Effects of forest cover type and ratio changes on runoff and its components

Changes in forest cover can affect not only the total runoff from a watershed, but also the runoff components (e.g., surface runoff, interflow, groundwater flow). In this study, based on the WetSpa model simulation method and the recursive digital filtering (RDF) method, the Banchengzi watershed in the mountainous region of Beijing, China, was selected to investigate how changes in forest cover type and cover percentage affect total runoff, surface runoff, interflow, and groundwater flow through scenario settings. Our results show that the difference between the WetSpa model and the RDF method for separating runoff components is small, with only 4.7% and 0.4% difference between the calibration and validation periods. Total runoff in different forest types followed the order shrub forest > coniferous forest > mixed forest > broadleaf forest. Regarding runoff components, the proportions of baseflow (sum of interflow and groundwater flow) to total runoff were 61.1% and 60.8% for broadleaf and mixed forests, which was significantly higher than those of 53.0% and 43.1% for coniferous and shrub forests. However, the proportion of shrub forest baseflow was high in wet years, and that of broadleaf forest baseflow was high in normal and dry years. The proportions of interflow and groundwater flow from various forest cover types to total runoff continued to increase with increasing forest cover rate. Our results have important implications for the implementation of afforestation projects and forest conservation programs, contributing to water resource regulation and ecosystem protection in watersheds.     

密云水库集水区森林的水文作用——以北庄小流域为例

 从径流小区、天然坡面径流场及流域3个尺度,对试验流域内森林植被对水文特征的影响进行研究。结果表明:试验流域2004年年径流系数为0.43,2005年为0.10,流域内产沙均为0。有林与无林2个天然坡面径流场相比,降雨与径流系数之间呈二次曲线关系,有林坡面径流系数2003年最大,为0.72,无林坡面径流系数2003年最大,为0.97,有林坡面产沙模数明显低于无林坡面,2004年产沙削减率为18.7%,2005年产沙削减率为77.3%。不同树种组成的径流小区产流量排序为板栗>刺槐>油松。对流域水质抽样检验结果表明,超标指标主要是总氮和总磷,其余水质指标均达到一类水质标准。总体来看,流域内森林植被的增加,明显增强林地的调洪、蓄水、减沙和改善水质的功能。     

诺敏河流域土地利用与覆被变化及其对水文过程的影响

流域土地利用/覆被变化及其水文效应是当前全球变化研究的重要内容.为正确认识大兴安岭森林采伐对水文过程的影响,以诺敏河流域为例,在遥感和地理信息系统技术支持下,结合地形图和卫星遥感影像数据,获取1954-2005年诺敏河流域5期土地利用/覆被数据,在GIS空间分析模块下分析诺敏河流域土地利用/覆被变化过程,并探讨土地利用/覆被变化对水文过程的影响.结果表明,近50 a诺敏河流域土地利用方式发生了明显变化,林地和草地分别减少1 940.1 km2和748.99 km2,与林草地的大面积减少相对应,耕地面积增加2 741.7 km2.自1998年实施大兴安岭天然林保护工程以后,林地采伐和耕地开垦速率明显降低;土地利用/覆被变化影响年径流量,林地大规模减少、耕地明显增加的后期土地利用较前期径流量有所增加,且随着降雨的增多,土地利用变化对径流的影响效应随之增强.同一降雨条件下土地利用/覆被变化对径流的影响在生长季具有明显差异.     

Responses of Riverine Macroinvertebrates to Zinc in Natural Streams: Implications for the Japanese Water Quality Standard

We conducted a field survey in Japanese streams and rivers to generate useful information about whether the Japanese water quality standard for zinc (Zn) in the freshwater environment (30 μg/L) is over- or underprotective of the populations and communities of lotic benthic macroinvertebrates. Many macroinvertebrate populations were reduced and community characteristics were altered at two polluted sites with Zn concentrations above 1,000 μg/L as compared with control sites with Zn concentrations below 30 μg/L. In contrast, at least one site among three polluted sites with Zn concentrations of 80–126 μg/L experienced noncritical effects (i.e., no significant difference was observed between the sample mean at a polluted site and that at the control sites, and the sample mean was within the minimum–maximum range of those at the control sites) for most of the ten community metrics for diversity and abundance. In addition, the abundances of 95% of the dominant taxa were not always significantly lower at more than one polluted site (Zn concentrations, ≥80 μg/L). Our results suggest that Zn concentrations below approximately 100 μg/L are likely to protect most aspects of richness and abundance of the riverine macroinvertebrate communities in the study areas. This study shows a case that the Japanese Zn standard is likely overprotective of the macroinvertebrate populations and communities.     

赤水河流域生态水文过程对土地利用/覆被变化的响应

[目的]分析赤水河流域近十年土地利用变化特征,探索生态文明建设背景下水资源空间分配与水文循环过程,以期为流域提供合理的土地利用规划依据及促进流域的可持续发展.[方法]以赤水河流域为研究对象,在1967～2020年的气候背景下,基于SWAT(Soil and Water Assessment Tool)模拟了流域2008...     

嫩江流域土地覆被变化对径流量的影响分析

以泥鳅河和科洛河流域为例分析了土地利用/土地覆被变化与河流径流量的关系。森林覆被变化导致了流域用水量的减少,而这部分并没有形成地表径流,而是存储在了森林和草地转变成的沼泽湿地中。科洛河流域耕地和林地面积的减少增加了地表径流,而且林地变化的影响大于耕地的变化。流域土地覆被变化与流域河流径流量的关系复杂,并非单一的覆被类型变化起主导作用,而是各种变化耦合作用影响了河流径流,但其中影响最为显著的是沼泽湿地的变化。     

Soil chemical and biological characteristics influence mineralization processes in different stands of a tropical wetland

In the Caribbean, Pterocarpus officinalis swamp forest, a coastal freshwater wetland, has been locally transformed by human activities into Colocasia esculenta monoculture (under the swamp forest) or pasture (where deforestation has occurred). The aim of this study was to evaluate the impact of three land uses of this tropical wetland (swamp forest, C. esculenta monoculture and pasture) on soil abiotic and biological features. We hypothesized that increasing the level of ecosystem alteration by agricultural intensification would negatively impact soil chemical characteristics, soil fauna diversity and carbon mineralization. As expected, land use significantly affected soil characteristics and changes followed the increasing intensity of land use. The ‘undisturbed system’, that is swamp forest, was characterized by a large soil organic matter content, a high level of soil moisture, a small phosphorus content and a slightly lower pH. These characteristics were correlated with a small faunal abundance and diversity and slow carbon (C) mineralization. The ‘low disturbance system’, that is C. esculenta monoculture, was the closest to swamp forest characteristics and changes between the both systems principally concerned a very slight decrease in organic matter content and very small increase in C mineralization and Coleoptera diversity. By contrast, all parameters (soil chemical characteristics, C mineralization and faunal abundance and diversity) were impacted in the most intensive land‐use, pasture. Our study confirmed that agricultural practices have an influence on soil fauna and C mineralization processes in wetlands. Moreover, our study suggested that a C. esculenta traditional agroecosystem under swamp forest cover could be considered as an ‘eco‐friendly’ agricultural practice.     

Variability in Soil Hydraulic Conductivity and Soil Hydrological Response Under Different Land Covers in the Mountainous Area of the Heihe River Watershed,Northwest China

Understanding the variability in soil hydraulic conductivity in the mountainous headwaters is critical to the modeling of mountainous runoff and the water resources management of river basins, especially in the arid and semiarid areas. In this study, a total of 32 soil profiles with five layers within 0–70 cm were sampled under different land cover types: forest, meadow, high coverage grassland (HCG), medium coverage grassland (MCG), and barren land in the upper stream of the Heihe river watershed, Northwest China. Saturated hydraulic conductivity (K _S) was measured for each sample. The vertical variation of K _S and soil hydrological response under different land covers were analyzed. Results show that K _S value in layer 5 was significantly lower than the values of above four layers. K _S decreased in the order of forest, meadow, HCG, MCG, and barren land, corresponding to the degree of vegetation degradation. The K _S decreased with depth under forest, HCG, and barren land, but increased first and then decreased under meadow and MCG. The dominant stormflow paths for different land covers were different: forest was dominated by deep percolation, HCG was dominated by subsurface flow (SSF), meadow was prevailed by Hortonian overland flow and had no SSF, while MCG and barren land were also dominated by Hortonian overland flow, but still formed SSF. This result provides important information for improving the accuracy of mountainous hydrological modeling and, in turn, leading to sustainable management of water resources in the study watershed. Copyright © 2016 John Wiley & Sons, Ltd.     

Decoupling effects of driving factors on sediment yield in the Chinese Loess Plateau

Investigations of runoff and sediment yield changes and their relationships with potential driving factors provide good insights for understanding the mechanisms of hydrological processes. This study attempted to present a comprehensive investigation on the spatiotemporal variations of sediment yield in the Loess Plateau using continuous observed data at 46 hydrological stations during 1961–2016, and its responses to changes of precipitation, land use/cover and vegetation cover were analyzed by using the Partial Least Squares-Structural Equation Model (PLS-SEM). The results indicated that sediment yield reduced pronouncedly during 1961–2016 in the Loess Plateau, and 77.9% of this variation was explained by the combined effects of precipitation, land-use change, vegetation dynamics and runoff reduction. Indirect effects of precipitation, land-use change, and vegetation cover on sediment yield were 0.242, ?0.528 and ?0.630 (P < 0.05), respectively, and direct effect of runoff on sediment yield was 0.833 (P < 0.05). According to the Pearson Correlation Coefficient, the strongest positive correlation existed between annual sediment yield and runoff (r = 0.88, P < 0.05), followed by vegetation cover (r = ?0.47, P < 0.05) and land-use change (i.e. forest land and grassland) suggesting their significant trapping effects on soil erosion. However, lower correlations were examined between sediment yield and precipitation indices (?0.14<r < 0.34), and a relatively higher relationship was examined between sediment yield and heavy rainfall (P₂₅) (r = 0.34). Overall, changes in runoff and land-use/vegetation cover well explained variations in sediment yield in the Loess Plateau. The findings are expected to provide scientific and technical support for future soil and water conservation planning in the Loess Plateau, and are valuable for sustainable water resources and sediment load management in the Yellow River Basin.     

基于SWAT模型的长江源土地利用/土地覆被情景变化对径流影响研究

土地利用/土地覆被变化对流域水资源循环过程及配置影响显著。为了研究土地利用/土地覆被情景变化对径流影响情况,以长江源流域为例,构建了适合该流域的分布式水文模型(SWAT),并模拟了不同土地利用/土地覆被情景下的流域年均径流量和径流深。模拟结果如下:当流域林地和草地面积增加到最大,径流量减少了16.7%,达到304.12m3/s,径流深减少14.02mm;当林地和草地面积减少,并逐步变为沙地、裸地,流域径流量增加16.1%,达到424.32m3/s,径流深也增加了13.49mm;当林地和草地面积减少到无植被覆盖,将使流域径流量增加28.4%,达到469.67m3/s,径流深增加23.88mm;在草地覆被最佳状况下,径流量有所增加,但增加幅度不大,只有5.6%,达到385.98m3/s,径流深增加4.72mm。综上所述,长江源流域林地和草地面积增加,导致径流减少,而沙地和裸地面积增加导致径流量增加。     

三种土地覆盖遥感数据在中国区域的精度分析

土地覆盖遥感数据的精度分析是数据应用的前提和基础。该文以中国科学院资源环境科学数据中心提供的2000年中国土地覆盖数据作为参考,基于对土地覆盖类型的归并,在各种土地覆盖类型的分布面积、空间位置等方面分析了GLC2000、MODIS V004和MODIS V005三种数据描述中国土地覆盖状况的能力,并引入差异性指数,深入分析影响土地覆盖数据精度的原因,得到以下主要结论:总体上各数据均能反映中国主要土地覆盖类型的分布情况,GLC2000、MODIS V004和MODIS V005数据的总体精度分别为62.8%、61.7%和61.9%;3种数据的乔木林地面积较参考数据均偏大,而建筑用地、湿地和水体的面积均偏小;乔木林地、灌木草地、耕地和裸地冰川的精度较高,建筑用地和湿地的精度较低;GLC2000数据在省级水平上对乔木林地和耕地的描述最准确,MODIS V005数据的平均用户精度和生产者精度最高;土地覆盖数据的精度随着数据差异性指数的增加而降低,随着差异性指数为1的区域面积比例的增加而升高;MODISV005数据的精度受土地覆盖差异性的影响相对较小。     

Successional changes in soil,litter and macroinvertebrate parameters following selective logging in a Mexican Cloud Forest

The environmental and vegetation shifts associated with logging disturbance and secondary succession in Tropical Montane Cloud Forests have been studied in detail, however little is known about the consequences that these changes have for the soil system. The present study was undertaken to determine the impact of selective logging and subsequent secondary succession on soil microenvironmental conditions, leaf litter quality and quantity, soil nutrient concentration and soil and litter macroinvertebrate community composition. The study was carried out in three successional chronosequences, two recently logged sites and two pristine tropical mountain cloud forest sites in Oaxaca, Mexico. Results showed that selective harvesting of Quercus spp. trees caused an increase in soil temperature of ca. 4 °C that is not completely reversed after 100 years of succession. During 100 years of secondary succession litter diversity increased and soil organic matter accumulated (16.4% increase in total C). The availability of cations (Ca, Mg, Na, and K) in the topsoil decreased by more than 50% as a result of logging, and only Mg increased again between 75 and 100 years after disturbance.Pristine cloud forests sustain a diverse litter and soil macroinvertebrate community, but its composition and diversity was negatively affected by logging. The effect of Quercus harvesting activities on the litter community was apparent within 2 months of disturbance (total abundance declined by ca. 65%, higher taxa richness by ca. 10% and diversity by ca. 35%). For the soil community there was a time-lag in the effect of logging. Two months after disturbance there was no significant effect on the soil community but 15 years after abandonment, total macroinvertebrate abundance in the soil was ca. 80% lower and higher taxa richness ca. 30% lower compared to undisturbed sites. Full recovery of the macroinvertebrate community composition appeared to take more than 100 years both in the litter and soil. Reduced abundances of Coleoptera and Enchytraeidae were apparent even after 100 years of succession. The endemic earthworm Ramiellona wilsoni was found almost exclusively in the pristine forests and therefore its abundance could be used as a sensitive indicator of disturbance in these forests.     

林下秸秆覆盖种植大球盖菇对苦驴河源头坡地清水产流的影响

[目的]探索秸秆覆盖种植大球盖菇模式对经济林(尤其是刚刚荒改坡的经济林)清水产流和改土控草的影响,为坡地水源涵养、生态保育、控草保肥提供技术支撑。[方法]在派河上游苦驴河的源头,选取2组不同种类的坡地经济林,利用秸秆覆盖种植大球盖菇技术,在大球盖菇生长的不同时期对该区域坡地水质、土壤有机质和杂草多样性进行分析。[结果]采用秸秆覆盖种植大球盖菇的技术,平均能有效降低该地区水中总氮42.68%～50.47%,总磷45.72%～46.74%和悬浮物(SS)33.41%～36.58%的含量,同时增加土壤有机质的含量,平均增长了10.17%～16.42%,减少该区域杂草多样性和种类,有效降低了该地水肥流失,可在较短时间内无害且快速地增加该区域清水产流能力。[结论]采用秸秆覆盖种植大球盖菇的技术,能有效降低坡地径流水中总氮、总磷和SS的含量,同时增加土壤有机质的含量,减少该区域杂草多样性和种类,起到控制水肥和水土流失作用,在当年荒改坡的坡地上,该作用更加明显。     

Runoff generation in a degraded Andean ecosystem: Interaction of vegetation cover and land use

Tropical mountain regions are affected by rapid land use/-cover change, which may threaten their (eco-)hydrological functions. Although there is a growing interest in evaluating the effect of land use/-cover change on mountain hydrology, quantitative assessments of the impact of land use/-cover on hydrological processes are hampered by the lack of field measurements characterizing runoff generation processes. In this paper, we present results from field experiments of rainfall runoff mechanisms in the southern Ecuadorian Andes. A rainfall simulator was used to quantify the hydrological response of distinct land use/-cover types to intense rainfall (about 40 mm/h). The rainfall runoff experiments indicate that degraded and abandoned land generate surface runoff within a few minutes after the start of the rainfall event. These lands have a very rapid and sharp hillslope hydrological response, as Hortonian overland flow is the dominant runoff generation mechanism. In contrast, surface runoff on arable and rangelands is rare, as their soils are characterized by a high infiltration capacity (i.e. > 29 mm/h). Our experiments provide evidence that runoff generation in degraded Andean ecosystems is mainly controlled by the surface vegetation cover and land management. When reducing the surface vegetation cover, the soil is increasingly affected by rapid hillslope runoff as the presence of large amounts of smectites in the outcropping soft rocks makes the material very prone to sealing and crusting, thereby enhancing runoff generation.     

东南沿海地区小流域土地利用/覆被变化的水文效应

[目的]研究我国东南沿海小流域土地利用/覆被变化的水文效应,为该区水土资源合理配置和可持续发展提供科学依据。[方法]以东南沿海福建省晋江山美水库集水区为例,运用SWAT水文模型。[结果](1)研究区土地利用变化表现为林地转向园地和建设用地、耕地转向建设用地的特征。(2)固定其他条件,将构建的模型2006年土地利用数据替换为1995年,对比分析发现2000—2010年全流域和典型子流域的年径流深增加,洪水期平均径流增加,枯水期径流基本减少。(3)从全流域空间角度看,径流量均增大,特别是研究区西部地区和东南部地区;同时径流量变率增大,稳性减小。(4)园地、林地、建设用地和水田是驱动区内水文变化的主要因子。[结论]研究区土地利用与覆被变化导致"洪水量更大,枯水量更小"的径流变化趋势。河川径流的变化受各地类变化的组合叠加效应影响,这种叠加效应还须进一步研究。     

SCS-CN模型在巢湖流域地表产流估算中的应用

降雨径流是引起土壤侵蚀的主要动力,因此预测不同降雨及下垫面条件下的径流量是土壤侵蚀预报和水土流失治理的关键。应用美国原水土保持局开发的流域水文模型SCS-CN模型对巢湖流域降雨—径流过程进行模拟。在ArcGIS 9.2软件支持下,估算2002—2006年巢湖流域地表年径流量并分析了不同土地覆被类型的产流状况。结果表明,巢湖流域地表降雨径流年际变化较大,径流量变化范围为591.323～1 557.136mm。不同土地覆被类型产流能力依次为:城镇用地>水田>未利用地>旱地>农村居民点>草地>林地>灌木林。     

Effect of land management on runoff and soil losses from two small watersheds in St Lucia

The influence of land use on runoff and soil loss was assessed on two small watersheds in the Eastern Caribbean island of St Lucia, under contrasting land management regimes. The data generated from these watersheds revealed that the soil losses from an intensively cultivated agricultural watershed were 20‐times higher in magnitude than that of a forested watershed both for peak rainfall event and for total duration of analysis. This was due to higher surface runoff rates and exposure of soil to direct raindrop impact within cultivated areas. Whereas the forest canopy cover in combination with higher infiltration capacities of the forested land reduced the erosive runoff from the forest watershed and thus the soil loss. Moreover, the energy intensities of large storms in excess of 40 mm were estimated and found to range between 400 MJ mm ha⁻¹ h⁻¹ and 1834 MJ mm ha⁻¹ h⁻¹. 1

1 Megajoules‐millimeters per hectare‐hour.

Soil loss from the agricultural watershed was strongly correlated (R² = 0·85) to storm energy‐intensity (EI₃₀). However, the correlation of soil loss with the EI₃₀ (R² = 0·71) was poor for the forest watershed due to the effect of canopy vegetation, which significantly reduced the energy of raindrop impact. Over the study period, cumulative soil losses were 10·0 t ha⁻¹ for the agricultural site and 0·5 t ha⁻¹ for the forest site. 2

2 Metric tons per hectare.

The largest storm observed during the study period resulted in erosion losses of 3·78 t ha⁻¹ and 0·2 t ha⁻¹ from the agricultural and forest sites respectively. The regression models were developed using the measured data for prediction of runoff and soil loss over the watersheds of St Lucia under similar conditions. This study contributed towards efficient watershed management planning and implementation of suitable water conservation measures in St Lucia. Copyright © 2005 John Wiley & Sons, Ltd.     

梯田、林地、草地减水减沙效益指标初探

通过对各地坡面径流场试验资料的系统整理，结合梯田、林地、草地的减水减沙机理，引入径流、泥沙水平和措施质量概念，分析得出了不同质量的梯田、林地、草地在不同的径流、泥沙水平年份的减水减沙效益指标，形成了一套较为完善的梯田、林地、草地减水减沙效益指标体系。     

Spatial and temporal patterns of vegetation recovery following sequences of forest fires in a Mediterranean landscape,Mt. Carmel Israel

The Mediterranean ecosystem of Mt. Carmel is subjected to increasing number of forest fires at various extents and severities due to increasing human activities. Accordingly, we tested whether in areas exposed to different fire histories vegetation regeneration is different in north versus south facing slopes, and the potential impact on erosion processes. Using remote sensing techniques we evaluated the Enhanced Vegetation Index (EVI) to monitor vegetation recovery following a single fire and three successive fires, using a series of Landsat images taken between 1985–2002. Following a single fire, vegetation cover reached pre-disturbance values within less than 5 years. Repeated fires caused further reduction of EVI values, especially at south facing slopes (SFS). The effects of three successive fires within 10 years, followed by a three year recovery period, however, are negligible when considering vegetation cover values. This was deduced as north facing slope EVI values returned to pre-disturbance conditions at the end of the 3 years and SFS EVI values to 80% of the pre-disturbance conditions. Our results indicate that Mediterranean eco-geomorphic systems are quite resilient, showing quick response, at least in terms of return to pre-disturbance states of vegetation cover, and hence of soil erosion rates. This is true not only in response to a disturbance caused by a single fire, but also for repetitive fire incidents.     

Urban Influences on Stream Chemistry and Biology in the Big Brushy Creek Watershed, South Carolina

Naturally high total dissolved solids and upstream agricultural runoff often mask the influence of urban land cover on stream chemistry and biology. We examined the influence of headwater urbanization on the water chemistry, microbiology, and fish communities of the Big Brushy Creek watershed, a 96 km² drainage basin in the piedmont of South Carolina, USA. Concentrations of most major anions and cations (especially nitrate, sulfate, chloride, sodium, potassium, and calcium) were highest in the urban headwaters and decreased downstream. Generally, the highest concentrations of suspended coliform bacteria occurred in the urban headwaters. In contrast, stream habitat quality and the abundance, species richness, and species diversity of fishes did not differ significantly between urban and rural sites. Discharge of wastewater treatment plant effluent at one rural location caused an increase in concentrations of many solutes and possibly the abundance of benthic algae. We hypothesize that atmospheric dry deposition and domestic animal wastes are important sources of stream solutes and of coliform bacteria, respectively, in the urban headwaters. The lack of significant differences in fish abundance and diversity between urban and rural sites may indicate that urban development in the Big Brushy Creek watershed has not yet degraded habitat conditions greatly for stream fishes. Alternatively, agriculture or other land uses may have degraded stream habitat quality throughout the watershed prior to urbanization.