Established Invasive Plant Species Monitoring Protocol: Pacific Island Network

Ainsworth, Alison; Jacobi, James; Loh, Rhonda; Christian, Julie; Yanger, Corie; Berkowitz, Paul

This document describes a protocol to monitor nonnative plant species that are established, but still rare in four focal terrestrial plant communities across five national parks within the Pacific Island Network. Nonnative plant species present a serious threat to Pacific Island ecosystems. Invasion by nonnative plants reduces native plant diversity and abundance, alters vegetation structure, and can lead to significant economic and cultural costs. Nonnative species that have a high potential to severely impact the integrity of terrestrial plant communities and biological diversity through competition and displacement are labeled “invasive.” Prevention of invasion or at least detecting invaders during the initial stages paired with rapid response is the most cost effective defense against invasive species. Once invasive species become established in focal plant communities, detailed distribution and abundance data are necessary to prioritize control efforts. Long-term monitoring of established nonnative plant species in focal terrestrial plant communities is critical for the effective management of these native ecosystems in PACN parks. These data aid in the identification of new invasive nonnative plant species within specific community types. Due to the high costs of invasive plant management, managers do not have sufficient funds to control all nonnative plant species within focal plant communities. Monitoring provides essential information about the frequency, distribution, and abundance of nonnative species, allowing them to assess changing threats to native ecosystems, formulate appropriate control strategies, and prioritize areas and species for management. Long-term monitoring allows resource managers to evaluate the efficacy of previous management actions such as herbicide treatments, biological controls, ungulate removal, and fencing. All PACN parks have made efforts to confront invasive plant species on some level (e.g., trail maintenance, habitat restoration, rare species management, ecosystem health), although to date, most invasive plant monitoring has been conducted in Hawaiian Island parks. Still, even within these parks invasive plant species monitoring has generally been limited to small spatial and temporal scales and focused primarily on invasive plant control efficacy. Each park will be surveyed once every five years, on a rotating basis, by a team of scientists and technicians who will report presence of nonnative plant species found in contiguous subplots along randomly located transects. In addition, for a select set of target species cover classes are assigned. Target species are identified prior to each field season with the assistance of park resource managers and will include all known invasives and any species currently controlled within the plant community. Fixed (permanent) and rotational (temporary) transects will be surveyed using a split panel design. This design allows for the use of permanent, fixed panel transects to detect temporal changes and temporary, rotational panel transects to assess status as well as increase spatial sampling over time. Together permanent and temporary transects provide greater ecological and statistical inference than either method alone. After each field season, the project lead will analyze these data and produce an annual report. Nonnative species richness and the frequency of each nonnative species are calculated from the presence/ absence data. Cover data aids managers with control prioritization and logistics and can provide a finer scale for detecting change over time. Data from the contiguous plots along each belt transect are used to generate thematic maps of nonnative plant distributions using GIS and provide additional information to resource managers who benefit from precise location data of nonnative species.

Established Invasive Plant Species Monitoring Protocol: Pacific Island Network

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