Estimation of the ecological water requirement for natural vegetation in the Ergune River basin in Northeastern China from 2001 to 2014

Wang

et al. 2020

Hydrological Processes

Section: Trends Of Et 0 and Climatic Variablesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Elevation‐dependent changes in reference evapotranspiration due to climate change

Wang

et al. 2020

Hydrological Processes

“…The optimization of stand density should be oriented towards improving ecosystem service functions. Most previous research focused on the optimization of stand density through the water balance principle [24,25]. Some studies considered different landform types to explore suitable stand density values for different micro-topographies [26].…”

Section: Introductionmentioning

confidence: 99%

Optimizing the Stand Density of Robinia pseudoacacia L. Forests of the Loess Plateau, China, Based on Response to Soil Water and Soil Nutrient

Hou

Wang

et al. 2019

Forests

Improving low-efficiency artificial forests represents a popular forest hydrological issue, and exploring the optimal stand density (OSD) of low-efficiency artificial forests is an effective method for improving the soil conditions of forestland to prevent the deterioration of ecological function. Water and nutrients were the main limiting factors for vegetation growth. However, relatively few studies addressed the optimization of stand density based on these two factors at the same time. In this study, a total of 176 standard plots (20 × 20 m2) with six stand densities (~500, ~1000, ~1500, ~2000, ~2500 and ~3000 plants·hm−2) were established to investigate the water resources (soil moisture content (SMC), soil evaporation rate (SER), and vegetation transpiration rate (VTR)) and soil nutrient resources (total nitrogen (TN), total phosphorus (TP), total potassium (TK), calcium (CaCO3), organic matter content (OMC)) in low-efficiency Robinia pseudoacacia forestland on the Loess Plateau in western Shanxi, China from June to September each year from 2017 to 2018. The relationships between stand density and water and nutrient resources were analysed with the response surface method (RSM). The RSM results indicated that the OSD averaged 1594 plants·hm−2 and ranged from 940 to 2386 plants·hm−2. The percentage of standard plots with an unreasonable stand density was 35.29%, and 65% of these plots had a value that was higher than the maximum in the range while 35% had a value that was lower than the minimum. These results indicate that the current stand density should be manipulated to fall within the identified OSD range to ensure the normal functions of soil and water conservation in R. pseudoacacia forests. The results of this study serve as a guide for optimizing the stand density of low-efficiency R. pseudoacacia forests in China.

“…In the improved Penman‐Monteith method with two additional coefficients K c and K p , the spatialization and dynamicalization of these two coefficients can improve the accuracy of ecological water requirement (EWR) calculations. Thus, after estimating the area of the riparian zone, we employed the improved Penman‐Monteith method to calculate the EWR of vegetation using the potential evapotranspiration of vegetation, soil moisture, and vegetation area to calculate plant evapotranspiration (ET p ) (Chi, Wang, Li, Liu, & Li, 2017).

EWR = A_{P} \times \sum_{normaln = 1}^{N} {ET}_{normalp, normaln} \times 10^{- 3},

where A P is the vegetation area (m 2 ), ET p,n is the plant evapotranspiration (mm·d −1 ) on the n th day, and N is the number of days in the plant growing season.

{ET}_{P} = K_{S} \times K_{C} \times {ET}_{0},

where ET 0 is the potential evapotranspiration of crops and is calculated as follows:

{ET}_{0} = \frac{0.408 normalΔ ((), R_{n} - normalG) + normalγ \frac{900}{normalT + 273} u_{2} ((), e_{s} - e_{a})}{normalΔ + normalγ ((), 1 + 0.34 u_{2})},

where Δ is the slope of saturation of the water vapor pressure–temperature curve (kPa/°C); T is the mean temperature (°C); Rn is the net radiation at the crop surface (MJ/m 2 ∙d); G is the soil heat flux density (MJ/m 2 ∙d); γ is the psychometric constant (kPa/°C); u 2 is the wind speed at the height of 2 m (m/s); e s is the saturation vapor pressure (kPa); and e a is the actual vapor pressure (kPa).

K_{S} = \frac{\ln ((), \frac{normalS - S_{W}}{S^{*} - S_{W}} \times 100 + 1)}{\ln 101},

where K S is the soil water limit coefficient; S represents the actual soil water...…”

Section: Methodsmentioning

confidence: 99%

New grassland riparian zone delineation method for calculating ecological water demand to guide management goals

Lan

2020

River Research & Apps

River flow provides water that maintains the ecological health of both the river itself and the adjoining riparian zones. However, there is a lack of clear definition and identification method of the riparian zone of inland river basins with narrow river channels and anthropogenic intervention reservoirs. In this study, we developed a new method to delineate semiarid grassland riparian zones by taking the Xilin River (Inner Mongolia, China) basin as a case study for providing an opportunity for a more accurate estimation of the ecological water demand of riparian zone. The extent of the riparian zones with different geomorphological and hydrological characteristics was determined by using unmanned aerial vehicle (UAV) images at five river sections along the reach under the combination of natural variations and the regulation by the dams. After mapping each river section, river length and riparian zone area were shown to have a strong relationship (ρs = 0.9; p < .05), which was extended to calculate the downstream riparian zone area by using its river length. Moreover, we applied the distribution flow method to calculate the river ecological water demand and employed the Penman‐Monteith method to calculate riparian zone ecological water demand. The results showed that the river ecological water demand of the downstream of the reservoir was approximately 6.5×106 m3 per year while riparian zone was 2075.1×106 m3. Only 36, 19, and 15% of the ecological water demand can be met in the hydrological wet, average, and dry years, respectively, because of improper reservoir management and the inability of the discharge of the reservoir to meet the ecological water demand of the downstream riparian zone. Our data illustrate the impact and importance of river flow on the downstream degradation of riparian grasslands and can motivate reservoir management in semiarid areas, which will be helpful to guide water regulations to meet environmental and ecological needs.