title: Ecology of vascular epiphytes in urban forests with special reference to the shrub epiphyte Griselinia lucida

authors: Bryan, Catherine Louise

subjects: Epiphyte

abstract: This research investigated the ecology of vascular epiphytes and vines in the Waikato region of the North Island, and the water relations of the shrub hemiepiphyte Griselinia lucida. The main goal was to develop robust recommendations for the inclusion of epiphytic species in urban forest restoration projects. To achieve this, three broad questions were addressed: 1. How are vascular epiphytes and vines distributed throughout the nonurban and urban areas of the Waikato region, and how does this compare to other North Island areas? 2. Why are some epiphyte and vine species absent from urban Hamilton and what opportunities exist for their inclusion in restoration projects? 3. How does Griselinia lucida respond to desiccation stress and how does this compare to its congener G. littoralis? To investigate questions one and two, an ecological survey of the epiphyte communities on host trees in Waikato (n=649) and Taranaki (n=101) was conducted, alongside canopy microclimate monitoring in five Waikato sites. Results show that epiphyte and vine populations in Hamilton City forests represent only 55.2 % of the total Waikato species pool, and have a very low average of 0.8 epiphyte species per host. In contrast, the urban forests of Taranaki support 87.9 % of the local species pool and have an average of 5.5 species per host tree. The low diversity and abundance in urban Waikato can be primarily attributed to the alteration of canopy microclimates by edge effects. Mean temperature and vapour pressure deficits in Waikato were 1.9 °C and 1.1 kPa (respectively) higher in the canopy of small urban patches than the larger, nonurban forests. These warmer and drier conditions are speculated to be interrupting species accumulation and community formation processes. This phenomenom is not as pronounced in Taranaki which has larger trees and higher rainfall. Epiphyte diversity and abundance was also found to be associated with seed dispersal distances and the size, bark type, and architecture of host trees. To link the microclimate findings with physiological limitations of epiphytes and to address question three, a desiccation tolerance experiment was conducted on the shrub hemiepiphyte Griselinia lucida. Moderate and severe levels of desiccation stress were applied to seedlings of G. lucida and its terrestrial congener, G. littoralis. Both species endured over two months of drought with negligible mortality. In G. lucida, stomatal conductance reduced to zero, and leaf bulk elastic modulus reduced from 8.09 (±0.51) MPa in the control group to 3.66 (±0.61) MPa under severe stress. When compared to G. littoralis, G. lucida exhibited a more acute response to stress and recovered faster with rewatering. However, the overall response of each species was similar and both species can be classified as desiccation postponers. To summarise and combine the findings of this research with existing information on Griselinia lucida, a contribution to the New Zealand Biological Flora Series for this species is presented. Recommendations for the inclusion of epiphytes in restoration projects are presented. Reintroductions should use epiphyte and vine species that are appropriate for the conditions of the target forest, and focus on large host trees in relatively humid microclimates.

text: Ecology of vascular epiphytes in urban forests with special reference to the shrub epiphyte Griselinia lucida This research investigated the ecology of vascular epiphytes and vines in the Waikato region of the North Island, and the water relations of the shrub hemiepiphyte Griselinia lucida. The main goal was to develop robust recommendations for the inclusion of epiphytic species in urban forest restoration projects. To achieve this, three broad questions were addressed: 1. How are vascular epiphytes and vines distributed throughout the nonurban and urban areas of the Waikato region, and how does this compare to other North Island areas? 2. Why are some epiphyte and vine species absent from urban Hamilton and what opportunities exist for their inclusion in restoration projects? 3. How does Griselinia lucida respond to desiccation stress and how does this compare to its congener G. littoralis? To investigate questions one and two, an ecological survey of the epiphyte communities on host trees in Waikato (n=649) and Taranaki (n=101) was conducted, alongside canopy microclimate monitoring in five Waikato sites. Results show that epiphyte and vine populations in Hamilton City forests represent only 55.2 % of the total Waikato species pool, and have a very low average of 0.8 epiphyte species per host. In contrast, the urban forests of Taranaki support 87.9 % of the local species pool and have an average of 5.5 species per host tree. The low diversity and abundance in urban Waikato can be primarily attributed to the alteration of canopy microclimates by edge effects. Mean temperature and vapour pressure deficits in Waikato were 1.9 °C and 1.1 kPa (respectively) higher in the canopy of small urban patches than the larger, nonurban forests. These warmer and drier conditions are speculated to be interrupting species accumulation and community formation processes. This phenomenom is not as pronounced in Taranaki which has larger trees and higher rainfall. Epiphyte diversity and abundance was also found to be associated with seed dispersal distances and the size, bark type, and architecture of host trees. To link the microclimate findings with physiological limitations of epiphytes and to address question three, a desiccation tolerance experiment was conducted on the shrub hemiepiphyte Griselinia lucida. Moderate and severe levels of desiccation stress were applied to seedlings of G. lucida and its terrestrial congener, G. littoralis. Both species endured over two months of drought with negligible mortality. In G. lucida, stomatal conductance reduced to zero, and leaf bulk elastic modulus reduced from 8.09 (±0.51) MPa in the control group to 3.66 (±0.61) MPa under severe stress. When compared to G. littoralis, G. lucida exhibited a more acute response to stress and recovered faster with rewatering. However, the overall response of each species was similar and both species can be classified as desiccation postponers. To summarise and combine the findings of this research with existing information on Griselinia lucida, a contribution to the New Zealand Biological Flora Series for this species is presented. Recommendations for the inclusion of epiphytes in restoration projects are presented. Reintroductions should use epiphyte and vine species that are appropriate for the conditions of the target forest, and focus on large host trees in relatively humid microclimates.

year: 2011

title: Stochastic calculus analysis of optical time-of-flight range imaging and estimation of radial motion

authors: Streeter, Lee

subjects: Velocimetry

abstract: Time-of-flight range imaging is analyzed using stochastic calculus. Through a series of interpretations and simplifications, the stochastic model leads to two methods for estimating linear radial velocity: maximum likelihood estimation on the transition probability distribution between measurements, and a new method based on analyzing the measured correlation waveform and its first derivative. The methods are tested in a simulated motion experiment from (−40)−(+40)  m/s(−40)−(+40)  m/s, with data from a camera imaging an object on a translation stage. In tests maximum likelihood is slow and unreliable, but when it works it estimates the linear velocity with standard deviation of 1 m/s or better. In comparison the new method is fast and reliable but works in a reduced velocity range of (−20)−(+20)  m/s(−20)−(+20)  m/s with standard deviation ranging from 3.5 m/s to 10 m/s.

text: Stochastic calculus analysis of optical time-of-flight range imaging and estimation of radial motion Time-of-flight range imaging is analyzed using stochastic calculus. Through a series of interpretations and simplifications, the stochastic model leads to two methods for estimating linear radial velocity: maximum likelihood estimation on the transition probability distribution between measurements, and a new method based on analyzing the measured correlation waveform and its first derivative. The methods are tested in a simulated motion experiment from (−40)−(+40)  m/s(−40)−(+40)  m/s, with data from a camera imaging an object on a translation stage. In tests maximum likelihood is slow and unreliable, but when it works it estimates the linear velocity with standard deviation of 1 m/s or better. In comparison the new method is fast and reliable but works in a reduced velocity range of (−20)−(+20)  m/s(−20)−(+20)  m/s with standard deviation ranging from 3.5 m/s to 10 m/s.

year: 2017

title: Sweet as – the [ADJ + as] intensifier construction in Māori English/ Aotearoa English.

authors: Calude, Andreea S.

abstract: We introduce the Waikato Māori English Conversation (MEC) corpus, which consists of 43 dyadic conversations between 49 young adults who self-recorded informal conversations with close friends, in their own homes, with no topic of conversation specified (83 hours of dialogue; nearly 800,000 words). The resulting materials are colloquial and unstructured, capturing a wider range of pragmatic and stylistic modes than is possible in a standard sociolinguistic interview. Here, we report on one such feature, the [ADJ + as] construction, for example: ‘sorry some of the questions are like awkward as’ and ‘that caused a big as drama eh’. This intensifier construction has been identified as a distinctive New Zealand English (NZE) innovation, yet little has been written about this it. However, the Waikato MEC corpus presents the opportunity to analyse the construction in a more systematic manner and to fill existing gaps in analyses of Māori English grammar.

text: Sweet as – the [ADJ + as] intensifier construction in Māori English/ Aotearoa English. We introduce the Waikato Māori English Conversation (MEC) corpus, which consists of 43 dyadic conversations between 49 young adults who self-recorded informal conversations with close friends, in their own homes, with no topic of conversation specified (83 hours of dialogue; nearly 800,000 words). The resulting materials are colloquial and unstructured, capturing a wider range of pragmatic and stylistic modes than is possible in a standard sociolinguistic interview. Here, we report on one such feature, the [ADJ + as] construction, for example: ‘sorry some of the questions are like awkward as’ and ‘that caused a big as drama eh’. This intensifier construction has been identified as a distinctive New Zealand English (NZE) innovation, yet little has been written about this it. However, the Waikato MEC corpus presents the opportunity to analyse the construction in a more systematic manner and to fill existing gaps in analyses of Māori English grammar.

year: 2025