土壤碳循环研究及中国稻田土壤固碳研究的进展与问题

土壤碳循环是与全球气候变化密切相关的重要地球表层系统过程,是国际地学和生态学界近年来的热点领域。本文简要概述了国际土壤碳循环研究的进展和发展态势,着重讨论了中国稻田土壤固碳研究已获得的认识。提出碳循环研究越来越走向与生物学的结合,且越来越依赖于长期试验和观测。中国稻田土壤的固碳水平、潜力已有较丰富的认识和资料积累,在团聚体尺度上也开展了较多的固碳机理的研究,包括物理保护、化学结合、生物学的稳定等。无论是野外还是实验室的培养均表明稻田土壤碳矿化潜力较低,这与团聚体的物理保护有关外,还与稻田土壤中存在的碳的化学结合而稳定的机制有关;固碳与农田生态系统生产力和生态服务功能的耦合机制是当前稻田土壤固碳研究的中心内容,一些研究已经表明生物多样性可能是控制碳稳定和温室气体减排与生产力提高的关键因素。未来研究的重点是定量表征固碳中碳更新的关键环节,同时需要加强对作物-土壤微生物相互作用对碳输入、转化和固定的影响及机理的研究。中国稻田土壤固碳与农业发展意义值得进一步重视。     

提升对土壤认识, 创新现代土壤学

土壤是农业生产的基础,是人类赖以生存的基石,也是人类食物与生态环境安全的保障。随着现代科技和国家社会经济的快速发展,土壤的地位与功能正在发生变化。本文基于土壤与土壤学科及国民经济发展需求的关系为出发点,指出了当前对我国土壤的重要性认识正在从农业生产向环境安全、资源利用、生态健康及全球变化等方向转变与提升。同时,明确了现代土壤学的内涵和创新现代土壤学的战略思想,全面、系统、前瞻性地提出了现代土壤学的研究前沿与特点,以及现代土壤学研究领域所面临的挑战与展望,为我国现代土壤学的发展指明了方向。     

植被恢复的土壤固碳效应：动态与驱动机制

植被恢复是影响土壤有机碳库动态变化的关键过程之一,阐明植被恢复过程中土壤有机碳的固持动态及其驱动机制,是全球变化下碳循环研究的热点和前沿问题。本文综述了近年来国内外关于植被恢复过程中土壤有机碳固定动态及其驱动机制方面的研究,剖析植被恢复中土壤有机碳固持动态及其影响因素,探讨植物碳输入对土壤有机碳动态变化的影响机制,揭示植被恢复中土壤有机碳固定的物理、化学和微生物驱动机制,并对目前研究中存在的问题进行总结,进而提出关于植被恢复的土壤固碳效应研究,亟需在土壤有机碳组分的动态、微生物结构和功能,以及植物—土壤—微生物对土壤有机碳固持的协同作用机制等方面进一步加强。本综述可为植被恢复与土壤固碳稳定机制研究指明未来的方向,进而为促进我国植被恢复的土壤碳循环研究,科学评价生态系统土壤固碳潜力和有效实施生态系统碳汇管理提供科学参考。     

农田土壤有机碳固定机制及其影响因子研究进展

全球气候变暖引起的环境问题已经引起各国政府及科学家的密切关注。农田土壤作为大气CO2的源和库,在全球碳循环中的重要角色日渐被认识。本文围绕土壤固碳的基本问题,总结了农田土壤固碳潜力、土壤有机碳固定机制及其影响因素的国内外研究进展。国内研究表明,目前耕地的地力不稳,土壤有机碳密度较低,农田土壤固碳的潜力较大。因此,加强不同区域农田土壤固碳潜力、固碳过程、固碳机理等方面的研究,设计合理优化的农业管理措施,是今后研究的重点。     

“气候变化、温室气体减排与土壤固碳固氮”专题征文通知

农业碳氮循环是全球碳氮循环中的重要组成部分,农业温室气体的减排对应对全球气候变化有重大意义。为了交流我国在农业碳氮循环领域的最新研究成果,本刊将集中刊登气候变化、温室气体减排与土壤固碳固氮方面的研究论文,包括：（1）农业温室气体减排的潜力与措施;（2）农业土壤固碳固氮新技术与措施;     

“气候变化、温室气体减排与土壤固碳固氮”专题征文通知

农业碳氮循环是全球碳氮循环中的重要组成部分,农业温室气体的减排对应对全球气候变化有重大意义。为了交流我国在农业碳氮循环领域的最新研究成果,本刊将集中刊登气候变化、温室气体减排与土壤固碳固氮方面的研究论文,包括：（1）农业温室气体减排的潜力与措施;（2）农业土壤固碳固氮新技术与措施;（3）农业生态系统中（种植业、养殖业、农业固废堆放等）碳氮循环规律与机理等。专辑征文请从学报网站上注册投稿（学报网址：www．aes．org．cn）,     

陆地生态系统碳循环对土地利用变化的响应

陆地生态系统碳循环在全球碳循环中占有重要地位,而土地利用变化是估测陆地生态系统碳储存与释放的最大不确定性因素。植被和土壤是陆地生态系统的两大碳库,是碳循环中的两个重要纽带,土地利用变化影响陆地生态系统土壤和植被碳的固定、积累与释放,从而影响整个碳循环过程。本文主要从土壤和植被碳库的角度出发,综述了近年来土地利用变化对陆地生态系统碳循环的影响及其机理,以及研究方法进展,着重分析了模型在此方面的应用;并提出了未来研究方向的展望。     

对第18届国际土壤学大会召开的认识与体会

1关于土壤学研究的一些新思路1.1土壤学研究的前沿是当前土壤科学研究的新方向这次土壤学大会的主题是“土壤科学的前沿:技术与信息时代”。研究纲领是“土壤学的进步”,也就是说,土壤科学研究的前沿,集中在土壤学的进步之上,即重点集中在遥感、地理信息系统、景观分析、分子尺度的先进分析技术、环境土壤生物学、植物/土壤界面过程、土壤过程和反演的计算机建模、精确农业以及其他信息科学和技术的应用等方面。     

稳定13C同位素示踪技术在农田土壤碳循环和团聚体 固碳研究中的应用进展

农田土壤有机碳库是全球碳循环的重要组成部分,其积累和分解直接影响陆地生态系统碳贮藏与全球碳平衡。土壤团聚体是土壤结构的物质基础和土壤肥力的重要载体,也是土壤有机碳的固定场所。稳定~(13)C同位素示踪技术是研究土壤碳动态变化的有效手段,能够揭示新输入碳在土壤及团聚体中赋存状态、周转过程以及微生物的调节机制。本文主要归纳与阐述了稳定~(13)C同位素示踪技术在农田土壤有机碳循环及土壤团聚体固碳机理方面的研究进展,提出~(13)C同位素示踪技术在未来土壤碳循环和固碳机制方面的主要研究方向。     

侵蚀条件下土壤有机碳流失研究进展

全球土壤有机碳库储量丰富且活跃,而作为碳流失主要驱动力的土壤侵蚀对陆地碳循环影响巨大,揭示其影响将对气候变化背景下深刻理解碳收支过程和相关政策的制定具有重要意义。该文主要介绍了近年来国内外关于水蚀和风蚀影响土壤有机碳流失过程的研究进展,分析了侵蚀条件下土壤碳的源汇争议,简述了土壤有机碳流失的原位和异位环境效应,并提出了相关研究的主要现实问题和未来发展方向。在侵蚀进程中,土壤有机碳的固定与流失并存,流失部分主要包括在地表径流泥沙和土壤呼吸过程中,当前相关研究多集中于侵蚀有机碳的去向问题。在一定的景观范围内,定量刻画侵蚀过程中土壤碳输入输出关系是今后区域碳循环研究领域亟待解决的关键科学问题。     

作物植硅体形态的应用及其封存有机碳研究进展

农田生态系统是陆地生态系统的重要组成部分，在维系生命的生长发育和环境的动态平衡等方面起着至关重要的作用，在其生长发育和环境演变的过程中储存大量的环境变化信息，能够反映古农业的发展变迁。植硅体是一种长期稳定存在于土壤中的非晶质二氧化硅颗粒物，它可以指示气候变化。近年来，植硅体分析主要应用在农业考古、古气候重建、生物地球化学循环和全球碳汇潜力估算的研究中。世界上作物分布广泛，作物栽培历史悠久，研究作物植硅体与植硅体碳，对探讨农业起源与发展，估算农田生态系统植硅体碳汇潜力，应对全球气候变化具有重要意义。本文在查阅国内外与作物植硅体研究相关文献的基础上，综述了作物植硅体的形态研究、植硅体在考古学中的应用、作物植硅体碳含量与分布、碳汇潜力以及植硅体碳汇在全球碳汇中的贡献，阐明了作物植硅体未来的研究方向。1）不同作物产生的植硅体形态不同，而且对作物植硅体形态的研究较多处于优势的禾本科中，其他作物的研究较少；2）作物植硅体碳含量与其本身的固碳能力和效率有关，不完全由植硅体含量的多少决定，此外，植硅体碳含量的多少也可能受生长环境和植物基因型的影响；3）不同生态系统中气候、地表植被、土壤环境等诸多因素直接或间接地影响区域植硅体的碳汇潜力；4）农田生态系统不同作物植硅体碳汇存在显著差异，施加硅肥或硅-磷复合肥、种植高植硅体含量和高植硅体碳含量的作物等均可显著提高农田生态系统碳汇潜力。今后应进一步研究不同作物植硅体碳汇，以帮助识别过去的农业碳汇，评估当前农业碳汇潜力；加强植物、根系、土壤迁移规律的探讨，进一步分析不同作物植硅体积累与碳汇效应；阐明不同植物吸硅机制、植物根系硅化过程与其植硅体含量、植硅体碳含量间的关系；了解西南喀斯特生态脆弱区农业碳汇潜力，以期为作物科学种植、农田生态系统碳汇估算等提供参考。     

Some perspectives on carbon sequestration in agriculture

One of the main options for greenhouse gas (GHG) mitigation identified by the IPCC is the sequestration of carbon in soils. Since the breaking of agricultural land in most regions, the carbon stocks have been depleted to such an extent, that they now represent a potential sink for CO₂ removal from the atmosphere. Improved management will however, be required to increase the inputs of organic matter in the top soil and/or decrease decomposition rates. In this paper we use data from selected regions to explore the global potential for carbon sequestration in arable soils. While realising that C sequestration is not limited to the selected regions, we have, however, focussed our review on two regions: (i) Canadian Prairies and (ii) The Tropics. In temperate regions, management changes for an increase in C involve increase in cropping frequency (reducing bare fallow), increasing use of forages in crop rotations, reducing tillage intensity and frequency, better crop residue management, and adopting agroforestry. In the tropics, agroforestry remains the primary method by which sequestration rates may be significantly increased. Increases in soil C may be achieved through improved fertility of cropland/pasture; on extensive systems with shifting cultivation cropped fallows and cover crops may be beneficial, and adopting agro forestry or foresting marginal cropland is also an alternative. In addition, in the tropics it is imperative to reduce the clearing of forests for conversion to cropland. Some regional analyses of soil C sequestration and sequestration potential have been performed, mainly for temperate industrialized North America where the majority of research pertaining to C sequestration has been carried out. More research is needed, especially for the Tropics, to more accurately capture the impact of region-specific interactions between climate, soil, and management of resources on C sequestration, which are lost in global level assessments. By itself, C sequestration in agricultural soils can make only modest contributions (3–6% of fossil fuel contributions) to mitigation of overall greenhouse gas emissions. However, effective mitigation policies will not be based on any single ‘magic bullet’ solutions, but rather on many modest reductions which are economically efficient and which confer additional benefits to society. In this context, soil C sequestration is a significant mitigation option.     

农田土壤有机碳固存的主要影响因子及其稳定机制

农田生态系统作为陆地生态系统的重要组成部分,在陆地生态系统碳循环过程中发挥重要作用。明确影响农田土壤有机截获的主要因素及土壤固碳的稳定机制,有助于控制和加强农田土壤碳库的固碳潜力,以及正确评价农业生产对全球气候变化的影响。因此,本文综合论述了影响农田土壤碳含量的自然和人为因素,详细阐述了土壤碳固定的物理、化学和生物稳定机制。并总结了已有研究的不足,对今后土壤固碳研究中的热点问题进行了展望。认为从土壤微生物学角度出发,深入研究微生物在土壤有机碳循环中的作用机制,并将地上部和地下部生态系统联系起来探讨土壤碳素稳定性机制更具有重要的意义。     

秸秆还田下土壤有机质激发效应研究进展

土壤有机质是农田肥力的基础与核心，对作物产量、农业环境，甚至地球碳循环意义重大。作物秸秆作为农田土壤有机碳库的重要外部补充，其还田过程对土壤有机碳周转和碳库平衡具有显著影响。激发效应是一种因新鲜有机质输入而导致土壤本底有机质矿化速率发生改变的现象。秸秆还田导致的土壤有机质分解激发，不仅涉及到秸秆资源化高效利用，还直接关系到农田土壤碳库的平衡及其功能，因此备受科学界关注。尽管对外源有机质输入引起的土壤有机质激发效应的理论研究已取得了较大进展，但如何结合最新的理论结果到秸秆还田固碳减排的生产实践中仍面临着较大的挑战，这主要归结于对农田土壤有机质分解激发效应的发生特点和规律，及其背后的土壤、气候、管理等相关的驱动因子和过程还未完全明确。据此，本文首先对土壤有机质分解激发效应发生的理论研究进展（包括：共代谢理论、氮矿化理论、化学计量比和微生物残体再利用）进行了系统综述。其次，结合已有的研究证据和理论假设进一步概述了秸秆还田过程中影响激发强度和方向的潜在驱动因素，如：秸秆类型和数量、还田方式、水肥管理、土壤属性、气候因子等。最后，从秸秆还田的高效性、农田碳库的可持续和农业环境的友好性出发，对秸秆还田土壤有机质分解激发的潜在研究方向进行了展望，并就秸秆还田改善土壤碳库的优化措施提出了建议。     

Does no‐till farming induce water repellency to soils?

Soil water repellency (SWR) is an intrinsic and dynamic soil property that can influence soil hydrology and crop production. Although several land use systems have been shown to induce water repellency in soil, the specific effects of no‐till cropping on SWR are poorly understood. This article reviews the impacts of no‐till on SWR and identifies research needs. No‐till cropping generally induces 1.5 to 40 times more SWR than conventional tillage, depending on soil type. This may result from near‐surface accumulation of hydrophobic organic C compounds derived from crop residues, microbial activity and reduced soil disturbance. While large SWR may have adverse impacts on soil hydrology and crop production, the level of SWR under no‐till relative to conventional tillage may contribute to aggregate stabilization and intra‐aggregate C sequestration. More research is needed to discern the extent and relevance of no‐till induced SWR. This includes: (1) further assessment of SWR under different tillage systems across a wide range of soil textures and climates, (2) comparison of the various methods for measuring SWR over a range of water contents, (3) inclusion of SWR in routine soil analysis and its use as a parameter to evaluate management impacts, (4) assessment of the temporal and spatial changes in SWR under field conditions, (5) further assessment of the impacts of the small differences in SWR between no‐till and conventionally tilled soils on crop production, soil hydrology and soil C sequestration, and (6) development of models to predict SWR for different tillage systems and soils.     

A modelling analysis of the potential for soil carbon sequestration under short rotation coppice willow bioenergy plantations

Abstract. Rising atmospheric CO₂ concentrations and their association with global climate change have led to several major international initiatives to reduce net CO₂ emissions, including the promotion of bioenergy crops such as short rotation coppice (SRC) willow. Although the above-ground harvested bio-fuel is likely to be the major contributor to the CO₂ mitigation potential of bioenergy crops, additional carbon may be sequestered through crop inputs into plantation soils.   Here, we describe a process-based model specifically designed to evaluate the potential for soil carbon sequestration in SRC willow plantations in the UK. According to the model predictions, we conclude that the potential for soil carbon sequestration in these plantations is comparable to, or even greater than, that of naturally regenerating woodland. Our preliminary, site-specific model output suggests that soil carbon sequestration may constitute about 5% of the overall carbon mitigation benefit arising from SRC plantations. Sensitivity analyses identified the following factors as the principal controls on rates and amounts of soil carbon sequestration under SRC: carbon inputs (net primary production), decomposition rates of the major soil carbon pools, initial soil carbon content (an inverse relationship with rates of soil carbon sequestration), crop/plantation management, and depth of soil being influenced by the bioenergy crop. Our results suggest that carbon sequestration potential is greatest in soils whose carbon content has been depleted to relatively low levels due to agricultural land use practices such as annual deep ploughing of agricultural soils.     

Soil organic N - An under-rated player for C sequestration in soils?

The availability of Soil Organic Nitrogen (SON) determines soil fertility and biomass production to a great extent. SON also affects the amounts and turnover rates of the soil organic carbon (SOC) pools. Although there is increasing awareness of the impact of the nitrogen (N) cycle on the carbon (C) cycle, the extent of this interaction and the implications for soil organic matter (SOM) dynamics are still under debate. Therefore, present knowledge about the inter-relationships of the soil cycles of C and N as well as current ideas about SON stabilization are summarized in this paper in order to develop an advanced concept of the role of N on C sequestration. Modeling global C-cycling, it was already recognized that SON and SOC are closely coupled via biomass production and degradation. However, the narrow C/N ratio of mature soil organic matter (SOM) shows further that the impact of SON on the refractory SOM is beyond that of determining the size of the active cycling entities. It affects the quantity of the slow cycling pool and as a major contributor it also determines its chemical composition. Although the chemical nature of SON is still not very well understood, both improved classical wet chemical analyses and modern spectroscopic techniques provide increasing evidence that almost the entire organic N in fire-unaffected soils is bound in peptide-like compounds and to a lesser extent in amino sugars. This clearly points to the conclusion, that such compounds have greater importance for SOM formation than previously assumed. Based on published papers, I suggest that peptides even have a key function in the C-sequestration process. Although the mechanisms involved in their medium and long-term stabilization are far from understood, the immobilization of these biomolecules seems to determine the chemistry and functionality of the slow cycling SOM fraction and even the potential of a soil to act as a C sink. Pyrogenic organic N, which derives mostly from incomplete combustion of plant and litter peptides is another under-rated player in soil organic matter preservation. In fire-prone regions, its formation represents a major N stabilization mechanism, leading to the accumulation of heterocyclic aromatic N, the stability of which is still not elaborated. The concept of peptide-like compounds as a key in SOM-sequestration implies that for an improved evaluation of the potential of soils as C-sinks our research focus as to be directed to a better understanding of their chemistry and of the mechanisms which are responsible for their resistance against biochemical degradation in soils.     

农田土壤固碳与增产协同效应研究进展

农田土壤固碳是提升土壤肥力、保障和实现农田持续稳定生产能力的关键所在。明确农田土壤固碳与作物增产的协同效应可为不同区域土壤培肥、维持和提升作物产量提供依据。农田土壤固碳明显受到气候、土壤属性、管理措施 (尤其是施肥和耕作)、轮作制度等因素的影响，且与农田作物产量密切相关，二者具有明显的协同效应。农田土壤有机碳与作物增产协同效应存在一定的阈值，且该阈值具有一定的区域差异。东北地区土壤有机碳阈值约为C 44～46 t/hm2，西北和华北地区约为C 22～28 t/hm2，南方地区约为C 33～37 t/hm2。经验方程和模型模拟结果表明，在不同区域，农田土壤每固定C 1.0 t/(hm2·a)有机碳，粮食作物产量可平均提升约0.7 t/hm2，但该响应值在各地区明显受到相应的环境及农田管理措施等因素的影响。深入理解农田固碳过程及其与作物生产力协同作用的机理，是指导不同区域合理培肥、提高土壤肥力、提高养分资源利用效率的关键举措。未来的研究方向和重点是明确不同区域农田土壤可实现的固碳潜力，进一步揭示集约化种植下农田土壤有机碳的固存机制，关注深层土壤有机碳固定对作物增产潜力的影响及贡献，并深入分析表征环境、人为因素等对农田土壤固碳增产协同效应的影响机制及调控原理。     

稻田土壤微生物残体积累对外源秸秆输入的响应研究进展

稻田土壤碳循环是我国陆地生态系统碳循环的重要组成部分。促进稻田生态系统碳的固定及稳定对减缓全球气候变化起着不容忽视的作用。微生物主导的有机碳转化过程是土壤碳循环研究的核心,微生物同化代谢介导的细胞残体迭代积累在土壤有机碳长期截获和稳定过程中发挥重要作用。与旱地土壤相比,关于稻田土壤中微生物残体积累动态对外源有机物质如作物秸秆输入的响应及主要影响因子的认识还相对有限,对微生物通过同化作用参与土壤固碳的过程和机制尚缺乏系统认识。基于此,本文介绍了微生物残体对土壤有机碳库形成和积累的重要性及评价指标,重点探讨了秸秆还田对稻田土壤微生物残体积累动态以及外源秸秆碳形成细胞残体转化过程的影响,分析了影响微生物残体积累转化的主要气候因素和土壤因素,最后提出了未来应借助先进的光谱和高分辨率成像技术并结合同位素示踪对微生物残体的稳定性与机理开展更为深入的研究。