Norman W. H. Mason

Manaaki Whenua - Landcare Research · Ecosystem Processes

Although disturbance is considered a major driver of plant invasions across many systems, our understanding of the mechanisms by which disturbance mediates understorey invasions in natural forests is limited. We used a national natural forest inventory dataset spanning New Zealand's wide climatic and soil fertility gradients to disentangle disturba...

Predicting the willingness of people to engage in passive surveillance is crucial to the success of community-based efforts to manage invasive species and conserve native biodiversity. We draw on the marketing concept of involvement, which reflects the personal importance of an issue or behaviour, to understand and measure the motivation of members...

Effects of plant diversity on grassland productivity, or overyielding, are found to be robust to nutrient enrichment. However, the impact of cumulative nitrogen (N) addition (total N added over time) on overyielding and its drivers are underexplored. Synthesizing data from 15 multi-year grassland biodiversity experiments with N addition, we found t...

Question Natural reforestation is an important component of climate mitigation and adaptation, but the ecological processes promoting or constraining it are poorly understood. In this study we employ a stand reconstruction approach (which uses ages of extant trees to estimate year of establishment for each individual tree) to test for general trait...

Much land has been cleared of indigenous forest for pastoral agriculture worldwide. In New Zealand, the clearance of indigenous forest on hill country has resulted in high food production, but waterways have become turbid, with high nutrient and E. coli concentrations. A range of on-farm mitigations are available, but it is unclear how they should...

The primary role for scientific information in addressing complex environmental problems, such as biological invasions, is generally assumed to be as a guide for management decisions. However, scientific information often plays a minor role in decision-making, with practitioners instead relying on professional experience and local knowledge. We exp...

Increasing plant diversity is often suggested as a way of overcoming some of the challenges faced by managers of intensive pasture systems, but it is unclear how to design the most suitable plant mixtures. Using innovative design theory, we identify two conceptual shifts that foster potentially beneficial design approaches. Firstly, reframing the g...

The primary role for science in addressing complex environmental problems, such as biological invasions, is generally assumed to be as a guide for management decisions. However, science often plays a minor role in decision-making, with practitioners instead relying on professional experience and local knowledge. We explore alternative pathways by w...

Context Soil organic matter (SOM) plays a vital role in carbon (C) storage and agricultural sustainability. Additions of bovine urine to soils can cause positive priming of soil C decomposition and represents a pathway for SOM loss. However, data is limited to a few soils. Aims We investigated the priming response to bovine urine of 27 dairy grazed...

Irrigation has been used for millennia to increase the quantity and reliability of food and fibre production in areas where lack of precipitation limits plant growth. Despite the importance of irrigation, our understanding of the impact of irrigation on soil carbon (C) and nitrogen (N) stocks is still limited, particularly for grazed grasslands. In...

1. Despite the fact that insects are suffering a global decline, little is known about the extent to which species loss affects functional diversity. Thus, to understand the relationship between taxonomic and functional diversity metrics, we focused on saproxylic beetles, which perform vital functions in forest ecosystems. 2. Beetles were collected...

Biological invasions are a major threat to biodiversity and human well‐being. Scientists and environmental managers typically seek ecological solutions to the biological invasion problem. However, micro‐scale social factors, such as landowner attitudes and social interactions that underlie landowners’ willingness to control invasive species, may pr...

Designing and implementing long-term management strategies for chronic biological invasions is amongst the most vexing ecological research problems. Two key challenges to resolving this problem are: (a) integrating science-based and values-based (e.g. spiritual, cultural, economic and ethical) knowledge sources and (b) developing durable knowledge...

Because plant and soil systems are strongly inter‐linked, manipulating plant traits in intensively managed agricultural systems could be used to improve soil functioning and sustainability. However, we have little understanding of whether the impacts of plant traits on soil systems are modified by other management practices, such as fertiliser use....

Overyielding, the primary metric for assessing biodiversity effects on ecosystem functions, is often partitioned into “complementarity” and “selection” components, but this reveals nothing about the role of increased resource use, resource-use efficiency, or trait plasticity. We obtained multiple overyielding values by comparing productivity in a f...

Understanding the mechanisms behind the successful invasion of alien plant species remains a significant research challenge in invasion ecology. There are surprisingly few cross-continental comparative studies which investigated interspecific trait differences between native and invaded ranges. Here, we compare leaf functional traits of sycamore (A...

Plant traits—the morphological, anatomical, physiological, biochemical and phenological characteristics of plants—determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research sp...

Maungatautari is a 3,240 ha pest-fenced ecosanctuary free of virtually all mammalian predators in Waikato, New Zealand. We used triennial 5-minute counts within the ecosanctuary and biennial surveys of residents up to 20 km from the perimeter pest fence to measure spillover of tūī from Maungatautari into the surrounding area over a 9-year period (2...

Flammability is an important plant trait, relevant to plant function, wildfire behaviour and plant evolution. However, systematic comparison of plant flammability across ecosystems has proved difficult because of varying methodologies and assessment of different fuels comprising different plant parts. We compared the flammability of plant species a...

Functional diversity (FD) has the potential to address many ecological questions, from impacts of global change on biodiversity to ecological restoration. There are several methods estimating the different components of FD. However, most of these methods can only be computed at limited spatial scales and cannot account for intraspecific trait varia...

Both intra‐ and interspecific differences in traits may modulate interactions between plants. Two mechanisms are hypothesized to regulate these effects: competitive hierarchies and trait dissimilarities, but it is unclear how the prevalence of each might depend on environmental conditions and on intra and interspecific differences. We sowed six rep...

Questions: How do the traits of pastoral species respond to growth in mixture, nitrogen addition and season? What are the impacts of trait plasticity on community aggregate trait values? Study site: A large-scale field experiment on intensively managed dairy pastures in New Zealand. Methods: We measured traits linked to rate of return on investment...

Effects of bovine urine on microbial functional attributes within the carbon (C) cycle have not previously been investigated. The magnitude of urine effects on microbial populations may be mediated by the ability of a soil to buffer changes to pH and electrical conductivity (EC) in response to urine. We examined changes in the metabolism of C subst...

Recent studies have concluded that native and invasive species share a common set of trait relationships. However, native species in isolated regions might be functionally constrained by their unique evolutionary histories such that they follow different carbon capture strategies than introduced species. We compared leaf traits relating to resource...

Model parameters and prior distributions used in the photosynthetic light response model. (DOCX)

Summary of leaf trait data for each species. (XLSX)

Description of the hierarchical Bayesian photosynthetic light response model. (DOCX)

R code for Bayesian photosynthetic light response model. (DOCX)

The effect of measurement error on biodiversity metrics is problematic for conservation planning and testing ecological theories, but there are few methods for including it in statistical analyses. We present a framework for incorporating measurement error in testing for significant change in almost any type of biodiversity metric. We used repeat m...

What makes an alien plant species a successful invader remains a challenging question in invasion ecology. Although comparing functional traits of exotic species between their native and invasive ranges represents a sensible step when studying invaders, this approach is rarely applied and always disconnected from demographic attributes. In this stu...

This report is the product of a Ministry for Primary Industries (MPI) commissioned project to explore the benefits of permanent forests compared with plantation forests and other land uses. The project is related to the Permanent Forest Sink Initiative (PFSI), which was established in 2008 and acts as a mechanism for landowners to access the value...

Invasive nitrogen (N)-fixing plants often fundamentally change key ecosystem functions, particularly N-cycling. However, the consequences of this for litter decomposition, and the mechanisms that underpin ecosystem responses, remain poorly understood. Moreover, few studies have determined how nutrient pools and fluxes shift as invader density incre...

Uncertainty about the mechanisms driving biomass change at broad spatial scales limits our ability to predict the response of forest biomass storage to global change. Here we use a spatially representative network of 874 forest plots in New Zealand to examine whether commonly hypothesised drivers of forest biomass and biomass change (diversity, dis...

Grazed pasture managers are increasingly being asked to enhance productivity while simultaneously reducing environmental impacts. Using plant traits to design plant communities that optimise ecosystem functions (e.g. productivity, nitrogen retention) may help achieve this. However, trait–function relationships in intensively grazed systems are larg...

Agricultural production systems face increasing threats from more frequent and extreme weather fluctuations associated with global climate change. While there is mounting evidence that increased plant community diversity can reduce the variability of ecosystem functions (such as primary productivity) in the face of environmental fluctuation, there...

Invasive plants can have both positive and negative impacts on ecosystem services (ES), with decisions on control often being characterised by conflicts over loss of their perceived positive impacts on individual ES following removal. We present an analytical framework to aid in reducing such conflicts by allocating control effort to both minimise...

New Zealand dairy farm systems mostly rely on ryegrass-white clover pastures. The inclusion of diverse sward mixtures within these systems offers a novel strategy to improve economic and environmental outcomes. However, the degree to which these mixtures offer advantages over traditional pastures is unknown. This analysis seeks to explore the role...

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Woody nitrogen (N) fixers are known to fix atmospheric N at very high rates. However, N leached from woody N fixers is rarely accounted for in catchment nutrient budgets. We conducted a scoping study to determine the potential impact of the invasive N fixer gorse (Ulex europaeus) on water quality in an agricultural catchment in New Zealand. With cu...

This study tests whether or not foliar flammability is related to resource-use and anti-herbivore defence strategies of plant species. We measured the flammability (at 400 °C) of 1640 dry and fresh leaves across 115 common native New Zealand woody and herbaceous species collected from sites throughout New Zealand. We used three indicators of foliar...

Figure S2. Mean combined abundance of the forbs chicory and plantain in ryegrass and tall fescue‐based plots (where sown) for each of the three years of the experiment.

Figure S1. Allocation of treatments to plots in the experiments.

Table S2. ANOVA table for a linear mixed‐effects model (A) including Year, Base grass identity, presence or absence of forbs and all possible interactions between them as fixed effects, with plot and block as random effects; and results from multimodel comparisons for all possible combinations of the predictors and their interactions (B).

Table S1. Seed sowing rates for each species in each mixture.

Table S3. Pearson correlations between biomass‐weighted trait values across ryegrass‐dominated plots.

Figure S3. Relationships between productivity and biomass‐weighted trait values for all plots.

Figure S4. Relationships between productivity and functional divergence (FDiv) across either ryegrass or tall fescue‐based plots (RG plots and TG plots respectively).

Figure S5. Productivity of ryegrass‐based and non‐ryegrass‐based plots in different seasons.

Figure S6. Mean biomass yield of the forb species (chicory and plantain), tall fescue and ryegrass in each season in each year.

Plant functional traits are thought to drive variation in primary productivity. However, there is a lack of work examining how dominant species identity affects trait–productivity relationships. The productivity of 12 pasture mixtures was determined in a 3-year field experiment. The mixtures were based on either the winter-active ryegrass (Lolium p...

Fulltext available for free from the publisher for first 50 days: http://authors.elsevier.com/a/1SvWIcZ3WXZZA Owing to the conceptual complexity of functional diversity (FD), a multitude of different methods are available for measuring it, with most being operational at only a small range of spatial scales. This causes uncertainty in ecological int...

Long-term (c. 40 years) tree population and soil data from conifer/angiosperm forests that have developed since the last major volcanic eruption (ad 232) in the central North Island of New Zealand were used to test the hypothesis that the shift from conifer to angiosperm dominance away from the eruption centre represents a chronosequence. The propo...

Recent studies have shown that accounting for intraspecific trait variation (ITV) may better address major questions in community ecology. However, a general picture of the relative extent of ITV compared to interspecific trait variation in plant communities is still missing. Here, we conducted a meta-analysis of the relative extent of ITV within a...

There is growing evidence of restoration success for wetland plant communities. However, little research has been done on the associated invertebrate community. We test whether restoring plant communities after peat extraction is sufficient for restoring the taxonomic and functional composition of beetle communities. We monitored taxonomic and trai...

Semi-natural meadows host a great number of species coexisting at fine spatial scales. Different assembly mechanisms, related to differences in functional traits between species, can influence such coexistence. Coexisting species could be either functionally dissimilar to occupy different niches (‘divergence’) or functionally similar due to exclusi...

QuestionsHow do inter-annual fluctuations in water availability affect the functional trait patterns along spatial gradients of resource availability and disturbance?LocationMediterranean grasslands in central Spain, near Madrid.Methods We surveyed plant communities from 66 sites under different grazing regimes (from heavy grazing to grazing abando...

Question Niche differentiation results in functionally diverse communities that are often composed of dominant species with contrasting trait values. However, many predictive trait‐based models that emphasize environmental filtering have implicitly assumed that traits exhibit unimodal distributions among individuals within communities centred on an...

Ecosystem science increasingly relies on highly derived metrics to synthesize across large datasets. However, full uncertainty associated with these metrics is seldom quantified. Our objective was to evaluate measurement error and model uncertainty in plot-based estimates of carbon stock and carbon change. We quantified the measurement error associ...

A key hypothesis in population ecology is that synchronous and intermittent seed production, known as mast seeding, is driven by the alternating allocation of carbohydrates and mineral nutrients between growth and reproduction in different years, i.e. ‘resource switching’. Such behaviour may ultimately generate bimodal distributions of long-term fl...