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1.
Influence of canopy and topographic position on soil moisture response to rainfall in a hilly catchment of Three Gorges Reservoir Area,China 总被引：2，自引：0，他引：2
Liu Muxing Wang Qiuyue Guo Li Yi Jun Lin Henry Zhu Qing Fan Bihang Zhang Hailin 《地理学报(英文版)》2020,30(6):949-968
Rainfall provides essential water resource for vegetation growth and acts as driving force for hydrologic process, bedrock weathering and nutrient cycle in the steep hilly catchment. But the effects of rainfall features, vegetation types, topography, and also their interactions on soil water movement and soil moisture dynamics are inadequately quantified. During the coupled wet and dry periods of the year 2018 to 2019, time-series soil moisture was monitored with 5-min interval resolution in a hilly catchment of the Three Gorges Reservoir Area in China. Three hillslopes covered with evergreen forest(EG), secondary deciduous forest mixed with shrubs(SDFS) and deforested pasture(DP) were selected, and two monitoring sites with five detected depths were established at upslope and downslope position, respectively. Several parameters expressing soil moisture response to rainfall event were evaluated, including wetting depth, cumulative rainfall amount and lag time before initial response, maximum increase of soil water storage, and transform ratio of rainwater to soil water. The results indicated that rainfall amount is the dominant rainfall variable controlling soil moisture response to rainfall event. No soil moisture response occurred when rainfall amounts was 8 mm, and all the deepest monitoring sensors detected soil moisture increase when total rainfall amounts was 30 mm. In the wet period, the cumulative rainfall amount to trigger surface soil moisture response in EG-up site was significantly higher than in other five sites. However, no significant difference in cumulative rainfall amount to trigger soil moisture response was observed among all study sites in dry period. Vegetation canopy interception reduced the transform ratio of rainwater to soil water, with a higher reduction in vegetation growth period than in other period. Also, interception of vegetation canopy resulted in a largeraccumulated rainfall amount and a longer lag time for initiating soil moisture response to rainfall. Generally, average cumulative rainfall amount for initiating soil moisture response during dry period of all sites(3.5–5.6 mm) were less than during wet period(5.7–19.7 mm). Forests captured more infiltration water compared with deforested pasture, showing the larger increments of both soil water storage for the whole soil profile and volumetric soil water content at 10 cm depth on two forest slopes. Topography dominated soil subsurface flow, proven by the evidences that less rainfall amount and less time was needed to trigger soil moisture response and also larger accumulated soil water storage increment in downslope site than in corresponding upslope site during heavy rainfall events. 相似文献
2.
1974～2007年若尔盖县湿地变化研究 总被引：2，自引：0，他引：2
选取1974～2007年期间的5期多源遥感影像数据作为数据源,在解决多源遥感影像(MSS、TM、ETM+和CBERS影像)和多时相(1月、6～9月)影像数据的遥感分类问题上,以模糊物元理论来解释多数据源和多时相数据之间的关系,设计关联函数概率转化的多源遥感数据分类物元模型,利用该模型得到了若尔盖县湿地区1974～2007年期间的地物类型分布,并进行了变化检测和概率修正算法处理,揭示了1974～2007年若尔盖县湿地变化特征.2007年,若尔盖县各类型湿地的面积占湿地总面积的比例分别为河流和湖泊1.37％、泥炭沼泽4.23％、沼泽化草甸9.91％和湿草甸6.04％.1974～2007年期间,若尔盖县的河流和湖泊、泥炭沼泽、沼泽化草甸和湿草甸的面积在减少,以旱生植物为主的中、低覆盖度草地、居民点、建筑用地和沙地面积在增加.泥炭沼泽主要向沼泽化草甸、湿草甸演替.人为因素则是在较短时间尺度上影响湿地变化的主要驱动力.不确定性问题仍是遥感分类与变化检测存在的主要问题. 相似文献
3.
利用微波遥感土壤水分产品监测东北地区春涝范围和程度 总被引：2，自引：0，他引：2
地表土壤水分是判断农田涝害的直接数据源,以欧洲太空局1978~2010 年微波遥感土壤水分产品、2013 年SMOS MIRAS L3 级土壤水分产品和气象站点的月降水数据为基础,结合土壤水分距平指数和土壤水分异常指数,分析2013 年东北地区春涝影响范围和严重程度。结果表明:① 东北地区以黑龙江省受涝面积最大,约11 万km2,约占黑龙江省总面积的1/4;② 比较多年的月降水数据与涝灾程度,发现冬春季节强降水是引发春涝的主要原因之一;③ 春涝的严重程度与高程呈现负相关关系,涝灾区域多集中在高程500 m以下。 相似文献
4.
Because of the aridity of the Namib Sand Sea, it has long been assumed that decomposition of buried plant material was largely independent of rainfall. Losses were attributed to consumption by detritivores that forage year-round. Moisture-limited micro-organisms were reported to occur in low densities in Namib sands, supporting the assumption that rainfall was insignificant in regulating decomposition. Observations of abundant macrofungal fruiting from buried plant material and herbivore dung, following a 12 mm rain, suggested the importance of rain-induced decomposition had been underestimated. We used cellulose substrates to compare material loss during dry periods and following differing amounts of rain. Strips of cotton cloth and filter paper, buried at 10 cm depths at five disjunct locations, were sequentially removed over 10 months. A period of at least 170 days elapsed before rains, ranging from 4–46 mm, fell at all locations. Material loss during the dry period averaged 8·2% (range 0–16·7%), and was attributed to macrodetritivore consumption. In marked contrast, an average of 84·1% of the material (range 64·7–97·2%) was lost following rains greater than 9 mm. Wet substrates were heavily colonized by fungi, and termites and tenebrionid beetle larvae were observed feeding on fungus-colonized substrates. Stepwise regression analysis revealed that rainfall, rather than duration of burial, was the primary factor determining substrate loss in the Namib Sand Sea. Although rain events are infrequent and ensuing periods of moist soil are brief, substrate loss following rains is highly significant relative to that occurring in the absence of rain. In contrast to more mesic deserts, rainfall is an important trigger of decomposition in the Namib Sand Sea where soils are too dry to support significant decomposition, except when episodically moistened by rain. 相似文献
5.
快速、无损监测农田土壤水分含量,是智慧农业的重要研究内容。以新疆南疆阿拉尔国家农业科技园区膜下滴灌棉田为研究对象,运用EM38-MK2大地电导率仪快速、高效的获取了4组不同时期的棉田土壤表观电导率数据,并同步采集表层土壤(0~20 cm)样品,通过构建表观电导率数据与室内测定含水量数据间的反演模型获取了测点的含水量数据,并按照土壤水分干旱分级标准对研究区土壤水分进行划分,综合利用GIS软件和地统计方法对土壤水分的时空变异性进行研究。结果表明:4个时期的土壤水分反演模型决定系数均大于0.80且均方根误差(RMSE)和平均绝对百分误差(MAPE)均较小,表明反演模型精度较高,土壤表观电导率与表层土壤水分相关性较好;不同时期土壤含水量数据表明土壤水分具有很强的时间变异性,变异性由中等变异转变为弱变异再转变为中等变异;受人为灌溉等因素的影响,变异函数模型也存在差异;半方差分析中4个时期的土壤水分块金值与基台值之比均大于75%,表明土壤水分在空间上趋近于弱空间相关;高程反距离权重(IDW)插值图及水分克里格插值图表明微地形是影响土壤水分分布的重要因素。本研究可为干旱区膜下滴灌棉田土壤水分动态监测提供重要的方法支撑,从而更好地指导农业灌溉。 相似文献
6.
土壤呼吸的微小变化会对大气CO2浓度产生重大影响,尤其在极端干旱区。通过对黑河下游额济纳旗四道桥的混合林、胡杨、柽柳、农田及裸地的土壤呼吸进行研究,结果表明：2014 年夏季5 种不同植被类型的土壤呼吸速率大小排序：胡杨柽柳混合林 > 柽柳 > 农田 > 胡杨 > 裸地,各类型的5 cm处土壤温度和湿度无明显变化规律,土壤温度在22～35 ℃,土壤湿度集中在13%～61%的变化范围。探究了5 种不同植被类型的土壤呼吸速率与土壤温度、土壤湿度、地表温度、空气温度及空气湿度的线性相关关系,发现它们的土壤呼吸速率与土壤温度、土壤湿度、空气温度、空气湿度之间无显著相关（P>0.05）,表明水热因子对土壤呼吸的影响具有很大的不确定性。 相似文献
7.
为分析不同高寒植物群落优势种的光合特性，探究影响光合作用的主要环境因子，选择若尔盖高原同纬度同海拔的沼泽湿地、湿草甸和干草甸样地，对比研究典型植物群落优势种木里苔草（Carex muliensis）、四川嵩草（Kobresia setchwanensis）和垂穗披碱草（Elymus nutans）光合日变化。结果表明：（1）由于水分条件差异显著（P<0.05），沼泽湿地优势种木里苔草的净光合速率（Pn）日变化呈单峰趋势，而湿草甸和干草甸优势种Pn则为双峰曲线，存在光合“午休”现象。（2）水分利用效率（WUE）日均值表现为干草甸优势种 > 湿草甸优势种 > 沼泽湿地优势种；各群落优势种光能利用效率（LUE）日均值无显著差异。（3）沼泽湿地优势种Pn主要受光合有效辐射（PAR）、气温（Ta）和空气相对湿度（RH）的影响；干草甸Ta和PAR为主要环境因子，湿草甸影响优势种Pn的主导因素为PAR。 相似文献
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9.
西江和北江及珠江三角洲西北部汇流区广泛发育全新世的泥炭-淤泥腐木地层,结合剖面的沉积相特征和14C测年数据,对全新世沉积环境和含腐木地层的分布和环境变化进行探讨,获得以下认识：1）在西江和北江下游海侵北界以上的陆相沉积序列中,厚层泥炭主要形成于中晚全新世（7.5―1.5 cal. ka B.P.）,集中堆积时间为5.0―1.5 cal. ka B.P.;2）珠江三角洲全新世海侵对三角洲边缘区陆相泥炭沼泽的形成起决定性作用,早全新世（约9―7 cal. ka B.P.）三角洲西北端的高速率河口相粉砂黏土沉积为后来的半咸水沼泽发育奠定了淤泥深厚的物质基础,而西江―北江下游陆相洪冲积或河漫滩沉积则在8 cal. ka B.P.左右开始发育,也为之后的水松泥炭沼泽繁盛奠定了基础;3）三水西南一带是中全新世西江―北江下游泛滥平原至古河口湾的过渡区,潮汐流与河流的双重作用是造成三角洲边缘区大面积泥炭沼泽湿地形成的主要原因;4）泥炭湿地生态环境大多在2.0―1.5 cal. ka B.P.前后在西江和北江被高位洪水平流沉积物埋藏,而在三角洲区域多被泛滥平原洪积物覆盖。多数剖面泥炭腐木迁移的原因与三角洲的快速加积作用导致的潮流与河流空间位置平衡被破坏和水文条件改变有关,晚全新世不断增强的人类农业活动和森林破坏与水土流失也是导致三角洲天然沼泽湿地消失的重要原因。 相似文献
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11.
干旱区内陆河流域荒漠河岸林群落生态过程与水文机制研究 总被引：15，自引：11，他引：4
干旱区内陆河流域生态水文过程研究已成为当今地理学、生态学研究的焦点,是开展生态恢复研究的重要内容。塔里木河下游断流河道的生态恢复是以沿自然河道生态输水为主要形式的,因此,有必要加深对塔里木河下游荒漠河岸林群落生态过程与水文机制的认识。在对塔里木河下游荒漠河岸林植被生态退化及其退化原因分析的基础上,综述了塔里木河下游典型植物生态水位的研究进展,阐述了植物适宜生态水位、胁迫地下水位和临界地下水位研究的阶段性成果,并进一步展望了未来研究的焦点问题。指出了群落生态水位、植被群落与土壤水分、盐分异质性的关系,提出植物水分利用机制是群落生态过程与水文机制研究的核心问题。 相似文献
12.
山东湿地植被类型和演替规律的研究 总被引：1，自引：1，他引：1
山东湿地共分布有湿地高等维管植物70科277种、苔藓植物12科24种,在植物种类组成上以莎草科和禾本科植物等最为丰富。植被类型有灌丛、灌草丛、草甸、盐生、沙生、沼生和水生植被等7种。湿地植被的分布既受地理位置、气候、海拔等影响,又受制于水分、土壤和土壤含盐量等因素。湿地演替是植物群落的演替过程,即随着湿地的发育,特别是土壤水分和营养的变化,导致植物种类和群落发生改变的过程。湿地植物群落演替是气候、水文以及地貌、土壤等自然要素综合作用的结果,客观反映了湿地的形成、发育与演替过程。 相似文献
13.
大小兴安岭高位泥炭孢粉纪录及泥炭发育和演替过程研究 总被引：9，自引：2，他引：9
根据３个高位泥炭剖面孢粉分析和＾１４Ｃ测年数据，以及植物残体、微量元素与营养元素等分析相互印证，揭示大小安岭分别５０００ａ Ｂ．Ｐ．和２７００ａ Ｂ．Ｐ．以来孢粉组合特征和植物群与气候演变过程。分析表明大小兴安岭高位泥炭形成了低、中和高位发育阶段的演变，大兴安岭高位泥形成晚于小兴安岭。１３００ａ Ｂ．Ｐ．大小兴安岭普遍发育高位泥炭。该区图强和汤北（９４－Ａ）高位泥炭剖面分别是大小兴安岭高位泥炭标准 相似文献
14.
《自然地理学》2013,34(1):54-78
The sensitivity of the near-surface weather variables and small-scale convection to soil moisture for Western Kentucky was investigated with the aide of the MM5 Penn State/NCAR mesoscale atmospheric model for three different synoptic conditions in June 2006. The model was initialized with FNL reanalysis from NCEP containing soil moisture data calculated with the Noah land surface model. Dry and wet experiments were performed in order to find the influence of soil moisture specification on boundary layer atmospheric variables. Dry experiments showed less available atmospheric moisture (between 2 and 6 g kg-1) at near-surface levels during all synoptic events consistent with slightly deeper boundary layers, higher lifting condensation levels and a larger Bowen ratio. As expected, precipitation rates were generally smaller than those of the control simulation. However, during a moderately strong synoptic event in early June, the dry experiments displayed larger precipitation rates compared to the control experiment (up to 5 mm in 3 hr) as the soil volumetric fraction was decreased from 0.05 to 0.15 (m3 m-3) with respect to the control simulation. Precipitation rates in wet experiments were also modulated by characteristics of synoptic conditions. In early June, precipitation rates slightly were larger than the control run (from 0.2 mm 3 h-1 to 1.4 mm 3 h-1) while in the other periods precipitation was reduced significantly. Both dry and wet anomaly experiments experienced reduced precipitation for different reasons. It was found, lifting condensation level, CAPE and low Bowen ratio were not sensitive markers of changes in soil moisture. Equivalent potential temperature was a better indicator of precipitation changes among all experiments. The controlling factor in these responses was the soil moisture content forcing vertical velocities. Thermodynamic conditions such as local stability played a less substantial role in controlling the precipitation processes. It was found that the response of planetary boundary layer variables under a variety of soil moisture conditions can be modified due to degree of synoptic forcing. Weak-to-moderate forcing favored convection while strong synoptic forcing tended to suppress it under dry soil moisture conditions. Wetter soils did not produce a response in horizontal wind fields as large as under the drier soils. 相似文献
15.
Throughfall, stemflow, evapotranspiration and infiltration are likely to vary with forest types, and consequently affect soil moisture regimes in different soil layers. In this study, the spatial and temporal characteristics of soil moisture were investigated to understand variations in soil moisture in three typical forests, including Phyllostachys pubescens forest (abbreviated as PPF), Schima superba forest (abbreviated as SSF) and Cunninghamia lanceolata forest (abbreviated as CLF) in the upper reaches of Lijiang River basin in southern China. The results showed that, (1) Litterfall and soil physical properties differed significantly in the three typical forests. Infiltration capacity in SSF was more favorable to soil moisture than in PPF and CLF. (2) Large variations were found in soil moisture at different forest stands and depths. Due to complicated vertical structures, there were obvious differences in soil moisture from the 0-20 cm soil layer to the 50-80 cm soil layer. (3) Average soil moisture in each layer was higher in SSF than in PPF and CLF. (4) Soil moisture in different layers correlated closely with precipitation (P<0.01) and the three typical forests had the same change trends with rainfall during the studying period. (5) In topsoil, soil moisture was influenced by soil properties which were mostly determined by litterfall, while in deep soil, soil moisture was affected by variations of soil characteristics, which were mostly determined by root distribution. This study provides a scientific basis for better understanding the relationships between forest vegetation and its hydrological effects, helping to facilitate water resources conservation and achieving wise forest management in the upper reaches of Lijiang River basin. 相似文献
16.
山丘型地区钉螺孳生数量与植被和土壤环境因子的关系 总被引：3，自引：0，他引：3
本文研究了四川仁寿山丘型地区钉螺孳生与植被和环境因素的关系。结果表明:(1)草本群落物种丰富度、草本盖度、草本高度影响钉螺的孳生数量,钉螺分布适宜的草本群落的物种丰富度为4～14,草本群落盖度为60%～100%,高度为20～50cm;(2)土壤水分含量、温度和盐分均影响钉螺的孳生数量,钉螺分布最适宜的土壤水分含量为20%～60%,温度为15～30℃,盐分为60～120ms/m;(3)各环境因子和钉螺密度曲线可以看出,物种丰富度、草本高度、草本盖度、土壤水分含量、土壤温度和盐分含量与钉螺密度间均呈现抛物线或抛物线状曲线;(4)在样地和样方水平,土壤水分含量和钉螺密度存在稳定的线性相关关系,表明土壤水分含量是影响钉螺孳生的主导因素。因此,钉螺对各环境因素存在适应范围,表明钉螺对潮湿环境具有严格的选择性和依赖性,这种生态特性和钉螺本身的生物学特征密切相连。 相似文献
17.
模拟增雨对荒漠土壤古菌多样性的影响 总被引：1，自引：0，他引：1
为探讨生长季增雨对荒漠土壤中古菌群落结构的影响，根据内蒙古磴口多年平均降水量，设计了模拟增雨试验，包括对照、2个增雨时段（生长季前期与后期）、每个时段2个增雨梯度（50%与100%）共计5种处理。增雨后提取荒漠土壤总DNA，对古菌群落编码16S rRNA基因的V4区进行Hiseq测序，分析古菌群落丰度、多样性及结构组成等。结果表明：该地区荒漠土壤中古菌群落均以奇古菌门（Thaumarchaeota）和广古菌门（Euryarchaeota）为优势菌群。NMDS和3种非相似性分析（MRPP、ANOSIM和Adonis）表明，生长季前期增雨未显著改变古菌的群落结构，生长季后期增雨显著改变了古菌的群落结构，当生长季后期增雨量达到100%时，古菌丰富度和多样性显著降低。与氨氧化过程密切相关的奇古菌门（Thaumarchaeota）相对丰度在生长季后期100%增雨条件下显著增加，将促进荒漠土壤的硝化过程。Mantel检验发现荒漠土壤古菌群落结构受土壤湿度、土壤温度、土壤硝态氮含量的影响。未来全球变化背景下降水格局变化将会对荒漠土壤古菌群落结构产生影响，并可能影响氮循环过程。 相似文献
18.
三江平原环型湿地土壤温度梯度的研究 总被引：21，自引：3，他引：18
三江平原环型湿地是低温 (碟型洼地 )和高温 (岛状林 )两种环境组合的典型区 ,为了研究三江平原环型湿地土壤温度梯度特征 ,对环型湿地 4种群落的土壤温度进行了观测。结果表明 ,由环型湿地的中心到边缘 ,土壤温度逐渐升高 ,土壤温度垂直变异由大逐渐减小。各群落深层土壤温度日变化不明显 ,而季节变化较明显 ,不同群落间深层土壤温度水平变异和垂直变异差异以 6月最大 ,8月和 10月份差异较小。这是由于环型湿地的中心到边缘 ,土壤层的厚度逐渐变薄 ,土壤水分含量逐渐降低 ,泥炭层的厚度逐渐变薄以至消失 ,冻结层融解时间逐渐推迟造成的。环型湿地中心的致冷效应有利于有机质的积累和保持环型湿地生态系统的稳定性。研究环型湿地的土壤温度梯度有助于从水热角度来进一步揭示沼泽湿地的生态环境效应 ,为湿地的保护及合理利用提供科学依据。 相似文献
19.
基于卫星遥感和再分析数据的青藏高原土壤湿度数据评估 总被引：5，自引：1，他引：4
土壤水是地表与大气在水热交换方面的关键纽带,是关键水循环要素,更是地表产汇流过程的关键控制因子。青藏高原是地球第三极,也是亚洲水塔,探讨青藏高原土壤水变化对于探讨青藏高原热力学特征变化及其对东亚乃至全球气候变化的影响具有重要意义,而获取高精度长序列大尺度土壤水数据集则是其关键。本文利用青藏高原100个土壤水站点观测数据,从多空间尺度（0.25°×0.25°,0.5°×0.5°,1°×1°）、多时间段（冻结和融化期）等角度,采用多评价指标（R、RMSE、Bias）,对多套遥感反演和同化数据（ECV、ERA-Interim、MERRA、Noah）进行全面评估。结果表明：① 除ERA外,其他数据均能反映青藏高原土壤水变化,且与降水量变化一致。而在那曲地区,遥感反演和同化数据均明显低估实测土壤水含量。从空间分布来看,MERRA和Noah与植被指数最为一致,可很好地反映土壤水空间变化特征;② 青藏高原大部分地区土壤水变化主要受降水影响,其中青藏高原西部边缘与喜马拉雅地区土壤水变化则受冰雪融水和降水的共同影响;③ 除阿里地区外,大部分遥感反演和同化数据在融化期与实测土壤水相关性高于冻结期,其中在那曲地区,遥感反演和同化数据均高估冻结期土壤含水量,却低估融化期土壤含水量。另外,遥感反演和同化数据对中大空间尺度土壤水的估计要好于对小空间尺度土壤水的估计。本研究为青藏高原土壤水研究的数据集选择提供重要理论依据。 相似文献
20.
Hajah Dulima Jali 《湿地科学》2007,5(1):13-19
Changes in redox potential(RP)are the resultof the combined effects between many chemical,physical and biological processes in the soil.Soil oxi-dation and reduction depend on soil respiration,diffu-sion of oxygen and carbon dioxide in soil and onchanges … 相似文献