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1. chinaXiv:202109.00011 [pdf]

Effects of water and nitrogen on growth and relative competitive ability of introduced versus native C4 grass species in the semi-arid Loess Plateau of China

DING Wenli; XU Weizhou; GAO Zhijuan; XU Bingcheng
Subjects: Geosciences >> Geography

Switchgrass is an introduced C4 grass in the semi-arid Loess Plateau of China, but there is a lack of information to assess its ecological invasive risk. In this study, Old World bluestems (native C4 grass) and switchgrass were sowed at five mixture ratios (8:0, 6:2, 4:4, 2:6 and 0:8) under two soil water levels (80% field capacity (FC) and 40% FC) and two nitrogen (N) treatments (0 and 100 mg N/kg dry soil, termed N0-unfertilized and N1-fertilized treatments, respectively) in a pot experiment in 2012. Biomass, root morphological traits and relative competitive abilities of these two species were analyzed. Results showed that biomass of both species was significantly greater under 80% FC or N fertilization, and switchgrass had a relatively larger root: shoot ratio (RSR). Total root length (TRL) and root surface area (RSA) of switchgrass were significantly higher under 80% FC irrespective of N treatment, while those of Old World bluestems were only significantly higher under N fertilization. N had no significant effect on TRL and RSA of switchgrass, while RSA of Old World bluestems significantly increased under 80% FC and N fertilization. Under 40% FC and N0-unfertilized treatment, the aggressivity of Old World bluestems was larger than zero at 2:6 and 4:4 mixture ratios of two species, whereas it was close to zero at 6:2 mixture ratio. Root competitive ability of switchgrass significantly increased under 80% FC or N fertilization. The aggressivity of Old World bluestems was negative at 6:2 mixture ratio under 80% FC and N fertilization, while it was positive at 2:6 mixture ratio. Switchgrass may become more aggressive when N deposition or rainfall increases, while a proper mixture ratio with appropriate water and N management could help with grassland management in the semi-arid Loess Plateau.

submitted time 2021-09-08 From cooperative journals:《Journal of Arid Land》 Hits5575Downloads165 Comment 0

2. chinaXiv:202109.00019 [pdf]

Reducing water and nitrogen inputs combined with plastic mulched ridge-furrow irrigation improves soil water and salt status in arid saline areas, China

LI Cheng; WANG Qingsong; LUO Shuai; QUAN Hao; WANG Naijiang; LUO Xiaoqi; ZHANG Tibin; DING Dianyuan; DONG Qin'ge; FENG Hao
Subjects: Geosciences >> Geography

Plastic mulched ridge-furrow irrigation is a useful method to improve crop productivity and decrease salt accumulation in arid saline areas. However, inappropriate irrigation and fertilizer practices may result in ecological and environmental problems. In order to improve the resource use efficiency in these areas, we investigated the effects of different irrigation amounts (400 (I1), 300 (I2) and 200 (I3) mm) and nitrogen application rates (300 (F1) and 150 (F2) kg N/hm2) on water consumption, salt variation and resource use efficiency of spring maize (Zea mays L.) in the Hetao Irrigation District (HID) of Northwest China in 2017 and 2018. Result showed that soil water contents were 0.2%–8.9% and 13.9%–18.1% lower for I2 and I3 than for I1, respectively, but that was slightly higher for F2 than for F1. Soil salt contents were 7.8%–23.5% and 48.5%–48.9% lower for I2 than for I1 and I3, but that was 1.6%–5.5% higher for F1 than for F2. Less salt leaching at the early growth stage (from sowing to six-leaf stage) and higher salt accumulation at the peak growth stage (from six-leaf to tasseling stage and from grain-filling to maturity stage) resulted in a higher soil salt content for I3 than for I1 and I2. Grain yields for I1 and I2 were significantly higher than that for I3 and irrigation water use efficiency for I2 was 14.7%–34.0% higher than that for I1. Compared with F1, F2 increased the partial factor productivity (PFP) of nitrogen fertilizer by more than 80%. PFP was not significantly different between I1F2 and I2F2, but significantly higher than those of other treatments. Considering the goal of saving water and nitrogen resources, and ensuring food security, we recommended the combination of I2F2 to ensure the sustainable development of agriculture in the HID and other similar arid saline areas.

submitted time 2021-09-08 From cooperative journals:《Journal of Arid Land》 Hits1953Downloads190 Comment 0

3. chinaXiv:202006.00238 [pdf]

Assessing the collapse risk of Stipa bungeana grassland in China based on its distribution changes

QIAO Xianguo; GUO Ke; LI Guoqing; ZHAO Liqing; LI Frank Yonghong; GAO Chenguang
Subjects: Geosciences >> History of Geosciences

The criteria used by International Union for Conservation of Nature (IUCN) for its Red List of Ecosystems (RLE) are the global standards for ecosystem-level risk assessment, and they have been increasingly used for biodiversity conservation. The changed distribution area of an ecosystem is one of the key criteria in such assessments. The Stipa bungeana grassland is one of the most widely distributed grasslands in the warm-temperate semi-arid regions of China. However, the total distribution area of this grassland was noted to have shrunk and become fragmented because of its conversion to cropland and grazing-induced degradation. Following the IUCN-RLE standards, here we analyzed changes in the geographical distribution of this degraded grassland, to evaluate its degradation and risk of collapse. Past (1950–1980) distribution areas were extracted from the Vegetation Map of China (1:1,000,000). Present realizable distribution areas were equated to these past areas minus any habitat area losses. We then predicted the grassland's present and future (under the Representative Concentration Pathway 8.5 scenario) potential distribution areas using maximum entropy algorithm (MaxEnt), based on field survey data and nine environmental layers. Our results showed that the S. bungeana grassland was mainly distributed in the Loess Plateau, Hexi Corridor, and low altitudes of the Qilian Mountains and Longshou Mountain. This ecosystem occurred mainly on loess soils, kastanozems, steppe aeolian soils and sierozems. Thermal and edaphic factors were the most important factors limiting the distribution of S. bungeana grassland across China. Since 56.1% of its past distribution area (4.9×104 km2) disappeared in the last 50 a, the present realizable distribution area only amounts to 2.2×104 km2. But only 15.7% of its present potential distribution area (14.0×104 km2) is actually occupied by the S. bungeana grassland. The future potential distribution of S. bungeana grassland was predicted to shift towards northwest, and the total area of this ecosystem will shrink by 12.4% over the next 50 a under the most pessimistic climate change scenario. Accordingly, following the IUCN-RLE criteria, we deemed the S. bungeana grassland ecosystem in China to be endangered (EN). Revegetation projects and the establishment of protected areas are recommended as effective ways to avert this looming crisis. This empirical modeling study provides an example of how IUCN-RLE categories and criteria may be valuably used for ecosystem assessments in China and abroad.

submitted time 2020-06-22 From cooperative journals:《Journal of Arid Land》 Hits7822Downloads910 Comment 0

4. chinaXiv:202006.00213 [pdf]

Coupling between the Grain for Green Program and a household level-based agricultural eco-economic system in Ansai, Shaanxi Province of China

LI Yue; WANG Jijun; HAN Xiaojia; GUO Mancai; CHENG Simin; QIAO Mei; ZHAO Xiaocui
Subjects: Geosciences >> Geography

The implementation of the Grain for Green Program (GGP) has changed the development track of the agricultural eco-economic system in China. In response to the results of a lag study that investigated the coupling between the GGP and the agricultural eco-economic system in a loess hilly region, we used a structural equation model to analyze the survey data from 494 households in Ansai, a district of Yan'an City in Shaanxi Province of China in 2015. The model clarified the direction and intensity of the coupling between the GGP and the agricultural eco-economic system. The coupling benefits were derived through linkages between the program and various chains in the agricultural eco-economic system. The GGP, the agroecosystem of Ansai and their potential coupling effects were in a state of general coordination. The agroecosystem directly affected the coupling effect, with the standardized path coefficient of 0.87, indicating that the agroecosystem in Ansai at this stage provided basic material support for the coupling between the GGP and the agricultural eco-economic system. The direct path coefficient of agroeconomic system impacted on the coupling effect was –0.76, indicating that partial contradictions occurred between the agroeconomic system and the coupling effect. Therefore, although the current agroecosystem in Ansai should be provided sufficient agroecological resources for the benign coupling between the program and the agricultural eco-economic system, agricultural development failed to effectively transform agroecological resources into agricultural economic advantages in this region, which resulted in a relative lag in the development of the agricultural economic system. Thus, the coupling between the GGP and the agricultural eco-economic system was poor. To improve the coupling and the sustainable development of the agricultural eco-economic system in cropland retirement areas, the industrial structure needs to be diversified, the agricultural resources (including agroecological resources, agricultural economic resources and agricultural social resources) need to be rationally allocated, and the chain structure of the agricultural eco-economic system needs to be continuously improved.

submitted time 2020-06-22 From cooperative journals:《Journal of Arid Land》 Hits1646Downloads817 Comment 0

5. chinaXiv:201809.00171 [pdf]

Changes in soil properties and erodibility of gully heads induced by vegetation restoration on the Loess Plateau, China

GUO, Mingming; WANG, Wenlong; KANG, Hongliang; YANG, Bo
Subjects: Geosciences >> History of Geosciences

Soil erosion on the Loess Plateau of China is effectively controlled due to the implementation of several ecological restoration projects that improve soil properties and reduce soil erodibility. However, few studies have examined the effects of vegetation restoration on soil properties and erodibility of gully head in the gully regions of the Loess Plateau. The objectives of this study were to quantify the effects of vegetation restoration on soil properties and erodibility in this region. Specifically, a control site in a slope cropland and 9 sites in 3 restored land-use types (5 sites in grassland, 3 in woodland and 1 in shrubland) in the Nanxiaohegou watershed of a typical gully region on the Loess Plateau were selected, and soil and root samples were collected to assess soil properties and root characteristics. Soil erodibility factor was calculated by the Erosion Productivity Impact Calculator method. Our results revealed that vegetation restoration increased soil sand content, soil saturated hydraulic conductivity, organic matter content and mean weight diameter of water-stable aggregate but decreased soil silt and clay contents and soil disintegration rate. A significant difference in soil erodibility was observed among different vegetation restoration patterns or land-use types. Compared with cropland, soil erodibility decreased in the restored lands by 3.99% to 21.43%. The restoration patterns of Cleistogenes caespitosa K. and Artemisia sacrorum L. in the grassland showed the lowest soil erodibility and can be considered as the optimal vegetation restoration pattern for improving soil anti-erodibility of the gully heads. Additionally, the negative linear change in soil erodibility for grassland with restoration time was faster than those of woodland and shrubland. Soil erodibility was significantly correlated with soil particle size distribution, soil disintegration rate, soil saturated hydraulic conductivity, water-stable aggregate stability, organic matter content and root characteristics (including root average diameter, root length density, root surface density and root biomass density), but it showed no association with soil bulk density and soil total porosity. These findings indicate that although vegetation destruction is a short-term process, returning the soil erodibility of cropland to the level of grassland, woodland and shrubland is a long-term process (8–50 years).

submitted time 2018-09-18 From cooperative journals:《Journal of Arid Land》 Hits3219Downloads1208 Comment 0

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