低丘红壤有机碳库的密度及变异

在中国科学院红壤生态实验站,采样分析了不同利用方式下土壤有机C 库的密度及其变异。结果表明,低丘红壤有机C 的密度0 ~ 20cm为(2.09 0.69) kg/m2,0 ~ 100 cm为(5.01 1.46) kg/m2; 全N密度0 ~ 20 cm为(0.20 0.07) kg/m2, 0 ~ 100 cm为(0.59 0.14) kg/m2。从裸地到稀疏荒草地,0 ~ 20 cm和0 ~ 100 cm土壤有机C 密度可以提高1.0 kg/m2和1.7 kg/m2;而从稀疏荒草地到人工林地或园地,0 ~ 20 cm和0 ~ 100 cm土壤有机C 密度可以提高0.7 kg/m2和0.9 kg/m2;稀疏荒草地如果开垦利用为水田,经长期培肥达到高度熟化,则0 ~ 20 cm和0 ~ 100 cm土壤有机C 密度可以提高2.3 kg/m2和4.4 kg/m2。即使不同类型的人工林地和园地之间,0 ~ 20 cm和0 ~ 100 cm土壤有机C 的密度差异也可达到1.0 kg/m2和3.5 kg/m2。不同地形部位之间0 ~ 20 cm和0 ~ 100 cm土壤有机C 密度差异达到1.3 kg/m2和2.9 kg/m2,全N密度差异达0.1 kg/m2和0.3 kg/m2;不同肥力水平之间0 ~ 20 cm和0 ~ 100 cm土壤有机C 密度差异达到1.5 ~ 2.2 kg/m2和2.8 ~ 4.1 kg/m2,全N密度差异达0.07 ~ 0.11 kg/m2和0.20 ~ 0.23 kg/m2; 强烈侵蚀可以降低0 ~ 20 cm和0 ~ 100 cm土壤有机C 密度1.4 kg/m2和2.2 kg/m2。因此,通过调整土地利用方式,可以提高土壤有机C 库密度,增     

氮、磷的农业非点源污染防治方法

非点源污染最主要的影响就是使水体富营养化、水质变差,从而影响到生产、生活、社会与经济的发展,其中氮、磷的农业非点源污染又是最主要的。经过30多年的研究,非点源污染研究逐渐从初期的定性化研究转向定量化,由统计、调查与机理研究转向实用治理研究。就众多的防治方法来看,大体可以分为两大类,即“源”(Source)防治和“汇”(Sink)防治。     

中国土壤有机碳密度和储量的估算与空间分布分析

基于 1∶40 0万的《中华人民共和国土壤图》和第二次土壤普查数据 ,运用地理信息系统技术 ,对中国土壤有机碳密度及储量做出估算 ,并且分析了土壤有机碳密度的空间分布差异。结果表明 :10 0cm深度的土壤有机碳密度介于 1 19kgm- 2 到 176 46kgm- 2 之间 ,2 0cm深度的土壤有机碳密度介于 0 2 7kgm- 2 到53 46kgm- 2 之间 ;10 0cm和 2 0cm深度的土壤有机碳储量分别为 84 4Pg (1Pg =10 15 g)和 2 7 4Pg ;土壤有机碳密度具有高度的空间变异性 ,东北地区、青藏高原的东南部、云贵高原等森林、草甸分布的地区有机碳密度最高 ,准噶尔盆地、塔里木盆地、阿拉善高原与河西走廊、柴达木盆地等沙漠化地区的土壤有机碳密度最低 ;土壤有机碳密度的空间分布主要受气候、植被以及人类活动的影响     

青藏高原农田生态系统碳平衡

为探讨青藏高原农田生态系统碳平衡规律及其影响因子 ,并揭示其对全球含碳温室气体源、汇变化的贡献与响应 ,1 998～ 1 999连续 2年在拉萨农业生态站农田用静态箱法和生物量取样法开展土壤—植被界面CO2 吸收与排放的试验研究。农作物生长季 ,以冬小麦为例 ,生长前期 (从播种到拔节 )土壤碳排放量高于植被碳固定 ,生长后期 (灌浆到成熟 )则是植被碳固定高于土壤碳排放量 ,从全年来看 ,土壤碳排放量略高于植被碳固定     

基于地理信息系统的土壤侵蚀研究

在非点源污染研究过程中 ,土壤流失量的计算是一个重要环节。结合地理信息系统和通用土壤流失方程 ,选择地形、植被、降雨量等因子 ,对松花湖流域常山地区土壤流失量进行了估算 ,并讨论了地形、植被等因子在土壤侵蚀中的影响 ,提出了相应的控制措施     

C and N natural abundance of the soil microbial biomass

Stable isotope analysis is a powerful tool in the study of soil organic matter formation. It is often observed that more decomposed soil organic matter is ¹³C, and especially ¹⁵N-enriched relative to fresh litter and recent organic matter. We investigated whether this shift in isotope composition relates to the isotope composition of the microbial biomass, an important source for soil organic matter. We developed a new approach to determine the natural abundance C and N isotope composition of the microbial biomass across a broad range of soil types, vegetation, and climates. We found consistently that the soil microbial biomass was ¹⁵N-enriched relative to the total (3.2 ‰) and extractable N pools (3.7 ‰), and ¹³C-enriched relative to the extractable C pool (2.5 ‰). The microbial biomass was also ¹³C-enriched relative to total C for soils that exhibited a C3-plant signature (1.6 ‰), but ¹³C-depleted for soils with a C4 signature (−1.1 ‰). The latter was probably associated with an increase of annual C3 forbs in C4 grasslands after an extreme drought. These findings are in agreement with the proposed contribution of microbial products to the stabilized soil organic matter and may help explain the shift in isotope composition during soil organic matter formation.     

Tillage-induced environmental conditions in soil and substrate limitation determine biogenic gas production

Tillage changes soil environmental conditions and controls the distribution of residues in the soil, both actions that affect the production and emission of soil biogenic gases (CO₂, N₂O, and CH₄). The objective of this study was to determine how tillage-induced environmental conditions and substrate quality affect the mineralization rate of easily metabolizable compounds and the subsequent production of these gases. Carbon compounds, with and without nitrogen, were applied to soil cropped to maize under tilled and no-till systems. Following substrate application in the spring and summer, biogenic gases were measured periodically at the soil surface (flux) and within the profile (concentration) at 10-, 20-, and 30-cm depths (i.e., within, at the bottom of, and below the plough layer). Strong CO₂ and N₂O responses to sucrose and glycine in both the field and the laboratory indicate that the soil was C- and N-limited. Surface fluxes of CO₂ and N₂O were greater in soils amended with glycine than with sucrose and were greater in tilled than no-till soils. Transient emission of CH₄ following the addition of glycine was observed and could be attributed to inhibition of N mineralization and nitrification processes on CH₄ oxidation. Laboratory and field measurements indicated that the larger substrate-induced CO₂ emission from the tilled soils could not be attributed to differences in the total biomass or the basal respiratory activity of the soils. Thus, there appears to be no underlying difference in the functional capacity of the microbial communities under different tillage regimes. Comparison of gas profiles indicates relative accumulation of CO₂ at depth in soils under no-till, as well as greater decline in profile CO₂ content with time in the tilled compared to the no-till soil. These results support the conclusion that greater CO₂ efflux from the tilled soils resulted from more rapid gas diffusion through the profile. Hence, the observed differences in gas fluxes between tilled and no-till soils can be attributed to differences in physical environment.     

耕作对旱区坡耕地土壤碳素转化及冬小麦产量的影响

利用长期定位试验(1999开始保护性耕作,2004年采样测定),在豫西旱区坡耕地上进行了不同耕作对土壤有机碳、微生物态碳及水分利用效率的影响研究。结果表明:深松覆盖和免耕覆盖处理的耕层有机碳增加较明显,以深松覆盖有机碳含量最高为6.79gkg-1,比传统耕作高13.82%,其次是免耕,较传统高11.58%,而少耕却较传统降低了1.38%,随着土层的加深,土壤有机碳含量降低,0～60cm有机碳平均值,深松和免耕较传统分别增加了14.08%、5.41%,少耕较传统减少1.12%。土壤微生物碳对耕作敏感,其含量免耕>深松>传统>少耕,分别为206.87mgkg-1、138.43mgkg-1、115.42mgkg-1和112.57mgkg-1,较传统增加79.3%、19.9%和-2.5%。土壤有机碳和土壤微生物态碳都有坡下富集现象。少耕、免耕、深松和传统的SMBC/SOC的值分别为1.91%、3.11%、2.04%和1.93%,免耕和深松对培肥地力、改善环境有好的应用前景;同时免耕覆盖与深松覆盖可提高产量,增产分别达10.22%与9.26%;可提高水分利用效率。     

Crop management effects on soil carbon sequestration on selected farmers’ fields in northeastern Ohio

Soil organic carbon (SOC) pool is the largest among terrestrial pools. The restoration of SOC pool in arable lands represents a potential sink for atmospheric CO₂. Restorative management of SOC includes using organic manures, adopting legume-based crop rotations, and converting plow till to a conservation till system. A field study was conducted to analyze soil properties on two farms located in Geauga and Stark Counties in northeastern Ohio, USA. Soil bulk density decreased with increase in SOC pool for a wide range of management systems. In comparison with wooded control, agricultural fields had a lower SOC pool in the 0–30 cm depth. In Geauga County, the SOC pool decreased by 34% in alfalfa (Medicago sativa L.) grown in a complex rotation with manuring and 51% in unmanured continuous corn (Zea mays L.). In Stark County, the SOC pool decreased by 32% in a field systematically amended with poultry manure and 40% in the field receiving only chemical fertilizers. In comparison with continuous corn, the rate of SOC sequestration in Geauga County was 379 kg C ha⁻¹ year⁻¹ in no-till corn (2 years) previously in hay (12 years), 760 kg C ha⁻¹ year⁻¹ in a complex crop rotation receiving manure and chemical fertilizers, and 355 kg C ha⁻¹ year⁻¹ without manuring. The rate of SOC sequestration was 392 kg C ha⁻¹ year⁻¹ on manured field in Stark County.