Increase In Basal Area Research Articles

Effects of longleaf pine planting density and other factors on stand structure and associated wildlife habitat

The primary objective of many longleaf pine (Pinus palustris) restoration programs is to enhance or restore habitat for wildlife dependent on herbaceous plant communities. Because herbaceous cover is inversely related to canopy cover, restoration programs often place restrictions on longleaf pine planting density. However, the influence of planting density on understory plant communities has been inadequately evaluated. Therefore, we initiated a study to examine the relative influences of planting density and other factors on overall understory composition and forage availability for white‐tailed deer (Odocoileus virginianus) and northern bobwhite (Colinus virginianus) in nine longleaf pine stands throughout the Coastal Plain of Alabama during 2017–2018. We found that coverage of herbaceous plants decreased 3.5%, coverage of woody plants decreased 2.4%, and coverage of northern bobwhite forage plants decreased 1.9% for each 1 m2/ha increase in longleaf pine basal area. However, planting density was not a significant predictor of current basal area, nor coverage of any functional group of plants we examined, likely because current longleaf pine density averaged only 46% (range = 30–64%) of seedling planting density. We did not detect an effect of prescribed fire on stand condition or understory plant communities, likely due to variability in fire timing and frequency. Our findings related to planting density were likely a function of low longleaf pine survival, which is not uncommon. Because of this and the inherent variability in growth rates for young longleaf pine stands, restoration programs should consider placing greater emphasis on post‐planting monitoring and management than planting density.

Adsorption of Methylene Blue by Hydroxyl-Aluminum Pillared Montmorillonite

A purified raw montmorillonite and hydroxy-aluminum pillared montmorillonite have been prepared from a natural bentonite from Maghnia, Algeria. These materials have been analyzed by X-ray fluorescence spectroscopy, X-ray diffraction, Infrared spectroscopy and nitrogen adsorption-desorption measurement. The pillared montmorillonite provided a certain increase of interlayer basal spacing and BET surface area and consequently the improvement of its capacities adsorption and decolorization of Methylene Blue. The adsorption properties of these materials were studied as a function of contact time, solution pH, initial Methylene Blue concentration and temperature. The adsorption kinetics and isotherms were well fitted by pseudo-second order and Freundlich models, respectively. In addition to that, thermodynamic studies showed an exothermic and a spontaneous process.

Evaluation of Vegetation after Four Years in a Caatinga Fragment in the State of Sergipe, Brazil

Abstract The comparison of vegetation at two different moments allows for recognizing the stability of plant communities. The structure and floristic composition of a Caatinga fragment in the municipality of Poco Verde, state of Sergipe, were evaluated after four years (2011-2015). Sampling was performed through 30 plots of 20 m × 20 m, considering individuals with circumference at breast height ≥ 6 cm. Despite the increase in density (0.79%) and basal area (4.82%), changes in floristic composition, in Shannon-Wiener diversity (from 3.33 nats.ind-1 to 3.30 nats.ind-1) and in Pielou equability (from 0.78 to 0.80) were small. None of the structural parameters evaluated (richness, density, basal area, importance value and Shannon-Wiener diversity) significantly differed between evaluation periods. The vegetation remained stable over time, tolerating current anthropization levels and enabling the use of its natural resources through planned management.

Adsorption of Methylene Blue by Hydroxyl-Aluminum Pillared Montmorillonite

A purified raw montmorillonite and hydroxy-aluminum pillared montmorillonite have been prepared from a natural bentonite from Maghnia, Algeria. These materials have been analyzed by X-ray fluorescence spectroscopy, X-ray diffraction, Infrared spectroscopy and nitrogen adsorption-desorption measurement. The pillared montmorillonite provided a certain increase of interlayer basal spacing and BET surface area and consequently the improvement of its capacities adsorption and decolorization of Methylene Blue. The adsorption properties of these materials were studied as a function of contact time, solution pH, initial Methylene Blue concentration and temperature. The adsorption kinetics and isotherms were well fitted by pseudo-second order and Freundlich models, respectively. In addition to that, thermodynamic studies showed an exothermic and a spontaneous process.

Crecimiento radial de especies de pino en rodales sujetos a cortas de selección en Santa María Lachixío, Oaxaca, México

Introduction: The evaluation of the effect of management activities on trees is essential to gain a better understanding of the processes occurring in the stands. Objective: To evaluate the effect of selection cutting on the growth of pine species in uneven-aged stands. Materials and methods: Thirty sampling sites were established in two mixed pine stands subjected to selection cutting in 2003. The stumps of this harvest were used as site centers and the growth of the residual trees was evaluated in a 10-m radius; tree-size variables and competition indices were calculated. Results and discussion: In the first five years after the harvest, 47 % of residual trees showed significant growth (P ≤ 0.05). Stump diameter, diameter at breast height and competition were the most important variables to explain growth. The competition area of the harvested individuals (stumps) showed influence up to a 15-m radius. The increase in basal area (IBA) was 71 % with respect to pre-harvest growth. This increase was related to the basal area sum of the residual trees and 1.3 m2 per site (41.3 m2·ha-1) was established as the threshold from which a release is nullified by residual competition. Conclusion: Selection cutting influences residual tree growth in a differentiated way; the response may be positive, negative or nil depending on size and local competition.

Population structure, soil characteristics and carbon stock of the regenerating banj oak forests in Almora, Central Himalaya

The present study is aimed to study regeneration status, population structure, soil characteristics and carbon stock of seven regenerating banj oak (Quercus leucotrichophora) forests in the central Himalaya. The phytosociological study was done by using ten 10 m × 10 m quadrat at each site. Biomass and carbon stock of trees were calculated by using regression equations. Soil samples were collected from three depths (0–10, 10–20 and 20–30 cm) by using soil corer. The tree density of two most dominant species of the study sites i.e. banj oak and pine (Pinus roxburghii) varied from 260–1200 trees ha−1 and 90–300 trees ha−1, respectively. Whereas, basal area of banj oak and pine varied between 5.5–21.0 m2 ha−1 and 6.4–26.0 m2 ha−1, respectively. Density-diameter curve indicated the increasing population of banj oak while declining pine in all the sites. Carbon density of the banj oak was found between 46.96–167.36 Mg ha−1 and in pine it was 17.18–72.95 Mg ha−1. Soil nutrient (especially carbon and nitrogen) improved with increase in density and basal area of forests. Additionally, substantial amount of carbon stored by these trees makes them viable for the region. Thus, identification and conservation of such forests are recommended.

Fine-scale habitat utilization by birds in an ancient oak (Quercus spp.) wood-pasture in southwestern Turkey

Wood-pastures are disappearing rapidly in the eastern Mediterranean basin due to changes in land use. Traditional farming by means of goat husbandry and pollarding has allowed many trees to become old, creating valuable habitats for biodiversity. Developing viable management schemes for habitats of conservation concern require studies aiming at identifying relationships between habitat structure and associated species. In this study, the associations between habitat structure and bird species diversity were studied on a fine scale, using data obtained from transect inventories in an oak wood-pasture in southwestern Turkey. Almost all species were most abundant where trunk size, basal area or tree density peaked. Diversity of ground-nesters was slightly and positively associated with an increase in basal area. Low canopy-nesters were positively associated with an increase in shrub density, whereas there was a negative association for high canopy-nesters. Secondary cavity-nesters were unrelated to the density of small trunk cavities but exhibited a positive association with basal area of trees. Contrarily, primary cavity-nesters preferred trees with larger cavities, although this was most likely due to the presence of other desirable attributes of the very same trees. The results of this study give important insights to the structural and spatial organization of bird assemblages in a little studied but rich, culturally managed ecosystem in the Mediterranean.

Effects of the occurrence of a cyclone and the dominance of a bamboo species on the dynamics of subtropical forest fragments

AbstractWith the intensification of global warming, the occurrence of large‐scale natural events is becoming even more common in tropical regions, which can impact the structure of plant communities. In this study, we evaluated the isolated and combined effects of an extratropical cyclone and the dominance of a native bamboo species (Merostachys skvortzovii) on floristic composition, diversity, demographic rates and the increment of trees in Atlantic Forest fragments in Southern Brazil. In 2014 (T1) and 2016 (T2), we sampled 56 plots of 200 m² for the effects of an extratropical cyclone in 2009 (T0). We also evaluated another 60 plots of the same size not in the direct path of this cyclone. Half of the plots in each group were covered by dense groupings of bamboos, as a result of past human activities, which could potentially limit natural regeneration. We observed an increase in richness and diversity indices (H′ and 1/D) from the first (T0) to the following assessments (T1 an T2) on the sites affected by the cyclone, when compared to non‐affected sites. After the cyclone, both density and basal area they decreased, but there was an increase in recruitment, mortality, turnover rates and basal area, as well as basal increment. The diameter increment on surviving individuals was higher in cyclone‐affected sites than in non‐affected sites. Bamboo cover did not affect richness or demographic rates (except mortality between T0 and T1). Natural impacts of this nature can lead to significant alterations of demographic rates, allowing the input of new species and influencing the pace of demographic processes.

Rarity of shortleaf, slash, and longleaf pine seedlings in oak-pine forest types: An assessment of associated environmental, stand, site, and disturbance factors

Determining the factors that influence the regeneration of pine in oak-pine forests is crucial for understanding natural regeneration dynamics and for planning forest management strategies. We investigated the vegetation structure and seedling dynamics of shortleaf, slash, and longleaf pine in oak-pine forest types of the southeastern United States. We used logistic regression with penalized maximum likelihood estimation because of the rarity of the regeneration from these pines. We performed canonical correlation, analysis of variance, and community structure analysis to produce multivariate relationships and statistical inferences. The classification accuracy of the logistic regression models for shortleaf, slash, and shortleaf pine were 96.0%, 96.7%, and 97.7%, respectively. The models indicated that environmental, climatic, stand, site productivity, and disturbance factors, or their combinations, had a significant influence on seedling occurrence. The probability of occurrence of seedlings of the three pine species increased with the increase in the overstory basal area from these species: one unit increase in overstory purity ratio of shortleaf, slash, and longleaf pine increased the odds of occurrence of their seedlings by approximately 51, 24, and 7 times, respectively.The probability of occurrence of shortleaf pine seedlings increased with increasing canopy openness in stands with a substantial proportion of shortleaf pine in the overstory. The increase in mean annual temperature and overstory basal area of slash pine increased the probability of occurrence of slash pine seedlings on wetter sites that had disturbance through harvesting and silvicultural treatments. The chances of occurrence of longleaf pine seedlings increased with increasing overstory basal area of longleaf pine, species diversity, and mean annual temperature in low density stands on low productive sites. The findings can help forest managers in designing and implementing silvicultural treatments to promote the natural regeneration of the three pines in oak-pine forests.

Anthropic disturbances as the main driver of a semideciduous seasonal forest fragment in Minas Gerais

Abstract The new environmental conditions imposed by disturbance events often create a mosaic of spots in different successional stages. Our objective was to describe the temporal variation of a semideciduous seasonal forest based on its anthropic disturbance history, verifying possible changes in forest dynamics and structure. We sampled the arboreal vegetation with a diameter at breast height (1.3 m above the ground; DBH) ≥ 5 cm in 15 permanent plots of 20 × 20 m where we performed four inventories (2003, 2005, 2007 and 2015). We observed a density decrease and a basal area increase, which indicates the late successional stage of the analyzed tree community. The phytosociological structure, richness and species diversity of the tree community did not show changes throughout the monitoring. However, the Protium spruceanum predominance may be a response to the environmental changes caused by the mining occurred in the area 250 years ago. The anthropic disturbances enduring influences make this type of work indispensable because it allows the ecological processes understanding, allowing a factual management of the forests by the its effective management and conservation.

Technical thinning age of eucalyptus trees grown in crop-forest integration systems

Abstract: The objective of this work was to determine indicator methods that help to establish the first thinning age of trees to be used in crop-livestock-forest integration systems based on the relationships between eucalyptus growth and soybean and corn production. The experiment followed a completely randomized block design, with four replicates and three production systems (crop monoculture, forest planting monoculture, and crop-forest integration). The percentage of entries and Veiga’s methods, as well as the target growth rates, were assessed to set the thinning age to be adopted for integration systems. The percentage of entries method, the age of the maximum mean annual volume increase, or tree age when diameter growth stagnation occurs did not prove adequate as a reference for thinning, when yields of agricultural crops are not jointly monitored. Methods focusing on controlling the basal area and target diameter increase are feasible to define the technical age for thinning implementation and control.

Shifting species and functional diversity due to abrupt changes in water availability in tropical dry forests

Abstract Recent insights show that tropical forests are shifting in species composition, possibly due to changing environmental conditions. However, we still poorly understand the forest response to different environmental change drivers, which limits our ability to predict the future of tropical forests. Although some studies have evaluated drought effects on tree communities, we know little about the influence of increased water availability. Here, we evaluated how an increase in water availability caused by an artificial reservoir affected temporal changes in forest structure, species and functional diversity, and community‐weighted mean traits. Furthermore, we evaluated how demographical groups (recruits, survivors and trees that died) contributed to these temporal changes in tropical dry forests. We present data for the dynamics of forest change over a 10‐year period for 120 permanent plots that were far from the water’s edge before reservoir construction and are now close to the water’s edge (0–60 m). Plots close to the water’s edge had an abrupt increase in water availability, while distant plots did not. Plots close to the water’s edge showed an increase in species and functional diversity, and in the abundance of species with traits associated with low drought resistance (i.e., evergreen species with simple leaves and low wood density), whereas plots far from the water’s edge did not change. Changes in overall community metrics were mainly due to recruits rather than to survivors or dead trees. Overall stand basal area did not change because growth and recruitment were balanced by mortality. Synthesis. Our results showed that tropical dry forests can respond quickly to abrupt changes in environmental conditions. Temporal changes in vegetation metrics due to increased water availability were mainly attributed to recruits, suggesting that these effects are lasting and may become stronger over time. The lack of increase in basal area towards the water’s edge, and the shift towards higher abundance of soft‐wooded species, could reduce the carbon stored and increase the forest’s vulnerability to extreme weather events. Further “accidental” large‐scale field experiments like ours could provide more insights into forest responses and resilience to global change.

Long-Term Changes in the Dominance of Drought Tolerant Trees Reflect Climate Trends on a Micronesian Island

Background: The Ogasawara (Bonin) Islands of Micronesia lie in the western Pacific Ocean and are unique in terms of their isolation, climate, soils and diversity of rare plant species. We hypothesized that the vegetation on the islands will be a robust model system to study long-term climate change impacts on vegetation dynamics.
 Methods: A large, long-term vegetation monitoring plot was established on Chichijima Island and measured in 1976 and 2017. It was located in an undisturbed dry forest area that contained many endemic and endangered species.
 Results: During the 41 year study period, total basal area of tree species increased by 24.6% and was dominated by Schima, Distylium and Pouteria, whereas tree density declined by 30%. Tree genera exhibiting the largest increases in basal area were Elaeocarpus, Ilex, Pandanus, Pouteria, Rhaphiolepis, Syzgium and Schima. During the study period, the annual average (23.2ºC), minimum and maximum temperatures increased by 0.5 to 0.8ºC, respectively. The average annual precipitation was 1276 mm with severe droughts occurring in 1980, 1990 and 2016. The largest increases in the basal area were exhibited in trees species with wide functional distribution and attributes, including drought tolerance.
 Conclusions: The results of this study suggest a link between the drought tolerance, species dominance and climate change at the study location. Our unique approach of linking functional attributes with long-term vegetation and climate change can serve as a model for other studies of global change impacts.

Fifty-Five Years of Change in a Northwest Georgia Old-Growth Forest

ABSTRACT Old-growth forests provide unique insight into historical compositions of forests in the eastern United States. Plots established within a mixed forest community within Marshall Forest in Rome, Georgia, in 1960 (and remeasured in 1989) were reassessed to determine changes in forest composition. The community has experienced approximately 10% increase in basal area since the previous measurement period. However, changes in species importance have occurred. Chestnut oak (Quercus montana), mockernut hickory (Carya tomentosa), white oak (Quercus alba), and flowering dogwood (Cornus florida) have all decreased in importance, while pignut hickory (Carya glabra), winged elm (Ulmus alata), yellow poplar (Liriodendron tulipifera), and red maple (Acer rubrum) have all increased in importance. Additionally, there are no Pinus spp. saplings in the study area, indicating seedlings are not being recruited into the midstory. These changes indicate continued succession to a composition increasingly dominated by ...

Temporal changes in species composition, diversity, and woody vegetation structure of savannas in the Cerrado-Amazon transition zone

ABSTRACT Vegetation in the transition between tropical forest and savanna is hyperdynamic and there is evidence that in the absence of fire, forest advances over savanna. Between 2008 and 2013 we evaluated changes in species composition and diversity and in the structure of the woody vegetation of savanna physiognomies in the transition between the Cerrado and Amazon biomes that were fire free for 11 years. The physiognomies form a gradient from savanna woodland (Typical Cerrado - TC), to low woodland (Dense Cerrado - DC), to woodland (locally called Cerradao - CO). We hypothesise that: 1) the more open physiognomies (TC and DC) are more dynamic compared to the closed physiognomy (CO); and 2) in the absence of fire vegetation tends to become more forested. We found that: 1) TC was more dynamic (e.g. greater increases in richness, diversity, and abundance of plants and basal area) than CO and DC; 2) The three physiognomies experienced an increase in basal area and abundance of individuals, but only certain key species contributed to these increases. These results indicate that the open physiognomies were more dynamic than the closed physiognomies, and in the absence of fire the savanna physiognomies became more forested and accumulated biomass.

Correction: A century of changing flows: Forest management changed flow magnitudes and warming advanced the timing of flow in a southwestern US river.

[This corrects the article DOI: 10.1371/journal.pone.0187875.].

From salamanders to greenhouse gases: does upland management affect wetland functions?

Although the effects of forest management on watershed hydrology are well recognized, little is known about how upland management affects the hydrology and functions of wetlands embedded within upland forests (hereafter, embedded wetlands). We simulated the effects of upland tree basal area (ie total cross‐sectional area of trees per land area) and different upland management approaches on wetland hydrological, biogeochemical, and habitat functions. Increases in upland basal area and associated forest evapotranspiration reduced wetland inundation depth and duration. Wetland global warming potential decreased with higher upland basal area, driven by lower methane production in drier wetlands. Amphibian habitat suitability decreased with increasing basal area due to reduced wetland inundation. Simulations of three common 25‐year management scenarios – namely, constant basal area, fire management, and pine plantation – highlighted impacts of forest structure that vary over time. Prescribed fires that recurred every 3 years generated cyclic patterns in wetland hydrology and function, whereas pine plantations transitioned from wet to dry regimes with stand growth. This work represents a first step to linking upland management, wetland hydrology, and wetland functions, highlighting opportunities for optimizing forest management to provide landscape‐scale ecosystem services.

A century of changing flows: Forest management changed flow magnitudes and warming advanced the timing of flow in a southwestern US river.

The continued provision of water from rivers in the southwestern United States to downstream cities, natural communities and species is at risk due to higher temperatures and drought conditions in recent decades. Snowpack and snowfall levels have declined, snowmelt and peak spring flows are arriving earlier, and summer flows have declined. Concurrent to climate change and variation, a century of fire suppression has resulted in dramatic changes to forest conditions, and yet, few studies have focused on determining the degree to which changing forests have altered flows. In this study, we evaluated changes in flow, climate, and forest conditions in the Salt River in central Arizona from 1914–2012 to compare and evaluate the effects of changing forest conditions and temperatures on flows. After using linear regression models to remove the influence of precipitation and temperature, we estimated that annual flows declined by 8–29% from 1914–1963, coincident with a 2-fold increase in basal area, a 2-3-fold increase in canopy cover, and at least a 10-fold increase in forest density within ponderosa pine forests. Streamflow volumes declined by 37–56% in summer and fall months during this period. Declines in climate-adjusted flows reversed at mid-century when spring and annual flows increased by 10–31% from 1964–2012, perhaps due to more winter rainfall. Additionally, peak spring flows occurred about 12 days earlier in this period than in the previous period, coincident with winter and spring temperatures that increased by 1–2°C. While uncertainties remain, this study adds to the knowledge gained in other regions that forest change has had effects on flow that were on par with climate variability and, in the case of mid-century declines, well before the influence of anthropogenic warming. Current large-scale forest restoration projects hold some promise of recovering seasonal flows.

Contribution of lianas to community‐level canopy transpiration in a warm‐temperate forest

Summary Lianas (woody climbers) have a greater amount of leaves relative to basal area or standing biomass than trees, and very wide vessels that permit efficient water transport. These features suggest that lianas possibly consume proportionally more water through transpiration than trees. Despite their potential importance, researchers have made only limited attempts to evaluate effects of lianas on forest water dynamics. We conducted sap flow measurements for 1 year using a thermal dissipation method for four species each of lianas and trees in a liana‐rich, warm‐temperate forest in Japan and estimated the contribution of lianas to stand canopy transpiration. Based on a calibration measuring water uptake rates from cut‐stem ends, the actual sap flux (Fd) in liana stems was several times greater than those estimated from the original calibration provided for the method. In the field, lianas showed an average of 2–4 times greater Fd than trees throughout the year. Except for this difference, diurnal and seasonal patterns of relative changes of Fd were similar in both groups. The whole‐plant transpiration (Qt) of sample plants was exponentially related to basal diameter for both lianas and trees; Qt of lianas increased more steeply with basal diameter than that of trees. By extrapolating the relationships between Qt and basal diameter to the inventory data of the study plot, we estimated that lianas contributed 12·8% to the annual stand canopy transpiration while comprising 2·3% of stand basal area, which probably reflected the top‐heavy architecture of lianas. Our results indicate that the contribution of lianas to forest water dynamics may be several times greater than their contribution to forest basal area. This implies that a slight increase of liana abundance might have greater effects on water dynamics and, through competitions with trees for limited water, the carbon sequestration capacity of forests than expected from the increase in basal area. This study underlines the necessity of evaluating the relative importance of lianas to forest water dynamics in forests world‐wide. A lay summary is available for this article.

Post-1935 changes in Pinyon-Juniper persistent woodland on the South Rim of Grand Canyon National Park, Arizona, USA

Pinyon-juniper (Pinus-Juniperus) persistent woodland (PJPW) is widespread in western North America. This study examined changes in PJPW on the South Rim of Grand Canyon National Park (GCNP), Arizona, USA based on resampling study plots established in 1935 that are the earliest-known, landscape-level, quantitative documentation of PJPW. Resampling provided data essential to understanding post-1935 dynamics and current conditions, as well as developing ecologically based management practices.Plots were divided into Core PJPW, Transition PJPW-Ponderosa Pine Forest (PJPW-PPF), and Seral PJPW. These differed greatly in their post-1935 vegetation dynamics. Core PJPW experienced high mortality of mid-diameter Juniperus osteosperma (JUOS) and Pinus edulis (PIED), large losses of total basal area, and increases of small-diameter JUOS. In context of other research, these changes indicate drought during 1953–1956, 1959–1964, and 2002–2011 led to increased mortality of JUOS and PIED and that Core PJPW is a dynamic system with phases of tree recruitment and mortality related to climate. In contrast, Transition PJPW-PPF was generally stable, likely as a result of less drought stress at the relatively high elevation where PJPW intergrades with PPF. Seral PJPW plots were early successional in 1935 and provided a uniquely long, quantitative documentation of succession. They changed most among the PJPW subtypes with large increases in total tree density and basal area as plots transitioned into tree-dominated successional stages.Current conditions of Core PJPW in GCNP provide a model for restoration of PJPW in areas of similar environment. Elsewhere, managers should consider using contemporary data from the area’s least-disturbed PJ vegetation. In general, the ultimate goal should be to restore to the least-altered present, not attempt to re-establish the past.Likewise, findings suggest ongoing management of PJPW in protected areas should not focus on restoration of historical stand structure and composition, as done in PPF. Instead, management should emphasize leaving naturally occurring processes unimpaired. These include disturbances such as stand-replacing fire and native insect outbreaks that historically led to varied spatial and temporal stand composition and structure. However, active management may be needed when modern anthropogenic factors have potential to substantially alter key processes, e.g., if increasing cover of invasive plants such as cheat grass (Bromus tectorum) is likely to change the historical fire regime. Also, management plans for adjacent vegetation types such as PPF, shrublands, and grasslands need to consider potential short- and long-term impacts on PJPW. Additional challenges to management of PJPW are likely to arise with further climate change.