Determination of species-area relationships and minimum sampling area for the shrub communities in the arid valley in the upper reach of the Minjiang River, China

The minimum sampling areas (MSAs) for the shrub communities in the arid valley in the upper reach of the Minjiang River, China, were studied by fitting community species-area relationships using 3 types of equations. The MSAs were determined at the proportional factor (ρ) 0.6, 0.7, 0.8 and 0.9. The proportional factors represent the proportion of the number of species within a sampling plot in the total number of species. The MSAs of the shrub communities at different elevations and on different slope faces for ρ = 0.6, 0.7 and 0.8 were all around 100 m². Hence, the MSAs could be set to be 100 m² (10 m × 10 m) at 60%–80% precision levels. For ρ = 0.9, that is, for a 90% precision level, the MSAs were less than 200 m² (10 m × 20 m). The MSAs and species richness increased gradually with the rising elevation. At the elevation below 2000 m, the MSAs and species richness on the north-facing slope were larger than those on the south-facing slope. However, at the elevation around 2200 m, there was no difference amongst different facing slopes. For the shrub communities in the arid valley in the upper reach of the Minjiang River, the species-area curves by fitting the first two equations are better than that by fitting the third equation.     

Habitat quality and drought effects on breeding mallard and other waterfowl populations in California,USA

As many as 500,000 waterfowl reside in California, USA, during summer, but little is known about the availability or quality of their habitats. Wetland size and distribution serve as proximate cues for habitat selection by breeding waterfowl in other parts of North America such as the Prairie Pothole Region. In heavily modified landscapes such as California's Central Valley, disturbance from factors like crop cultivation and urban development may limit access, affect survival, and decrease reproductive success. Water limitations due to recurring seasonal droughts pose another potential threat to breeding waterfowl. Spatial and temporal disparities in environmental resources may provide clearer indications of ultimate habitat selection. We addressed waterfowl habitat selection in 9 regions surveyed annually by California's Department of Fish and Wildlife to determine relative importance of drought severity, wetland area, and habitat quality on mallard (Anas platyrhynchos) and other waterfowl population dynamics from 2007–2019. High-quality habitat supports long-term population persistence of waterfowl. This study period included an extended drought (2012–2015) and flooding (2016–2017). Statewide, habitat quality was the best predictor of mallard and other waterfowl population fluctuations. The model that included intermediate habitat quality, which accounted for influence of adjacent land-use, outperformed models that included wetland area alone. At the regional level, drought severity out-ranked other variables in most regions, suggesting management at regional scales must account for climate. Drought accounted for bird declines in some regions and possible increases in others. This information could be used to identify areas for conservation priority based on projected drought frequency and severity.     

湿热河谷芭蕉群落优势物种空间分布格局与竞争对称性研究

竞争关系的对称性是塑造植物物种空间分布格局和影响物种共存重要机制之一,对其开展研究不仅对于揭示植物群落构建机制具有重要意义,也有助于解析群落演替的驱动力。在贵州赤水湿热河谷内的芭蕉群落中建设固定样地,对1989棵植物个体进行空间定位和物种识别并记录胸径等个体属性。采用对数相关函数和标记变异系数分析（marked variogram）等空间统计方法检测优势种的空间分布格局和竞争对称性,结果如下：（1）芭蕉（Musa sp.）,粗糠柴（M.philippensis）,粗叶木（L.chinensis）,川钓樟（L.pulcherrima）,红果黄肉楠（A.cupularis）等5种优势种均表现为小尺度下的种内聚集分布,其中芭蕉主要采用克隆繁殖,其重要值达33.6%,且种内聚集度最大。（2）芭蕉种群在5 m尺度下呈现出显著的种内对称性竞争,这一竞争过程减少了种群自疏作用并推动种内聚集分布格局的形成,增加了该种群在森林中的生存力。（3）芭蕉与其余4种优势种之间的不对称竞争过程导致了种间负关联。结果表明,不同优势种在种间竞争对称性上的差异说明了植物种群繁殖和扩散方式是群落构建的重要影响因素之一,相比于有性繁殖过程,采用无性克隆繁殖的植物个体可通过种内对称竞争机制来减少自疏以增加种群生存力,并通过与相邻异种个体的不对称竞争过程来提升种群获取有限资源的能力,进而成为演替中的优势个体。研究结果可为今后制定植物物种多样性保护政策提供科学参考。     

岷江干旱河谷优势灌丛对土壤微生物群落组成的影响

通过调查岷江干旱河谷两河口、飞虹、撮箕和牟托4个样地优势灌丛及其灌丛间空地的表土土壤物理化学性质和微生物群落组成,探讨植物灌丛群落对土壤微生物群落组成的影响。研究发现不同灌丛种类对土壤微生物群落组成以及土壤物理化学性质并没有显著影响,而同一样地灌丛与空地间的差异却较为显著。灌丛下比空地土壤中具有更高的有机质、养分含量,更高的土壤含水量和更低的容重,而灌丛下相对富集的养分资源是造成灌丛与空地间微生物群落组成差异的主要原因。不同样地影响微生物群落的主要因子存在一定差异,但与氮相关的因子(总氮、有效氮、碳/氮比)对土壤微生物群落着非常重要的影响,特别是对土壤微生物群落总生物量和细菌类群(革兰氏阳性菌、革兰氏阴性菌、细菌等)。虽然不同灌丛和空地下土壤中细菌群落都没有显著地变化,但真菌和菌根真菌却明显的在灌丛下富集。在飞虹和牟托样地,总磷和碳/磷比与真菌类群,主要指真菌和菌根真菌,表现出显著正相关性,这或许反映了真菌类群对于该区域磷循环的重要作用。研究结果揭示了灌丛植被在干旱河谷地区地下生态系统中的重要作用,以及氮、磷这两种养分元素对土壤微生物群落的重要影响。同时,未来对于干旱河谷地区植物-土壤关系的研究应该关注真菌和菌根真菌类群的作用。     

澜沧江流域北部中华蜜蜂有毒蜂蜜孢粉学和营养生态位分析

为分析澜沧江流域北部人食用蜂蜜中毒的原因,于2013年6—9月份,对该区域蜜蜂和蜜源植物的分布情况进行了调查,观察蜜蜂采集有毒蜜源植物的行为,并进一步调查了蜜蜂巢内蜂蜜、蜂花粉的储存情况,采集了中华蜜蜂蜂蜜样品,进行蜂蜜孢粉学与营养生态位分析。该区域有大量采用传统方式进行人工饲养的中华蜜蜂(Apis cerana cerana),及少量野生中华蜜蜂、黑色小蜜蜂(Apis audreniformis)、黑色大蜜蜂(Apis laboriosa smith)群体分布;人工饲养的中华蜜蜂蜂巢内部结构与野生中华蜜蜂蜂巢相似,为自然蜂巢,内有充足的蜜粉储存,部分蜂群蜂巢内虫害严重。该区域内主要蜜源植物为荞麦(Fagopyrum esculentum Moench),其他零星辅助蜜源较多,部分地点南烛(Vaccinium bracteatum Thunb)、昆明山海棠(Tripterygium hypoglaucum(Levl.)Hutch)连片集中分布。对中华蜜蜂蜂蜜进行孢粉学和营养生态位分析,结果表明:中华蜜蜂蜂蜜标本中含有有毒蜜源植物南烛、昆明山海棠花粉,部分样品中南烛、昆明山海棠的花粉含所占比例较高;中华蜜蜂的营养生态位宽度为0.22,比其他地区中华蜜蜂生态位指数小,推测澜沧江水电枢纽的修建等人为原因已对蜜蜂种类、蜜源植物的物种组成、群落结构造成了较大影响。     

Hydrological responses of a valley‐bottom wetland to land‐use/land‐cover change in a South African catchment: making a case for wetland restoration

Valley‐bottom wetlands are valuable assets as they provide many ecosystem services to mankind. Despite their value, valley‐bottom wetlands are often exploited and land‐use/land‐cover (LULC) change results in trade‐offs in ecosystem services. We coupled physically based hydrological modeling and spatial analysis to examine the effects of LULC change on water‐related ecosystem services in the Kromme catchment: an important water‐providing catchment for the city of Port Elizabeth. LULC scenarios were constructed to match 5 different decades in the last 50 years to explore the potential effects of restoring the catchment to different historic benchmarks. In the Kromme catchment, valley‐bottom wetlands have declined by 84%, driven by key LULC changes: an increase in irrigated land (307 ha) and invasion by alien trees (336 ha). If the wetlands were restored to the relatively pristine extent and condition of the 1950s, riverflow could increase by approximately 1.13 million m³/a, about 6% of the current supply to Port Elizabeth. Wetland restoration would also significantly improve the catchment's ability to absorb extreme rainfall events, decreasing flood damage. We conclude that in the face of the water scarcity in this region, all ecosystem services, particularly those related to water flow regulation, should be taken into account by decision makers in charge of land zonation. Zonation decisions should not continue to be made on the basis of provisioning ecosystem services alone (i.e. food provision or dam yield). We recommend prioritization of the preservation and restoration of valley‐bottom wetlands providing water‐related ecosystem services to settlements downstream.     

A distinctive new subspecies of Scytalopus griseicollis (Aves,Passeriformes, Rhinocryptidae) from the northern Eastern Cordillera of Colombia and Venezuela

We describe a new subspecies of Pale-bellied Tapaculo Scytalopus griseicollis from the northern Eastern Cordillera of Colombia and Venezuela. This form differs diagnosably in plumage from described subspecies Scytalopus griseicollis griseicollis and Scytalopus griseicollis gilesi and from the latter in tail length. It is also differentiated non-diagnosably in voice from both these populations. Ecological niche modelling analysis suggests that the new subspecies is restricted to the Andean montane forest and páramo north of both the arid Chicamocha valley and the Sierra Nevada del Cocuy.     

Centipede (Chilopoda) richness and diversity in the Bug River valley (Eastern Poland)

The main aim of the survey was to describe the diversity and richness of Chilopoda in the selected area of the Bug River valley. The study sites were located in two regions differing in the shape of the valley, the presence of thermophilous habitats and the size of riparian forests. Pitfall traps were used as a sampling method. As a result, 444 specimens belonging to 12 centipede species of two orders – Geophilomorpha (four species) and Lithobiomorpha (eight species) were caught. Lithobius (Monotarsobius) curtipes C.L.Koch, 1847, Pachymerium ferrugineum (C.L.Koch, 1835), Lamyctes (Lamyctes) emarginatus (Newport, 1844) and Lithobius (Monotarsobius) dudichi Loksa, 1947 were the most common and the most numerous species. Of particular note is Lithobius dudichi found in Poland for the first time and previously known based on a single specimen. Two to 10 Chilopoda species were found in each habitat under investigation. The greatest species richness was found in thermophilous thickets (10 species), sandy grasslands (eight), xerothermic grasslands (eight) and mesic meadows (six). The fewest number of species (two) was found in rushes at oxbows and in wet meadows. We found differences in the species composition and the number of Chilopoda between the lower (102 specimens, six species) and the middle (324 specimens, 11 species) section of the river valley. Our results confirm the need to protect xerothermic habitats, unique almost throughout entire Central Europe, which due to their distribution and their small area covered are fairly easily subject to the process of destruction.     

Plant community complexity in the arid valley of Minjiang River, southwestern China

Biocomplexity theory is becoming increasingly important in understanding natural vegetation dynamics and interrelation among all components of the ecosystem. In this study, based on the field investigation of plant species and environmental factors (altitude, microtopography, soil water content, and soil nutrients) in an arid valley of the upper reaches of Minjiang River, Sichuan Province, southwestern China, plant community complexity and its relationship with environmental factors, community diversity, species evenness and richness were studied. Both total and structural complexities of the communities showed a “high- low-high” tendency with the increase in altitude of the area, which meant that the complexity of communities was the highest at the sites of low and high altitude, whereas it was the lowest at the sites of intermediate altitude. It was found that the total community complexity had significant quadratic correlations with soil organic matter (SOM) content, total nitrogen (N), hydrolyzable N, soil water content, and available potassium (K), whereas it had no significant correlations with soil total K, total phosphorus (P), available P, and pH value. The total community complexity positively correlated with community diversity, species evenness and species richness, whereas the structural complexity negatively correlated with the community evenness. Of the two components of the total community complexity, namely, the structural complexity and the structural diversity, the structural complexity was more sensitive than the structural diversity to the changes of species in the community, which was not only related to the community evenness but also to the community richness. The relative contribution of both the structural complexity and the structural diversity to the total complexity would be different for different study areas or ecosystems.     

Trypanosoma cruzi (Kinetoplastida Trypanosomatidae): ecology of the transmission cycle in the wild environment of the Andean valley of Cochabamba, Bolivia

An active Trypanosoma cruzi transmission cycle maintained by wild rodents in the Andean valleys of Cochabamba Bolivia is described. Wild and domestic Triatoma infestans with 60% infection with T. cruzi were found and was evidenced in 47.5% (rodents) and 26.7% (marsupial) by parasitological and/or serologycal methods. Phyllotis ocilae and the marsupial species Thylamys elegans, are the most important reservoirs followed by Bolomys lactens and Akodon boliviensis. In spite of both genotypes (TCI and TCII) being prevalent in Bolivia, in our study area only T. cruzi I is being transmitted. Our data suggest that wild T. infestans and wild small mammals play an important role in the maintenance of the transmission cycle of T. cruzi. Furthermore, the finding of high prevalence of T. cruzi infection in wild T. infestans point to the risk of the dispersion of Chagas' disease.