title: Temporal patterns in the stability, persistence and condition of stream macroinvertebrate communities: relationships with catchment land-use and regional climate

authors: Collier, Kevin J.

subjects: bioassessment

abstract: 1. A spatially-extensive data set of stream macroinvertebrate communities from 49 northern New Zealand sites sampled over a 10-year period was analysed to assess relationships between the environment (catchment land-cover, landscape position and regional-scale weather patterns), and (i) community persistence and stability based on the constancy of species occurrence (presence–absence) and abundance (per cent composition), respectively and (ii) the temporal variability of various community condition metrics.
2. No significant relationship was evident between community stability or persistence within sites and a gradient of increasing land-use stress (LUS) based on types of upstream land-cover, with interannual mean similarities at all sites falling within the standard deviations recorded at long-term reference sites. In contrast, condition metrics were inversely related to LUS. Land-use appeared to be a key factor influencing community composition among sites whereas climate influenced stability and persistence within sites.
3. Three response trajectories of community variability to increasing LUS were distinguished based on the coefficient of variation of mean interannual similarities, such that (i) persistence and stability appeared to be more variable at developed sites with low LUS and at sites with high stress relative to the variability experienced naturally, but similar to the natural range at intermediate levels of stress (‘sinusoidal response’); (ii) variability in Ephemeroptera, Plecoptera and Trichoptera metrics increased at low-to-moderate stress and then accelerated rapidly at highly developed sites (‘stepped-exponential response’) and (iii) variability in a pollution tolerance metric increased rapidly and then maintained a similar level of variability along the remaining stress gradient (‘plateau response’).
4. The results of this study have implications for biomonitoring approaches that assume high temporal persistence and stability of communities to define site impairment. Misclassifications caused by interannual variability could lead to misinterpretation of site condition, if conclusions are based on single annual surveys. Temporal variability in stability and persistence may help distinguish low levels of impairment where a predominantly healthy fauna experiences increased environmental fluctuations.

text: Temporal patterns in the stability, persistence and condition of stream macroinvertebrate communities: relationships with catchment land-use and regional climate 1. A spatially-extensive data set of stream macroinvertebrate communities from 49 northern New Zealand sites sampled over a 10-year period was analysed to assess relationships between the environment (catchment land-cover, landscape position and regional-scale weather patterns), and (i) community persistence and stability based on the constancy of species occurrence (presence–absence) and abundance (per cent composition), respectively and (ii) the temporal variability of various community condition metrics.
2. No significant relationship was evident between community stability or persistence within sites and a gradient of increasing land-use stress (LUS) based on types of upstream land-cover, with interannual mean similarities at all sites falling within the standard deviations recorded at long-term reference sites. In contrast, condition metrics were inversely related to LUS. Land-use appeared to be a key factor influencing community composition among sites whereas climate influenced stability and persistence within sites.
3. Three response trajectories of community variability to increasing LUS were distinguished based on the coefficient of variation of mean interannual similarities, such that (i) persistence and stability appeared to be more variable at developed sites with low LUS and at sites with high stress relative to the variability experienced naturally, but similar to the natural range at intermediate levels of stress (‘sinusoidal response’); (ii) variability in Ephemeroptera, Plecoptera and Trichoptera metrics increased at low-to-moderate stress and then accelerated rapidly at highly developed sites (‘stepped-exponential response’) and (iii) variability in a pollution tolerance metric increased rapidly and then maintained a similar level of variability along the remaining stress gradient (‘plateau response’).
4. The results of this study have implications for biomonitoring approaches that assume high temporal persistence and stability of communities to define site impairment. Misclassifications caused by interannual variability could lead to misinterpretation of site condition, if conclusions are based on single annual surveys. Temporal variability in stability and persistence may help distinguish low levels of impairment where a predominantly healthy fauna experiences increased environmental fluctuations.

year: 2007

title: Advancing tephrochronology as a global dating tool: applications in volcanology, archaeology, and palaeoclimatic research

authors: Lane, C.S.

abstract: Layers of far-travelled volcanic ash (tephra) from explosive volcanic eruptions provide stratigraphic and numerical dating horizons in sedimentary and volcanic sequences. Such tephra layers may be dispersed over tens to thousands of kilometres from source, reaching far beyond individual volcanic regions. Tephrochronology is consequently a truly global dating tool, with applications increasingly widespread across a range of Quaternary and geoscience disciplines. This special issue of the International Focus Group on Tephrochronology and Volcanism (INTAV) showcases some of the many recent advances in tephrochronology, from methodological developments to diverse applications across volcanological, archaeological, and palaeoclimatological research.

text: Advancing tephrochronology as a global dating tool: applications in volcanology, archaeology, and palaeoclimatic research Layers of far-travelled volcanic ash (tephra) from explosive volcanic eruptions provide stratigraphic and numerical dating horizons in sedimentary and volcanic sequences. Such tephra layers may be dispersed over tens to thousands of kilometres from source, reaching far beyond individual volcanic regions. Tephrochronology is consequently a truly global dating tool, with applications increasingly widespread across a range of Quaternary and geoscience disciplines. This special issue of the International Focus Group on Tephrochronology and Volcanism (INTAV) showcases some of the many recent advances in tephrochronology, from methodological developments to diverse applications across volcanological, archaeological, and palaeoclimatological research.

year: 2017

title: Communicating towards justice in ‘The Subaltern Voice’ (TSV)

authors: Humphries, Maria

subjects: subaltern

abstract: We write with a voice of the marginalised in mind, as both marginalised women scholars writing from a critical perspective on human organisation and as privileged human beings with concern for those more dangerously excluded from The Master’s House. The voice we raise does not plead for assimilation into circumstances as they are. It calls for radical change. Our ideas originate in research with Māori women accountants employed in organisations expressing commitment to Māori involvement. From that research we learned that aspiring to bicultural ways of being in a context prematurely deemed post-colonial is fraught with risks of co-option and unintentional collusion. Accordingly we are committed to further exposing neo-colonialism and to experiment with The Subaltern Voice (TSV) as a heuristic for this work. Asking what might be said in TSV that is different from what can be said in more commonly heard voices calling for inclusion has brought us to new thoughts about our own engagement with ‘The Empire’. Not only as it continues to colonise Māori locally and indigenous peoples globally, but from the myriad of places we take our positions to speak, sometimes ‘from the margins’ and other times from within the relative comforts of The Master’s House.

text: Communicating towards justice in ‘The Subaltern Voice’ (TSV) We write with a voice of the marginalised in mind, as both marginalised women scholars writing from a critical perspective on human organisation and as privileged human beings with concern for those more dangerously excluded from The Master’s House. The voice we raise does not plead for assimilation into circumstances as they are. It calls for radical change. Our ideas originate in research with Māori women accountants employed in organisations expressing commitment to Māori involvement. From that research we learned that aspiring to bicultural ways of being in a context prematurely deemed post-colonial is fraught with risks of co-option and unintentional collusion. Accordingly we are committed to further exposing neo-colonialism and to experiment with The Subaltern Voice (TSV) as a heuristic for this work. Asking what might be said in TSV that is different from what can be said in more commonly heard voices calling for inclusion has brought us to new thoughts about our own engagement with ‘The Empire’. Not only as it continues to colonise Māori locally and indigenous peoples globally, but from the myriad of places we take our positions to speak, sometimes ‘from the margins’ and other times from within the relative comforts of The Master’s House.

year: 2009