Scientia Agricultura Sinica

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LCA-Based Assessment of Hulunber Ecological Grassland Technology Integration Demonstration

LIU XinChao,WANG LuLu,WU RuQun,XIN XiaoPing,SUN HaiLian,JIANG MingHong,LI XiaoShuang,WANG Miao,LIU Yun,SHAO ChangLiang

Scientia Agricultura Sinica 2020, 53 (13): 2703-2714. DOI: 10.3864/j.issn.0578-1752.2020.13.018

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【Objective】 This study evaluated the comprehensive environmental effect of the process of intensive cow breeding-livestock manure utilization-natural grassland improvement. 【Method】 At first, the life cycle inventory of the milk produced under different dairy cattle cultivation modes was established. Then the comprehensive environment effects (greenhouse gas emissions, land occupation, water consumption and non-renewable energy consumption) and overall economic benefits in the whole life cycle of milk production were quantitatively analyzed by combining the experimental data of intensive cow breeding, manure utilization (including microbial fermentation organic fertilizer, earthworm breeding organic fertilizer, and mushroom breeding) and natural grassland improvement with the input data of local animal production and management. The function unit was 1 ton of standard milk (FPCM) in this analysis. 【Result】 The results showed that the mean gross income of local herdsmen’s grazing farms and intensive dairy farms was 8 900 yuan and 211 yuan per adult cow, respectively. If the operating cost was deducted, the net income of each adult cow in the two modes was 4 200 yuan (herdsmen’s grazing farm) and 4 100 yuan (intensive farm), respectively. The environmental impact caused by the production of 1 ton FPCM in intensive farm was 1.19 hm² of grassland, 0.15 hm² of arable land, 216.47 t of water, 1 944.19 MJ of fossil fuel and 0.73 t of CO_2eq of greenhouse gas. In addition to the grassland area (3.25 hm²), the environmental impact of milk production by herdsmen’s grazing farms were less than that of intensive dairy farms (0.04 hm² of cultivated land, 70.70 t of water, 892.80 MJ of fossil fuel and 0.55 t of CO_2eq greenhouse gas). Natural clipped grassland improvement could significantly increase the hay yield per hectare grassland (increased for 68.57%) and income (increased for 10.71%), it could reduce the grassland area occupied by 40.50%, but the increase of fertilization and fuel consumption in the improvement would cause environmental problems (such as more greenhouse gas emissions 17.70 times) and more fuel consumption (2.10 times). In terms of the application of livestock manure treatment and utilization technology, the cattle manure produced by intensive farms was treated and utilized through microbial fermentation, earthworm treatment and mushroom cultivation, the net income generated was equivalent to about 5%-12% of the net income generated by milk production, and the overall environmental impact was relatively small. 【Conclusion】 Intensive farms had obvious advantages in improving grassland utilization efficiency, and had great potential in improving feed energy conversion efficiency, as well as milk yield and quality. However, intensive dairy farming would increase the planting area of alfalfa, oats and other high protein forages, and cause adverse environmental effects such as more greenhouse gas emissions, more water and energy consumption. In addition, the technology of natural grassland improvement and livestock manure treatment and utilization had great application potential in Hulunber animal husbandry.

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The Spatial-Temporal Distribution of Different Grassland Types in Hulunber Grassland Based on Remote Sensing from 1992 to 2015

ZHU XiaoYu,XU DaWei,XIN XiaoPing,SHEN BeiBei,DING Lei,WANG Xu,CHEN BaoRui,YAN RuiRui

Scientia Agricultura Sinica 2020, 53 (13): 2715-2727. DOI: 10.3864/j.issn.0578-1752.2020.13.019

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【Background】 Hulunber grassland, as the main part of temperate steppe in China, possesses its important position in grassland animal husbandry production and plays the ecological buffer function with its unique geographical location, typical ecological climate and representative production mode. 【Objective】 Grassland, as one of the most important terrestrial ecosystems, has great significance in agricultural and animal husbandry production, ecological and environmental protection, climate change and other aspects. The spatial distribution and change of different grassland types are the basis of grassland research and management. 【Method】 In this paper, different land cover and grassland types in Hulunber grassland were taken as research objects, remote sensing images in 1992 and 2015 were treated as data sources, support vector machine and object-based image analysis classification were used to obtain the spatial distribution in the study area. The temporal and spatial change characteristics were studied by geostatistics, and the effects of climate change and human activities were analyzed by the potential distribution of zonal grassland types classified by plant-habitat classification, social statistical data and the transformation process. 【Result】 The area of cropland, forestland, sandy and alkaline land, building land increased, while the area of grassland and water decreased. Grassland is the largest coverage type in the study area, the areas were 7 601 258 hm² and 7 148 085 hm² in 1992 and 2015 respectively, with a 5.96% reduction. Steppe, meadow steppe and lowland meadow had large distribution areas, accounting for more than 70% of the study area, while mountain meadow and swamp had relatively small distribution area, accounting for about 2%. Except the increase of steppe area, the area of other grassland types decreased. The area of steppe increased by 283 790 hm², with an increase rate of 7.12%. The area of meadow steppe showed the largest decrease, with a decrease of 563 439 hm² and a decrease of 28.72%. In the study area, the grassland types with relatively humid water status were mainly converted to relatively arid ones, with the transfered area of 466 687 hm² from 1992 to 2015, and grassland types with relatively dry water status converted to relatively humid ones with a total area of 212 330 hm². 【Conclusion】 The spatial distribution of different grassland and land cover types in Hulunber grassland changed dramatically. The impacts of climate change are trend, long-term and hard to recover, and the impacts of human activities are fragmentary, reversible and easy to recover.

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Analysis of Spatial-Temporal Characteristics of Drought Variation in Grassland Area of Inner Mongolia Based on TVDI

CHENG Wei, XIN XiaoPing

Scientia Agricultura Sinica 2020, 53 (13): 2728-2742. DOI: 10.3864/j.issn.0578-1752.2020.13.020

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【Objective】 To study the spatio-temporal characteristics of temperature vegetation drought index (TVDI) in the grassland area of Inner Mongolia in the past 18 years and to explore the relationship between TVDI and meteorological factors, so as to provide theoretical reference for ecological warning and ecological restoration of the study area. 【Method】 Based on MODIS enhanced vegetation index (EVI) and land surface temperature (LST) products to build Ts-EVI characteristic space, according to the characteristic space to calculate TVDI, for normal value of accumulated year of TVDI using unary the Theil-Sen Median trend analysis and Mann-Kendall examination to study the spatial distribution, time-varying characteristics and spatiotemporal evolution trend of drought in the study area during 18 years. 【Result】 On the whole, the average drought degree of grassland in Inner Mongolia is high in southwest and low in northeast, and the average annual TVDI of all grassland types is in order of temperate desert type>temperate steppe-desert type>temperate desert-steppe type>marsh type>temperate steppe type>temperate meadow-steppe type>lowland meadow type>montane meadow type. Among them, the desert grasslands (temperate desert type, temperate steppe-desert type and temperate desert-steppe type) are mainly in the state of severe and mild drought, while non-desert grasslands (temperate steppe type, temperate meadow steppe type, lowland meadow type, mountain meadow type and marsh type) are mainly in the state of mild drought, normal state and mild wetness. Over the past 18 years, the desert grassland has been gradually drying out. In contrast, the non-desert grassland is basically getting wet slowly except for temperate steppe type. In terms of spatial distribution, the total area ratios of the three types of desert grasslands with stable drought degree and drying tendency (slight drying, drying and significant drying) are respectively 44.93% and 55.01%. The total area ratios of the five types of non-desert grassland with stable drought degree and wetting trend (slightly wetting, wetting and significantly wetting) were 72.19% and 24.27%, respectively. 【Conclusion】 Therefore, in the past 18 years, the drought situation of desert grassland is mainly stable and continuous drying, and there are more areas that keep drying, so the ecological environment of grassland continues to deteriorate. The drought situation of non-desert grassland is mainly stable, a small part of the area has a tendency of becoming wet, so the ecological environment of grassland is improving steadily. In addition, the lack of precipitation has a significant effect on the drought degree of non-desert grassland, but not on the desert grassland. The increase of temperature only has a significant effect on the drought degree of the temperate steppe type and the temperate steppe-desert type.

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Temporal and Spatial Variation of Productivity and Its Response to Climate in Semi-Arid Pasture of Forage Harvesting Area

MAO PingPing,SHEN BeiBei,DING Lei,ZHU XiaoYu,XIN XiaoPing,YAN YuChun,WANG Xu,YAN RuiRui,XU LiJun,CHEN BaoRui

Scientia Agricultura Sinica 2020, 53 (13): 2743-2756. DOI: 10.3864/j.issn.0578-1752.2020.13.021

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【Objective】 This study aimed to simulate the productivity of hay-land in the semi-arid pastoral region, to evaluate the grassland degradation and to explore the impact of climate on grassland production. 【Method】 The potential productivity of hay-land from 2000 to 2017 was calculated by using Miami and Thornthwaite model, and compared with the MODIS NPP products (MOD17A2H), which represented the actual productivity. 【Result】 From 2000 to 2017, both actual productivity and potential productivity of hay-land in semi-arid pastoral region increased with rising precipitation, with mean value of 295.24 and 557.79 g C?m^-2?a^-1, respectively. Both the potential and actual productivity were the highest in meadow steppe, which were 589.68 and 349.78 g C?m^-2?a^-1, respectively, and with the lowest coefficient of variation. The potential productivity was the lowest in mountainous meadow with an average value of 518.72 g C?m^-2?a^-1, while the actual productivity was the lowest in the typical steppe with 269.52 g C?m^-2?a^-1. The inter-annual change rate of potential productivity was the highest in the meadow steppe, which was 6.30 g C?m^-2?a^-1, and the actual productivity was the highest in mountainous meadow with 4.44 g C?m^-2?a^-1. The actual productivity showed significant positive relationship with precipitation in 95.88% of the hay-land steppe, however, showed negative correlation with temperature in 5.70% of the area. 【Conclusion】 The climatic production potential of forage harvesting area increased from west to east. Under the influence of hydrothermal conditions, the actual productivity gradually decreased in the east and west foothills of the Daxing’an Mountain range, and its response to precipitation was higher than that of temperature. The average annual utilization rate of climate resources was the same as the actual productivity, and the average utilization rate of climate resources was 55.09%. The grassland of meadow grassland had the highest utilization rate of climate resources, which was as high as 60.34%.

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Biomass Carbon Storage and Its Effect Factors in Steppe and Agro-Pastoral Ecotones in Northern China

XIN XiaoPing,DING Lei,CHENG Wei,ZHU XiaoYu,CHEN BaoRui,LIU ZhongLing,HE GuangLi,QING GeLe,YANG GuiXia,TANG HuaJun

Scientia Agricultura Sinica 2020, 53 (13): 2757-2768. DOI: 10.3864/j.issn.0578-1752.2020.13.022

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【Objective】 The grassland ecosystem plays an important role in the global carbon balance. The study of grassland carbon pool and its driving force is a hot point of vegetation ecology. This study investigated the vegetation carbon density and its spatial pattern in the steppe and agro-pastoral ecotones of northern China. The major factors driving the spatial variation of grassland vegetation carbon density were identified, as well as the relative contribution of climate, soil texture, grazing intensity and other factors to the grassland vegetation carbon pool. 【Method】 Using the survey data of the grassland vegetation in northern grassland during 2002 and 2009, combined with the MODIS/NDVI remote sensing data and 1:1 million grassland type map, the estimation model of above- and below-ground biomass in the main grassland types of northern China was established. Based on 255 county-level administrative units in the study area, the relationship between grassland vegetation carbon density and climate factors, soil texture and livestock carrying capacity were explored, and derived the relative contribution of different driving factors to grassland carbon density using the general linear model (GLM). 【Result】 (1) The average above-ground biomass (AGB) of the steppe and agro-pastoral ecotones of northern China was 36.9 g C·m^-2, and the below-ground biomass (BGB) was 362.9 g C·m^-2, nearly 10 times the AGB. Both the above- and below-ground biomass decreased from east to west, and followed logarithmic normal distribution. The biomass carbon density of grassland types was significantly different. (2) In the whole study region and steppe sub-region, desert sub-region, agro-pastoral sub-region, the AGB showed a significantly positive correlation with mean annual precipitation (MAP) and soil clay content (Clay%), a significantly negative relationship with the mean annual temperature (MAT) and soil sand content (Sand%). The AGB increased with livestock carrying capacity except in the steppe sub-region where were very heavily grazed. (3) General Linear Model (GLM) analysis indicated that the MAP, MAT, Clay% and grazing intensity explained 29.6% (P<0.001), 5.8% (P<0.001), 0.8% (P<0.05) and 1.3% (P<0.001) of AGB variation, respectively, and the MAP, MAT and Sand% contributed to 12.1% (P<0.001), 6.8% (P<0.001) and 1.9% (P<0.005) to BGB variation, respectively, and the grazing intensity had minor contribution to BGB. 【Conclusion】 Climate factors especially MAP was the dominate driving factor of grassland vegetation carbon density, and its impact on AGB was more obvious than on BGB. Soil texture also had a significant contribution to the grassland vegetation carbon density, especially on the BGB. Grazing intensity explained only 1.3% of the AGB and had no impact on BGB. This finding indicated that the climate factors were major contributor grassland vegetation carbon density comparing with grazing intensity.

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