内蒙古乌兰布和沙漠样中磷形态分析及生物可获磷研究

采用6步连续提取法对采集于乌兰布和沙漠磴口段沙样中磷的各种存在形态进行了分析测定,并对沙样进行了分级形态研究及生物可利用磷的估算。结果表明:在所取沙样中总磷(∑Pi)平均含量为251.32μg·g-1,其主要成分为无机磷(IP),占∑Pi含量的96.2%;有机磷(Or-P)占∑Pi的3.8%。在所有不同粒径沙样中,钙结合态磷(Ca-P)含量最高,平均为233.72μg.g-1,占∑Pi的93.0%;其他各形态磷含量的高低顺序依次为:有机磷(Or-P)、铁结合态磷(Fe-P)、弱吸附态磷(Ads-P)、铝结合态磷(Al-P)、闭蓄态磷(Obs-P)。在所取沙漠颗粒物样中,∑Pi、Ca-P、Fe-P含量均随沙样粒径的减小而增大,其中∑Pi、Ca-P的变化幅度较大,而Fe-P的变化幅度较小;Or-P含量随粒径的减小而降低;Ads-P、Obs-P、Al-P含量随粒径变化的规律性不强。所取沙样中潜在的生物可获得磷的量约占总磷的6.6%。

土壤中持久性有机污染物生物有效性研究

土壤是环境中持久性有机污染物(persistent organic pollutants,POPs)的汇,大部分POPs(如PAHs、PCBs和PBDEs等)具有持久性,在土壤中广泛分布,并可通过食物链蓄积,对人体和生态环境造成不利影响。当量化POPs暴露进行人体健康风险评估时,通常假设土壤中的POPs是100%生物有效的,即可全部被吸收到人体循环中。然而,这种假设可能会高估暴露剂量,从而影响风险评估的准确性。近20年来,研究人员开发了一些用于测定土壤中POPs生物有效性的体内和体外方法。对目前测定土壤POPs生物有效性的动物实验(体内方法)、测定生物可获得性的仿生学提取实验(体外方法),以及POPs生物有效性研究的挑战与发展进行了综述。

Improved Model for Semideciduous Seasonal ForestProduction of Leaves and Deciduousness

The climate,mainly the water availability and temperature,drives the renewal of biomass inseasonal forest ecosystem,and the greenness and leaf area of its canopy are responsive climate variations.This study verified models to explain the phenomenon of leaf production and deciduousness by time,with LAI（Leaf Area Index）,NDVI（Normalized Difference VegetationIndex）and climate variables,on period 2011-2016. The data were obtained in satellite images and in plots installed at forestmonitoring sites,visited monthly.The analysis incorporated the water balance.Three equations were compared,two alreadypublished and the equation that was adjusted in this work.The model was improved and validated with new variables and data.It is possible to estimate the fall and renew of leaves biomass in semideciduous forests with reasonable precision.

Opposed elevational variation in prevalence and intensity of endoparasites and their vectors in a lizard

Studying the causes of parasite geographic distribution is relevant to understand ecological and evolutionary processes that affect host populations as well as for species conservation. Temperature is one of the most important environmental variables affecting parasite distribution, as raising temperatures positively affect development, reproduction, and rate of transmission of both endo- and ectoparasites. In this context, it is generally accepted that, in mountains, parasite abundance decreases with elevation. However, empirical evidence on this topic is limited. In the present study, we analyzed the elevational variation of hemoparasites and ectoparasites of a lizard, Psammodromus algirus, along a 2,200-m elevational gradient in Sierra Nevada （SE Spain）. As pre- dicted, ectoparasite （mites, ticks, mosquitoes, and sandflies） abundance decreased with elevation. However, hemoparasite prevalence and intensity in the lizard augmented with altitude, showing a pattern contrary to their vectors （mites）. We suggest that tolerance to hemoparasites may increase with elevation as a consequence of lizards at high altitudes taking advantage of increased body condition and food availability, and reduced oxidative stress. Moreover, lizards could have been selected for higher resistance against hemoparasites at lowlands （where higher rates of replication are expected）, thus reducing hemoparasite prevalence and load. Our findings imply that, in a scen- ario of climate warming, populations of lizards at high elevation may face increased abundance of ectoparasites, accompanied with strong negative effects.

Changes in feeding selectivity of freshwater invertebrates across a natural thermal gradient

Environmental warming places physiological constraints on organisms, which may be mitigated by their feeding behavior. Theory predicts that consumers should increase their feeding selectivity for more energetically valuable resources in warmer environments to offset the disproportionate increase in metabolic demand relative to ingestion rate. This may also result in a change in feeding strategy or a shift towards a more specialist diet. This study used a natural warming experiment to investigate temperature effects on the feeding selectivity of three freshwater invertebrate grazers： the snail Radix balthica, the blackfly larva Simulium aureum, and the midgefly larva Eukiefferiella minor. Chesson＇s Selectivity Index was used to compare the proportional abundance of diatom species in the guts of each invertebrate species with corresponding rock biofilms sampled from streams of different tem- perature. The snails became more selective in warmer streams, choosing high profile epilithic diatoms over other guilds and feeding on a lower diversity of diatom species. The blackfly larvae appeared to switch from active collector gathering of sessile high profile diatoms to more passive filter feeding of motile diatoms in warmer streams. No changes in selectivity were observed for the midgefly larvae, whose diet was representative of resource availability in the environment. These results suggest that key primary consumers in freshwater streams, which constitute a major portion of invertebrate biomass, can change their feeding behavior in warmer waters in a range of different ways. These patterns could potentially lead to fundamental changes in the flow of energy through freshwater food webs.