Biology subjects

Buckley, H. L.

Publications and source records attributed to Buckley, H. L..

5 recordsLinked to original sources

bioRxiv2021

Land-use history impacts spatial patterns and composition of woody plant species across a 35-hectare temperate forest plot

Land-use history is the template upon which contemporary plant and tree populations establish and interact with one another and exerts a legacy on the structure and dynamics of species assemblages and ecosystems. We use the first census (2010-2014) of a 35-ha forest-dynamics plot at the Harvard Forest in central Massachusetts to explore such legacies. The plot includes 108,632 live stems [≥] 1 cm in diameter (2215 individuals/ha) and 7,595 dead stems [≥] 5 cm in diameter. Fifty-one woody plant species were recorded in the plot, but two tree species-- Tsuga canadensis (eastern hemlock) and Acer rubrum (red maple)--and one shrub-- Ilex verticillata (winterberry)--comprised 56% of all stems. Live tree basal area averaged 42.25 m2/ha, of which 84% was represented by T. canadensis (14.0 m2/ ha), Quercus rubra (northern red oak; 9.6 m2/ ha), A. rubrum (7.2 m2/ ha) and Pinus strobus (eastern white pine; 4.4 m2/ ha). These same four species also comprised 78% of the live aboveground biomass, which averaged 245.2 Mg/ ha, and were significantly clumped at distances up to 50 m within the plot. Spatial distributions of A. rubrum and Q. rubra showed negative intraspecific correlations in diameters up to at least a 150-m spatial lag, likely indicative of competition for light in dense forest patches. Bivariate marked point-pattern analysis showed that T. canadensis and Q. rubra diameters were negatively associated with one another, indicating resource competition for light. Distribution and abundance of the common overstory species are predicted best by soil type, tree neighborhood effects, and two aspects of land-use history: when fields were abandoned in the late 19th century and the succeeding forest types recorded in 1908. In contrast, a history of intensive logging prior to 1950 and a damaging hurricane in 1938 appear to have had little effect on the distribution and abundance of present-day tree species.

ecology↗

bioRxiv2020

Modelling movement and landscape connectivity of New Zealand native birds in highly structured agroecosystem networks

Understanding how spatial heterogeneity affects movement and dispersal is critical for maintaining functional connectivity in agroecosystems. Least-cost path models are popular conservation tools to quantify the cost of a species dispersing though the landscapes. However, the variability of species in life history traits and landscape configurations can affect their space-use patterns and should be considered in agroecosystem management aiming to improve functional biodiversity. In this study, we modelled the connectivity properties of native species on a real agroecosystem landscape dominated by sheep and beef farming in north Canterbury, New Zealand, where the recovery of native bird population is desired. We chose two species to act as case studies that were contrasting in their mobility: New Zealand pigeon/kerer[u] (Hemiphaga novaeseelandiae; highly mobile) and southern brown kiwi/tokoeka (Apteryx australis; flightless). Networks of the least-cost paths of kerer[u] and tokoeka were constructed based on their habitat preferences and movement capacities, and we compared and contrasted the connectivity properties and network topographies of their networks. We then compared the network metrics of western side (higher density of forest) with the eastern side (dominated by grazed grassland) of the study area where the vegetation composition was vastly different for both species. The results shown three variables were the most important contributors to the structure of the dispersal networks: the nature of the matrix, spatial structure of vegetation patches, and the gap-crossing ability of the study species. Tokoeka were able to utilise smaller habitat patches as stepping-stones for dispersal, while kerer[u] can select more preferred habitat patches due to their high movement capacity. In contrast to the eastern side, we observed the western/forested side to have more, and stronger, links among habitat patches for both species, due to the presence of several large patches of native forest. Our work suggested that one size does not fit all, rather, conservation strategies that account for species life histories and movement traits are required to identify and preserve a connected ecological network.

ecology↗

bioRxiv2019

Non-production vegetation has a positive effect on ecological processes in agroecosystems

An ever-expanding human population, ongoing global climatic changes, and the spread of intensive farming practices is putting increasing pressure on agroecosystems and the inherent biodiversity they contain. Non-production vegetation elements, such as woody patches, riparian margins, and inter-crop and restoration plantings, are vital for conserving biodiversity in agroecosystems and are therefore considered key to sustaining the biotic and abiotic processes underpinning sustainable and resilient agroecosystems. Despite this critical role, there is a surprising lack of synthesis of which types of non-production vegetation elements drive and/or support ecological processes and the mechanisms by which this occurs. Using a systematic, quantitative literature review of 342 articles, we asked: what are the effects of non-production vegetation elements on agroecosystem processes and how are these processes measured within global agroecosystems? Our literature search focussed on the effects of non-production vegetation related to faunal, weed, disease, and abiotic processes. The majority (61%) of studies showed positive effects on ecological processes: non-production vegetation increased the presence, level or rate of the studied process. However, rather than directly measuring ecosystem processes, 83% of studies inferred processes using proxies for ecosystem function, such as biodiversity and soil physicochemical properties. Studies that directly measured non-production vegetation effects focussed on a limited number of vegetation effects including comparisons of vegetation types, farm-scale configuration, and proximity to vegetation. Moreover, studies directly measuring ecosystem processes were similarly limited, dominated by invertebrate biocontrol, predator and natural enemy spillover, animal movement, and ecosystem cycling. We identify research gaps and present a pathway for future research in understanding the ecosystem components and processes that build resilient, sustainable agroecosystems.

ecology↗

bioRxiv2018

Multivariate methods for testing hypotheses of temporal community dynamics

For ecological research to make important contributions towards understanding and managing temporally-variable global change processes, such as responses to land-use and climatic change, we must have effective and comparable ways to quantify and analyse compositional change over time in biological communities. These changes are the sum of local colonisation and extinction events, or changes in the biomass and relative abundance of taxa within and among samples. We conducted a quantitative review of currently available methods for the analysis of multivariate datasets collected at temporal intervals. This review identified the need for the application of quantitative, hypothesis-based approaches to understand temporal change in community composition, particularly for small datasets with less than 15 temporal replicates. To address this gap, we: (1) conceptually present how temporal patterns in community dynamics can be framed as specific, testable hypotheses; (2) provide three fully-worked case-studies, complete with R code, demonstrating multivariate analysis methods for temporal hypothesis testing and pattern visualisation; and (3) present a road map for testing specific, quantitative hypotheses relating to the underlying mechanisms of temporal community dynamics.

ecology↗

bioRxiv2017

When a foundation crumbles: forecasting forest community dynamics following the decline of the foundation species Tsuga canadensis

AbstractIn the forests of northeastern North America, invasive insects and pathogens are causing major declines in some tree species and a subsequent reorganization of associated forest communities. Using observations and experiments to investigate the consequences of such declines are hampered because trees are long-lived. Simulation models can provide a means to forecast possible futures based on different scenarios of tree species decline, death, and removal. Such modeling is particularly urgent for species such as eastern hemlock (Tsuga canadensis), a foundation species in many northeast forest regions that is declining due to the hemlock woolly adelgid (Adelges tsugae). Here, we used an individual-based forest simulator, SORTIE-ND, to forecast changes in forest communities in central Massachusetts over the next 200 years under a range of scenarios: a no-adelgid, status-quo scenario; partial resistance of hemlock to the adelgid; adelgid irruption and total hemlock decline over 25 years, adelgid irruption and salvage logging of hemlock trees; and two scenarios of preemptive logging of hemlock and hemlock/white pine.We applied the model to six study plots comprising a range of initial species mixtures, abundances, and levels of hemlock dominance. Simulations indicated that eastern white pine, and to a lesser extent black birch and American beech, would gain most in relative abundance and basal area following hemlock decline. The relative dominance of these species depended on initial conditions and the amount of hemlock mortality, and their combined effect on neighborhood-scale community dynamics. Simulated outcomes were little different whether hemlock died out gradually due to the adelgid or disappeared rapidly following logging. However, if eastern hemlock were to become partially resistant to the adelgid, hemlock would be able to retain its dominance despite substantial losses of basal area. Our modeling highlights the complexities associated with secondary forest succession due to ongoing hemlock decline and loss. We emphasize the need both for a precautionary approach in deciding between management intervention or simply doing nothing in these declining hemlock forests, and for clear aims and understanding regarding desired community- and ecosystem-level outcomes.

ecology↗