Revegetation Does Not Decrease Water Yield in the Loess Plateau of China

Yan

et al. 2022

Forests

Constructing protective forests to control water and soil erosion is an effective measure to address land degradation in the Bashang Plateau of North China, but forest dieback has occurred frequently due to severe water deficits in recent decades. However, transpiration dynamics and their biophysical control factors under various soil water contents for different forest functional types are still unknown. Here, canopy transpiration and stomatal conductance of a 38-year-old Ulmus pumila L. and a 20-year-old Caragana korshinskii Kom. were quantified using the sap flow method, while simultaneously monitoring the meteorological and soil water content. The results showed that canopy transpiration averaged 0.55 ± 0.34 mm d−1 and 0.66 ± 0.32 mm d−1 for U. pumila, and was 0.74 ± 0.26 mm d−1 and 0.77 ± 0.24 mm d−1 for C. korshinskii in 2020 and 2021, respectively. The sensitivity of canopy transpiration to vapor pressure deficit (VPD) decreased as soil water stress increased for both species, indicating that the transpiration process is significantly affected by soil drought. Additionally, canopy stomatal conductance averaged 1.03 ± 0.91 mm s−1 and 1.34 ± 1.22 mm s−1 for U. pumila, and was 1.46 ± 0.90 mm s−1 and 1.51 ± 1.06 mm s−1 for C. korshinskii in 2020 and 2021, respectively. The low values of the decoupling coefficient (Ω) showed that canopy and atmosphere were well coupled for both species. Stomatal sensitivity to VPD decreased with decreasing soil water content, indicating that both U. pumila and C. korshinskii maintained a water-saving strategy under the stressed water conditions. Our results enable better understanding of transpiration dynamics and water-use strategies of different forest functional types in the Bashang Plateau, which will provide important insights for planted forests management and ecosystem stability under future climate changes.

Section: Introductionmentioning

confidence: 99%

Canopy Transpiration and Stomatal Conductance Dynamics of Ulmus pumila L. and Caragana korshinskii Kom. Plantations on the Bashang Plateau, China

Yan

et al. 2022

Forests

“…Understanding this role of vegetation is critical for water management under future climatic conditions, especially in the face of global warming and rising atmospheric CO 2 concentrations. Numerous studies have been conducted to explore changes in water resources due to vegetation restoration in China (Farley et al., 2005; Murray et al., 2012; Su & Fu, 2013; Zhang et al., 2022). Our previous studies (Shao et al., 2019, 2021) also confirmed this: vegetation restoration significantly increased regional evaporative water consumption.…”

Section: Discussionmentioning

confidence: 99%

“…Satellite records show that earth is greening, largely driven by vegetation restoration since the 1980s, with one of the largest contributions from China, accounting for 25% of the global increase in vegetation (Chen et al., 2019; Piao et al., 2019). Greening has exerted a notable influence on vegetation growth processes and related hydrological processes through changes in: (a) leaf area index (LAI), which is a measure of canopy abundance (Chen et al., 2020); (b) dynamic effective rooting depth ( Zr ), which determines the water access for plants and alters the soil moisture ( SM ) profile (Liu et al., 2022; Yang, Donohue, & McVicar, 2016); and (c) evapotranspiration ( ET ) and ET partitioning (consisting of transpiration ( T ), canopy interception evaporation ( E i ) and soil evaporation ( E b )), which lead to regional changes in the hydrological cycle, water availability and ecological sustainability (Jasechko et al., 2013; Jung et al., 2010; Lian et al., 2018; Shao et al., 2021; Teo et al., 2022; Zhang et al., 2022). LAI, as an above‐ground vegetation feature, and Zr , as a below‐ground vegetation feature, synergistically modulate ET .…”

Section: Introductionmentioning

confidence: 99%

Implementation of Dynamic Effective Rooting Depth in Evapotranspiration Model Deepens Understanding of Evapotranspiration Partitioning Under Soil Moisture Gradients in China

Shao

Water Resources Research

2022

Self Cite

Evapotranspiration (ET) is a key component of water cycle and is strongly modulated by below‐ground (e.g., dynamic effective rooting depth, Zr) and above‐ground (e.g., LAI and canopy height, CH) vegetation dynamics. Existing studies mainly focus on the effect of above‐ground vegetation dynamics on ET, while it is still unclear how Zr affects ET. Moreover, it is challenging to parameterize Zr dynamically in large‐scale hydrological and biogeochemical models due to data scarcity. Here, we estimate Zr in China from 1982 to 2015 based on Guswa's carbon cost‐benefit model, and update ET partitioning algorithm by replacing CH with Zr in PT‐JPLsm model to form the PT‐JPLzr model. We find that root mean square error (RMSE) between modeled (based on PT‐JPLzr model) and observed ET is 8.25% lower than that of PT‐JPLsm model at 16 in‐situ ET observation sites. Comparing with T/ET from the satellite‐based products, our results highlight the improved performance of PT‐JPLzr (R2 = 0.66) due to incorporated Zr, which is superior to that of PT‐JPLsm model (R2 = 0.62). Transpiration (T) limited by changes in soil moisture (SM) is more sensitive to Zr than CH. Thus, Zr improves the PT‐JPL model performance by affecting the sensitivity of T to soil moisture deficit. Moreover, SM and LAI are main drivers of T/ET spatial variability in drier and wetter regions, respectively. These findings highlight the critical role of Zr in regulating the effects of soil moisture deficit on ET.

“…In order to have the same spatial resolution between WRF simulations and observation-based gridded datasets, we resample WRF simulations to rectilinear grid with a 0.1° spatial resolution using a simple weighted squared distance method (Schwitalla et al, 2008). Detailed descriptions of these datasets are provided in Zhang et al (2022).…”

Section: Data Setsmentioning

confidence: 99%

Response of Erosive Precipitation to Vegetation Restoration and Its Effect on Soil and Water Conservation Over China's Loess Plateau

Water Resources Research

Tian

et al. 2023

Self Cite

Vegetation restoration is commonly recognized as one of the most effective measures for soil and water conservation (Feng et al., 2016;Teo et al., 2022;Wang et al., 2016). From a water conservation point of view, vegetation restoration can enhance rainfall infiltration as the presence of root/plant residue and increased surface roughness can reduce the amount and velocity of surface runoff (Dunne et al., 1991;Wang et al., 2012Wang et al., , 2013. Vegetation restoration also increases soil water holding capacity and can hold more soil water in place by physically binding soil particles together (Ran et al., 2013;Yang et al., 2016). From a soil conservation point of view, vegetation restoration can intercept rainfall and reduce its energy to prevent splash erosion. It also slows down and reduces surface runoff to mitigate flood and sheet erosion (Guo et al., 2019). Moreover, vegetation restoration can anchor and reinforce soil particles with its spreading root systems (Legates et al., 2011) and stabilize hillslopes through axial root reinforcement to weaken gravitational erosion (Burylo et al., 2011). While these soil and water conservation benefits from vegetation restoration have been investigated from the land-atmosphere coupling perspective (Forzieri et al., 2017;Li et al., 2018;Zhang et al., 2021Zhang et al., , 2022, these studies generally focus on total precipitation (P) changes without further understanding the feedbacks between vegetation restoration and erosive P through revegetation-induced redistributions of water and energy budgets. Moreover, it is still not clear how the erosive proportion of total P responds to large-scale revegetation and to what extent it affects soil conservation (Li et al., 2018;Trenberth, 1999). Improved understanding of land-atmosphere interactions with explicit representation of vegetation dynamics is, therefore, key toward a more comprehensive assessment of the