title: Distribution of nematodes in pasture soil across seasons and in combination with plant species and fertiliser application

authors: Rohan, Thamaraichelve

subjects: Soil Nematodes

abstract: The intensification of pastoral land use has increased with the use of fertilisers and the selection of highly productive pasture plant species to increase pasture production. When choosing a ryegrass cultivar infected with selected endophyte fungus, ploidy choices are vital for determining pasture production. Modern perennial ryegrass cultivars and White clover plant species mixtures and nitrogen fertiliser with seasonal climatic characteristics can influence the soil biodiversity and soil functions in a pastoral system. Pasture soils have unique systems with different soil faunal and microbial communities, including soil-dwelling nematodes and plant species composition. Nematodes have the potential to be indicators of soil processes and condition because of their abundance and ubiquity; they are simple multicellular animals, and highly diverse, taxonomically or functionally or both. They occupy multiple trophic positions in the soil food web and play a significant role in the decomposition of soil organic matter, the mineralisation of plant nutrients and nutrient cycling. The distribution of the nematode community can be influenced directly and indirectly by various management activities, including nitrogen fertiliser application and plant species, and the changing climatic conditions during seasons. The magnitude of these biotic and abiotic impacts was studied through analysis of the nematode community. Our study examined the impact on the nematode community of combinations of low and high rates of nitrogen application, clover presence and absence, and two different ranges of ryegrass cultivars, One50 (diploid AR37) and Base (tetraploid AR37), during two seasons. Sampling was carried out twice a year (autumn and spring) for two years (2013 and 2014) to investigate the distribution pattern between the seasons when host plants are actively growing and nematode activity is high. Soil samples were collected in the North Island of New Zealand from two sites in the Waikato and the Manawatu. Soil nematode assemblages are different between these chosen sites. Soil nematodes were extracted from soil samples, identified, enumerated, and assigned to the total nematode population, the plant parasitic group and trophic groups.
A total of 24 taxa of nematodes were found in this study, comprising 9 plant feeders, 3 fungal feeders, 8 bacterial feeders, 3 predators, and 1 omnivore. However, the range of taxon richness per sample collection period was 12 to 14. Overall, plant feeders (Tylenchids, Paratylenchus, Pratylenchus), fungal feeders (Aphelenchus, Aphelenchoides), and bacterial feeders (Cephalobids and Panagrolaimus) were the most common nematodes found in both regions. Meloidogyne abundance in the Waikato site was relatively high compared with the Manawatu. In contrast, Longidorous and Diplogaster were more abundant in Manawatu than Waikato. In both study sites, predators and omnivores were relatively low compared with plant, fungal and bacterial feeders; however, c-p 1 taxon of Panagrolaimdae and Rhabditide are most common in autumn. 
Significant differences in the nematode community were observed with substantial impact changes (season), especially in the total nematode and Maturity Index (MI) measures. Interestingly, a relatively small difference in nitrogen fertiliser (N) input (in on-farm terms) resulted in a consistent, although not significant, decrease in MI at a high rate of N application. This reflects a proportional increase in resource opportunist nematodes (c-p 1 and 2), probably in response to the pulse of microbial growth post-fertilisation. Ryegrass cultivar/ploidy impacts were observed on the plant-feeding component of the nematode community (Plant Parasitic Index (PPI)). An interesting seasonal contrast between MI (greatest in spring) and PPI (greatest in autumn) shows how these two components of the nematode community respond to food resources and seasonal conditions with PPI relying directly on plant growth. We have used a range of different statistical properties to interpret the complex datasets generated from the soil community and environmental interactions. The analysis approaches taken here is often used for analysis of among-species relationships, but are also increasingly used for functional interpretation of ecosystem networks, including those generated by molecular approaches.
We conclude that the addition of even moderate rates of N to the soil has implications for soil functioning and sustainable use given that a more structured(i.e., greater MI) nematode community is a desirable indicator of soil health. The ability to graphically represent the range of the strength of interactions amongst the members of the nematode community adds new insights to these datasets and facilitates bringing together the results of morphological and molecular studies within a common framework of representation and hence understanding the function of ecosystem networks.

text: Distribution of nematodes in pasture soil across seasons and in combination with plant species and fertiliser application The intensification of pastoral land use has increased with the use of fertilisers and the selection of highly productive pasture plant species to increase pasture production. When choosing a ryegrass cultivar infected with selected endophyte fungus, ploidy choices are vital for determining pasture production. Modern perennial ryegrass cultivars and White clover plant species mixtures and nitrogen fertiliser with seasonal climatic characteristics can influence the soil biodiversity and soil functions in a pastoral system. Pasture soils have unique systems with different soil faunal and microbial communities, including soil-dwelling nematodes and plant species composition. Nematodes have the potential to be indicators of soil processes and condition because of their abundance and ubiquity; they are simple multicellular animals, and highly diverse, taxonomically or functionally or both. They occupy multiple trophic positions in the soil food web and play a significant role in the decomposition of soil organic matter, the mineralisation of plant nutrients and nutrient cycling. The distribution of the nematode community can be influenced directly and indirectly by various management activities, including nitrogen fertiliser application and plant species, and the changing climatic conditions during seasons. The magnitude of these biotic and abiotic impacts was studied through analysis of the nematode community. Our study examined the impact on the nematode community of combinations of low and high rates of nitrogen application, clover presence and absence, and two different ranges of ryegrass cultivars, One50 (diploid AR37) and Base (tetraploid AR37), during two seasons. Sampling was carried out twice a year (autumn and spring) for two years (2013 and 2014) to investigate the distribution pattern between the seasons when host plants are actively growing and nematode activity is high. Soil samples were collected in the North Island of New Zealand from two sites in the Waikato and the Manawatu. Soil nematode assemblages are different between these chosen sites. Soil nematodes were extracted from soil samples, identified, enumerated, and assigned to the total nematode population, the plant parasitic group and trophic groups.
A total of 24 taxa of nematodes were found in this study, comprising 9 plant feeders, 3 fungal feeders, 8 bacterial feeders, 3 predators, and 1 omnivore. However, the range of taxon richness per sample collection period was 12 to 14. Overall, plant feeders (Tylenchids, Paratylenchus, Pratylenchus), fungal feeders (Aphelenchus, Aphelenchoides), and bacterial feeders (Cephalobids and Panagrolaimus) were the most common nematodes found in both regions. Meloidogyne abundance in the Waikato site was relatively high compared with the Manawatu. In contrast, Longidorous and Diplogaster were more abundant in Manawatu than Waikato. In both study sites, predators and omnivores were relatively low compared with plant, fungal and bacterial feeders; however, c-p 1 taxon of Panagrolaimdae and Rhabditide are most common in autumn. 
Significant differences in the nematode community were observed with substantial impact changes (season), especially in the total nematode and Maturity Index (MI) measures. Interestingly, a relatively small difference in nitrogen fertiliser (N) input (in on-farm terms) resulted in a consistent, although not significant, decrease in MI at a high rate of N application. This reflects a proportional increase in resource opportunist nematodes (c-p 1 and 2), probably in response to the pulse of microbial growth post-fertilisation. Ryegrass cultivar/ploidy impacts were observed on the plant-feeding component of the nematode community (Plant Parasitic Index (PPI)). An interesting seasonal contrast between MI (greatest in spring) and PPI (greatest in autumn) shows how these two components of the nematode community respond to food resources and seasonal conditions with PPI relying directly on plant growth. We have used a range of different statistical properties to interpret the complex datasets generated from the soil community and environmental interactions. The analysis approaches taken here is often used for analysis of among-species relationships, but are also increasingly used for functional interpretation of ecosystem networks, including those generated by molecular approaches.
We conclude that the addition of even moderate rates of N to the soil has implications for soil functioning and sustainable use given that a more structured(i.e., greater MI) nematode community is a desirable indicator of soil health. The ability to graphically represent the range of the strength of interactions amongst the members of the nematode community adds new insights to these datasets and facilitates bringing together the results of morphological and molecular studies within a common framework of representation and hence understanding the function of ecosystem networks.

year: 2018

title: Workshop Session 2

authors: LakesWater Quality Society

abstract: Workshop Session 2

text: Workshop Session 2 Workshop Session 2

year: 2013

title: Talk More: Student Learning Through Reciprocal Conversations

authors: Grant, Sarah

subjects: oral language

abstract: This research explored ways of improving the oral language development of Year 1 children in four low decile mainstream schools who were making limited progress in literacy. Over 82% of these students were Māori.  Due to the continued impact of past educational policies and the subsequent interruption of the intergenerational transmission of the mother tongue, many Māori children are not exposed to proficient and fluent models either of spoken English or of spoken Māori.  Such children struggle to make the English literacy progress expected of them by schools and communities. The central focus of the research was to evaluate a claim that Year 6 students (tuākana)  could make a substantial improvement in the oral language achievement of  Year 1 students (teina), through engaging with them in regular conversational contexts using the TALES (Talk, Ask, Listen, Encourage, and Say) procedures. This pedagogical approach is understood as one which was culturally responsive for these students. 

Quantitative analysis of data from three quantitative outcome measures (Record of Oral Language, Junior Oral Screening Tool, and Auditory-Vocal Association Assessment of Verbal Attainments) demonstrated that there were substantial oral language gains for the 72 teina students involved in the study. The quantitative analysis also demonstrated that these gains occurred most strongly during the phases in which the TALES procedures were being implemented by the 72 tuākana students, in accord with the multiple baseline design. Detailed qualitative analysis of a random sample of six of the 72 pairs illustrated both the effectiveness of the tuākana language interaction with the teina, and the different ways that the tuākana were able to implement the TALES procedure. Analysis of five minute probes of transcripts over six weeks from these six tuākana - teina pairs indicated that a wide range of literacy activities and conversations took place. The unique learning needs and personal learning intentions of each tuakana and teina were successfully monitored using this five minute probe procedure. Powerful reciprocal learning processes were evident in transcripts of conversations between the tuākana and the teina, and also within feedback and feed-forward meetings between the tuākana and key teachers.  

The substantial oral language gains for the teina students in this study  were achieved within learning contexts that were social and  interactive, and that embodied the principles of ako (learning and teaching roles were shared) and whakawhanaungatanga (building caring and  supportive relationships). These principles are among those that underpin pedagogies that are culturally responsive (Bishop  Glynn, 1999; Glynn, Wearmouth,  Berryman, 2006; Ladson-Billings, 1995, 2006) and transformative. The results of this research study give a clear message to mainstream non-Māori teachers, that they can make a positive and substantial difference to the learning outcomes of their Māori students.

text: Talk More: Student Learning Through Reciprocal Conversations This research explored ways of improving the oral language development of Year 1 children in four low decile mainstream schools who were making limited progress in literacy. Over 82% of these students were Māori.  Due to the continued impact of past educational policies and the subsequent interruption of the intergenerational transmission of the mother tongue, many Māori children are not exposed to proficient and fluent models either of spoken English or of spoken Māori.  Such children struggle to make the English literacy progress expected of them by schools and communities. The central focus of the research was to evaluate a claim that Year 6 students (tuākana)  could make a substantial improvement in the oral language achievement of  Year 1 students (teina), through engaging with them in regular conversational contexts using the TALES (Talk, Ask, Listen, Encourage, and Say) procedures. This pedagogical approach is understood as one which was culturally responsive for these students. 

Quantitative analysis of data from three quantitative outcome measures (Record of Oral Language, Junior Oral Screening Tool, and Auditory-Vocal Association Assessment of Verbal Attainments) demonstrated that there were substantial oral language gains for the 72 teina students involved in the study. The quantitative analysis also demonstrated that these gains occurred most strongly during the phases in which the TALES procedures were being implemented by the 72 tuākana students, in accord with the multiple baseline design. Detailed qualitative analysis of a random sample of six of the 72 pairs illustrated both the effectiveness of the tuākana language interaction with the teina, and the different ways that the tuākana were able to implement the TALES procedure. Analysis of five minute probes of transcripts over six weeks from these six tuākana - teina pairs indicated that a wide range of literacy activities and conversations took place. The unique learning needs and personal learning intentions of each tuakana and teina were successfully monitored using this five minute probe procedure. Powerful reciprocal learning processes were evident in transcripts of conversations between the tuākana and the teina, and also within feedback and feed-forward meetings between the tuākana and key teachers.  

The substantial oral language gains for the teina students in this study  were achieved within learning contexts that were social and  interactive, and that embodied the principles of ako (learning and teaching roles were shared) and whakawhanaungatanga (building caring and  supportive relationships). These principles are among those that underpin pedagogies that are culturally responsive (Bishop  Glynn, 1999; Glynn, Wearmouth,  Berryman, 2006; Ladson-Billings, 1995, 2006) and transformative. The results of this research study give a clear message to mainstream non-Māori teachers, that they can make a positive and substantial difference to the learning outcomes of their Māori students.

year: 2009