我国主要农耕区水稻土有机碳含量分布及影响因素研究

水稻土是我国主要的耕作土壤之一,水稻土有机碳变化与全球气候变化息息相关,因此研究我国主要农耕区水稻土有机碳含量分布特征及影响因素具有重要的现实意义。本文基于全国多目标地球化学调查1：250000土壤数据库,以行政区划分析了水稻土有机碳分布规律,从土壤pH值、年均气温、年均降雨量、耕作方式等角度探讨了其对水稻土有机碳含量...     

基于神经网络模型的中国表层土壤有机质空间分布模拟方法

基于全国第二次土壤普查得到的6 241个典型土壤剖面数据,采用主成分分析方法和径向基函数神经网络模型建立不同植被类型—土纲单元内土壤有机质与气候、地形和植被等环境因子间的非线性关系,模拟全国表层土壤有机质的空间分析格局。结果表明,该模型具有较准确的预测能力,性能指数达到1.94。与普通克里格法、反比距离法和多元回归模型相比,神经网络模型对621个验证点模拟结果与实测值的相关系数为0.799,分别提高了0.265、0.181和0.120,平均绝对误差分别降低了4.25、4.43和2.34 g/kg,平均相对误差分别降低了30.16%、32.66%和5.93%,均方根误差则分别降低了8.61、8.24和6.24 g/kg;从模拟结果图来看,神经网络模型能够提供更多的细节信息。该方法为大尺度土壤性质空间分布模拟提供了有益的参考。     

中国东部农耕区土壤微生物碳的分布及影响因素

对中国东部不同纬度带的6个地区的土壤微生物碳进行了研究。结果表明土壤微生物碳的分布受地理位置的影响较为明显:由北向南,东北地区的土壤微生物碳要高于其他地区。作为土壤有机质变化的灵敏度指标———微生物熵(微生物碳/总有机碳),在同一耕作方式下,其在不同地区的变化受土壤利用方式的影响较为明显:在连作系统下,菜地>粮地;而在轮作系统下,粮食-蔬菜轮作>蔬菜-蔬菜轮作。利用相关性分析寻求影响微生物碳分布的环境因素,结果表明,微生物碳(Micro-C)与土壤有机碳(TOC)、全氮(TN)、土壤含水率呈极显著正相关,而有机碳和全氮的分布主要受地理位置的影响。对不同土壤类型的微生物碳和微生物熵进行相关性分析,结果显示pH、年均温、含水率、TOC和TN是主要影响因素,关键影响因素因土壤类型不同而各异。     

Soil water-salt dynamics state and associated sensitivity factors in an irrigation district of the loess area: a case study in the Luohui Canal Irrigation District,China

Soil salinisation determines the distribution pattern of crop processes in irrigation districts. The research presented here was conducted in the Luohui Canal Irrigation District, which is located in the loess area of Shaanxi Province, China. A back-propagation artificial neural network (BPANN) for the soil water-salt state was established to predict soil salinity and alkalinity. The degree of influence of numerous factors on the dynamics was quantitatively determined using the default factor testing method and verified with grey relational analysis. The results show that the BPANN prediction accuracy is very high, and it can efficiently depict the comprehensive relationships between the influential factors and dynamic states. The influence of soil moisture, evaporation, groundwater salt and groundwater depth on the dynamics is significant in the region. The current irrigation method, used for many years, cannot meet the water necessities for the vegetation, causing the groundwater levels to decline and a lowering of the soil moisture zone, leading to the occurrence of serious soil salinisation. Under the action of evaporation, more salt accumulates in the upper part of the soil, resulting in extensive soil salinisation. The higher the groundwater salt content, the more salt is carried by rising capillary water, and the more the soil is salinised. If groundwater depth was to exceed the critical water table, then groundwater and salt would move to the soil surface by moisture evaporation, and salt would build up on the soil surface in this irrigation district. The interactions between each factor forms a complex coupling relationship state.     

Exploring the effects of water on vegetation change and net primary productivity along the IGBP Northeast China Transect

To understand the mechanisms underlying the effects of climate variation, especially the effects of water on vegetation, vegetation type and distribution as well as climate data and soil type were used to simulate present vegetation distributions and net primary productivity (NPP) under present and future climate scenarios SRES-A2 and SRES-B2. A natural vegetation NPP model was also applied to calculate future vegetation NPP. The results showed that water played a dominant role not only in the distribution of vegetation, but also in the rate of change in the vegetation area. Analysis of NPP showed that precipitation had more effects on the amount of biome NPP than temperature did. Different effects were observed for the rate of change in NPP. In cases where biomes remain unaltered, the variation in annual precipitation could account for 39% of the variation in NPP. In cases where biomes changed, 45% of NPP was caused by temperature variation. Regarding the variation in transect production, −2.85% resulted from the change in vegetation structure when compared with present NPP, and 7.69% from the climate change under scenario SRES-B2; these values were −7.4 and 19.56%, respectively, under scenario SRES-A2. The results showed water served as a dominant factor controlling the vegetation distributions and NPP. However, temperature became determinant where the biomes changed, impacting the rate of change in vegetation NPP when the climate changed. The results also showed that water would have a positive effect on transect production, and the structure of vegetation had a negative effect under the projected future climate.     

Organic carbon and its oxidation stability characteristics of shallow soil in frozen soil area of Three River Source Region北大核心CSCD

As the most important part of the global carbon cycle,soil carbon pool is the largest carbon pool in terrestrial ecosystems. Soil carbon pool in permafrost regions is the most sensitive carbon pool to climate change. Weak climate change will have a huge impact on the organic carbon production in the shallow soil,and then affect the regional landscape and ecology. As an indicator reflecting the antioxidant capacity of soil organic carbon,oxidation stability affects the quantity and quality of soil organic carbon,and its variation has a certain regularity in the alpine permafrost region under the influence of climatic factors. In order to explore the distribution characteristics of soil organic carbon and its oxidation stability in frozen soil,based on the experimental data and the climatic data from 2011 to 2019,the random forest model was used to conduct multi-factor digital mapping on soil organic carbon content,soil organic carbon components with different oxidation difficulty degrees,and soil organic carbon oxidation stability coefficient and environmental variables（average annual precipitation,average annual sunshine hours,average annual air temperature,and altitude）and analyze the controlling factors. The results showed that the model had an interpretation degree of more than 54% for the shallow soil organic carbon in frozen soil area of Three River Source Region,and the digital mapping could reflect the distribution of soil organic carbon well. Soil organic carbon was mainly affected by precipitation and sunshine duration,and temperature took second place. The spatial distribution of components with different oxidation difficulty is different,but the oxidation stability has the distribution characteristics of high in the north and low in the south. Cold and dry are conducive to improving the oxidation stability of organic carbon in shallow soil of frozen soil area. © 2022 Science Press (China).     

内蒙古中北部土壤碳库构成及其影响因素

采用网格采样法荻取内蒙古中北部半干旱区土壤样品共527件,分析其碳库构成特征及其影响因素,并初步评估了未来气候变化背景下的碳库变化趋势。结果表明,研究区土壤碳库仍以有机碳为主,不同土壤类型中有机碳占总碳61％～97％,其中沼泽土有机碳密度最高,风沙土最低,盐土无机碳密度最高,暗棕壤最低;在空间分布上,土壤碳受气温和降水...     

青海省土壤有机碳储量估算及其源汇因素分析

收集了青海省第二次土壤普查资料的2 856个土壤统计剖面数据,计算了20世纪80年代青海省土壤0～20 cm和0～65 cm深度的土壤有机碳密度,根据1∶400万数字化土壤类型图,统计了不同类型土壤的土壤有机碳储量。结合本研究采集的105个表层土壤数据,估算了青海省典型地区土壤有机碳近30年来的年均变化量。研究建立了土壤有机碳含量与温度、降雨等气候因子的关系方程,根据青海省土地利用现状估算了不同时期土地利用方式变化对青海省土壤碳源汇转化的影响。结果显示:(1)0～20 cm表土层SOCD20加权平均值为4.509 kg/m2,其值在各类型土壤间差异较为显著,SOCR20为2.953 Pg;0～65 cm的SOCD65加权平均值为13.597 kg/m2,SOCR65为8.904 Pg。由于受气候、土壤类型、植被类型、海拔等因素的影响,青海省土壤有机碳密度的分布呈现自东南向西北递减的带状分布特征;(2)近30年来青海省有机碳含量明显下降;(3)根据气象站的资料,分析了近50年来的年均气温变化趋势,预测在全球变暖背景下青藏高原土壤将表现出碳源效应,而研究区愈加明显的人类活动影响、大面积草地退化等土地利用方式改变也是造成土壤碳释放的主要原因之一。     

青藏高原坡面冻土土壤水分空间变异特性

为深入揭示坡面冻土水分运移规律及其主要影响因子,以青藏高原巴颜喀拉山北坡为例,结合冻融变化过程,研究不同地形条件冻土土壤水分空间变异特征,利用分类回归树模型（CART）和典范对应分析（CCA）识别影响坡面冻土土壤水分空间异质性的主控因子及其相互作用关系。研究结果表明:①受坡面地形与冻融过程影响,冻结期坡面冻土土壤水分侧向流动减弱,以垂直迁移为主,上坡位含量高于下坡位,反之,融化期上坡位含量则低于下坡位。②影响坡面冻土土壤水分的主要环境因子为高程、土壤质地、土壤温度和植被覆盖度,但在不同冻融阶段下其影响因子存在差异,在冻结状态下主要因子为高程、土壤质地和土壤温度,其相对贡献率分别达到19.97%、19.45%和9.56%;在融化阶段下主要因子为高程、植被覆盖度和土壤质地,其相对贡献率分别为37.4%、14.9%和10.7%。③ 0~20 cm浅层深度上影响坡面冻土土壤水分的主要因素为坡度、高程和植被覆盖度,其相关系数分别高达0.941 2、0.903 9和0.563 1;中下层深度上其主要影响因素较为复杂。     

三角洲—浅海沉积体系陆源有机质分布控制因素

三角洲-浅海沉积体系中同时存在陆源有机质与海洋有机质,向深水方向陆源有机质的分布受限,但越来越多的深水区油气勘探实践发现陆源有机质的贡献,证明陆源有机质在深水区的存在及其对油气生成具有重要意义。通过系统分析陆源有机质的分布规律,从而阐述了影响陆源有机质分布的主要因素及其相互关系。研究结果表明:陆源有机质的分布受碎屑粒度、矿物组成、有机质组成、水动力类型、水动力强度、水体盐度及pH值等多因素控制,各因素间相互联系、相互影响。将其控制因素可系统归纳为物源条件、搬运条件及沉积与保存条件。水动力类型与水动力强度是陆源有机质存在于深水区的关键因素,生物作用可能成为陆源有机质分布的主控因素,环境因素及成岩作用是影响陆源有机质保存的重要因素。     

毛乌素沙地裸地与植被覆盖下非冻结期土壤水分时空分布特征

在水资源短缺的沙地生态系统中,土壤水分是植被恢复和水资源管理的主要控制因子,正确认识沙地土壤水分的分布特征及时空变化规律是促进沙地水资源可持续发展的基础。以毛乌素沙地为研究区,利用原位试验观测、经典统计学分析和聚类分析相结合的方法,揭示了有无植被覆盖下的土壤剖面水分时空变化特征,探讨了植物生长对土壤水分布的影响。结果表明：在2016年非冻结期内,地下水水位埋深较浅时,裸地与植被覆盖情况下土壤平均含水率均随土壤深度的增加而增大,可将0～350 cm土层划分为气候影响层、过渡层与地下水影响层。裸地剖面平均含水率为23.59%,变异系数为4.24%,属于弱变异,剖面含水率在观测期间明显上升,并在8月中旬强降雨时上升速率达到最大;植被覆盖下土壤剖面平均含水率为17.74%,变异系数为15.61%,属于中等变异,剖面含水率在观测期间显著下降,在8月沙柳发育成熟后剖面含水率下降最快。在垂向深度上,植被对土壤剖面含水率的影响近似呈高斯曲线变化,对过渡层含水率的影响最大,占总影响的50%以上,对气候影响层与地下水影响层的影响相对较小,且随着植物生长,气候影响层受到的相对影响逐渐减弱,地下水影响层受到的...     

基于主成分分析的青藏高原多年冻土区高寒草地土壤质量评价

土壤质量评价是提高对土壤质量理解的关键环节。为了了解青藏高原多年冻土区高寒草地土壤质量的基本情况,在青藏高原腹地西大滩至安多地区,根据不同海拔梯度和植被盖度共采集了154个土壤样品。通过主成分分析（PCA）法确定了影响青藏高原多年冻土区高寒草地土壤质量的最小数据集（MDS）：全氮、全磷、全钾。根据影响土壤质量的最小数据集对青藏高原多年冻土区高寒草地土壤质量进行评价,得出了不同海拔、不同植被盖度下的土壤质量指数（SQI）。通过对不同海拔、不同植被盖度的土壤质量指数进行对比研究表明：随着海拔的升高,SQI呈增加的趋势,即海拔4 300～4 600 m（0.270±0.043） < 海拔4 600～4 900 m（0.326±0.061） < 海拔4 900～5 200 m（0.410±0.075）;随着植被盖度的增加,SQI也呈现增加的变化趋势,即植被盖度小于50%（0.262～0.265） < 植被盖度大于50%（0.336～0.344）。在分别考虑了有机质、盐分、土壤水分对土壤质量的影响下得出的土壤质量指数值与基于最小数据集得到的土壤质量指数相一致,说明基于主成分分析的最小数据集可以对青藏高原多年冻土区高寒草地土壤质量做出较准确的评价。     

Abiotic Limitation of Non-native Plants in the High Salt Marsh Transition Zone

Native plants in the upland to high-marsh transition zone of southern California salt marshes are mostly perennials and therefore experience the abiotic stress of low soil moisture and high soil salinity throughout much of the year. However, many annual non-native plants reproduce during the brief period of reduced salinity and increased moisture during winter rainfall. We investigated the seasonal and spatial variation in vegetation and soil properties of the transition zone using an observational study. Next, we explored the potential for managing non-native plants using a field experiment with varying timing, quantity, and frequency of salt addition treatments. The observational study showed that the distribution of non-native plants is related to changes in soil salinity and soil moisture that accompany changes in elevation, although there are variations among species. In the field experiment, salt was effective at reducing non-native plant cover, but the timing of treatment was important. Although additional work is needed to refine the salt treatments, this work supports the idea that altering abiotic conditions can effectively reduce the presence of non-native species in the upland to high-marsh transition zone.     

青藏高原多年冻土和季节性冻土区土壤水分变化及其与降水的关系

使用地面观测数据对欧洲空间局(ESA)发布的气候变化倡议(CCI)土壤水分产品进行精度校准,结合青藏高原及其周边降水气象站数据,分析土壤水分动态变化及其与降水的关系.结果表明:(1)校正后的CCI主被动组合产品所反演的青藏高原土壤水分获得了更高的精度,且显示1986～2016年暖季土壤水分在多年冻土区的逐年变化更为稳定...     

祁连山黑河上游多年冻土区不同植被类型土壤有机碳密度分布特征

山地多年冻土的异质性影响其植被类型的分布特征,且对有机碳的分布也具有重要影响。通过采集黑河上游多年冻土区三种典型植被类型（高寒沼泽草甸、高寒草甸、高寒草原）8个活动层的土壤样品,测定其土壤有机碳密度及其理化性质。结果表明：高寒沼泽草甸土壤有机碳密度最高（49.50 kg·m^-2）,高寒草甸次之（11.22 kg·m^-2）,高寒草原最低（7.30 kg·m^-2）。土壤有机碳密度的剖面垂直分布特征具有差异性,高寒沼泽草甸土壤有机碳密度随深度变化不明显,高寒草原和高寒草甸土壤有机碳密度随深度逐渐减小,存在显著的表层聚集性。有机碳密度与土壤含水率和细粒含量呈显著正相关,与pH值呈显著负相关关系。一般线性模型结果表明土壤含水率、pH值和土壤颗粒组成解释了96.39%的有机碳密度变异,其中土壤含水率贡献了81.53%,pH值和土壤粒度分别贡献了9.33%和4.75%。研究表明多年冻土区不同植被类型土壤有机碳密度分布特征具有明显差异,山地多年冻土土壤含水率是控制有机碳密度分布特征的重要影响因素。     

喀斯特溶槽岩-土界面优势流及其对土壤水分动态的影响

通过对两个典型溶槽剖面的野外入渗实验,结合对入渗锋面的红外成像和染色示踪,分析溶槽中土壤湿润锋运移受岩—土界面优势流、初始水分状态（干湿程度和不均匀分布）及植被根系的影响程度。其结果表明:岩—土界面优势流增加入渗锋面到达处的土壤含水率是溶槽中部的1.1～14.5倍,但岩—土界面优势流形成的侧向水势梯度可降低优势流锋面下移;初始入渗中表土湿润锋运移主要受植被根系大孔隙优势流的影响,岩—土界面优势流作用不显著,但随着入渗深度的加大,岩—土界面优势流侧向弥散对湿润锋运移和土壤水分的影响加强。      

Analysis of impact factors on scrubland soil respiration in the southern Gurbantunggut Desert,central Asia

Monitoring soil CO₂ respiration with chamber measurements and identifying controlling factors such as the diversity of vegetation species, moisture and temperature can help guide desert scrubland management. Soil CO₂ respiration and potential controlling factors at four sites in desert scrubland were examined along the Sangong River Basin (SRB) in northwestern China in 2004. Soil CO₂ respiration descended along the SRB as did the diversity of vegetation species, air temperature and air humidity. The two sites of the field station (FS) and the north desert (ND) and the low reaches of the SRB among these locations were monitored to analyze the effects of pH value, soil organic carbon (SOC), total nitrogen (TN) and calcium carbonate (CaCO₃) on soil CO₂ respiration during the growing season in 2005. The ND site was located at the southern edge of the Gurbantunggut Desert; the FS site was in the border area of the SRB Alluvial Fan. One-way ANOVA was performed. The result showed that air humidity and CaCO₃ content had a strong influence on soil CO₂ respiration; SOC content was a limitation to soil CO₂ respiration in the arid-desert zone. Effective management activities can attenuate soil CO₂ respiration and keep carbon balance trends at a desirabe level in desert scrublands.     

塔里木盆地荒漠植物与表土碳同位素组成研究

表土有机质碳同位素组成(δ¹³C_org)反映了来自于地表各种植物δ¹³C_org的一个混合信息.要从沉积物δ¹³C_org中提取可靠的植被信息,需要系统研究现代表土有机质δ¹³C_org与地表植被δ¹³C_org的差异.初步研究了塔里木盆地主要现代植被及土壤碳同位素组成,对比不同地区土壤和地表植被δ¹³C_org的差异.结果表明:塔里木盆地柽柳属种群中植物与表土碳同位素组成之间存在显著相关关系,说明在干旱地区土壤中微生物和水生生物等的干扰因素可以忽略,其现代土壤的同位素组成只与地表相应的主要植被类型有关.塔里木盆地柽柳属种群中表土有机质δ¹³C_org值比地表植被δ¹³C_org值平均偏正1.71‰左右,不同于其它地区表土和地表植被δ¹³C_org差异(2.2‰,1‰,0.5‰)的结果,反映不同地区表土和地表植被有机质δ¹³C_org值差异不同.在利用沉积物δ¹³C_org值提取古生态植被信息时,应考虑到不同地区土壤有机质与地表植被δ¹³C_org值的不同差异会影响植被中C₃、C₄植物组成情况.     

青藏高原东缘高寒草甸退化过程中植物群落物种多样性、生产力与土壤特性的关系

为了阐明高寒草甸退化过程中植物群落物种多样性、生产力与土壤特性的关系, 在青藏高原东缘的玛曲县沿着高寒草甸退化梯度选取了轻度退化草甸、中度退化草甸、重度退化草甸和沙化草甸, 测定了高寒草甸退化过程中植物群落物种多样性、生产力与土壤理化性状. 结果表明: 从轻度退化到中度、重度和沙化草甸, 植被地下生物量分别降低了36%、48%和91%, 总生物量分别降低了34%、47%和91%, 土壤有机碳分别下降了18%、81%和97%, 全N分别下降了25%、82%和95%, 全P含量分别下降了14%、33%和41%. 随着高寒草甸的退化, 植被群落的生物多样性和地上生物量呈先稳定后降低的趋势, 土壤砂粒含量、pH值和全K含量呈增加趋势, 黏粉粒呈降低趋势, 速效N、速效P和速效K呈先增加后降低的趋势. 相关分析表明, 群落物种多样性和生产力与土壤有机碳、全N、全P、速效N、速效P、速效K、黏粒含量、粉粒含量、水分含量均呈显著正相关(P<0.01), 而与土壤砂粒、全K和pH值均呈显著负相关(P<0.05). 因此, 高寒草甸退化过程中, 土壤质地、养分和水分等的复杂变化及其相互关系共同决定着高寒草甸群落物种多样性和生产力的变化. 同时, 植被生产力和土壤碳、氮的降低产生明显的正反馈效应, 导致在重度退化阶段和沙化阶段, 植被生产力和土壤碳氮的急剧下降.     

Variable rainfall limits the germination of upper intertidal marsh plants in Southern California

Temporal variation in rainfall created a germination window for seedling establishment in the upper intertidal marshes of southern California. In this highly variable climate, total annual rainfall was highly variable, as was the timing and size of rainfall during the wet season. Daily rainfalls>3.0 cm were rare in the long-term record but created germination opportunities that had two components: low salinity and high moisture. During the 1996–1997 wet season, only one-day rainfalls>3.0 cm resulted in large increases in soil moisture and decreases in soil salinity. Germination in the upper intertidal marsh of three wetlands followed two large (>3.0 cm) rainfall events in the relatively dry 1996–1997 season and multiple medium and small rainfall events in the wetter 1997–1998 season. In addition to rainfall, plant cover and soil texture influenced, spatial and temporal variation in soil salinity and moisture. Daily and weekly sampling adequately described soil moisture and salinity so that germination could be predicted; monthly sampling would have missed the low-salinity and high-moisture events that trigger germination.