Controls on soil respiration in semiarid soils

Soil respiration in semiarid ecosystems responds positively to temperature, but temperature is just one of many factors controlling soil respiration. Soil moisture can have an overriding influence, particularly during the dry/warm portions of the year. The purpose of this project was to evaluate the influence of soil moisture on the relationship between temperature and soil respiration. Soil samples collected from a range of sites arrayed across a climatic gradient were incubated under varying temperature and moisture conditions. Additionally, we evaluated the impact of substrate quality on short-term soil respiration responses by carrying out substrate-induced respiration assessments for each soil at nine different temperatures. Within all soil moisture regimes, respiration rates always increased with increase in temperature. For a given temperature, soil respiration increased by half (on average) across moisture regimes; Q₁₀ values declined with soil moisture from 3.2 (at −0.03 MPa) to 2.1 (−1.5 MPa). In summary, soil respiration was generally directly related to temperature, but responses were ameliorated with decrease in soil moisture.     

Reptile diversity and rodent community structure across a political border

The peace treaty between Israel and Jordan found the Arava desert ecosystem, shared by the two countries, in a state of developmental dichotomy. On the Israeli side, vast lands have been settled and transformed into agricultural fields, while the Jordanian side has remained relatively intact and inhabited by only a few traditional and pastoral societies. This study examined the effect of different landscape units and proximity to agriculture on reptile diversity and rodent community structure on both sides of the border. It appears that in addition to the effect of proximity to agricultural fields and landscape habitat, the border between the two countries may play a role in determining diversity on the respective sides. While reptile abundance was generally higher on the Israeli side of the border, diversity was found to be significantly higher on the Jordanian side. Rodent community structure also revealed significant differences between the two sides of the border, mainly due to the more favorable conditions for psammophilic gerbils in Jordan. When comparing Western society with pastoral traditional society, it appears that development activities of the former have altered diversity and community structure of the taxa studied in the Arava. We suggest that in addition to the effects of habitats and human disturbances, such as modern agricultural practices, cultural differences between societies should be considered when conservation plans are developed for cross-border ecosystems.     

库姆塔格沙漠及周边地表覆被变化监测

[目的]研究库姆塔格沙漠及周边区域地表覆被变化状况。[方法]通过遥感技术对库姆塔格沙漠及周边区域的地表覆被变化状况进行监测,并对该区1990年代、2000年代和2010年代的TM影像进行处理和分类,而后应用ArcGis软件对3期数据进行对比分析。[结果](1)该地区植被面积一直在增长,但仍然占很小比重,戈壁与裸地则占很大比重;(2)沙漠面积经历一个先增长后减少的过程,总体仍是增长;(3)湿地的稳定性最差,湿地的变动取决于水分的积聚与流失。[结论]人类已经着手改善该地生态环境,并取得一定效果。山地和库姆塔格沙漠南缘是绿化和防沙治沙的重点区域。     

乌兰布和沙漠东北部天然植被动态及生态用水量研究

乌兰布和沙漠东北部的不同地类导致该地区天然植被生境差异，进而形成了有不同顶级植物组成的天然植物群落。本文在不同时期卫星影像解译的土地利用类型基础上，分析了乌兰布和沙漠东北部天然植被生境动态变化。结果表明，该地区固定半固定沙地面积均有所减少，流动沙地扩大，同时盐碱地大大萎缩。在此基础上，用间接推求方法估算了该地区天然植被的生态用水量，其中柠条群落的生态用水量占整个研究区域生态用水总量的50．01％，油蒿＋白刺＋沙冬青群落占41．03％，梭梭群落占7．38％，盐碱地柽柳群落占1．58％。     

Effects of grazing practices and fossorial rodents on a winter avian community in Chihuahua, Mexico

Chihuahuan Desert grasslands are important wintering grounds for grassland and shrub-adapted birds. Many species belonging to these assemblages are currently exhibiting population declines. One area recognized for its importance to biological diversity, including grassland birds, is the Janos-Nuevo Casas Grandes black-tailed prairie dog (Cynomys ludovicianus) complex in northwestern Chihuahua, Mexico, an area containing 58 colonies with 30,000 ha of prairie dogs. This is one of the largest remaining prairie dog complexes and the only intact complex in the Chihuahuan Desert. In its current condition, a large percentage of this complex is of reduced value to wildlife. Overgrazing on communal (ejido) lands has resulted in areas being comprised of annual grasses and forbs. The density of active prairie dog burrows and banner-tailed kangaroo rat (Dipodomys spectabilis) mounds as well as avian diversity and abundance were lower on ejido lands than an adjacent private ranchland with and without prairie dogs. Few avian species used overgrazed portions of the prairie dog colony. Community similarity among plot types was low due to different management practices and differences on and off colony. To retain, and in many instances restore the biological diversity of this important region it is essential to work with local ejidos on grazing management.     

戈壁荒漠区光伏发电项目水土流失特征及其影响指数

以河西走廊地区9个已建成的典型光伏发电项目为研究对象,对不同防治分区的水土流失特征进行对比分析,在此基础上应用水土流失影响指数计算、分析和评级方法,计算戈壁荒漠区光伏发电项目的水土流失影响指数。首次指明国内戈壁荒漠区光伏发电项目的水土流失影响指数范围。结果表明：光伏发电项目各防治分区扰动地表面积所占比例从大到小依次为光电池板布置区（68.72%）〉道路区（27.17%）〉其他防治区（1.77%）〉管理区（1.18%）〉施工营地区（1.15%）;挖方量所占比例从大到小依次为光电池板布置区（65.09%）〉道路区（30.45%）〉管理区（1.82%）〉施工营地区（1.48%）〉其他防治区（1.15%）,光电池板布置区和道路区是光伏发电项目施工扰动最大的区域。这些区域的基础开挖、搬运和填筑等土建工程也是产生水土流失的重点环节,戈壁荒漠区光伏发电项目建设的水土流失影响指数为0.419。     

1989—2019年库布齐沙漠植被覆盖度的时空变化

[目的]探究库布齐沙漠近1989—2019年植被覆盖度的时空动态变化规律,为库布齐沙漠植被恢复及生态建设提供理论参考和基础数据。[方法]以1989—2019年每5 a为1期(共7期)的Landsat影像为数据源,结合归一化植被指数(NDVI)像元二分法模型,利用ENVI 5.3和ArcGIS 10.2分析库布齐沙漠1989—2019年植被覆盖度(FVC)时空动态变化特征。[结果](1)在时间变化上,近30 a间库布齐沙漠植被覆盖度整体呈增长趋势,平均植被覆盖度由0.104增长到0.243。在空间分布上,库布齐沙漠植被覆盖度呈现由西向东、向北增加的特征。(2)库布齐沙漠植被覆盖在1999—2004年和2009—2014年均呈现退化趋势,平均植被覆盖度分别减少0.053和0.054,退化面积分别为3 870.22和6 093.59 km~2,退化程度均以植被覆盖度减少10%～30%为主。[结论] 1989—2019年库布齐沙漠植被覆盖度总体有所改善,未来该区生态修复重点关注低植被覆盖区域。     

基于风洞试验的风沙区光伏阵列近地表形态变化规律研究

[目的] 研究库布齐沙漠中段沙区光伏阵列扰动下地表形态变化规律及其与风环境的关系,为科学制定沙区光伏电站次生风沙危害防治技术方案提供理论依据。[方法] 运用风洞试验方法,分析光伏阵列与风向之间夹角为0°,45°,90°,135°和180°时光伏阵列地表蚀积空间分布规律和地表形态剖面特征。[结果] 夹角为±90°时,迎风侧前两排电板区域地表蚀积变化表现为风蚀以中度和重度为主,堆积以轻度为主。第3—5排电板区域在前两排电板的遮蔽作用下风沙活动强度大幅降低。夹角为±45°时所有电板区域蚀积变化规律较为相似;45°时蚀积变化表现为风蚀以中度和重度为主,堆积以中度和轻度为主,小范围出现重度堆积现象;-45°时风蚀和堆积均表现为以轻度和中度为主。以8 m/s风速条件为例,不同夹角条件光伏阵列地表蚀积强度表现为：45°>90°>-45°>-90°>0°。夹角为0°时最小,蚀积变化极差仅为1.265 cm。夹角为45°时最大,蚀积变化极差可达5.429 cm。夹角绝对值相等符号相反风况条件下,夹角为正值相较负值时光伏阵列地表风沙活动更为强烈。夹角为45°时蚀积强度是夹角为-45°时的1.566倍,夹角为90°时则是夹角为-90°时的1.269倍。[结论] 沙区光伏阵列次生风沙危害的防治技术方案设计应充分考虑区域主害风向条件。     

三种荒漠植物叶绿素荧光参数日变化特征

利用Photosynq MultiseQ多功能植物测量仪测定塔克拉玛干沙漠腹地3种主要防护林植物头状沙拐枣、多枝柽柳和梭梭的叶绿素荧光参数日变化,探讨其与环境因子的关系,以揭示3种植物对极端环境的适应策略,为沙漠公路防护林的管护提供理论依据。结果表明：1）3种土壤都呈碱性;0~30 cm土层中的电导率（EC）远高于30 cm以下的土层。1 m内梭梭土层中的含水量高于多枝柽柳高于头状沙拐枣。2）3种植物的光合有效辐射（PAR）、叶片温度和线性电子传递（LEF）及植物周围的大气温度日变化均先升后降,且都在14：00达到最高;而大气湿度、实际光化学效率Y_（II）日变化均呈‘V’型。3）PAR基本上与3种植物的LEF、非光化学淬灭系数（NPQ）、调节性能量耗散量子产量Y_（NPQ）、非调节性能量耗散量子产量Y_（NO）呈显著正相关,与实际光化学效率Y_（II）呈显著负相关;3种植物的Y_（II）与Y_（NPQ）、Y_（NO） 均呈极显著负相关。3种植物的LEF、Y_（II）、Y_（NPQ）的日均值差异不显著,但梭梭与多枝柽柳的NPQ和Y_（NO）日均值差异显著。4）在3种植物的叶绿素荧光参数中,梭梭和头状沙拐枣的LEF、NPQ和Y_（II）要高于多枝柽柳;而多枝柽柳的Y_（NO）要显著高于头状沙拐枣和梭梭。因此,高温和高光均对3种植物造成了不同程度的影响,通过主成分分析表明,3种植物的抗逆性强弱顺序分别为梭梭>头状沙拐枣>多枝柽柳。