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Aims: The Myrtaceae is a woody family that plays an important role in forest ecosystems globally. The recent spread of myrtle rust, caused by a fungal pathogen (Austropuccinia psidii), from its native South America into New Zealand (NZ), highlights the need to quantify the ecological importance of Myrtaceae in NZ woody ecosystems. Location: New Zealand. Methods: Using NZ nationwide forest and shrubland inventory data, collected from 2009 to 2014, we quantified the ecological importance of Myrtaceae based on its richness and abundance relative to co-occurring woody families. We then explored how climate and forest stand structure affect Myrtaceae importance in general and by tribe and growth form. Finally, we compared functional traits associated with plant growth and reproductive strategies with other dominant woody families and determined Myrtaceae's contributions to community-weighted mean (CWM) trait values. Results: Myrtaceae occurred in 74% of the study plots and its importance value was the second highest across the woody families. It was the only one in which climbers substantially contributed to the importance value (17%). Greater Myrtaceae importance values were associated with warmer and more mesic climates and early forest successional stages. Climate associations were similar within tribes and growth forms, whereas forest structure effects varied. Myrtaceae was functionally distinct from most co-occurring woody families. Contributions to CWM wood density, maximum height, and specific leaf area values were significantly greater than expected from its importance value. Conclusions: Myrtaceae is the second most ecologically important woody family in NZ woody ecosystems. The family has a distinctive functional trait spectrum associated with high wood density and tall stature, ensuring large and enduring carbon stocks. There will potentially be large and deleterious outcomes in forest ecosystems if taxon-specific pathogens, such as Austropuccinia psidii, spread and significantly reduce Myrtaceae importance. [ABSTRACT FROM AUTHOR]

Background: The tree stem density which optimises merchantable timber yield (volume per unit area) is unknown for most of New Zealand's indigenous tree species. While moderate thinning of even-aged stands can promote yield, intense thinning may decrease yield by creating space that cannot be filled by residual trees, increasing tree mortality or reducing tree height. We quantified the effects of density on silver beech (Lophozonia menziesii (Hook.f.) Heenan & Smissen) tree growth, height and mortality, identified the density leading to optimal merchantable yield and assessed if this density varied with stand age. Methods: Tree stem diameter growth, height, and mortality responses to density were determined using tagged individuals monitored over time on a long-term thinning trial combined with flexible, multilevel, non-linear models. Empirical stand yield responses to density were determined and compared to yield--density relationships in simulated stands. The stand simulations projected beyond the monitored stand ages using the tree-level responses fitted to empirical data. Results: Low densities (≤400 stems ha-1) sustained fast tree growth for longer than high densities (≥700 stems ha-1) after thinning, but density did not consistently affect merchantable tree heights. The probability of tree mortality increased after intense thinning, but only temporarily, and never exceeding c. 0.01 year-1. A regression of yield--density relationships identified an empirical optimum of c. 570 stems ha-1 for stand ages of 48 and 58 years. At this density, merchantable yield at 58 years was seven-fold greater than that in unthinned stands. The simulations suggested moderately higher densities for optimal yield than our empirical optimum, a moderate increase in optimal densities with stand age, and that c. 90 % of potential cumulative yield was attained at 80 years. Conclusions: Because thinning increased tree growth, but had minimal effect on tree mortality, our results alleviate concerns about the stability and productivity of thinned stands. Densities that optimise yield are about two-fold greater than those previously recommended for silver beech and they remain relatively stable as stands age. This suggests that a single density will be adequate for a range of harvest ages, although harvest should take place before a stand age of 80 years. Such conclusions are relevant to managing regeneration within coupes harvested under existing legislation and to areas planted with silver beech. [ABSTRACT FROM AUTHOR]

The ecological impacts of feral pigs (Sus scrofa) are of concern in many places around the world. One noticeable impact is soil disturbance, although the causes and consequences are often unclear. We measured the effect of ground disturbance by feral pigs on seedling recruitment and soil ecology over 25 months on a forested riparian terrace at Waitutu, south Fiordland, New Zealand, and assessed the diet of pigs from the area from stomach contents of animals shot by hunters. Foraging by feral pigs for below-ground food disturbed between 7.4% and 12.4% of the soil. Pigs were seven times more likely to redisturb a site than to disturb a new site. Below-ground food items constituted a third of pigs' diet and were dominated by stag beetle larvae. Sites disturbed by feral pigs had shorter seedlings compared with undisturbed sites, but this was due to pigs' choice of sites rather than a consequence of the disturbance. Net temporal changes in density and height of seedlings were similarly slow in both disturbed and undisturbed sites. The basal respiration of microbes in soils recently disturbed by pigs was significantly higher than that for undisturbed soils. There was a suggestion that disturbed soils had higher ratios of fungi to bacteria than undisturbed soils (P = 0.06). This may reflect either disturbance favouring fungi over bacteria or selection of sites with more fungi or more of their main prey, the fungivorous stag beetle Dorcus helmsii. Our results indicate that pigs disturb soil primarily to forage for food and that the consequences of disturbance for seedling regeneration and soil ecology are limited or neutral. The consequences of ground disturbance and predation for populations of animal prey, such as the stag beetles, require further investigation. [ABSTRACT FROM AUTHOR]

Plant functional traits capture important variation in plant strategy and function. Recent literature has revealed that within-species variation in traits is greater than previously supposed. However, we still have a poor understanding of how intraspecific variation is coordinated among different traits, and how it is driven by environment. We quantified intraspecific variation in wood density and five leaf traits underpinning the leaf economics spectrum (leaf dry matter content, leaf mass per unit area, size, thickness and density) within and among four widespread Nothofagus tree species in southern New Zealand. We tested whether intraspecific relationships between wood density and leaf traits followed widely reported interspecific relationships, and whether variation in these traits was coordinated through shared responses to environmental factors. Sample sites varied widely in environmental variables, including soil fertility (25–900 mg kg–1 total P), precipitation (668–4875 mm yr–1), temperature (5.2–12.4 °C mean annual temperature) and latitude (41–46 °S). Leaf traits were strongly correlated with one another within species, but not with wood density. There was some evidence for a positive relationship between wood density and leaf tissue density and dry matter content, but no evidence that leaf mass or leaf size were correlated with wood density; this highlights that leaf mass per unit area cannot be used as a surrogate for component leaf traits such as tissue density. Trait variation was predicted by environmental factors, but not consistently among different traits; e.g., only leaf thickness and leaf density responded to the same environmental cues as wood density. We conclude that although intraspecific variation in wood density and leaf traits is strongly driven by environmental factors, these responses are not strongly coordinated among functional traits even across co-occurring, closely-related plant species. [ABSTRACT FROM AUTHOR]

• 441 root:shoot records were compiled for 32 locations in south temperate forests. • Root:shoot ratios were size-invariant in most tree taxa assessed. • Most dicots had similar root:shoot ratios between south and north temperate forests. • Divergences in root allocation were only noted for gymnosperms and tree ferns. • Low rainfall:temperature ratio conditions led to high root biomass allocation. Accurate quantification of total forest biomass requires sound estimates of root biomass. Because roots are challenging to measure in situ , data are sparse, and this has limited our understanding of root allocation across a range of forest types. Increased sampling in the oceanic and cool temperate forests of the southern hemisphere means we are now able to better understand biomass allocation in this biome. Here we compile and systematically review root:shoot ratios for these forests and examine the taxonomic, regional, and environmental determinants of variability in biomass allocation to roots. Specifically, we assess whether limited access to resources resulting from low temperatures or low rainfall:temperature ratios increases root allocation. A literature and database search identified 441 root:shoot records from 25 studies and 32 locations around the South Pacific. Records were weighted by excavated area as a measure of sampling effort. Root:shoot ratios for eucalypts in southeast Australia (0.277) and southern beech in South America (0.275) were 6–7% above the global mean of 0.26, while southern beech (0.233) and other dicots (0.234) in New Zealand were consistent with values reported for temperate (mostly northern hemisphere) broadleaved forests. Low root:shoot ratios (of trees ≥5 cm stem diameter) relative to the global mean were noted for South American gymnosperms (0.219), seemingly driven by low values in the Cupressaceae, and New Zealand tree ferns (0.194). Size effects were taxon dependent, with a marked decline in root:shoot ratios with increasing stem size for the southern beech in South America and modest effects for other combinations of taxa and region. A clear signal of increasing root allocation with declining rainfall:temperature ratios was detected, but no major effects of temperature were noted within the range of the data. Our findings support current approaches to biomass and carbon estimation but leave room for refinement, with specific recommendations given for the New Zealand context. [ABSTRACT FROM AUTHOR]

Plant functional traits capture important variation in plant strategy and function. Recent literature has revealed that within-species variation in traits is greater than previously supposed. However, we still have a poor understanding of how intraspecific variation is coordinated among different traits, and how it is driven by environment. We quantified intraspecific variation in wood density and five leaf traits underpinning the leaf economics spectrum (leaf dry matter content, leaf mass per unit area, size, thickness and density) within and among four widespread Nothofagus tree species in southern New Zealand. We tested whether intraspecific relationships between wood density and leaf traits followed widely reported interspecific relationships, and whether variation in these traits was coordinated through shared responses to environmental factors. Sample sites varied widely in environmental variables, including soil fertility (25-900 mg kg(-1) total P), precipitation (668-4875 mm yr(-1)), temperature (5.2-12.4 °C mean annual temperature) and latitude (41-46 °S). Leaf traits were strongly correlated with one another within species, but not with wood density. There was some evidence for a positive relationship between wood density and leaf tissue density and dry matter content, but no evidence that leaf mass or leaf size were correlated with wood density; this highlights that leaf mass per unit area cannot be used as a surrogate for component leaf traits such as tissue density. Trait variation was predicted by environmental factors, but not consistently among different traits; e.g., only leaf thickness and leaf density responded to the same environmental cues as wood density. We conclude that although intraspecific variation in wood density and leaf traits is strongly driven by environmental factors, these responses are not strongly coordinated among functional traits even across co-occurring, closely-related plant species.