scholarly journals Patterns of shrub abundance and relationships with other plant types within the forest–tundra ecotone in northern Canada

2018 ◽  
Vol 4 (4) ◽  
pp. 691-709 ◽  
Author(s):  
Karen A. Harper ◽  
Amanda A. Lavallee ◽  
Pavel Dodonov
Keyword(s):  
Wavelet Analysis ◽  
Spatial Pattern ◽  
Soil Ph ◽  
Environmental Variables ◽  
Generalized Least Squares ◽  
Tree Cover ◽  
Cascading Effects ◽  
Forest Tundra ◽  
Plant Groups ◽  
Tall Shrub

Throughout the forest–tundra ecotone where trees and tall shrubs are becoming more abundant, knowledge of associations between shrubs and surrounding vegetation could inform predictions of their changing relationships. We assessed shrubs in 1 m × 1 m contiguous quadrats along two ∼450 m transects across tundra and ecotone landscapes near Churchill, Canada to determine patterns in relation to lakeshore edges, soil pH, microtopography, and other plant groups. We used wavelet analysis to assess patterns and generalized least squares for relationships with environmental variables. Shrubs were taller and more diverse at edges, particularly in tundra. The ecotone was more complex than tundra with greater variation in tall shrub and tree cover, shrub height, and microtopography. Shrub richness was positively correlated with microtopography but exhibited no relationship with pH. Bivariate relationships of shrubs with other plant groups varied for different scales. In tundra, shrub richness was negatively correlated with graminoids, forbs, and moss, but positively correlated with lichens within 1 m; opposite relationships were found at 4–60 m scales. Relationships in the ecotone were reversed and more complex at different scales. As trees encroach in the tundra, the spatial pattern of shrubs will become more complex at a variety of scales, likely with cascading effects on other plant types.

scholarly journals Tree spatial pattern within the forest–tundra ecotone: a comparison of sites across CanadaThis article is a contribution to the series Tree recruitment, growth, and distribution at the circumpolar forest–tundra transition.

2011 ◽  
Vol 41 (3) ◽  
pp. 479-489 ◽  
Author(s):  
Karen A. Harper ◽  
Ryan K. Danby ◽  
Danielle L. De Fields ◽  
Keith P. Lewis ◽  
Andrew J. Trant ◽  
...  
Keyword(s):  
Climate Change ◽  
Spatial Pattern ◽  
Patch Size ◽  
Forest Tree ◽  
Tree Cover ◽  
Site Specific ◽  
Forest Tundra ◽  
Local Variance ◽  
Tree Spatial Pattern ◽  
Subarctic Forest

Although many studies have focused on factors influencing treeline advance with climate change, less consideration has been given to potential changes in tree spatial pattern across the forest–tundra ecotone. We investigated trends in spatial pattern across the forest–tundra ecotone and geographical variation in the Yukon, Manitoba, and Labrador, Canada. Tree cover was measured in contiguous quadrats along transects up to 100 m long located in Forest, Ecotone, and Tundra sections across the forest–tundra transition. Spatial patterns were analyzed using new local variance to estimate patch size and wavelet analysis to determine the scale and amount of aggregation. Compared with the Forest, tree cover in the Ecotone was less aggregated at most sites, with fewer smaller patches of trees. We found evidence that shorter trees may be clumped at some sites, perhaps due to shelter from the wind, and we found little support for regular spacing that would indicate competition. With climate change, trees in the Ecotone will likely become more aggregated as patches enlarge and new patches establish. However, results were site-specific, varying with aspect and the presence of krummholz (stunted trees); therefore, strategies for adaptation of communities to climate change in Canada’s subarctic forest would need to reflect these differences.

scholarly journals Environmental variables and Piper assemblage composition: a mesoscale study in the Madeira-Purus interfluve, Central Amazonia

2011 ◽  
Vol 11 (3) ◽  
pp. 83-91 ◽  
Author(s):  
Carolina Bernardes ◽  
Flávia Regina Capellotto Costa
Keyword(s):  
Environmental Variables ◽  
Environmental Variable ◽  
Canopy Openness ◽  
Assemblage Composition ◽  
Cation Content ◽  
Litter Depth ◽  
Plant Assemblage ◽  
Plant Groups ◽  
Central Amazonia ◽  
Floristic Variation

This study aimed to determine the effects of canopy openness, litter depth, soil cation content and texture on Piper assemblage composition at a mesoscale. Piper assemblage composition and environmental variables were inventoried in 41 0.125 ha (250 × 5 m) plots placed in a terra firme forest located in the Madeira-Purus interfluve, Central Amazonia. Ordination of the 41 plots by Non-metric Multidimensional Scaling (NMDS) in one dimension captured 58% of the floristic variation and was used as the response variable in multiple regression models. Environmental variables explained 39% of the variation in Piper assemblage composition, which was significantly related to litter depth, soil texture and canopy openness, but not to the cation content. Effects of edaphic components on plant assemblage structure have been reported for different plant groups, however the strong effect of litter depth at a mesoscale had not yet been demonstrated. We suggest that litter depth variation not only influences the structure of Piper assemblages, but also of other plant groups at a mesoscale, as this environmental variable has a direct or indirect effect on species germination and establishment.

scholarly journals Analysis of juvenile North Atlantic albacore (Thunnus alalunga) catch per unit effort by surface gears in relation to environmental variables

2005 ◽  
Vol 62 (7) ◽  
pp. 1475-1482 ◽  
Author(s):  
Nicolas Goñi ◽  
Haritz Arrizabalaga
Keyword(s):  
North Atlantic ◽  
Environmental Variables ◽  
Negative Relationship ◽  
Generalized Least Squares ◽  
Catch Per Unit Effort ◽  
Seasonal Thermocline ◽  
Unit Effort ◽  
Negative Effect ◽  
Thunnus Alalunga ◽  
Age Structured

Abstract The relationship between the catch per unit effort (cpue) of trolling and baitboat fisheries targeting juvenile North Atlantic albacore (Thunnus alalunga, Bonnaterre, 1788) and several environmental variables was studied. A multiple linear regression and a generalized least squares model (GLS) showed a significant negative relationship between age 2 albacore trolling and baitboat cpue, and the average agitation of the sea and the duration of insolation. No clear relationship was found between the juvenile albacore cpue and sea surface temperature, precipitation, and NAO or Gulf Stream Index. Underlying processes that could explain the negative effect of agitation and insolation are discussed, especially relating to the habitat of age 2 albacore above the seasonal thermocline. Results highlight the necessity of considering environmental variables in the standardization of albacore cpue series used for calibrating age-structured stock assessments.

Grazers, browsers, and fire influence the extent and spatial pattern of tree cover in the Serengeti

2009 ◽  
Vol 19 (1) ◽  
pp. 95-109 ◽  
Author(s):  
Ricardo M. Holdo ◽  
Robert D. Holt ◽  
John M. Fryxell
Keyword(s):  
Spatial Pattern ◽  
Tree Cover

scholarly journals Soil mite communities (Acari: Mesostigmata) as indicators of urban ecosystems in Bucharest, Romania

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
M. Manu ◽  
R. I. Băncilă ◽  
C. C. Bîrsan ◽  
O. Mountford ◽  
M. Onete
Keyword(s):  
Air Temperature ◽  
Soil Ph ◽  
Environmental Variables ◽  
Penetration Resistance ◽  
Soil Core ◽  
Urban Green ◽  
Soil Penetration Resistance ◽  
Green Areas ◽  
Soil Mite ◽  
Mite Communities

AbstractThe aim of the present study was to establish the effect of management type and of environmental variables on the structure, abundance and species richness of soil mites (Acari: Mesostigmata) in twelve urban green areas in Bucharest-Romania. Three categories of ecosystem based upon management type were investigated: protected area, managed (metropolitan, municipal and district parks) and unmanaged urban areas. The environmental variables which were analysed were: soil and air temperature, soil moisture and atmospheric humidity, soil pH and soil penetration resistance. In June 2017, 480 soil samples were taken, using MacFadyen soil core. The same number of measures was made for quantification of environmental variables. Considering these, we observed that soil temperature, air temperature, air humidity and soil penetration resistance differed significantly between all three types of managed urban green area. All investigated environmental variables, especially soil pH, were significantly related to community assemblage. Analysing the entire Mesostigmata community, 68 species were identified, with 790 individuals and 49 immatures. In order to highlight the response of the soil mite communities to the urban conditions, Shannon, dominance, equitability and soil maturity indices were quantified. With one exception (numerical abundance), these indices recorded higher values in unmanaged green areas compared to managed ecosystems. The same trend was observed between different types of managed green areas, with metropolitan parks having a richer acarological fauna than the municipal or district parks.

scholarly journals Floodplains as an Achilles’ heel of Amazonian forest resilience

2017 ◽  
Vol 114 (17) ◽  
pp. 4442-4446 ◽  
Author(s):  
Bernardo M. Flores ◽  
Milena Holmgren ◽  
Chi Xu ◽  
Egbert H. van Nes ◽  
Catarina C. Jakovac ◽  
...  
Keyword(s):  
Forest Structure ◽  
Large Scale ◽  
Amazon Basin ◽  
Climatic Variation ◽  
Tree Cover ◽  
Cascading Effects ◽  
Forest Resilience ◽  
Central Amazonia ◽  
Lowland Forests ◽  
The Impact

The massive forests of central Amazonia are often considered relatively resilient against climatic variation, but this view is challenged by the wildfires invoked by recent droughts. The impact of such fires that spread from pervasive sources of ignition may reveal where forests are less likely to persist in a drier future. Here we combine field observations with remotely sensed information for the whole Amazon to show that the annually inundated lowland forests that run through the heart of the system may be trapped relatively easily into a fire-dominated savanna state. This lower forest resilience on floodplains is suggested by patterns of tree cover distribution across the basin, and supported by our field and remote sensing studies showing that floodplain fires have a stronger and longer-lasting impact on forest structure as well as soil fertility. Although floodplains cover only 14% of the Amazon basin, their fires can have substantial cascading effects because forests and peatlands may release large amounts of carbon, and wildfires can spread to adjacent uplands. Floodplains are thus an Achilles’ heel of the Amazon system when it comes to the risk of large-scale climate-driven transitions.

scholarly journals Oceanic and climatic drivers of mangrove changes in the Gulf of Urabá, Colombian Caribbean

2017 ◽  
Vol 43 (5) ◽  
pp. 972-985
Author(s):  
July A. Suárez ◽  
Ligia E. Urrego ◽  
Andrés Osorio ◽  
Hiara Y. Ruiz
Keyword(s):  
Organic Matter ◽  
Spatial Pattern ◽  
Environmental Variables ◽  
Anthropogenic Disturbance ◽  
Basal Area ◽  
Tree Height ◽  
Avicennia Germinans ◽  
Water Salinity ◽  
Structural Development ◽  
Mangrove Species

The Gulf of Uraba is the largest estuary on the Caribbean coast of Colombia. The aim of this research was to analyse the oceanic, climatic and environmental variables that influence mangrove structure and composition in the gulf. Based on the availability of remote sensing, the study area was divided into western and eastern zones. The spatial pattern of environmental variables (water salinity, pH and percentage of organic matter, sand, silt and clay in the soils) and oceanic and climatic variables (winds, wave height and wave period) was analysed. The relationship of these variables with variables of vegetation structure (basal area, diameter at breast height, tree height, and abundance of seedlings of mangrove species in 1 m2 subplots) was analysed in 27 plots of 500 m2 containing fringe mangroves and 5 plots containing basin mangroves. Mangroves of the western zone showed a higher structural development and were dominated by Rhizophora mangle (red mangrove). This zone is supplied by fresh water and sediments, and the soils have a high content of organic matter and clay and a low degree of anthropogenic disturbance. The eastern zone was characterized by higher pore water salinity due to lower freshwater input from rivers. In this area there is a smaller impact of waves and winds, higher sedimentation rates, high anthropogenic disturbance and mangroves are dominated by Avicennia germinans (black mangrove). Although Laguncularia racemosa (white mangrove) did not show a particular spatial pattern, due to its tolerance to open canopy conditions it was commonly found in anthropogenically disturbed areas.

Tree cover response to climate change in the forest-tundra of north-central Canada: fire-driven decline, not northward advance

Ecoscience ◽  
2018 ◽  
Vol 26 (2) ◽  
pp. 133-148 ◽  
Author(s):  
Kevin P. Timoney ◽  
Steven D. Mamet ◽  
Ryan Cheng ◽  
Peter Lee ◽  
Anne L. Robinson ◽  
...  
Keyword(s):  
Climate Change ◽  
Tree Cover ◽  
North Central ◽  
Forest Tundra ◽  
Central Canada

scholarly journals Habitat modelling locates nesting areas of the Endangered Black-capped Petrel Pterodroma hasitata on Hispaniola and identifies habitat loss

2020 ◽  
pp. 1-18
Author(s):  
YVAN G. SATGÉ ◽  
ERNST RUPP ◽  
ADAM BROWN ◽  
PATRICK G. R. JODICE
Keyword(s):  
Habitat Loss ◽  
Forest Fires ◽  
Environmental Variables ◽  
Linear Models ◽  
Habitat Characteristics ◽  
Tree Cover ◽  
Suitable Habitat ◽  
Nesting Habitat ◽  
Understorey Vegetation ◽  
Breeding Sites

Summary The Black-capped Petrel or Diablotin Pterodroma hasitata has a fragmented and declining population estimated at c.1,000 breeding pairs. On land, the species nests underground in steep ravines with dense understorey vegetation. The only confirmed breeding sites are located in the mountain ranges of Hispaniola in the Caribbean, where habitat loss and degradation are continuing threats. Other nesting populations may still remain undiscovered but, to locate them, laborious in situ nest searches must be conducted over expansive geographical areas. To focus nest-search efforts more efficiently, we analysed the environmental characteristics of Black-capped Petrel nesting habitat and modeled suitable habitat on Hispaniola using openly available environmental datasets. We used a univariate generalized linear model to compare the habitat characteristics of active Black-capped Petrel nests sites with those of potentially available sites (i.e. random pseudo-absences). Elevation, distance to coast, and the influence of tree cover and density emerged as important environmental variables. We then applied multivariate generalized linear models to these environmental variables that showed a significant relationship with petrel nesting activity. We used the top performing model of habitat suitability model to create maps of predicted suitability for Hispaniola. In addition to areas of known petrel activity, the model identified possible nesting areas for Black-capped Petrels in habitats not previously considered suitable. Based on model results, we estimated the total area of predicted suitable nesting habitat for Black-capped Petrels on Hispaniola and found that forest loss due to hurricanes, forest fires, and encroachment from agriculture had severely decreased availability of predicted suitable habitat between 2000 and 2018.

scholarly journals Sistem Pakar Diagnosis Potensi Penyebaran Penyakit pada Tanaman Cabai Menggunakan Fuzzy Mamdani

2018 ◽  
Vol 6 (2) ◽  
pp. 71-75
Author(s):  
Deni Setiyo Wibowo ◽  
Yessy Yanitasari ◽  
Dedih Dedih
Keyword(s):  
Expert System ◽  
Environmental Factors ◽  
Air Temperature ◽  
Soil Ph ◽  
Environmental Variables ◽  
Solar Irradiation ◽  
Disease Spread ◽  
Air Humidity ◽  
Input Output ◽  
Fuzzy Input

This research developed expert system using fuzzy Mamdani to diagnose the spread of diseases affecting the growth of chili plants based on environmental factors. Environmental variables used as fuzzy input parameters are soil pH, air temperature, air humidity and solar irradiation. The input-output relationship uses 81 rules with the AND operator and the MIN implication function. For a case, the results showed that the percentage of the potential spread of the disease showed 60.25%, so the category of potential disease spread with soil PH 7.5 pH, 28 ° C air temperature and air humidity 75 RH and 35% sun irradiance is moderate.

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