Main Participants: QIN Wei, FAN Haoming, XU Xiaohong, YIN Zhe, ZhANG Yu, XU Jinzhong, DU Pengfei, DONG Yifan, ZHANG Bin, HUANG Donghao, WEN Yanru, CUI Bin, YANG Qingnan, LI Zhen, JIAO Jian

The black soil region in Northeast China, one of the world’s four major black soil regions, plays an irreplaceable cornerstone for China’s national food security. Over the past hundred years, agricultural reclamation has caused serious erosion and degradation of black soil in that region. In 2011, China's first nationwide survey on water conservancy found more than 290,000 erosion gullies with a length of over 100 meters in that region, of which nearly 60% were located on arable land, posing a serious threat to China’s food security and regional eco-environment. However, the distribution pattern and driving factors of erosion gullies in the black soil region remain unclear, and the development process and prevention and control mechanism are complex and different. Technological support in these regards hence remains insufficient.

Under the support of a number of major projects, the research team has been working on the entire chain from basic research, key technologies to demonstration application for ten years, intending to provide technological support for the prevention and control of erosion gullies and the protection of black soil in Northeast China.

·   Revealing the spatial and temporal distribution characteristics of erosion gullies and the influence attribution;

·   Elucidating the key driving factors for the development of erosion gullies and the mechanism of functioning of those factors;

·   Identifying the rate of development and evolution of erosion gullies and building relative evaluation and prediction models;

·   Quantifying the changes in sediment deposits and sediment delivery contributions of erosion gullies on multi-time scales;

·   Developing eco-friendly, land-saving technologies for management of gullies and establishing relative grading and classification standards;

·   Proposing countermeasures for prevention and control of gully systems and relative consulting recommendations.

·   Having made it clear that most erosion gullies in Northeast China were formed in the 1950s and 1960s mainly due to accelerated erosion following large-scale farming during snowmelt and rainfall periods, the two developmental stages contributing respectively 30% and 70% to the expansion;

·   Having revealed the spacial distribution characteristics of erosion gullies on multiple scales (region-wide, sub-region-wide and basin-wide), and having identified the "two zones and a belt" where developmental erosion gullies in the region are concentrated, thus providing target areas of critical layout;

·   Having elucidated how natural factors such as topography, rainfall, snowmelt and soil moisture, and anthropogenic factors such as tractor roads and old terraces influence the development of erosion gullies and having identified the characteristics of geomorphic differentiation driven by erosion gully development in small watersheds;

·   Having identified the rate of development and evolution of erosion gullies on different temporal and spatial scales in typical black soil regions, having quantified the sediment delivery contributions of erosion gullies to small watersheds at different times, and having established for the first time a risk assessment model for erosion gully development through the random forest algorithm and a model for estimation of three-dimensional volume of erosion gullies based on two-dimensional morphological parameters;

·   Having proposed a new series of eco-friendly, land-saving erosion gully control technologies for the catchment, head, slope and bottom of erosion gullies, and having formed technical standards for grading and classification of erosion gullies;

·   Having identified the key technological problems in the prevention and control of erosion gullies in Northeast China in light of the national ecological development needs in China’s 14^th Five-Year Plan period, and having proposed macro-level countermeasures for systematic control of eriosion gullies.

Theories and technologies for erosion gully prevention and control developed in this research have been widely applied to the protection of the black soil region in Northeast China and have been demonstrated and promoted in the management of more than 150 erosion gullies in major national soil and water conservation projects.

The technological achievements have been adopted by provincial and ministerial technical documents, such as the Technical Guide for Erosion Gully Control in the Black Soil Region in Northeast China issued by the Songliao River Water Resources Commission of the Ministry of Water Resources (MWR) of China and the Action Plan for the Control of Erosion Gullies issued by the Heilongjiang Province, guiding the protection and management of black soil in Northeast China.

These achievements have provided necessary technical support for the preparation of land conservation plans for the 14^th Five-Year Plan period by MWR and the four northeastern provinces, and will continue to play a significant role in China’s black soil conservation.

Fig.1 The main forming period and seasonal variation of erosion gullies in Northeast China

Fig.2 Areas with concentrated developmental erosion gullies in black soil regions in Northeast China

Fig.3 Development of risk assessment model and the model for three-dimensional estimation of erosion gully volume in Northeast China

Fig.4 Sediment sources and interannual sediment contribution of erosion gullies in a typical farming watershed in black soil regions in Northeast China

Fig.5 Ecological, land-saving gully management technologies for black soil regions in Northeast China