松嫩平原玉米带土壤碳氮储量的空间特征

利用第二次全国和县级土壤普查的382个典型土壤剖面资料和1∶50万数字化土壤图建立土壤剖面空间数据库,利用土壤类型法估算松嫩平原玉米带土壤碳、氮储量,分析土壤有机碳、氮密度的空间分布特征,探讨土壤有机碳、氮密度与土壤类型和土地利用类型之间的关系.结果表明:松嫩平原玉米带土壤有机碳、氮储量分别为(163.12±26.48)Tg和(9.53±1.75)Tg,土壤碳、氮储量主要集中在草甸土、黑钙土和黑土等土类中.土壤有机碳、氮密度分别为5.51～25.25和0.37～0.80kg·m-2,土壤C/N值大致在7.90～12.67.土壤有机碳、氮密度的空间分布均表现为东部和北部高、西部低.在不同土地利用类型中,旱田土壤的有机碳密度最高,为(19.07±2.44)kg·m-2;林地土壤的氮密度最高,为(0.82±0.25)kg·m-2;水田土壤的碳、氮密度均较低.     

安徽省森林碳储量现状及固碳潜力

为阐明安徽省不同林龄的森林生态系统的碳储量现状, 以及现有自然环境条件下顶极森林生态系统的固碳潜力, 采用野外样地调查和BIOME4模型方法对此进行研究。安徽省森林生态系统的现状总碳储量为714.5 Tg C, 其中植被碳402.1 Tg C、土壤碳312.4 Tg C。从幼龄林至过熟林的生长过程中, 森林生态系统的总碳密度和植被碳密度都呈现增长趋势。但土壤碳密度从幼龄林至近熟林阶段呈增加趋势, 近熟林以后出现减少趋势。安徽省幼龄林和中龄林占森林总面积的75%, 若幼、中龄林发展到近熟林阶段, 将增加125.4 Tg C。BIOME4模拟显示: 当森林发展到气候顶极森林时, 安徽省森林生态系统将增加245.7 Tg C, 即总固碳潜力包括植被固碳153.7 Tg C, 土壤固碳92.0 Tg C。     

农田生态系统土壤有机碳库及其影响因子

土壤有机碳(SOC)的数量和质量在很大程度上与维持和提高土壤肥力密切相关。农田生态系统土壤碳库研究一直是农业、生态和环境领域的一个主要方向。土地利用、耕作、作物类型、种植密度、灌溉、施肥以及其他人为活动等,对农田生态系统土壤有机碳库的变化均能产生影响。本文综合评述了农田生态系统土壤有机碳库及其影响因子,土壤碳截获潜力,维持和提高土壤有机碳库的措施,以及农田土壤碳截获在温室气体减排及气候变化中的潜在作用等,最后提出了农田生态系统土壤有机碳库研究的主要方向。     

中国陆地生态系统土壤有机碳变化研究进展

通过文献资料, 对中国陆地生态系统土壤有机碳变化研究进行评述. 20世纪80年代初至21世纪初, 中国森林、草地、灌丛和农田土壤有机碳库合计年均增加(71±19) Tg/a, 三江平原沼泽湿地垦殖导致土壤有机碳损失(6±2) Tg/a. 该结果存在极大的不确定性, 尤其是对森林、灌丛和草地碳库变化的估计. 未来研究需重点关注土地利用变化及其碳源、碳汇效应, 放牧管理对草地土壤有机碳库的影响, 灌丛和非森林树木(经济林、防护林及四旁绿化造林)土壤有机碳变化估算, 深层土壤有机碳变化的测定和估算, 中国土壤的固碳潜力及陆地生态系统碳收支模型开发.     

河南封丘县域农田土壤固碳速率空间变异特征及其影响因素

农田土壤固碳速率是评价土壤固碳效应和潜力的重要指标,精确估算区域农田土壤固碳速率对土壤地力及环境效应均具有重要意义.本研究选取黄淮海平原典型潮土区河南省封丘县为研究区域,按照土壤利用-土壤类型联合单元布点法,于2011年采集了70个耕层土样,测定了土壤有机碳含量、机械组成、容重、pH,并与全国第二次土壤普查(1981年)数据进行对比分析,结合地统计方法和GIS技术研究了该地区近30年农田土壤固碳速率的空间变异特征,利用显著性检验、回归分析、方差分析等方法定量分析了该区域农田土壤固碳速率的影响因素.结果表明: 近30年封丘县域土壤固碳速率平均值为0.33 t C·hm^-2·a^-1,变异系数为74%,属于中等变异性;土壤固碳速率的变化在东西方向上表现为西高东低、中部高南北低,呈片状分布,区域结构性因素是引起农田土壤固碳速率空间分布差异的主导因素,如土壤类型、机械组成、容重、pH,可解释空间变异的59.5%,其次是随机性因素,如秸秆还田量、施肥量,可解释空间变异的40.5%.     

天山北麓新人工绿洲扩张过程中的碳库格局变化与碳库迁移

基于地面调查数据、气象数据和遥感数据分析了40年来天山北麓新人工绿洲迅速扩张对区域植被和土壤的碳库格局、碳库迁移及碳储量的影响,结果如下:1976-2016年,研究区农田面积占比从3.25%增加到40%以上,沼泽消失,水库干涸,灌丛大幅减少,土壤盐碱化过程停止,裸盐碱地面积40年里减少近70%,新生草地在裸盐碱地上形成;2016年6月植被有效碳储量约为0.122Tg,比1976年下降了15.7%,成为一个弱的碳源;土壤碳库在干旱地区陆地生态系统碳库中占绝对主导地位,1976年研究区(0-60cm)的土壤有机碳储量为7.814Tg,其中耕地仅占4.2%,1996年土壤有机碳储量比1976年减少12.4%,呈明显碳源特征,到2016年,耕地土壤有机碳储量占比超过50%,总碳储量与1996年相比微降1.2%,土壤碳库重新趋于稳定。其中,裸盐碱地土壤碳库在向耕地、灌丛地、草地土壤碳库的迁移过程中贡献了1.265Tg的碳储量增量,草地土壤碳库在向耕地、灌丛地碳库的迁移过程中贡献了0.894Tg的碳储量增量;若维持现有耕地规模不再进行新的垦荒活动,40a垦荒造成的土壤碳库损失可以逐渐恢复并重新形成碳汇效应。     

亚热带果园土壤固碳潜力估算——以永春县为例

为了解亚热带果园土壤的固碳潜力, 比较分析了永春县果园土壤有机碳含量在1982 年到2010 年的变化, 并估算了现有经营条件下亚热带果园土壤的固碳潜力。结果表明, 近28 年来, 永春县果园表层土壤有机碳含量总体呈上升的趋势;不同气候区域的土壤有机碳年均变幅为南亚热带气候区 > 过渡带 > 中亚热带气候区。有机碳年均变幅与初始有机碳含量的相关分析表明, 永春县果园土壤有机碳潜在储存能力估计值为13.74~21.05 g kg^-1。按照2010 年的土地利用方式、耕作措施、施肥水平和气候条件, 永春县果园土壤的固碳潜力为64108.77 t。这些有助于认识和评价我国果园土壤碳汇能力和固碳潜力。     

基于模型的农田土壤固碳潜力估算

农田生态系统在陆地碳循环中具有重要地位. 增加农田土壤有机碳的固定不仅有助于减缓大气CO₂浓度增加速率, 而且对保障国家粮食安全具有重要意义. 基于农田土壤碳饱和理论, 分析了全球95个覆盖温带、热带、亚热带等不同气候区农田长期定位试验数据, 并构建了由气温、降水、土壤黏粒含量和pH驱动的农田土壤固碳潜力模型(R₂=0.58, n=76). 中国的长期定位试验较好地验证了这一模型(R₂=0.74, n=19). 模型敏感性分析表明, 低温湿润地区、高黏粒含量和低pH的土壤具有相对较高的固碳潜力; 高温低湿地区、低黏粒含量和高pH的土壤则较低. 利用所建模型和气候、土壤等基础数据, 对中国河南省农田土壤固碳潜力进行了估算. 结果表明, 该省农田表土(0~20 cm)碳饱和密度平均约为32 t/ha, 南部地区相对较高. 按该省第2次土壤普查的有机碳密度估算, 未来可望增加土壤固碳约为100 Tg.     

采伐对豫西退耕还林工程固碳的影响

以豫西退耕还林工程重点县嵩县为研究对象,收集了嵩县2002—2010年退耕还林工程逐年实施的造林面积、树种等数据,利用合适的人工林蓄积量生长方程和和中国退耕还林后的土壤有机碳变化的研究结果,结合各树种的木材密度、生物量扩展因子、碳含量等参数,在采伐和无采伐两种情景模式下对其退耕还林工程在2002—2050年的碳储量及其变化进行估算。结果表明:2010年,工程林总碳储量为0.470 Tg(Tg=10~(12)g),工程实施期间,工程前期碳储量高于后期;土壤有机碳库在2002—2010年期间年固碳量均为负值,表现为碳排放,2011年后土壤年固碳量开始增加;在两种情境模式下,工程林年固碳量最高峰都在2015年,2033年以后采伐情景的年固碳量大于无采伐情景。预计到2020、2030、2040和2050年,嵩县退耕还林工程在无采伐情境下的固碳增汇潜力分别为0.760、1.464、1.852和1.985 Tg,在采伐情景下的固碳增汇潜力分别为0.760、1.240、1.657和2.000 Tg,从长时间来看,豫西退耕还林工程林在采伐情景下具有较大的碳汇潜力,因此,对退耕还林工程林实施适度的采伐可以提高工程的碳汇能力。     

引黄灌区土壤有机碳密度剖面特征及固碳速率

为揭示灌溉耕作对土壤有机碳密度剖面(0—100 cm)分布产生的影响,通过在宁夏引黄灌区进行实地调查与采样,以无灌溉耕作的自然土壤作为对照,研究不同灌溉耕作时间序列下灌区土壤有机碳密度的剖面分布特征,并估算其平均固碳速率。结果表明:灌区土壤有机碳含量具有随土层深度增加而下降的剖面分布特征,灌溉耕作对增加表层土壤有机碳含量作用最明显;灌区土壤剖面碳密度与灌溉耕作时间和土壤类型均显著相关(P0.01),相关系数分别为0.63和0.74,且因灌溉耕作时间和土壤类型的不同,土壤有机碳密度差异性显著(P0.05);灌溉耕作影响的土层深度及剖面土壤有机碳密度的增加量因灌溉耕作时间长短的不同而异;引黄灌区5类土壤的平均固碳速率为0.53 MgC·hm-2·a-1。引黄灌溉耕作在增加农田土壤固碳中发挥着重要作用。     

新疆焉耆盆地绿洲区农田土壤有机碳储量动态模拟

以焉耆盆地绿洲区丝路重镇——焉耆回族自治县长期定位监测的数据为基础,实地采集800个土样进行土壤有机碳(SOC)实验室测试,进行点位模拟校验模型,并拓展到区域模拟,采用BCCC-CSM1.1气候模式,研究农田土壤有机碳密度分布特征及有机碳储量空间分布格局,为气候变化条件下,绿洲区耕地SOC储量和SOC密度变化提供数据支持。结果表明:(1) DNDC模型能够较好地模拟研究区农田的SOC及其动态变化,相关系数大于0.96,模拟值与观测值的均方根误差(RMSE)在0.48%—13.08%之间,模拟值与实测值显著相关。(2)点位模拟不同处理间SOC变化显示,不同土壤质地土壤有机碳含量差异明显,5年来SOC增长趋势表现为粉砂质壤土壤土砂质壤土。(3) 2017年焉耆县农田表层土壤有机碳总储量为0.44 Tg C,在未来30年里,在相应农业措施下,研究区农田0—20 cm土层SOC密度和储量呈显著增加趋势,单位面积碳增量增幅为-7%—29%;新增固碳量3.708×10~8—1.978×10~9 t,增幅为-5%—48%,呈现出"碳汇"趋势,这对恢复农田SOC的平衡和绿洲农业的可持续发展至关重要。     

Contemporary carbon stocks of mineral forest soils in the Swiss Alps

Soil organic carbon (SOC) has been identified as the main globalterrestrial carbon reservoir, but considerable uncertainty remains as toregional SOC variability and the distribution of C between vegetationand soil. We used gridded forest soil data (8–km × 8–km)representative of Swiss forests in terms of climate and forest typedistribution to analyse spatial patterns of mineral SOC stocks alonggradients in the European Alps for the year 1993. At stand level, meanSOC stocks of 98 t C ha^–1 (N = 168,coefficient of variation: 70%) were obtained for the entiremineral soil profile, 76 t C ha^–1 (N =137, CV: 50%) in 0–30 cm topsoil, and 62 t Cha^–1 (N = 156, CV: 46%) in0–20 cm topsoil. Extrapolating to national scale, we calculatedcontemporary SOC stocks of 110 Tg C (entire mineral soil, standarderror: 6 Tg C), 87 Tg C (0–30 cm topsoil, standarderror: 3.5 Tg C) and 70 Tg C (0–20 cm topsoil, standarderror: 2.5 Tg C) for mineral soils of accessible Swiss forests(1.1399 Mha). According to our estimate, the 0–20 cm layers ofmineral forest soils in Switzerland store about half of the Csequestered by forest trees (136 Tg C) and more than five times morethan organic horizons (13.2 Tg C).At stand level, regression analyses on the entire data set yielded nostrong climatic or topographic signature for forest SOC stocks in top(0–20 cm) and entire mineral soils across the Alps, despite thewide range of values of site parameters. Similarly, geostatisticalanalyses revealed no clear spatial trends for SOC in Switzerland at thescale of sampling. Using subsets, biotic, abiotic controls andcategorial variables (forest type, region) explained nearly 60%of the SOC variability in topsoil mineral layers (0–20 cm) forbroadleaf stands (N = 56), but only little of thevariability in needleleaf stands (N = 91,R ² = 0.23 for topsoil layers).Considerable uncertainties remain in assessments of SOC stocks, due tounquantified errors in soil density and rock fraction, lack of data onwithin-site SOC variability and missing or poorly quantifiedenvironmental control parameters. Considering further spatial SOCvariability, replicate pointwise soil sampling at 8–km × 8–kmresolution without organic horizons will thus hardly allow to detectchanges in SOC stocks in strongly heterogeneous mountain landscapes.     

Storage and sequestration potential of topsoil organic carbon in China's paddy soils

Carbon (C) storage and sequestration in agricultural soils is considered to be an important issue in the study of terrestrial C cycling and global climatic change. The baseline C stock and the C sequestration potential are among the criteria for a region or a state to adopt strategies or policies in response to commitment to the Kyoto Protocol. Paddy soils represent a large portion of global cropland. However, little information on the potential of C sequestration and storage is available for such soils. In this paper, an estimation of the topsoil soil organic carbon (SOC) pool and the sequestration potential of paddy soils in China was made by using the data from the 2nd State Soil Survey carried out during 1979–1982 and from the nationwide arable soil monitoring system established since then. Results showed that the SOC density ranged from 12 to 226 t C ha^?1 with an area‐weighted mean density of 44 t C ha^?1, which is comparable to that of the US grasslands and is higher than that of the cultivated dryland soils in China and the US. The estimated total topsoil SOC pool is 1.3 Pg, with 0.85 Pg from the upper plow layer and 0.45 Pg from the plowpan layer. This pool size is ～2% of China's total storage in the top 1 m of the soil profiles and ～4% of the total topsoil pool, while the area percentage of paddy soil is 3.4% of the total land. The C pool in paddy soils was found predominantly in southeast China geographically and in the subgroups of Fe‐accumulating and Fe‐leaching paddy soils pedogenetically. In comparison with dryland cultivation, irrigation‐based rice cultivation in China has induced significant enrichment of SOC storage (0.3 Pg) in paddy soils. The induced total C sequestration equals half of China's total annual CO₂ emission in the 1990s. Estimates using different SOC sequestration scenarios show that the paddy soils of China have an easily attainable SOC sequestration potential of 0.7 Pg under present conditions and may ultimately sequester 3.0 Pg. Soil monitoring data showed that the current C sequestration rate is 12 Tg yr^?1. The total C sequestration potential and the current sequestration rate of the paddy soils are over 30%, while the area of the paddy soils is 26% that of China's total croplands. Therefore, practicing sustainable agriculture is urgently needed for enhancing SOC storage to realize the ultimate SOC sequestration of rice‐based agriculture of China, as the current C sequestration rate is significantly lower than the potential rate.     

Increase in soil organic carbon stock over the last two decades in China's Jiangsu Province

Estimates of regional and national topsoil soil organic carbon (SOC) stock change may help evaluating the soil role in mitigation of greenhouse gas (GHG) emissions through carbon (C) sequestration in soils. However, understanding of the exact mitigation role is often constrained by the uncertainty of the stock estimation associated with different methodologies. In this paper, a soil database of topsoil (0–20 cm) SOC measurements of Jiangsu Province, China, obtained from a soil survey in 1982, and from a geological survey in 2004, was used to analyze the variability of topsoil SOC among soil groups and among soil regions, and to estimate the change in SOC stocks that have occurred in the province over the last two decades. The soil survey data was obtained from measurements of 662 690 randomly collected samples, while the geological survey data was from 24 167 samples taken using a 2 km × 2 km grid. Statistical analysis was conducted on SOC values for 1982 and 2004 for different categories of soil groups, soil regions, and administrative municipalities, respectively. Topsoil SOC storage was then calculated and the provincial topsoil SOC stock was estimated for each sampling time. There were remarkable differences in SOC levels between soil groups and soil regions and different municipalities. The grid sampling with the geological survey in 2004 yielded smaller variability of topsoil SOC averages, both with soil groups and with soil spatial distribution than the random sampling method used in 1982. Variation of SOC was greater with soil groups than with soil regions in both sampling times, although it was less variable across soil taxonomic categories than within a spatial category. Little variance of the SOC level with soil groups could be explained by clay content. However, the prevalence of paddy fields in the total cropland area governed the regional and municipal average SOC levels. The average provincial topsoil SOC content increased from 9.45 g kg⁻¹ in 1982 to 10.9 g kg⁻¹ in 2004, and the total provincial topsoil SOC stock was enhanced from 149.0±58.1 Tg C in 1982 to 173.2±51.4 Tg C in 2004, corresponding to a provincial average SOC sequestration rate of 0.16±0.09 t C ha⁻¹ yr⁻¹. The SOC sequestration trend for the last two decades could be, in part, attributed to the enhanced agricultural production, symbolized by the grain yield per hectare. The results of SOC stock changes suggest a significant C sequestration in soils of Jiangsu, China, during 1980–2000, with paddy management playing an important role in regional SOC storage and sequestration capacity.     

Topsoil organic carbon storage of China and its loss by cultivation

Topsoil is very sensitive to human disturbance under the changing climate. Estimates of topsoil soil organic carbon (SOC) pool may be crucial for understanding soil C dynamics under human land uses and soil potential of mitigating the increasing atmospheric CO₂ by soil C sequestration. China is a country with long history of cultivation. In this paper, we present an estimate of topsoil SOC pool and cultivation-induced pool reduction of China soils based upon the data of all the soil types identified in the 2nd national soil survey conducted during 1979–1982. The area of cultivated soils of China amounted to 138 × 10⁶ ha while the uncultivated soils occupied 740 × 10⁶ ha in 1980. Topsoil SOC density ranged from 0.77 to 1489 t Cha⁻¹ in uncultivated soils and 3.52 to 591 t Cha⁻¹ in cultivated soils with the average being 50 ± 47 t Cha⁻¹ and 35 ± 32 t Cha⁻¹, respectively. Geographically, the maximum mean topsoil SOC density was found in northeastern China, being of 70 ± 104 t Cha⁻¹ for uncultivated soils and of 57 ± 54 t Cha⁻¹ for cultivated soils, respectively. The lowest topsoil SOC density for uncultivated soils was found in East China, being of 38 ± 33 t Cha⁻¹ and that for cultivated soils in North China, being of 30 ± 30 t Cha⁻¹. There is still uncertainty in estimating the total topsoil SOC of uncultivated soils because a large portion of them was not surveyed during the 2nd Soil Survey. However, an estimate of total SOC for cultivated soils amounted to 5.1 Pg. On average, cultivation of China’s soils had induced a decrease of SOC density of 15 t Cha⁻¹ giving rise to an overall pool reduction at 2 Pg. This is significantly smaller than the total SOC pool decline of 7 Pg due to cultivation of natural soils in China reported by Wu et al. (Glob. Change Biol. 2003, 9: 305–315), who made a pool estimation of whole soil profile assuming 1 m depth for all soils. As the mean topsoil SOC density of China was lower than the world average value given by Batjes (J. Soil Sci. 1996, 47: 151–163), China may be considered as a country with low SOC density and may have great potential for C sequestration under well defined management. However, the dynamics of topsoil C storage in China agricultural soils since 1980’s and the effects of modern agricultural developments on C dynamics need further study for elucidating the role of China agriculture in global climatic change.     

1981-2019年华北平原农田土壤有机碳储量的时空变化及影响机制

农业土壤具有可观的固碳及减碳潜力,有助于减缓人类温室气体排放导致的气候变化。为了更好地了解华北平原土壤有机碳储量动态及其驱动因子,结合荟萃分析、随机森林机器学习模型和卫星遥感数据,研究了1981-2019年间中国华北平原农田土壤有机碳储量的时空变化及其驱动因子。结果表明,1981-2019年间华北平原0-20 cm农田土壤有机碳储量约为（523.10±79.36） Tg C （（14.56±1.66） Mg C/hm²）,并以5.94 Tg C/a （0.12 Mg C hm^-2 a^-1）的年固持速率稳步增长,占比约为中国农田每年新增土壤有机碳的23.3%。其中,常规农田管理措施,包括无机肥施用、有机肥施用和秸秆还田,对土壤有机碳增长的贡献平均为25.1%,即1.49 Tg C/a （0.03 Mg C hm^-2 a^-1）。相比对照组,氮磷钾无机肥施用可提高22.7%-26.0%的土壤有机碳固定速率,有机肥可提高48.3%,秸秆还田可提高23.4%。同时,上述常规农田管理措施对土壤有机碳的积累作用受到土壤本身理化性质的调控,在温度和降水较高的气候条件下更显著。值得注意的是,无论是无机肥施用、有机肥施用还是秸秆还田,当投入量超过农作物和土壤微生物对碳和养分的需求时,土壤有机碳累积速率会显著下降。这也导致2000年后土壤有机碳固持速率明显减缓,由9.4 Tg C/a下降为3.5 Tg C/a。总的来说,过去几十年农田管理措施的改进显著提高了华北平原农田土壤有机碳的增加速率,而未来华北平原农田系统固碳潜力仍然可观,但亟待明确在保证粮食产量的同时不同气候和土壤环境条件下最佳固碳所需的化肥、有机肥和秸秆投入量。     

Uncertainty in estimating land use and management impacts on soil organic carbon storage for US agricultural lands between 1982 and 1997

Uncertainty was quantified for an inventory estimating change in soil organic carbon (SOC) storage resulting from modifications in land use and management across US agricultural lands between 1982 and 1997. This inventory was conducted using a modified version of a carbon (C) accounting method developed by the Intergovernmental Panel on Climate Change (IPCC). Probability density functions (PDFs) were derived for each input to the IPCC model, including reference SOC stocks, land use/management activity data, and management factors. Change in C storage was estimated using a Monte‐Carlo approach with 50 000 iterations, by randomly selecting values from the PDFs after accounting for dependencies in the model inputs. Over the inventory period, mineral soils had a net gain of 10.8 Tg C yr^?1, with a 95% confidence interval ranging from 6.5 to 15.3 Tg C yr^?1. Most of this gain was due to setting‐aside lands in the Conservation Reserve Program. In contrast, managed organic soils lost 9.4 Tg C yr^?1, with a 95% confidence interval ranging from 6.4 to 13.3 Tg C yr^?1. Combining these gains and losses in SOC, US agricultural soils accrued 1.3 Tg C yr^?1 due to land use and management change, with a 95% confidence interval ranging from a loss of 4.4 Tg C yr^?1 to a gain of 6.9 Tg C yr^?1. Most of the uncertainty was attributed to management factors for tillage, land use change between cultivated and uncultivated conditions, and C loss rates from managed organic soils. Based on the uncertainty, we are not able to conclude with 95% confidence that change in US agricultural land use and management between 1982 and 1997 created a net C sink for atmospheric CO₂.     

白洋淀湿地区土壤有机碳密度及储量的空间分布特征

湿地生态系统碳储量是陆地生态系统碳循环的重要组成部分,提供重要的生态系统服务功能。白洋淀湿地是国家重要生态湿地和华北平原最大的淡水湿地,同时是雄安新区的核心水系,湿地区土壤碳储量的估算研究将为湿地生态系统服务评估和湿地生态恢复提供数据支撑。研究通过对白洋淀湿地7种不同地类的105个土壤剖面进行分层取样,揭示了其湿地土壤有机碳密度及储量的空间分布特征,结果表明：（1）白洋淀湿地区土壤有机碳含量整体偏低,在各层土壤中,淹水芦苇湿地的有机碳含量均显著高于其他植被类型,约为其他类型土壤碳含量的3倍左右。（2）在各植被类型中土壤有机碳含量均以表层（0-20 cm）最高,其分配比例均集中在30%左右,随着土壤剖面深度的增加,湿地土壤的有机碳含量逐渐减少。（3）不同植被类型土壤有机碳含量与土壤有机碳密度的差异显著,具体表现为：乔木园地 < 旱地 < 常绿针叶林 < 落叶阔叶林 < 水田 < 台田芦苇 < 淹水芦苇。（4）根据估算,白洋淀湿地区的土壤有机碳储量约为5816.77×10³Mg。随着雄安新区环境治理工作的推进,白洋淀湿地区生态系统固碳将呈现持续向好态势,结合生态恢复和土地布局优化,尽量减少雄安新区建设中土地流转带来的碳排放影响,对提高区域生态效益具有重要意义。     

松嫩平原玉米带农田土壤氮密度时空格局

基于1980年吉林省第二次全国土壤普查剖面资料和2003—2006年的实测数据,估算了松嫩平原玉米带不同土壤类型农田表层(0—20 cm)土壤氮密度和储量,分析了该地区土壤氮密度的25a时空变化特征及其原因。结果表明,两个时期松嫩平原玉米带农田土壤氮密度的空间分布格局基本一致,中部高、边缘低,平均土壤氮密度变化不大,均为0.31 kg/m2,但25 a间不同土壤类型和土地利用方式的土壤氮密度变化趋势存在差异,暗棕壤、水稻土和沼泽土的氮密度上升,其它类型土壤的氮密度不变或下降,旱田的氮密度不变,水田的氮密度明显下降,25 a间研究区内的农田土壤总氮储量每年减少7.6×105kg。25 a间土壤氮密度的变化与1980年的初始值负相关,土壤氮密度的新稳定状态值为0.32 kg/m2。如保持1980年的土地利用方式和栽培耕作措施不变,该地区农田土壤总固氮潜力为5.18×106kg/a。但实际上,与固氮潜力相比,2005年该区农田土壤总氮储量偏低了1.20×108kg。因此,今后该区应多注重肥料的合理施用,加强农田管理,尤其是旱田改水田的管理。     

1980-2010年北京市农用地碳储量对土地利用变化的响应

分析北京市农用地碳储量对土地利用变化的响应,对快速城市化和工业化区域及全国农用地低碳利用调控具有重要意义。利用1980年第二次土壤普查数据与2010年测土配方施肥项目成果土壤数据核算北京市农用地表层土壤碳储量,利用生物量遥感信息（NDVI）模型反演林地、草地植被碳储量,对北京市土地利用变化造成的农用地碳储量变化进行研究,结果表明：1）1980-2010年,北京市农用地碳储量由75.29 Tg-C增至81.13Tg-C,增加5.83 Tg-C,其中,土壤碳储量减少7.51 Tg-C,植被碳储量增加13.34 Tg-C;2）30年间,北京市农用地面积减少14.11×10⁴ hm²,其中,耕地流失最为显著,主要去向为建设用地和林地,林地面积略有增加;3）北京市用地类型保持不变的农用地土壤碳储量减少297.63×10⁴ t,植被碳储量增加1095.21×10⁴ t,共计增加797.58×10⁴ t,其中,用地类型保持不变的耕地、林地碳储量增加,草地碳储量减少;4）30年间,土地利用类型转化使北京市农用地土壤碳储量减少75.71×10⁴ t,植被碳储量增加212.49×10⁴ t,共计增加136.78×10⁴ t,其他用地类型转为林地使碳储量增加,有利于碳汇的形成,林地转出为其他用地类型均会造成一定碳排放;5）平原造林、退耕还林等工程有利于增加北京市农用地固碳量。未来北京市可通过控制农用地面积减少量,优化农用地内部结构,降低用地类型间的转换频率以提高农用地碳储量。研究可为其他区域及全国在快速城市化工业化过程中提升农用地碳储量提供一定参考。