substrate addition for periphyton development on production of giant freshwater prawn. C/N ratios of 10, 15 and 20 were investigated in 40 m^− 2 ponds stocked with 2 prawn juveniles (5.023 ± 0.02 g) m^− 2 with or without added substrates for periphyton development. The various treatment combinations of C/N ratio and periphyton substrate addition are abbreviated as ‘CN10’, ‘CN15’, ‘CN20’, ‘CN10 + P’, ‘CN15 + P’ and ‘CN20 + P’, P representing periphyton substrate. A locally formulated and prepared feed containing 30% crude protein with C/N ratio10 was applied. Tapioca starch was used as carbohydrate source for manipulating C/N ratio and applied to the water column separately from the feed. Increasing the C/N ratio from 10 to 20 reduced (P < 0.001) the total ammonia-nitrogen (TAN), nitrite–nitrogen (NO₂–N) and nitrate–nitrogen (NO₃–N) in water column and total Kjeldahl nitrogen (TKN) in sediment. The addition of substrates only influenced the NO₂–N concentration in the water column (P < 0.001). Increasing the C/N ratio raised the total heterotrophic bacterial (THB) population in the water column, sediment and periphyton (P < 0.001). It also increased the dry matter (DM), ash free dry matter (AFDM), and chlorophyll a content of periphyton (P < 0.001). The lowest specific growth rate (SGR), the highest food conversion ratio (FCR), and the lowest protein efficiency ratio (PER) were recorded in treatment CN10 (P < 0.05). The addition of substrates did not influence size at harvest (P > 0.05) but improved the survival from 62.8 to 72% (P < 0.001). Increasing the C/N ratio from 10 to 20 increased the net yield by 40% and addition of substrate increased the net yield by 23%. The combination of C/N ratio control and substrate addition increased the net yield by 75% from 309 (CN10) to 540 (CN20 + P) kg ha^− 1 (120 days)^− 1. This 75% higher production concurred with (1) a lower inorganic nitrogen content in the water column, (2) a higher THB abundance supplying additional single cell protein to augment the prawn production, and (3) an improved periphyton productivity and quality.     

氮素化学形态及添加剂量对温带森林土壤N2O排放的影响

土壤中氮形态和氮剂量的有效性是影响土壤氧化亚氮(N₂O)排放的重要因子。为了提高氮素化学形态及添加剂量对温带森林土壤N₂O排放的影响,本研究在北京林业大学实验林场,以温带油松林土壤为研究对象,通过野外氮添加控制实验,采用静态箱/气相色谱法分析不同水平(对照,CK:0 kg/(hm2·a); 低氮,LN:50 kg/(hm2·a); 中氮,MN:100 kg/(hm2·a); 高氮,HN:150 kg/(hm2·a))和不同形态(混合态氮,AN:NH₄NO₃; 铵态氮,As:(NH₄)₂SO₄; 硝态氮,Na:NaNO₃)的氮添加对温带油松林土壤N₂O排放通量的影响。结果表明:氮添加处理样地N₂O排放表现出明显的季节性变化特征,排放高峰出现在6—8月,其他季节土壤N₂O排放通量相对较低,最小值出现在1月。不同氮添加处理均促进了土壤N₂O的排放:在不同水平的氮添加下,随着氮添加水平的增加,土壤N₂O排放通量也升高,表现为HN＞MN＞LN＞CK。不同形态的氮输入对N₂O排放的促进作用表现为:AN＞As＞Na,As添加与AN和Na添加没有显著差异(P>0.05),但AN添加与Na添加之间差异显著(P＜0.05)。此外,空气温度、土壤温度和土壤孔隙含水量也可以影响土壤N₂O的排放。年度土壤N₂O排放系数范围是0.34%~0.94%,年均排放系数为0.364%,低于联合国政府间气候变化委员会(IPCC)推荐的默认值。      

Impact of inorganic nitrogen additions on microbes in biological soil crusts

Many studies have shown that changes in nitrogen (N) availability affect the diversity and composition of soil microbial community in a variety of terrestrial systems, but less is known about the responses of microbes specific to biological soil crusts (BSCs) to increasing N additions. After seven years of field experiment, the bacterial diversity in lichen-dominated crusts decreased linearly with increasing inorganic N additions (ambient N deposition; low N addition, 3.5 g N m⁻² y⁻¹; medium N addition, 7.0 g N m⁻² y⁻¹; high N addition, 14.0 g N m⁻² y⁻¹), whereas the fungal diversity exhibited a distinctive pattern, with the low N-added crust containing a higher diversity than the other crusts. Pyrosequencing data revealed that the bacterial community shifted to more Cyanobacteria with modest N additions (low N and medium N) and to more Actinobacteria and Proteobacteria and much less Cyanobacteria with excess N addition (high N). Our results suggest that soil pH, together with soil organic carbon (C), structures the bacterial communities with N additions. Among the fungal communities, the relative abundance of Ascomycota increased with modest N but decreased with excess N. However, increasing N additions favored Basidiomycota, which may be ascribed to increases in substrate availability with low lignin and high cellulose contents under elevated N conditions. Bacteria/fungi ratios were higher in the N-added samples than in the control, suggesting that the bacterial biomass tends to dominate over that of fungi in lichen-dominated crusts after N additions, which is especially evident in the excess N condition. Because bacteria and fungi are important components and important decomposers in BSCs, the alterations of the bacterial and fungal communities may have implications in the formation and persistence of BSCs and the cycling and storage of C in desert ecosystems.     

重金属Pb与抗生素对发光菌的联合毒性研究

重金属是水环境中的典型无机污染物,随着水体中抗生素检出率的增加,重金属和抗生素的复合污染及其效应已成为环境领域的研究热点。通过研究重金属和抗生素对发光菌的发光抑制作用,可以了解重金属和抗生素的毒性效应,为评估重金属和抗生素复合污染在水环境中的潜在风险提供理论依据。本文利用便携式急性毒性检测仪,系统研究了重金属Pb和6种抗生素(四环素、氧四环素、氯四环素、磺胺二甲基嘧啶、磺胺甲基嘧啶和磺胺嘧啶)对费氏弧菌的单一和联合急性毒性,得到了单一污染物的半数效应浓度,并对重金属Pb和抗生素所组成的二元、三元复合污染体系的联合作用进行初步探讨。研究表明,当Pb与抗生素共存时,对发光菌的急性毒性急剧上升。因此,在评价Pb与抗生素二元或多元复合污染体系的生态风险时,应考虑其联合毒性作用。     

Comparative performance of the highly invasive Mimosa invisa and its less invasive subspecies under different nutrient and light conditions

Invasive plants may be more plastic than non‐invasive plants and maintain high fitness under various environmental conditions. Previous studies mainly focused on the comparisons between invasive and native plants, and comparisons between highly invasive and less invasive exotic species are still relatively rare, especially for comparisons at the subspecies level. This study examined the effects of nutrient addition and shading on the performance of the highly invasive Mimosa invisa and its less invasive subspecies M. invisa var. inermis under either isolated or competitive conditions. Nutrient addition increased biomass and plant height and decreased root‐to‐shoot ratio (R/S). Shading decreased biomass and R/S and increased plant height. Under isolated conditions, the two invaders did not differ in R/S, plant height and plasticity of these traits in response to nutrient addition or shading, and the two invaders also did not differ in biomass production under each of the nutrient and light treatments. When the two invaders competed with each other, M. invisa outcompeted M. invisa var. inermis under high soil nutrient conditions, and the two invaders did not differ in performance under other growth conditions. Thus, only considering competition may we find out the difference between highly invasive species and their closely related, less invasive subspecies. Management of M. invisa should focus on habitats with high soil nutrient availability, in which M. invisa is more likely to dominate.     

黄瓜单体异附加系的筛选与观察

 将甜瓜属异源三倍体与栽培黄瓜‘北京截头’杂交，经胚胎拯救获得了两个2n=15 (14C+1H)的单体异附加系，编号分别为02—17和02—39。02一l7植株叶形为戟形，02—39为深陷的掌状形，并且果刺均为白色，不同于异源三倍体的掌状心脏形和黑刺，果形比异源三倍体黄瓜长而更接近普通黄瓜。细胞学研究发现，单体异附加系在终变期和中期I染色体构型主要是由7个二价体和1个单价体构成，出现三价体的频率为4％ ～5％ ，中期Ⅱ不均等分裂形成不同的两极，一极染色体为8条，另一极为7条。RAPD分析证明它们分刖附加了野生种Cucum／s hystrix的染色体。