铜尾矿废弃地生物土壤结皮固氮微生物多样性

生物土壤结皮能够有效提高矿业废弃地有机质和氮的积累,促进植被的恢复.本研究基于固氮微生物的nifH基因多样性,以铜陵铜尾矿废弃地3种类型的生物土壤结皮(藻结皮、藓结皮和藻-藓混合结皮)为对象,利用变性梯度凝胶电泳(DGGE)技术研究生物土壤结皮中固氮微生物的多样性以及废弃地植物群落发育对其产生的影响.结果表明： 尾矿库裸地表面的藻结皮的固氮微生物多样性最高,其次为维管植物群落下的藻-藓混合结皮,苔藓结皮的固氮蓝藻多样性最低;随着维管植物群落高度和盖度的增加,固氮微生物多样性降低,铜尾矿废弃地的pH、水分、有机质、养分含量(氮和磷)以及有效态和总重金属浓度对固氮微生物多样性的影响均不显著.测序和系统发育分析表明,废弃地结皮中固氮微生物以蓝藻为主,主要为不具有异形胞的丝状蓝藻.
     

自然演替过程中铜尾矿土壤酶活性的变化

铜陵矿区堆放了大量不同时期的铜尾矿,形成大量铜尾矿废弃地,其中的大部分铜尾矿废弃地处于自然生态恢复状态。并形成典型的原生演替系列。为探讨废弃地自然生态恢复中不同演替阶段植物群落变化与土壤酶活性变化的关系,对铜陵3处不同时期弃置的尾矿废弃地进行了调查。随着自然生态系统演替的进行,尾矿中土壤酶活性逐步提高,维管植物群落下尾矿中土壤酶活性〉隐花植物结皮下尾矿中土壤酶活性〉裸地处土壤酶活性;位于植物群落下的尾矿废弃地中脲酶、碱性磷酸酶、过氧化氢酶的活性从表层至下层逐渐降低。不同植物群落对尾矿中土壤酶活性影响有很大差异,位于木贼群落下的尾矿中几种土壤酶的活性高于位于白茅群落和中华结缕草群落下的尾矿中酶的活性。相关分析表明,土壤酶活性与有机质、总N表现出显著的正相关。     

土壤有机氮组分的年际变化及其对秸秆还田的响应

阐明土壤有机氮组分的年际变化特征及其对秸秆还田的响应对合理调控土壤有机氮库和土壤可持续利用具有重要意义。在沈阳农田生态系统国家野外科学观测研究站进行田间微区试验(土壤类型为潮棕壤),设置单施氮肥(200 kg N·hm^-2,下同)、50%秸秆还田配施氮肥和100%秸秆还田配施氮肥3个处理,采用Bremner酸水解法对试验第1、3、6、9年的土壤有机氮组分进行分级。结果表明: 氨基酸态氮含量随着耕作年限的增加逐渐提升,提升幅度为39.8%;酸解未知态氮含量提升幅度为10.8%,且在第3年时最高;土壤总氮和其他有机氮组分含量随耕作年限变化不大。相对容易矿化的酸解总氮占土壤总氮的比例随耕作年限的增加逐渐增加,比较稳定的未酸解态氮占土壤总氮的比例随耕作年限的增加逐渐下降,说明随着耕作年限的增加土壤氮素有效性提高,土壤供氮能力增强。与单施氮肥相比,加入秸秆提高了土壤总氮和各酸解态氮含量,秸秆还田量越多,提升效果越明显。秸秆还田对酸解态氮组分的影响主要发生在试验第6、9年,增加的土壤总氮主要为氨基酸态氮和酸解未知态氮,从而提高了土壤中酸解态氮占土壤总氮的比例。秸秆还田能够提升土壤氮库容,提高土壤保氮供氮能力。     

不同施肥对雷竹林径流及渗漏水中氮形态流失的影响

雷竹经营过程中化肥的大量施用,是产区水体污染的主要原因之一,养分管理技术可有效控制面源污染。为了探明减量施肥和有机肥施用对雷竹不同氮形态流失的影响,2012年在浙江省临安市雷竹产区设置了4种施肥处理:对照(CK);常规施肥(CF);减量无机(DI);减量有机无机(DOI),试验于5月18日、9月7日、11月9日分别施用肥料总量的40%,30%和30%,施肥后均进行浅翻,深度5 cm左右。通过建立径流场和土壤渗漏水收集装置,同时在试验田附近布置量雨筒,观察2012年不同氮形态浓度及流失负荷随降雨量的动态变化。研究结果表明:不同施肥处理径流水硝态氮、水溶性有机氮(WSON)以及颗粒态氮的浓度分别在3.82-6.82 mg/L、0.89-1.85 mg/L和0.89-1.83 mg/L,其占总氮的百分比分别为60.9%-68.2%、16.0%-18.1%和15.1%-21.6%。不同施肥处理渗漏水中硝态氮、铵态氮及WSON的浓度分别在26.2-92.5 mg/L、0.50-6.42 mg/L和6.57-12.6 mg/L,其占总氮的百分比分别为75.8%-82.9%、1.50%-6.36%和11.2%-20.6%。不同施肥处理径流水的氮总流失负荷,减量无机和减量有机无机相对于常规施肥来说减少了46.9%和23.1%;不同施肥处理的渗漏水的氮总流失负荷,减量无机和减量有机无机相对于常规施肥来说减少了19.1%和52.1%,可见减量施肥和减量有机无机减少氮流失的效果显著。     

鄂西北丹江口库区大气氮沉降

利用雨量器在鄂西北丹江口库区连续3a采集降雨样品,研究了大气氮沉降的变化动态。结果表明:2009—2011年月均总氮(TN)浓度为3.70—10.36 mg/L,与当月降雨量呈极显著线性负相关(R=-0.592**,n=32),季均TN浓度为冬季(8.21 mg/L)春季(3.94 mg/L)秋季(3.23 mg/L)夏季(2.70 mg/L),年均TN浓度为3.70 mg/L。大气氮素年均干湿总沉降量为26.53 kg/hm2,其中干沉降为7.80 kg/hm2,占总沉降量的29.4%;湿沉降为18.73 kg/hm2,占总沉降量的70.6%。干沉降中铵态氮(NH+4-N)、硝态氮(NO-3-N)、可溶性有机氮(DON)和颗粒态氮(PN)分别占TN的22.1%、16.8%、37.2%和23.9%,湿沉降中它们分别为TN的36.6%、34.4%、12.9%和16.1%。     

高原鼠兔挖掘活动对土壤中氮素含量的影响

本文通过测定不同类型高原鼠兔鼠丘和鼠丘下0 ～ 10 cm 土壤中总氮、铵态氮和硝态氮的含量变化,分析了高原鼠兔挖掘活动对土壤中无机氮含量的影响,并通过测定高原鼠兔鼠丘密度,计算了每只高原鼠兔对氮素循环的贡献。研究结果表明:不同类型鼠丘土壤中总氮含量无明显变化,铵态氮、硝态氮和无机氮含量处理间变化趋势为当年鼠丘>两年鼠丘> 多年鼠丘> 对照。方差分析结果表明,硝态氮含量在5 月时差异显著,当年鼠丘和两年鼠丘显著大于多年鼠丘和对照,无机氮含量在5 月和9 月表现为当年鼠丘显著高于对照。在不同月份,铵态氮含量月间变化趋势为5 ～ 8 月逐渐降低,至9 月略有增加,硝态氮和无机氮含量呈现“高- 低- 高-低- 高”的“W”变化趋势。方差分析结果显示,铵态氮、硝态氮和无机氮含量月间变化显著。不同类型鼠丘下0 ～ 10 cm 土壤中铵态氮、硝态氮和无机氮含量处理间和月份间变化趋势与鼠丘土壤中变化趋势基本一致,但硝态氮和无机氮含量在当年鼠丘中均显著高于对照,且不同月份间铵态氮、硝态氮和无机氮的含量差异显著(P
< 0.05)。每只高原鼠兔挖掘活动所形成的鼠丘土壤中的铵态氮、硝态氮和无机氮分别增加了162.6 mg/ kg、355.1 mg/kg 和497.7 mg/ kg。     

不同植物群落下铜尾矿废弃地生物结皮中真菌群落结构的比较

分布于铜尾矿废弃地的裸地表面及维管植物群落中的生物土壤结皮在尾矿废弃地生态恢复过程中扮演重要角色。利用分子生物学技术探讨了不同维管植物下以及不同演替阶段的生物土壤结皮中真菌的多样性及其群落结构的变化。结果表明:生物土壤结皮中的真菌主要包括子囊菌门(Ascomycota)、担子菌门(Basidiomycota)和壶菌门(Chytridiomycota),其中子囊菌门占绝对优势,其相对丰度为55.12%—87.73%,其次为担子菌门相对丰度为12.27%—43.86%;不同样本真菌群落结构在门、纲、目以及属的水平存在显著差异;生物土壤结皮中真菌群落结构和多样性的差异与维管植物群落类型以及演替阶段不同的生物土壤结皮的类型有关,与基质化学性质之间无显著的相关性。     

长江口岛屿沙洲湿地陆向发育过程中表层沉积物氮营养盐的变化

研究针对长江口岛屿沙洲湿地陆向发育的不同时期表层沉积物中氮营养盐的变化规律,得出：（1）长江口岛屿沙洲湿地陆向发育过程中,表层沉积物环境也在不断变化,氮营养盐含量逐步增加,处在陆向发育前期的白茆沙,全氮含量较低,仅为30 mg/kg,而发育较为成熟的崇明东滩全氮含量较高,达470 mg/kg;同时随着岛屿沙洲湿地陆向发育,表层沉积物全氮分布越来越不均匀;（2）长江口岛屿沙洲湿地随高程梯度,全氮的含量逐步增加,其中芦苇带最高,420 mg/kg,光滩最低,110 mg/kg;这也说明岛屿沙洲陆向发育过程中,表层沉积物全氮含量逐步增加;另外,各形态无机氮含量占其所在高程无机氮的比例相对稳定,其中氨氮最高,59%～60%,亚硝酸盐最低,17%～19%,氨氮是无机氮的主要存在形式.     

外源输入氮素在藓类生物土壤结皮中各氮组分的分配特征与归趋途径

针对黄土高原典型藓类生物结皮,以无结皮裸地为对照,通过野外原位同位素标记试验,在标记后1~30 d连续取样测定,示踪外源添加¹⁵N在生物结皮中各氮组分的分配特征,并分析¹⁵N在土壤-微生物-藓植株中的归趋途径,对比揭示生物结皮对土壤氮循环的影响。结果表明: 1)生物结皮的全氮、微生物生物量氮、可溶性有机氮中¹⁵N含量分别平均比裸地高2.9、17.5、9.0倍,且藓植株固定的¹⁵N含量高达4.73 mg·kg^-1。2)生物结皮的¹⁵N残留率平均为13.0%,其氮固持能力是裸地(3.3%)的4.0倍;生物结皮中各组分¹⁵N占全氮的比率依次为微生物生物量氮(54.3%)>藓植株氮(22.5%)>可溶性有机氮(6.2%),而裸地则为微生物生物量氮(11.5%)>可溶性有机氮(2.6%),显示生物结皮中微生物和藓植株的氮固持能力合计比裸地高65.3%。3)生物结皮中微生物生物量¹⁵N的转移量和库容量分别比裸地高17.2和20.5倍,但其周转率为每月5.8次,低于裸地的每月7.2次,其周转期是裸地的1.2倍。综上,与无结皮裸地相比,生物结皮具有更高的氮固持能力,同时能够改变土壤各氮组分的分配率,因此,在干旱生态系统土壤氮循环过程中具有重要作用。     

黄土高原沟壑区森林带不同植物群落土壤氮素含量及其转化

为了探讨在黄土高原退耕还林还草过程中植物群落对土壤氮素含量及形态分布的影响,本文选择退耕历史较长的黄土高原沟壑区——安塞县洞子沟流域8种典型植物群落下0-10cm和10-20cm的土壤为对象,测定了土壤中有机氮、矿化氮、微生物量氮、硝态氮和铵态氮的含量。结果表明,从草本群落到乔灌草群落,土壤各形态氮素含量均增加,整体表现为乔灌草群落>灌草群落>草本群落。然而人工刺槐林的土壤氮素水平远低于自然恢复的乔灌草群落,甚至低于灌草群落。0-10cm 土层各形态氮素均高于10-20cm 土层。硝态氮对植物群落的变化最为敏感,可作为土壤氮素水平的敏感指标。土壤有机质、pH、容重与氮素含量极显著相关,各种氮素间极显著正相关。各种氮素占总氮的比例对总氮的变化有着不同的响应,有机氮、可矿化氮和微生物量氮占总氮的比例相对稳定,硝态氮占总氮的比例随总氮含量的增加而增加,铵态氮占总氮的比例随总氮含量的增加而降低。     

The nitrogen status of Austrian forest ecosystems as influenced by atmospheric deposition,biomass harvesting and lateral organomass exchange

Measurements of the deposition rates of atmospheric trace constituents to forest ecosystems in Austria have shown that the deposition of plant utilizable nitrogen compounds is in the range from 12 kg N to more than 30 kg N ha^-1 a^-1. Locally, even higher deposition rates are encountered as a consequence of point sources or special deposition mechanisms such as fog interception, hoar frost formation, and accumulation in snow drifts. In order to place these values into perspective, they are compared with the nitrogen demand of past and present forest land use and with natural processes of nitrogen depletion and accumulation in forest ecosystems. During wind erosion of forest litter, woody material with a wide C/N-ratio remains on the windward side of ridges, while nutrient-rich material with a narrow C/N-ratio is deposited on the leeward side. As a result, total nitrogen storage in the forest soil as well as overall C/N-ratios change dramatically along a transect over a ridge, thus indicating a strong influence of litter C/N ratio on nitrogen retention in the forest soil. A study of nitrogen stores in the soil of beech ecosystems of the same yield class in the Vienna Woods showed a significant correlation of total N-content with base saturation. These results suggest that nitrogen storage capacity of forest soils may be managed by liming and tree species selection. As knowledge is still meagre, a special study on factors which determine nitrogen storage in forest soils is proposed within the FERN-programme.     

Yield of nitrogen from minimally disturbed watersheds of the United States

Watersheds of the US Geological Survey's Hydrologic Benchmark Network program were used in estimating annual yield of total nitrogen and nitrogen fractions (ammonium, nitrate, dissolved organic N, particulate N) in relation to amount of runoff, elevation, and watershed area. Only watersheds minimally disturbed with respect to the nitrogen cycle were used in the analysis (mostly natural vegetation cover, no point sources of N, atmospheric deposition of inorganic N < 10 kg ha^–1 y^–1). Statistical analysis of the yields of total nitrogen and nitrogen fractions showed that elevation and watershed area bear no significant relationship to nitrogen yield for these watersheds. The yields of total nitrogen and nitrogen fractions are, however, strongly related to runoff (r ² = 0.91 for total N). Annual yield increases as runoff increases, but at a rate lower than runoff; annual discharge-weighted mean concentrations decline as annual runoff increases. Yields of total nitrogen and most nitrogen fractions bear a relationship to runoff that is nearly indistinguishable from a relationship that was documented previously for minimally disturbed watersheds of the American tropics. Overall, the results suggest strong interlatitudinal convergence of yields and percent fractionation for nitrogen in relation to runoff.     

The cycling of organic nitrogen through the atmosphere

Atmospheric organic nitrogen (ON) appears to be a ubiquitous but poorly understood component of the atmospheric nitrogen deposition flux. Here, we focus on the ON components that dominate deposition and do not consider reactive atmospheric gases containing ON such as peroxyacyl nitrates that are important in atmospheric nitrogen transport, but are probably not particularly important in deposition. We first review the approaches to the analysis and characterization of atmospheric ON. We then briefly summarize the available data on the concentrations of ON in both aerosols and rainwater from around the world, and the limited information available on its chemical characterization. This evidence clearly shows that atmospheric aerosol and rainwater ON is a complex mixture of material from multiple sources. This synthesis of available information is then used to try and identify some of the important sources of this material, in particular, if it is of predominantly natural or anthropogenic origin. Finally, we suggest that the flux of ON is about 25 per cent of the total nitrogen deposition flux.     

Nitrogen inputs to a marine embayment: the importance of groundwater

We examined the importance of nitrogen inputs from groundwater and runoff in a small coastal marine cove on Cape Cod, MA, USA. We evaluated groundwater inputs by three different methods: a water budget, assuming discharge equals recharge; direct measurements of discharge using bell jars; and a budget of water and salt at the mouth of the Cove over several tidal cycles. The lowest estimates were obtained by using a water budget and the highest estimates were obtained using a budget of water and salt at the Cove mouth. Overall there was more than a five fold difference in the freshwater inputs calculated by using these methods. Nitrogen in groundwater appears to be largely derived from on site septic systems. Average nitrate concentrations were highest in the region where building density was greatest. Nitrate in groundwater appeared to behave conservatively in sandy sediments where groundwater flow rates were high (> 11/m²/h), indicating that denitrification was not substantially reducing external nitrogen loading to the Cove. Nitrogen inputs from groundwater were approximately 300 mmol-N/m³/y of Cove water. Road runoff contributed an additional 60 mmol/m³/y. Total nitrogen inputs from groundwater and road runoff to this cove were similar in magnitude to river dominated estuaries in urbanized areas in the United States.     

The impact of humans on the nitrogen cycle,with focus on temperate arable agriculture

The 6 billion people alive today consume about 25 million tonnes of protein nitrogen each year, a requirement that could well increase to 40–45 million tonnes by 2050. Most of them ultimately depend on the Haber-Bosch process to fix the atmospheric N₂ needed to grow at least part of their protein and, over the earth as a whole, this dependency is likely to increase. Humans now fix some 160 million tonnes of nitrogen per year, of which 98 are fixed industrially by the Haber-Bosch process (83 for use as agricultural fertilizer, 15 for industry), 22 during combustion and the rest is fixed during the cultivation of leguminous crops and fodders. These 160 million tonnes have markedly increased the burden of combined nitrogen entering rivers, lakes and shallow seas, as well as increasing the input of NH₃, N₂O, NO and NO₂ to the atmosphere. Nitrogen fertilizers give large economic gains in modern farming systems and under favourable conditions can be used very efficiently. Losses of nitrogen occur from all systems of agriculture, with organic manures being particularly difficult to use efficiently. Although nitrate leaching has received much attention as an economic loss, a cause of eutrophication and a health hazard, gaseous emissions may eventually prove to be the most serious environmentally. Scientists working on the use and fate of nitrogen fertilizers must be careful, clear headed and vigilant in looking for unexpected side effects.     

Nitrogen outputs from fecal and urine deposition of small mammals: implications for nitrogen cycling

The contribution of small mammals to nitrogen cycling could have repercussions for the producer community in the maintaining or perhaps magnifying of nitrogen availability. Our objective was to model nitrogen outputs (deposition of feces and urine) of small mammals in an old-field ecosystem and estimate the amount of fecal and urinary nitrogen deposited annually. To address this objective, we used models from laboratory studies and combined these with data from field studies to estimate dietary nitrogen and monthly and annual nitrogen outputs from fecal and urine deposition of five rodent species. The models accounted for monthly fluctuations in density and biomass of small-mammal populations. We estimated that the minimal amount of nitrogen deposited by rodents was 1.0 (0.9–1.1) and 2.7 (2.6–2.9) kg Nha⁻¹ year⁻¹ from feces and urine, respectively, for a total contribution of 3.7 (3.5–4.0) kg Nha⁻¹ year⁻¹. Hispid cotton rats (Sigmodon hispidus) accounted for >75% of the total nitrogen output by small mammals. Our estimates of annual fecal and urinary nitrogen deposited by rodents were comparable to nitrogen deposits by larger herbivores and other nitrogen fluxes in grassland ecosystems and should be considered when assessing the potential effects of herbivory on terrestrial nitrogen cycles.     

Available soil nitrogen in relation to fractions of soil nitrogen and other soil properties

The available N of 27 soils from England and Wales was assessed from the amounts of N taken up over a 6-month period by perennial ryegrass grown in pots under uniform environmental conditions. Relationships between availability and the distribution of soil N amongst various fractions were then examined using multiple regression. The relationship: available soil N (mg kg^–1 dry soil)=(N_min×0.672)+(N_inc×0.840)+(N_mom×0.227)–5.12 was found to account for 91% of the variance in available soil N, where N_min=mineral N, N_inc=N mineralized on incubation and N_mom=N in macro-organic matter. The N mineralized on incubation appeared to be derived largely from sources other than the macro-organic matter because these two fractions were poorly correlated. When availability was expressed in terms of available organic N as % of soil organic N (N_ao) the closest relationship with other soil characteristics was: N_ao=[N_inc×(1.395–0.0347×CN_mom]+[N_mom×0.1416], where CN_mom=CN ratio of the macro-organic matter. This relationship accounted for 81% of the variance in the availability of the soil organic N.The conclusion that the macro-organic matter may contribute substantially to the available N was confirmed by a subsidiary experiment in which the macro-organic fraction was separated from about 20 kg of a grassland soil. The uptake of N by ryegrass was then assessed on two subsamples of this soil, one without the macro-organic matter and the other with this fraction returned: uptake was appreciably increased by the macro-organic matter.     

Time course of N2 fixation in common bean (Phaseolus vulgaris L.)

Field and greenhouse experiments were conducted to assess the nitrogen fixation rates of four cultivars of common bean (Phaseolus vulgaris L.) at different growth stages. The ¹⁵N isotope dilution technique was used to quantify biological nitrogen fixation. In the greenhouse, cultivars M4403 and Kallmet accumulated 301 and 189 mg N plant^–1, respectively, up to 63 days after planting (DAP) of which 57 and 43% was derived from atmosphere. Under field conditions, cultivars Bayocel and Flor de Mayo RMC accumulated in 77 DAP, 147 and 135 kg N ha^–1, respectively, of which approximately one-half was derived from the atmosphere. The rates of N₂ fixation determined at different growth stages increased as the plants developed, and reached a maximum during the reproductive stage both under field and greenhouse conditions. Differences in translocation of N were observed between the cultivars tested, particularly under field conditions. Thus, the fixed N harvest index was 93 and 60 for cultivars Flor de Mayo and Bayocel, respectively. In early stages of growth, the total content of ureides in the plants correlated with the N fixation rates. The findings reported in the present paper can be used to build a strategy for enhancing biological N₂ fixation in common bean.     

嫁接与施氮对甜瓜产量和氮素吸收、利用的影响

通过裂区设计田间试验,主区为2种栽培方式(嫁接栽培和自根栽培),副区为4个施氮水平(0、120、240、360 kg N·hm^-2),研究了栽培方式和施氮量对甜瓜产量和品质、氮素运移和分配,以及氮素利用率的影响.结果表明: 嫁接栽培的甜瓜商品瓜产量较自根甜瓜提高了7.3%,可溶性固形物含量降低了0.16%～3.28%;生长前期嫁接栽培甜瓜氮素累积量较自根栽培低,结果后嫁接栽培氮素累积量显著升高,收获时植株氮素累积量较自根栽培增加了5.2%,果实中的氮素累积量提高了10.3%;嫁接栽培植株氮素向果实的转移量较自根栽培提高了20.9%,嫁接栽培果实中的氮素分配率在80%以上,自根栽培的分配率在80%以下;在同一施氮水平下,嫁接栽培的甜瓜氮素吸收利用率较自根栽培提高了1.3%～4.2%,氮素农学效率提高了2.73～5.56 kg·kg^-1,氮素生理利用率提高了7.39～16.18 kg·kg^-1;从商品瓜产量、氮素吸收量和氮素利用率综合考虑,施氮量240 kg·hm^-2为本区域嫁接甜瓜较适宜的氮素用量.     

Mechanisms of plant species impacts on ecosystem nitrogen cycling

Plant species are hypothesized to impact ecosystem nitrogen cycling in two distinctly different ways. First, differences in nitrogen use efficiency can lead to positive feedbacks on the rate of nitrogen cycling. Alternatively, plant species can also control the inputs and losses of nitrogen from ecosystems. Our current understanding of litter decomposition shows that most nitrogen present within litter is not released during decomposition but incorporated into soil organic matter. This nitrogen retention is caused by an increase in the relative nitrogen content in decomposing litter and a much lower carbon‐to‐nitrogen ratio of soil organic matter. The long time lag between plant litter formation and the actual release of nitrogen from the litter results in a bottleneck, which prevents feedbacks of plant quality differences on nitrogen cycling. Instead, rates of gross nitrogen mineralization, which are often an order of magnitude higher than net mineralization, indicate that nitrogen cycling within ecosystems is dominated by a microbial nitrogen loop. Nitrogen is released from the soil organic matter and incorporated into microbial biomass. Upon their death, the nitrogen is again incorporated into the soil organic matter. However, this microbial nitrogen loop is driven by plant‐supplied carbon and provides a strong negative feedback through nitrogen cycling on plant productivity. Evidence supporting this hypothesis is strong for temperate grassland ecosystems. For other terrestrial ecosystems, such as forests, tropical and boreal regions, the data are much more limited. Thus, current evidence does not support the view that differences in the efficiency of plant nitrogen use lead to positive feedbacks. In contrast, soil microbes are the dominant factor structuring ecosystem nitrogen cycling. Soil microbes derive nitrogen from the decomposition of soil organic matter, but this microbial activity is driven by recent plant carbon inputs. Changes in plant carbon inputs, resulting from plant species shifts, lead to a negative feedback through microbial nitrogen immobilization. In contrast, there is abundant evidence that plant species impact nitrogen inputs and losses, such as: atmospheric deposition, fire‐induced losses, nitrogen leaching, and nitrogen fixation, which is driven by carbon supply from plants to nitrogen fixers. Additionally, plants can influence the activity and composition of soil microbial communities, which has the potential to lead to differences in nitrification, denitrification and trace nitrogen gas losses. Plant species also impact herbivore behaviour and thereby have the potential to lead to animal‐facilitated movement of nitrogen between ecosystems. Thus, current evidence supports the view that plant species can have large impacts on ecosystem nitrogen cycling. However, species impacts are not caused by differences in plant quantity and quality, but by plant species impacts on nitrogen inputs and losses.