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Water-Soil-Vegetation Dynamic Interactions in Changing Climate

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A special issue of Water (ISSN 2073-4441). This special issue belongs to the section "Hydrology".

Deadline for manuscript submissions: closed (31 March 2017) | Viewed by 69573

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Special Issue Editors

Prof. Dr. Xixi Wang

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Guest Editor

Department of Civil and Environmental Engineering, Civil and Environmental Engineering, Old Dominion University, Norfolk, VA 23529, USA
Interests: effects of climate change versus human activity on water resources; water–soil–vegetation nexus and equilibrium in changing climate; watershed hydrology and stormwater management
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Xuefeng Chu

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Department of Civil and Environmental Engineering, North Dakota State University, Fargo, ND 58105, USA
Interests: watershed modelling; environmental modelling; vadose zone hydrology; hydrotopographic analysis; groundwater modelling
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Prof. Dr. Tingxi Liu

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College of Water Conservancy and Civil Engineering, Inner Mongolia Agricultural University, Hohhot, Inner Mongolia Autonomous Region 010018, China

Prof. Dr. Xiangju Cheng

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School of Civil Engineering and Transportation, South China University of Technology, Guangzhou, China
Interests: hydraulics and river dynamics; environmental and ecological hydraulics; pollution control and ecological restoration of rivers, lakes, reservoirs, ponds
Special Issues, Collections and Topics in MDPI journals

Dr. Rich Whittecar

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Guest Editor

Department of Ocean, Earth & Atmospheric Sciences, Old Dominion University, Norfolk, VA 23529-0241, USA

Special Issue Information

Dear Colleagues,

Water, soil, and vegetation are the key elements in the Earth’s system. Their dynamic interactions affect, and are affected by, anthropogenic activity (e.g., grazing, farming, or urbanization) and climate change. For a given area, inappropriate land management practices can result in soil and vegetation degradation, which, in turn, will inevitably alter natural hydrologic processes. The possible consequences are more severe flooding, drought, and pollution of lakes and streams. On the other hand, an altered hydrologic condition tends to prompt soil erosion through wind and water, which, in turn, can cause further vegetation degradation or even loss. Such interactions will likely become more interwoven in changing climate because the non-stationary climate, superimposed on human interventions, can further deteriorate the already-altered hydrologic condition. With this regard, our understanding is very limited with few algorithms and parameterization schemes that can be used to account for these dynamic interactions. As a result, existing models were poorly designed to represent such important dynamic interactions. We invite authors to submit original field-experimental and modeling studies, as well as review articles that address: (1) interrelations between hydrologic alteration and soil and/or vegetation degradation with climate change as a possible additional factor; and (2) consequences from the alternation of natural hydrology in rural and urban environment.

Potential topics include, but are not limited to:

Development or application of mathematical models and/or algorithms that link hydrologic processes with soil properties and vegetation characteristics;
Examination of how, and to what extent, natural hydrologic processes have been altered by human activity versus climate change;
Examination of how climate change and human activity affect soil water flow and transport processes;
Analysis of threshold conditions for soil and land degradation to incept;
Examination of physical mechanisms of heat-water-vapor movement and transformation in soils with a top dry layer;
Examination of climate change effects on water-soil-vegetation interactions;
Study of the fate and transport of pollutants in streams and lakes from altered hydrology.

Dr. Xixi Wang
Dr. Xuefeng Chu
Prof. Dr. Tingxi Liu
Prof. Dr. Xiangju Cheng
Dr. Rich Whittecar
Guest Editors

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Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Water is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

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Editorial

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396 KiB

Open AccessEditorial

Water–Soil–Vegetation Dynamic Interactions in Changing Climate

by Xixi Wang, Xuefeng Chu, Tingxi Liu, Xiangju Cheng and Rich Whittecar

Water 2017, 9(10), 740; https://doi.org/10.3390/w9100740 - 28 Sep 2017

Cited by 7 | Viewed by 5372

Abstract

Previous studies of land degradation, topsoil erosion, and hydrologic alteration typically focus on these subjects individually, missing important interrelationships among these important aspects of the Earth’s system. However, an understanding of water–soil–vegetation dynamic interactions is needed to develop practical and effective solutions to sustain the globe’s eco-environment and grassland agriculture, which depends on grasses, legumes, and other fodder or soil-building crops. This special issue is intended to be a platform for a discussion of the relevant scientific findings based on experimental and/or modeling studies. Its 12 peer-reviewed articles present data, novel analysis/modeling approaches, and convincing results of water–soil–vegetation interactions under historical and future climates. Two of the articles examine how lake/pond water quality is related to human activity and climate. Overall, these articles can serve as important references for future studies to further advance our understanding of how water, soil, and vegetation interactively affect the health and productivity of the Earth’s ecosystem. Full article

(This article belongs to the Special Issue Water-Soil-Vegetation Dynamic Interactions in Changing Climate)

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Research

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4818 KiB

Open AccessArticle

Pixel-Level Spatiotemporal Analyses of Vegetation Fractional Coverage Variation and Its Influential Factors in a Desert Steppe: A Case Study in Inner Mongolia, China

by Yifan Song, Zhongxiao Guo, Yajing Lu, Denghua Yan, Zilong Liao, Huiwen Liu and Yingjie Cui

Water 2017, 9(7), 478; https://doi.org/10.3390/w9070478 - 29 Jun 2017

Cited by 19 | Viewed by 4448

Abstract

Determining vegetation variation and its influential factors in a desert steppe under the impacts of climate change and human activities is crucial and meaningful for improving the understanding of desertification and taking targeted measures in ecological restoration. As compared to a large spatial scale such as a region or a whole catchment, which are more common in published studies, a micro perspective at the pixel level is provided in this study to investigate the vegetation fractional coverage dynamics and build the correlations between vegetation fractional coverage and its multiple influential factors, including precipitation, temperature, soil water, groundwater and human activities in a desert steppe region in the Inner Mongolia Autonomous Region, China. The average vegetation fractional coverage in August for the years 2000–2011 is 0.38 in the study area. The interaction of rain (R = 0.80) and heat (R = −0.76) significantly determines the growth and distribution of the vegetation in the study area. Besides, the effects of some other factors on vegetation fractional coverage should not be neglected, including groundwater (R = 0.04), available water content of soil (R = 0.23) and livestock density (R = 0.28). From the perspective of centre dynamics for the years 2000–2011, the annual precipitation centre has better synchronism with the vegetation centre, while the movement of the temperature centre is more stable. Full article

(This article belongs to the Special Issue Water-Soil-Vegetation Dynamic Interactions in Changing Climate)

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3049 KiB

Open AccessArticle

The Critical Depth of Freeze-Thaw Soil under Different Types of Snow Cover

by Qiang Fu, Renjie Hou, Tianxiao Li, Peiru Yan and Ziao Ma

Water 2017, 9(6), 370; https://doi.org/10.3390/w9060370 - 25 May 2017

Cited by 12 | Viewed by 5110

Abstract

Snow cover is the most common upper boundary condition influencing the soil freeze-thaw process in the black soil farming area of northern China. Snow is a porous dielectric cover, and its unique physical properties affect the soil moisture diffusion, heat conduction, freezing rate and other variables. To understand the spatial distribution of the soil water-heat and the variable characteristics of the critical depth of the soil water and heat, we used field data to analyze the freezing rate of soil and the extent of variation in soil water-heat in a unit soil layer under bare land (BL), natural snow (NS), compacted snow (CS) and thick snow (TS) treatments. The critical depth of the soil water and heat activity under different snow covers were determined based on the results of the analysis, and the variation fitting curve of the difference sequences on the soil temperature and water content between different soil layers and the surface 5-cm soil layer were used to verify the critical depth. The results were as follows: snow cover slowed the rate of soil freezing, and the soil freezing rate under the NS, CS and TS treatments decreased by 0.099 cm/day, 0.147 cm/day and 0.307 cm/day, respectively, compared with that under BL. In addition, the soil thawing time was delayed, and the effect was more significant with increased snow cover. During freeze-thaw cycles, the extent of variation in the water and heat time series in the shallow soil was relatively large, while there was less variation in the deep layer. There was a critical stratum in the vertical surface during hydrothermal migration, wherein the critical depth of soil water and heat change gradually increased with increasing snow cover. The variance in differences between the surface layer and both the soil water and heat in the different layers exhibited “steady-rising-steady” behavior, and the inflection point of the curve is the critical depth of soil freezing and thawing. This critical layer is a demarcation point between frozen soil and non-frozen soil, delineating the boundary between soil water and heat migration and non-migration. Furthermore, with increasing snow cover thickness and increasing density, the critical depth gradually increased. Full article

(This article belongs to the Special Issue Water-Soil-Vegetation Dynamic Interactions in Changing Climate)

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1929 KiB

Open AccessArticle

Upscaling Stem to Community-Level Transpiration for Two Sand-Fixing Plants: Salix gordejevii and Caragana microphylla

by Limin Duan, Yang Lv, Xue Yan, Tingxi Liu and Xixi Wang

Water 2017, 9(5), 361; https://doi.org/10.3390/w9050361 - 22 May 2017

Cited by 7 | Viewed by 4556

Abstract

The information on transpiration is vital for sustaining fragile ecosystem in arid/semiarid environment, including the Horqin Sandy Land (HSL) located in northeast China. However, such information is scarce in existing literature. The objectives of this study were to: (1) measure sap flow of selected individual stems of two sand-fixing plants, namely Salix gordejevii and Caragana microphylla, in HSL; and (2) upscale the measured stem-level sap flow for estimating the community-level transpiration. The measurements were done from 1 May to 30 September 2015 (i.e., during the growing season). The upscaling function was developed to have one dependent variable, namely sap flow rate, and two independent variables, namely stem cross-sectional area of Salix gordejevii and leaf area of Caragana microphylla. The results indicated that during the growing season, the total actual transpiration of the Salix gordejevii and Caragana microphylla communities was found to be 287 ± 31 and 197 ± 24 mm, respectively, implying that the Salix gordejevii community might consume 1.5 times more water than the Caragana microphylla community. For this same growing season, based on the Penman–Monteith equation, the total actual evapotranspiration for these two communities was estimated to be 323 and 229 mm, respectively. The daily transpiration from the upscaling function was well correlated with the daily evapotranspiration by the Penman–Monteith equation (coefficient of determination R² ≥ 0.67), indicating the applicability of this upscaling function, a useful tool for managing and restoring sand-fixing vegetations. Full article

(This article belongs to the Special Issue Water-Soil-Vegetation Dynamic Interactions in Changing Climate)

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7840 KiB

Open AccessFeature PaperArticle

Coupled Infiltration and Kinematic-Wave Runoff Simulation in Slopes: Implications for Slope Stability

by J. Michael Johnson and Hugo A. Loáiciga

Water 2017, 9(5), 327; https://doi.org/10.3390/w9050327 - 05 May 2017

Cited by 8 | Viewed by 4692

Abstract

Shallow translational slides are common in slopes during heavy rainfall. The classic model for the occurrence of translational slides in long slopes assumes rising saturation above a slip surface that reduces the frictional strength by decreasing the effective stress along soil discontinuities. The classic model for translational slope failure does not conform well to the nature of homogenous soils that do not exhibit discontinuities propitious to create perched groundwater over the soil discontinuity or slip surface. This paper develops an alternative methodology for the coupled numerical simulation of runoff and infiltration caused by variable rainfall falling on a slope. The advancing depth of infiltration is shown to affect the translational stability of long slopes subjected to rainfall, without assuming the perching of soil water over the slip surface. This new model offers an alternative mechanism for the translational stability of slopes that are saturated from the slope surface downwards. A computational example illustrates this paper’s methodology. Full article

(This article belongs to the Special Issue Water-Soil-Vegetation Dynamic Interactions in Changing Climate)

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9858 KiB

Open AccessArticle

Spatiotemporal Distribution of Eutrophication in Lake Tai as Affected by Wind

by Wenhui Zhang, Qiujin Xu, Xixi Wang, Xiaozhen Hu, Cheng Wang, Yan Pang, Yanbin Hu, Yang Zhao and Xiao Zhao

Water 2017, 9(3), 200; https://doi.org/10.3390/w9030200 - 10 Mar 2017

Cited by 17 | Viewed by 4754

Abstract

One common hypothesis is that wind can affect concentrations of nutrients (i.e., nitrogen and phosphorus) and chlorophyll-a (Chl-a) in shallow lakes. However, the tests of this hypothesis have yet to be conclusive in existing literature. The objective of this study was to use long-term data to examine how wind direction and wind speed affect the spatiotemporal variations of total nitrogen (TN), total phosphorus (TP) and Chl-a in Lake Tai, a typical shallow lake located in east China. The results indicated that the concentrations of nutrients and Chl-a tended to decrease from the northwest to the southeast of Lake Tai, with the highest concentrations in the two leeward bays (namely Meiliang Bay and Zhushan Bay) in the northwestern part of the lake. In addition to possible artificial reasons (e.g., wastewater discharge), the prevalent southeastward winds in warm seasons (i.e., spring and summer) and northwestward winds in cool seasons (i.e., fall and winter) might be the major natural factor for such a northwest-southeast decreasing spatial pattern. For the lake as a whole, the concentrations of TN, TP and Chl-a were highest for a wind speed between 2.1 and 3.2 m·s⁻¹, which can be attributed to the idea that the wind-induced drifting and mixing effects might be dominant in the bays while the wind-induced drifting and resuspension effects could be more important in the other parts of the lake. Given that the water depth of the bays was relatively larger than that of the other parts, the drifting and mixing effects were likely dominant in the bays, as indicated by the negative relationships between the ratios of wind speed to lake depth, which can be a surrogate for the vertical distribution of wind-induced shear stress and the TN, TP and Chl-a concentration. Moreover, the decreasing temporal trend of wind speed in combination with the ongoing anthropogenic activities will likely increase the challenge for dealing with the eutrophication problem of Lake Tai. Full article

(This article belongs to the Special Issue Water-Soil-Vegetation Dynamic Interactions in Changing Climate)

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9024 KiB

Open AccessArticle

Decreased Streamflow in the Yellow River Basin, China: Climate Change or Human‐Induced?

by Bin Li, Changyou Li, Jianyu Liu, Qiang Zhang and Limin Duan

Water 2017, 9(2), 116; https://doi.org/10.3390/w9020116 - 13 Feb 2017

Cited by 33 | Viewed by 6273

Abstract

Decreased streamflow of the Yellow River basin has become the subject of considerable concern in recent years due to the critical importance of the water resources of the Yellow River basin for northern China. This study investigates the changing properties and underlying causes for the decreased streamflow by applying streamflow data for the period 1960 to 2014 to both the Budyko framework and the hydrological modelling techniques. The results indicate that (1) streamflow decreased 21% during the period 1980–2000, and decreased 19% during the period 2000–2014 when compared to 1960–1979; (2) higher precipitation and relative humidity boost streamflow, while maximum/minimum air temperature, solar radiation, wind speed, and the underlying parameter, n, all have the potential to adversely affect them; (3) decreased streamflow is also linked to increased cropland, grass, reservoir, urban land, and water areas and other human activities associated with GDP and population; (4) human activity is the main reason for the decrease of streamflow in the Yellow River basin, with the mean fractional contribution of 73.4% during 1980–2000 and 82.5% during 2001–2014. It is clear that the continuing growth of humaninduced impacts on streamflow likely to add considerable uncertainty to the management of increasingly scarce water resources. Overall, these results provide strong evidence to suggest that human activity is the key factor behind the decreased streamflow in the Yellow River basin. Full article

(This article belongs to the Special Issue Water-Soil-Vegetation Dynamic Interactions in Changing Climate)

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3026 KiB

Open AccessArticle

SWAT Modeling for Depression-Dominated Areas: How Do Depressions Manipulate Hydrologic Modeling?

by Mohsen Tahmasebi Nasab, Vishal Singh and Xuefeng Chu

Water 2017, 9(1), 58; https://doi.org/10.3390/w9010058 - 17 Jan 2017

Cited by 35 | Viewed by 7884

Abstract

Modeling hydrologic processes for depression-dominated areas such as the North American Prairie Pothole Region is complex and reliant on a clear understanding of dynamic filling-spilling-merging-splitting processes of numerous depressions over the surface. Puddles are spatially distributed over a watershed and their sizes, storages, and interactions vary over time. However, most hydrologic models fail to account for these dynamic processes. Like other traditional methods, depressions are filled as a required preprocessing step in the Soil and Water Assessment Tool (SWAT). The objective of this study was to facilitate hydrologic modeling for depression-dominated areas by coupling SWAT with a Puddle Delineation (PD) algorithm. In the coupled PD-SWAT model, the PD algorithm was utilized to quantify topographic details, including the characteristics, distribution, and hierarchical relationships of depressions, which were incorporated into SWAT at the hydrologic response unit (HRU) scale. The new PD-SWAT model was tested for a large watershed in North Dakota under real precipitation events. In addition, hydrologic modeling of a small watershed was conducted under two extreme high and low synthetic precipitation conditions. In particular, the PD-SWAT was compared against the regular SWAT based on depressionless DEMs. The impact of depressions on the hydrologic modeling of the large and small watersheds was evaluated. The simulation results for the large watershed indicated that SWAT systematically overestimated the outlet discharge, which can be attributed to the failure to account for the hydrologic effects of depressions. It was found from the PD-SWAT modeling results that at the HRU scale surface runoff initiation was significantly delayed due to the threshold control of depressions. Under the high precipitation scenario, depressions increased the surface runoff peak. However, the low precipitation scenario could not fully fill depressions to reach the overflow thresholds in the selected sub-basins. These results suggest the importance of depressions as gatekeepers in watershed modeling. Full article

(This article belongs to the Special Issue Water-Soil-Vegetation Dynamic Interactions in Changing Climate)

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2459 KiB

Open AccessArticle

Effects of Nonaerated Circulation Water Velocity on Nutrient Release from Aquaculture Pond Sediments

by Xiangju Cheng, Dantong Zhu, Xixi Wang, Deguang Yu and Jun Xie

Water 2017, 9(1), 6; https://doi.org/10.3390/w9010006 - 24 Dec 2016

Cited by 11 | Viewed by 5225

Abstract

Sustaining good water quality in aquaculture ponds is vital. Without an aerator, the dissolved oxygen in ponds comes primarily from mass transfer at the water-ambient atmosphere interface. As sediment can seriously affect water quality, this study used indoor experiments to examine the nutrient (nitrogen and phosphorus) release mechanisms and fluxes from sediment in aquaculture ponds with moving water but no aeration. The results showed that the ammonia nitrogen (NH₃-N) concentration in the overlying water was inversely proportional to flow velocity and that a higher flow velocity tended to result in a lower concentration in the overlying water, a steeper vertical gradient of concentration within the bed sediments, and a faster release rate from the sediments. The sediment disturbed by flowing water released more nitrate nitrogen (NO₃-N) and nitrite nitrogen (NO₂-N) into the overlying water and NO₂-N could become oxidized into NO₃-N. In still water, NO₃-N was released gradually and some anaerobic NO₃-N was nitrified into NO₂-N. Phosphorus release from the sediments was controlled by the adsorption–desorption balance, with the phosphorus concentration in the overlying water dropping gradually to a steady value from its initial maximum. The relationship between NH₃-N release flux and flow rate is described by a cubic function. Full article

(This article belongs to the Special Issue Water-Soil-Vegetation Dynamic Interactions in Changing Climate)

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5033 KiB

Open AccessArticle

Impact of Climate Change on Drought in the Upstream Yangtze River Region

by Guihua Lu, Hongwei Wu, Heng Xiao, Hai He and Zhiyong Wu

Water 2016, 8(12), 576; https://doi.org/10.3390/w8120576 - 07 Dec 2016

Cited by 11 | Viewed by 4528

Abstract

Based on Coupled Model Intercomparison Project Phase 5 (CMIP5) dataset and a variable infiltration capacity (VIC) hydrological model, this study assesses the possible influence of climate change in the upstream region of the Yangtze River on droughts in the future 30 years. Long-term daily soil moisture content were simulated by VIC model at a 50 km × 50 km resolution from 1951 to 2013. Regional historical drought events were then recognized based on soil moisture anomaly percentage index and validated with field data. Five relatively independent representative global circulation models were selected and the outputs of them were downscaled temporally and spatially as the inputs of VIC model for daily soil moisture content simulations both in the period of 1971–2000 for the present-day climate and in the period of 2021–2050 for the future. The results show that the projected annual mean temperature is likely to increase from 1.4 °C to 1.8 °C. The projected change in mean annual precipitation could be increased slightly by 0.6% to 1.3%, but the trend of precipitation change in summer and autumn might be opposite of that. Comparing the drought characteristics values recognized in 1971–2000, seven to eight additional regional drought events are likely to happen in 2021–2050. Drought duration and drought intensity are also likely to extend for 18 d to 25 d and increase by 1.2% to 6.2%, respectively. But, drought area could decrease slightly by 1.3% to 2.7% on average. These changes in drought characteristics values suggest that regional drought could become more severely prolonged and frequent in future. Full article

(This article belongs to the Special Issue Water-Soil-Vegetation Dynamic Interactions in Changing Climate)

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3709 KiB

Open AccessArticle

Terrestrial Sediment Yield Projection under the Bias-Corrected Nonstationary Scenarios with Hydrologic Extremes

by Soojin Moon and Boosik Kang

Water 2016, 8(10), 433; https://doi.org/10.3390/w8100433 - 01 Oct 2016

Cited by 3 | Viewed by 4905

Abstract

For reliable prediction of sediment yield in a watershed, fine-scale projections for hydro-climate components were first obtained using the statistical bias correction and downscaling scheme based on the combination of an Artificial Neural Network (ANN), Nonstationary Quantile Mapping (NSQM) and Stochastic Typhoon Synthesis (STS) sub-modules. Successively, the hydrologic runoff and sediment yield from the land surfaces were predicted through the long-term continuous watershed model, Soil and Water Assessment Tool (SWAT), using the bias-corrected and downscaled Regional Climate Model (RCM) output under the Intergovernmental Panel on Climate Change’s (IPCC’s) A1B climate change scenario. The incremental improvement of the combined downscaling process was evaluated successfully during the baseline period, which provides projected confidence for the simulated future scenario. The realistic simulation of sediment yield is closely related to the rainfall event with high intensity and frequency. During the long-term future period, the Coefficient of River Regime (CORR) reaches 353.9 (27.2% increase with respect to baseline). The projection for annual precipitation by 2040 and 2100 is a 25.7% and a 57.2% increase with respect to the baseline period, respectively. In particular, the increasing CORR rate (33.4% and 72.5%) during the flood season is much higher than that for the annual total amount. However, the sediment yield is expected to increase by 27.4% and 121.2% during the same periods, which exhibits steeper trends than the hydrologic runoff. The June, July, August (JJA) season occupies 83.0% annual total sediment yield during the baseline period, which is similar during the projection period. The relative change of sediment yield is 1.9-times higher than that of dam inflows. Full article

(This article belongs to the Special Issue Water-Soil-Vegetation Dynamic Interactions in Changing Climate)

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7298 KiB

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Contributions of Climate Variability and Human Activities to Runoff Changes in the Upper Catchment of the Red River Basin, China

by Yungang Li, Daming He, Xue Li, Yueyuan Zhang and Liyan Yang

Water 2016, 8(9), 414; https://doi.org/10.3390/w8090414 - 21 Sep 2016

Cited by 23 | Viewed by 5549

Abstract

Quantifying the effects of climate variability and human activities on runoff changes will contribute to regional water resource planning and management. This study aims to separate the effects of climate variability and human activities on runoff changes in the upper catchment of the Red River Basin in China. The Mann–Kendall test and Pettitt’s test methods were applied to identify the trends and change points of the hydro-meteorological variables. The hydrological sensitivity, climate elasticity and hydrological simulation methods were adopted to estimate the contributions of climate variability and human activities to runoff changes. Results showed that annual runoff significantly decreased by 1.57 mm/year during the period of 1961–2012. A change point in annual runoff coefficient occurred in 2002. Accordingly, the annual runoff series were divided into the baseline period (1961–2002) and the impacted period (2003–2012). Mean annual runoff of the impacted period decreased by 29.13% compared with the baseline period. Similar estimates of the contributions of climate variability and human activities were obtained by the three different methods. Climate variability was estimated to be responsible for 69%–71% of the reduction in annual runoff, and human activities accounted for 29%–31%. Climate variability was the main driving factor for runoff decrease in the catchment. Full article

(This article belongs to the Special Issue Water-Soil-Vegetation Dynamic Interactions in Changing Climate)

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Estimated Grass Grazing Removal Rate in a Semiarid Eurasian Steppe Watershed as Influenced by Climate

by Xixi Wang, Shohreh Pedram, Tingxi Liu, Ruizhong Gao, Fengling Li and Yanyun Luo

Water 2016, 8(8), 339; https://doi.org/10.3390/w8080339 - 09 Aug 2016

Cited by 9 | Viewed by 5307

Abstract

Grazing removal rate of grasses needs to be determined for various climate conditions to address eco-environmental concerns (e.g., desertification) related to steppe grassland degradation. The conventional approach, which requires survey data on animal species and heads as well as grass consumption per individual animal, is too costly and time-consuming to be applied at a watershed scale. The objective of this study was to present a new approach that can be used to estimate grazing removal rate with no requirement of animal-related data. The application of this new approach was demonstrated in a Eurasian semiarid typical-steppe watershed for an analysis period of 2000 to 2010. The results indicate that the removal rate tended to become larger, but its temporal variation tended to become smaller, from the upstream to downstream. Averaged across the watershed, the removal rate ranged from 63.9 to 401.0 g DM m⁻² (or 22.4 to 60.9%) during the analysis period. As expected, the removal rate in an atmospherically wetter year was higher than that in an atmospherically drier year. Nevertheless, none of the eleven analysis years had a removal rate higher than the threshold value of 65%, above which the risk of grassland degradation would become much greater. Full article

(This article belongs to the Special Issue Water-Soil-Vegetation Dynamic Interactions in Changing Climate)

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