Modeling rainfall interception loss by two xerophytic shrubs in the Loess Plateau

Rainfall interception loss plays an important role in ecohydrological processes in dryland shrub ecosystems, but its drivers still remain poorly understood. In this study, a statistical model was developed to simulate interception loss based on the mass balance measurements arising from the partitioning of rainfall in 2 dominant xerophytic shrub (Hippophae rhamnoides and Spiraea pubescens) communities in the Loess Plateau. We measured throughfall and stemflow in the field under natural rainfall, calculated the canopy storage capacity in the laboratory, and identified key factors controlling these components for the 2 shrubs. We quantified and scaled up the stemflow and the canopy storage capacity measurements from the branches and/or leaves to stand level. The average interception loss, throughfall, and stemflow fluxes account for 24.9%, 72.2%, and 2.9% of the gross rainfall for H. rhamnoides, and 19.2%, 70.7%, and 10.1% for S. pubescens, respectively. Throughfall increased with increasing rainfall for both shrubs; however, it was only correlated with the leaf area index for S. pubescens. For stemflow measured from individual branches, we found that the rainfall amount and basal diameter are the best predictors for H. rhamnoides, whereas rainfall amount and branch biomass appear to be the best predictors for S. pubescens. At the stand level, stemflow production is affected by the rainfall amount for H. rhamnoides, and it is affected by both the rainfall amount and the leaf area index for S. pubescens. The canopy storage capacity of H. rhamnoides (1.07–1.28 mm) was larger than S. pubescens (0.88–1.07 mm), and it is mainly determined by the branches and stems of H. rhamnoides and the leaves of S. pubescens. The differences in interception loss between the 2 shrub stands are mainly attributed to different canopy structures that induced differences in stemflow production and canopy storage. We evaluated the effects of canopy structure on rainfall interception loss, and our developed model provides a better understanding of the effects of the canopy structure on the water cycles in dryland shrub ecosystems.     

Long-term variations of rainfall interception in different growth stages of Chinese fir plantations

Abstract

The dynamic properties of rainfall interception were investigated at three growth stages in Chinese fir plantations. The results showed that the annual interception ratio was significantly higher in mature stands than in young stands. For a storm event, interception rainfall amount increased with increasing rainfall, but interception ratio decreased. In contrast to dry season conditions, the interception amount was high in the wet seasons, while the interception ratio was low. The rates of change in interception ratio were extremely rapid in small rainfall events. There was little stemflow in Chinese fir forests due to the pyramid-shaped crowns and thick rough bark of the trees. The power model was suitable to describe the interception process for an individual rainfall event for stands of any age. Our results indicate that the interception process varied for stands of different ages in Chinese fir plantations due to contrasting canopy structures.     

A Linking Test that investigates the feasibility of inverse modelling: application to a simple rainfall interception model for Mt Gambier,southeast South Australia

Interception loss has an important influence on the water yield of forested areas. Nevertheless, in most studies stemflow is not measured, therefore the question of how to determine the feasibility of optimizing interception and stemflow parameters simultaneously by matching daily simulated throughfall to fortnightly measurements of cumulative throughfall is an important one. By applying a daily empirical interception model, a goodness fit of 2·2 mm/day is obtained between observed and simulated cumulative throughfall. However, by applying the simple but robust Linking Test, it was shown that the parameters are non‐unique and falsely linked, i.e. inter‐relationships between different vegetation parameter sets give similar throughfall but non‐unique net precipitation. The Linking Test investigates the causes of obtaining falsely linked parameters and shows that objective equifinality is not the source of the problem. Objective equifinality occurs when an inappropriate objective function is used. The Linking Test also shows that falsely linked parameters are not caused by measuring throughfall on a non‐daily basis (termed frequency sampling equifinality). By expanding the interception model to the second degree, it was found that the non‐uniqueness is due to the inherent nature of interception and stemflow functions that behave similarly and therefore can easily compensate each other (termed similarity equifinality). It is also shown that a simple daily empirical exponential interception model developed for conifers in the uplands of the United Kingdom is suitable to model interception in Pinus radiata plantations in the Mediterranean climate of southern Australia by using only daily gross precipitation data and two parameters. Copyright © 2009 John Wiley & Sons, Ltd.     

Precipitation interception in Australian tropical rainforests: II. Altitudinal gradients of cloud interception,stemflow, throughfall and interception

This article presents a comprehensive study of canopy interception in six rainforests in Australia's Wet Tropics for periods ranging between 2 and 3·5 years. Measurements of rainfall, throughfall, stemflow and cloud interception were made at sites characterized by different forest types, canopy structure, altitude, rainfall and exposure to prevailing winds. Throughfall at these sites ranged between 64 and 83% of total precipitation inputs, while stemflow ranged between 2 and 11%. At sites higher than 1000 m, cloud interception was found to contribute up to 66% of the monthly water input to the forest, more than twice the rainfall at these times. Over the entire study period, cloud interception accounted for between 4 and 30% of total precipitation inputs, and was related more to the exposure of sites to prevailing winds than to altitudinal differences alone. Over the duration of the study period, interception losses ranged between 22 and 29% of total water input (rainfall and cloud interception) at all sites except the highest altitude site on Bellenden Ker, where interception was 6% of total water input. This smaller interception loss was the result of extremely high rainfall, prolonged immersion in cloud and a sparser canopy. On a monthly basis, interception losses from the six sites varied between 10 and 88% of rainfall. All sites had much higher interception losses during the dry season than in the wet season because of the differences in storm size and rainfall intensity. The link between rainfall conditions and interception losses has important implications for how evaporative losses from forests may respond to altered rainfall regimes under climate change and/or large‐scale atmospheric circulation variations such as El Niño. Copyright © 2007 John Wiley & Sons, Ltd.     

Interception losses in three non‐native Hawaiian forest stands

Interception losses in stands of non‐native trees in Hawaiian forests and their potential negative impacts on fresh water availability are poorly understood. In this study, a canopy water balance analysis was conducted to estimate interception losses using measurements of rainfall (RF), throughfall (TF), and stemflow (SF) at three locations, each dominated by one or more of the following non‐native tree species: Psidium cattleianum Sabine (Strawberry guava), Schinus terebinthifolius Raddi (Christmas berry), Syzygium cumini (L.) Skeels (Java plum), and Coffea arabica L. (Coffee). Mean TF expressed as percentage of total RF was the lowest (43.3%) under a monotypic stand of P. cattleianum and the highest (56.5%) under mixture of S. terebinthifolius, P. cattleianum, and S. cumini. Observed SF was highest (33.9%) under P. cattleianum and lowest (3.6%) under a mixture of S. terebinthifolius, P. cattleianum, and S. cumini. The relatively high SF under P. cattleianum can be attributed to its smooth bark, stem density, and steep branching. The mean observed canopy interception varied between 23% under P. cattleianum and 45% at the site dominated by C. arabica. Mean direct TF coefficients from individual events at each location ranged from a low of 0.36 under the canopy dominated by C. arabica to a high of 0.51 under the canopy dominated by S. terebinthifolius, P. cattleianum, and S. cumini. In contrast, the mean SF partitioning coefficients from individual storm events at each location ranged from a low of 0.05 under the canopy dominated by S. terebinthifolius, P. cattleianum, and S. cumini to a high of 0.37 under P. cattleianum. Mean canopy storage capacity was highest (1.90) at the site dominated by S. terebinthifolius, P. cattleianum, and S. cumini whereas trunk storage capacity was highest (0.54) under the P. cattleianum. Copyright © 2012 John Wiley & Sons, Ltd.     

Precipitation interception in Australian tropical rainforests: I. Measurement of stemflow,throughfall and cloud interception

Methods for measuring throughfall, stemflow and, hence, interception in the tropical rainforests of the Wet Tropics region of North Queensland, Australia, were tested at three sites for between 581 and 787 days. The throughfall system design was based on long troughs mounted beneath the canopy and worked successfully under a range of rainfall conditions. Comparison of replicated systems demonstrated that the methodology is capable of capturing the variability in throughfall exhibited beneath our tropical rainforest canopies. Similarly, the stemflow system design which used spiral collars attached to sample trees worked well under a range of rainfall conditions and also produced similar estimates of stemflow in replicated systems. Higher altitude rainforests (>1000 m) in North Queensland can receive significant extra inputs of water as the canopy intercepts passing cloud droplets. This additional source of water is referred to as ‘cloud interception’ and an instrument for detecting this is described. The results obtained from this gauge are compared with cloud interception estimates made using a canopy water balance method. This method is based on stemflow and throughfall measurements and provides an alternative means to fog or cloud interception gauge calibration techniques used in the literature. Copyright © 2007 John Wiley & Sons, Ltd.     

Prediction of Chinese Loess Plateau summer rainfall using Pacific Ocean spring sea surface temperature

The Loess Plateau in China constitutes an important source area for both water and sediments to the Yellow River. Thus, improved prediction techniques of rainfall may lead to better estimation of discharge and sediment content for the Yellow River. Consequently, the objective of this study was to establish better links between rainfall of the Loess Plateau in China and sea surface temperature (SST) in the Pacific Ocean. Results showed that there is a strong lagged correlation between and SST and rainfall. The SST for Micronesia and areas south of the Aleutian Islands showed significant correlations (s.f. < 0·001; 99·9%) with rainfall over the dryer region of the Loess Plateau for a lag of 4 to 6 months. The SST over the equator on the east Pacific Ocean also showed significant negative correlation with rainfall. Low and middle latitude areas (S10–20° and around 30° ) of the south‐east Pacific Ocean displayed significant positive and negative correlation with rainfall on the semiarid Loess Plateau. The differenced SST values (positive SST minus negative SST) increased these correlations with rainfall. An artificial neural network (ANN) model was used to predict summer rainfall from the differenced SST during the spring period. The correlation between predicted and observed monthly rainfall was in general larger than 0·7. This indicates that major annual rainfall (during summer season) can be predicted with good accuracy using the suggested approach. Copyright © 2008 John Wiley & Sons, Ltd.     

Modelling rainfall partitioning with sparse Gash and Rutter models in a downy oak stand in leafed and leafless periods

Application of models for estimating rainfall partitioning in deciduous forests may be considered time consuming and laborious given the need for two different parameter sets to describe leafed and leafless periods. This paper reports how rainfall partitioning modelling was done for a downy oak forest plot (Eastern Pyrenees Mountains, NE Spain) using sparse Rutter and Gash interception loss models and their suitability for such studies. Moreover, variability in model sensitivity is evaluated, and an attempt to simplify their application is also presented. The estimation error for interception loss in the leafed period was ?26.3% and ?4.2% with the Rutter model and the Gash model applied with Penman–Monteith‐based evaporation rate, respectively. The estimate for the leafless period was less accurate in both models, suggesting that modelling in the leafless period is more susceptible to error. Nevertheless, with the Gash model, the result was well below the expected measurement error. Models proved to be highly sensitive to change in canopy cover in all periods tested. The Rutter model was especially sensitive to zero plane displacement changes in the leafed period, while the Gash model showed high linear sensitivity to evaporation rate. In addition, a decrease in rainfall rate affects the estimation of interception loss more than an increase in it. Regardless of its high sensitivity to these parameters, the Gash model yielded a good estimate of rainfall partitioning for the total period, when only one set of parameters was used, although event‐based error compensation occurred, and some periods were over or underestimated. Copyright © 2011 John Wiley & Sons, Ltd.     

Soil erosion and sediment interception by check dams in a watershed for an extreme rainstorm on the Loess Plateau,China

The magnitude of soil erosion and sediment load reduction efficiency of check dams under extreme rainstorms is a long-standing concern. The current paper aims to use check dams to deduce the amount of soil erosion under extreme rainstorms in a watershed and to identify the difference in sediment interception efficiency of different types of check dams. Based on the sediment deposition at 12 check dams with 100% sediment interception efficiency and sub-catchment clustering by taking 12 dam-controlled catchments as clustering criteria, the amount of soil erosion resulting from an extreme rainstorm event on July 26, 2017 (named “7·26” extreme rainstorm) was estimated in the Chabagou watershed in the hill and gully region of the Loess Plateau. The differences in the sediment interception efficiency among the check dams in the watershed were analyzed according to field observations at 17 check dams. The results show that the average erosion intensity under the “7–26” extreme rainstorm was approximately 2.03 × 10⁴ t/km², which was 5 times that in the second largest erosive rainfall in 2017 (4.15 × 10³ t/km²) and 11–384 times that for storms in 2018 (0.53 × 10² t/km² - 1.81 × 10³ t/km²). Under the “7–26” extreme rainstorm, the amount of soil erosion in the Chabagou watershed above the Caoping hydrological station was 4.20 × 10⁶ t. The sediment interception efficiency of the check dams with drainage canals (including the destroyed check dams) and with drainage culverts was 6.48 and 39.49%, respectively. The total actual sediment amount trapped by the check dams was 1.11 × 10⁶ t, accounting for 26.36% of the total amount of soil erosion. In contrast, 3.09 × 10⁶ t of sediment were input to the downstream channel, and the sediment deposition in the channel was 2.23 × 10⁶ t, accounting for 53.15% of the total amount of soil erosion. The amount of sediment transport at the hydrological station was 8.60 × 10⁵ t. The Sediment Delivery Ratio (SDR) under the “7·26” extreme rainstorm was 0.21. The results indicated that the amount of soil erosion was huge, and the sediment interception efficiency of the check dams was greatly reduced under extreme rainstorms. It is necessary to strengthen the management and construction technology standards of check dams to improve the sediment interception efficiency and flood safety in the watershed.     

Measuring interception loss and canopy storage in dryland vegetation: a brief review and evaluation of available research strategies

The interception storage capacity has been measured for a range of dryland plants. Interception losses over time, however, arise in rain events that deliver either less or more than the canopy capacity. The fate of water in these cases depends on the efficiency with which the intercepted water is returned to the atmosphere by evaporation from the plant canopies. Two primary methods to estimate interception losses are (i) calibrated process‐based models of interception and evaporative loss and (ii) direct measurement. Models have been applied only rarely to dryland plant communities, and direct measurement techniques are in need of additional testing and refinement. Most published estimates of interception loss in dryland plant communities therefore appear to be based upon inadequate data and methods. Research needs in this area are highlighted. Copyright © 2000 John Wiley & Sons, Ltd.     

Assessing climate change impacts on the ecohydrology of the Jinghe River basin in the Loess Plateau,China

Abstract

Quantifying the impacts of climate change on the hydrology and ecosystem is important in the study of the Loess Plateau, China, which is well known for its high erosion rates and ecosystem sensitivity to global change. A distributed ecohydrological model was developed and applied in the Jinghe River basin of the Loess Plateau. This model couples the vegetation model, BIOME BioGeochemicalCycles (BIOME-BGC) and the distributed hydrological model, Water and Energy transfer Process in Large river basins (WEP-L). The WEP-L model provided hydro-meteorological data to BIOME-BGC, and the vegetation parameters of WEP-L were updated at a daily time step by BIOME-BGC. The model validation results show good agreement with field observation data and literature values of leaf area index (LAI), net primary productivity (NPP) and river discharge. Average climate projections of 23 global climate models (GCMs), based on three emissions scenarios, were used in simulations to assess future ecohydrological responses in the Jinghe River basin. The results show that global warming impacts would decrease annual discharge and flood season discharge, increase annual NPP and decrease annual net ecosystem productivity (NEP). Increasing evapotranspiration (ET) due to air temperature increase, as well as increases in precipitation and LAI, are the main reasons for the decreasing discharge. The increase in annual NPP is caused by a greater increase in gross primary productivity (GPP) than in plant respiration, whilst the decrease in NEP is caused by a larger increase in heterotrophic respiration than in NPP. Both the air temperature increase and the precipitation increase may affect the changes in NPP and NEP. These results present a serious challenge for water and land management in the basin, where mitigation/adaption measures for climate change are desired.

Editor Z.W. Kundzewicz; Associate editor D. Yang

Citation Peng, H., Jia, Y.W., Qiu, Y.Q., and Niu, C.W., 2013. Assessing climate change impacts on the ecohydrology of the Jinghe River basin in the Loess Plateau, China. Hydrological Sciences Journal, 58 (3), 651–670.     

Chemistry of rainfall,throughfall and stemflow in a eucalypt forest and a pine plantation in south-eastern Australia: 1. Rainfall

Rainfall samples were collected from several hundred rainfall events. Up to nine samples per event were collected from sites 3–500 m apart. They differed substantially in both concentration and composition, even though great care was taken to wash all collectors beforehand. Dryfall, storage and analytical procedures could not explain the variation. When data for rainfall events of similar size (but very different cation inputs) were examined, the major differences were associated with the prevailing wind direction. Events leading to high concentrations were associated with easterly winds and showed the influence of a marine source. Chemical concentration and composition were not altered by the occurrence of a drought year followed by a very wet year. The mean pH was 5·3 and ranged from 4·6 to 5·8. For a given event, a difference of 0·5 often occurred between collection sites. Regular seasonal variations in the concentration of NO₃-N and the NO₃/NH₄ ratio occurred, with the ratio being higher in summer due primarily to bush fires. Organic nitrogen comprised 14% of total nitrogen.     

Winter rainfall interception by two mature open‐grown trees in Davis,California

A rainfall interception measuring system was developed and tested for open‐grown trees. The system includes direct measurements of gross precipitation, throughfall and stemflow, as well as continuous collection of micrometeorological data. The data were sampled every second and collected at 30‐s time steps using pressure transducers monitoring water depth in collection containers coupled to Campbell CR10 dataloggers. The system was tested on a 9‐year‐old broadleaf deciduous tree (pear, Pyrus calleryana ‘Bradford’) and an 8‐year‐old broadleaf evergreen tree (cork oak, Quercus suber) representing trees having divergent canopy distributions of foliage and stems. Partitioning of gross precipitation into throughfall, stemflow and canopy interception is presented for these two mature open‐grown trees during the 1996–1998 rainy seasons. Interception losses accounted for about 15% of gross precipitation for the pear tree and 27% for the oak tree. The fraction of gross precipitation reaching the ground included 8% by stemflow and 77% by throughfall for the pear tree, as compared with 15% and 58%, respectively, for the oak tree. The analysis of temporal patterns in interception indicates that it was greatest at the beginning of each rainfall event. Rainfall frequency is more significant than rainfall rate and duration in determining interception losses. Both stemflow and throughfall varied with rainfall intensity and wind speed. Increasing precipitation rates and wind speed increased stemflow but reduced throughfall. Analysis of rainfall interception processes at different time‐scales indicates that canopy interception varied from 100% at the beginning of the rain event to about 3% at the maximum rain intensity for the oak tree. These values reflected the canopy surface water storage changes during the rain event. The winter domain precipitation at our study site in the Central Valley of California limited our opportunities to collect interception data during non‐winter seasons. This precipitation pattern makes the results more specific to the Mediterranean climate region. Copyright © 2000 John Wiley & Sons, Ltd.     

Interception losses from Miscanthus at a site in south‐east England—an application of the Gash model

Concern has been expressed that Miscanthus x giganteus, a dedicated biomass crop, may have a high water use, with implications for its economic yield and impacts on water resources. There is particular uncertainty about one component of the water use, the interception loss. Measurements of the interception loss were made in a plot of the crop at a site in south‐east England, during 1997/1998 and 1998/1999. The measured interception losses were 25 and 24% of gross rainfall, respectively. Winter interception losses are relatively high, which is attributed to the slow rate of leaf loss. A Monte Carlo procedure was used to optimize three of the parameters of the Gash interception model on the 1997/1998 data. The simulated values had an uncertainty of 1·1 mm per storm in 1997/1998 and 2·9 mm per storm in 1998/1999. The model was also used to investigate the potential effect of the evaporation rate being overestimated due to the measurements being made in an experimental plot. This showed that the interception losses might be reduced to 21 and 18% in field scale plantations. A consideration of the relative interception rate demonstrated that the crop behaved more like a forest, in terms of the interception losses, during the winter months. © Crown Copyright 2010. Reproduced with the permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd.     

Field studies on the influence of rainfall intensity,vegetation cover and slope length on soil moisture infiltration on typical watersheds of the Loess Plateau,China

Soil moisture is a key process in the hydrological cycle. During ecological restoration of the Loess Plateau, soil moisture status has undergone important changes, and infiltration of soil moisture during precipitation events is a key link affecting water distribution. Our study aims to quantify the effects of vegetation cover, rainfall intensity and slope length on total infiltration and the spatial variation of water flow. Infiltration data from the upper, middle and lower slopes of a bare slope, a natural grassland and an artificial shrub grassland were obtained using a simulated rainfall experiment. The angle of the study slope was 15° and rainfall intensity was set at 60, 90, 120, 150, and 180 mm/hr. The effect these factors have on soil moisture infiltration was quantified using main effect analysis. Our results indicate that the average infiltration depth (ID) of a bare slope, a grassland slope and an artificial shrub grassland slope was 46.7–73.3, 60–80, and 60–93.3 cm, respectively, and average soil moisture storage increment was 3.5–5.7, 5.0–9.4, and 5.7–10.2 mm under different rainfall intensities, respectively. Heavy rainfall intensity and vegetation cover reduced the difference of soil infiltration in the 0–40 cm soil layer, and rainfall intensity increased surface infiltration differences on the bare slope, the grassland slope and the artificial shrub grassland slope. Infiltration was dominated by rainfall intensity, accounting for 63.03–88.92%. As rainfall continued, the contribution of rainfall intensity to infiltration gradually decreased, and the contribution of vegetation cover and slope length to infiltration increased. The interactive contribution was: rainfall intensity * vegetation cover > vegetation cover * slope length > rainfall * slope length. In the grass and shrub grass slopes, lateral flow was found at a depth of 23–37 cm when the slope length was 5–10 m, this being related to the difference in soil infiltration capacity between different soil layers formed by the spatial cross-connection of roots.     

Assessing and regulating the impacts of climate change on water resources in the Heihe watershed on the Loess Plateau of China

Climate change can cause considerable changes in water resources and assessing the potential impacts can provide important information for regional sustainable development. The objectives were to evaluate the possible impacts of climate change during 2010-2039 on water resources (runoff, soil water content, and evapotranspiration) in the Heihe watershed on the Loess Plateau of China and to further explore adaptive measures to cope with the changes. Projections of four climate models (CCSR/NIES, CGCM2, CSIRO...     

A mathematical model of soil moisture spatial distribution on the hill slopes of the Loess Plateau

Based on important factors that affect soil moisture spatial distribution, such as the slope gradients, land use, vegetation cover, and surface water diffusion characteristics together with field measurements of soil moisture data obtained from the surface soil under different land use structures, a soil moisture spatial distribution model was established. The diffusion degree coefficient of surface water for different vegetations was estimated from soil moisture values obtained from field measurements. The model can be solved using the finite unit method. The soil moisture spatial distribution on the hill slopes in the Loess Plateau were simulated by the model. A comparison of the simulated values with measurement data shows that the model is a good fit.     

A semi‐theoretical model of canopy rainfall interception for a broad‐leaved tree

Through a series of simulation experiments in the laboratory on the broad‐leaved tree Acer mono Maxim, we obtain interception datasets of individual events under different rainfall intensities and leaf area indexes (LAIs). Based on the data, the relationship between rainfall intensity and maximum interception of per unit LAI is quantified. The variation of interception with canopy wetness index is also identified. Hence, an interception model, in which interception is calculated using rainfall intensity and LAI, is constructed with consideration of canopy wetness. Finally, according to the validation experiments, it is concluded that the precision of the model is 92·7%. Copyright © 2007 John Wiley & Sons, Ltd.     

Holocene dust accumulation and the formation of polycyclic cinnamon soils (luvisols) in the Chinese Loess Plateau

Chinese loess–palaeosol sequences are well known for their records of monsoonal climatic variations. However, the modern processes of dust accumulation and soil formation remain poorly understood. A high‐resolution investigation on modern soils, including the measurement of magnetic susceptibility, particle‐size distribution, total Fe, total organic carbon, CaCO₃ content, and optical stimulated luminescence (OSL) dating was carried out on the Zhouyuan loess tableland in the southern Loess Plateau. The results indicate that modern cinnamon soils (luvisols) have developed on contemporarily accumulated aeolian dust during the Holocene. The aeolian loess accumulated during the Younger Dryas was identi?ed in the top part of the Malan Loess that underlay the modern soil by OSL dating and proxy climatic data. It indicates that the Malan Loess accumulated during the last glaciation (marine isotope stages 2–4) does not serve as the parent material for the modern soils. Pedogenesis of the soils started with the increased precipitation and soil moisture that have occurred on the loess tableland since the early Holocene. Precipitation‐driven pedogenesis and organic activities are responsible for the leaching of CaCO₃, decomposition of mineral dust and the production of clay and ferromagnetic minerals. Drier intervals have interrupted soil formation several times, and therefore pro?les with multiple soils have been developed at many sites on the loess tableland. At places where soil erosion was relatively strong, either a single soil or welded soils are preserved in the Holocene pro?les. This does not necessarily mean, however, that modern soils over the plateau have been developed without interruption under a constantly warmer, moister climate. This is signi?cant for understanding the surface processes and climatic variation during the formation of the numerous palaeosols over the Loess Plateau in the Quaternary. Copyright © 2003 John Wiley & Sons, Ltd.