Proportionate spatial sampling and equal-time sampling of mobile animals: A dilemma for inferring areal dependence

R. Mac Nally, Gregory Horrocks

    Research output: Contribution to journalArticle

    21 Citations (Scopus)

    Abstract

    Patch or island area is one of the most frequently used variables for inference in conservation biology and biogeography, and is often used in ecological applications. Given that all of these disciplines deal with large spatial scales, exhaustive censusing is not often possible, especially when there are large numbers of patches (e.g. for replication and control purposes). Therefore, data for patches or islands are usually collected by sampling. We argue that if area is to be used as an inferential factor, then the objects under study (i.e. the patches) must be characterized on an areal basis. This necessarily means that fixed-area sampling is inadequate (e.g. a single standard quadrat or transect set within patches irrespective of the patch area) and that some form of area-proportionate sampling is needed (e.g. a fixed areal proportion of each patch is surveyed by random allocation of standard quadrats across each patch). However, use of area-proportionate sampling is not usually dissociated from the increased temporal intensity of sampling that arises from using this approach. The dilemma we see is deciding how much of the area-specificity of variables such as species richness, rare-species indices or probabilities of occurrence of individual species is related to the area-proportionate survey protocol and how much is due to the temporal intensity of surveys.
    We undertook a study in which we balanced temporal and spatial effects by increasing the time spent surveying smaller patches of vegetation to account for the area-ratio difference. The estimated species richness of birds of the
    box–ironbark system of central Victoria, Australia, was found to depend strongly upon area when area-proportionate sampling alone was performed. When time-balancing was imposed upon area-proportionate sampling, the differences between smaller (10-ha) and larger (40-ha) areas were much reduced or effectively disappeared. We show that species found in the additional surveys used to conduct the time-balancing were significantly less abundant than
    species recorded in area-proportionate sampling. This effect is probably most severe for mobile animals, but may emerge in other forms of sampling.
    Original languageEnglish
    Pages (from-to)405-415
    Number of pages11
    JournalAustral Ecology
    Volume27
    Issue number4
    DOIs
    Publication statusPublished - 2002

    Fingerprint

    animal
    sampling
    animals
    Victoria (Australia)
    species richness
    species diversity
    rare species
    biogeography
    surveying
    transect
    bird
    Biological Sciences
    vegetation
    birds
    effect

    Cite this

    @article{79dbabbb2c0a4a5abd645f92746533e5,
    title = "Proportionate spatial sampling and equal-time sampling of mobile animals: A dilemma for inferring areal dependence",
    abstract = "Patch or island area is one of the most frequently used variables for inference in conservation biology and biogeography, and is often used in ecological applications. Given that all of these disciplines deal with large spatial scales, exhaustive censusing is not often possible, especially when there are large numbers of patches (e.g. for replication and control purposes). Therefore, data for patches or islands are usually collected by sampling. We argue that if area is to be used as an inferential factor, then the objects under study (i.e. the patches) must be characterized on an areal basis. This necessarily means that fixed-area sampling is inadequate (e.g. a single standard quadrat or transect set within patches irrespective of the patch area) and that some form of area-proportionate sampling is needed (e.g. a fixed areal proportion of each patch is surveyed by random allocation of standard quadrats across each patch). However, use of area-proportionate sampling is not usually dissociated from the increased temporal intensity of sampling that arises from using this approach. The dilemma we see is deciding how much of the area-specificity of variables such as species richness, rare-species indices or probabilities of occurrence of individual species is related to the area-proportionate survey protocol and how much is due to the temporal intensity of surveys.We undertook a study in which we balanced temporal and spatial effects by increasing the time spent surveying smaller patches of vegetation to account for the area-ratio difference. The estimated species richness of birds of thebox–ironbark system of central Victoria, Australia, was found to depend strongly upon area when area-proportionate sampling alone was performed. When time-balancing was imposed upon area-proportionate sampling, the differences between smaller (10-ha) and larger (40-ha) areas were much reduced or effectively disappeared. We show that species found in the additional surveys used to conduct the time-balancing were significantly less abundant thanspecies recorded in area-proportionate sampling. This effect is probably most severe for mobile animals, but may emerge in other forms of sampling.",
    author = "{Mac Nally}, R. and Gregory Horrocks",
    note = "Cited By :19 Export Date: 6 June 2017",
    year = "2002",
    doi = "10.1046/j.1442-9993.2002.01194.x",
    language = "English",
    volume = "27",
    pages = "405--415",
    journal = "Austral Ecology",
    issn = "1442-9985",
    publisher = "Wiley-Blackwell",
    number = "4",

    }

    Proportionate spatial sampling and equal-time sampling of mobile animals: A dilemma for inferring areal dependence. / Mac Nally, R.; Horrocks, Gregory.

    In: Austral Ecology, Vol. 27, No. 4, 2002, p. 405-415.

    Research output: Contribution to journalArticle

    TY - JOUR

    T1 - Proportionate spatial sampling and equal-time sampling of mobile animals: A dilemma for inferring areal dependence

    AU - Mac Nally, R.

    AU - Horrocks, Gregory

    N1 - Cited By :19 Export Date: 6 June 2017

    PY - 2002

    Y1 - 2002

    N2 - Patch or island area is one of the most frequently used variables for inference in conservation biology and biogeography, and is often used in ecological applications. Given that all of these disciplines deal with large spatial scales, exhaustive censusing is not often possible, especially when there are large numbers of patches (e.g. for replication and control purposes). Therefore, data for patches or islands are usually collected by sampling. We argue that if area is to be used as an inferential factor, then the objects under study (i.e. the patches) must be characterized on an areal basis. This necessarily means that fixed-area sampling is inadequate (e.g. a single standard quadrat or transect set within patches irrespective of the patch area) and that some form of area-proportionate sampling is needed (e.g. a fixed areal proportion of each patch is surveyed by random allocation of standard quadrats across each patch). However, use of area-proportionate sampling is not usually dissociated from the increased temporal intensity of sampling that arises from using this approach. The dilemma we see is deciding how much of the area-specificity of variables such as species richness, rare-species indices or probabilities of occurrence of individual species is related to the area-proportionate survey protocol and how much is due to the temporal intensity of surveys.We undertook a study in which we balanced temporal and spatial effects by increasing the time spent surveying smaller patches of vegetation to account for the area-ratio difference. The estimated species richness of birds of thebox–ironbark system of central Victoria, Australia, was found to depend strongly upon area when area-proportionate sampling alone was performed. When time-balancing was imposed upon area-proportionate sampling, the differences between smaller (10-ha) and larger (40-ha) areas were much reduced or effectively disappeared. We show that species found in the additional surveys used to conduct the time-balancing were significantly less abundant thanspecies recorded in area-proportionate sampling. This effect is probably most severe for mobile animals, but may emerge in other forms of sampling.

    AB - Patch or island area is one of the most frequently used variables for inference in conservation biology and biogeography, and is often used in ecological applications. Given that all of these disciplines deal with large spatial scales, exhaustive censusing is not often possible, especially when there are large numbers of patches (e.g. for replication and control purposes). Therefore, data for patches or islands are usually collected by sampling. We argue that if area is to be used as an inferential factor, then the objects under study (i.e. the patches) must be characterized on an areal basis. This necessarily means that fixed-area sampling is inadequate (e.g. a single standard quadrat or transect set within patches irrespective of the patch area) and that some form of area-proportionate sampling is needed (e.g. a fixed areal proportion of each patch is surveyed by random allocation of standard quadrats across each patch). However, use of area-proportionate sampling is not usually dissociated from the increased temporal intensity of sampling that arises from using this approach. The dilemma we see is deciding how much of the area-specificity of variables such as species richness, rare-species indices or probabilities of occurrence of individual species is related to the area-proportionate survey protocol and how much is due to the temporal intensity of surveys.We undertook a study in which we balanced temporal and spatial effects by increasing the time spent surveying smaller patches of vegetation to account for the area-ratio difference. The estimated species richness of birds of thebox–ironbark system of central Victoria, Australia, was found to depend strongly upon area when area-proportionate sampling alone was performed. When time-balancing was imposed upon area-proportionate sampling, the differences between smaller (10-ha) and larger (40-ha) areas were much reduced or effectively disappeared. We show that species found in the additional surveys used to conduct the time-balancing were significantly less abundant thanspecies recorded in area-proportionate sampling. This effect is probably most severe for mobile animals, but may emerge in other forms of sampling.

    U2 - 10.1046/j.1442-9993.2002.01194.x

    DO - 10.1046/j.1442-9993.2002.01194.x

    M3 - Article

    VL - 27

    SP - 405

    EP - 415

    JO - Austral Ecology

    JF - Austral Ecology

    SN - 1442-9985

    IS - 4

    ER -