Animal pollination of plants is a crucial ecosystem service for maintaining global biodiversity and ecosystem function. High pollinator abundance and diversity can likewise improve the reproductive success of the plant community. Plant–pollinator interaction networks have the potential to identify dominant, specialist, and generalist pollinator species within a system, and their host plant counterparts. Understanding these relationships is paramount for buffering natural systems from biodiversity loss in a world where pollinator abundances continue to decline rapidly. San Bruno Mountain (SBM) in California, USA is one of the last natural, open spaces in the urban landscape of the northern San Francisco Peninsula. We conducted a series of timed meanders and vegetation surveys at eight sample sites within SBM (four grassland and four coastal scrub sites) to identify plant species prevalence and pollinator species visitation of flowering plants. We used nonmetric multidimensional scaling (NMDS), similarity percentage analysis, and bipartite networks to examine plant and pollinator species richness, community composition, and trophic interactions across the SBM landscape in grassland and coastal scrub habitats. We encountered a total of 59 pollinator and 135 plant species over the course of the study. While species richness did not vary significantly between vegetation types, the NMDS results revealed significant differences between grassland and coastal scrubland plant and pollinator community composition. The bipartite analyses identified generalist pollinators and plant host species as important contributors to the biodiversity of SBM due to the high numbers of interactions between these pollinator and plant taxa across the landscape. These results also highlight the conservation importance of specialist pollinators and their plant host plant taxa for maintaining high diversity and ecosystem integrity. In the future, adaptive restoration activities could be used at SBM and other similar open land habitats to bolster the abundance of native herbaceous flowering pollinator host plants in the area.

Biodiversity monitoring is a difficult and expensive activity that is chronically underfunded. Visual Encounter Surveys (VES) are a common monitoring tool for poikilothermic organisms in streams and rivers, but many species are challenging to detect with this method. Environmental DNA (eDNA) detection methods have been growing in popularity as a supplement or replacement for VES for aquatic species, but they are not yet widely adopted, in part due to perceived costs, a lack of understanding about their efficacy, and a lack of technical expertise. We implemented a paired VES and eDNA survey of 13 species (6 native and 7 invasive) in three rivers within and around Sequoia and Kings Canyon National Parks (SEKI). We found that species detection using eDNA methods was consistently higher compared to traditional snorkel VES, and eDNA was an accurate, cost-effective method for detecting biodiversity. Using eDNA and VES techniques, we were able to conduct a survey of aquatic biodiversity in areas within and neighboring the SEKI boundary. Our work highlights the potential for eDNA methods to be used in conjunction with traditional VES to minimize costs and improve capacity for resource management.

The estimation of year of germination based on saguaro cactus (Carnegiea gigantea) growth rates is essential for understanding population dynamics. To assess how habitat and climate interact to influence growth rate, we resurveyed 614 saguaro cacti on 11 historical study plots in Saguaro National Park (SNP), including the plots where classic saguaro age–height models were developed. We classified plots into four groups based on their topographic position (bajada or rocky slope) and park district (east or west), compared actual to predicted height distributions, assessed the distributions for (dis)similarity using the Jensen-Shannon distance, tested for significance with Fisher's exact test, and calculated growth rate adjustment factors with the Drezner method. We found that saguaro growth rates slowed significantly for three of the four combinations of topographic position and district from 1975 to 2014. Observed height class distributions differed significantly from the predicted for rocky slopes but not for bajada habitats. Variability in saguaro growth rates among populations in different habitats over a short distance through time may have scientific and ecological implications, including decreasing the accuracy of population age calculations and delaying the onset of flowering and branching. We encourage SNP to continue the ongoing long-term studies to quantify the resulting effects of climate change and to incorporate the results of this study into interpretative programs and literature.

Like many open habitats, sustainability of oak savannas in midwestern North America depends on periodic disturbances such as fires to curtail encroachment by tall woody plants. An uncertainty in restoring and sustaining oak savannas is how frequently fires must occur to maintain the groundlayer plant diversity savannas are known for and what levels of tree canopy and sapling layer encroachment trigger shifts in groundlayers. In an oak savanna undergoing restoration in northwestern Ohio, we examined how groundlayers changed with temporal variation in tree (≥10 cm in diameter) and sapling (<10 cm) layers and prescribed fires by remeasuring permanent plots up to 17 times from 1988 to 2021. Groundlayer cover was maximized when tree basal area was <13 m²/ha (35% tree canopy cover), there were fewer than 100 trees/ha, and fire had occurred since the previous growing season. Illustrating attrition in groundlayers above these thresholds, two-thirds of savanna groundlayer cover disappeared when tree density exceeded 100/ha and over 2 y passed without fires. Through savanna species persisting at low cover, species richness endured longer between fires (4+ years), doubled during periods with at least one fire in 3 y, and increased by a third when saplings were sparse (<80 stems/ha). Savanna groundlayers during the 34 y study fluctuated with intermittent increases and decreases associated with dynamics in trees, saplings, and time since fire. Although they require a major commitment because their benefits are so transient, frequent, low-severity prescribed fires appear capable of sustaining savanna groundlayer diversity indefinitely under prevailing conditions.

Live stakes are woody cuttings from wetland tree and shrub species that can root in moist soil. The use of live stakes in riparian and wetland restoration is becoming an increasingly popular technique because of relatively low costs and maintenance. However, the success of live stakes likely depends on the species, environmental conditions, and planting treatments. In particular, the benefit of artificial rooting hormone or weed control strategies have not been widely studied, particularly for eastern North American species. We performed a common garden experiment with 1800 live stakes of eight species commonly used in restoration, where stakes were randomly blocked by species and treatments, including herbicide application to control invasive plants and rooting hormone to encourage growth. We examined how the use of herbicide and rooting hormone, species, stake diameter, and planting depth of stakes affected live stake survival and growth. We found survival, growth, and response to treatments were species-dependent, and that buttonbush (Cephalanthus occidentalis), elderberry (Sambucus canadensis), and silky dogwood (Cornus obliqua) were the species with the greatest survival one year post-planting. The only species that benefited from treatments were red osier dogwood (Cornus sericea) and buttonbush, which had the best survival with rooting hormone, and silky dogwood, which had the best survival with both treatments. In addition, buttonbush showed significant clustering of surviving stakes, possibly indicating buttonbush might be most sensitive to differences in microhabitat conditions. Lastly, we provide an analysis to help conservation professionals gain insight into live stake survival, species selection, and best management practices.

Forest management has the potential to drive demographic shifts among woody plants in the forest understory, which may impact the success of nonnative species and can determine future trajectories of forest communities. Here, we consider the relationships between nonnative fruiting shrubs, frugivores, and forest management practices in a young mixed mesophilic hardwood forest, exploring how forest management influences both fruit production and bird-mediated fruit handling in nonnative shrubs within the forest understory. Specifically, we measured fruit production in the nonnative shrub, Rhamnus frangula, and handling of artificial fruit mimics within 1 ha forest plots subjected to one of three management treatments: (1) overstory thinning (thinning of the forest canopy trees by 20% using a mix of girdling and selective-felling), (2) overstory thinning coupled with nonnative shrub removal, or (3) unmanaged control. We found forest management to be a driver of both fruit production in Rhamnus frangula and fruit handling by birds in the forest understory, with higher productivity and rates of fruit handling in areas with overstory thinning relative to controls. These shifts in fruit availability and plant–animal interactions have the potential to serve as a pathway by which forest management may alter future forest communities, possibly promoting nonnative species such as Rhamnus frangula in the forest understory.