The effect of petrocalcic horizons on the content and distribution of organic carbon in a Mediterranean semiarid landscape

Petrocalcic horizons are frequent in soils of semiarid landscapes. A survey of SIC and SOC contents made in Southern Spain in a pilot area with well defined geomorphological surfaces showed that topsoils overlying petrocalcic horizons are almost twice as rich in SOC as soil of similar depth without petrocalcic horizons. This could be due to impedance to root penetration, changes in redox potential and soil water availability caused by the presence of indurated crust. Soil age, on the contrary, seems not be an essential factor, since only a short time is required to reach a steady state in SOC in comparison to the time span available for soil formation on the different geomorphic surfaces.     

Quantifying terrestrial carbon stocks: examining the spatial variation in two upland areas in the UK and a comparison to mapped estimates of soil carbon

Intensive field surveys were undertaken in two upland catchments in the UK, Plynlimon in mid-Wales and Glensaugh in North East Scotland. The survey was to examine the spatial variation across the area and to assess the accuracy of the database underpinning the soil carbon map for the UK. In each area three 1-km² squares were sampled on a 200-m grid, with samples taken from both the organic and mineral horizons. Carbon stock was estimated, from the sample data, for each 1-km² square and compared with values from the UK database for that square. The results showed large differences between some squares, particularly for Plynlimon. In this area, the overall discrepancy between field and database values was 45%, compared with 8% for Glensaugh. Various sources of uncertainty were examined, including bulk density, organic horizon depth, and the proportion of different soil types within a square. The value for bulk density, assumed to determine carbon stock, had a significant effect on the estimates. In both catchments the organic layer showed a gradual decrease in bulk density with depth, resulting in a large proportion of the carbon being stored in the top part of the profile. The soil types, mapped during the survey, also showed large differences from those previously identified for each 1-km² square. This would have a considerable effect on the estimates of carbon stock within the UK database. It highlights that caution needs to be used when interpreting the UK soil map at this spatial scale.     

Assessing scale effects on modelled soil organic carbon contents as a result of land use change in Belgium

This paper explores the influence of spatial scale on modelled projections of soil organic carbon (SOC) content. The effect of land use change (LUC) on future SOC stocks was estimated using the Rothamsted Carbon model for a small area of southern Belgium. The study assumed no management change and used a single climate change scenario. Three model experiments were used to identify how data scale affects predicted SOC stocks: (i) using European LUC datasets at a resolution of 10′ and assuming equal distribution of change within the study area, (ii) using more accurate regional data aggregated to the 10’ resolution, and (iii) using the regional data at a spatial resolution of 250 m. The results show that using coarse resolution (10′) data is inappropriate when modelling SOC changes in the study area as only the methods using precise data predict a change in SOC stocks similar to those reported in the literature. This is largely because of differences in model parameterisation. However, precisely locating LUC does not significantly affect the results. The model, using either pan‐European or region‐specific precise data predicts an average SOC increase of 1 t C ha^?1 (1990–2050), mainly resulting from afforestation of 13% of agricultural land.     

新疆三工河流域土壤碳库的估算

以土壤生态系统为基本单元,在对土壤有机碳、无机碳及相关资料调查分析的基础上结合GIS技术,对三工河流域土壤碳库进行了估算。结果表明三工河流域总碳储量约为11. 18Pg,其中有机碳占48. 54%,约为5. 43Pg,无机碳约占到51. 46%,约为5. 75Pg。     

黔中石漠化地区水土保持措施对土壤有机碳的影响

土地石漠化是中国西南喀斯特地区的重大生态问题,石漠化治理引发土壤碳转变并对陆地碳循环产生影响。然而,石漠化地区水土保持措施对土壤有机碳的影响机制还不明确。选取典型石漠化区梯田嵌套鱼鳞坑(NL)、鱼鳞坑(FSP)、梯田(TR) 3种水土保持措施作为研究对象,以无任何水土保持措施的退耕还林地(CK)作为对照,研究不同水土保持措施土壤有机碳含量分布规律。结果表明：鱼鳞坑土壤有机碳含量分别是梯田嵌套鱼鳞坑和梯田的1.4,6.2倍,有机碳储量分别比梯田嵌套鱼鳞坑和梯田提高30.78%和444.44%,活性有机碳含量也显著大于其他2种水土保持措施,因此固碳效果最好。土壤有机碳储量与活性有机碳组分易氧化碳、可溶性碳、微生物量碳呈极显著相关(p<0.01),易氧化碳与可溶性碳、微生物量碳呈极显著相关(p<0.01),可溶性碳与微生物量碳呈显著相关(p<0.05),因此土壤活性有机碳组分能在一定程度上反映土壤质量变化情况。鱼鳞坑和梯田措施土壤全氮含量和碳氮比的增加会促进土壤有机碳固存。鱼鳞坑可作为石漠化地区生态恢复中优先考虑的治理措施。     

干旱半干旱区农田土壤碳垂直剖面分布特征研究

以中国干旱半干旱区农田土壤为研究对象,通过收集自然农田和长期定位站点(178个剖面,0~100 cm土层)农田土壤碳的数据并对其进行整合,分析了农田土壤有机碳和无机碳含量的垂直剖面分布特征及其影响因素。结果表明,随土层深度增加,农田土壤有机碳呈下降趋势,表层含量高于底层;不同地区农田土壤无机碳含量变化趋势不一,随土壤深度增加整体呈现升高的趋势,但是也有一些地区呈现下降趋势。土壤剖面深度为100 cm的农田土壤有机碳和无机碳密度平均值分别为8.33和15.83 kg m-2,农田土壤无机碳储量大约是土壤有机碳的2倍。土壤深度为0~30 cm的有机碳占100 cm总有机碳含量的45%,无机碳仅占100 cm总无机碳含量的29%;土壤无机碳主要集中在30~100 cm土层,占100 cm总无机碳含量的71%,远高于有机碳在此土层占100 cm总有机碳含量的百分比(55%)。综合自然农田和长期定位站点农田土壤碳的数据,土壤容重与土壤p H是影响农田土壤有机碳和无机碳分布特征的重要因素:自然农田土壤有机碳与土壤p H(R2=0.61,p0.01)和土壤容重(R2=0.64,p0.01)呈显著负相关;长期定位站点土壤无机碳与土壤p H(R2=0.56,p0.01)和土壤容重(R2=0.63,p0.01)呈显著正相关。中国干旱半干旱区农田土壤有机碳和无机碳的分布特征与影响因素,将为陆地生态系统碳储量估算提供数据基础与理论支撑。     

Carbon Stocks in Different Soil Types under Diverse Rainfed Production Systems in Tropical India

Soil carbon (C) pool plays a crucial role in the soil's quality, availability of plant nutrients, environmental functions, and global C cycle. Drylands generally have poor fertility and little organic matter and hence are candidates for C sequestration. Carbon storage in the soil profile not only improves fertility but also abates global warming. Several soils, production, and management factors influence C sequestration, and it is important to identify production and management factors that enhance C sequestrations in dryland soils. The objective of the present study was to examine C stocks at 21 sites under ongoing rainfed production systems and management regimes over the last 25 years on dominant soil types, covering a range of climatic conditions in India. Organic C stocks in the soil profiles across the country showed wide variations and followed the order Vertisols > Inceptisols > Alfisols > Aridisols. Inorganic C and total C stocks were larger in Vertisols than in other soil types. Soil organic C stocks decreased with depth in the profile, whereas inorganic C stocks increased with depth. Among the production systems, soybean‐, maize‐, and groundnut‐based systems showed greater organic C stocks than other production systems. However, the greatest contribution of organic C to total C stock was under upland rice system. Organic C stocks in the surface layer of the soils increased with rainfall (r = 0.59*), whereas inorganic C stocks in soils were found in the regions with less than 550 mm annual rainfall. Cation exchange capacity had better correlation with organic C stocks than clay content in soils. Results suggest that Indian dryland soils are low in organic C but have potential to sequester. Further potential of tropical soils to sequester more C in soil could be harnessed by identifying appropriate production systems and management practices for sustainable development and improved livelihoods in the tropics.     

不同施肥方式对灌漠土土壤有机碳、无机碳和微生物量碳的影响

利用武威市白云试验站18a长期定位试验资料,研究了不同施肥条件下,土壤有机碳、无机碳和微生物量碳在0-40 cm土层的变化状况.结果表明,氮肥与有机肥长期配合施用和长期施用农肥可以在0 20 cm土层增加土壤有机碳含量,减少土壤中的无机碳含量,增加土壤微生物量碳含量;单施秸秆可增加土壤有机碳,而对无机碳和微生物量碳影响无明显差异;长期施用氮肥对土壤的有机碳、无机碳和微生物量碳均无明显差异.土壤有机碳与土壤无机碳含量呈显著负相关关系,而与土壤微生物量碳呈显著正相关关系.     

免耕对华北地区潮土碳库特征的影响

以实施7年的中国科学院禹城综合试验站冬小麦-夏玉米轮作免耕长期定位试验场为对象,系统研究免耕条件下土壤总碳(TC)、有机碳(SOC)、无机碳(SIC)的变化,为进一步评价免耕措施对华北地区潮土碳库的影响提供数据支持。研究设置免耕秸秆覆盖(NTRC)、免耕施用有机肥(NTRR)、常规耕作(CT)3种处理,分析表层(0-20cm)及深层(20-60cm)土壤TC、SOC及SIC的变化特征和影响因素。主要结果为:NTRC和NTRR能够增加0-20cm土层TC含量及储量,但降低20-60cm土层TC含量及储量,0-60cm总碳储量表现为NTRC>CT>NTRR;与CT相比,NTRC能够显著增加0-20cm而降低20-60cm土层SOC含量及储量,NTRR增加了0-5cm土层SOC含量及储量,在5-60cm则呈降低趋势,0-60cm土层SOC储量表现为CT>NTRC>NTRR;NTRC增加了0-60cm土层SIC储量,而NTRR则影响较小。TC与SOC呈显著正相关(P<0.05),而与SIC呈显著负相关(P<0.05),说明总碳的变化趋势与SOC一致,与SIC相反。     

青藏高原高寒草地土壤pH值的大尺度格局及其与气候、土壤因子的关系

Soil acidity is an important parameter that can regulate ecosystem structure and function. However, a quantitative understanding of the relationships between soil pH and environmental factors remains unavailable. In this study, relationships of soil pH with both climatic and edaphic factors in alpine grasslands on the Tibetan Plateau, China were quantified using data obtained from a regional soil survey during 2001-2004. Our results showed that soil pH decreased along the gradient of both mean annual temperature and precipitation. Likewise, soil pH exhibited consistent negative correlations with soil moisture and silt content. However, soil organic and inorganic carbon contents played opposite roles in shaping patterns of soil pH： the accumulation of soil organic matter led to higher soil acidity, while the existence of soil inorganic matter was favorable for maintaining higher soil alkalinity. The variation partitioning analysis indicated that the combination of climatic and edaphic variables explained 74.3% of the variation in soil acidity. These results suggest that soil pH could be predicted from routinely-measured variables, allowing a robust pedotransfer function to be developed. The pedotransfer function may facilitate land surface models to generate more reliable predictions on ecosystem structure and function around the world.     

稻油复种不同措施下土壤有机碳组分积累及其稳定性特征

复种油菜是南方稻区促进稳粮增油的重要种植模式,研究秸秆全量还田下,稻油复种不同种植措施对土壤有机碳积累及其稳定性特征的影响,对深入解析稻田土壤碳循环、充分利用冬闲田种植油菜具有重要意义。基于田间定位试验（8年）,以水稻-水稻-冬闲（稻稻闲）为对照,探究水稻–水稻–油菜（稻稻油）、水稻–油菜翻耕（稻油翻）和水稻–油菜免耕（稻油免）三种稻油复种处理下土壤有机碳及其组分积累特征。结果表明：相对稻稻闲,稻油复种各处理使有机碳含量在0～20 cm土层增加5.28%～25.13%,尤其稻稻油处理,在20～40 cm土层增幅为18.48%～43.97%,其中稻油翻和稻油免处理达到显著水平;稻油复种均显著提高了不同层次土壤中矿物结合态有机碳（Mineral-associated organic carbon,MAOC）含量。同时,在0～20 cm和20～40 cm土层中,稻油复种各处理均显著降低了有机碳中颗粒态有机碳（Particulate organic carbon,POC）的比例,提高了其MAOC的占比,且在两个土层中提高比例分别为2.31%～7.49%和1.56 %～2.66%。其原因可能是稻油复种不同程度地提高了0～20 cm土层中有机碳转化相关酶（β-葡萄糖苷酶、β-1,4-葡聚糖酶和漆酶）活性以及微生物生物量碳,进而促进土壤颗粒有机碳向矿物结合态有机碳的转化。综上,秸秆全量还田下冬季复种油菜促进了稻田土壤有机碳的积累,且提高了矿物结合态有机碳的占比,增强了土壤碳库的稳定性。     

荒漠草原沙漠化对土壤无机碳和有机碳的影响

以空间代替时间的方法,通过对宁夏荒漠草原不同沙漠化阶段土壤有机碳(SOC)和无机碳(SIC)的研究,探讨荒漠草原沙漠化对土壤SIC、SOC及不同粒径组分土壤SIC、SOC分布特征的影响。结果表明:(1)随着荒漠草原沙漠化程度的加剧,0—10cm土层各粒径组分土壤SIC和SOC含量呈下降趋势。半固定沙地和流动沙地各粒径组分土壤SIC含量均表现为黏粉粒无机碳(CSIC)>细砂粒无机碳(FIC)>粗砂粒无机碳(CIC),而SOC含量均表现为细砂粒有机碳(FOC)>粗砂粒有机碳(COC)>黏粉粒有机碳(CSOC)。(2)随着荒漠草原沙漠化程度的加剧,0—30cm土层土壤无机碳(SICD)、土壤有机碳(SOCD)和土壤总碳(STCD)密度均表现为荒漠草原>固定沙地>半固定沙地>流动沙地。固定沙地、半固定沙地和流动沙地土壤SOCD、SICD分别比荒漠草原降低了18.5%,57.7%,60.5%和6.7%,35.9%,47.0%。(3)0—10cm土层各粒径组分土壤SOC和SIC含量、全土SOC含量与0—30cm土层SOC和SIC均呈显著正相关关系,其中土壤粗砂粒有机碳和粗砂粒无机碳对SOC影响最大,而土壤黏粉粒有机碳和黏粉粒无机碳与全土SIC含量呈显著负相关关系。因此,沙漠化防治对于减少荒漠草原土壤碳损失极为重要。     

长期不同施肥和土地利用方式对塿土耕层碳储量的影响

利用土20年长期肥料定位试验研究了不同土地利用方式和施肥对土壤有机碳和无机碳储量变化的影响。试验包括休闲（Fallow, FL）、 撂荒（Setaside, SL）、 不施肥（CK）、 单施氮（N）、 氮钾（NK）、 磷钾（PK）、 氮磷（NP）、 氮磷钾（NPK）、 氮磷钾配合秸秆还田（SNPK）、 氮磷钾配合低量有机肥（M1NPK）和氮磷钾配合高量有机肥（M2NPK）11个处理。结果表明,CK和 FL 处理等质量耕层土壤有机碳储量仍维持在试验前水平,NP和 SL 处理显著提高了耕层土壤有机碳储量,年均增加分别达到 347 kg/hm2 和518 kg/hm2, 此4个处理等质量耕层土壤无机碳储量均较试验开始前（Initial soil, IniS）显著下降,尤其是NP处理显著低于其它3个处理。与IniS和CK相比,除NK处理外的所有施肥处理均显著地提高了等质量耕层土壤有机碳储量,其大小顺序为 M2NPKM1NPKSNPKNPKNPPKN,最大年均增加量为M2NPK 944 kg/hm2,最小为N 127 kg/hm2。施肥处理除PK和M2NPK处理外,其它处理等质量耕层土壤无机碳储量均较试验前明显降低,可能是由于土壤酸化所致。PK和M2NPK处理无机碳储量能够维持不下降,表明土壤无机碳和有机碳在适合条件下可能有某种关系。试验结果还显示,长期试验20年除M1NPK和M2NPK处理外,其它处理耕层土壤容重均明显高于试验开始前,表明等质量土壤碳储量与等深度碳储量相比可以更好地反映土壤碳的变化。     

黄土丘陵区不同恢复年限对天然草地土壤碳库动态的影响

[目的]揭示不同恢复年限的天然草地土壤碳库动态变化及其剖面分布特征,全面认识和理解天然草地恢复下土壤有机库、无机碳库的动态特征。[方法]采用野外调查与室内试验分析相结合的方法,以农田为对照,对黄土丘陵区不同恢复年限(11,16,22和35a)的天然草地土壤有机碳(SOC)、无机碳(SIC)、总碳(STC)的动态变化及其剖面分布特征进行了探讨。[结果](1)天然草地恢复过程中表层(0—10cm)SOC含量随植被恢复年限显著增加,下层(10—100cm)SOC含量随植被恢复年限变化不明显;0—100cm土层SOC储量呈先减少后增加趋势,但仍未达到农田SOC储量的水平。(2)天然草地0—20cm土层SIC含量呈相对脱钙现象,0—100cm土层SIC库储量约为SOC库储量的2.7~4.5倍。土壤无机碳库随植被恢复年限的增加无明显变化,但SIC的剖面分布深度发生改变。(3)土壤总碳库随恢复年限增加无明显变化,0—100cm土层SIC储量在STC库中所占比例约为75.6%~86.0%。[结论]短时间内天然草地的土壤碳汇效应并不明显,碳库增汇效应需要长期的过程。     

不同地表覆盖栽培对旱地土壤有机碳、无机碳和轻质有机碳的影响

通过田间长期定位试验,分层采集冬小麦-休闲种植体系0—40 cm土层的土样,研究了常规、地表覆膜和覆草栽培对土壤有机碳、无机碳和轻质有机碳的影响。结果表明,覆膜或覆草可以显著增加地上部小麦生物量和子粒产量。不同地表覆盖对0—40 cm土层的无机碳含量和分布无显著影响,但与常规栽培相比,地表覆膜使0—5 cm土层的有机碳含量显著降低,0—40 cm各土层轻质有机碳表现出明显降低趋势,平均降低 C 6.1~74.5 mg/kg;地表覆草却表现出明显增加土壤轻质有机碳的趋势,0—5,5—10,10—20 cm土层的轻质有机碳含量分别增加C 235.2、190.0和144.9 mg/kg,相当于常规的38.7%,32.9%和34.5%。同时,覆草栽培还表现出降低0—10 cm土层轻质有机质含碳量的趋势,并使0—20 cm土层轻质有机碳占有机碳的比例显著高于常规栽培和地表覆膜处理。可见,地表长期覆膜不利于旱地土壤有机碳累积,覆草不仅可以增加表层土壤的轻质有机碳累积,还可改善土壤碳氮组成。