Mark O. Kimberley

Diversity and succession of adventive and indigenous vascular understorey plants in Pinus radiata plantation forests in New Zealand

Abstract The vegetation of Pinus radiata plantation forests in New Zealand was studied to examine how the indigenous flora has responded to this novel habitat. A chronosequence of stands about 5, 16 and 27 years was assessed in each of four different biogeographic regions to test the effects of several stand and site factors on the succession of vascular understorey plant communities. A total of 202 indigenous and 70 adventive vascular plant species were found across all study areas, with considerable geographic variation among forests in species composition, species richness (range 48–135 species), and the percentage of indigenous species (50–86%). Both richness and cover of adventive species decreased significantly over time, whereas richness and cover of indigenous species was highest in the oldest stands, and overall species richness was lowest at mid-rotation. The guild composition changed from dominance of grasses and forbs in young stands to dominance of ferns and understorey trees in mature stands. These temporal changes were accompanied by a decrease in light-demanding pioneer species and an increase in shade tolerant, later seral species adapted to a forest environment. Measurements of the degree of canopy closure in stands with low or high stocking and modelling of temporal changes of canopy closure indicated that these understorey plant dynamics are influenced by changes in light availability as stands age. Despite the successional changes within forests, geographic variation more strongly influenced understorey communities because stands within a forest area were grouped together in DCA and TWINSPAN analyses, along rainfall and temperature gradients. Although the canopy species of such intensively managed plantation forests is an alien element in the New Zealand flora, the sheltered forest environment of older stands allows the establishment of a mostly indigenous forest understorey community with considerable similarities to indigenous forests located nearby.

Effectiveness of the International Phytosanitary Standard ISPM No. 15 on Reducing Wood Borer Infestation Rates in Wood Packaging Material Entering the United States

Numerous bark- and wood-infesting insects have been introduced to new countries by international trade where some have caused severe environmental and economic damage. Wood packaging material (WPM), such as pallets, is one of the high risk pathways for the introduction of wood pests. International recognition of this risk resulted in adoption of International Standards for Phytosanitary Measures No. 15 (ISPM15) in 2002, which provides treatment standards for WPM used in international trade. ISPM15 was originally developed by members of the International Plant Protection Convention to “practically eliminate” the risk of international transport of most bark and wood pests via WPM. The United States (US) implemented ISPM15 in three phases during 2005–2006. We compared pest interception rates of WPM inspected at US ports before and after US implementation of ISPM15 using the US Department of Agriculture AQIM (Agriculture Quarantine Inspection Monitoring) database. Analyses of records from 2003–2009 indicated that WPM infestation rates declined 36–52% following ISPM15 implementation, with results varying in statistical significance depending on the selected starting parameters. Power analyses of the AQIM data indicated there was at least a 95% chance of detecting a statistically significant reduction in infestation rates if they dropped by 90% post-ISPM15, but the probability fell as the impact of ISPM15 lessened. We discuss several factors that could have reduced the apparent impact of ISPM15 on lowering WPM infestation levels, and suggest ways that ISPM15 could be improved. The paucity of international interception data impeded our ability to conduct more thorough analyses of the impact of ISPM15, and demonstrates the need for well-planned sampling programs before and after implementation of major phytosanitary policies so that their effectiveness can be assessed. We also present summary data for bark- and wood-boring insects intercepted on WPM at US ports during 1984–2008.

Predicting how altering propagule pressure changes establishment rates of biological invaders across species pools

Biological invasions resulting from international trade can cause major environmental and economic impacts. Propagule pressure is perhaps the most important factor influencing establishment, although actual arrival rates of species are rarely recorded. Furthermore, the pool of potential invaders includes many species that vary in their arrival rate and establishment potential. Therefore, we stress that it is essential to consider the size and composition of species pools arriving from source regions when estimating probabilities of establishment and effects of pathway infestation rates. To address this, we developed a novel framework and modeling approach to enable prediction of future establishments in relation to changes in arrival rate across entire species pools. We utilized 13 828 border interception records from the United States and New Zealand for 444 true bark beetle (Scolytinae) and longhorned beetle (Cerambycidae) species detected between 1949 and 2008 as proxies for arrival rates to model the relationship between arrival and establishment rates. Nonlinearity in this relationship implies that measures intended to reduce the unintended transport of potential invaders (such as phytosanitary treatments) must be highly effective in order to substantially reduce the rate of future invasions, particularly if trade volumes continue to increase.

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...

Soil CO2 flux dynamics in the two main plantation forest types in subtropical China

Chinese Fir and Moso bamboo are the two most important forest plantation species in subtropical China. However, information on greenhouse gas emissions from these forests is still scarce. A field study was carried out to compare soil CO(2) flux dynamics in Chinese Fir and Moso bamboo forests over a 12-month period using the LI-8100 Soil CO(2) Flux System. The soil CO(2) flux in both forest types showed similar daily and seasonal dynamic patterns with the highest soil CO(2) efflux at 14:00-16:00 in summer and the lowest in winter. Moso bamboo forest showed significant higher (P<0.01) annual mean soil CO(2) fluxes (52.9 t CO(2)ha(-1)yr(-1)) than Chinese fir forest (27.9 t CO(2)ha(-1)yr(-1)). The large difference in soil CO(2) fluxes may potentially influence the carbon cycle of the two forest types at the ecosystem scale. The CO(2) flux from the soil showed a significant positive correlation (P<0.0001) with soil temperature at 5 cm depth, a significant negative correlation (P<0.01) with air relative humidity, and no significant correlation with soil moisture in either forest types. The Q(10) value of soil respiration was higher in Chinese fir than Moso bamboo forest, indicating that soil respiration under Chinese fir forest will be more sensitive to temperature change. This study contributes to better understanding of the role Moso bamboo and Chinese fir forests may play in carbon cycle and global warming mitigation.

Environmental and nutritional responses of a Pinus radiata plantation to biosolids application

Since the mid-1990s, a Pinus radiata (D. Don) plantation growing on a sandy, low fertility soil at Rabbit Island near Nelson, New Zealand received aerobically digested liquid biosolids. An experimental research trial was established on the site to investigate the effects of biosolids applications on tree growth, nutrition, soil and ground water quality. Biosolids were applied to the trial site in 1997 and 2000, at three application rates: 0 (control), 300 (standard) and 600 kg N ha−1 (high). Biosolids application significantly increased tree growth. This was mainly attributed to improved N supply, demonstrated by the enhanced N concentration in the tree foliage. Soil analysis indicated that biosolids application have not caused significant changes in concentrations of most nutrients. However, biosolids treatments significantly increased the available P (Olsen P). Of the heavy metals only total Cu concentrations in the soil increased after biosolids application. Groundwater quality, which was monitored quarterly, has not been affected by biosolids application. The concentrations of nitrate and heavy metals in groundwater were well below the maximum acceptable values in drinking water standards. Biological treatment of sewage and digestion of sewage sludge resulted in the enrichment of 15N in the biosolids (δ15N values between 5.0 and 8.7‰). Such enrichment was used as a tracer to study the fate of biosolids derived N. The elevated δ15N in biosolids treated pine foliage indicated that a considerable amount N was sourced from biosolids. Analysis of δ15N in understorey plants showed that both non-legume and legume understorey plants took up N from the biosolids, and acted as a N sink, reducing N availability for leaching. Our study showed that application of biosolids to a plantation forest can significantly improve tree nutrition and site productivity without resulting in any measurable adverse effect on the receiving environment.

Aerial Application of Pheromones for Mating Disruption of an Invasive Moth as a Potential Eradication Tool

Biological invasions can cause major ecological and economic impacts. During the early stages of invasions, eradication is desirable but tactics are lacking that are both effective and have minimal non-target effects. Mating disruption, which may meet these criteria, was initially chosen to respond to the incursion of light brown apple moth, Epiphyas postvittana (LBAM; Lepidoptera: Tortricidae), in California. The large size and limited accessibility of the infested area favored aerial application. Moth sex pheromone formulations for potential use in California or elsewhere were tested in a pine forest in New Zealand where LBAM is abundant. Formulations were applied by helicopter at a target rate of 40 g pheromone per ha. Trap catch before and after application was used to assess the efficacy and longevity of formulations, in comparison with plots treated with ground-applied pheromone dispensers and untreated control plots. Traps placed at different heights showed LBAM was abundant in the upper canopy of tall trees, which complicates control attempts. A wax formulation and polyethylene dispensers were most effective and provided trap shut-down near ground level for 10 weeks. Only the wax formulation was effective in the upper canopy. As the pheromone blend contained a behavioral antagonist for LBAM, ‘false trail following’ could be ruled out as a mechanism explaining trap shutdown. Therefore, ‘sensory impairment’ and ‘masking of females’ are the main modes of operation. Mating disruption enhances Allee effects which contribute to negative growth of small populations and, therefore, it is highly suitable for area-wide control and eradication of biological invaders.

Modelling variation in wood density within and among trees in stands of New Zealand-grown radiata pine

BackgroundDensity is an important wood property due to its correlation with other wood properties such as stiffness and pulp yield, as well as being central to the accounting of carbon sequestration in forests. It is influenced by site, silviculture, and genetics, and models that predict the variation in wood density within and among trees are required by forest managers so that they can develop strategies to achieve certain wood density targets. The aim of the study presented here was to develop a wood density model for radiata pine (Pinus radiata D. Don) growing in New Zealand.MethodsThe model was developed using an extensive historical dataset containing wood density values from increment cores and stem discs that were obtained from almost 10,000 trees at over 300 sites. The model consists of two sub-models: (1) a sub-model for predicting the radial variation in breast-height wood density and (2) a sub-model for predicting the distribution of density vertically within the stem.ResultsThe radial variation in breast-height wood density was predicted as a function of either ring number or both ring number and ring width, with the latter model better accounting for the effects of stand spacing. Additional model components were also developed in order to convert from annual ring density values to a whole-disc density, predict log density from disc densities, and account for the variation in wood density among individual trees within in a stand. The model can be used to predict the density of discs or logs cut from any position within a tree and can utilise measured outerwood density values to predict the density by log height for a particular stand. It can be used in conjunction with outerwood density to predict wood density distributions by logs for stands of any specified geographic location and management regime and is designed to be able to incorporate genetic adjustments at a later stage.ConclusionsThe analysis has confirmed and quantified much of the previous knowledge on the factors that affect the variation in wood density in radiata pine, particularly the influences of site factors and silviculture. It has also quantified the extent and patterns of variation in wood density within and among trees.

The contribution of spray formulation component variables to foliar uptake of agrichemicals.

BACKGROUND The objective of the present study was to determine the contribution of the active ingredient (AI) and surfactant, and their concentrations, to the foliar uptake of agrichemicals, and to examine the physical properties that would need to be included in a model for foliar uptake. RESULTS All spray formulation component variables significantly affected uptake, explaining 73% of the deviance. The deviance explained by each factor ranged from 43% (AI concentration nested within AI) to 5.6% (surfactant). The only significant interaction was between AI and surfactant, explaining 15.8% of the deviance. Overall, 90% of the deviance could be explained by the variables and their first-order interactions. CONCLUSIONS Uptake increased with increasing lipophilicity of the AI at concentrations below those causing precipitation on the leaf surface. AI concentration had a far greater (negative) effect on the uptake of the lipophilic molecule epoxiconazole. The uptake of 2-deoxy-D-glucose (DOG) and 2,4-dichlorophenoxyacetic acid (2,4-D) increased with increasing hydrophile-lipophile balance (HLB) of the surfactant, the effect of HLB being far greater on the hydrophilic molecule DOG. However, the differences observed in epoxiconazole uptake owing to the surfactant were strongly positively related to the spread area of the formulation on the leaf surface. For all AIs, uptake increased in a similar manner with increasing molar surfactant concentration.

Distribution of heavy metals in a sandy forest soil repeatedly amended with biosolids

The suitability for land application of biosolids can be limited by the presence of heavy metals. We investigated the distribution of heavy metals in the soil of a research trial within a Pinus radiata (D. Don) plantation following repeated applications of aerobically digested liquid biosolids. The trial is located on a sandy soil at Rabbit Island near Nelson, New Zealand. Biosolids were applied in 1997, 2000, and 2003, at 3 application rates: 0 (control), 300 (standard), and 600 kg N/ha (high). Litter layer and soil samples (down to 1 m) were taken from the trial site and analysed to assess the accumulation of heavy metals (Cu, Zn, Cd, Cr, Pb, and Ni) within the soil profile and the effect of repeated biosolids application on metal availability and mobility. Sequential fractionation methods were used to evaluate the distribution of exchangeable, specifically sorbed, oxide bound, organic bound, and residual fractions of the metals. Concentrations of Cr, Cu, Pb, and Zn in the litter layer were significantly (P < 0.05) higher in the high biosolids-treated plots than the control, indicating that the litter layer had retained considerable amounts of biosolids-derived metals. Significantly elevated concentrations of environmentally available Cu in the topsoil (0–0.1 m) were observed in plots receiving the high biosolids treatment and residual Cu concentration was significantly higher in the biosolids treatments, but apart from an accumulation of oxide-bound Zn in the 0.1–0.25 m layer, no accumulation of other metals in the soil was observed. The residual fraction was the most abundant pool for all metals examined, indicating low bioavailability. Total concentrations of the metals in both biosolids-treated and untreated control soils were very low (e.g. <7 mg Cu/kg, <30 mg Zn/kg). Although there were no significant changes in concentrations below the topsoil, mass balance calculation implied that a proportion of biosolids-derived Zn in the high biosolids treatment may have been leached through the soil profile.