Numerical abundance and biodiversity of below-ground taxocenes along a pH gradient across the Netherlands

Aim Taxocenes are regulated by different kinds of predictors, but can broad‐scale patterns of prokaryotes (bacteria) and eukaryotes (such as fungi and invertebrates) be ascribed to soil acidity? We sought to test for relationships between the numerical abundances of bacteria, microfungi, nematodes and arthropods along a pH gradient. Location 284 agro‐ecosystems on Pleistocene sand across the Netherlands. Methods Generalized Linear Models (GLM) and stepwise regressions were applied, using soil‐ and leaf‐litter organisms sampled from a land‐cover network. Results The major variation in the numerical abundance of the organisms belonging to the investigated taxocenes could be ascribed to soil acidity. Contrary to expectations, the effects of temperature on numerical abundance were significant only for Fungi and Nematoda (P < 0.0001). Geographical co‐ordinates always play a minor role. The often‐suggested close correlation between the numerical abundance of eukaryotes and their local taxonomic diversity applied only to Arthropoda and Fungi (P < 0.00001). Only the number of bacterial DNA bands seemed to reflect the taxa–area relationship (F‐value = 22.45, P < 0.0001). Main conclusions There were strong relationships between the numerical abundances of all the investigated taxocenes and the field‐measured soil acidity (P < 0.0001). The largest effects were detected in the Fungi, which tended to be much more acid‐tolerant than Bacteria. These patterns imply ecological shifts in the detrital soil food web and deserve further investigation.     

Climatic and biotic extreme events moderate long‐term responses of above‐ and belowground sub‐Arctic heathland communities to climate change

Climate change impacts are not uniform across the Arctic region because interacting factors causes large variations in local ecosystem change. Extreme climatic events and population cycles of herbivores occur simultaneously against a background of gradual climate warming trends and can redirect ecosystem change along routes that are difficult to predict. Here, we present the results from sub‐Arctic heath vegetation and its belowground micro‐arthropod community in response to the two main drivers of vegetation damage in this region: extreme winter warming events and subsequent outbreaks of the defoliating autumnal moth caterpillar (Epirrita autumnata). Evergreen dwarf shrub biomass decreased (30%) following extreme winter warming events and again by moth caterpillar grazing. Deciduous shrubs that were previously exposed to an extreme winter warming event were not affected by the moth caterpillar grazing, while those that were not exposed to warming events (control plots) showed reduced (23%) biomass from grazing. Cryptogam cover increased irrespective of grazing or winter warming events. Micro‐arthropods declined (46%) following winter warming but did not respond to changes in plant community. Extreme winter warming and caterpillar grazing suppressed the CO₂ fluxes of the ecosystem. Evergreen dwarf shrubs are disadvantaged in a future sub‐Arctic with more stochastic climatic and biotic events. Given that summer warming may further benefit deciduous over evergreen shrubs, event and trend climate change may both act against evergreen shrubs and the ecosystem functions they provide. This is of particular concern given that Arctic heath vegetation is typically dominated by evergreen shrubs. Other components of the vegetation showed variable responses to abiotic and biotic events, and their interaction indicates that sub‐Arctic vegetation response to multiple pressures is not easy to predict from single‐factor responses. Therefore, while biotic and climatic events may have clear impacts, more work is needed to understand their net effect on Arctic ecosystems.     

高寒草甸生态系统蚁丘对小型土壤节肢动物群落的影响

为查明高寒草甸中蚁丘对小型土壤节肢动物群落的影响,2018年5、7和10月分别在若尔盖高寒草甸内选取6个直径在30-35 cm间的蚁丘作为调查对象,并选取距相应蚁丘2 m处的点作为对照,采集蚁丘和对照的土壤样品,用Tullgren法分离小型土壤节肢动物。结果表明：（1）蚁丘可以明显改变高寒草甸小型土壤节肢动物群落组成结构,主要类群由螨类转变为跳虫;（2）蚁丘中的长角跳目、前气门亚目和甲螨亚目的个体密度均显著高于对照（P<0.05）,但仅有甲螨亚目个体百分比在群落中所占比例显著高于对照（P<0.05）;（3）蚁丘可以显著提高小型土壤节肢动物群落密度和多样性,尤其能够使部分菌食性跳虫（库跳属、隐跳属、符跳属）和腐食性螨类（布伦螨属、双瘤吸螨属、微奥甲螨属及下盾甲螨属）的个体数量大幅增加;（4）从5月到10月,小型土壤节肢动物群落的个体密度在蚁丘中呈先增加后下降的变化趋势（P<0.05）,在对照中呈持续增加（P>0.05）,而类群数和Shannon多样性指数在蚁丘和对照中均呈增加趋势,但仅在对照有显著差异（P<0.05）;（5）小型土壤节肢动物的类群数、Shannon多样性指数与有机质含量呈显著正相关（P<0.05）,个体密度与土壤容重呈显著负相关（P<0.05）。研究结果表明,蚁丘能够改变小型土壤节肢动物群落组成结构,并显著提高小型土壤节肢动物群落个体密度和多样性。     

Large-scale spatial patterns in the distribution of Collembola (Hexapoda) species in Antarctic terrestrial ecosystems

Aim  We tested whether the distribution of three common springtail species ( Gressittacantha terranova , Gomphiocephalus hodgsoni and Friesea grisea ) in Victoria Land (Antarctica) could be modelled as a function of latitude, longitude, altitude and distance from the sea.
Location  Victoria Land, Ross Dependency, Antarctica.
Methods  Generalized linear models were constructed using species presence/absence data relative to geographical features (latitude, longitude, altitude, distance from sea) across the species' entire ranges. Model results were then integrated with the known phylogeography of each species and hypotheses were generated on the role of climate as a major driver of Antarctic springtail distribution.
Results  Based on model selection using Akaike's information criterion, the species' distributions were: hump-shaped relative to longitude and monotonic with altitude for Gressittacantha terranova ; hump-shaped relative to latitude and monotonic with altitude for Gomphiocephalus hodgsoni ; and hump-shaped relative to longitude and monotonic with latitude, altitude and distance from the sea for Friesea grisea .
Main conclusions  No single distributional pattern was shared by the three species. While distributions were partially a response to climatic spatial clines, the patterns observed strongly suggest that past geological events have influenced the observed distributions. Accordingly, present-day spatial patterns are likely to have arisen from the interaction of historical and environmental drivers. Future studies will need to integrate a range of spatial and temporal scales to further quantify their respective roles.     

A new species and a newly recorded species of Paronellinae (Collembola: Paronellidae) from China

记述采自中国海南的弹尾纲爪(虫兆)亚科1新种:海南丽(虫兆)Callyntrura hainanensis sp.nov.和1新记录种:冲绳盐虫兆Salina okinawana Yoshii,1983,该新种与广东丽(虫兆)C.guangdongensis Ma,2012在体色等方面相似,但是在毛序上存在很大的不同。文中还对冲绳盐(虫兆)的一些特征做了补充描记。     

Metal accumulation strategies in saprophagous and phytophagous soil invertebrates: a quantitative comparison

To quantitatively reveal accumulation patterns of environmentally relevant heavy metals in selected saprophagous or phytophagous soil invertebrates, adults of the species Porcellio scaber (Isopoda), Tetrodontophora bielanensis (Collembola), Julus scandinavius (Diplopoda), and Deroceras reticulatum (Gastropoda) were exposed to lead-, cadmium-, or zinc-contaminated food and soil for three weeks. The heavy metal concentrations in the food, the substrate, and the bodies of the invertebrates were measured by atomic absorption spectrophotometry (AAS). The investigated species were found to differ in their metal accumulation strategies, which is interpreted as a consequence of different detoxification mechanisms.     

The effects of drought upon epigeal Collembola from arable soils

1 Springtails (Hexapoda, Collembola) are usually associated with moist microhabitats. However, some species show adaptations to ecosystems subjected to periodic desiccation. This study examined the effects of short-term drought conditions upon epigeal Collembola collected from arable fields. 2 An emergence trap was used in the laboratory to investigate collembolan activity, particularly the emergence of newly hatched juveniles from soils subjected to a simulated drought and to varied levels of simulated rainfall. 3 Addition of water to soils subjected to a 4-month simulated drought resulted in synchronized emergence of juveniles of Sminthurinus elegans, Sminthurus viridis and Bourletiella hortensis. As anhydrobiotic nymphs were not found in the soil, these juveniles are likely to have recently hatched from eggs in the soil. 4 The same species were shown to emerge when desiccated soil samples were treated with simulated heavy rainfall. No emergence occurred in soils which received no water, whilst only a few juveniles were present under a regime of the lowest monthly rainfall recorded for the area in the spring. 5 This study provides the first evidence that in northern European arable systems some epigeal Collembola can survive considerable periods of drought as eggs, emergence of which is triggered by rainfall. These findings have implications for the effects of predicted climatic changes upon collembolan populations, the recovery of collembolan communities following pesticide applications in agroecosystems, and also provide a plausible mechanism for dispersal of Collembola as wind-blown eggs.