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.

Problematic plant monitoring in Arkansas Post National Memorial: 2006–2019

Managers are challenged with the impact of problematic plants, including exotic, invasive, and pest plant species. Information on the cover, distribution, and location of these plants is essential for developing risk-based approaches to managing these species. Based on surveys conducted in 2006, 2011, 2015, and 2019, Heartland Network staff and contractors identified a cumulative total of 28 potentially problematic plant taxa in Arkansas Post National Memorial. Of the 23 species found in 2019, we characterized 9 as very low frequency, 7 as low frequency, 5 as medium frequency, and 2 as high frequency. Cover of all species was low with a single species slightly exceeding a 1-acre threshold based on a midpoint estimate. Efforts to control the woody invasive black locust, Chinese privet, and hardy orange appear to have successfully reduced the cover of these plants across the Memorial Unit. Japanese stiltgrass may have been increasing as recently as 2015, but a combination of recent flooding and control efforts may have stemmed the spread of this invasive grass. Efforts to control localized patches of Chinaberry tree also appear to have reduced the cover of this species. Outside of the problematic species currently subject

Ligustrum sinense (Chinese privet).

A datasheet on Ligustrum sinense covering, as an economically important tree, its taxonomy, importance, silviculture, distribution, biology and ecology, uses, products and pests.

Effects of Chinese Privet on Bees and Their Vertical Distribution in Riparian Forests

Chinese privet (Ligustrum sinense Lour.), is known to negatively affect biodiversity near the ground in invaded forests by forming thick layers of non-native vegetation in the midstory. Whether these effects extend above the shrub layer into the canopy remains unclear. We sought to test this question by using flight-intercept traps (clear plastic panels attached to a white bucket) to sample bees at three heights (0.5, 5, and 15 m) in plots in which L. sinense had or had not been experimentally eliminated. Privet removal (i.e., restoration) resulted in significantly higher bee abundance, richness, and diversity than in invaded sites, but this effect was only observed at 0.5 m. In restored plots, bee diversity was generally higher at 5 and 15 m than near the forest floor, but there were no differences between traps at 5 and 15 m. Our findings show that bees will benefit from the removal of invasive shrubs near the forest floor but not in the canopy. Why bee diversity is higher in the canopy than near the ground in temperate deciduous forests remains unknown. Study Implications Chinese privet is recognized as one of the most problematic plants invading southeastern US forests where it has strong negative effects on native plant and insect diversity near the forest floor. This study tested the impacts of privet removal on the diversity of bees at three heights to determine whether the effects of removing privet extend into the canopies of temperate deciduous forests. The findings indicate that management activities aimed at eliminating Chinese privet will greatly increase bee activity near the forest floor but will not immediately impact bee numbers in the canopy.

The ecological effects of Chinese privet (Ligustrum sinense) invasion: a synthesis

Chinese privet (Ligustrum sinense Lour.) is a deciduous to evergreen shrub with an expansive nonnative global range. Control costs are often high, so land managers must carefully consider whether the plant’s potential negative effects warrant active management. To help facilitate this decision-making process, we reviewed and synthesized the literature on the potential ecological effects of L. sinense invasion. We also identified research gaps in need of further study. We found ample evidence of negative relationships between L. sinense invasion and native plant communities. While observational studies are not able to confirm whether L. sinense is driving these relationships, experimental evidence suggests that there is a cause–effect relationship. Of particular concern is the possibility that L. sinense could suppress forest regeneration and cause areas to transition from forest to L. sinense–dominated shrublands. Although this outcome would obviously impact a wide variety of wildlife species, empirical evidence of negative effects of L. sinense on wildlife are limited, and some species may actually benefit from the additional cover and foraging opportunities that L. sinense can provide. Further research on the potential effects of L. sinense invasion on large-scale forest structure and wildlife populations is needed. In areas where L. sinense invasion is a concern, evidence suggests early detection and management can mitigate control costs.