Michael S. Watt

Development of models to predict Pinus radiata productivity throughout New Zealand

Development of spatial surfaces describing variation in productivity across broad landscapes at a fine resolution would be of considerable use to forest managers as decision support tools to optimi...

The Invasive Buddleja davidii (Butterfly Bush)

Buddleja davidii Franchet (Synonym. Buddleia davidii; common name butterfly bush) is a perennial, semi-deciduous, multi-stemmed shrub that is resident in gardens and disturbed areas. Since its introduction to the United Kingdom from China in the late 1800s, B. davidii has become an important component in horticulture and human culture. Despite its popularity as a landscape plant, B. davidii is considered problematic because of its ability to naturalize outside of gardens and rapidly invade and dominate disturbed natural areas across a wide range of physical conditions. The primary goal of this paper is to synthesize what is known about B. davidii in order to understand the impacts caused by the continued presence of B. davidii in gardens and natural landscapes. We also address management of B. davidii and discuss the repercussions of management strategies and policies currently implemented to protect or remove B. davidii from natural ecosystems.ZusammenfassungBuddleja davidii Franchet (Synonym Buddleia davidii, umgangsprachlich “Schmetterlingsflieder”) ist ein ausdauernder, halb-immergruener, mehrstaemmiger Busch welcher in Gaerten und auf Umbruchflaechen gedeiht. Seit seiner Einfuehrung in die UK aus China im spaeten 19. Jahrhundert hat B. davidii in Pflanzenzucht und Kultivierung stark an Bedeutung gewonnen. Unabhaengig von seiner Beliebtheit in der Landschaftsgestaltung stellt B. davidii wegen seiner Faehigkeit, sich ueber Gartengrenzen hinaus unter einer Vielzahl von Wachstumsbedingungen in gestoerten Naturgebieten schnell auszubreiten und dort die einheimische Flora zu dominieren, ein grosses Problem dar. Das Ziel der vorliegenden Rezension ist es eine Synopsis zu erstellen, welche die Auswirkungen und Gefahren der konstanten Praesenz von B. davidii in Gaerten und der Naturlandschaft verdeutlicht. Management Optionen und -Fehlschlaege sowie aktuelle Regulationen zu dem Zwecke B. davidii aus natuerlichen Ecosystemen zu entfernen oder sein vordringen zu verhindern, werden ebenfalls diskutiert.

Wood properties of juvenile Pinus radiata growing in the presence and absence of competing understorey vegetation at a dryland site

Pinus radiata D. Don trees were grown in the presence and absence of the woody weed broom (Cytisus scoparius L.) on a dryland site for 2 years to determine the effects of competition from weeds on wood properties in juvenile trees. Wood property measurements made on cross-sections from the bark to the pith were scaled to convert results from distance to a time basis using sigmoidal equations fitted to monthly measurements of tree diameter. When averaged across the 2 years, the presence of the weeds significantly increased wood density (+11%), wall thickness (+6%) and modulus of elasticity (MOESS, +93%), and significantly reduced microfibril angle (MFA, −21%) and radial diameter (−8%). Radial growth rate was significantly correlated to wood density, and this relationship held across both treatment and age. At the seasonal scale, there was close correspondence between changes in MFA and growth rate. Ring width was significantly related to both MFA and MOESS at the annual scale. Although both of these relationships held across treatments, year significantly influenced the value of coefficients in the relationships. The results highlight the direct effects of the presence of weeds on wood properties and the need to consider silvicultural treatments appropriate for balancing gains in productivity with losses in wood quality for timber production.

The potential global distribution of the invasive weed Nassella neesiana under current and future climates

Nassella neesiana (Trin. and Rupr.) (Chilean needle grass), native to South America, has naturalised sporadically in the UK, France, Italy and Spain, and more widely in Australia and New Zealand, where it has become a serious grassland weed. As a first step towards a global risk analysis we project a CLIMEX model of N. neesiana distribution globally under current climate and six future climate scenarios. Under current climate, areas not yet invaded, but climatically suitable, are eastern and south-western Africa, the north-west coast and south-eastern USA in North America, high-elevation areas in Central America, south-eastern China, northern Africa along the Mediterranean Sea, parts of Nepal, India and Pakistan, and Europe. Under the future climate scenarios, a mean global reduction of 32% in the area of suitable climate is projected, with marked reductions in the native range (34%) and also in Africa (67%), Asia (30%), North America (36%), and Australia (42%). These range contractions are primarily attributable to projected increases in temperatures leading to lethal heat stress excluding the plant from areas currently designated as sub-tropical and tropical humid. By contrast, projected expansions eastward in Europe and westward in New Zealand, result in increases in suitable area of 70 and 60%, respectively. Based on these results, which were consistent across the climate-change scenarios, the countries most at risk from N. neesiana are located in western and eastern Europe. A prudent biosecurity strategy would be to prevent the species spreading from the nascent foci already established there. Such a containment strategy would require controls to limit human-assisted dispersal of the species’ fruit and to ban the species from propagation and distribution throughout Europe.

The influence of nitrogen and phosphorus supply and genotype on mesophyll conductance limitations to photosynthesis in Pinus radiata

Mesophyll conductance, g(m), may pose significant limitations to photosynthesis and may be differentially affected by nutrition and genotype in Pinus radiata D. Don. Simultaneous measurements of gas exchange and chlorophyll fluorescence were made to determine g(m), using the constant J method (Harley, P.C., F. Loreto, G. Di Marco and T.D. Sharkey. 1992. Theoretical considerations when estimating the mesophyll conductance to CO(2) flux by analysis of the response of photosynthesis to CO(2). Plant Physiol. 98:1429-1436), in a fast- and a slow-growing clone of P. radiata grown in a greenhouse with a factorial combination of nitrogen (N) and phosphorus (P) supply. Values of g(m) increased linearly with the rate of photosynthesis at saturating irradiance and ambient CO(2) concentration, A(sat) (g(m) = 0.020A(sat), r(2) = 0.25, P < 0.001) and with stomatal conductance to CO(2) transfer, g(s) (g(m) = 1.16g(s), r(2) = 0.14, P < 0.001). Values of g(m) were greater than those of stomatal conductance, g(s), and the ratio (g(m)/g(s)) was not influenced by single or combined N and P additions or clone with a mean (+/-SE) value of 1.22 +/- 0.06. Relative limitations to mesophyll conductance, L(m) (16%) to photosynthesis, were generally greater than those imposed by stomata, L(s) (13%). The mean (+/-SE) CO(2) concentration in the intercellular air spaces (C(i)) was 53 +/- 3 mumol mol(-1) lower than that in the atmosphere (C(a)). Mean (+/-SE) CO(2) concentration in the chloroplasts (C(c)) was 48 +/- 2 mumol mol(-1) lower than C(i). Values of L(s), L(m) and CO(2) diffusion gradients posed by g(s) (C(a) - C(i)) and g(m) (C(i) - C(c)) did not significantly differ with nutrient supply or clone. Mean values of V(cmax) and J(max) calculated on a C(c) basis were 15.4% and 3.1% greater than those calculated on a C(i) basis, which translated into different slopes of the J(max)/V(cmax) relationship (C(c) basis: J(max) = 2.11V(cmax), r(2) = 0.88, P < 0.001; C(i) basis: J(max) = 2.43V(cmax), r(2) = 0.86, P < 0.001). These results will be useful for correcting estimates of V(cmax) and J(max) used to characterize the biochemical properties of photosynthesis for P. radiata.

Distribution of Swiss needle cast in New Zealand in relation to winter temperature

Phaeocryptopus gaeumannii, the causal agent of Swiss needle cast disease, is widely distributed throughout New Zealand, where the disease may cause significant growth losses in Douglas-fir (Pseudotsuga menziesii) plantations. In western Oregon, where the pathogen is native, pathogen abundance and disease severity are correlated with mean daily winter temperatures and spring moisture, enabling the development of climate-based disease prediction models. The distribution of P. gaeumannii and severity of Swiss needle cast was surveyed in 16 Douglas-fir plantations throughout NewZealand in 2005. Retention of foliagewas assessed in the field and samples of 1- and 2-year-old needleswere collected for assessment of P. gaeumannii abundance. Foliage retention and abundance of P. gaeumannii varied across sites. Less colonisation by P. gaeumannii and greater needle retention was found in the South Island. Abundance of P. gaeumannii was found to be positively correlated with August minimum temperature and June average temperature, and showed a similar relationship to winter temperature as observed in western Oregon. These data will be used to derive a disease prediction model for Swiss needle cast in New Zealand that can be used to guide further research and provide short- and long-term disease risk predictions and cost/benefit analyses.

A survey of herbicide use and a review of environmental fate in New Zealand planted forests

BackgroundThis paper examines current herbicide use in New Zealand planted forests. Compliance of key herbicides with existing Forest Stewardship Council (FSC) standards, the key environmental certification body within New Zealand, is also reviewed.MethodsInformation obtained from a survey of six forest companies operating in New Zealand was used to identify major herbicides used by the New Zealand planted forest industry, estimate quantity of herbicides used on an annual basis and also determine changes in weed management practices motivated by certification.ResultsGlyphosate was the most widely used active ingredient in pre-plant weed control with terbuthylazine and hexazinone used most widely for post-plant weed control. Together these herbicides comprise 90% of the estimated 447 tonnes of active ingredient that is annually used. Average aerial application rates for these three active ingredients were estimated at 3.3 kg ha-1, 7.0 kg ha-1 and 1.8 kg ha-1, respectively.Use of terbuthylazine and hexazinone is restricted on FSC-certified forests subject to derogation. Environmental certification has resulted in a shift from broadcast application of terbuthylazine and hexazinone to greater use of spot weed control in the first year after tree planting. Spot weed control can reduce the amount of active ingredient used by up to 89%. Non-chemical weed control is not widely used by the forest industry as it is not as cost-effective as current herbicide regimes.A review of the literature indicated that, when used operationally and according to label registrations, these herbicides are unlikely to have any negative impacts on the planted forest environment. Although they have been detected in groundwater, under multiple land uses, concentrations were at levels below documented safe drinking standards. There are limited data for forest soil and no data on the effects of these herbicides on aquatic biota in New Zealand.ConclusionsAt present time there is insufficient information to support or refute the prohibition of terbuthylazine and hexazinone in New Zealands planted forests. This has highlighted a need to conduct field studies to determine the fate and behaviour of terbuthylazine and hexazinone in planted forests in New Zealand.

Development of a model describing modulus of elasticity across environmental and stand density gradients in plantation-grown Pinus radiata within New Zealand

Modulus of elasticity (E) is an important property in plantation grown softwoods that describes resistance of timber to deformation under load and is a key criterion in machine stress grading. This...

Linking Climate Suitability, Spread Rates and Host-Impact When Estimating the Potential Costs of Invasive Pests

Biosecurity agencies need robust bioeconomic tools to help inform policy and allocate scarce management resources. They need to estimate the potential for each invasive alien species (IAS) to create negative impacts, so that relative and absolute comparisons can be made. Using pine processionary moth (Thaumetopoea pityocampa sensu lato) as an example, these needs were met by combining species niche modelling, dispersal modelling, host impact and economic modelling. Within its native range (the Mediterranean Basin and adjacent areas), T. pityocampa causes significant defoliation of pines and serious urticating injuries to humans. Such severe impacts overseas have fuelled concerns about its potential impacts, should it be introduced to New Zealand. A stochastic bioeconomic model was used to estimate the impact of PPM invasion in terms of pine production value lost due to a hypothetical invasion of New Zealand by T. pityocampa. The bioeconomic model combines a semi-mechanistic niche model to develop a climate-related damage function, a climate-related forest growth model, and a stochastic spread model to estimate the present value (PV) of an invasion. Simulated invasions indicate that Thaumetopoea pityocampa could reduce New Zealand’s merchantable and total pine stem volume production by 30%, reducing forest production by between NZ

The influence of N and P supply and genotype on carbon flux and partitioning in potted Pinus radiata plants

1,550 M to NZ