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1. chinaXiv:202110.00017 [pdf]

Delayed seed dispersal species and related traits in the desert of the United Arab Emirates

Subjects: Geosciences >> Geography

The ability of plants to safely retain seeds in the mother plant is an adaptive mechanism described in many desert plants. However, research about delayed seed dispersal species in the desert of the United Arab Emirates (UAE) is lacking. This study aims to identify these delayed seed dispersal species and assess the relationships of the presence of delayed seed dispersal with plant growth form, habit, spatial dispersal, antitelechoric mechanism, and seed release time. The relationships between the presence of delayed seed dispersal and the above studied traits were assessed by using the Pearson Chi-square test and Nonlinear Principal Components Analysis (NLPCA). Results showed that a total of 46 delayed seed dispersal species were recorded (15.0% of 307 studied species) and the highest incidence occurred in the Fabaceae family (17.4%). Delayed seed dispersal species were predominantly perennial plants (73.9%) with spatial restricted dispersal (67.4%), which released seed in the dry season (45.7%). The dominant groups of delayed seed dispersal species were persistent fruits species and synaptospermy (28.3%). All graminoids showed persistent lignified fruits, while prostrate annuals were basicarpic species with myxospermy. Sandy habitats had the highest number of delayed seed dispersal species (54.3%), whereas salt flats had the lowest (23.9%). In the desert of the UAE, delayed seed dispersal species spread seeds until the end of the dry and windy season, thus breaking seed dormancy at this time and ensuring seed germination in the next arrival of the rainy season. This morphological and ecological adaptation of delayed dispersal species is essential to the survival and sustainable development of vegetation in desert environments.

submitted time 2021-10-11 From cooperative journals:《Journal of Arid Land》 Hits7613Downloads302 Comment 0

2. chinaXiv:202110.00019 [pdf]

Effects of different ridge-furrow mulching systems on yield and water use efficiency of summer maize in the Loess Plateau of China

CHEN Pengpeng; GU Xiaobo; LI Yuannong; QIAO Linran; LI Yupeng; FANG Heng; YIN Minhua; ZHOU Changming
Subjects: Geosciences >> Geography

Ridge-furrow film mulching has been proven to be an effective water-saving and yield-improving planting pattern in arid and semi-arid regions. Drought is the main factor limiting the local agricultural production in the Loess Plateau of China. In this study, we tried to select a suitable ridge-furrow mulching system to improve this situation. A two-year field experiment of summer maize (Zea mays L.) during the growing seasons of 2017 and 2018 was conducted to systematically analyze the effects of flat planting with no film mulching (CK), ridge-furrow with ridges mulching and furrows bare (RFM), and double ridges and furrows full mulching (DRFFM) on soil temperature, soil water storage (SWS), root growth, aboveground dry matter, water use efficiency (WUE), and grain yield. Both RFM and DRFFM significantly increased soil temperature in ridges, while soil temperature in furrows for RFM and DRFFM was similar to that for CK. The largest SWS was observed in DRFFM, followed by RFM and CK, with significant differences among them. SWS was lower in ridges than in furrows for RFM. DRFFM treatment kept soil water in ridges, resulting in higher SWS in ridges than in furrows after a period of no water input. Across the two growing seasons, compared with CK, RFM increased root mass by 10.2% and 19.3% at the jointing and filling stages, respectively, and DRFFM increased root mass by 7.9% at the jointing stage but decreased root mass by 6.0% at the filling stage. Over the two growing seasons, root length at the jointing and filling stages was respectively increased by 75.4% and 58.7% in DRFFM, and 20.6% and 30.2% in RFM. Relative to the jointing stage, the increased proportions of root mass and length at the filling stage were respectively 42.8% and 94.9% in DRFFM, 63.2% and 115.1% in CK, and 76.7% and 132.1% in RFM, over the two growing seasons, showing that DRFFM slowed down root growth while RFM promoted root growth at the later growth stages. DRFFM treatment increased root mass and root length in ridges and decreased them in 0–30 cm soil layer, while RFM increased them in 0–30 cm soil layer. Compared with CK, DRFFM decreased aboveground dry matter while RFM increased it. Evapotranspiration was reduced by 9.8% and 7.1% in DRFFM and RFM, respectively, across the two growing seasons. Grain yield was decreased by 14.3% in DRFFM and increased by 13.6% in RFM compared with CK over the two growing seasons. WUE in CK was non-significantly 6.8% higher than that in DRFFM and significantly 22.5% lower than that in RFM across the two growing seasons. Thus, RFM planting pattern is recommended as a viable water-saving option for summer maize in the Loess Plateau of China.

submitted time 2021-10-11 From cooperative journals:《Journal of Arid Land》 Hits7496Downloads337 Comment 0

3. chinaXiv:202110.00020 [pdf]

Response of C:N:P in the plant-soil system and stoichiometric homeostasis of Nitraria tangutorum leaves in the oasis-desert ecotone, Northwest China

WEI Yajuan; DANG Xiaohong; WANG Ji; GAO Junliang; GAO Yan
Subjects: Geosciences >> Geography

Nitraria tangutorum nebkhas are widely distributed in the arid and semi-arid desert areas of China. The formation and development of N. tangutorum nebkhas are the result of the interaction between vegetation and the surrounding environment in the process of community succession. Different successional stages of N. tangutorum nebkhas result in differences in the community structure and composition, thereby strongly affecting the distribution of soil nutrients and ecosystem stability. However, the ecological stoichiometry of N. tangutorum nebkhas in different successional stages remains poorly understood. Understanding the stoichiometric homeostasis of N. tangutorum could provide insights into its adaptability to the arid and semi-arid desert environments. Therefore, we analyzed the stoichiometric characteristics of N. tangutorum in four successional stages, i.e., rudimental, developing, stabilizing, and degrading stages using a homeostasis model in an oasis-desert ecotone of Northwest China. The results showed that soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) contents and their ratios in the 0–100 cm soil depth were significantly lower than the averages at regional and global scales and were weakly influenced by successional stages in the oasis-desert ecotone. TN and TP contents and C:N:P in the soil showed similar trends. Total carbon (TC) and TN contents in leaves were 450.69–481.07 and 19.72–29.35 g/kg, respectively, indicating that leaves of N. tangutorum shrubs had a high storage capacity for C and N. Leaf TC and TN contents and N:P ratio increased from the rudimental stage to the stabilizing stage and then decreased in the degrading stage, while the reverse trend was found for leaf C:N. Leaf TP content decreased from the rudimental stage to the degrading stage and changed significantly in late successional stages. N:P ratio was above the theoretical limit of 14, indicating that the growth of N. tangutorum shrubs was limited by P during successional stages. Leaf N, P, and N:P homeostasis in four successional stages was identified as ''strictly homeostasis''. Redundancy analysis (RDA) revealed that soil acidity (pH) and the maximum water holding capacity were the main factors affecting C:N:P stoichiometric characteristics in N. tangutorum leaves. Our study demonstrated that N. tangutorum with a high degree of stoichiometric homeostasis could better cope with the arid desert environment.

submitted time 2021-10-11 From cooperative journals:《Journal of Arid Land》 Hits7504Downloads340 Comment 0

4. chinaXiv:202110.00021 [pdf]

Plant cover as an estimator of above-ground biomass in semi-arid woody vegetation in Northeast Patagonia, Argentina

Subjects: Geosciences >> Geography

The quantification of carbon storage in vegetation biomass is a crucial factor in the estimation and mitigation of CO2 emissions. Globally, arid and semi-arid regions are considered an important carbon sink. However, they have received limited attention and, therefore, it should be a priority to develop tools to quantify biomass at the local and regional scales. Individual plant variables, such as stem diameter and crown area, were reported to be good predictors of individual plant weight. Stand-level variables, such as plant cover and mean height, are also easy-to-measure estimators of above-ground biomass (AGB) in dry regions. In this study, we estimated the AGB in semi-arid woody vegetation in Northeast Patagonia, Argentina. We evaluated whether the AGB at the stand level can be estimated based on plant cover and to what extent the estimation accuracy can be improved by the inclusion of other field-measured structure variables. We also evaluated whether remote sensing technologies can be used to reliably estimate and map the regional mean biomass. For this purpose, we analyzed the relationships between field-measured woody vegetation structure variables and AGB as well as LANDSAT TM-derived variables. We obtained a model-based ratio estimate of regional mean AGB and its standard error. Total plant cover allowed us to obtain a reliable estimation of local AGB, and no better fit was attained by the inclusion of other structure variables. The stand-level plant cover ranged between 18.7% and 95.2% and AGB between about 2.0 and 70.8 Mg/hm2. AGB based on total plant cover was well estimated from LANDSAT TM bands 2 and 3, which facilitated a model-based ratio estimate of the regional mean AGB (approximately 12.0 Mg/hm2) and its sampling error (about 30.0%). The mean AGB of woody vegetation can greatly contribute to carbon storage in semi-arid lands. Thus, plant cover estimation by remote sensing images could be used to obtain regional estimates and map biomass, as well as to assess and monitor the impact of land-use change on the carbon balance, for arid and semi-arid regions.

submitted time 2021-10-11 From cooperative journals:《Journal of Arid Land》 Hits6669Downloads334 Comment 0

5. chinaXiv:202110.00022 [pdf]

Assessing the response of dryland barley yield to climate variability in semi-arid regions, Iran

Subjects: Geosciences >> Geography

Precipitation and temperature are the most abiotic factors that greatly impact the yield of crop, particularly in dryland. Barley, as the main cereal is predominantly cultivated in dryland and the livelihood of smallholders depends on the production of this crop, particularly in arid and semi-arid regions. This study aimed to investigate the response of the grain yield of dryland barley to temperature and precipitation variations at annual, seasonal and monthly scales in seven counties of East and West Azerbaijan provinces in northwestern Iran during 1991–2010. Humidity index (HI) was calculated and its relationship with dryland barley yield was evaluated at annual and monthly scales. The results showed that the minimum, maximum and mean temperatures increased by 0.19°C/a, 0.11°C/a and 0.10°C/a, respectively, while annual precipitation decreased by 0.80 mm/a during 1991–2010. Climate in study area has become drier by 0.22/a in annual HI during the study period. Negative effects of increasing temperature on the grain yield of dryland barley were more severe than the positive effects of increasing precipitation. Besides, weather variations in April and May were related more to the grain yield of dryland barley than those in other months. The grain yield of dryland barley was more drastically affected by the variation of annual minimum temperature comparing with other weather variables. Furthermore, our findings illustrated that the grain yield of dryland barley increased by 0.01 t/hm2 for each unit increase in annual HI during 1991–2010. Finally, any increase in the monthly HI led to crop yield improvement in the study area, particularly in the drier counties, i.e., Myaneh, Tabriz and Khoy in Iran.

submitted time 2021-10-11 From cooperative journals:《Journal of Arid Land》 Hits7805Downloads1132 Comment 0

6. chinaXiv:202110.00023 [pdf]

Climate change impacts on the streamflow of Zarrineh River, Iran

Subjects: Geosciences >> Geography

Zarrineh River is located in the northwest of Iran, providing more than 40% of the total inflow into the Lake Urmia that is one of the largest saltwater lakes on the earth. Lake Urmia is a highly endangered ecosystem on the brink of desiccation. This paper studied the impacts of climate change on the streamflow of Zarrineh River. The streamflow was simulated and projected for the period 1992–2050 through seven CMIP5 (coupled model intercomparison project phase 5) data series (namely, BCC-CSM1-1, BNU-ESM, CSIRO-Mk3-6-0, GFDL-ESM2G, IPSL-CM5A-LR, MIROC-ESM and MIROC-ESM-CHEM) under RCP2.6 (RCP, representative concentration pathways) and RCP8.5. The model data series were statistically downscaled and bias corrected using an artificial neural network (ANN) technique and a Gamma based quantile mapping bias correction method. The best model (CSIRO-Mk3-6-0) was chosen by the TOPSIS (technique for order of preference by similarity to ideal solution) method from seven CMIP5 models based on statistical indices. For simulation of streamflow, a rainfall-runoff model, the hydrologiska byrans vattenavdelning (HBV-Light) model, was utilized. Results on hydro-climatological changes in Zarrineh River basin showed that the mean daily precipitation is expected to decrease from 0.94 and 0.96 mm in 2015 to 0.65 and 0.68 mm in 2050 under RCP2.6 and RCP8.5, respectively. In the case of temperature, the numbers change from 12.33°C and 12.37°C in 2015 to 14.28°C and 14.32°C in 2050. Corresponding to these climate scenarios, this study projected a decrease of the annual streamflow of Zarrineh River by half from 2015 to 2050 as the results of climatic changes will lead to a decrease in the annual streamflow of Zarrineh River from 59.49 m3/s in 2015 to 22.61 and 23.19 m3/s in 2050. The finding is of important meaning for water resources planning purposes, management programs and strategies of the Lake's endangered ecosystem.

submitted time 2021-10-11 From cooperative journals:《Journal of Arid Land》 Hits3933Downloads562 Comment 0

7. chinaXiv:202110.00024 [pdf]

Spatiotemporal changes in water, land use, and ecosystem services in Central Asia considering climate changes and human activities

YU Yang; CHEN Xi; Ireneusz MALIK; Malgorzata WISTUBA; CAO Yiguo; HOU Dongde; TA Zhijie; HE Jing; ZHANG Lingyun; YU Ruide; ZHANG Haiyan; SUN Lingxiao
Subjects: Geosciences >> Geography

Central Asia is located in the hinterland of Eurasia, comprising Kazakhstan, Uzbekistan, Kyrgyzstan, Turkmenistan, and Tajikistan; over 93.00% of the total area is dryland. Temperature rise and human activities have severe impacts on the fragile ecosystems. Since the 1970s, nearly half the great lakes in Central Asia have shrunk and rivers are drying rapidly owing to climate changes and human activities. Water shortage and ecological crisis have attracted extensive international attention. In general, ecosystem services in Central Asia are declining, particularly with respect to biodiversity, water, and soil conservation. Furthermore, the annual average temperature and annual precipitation in Central Asia increased by 0.30°C/decade and 6.9 mm/decade in recent decades, respectively. Temperature rise significantly affected glacier retreat in the Tianshan Mountains and Pamir Mountains, which may intensify water shortage in the 21st century. The increase in precipitation cannot counterbalance the aggravation of water shortage caused by the temperature rise and human activities in Central Asia. The population of Central Asia is growing gradually, and its economy is increasing steadily. Moreover, the agricultural land has not been expended in the last two decades. Thus, water and ecological crises, such as the Aral Sea shrinkage in the 21st century, cannot be attributed to agriculture extension any longer. Unbalanced regional development and water interception/transfer have led to the irrational exploitation of water resources in some watersheds, inducing downstream water shortage and ecological degradation. In addition, accelerated industrialization and urbanization have intensified this process. Therefore, all Central Asian countries must urgently reach a consensus and adopt common measures for water and ecological protection.

submitted time 2021-10-11 From cooperative journals:《Journal of Arid Land》 Hits3570Downloads306 Comment 0

8. chinaXiv:202110.00026 [pdf]

城市绿色基础设施生态系统服务供需关系及空间优化 ——以西安市为例

Subjects: Geosciences >> Geography

维持城市生态系统服务供需平衡是建设宜居城市、提高城市居民福祉的基础,同时对区域 经济与可持续发展具有重要意义。以西安市建成区为例,基于 2018 年遥感数据、统计数据和实地 调研等多源数据,构建粮食需求、水资源需求、固碳释氧、空气净化、高温调节、减弱噪声和休闲娱 乐服务需求测算模型,并应用 ArcGIS 等分析工具,对研究区城市绿色基础设施(Urban green infra? structure,UGI)服务供需空间匹配关系进行评估和分析,最后运用最小累积阻力模型识别生态源地 和生态廊道,对西安市 UGI 空间格局进行优化。结果表明:(1)西安市建成区 UGI 分布不均匀,破 碎化程度高,连通性较差。UGI 提供的生态系统服务总价值小于居民对服务需求总价值,在空间上 表现为显著不匹配性。(2)不同生态系统服务供需匹配状况存在差异,高温调节服务、空气净化服 务和休闲娱乐服务供大于求,匹配状况较好;粮食供给、固碳释氧、水源涵养和减弱噪声服务供小 于求,供需赤字。(3)研究区生态系统服务供需具有显著空间异质性,随着人口集聚程度的提高,大 部分生态系统服务(如高温调节、减弱噪声等)供需的空间匹配程度显著下降,在空间上表现为由 城市中心的严重失调向边缘的良好匹配渐变。(4)研究区生态源地斑块面积较小,破碎化程度高, 连接度低,UGI 网络缺乏主干生态廊道。通过构建由沿渭河、秦岭北麓 2 个生态走廊,沣河、潏河、 灞河等 7 个生态保育区及沿道路绿化带等组成的 UGI 网络,可使生态系统服务供需空间关系更趋 协调。

submitted time 2021-10-10 From cooperative journals:《干旱区地理》 Hits4353Downloads554 Comment 0

9. chinaXiv:202110.00027 [pdf]


杨振民; 刘新平
Subjects: Geosciences >> Geography

阿克苏河流域作为西北干旱区内陆河,生态环境极为脆弱,研究其生态安全格局对优化区 域国土空间开发保护格局,推动生产生活方式向绿色转型,促进人与自然和谐共生具有重要战略 意义。基于研究区本底特征,运用空间主成分分析法(SPCA)对阿克苏河流域 1980—2018 年生态 承载力时空演变进行评估监测,利用最小累积阻力(MCR)模型提取生态廊道及生态节点,构建生 态安全格局。研究表明:(1)阿克苏河流域生态承载力空间差异明显,以中等承载为主,生态承载 优势区呈现由中东部向西部转移趋势。(2)阿克苏河流域生态承载力呈增长趋势。近 40 a 阿克苏 河流域整体生态承载力呈上升趋势,强承载区面积不断增加,弱承载区面积呈现波动下降趋势,表 明流域环境有所改善。(3)生态源地占整体面积较少,分布较为集中。根据生态承载力评估结果, 提取生态源地 23465.21 km2,约占研究区面积的 35.61%。生态源地集中分布于流域中部地区,北部 高山地区与西南部盆地、沙漠地区分布较少。(4)利用 MCR 模型及遥感影像,将阿克苏河流域划分 为 16 个生态安全格局分区,提取生态廊道 67 条,识别生态节点 71 处,并结合生态承载力评估结果, 对流域生态空间结构提出优化建议。

submitted time 2021-10-10 From cooperative journals:《干旱区地理》 Hits3945Downloads227 Comment 0

10. chinaXiv:202110.00028 [pdf]


Subjects: Geosciences >> Geography

水生态文明建设是新疆干旱区生态文明建设的关键,中国特色社会主义事业“五位一体”总 体布局对生态文明建设做出了战略部署。目前对干旱区水生态文明建设应关注的问题,水资源如 何保障和服务水生态文明建设等问题并不清晰。本文从水生态文明建设的角度综述了干旱区水 资源开发的生态环境效应研究和水生态文明研究,重点探讨了新疆水生态文明建设需坚持的重要 原则,提出了协调经济社会系统和生态系统的水资源保护利用策略。

submitted time 2021-10-10 From cooperative journals:《干旱区地理》 Hits3963Downloads215 Comment 0

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