Regeneration of Quercus spp. along interactive forest boundaries in a fragmented peri-urban landscape of Mexico City

SummaryBiodiversity conservation in forest fragments surrounded by a low-quality matrix requires an understanding of how ecological conditions prevailing in the matrix enter the fragments and interact with local habitat conditions. We assessed the regeneration of oak species along edge–interior gradients in forest fragments at the periphery of Mexico City. The abundance of oak saplings was sampled along transects to the forest, while the edge effect was analysed using segmented zero-inflated Poisson models for abundance data. Three oak species were dominant in terms of their relative abundances: Quercus laeta, Quercus castanea and Quercus obtusata. Regeneration of nine oak species responded nonlinearly to the edge distance, with greater sapling abundance from the edge up to 10 m into the fragment. Canopy cover and tree height decreased from edge to fragment interior, while saplings increased in open areas within the fragments (i.e., independent of edge distance). A posterior analysis indicated that Q. obtusata reacted positively to edges. These results indicate that oak regeneration is promoted by suitable habitat conditions near the boundaries. Therefore, we suggest that forest management should focus on promoting seed production and oak establishment in forest interior habitats.

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Matrix and habitat quality in a montane cloud-forest landscape: amphibians in coffee plantations in central Veracruz, Mexico

Wildlife Research ◽

10.1071/wr12076 ◽

2013 ◽

Vol 40 (1) ◽

pp. 25 ◽

Cited By ~ 8

Author(s):

Rene Murrieta-Galindo ◽

Fabiola López-Barrera ◽

Alberto González-Romero ◽

Gabriela Parra-Olea

Keyword(s):

Population Density ◽

Habitat Quality ◽

Human Population ◽

Cloud Forest ◽

Canopy Cover ◽

Forest Fragments ◽

Landscape Matrix ◽

Plant Structure ◽

Human Population Density ◽

The Matrix

Context The processes of fragmentation, habitat loss, degradation and their combined effects are formidable threats to amphibian populations. Aims We evaluate the effect of three land use-type variables and nine landscape matrix quality factors on amphibian presence in four coffee agro-ecosystems and two cloud-forest fragments in central Veracruz, Mexico. Methods Each site was thoroughly searched using the visual-encounter survey technique along different trails in the most feasible microhabitats for detecting amphibians during four rainy seasons (2005, 2006, 2008 and 2009). Centred on the location where each amphibian species was first recorded, we established what we refer to as a buffer area within a radius of 1.5 km. A Co-Inertia mathematical model was used to determine which of the explanatory variables contributed to maintaining amphibian diversity. The landscape variables were landscape-quality index, open areas, canopy cover (low, intermediate, dense) at the matrix level, river, road and human population density and site size. Local variables were elevation, plant-structure and biological-impact indices. Key results During the study we recorded 1078 amphibians belonging to 26 species, 17 genera and 10 families. The variables explaining the composition of amphibian diversity were river and human population density, low canopy cover at the matrix level, elevation, site size and plant-structure index. Amphibian diversity increased as the structural complexity of the habitat increased, and the former was positively correlated with fragment size. Conclusion The present study indicated that coffee agro-ecosystems and the cloud-forest fragments in the region form a gradient in habitat quality and landscape variables that exert a differential influence on amphibian assemblages, and that each species responds uniquely to different variables. Implications Coffee agro-ecosystems and forest fragments cannot be seen as homogenous patches with a certain habitat quality, separate from the landscape matrix in which they are immersed. Stakeholders are not advised to rely on a single strategy to conserve the amphibian community, but rather should aim to maintain a heterogeneous landscape with forest fragments and coffee agro-ecosystems that have a complex vertical plant structure at the habitat level, especially in highly river-dense landscapes.

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Microclimate of Atlantic forest fragments: regional and local scale heterogeneity

Brazilian Archives of Biology and Technology ◽

10.1590/s1516-89132006000700011 ◽

2006 ◽

Vol 49 (6) ◽

pp. 935-944 ◽

Cited By ~ 13

Author(s):

Flavio Nunes Ramos ◽

Flavio Antonio Maës Santos

Keyword(s):

Air Temperature ◽

Regional Scale ◽

Canopy Cover ◽

Local Scale ◽

Climatic Conditions ◽

Forest Fragments ◽

Matrix Structure ◽

Forest Fragment ◽

Soil Humidity ◽

The Matrix

The aim of this work was to investigate whether (i) the organisms within different fragments, on regional scale (separated by up to 100 km), could be submitted to similar climatic conditions (rainfall and temperature), and whether (ii) the edge formation in forest fragments could stimulate microclimatic changes (canopy cover, air temperature and soil humidity), on local scale. The organisms within different fragments, on regional scale, were submitted to different climatic conditions, and the edge formation in the forest fragment stimulated microclimatic changes, on local scale, although in a heterogenic way. Not just the distance from the edge influenced the microclimatic differences. Probably, the edge age, location, the matrix structure, as well as, gap proximity could change the microclimatic even within edges.

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Development and Performance Evaluation of a Very Low-Cost UAV-Lidar System for Forestry Applications

Remote Sensing ◽

10.3390/rs13010077 ◽

2020 ◽

Vol 13 (1) ◽

pp. 77

Author(s):

Tianyu Hu ◽

Xiliang Sun ◽

Yanjun Su ◽

Hongcan Guan ◽

Qianhui Sun ◽

...

Keyword(s):

Forest Inventory ◽

Low Cost ◽

Canopy Cover ◽

Tree Height ◽

Flying Height ◽

Tree Level ◽

Forest Site ◽

Lidar System ◽

Individual Tree ◽

Gap Fraction

Accurate and repeated forest inventory data are critical to understand forest ecosystem processes and manage forest resources. In recent years, unmanned aerial vehicle (UAV)-borne light detection and ranging (lidar) systems have demonstrated effectiveness at deriving forest inventory attributes. However, their high cost has largely prevented them from being used in large-scale forest applications. Here, we developed a very low-cost UAV lidar system that integrates a recently emerged DJI Livox MID40 laser scanner (~$600 USD) and evaluated its capability in estimating both individual tree-level (i.e., tree height) and plot-level forest inventory attributes (i.e., canopy cover, gap fraction, and leaf area index (LAI)). Moreover, a comprehensive comparison was conducted between the developed DJI Livox system and four other UAV lidar systems equipped with high-end laser scanners (i.e., RIEGL VUX-1 UAV, RIEGL miniVUX-1 UAV, HESAI Pandar40, and Velodyne Puck LITE). Using these instruments, we surveyed a coniferous forest site and a broadleaved forest site, with tree densities ranging from 500 trees/ha to 3000 trees/ha, with 52 UAV flights at different flying height and speed combinations. The developed DJI Livox MID40 system effectively captured the upper canopy structure and terrain surface information at both forest sites. The estimated individual tree height was highly correlated with field measurements (coniferous site: R2 = 0.96, root mean squared error/RMSE = 0.59 m; broadleaved site: R2 = 0.70, RMSE = 1.63 m). The plot-level estimates of canopy cover, gap fraction, and LAI corresponded well with those derived from the high-end RIEGL VUX-1 UAV system but tended to have systematic biases in areas with medium to high canopy densities. Overall, the DJI Livox MID40 system performed comparably to the RIEGL miniVUX-1 UAV, HESAI Pandar40, and Velodyne Puck LITE systems in the coniferous site and to the Velodyne Puck LITE system in the broadleaved forest. Despite its apparent weaknesses of limited sensitivity to low-intensity returns and narrow field of view, we believe that the very low-cost system developed by this study can largely broaden the potential use of UAV lidar in forest inventory applications. This study also provides guidance for the selection of the appropriate UAV lidar system and flight specifications for forest research and management.

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Adjudicating Perspectives on Forest Structure: How Do Airborne, Terrestrial, and Mobile Lidar-Derived Estimates Compare?

Remote Sensing ◽

10.3390/rs13122297 ◽

2021 ◽

Vol 13 (12) ◽

pp. 2297

Author(s):

Jonathon J. Donager ◽

Andrew J. Sánchez Meador ◽

Ryan C. Blackburn

Keyword(s):

Ponderosa Pine ◽

Laser Scanning ◽

Canopy Cover ◽

Basal Area ◽

Tree Height ◽

Absolute Error ◽

Forest Monitoring ◽

Individual Tree ◽

Structural Configurations ◽

Individual Trees

Applications of lidar in ecosystem conservation and management continue to expand as technology has rapidly evolved. An accounting of relative accuracy and errors among lidar platforms within a range of forest types and structural configurations was needed. Within a ponderosa pine forest in northern Arizona, we compare vegetation attributes at the tree-, plot-, and stand-scales derived from three lidar platforms: fixed-wing airborne (ALS), fixed-location terrestrial (TLS), and hand-held mobile laser scanning (MLS). We present a methodology to segment individual trees from TLS and MLS datasets, incorporating eigen-value and density metrics to locate trees, then assigning point returns to trees using a graph-theory shortest-path approach. Overall, we found MLS consistently provided more accurate structural metrics at the tree- (e.g., mean absolute error for DBH in cm was 4.8, 5.0, and 9.1 for MLS, TLS and ALS, respectively) and plot-scale (e.g., R2 for field observed and lidar-derived basal area, m2 ha−1, was 0.986, 0.974, and 0.851 for MLS, TLS, and ALS, respectively) as compared to ALS and TLS. While TLS data produced estimates similar to MLS, attributes derived from TLS often underpredicted structural values due to occlusion. Additionally, ALS data provided accurate estimates of tree height for larger trees, yet consistently missed and underpredicted small trees (≤35 cm). MLS produced accurate estimates of canopy cover and landscape metrics up to 50 m from plot center. TLS tended to underpredict both canopy cover and patch metrics with constant bias due to occlusion. Taking full advantage of minimal occlusion effects, MLS data consistently provided the best individual tree and plot-based metrics, with ALS providing the best estimates for volume, biomass, and canopy cover. Overall, we found MLS data logistically simple, quickly acquirable, and accurate for small area inventories, assessments, and monitoring activities. We suggest further work exploring the active use of MLS for forest monitoring and inventory.

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Habitat associations and conservation status of an endemic forest dwarf chameleon (Bradypodion sp.) from South Africa

Oryx ◽

10.1017/s0030605306000408 ◽

2006 ◽

Vol 40 (2) ◽

pp. 183-188 ◽

Cited By ~ 6

Author(s):

Walter J. Reisinger ◽

Devi M. Stuart-Fox ◽

Barend F.N. Erasmus

Keyword(s):

South Africa ◽

Conservation Status ◽

Canopy Cover ◽

Iucn Red List ◽

Habitat Associations ◽

Suitable Habitat ◽

Area Of Occupancy ◽

Forest Interior ◽

Forest Remnants ◽

Iucn Red List Criteria

We quantified habitat associations and evaluated the conservation status of a recently identified, undescribed species of dwarf chameleon, Bradypodion sp. nov. Dhlinza, endemic to scarp forest remnants in KwaZulu-Natal Province, South Africa. At the microhabitat scale the Dhlinza dwarf chameleon was found more often in forest gaps and near paths than highly disturbed edges or forest interior. Chameleon presence was not explained by forest physiognomic variables such as vine cover, shrub and tree density, or canopy cover. Presence near gaps may be better explained by the combined effects of the thermal microenvironment and food availability. The species is moderately common where it occurs, with estimated densities of 4.7, 8.7 and 29.7 individuals per ha within forest interior, edges and gaps respectively. At the landscape scale, the chameleon occurs only in three remnant forests: the Dhlinza, Entumeni and Ongoye Forests. The species' extent of occurrence was estimated to be 88 km2 and its area of occupancy 49 km2. Based on the small area of remaining suitable habitat, this species meets the requirements for categorization as Endangered according to IUCN Red List criteria.

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Augmentation of Traditional Forest Inventory and Airborne Laser Scanning with Unmanned Aerial Systems and Photogrammetry for Forest Monitoring

Remote Sensing ◽

10.3390/rs10101562 ◽

2018 ◽

Vol 10 (10) ◽

pp. 1562 ◽

Cited By ~ 17

Author(s):

Kathryn Fankhauser ◽

Nikolay Strigul ◽

Demetrios Gatziolis

Keyword(s):

Laser Scanning ◽

Canopy Cover ◽

Tree Height ◽

Forest Monitoring ◽

Unmanned Aerial Systems ◽

Aerial Laser Scanning ◽

Forest Inventories ◽

Airborne Laser ◽

Aerial Systems

Forest inventories are constrained by resource-intensive fieldwork, while unmanned aerial systems (UASs) offer rapid, reliable, and replicable data collection and processing. This research leverages advancements in photogrammetry and market sensors and platforms to incorporate a UAS-based approach into existing forestry monitoring schemes. Digital imagery from a UAS was collected, photogrammetrically processed, and compared to in situ and aerial laser scanning (ALS)-derived plot tree counts and heights on a subsample of national forest plots in Oregon. UAS- and ALS-estimated tree counts agreed with each other (r2 = 0.96) and with field data (ALS r2 = 0.93, UAS r2 = 0.84). UAS photogrammetry also reasonably approximated mean plot tree height achieved by the field inventory (r2 = 0.82, RMSE = 2.92 m) and by ALS (r2 = 0.97, RMSE = 1.04 m). The use of both nadir-oriented and oblique UAS imagery as well as the availability of ALS-derived terrain descriptions likely sustain a robust performance of our approach across classes of canopy cover and tree height. It is possible to draw similar conclusions from any of the methods, suggesting that the efficient and responsive UAS method can enhance field measurement and ALS in longitudinal inventories. Additionally, advancing UAS technology and photogrammetry allows diverse users access to forest data and integrates updated methodologies with traditional forest monitoring.

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The Extent of Seasonally Suitable Habitats May Limit Forage Fish Production in a Temperate Estuary

Frontiers in Marine Science ◽

10.3389/fmars.2021.706666 ◽

2021 ◽

Vol 8 ◽

Author(s):

Mary C. Fabrizio ◽

Troy D. Tuckey ◽

Aaron J. Bever ◽

Michael L. MacWilliams

Keyword(s):

Chesapeake Bay ◽

Habitat Suitability ◽

Reference Points ◽

Suitable Habitat ◽

Habitat Conditions ◽

Forage Production ◽

Forage Fishes ◽

Annual Variations ◽

Suitable Habitats ◽

Bay Anchovy

The sustained production of sufficient forage is critical to advancing ecosystem-based management, yet factors that affect local abundances and habitat conditions necessary to support aggregate forage production remain largely unexplored. We quantified suitable habitat in the Chesapeake Bay and its tidal tributaries for four key forage fishes: juvenile spotted hake Urophycis regia, juvenile spot Leiostomus xanthurus, juvenile weakfish Cynoscion regalis, and bay anchovy Anchoa mitchilli. We used information from monthly fisheries surveys from 2000 to 2016 coupled with hindcasts from a spatially interpolated model of dissolved oxygen and a 3-D hydrodynamic model of the Chesapeake Bay to identify influential covariates and construct habitat suitability models for each species. Suitable habitat conditions resulted from a complex interplay between water quality and geophysical properties of the environment and varied among species. Habitat suitability indices ranging between 0 (poor) and 1 (superior) were used to estimate seasonal and annual extents of suitable habitats. Seasonal variations in suitable habitat extents in Chesapeake Bay, which were more pronounced than annual variations during 2000–2016, reflected the phenology of estuarine use by these species. Areas near shorelines served as suitable habitats in spring for juvenile spot and in summer for juvenile weakfish, indicating the importance of these shallow areas for production. Tributaries were more suitable for bay anchovy in spring than during other seasons. The relative baywide abundances of juvenile spot and bay anchovy were significantly related to the extent of suitable habitats in summer and winter, respectively, indicating that Chesapeake Bay habitats may be limiting for these species. In contrast, the relative baywide abundances of juvenile weakfish and juvenile spotted hake varied independently of the spatial extent of suitable habitats. In an ecosystem-based approach, areas that persistently provide suitable conditions for forage species such as shoreline and tributary habitats may be targeted for protection or restoration, thereby promoting sufficient production of forage for predators. Further, quantitative habitat targets or spatial thresholds may be developed for habitat-limited species using estimates of the minimum habitat area required to produce a desired abundance or biomass; such targets or thresholds may serve as spatial reference points for management.

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Dispersal across habitat boundaries: uncovering the demographic fates of populations in unsuitable habitat

10.1101/2021.03.22.436493 ◽

2021 ◽

Author(s):

Megan C. Szojka ◽

Rachel M. Germain

Keyword(s):

Temporal Variability ◽

Adult Life ◽

Adult Plant ◽

Suitable Habitat ◽

Life Stages ◽

Habitat Types ◽

The Matrix ◽

Probabilistic Process ◽

Habitat Boundaries ◽

Matrix Patch

AbstractPatchy landscapes are characterized by abrupt transitions among distinct habitat types, forcing species to cross habitat boundaries in order to spread. Since seed dispersal is a probabilistic process, with a kernel that decays with distance, most individuals will fail to reach new, suitable habitat. Although failed dispersers are presumed dead in population models, their demographic fates may not be so simple. If transient survival is possible within unsuitable habitat, then through time, individuals may be able to reach distant, suitable habitat, forming new populations and buffering species from extinction. In a fragmented Californian grassland, we explored the fates of individuals that crossed habitat boundaries, and if those fates differed among specialists dispersing from two habitat types: serpentine habitat patches and the invaded non-serpentine matrix. We surveyed the diversity of seedbank and adult life stages along transects that crossed boundaries between patches and the matrix. First, we considered how patch specialists might transiently survive in the matrix via seed dormancy or stepping-stone populations. Second, we investigated the dispersal of an invasive matrix specialist (Avena fatua) into patches, to assess if sink populations existed across the habitat boundary. We found that dormancy maintained populations of patch specialists deep into the matrix, as abundances of seedbanks and of adult plant communities differed with distance into the matrix. We found evidence that these dormant seeds disperse secondarily with vectors of material flows in the landscape, suggesting that they could eventually reach suitable patches even if they first land in the matrix. We found that A. fatua were largely absent deep in patches, where reproductive outputs plummeted and there was no evidence of a dormant seedbank. Our results not only reveal the demographic fates of individuals that land in unsuitable habitat, but that their ecological consequences differ depending on the direction by which the boundary is crossed (patch → matrix ≠ matrix → patch). Dormancy is often understood as a mechanism for persisting in face of temporal variability, but it may serve as a means of traversing unsuitable habitat in patchy systems, warranting its consideration in estimates of habitat connectivity.

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Extensive forest management contributes to maintain suitable habitat characteristics for the endangered Atlantic-Gaspésie caribou

Canadian Journal of Forest Research ◽

10.1139/cjfr-2016-0038 ◽

2016 ◽

Vol 46 (7) ◽

pp. 933-942 ◽

Cited By ~ 8

Author(s):

Marie-Audrey Nadeau Fortin ◽

Luc Sirois ◽

Martin-Hugues St-Laurent

Keyword(s):

Forest Management ◽

Maximum Sustainable Yield ◽

Habitat Characteristics ◽

Coniferous Forests ◽

Suitable Habitat ◽

Habitat Conditions ◽

Natural Forests ◽

Forest Practices ◽

Partial Canonical Correspondence Analysis ◽

Conservation Of Endangered Species

Extensive forest management aims at minimizing differences between managed and natural forests and at contributing to the conservation of endangered species such as the Atlantic-Gaspésie caribou. The decline of this isolated population was exacerbated by intensive forest practices, as the over-representation of regenerating forests supports high densities of bears and coyotes. These predators select such stands for the high availability of berries and browse suitable to alternative prey, especially moose. Our objective was to verify whether extensive treatments can provide suitable habitat characteristics for caribou. We compared the impacts of different intensive and extensive treatments on habitat attributes known to be selected by caribou, moose, and their predators. We sampled 291 sites in seven treatments and in mature coniferous forests (as the control). A partial canonical correspondence analysis highlighted which treatments maintain habitat attributes that are comparable with those found in mature forests, including some characteristics suitable for caribou such as a substantial biomass of arboreal lichen and a lower availability of resources for predators. Although being more suitable than the three intensive treatments tested, none of the four extensive treatments we studied provided similar habitat conditions to mature forest. Favouring extensive treatments could nevertheless be a relevant conservation compromise at the forest stand level, but their utility remains uncertain under the maximum sustainable yield paradigm as they impact a larger area.

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Testing the Risk-Disturbance Hypothesis in a Fragmented Landscape: Nonlinear Responses of House Sparrows to Humans

The Condor ◽

10.1093/condor/105.2.316 ◽

2003 ◽

Vol 105 (2) ◽

pp. 316-326 ◽

Cited By ~ 2

Author(s):

Esteban Fernández-Juricic ◽

Angel Sallent ◽

Ruben Sanz ◽

Iñaki RodrÍguez-Prieto

Keyword(s):

Resource Use ◽

Urban Landscape ◽

Passer Domesticus ◽

Mechanistic Explanation ◽

Fragmented Landscape ◽

Forest Fragments ◽

House Sparrows ◽

Trade Off ◽

Nonlinear Responses ◽

Consumption Rates

Abstract We used House Sparrows (Passer domesticus) as a model species to assess responses to different levels of human visitation in a fragmented urban landscape. Regionally, we analyzed linear and nonlinear variation in breeding densities in relation to observed pedestrian rates in forest fragments. Locally, we tested experimentally the resource-use–disturbance trade-off hypothesis, which suggests that an increase in the frequency of human visitation decreases the frequency of resource use by an animal, assuming that individuals react to humans as if they were potential predators, and that responses depend upon the probability of visually detecting humans. Breeding densities peaked at intermediate pedestrian rates in two consecutive years. Consumption rates of artificial food within fragments were higher at intermediate pedestrian rates, which may indicate that this species uses people as cues to find food. Consumption rates decreased at high pedestrian rates as a result of low tolerance to people and a reduction in the time devoted to foraging. Our results imply a balance between attraction to and avoidance of humans to account for these nonlinear responses, and that the resource-use–disturbance trade-off hypothesis can be a useful mechanistic explanation for understanding the responses to humans of species that may receive a direct or indirect benefit from human presence. Probando la Hipótesis del Riesgo-Perturbación en un Paisaje Fragmentado: Respuestas No Lineales de Passer domesticus hacia Humanos Resumen. Se escogió a Passer domesticus como especie modelo para analizar su respuesta a distintos niveles de perturbación humana en un ambiente urbano fragmentado. Regionalmente, se analizaron las variaciones lineales y no-lineales en las densidades reproductivas con relación a la tasa observada de visitantes a fragmentos forestales. Localmente, se comprobó experimentalmente la hipótesis del balance entre el uso del recurso y perturbación, la cual analiza la relación entre la frecuencia de visita y la frecuencia de uso del recurso, suponiendo que los animales reaccionan hacia los humanos como si fuesen depredadores, y que las respuestas dependen de las probabilidades de detección de humanos. Las densidades reproductivas en dos años consecutivos fueron más elevadas con tasas de visita intermedias. Las tasas de consumo dentro de fragmentos mostraron un pico cuando la frecuencia de visita fue intermedia, lo que sugiere que esta especie utiliza a los humanos como indicadores de alimento; pero la tasa de consumo disminuyó con frecuencias de visita mas elevadas como resultado de la baja tolerancia hacia humanos y la reducción del tiempo dedicado a la alimentación. Nuestros resultados indican que un balance entre atracción y repulsión hacia humanos está involucrado en las respuestas no lineales y que la hipótesis del balance entre el uso del recurso y el disturbio puede ser una explicación apropiada para comprender las respuestas de especies que reciben un beneficio directo o indirecto de la presencia humana.

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