森林转换对土壤活性有机碳组分的影响

为了研究林型转换对土壤活性有机碳组分的影响,在安徽皖南地区蔡家桥林场选取了马尾松次生林、湿地松人工林以及杉木人工林3种森林类型,分别采集了0—10,10—30,30—50 cm的土壤,测定了土壤有机碳(SOC)、颗粒有机碳(POC)、易氧化有机碳(EOC)、微生物生物量碳(MBC)、可溶性有机碳(DOC)以及土壤理化指标,分析了林型转换后土壤活性有机碳组分变化特征及其与土壤理化因子间的相关关系。结果表明：(1)马尾松次生林转换成湿地松人工林和杉木人工林后主要对0—10 cm土壤活性有机碳组分产生影响,其中土壤SOC,POC,EOC含量均在林型转换后出现下降,DOC含量上升,而MBC在林型转换前后无显著差异。(2)林型转换后各土层POC/SOC均出现下降,DOC和EOC占SOC比例总体呈升高趋势,MBC/SOC则未表现出明显规律。(3)土壤有机碳与活性碳组分以及TN,EC,NH⁺₄-N,NO^-₃-N均呈极显著正相关,各活性碳组分之间也存在极显著正相关关系(p<0.01)。综上,马尾松次生林转换成...     

基于灰渣和猪粪制造的有机无机复混肥对土壤易变性有机碳的影响

通过田间试验研究了不施肥（CK）、化肥（NPK）、基于灰渣和猪粪制造的有机无机复混肥高、中、低水平（CFI、CF2和CF3）5种施肥处理下0～60cm土壤易变性有机碳含量及其在玉米生长期内的动态变化。结果表明：CF1、CF2和CF3处理能显著提高0～60cm土壤总有机碳（TOC）和易变性有机碳的含量及易变性有机碳的活性（P〈0．05）,其中以CF2处理提高最显著;施肥对土壤易变性有机碳影响随着土层的加深而减弱。土壤易氧化有机碳（ROC）、溶解性有机碳（DOC）、水溶性有机碳（WSOC）这3种易变性有机碳中ROC和DOC可以作为指示土壤有机碳对有机无机复混肥敏感的指标,可用于预测土壤有机碳的变化趋势。研究基于灰渣和猪粪制造的有机无机复混肥对土壤有机碳库含量的影响,还需进行长期的定位试验。     

采伐干扰对东北温带次生林土壤碳矿化和活性有机碳的影响

在黑龙江东部的张广才岭选择典型次生杂木林进行不同采伐处理,一个生长季后测定了土壤潜在碳矿化速率和活性有机碳含量.结果表明:在28℃条件下经过90d的培养,土壤潜在碳矿化速率和碳矿化总量在所测定的土层中(0-10 cm,10-20 cm,20-30 cm)均表现为:50%强度采伐>皆伐后农作>25%强度采伐≌对照>皆伐后造林的变化趋势,但各处理间差异不显著.土壤易氧化碳含量在3个土层50%强度采伐均显著高于对照.土壤微生物碳含量在0-10 cm和10-20 cm土层,50%强度采伐显著高于对照.在0-10 cm土层,皆伐后造林显著低于对照.水溶性有机碳含量在0-10 cm和10-20 cm土层,50%强度采伐显著高于对照,在20-30cm土层,皆伐后造林显著低于对照,这说明在东北温带次生林中,较大强度的择伐短期内可增加土壤活性有机碳含量.而皆伐后造林可导致土壤活性有机碳出现下降趋势.     

土壤中可溶性氮和pH对有机肥和化肥的短期响应

通过温室盆栽试验,施用猪粪堆肥(PC)、污泥堆肥(SC)、菜籽饼肥(CM)和无机化肥(IF)后,对土壤pH值和不同形态氮素的短期响应进行研究,探讨土壤可溶性无机氮、有机氮及土壤pH值之间的相互关系。结果表明,CM,PC和IF处理的pH值都呈现先快速下降后缓慢回升的趋势,但PC处理下降幅度较小;而SC处理和不施肥对照(CK)处理的pH值基本不变;不同施肥处理均提高了土壤中氮素水平,3种有机肥中以CM处理最显著地提高了土壤中总可溶性氮(TDN)、NH4+-N、NO3--N和可溶性有机氮(DON)浓度,PC处理的次之,SC处理的最弱,而IF处理与CM处理提高幅度相似。不同施肥处理中土壤可溶性氮表现出不同的短期响应,IF处理和CM处理的TDN分别经过11,13d的稳定期后迅速上升到一个较高的水平,至31d开始下降;PC处理和SC处理未出现突然升高的现象,而是前20d较稳定在一定的范围内波动,之后缓慢下降,总体与对照趋势一致。不同处理土壤中NH4+-N均呈下降趋势;IF处理、CM处理的NO3--N呈增加趋势,PC处理的呈先增加后降低趋势,而SC处理的呈缓慢下降趋势,结果说明不同有机肥在土壤中的转化存在明显的差异。相关性分析显示,CM处理、IF处理的土壤pH值与NH4+-N呈极显著正相关,而与NO3--N呈极显著负相关;除PC处理外,其他处理的DON含量与TDN具有显著正相关性,而PC处理的DON同时与NH4+-N、NO3--N呈显著负相关。     

水土保持措施对红壤缓坡地土壤活性有机碳及酶活性的影响

基于植物篱和稻草覆盖控制红壤坡耕地水土流失的长期定位试验,以花生常规等高种植为对照(CK),研究红壤缓坡地香根草篱(H)、稻草覆盖(M)、稻草覆盖+香根草篱(HM)3种水保措施下旱、雨季土壤活性有机碳含量及土壤酶活性变化特征,探讨不同水保措施对土壤活性有机碳含量及土壤酶活性的影响。结果表明∶(1)稻草覆盖、香根草篱处理均能显著提高土壤微生物生物量碳含量(p0.05),其中稻草覆盖和香根草篱相结合效果最佳,且在旱季提升效果优于雨季;而稻草覆盖是提高土壤可溶性有机碳含量的主要影响因素;(2)稻草覆盖和稻草覆盖+香根草篱2种水土保持措施均能显著提高雨季土壤酶活性(p0.05),其中稻草覆盖起决定作用;各水土保持措施对旱季土壤酶活性的影响较小。(3)相关性分析表明,土壤β-葡(萄)糖苷酶和纤维素酶活性与土壤活性有机碳含量呈现良好的相关性(p0.05),对于评价红壤缓坡地水土保持措施土壤环境质量功能、指导实际生产等方面具有重要意义。     

Priming depletes soil carbon and releases nitrogen in a scrub-oak ecosystem exposed to elevated CO2

Elevated atmospheric CO₂ tends to stimulate plant productivity, which could either stimulate or suppress the processing of soil carbon, thereby feeding back to atmospheric CO₂ concentrations. We employed an acid-hydrolysis-incubation method and a net nitrogen-mineralization assay to assess stability of soil carbon pools and short-term nitrogen dynamics in a Florida scrub-oak ecosystem after six years of exposure to elevated CO₂. We found that soil carbon concentration in the slow pool was 27% lower in elevated than ambient CO₂ plots at 0-10 cm depth. The difference in carbon mass was equivalent to roughly one-third of the increase in plant biomass that occurred in the same experiment. These results concur with previous reports from this ecosystem that elevated CO₂ stimulates microbial degradation of relatively stable soil organic carbon pools. Accordingly, elevated CO₂ increased net N mineralization in the 10-30 cm depth, which may increase N availability, thereby allowing for continued stimulation of plant productivity by elevated CO₂. Our findings suggest that soil texture and climate may explain the differential response of soil carbon among various long-term, field-based CO₂ studies. Increased mineralization of stable soil organic carbon by a CO₂-induced priming effect may diminish the terrestrial carbon sink globally.     

蚯蚓粪与化肥配施对西瓜地土壤活性有机碳及酶活性的影响

[目的]探讨蚯蚓粪与化肥配施对西瓜种植的作用,为土壤培肥制度的建立及西瓜生产提供参考。[方法]以"黑彤K-8"为试材,通过大田试验研究了N100(尿素提供100%的氮)、M10N90(蚯蚓粪和尿素分别提供10%和90%的氮)、M30N70(蚯蚓粪和尿素分别提供30%和70%的氮)和M50N50(蚯蚓粪和尿素各提供50%的氮)等不同处理对土壤活性有机碳、碳库管理指数(CPMI)、酶活性和西瓜产量的影响。[结果]同N100处理相比,配施蚯蚓粪处理的高活性、中活性和活性有机碳含量均明显升高;M30N70处理的活性有机碳含量和CPMI显著高于其他处理,比N100处理分别高出30.10%和37.28%;同时,脲酶和蔗糖酶活性亦明显高于其它处理,其中蔗糖酶活性分别较CK,N100,M10N90和M50N50处理提高84.66%,62.33%,47.26%和22.46%。此外,M30N70处理的西瓜产量和肥料生产率最高,它可使西瓜产量分别比N100,M10N90和M50N50处理高出26.49%,13.34%,6.27%;M30N70处理的肥料生产率分别比N100,M10N90和M50N50处理高出166.50%,54.11%,21.37%。相关分析结果表明,运用土壤活性有机碳和碳库管理指数表征土壤酶活性、西瓜产量及肥料生产率的变化,比土壤总有机碳更具灵敏性。[结论]蚯蚓粪与化肥配施对西瓜生长具有显著的促进生长效果,其中3∶7比例配施的效果优于1∶9和5∶5比例。     

黄土区刺槐林土壤含水量变化对土壤呼吸强度的影响

通过室内培养实验来评估土壤含水量的变化对土壤枯落物层、不同深度土壤层及DOC淋失后的土壤呼吸的影响.采集安塞纸坊沟31a刺槐林土样及林下混合枯落物,通过碱液吸收法测定100％,20％和2％含水量条件下3个深度土样(20,40和60 cm);去除DOC土样(仅100％含水量条件下);3种处理枯落物混合土样(林下混合枯落物、刺槐枯落物和草本类枯落物)培养过程中CO2的累计释放量.结果表明,100％和20％含水量条件下各深度土壤CO2释放量为20 cm土样＞60 cm土样＞40 cm土样;20 cm土样去除DOC后CO2释放量明显减少,40 cm明显增加,60 cm没有明显变化;混合枯落物土样在l00％含水量条件下CO2释放量最高;20％和2％含水量条件下刺槐枯落物CO2释放量明显大于草类,而100％含水量条件下草类枯落物略大于刺槐枯落物.研究证明土壤含水量对SOC组分含量和枯落物种类不同的土壤层呼吸强度存在差异性影响,强降水对DOC的淋失可造成表层土壤呼吸的减弱.     

有机无机氮肥配施下洛阳烟田土壤N2O排放特点及其控制因素

随着农田化肥使用量的逐年增加和土壤退化问题日趋严重,农田温室气体排放关注度持续提高,为研究旱作植烟土壤N_2O排放特征及影响机理,设置6个田间试验处理,分别为CK0(不施肥处理)、CK1(100%无机氮)、T1(50%无机氮+50%饼肥氮)、T2(50%无机氮+50%羊粪肥氮)、T3(25%无机氮+75%饼肥氮)、T4(25%无机氮+75%羊粪肥氮),各处理施氮量均为45 kg/hm²,烟田施用基肥后起142天内测量不同处理土壤N_2O排放通量、硝态氮、铵态氮含量、根层温度和含水率。结果表明:(1)基肥施入后的3~7天内,土壤N_2O排放通量进入高峰,无机肥处理和有机无机肥配施处理的高峰期分别可维持20,9天,追肥后3天再次出现排放峰并持续9天,随后伴随烟株的生长发育,烟地N_2O排放通量逐渐趋向稳定。(2)基肥施用后仅1个月内N_2O累积排放量可达到总排放量的27.4%~32.6%;处理间N_2O排放量和排放系数均表现为无机>有机+无机(1∶1)>有机+无机(3∶1),无机肥配施有机肥明显降低了肥料中氮素以N_2O形态的损失量;与无机肥相比,T1和T2烟叶产量分别增加9.44%和6.37%,T1、T2、T3和T4处理的N_2O排放强度有着不同程度的降低。(3)主成分分析结果显示,在不施肥烟地中0—5 cm土壤温度和含水率是N_2O排放通量主导因子,利用相关性分析此环境下温度和水分分别与N_2O排放通量间呈现显著和极显著正相关关系;施肥后土壤铵态氮含量和土壤含水率是烟地N_2O排放通量的主导因子且相关性分析均呈现极显著正相关关系。综上,旱地植烟土壤N_2O排放受氮肥种类影响较大,施肥后N_2O排放通量对土壤温度响应减弱,主要受土壤铵态氮含量和含水量的影响;在总氮量相同情况下,有机无机肥配施比例为1∶1时明显降低土壤N_2O排放并提高了产量,该比例饼肥和羊粪肥处理分别将烟地N_2O排放强度降低20.4%和23.7%。     

Change in Soil Microbial and Enzyme Activities in Response to the Addition of Rock-Phosphate-Enriched Compost

Phosphorus (P) is considered a nonrenewable resource that plays a key role in agriculture and such studies are needed to evaluate alternative sources of this element. In the current study, objectives were to evaluate soil microbial respiration and enzymatic activity resulting from the addition of rock-phosphate-enriched organic compost to soil under incubation conditions. An organic-mineral compost (OMC) was produced by aerobically composting a mixture of coffee grain trash (62%), bovine manure (7%), phosphate rock (28%), and gypsum (3%) for 3 months. Different amounts of OMC were added in a portion (100 g) of soil, and then this mixture was incubated for 28 days. After this time, soil microbial respiration (SMR), biochemical parameters, and available P were evaluated. The addition of OMC led to significant increase in SMR, dehydrogenase, fluorescein diacetate hydrolysis, β-glucosidase, and phosphatase activity, which were dependent on the added amounts of the compost. The values of available P in soil increased significantly (13 times) with the OMC addition when compared to the control.The assay showed that P-enriched OMC application impacted soil function and improved soil biochemical properties. These results suggest that this practice may be of great importance for soil fertilization.     

Carbon Mineralization and Water-Extractable Organic Carbon and Nitrogen as Predictors of Soil Health and Nitrogen Mineralization Potential

ABSTRACT

The United States Department of Agriculture Natural Resources Conservation Service (NRCS) launched a national “Soil health initiative” in 2012; as a part of that effort, a soil health index (SHI) has been developed. The SHI is calculated using results of three soil tests: 24-h carbon mineralization following rewetting of air-dried soil (C_min, by the “Solvita” proprietary method) and water-extractable organic carbon (C) and nitrogen (N). These tests are being promoted both as the inputs into the SHI calculation and as predictors of soil N mineralization potential. Soil was collected from 35 California fields in annual crop rotations; 20 fields were under certified organic management and the other 15 under conventional management, to provide a range of soil properties and management effects. Carbon mineralization was determined by the Solvita method, and by a comparison method utilizing head space carbon dioxide (CO₂) monitoring by infrared gas analyzer (IRGA); additionally, two soil wetting protocols were compared, capillary wetting (the Solvita method) and wetting to 50% water-filled pore space (WFPS). Both water-extractable C (WEOC) and N (WEON) were determined using NRCS-recommended protocols. Net N mineralization (N_min) was also determined after a 28-day aerobic incubation at 25°C. Solvita C_min was highly correlated with the IRGA method using capillary wetting (R² = 0.81). However, capillary soil wetting resulted in high gravimetric water content that significantly suppressed C_min compared to the 50% WFPS method. N_min was correlated with Solvita C_min (r = 0.54) and with WEOC and WEON (r = 0.62 for each comparison); combining these three measurements into the SHI slightly improved the correlation with N_min. The organically managed soils scored higher than the conventional soils on the SHI, with a minority of organic soils and the majority of conventional soils scoring below the NRCS target threshold. SHI and soil organic matter were correlated, suggesting an inherent bias that would complicate the application of a national SHI standard.     

有机肥施用对植烟土壤氮素矿化及土壤酶和微生物群落的影响

为探索不同有机肥对植烟土壤氮素矿化及土壤微生态的影响。在等氮(100 mg/kg)投入和30℃条件下对施入不同有机肥(植物源有机肥、芝麻饼肥、生物质炭有机肥)的土壤进行室内培养，分析不同时期土壤NO3–-N和NH4+-N含量、土壤酶活性及细菌群落多样性的变化。结果表明：施用不同有机肥均可提高土壤矿质氮含量，在培养前期以饼肥矿化量最高，矿化速率最快，而后期为生物质炭有机肥处理的氮素矿化量、矿化速率高于其他处理；施用生物质炭有机肥、植物源有机肥均可显著提高土壤脲酶、硝酸还原酶活性，芝麻饼肥对蛋白酶、蔗糖酶活性有显著的提升作用；相较不施有机肥处理，添加不同有机肥的土壤细菌多样性明显提升。优势菌门为变形菌门、酸杆菌门、拟杆菌门、浮霉菌门，优势菌属为Sphingomonas、RB41,Sphingomonas在不施有机肥处理中最高，RB41在生物质炭有机肥处理中最高。Sphingomonas与蔗糖酶活性呈正相关关系，与脲酶、硝酸还原酶均呈负相关关系；PCA分析显示，生物质炭有机肥处理的细菌群落结构与其他处理相比差异较大。施用芝麻饼肥有利于促进早期氮素矿化，提高矿化量，而生物质炭有机肥后期矿化量较...     

煤粉尘添加量与温度对山西省两种土壤碳释放规律的影响

采用室内培养试验, 观测不同温度和不同煤粉尘用量条件下山西省电厂土和焦化厂土两种土壤的碳释放规律。结果表明, 室温(16~23 ℃)和25 ℃恒温下, 培养前期(4~9 d)土壤CO₂ 的释放量均为最大, 且25 ℃ 恒温培养土壤CO₂ 的释放量是室温条件下的2 倍左右。随煤粉尘添加量的增加, 土壤CO₂ 的释放量显著增加,且土壤活性有机质相应增加, 添加高量煤粉尘土壤CO₂ 的释放量最高达57.5 mg·kg^-1·d^-1, 两种土壤活性有机碳的增幅为0.3~3.8 g·kg^-1。不同温度和不同煤粉尘用量条件下电厂土释放的CO₂ 均高于焦化厂土, 可能是电厂土含有较高的有机碳和较低的黏粒所致。由此可知, 温度是影响土壤有机碳分解的主要因素, 其次是添加煤粉尘的量, 土壤理化性质也是原因之一。本研究表明, 煤粉尘的降落一方面增加了土壤CO₂ 的释放, 另一方面增加了土壤碳库。     

Soil CO2 efflux vs. soil respiration: Implications for flux models

In the long term, all CO₂ produced in the soil must be emitted by the surface and soil CO₂ efflux (FCO₂) must correspond to soil respiration (R_soil). In the short term, however, the efflux can deviate from the instantaneous soil respiration, if the amount of CO₂ stored in the soil pore-space (SCO₂) is changing. We measured FCO₂ continuously for one year using an automated chamber system. Simultaneously, vertical soil profiles of CO₂ concentration, moisture, and temperature were measured in order to assess the changes in the amount of CO₂ stored in the soil. R_soil was calculated as the sum of the rate of change of the CO₂ storage over time and FCO₂. The experiment was split into a warm and a cold season. The dependency of soil respiration and soil efflux on soil temperature and on soil moisture was analyzed separately. Only the moisture-driven model of the warm season was significantly different for FCO₂ and R_soil. At our site, a moisture-driven soil-respiration model derived from CO₂ efflux data would underestimate the importance of soil moisture. This effect can be attributed to a temporary storage of CO₂ in the soil pore-space after rainfalls where up to 40% of the respired CO₂ were stored.     

设施土壤微生物结构和酶活性对减量化肥配施有机肥的响应

通过两年三季田间定位小区试验,研究减量20%化肥配施精制有机肥(COF)、减量20%化肥配施生物有机肥(CBIO)、常规施肥(CCF,100%NPK)和不施肥(CK)处理对设施菊花产量、土壤微生物区系和酶活性的影响。结果表明,连续种植3季后,与CK处理相比,CCF、COF和CBIO处理均显著提高了设施菊花产量、产值、土壤养分含量和酶活性,并改变了土壤微生物区系。与CCF处理相比,COF和CBIO处理均显著增加了土壤细菌、放线菌数量和细菌/真菌值,并降低了真菌数量,且CBIO处理还显著提高了土壤速效养分含量和土壤酶活性并稳定提升土壤酶活性,同时显著提高了设施菊花产量和产值,连续效应明显。CBIO处理的设施菊花产值、土壤碱解氮、速效钾和脲酶活性均显著高于COF处理。除蔗糖酶和中性磷酸酶活性仅受施肥处理影响外,土壤脲酶、脱氢酶、过氧化氢酶活性和土壤微生物数量均受种植时间和施肥处理的交互作用影响,但主要受施肥处理影响。减量化肥配施生物有机肥对于提高作物产量,调控土壤微生物区系和提升土壤肥力作用显著,有利于土壤微生物态环境的发展。     

改良剂对旱地红壤活性有机碳及土壤酶活性的影响

针对江西旱地红壤肥力低下、生产力不高等突出问题,基于长期野外旱地红壤定位试验,研究了改良剂(生物质炭和过氧化钙)对旱地红壤活性有机碳及与碳代谢相关酶活性的影响。试验设置生物质炭施用量0(C0)、758(C1)、1 515(C2)kg/hm2和过氧化钙施用量0(Ca0)、61(Ca1)、121(Ca2)kg/hm2,生物质炭和过氧化钙单施和配施共9个处理,即CK、C0Ca1、C0Ca2、C1Ca0、C1Ca1、C1Ca2、C2Ca0、C2Ca1、C2Ca2。结果表明,生物质炭单施和配施均在一定程度上提高了旱地红壤有机碳及活性碳组分,且效果优于单施过氧化钙。C2Ca0、C2Ca1和C2Ca2处理土壤有机碳增加较显著。生物质炭和过氧化钙显著提高土壤活性有机碳组分,与对照(CK)相比,其中C1Ca0处理的微生物生物量碳平均增加了45.22%,C1Ca2处理的可溶性有机碳平均增加了21.34%,C1Ca0处理的颗粒有机碳平均增加了20.72%,C2Ca2处理的易氧化有机碳平均增加了22.19%。生物质炭和过氧化钙对提高碳库管理指数均有较好的效果,0~10 cm和10~20 cm土层分别平均增加了11.09%、14.07%。添加生物质炭对旱地红壤酶活性均有促进作用,且对0~10 cm土层土壤酶的影响较10~20 cm土层明显;配施C2Ca2明显提高旱地红壤淀粉酶、纤维素酶和β-葡糖苷酶活性,C1Ca1明显提高红壤蔗糖酶活性。因此,生物质炭和过氧化钙能有效改善旱地红壤活性有机碳组分以及与碳代谢相关酶活性,且生物质炭与过氧化钙配合施用对土壤改良的效果更好。     

生物炭还田对植烟土壤活性有机碳及酶活性的影响

为探索不同来源的生物炭及其还田方式对连作植烟土壤的改良效果,以四川盐源红壤为研究对象,通过田间试验研究了不同生物炭类型(玉米秸秆生物炭YM、油菜秸秆生物炭YC)配合不同还田方式(条施、穴施、条施+穴施)下,土壤有机碳组分和土壤酶活性在烤烟不同生育期的变化特征.结果 表明,生物炭类型和还田方式显著改变了土壤总有机碳(TO...     

Uncoupling of microbial CO2 production and release in frozen soil and its implications for field studies of arctic C cycling

Knowledge of seasonal trends and controls of soil CO₂ emissions to the atmosphere is important for simulating atmospheric CO₂ concentrations and for understanding and predicting the global carbon cycle. This is particularly the case for high arctic soils subject to extreme fluctuating environmental conditions. Based on field measurements of soil CO₂ efflux, temperature, water content, pore gas composition in soil and frozen cores as well as detailed temperature experiments performed in the laboratory, we evaluated seasonal controls of CO₂ effluxes from a well-drained tundra heath site in NE-Greenland. During the growing season, near-surface temperatures correlated well with observed CO₂ effluxes (r²>0.9). However, during intensive thawing of near-surface layers we observed up to 1.5-fold higher effluxes than expected due to temperature alone. These high rates were consistent with high CO₂ concentrations in frozen soil (>10% CO₂) and suggested a spring burst event during soil thawing and a corresponding trapping of produced CO₂ during winter. Laboratory experiments revealed that microbial soil respiration continued down to a least −18 °C and that up to 80% of the produced CO₂ was trapped in soil at temperatures between 0 and −9 °C. The trapping of CO₂ in frozen soil was positively correlated with soil moisture (r²=0.85) and led to an abrupt change of the temperature sensitivity (Q₁₀) observed for soil CO₂ release at 0 °C with Q₁₀ values below 0 °C being up to 100-fold higher than above 0 °C. The results of sub-zero CO₂ production allowed us to predict the microbial soil respiration throughout the year and to evaluate to what extent burst events during thawing can be explained by the release of CO₂ being produced and trapped during winter. Taking only the upper 20 cm of the soil into account, winter soil respiration accounted for about 40% of the annual soil respiration. At least 14% of the winter CO₂ production was trapped during the winter 2000-2001 and observed to be released upon thawing. Thus, the site-specific winter soil respiration is an important part of the annual C cycle and CO₂ trapping should be accounted for in future field and modelling studies of soil respiration dynamics in arctic ecosystems. In conclusion, we have discovered a soil moisture dependent uncoupling of CO₂ production and release in frozen soils with important implications for future field studies of Arctic C cycling.     

Mineralization and Nutrient Release of an Organic Fertilizer Made by Flour,Meat, and Crop Residues in Two Vineyard Soils with Different pH Levels

The mineralization and nutrient evolution of an organic fertilizer compost of flour, meat, and crop residues was evaluated in two vineyard soils. A lysimetric testing, using 2.2-L Büchner funnels, was carried out to study the evolution of pH, electrical conductivity, and nutrients during the 400-day experiment. The net mineralization for two different doses of the fertilizer mixed with the soils was compared with an unfertilized control. The pH value of the acidic soil decreased to values less than 4.5 because of the yield of hydrogen (H⁺) in the organic fertilizer mineralization, whereas the soluble aluminium (Al³⁺) increased quickly in the leachates. The mineralization process was quicker in the alkaline soil (with a maximum mineralization rate of 0.83 mg nitrogen (N) kg^?1 day^?1 for the 8 Mg ha^?1 dose and 0.43 mg N kg^?1 day^?1 for the 4 Mg ha^?1 dose) in comparison with the acidic soil, which reduced these rates up to 50%. The N-nitrate (NO₃) amounts yielded in a year were 150 and 79 kg N ha^?1 for the 8 and 4 Mg ha^?1 doses respectively in the alkaline soil, enough to cover the vineyard N demand. These values were reduced to 50% and 60% of N-NO₃ for the acidic soil, indicating the important effect of pH in the mineralization.     

有机肥替代化肥氮素对麦田土壤碳氮迁移特征的影响

利用小麦田间试验,设置控释尿素(CRU)、有机肥(OF)替代30%,50%,70%控释尿素氮量处理,并以普通尿素(Urea)为对照,研究等氮条件下有机肥替代不同比例化肥氮素对土壤碳氮迁移特征及小麦产量的影响。结果表明:有机肥处理小麦总生物量较Urea显著增加13.83%～17.57%,籽粒产量增加1.6%～10.5%,随有机肥替代化肥氮素比例增加,籽粒增产效应降低,70%OF与Urea无显著差异,但显著低于CRU处理。CRU、30%OF和50%OF处理氮素农学效率较Urea显著提高90.2%～124.4%,70%OF与Urea相比差异不显著。有机肥比例增加,土壤总碳含量呈上升趋势,且高于CRU和Urea;全氮含量大致呈下降趋势,整个生育期先增加后降低,30%OF自灌浆期至成熟期含量高于其他施氮处理。随土层深度增加,硝态氮和铵态氮含量减少,有机肥比例增加,各层土壤硝态氮减少,铵态氮增加(尤以返青期最为显著);整个生育期土壤无机氮呈下降趋势,但与Urea相比,有机肥处理的硝态氮主要集中在0—40 cm土层,且0—100 cm土壤铵态氮含量高于Urea和CRU(苗期除外)。因此,用30%～50%有机肥替代化肥氮素,配合控释尿素施用,可显著增加土壤总碳和铵态氮含量,减少60—100 cm土壤硝态氮淋溶,提高小麦氮素利用率和籽粒产量。