外源铁补给对潜流人工湿地脱氮效率影响的模拟研究

通过模拟实验,研究不同浓度外源铁补给对种植芦苇(Phragmites australis)的潜流人工湿地氮元素去除能力的影响,并初步探讨了其作用机理。结果表明,铁补给有利于促进人工湿地对水体中总氮和硝态氮的去除效率,且高浓度铁(50 mg/L)的促进作用比低浓度铁(25 mg/L)更强;但由于二价铁氧化过程中与铵态氮的硝化作用竞争吸氧,使铁补给仅仅促进了上层人工湿地对水体中铵态氮的净化作用,不利于下层人工湿地对铵态氮的净化。外源铁进入人工湿地系统后,其浓度迅速下降,且上层人工湿地水体中的二价铁浓度低于下层人工湿地,而上层人工湿地水体中的可溶性总铁和三价铁浓度高于下层人工湿地。随着水力停留时间的增加,人工湿地水体的pH总体上先升高后降低,而氧化还原电位则先降低后升高;对pH而言,加铁处理的人工湿地水体的pH总体上低于对照组,且下层人工湿地水体的pH低于上层,对照组则相反;对于氧化还原电位,加铁处理的人工湿地水体的氧化还原电位高于对照组,且下层氧化还原电位高于上层,对照组则相反。外源铁补给可以在一定程度上促进人工湿地对总氮和硝态氮以及上层人工湿地对铵态氮的去除效率,同时,外源铁自身的浓度和形态以及系统水体的pH和氧化还原电位也将发生显著变化。     

黑河流域干旱生态系统红砂荒漠空间斑块结构及其生态适应策略（英文）

In many arid ecosystems,vegetation frequently occurs in high-cover patches interspersed in a matrix of low plant cover.However,theoretical explanations for shrub patch pattern dynamics along climate gradients remain unclear on a large scale.This context aimed to assess the variance of the Reaumuria soongorica patch structure along the precipitation gradient and the factors that affect patch structure formation in the middle and lower Heihe River Basin(HRB).Field investigations on vegetation patterns and heterogeneity in soil properties were conducted during 2014 and 2015.The results showed that patch height,size and plant-to-patch distance were smaller in high precipitation habitats than in low precipitation sites.Climate,soil and vegetation explained 82.5% of the variance in patch structure.Spatially,R.soongorica shifted from a clumped to a random pattern on the landscape towards the MAP gradient,and heterogeneity in the surface soil properties(the ratio of biological soil crust(BSC) to bare gravels(BG)) determined the R.soongorica population distribution pattern in the middle and lower HRB.A conceptual model,which integrated water availability and plant facilitation and competition effects,was revealed that R.soongorica changed from a flexible water use strategy in high precipitation regions to a consistent water use strategy in low precipitation areas.Our study provides a comprehensive quantification of the variance in shrub patch structure along a precipitation gradient and may improve our understanding of vegetation pattern dynamics in the Gobi Desert under future climate change.     

Spatial patch structure and adaptive strategy for desert shrub of Reaumuria soongorica in arid ecosystem of the Heihe River Basin

In many arid ecosystems, vegetation frequently occurs in high-cover patches interspersed in a matrix of low plant cover. However, theoretical explanations for shrub patch pattern dynamics along climate gradients remain unclear on a large scale. This context aimed to assess the variance of the Reaumuria soongorica patch structure along the precipitation gradient and the factors that affect patch structure formation in the middle and lower Heihe River Basin (HRB). Field investigations on vegetation patterns and heterogeneity in soil properties were conducted during 2014 and 2015. The results showed that patch height, size and plant-to-patch distance were smaller in high precipitation habitats than in low precipitation sites. Climate, soil and vegetation explained 82.5% of the variance in patch structure. Spatially, R. soongorica shifted from a clumped to a random pattern on the landscape towards the MAP gradient, and heterogeneity in the surface soil properties (the ratio of biological soil crust (BSC) to bare gravels (BG)) determined the R. soongorica population distribution pattern in the middle and lower HRB. A conceptual model, which integrated water availability and plant facilitation and competition effects, was revealed that R. soongorica changed from a flexible water use strategy in high precipitation regions to a consistent water use strategy in low precipitation areas. Our study provides a comprehensive quantification of the variance in shrub patch structure along a precipitation gradient and may improve our understanding of vegetation pattern dynamics in the Gobi Desert under future climate change.

     

中国北方干湿过渡区生态系统生产力的气候变化风险评估

气候变化风险是人类社会发展面临的严峻挑战,评估识别对气候波动响应敏感且复杂的干湿过渡区生态系统所面临的气候变化风险是一个重要科学问题,对区域气候治理和风险管理具有科学意义.本文利用参与耦合模式比较计划第五阶段(CMIP5)的多气候模式多情景数据,通过改进和验证Lund-Potsdam-Jena(LPJ)动态全球植被模型...     

The effects of the identity of shrub species on the distribution and diversity of ground arthropods in a sandy desert ecosystem of northwestern China

Shrub is an important factor on structuring ground arthropod communities in desert ecosystems. In this study, in order to determine how shrubs and their species influence ground arthropod distribution patterns in a sandy desert scrubland dominated by two different shrub species, Calligonum mongolicum and Nitraria sphaerocarpa, the ground arthropods were sampled with pitfall traps during spring, summer and autumn. At the community level, total arthropod abundance was shown to be significantly higher under shrubs than in intershrub bare areas in spring; similar patterns occurred in terms of the richness of arthropod groups in the spring and over three seasons, suggesting season-specific shrub presence effects on arthropod activity. In addition, more arthropods were found under N. sphaerocarpa shrubs than under C. rnongolicum shrubs in autumn, suggesting season-specific effects of shrub species of arthropod activity, whereas more arthropods taxa were captured under C. mongoIicum than N. sphaerocarpa. At the trophic group level, the abundances of predator and herbivore arthropods were significantly greater under shrubs than in intershrub bare habitats, whereas herbivore arthropods were more abundant under N. sphaerocarpa than C. rnongolicum, and an opposite rule was detected for predator arthropods At the family level, the mean abundances of Carabidae, Curculionidae, Gnaphosidae and Lycosidae were significantly higher in the shrub microhabitats than in the intershrub bare habitat, there was no significant difference between habitats on the mean abundances of Formicidae and Tenebrionidae. The study results suggested that shrub presence and shrub species variation are important determinants of ground arthropod assemblages in this desert ecosystem, but the responses of ar- thropods differed among trophic and taxonomic groups.     

Seed germination responses of Periploca sepium Bunge, a dominant shrub in the Loess hilly regions of China

Experiments were conducted to determine the effects of temperature, light, osmotic stress, hydration-dehydration regime and stress relief on the seed germination of Periploca sepium Bunge (Chinese silk vine Asclepiadaceae), which is a native shrub in the Loess Plateau of Northwest China. Freshly harvested seeds germinated equally well in both light and darkness. Seeds germinated under all of tested temperature regimes, and much faster when temperature was maintained at 30, 35, and 30/20, 30/25, 35/25, 35/30 °C range, with more than 90% of seeds germinating within 2 days. Moderate osmotic stress did not inhibit germination at any tested temperature. At 30 °C, seed germination was not affected significantly above −0.8 MPa. The hydration-dehydration pretreatment showed none side effects on P. sepium seeds and the seeds germinated more rapidly as soon as optimal water condition was restored. These results show the advantages of P. sepium, which is a competitive and widespread shrub in dry areas, and provide useful information for vegetation restoration in these drought-prone regions.