中国森林生态系统碳平衡研究

森林生态系统是陆地生态系统的主体, 它不仅具有改善和维护区域生态环境的功能, 而且在全球碳平衡中起着巨大的作用, 充分发挥森林的固碳能力关系到能否降低大气CO₂浓度和抑制全球变暖趋势。文中就我国森林生态系统固碳功能和碳储量的研究进行了概括, 并对未来森林生态系统碳循环研究提出一些看法。     

Quantifying microbial biomass phosphorus in acid soils

 This study aimed to validate the fumigation-extraction method for measuring microbial biomass P in acid soils. Extractions with the Olsen (0.5 M NaHCO₃, pH 8.5) and Bray-1 (0.03 M NH₄F–0.025 M HCl) extractants at two soil:solution ratios (1 : 20 and 1 : 4, w/v) were compared using eight acid soils (pH 3.6–5.9). The data indicated that the flushes (increases following CHCl₃-fumigation) of total P (P_t) and inorganic P (P_i) determined by Olsen extraction provided little useful information for estimating the amount of microbial biomass P in the soils. Using the Bray-1 extractant at a soil:solution ratio of 1 : 4, and analysing P_i instead of P_t, improves the reproducibility (statistical significance and CV) of the P flush in these soils. In all the approaches studied, the P_i flush determined using the Bray-1 extractant at 1 : 4 provided the best estimate of soil microbial biomass P. Furthermore, the recovery of cultured bacterial and fungal biomass P added to the soils and extracted using the Bray-1 extractant at 1 : 4 was relatively constant (24.1–36.7% and 15.7–25.7%, respectively) with only one exception, and showed no relationship with soil pH, indicating that it behaved differently from added P_i (recovery decreased from 86% at pH 4.6 to 13% at pH 3.6). Thus, correcting for the incomplete recovery of biomass P using added P_i is inappropriate for acid soils. Although microbial biomass P in soil is generally estimated using the P_i flush and a conversion factor (k _P) of 0.4, more reliable estimates require that k _P values are best determined independently for each soil. Received: 3 February 2000     

Soil microbial biomass carbon and nitrogen as affected by cropping systems

 The impacts of crop rotations and N fertilization on microbial biomass C (C_mic) and N (N_mic) were studied in soils of two long-term field experiments initiated in 1978 at the Northeast Research Center (NERC) and in 1954 at the Clarion-Webster Research Center (CWRC), both in Iowa. Surface soil samples were taken in 1996 and 1997 from plots of corn (Zea mays L.), soybeans (Glycine max (L.) Merr.), oats (Avena sativa L.), or meadow (alfalfa) (Medicago sativa L.) that had received 0 or 180 kg N ha^–1 before corn and an annual application of 20 kg P and 56 kg K ha^–1. The C_mic and N_mic values were determined by the chloroform-fumigation-extraction method and the chloroform-fumigation-incubation method, respectively. The C_mic and N_mic values were significantly affected (P<0.05) by crop rotation and plant cover at time of sampling, but not by N fertilization. In general, the highest C_mic and N_mic contents were found in the multicropping systems (4-year rotations) taken in oats or meadow plots, and the lowest values were found in continuous corn and soybean systems. On average, C_mic made up about 1.0% of the organic C (C_org), and N_mic contributed about 2.4% of the total N (N_tot) in soils at both sites and years of sampling. The C_mic values were significantly correlated with C_org contents (r≥0.41**), whereas the relationship between C_mic and N_tot was significant (r≤0.53***) only for the samples taken in 1996 at the NERC site. The C_mic : N_mic ratios were, on average, 4.3 and 6.4 in 1996, and 7.6 and 11.4 in 1997 at the NERC and CWRC sites, respectively. Crop rotation significantly (P<0.05) affected this ratio only at the NERC site, and N fertilization showed no effect at either site. In general, multicropping systems resulted in greater C_mic : C_org (1.1%) and N_mic : N_tot (2.6%) ratios than monocropping systems (0.8% and 2.1%, respectively). Received: 9 February 1999     

Meeting the UK's climate change commitments: options for carbon mitigation on agricultural land

Abstract. Under the Kyoto Protocol, the European Union is committed to an 8% reduction in CO₂ emissions, compared to baseline (1990) levels, during the first commitment period (2008–2012). However, within the overall EU agreement, the UK is committed to a 12.5% reduction. In this paper, we estimate the carbon mitigation potential of various agricultural land-management strategies (Kyoto Article 3.4) and examine the consequences of UK and European policy options on the potential for carbon mitigation.
We show that integrated agricultural land management strategies have considerable potential for carbon mitigation. Our figures suggest the following potentials (Tg yr⁻¹) for each scenario: animal manure, 3.7; sewage sludge, 0.3; cereal straw incorporation, 1.9; no-till farming, 3.5; agricultural extensification, 3.3; natural woodland regeneration, 3.2 and bioenergy crop production, 4.1. A realistic land-use scenario combining a number of these individual management options has a mitigation potential of 10.4 Tg C yr⁻¹ (equivalent to about 6.6% of 1990 UK CO₂-carbon emissions). An important resource for carbon mitigation in agriculture is the surplus arable land, but in order to fully exploit it, policies governing the use of surplus arable land would need to be changed. Of all options examined, bioenergy crops show the greatest potential. Bioenergy crop production also shows an indefinite mitigation potential compared to other options where the potential is infinite.
The UK will not attempt to meet its climate change commitments solely through changes in agricultural land-use, but since all sources of carbon mitigation will be important in meeting these commitments, agricultural options should be taken very seriously.     

Comparison of the difference method and 15N technique for studying the fate of nitrogen from plant residues in soil

We compared the dynamics of net mineralization of nitrogen (N) derived from white clover material (Ndfc) as measured by the difference and the ¹⁵N methods in a pot experiment with a sandy loam (15°C and pF 2.4) planted with Italian ryegrass. On day 22, mineralized Ndfc (soil mineral N plus plant N uptake) was 5.8% and 1.3% of added N for the ¹⁵N and the difference methods, respectively. The discrepancy was reduced on day 43. On day 64, the relationship was reversed, and on day 98 the values given by the two methods were 22.8% and 29.5%, respectively. The results obtained by the two methods were linearly correlated (r = 0.987) and, on average, did not differ significantly. Nevertheless, the different temporal patterns led to appreciably different parameter values as estimated by fitting of a reparameterized Richards model. On day 22, clover amendment reduced mineralized N derived from soil (Ndfs) by 3.4 mg N pot^–1. The reason for this was that the clover amendment led to a reduction in plant growth and uptake of Ndfs, most likely because of allelopathy, while mineral Ndfs did not increase correspondingly. Clover-induced Ndfs in the microbial biomass of 5.1 mg N pot^–1 suggested that the mineral Ndfs not taken up by plants had been reimmobilized. Towards the end of the experiment, clover-induced Ndfs in the biomass declined to 1.5 mg N pot^–1, while mineralized Ndfs due to clover amendment increased to 5.1 mg N pot^–1. The results strongly suggested that this increase was caused by a real stimulation of humus N mineralization by clover amendment rather than by isotope displacement or pool substitution. Received: 5 May 1997     

土壤微生物多样性研究方法的进展

对土壤微生物的4类研究方法即:传统微生物培养法、微生物标记物法、BIOLOGGN微平板法和微生物分子生物技术方法及其应用特点进行了简要的评述和分析,旨在通过比较寻求能够揭示土壤微生物群落结构的最佳方法。分子生物技术方法与传统研究方法等相结合将是大力推动土壤微生物研究的有效方式。     

不同秸秆还田方式对红壤性质及花生生长的影响

通过田间小区试验研究化肥配合不同秸秆还田方式对红壤养分、生物学特性和作物生长的影响。结果表明,与其他(NPK、NPKD1、NPKD2)处理相比,氮磷钾化肥配合秸秆直接还田(NPKJG)处理土壤碱解氮降低了7.88%~31.37%,速效磷降低了7.72%~23.81%。各处理土壤脲酶活性在花生的生长期间先降低后升高,而转化酶活性先升高后降低(除NPK处理的转化酶活性持续降低外)。氮磷钾化肥配合Fe SO4促腐秸秆堆肥还田处理(NPKD2)提高了土壤脲酶活性26.14%,而配合碱渣促腐秸秆堆肥处理(NPKD1)提高了土壤转化酶活性66.13%。氮磷钾化肥配合Fe SO4促腐秸秆堆肥处理土壤微生物生物量碳含量较高,且提高了花生各农艺性状指标和产量。     

镉胁迫对白车轴草生长、镉含量及养分分配的影响

为了解镉(Cd)胁迫对白车轴草(Tritolium repens L.)生长发育以及养分的吸收、累积与分配的影响,采用盆栽试验,研究了不同浓度镉处理下白车轴草幼苗的生长、生物量及碳(C)、氮(N)、磷(P)和钾(K)的积累与分配特征。结果表明:随镉胁迫浓度增加,植株幼苗叶面积、主根长、侧根数、侧根长及地上部高先升高后降低,叶柄长明显降低;而根、茎、叶中镉含量逐渐升高,且根系大于茎叶。同时,植物各器官生物量生产及C、N、P和K积累量均表现出随镉添加量的增加而先升高后降低,高浓度镉胁迫处理(50.00、100.00和200.00 mg·kg-1)明显抑制植株生物量生产以及C、N、P和K的积累,显著改变了生物量及其C、N、P和K积累量的分配格局,但低浓度镉处理(12.50mg·kg-1)却无明显影响。一定浓度的镉胁迫处理(12.50和25.00 mg·kg-1)降低植株N、P、K的利用效率,但高浓度镉处理(200.00 mg·kg-1)则提高植株N、P、K的利用效率。本研究为城市园林绿化及镉污染土壤的修复提供了应用潜力,同时也为牧草的安全评估提供了科学借鉴。     

潮土小麦碳氮含量对长期不同施肥模式的响应

【目的】以潮土21年长期定位试验为基础,分析不同施肥模式下冬小麦不同生育期的地上部生物量、碳氮含量、碳氮比及碳氮积累量,探讨冬小麦碳氮含量对不同施肥模式的响应规律。【方法】试验包括不施肥(CK)、单施氮肥(N)、施氮磷肥(NP)、施氮钾肥(NK)、氮磷钾配施(NPK)、氮磷钾肥配施有机肥(NPKM)、施氮磷钾肥及玉米秸秆还田(NPKS)7个处理。在2011 2012年冬小麦生长季,分别采集越冬、拔节、灌浆、成熟四个生育时期地上部植株样品,利用Euro Vector EA3000型元素分析仪对小麦植株样品的全碳、全氮含量进行测定。【结果】NPK、NPKM和NPKS处理均能显著提高各生育期小麦地上部干重,其中NPKM处理小麦地上部干重在越冬、拔节、灌浆、成熟期分别比CK提高了111%、194%、238%、206%,除越冬期外,等量氮肥条件下,NPK、NPKM和NPKS 3个处理间小麦同一生育期地上部干重无显著差异,说明与氮磷钾配施相比,有机无机配施与秸秆还田这两种措施并不能显著提高小麦地上部生物量;小麦地上部碳含量受不同施肥影响很小,不同生育期小麦地上部碳含量平均值为410 g/kg;小麦成熟期地上部氮含量以N和NK处理最高,分别达到19.4和18.1 g/kg,其中N处理小麦地上部氮含量分别比NPKM和NPKS处理高52%和66%。随着生育期的推移,各处理小麦氮含量逐渐降低,总体表现为越冬期拔节期灌浆期≥成熟期;在整个生育期中各施肥处理碳含量基本保持不变而氮含量呈逐渐下降趋势,这就使得各施肥处理地上部分C/N比随生育期的推移呈逐渐增加趋势;不同施肥下小麦碳积累量差异性和地上部干物质重差异性规律一致,而不同施肥下地上部氮积累量差异性不同于干物质重的差异性,以NP处理最高,达545 kg/hm2,分别比NPKM和NPKS处理高61%和68%。【结论】施肥方式不能显著改变小麦碳含量但能影响氮含量,因此小麦生物量大小决定了其碳的积累量,相应地,C/N比大小则由氮含量决定。氮磷钾配施、有机无机配施及秸秆还田处理下,小麦具有较高的生物量从而具有较高的碳氮积累量,这有利于增加农田系统碳、氮积累,提升土壤碳、氮肥力。     

紫云英与化肥配施对安徽沿江双季稻区土壤生物学特性的影响

【目的】紫云英-水稻轮作生产体系是近年来为解决大面积冬闲田而提出的水稻生产新模式。研究紫云英-水稻轮作模式下,不同量紫云英与化肥配施对稻谷增产效果及稻田土壤生物学特性的影响,为合理施用紫云英,有效改善稻田土壤微生态环境、提高土壤质量、保证水稻高产稳产提供理论支撑。【方法】以安徽省农科院土壤肥料研究所2008年设置的紫云英-稻-稻定位试验为平台,分析了5种不同施肥模式下[不施紫云英和化肥(CK)、100%化肥不施紫云英以及70%化肥分别配施紫云英7500、15000、30000 kg/hm2])稻田耕层土壤(0—20 cm)微生物量碳、微生物量氮(SMBC、SMBN)和土壤酶活性的变化,及土壤生物学特性与土壤养分的相关性,并以水稻农艺性状和产量检验了土壤生产力。【结果】1)施用紫云英绿肥能够显著提高水稻籽粒产量,增加水稻单位面积的有效穗数和水稻结实率。尤其是70%化肥配施紫云英15000 kg/hm2处理,稻谷产量达7604.53 kg/hm2,比未施肥处理和单施化肥处理分别增产228.06%和36.29%,差异达显著水平。2)与对照相比,单施化肥处理土壤微生物量碳、氮增加,脲酶、酸性磷酸酶活性提高,过氧化氢酶活性降低;70%化肥的条件下,配施紫云英处理土壤微生物量及土壤酶活性显著高于单施化肥及对照处理,且随紫云英施用量的提高而增加。整个生育期,与对照相比,施紫云英处理土壤微生物量碳、氮分别提高21.03%~142.33%、19.97%~83.91%,土壤脲酶、酸性磷酸酶、过氧化氢酶活性分别提高10.12%~100.33%、10.22%~43.23%、0.14%~7.28%。土壤微生物量及脲酶、酸性磷酸酶与土壤有机质、全氮、碱解氮呈显著或极显著正相关;过氧化氢酶与土壤养分之间无明显相关性。【结论】紫云英绿肥与化肥长期配合施用可显著提高水稻产量、土壤微生物量及土壤酶活性,改善稻田土壤的微生态环境。本试验条件下,在70%化肥施用量的前提下,紫云英施用量以15000~30000 kg/hm2的综合效果较好。故适量紫云英与化肥配施有利于提高土壤生产能力,是安徽沿江双季稻区稻田增产和培肥地力的有效途径。