Guobin Liu

A comparison of soil qualities of different revegetation types in the Loess Plateau, China

Serious soil erosion has resulted in widespread land degradation in the Loess Plateau of China. In the past two decades, great efforts have been made to restore degraded soil such as reconverting croplands into forestlands or grasslands. A comparison of soil qualities of different revegetation types has important implications in soil reclamation. Our study investigated the effect of different revegetation types on the physicochemical and microbial soil properties in the Loess Plateau, with the aim of determining which revegetation type has the best capacity for soil recovery. The vegetation types included two shrublands (Caragana korshinskii and Hippophae rhamnoides), two grasslands (Astragalus adsurgens and Panicum virgatum), and two species from croplands that were abandoned for natural recovery (Artemisia capillaries and Heteropappus altaicus). Among the plants studied, H. altaicus and A. capillaries had the highest values of soil organic C, total N, total P, available N, available P, moisture content, microbial biomass C (MBC), substrate-induced respiration, saccharase, urease, catalase, and peroxidase. Soil sampled from the A. adsurgens plot had the highest bulk density and microbial biomass N, and soil from the H. rhamnoides plot had the highest metabolic quotient (basal respiration/MBC). The soil quality index, which was obtained based on the available N, metabolic quotient, MBC, urease, polyphenol oxidase, and bulk density, shows that the abandoned cropland for natural recovery had the highest soil quality, followed by grassland, and then shrubland. Vegetation types affect the physicochemical and microbial properties of soils in arid climatic conditions. Abandoned cropland for natural recovery has the best capacity for improving soil quality in the Loess Plateau among all studied revegetation types. Our study suggests that in the Loess Plateau, natural recovery is the best choice for soil revegetation of sloping croplands.

A study of soil surface characteristics in a small watershed in the hilly, gullied area on the Chinese Loess Plateau

Soil surface characteristics are closely related to soil surface depressional storage, infiltration, runoff generation and soil erosion, especially in highly erodible loess soil. Soil surface random roughness, soil cohesion and aggregate stability are necessary parameters in the Limburg Soil Erosion Model (LISEM) and helpful in developing alternative land-use and conservation strategies. Over a period of 2 years, soil surface characteristics were measured continuously in Danangou, a small catchment in the hilly, gullied loess area in China, with the support of the Erochina project. The results show that soil surface random roughness, soil cohesion and aggregate stability differed significantly between land-use types. Ranking the types on soil roughness during the monitoring period yielded the sequence cropland>orchard and wasteland and fallow land>shrubland>woodland. The corresponding sequence for aggregate stability was approximately wasteland and woodland>cropland and orchard>shrubland>fallow land. Cohesion in the different land-use types in the catchment was smallest for cropland and largest for wasteland. There were no significant differences between croplands with different topographical characteristics. All of these soil surface characteristics showed significant temporal variation over the monitoring period. Temporal variations in roughness for shrubland and woodland over the 2-year period were significantly greater than those for other land-use types. There were also considerable variations in cohesion for shrubland, woodland and wasteland. In 1998, the weighted average values of roughness, aggregate stability and cohesion for the entire catchment were 1.113 cm, 13.6 drops and 0.131 kg/cm2, respectively, with C.V. values of 9.6%, 32.05% and 21.11%. The corresponding values for 1999 were 1.616 cm, 11.52 drops and 0.100 kg/cm2, with C.V. values of 16.0%, 15.41% and 33.33%. The temporal and spatial variations in soil surface characteristics in the catchment should be carefully taken into account in LISEM calibration and validation.

Restoration and development of the degraded Loess Plateau, China

This book presents state-of-the-art scientific evidence and technological innovations to restore lands on the Loess Plateau of China, known worldwide for its serious land degradation and desertification problems. Supported by a rapidly developing Chinese economy and the dissemination of effective technology, the Grain-for-Green Project and Western Development Action launched by the Chinese government have resulted in successful ecological restoration and protection over the past 30 years. These programs have contributed not only to conservation of soil and water, but also to economic development. At the same time, however, these developmental interventions have brought new challenges that have not yet been fully addressed. The book describes (1) case studies of success and failure in practice, including rare success stories of combating desertification; (2) technical issues such as erosion control and breeding of stress-tolerant plant species, and socioeconomic measures taken by the Chinese government and lending policies with support from the World Bank; and (3) comprehensive measures against desertification, such as water and wind erosion, salinization, and deforestation. This volume is recommended for researchers and students above the undergraduate level in diverse fields including soil science, rural engineering, social technology and civil engineering, biology, ecology, climatology, physical and human geography, and developmental economics, among others. It also serves as a valuable resource for engineers, government officials, and NPOs and NGOs involved in afforestation, ecological restoration, combating desertification, disaster prevention, and sustainable rural development.

Factors Affecting Domestic Water Consumption in Rural Households upon Access to Improved Water Supply: Insights from the Wei River Basin, China

Comprehensively understanding water consumption behavior is necessary to design efficient and effective water use strategies. Despite global efforts to identify the factors that affect domestic water consumption, those related to domestic water use in rural regions have not been sufficiently studied, particularly in villages that have gained access to improved water supply. To address this gap, we investigated 247 households in eight villages in the Wei River Basin where three types of improved water supply systems are implemented. Results show that domestic water consumption in liters per capita per day was significantly correlated with water supply pattern and vegetable garden area, and significantly negatively correlated with family size and age of household head. Traditional hygiene habits, use of water appliances, and preference for vegetable gardening remain dominant behaviors in the villages with access to improved water supply. Future studies on rural domestic water consumption should pay more attention to user lifestyles (water appliance usage habits, outdoor water use) and cultural backgrounds (age, education).

Proline Accumulation in Leaves of Periploca sepium via Both Biosynthesis Up-Regulation and Transport during Recovery from Severe Drought

Drought resistance and recovery ability are two important requisites for plant adaptation to drought environments. Proline (Pro) metabolism has been a major concern in plant drought tolerance. However, roles of Pro metabolism in plant recovery ability from severe drought stress are largely unexplored. Periploca sepium Bunge has gained increasing attention for its adaptation to dry environments. Here, we investigated Pro metabolism in different tissues of P. sepium seedlings in the course of drought stress and recovery. We found that leaf Pro metabolism response during post-drought recovery was dependant on drought severity. Pro biosynthesis was down-regulated during recovery from -0.4 MPa but increased continually and notably during recovery from -1.0 MPa. Significant correlation between Pro concentration and Δ1-pyrroline-5-carboxylate synthetase activity indicates that Glutamate pathway is the predominant synthesis route during both drought and re-watering periods. Ornithine δ-aminotransferase activity was up-regulated significantly only during recovery from −1.0 MPa, suggesting positive contribution of ornithine pathway to improving plant recovery capacity from severe drought. In addition to up-regulation of biosynthesis, Pro transport from stems and roots also contributed to high Pro accumulation in leaves and new buds during recovery from −1.0 MPa, as indicated by the combined analysis of Pro concentration and its biosynthesis in stems, roots and new buds. Except its known roles as energy, carbon and nitrogen sources for plant rapid recovery, significant positive correlation between Pro concentration and total antioxidant activity indicates that Pro accumulation can also promote plant damage repair ability by up-regulating antioxidant activity during recovery from severe drought stress.

Effects of vegetation cover and rainfall intensity on sediment-associated nitrogen and phosphorus losses and particle size composition on the Loess Plateau

Vegetation and rainfall are two important factors affecting soil erosion and the resulting nutrients loss on the Chinese Loess Plateau. Field experiments under simulated rainfall condition were conducted to investigate the effect of rainfall intensity and vegetation (Caragana korshinskii) cover on soil loss, sediment-associated nitrogen (N) and phosphorus (P) loss, and particle size distribution (PSD) of the eroded sediment. Treatments included three rainfall intensities (60, 100, and 140 mm h−1 [2.364, 3.94, and 5.516 in hr−1]) with each producing 60 min of rainfall and three plots (0%, 30%, and 80%) with the same gradient of 15°. The results showed that vegetation cover, rainfall intensity, and their interaction all had significant effect on sediment and the associated N and P loss. In general, higher rainfall intensity and lower coverage produced higher sediment and consequently higher nutrient loss but led to a lower enrichment ratio for N (ERN) in sediments. Vegetation cover had no marked effect on enrichment ratio of P (ERP). A strong positive linear relation was observed between soil loss and N and P loss. The eroded sediment contained more fine particles (clay and silt, < 20 μm [7.874 × 10-4 in]) compared to the original surface soil. Under the same cover condition, the percentage of clay significantly decreased with increasing rainfall intensity (p < 0.05). The ERN and ERP were positively correlated with ER clay. This suggested that the clay fraction (<2 μm [7.874 × 10-5 in]) was preferentially eroded and that N and P were mainly adsorbed onto or contained within this particle fraction.

Age-related changes of carbon accumulation and allocation in plants and soil of black locust forest on Loess Plateau in Ansai County, Shaanxi Province of China

The effects of reforestation on carbon (C) sequestration in China’s Loess Plateau ecosystem have attracted much research attention in recent years. Black locust trees (Robinia pseudoacacia L.) are valued for their important use in reforestation and water and soil conservation efforts. This forest type is widespread across the Loess Plateau, and must be an essential component of any planning for C sequestration efforts in this fragile ecological region. The long-term effects of stand age on C accumulation and allocation after reforestation remains uncertain. We examined an age-sequence of black locust forest (5, 9, 20, 30, 38, and 56 yr since planting) on the Loess Plateau to evaluate C accumulation and allocation in plants (trees, shrubs, herbages, and leaf litter) and soil (0–100 cm). Allometric equations were developed for estimating the biomass of tree components (leaf, branch, stem without bark, bark and root) with a destructive sampling method. Our results demonstrated that black locust forest ecosystem accumulated C constantly, from 31.42 Mg C/ ha (1 Mg = 106 g) at 5 yr to 79.44 Mg C/ha at 38 yr. At the ‘old forest” stage (38 to 56 yr), the amount of C in plant biomass significantly decreased (from 45.32 to 34.52 Mg C/ha) due to the high mortality of trees. However, old forest was able to accumulate C continuously in soil (from 33.66 to 41.00 Mg C/ha). The C in shrub biomass increased with stand age, while the C stock in the herbage layer and leaf litter was age-independent. Reforestation resulted in C re-allocation in the forest soil. The topsoil (0–20 cm) C stock increased constantly with stand age. However, C storage in sub-top soil, in the 20–30, 30–50, 50–100, and 20–100 cm layers, was age-independent. These results suggest that succession, as a temporal factor, plays a key role in C accumulation and re-allocation in black locust forests and also in regional C dynamics in vegetation.

Soil Microbial Community Composition During Natural Recovery in the Loess Plateau, China

This study aimed to determine the characteristics of soil microbial community composition and its relationship with soil chemical properties during natural recovery in the Loess Plateau. The soil microbial community composition was analyzed by comparing the soil microbial phospholipid fatty acids (PLFAs) of eight croplands abandoned for 1, 3, 5, 10, 13, 15, 20, and 30 yr in the Dunshan watershed, northern Loess Plateau, China. The results showed that soil organic carbon, total nitrogen, soil microbial biomass carbon, and soil microbial biomass nitrogen significantly increased with the abandonment duration, whereas the metabolic quotient significantly decreased. The Shannon richness and Shannon evenness of PLFAs significantly increased after 10 yr of abandonment. Gram-negative, Gram-positive, bacterial, fungal, and total PLFAs linearly increased with increased abandonment duration. Redundancy analysis showed that the abandonment duration was the most important environmental factor in determining the PLFA microbial community composition. The soil microbial PLFAs changed from anteiso- to iso-, unsaturated to saturated, and short- to long-chain during natural recovery. Therefore, in the Loess Plateau, cropland abandonment for natural recovery resulted in the increase of the soil microbial PLFA biomass and microbial PLFA species and changed the microbial from chemolithotrophic to a more heterotrophic community.

Effect of Different Vegetation Types on the Rhizosphere Soil Microbial Community Structure in the Loess Plateau of China

Abstract The Loess Plateau in China is one of the most eroded areas in the world. Accordingly, vegetation restoration has been implemented in this area over the past two decades to remedy the soil degradation problem. Understanding the microbial community structure is essential for the sustainability of ecosystems and for the reclamation of degraded arable land. This study aimed to determine the effect of different vegetation types on microbial processes and community structure in rhizosphere soils in the Loess Plateau. The six vegetation types were as follows: two natural grassland (Artemisia capillaries and Heteropappus altaicus), two artificial grassland (Astragalus adsurgens and Panicum virgatum), and two artificial shrubland (Caragana korshinskii and Hippophae rhamnoides) species. The microbial community structure and functional diversity were examined by analyzing the phospholipid fatty acids (PLFAs) and community-level physiological profiles. The results showed that rhizosphere soil sampled from the H. altaicus and A. capillaries plots had the highest values of microbial biomass C, average well color development of carbon resources, Gram-negative (G−) bacterial PLFA, bacterial PLFA, total PLFA, Shannon richness, and Shannon evenness, as well as the lowest metabolic quotient. Soil sampled from the H. rhamnoides plots had the highest metabolic quotient and Gram-positive (G+) bacterial PLFA, and soil sampled from the A. adsurgens and A. capillaries plots had the highest fungal PLFA and fungal:bacterial PLFA ratio. Correlation analysis indicated a significant positive relationship among the microbial biomass C, G− bacterial PLFA, bacterial PLFA, and total PLFA. In conclusion, plant species under arid climatic conditions significantly affected the microbial community structure in rhizosphere soil. Among the studied plants, natural grassland species generated the most favorable microbial conditions.

Fractal features of soil profiles under different land use patterns on the Loess Plateau, China

Fractal theory is becoming an increasingly useful tool to describe soil structure dynamics for a better understanding of the performance of soil systems. Changes in land use patterns significantly affect soil physical, chemical and biological properties. However, limited information is available on the fractal characteristics of deep soil layers under different land use patterns. In this study, the fractal dimensions of particle size distribution (PSD) and micro-aggregates in the 0–500 cm soil profile and soil anti-erodibility in the 0–10 cm soil profile for 10 typical land use patterns were investigated in the Zhifanggou Watershed on the Loess Plateau, China. The 10 typical land use patterns were: slope cropland, two terraced croplands, check-dam cropland, woodland, two shrublands, orchard, artificial and natural grasslands. The results showed that the fractal dimensions of PSD and micro-aggregates were all significantly influenced by soil depths, land use patterns and their interaction. The plantations of shrubland, woodland and natural grassland increased the amount of larger micro-aggregates, and decreased the fractal dimensions of micro-aggregates in the 0–40 cm soil profile. And they also improved the aggregate state and aggregate degree and decreased dispersion rate in the 0–10 cm soil profile. The results indicated that fractal theory can be used to characterize soil structure under different land use patterns and fractal dimensions of micro-aggregates were more effective in this regard. The natural grassland may be the best choice for improving soil structure in the study area.