Impact Of Vegetation Restoration Research Articles

Vegetation restoration limited microbial carbon sequestration in areas affected by soil erosion

The impact of vegetation restoration on soil structure, nutrients, and microorganisms in eroded areas has been extensively studied, but the effect of vegetation restoration on carbon-sequestering bacterial communities and their associated carbon fixation capacity remains largely unknown. In this study, we focused on the 0–20 cm soil layer in eroded and vegetation restoration sites in areas of southern China that have been severely affected by soil erosion and utilized 13C stable isotope labeling and high-throughput sequencing technologies to investigate the influence of vegetation restoration on carbon-sequestering bacterial communities and their carbon sequestration potential. Compared with eroded areas, vegetation restoration areas presented greater soil nutrient contents and greater diversity of bacteria with carbon sequestration functions. Vegetation restoration also altered the composition of carbon-sequestering bacterial communities by increasing the soil alkali-hydrolyzable nitrogen content, with the dominant carbon-sequestering bacteria shifting from Nocardia to Bradyrhizobium. However, the microbial carbon sequestration rate in soil erosion areas significantly increased by 2.15 times compared with that in vegetation restoration areas. Among the factors considered, pH (68.90 %, P = 0.000) was identified as the primary explanatory factor regulating changes in the microbial carbon sequestration rate. Our results are important for revealing the role of vegetation restoration in the global carbon cycle and elucidating the role of microorganisms in the soil carbon cycle.

Effect of vegetation restoration type and topography on soil water storage and infiltration capacity in the Loess Plateau, China

Vegetation restoration effectively mitigates soil erosion and improves soil properties, but in drylands, it can lead to soil water scarcity and disrupt ecological balance. Until now, limited research has examined the combined effects of vegetation restoration type and topography on soil water and infiltration in the Loess Plateau of China. Here, we investigated soil water content (SWC), soil water storage (SWS), soil infiltration rates and related soil properties in typical forestland, shrubland, and grassland across five slope positions on steep slopes, and compared them with cropland. The results indicated that vegetation restoration significantly decreased SWS compared to cropland. Across the entire 0–500 cm depth, reductions were observed at 30.9 %, 33.2 %, and 20.8 % for forestland, shrubland, and grassland, respectively, with forestland and shrubland demonstrating a more pronounced decrease, particularly in deeper soil layers. Shrubland had the lowest SWS on the upper, middle, and top slopes, while forestland showed the lowest SWS on the lower and foot slopes. In terms of infiltration, vegetation restoration generally increased steady infiltration rate but resulted in reduced initial and mean infiltration rates (except for shrubland). Shrubland had the highest infiltration rates, followed by forestland, while grassland had the lowest rates. Soil infiltration rates decreased gradually along the slope, indicating that the impact of vegetation restoration on soil infiltration improvement weakened with lower slope positions. Vegetation restoration type had a stronger direct and total effects on infiltration than slope position. Yet, the indirect influence of slope position through clay content and SWC outweighed that of vegetation restoration type. Our findings highlight the comprehensive assessment of the eco-hydrological effects of vegetation restoration is essential for identifying suitable species and designing optimal spatial distribution, ultimately maximizing the ecological benefits of the restoration. These insights can offer valuable guidance for ecological restoration and land management in fragile dryland ecosystems.

The Impact of Artificial Restoration of Alpine Grasslands in the Qilian Mountains on Vegetation, Soil Bacteria, and Soil Fungal Community Diversity.

To understand how the soil microbial community structure responds to vegetation restoration in alpine mining areas, this study specifically examines the grassland ecosystem in the Qianmalong mining area of the Qilian Mountains after five years of artificial restoration. High-throughput sequencing methods were employed to analyze soil bacteria and fungi microbial characteristics in diverse grassland communities. Combined with modifications in vegetation diversity as well as soil physicochemical properties, the impact of vegetation restoration on soil microbiome diversity in this alpine mining area was investigated. The findings indicated that the dominant plants were Cyperus rotundus, Carex spp., and Elymus nutans. As the extent of the grassland's restoration increased, the number of plant species, importance values, and plant community diversity showed an increasing trend. The plant functional groups were mainly dominated by Cyperaceae, followed by Poaceae. Plant height, density, plant cover, frequency, and aboveground biomass showed an increasing trend, and soil water content (SWC) increased. While soil pH and soil electrical conductivity (EC) exhibited a declining trend, available phosphorus (AP), total phosphorus (TP), total nitrogen (TN), nitrate nitrogen (NO3-N), soil organic carbon (SOC), and soil water content (SWC) showed an increasing trend. The dominant bacterial communities were Actinobacteriota, Proteobacteria, Acidobacteriota, Chloroflexi, Firmicutes, and Gemmatimonadota, while the dominant fungal communities were Ascomycota, Mortierellomycota, Basidiomycota, unclassified_k_Fungi, and Glomeromycota. Significant differences were detected within soil microbial community composition among different degrees of restoration grasslands, with bacteria generally dominating over fungi. SWC, TP, and TN were found to be the main soil physicochemical factors affecting the distribution of soil bacterial communities' structure; however, SOC, TN, and NO3-N were the primary factors influencing the soil distribution of fungal communities. The results of this study indicate that different degrees of vegetation restoration in alpine mining areas can significantly affect soil bacterial and fungal communities, and the degree of restoration has varying effects on the soil bacteria and fungi community structure in alpine mining areas.

Study on the Impact of Vegetation Restoration on Groundwater Resources in Tianshan Mountain and Yili Valley in Xinjiang, China

China has implemented a series of ecological protection and restoration projects in Tianshan Mountain and Yili Valley in Xinjiang, which have significantly improved regional vegetation coverage. Vegetation improves soil structure through roots, especially increasing non-capillary porosity, which enhances the precipitation infiltration performance, thus reducing surface runoff, increasing the interception and infiltration of groundwater resources, and enhancing regional water retention capacity of soil. In order to quantitatively study the impact of ecological conservation and restoration (represented by fraction of natural vegetation coverage, FVC) on groundwater storage (GWS), we investigated GWS changes in this region, identified the main factors, and quantified their relative impacts. Here, we combined data from the Gravity Recovery and Climate Experiment (GRACE) satellite, GRACE Follow-On (GRACE-FO), and Global Land Data Assimilation System (GLDAS) hydrological model from January 2003 to December 2020 and evaluated GWS changes. We used the variable importance in projection and partial least squares regression methods to determine the main influencing factors. We found that (1) before and after 2012, GWS decreased at a rate of 0.80 cm/yr and 0.75 cm/yr (with statistical significance p < 0.01), respectively. (2) Before 2012, the main factors affecting the decrease in GWS were agricultural planting areas, and after 2012, they were temperature, evaporation, and FVC, with relative contributions of 54.72%, 34.59%, and 10.69%, respectively. FVC has a positive regulating effect on the increase in regional GWS.

Superior improvement on soil quality by Pennisetum sinese vegetation restoration in the dry-hot valley region, SW China

Vegetation restoration is a good way to improve soil quality and reduce erosion. However, the impact of vegetation restoration on soil quality in the dry-hot valley region has been overlooked for many years. This study aimed to reveal the effects of Pennisetum sinese (PS) and natural vegetation (NV) on soil quality and then to explore the feasibility of introducing PS for the vegetation restoration of the dry-hot valley region. The PS and NV restoration areas deserted land evolving from cultivated land (CL) have been established since 2011. The results showed that the soil properties were obviously improved by PS from the dry to wet seasons, except for the soil available phosphorous. The comprehensive soil quality indexes of the three typical seasons (dry, dry-wet, and wet) were determined by using nonlinear weighted additive (NLWA) based on the total dataset, significant dataset and minimum dataset (MDS). The results indicated that the comprehensive minimum dataset soil quality index (MDS-SQI) of the three typical seasons evaluate soil quality well. The soil quality of PS was significantly greater than that of CL and NV (P < 0.05), as shown by the MDS-SQI. Additionally, PS could maintain a stable soil quality in the three typical seasons, while both CL and NV had obvious fluctuations. In addition, the result of the generalized linear mode suggested that the vegetation type had the greatest impact on the soil quality (44.51 %). Comprehensively, vegetation restoration in the dry-hot valley region has a positive impact on the soil properties and quality. PS is a great candidate species for the early vegetation restoration in the dry-hot valley region. This work provides a reference for vegetation restoration and rational utilization of soil resources in degraded ecosystems in dry-hot valleys and other soil erosion areas.

Response of heterotrophic respiration to vegetation restoration in a karst area of SW China

AbstractThe Grain‐for‐Green Program in China aims to restore sloping karst cropland severely degraded by intensive agriculture to secondary forest. Heterotrophic respiration (Rh) is a major process of carbon release from soils and is associated with the sequestration of soil organic carbon (SOC). However, we still do not have a comprehensive understanding of Rh and what drives it along soil profile horizons during the natural vegetative recovery process in typical karst soils. We investigated the responses of Rh (C release per gram of soil) and specific Rh (C release per gram of SOC) in soil horizons from the soil surface to bedrock at the different vegetation recovery stages in a karst region. Coincident soil microbial properties (e.g., bacterial and fungal abundance, total microbial biomass, potential enzyme activities) and physicochemical properties were quantified. Vegetation restoration after cropland abandonment significantly increased Rh rates due to increased soil nutrients and microbial biomass, bacterial abundances, and hydrolase activities (all, p &lt; 0.05). The rates of Rh enhanced in sloping cropland (SC) from the soil surface to bedrock but reduced in the recovering stages (ASC: abandoned sloping cropland and SF: secondary forest) and primary forest (PF). The specific Rh between SF (1.34 mg CO2‐C g−1 SOC d−1) and PF (1.32 mg CO2‐C g−1 SOC d−1) were not significantly different but both of them were greater than those in SC (0.79 mg CO2‐C g−1 SOC d−1) and ASC (0.8 mg CO2‐C g−1 SOC d−1). Soil physicochemical properties and microbial properties explained approximately 48% and 22% of the variations in Rh along vegetation recovery, respectively. Nitrogen to phosphorus stoichiometry exerted the most direct and positive effects on Rh, suggesting the importance of managing soil nutrient status to regulate carbon decomposition during vegetation recovery in karst soils. The increased microbial biomass was the most important microbial factor regulating Rh in later vegetation recovery phases. Our results provide scientific insight into the impact of vegetation restoration on Rh in degraded ecosystems, which is important for reducing carbon loss in karst soils.

植被和梯田对黄土高原小流域泥沙连通性的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 植被和梯田对黄土高原小流域泥沙连通性的影响 DOI: 10.5846/stxb202204211096 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金面上项目(42177319) Effects of terrace and vegetation on sediment connectivity in a small watershed on the Loess Plateau Author: Affiliation: Fund Project: The National Natural Science Foundation of China (General Program, Key Program, Major Research Plan)（42177319） 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:黄土高原经过长期水土流失治理,泥沙问题得到有效解决,但植被恢复和梯田修建对泥沙空间输移的影响尚未完全揭示。通过土地利用数据和Landsat影像确定梯田分布和植被覆盖情况,使用能表征植被和梯田对泥沙输移的阻滞作用的植被覆盖与作物管理因子和工程因子计算泥沙连通性指数(IC),分析泥沙连通性的时空动态变化,量化植被与梯田共同影响下黄土高原第三副区典型流域泥沙连通性。调整权重因子模拟不同情景下泥沙连通性指数的计算,分析植被与梯田对泥沙连通性的单独影响。结果表明由于植被快速恢复和梯田大面积修建,IC在35年间(1986-2020年)从-3.42到-9.17显著下降。情景模拟发现,在1986-1999年间,梯田为泥沙连通性减弱主要驱动因素,1999年后植被与梯田共同作用。植被影响下的IC从1986年到2020年下降73.05%,在1986-2020年间梯田影响下IC下降26.75%。在空间上梯田及高植被覆盖度区域呈弱泥沙连通性,中下游主沟及部分支沟区域为强泥沙连通性。总体而言,植被恢复和梯田修建减弱泥沙输移能力,流域输沙路径集中于主沟中下游及部分支沟区域。研究结果有助于深化黄土丘陵区小流域植被恢复和梯田修建影响下泥沙变化研究。 Abstract:After long-term soil erosion control on the Loess Plateau, the sediment problem has been effectively solved, but the impact of vegetation restoration and terrace construction on the spatial transport of sediment has not been fully revealed. This study uses land use data and Landsat images to determine the distribution of terraces and vegetation coverage, and uses vegetation coverage and crop management factors and engineering factors, which could characterize the resistance of vegetation and terraces to sediment transport, to calculate sediment. The index of connectivity (IC) was applied to analyze the temporal and spatial dynamic changes of sediment connectivity, the combined effects of vegetation and terraces on sediment connectivity of typical watersheds in the third subregion of the Loess Plateau are quantified. Weighting factors were adjusted to simulate the calculation of the sediment connectivity index under different scenarios and analyze the separate effects of vegetation and terraces on sediment connectivity. The results showed that IC significantly decreased from -3.42 to -9.17 in 35 years (1986-2020) due to the rapid vegetation restoration and the large-scale construction of terraces. The scenario simulation found that the terraced fields were the main driving factor for the weakening of sediment connectivity between 1986 and 1999. After 1999, vegetation and terraced fields worked together. The IC under the influence of vegetation decreased by 73.05% from 1986 to 2020, and the IC under the influence of terraced fields decreased by 26.75% from 1986 to 2020. In space, terraces and areas with high vegetation coverage showed weak sediment connectivity, while the main ditch and some branch ditch areas in the middle and lower reaches have strong sediment connectivity. In general, vegetation restoration and terrace construction decreased the sediment transport capacity, and the sediment transport paths in the basin were concentrated in the middle and lower reaches of the main ditch and some branch ditch areas. The results of this study can help to deepen the study of sediment changes under the influence of vegetation restoration and terrace construction in small watersheds in the loess hilly area. 参考文献 相似文献 引证文献

Comprehensive evaluation and scenario simulation of carrying capacity of water resources in Mu Us Sandy Land, China

Abstract With the rapid improvement in socioeconomic conditions globally, the demand for water resources has dramatically increased. Evaluating water resource carrying capacity (WRCC) is crucial for regional sustainable development. To date, limited attention has been paid to WRCC in areas of predominantly sandy land, with the impact of vegetation restoration in ecologically degraded areas on WRCC remaining unclear. In this study, using a comprehensive evaluation index and a system dynamics model, we evaluated the WRCC of the Mu Us Sandy Land, Inner Mongolia, China, from 2000 to 2019 then projected to 2030. Our results show WRCC has decreased since 2000, reaching a general state by 2019. In a future scenario where historical development remains unabated, WRCC will continue to decline to a poor carrying state by 2030. The comprehensive scheme based on industrial restructuring and water conservation performed the best in terms of WRCC, continuously increasing and returning to a general carrying state by 2030. Our findings highlight the WRCC of the Mu Us Sandy Land is not optimistic and subsequent ecological restoration should proceed with caution. A comprehensive scheme is an optimal development strategy for the future.

Impact of vegetation restoration on ecosystem services in the Loess plateau, a case study in the Jinghe Watershed, China

Assessing ecosystem services (ESs) is vital for the environment development. This study explored the variation characteristics of ESs under the restoring vegetation since the Grain for Green Project (GFGP) in Jinghe Watershed, which is a typical watershed experiencing severe soil erosion in the Loess Plateau of China. Herein, the fractional vegetation cover (FVC) is selected as an indicator of the changes in vegetation restoration from 2000 to 2020. Simulations of ESs are based on the Soil and Water Assessment Tool (SWAT), Carnegie Ames-Stanford Approach (CASA) model, Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST). This paper analyzed the spatiotemporal heterogeneity in vegetation coverage and the response of vegetation coverage to ESs in the Jinghe Watershed with Mann-Kendall test, Pearson correlation coeffificient R and the gray relational analysis (GRA). The results showed that: (1) Since the implementation of the GFGP, the area of forests and grassland has increased significantly. The proportion of vegetation restoration area was 95.15 %; (2) At the whole watershed scale, vegetation restoration and soil conservation (SC), water yied (WY), net primary production (NPP) and habitat quality (HQ) were synergistic relationships, while focusing on the sub-watershed scale, vegetation restoration and SC and HQ were transformed into trade-off relationships in some sub-watershed. (3) Vegetation restoration in the Jinghe Watershed had positive effects on SC, WY, NPP, and HQ. The order of relevance with vegetation restoration was: SC > HQ > NPP > WY, indicating that vegetation restoration in the Jinghe Watershed has the highest closeness to SC. This study showed that since the implementation of the GFGP, vegetation coverage in the Jinghe Watershed has significantly restored, which has promoted the improvement of ESs.

Characteristic and Attribution of Runoff Variation in the Yanhe River Basin, Loess Plateau, Based on the Budyko Hypothesis

The ecological restoration projects in the Loess Plateau (LP) has significantly altered the underlying surface conditions, coupled with a warming–wetting climate, which has profoundly affected the regional water cycle. Evaluating the response of runoff to external environmental change and quantitatively identifying the contribution of anthropogenic interference and climate change are prerequisites for efficient utilization of water resources in arid/semi-arid regions. Daily recorded data of hydrological and meteorological elements between 1969 and 2019 and the elasticity coefficient method based on Budyko hypothesis were used for attribution analysis of runoff change in the Yanhe River basin. The results show the following: (1) the measured runoff decreased significantly (p &lt; 0.05, –0.2845 mm year−1), and suggested substantial difference before and after 2000; (2) the area of woodland and grassland had a sharp increase from 2000, while the elasticity of runoff to precipitation, potential evapotranspiration (ET0), and vegetation all decreased; (3) the improvement of underlying surface conditions has become the leading factor of runoff reduction with a contribution of 96.78%; (4) the impact of vegetation restoration on runoff reduction is effective within a certain threshold. We consider that more attention should be paid to the afforestation scale and its possible negative eco-hydrological effects in future ecological restoration.

Response of deep soil moisture to different vegetation types in the Loess Plateau of northern Shannxi, China

Deep soil moisture is a highly important source of water for vegetation in the semiarid Loess Plateau of China, vegetation restoration reduced the deep soil moisture, but how to better quantify the impact of vegetation restoration on deep soil moisture is lack of certain understanding. To explore the impact exerted by different types of vegetation on deep layers of the soil moisture, the 0–10 m soil moisture content profile was measured before and after the rainy season in Armeniaca sibirica, Robinia pseudoacacia, Populus simonii, Pinus tabuliformis, Hippophae rhamnoides and in natural grassland in Wuqi County in Shannxi Province. These results showed that the highest soil moisture in the shallow layers (0–200 cm) was exhibited in the P. simonii forest, which was followed by that in the natural grassland. Both of these results were significantly higher than that those of the A. sibirica, P. tabuliformis, H. rhamnoides and R. pseudoacacia forests. The soil moisture in the deep layer (200–1000 cm) of the natural grassland was significantly higher than that of the other vegetation types. The annual precipitation that recharges the depth of soil moisture was the highest in natural grassland and the lowest in P. simonii. The inter-annual soil moisture replenishment is primarily affected by rainfall and vegetation types. Compared with the natural grassland, the CSWSD (the comparison of the soil moisture storage deficit) of different vegetation types varies. In the shallow soil layer, P. simonii is the lowest, and R. pseudoacacia is the highest. In the deep soil layer, R. pseudoacacia and P. simonii are the highest; H. rhamnoides is the second highest, and A. sibirica and P. tabuliformis are the lowest. These results indicate that vegetation restoration can significantly reduce the amount of water in the deep layers of the soil. In the future vegetation restoration, we suggest emphasizing natural development more strongly, since it can better maintain the local vegetation stability and soil moisture balance.

Impact of vegetation restoration on soil organic carbon stocks and aggregates in a karst rocky desertification area in Southwest China

The objectives of the study were as follows: (a) to determine the response of soil organic carbon (SOC) fractions to vegetation restoration; (b) to examine the contributions of aggregate-associated OC to total soil OC accumulation along vegetation restoration, (c) to identify the factors that affect SOC accumulation along natural vegetation restoration in a karst region in Southwest China. Four vegetation restoration stages, namely, grassland, shrubland, shrub-arbor mixed forestland, and arbor forestland, were compared with cropland (CL). Soil samples were collected at depths of 0–10 cm and separated into five aggregate size fractions. SOC, light fraction OC (LFOC), easily oxidizable OC (EOC), and aggregate-associated OCs were determined for different aggregate sizes and total soil. Natural vegetation restoration increased macroaggregate amount but decreased the fractions of meso- and microaggregates. Vegetation restoration significantly increased total SOC, EOC, and LFOC concentrations and stocks and soil aggregate-associated OC concentrations. The responses of EOC and LFOC in total soil and soil aggregates were more sensitive than those of SOC along with vegetation restoration. Aggregate-associated OC concentrations generally increased with a decrease in aggregate size. Macro- and microaggregate-associated OC stocks increased, but mesoaggregate-associated OC stocks decreased following the conversion of CL to a natural vegetation ecosystem. The increase in SOC stocks was primarily attributed to the macroaggregate-associated OC stocks and their changes. OC concentrations and stocks in total soil and the soil aggregates were significantly positively related to exchangeable calcium content. Vegetation restoration considerably affects the amount of soil aggregates, OC concentrations, and stocks in total soil and soil aggregates. Changes in OC concentrations and stocks can be more pronounced in the liable carbon fraction than in total SOC. The increase in SOC was mostly attributed to OC accumulation in macroaggregates. Exchangeable calcium also affected soil OC accumulation in total soil and soil aggregates.

Impact of vegetation restoration on plants and soil C:N:P stoichiometry on the Yunwu Mountain Reserve of China

Natural succession plays an important role in the accumulation and distribution of soil and plant stoichiometry. Little is known about the effects of grazing exclusion on soil and plant stoichiometry across a natural succession. Thus, this experiment was designed to measure soil and plant C:N:P stoichiometry following a chronosequence after the grazing exclusion (age ranged from 1-, 12-, 20- to 30 years) in northwestern China. Our results indicated that the vegetation succession had significant effects on the soil organic carbon, soil total N contents and plant total C, N and P contents, as well as the soil C:P and N:P ratios and the plant C:N, C:P and N:P ratios. The soil organic C, total N concentration and the soil C:P and N:P ratios increased with the increasing restoration age. The soil total P and C:N ratio remained relatively stable between the different successional ages. The plant nutrients in the different plant tissues showed different trends across the succession. The living biomass N and P contents showed an increase across the succession, whereas root N and P contents remained stable. The root, litter and living biomass N:P ratios significantly decreased in the first 12 years and subsequently increased. The value of the living biomass N:P ratio suggested that the grasslands in northwestern China were limited by N in the first 12 years, and those in 20 and 30-year-old restored grasslands were constrained by the deficit of N, P and other nutrients. These results demonstrated that the grazing exclusion with a natural restoration was an effective measure to accumulate the soil organic carbon and total N contents and improve the limitation of grassland.

Impact of vegetation restoration on hydrological processes in the middle reaches of the Yellow River, China

Sediment discharge from the Yellow River originates mainly from the drainage area between Hekouzhen and Longmen, i.e., the Helong area. Spatial-temporal variations of the vegetation cover in this area during the 1981–2007 period have been investigated using GIMMS and SPOT VGT NDVI data. We have also analyzed the interannual variations in vegetation cover and changes in annual runoff and sediment discharge, the consequences from precipitation change and the Grain for Green Project (GGP). The results show that vegetation cover of the Helong area has increased during the 1981–2007 period. The northwestern part the Helong area, where the flat sandy lands are covered by grass, has experienced the largest increase. The region where the vegetation cover has declined is largely found in the southern and southeastern Helong area, which is a gullied hilly area or forested. Although precipitation was relatively low during the 1999–2007 period, the vegetation cover showed a significant increase in the Helong area, due to the implementation of the GGP. During this period, the most significant improvement in the vegetation cover occurred mainly in the gullied hilly areas of the Loess Plateau, such as the drainage basins of the Kuyehe and Tuweihe rivers and the middle and lower reaches of the Wudinghe and Yanhe rivers. A comparison of the average annual maximum NDVI between the earlier (1998–2002) stage and the next five years (2003–2007) of the GGP indicates that the areas with increases of 10% and 20% in NDVI account for 72.5% and 36.4% of the total area, respectively. Interannual variation of annual runoff and sediment discharge shows a declining trend, especially since the 1980s, when the decrease became very obvious. Compared with the 1950–1969 period, the average runoff during the 1980–2007 period was reduced by 34.8×108 m3 and the sediment discharge by 6.4×108 t, accounting for 49.4% and 64.9% of that in the 1950–1969 period, respectively. There is a positive correlation between the annual maximum NDVI and annual runoff and sediment discharge. This correlation was reversed since the implementation of the GGP in 1999 and vegetation cover in the Helong area has increased, associated with the decrease in runoff and sediment discharge. Less precipitation has been an important factor driving the decrease in runoff and sediment discharge during 1999–2007. However, restoration and improvement of the vegetation cover may also have played a significant role in accelerating the decrease in annual runoff and sediment discharge by enhancing evapotranspiration and alleviating soil erosion.

The impact of vegetation restoration on erosion-induced sediment yield in the middle Yellow River and management prospect

According to the characteristics of water and erosion environments of different natural zones on the Loess Plateau, this paper studies changes of vegetation types, distribution boundaries of forest and grass as well as restoration capacity of vegetation in different natural zones in the middle Yellow River. The annual precipitation of 530 mm is the critical annual precipitation for forest and grass distribution in the middle Yellow River. Among the zonal and azonal envi-ronmental factors affecting watershed sediment yield, the intermediate diameter D 50 (mm) of suspended load and forest coverage ( V , %) play the leading role. Of them the effect weight of forest coverage ( V , %) on catchments sediment yield is only 3.4% less than the role of the in-termediate diameter ( D 50 , mm), they are almost the same. To effectively control soil erosion in semiarid, especially in hilly-gullied areas and make sediment transport modulus reduce to less than 6000 t/km 2 , it is rather difficult by merely relying on natural restoration of forest. In the process of cultivated land conversion into forest land and grassland, measures suiting local conditions should be adopted in tree species selection and artificial afforestation (grass planting) based on management with biological measures for slopeland and engineering measures for hilly-gullied areas, so that watershed forest coverage in key counties can reach at least over 30%. Compared with the standard period of precipitation prior to the 1960s, with the decrease of an-nual precipitation at various periods, plant productivities decline to different degrees under natural conditions. The main reason accountable for the low survival rate of new seedlings and grass over years is due to precipitation decrease. In light with regression models of annual pre-cipitation and natural vegetation productivities, it is possible to obtain estimated values of wa-tershed natural vegetation productivity and eco-water consumption needed for the restoration to the standard period respectively for the present time or arbitrary period since the 1970s, thus providing a scientific basis for forest and grassland restoration in the middle Yellow River and the management prospect.