•Soil and water conservation functions under various forest types were compared.•Different forest types exhibit variations in rainfall distribution and soil properties.•Natural forests outperform in ...understory biodiversity and interspecific repeatability.•Arborous and litter layers significantly influence forest ecological functions.•This study provides implications for afforestation in ecologically vulnerable areas.
Afforestation is widely acknowledged as an effective approach for enhancing ecological conditions. Considering the challenging ecological environment on the Loess Plateau, prioritizing soil and water conservation functions in stands is crucial. The study aimed to ascertain the future development direction of forestry on the Loess Plateau by examining two representative forest types: planted forest (Robinia pseudoacacia pure forest and Pinus tabulaeformis pure forest), and natural secondary forest (a mixed forest of Quercus liaotungensis and Populus davidiana). The assessment centered on the soil and water conservation functions of the two forest types, encompassing the water conservation function (rainfall distribution and changes in multi-year soil moisture storage (0–200 cm)), soil conservation function (soil physicochemical properties), and understory plant diversity and stability. The results indicated that natural secondary forests outperformed planted forests in terms of water conservation function by effectively converting more precipitation into soil moisture, reducing runoff, and maintaining higher soil moisture storage. Additionally, natural secondary forests exhibited superior soil conservation functions compared to planted forests, characterized by higher soil porosity and nutrient properties. The variation in community structure between the shrub and herbaceous layers was more significant among different forests than within each forest (P < 0.05). Natural secondary forests exhibited higher understory shrub and herb biodiversity and interspecific repeatability compared to planted forests. Therefore, natural secondary forests are a more suitable forest type considering the natural conditions and silvicultural objectives of the Loess Plateau. To enhance the quality of afforestation, it is recommended to adopt near-natural planting patterns that replicate the environmental conditions of natural forests. For instance, actively creating mixed forests that emulate the tree species composition of natural forests and gradually reducing dependence on a single dominant tree species. Furthermore, the arborous and litter layers had a more direct and substantial influence on soil and water conservation functions compared to the shrub and herb layers. Foresters should prioritize regulating stand structure, such as increasing canopy variability, to enhance the water conservation function of stands. Additionally, they should actively protect the understory litter to fulfill its role in enhancing soil quality. This study provides a theoretical foundation and practical guidance for the implementation of vegetation restoration in ecologically vulnerable areas, such as the Loess Plateau.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•The eco-hydrological benefits under planted and natural forest were compared.•Soil properties and vegetation attributes differ among different vegetation types.•Soil water storage (SWS) in natural ...forest is more than that in planted forests.•Herbaceous attributes are key eco-factors to hydrological regulation functions.•Results provide a support and guidance for afforestation in a close-to-nature way.
Vegetation restoration serves as a long-term and important strategic initiative in ecologically-fragile locations worldwide, while the ecological effects of long-term vegetation restoration must be thoroughly investigated to support ecological restoration in these regions. The Loess Plateau is a typical area where the eco-environment has been improved by vegetation restoration in China, wherein four representative sites: the P. tabulaeformis planted forest, P. orientalis planted forest, R. pseudoacacia planted forest and the natural Secondary forest were selected as examples of typical planted and natural forests in this study. To analyze the ecological benefits of different vegetation restoration types and discuss a more sustainable pattern of afforestation in the future, soil properties in 0–100 cm, vegetation attributes at four synusiae, and hydrological regulation functions (the rainfall distributions of 23 rainfall events and 10 years of soil water storage) were measured and compared. The results showed that: (1) the soil properties of natural Secondary forest, in particular, soil water-retention capacities, were better than those of the planted forests; (2) the biomass of arborous synusia in natural Secondary forest was less than that in the planted forests, whereas it was significantly higher at shrub and herbaceous synusiae; (3) there were differences in rainfall redistribution among the natural and planted forests examined in this study, and the natural forest exhibited the highest soil water storage (414.33 mm) during the last decade; (4) according to the structural equation model (SEM), the vegetation attributes at arborous and herbaceous synusiae had the most direct and total effect on the hydrological regulation functions in the ecosystems. The results indicate that afforestation should be conducted in a way of near-natural restoration, which can provide guidance for future vegetation restoration in the Loess Plateau and other ecologically vulnerable areas.
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GEOZS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Agroforestry has been widely practiced in the Loess Plateau region of China because of its prominent effects in reducing soil and water losses, improving land-use efficiency and increasing economic ...returns. However, the agroforestry practices may lead to competition between crops and trees for underground soil moisture and nutrients, and the trees on the canopy layer may also lead to shortage of light for crops. In order to minimize interspecific competition and maximize the benefits of tree-based intercropping systems, we studied photosynthesis, growth and yield of soybean (Glycine max L. Merr.) and peanut (Arachis hypogaea L.) by measuring photosynthetically active radiation, net photosynthetic rate, soil moisture and soil nutrients in a plantation of apple (Malus pumila M.) at a spacing of 4 m × 5 m on the Loess Plateau of China. The results showed that for both intercropping systems in the study region, soil moisture was the primary factor affecting the crop yields followed by light. Deficiency of the soil nutrients also had a significant impact on crop yields. Compared with soybean, peanut was more suitable for intercropping with apple trees to obtain economic benefits in the region. We concluded that apple-soybean and apple-peanut intercropping systems can be practical and beneficial in the region. However, the distance between crops and tree rows should be adjusted to minimize interspecies competition. Agronomic measures such as regular canopy pruning, root barriers, additional irrigation and fertilization also should be applied in the intercropping systems.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A number of studies have focused on the capacity of urban trees and shrubs to serve as efficient biological filters to mitigate air pollution. In this study, five different tree species were assessed ...for this function. Kerria japonica, Sophora japonica, Philadelphus pekinensis, Gleditsia sinensis, and Prunus persica 'Atropurpurea' were tested in a deposition chamber using (NH4)2SO4 particles. We quantified and compared the capability of all tested trees to remove particles by assessing deposition velocity, a measure of the ability to remove particles. When placed in the deposition chamber, S. japonica had the greatest deposition velocity, followed by Philadelphus pekinensis, G. sinensis, Prunus persica 'Atropurpurea,' and K. japonica, in descending order. In addition, the comparison of deposition velocities among these species suggested that certain leaf geometries and surface characteristics of broadleaf trees, such as trichomes and grooves, increased particle capture. However, these results change under a different simulation condition using ambient air, suggesting that some trees actually increase pollutant number concentrations more than reduce particle concentration. This outcome can be explained by the aerodynamic effect of trees exceeding the filtering capacity of vegetation under some conditions. This highlights the difficulty of generalizing species selection criteria for practice use. Accordingly, our results indicate that using vegetation to reduce particle pollution and improve the air quality is not a universally advisable and viable solution.
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The Soil Conservation Service curve number (SCS-CN) method has been widely used in rainfall-runoff modelling; however, the direct effects of rainfall intensities and duration, which are major factors ...in hydrological engineering design, on its parameters (initial abstraction ratio (λ) and potential maximum storage (S), the latter is transformed into curve number (CN)) have seldom been studied. In this study, we chose simulated rainfall experiments on runoff plots (30 mm/h, 180 min; 60 mm/h, 90 min; 90 mm/h, 60 min) to obtain synchronized rainfall-runoff data and calculated the parameters using general model fitting and event analysis methods every ten minutes throughout the duration. The results indicate that the parameters changed with rainfall intensities and duration. S decreased as the rainfall intensities increased. Under the same rainfall intensity, the S increased with the duration overall. The corresponding λ changed with rainfall intensities and duration, and has no obvious relationship under different rainfall intensities. Initial abstraction in the event analysis method is the same as the actual situation and we chose these parameters obtained with the event analysis method as our selected parameters. These selected parameters and the parameters obtained using Fu et al.’s method which was based on the standardized procedure in NEH-630 were evaluated by the Nash–Sutcliffe efficiency (NSE), the percentage deviation coefficient (PBIAS), and the ratio of the root mean square error to the standard deviation of measured data (RSR). The results show that the statistics for the selected parameters satisfied the evaluating standard, and have a better value, while the statistics for the parameters obtained by Fu et al.’s method declined as the rainfall intensity increased, and PBAIS was out of the standard range under 90 mm/h rainfall intensity condition. This indicates that the rainfall intensities and duration have important effects on the parameters of the model, and the parameters vary dynamically with the rainfall intensity and duration. These results could be useful for hydrological design in which engineers consider the return period (i.e., rainfall intensities and duration).
•The soil and water conservation function of stands was evaluated quantitatively.•The effects of stand structure factors on functional indices were studied.•The optimal stand structure configuration ...to improve the function was determined.•The optimization suggestions of stand structure were put forward.
The analysis of complex relationship between stand structure and soil and water conservation function (SWCF) of forests and the precise adjustment of stand structure based on an improvement in function are the key technical problems of forestry ecological engineering construction in the Loess Plateau. This study was conducted in the Caijiachuan watershed of the Loess Plateau in western Shanxi, China. Sixty standard plots (20 × 20 m2), including 20 stand densities (900 ∼ 2,800 plants·hm−2), of Robinia pseudoacacia L. were established in the watershed. The 10 factors of stand structure and four functional indices of the SWCF, including 29 sub-functional indices, were investigated and monitored each year from June to September in 2016 to 2019. The results indicated that there are differences in the SWCF under different stand structures, and the differences are concentrated in the water conservation function (FWC) and soil conservation function (FSC) of functional indices of the SWCF. In particular, they are reflected in the soil moisture and hydrological characteristics of the litter of sub-functional indices. Stand structure factors could effectively explain the differences of functional indices of the SWCF of a R. pseudoacacia forest, and a rate of 81.4% of functional indices could be explained by stand structure factors. Based on the configuration of the optimal stand structure (included a stand density of 1,800 plants·hm−2, mean diameter at breast height of 15.19 cm, mean tree height of 10.49 m, leaf area index of 2.86, canopy density of 0.85, uniform angle index of 0.50, story differentiation of 0.59, diameter dominance of 0.45, and biomass dominance of 0.46), the density of existing stands was concentrated in the range of 1,500 ∼ 1,900 plants·hm−2 and was more effective at optimizing the SWCF. The optimization strategy of the stand structure of the R. pseudoacacia forest in the study area should focus on increasing the differentiation of forest layer, enrich the vertical structure of the stand and maintain a random distribution pattern of trees. The overall growth of the stand remained uniform, avoiding the excessive dominance of individual trees and unreasonable stand density. These results will provide a more scientific and complete reference to optimize the stand structure of the R. pseudoacacia forest in the Loess Plateau.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
To identify a vegetation configuration pattern with a high-efficiency purification ability for total nitrogen (TN), available nitrogen (AN), total phosphorous (TP), available phosphorous (AP), and ...chemical oxygen demand (COD) based on comprehensive assessment results, a water discharge experiment was performed in the Luan River in China with the following riparian forests: I, pure broad-leaved; II, mixed broad-leaved; III, mixed coniferous and broad-leaved; IV, mixed coniferous; and V, pure coniferous. From the riparian buffer zone to the river channel, the evaluation showed that pattern I had the highest purification ability at 1 m and 2 m; at a width of 4 m, pattern III had the highest purification ability; at a distance of 7 m, pattern V showed the highest purification ability; at 10 m, pattern IV showed the highest purification ability, pattern II the lowest. It is advisable to give priority to plant coniferous species from 0 m to 4 m from the river bank, while it is advisable to give priority to plant broad-leaved species from 4 m to 10 m from the river bank. We therefore recommend these vegetation configuration patterns in the development and management of runoff purification systems.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Alley cropping allows the famer to effectively use available resources and yield more benefits. Choosing suitable associated crop and mitigating the competition between trees and crops are crucial ...for designing the alley cropping systems. We conducted a long-term experiment, including apple (Malus pumila)/peanut (Arachis hypogaea), apple/millet (Setaria italica) and apple/maize (Zea mays) alley cropping systems with conventional intercropping distance, and corresponding monocultures (Exp.1), and a short-term experiment with improved intercropping distance in the same three combinations (Exp.2) in the Loess Plateau, China. The results showed crop yields in three alley cropping systems were lower than the corresponding monocultures. Apple yields were significantly constrained by millet and maize in the alley cropping systems, but not sensitive to the presence of peanut. Land equivalent ratios (LERs) ranged from 0.44 to 0.89 before the tree bore fruit. The LERs were greater than 1.0 after the tree bore fruit, and the apple trees made a decisive contribution to the land use advantage. Net present values of three alley cropping systems were on average 60.1% higher than the corresponding monocultures across the alley cropping period. The maximum annual present value in the first–fifth, sixth and seventh–ninth years after the alley cropping establishment was observed in the apple/maize, apple/millet and apple/peanut system, respectively. These results highlight that choosing the optimal alley cropping management and suitable associated crops at different years after establishment may allow farmers to increase the land use efficiency and economic profitability.
The enhancement of the ecological functions of forests through stand structure optimization is a key issue for high-quality forestry and its sustainable development on the Loess Plateau. In this ...study, fifty standard plots of Pinus tabuliformis Carr. forest were established in the Loess Plateau of western Shanxi, China. Eleven factors of the stand structure, three topographical factors, and four functional indices of the ecological function, including 20 sub-functional indices, were investigated and monitored. The study results indicated that the stand structure and topographical conditions could significantly affect the ecological functions of the Pinus tabuliformis forest, which was primarily reflected in the water-holding function, soil improvement function, and diversity function of understory plants, but had little effect on the function of reducing runoff and sediment yield on slope. We found that the stand density and uniform angle index could be used to achieve the optimal regulation of the stand structure to enhance the ecological functions of the Pinus tabuliformis forest. Overall, the optimization strategy for the stand structure of Pinus tabuliformis on the Loess Plateau should be to (1) determine the characteristics of the regulation target by understanding the stand structure and its ecological function characteristics through stand surveys on the altitude of the stand, stand density, uniform angle index of the individual trees in the sample plot, and average uniform angle index of the sample plot; (2) determine the optimization target by quantifying and analyzing the ecological functions of the stand, selecting a certain functional index as the optimization target, and specifying the degree of improvement in the functional index; and (3) substitute the optimization target and elevation of the stand into the corresponding stand structure optimization model and determine the regulation direction and regulation range of the stand density, uniform angle index, and specific stand structure regulation measures. The results of this study serve as a guide for optimizing the stand structure on the Loess Plateau.
The accurate estimation of forest biomass is important to evaluate the structure and function of forest ecosystems, estimate carbon sinks in forests, and study matter cycle, energy flow, and the ...effects of climate change on forest ecosystems. Biomass additivity is a desirable characteristic to predict each component and the total biomass since it ensures consistency between the sum of the predicted values of components such as roots, stems, leaves, pods, and branches and the prediction for the total tree. In this study, 45 Robinia pseudoacacia L. trees were harvested to determine each component and the total biomass in the Loess Plateau of western Shanxi Province, China. Three additive systems of biomass equations of R. pseudoacacia L., based on the diameter at breast height (D) only and on the combination of D and tree height (H) with D2H and DbHc, were established. To ensure biomass model additivity, the additive system of biomass equations considers the correlation among different components using simultaneous equations and establishes constraints on the parameters of the equation. Seemingly uncorrelated regression (SUR) was used to estimate the parameters of the additive system of biomass equations, and the jackknifing technique was used to verify the accuracy of prediction of the additive system of biomass equations. The results showed that (1) the stem biomass contributed the most to the total biomass, comprising 51.82% of the total biomass, followed by the root biomass (24.63%) and by the pod and leaf biomass, which accounted for the smallest share, comprising 1.82% and 2.22%, respectively; (2) the three additive systems of biomass equations of R. pseudoacacia L. fit well with the models and were effective at making predictions, particularly for the root, stem, above-ground, and total biomass (R2adj > 0.812; root mean square error (RMSE) < 0.151). The mean absolute error (MAE) was less than 0.124, and the mean prediction error (MPE) was less than 0.037. (3) When the biomass model added the tree height predictor, the goodness of fit R2adj increased, RMSE decreased, and the accuracy of prediction was much improved. In particular, the additive system, which was developed based on DbHc combination prediction factors, was the most accurate. The additive system of biomass equations established in this study can provide a reliable and accurate estimation of the individual biomass of R. pseudoacacia L. in the Loess region of western Shanxi Province, China.
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