模拟氮沉降对甜槠林分凋落物及主要养分归还量的影响

选取亚热带典型的常绿阔叶甜槠林为研究对象,从2011年4月至2013年6月进行模拟氮(N)沉降试验,以探讨甜槠林凋落物养分归还量对N沉降的响应。氮沉降水平分别为:对照(CK,0 kg N hm-2a-1),低氮(LN,50 kg N hm-2a-1),高氮(HN,100 kg N hm-2a-1),高氮+磷(HN+P,100 kg N hm-2a-1+50 kg P hm-2a-1),每个处理重复3次。在模拟氮沉降2 a后,于2012年7月开始收集各样地的凋落物样品,分析凋落物及其养分归还量。结果表明:不同处理凋落物量没有显著差异,表明氮沉降增加没有显著提高林分凋落物产量;不同处理落叶、落枝中N、P、K、Ca、Mg含量均无显著差异,表明氮沉降亦没有显著增加凋落物各养分含量;模拟氮沉降处理均增加了各养分元素年归还量,但不同元素对N沉降的响应不同。N、K和Mg年归还量与CK存在显著差异,而P和Ca年归还量与CK处理无显著差异。     

Elevational Patterns of Acid Deposition into a Forest and Nitrogen Saturation on Mt. Oyama, Japan

Virgin fir trees have been dying on Mt. Oyama, which is located in the southwestern part of Kanto Plain, although the frequency of death seems to be reducing recently. We report elevational patterns of acid deposition in precipitation and throughfall under fir and cedar canopies and nitrogen saturation in the forest ecosystem on Mt. Oyama. The deposition fluxes of major inorganic ions in precipitation were nearly constant regardless of elevation except for hydrogen and ammonium ions, whereas the deposition fluxes of all major inorganic ions in throughfall among cedar increased. The 5-year average of annual nitrate deposition in precipitation from 1994 to 1998 showed 19.3 – 23.5 kg ha^?1 yr^?1 (annual inorganic total N deposition: 9.6 – 10.7 kgN ha^?1 yr^?1) at four sites ranging in elevation from 500 to 1252 m, whereas the deposition in both cedar and fir throughfall was over 6 times greater than that in precipitation. The average soil surface nitrate concentration in 1998 was 140 µg g^?1 (the range: 21.1 – 429 µg g^?1, n=80) and the 7-year average of nitrate concentration in stream water from 1992 to 1998 was 4.81 mg L^?1 (the range: 2.38 – 20.6 mg L^?1, n=317). Our results indicate that nitrogen saturation is occurring in the forest ecosystem because of high N deposition, probably via acid fog, on Mt. Oyama.     

Effects of Chronic Nitrogen Amendments on Production of Dissolved Organic Carbon and Nitrogen in Forest Soils

Chronic N deposition has been hypothesized to affect DOC production in forest soils due to the carbon demand exerted by microbial immobilization of inorganic N. We tested this hypothesis in field experiments at the Harvard Forest, Petersham, Massachusetts, USA. During four years of sampling soil solution collected beneath the forest floor in zero-tension lysimeters, we observed little change in DOC concentrations (10-30% increase, not statistically significant) associated with elevated N inputs, but did observe significant increases in DON concentrations. Both DOC and DON varied seasonally with highest concentrations in summer and autumn. Mean DON concentrations increased 200-300 % with the highest rate of inorganic N fertilization, and concentrations of DON were highest in samples with high inorganic N concentrations. We conclude that the organic chemistry of soil solution undergoes qualitative changes as a result of long-term N amendment at this site, with small changes in DOC, large increases in DON, and a decline in the C:N ratio of dissolved organic matter.     

Effects of Weak Acids on Canopy Leaching and Uptake Processes in a Coniferous-Deciduous Mixed Evergreen Forest in Central-South China

The effects of Weak acids (WA) on the canopy leaching and uptake processes are evaluated by comparing the leached base cations or the absorbed protons while including and excluding WA, e.g. the WA-included method and the WA-excluded method. The seasonal WA throughfall flux is even larger than twice the bulk precipitation flux except summer, which not only partly agrees with the conclusion that the total deposition of WA equals twice the bulk or dry deposition flux in European Intensive Monitoring plots (level II), but also indicates the significant canopy leaching of WA in Shaoshan forest. The seasonal canopy leaching of base cations in association with WA accounts for 6–30% of the total base cations in throughfall, with an annual mean of 23%, which is slightly higher than the 15% at the Speulder forest in The Netherlands. The canopy exchange capacity of H⁺ to NH₄ ⁺ is closed to 6.0 while neglecting the WA exchange, which probably supports the assumption that the exchange capacity of H⁺ is six times that of NH₄ ⁺. Simultaneously, we suggest that the WA is competitive to a certain extent with protons to leach base cations of plant tissues during the canopy exchange processes.     

模拟氮沉降对内蒙古典型草地土壤pH和电导率的影响

陆地生态系统氮沉降增加可导致土壤酸化,从而可能造成土壤生态系统结构和功能的退化。依托内蒙古典型草地设置的模拟氮沉降试验,研究了连续6年9个氮添梯度(0、1、2、3、5、10、15、20、50 g m~(-2)a~(-1)),2个氮添加频次(一年两次或一月一次)及2种管理方式(封育或刈割)等4种模式对土壤p H和电导率的影响。结果表明,4种模式下氮添加量3 g m~(-2)a~(-1)以下4个处理间的土壤p H无显著差异,在氮添加量为20 g m~(-2)a~(-1)(与我国粮食作物年施氮量接近)时,土壤p H分别比对照平均降低了1.1~1.9个单位;封育一年两次添加氮素在添加量5 g m~(-2)a~(-1)以上时土壤p H显著下降,而封育每月一次添加氮素在添加量20 g m~(-2)a~(-1)以上时,土壤p H才出现显著下降的现象。4种模式下土壤p H与土壤阳离子交换量及土壤交换性钙呈极显著正相关,说明高量氮添加促进了土壤中盐基离子的耗竭。高量氮添加(50 g m~(-2)a~(-1))显著增加了土壤EC值;除封育每月一次添加氮素处理外,氮添加10 g m~(-2)a~(-1)以下各处理间的土壤电导率(EC)无显著差异;土壤EC值与土壤硝态氮含量呈极显著正相关。研究结果将为我国北方半干旱草地土壤酸化的量化表征及氮素管理提供数据支撑。     

施用腐植酸对夏玉米产量、氮素吸收及氮肥利用率的影响

为了探究腐植酸与无机肥料配施对夏玉米产量、氮素吸收及氮肥利用率的影响,于2014年始在河南省南阳市卧龙区英庄镇开展田间定位试验,共设置单施磷钾肥、常规施肥、常规施肥+3 000kg·hm~(-2)腐植酸、常规施肥减氮15%+3 000 kg·hm~(-2)腐植酸、常规施肥减氮30%+3 000 kg·hm~(-2)腐植酸等5个处理,分析不同氮肥运筹下夏玉米产量和氮肥利用的特征。结果表明,施用腐植酸可以有效改善夏玉米的农艺性状,提高夏玉米的产量,促进植株对氮素的累积和提高氮肥的利用率。其中,以常规施肥减氮15%+腐植酸处理效果最佳,与常规施肥相比,产量增加8.68%~12.96%,籽粒氮含量、籽粒氮累积量、地上部总氮累积量分别增加2.83%~3.92%、11.75%~19.74%、8.83%~19.41%,氮肥利用率增加52.00%~116.55%。因此,常规施肥减氮15%+3 000 kg·hm~(-2)腐植酸是本研究区域最佳的施肥模式,对实现现代农业生产的高产高效、资源节约和生态环境保护具有重要意义,是值得推荐的肥料运筹方式。     

Effects of Simulated Acid Rain on Pinus densiflora: Inhibition of Net Photosynthesis by the Pheophytization of Chlorophyll

This research addressed the effects of simulated acid rain on the chlorophyll contents of leaves of Pinus densiflora, on the net photosynthetic rate on a unit chlorophyll basis, and on chlorophyll degradation. When NO₃- concentrations in rain water increased, the chlorophyll_a+b contents of the leaves increased in parallel, even though the pH of the simulated rain decreased. The nitrogen content of the rain was sufficient to stimulate the production of chlorophyll and was able to override any degradative effect expected due to the H⁺ input from acid rain. The absorption spectrum of chlorophyll extracted from the leaves exposed to acid rain showed peaks at 665, 606 and 535 nm, characteristic of pheophytin a, indicating degradation of chlorophyll to pheophytin. Net photosynthetic rate on the basis of chlorophyll content was reduced by acid rain, even though the total chlorophyll content of the leaves was increased. The acid rain does, therefore, simultaneously increase chlorophyll content and reduce the efficiency of the use of chlorophyll in photosynthesis. This reduced efficiency may be linked to the increase in the rate of degradation of chlorophyll to pheophytin.     

模拟酸雨对茶园土壤中铅的溶出及形态转化的影响

采用模拟酸雨连续淋洗的方法,研究了茶园土壤的酸化以及不同铅污染程度土壤中铅的溶出和形态转化规律。结果表明,土壤的酸化程度受酸雨酸性强度的控制,酸雨pH越低,土壤酸化程度越强;土壤中铅的溶出总量随模拟酸雨的酸度和土壤本身含铅量的增加而增加,但是土壤滤液中铅含量随时间变化的规律只受模拟酸雨的pH影响;土壤铅污染程度越严重,其中的活性态铅含量越高,同时pH<4.5的酸雨会使土壤中的非活性态铅大量向活性态转化,这将导致土壤中铅的活化而增加其生态风险。     

铅与酸雨对大豆鼓粒期根系氮素营养的复合影响

了解铅（Pb）与酸雨（AR）对植物氮素营养复合影响是科学评价AR和Pb伤害植物的重要依据,但相关报道较少。氮素是构成植物体内蛋白质的主要成分,而蛋白质既是细胞分裂、生长与能量代谢的物质基础,也是影响根系生长的重要条件。因此,本文以重要经济作物大豆（Glycine max）为试材,选取硝态氮含量、硝酸还原酶活性（NRA）、亚硝酸还原酶活性（NiRA）和铵态氮含量4个氮素营养指标为考察目标,     

模拟酸雨条件下海泡石对污染红壤镉、铅淋溶的影响

采用填充土柱淋溶试验研究不同pH值模拟酸雨和海泡石添加量对重金属污染红壤Cd、Pb淋溶的影响.结果表明,Cd在酸雨pH值较低时累积淋溶量较大,Pb的累积淋溶量随酸雨pH值的降低逐渐增加,pH值为3.5处理的Pb总累积淋溶量显著高于其他pH值处理(高出54.9％).与对照相比,模拟酸雨pH值为3.5时,添加5 g/kg和10 g/kg海泡石处理Cd的总累积淋溶量明显增加(分别增加24.6％和26.3％),而Pb的总累积淋溶量分别显著降低34.7％和25.7％;酸雨pH值为4.5时,添加5 g/kg和10g/kg海泡石处理降低了Cd的累积淋溶量(分别降低13.0％和1.4％),而Pb的淋溶量随海泡石添加量的增加而降低,10 g/kg海泡石处理的Pb总累积淋溶量显著下降17.6％;pH值为5.5和6.5时,海泡石处理Cd累积淋溶量均有所下降,而对Pb的淋溶无显著降低效果.酸雨酸性强度的增大增加了Cd、Pb的淋溶风险,且Pb比Cd敏感.添加海泡石可有效减少酸雨对土壤中Pb的淋溶,但其对Cd淋溶的影响受酸雨酸性强度的影响.     

水肥耦合对油茶林地土壤全氮和产量的影响研究

从浙江省临安市采集了水田及其改雷竹林的4个系列土壤(包括长期种植水稻的农田、水田改种雷竹6年、12和15年的农地)的代表性剖面的分层样品(种雷竹前土壤为发生学分类中的黄泥田,属系统分类的铁聚水耕人为土),采用田间形态观察与室内理化分析相结合的方法对土壤进行了鉴定。结果表明,黄泥田种植雷竹后土壤人为滞水水分状况消失,逐渐向湿润水分状况转变;水耕条件下形成的水耕表层因深耕被破坏而逐渐消失,而水耕氧化还原层的特征可残留在土体中;土壤有机碳和磷素明显积累,土壤中络合态铁显著增加。与此同时,土壤类型也逐渐由普通铁聚水耕人为土向普通铁质湿润雏形土、最后向黄色铝质湿润雏形土演化。结果表明,人为的强烈影响可使土壤类型在短时间尺度内发生改变。     

氮素营养对干旱地区小麦光合生理的影响

对不同供氮条件下小麦光合速率、蒸腾速率、细胞间隙CO2浓度的分析表明,土壤水分胁迫下,细胞间隙CO2浓度日变化则呈"W"型,叶片光合速率和蒸腾速率日变化均呈单峰型,光合峰值出现在上午10:00前后,蒸腾峰值则出现在上午11:00前后;土壤水分胁迫下,过多施用氮肥可使作物细胞间隙CO2浓度下降,显著抑制叶片蒸腾和光合速率,合适的施氮量应保持在90kg/hm2左右。     

Effects of a Simulated Agricultural Runoff Event on Sediment Toxicity in a Managed Backwater Wetland

We examined the effects of an amended mixture of three pesticides, atrazine (72.7?g), S-metolachlor (54.5?g), and permethrin (both cis and trans isomers; 11.4?g), on 10-day sediment toxicity to Hyalella azteca in a managed natural backwater wetland after a simulated agricultural runoff event. Sediment samples were collected at 10, 40, 100, 300, and 500?m from inflow 13?days prior to amendment and 1, 5, 12, 22, and 36?days post-amendment. Background pesticide concentrations ranged from <1 to 977, <1 to 119, and <1 to 2???g?kg^?1, for atrazine, S-metolachlor, and permethrin, respectively. Average post-amendment atrazine and S-metolachlor were 2,915?C3,927 and 3?C20???g?kg^?1, respectively at 10?C40?m and 538?C872 and <1???g?kg^?1, respectively at 300?C500?m. Average post-amendment permethrin was 65?C200???g?kg^?1 at 10?C40?m and 1?C10???g?kg^?1 at 300?C500?m. H. azteca 10-day survival varied spatially and temporally up to 100?m from inflow. Animal growth, independent of survival, was reduced 40 and 100?m from inflow on day?36, showing continued sediment toxicity of up to 100?m from inflow more than 1?month after amendment. Animal survival and growth were unaffected at 300 and 500?m from inflow throughout the study period. Correlations of pesticide concentrations and H. azteca responses indicated that observed sediment toxicity was primarily from permethrin with potential additional synergistic toxicity from atrazine and methyl parathion. Study results indicate that natural backwater wetlands can be managed to ameliorate pesticide mixture 10-day sediment toxicity to H. azteca within 300?m of inflow and smaller wetlands (??100?m) may require several months of effluent retention to mitigate effects.     

Effects of Curtailment of Nitrogen Fertilizer on Biological Properties and Tea Leaf Yield in Acid Tea Field Soils

In Japan, the soils in tea fields are further acidified by heavy application of nitrogen fertilizer. In the long-term fertilizer application fields, available P, total carbon and nitrogen contents had the highest in the Multi-F plot, followed by the 98-D.F plot and the smallest in the 95-D.F plot. Soil enzymes activity had the highest the Multi-F plot. It was estimated that all of the enzyme activity were often corresponded with the results of the organic matter and the available P contents. The number of fungi under acidic condition had the close relation since change of these enzymes activity. It was evident that fungi were participated in carbon, nitrogen and phosphorus metabolism in acid tea field soils. It became clear that the number of fungi and enzymes activity decreased corresponding well with the available P and the organic matter contents depend on fertilization management. Moreover in case of qualities of green tea, generally difference between experimental plots and Multi-F plot were to be small. It was indicated that influence to the yields by curtailment of the amount of nitrogen fertilization was small.     

Simulation of Increased Nitrogen Deposition to a Montane Forest Ecosystem: Partitioning of the Added 15N

Nitrogen (N) was added over two years to a spruce-dominated (Picea abies) montane forest at Alptal, central Switzerland. A solution of ammonium nitrate (NH₄NO₂) was frequently sprinkled on the forest floor (1500 m²) to simulate an additional input of 30 kg N ha^-1 yr^-1 over the ambient 12 kg bulk inorganic N deposition. The added nitrogen was labelled with ¹⁵NH₄ ¹⁵NO₃ during the first year. Results are compared to a control plot. Neither the trees nor the ground vegetation showed any increase in their N content. Only 4.1% of N in the ground vegetation came from the N addition. Current-year needles contained 11 mg N g^-1 dry weight, of which only 2% was from labelled N; older needles had approximately half as much ¹⁵N. The uptake from the treatment was therefore very small. Redistribution of N also took place in the trunks: 1 to 2-year-old wood contained 0.7% labelled N, tree rings dating back 3 to 14 years contained 0.4%. Altogether, the above-ground vegetation took up 12% of the labelled N. Most ¹⁵N was recovered in the soil: 13% in litter and roots, 63% in the sieved soil. Nitrate leaching accounted for 10%. Factors thought to be influencing N uptake are discussed in relation to plant use of N and soil conditions.     

Phenological Disorder Induced by Atmospheric Nitrogen Deposition: Original Causes of Pine Forest Decline over Japan. Part I. Phenological Disorder,Cold Death of Apical Shoots of Red Pine Subjected to Combined Exposures of Simulated Acid Rain and Soil Acidification,and Implications for Forest Decline

Seeds of red pine (Pinus densiflora Sieb. and Zucc.) were sown in red-yellow soil artificially adjusted to pH (H₂O) 4.10, 4.60 or 5.90 by adding H₂SO₄ solution to the soil (pH 5.90), and the three-month seedlings were exposed to simulated acid rain at pH 2.0, 3.0 or 5.6 for 10 minutes once, 3 times a week, for 12 months from 4 August 1994 to 3 August 1995 alone or in combination. Significant interactive effects between acid rain and soil acidification on growth and whole-plant net photosynthetic rate, and cold death ratio of new apical shoots following a cold snap were observed in a quadratic response pattern. The simulated acid rain increased budburst, new needle spread and elongation, and new apical shoot death percentage following a cold snap, but did not induce visible injury. In the highest soil acidity treatment at a soil pH 4.1, whole-plant net photosynthetic rate and seedling height exhibited a quadratic responses with increasing rain acidities. On the other hand, soil acidification caused leaf yellowing. The death percentage of new apical shoot of seedlings exposed to rain pH 2.0 following a cold snap was linearly enlarged with increasing soil acidities. With increasing soil acidity, height and whole-plant net photosynthesis of the seedlings exposed to rain pH 3.0 exhibited a linear increase response, while height of seedlings exposed to control rain exhibited a quadratic response. It is suggested that the results provide experimental evidency for phenological disturbances and an enhancement of frost risk by direct acid rain and indirect longterm soil acidification which may be significant in forest decline.     

The Effect of Nitrogen Catch Crops on the Nitrogen Nutrition of a Succeeding Crop: I. Effects through Mineralization and Pre-emptive Competition

Abstract

The effects of catch crops on the nitrogen nutrition of a succeeding carrot crop were investigated. An attempt was made to distinguish the effects of growth and nitrogen uptake by the catch crop from the effect of mineralization of its residues. It was found that growth and nitrogen uptake by catch crops could reduce the nitrogen supply to the succeeding carrot crop through pre-emptive competition, whereas mineralization of nitrogen from the catch crop residues increased the nitrogen supply to the carrot crop. Nitrogen uptake by the carrots was thus highest where catch crop residues were incorporated on plots where no catch crop had been grown. The effect of the mineralization was found mainly to influence topsoil mineral nitrogen contents and the early nitrogen uptake by carrots, whereas the effect of pre-emptive competition was to reduce subsoil mineral nitrogen content and the nitrogen uptake by carrots late in the growing season. The apparent recovery of catch crop nitrogen by carrots was between 8 and 33%.     

林地开垦后对不同质地红壤碳氮和磷库的影响

林地开垦农用后,土壤有机C和总N、P的浓度及在各团聚体粒级中的分布可发生较大的变化。对亚热带山地两类不同质地的红壤研究表明,林地开垦为旱地和茶园后,有机质和全N明显下降,全P呈轻微下降。下降量壤质土壤(黄泥土)大于粘质土壤(黄粘泥)。表土(0～15cm)的有机C和总N、P下降大于亚表土(15～30cm)。在三个团聚体粒级中,砂粒中有机C和总N、P的下降幅度最大,并随粒径变细下降幅度逐渐变小,表明与砂粒和粉砂结合的有机C和N、P易受利用方式的改变而变化。从林地到茶园、旱地,各团聚体粒级中有机P及有机P占总P的比例趋向下降。砂粒和粉砂中Olsen-P也呈下降的趋势。