Long-Term Suppression of Hardwood Regeneration by Chinese Privet (Ligustrum sinense)

Native hardwood regeneration in the southeast United States is hindered by repeat disturbance events and the presence of invasive species. Our study aimed to determine the ability of native species in an unmanaged urban forest fragment to persist following high winds from hurricane Gustav in 2008 and subsequent salvage logging. In 2009, researchers estimated the density and composition of the regeneration and overstory trees as well as percent crown cover of invasive Chinese privet. Percent Chinese privet cover was visibly high, leading them to believe it may be inhibiting native hardwood establishment. Ten years later in 2019, we returned to the plots to take repeat measurements. Forest composition remains the same and privet crown cover remains high. There has been no increase in regenerating individuals, and overstory trees per hectare and basal area remains low. These results confirm that the heavy Chinese privet presence is persistent long term and will require management to promote reproduction of native overstory tree species.

Changes in forest composition and associated biophysical climate feedbacks across boreal North America

Deciduous tree cover is expected to increase in North American boreal forests with climate warming and wildfire occurrence. This shift in composition can generate biophysical cooling effects via increased land surface albedo. Here we use newly derived maps of continuous tree canopy and fractional deciduous cover to assess change over recent decades. We find on average a small net decrease in deciduous fraction cover from 2000 to 2015 across boreal North America, and from 1992 to 2015 across Canada, despite extensive fire disturbance that locally increased deciduous vegetation. We further find a near-neutral net biophysical change in radiative forcing across the domain due to relatively small net changes in albedo. Thus, while there have been widespread changes in forest composition over the past several decades across the domain, the net changes in composition and associated post-fire radiative forcing have not yet induced systematic negative feedbacks to climate warming.

Fuelwood Harvest and No Harvest Effects on Forest Composition, Structure, and Diversity of Arasbaran Forests—A Case Study

The impact of fuelwood harvesting on forest structure and composition is not clear, especially on the understudied and scarce Arasbaran forests in Iran. This research compared woody species density, species diversity, forest composition, and regeneration status in areas of continuous and ceased fuelwood harvesting in Arasbaran forests. We expected fuelwood harvesting to decrease stem density, species diversity, tree size (diameter at the breast height (DBH) and height), and shift composition away from preferred fuelwood species. We measured woody species size and frequency and identified species in three fuelwood harvest and three no harvest sites, with six sample plots (100 m × 50 m) per site. Results tended to show differences in composition, diversity, woody species height, and density. Carpinus orientalis, a preferred fuelwood species, tended to be more dominant in no harvest (importance values index (IVI) = 173.4) than harvest areas (IVI = 4.4). The diversity or richness of woody species tended to be higher in harvest (20 ± 1 species per ha) than in no harvest (14 ± 2 species per ha) areas, and other measures of diversity supported this trend as well. Harvest areas tended to also be characterized by shorter tree height and lower density of trees, a higher density of regeneration, and fewer small pole-sized trees than no harvest areas. Ongoing fuelwood harvests may further shift composition and structure away from no harvest area, compromising future fuelwood availability, but further detailed research is needed. Close to nature practices may be useful in sustaining fuelwood harvest areas and diversifying areas where fuelwood harvesting has ceased.

Forest Water Use is Increasingly Decoupled from Water Availability Even During Severe Drought

Context: Key to understanding forest water balances is the role of tree species regulating evapotranspiration (ET), but the synergistic impact of forest species composition, topography, and water availability on ET and how this shapes drought sensitivity across the landscape remains unclear.Objectives: Our aims were to quantify (1) the effect of forest composition and topography including elevation and hillslope gradients on the relationship between ET and water availability, and (2) whether the relationship has changed over time. Methods: We used remotely sensed Landsat and MODIS ET to quantify forest ET across the Blue Ridge ecoregion of the southeastern USA. Then quantified metrics describing ET responses to water availability and trends in responses over time and assessed how these metrics varied across elevation, hillslope, and forest composition gradients. Results: We demonstrated forest ET is becoming less constrained by water availability at the expense of lateral flow. Drought impacts on ET diverged along elevation and hillslope gradients, and that divergence was more pronounced with increasingly severe drought, indicating high elevation and drier, upslope regions tend to maintain ET rates even during extreme drought. We identified a decoupling of ET from water availability over time, and found this process was accelerated at higher elevations and in areas with more diffuse-porous trees. Conclusions: Given the large proportion of forests on the landscape distributed across high elevation and upslope positions, reductions in downslope water availability could be widespread, amplifying vulnerability of runoff, the health of downslope vegetation, and aquatic biodiversity.

Agarwood Tree Characteristics based on Different Growing Habitat and Ecophysiological Attributes in the Papuan Tropical Forests

Understanding tropical forest characteristics, including forest derivative products such as agarwood, is pivotal. This study focused on perceiving an ideal habitat of the lowland tropical forest ecosystem of West Papua for agarwood-producing tree species. In further, this study identified a close association of biotic and abiotic characteristics to underpin agarwood-producing tree growth. Six sites in three different locations were established to ascertain forest composition and the associated insects. Soil samples were collected to analyze their physical and chemical properties using the Kjeldahl, the Walky and Black, and Atomic Absorption Spectrophotometry (AAS). In addition, temperature, relative humidity, and light intensity were measured. The results noticed two agarwood producing species, Gyrinops caudate and Aquilaria sp., found at an altitude of 400–402 masl in Manokwari, 200–300 masl in Teluk Wondama, and 167.7 masl in Teluk Bintuni. There were no significant differences in temperature, relative humidity, and light intensity. The soil cation exchange capacity was moderate in Manokwari, but it was low in Teluk Wondama and Teluk Bintuni. Total C-organic content in three research sites was classified as high. However, total N content in the three research sites was in the moderate category. The ideal habitat for agarwood in the West Papua forest is from the lowlands to the highlands. Environmental conditions that support the growth of agarwood are moderate temperature, high humidity, and moderate light intensity. Soil fertility also affected the natural growth of agarwood trees. Keywords: abiotic, agarwood association, lowland tropical forest, soil characteristics

Understanding the Long-Term Impact of Bamboos on Secondary Forests: A Case for Bamboo Management in Southern Brazil

As secondary forests become more common around the world, it is essential to understand successional pathways to ensure their proper forest management. Despite optimism about secondary forests in terms of landscape restoration, the influence of invasive species on their development has been poorly explored. Here, forest plots in the Araucaria Forest, Southern Brazil, are used to compare forest dynamics over a 14-year period between unmanaged bamboo forest development (control) and the removal of bamboo. Six control plots (15 × 15 m) were monitored for all adult trees since 2007 alongside six adjacent removal plots; after the initial measurement of the control in 2007, all plots were measured bi-annually from 2010 to 2020. Comparisons were based on tree species diversity, composition, and structure parameters. Removal plots show a trend towards developing a forest composition with more secondary and late successional species while the control plots demonstrate succession restricted to the pioneer trees that regenerated immediately after bamboo die-off (2005–2006). Without the presence of bamboos, removal plots are mirroring the well-known successional pathway typical of the Araucaria Forest. Conversely, bamboos are effectively arresting successional development in the control, resulting in lower levels of diversity and less complex forest structure. For the first time, this study presents a direct analysis of the influence of bamboos on forest succession, providing evidence on which practices to manage bamboo forests can be developed so these secondary forests can fulfill their ecological and economic potential.