Forestland change and soil erosion in karst watershed under the Grain to Green Project

<div>With the implementation of the Grain to Green Project, the vegetation growth in karst region in southwest China has increased. In order to explore whether the growth of trees can be sustained after artificial afforestation in karst area and the influence of the forestland change on soil erosion, the WaTEM/SEDEM model was used to simulate the 11 stages of annual soil erosion in the past 33 years in Chongan river drainage basin in Guizhou, and the dominant influencing factors of soil erosion change in the past 33 years were discussed based the pixel scale in this study. The results showed that the forestland increased in a fluctuating way after the conversion project, and the decrease of forestland was mainly caused by drought, especially in the area where the dolomites were distributed. Therefore, the change of forestland caused no significant improvement in soil erosion since the Grain to Green Project.</div>

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An Assessment of Soil’s Nutrient Deficiencies and Their Influence on the Restoration of Degraded Karst Vegetation in Southwest China

Forests ◽

10.3390/f11080797 ◽

2020 ◽

Vol 11 (8) ◽

pp. 797 ◽

Cited By ~ 1

Author(s):

Yuguo Liu ◽

Changcheng Liu ◽

Matteo Rubinato ◽

Ke Guo ◽

Jinxing Zhou ◽

...

Keyword(s):

Soil Erosion ◽

Southwest China ◽

Karst Area ◽

Karst Region ◽

Agricultural Expansion ◽

Nutrient Deficiencies ◽

Land Area ◽

Human Disturbances ◽

Karst Areas ◽

Karst Landscapes

The distribution of karst landscapes over the Earth’s surface, to a large extent, follows the distribution of carbonate (limestone and dolomite) and gypsum rocks and together these make up about 12% of the Earth’s land area, and the largest karst region in to world is in Southwestern China. Characterized by a unique set of landforms, these geographical areas also differ from other geomorphic regions by the presence of cave systems in the subsurface. Unfortunately, due to human disturbances, such as deforestation, agricultural expansion, livestock overgrazing and fire, these regions have been affected by varying degrees of degradation, which could also be worsened if water and soil erosion phenomena typical of these areas are considered. Therefore, there is a need to implement measures and strategies to protect these karst areas and develop plans to restore vegetation in this region. To support local and national authorities to achieve this goal, this study aims to characterize nutrient deficiencies in degraded areas and estimate what could be the thresholds required to facilitate the restoration of vegetation in karst areas in southwest China. The results obtained confirm that the total element concentrations for Soil Organic Carbon (SOC), N, K, Ca, P, S and Mg were relatively high in the study karst area in southwest China. However, the total amounts of soil nutrients stored were very low due to the limited amount of soil identified as a consequence of previous deforestation processes undertaken within this study area and this aspect needs to be taken into consideration if aiming at a positive success of future restoration processes.

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Tracer vertical movement and its affecting factors in karst soil profiles using the simulated leaching method

10.5194/ismc2021-33 ◽

2021 ◽

Author(s):

Jianghu He ◽

Keli Zhang ◽

Zihao Cao ◽

Qihua Ke

Keyword(s):

Soil Erosion ◽

Soil Loss ◽

Southwest China ◽

Vertical Movement ◽

Karst Area ◽

Affecting Factors ◽

Tracer Movement ◽

Traditional Research ◽

Movement Distance ◽

Karst Geomorphology

Soil erosion is a severe issue in Southwest China due to complex karst geomorphology and excessive farming activities. It is also difficult to observe and evaluate using traditional research methods. Fortunately, as a supplement to traditional methods, the 137Cs tracing technique has strong potential to monitor and evaluate soil loss in karst regions. However, 137Cs might move downward with tiny particles under adequate rainfall conditions. This is critical because it directly affects accuracy of using the 137Cs conversion model to evaluate soil erosion. Thus, in our study, in order to explore whether tracers actually moved vertically and to evaluate the movement distance and the factors influencing the movement, magnetic powder (Fe3O4) and rare earth oxides (CeO2 and La2O3) were used as the substitute tracers under different conditions (rainfall and leaching area) of a simulated leaching experiment, which possess similar properties as 137Cs and have no toxicity problems in humans and the environment. The results showed that tracers moved downward 6 cm when water was added to simulate 1-10-year rainfall conditions and 8 cm when water was added to simulate 15-20-year rainfall conditions. The movement distance of tracers increased slowly with increasing water input, and the concentration of the tracers that moved related indirectly to the leaching area. Tracer movement at the edge of the simulated profile was affected by tracer type and concentration since there was no transition layer between soil and plastic column. Our field observations in two karst watersheds showed that ignoring the vertical movement of tracer can cause the overestimation of soil loss amount by 6.90% and 22.22% respectively. This study proved that in the karst area of Southwest China with abundant rainfall, 137Cs would move vertically, and the soil loss will be overestimated if the vertical movement distance of the tracer is ignored.

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Evaluation and Tradeoff Analysis of Ecosystem Service for Typical Land-Use Patterns in the Karst Region of Southwest China

Forests ◽

10.3390/f11040451 ◽

2020 ◽

Vol 11 (4) ◽

pp. 451 ◽

Cited By ~ 1

Author(s):

Zhigang Zou ◽

Fuping Zeng ◽

Kelin Wang ◽

Zhaoxia Zeng ◽

Hui Tang ◽

...

Keyword(s):

Land Use ◽

Southwest China ◽

Fruit Trees ◽

Karst Area ◽

Karst Region ◽

Land Use Patterns ◽

Cultural Services ◽

Use Patterns ◽

Regulating Services ◽

Provisioning Services

Although many land-use patterns have been established to restore vegetation and eliminate poverty in the karst area in southwest China, the ecosystem services (ESs) of these patterns are still not fully understood. To compare the differences in seven typical monoculture patterns and three agroforestry patterns, their ESs and tradeoffs were analyzed within the Millennium Ecosystem Assessment Framework. Compared with the local traditional corn pattern, the marigold pattern improved provisioning, regulating, and cultural services by >100%. The pomegranate pattern provided far more provisioning services than the other patterns. The apple + soybean intercropping pattern reduced regulating services, and eventually, its Total ESs (TES) and ecosystem multifunctionality index (EMF) also decreased. Cultural services will be enhanced by the introduction of fruit trees, as well as intercropping. Orange + peach had the greatest negative tradeoffs between provisioning and regulating services (P-R), provisioning and supporting services (P-S), and provisioning and cultural services (P-C), which indicates that the provisioning services urgently require improvement. Peach + pumpkin intercropping decreased the negative tradeoffs of P-R, P-S, and P-C (all > 10%), while pomegranate + grass intercropping increased the negative tradeoffs of R-S and R-C (all > 100%). Our results suggest that all six of these patterns are worthy of promotion but the pomegranate pattern should be given priority. Among the three intercropping patterns studied herein, the apple + soybean pattern should be redesigned to improve performance.

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Soil erosion impacts on nutrient deposition in a typical karst watershed

10.5194/ismc2021-74 ◽

2021 ◽

Author(s):

Li Chengfang ◽

Wang Zhongcheng ◽

Li Zhenwei ◽

Xu Xianli

Keyword(s):

Soil Erosion ◽

Nutrient Dynamics ◽

Southwest China ◽

Clay Content ◽

Nutrient Concentrations ◽

Deposition Rates ◽

Nutrient Deposition ◽

Peak Cluster ◽

The Past ◽

Karst Depression

Soil erosion has a significant influence on nutrient redistribution and deposition. However, the effect of soil erosion on nutrient deposition remains unclear in karst areas such as southwest China, which represents an ecologically fragile zone experiencing severe soil erosion. The objective of this study was to investigate the characteristics of soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) deposition in a karst watershed of southwest China over the past 60 years and evaluate the relationship between soil erosion and nutrient deposition. The peak-cluster depressions in southwest China are typical for the geomorphological type, which is an ideal place to determine the sediment chronology, and the estimation of sediment and nutrient deposition rates. Three soil profiles were excavated in a typical karst depression. The characteristics of 137Cs, 210Pbex, particle size distribution, and nutrients at different soil depths were investigated to evaluate the effect of soil erosion on nutrient deposition. Results showed that there was a significant negative correlation between nutrient concentrations and clay content (P<0.001). Generally, compared with 137Cs, 210Pbex had a higher correlation with SOC and TN. In an undisturbed sediment profile, Pb/Cs can reflect nutrient dynamics better than a single nuclide. The nutrient deposition rates increased before 1953, reached its maximum in 1954-1956, and then dropped rapidly from 1957 to 2015. The sediment deposition rates were negatively correlated with nutrient concentrations (P<0.01), but had a positive influence on nutrient deposition rates (P<0.01). This implies that the temporal variation in nutrient deposition rates over the past 60 years was dominated by soil erosion rather than nutrient concentrations. This study provides a new insight to explore the historical nutrient deposition rates in a peak-cluster karst depression, and may help effectively control soil erosion and sustainable development of agro-ecosystems.

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Spatial and temporal characteristics of soil erosion in a typical karst basin in southwest China and its response to the landscape pattern of rock desertification

10.21203/rs.3.rs-1107552/v1 ◽

2021 ◽

Author(s):

Jiayong Gao ◽

Rui Li ◽

Maolin He ◽

Pingping Yang ◽

Jun Jing

Keyword(s):

Land Use ◽

Soil Erosion ◽

River Basin ◽

Landscape Pattern ◽

Karst Area ◽

Karst Region ◽

Patch Type ◽

Severe Erosion ◽

Strong Erosion ◽

Landscape Level

Abstract Soil erosion is a process of migration and redistribution of soil substances in the landscape, which is regulated by topography, vegetation, human activities and their spatial pattern. At the watershed scale, changes in landscape pattern are important factors in determining the degree of soil erosion. Taking Dabang River Basin as the study area, based on the three phases of land use data, remote sensing image data and daily rainfall data from eight stations in the basin in 2010, 2015 and 2020, the rocky desertification factor (D) was introduced into the general soil loss equation RUSLE to calculate the soil erosion in Karst and non-Karst Areas in 2010, 2015 and 2020 respectively. The relationship between landscape pattern and soil erosion was analyzed from two aspects: type level index and landscape level index. The results showed that: 1) From 2010 to 2020, the average soil erosion modulus in The Dabang River Basin decreased first and then increased. The average soil erosion modulus in the non-karst region was about twice that in the karst region, and the average soil erosion modulus in the karst region decreased first and then increased. The mean soil erosion modulus in the non-karst area showed an increasing trend; 2) Under different slope grades, the erosion was mainly slight and mild, and the area of slight erosion was the largest, and the area of very strong and severe erosion increased as the slope increased. the area of strong, very strong and severe erosion increased in the slope zone below 15°, the area of light and moderate erosion decreased, and the area of slight, strong and very strong erosion increased in the slope zone from 15 to 25°, and the area of slight erosion increased in the slope zone above 25° area increased and light, moderate and strong erosion area decreased in the slope zone above 25°; 3) The landscape pattern of the Dadang River Basin changed significantly from 2010 to 2020. At the landscape level, the number of patches increased and the average patch area decreased. At the type level, the area of paddy field, woodland and shrubland decreases and the area of dry land, grassland, construction land and water body increased, and the dominant land type in the watershed changed from woodland to grassland; 4) The amount of soil erosion was positively correlated with patch type area, landscape percentage, maximum patch index and aggregation index, and positively correlated with edge density; 5) There was a linear relationship between soil erosion and Shannon diversity index (SHDI) and Shannon mean index (SHEI) at landscape level. The results can provide reference for land use planning and soil and water conservation measures.

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Streamflow change induced by climate change and vegetation recover in a karst region of southwest China

10.5194/egusphere-egu21-3629 ◽

2021 ◽

Author(s):

Lianbin Cai ◽

Xi Chen ◽

Zhicai Zhang

Keyword(s):

Climate Change ◽

Carbonate Rock ◽

Southwest China ◽

Karst Area ◽

Karst Region ◽

Primary Role ◽

Distributed Hydrological Model ◽

Carbonate Area ◽

The Impact ◽

Impacts Of Climate Change

In carbonate rock regions, the bedrock compositions strongly influence regolith properties that, in turn, might play the primary role in plant growth and hydrological processes. Since bedrock experiences uneven weathering processes due to different regolith materials in a karst area, how hydrological functions of bedrock layer and overlying vegetation rely on the bedrock weathering degree is seldom investigated. The objectives of this study are to quantify the impacts of climate change and reforestation on runoff in a watershed with two main bedrocks (dissolvable carbonate rock in karst area and detrital rock in non-karst area) in southwest China. The analyses are firstly executed by decomposion of the hydro-meteorological series into two series (T1, 1992-2003 and T2, 2004-2015), which have different hydro-meteorological responses due to reforestation. This study investigates the impacts of climate change and reforestation on runoff using two approaches: the sensitivity-based approach (Budyko hypothesis) is applied to estimate the overall watershed change in runoff attributed to human activities and climate change, and a distributed hydrological model based on simple soil water balance routing is used to estimate change in runoff and hydrographs in the two main bedrock areas. The results show that the hydrological modelling overestimates climate induced decrease of streamflow (88.6%), compared to estimated result by the Budyko formula (76.6%). The decrease of mean precipitation from T1 to T2 in the non-carbonate area is very close to the carbonate area, the proportion of the climate change induced decrease of streamflow in the non-carbonate area (86.3%) is less than the carbonate area (90.5%), indicating that the drier climate tendency takes a greater effect on decrease of streamflow in the carbonate area than the non-carbonate area. By contrast, there is a greater alteration of land cover/use in the non-carbonate area than the carbonate area. These findings will help develop a better understanding of the impact of climate change and reforestation on runoff in southwest China.

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Bedrock-associated belowground and aboveground interactions and their implications for vegetation restoration in the karst critical zone of subtropical Southwest China

Progress in Physical Geography Earth and Environment ◽

10.1177/0309133320949865 ◽

2020 ◽

pp. 030913332094986

Author(s):

Hongyan Liu ◽

Jingyu Dai ◽

Chongyang Xu ◽

Jian Peng ◽

Xiuchen Wu ◽

...

Keyword(s):

Southwest China ◽

Soil Formation ◽

Critical Zone ◽

Vegetation Restoration ◽

Research Progress ◽

Karst Region ◽

Vegetation Ecology ◽

Rocky Desertification ◽

Vegetation Growth ◽

Soil Features

The role of bedrock geochemistry in vegetation growth within karst areas has been examined in recent works, implying that the approach of the critical zone (CZ) extending from the canopy to the groundwater bottom enhances the understanding of vegetation ecology. In this paper, the research progress of vegetation ecology associated with bedrock features in the karst CZ in subtropical Southwest China is systematically reviewed. There are great differences in soil formation and soil features (water-holding capacity, particle size, and soil chemistry) between karst and non-karst regions, even between dolomite and limestone within a karst region. Water and soil are easily leached due to the connected underground crevices in karst, particularly in limestone-dominated regions, leading to water deficits in karst CZ plants in subtropical Southwest China. The development of plant roots in crevices affects the water and nutrient absorption by plants and microbial activities in the soil, which form the basis for vegetation distribution and growth in the karst CZ. The organic acids from plants also increase weathering rates. As extensive human activities have accelerated vegetation degradation and soil erosion and further led to rocky desertification characterized by increasing areas of rock exposure, state-of-the-art knowledge about the effects of bedrock-associated belowground and aboveground interactions can guide the implementation of vegetation restoration and the control of further rocky desertification in the subtropical karst CZ.

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Insights into Distribution of Soil Available Heavy Metals in Karst Area and Its Influencing Factors in Guilin, Southwest China

Forests ◽

10.3390/f12050609 ◽

2021 ◽

Vol 12 (5) ◽

pp. 609

Author(s):

Fen Huang ◽

Xiaomei Wei ◽

Tongbin Zhu ◽

Zhuanxi Luo ◽

Jianhua Cao

Keyword(s):

Heavy Metals ◽

Influencing Factors ◽

Calcareous Soil ◽

Pearson Correlation ◽

Red Soil ◽

Karst Area ◽

Karst Region ◽

Available Phosphorus ◽

Available Nitrogen ◽

Clastic Rocks

The bioavailable contents of heavy metals in karstic soils are a subject of increasing concern since the uptake of heavy metals by plants can pose a severe threat to food safety and public health. However, the bioavailable contents of heavy metals and their effective factors are poorly understood in karst regions. Calcareous soil and red soil developed from carbonate and clastic rocks, respectively, were chosen from a typical karst region (Guilin) of southwestern China, and the total (CT) and available (CA) contents of 11 heavy metals, as well as their influencing factors in soil profiles, were investigated. The results showed that calcareous soil has greater soil organic carbon, total nitrogen, available nitrogen, available potassium, and calcium (Ca) contents than red soil, but lower available phosphorus and C:N. Acid-soluble Ca (Aca) was the dominant fraction in both types of soil. Heavy metals were highly accumulated in calcareous soil, mainly controlled by secondary enrichment in the processing of carbonate rock weathering. For the majority of metals, calcareous soil had higher CT and lower CA than red soil. According to a redundancy analysis (RDA) and Pearson correlation coefficient, the high pH and Ca content in calcareous soils were primary factors influencing both the CT and CA of the metals, especially residual Ca to CT and Aca to CA. Additionally, higher soil cation exchange capacity and clay minerals also probably improved the immobility of heavy metals.

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