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Forest growth in tropical regions is regulated in part by climatic factors, such as precipitation and temperature, and by soil factors, such as nutrient availability and water storage capacity. We examined a decade of growth data from Eucalyptus clonal plantations from over 113,000 forest inventory plots across a 10 million-ha portion of Mato Grosso do Sul in southwestern Brazil. From this full dataset, three subsets were screened: 71,000 plots to characterize growth and yield across water table depth classes, 17,000 plots to build generalized models, and 50,000 plots for clone-based analyses. Average precipitation varied little across the region (1150 to 1270 mm yr(-1)), but water table depth ranged from less than 10 m to over 100 m. Where the water table was within 10 m of the surface, about 20 % of the total water used by trees came from this saturated zone. Water tables deeper than 50 m contributed very little to tree water use. Sites with a water table within 10 m averaged 47 m(3) ha(-1) yr(-1) in stem growth (mean annual increment, MAI) across a full rotation, compared to less than 37 m(3) ha(-1) yr(-1) for sites with water tables deeper than 50 m. Drought-induced canopy damage rose from 7 % to 30 % along the water tables depth gradient, while tree mortality rose nearly fourfold. The optimal stocking level was about 1360 trees ha(-1) where water tables were accessible, declining to 1080 trees ha(-1) where they were not. Among the 15 most planted Eucalyptus clones, increases in MAI from the lowest to highest water table depths ranged from + 4.8 to + 16.8 m(3) ha(-1) yr(-1) , reflecting significant genotype-environment interactions. On average, MAI decreased by 0.8 m(3) ha(-1) yr(-1) (ranging from 0.4 to 1.4) for every 10 m increase in water table depth. Similarly, the Site Index at base age 7 years declined from 31 m to 27 m, with an average reduction of 0.25 m per 10 m increase in water table depth. Physiographic modeling of water table depths offers useful information for forest management practices like forest inventory and planning, clonal allocation, optimized planting densities, fertilization strategies, coppice techniques, and other landscape-specific strategies like tree breeding zones.

期刊论文 2025-08-01 DOI: 10.1016/j.foreco.2025.122771 ISSN: 0378-1127

In the process of using transportation infrastructure, contact erosion between different particle sizes soil layers can easily occur under complex hydro-mechanical coupling, leading to deformation and damage of structures. To investigate indirect erosion between soil layers under cyclical load effects from a microscopic perspective, a volume of fluid-discrete element method (VOF-DEM) coupled method was adopted in this study. The influence of different water table levels and particle size ratios (PSR) was considered. The study found that: (1) The compressive effect of coarse particles during loading and the stress relaxation effect during unloading can both cause migration of fine particles within one loading-unloading cycle; (2) Immersion of the contact surface between coarse and fine particles is a key factor in inducing particle migration, with the interaction between particles being the most intense at the contact surface; (3) Fully saturated soil experiences the most severe particle erosion and macroscopic deformation; (4) Reducing PSR can effectively improve the integrity of soil structure and suppress erosion of fine particles; (5) Particle migration inevitably leads to axial deformation of the soil, resulting in reduced stiffness and increased energy dissipation during loading-unloading cycles. This study provides new insights into contact erosion under complex hydraulic coupling from a microscopic perspective.

期刊论文 2025-04-01 DOI: 10.1016/j.compgeo.2025.107090 ISSN: 0266-352X

The stratigraphic uncertainty and rotated anisotropy of soil properties exist widely in nature. Recent studies have shown that the slope stability was significantly influenced by these two uncertainties. However, there is no proper method for simulating these two uncertainties at the same time, and the influence of the two uncertainties has not been considered in previous unsaturated soil slope stability analysis. This paper aims to propose a coupled method for characterizing the stratigraphic uncertainty and rotated anisotropy of soil properties, and investigate the unsaturated soil slope stability considering the two uncertainties. Through a slope case, the proposed method for characterizing the two uncertainties is examined. The effect of rotational angle on the slope stability and groundwater table is studied. In addition, four different uncertainty considerations are chosen to compare their influence on the slope stability and groundwater table. The results show that the proposed method can well characterize the two uncertainties at the same time. The rotational anisotropy of soil properties has a substantial impact on the slope stability and groundwater table. The rotational angles corresponding to the maximum and minimum reliability index of slope depend on the uncertainty considerations in the slope stability analysis. The slope reliability index only considering stratigraphic uncertainty is the highest, and the slope reliability index considering stratigraphic uncertainty and rotated anisotropy of soil properties is the lowest.

期刊论文 2024-02-01 DOI: 10.1002/nag.3642 ISSN: 0363-9061

Alpine regions' groundwater is crucial to the worldwide hydrological cycle. However, due to the harsh environmental conditions, the distribution and evolution characteristics await clarification. The study area was selected to be the Nagqu River Basin in the Nu-Salween River's source region. In 2019-2021, we gathered 88,000 monitoring data from nine observation wells and examined the spatiotemporal groundwater table changes in various permafrost zones and freeze- thaw cycles. During the freezing period, entirely frozen period, thawing period, and entirely thawed period, the groundwater table change rates in the permafrost zone were 2.14, 1.54, 1.55, and 2.01 times larger than in the seasonal frost zone, and fluctuation amplitudes were 1.97, 1.28, 1.01 and 1.31 times larger. The average groundwater table change rate and fluctuation amplitude were greatest during the entirely thawed period and lowest during the thawing period, with the maximum change rate reaching 3.64 cm/d during the entirely thawed period of 2019-2020 in the permafrost zone and the minimum change rate of 0.12 cm/d during the thawing period of 2019-2020 in the seasonal frost zone.

期刊论文 2023-01-01 DOI: 10.15244/pjoes/168803 ISSN: 1230-1485

Wet alpine meadows generally act as a significant carbon sink, since their low rate of soil decomposition determines a much smaller ecosystem respiration (Re) than photosynthesis. However, it remains unclear whether the low soil decomposition rate is determined by low temperatures or by nearly-saturated soil moisture. We explored this issue by using five years of measurements from two eddy-covariance sites with low temperature and significantly different soil water conditions. The results showed that both sites were carbon sinks. However, despite a smaller annual gross primary productivity, the wet site with a shallow groundwater showed a much higher carbon use efficiency and larger carbon sink than the dry site (which had a deeper water table) due to its much lower Re. Our analyses showed that Re of the wet site was significantly decreased under the nearly-saturated soil condition during the unfrozen seasons. This effect of nearly-saturated soil water on Re increased with soil depths. In contrast, at the dry site the high soil water content favored Re. The corresponding soil temperature at both sites expectedly showed large and positive effects on Re. These results demonstrated that the high carbon sink of the wet alpine meadow was mainly caused by the inhibiting effects of the nearly-saturated soil condition on soil respiration rather than by the low temperatures. Therefore, we argue that a warming-induced shrinking cryosphere may affect the carbon dynamics of wet and cold ecosystems through changes in soil hydrology and its impact on soil respiration. In addition, our study highlights the different responses of soil respiration to warming across soil depths. The thawing of frozen soil may cause larger CO2 emission in the top soil, while it may also partially contribute to slowing down soil carbon decomposition in the deep soil through decreasing metabolic activity of aerobic organisms.

期刊论文 2021-02-15 DOI: 10.1016/j.agrformet.2020.108254 ISSN: 0168-1923

Polygonal peatlands are carbon-rich permafrost ecosystems that will likely be significantly affected by climate change. However, studies are often constrained to one measurement per day, which impedes assessments of the temporal variability in carbon fluxes. For this reason, we measured ecosystem respiration (ER) of CO2 in a polygonal peatland underlain by continuous permafrost over an entire growing season to determine the effects of temperature and water table depth on the temporal variability of ER. We used four automated closed chambers to measure ER under varying temperature and soil moisture regimes. Temporal variability was approximately the same for the four plots, on both a diurnal and a seasonal scale. Both diurnal and seasonal variations in ER were strongly controlled by changes in soil surface temperature. Fluctuations of the water table depth associated with important rainfall events was also an important factor affecting ER on the seasonal scale. We found that water table level fluctuations below 20-25 cm did not significantly affect ER and that most soil respiration took place in the top 10 cm, likely in the surface 2 cm. Our results highlight the importance of monitoring future changes in tundra hydrology, which will determine the depth of organic matter available for aerobic decomposition.

期刊论文 2018-03-01 DOI: 10.1139/as-2016-0045

\ Northern peatlands have accumulated a large amount of organic carbon (C) in their thick peat profile. Climate change and associated variations in soil environments are expected to have significant impacts on the C balance of these ecosystems, but the magnitude is still highly uncertain. Verifying and understanding the influences of changes in environmental factors on C gas fluxes in biogeochemical models are essential for forecasting feedbacks between C gas fluxes and climate change. In this study, we applied a biogeochemical model, DeNitrification-DeComposition (DNDC), to assess impacts of air temperature (T-A) and water table (WT) on C gas fluxes in an Alaskan peatland. DNDC was validated against field measurements of net ecosystem exchange of CO2 (NEE) and CH4 fluxes under manipulated surface soil temperature and WT conditions in a moderate rich fen. The validation demonstrates that DNDC was able to capture the observed impacts of the manipulations in soil environments on C gas fluxes. To investigate responses of C gas fluxes to changes in T-A and soil water condition, we conducted a series of simulations with varying T-A and WT. The results demonstrate that (1) uptake rates of CO2 at the site were reduced by either too colder or warmer temperatures and generally increased with increasing soil moisture; (2) CH4 emissions showed an increasing trend as T-A increased or WT rose toward the peat surface; and (3) the site could shift from a net greenhouse gas (GHG) sink into a net GHG source under some warm and/or dry conditions. A sensitivity analysis evaluated the relative importance of T-A and WT to C gas fluxes. The results indicate that both T-A and WT played important roles in regulating NEE and CH4 emissions and that within the investigated ranges of the variations in T-A and WT, changes in WT showed a greater impact than changes in T-A on NEE, CH4 fluxes, and net C gas fluxes at the study fen.

期刊论文 2015-07-01 DOI: 10.1002/2014JG002880 ISSN: 2169-8953
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