title: Root traits of New Zealand trees: Community-level responses to a soil fertility gradient, and plastic responses to nutrient availability

authors: Kramer-Walter, Kris Rushton

subjects: roots

abstract: The study of plant traits has great application for understanding plant distribution patterns and community assembly at a variety of scales. Roots are a vital component of plant water and nutrient uptake strategy, and yet root traits are not as well understood as leaf or stem traits. In this thesis I aimed to determine the relationships between seedling fine root, leaf, and stem traits of New Zealand tree species, and investigate whether these traits related to species‟ abundance along a soil fertility gradient. I also investigated how seedling traits compare with adult traits, and whether nutrient availability or method of fertiliser application affected seedling trait expression. To achieve these goals, I measured root, leaf, and stem traits on seedlings of 66 native tree species, and combined this with relative abundance data along a strong soil fertility gradient at Puketī forest. I used principle component analysis and ordination to assess the dimensionality of trait variation across species; and linear regressions to compare community-weighted mean (CWM) traits vs. a summarised axis of soil fertility. I also performed regression analysis between seedling traits and adult traits from the literature. To assess the effects of nutrient availability and application I grew four native tree species under three nutrient treatments: low, pulsed, and slow release. I used two-way ANOVA and co-efficient of variation analyses to determine the strength of responses to nutrient treatments.
Dry matter content was positively associated across leaves, roots, and stems, and negatively associated with root nitrogen concentration and relative growth rate, suggesting that at least as seedlings, traits associated with a fast or slow growth strategy are co-ordinated across organs. Root diameter and SRL were independent from this axis of fast-slow growth, suggesting that SRL does not have a direct effect on seedling growth rates and nutrient foraging. A third axis of variation was also identified, strongly influenced by root phosphorus and nitrogen concentrations, but was difficult to interpret. Regression of CWM traits vs. soil fertility showed that traits which comprised the fast-slow PCA axis co-varied strongly with soil fertility. Neither root diameter nor SRL were significantly related to soil fertility, supporting the conclusion that SRL is not adaptive to nutrient foraging ability. Seedling morphology traits are generally well correlated with adults, but tend to be oriented towards a more “acquisitive” growth strategy, suggesting that species may down-regulate their growth over ontogenetic development. The absence of correlation between SRL and soil fertility suggests that alternative root traits may be more applicable for understanding species foraging strategy.
Species‟ responses to the nutrient treatments differed for most traits. Root-to-shoot ratio, growth rate, and root nutrient concentrations responded strongly to nutrient availability, and morphological traits did not respond as strongly. Slow release and pulse treatments were typically similar, and both significantly different to low nutrient treatment. These results suggest that it is practical to compare morphological trait data between studies, provided plants are raised in environments conducive to growth, but that nutrient concentrations and biomass allocation traits can be strongly influenced by soil fertility.

text: Root traits of New Zealand trees: Community-level responses to a soil fertility gradient, and plastic responses to nutrient availability The study of plant traits has great application for understanding plant distribution patterns and community assembly at a variety of scales. Roots are a vital component of plant water and nutrient uptake strategy, and yet root traits are not as well understood as leaf or stem traits. In this thesis I aimed to determine the relationships between seedling fine root, leaf, and stem traits of New Zealand tree species, and investigate whether these traits related to species‟ abundance along a soil fertility gradient. I also investigated how seedling traits compare with adult traits, and whether nutrient availability or method of fertiliser application affected seedling trait expression. To achieve these goals, I measured root, leaf, and stem traits on seedlings of 66 native tree species, and combined this with relative abundance data along a strong soil fertility gradient at Puketī forest. I used principle component analysis and ordination to assess the dimensionality of trait variation across species; and linear regressions to compare community-weighted mean (CWM) traits vs. a summarised axis of soil fertility. I also performed regression analysis between seedling traits and adult traits from the literature. To assess the effects of nutrient availability and application I grew four native tree species under three nutrient treatments: low, pulsed, and slow release. I used two-way ANOVA and co-efficient of variation analyses to determine the strength of responses to nutrient treatments.
Dry matter content was positively associated across leaves, roots, and stems, and negatively associated with root nitrogen concentration and relative growth rate, suggesting that at least as seedlings, traits associated with a fast or slow growth strategy are co-ordinated across organs. Root diameter and SRL were independent from this axis of fast-slow growth, suggesting that SRL does not have a direct effect on seedling growth rates and nutrient foraging. A third axis of variation was also identified, strongly influenced by root phosphorus and nitrogen concentrations, but was difficult to interpret. Regression of CWM traits vs. soil fertility showed that traits which comprised the fast-slow PCA axis co-varied strongly with soil fertility. Neither root diameter nor SRL were significantly related to soil fertility, supporting the conclusion that SRL is not adaptive to nutrient foraging ability. Seedling morphology traits are generally well correlated with adults, but tend to be oriented towards a more “acquisitive” growth strategy, suggesting that species may down-regulate their growth over ontogenetic development. The absence of correlation between SRL and soil fertility suggests that alternative root traits may be more applicable for understanding species foraging strategy.
Species‟ responses to the nutrient treatments differed for most traits. Root-to-shoot ratio, growth rate, and root nutrient concentrations responded strongly to nutrient availability, and morphological traits did not respond as strongly. Slow release and pulse treatments were typically similar, and both significantly different to low nutrient treatment. These results suggest that it is practical to compare morphological trait data between studies, provided plants are raised in environments conducive to growth, but that nutrient concentrations and biomass allocation traits can be strongly influenced by soil fertility.

year: 2015

title: Processing, microstructure and mechanical properties of TiₓAlᵧ/Al₂O₃ and Al₂Ti₄C₂/TiₓAlᵧ/Al₂O₃/TiC composites

authors: Cai, Z.H.

abstract: The TiₓAlᵧ/Al₂O₃ metal-ceramic composites materials [TiₓAlᵧ is α-Ti(Al,O), Ti₃Al, or TiAl] and Al₂Ti₄C₂/TiₓAlᵧ/Al₂O₃/TiC ceramic-ceramic composites with different volume fractions of ceramic reinforcement phases were synthesized using a complex combination of high energy mechanical milling, thermal treatment and powder consolidation processes. The thermal treatment process included reactions between carbon and TiO₂, and between Al and TiO₂, TiO₃ or TiOₙC₁₋ₙ, which was produced by reacting TiO₂ and carbon. Heat treating C/TiO₂ composite powder produced pure TiO₃. Pure TiO could not be obtained by only increasing the carbon to TiO₂ ratio in the C/TiO₂ composite powder. Instead, TiOₙC₁₋ₙ solid solution was formed. Reaction kinetic studies showed that higher carbon to TiO₂ ratios accelerated the reaction due to refinement of the C/TiO₂ composite structure. Reactions between Al and TiOₙC₁₋ₙ formed Al₂Ti₄C₂/Al₂O₃ ceramic-ceramic composite. When the aluminum content of the starting Al/TiOₙC₁₋ₙ composite powders was increased, Al₂Ti₄C₂ still formed, but small amounts of Ti₃Al or TiAl also formed. Producing TiC from Al and TiOₙC₁₋ₙ reaction depended on the value of n in the TiOₙC₁₋ₙ phase. When n is small enough, TiC formed; otherwise TiC did not form.

This study found that fully dense matrix phase of TiₓAlᵧ/Al₂O₃ and Al₂Ti₄C2/TiₓAlᵧ/Al₂O₃/TiC formed after sintering at 1550°C. The Al₂O₃ particles became fully sintered when the composites were sintered at 1650°C but not at 1550°C. The Al₂O₃ particles in the α-Ti(Al,O) and Ti₃Al based composites had a high coarsening rate above 1550°C, indicating that the oxygen and Al diffusion rates of α-Ti(Al,O) and Ti₃Al are very high at these temperatures. The Al₂O₃ particles in TiAl based composites also had a high coarsening rate above 1550°C, caused by TiAl being liquid at these temperatures. The Al₂O₃ particles in the Al₂Ti₄C₂/TiₓAlᵧ/Al₂O₃/TiC based composites had a much lower coarsening rate because of the Al₂Ti₄C₂ matrix the lower oxygen content and high melting point decreases oxygen and aluminum mobility.

The size and volume fraction of Al₂O₃ particles in the composites strongly affected the mechanical properties of the TiₓAlᵧ and Al₂Ti₄C₂ based composites. Hardness of α-Ti(Al,O), Ti₃Al, and Al₂Ti₄C₂ based composites was 800-1600 VHN and hardness of TiAl based composites was 150-500 VHN. Bending strength of TiₓAlᵧ/Al₂O₃ composites was 105-230 MPa and bending strength of Al₂Ti₄C₂/TiₓAlᵧ/Al₂O₃/TiC based composites was 250-460 MPa. It appeared that 10 μm might be the critical size of Al₂O₃ particles. Below 10 μm bending strength dramatically improved with deceasing the Al₂O₃ particle size in the composites. The fracture toughness of these composites was 2-4.5MPa•m¹/². Composite hardness increased and bending strength decreased with increasing Al₂O₃ particle size and volume fraction.

text: Processing, microstructure and mechanical properties of TiₓAlᵧ/Al₂O₃ and Al₂Ti₄C₂/TiₓAlᵧ/Al₂O₃/TiC composites The TiₓAlᵧ/Al₂O₃ metal-ceramic composites materials [TiₓAlᵧ is α-Ti(Al,O), Ti₃Al, or TiAl] and Al₂Ti₄C₂/TiₓAlᵧ/Al₂O₃/TiC ceramic-ceramic composites with different volume fractions of ceramic reinforcement phases were synthesized using a complex combination of high energy mechanical milling, thermal treatment and powder consolidation processes. The thermal treatment process included reactions between carbon and TiO₂, and between Al and TiO₂, TiO₃ or TiOₙC₁₋ₙ, which was produced by reacting TiO₂ and carbon. Heat treating C/TiO₂ composite powder produced pure TiO₃. Pure TiO could not be obtained by only increasing the carbon to TiO₂ ratio in the C/TiO₂ composite powder. Instead, TiOₙC₁₋ₙ solid solution was formed. Reaction kinetic studies showed that higher carbon to TiO₂ ratios accelerated the reaction due to refinement of the C/TiO₂ composite structure. Reactions between Al and TiOₙC₁₋ₙ formed Al₂Ti₄C₂/Al₂O₃ ceramic-ceramic composite. When the aluminum content of the starting Al/TiOₙC₁₋ₙ composite powders was increased, Al₂Ti₄C₂ still formed, but small amounts of Ti₃Al or TiAl also formed. Producing TiC from Al and TiOₙC₁₋ₙ reaction depended on the value of n in the TiOₙC₁₋ₙ phase. When n is small enough, TiC formed; otherwise TiC did not form.

This study found that fully dense matrix phase of TiₓAlᵧ/Al₂O₃ and Al₂Ti₄C2/TiₓAlᵧ/Al₂O₃/TiC formed after sintering at 1550°C. The Al₂O₃ particles became fully sintered when the composites were sintered at 1650°C but not at 1550°C. The Al₂O₃ particles in the α-Ti(Al,O) and Ti₃Al based composites had a high coarsening rate above 1550°C, indicating that the oxygen and Al diffusion rates of α-Ti(Al,O) and Ti₃Al are very high at these temperatures. The Al₂O₃ particles in TiAl based composites also had a high coarsening rate above 1550°C, caused by TiAl being liquid at these temperatures. The Al₂O₃ particles in the Al₂Ti₄C₂/TiₓAlᵧ/Al₂O₃/TiC based composites had a much lower coarsening rate because of the Al₂Ti₄C₂ matrix the lower oxygen content and high melting point decreases oxygen and aluminum mobility.

The size and volume fraction of Al₂O₃ particles in the composites strongly affected the mechanical properties of the TiₓAlᵧ and Al₂Ti₄C₂ based composites. Hardness of α-Ti(Al,O), Ti₃Al, and Al₂Ti₄C₂ based composites was 800-1600 VHN and hardness of TiAl based composites was 150-500 VHN. Bending strength of TiₓAlᵧ/Al₂O₃ composites was 105-230 MPa and bending strength of Al₂Ti₄C₂/TiₓAlᵧ/Al₂O₃/TiC based composites was 250-460 MPa. It appeared that 10 μm might be the critical size of Al₂O₃ particles. Below 10 μm bending strength dramatically improved with deceasing the Al₂O₃ particle size in the composites. The fracture toughness of these composites was 2-4.5MPa•m¹/². Composite hardness increased and bending strength decreased with increasing Al₂O₃ particle size and volume fraction.

year: 2002

title: Harakeke: Enhancing Māori Student Engagement and Achievement in a Mainstream Primary School

authors: Anderson, Diana

subjects: Harakeke

abstract: Ministry of Education research indicates that the inclusion of culture and te reo
Māori in teaching can help improve Māori student education. If students can find
the links between what is being taught and the relevance to their own lives then
information will be easier to retain. Research has also shown that environmental
education provides relevant learning that can connect students to their world.
Māori indigenous knowledge (IK) and environmental education (EE) share many
commonalities. One such similarity is the relationship between tangata (people)
and nature. While the sometimes destructive nature of this relationship has lead to
global environmental issues, this study explores the combination of IK and EE to
enhance Māori student engagement and achievement in a mainstream primary
school.
An intervention unit based on harakeke was designed delivered in a Year 5/6
boys' only class in a suburban mainstream primary school, over a 10 week period.
The environmental and socio-cultural significance of harakeke enabled a range of
kaupapa (themes) to be included in the unit. This included; eeling and how to
make and use a hinaki (eel/fish trap), karakia (prayer) and the relevance when
harvesting kai (food) and resources. Each kaupapa also provided the opportunity
for students to increase their te reo Māori vocabulary, with the introduction of
kaupapa specific words. The Māori kaupapa also enabled the students to view EE
from a Māori perspective, including the introduction of rahui - a form of
conservation.
The findings indicated that the incorporation of a Māori kaupapa strengthened
student engagement, improved student use of te reo Māori, improved the selfesteem
and confidence for some students, increased students' awareness of
harakeke and the value and versatility of the plant, and increased their awareness
from a Māori perspective on sustainable harvesting.
Bringing Māori kaupapa into the classroom allowed the classroom teacher, who
was Māori, the opportunity to share her own lived experiences of IK, as these are
passed down from generation to generation, and people are born into them. The
Page | iii
familiarity of whanau offered the teacher the opportunity to bring this concept into
the classroom and teach values that could flow into all curriculum areas while
strengthening relationships between the teacher and student, student and student
and teacher and student whanau.
This study has shown that both IK and EE, while each complex in their own right,
have the ability to provide a holistic curriculum approach that can lead to
engagement and achievement by Māori students in a mainstream school.

text: Harakeke: Enhancing Māori Student Engagement and Achievement in a Mainstream Primary School Ministry of Education research indicates that the inclusion of culture and te reo
Māori in teaching can help improve Māori student education. If students can find
the links between what is being taught and the relevance to their own lives then
information will be easier to retain. Research has also shown that environmental
education provides relevant learning that can connect students to their world.
Māori indigenous knowledge (IK) and environmental education (EE) share many
commonalities. One such similarity is the relationship between tangata (people)
and nature. While the sometimes destructive nature of this relationship has lead to
global environmental issues, this study explores the combination of IK and EE to
enhance Māori student engagement and achievement in a mainstream primary
school.
An intervention unit based on harakeke was designed delivered in a Year 5/6
boys' only class in a suburban mainstream primary school, over a 10 week period.
The environmental and socio-cultural significance of harakeke enabled a range of
kaupapa (themes) to be included in the unit. This included; eeling and how to
make and use a hinaki (eel/fish trap), karakia (prayer) and the relevance when
harvesting kai (food) and resources. Each kaupapa also provided the opportunity
for students to increase their te reo Māori vocabulary, with the introduction of
kaupapa specific words. The Māori kaupapa also enabled the students to view EE
from a Māori perspective, including the introduction of rahui - a form of
conservation.
The findings indicated that the incorporation of a Māori kaupapa strengthened
student engagement, improved student use of te reo Māori, improved the selfesteem
and confidence for some students, increased students' awareness of
harakeke and the value and versatility of the plant, and increased their awareness
from a Māori perspective on sustainable harvesting.
Bringing Māori kaupapa into the classroom allowed the classroom teacher, who
was Māori, the opportunity to share her own lived experiences of IK, as these are
passed down from generation to generation, and people are born into them. The
Page | iii
familiarity of whanau offered the teacher the opportunity to bring this concept into
the classroom and teach values that could flow into all curriculum areas while
strengthening relationships between the teacher and student, student and student
and teacher and student whanau.
This study has shown that both IK and EE, while each complex in their own right,
have the ability to provide a holistic curriculum approach that can lead to
engagement and achievement by Māori students in a mainstream school.

year: 2009