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In south-central Chile, the dynamics of southern beech (Nothofagaceae) stands vary predictably along climatic gradients. Beeches form persistent stands at high elevations, but their establishment on lowland sites depends mainly on catastrophic disturbances. In New Zealand, nearly all studies of beech forest dynamics to date have reported all-sized, persistent populations. However, previous work has focused largely on the South Island or on North Island mountains, where beeches are widespread and often dominant. Little is known about beech dynamics in the warm North Island lowlands, where beeches are less common. We aimed to clarify the circumstances that enable beeches to establish on lowland sites in the North Island. We measured population structures of beeches and associated species on 11 plots distributed across a range of climate, lithology and topography. On sites where the most shade-tolerant broadleaved trees were absent or uncommon, all-sized populations showed that beech regeneration did not depend on major disturbances. These stands were located mostly on steep faces or ridges with soil carbon:nitrogen ratios > 18, usually with ericaceous understoreys. On sites with higher N availability, where shade-tolerant broadleaved trees were abundant, beech populations were generally sparser, with restricted age ranges. One of these ± even-aged beech stands appeared to have established after windthrow, the other four after fires. Recent dieback of Weinmannia racemosa associated with insect attack had resulted in another wave of beech regeneration in one of the post-fire stands. Establishment on landslides appears to only rarely enable beeches to capture new sites in the lowland North Island. We conclude that beeches form stable self-replacing stands on lowland North Island sites with low nitrogen availability, but that exogenous disturbances occasionally enable beeches to establish as pioneers on sites with higher nitrogen availability. The early successionalrole commonly seen in lowland south-central Chile thus appears less widespread in New Zealand. [ABSTRACT FROM AUTHOR]

Wind is the major abiotic disturbance in New Zealand's planted forests, but little is known about how the risk of wind damage may be affected by future climate change. We linked a mechanistic wind damage model (Forest GALES) to an empirical growth model for radiata pine ( Pinus radiata D. Don) and a process-based growth model ( cenw) to predict the risk of wind damage under different future emissions scenarios and assumptions about the future wind climate. The cenw model was used to estimate site productivity for constant CO2 concentration at 1990 values and for assumed increases in CO2 concentration from current values to those expected during 2040 and 2090 under the B1 (low), A1B (mid-range) and A2 (high) emission scenarios. Stand development was modelled for different levels of site productivity, contrasting silvicultural regimes and sites across New Zealand. The risk of wind damage was predicted for each regime and emission scenario combination using the Forest GALES model. The sensitivity to changes in the intensity of the future wind climate was also examined. Results showed that increased tree growth rates under the different emissions scenarios had the greatest impact on the risk of wind damage. The increase in risk was greatest for stands growing at high stand density under the A2 emissions scenario with increased CO2 concentration. The increased productivity under this scenario resulted in increased tree height, without a corresponding increase in diameter, leading to more slender trees that were predicted to be at greater risk from wind damage. The risk of wind damage was further increased by the modest increases in the extreme wind climate that are predicted to occur. These results have implications for the development of silvicultural regimes that are resilient to climate change and also indicate that future productivity gains may be offset by greater losses from disturbances. [ABSTRACT FROM AUTHOR]

Wind has a significant impact on planted forests in New Zealand, but the extent of loss and its spatial and temporal variability have not been quantified. Therefore, a formal analysis was undertaken using a database containing 78 records of wind damage in planted forests that spanned the period between 1945 and 2010. Approximately 63 000 ha of damage was recorded during this period. The damage that occurred in a single event ranged from 2.8 to 26 000 ha, with a median of 90 ha, and in most cases was confined to a single wood supply region. The relative risk of wind damage for each wood supply region was estimated by calculating the percentage of total net stocked area (NSA) that has been damaged by wind. Across all wood supply regions, an average of 0.21 per cent of NSA per annum has been damaged by wind; however, in the most affected region, the average level of damage was 0.94 per cent of NSA per annum, whereas in the least affected region it was 0.03 per cent. The probability of different levels of annual damage was modelled along with the level of damage associated with different return periods using a generalized Pareto distribution. Using this model, the mean return period for 500 ha of damage was estimated to be 5.0 years with 95% confidence interval (4.5, 6.2) years, whereas for 1000 ha of damage it was estimated to be 6.4 (4.8, 9.9) years. [ABSTRACT FROM PUBLISHER]

Abstract: The biogeochemical stability of soil P is often assumed to be related to its solubility but there are few tests of this assumption. We determined differences in forms of soil P among stages of stand development in a replicated (N=3) age sequence of Nothofagus stands developed after catastrophic disturbance by windthrow in New Zealand. Seedling, sapling, pole, and mature stages used were approximately 10, 25, 120 and >150years old, respectively. We hypothesized that insoluble soil P forms would not differ among stages of stand development. Organic forms of soil P depended significantly on stage of stand development. Concentrations of labile (NaHCO3 extractable) and non-labile (NaOH extractable) organic P were significantly greater in the mature stage than in sapling and pole stages. The concentration of occluded organic P (NaOH extractable following extraction with acid) was significantly lower in the seedling and pole stages than in the other stages. The concentration of inorganic P did not depend on stage of stand development except in the case of mineral P (HCl extractable) where the seedling stands had significantly lower concentrations of mineral P than the other stages. This was probably due to different topographical conditions for the seedling stands as compared to the other stands which may have affected long term soil processes such as weathering and leaching. The return of P in litterfall was similar among stages. The storage of P in stemwood was low in the seedling and sapling stages but high in the pole and mature stages whereas the storage of P in coarse woody debris was high in the seedling and sapling stages but low in the pole and mature stages. The storage of P in the forest floor was significantly higher in the pole stage than in the other stages which all had similar amounts of P in the forest floor. The differences in soil organic P forms among stages of stand development could be explained by above ground processes such as accumulation of P in stemwood and release of P from the forest floor and decomposing CWD. Labile and non-labile pools of soil organic P were correlated with the concentration of organic C whereas occluded organic P was unrelated to organic C. Our results suggest that neither labile, non-labile nor occluded organic P is stable during stand development. [Copyright &y& Elsevier]

Toppling, or the windthrow, of young (<2-3 years of age) trees is a problem in some regions of the world, including New Zealand. In that country, the incidence of toppling of young radiata pine (Pinus radiata D. Don) trees is a concern to foresters. Toppling differs from wind damage in older forests as trees are not blown completely over, but instead attain a lean; a tree is said to have toppled when this lean exceeds 150 from vertical. Impacts of toppling include a higher incidence of stems with basal sweep and reduced selection choice at the time of pruning and thinning. When trees from toppled stands are harvested, basal sweep results in reduced yields of clearwood and increased levels of compression wood in sawn timber. This paper discusses the phenomenon of toppling and presents an overview of research that has been carried out to identify key causal factors and evaluate treatments which reduce this risk. Due to confounding influences, it is often difficult to experimentally determine those factors responsible. Therefore, a mechanistic model is proposed, which aims to predict the probability that a tree will topple, as well as allowing the effect of different management actions to be evaluated. [ABSTRACT FROM AUTHOR]

The long-term management of natural capital is essential for the stable and resilient flow of ecosystem services for future generations facing climatic uncertainty. Understanding its resilience to extreme natural events, using biological principles, and integrating them into more holistic systems-wide modelling techniques is crucial to evaluate and design the wider economic impacts from alternative management interventions. Here we developed a probabilistic and system-wide bio-economic model to measure extreme economic impacts from natural events using the financial concept of Value at Risk. We have applied the new extreme economic impact metric to measure the economy-wide impact from the disruption of mountain-biking recreational services in the Whakarewarewa peri-urban forest in Rotorua, New Zealand from a potential windthrow event. We identified that extreme natural events, such as windthrows, could exert a substantial impact on the urban forest-dependent regional economy. This impact could potentially be intensified by the CO 2 forest fertilization effects predicted under future climate scenarios and by adopting low-intensity silvicultural regimes currently rewarded by national climate change mitigation policies. Some of the insights from this study could be the precursors to develop robust adaptation strategies using robust decision-making techniques considering inclusive environmental-economic accounting frameworks. • Natural capital management is essential for services' resilience under climate change • Bio-economic model measuring impacts from extreme natural events using value-at-risk • Case of disrupted mountain-biking activities in urban forest from windthrow event • Climate change effects on forests will have wider impacts through ecosystem services • Managing forests to sequester carbon could have wide, unintended economic consequences [ABSTRACT FROM AUTHOR]