title: Preliminary estimates of mass-loss rates, changes in stable isotope composition, and invertebrate colonisation of evergreen and deciduous leaves in a Waikato, New Zealand, stream.

authors: Hicks, Brendan J.

subjects: mass loss

abstract: Rates of mass loss are important in the choice of tree species used in riparian rehabilitation because leaves that break down fast should contribute to stream food-webs more rapidly than leaves that break down more slowly. To examine comparative mass-loss rates of some native evergreen and introduced deciduous trees in a New Zealand stream, fallen leaves were incubated in bags with 2 x 3 mm mesh openings. The native trees were mahoe (Melicytus ramiflorus), kahikatea (Dacrycarpus dacrydioides), silver beech (Nothofagus menziesii), rewarewa (Knightia excelsa), tawa (Beilschmiedia tawa), and the introduced trees were silver birch (Betula pendula) and alder (Alnus glutinosa). The leaf bags were left in the Mangaotama Stream for 28 days from mid April to mid May 1995 when mean water temperature was 14.5deg.C, giving a total of 406 degree days. Rates of mass loss followed the sequence: mahoe > silver birch > alder > kahikatea > silver beech > rewarewa > tawa. Mean mass-loss rate for mahoe, assuming a negative exponential model, was 0.0507 k day-1 (0.00350 k (degree day)-1), and for tawa was 0.0036 k day-1 (0.00025 k (degree day)-1). C:N ratio decreased on average from 45:1 to 35:1, and d15N increased between 0.7 and 3.0[[perthousand]] (1.8 +/- 0.41[[perthousand]], mean +/-1 standard error), excluding kahikatea. Changes in d13C were smaller and not consistent in direction. Biomass of invertebrates was greatest in bags that had lost 25-45% of their initial leaf biomass.

text: Preliminary estimates of mass-loss rates, changes in stable isotope composition, and invertebrate colonisation of evergreen and deciduous leaves in a Waikato, New Zealand, stream. Rates of mass loss are important in the choice of tree species used in riparian rehabilitation because leaves that break down fast should contribute to stream food-webs more rapidly than leaves that break down more slowly. To examine comparative mass-loss rates of some native evergreen and introduced deciduous trees in a New Zealand stream, fallen leaves were incubated in bags with 2 x 3 mm mesh openings. The native trees were mahoe (Melicytus ramiflorus), kahikatea (Dacrycarpus dacrydioides), silver beech (Nothofagus menziesii), rewarewa (Knightia excelsa), tawa (Beilschmiedia tawa), and the introduced trees were silver birch (Betula pendula) and alder (Alnus glutinosa). The leaf bags were left in the Mangaotama Stream for 28 days from mid April to mid May 1995 when mean water temperature was 14.5deg.C, giving a total of 406 degree days. Rates of mass loss followed the sequence: mahoe > silver birch > alder > kahikatea > silver beech > rewarewa > tawa. Mean mass-loss rate for mahoe, assuming a negative exponential model, was 0.0507 k day-1 (0.00350 k (degree day)-1), and for tawa was 0.0036 k day-1 (0.00025 k (degree day)-1). C:N ratio decreased on average from 45:1 to 35:1, and d15N increased between 0.7 and 3.0[[perthousand]] (1.8 +/- 0.41[[perthousand]], mean +/-1 standard error), excluding kahikatea. Changes in d13C were smaller and not consistent in direction. Biomass of invertebrates was greatest in bags that had lost 25-45% of their initial leaf biomass.

year: 1999-06-01

title: Protogynous sex change in sexually immature spotty wrasse (Notolabrus celidotus)

authors: Hamer, Tessa Ellen

subjects: Aquaculture

abstract: One of the most unique forms of sexual plasticity can be witnessed in sequentially hermaphroditic fish, which begin as one sex and change to another at some stage in their lifecycle. The endemic protogynous spotty wrasse (Notolabrus Celidotus), has historically been considered monandric although two male morphs appear to exist. To date the majority of research has focused on sexually mature females that are changing sex to become terminal phase males. The current study seeks to describe sex change in sexually immature females that are transitioning to become initial phase males. This was achieved through analysis of gonadal histology as well as expression of three key sex differentiation related genes (amh, dmrt1 and cyp19a1a). Fish (n=141) were caught from the Tauranga Harbour ranging in size from 52-270 mm TL from May-June 2022. The smallest transitional fish identified was 52 mm TL and the smallest IP male detected in this study were 72 mm TL, indicating IP male spotty wrasse likely reach sexual maturity at a much earlier and smaller developmental stage than previously realised. Expression of amh and dmrt1 showed a clear male-bias across sex change, with the former being upregulated in early sex change. The aromatase gene, cyp19a1a showed an overall female-biased expression pattern despite having some unexpected upregulation in the mid stages of sex change. The results supported previous reports that all juvenile spotty wrasse are female first before some individuals undergo pre-maturational sex change to become IP males. Having clarified the process of sex change leading to IP male formation and considering data from other studies of IP and TP testicular structure in this species, it seems no longer tenable to consider them monandric.

text: Protogynous sex change in sexually immature spotty wrasse (Notolabrus celidotus) One of the most unique forms of sexual plasticity can be witnessed in sequentially hermaphroditic fish, which begin as one sex and change to another at some stage in their lifecycle. The endemic protogynous spotty wrasse (Notolabrus Celidotus), has historically been considered monandric although two male morphs appear to exist. To date the majority of research has focused on sexually mature females that are changing sex to become terminal phase males. The current study seeks to describe sex change in sexually immature females that are transitioning to become initial phase males. This was achieved through analysis of gonadal histology as well as expression of three key sex differentiation related genes (amh, dmrt1 and cyp19a1a). Fish (n=141) were caught from the Tauranga Harbour ranging in size from 52-270 mm TL from May-June 2022. The smallest transitional fish identified was 52 mm TL and the smallest IP male detected in this study were 72 mm TL, indicating IP male spotty wrasse likely reach sexual maturity at a much earlier and smaller developmental stage than previously realised. Expression of amh and dmrt1 showed a clear male-bias across sex change, with the former being upregulated in early sex change. The aromatase gene, cyp19a1a showed an overall female-biased expression pattern despite having some unexpected upregulation in the mid stages of sex change. The results supported previous reports that all juvenile spotty wrasse are female first before some individuals undergo pre-maturational sex change to become IP males. Having clarified the process of sex change leading to IP male formation and considering data from other studies of IP and TP testicular structure in this species, it seems no longer tenable to consider them monandric.

year: 2023

title: Dendroarchaeology in New Zealand: extending the range of archaeologically useful species beyond kauri (Agathis australis)

authors: Boswijk, Gretel

abstract: Accurately establishing calendar dates for Māori wooden objects would place them in a secure temporal context and enable aspects of manufacturing and use to be explored within and between sites, and across time. Dendrochronology has the potential to produce accurate and precise calendar dates for wooden artefacts but in New Zealand application of this technique to Māori cultural material is limited as there is almost no overlap between wood species found in archaeological contexts and tree-species with proven suitability for tree-ring dating. Here we identify five archaeologically-useful species – kahikatea (Dacrycarpus dacrydioides), matai (Prumnopitys taxifolia), miro (Prumnopitys ferruginea), rimu (Dacrydium cupressinum) and totara (Podocarpus totara) – and assess their potential for dendrochronology. Of these, matai, miro and totara are identified as species that should be the subject of further comprehensive dendrochronological investigation.

text: Dendroarchaeology in New Zealand: extending the range of archaeologically useful species beyond kauri (Agathis australis) Accurately establishing calendar dates for Māori wooden objects would place them in a secure temporal context and enable aspects of manufacturing and use to be explored within and between sites, and across time. Dendrochronology has the potential to produce accurate and precise calendar dates for wooden artefacts but in New Zealand application of this technique to Māori cultural material is limited as there is almost no overlap between wood species found in archaeological contexts and tree-species with proven suitability for tree-ring dating. Here we identify five archaeologically-useful species – kahikatea (Dacrycarpus dacrydioides), matai (Prumnopitys taxifolia), miro (Prumnopitys ferruginea), rimu (Dacrydium cupressinum) and totara (Podocarpus totara) – and assess their potential for dendrochronology. Of these, matai, miro and totara are identified as species that should be the subject of further comprehensive dendrochronological investigation.

year: 2019