THE EFFECTS OF PHYSICAL DISTURBANCE ONAFROPTILUM SUDAFRICANUM(EPHEMEROPTERA: BAETIDAE) POPULATION DENSITIES IN A KENYAN MOUNTAIN STREAM

Beaver dam analogues (BDAs) are becoming an increasingly popular stream restoration technique. One ecological function BDAs might help restore is suitable habitat conditions for fish in streams where loss of beaver dams and channel incision has led to their decline. A critical physical characteristic for fish is stream temperature. We examined the thermal regime of a spring-fed Canadian Rocky Mountain stream in relation to different numbers of BDAs installed in series over three study periods (April–October; 2017–2019). While all BDA configurations significantly influenced stream and pond temperatures, single- and double-configuration BDAs incrementally increased stream temperatures. Single and double configuration BDAs warmed the downstream waters of mean maxima of 9.9, 9.3 °C by respective mean maxima of 0.9 and 1.0 °C. Higher pond and stream temperatures occurred when ponding and discharge decreased, and vice versa. In 2019, variation in stream temperature below double-configuration BDAs was lower than the single-configuration BDA. The triple-configuration BDA, in contrast, cooled the stream, although the mean maximum stream temperature was the highest below these structures. Ponding upstream of BDAs increased discharge and resulted in cooling of the stream. Rainfall events sharply and transiently reduced stream temperatures, leading to a three-way interaction between BDA configuration, rainfall and stream discharge as factors co-influencing the stream temperature regime. Our results have implications for optimal growth of regionally important and threatened bull and cutthroat trout fish species.

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Landscape heterogeneity buffers biodiversity of simulated meta-food-webs under global change through rescue and drainage effects

Nature Communications ◽

10.1038/s41467-021-24877-0 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Remo Ryser ◽

Myriam R. Hirt ◽

Johanna Häussler ◽

Dominique Gravel ◽

Ulrich Brose

Keyword(s):

Habitat Fragmentation ◽

Food Web ◽

Food Webs ◽

Landscape Heterogeneity ◽

Landscape Connectivity ◽

Biodiversity Loss ◽

Mechanistic Explanation ◽

Population Densities ◽

Rescue Effect ◽

Drainage Effect

AbstractHabitat fragmentation and eutrophication have strong impacts on biodiversity. Metacommunity research demonstrated that reduction in landscape connectivity may cause biodiversity loss in fragmented landscapes. Food-web research addressed how eutrophication can cause local biodiversity declines. However, there is very limited understanding of their cumulative impacts as they could amplify or cancel each other. Our simulations of meta-food-webs show that dispersal and trophic processes interact through two complementary mechanisms. First, the ‘rescue effect’ maintains local biodiversity by rapid recolonization after a local crash in population densities. Second, the ‘drainage effect’ stabilizes biodiversity by preventing overshooting of population densities on eutrophic patches. In complex food webs on large spatial networks of habitat patches, these effects yield systematically higher biodiversity in heterogeneous than in homogeneous landscapes. Our meta-food-web approach reveals a strong interaction between habitat fragmentation and eutrophication and provides a mechanistic explanation of how landscape heterogeneity promotes biodiversity.

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The role of bacterial urease activity on the uniformity of carbonate precipitation profiles of bio-treated coarse sand specimens

Scientific Reports ◽

10.1038/s41598-021-85712-6 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Charalampos Konstantinou ◽

Yuze Wang ◽

Giovanna Biscontin ◽

Kenichi Soga

Keyword(s):

Calcium Carbonate ◽

Calcium Chloride ◽

Urease Activity ◽

Coarse Sand ◽

Carbonate Precipitation ◽

Population Densities ◽

Carbonate Cements ◽

Microbially Induced Carbonate Precipitation

AbstractProtocols for microbially induced carbonate precipitation (MICP) have been extensively studied in the literature to optimise the process with regard to the amount of injected chemicals, the ratio of urea to calcium chloride, the method of injection and injection intervals, and the population of the bacteria, usually using fine- to medium-grained poorly graded sands. This study assesses the effect of varying urease activities, which have not been studied systematically, and population densities of the bacteria on the uniformity of cementation in very coarse sands (considered poor candidates for treatment). A procedure for producing bacteria with the desired urease activities was developed and qPCR tests were conducted to measure the counts of the RNA of the Ure-C genes. Sand biocementaton experiments followed, showing that slower rates of MICP reactions promote more effective and uniform cementation. Lowering urease activity, in particular, results in progressively more uniformly cemented samples and it is proven to be effective enough when its value is less than 10 mmol/L/h. The work presented highlights the importance of urease activity in controlling the quality and quantity of calcium carbonate cements.

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Nitrogen supply and physical disturbance shapes Arctic stream nitrogen uptake through effects on metabolic activity

Freshwater Biology ◽

10.1111/fwb.13734 ◽

2021 ◽

Author(s):

Maria Myrstener ◽

Steven A. Thomas ◽

Reiner Giesler ◽

Ryan A. Sponseller

Keyword(s):

Metabolic Activity ◽

Nitrogen Uptake ◽

Nitrogen Supply ◽

Physical Disturbance

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Ostrich population densities and temporal dynamics in coupled social-ecological systems: Suitable indicators for the ecological effectiveness of protected areas?

Ecological Indicators ◽

10.1016/j.ecolind.2021.107348 ◽

2021 ◽

Vol 125 ◽

pp. 107348

Author(s):

Alisha N. Griffin ◽

John Kioko ◽

Ole Theisinger ◽

Christian Kiffner

Keyword(s):

Protected Areas ◽

Temporal Dynamics ◽

Ecological Systems ◽

Population Densities ◽

Social Ecological Systems ◽

Social Ecological

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Intercropping Rosemary (Rosmarinus officinalis) with Sweet Pepper (Capsicum annum) Reduces Major Pest Population Densities without Impacting Natural Enemy Populations

Insects ◽

10.3390/insects12010074 ◽

2021 ◽

Vol 12 (1) ◽

pp. 74

Author(s):

Xiao-wei Li ◽

Xin-xin Lu ◽

Zhi-jun Zhang ◽

Jun Huang ◽

Jin-ming Zhang ◽

...

Keyword(s):

Integrated Pest Management ◽

Pest Management ◽

Pest Control ◽

Natural Enemies ◽

Natural Enemy ◽

Sweet Pepper ◽

Population Densities ◽

Pest Population ◽

Major Pest ◽

Population Suppression

Intercropping of aromatic plants provides an environmentally benign route to reducing pest damage in agroecosystems. However, the effect of intercropping on natural enemies, another element which may be vital to the success of an integrated pest management approach, varies in different intercropping systems. Rosemary, Rosmarinus officinalis L. (Lamiaceae), has been reported to be repellent to many insect species. In this study, the impact of sweet pepper/rosemary intercropping on pest population suppression was evaluated under greenhouse conditions and the effect of rosemary intercropping on natural enemy population dynamics was investigated. The results showed that intercropping rosemary with sweet pepper significantly reduced the population densities of three major pest species on sweet pepper, Frankliniella intonsa, Myzus persicae, and Bemisia tabaci, but did not affect the population densities of their natural enemies, the predatory bug, Orius sauteri, or parasitoid, Encarsia formosa. Significant pest population suppression with no adverse effect on released natural enemy populations in the sweet pepper/rosemary intercropping system suggests this could be an approach for integrated pest management of greenhouse-cultivated sweet pepper. Our results highlight the potential of the integration of alternative pest control strategies to optimize sustainable pest control.

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Surveying Potential Vectors of Apple Proliferation Phytoplasma: Faunistic Analysis and Infection Status of Selected Auchenorrhyncha Species

Insects ◽

10.3390/insects12010012 ◽

2020 ◽

Vol 12 (1) ◽

pp. 12

Author(s):

Stefanie Fischnaller ◽

Martin Parth ◽

Manuel Messner ◽

Robert Stocker ◽

Christine Kerschbamer ◽

...

Keyword(s):

New Records ◽

Regional Scale ◽

Insect Vectors ◽

Infection Status ◽

Apple Proliferation ◽

Population Densities ◽

South Tyrol ◽

Candidatus Phytoplasma Mali ◽

Cacopsylla Melanoneura

Apple proliferation (AP) is one of the economically most important diseases in European apple cultivation. The disease is caused by the cell-wall-less bacterium ’ Candidatus Phytoplasma mali’, which is transmitted by Cacopsylla picta (Foerster) and Cacopsylla melanoneura (Foerster) (Hemiptera: Psylloidea). In South Tyrol (Italy), severe outbreaks were documented since the 1990s. Infestation rates of AP do not always correlate with the population densities of the confirmed vectors, implying the presence of other, so far unknown, hemipterian vectors. By elucidating the species community of Auchenorrhyncha (Insecta: Hemiptera) at a regional scale, more than 31,000 specimens were captured in South Tyrolean apple orchards. The occurrence of 95 species was confirmed, whereas fourteen species are new records for this territory. Based on the faunistical data, more than 3600 individuals out of 25 species were analyzed using quantitative PCR to assess the presence of AP phytoplasma. The pathogen was sporadically detected in some individuals of different species, for example in Stictocephala bisonia Kopp and Yonk (Hemiptera: Membracidae). However, the concentration of phytoplasma was much lower than in infected C. picta and C. melanoneura captured in the same region, confirming the role of the latter mentioned psyllids as the main insect vectors of AP- phytoplasma in South Tyrol.

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