Natural Treefall Gaps Research Articles

Short-term effects in canopy gap area on the recovery of compacted soil caused by forest harvesting in old-growth Oriental beech (Fagus orientalis Lipsky) stands

Natural treefall gaps have a substantial role in maintaining soil and plant diversity in old-growth forests. However, the amount of information on the effects of gaps on the recovery of physical and chemical properties of compacted soils is scarce. We tested the hypothesis that natural treefall gaps accelerate the restoration of compacted soil by enhancing biological and microbial activity in the topsoil after a period of five years. Five years after a ground-based skidding operation in the Hyrcanian forest, the recovery levels of soil properties were compared among different treatments including natural canopy gaps with an area of 200 m2 (NCG), clear-cuts with an area of 1600 m2 (CC), disturbed trails under a dense canopy (DDC), and an undisturbed area (UND) as control. The lowest soil bulk density (1.07 g cm-3), penetration resistance (1.11 MPa), and the highest macroporosity (36.3%), and sand content (14.4%) among treatments were recorded for the NCG followed by DDC and CC treatments. Significantly lower values of soil pH, and electric conductivity and the highest values of soil organic C, total N, available P, K, Ca, and Mg were detected under the NCG followed by the DDC and CC treatments, as compared to the UND area. The highest values of earthworm density and dry mass, and soil microbial respiration were found in the NCG followed by the DDC and CC treatments. Fine root biomass was significantly higher in the UND area (92.27 g m-2) followed by the DDC, NCG and CC treatments. We can conclude that the effects of gap size on the recovery values of compacted soil were significant in terms of greater nutrient availability and higher earthworm density and dry mass, suggesting that mimicking natural canopy gap was more effective than the clear-cut gap (CC) for the resilience of the forest stand in the restoration of soil quality.

Low- to Moderate-Level Forest Disturbance Effects on Plant Functional Traits and Associated Soil Microbial Diversity in Western Himalaya

This study quantifies the effect of low- to moderate-intensity anthropogenic activities and natural activities affecting less than 40% of the canopy cover on major plant functional traits and associated soil microbial diversity in western Himalayan temperate forests. Plots of 0.1 ha were placed in the temperate forests along disturbance gradient and were categorized based on lopping intensity, deadwood counts, grazing, and litter removal. Plots were classified into three classes, i.e., low disturbance intensity (LDI) and moderate disturbance intensities (MDI1 and MDI2) based on lopping activities and canopy cover. The study was conducted on functional traits related to growth and survival strategies of a species in a complex forest ecosystem. Furthermore, DNA was extracted and metagenome of soil samples was performed using Illumina MiSeq platform from three disturbance classes to study the effect of disturbance and plant traits on microbial diversity. Tree basal area was found to be most significantly affected by disturbance intensity. Total density was found to be greater for the LDI site. Specific leaf area (SLA) and crown cover (CC) were the most affected traits in the moderately disturbed sites, whereas maximum plant height (HT) and seed mass (SM) were least affected by disturbance. Soil microbial diversity was found to be negatively associated with disturbance index. Microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) were found to be significantly higher in LDI sites. Disturbance level elicited variation in microbial community composition.Proteobacteriawas the most abundant phylum andPhenylobacterium,DA101, andCandidatus solibacterwere mainly abundant at the genus level. A decreasing level of disturbance due to the absence of human residences in the LDI site led to the dominance ofPhenylobacterium(27%) which reduced to 18% in MDI1 site. Shannon alpha bacterial diversity and plant species diversity (H′) were found to be greatest for MDI2 site. In forests with varying levels of management, treefall gaps due to low levels of logging intensity might have a similar effect to those of reduced lopping intensities and deadwood count (due to natural disturbances) in the study sites. The study concludes that moderate disturbance is important for promoting species diversity and species richness (SR), but species having conservative ecological strategies would be more prone to continued disturbance intensity. Therefore, low- to moderate-level disturbance in such forests can be used as a model for natural treefall gaps, and moderate-level disturbance intensity plays a powerful role in buffering ecosystem processes.

Birds associated with treefall gaps in a lowland forest in southwestern Brazilian Amazonia

ABSTRACT Natural communities are dynamic systems in time and space. The spatial distribution of plants and animals tends to coincide with the availability of resources needed for the survival and reproduction of each species. Natural treefall gaps offer a number of resources that influence the distribution of birds within the forest. We compared the understory bird assemblages of natural treefall gaps (15 sampling points) with those found in the adjacent forest (15 points) in the Humaitá Forest Reserve in southwestern Brazilian Amazonia. We used mist-nets to sample birds and obtained 700 captures of 105 species. Species richness, number of individuals, and species composition were all similar between gaps and forest, although six species presented some degree of association with the gaps, and nine with the forest. Nectarivores preferred gaps significantly over forest, whereas insectivores and frugivores were distributed equally between gaps and forest. Vegetation height and density differed between gaps and forest, and influenced the distribution of bird species in the two environments. Fruit availability was positively correlated with frugivore abundance in gaps. Overall, 33.3% of the birds associated with the treefall gaps are from lower forest canopy, while the others are understory species. We showed that the use of natural gaps by birds in a fragmented landscape of the Amazon forest contributes to the environmental heterogeneity and succession dynamics following natural events of habitat disturbance.

Change in disturbance regime facilitates invasion by Bellucia pentamera Naudin (Melastomataceae) at Gunung Palung National Park, Indonesia

In tropical rainforests, gaps created by fallen canopy trees are the primary colonization sites for pioneer species. Selective logging mimics these natural disturbances in that only a single tree is felled, creating a gap of comparable size. Rates of tree felling greatly exceed natural mortality rates, however, changing disturbance regime by increasing the number of gaps in logged areas compared to intact forest. Little is known about whether gaps in logged forests are qualitatively different as well. At Gunung Palung National Park in West Kalimantan, Indonesia, a period of selective logging in areas adjacent to the research station created a natural experiment permitting comparison of populations of the invasive pioneer tree Bellucia pentamera in selectively logged and undisturbed forest. We sought to first establish whether canopy gaps are necessary for invasion by B. pentamera. We then examined whether the type of gap (logging vs. natural treefall) had an effect on recruitment. Finally, we compared populations in natural treefall gaps in logged and undisturbed forest to estimate the effect of logging on population size. Bellucia pentamera was limited to gaps, regardless of canopy tree density. Furthermore, gaps created by selective logging supported significantly more B. pentamera individuals than natural gaps. Finally, natural treefall gaps in the disturbed area contained significantly more individuals than gaps in the undisturbed forest. Therefore, it appears that selective logging not only created more gaps for B. pentamera, these gaps in particular promoted greater abundance of this invader and led to a population increase throughout the disturbed habitat.

Are Leaf-Litter Ants (Formicidae) Distributed Differentiated between Inner Zones of Natural Treefall Gaps?

Are Leaf-Litter Ants (Formicidae) Distributed Differentiated between Inner Zones of Natural Treefall Gaps?

Using repeated small-footprint LiDAR acquisitions to infer spatial and temporal variations of a high-biomass Neotropical forest

In recent years, LiDAR technology has provided accurate forest aboveground biomass (AGB) maps in several forest ecosystems, including tropical forests. However, its ability to accurately map forest AGB changes in high-biomass tropical forests has seldom been investigated. Here, we assess the ability of repeated LiDAR acquisitions to map AGB stocks and changes in an old-growth Neotropical forest of French Guiana. Using two similar aerial small-footprint LiDAR campaigns over a four year interval, spanning ca. 20 km2, and concomitant ground sampling, we constructed a model relating median canopy height and AGB at a 0.25-ha and 1-ha resolution. This model had an error of 14% at a 1-ha resolution (RSE = 54.7 Mg ha− 1) and of 23% at a 0.25-ha resolution (RSE = 86.5 Mg ha− 1). This uncertainty is comparable with values previously reported in other tropical forests and confirms that aerial LiDAR is an efficient technology for AGB mapping in high-biomass tropical forests. Our map predicts a mean AGB of 340 Mg ha− 1 within the landscape. We also created an AGB change map, and compared it with ground-based AGB change estimates. The correlation was weak but significant only at the 0.25-ha resolution. One interpretation is that large natural tree-fall gaps that drive AGB changes in a naturally regenerating forest can be picked up at fine spatial scale but are veiled at coarser spatial resolution. Overall, both field-based and LiDAR-based estimates did not reveal a detectable increase in AGB stock over the study period, a trend observed in almost all forest types of our study area. Small footprint LiDAR is a powerful tool to dissect the fine-scale variability of AGB and to detect the main ecological controls underpinning forest biomass variability both in space and time.

Influence of gap size on carbon and nitrogen biogeochemical cycling in Northern hardwood forests of the Upper Peninsula, Michigan

The objective of this study is to determine the effect of treefall gap size on carbon and nitrogen biogeochemistry in the Northern hardwood forest. The size of the gap controls the microclimate, particularly solar radiation, soil temperature, and soil moisture, which can alter nutrient cycling. However, in Northern hardwood forests, our understanding of the relation between biogeochemistry and gap size is incomplete. Twelve natural treefall gaps ranging in size from 27 to 590 m2 and four control plots located under closed canopy were identified in Upper Michigan in May 2008. Concentrations of ammonium and nitrate were measured in throughfall and soil leachates; soil respiration rates were measured in soil; and nutrient pools were measured in vegetative biomass, forest floor (Oe, Oi horizons), mineral soil, and microbial biomass. Gap size was positively correlated with sapling biomass density and throughfall ammonium concentration but negatively correlated with microbial biomass, endomycorrhizal biomass, and soil respiration. Gap size was unrelated to all other parameters measured. The results of this study suggest that in the Northern hardwood forest, vegetative recovery and a reduction in microbial biomass may limit the influence larger gaps have on nutrient cycling.

The impact of community-based forest management on timber treeregeneration in north-eastern Honduras, with specific reference tobig-leaf mahogany (Swietenia macrophylla)

Reduced-impact logging is used to minimise the negative effects of selective logging. However, it has been suggested that low-impact logging may create too little disturbance for the regeneration of the light-demanding timber tree species, hence compromising forest productivity. This study evaluates the impact of low-intensity, non-mechanised, certified community forest management on timber tree regeneration. Particular attention was paid to big-leaf mahogany (Swietenia macrophylla), which has a regeneration pattern linked with large-scale disturbances. Logging gaps were compared to natural treefall gaps of an unlogged forest. There were more species of the light-demanding timber trees, but fewer individuals of the shade-tolerant timber species in the certified forest logging gaps, compared to unlogged forest treefall gaps. Furthermore, significant differences were found in the environmental characteristics of the logging and natural treefall gaps, although these only partially explained the differences in timber regeneration. Mahogany was found in over half of the logged forest gaps, whilst being nearly absent in the natural treefall gaps. However, all mahoganies in the established logging gaps were seedling-sized, indicating that regeneration may be hampered due to competing vegetation. The results of the study suggest that low-impact forest management may, at least in the short term, favour light-demanding species over the shade-tolerant ones, similarly to conventional forest management.

Relative abundance of amphibians in forest canopy gaps of natural origin vs. timber harvest origin

Small-scale canopy gaps created by logging may retain adequate habitat structure to maintain amphibian abundance. We used pitfalls with drift fences to measure relative abundance of amphibians in 44 harvested gaps, 19 natural treefall gaps, and 36 closed-canopy forest plots. Metamorphs had relatively lower capture rates in large harvest gaps for Ambystoma maculatum, Lithobates catesbeianus, L. clamitans, and L. sylvaticus but we did not detect statistically significant (p < 0.1) differences among gap types for Lithobates palustris metamorphs. L. clamitans juveniles and L. sylvaticus juveniles and adults had relatively lower capture rates in large harvest gaps. For juvenile-adult A. maculatum, we caught relatively fewer individuals in all gap types than in closed-canopy areas. Some groups with overall lower capture rates (immature Plethodon cinereus, juvenile L. palustris) had mixed differences among gap types, and Notophthalmus viridescens (efts) and adult P. cinereus showed no differences among gap types. One species, L. clamitans, was captured more often at gap edges than gap centers. These results suggest that harvest gaps, especially small gaps, provided habitat similar to natural gaps for some, but not all, amphibian species or life-stages.

The effects of gap size on some microclimate variables during late summer and autumn in a temperate broadleaved deciduous forest

The creation of gaps can strongly influence forest regeneration and habitat diversity within forest ecosystems. However, the precise characteristics of such effects depend, to a large extent, upon the way in which gaps modify microclimate and soil water content. Hence, the aim of this study was to understand the effects of gap creation and variations in gap size on forest microclimate and soil water content. The study site, in North West England, was a mixed temperate broadleaved deciduous forest dominated by mature sessile oak (Quercus petraea), beech (Fagus sylvatica) and ash (Fraxinus excelsior) with some representatives of sycamore (Acer pseudoplatanus). Solar radiation (I), air temperature (T(A)), soil temperature (T(S)), relative humidity (h), wind speed (v) and soil water content (Psi) were measured at four natural treefall gaps created after a severe storm in 2006 and adjacent sub-canopy sites. I, T(A), T(S), and Psi increased significantly with gap size; h was consistently lower in gaps than the sub-canopy but did not vary with gap size, while the variability of v could not be explained by the presence or size of gaps. There were systematic diurnal patterns in all microclimate variables in response to gaps, but no such patterns existed for Psi. These results further our understanding of the abiotic and consequent biotic responses to gaps in broadleaved deciduous forests created by natural treefalls, and provide a useful basis for evaluating the implications of forest management practices.

A comparison of bird communities in the anthropogenic and natural-tree fall gaps of a reduced-impact logged subtropical forest in Bolivia

AbstractWe studied bird community composition and abundance within four vegetation and disturbance categories located within selectively logged and unlogged forest in a Bolivian subtropical lowland forestry concession. The logged forest was subject to reduced-impact logging between 1 and 4 years prior to our study. The four categories were: 1) ‘gap’ points possessing natural or anthropogenic tree-fall gaps; 2) ‘target’ points with one of five commercial tree species of harvestable size; 3) ‘future’ points possessing a commercial tree below harvestable size and 4) ‘non-target’ points not possessing harvestable tree species. The bird community composition of logging gaps significantly differed from that found within natural tree-fall gaps in the unlogged forest P< 0.05. Species richness was higher in natural tree-fall gaps than in anthropogenic gaps. Furthermore, a higher proportion of disturbance sensitive species were associated with natural-tree fall gaps, whereas a higher proportion of disturbance tolerant species were associated with anthropogenic gaps. No significant difference was detected in the bird community composition for the other three vegetation categories surveyed. We discuss the conservation and silvicultural repercussions of these results.

Effects of distinct types of disturbance on seed rain in the Atlantic forest of NE Brazil

In disturbed sites, some groups of seeds might be excluded from the seed rain due to their dispersal modes or seed size, and some groups might be successful as a result of dis- turbance effects. In the present study, we examined the seed rain in natural treefall gaps and in an area of regenerating forest following an accidental burning, which occurred 4 years before this study. Both of these disturbed areas were compared with nearby forest understorey. The number of seeds, number of species, and proportion of wind-dispersed seeds were com- pared between these disturbed and undisturbed areas. The treefall gaps have received lower numbers of seeds and species than the nearby understorey, but the number of wind-dispersed seeds did not differ between these areas. The lowest seed number observed in treefall gaps can be attributed to a lower number of animal- dispersed seeds, suggesting that animals may be avoiding treefall gap areas. A higher number of seeds and a lower number of species were ob- served in the burned area when compared to the adjacent understorey. The high number of small-sized seeds and of wind-dispersed seeds in the burned area was almost surely a conse- quence of the local production of the pioneer plants established after the burning. In this study, substantial differences were observed in the characteristics of the seed rain at disturbed sites, when compared with undisturbed under- storey. However, these two distinct types of disturbance showed quite differing patterns, as treefall gaps received lower number of seeds while the burned area received a higher number of seeds, with a greater proportion of wind- dispersed seeds. The exception was for species richness, which was quite low at both these disturbed sites.

Vegetation structure, phenology, and regeneration in the natural and anthropogenic tree-fall gaps of a reduced-impact logged subtropical Bolivian forest

Reduced-impact logging is a type of selective logging that incorporates a variety of techniques aimed at lowering levels of damage to the residual stand. In a Bolivian subtropical humid forest we studied differences in gap size, vegetation structure, regeneration and phenology between anthropogenic and natural gaps in a reduced-impact logged and unlogged forest. Harvesting took place between 1 and 4 years previously. Logging gaps were significantly larger than natural gaps (d.f. 1, variance ratio (vr.) 6.38, p = 0.014) and had significantly lower coverage of lianas (d.f. 1, vr. 8.64, p < 0.01). Seedlings were more prevalent in logging gaps than in natural tree-fall gaps (d.f. 1, vr. 13.97, p < 0.001), as were members of the herbaceous genus Heliconia (d.f. 4, vr. 3.05, p = 0.023). In larger gaps microclimatic conditions favour the regeneration of non-commercial pioneer species. We propose that ground disturbance during bole removal causes higher rates of mortality to shade-tolerant species in advanced stages of regeneration. This removes the competitive height advantage needed by shade-tolerant species to compete within gaps, and thus further promotes the opportunity for pioneer species to dominate gap regeneration. These observed differences between anthropogenic and natural tree-fall gaps are of direct importance to forest managers attempting to understand how disturbance associated with reduced-impact logging influences the regeneration of commercial tree species in Bolivian forestry concessions. We discuss the ecological and silvicultural implications of these results.

Successful invasion of the neotropical species Piper aduncum in rain forests in Papua New Guinea

Abstract. Piper aduncum is a neotropical invasive species which has spread throughout Papua New Guinea over the past three decades. It has become a most successful alien woody plant in New Guinea, occurring from sea level up to 2000 m a.s.l. The species prefers initial stages of forest succession and is particularly common in recently abandoned gardens representative of a system of swidden agriculture. It often attains high cover, suppresses other pioneer species and becomes the absolute dominant species in these habitats. The species is now also spreading into naturally disturbed habitats far from direct human influence, such as natural tree-fall gaps, landslides and frequently flooded stream banks. It has, however, never been found in a closed primary forest. The species germinates from faeces of mammal and bird species, and we conclude that dispersal through endozoochory contributes to this species’ extraordinary success in Papua New Guinea. A similar invasion behaviour has been documented over a large geographic area, from Malaysia to Fiji. Piper aduncum has attributes which are common amongst successful invasive species: (1) a large native geographic range; (2) aggressively colonizing disturbed habitats in its native area; (3) relatively small seeds; (4) a short juvenile period; (5) a large seed production every year.

Tree diversity in tropical rain forests: a validation of the intermediate disturbance hypothesis.

The "intermediate disturbance hypothesis," which postulates maximum diversity at intermediate regimes of disturbance, has never been clearly proved to apply to species-rich tropical forest tree communities and to local-scale canopy disturbances that modify light environments. This hypothesis was tested on a sample of 17,000 trees in a Guianan forest, 10 years after a silvicultural experiment that added to natural treefall gaps a wide range of disturbance intensities. Species richness, standardized to eliminate density effects, peaked at intermediate disturbance levels, particularly when disturbance intensity was estimated through the percentage of stems of strongly light-dependent species.

Influence of Treefall Gaps on Distributions of Breeding Birds within Interior Old-Growth Stands in Białowieża Forest, Poland

Breeding birds were counted using point counts at 50 treefall gaps and 50 closed-canopy sites within one of the largest tracts of old-growth forest in Europe. Numbers of species and individuals were slightly, but significantly, higher at gaps. Overall bird species composition differed substantially at gaps and non-gaps. Dunnock (Prunella modularis), Blackcap (Sylvia atricapilla), and Chiffchaff (Phylloscopus collybita) were significantly more abundant at gaps. Wood Warbler (Phylloscopus sibilatrix) and Red-breasted Flycatcher (Ficedula parva) were significantly more abundant at non-gaps. Warblers (Sylviidae), ground insectivores, ground nesters, and short-distance migrants were significantly more abundant at gaps, but no species groups were more abundant at non-gaps. Eight species breeding in forest edges and young plantations in eastern Poland were not recorded in natural treefall gaps. The proportion of tropical migrant passerines was considerably higher in closed-canopy stands (0.47) than at gaps (0.29), which contrasts with the situation in most managed European forests where the highest proportions of tropical migrants typically occur in young-growth forests.

Influence of Treefall Gaps on Distributions of Breeding Birds Within Interior Old-Growth Stands in Białowieża Forest, Poland

AbstractBreeding birds were counted using point counts at 50 treefall gaps and 50 closed-canopy sites within one of the largest tracts of old-growth forest in Europe. Numbers of species and individuals were slightly, but significantly, higher at gaps. Overall bird species composition differed substantially at gaps and non-gaps. Dunnock (Prunella modularis), Blackcap (Sylvia atricapilla), and Chiffchaff (Phylloscopus collybita) were significantly more abundant at gaps. Wood Warbler (Phylloscopus sibilatrix) and Red-breasted Flycatcher (Ficedula parva) were significantly more abundant at non-gaps. Warblers (Sylviidae), ground insectivores, ground nesters, and short-distance migrants were significantly more abundant at gaps, but no species groups were more abundant at non-gaps. Eight species breeding in forest edges and young plantations in eastern Poland were not recorded in natural treefall gaps. The proportion of tropical migrant passerines was considerably higher in closed-canopy stands (0.47) than at gaps (0.29), which contrasts with the situation in most managed European forests where the highest proportions of tropical migrants typically occur in young-growth forests.

INFLUENCE OF TREEFALL GAPS ON DISTRIBUTIONS OF BREEDING BIRDS WITHIN INTERIOR OLD-GROWTH STANDS IN BIAŁOWIEŻA FOREST, POLAND

Abstract Breeding birds were counted using point counts at 50 treefall gaps and 50 closed-canopy sites within one of the largest tracts of old-growth forest in Europe. Numbers of species and individuals were slightly, but significantly, higher at gaps. Overall bird species composition differed substantially at gaps and non-gaps. Dunnock (Prunella modularis), Blackcap (Sylvia atricapilla), and Chiffchaff (Phylloscopus collybita) were significantly more abundant at gaps. Wood Warbler (Phylloscopus sibilatrix) and Red-breasted Flycatcher (Ficedula parva) were significantly more abundant at non-gaps. Warblers (Sylviidae), ground insectivores, ground nesters, and short-distance migrants were significantly more abundant at gaps, but no species groups were more abundant at non-gaps. Eight species breeding in forest edges and young plantations in eastern Poland were not recorded in natural treefall gaps. The proportion of tropical migrant passerines was considerably higher in closed-canopy stands (0.47) than at g...

Effect of treefall gaps on the patchiness and species richness of Neotropical ant assemblages.

Natural formation of treefall gaps plays an integral role in the ecological and evolutionary dynamics of many tropical forests, affecting the spatiotemporal distribution of plants and the animals that interact with them. This study examines the impact of treefall gaps on the spatial and temporal patchiness of ant assemblages in a moist lowland forest in Panama. Using pitfall traps and honey baits, we compared ant assemblages in five 1 to 2-year-old treefall gaps (ca 100 m2) and five adjacent plots (ca 100 m2) in undisturbed forest understory at three different times of year (late wet season, late dry season, and early wet season). We found little evidence that ant assemblages respond dramatically to the formation of treefall gaps and the differences in habitat qualities they produce. Ant abundance, species richness, species composition, and rates of resource discovery did not differ between gaps and forest understory. However, we did find significant differences in numerical abundance related to forest stratum (ground vs vegetation) and resource type in pitfall traps (oil-cockroach vs honey), and significant differences in ant species richness and rates of resource discovery across seasons. While habitat effects by themselves were never statistically significant, habitat and seasonal differences in species richness interacted significantly to produce complex, season-dependent differences among gap and forest habitats. These results suggest that the formation of natural treefall gaps has less of an effect on Neotropical ant assemblages compared to other groups of organisms (e.g., plants, birds) or other causes of patchiness (e.g., ant mosaics, moisture availability, army ant predation). The results of our study also have important implications for the underlying causes of habitat differences in the distribution of ant-defended plants.

The Impact of Individual Tree Harvesting on Thermal Environments of Lizards in Amazonian Rain Forest

Single‐tree harvesting with on‐site lumber production produces gaps in Amazonian forest canopy that are structurally different from natural treefall gaps. Harvest gaps are much more open, and there is neither leaf litter nor partial shading as in natural treefalls, so these anthropogenic gaps receive more intense sunlight. We used HOBO XT temperature and light data loggers to measure thermal environments in forest patches. These data were combined with data on lizard activity, activity temperatures, and habitat use to determine whether human‐made gaps influence the structure of Amazon forest lizard assemblages. Human‐made treefalls are not only more extreme thermally than surrounding forest habitat patches and natural treefalls, but they are warmer than expected based on increased light alone. Large‐bodied teiid lizards, which are typically uncommon or rare within forest, bask in sun in treefalls to gain heat. The body temperatures of these heliotherms average 36.1° C. Nonheliothermic species avoid treefalls and remain in shade within the forest. Their body temperatures average 27.7° C. Heliothermic lizards using treefall gaps are large‐bodied predaceous species that feed on vertebrates as well as invertebrates. Increasing the number of anthropogenic treefall gaps in a forest may increase the immigration and population growth of heliothermic lizards, thereby increasing their population density. Predation by these lizards and dominance over smaller lizards in interference competition (for food) may have a cascading effect on forest species, changing community structure.Impacto de la Cosecha Individual de Arboles en Ambientes Termales de Lagartijas de Bosques Tropicales Lluviosos del AmazonasLa cosecha de árboles individuales con producción de madera en el sitio crea espacios en el dosel del bosque amazónico que son estructuralmente diferentes a los espacios creados por la caída natural de árboles. Espacios por cosecha son mucho mas abiertos y no dejan ni hojarasca, ni sombreado parcial como sucede en la caída natural de árboles, esto ocasiona que estas áreas abiertas por actividades antropogénicas reciban relativamente mayor iluminación solar. Utilizamos colectores de datos de temperatura HOBO XT y de intensidad luminosa para medir ambientes termales en parches del bosque. Estos datos se combinaron con datos de actividad de lagartijas, temperaturas de actividad y uso del hábitat para determinar si los espacios abiertos por humanos influencían la estructura de los ensamblajes de lagartijas del Amazonas. La caída de árboles provocada por humanos no son únicamente mas exstremos térmicamente que los parches de hábitat boscoso circundantes y los espacios abiertos provocados por la caída natural de arboles, sino que fueron mas calientes de lo esperado debido al incremento de la intensidad luminosa. Lagartijas de cuerpo grande poco comunes o raras dentro del bosque se asolean en áreas abiertas para incrementar el calor. Las temperaturas corporales de estas lagartijas heliotérmicas promedian 36.1° C. La mayoría de las especies de lagartijas no heliotérmicas evitan las áreas abiertas y permanecen en la sombra dentro del bosque. Las temperatures corporales de éstas últimas promedia 27.7° C. Las lagartijas heliotérmicas que utilizan los espacios abiertos presentan cuerpos grandes y son especies depredadoras que se alimentan tanto de vertebrados como de invertebrados. El incremento de espacios abiertos ocasionados por actividades antropogénicas en un bosque puede incrementar la inmigración y crecimiento poblacional de lagartijas heliotérmicas, incrementando en consecuencia la densidad poblacional. La depredación de estas lagartijas y su dominio sobre otras lagartijas pequeñas en competencia por interferencia (por alimento) puede tener un efecto de cascada sobre especies del bosque, cambiando la estructura de la comunidad.