Exotic Forest Plantations Research Articles

A multi-taxa assessment of nestedness patterns across a multiple-use Amazonian forest landscape

Understanding how biodiversity is partitioned among alternative land-uses is an important first step for developing effective conservation plans in multiple-use landscapes. Here, we analysed nestedness patterns of species composition for nine different taxonomic groups [dung beetles, fruit-feeding butterflies, orchid bees, scavenger flies, leaf-litter amphibians, lizards, bats, birds and woody plants (trees and lianas)] in a multiple-use forestry landscape in the Brazilian Amazon containing primary, secondary and Eucalyptus plantation forests. A formal nestedness analysis was performed to investigate whether species-poor land-uses were comprised of a subset of species from more diverse forests, and the extent to which this pattern varied among taxa. At the landscape-scale the species-by-sites matrices were significantly nested for all nine taxonomic groups when both sites and species were sorted to maximally pack the species/occurrence matrix and, except for orchid bees when sorted by land-use intensity (primary forest to Eucalyptus plantation). Different patterns emerged when we conducted pairwise analyses of nestedness between the three forest types: (a) most of the taxonomic groups were nested in accordance with increased land-use intensity; (b) neither orchid bees nor leaf-litter amphibians from secondary forest made up a significant nested subset of primary forest species, although species found in Eucalyptus plantation sites were nested within secondary forest communities; and (c) lizards from Eucalyptus plantations were not a nested subset of either primary or secondary forest. Our findings emphasize the complex nature of patterns of species occupancy in tropical multiple-use forestry landscapes, and illustrate that there may be no easy solutions to questions regarding the conservation value of secondary and exotic plantation forests.

Deforestación en ecosistemas templados de la precordillera andina del centro-sur de Chile

SUMMARY A multitemporal analysis to determine the land cover change was conduced in the pre-Andean range of Maule region of Chile. We used satellite imagery from the year 1989 and 2003 to analyze the likely causes of native forest change. In this period, there was a reduction in native forest area of 44% in the study area, which is equivalent to an annual forest loss rate of 4.1%. The native forest area is replaced by shrublands (29%) and exotic forest plantations (27%). A great proportion of current exotic forest plantations are established on lands that were native forest in 1989 (63%). Most forest loss was associated with intermediate elevation and less distance to road network, where native forest area dominated. Native forest replacing by shrublands was associated to selective forest logging and firewood, which leads to degradation of these forests. Native forest replacing by exotic forest plantations was the result of the forestation incentive and an increase in the demand for forest products such as wood and pulp. Because of multiple impacts of the forest loss, we propose to focus the government incentives. Priority areas for incentives must be characterized by high forest loss rate and poverty, presence of threatened species and low availability of water from catchments. Moreover, we propose to prioritize the connectivity of the current network protected areas and to develop an effective forest management monitoring system using advanced technologies.

Nuevos registros de poblaciones amenazadas de Pilgerodendron uviferum D.Don (Florin) en su límite norte en la Cordillera de la Costa chilena

We describe twelve previously undocumented Pigerodendron uviferum D.Don (Florin) populations outside of protected areas at the northern limit of the Chilean Coast Range (from 39o43'-40o S), extending their northern limits. These small swamp-populations are isolated within a matrix of pastures and exotic forest plantations, and are subject to “chronic” anthropogenic disturbances.

A DNA-based method for detection ofPeridermium harknessii, the causal agent of western gall rust

Peridermium harknessii is not present in the southern hemisphere yet it poses a serious threat to Pinus radiata cultivation in exotic forest plantations there. If a suspected incursion were to occur, it would be necessary to rapidly confirm the presence of P. harknessii within non-sporulating galls. With this in mind, we have developed a DNA-based identification system, using the first intergenic spacer region (IGS-1), that is able to detect the presence of the pathogen within galled tissue. The PCR primers are highly specific and with the exception of the closest relative, Cronartium quercuum f. sp. banksianae, they did not cross react with any of the 11 species within the closely related genera Cronartium and Peridermium that were tested. Phylogenetic analysis of the IGS-1 region confirmed that C. quercuum f. sp. banksianae is the closest relative to P. harknessii. The PCR primers and protocol reported here should prove useful in the event of a suspected western gall rust disease outbreak in exotic P. radiata plantations.

WATER-USE EFFICIENCY WITHIN A SELECTION OF INDIGENOUS AND EXOTIC TREE SPECIES IN SOUTH AFRICA AS DETERMINED USING SAP FLOW AND BIOMASS MEASUREMENTS

South Africa has limited indigenous timber-producin g forests. Recognition early in the 20 th century that demand for timber had exceeded the su pply available from indigenous forests forced South Africa to accelerat e the expansion of its own exotic plantation forest industry. This then resulted in c oncerns about impacts on water resources, and led to regulation of the industry. N umerous local and international studies have subsequently proven that exotic forest plantat ions do consume more water than the grasslands or scrublands they typically replace, an d hence reduce water yield (streamflow) from afforested catchments. Conversely, there is a widespread perception that indigenous tree species, in contrast to exotic plantation species, are water-wise and deserve to be planted more widely to expand forestr y while still conserving our scarce water resources. However, data on the water-use of indigenous trees and forests are scarce and indirect. To broaden understanding of both the growth and water-use rates of indigenous tree species, research was undertaken on their water-use efficiency (WUE), defined as mass of utilisable wood produced per uni t of water transpired. Hourly sap flow rates (water use) over a 12-month period were recor ded in a diverse selection of six indigenous tree species, while stem and branch dime nsions were recorded at fixed positions on the trees at the start and end of the monitoring period, to permit whole-tree volume growth increments to be recorded. Rates of growth and water-use were used to calculate WUE and were compared to existing data for exotic plantation species. WUE in the indigenous species studied was lower than for e xotic plantation species, however overall water-use was also low in the indigenous sp ecies. It was concluded that the relatively lower WUE of the indigenous species stud ied was more a consequence of slow growth rates as opposed to high water-use rates.

Aggregate stability and related properties in NW Patagonian Andisols

Resilience is an ecological concept explaining responses to disturbance or stress. For the soil system, it is defined as the ability of the soil to recover its condition of origin. Not much is known about the factors and processes that determine soil resilience and this research project was conducted to study soil resilience through analysis of changes in aggregate stability of Andisols supporting Pinus ponderosa Dougl. that replaced former Nothofagus sp. forest. Five sites with three treatments each were selected. Treatments included native forest, thinned exotic plantation forest and non-thinned exotic plantation forest. Bulk density and aggregate stability of the first 5 cm of the A-horizon were determined in undisturbed samples at field moisture, and the aggregate size distribution was determined involving the fractions of 8–2; 2–0.25; 0.25–0.053 and < 0.053 mm (diameter). The results indicated that the percentage of aggregates between 2 and 0.25 mm was significantly higher under Nothofagus (39.7%) than under pine without thinning (28.8%), with soil under thinned pine (32.0%) in between. The decrease in macroaggregates under pine without thinning was accompanied by a decrease in organic carbon content (from 70.2 g kg - 1 to 42.4 g kg - 1 ). Other results of importance were i) the high water stable aggregates under the different types of vegetation (> 80% of > 0.25 mm aggregates), indicating the relatively high stability of such Andisols; ii) highest organic matter contents found in the smallest sized aggregates, and iii) formation of stable soil aggregates to be significantly correlated with organic matter, Al activity, base content and soil reaction.

Effects of surrounding landscape composition on the conservation value of native and exotic habitats for native forest birds

The contribution of different production land uses to the conservation of native forest birds in modified, fragmented landscapes is a question of increasing relevance worldwide. Here, we tested the hypothesis that the abundance of native forest birds increases with increasing area of exotic plantation forests surrounding native forest remnants due to a reduction of negative effects of forest fragmentation and the provision of additional habitat. Conversely, farmland was not expected to provide such benefits to the same extent. Nine species of native birds were sampled in 238 plots in native forests, exotic plantation forests and mixed farmland on Banks Peninsula, South Island, New Zealand, where these land cover types are highly interspersed in a variety of spatial configurations. Around each sampling plot we determined the cover of native forest, plantation forest and mixed farmland within seven buffer zones ranging in radius from 200 m to 3000 m, using the New Zealand Land Cover Database 2. In native forests, the abundance of all but one species was negatively correlated with the amount of farmland surrounding points whereas the opposite applied when points were surrounded by native forest. There was a variable effect for native forest surrounded by plantation forest. In exotic plantation forests and farmland, the abundance of most species was positively correlated with the amount of native forest surrounding points. By contrast, for most species there was a small or moderate negative correlation with surrounding plantation forest. In farmland plots, bird abundance was positively correlated with native forest cover whereas plantation forest and farmland cover negatively affected most species. These results suggest that exotic plantation forests may mitigate effects of forest fragmentation for some native forest birds but not for others, and this appeared to depend on the landscape context. The maintenance of native forest remnants and forest restoration across the landscape, including within production land areas are important for the long-term conservation of the New Zealand's forest avifauna.

Non-native plantation forests as alternative habitat for native forest beetles in a heavily modified landscape

The once extensive native forests of New Zealand’s central North Island are heavily fragmented, and the scattered remnants are now surrounded by a matrix of exotic pastoral grasslands and Pinus radiata plantation forests. The importance of these exotic habitats for native biodiversity is poorly understood. This study examines the utilisation of exotic plantation forests by native beetles in a heavily modified landscape. The diversity of selected beetle taxa was compared at multiple distances across edge gradients between each of the six possible combinations of adjacent pastoral, plantation, clearfell and native forest land-use types. Estimated species richness (Michaelis–Menten) was greater in production habitats than native forest; however this was largely due to the absence of exotic species in native forest. Beetle relative abundance was highest in clearfell-harvested areas, mainly due to colonisation by open-habitat, disturbance-adapted species. More importantly, though, of all the non-native habitats sampled, beetle species composition in mature P. radiata was most similar to native forest. Understanding the influence of key environmental factors and stand level management is important for enhancing biodiversity values within the landscape. Native habitat proximity was the most significant environmental correlate of beetle community composition, highlighting the importance of retaining native remnants within plantation landscapes. The proportion of exotic beetles was consistently low in mature plantation stands, however it increased in pasture sites at increasing distances from native forest. These results suggest that exotic plantation forests may provide important alternative habitat for native forest beetles in landscapes with a low proportion of native forest cover.

Relevance of exotic pine plantations as a surrogate habitat for ground beetles (Carabidae) where native forest is rare

Plantation forests are of increasing importance worldwide for wood and fibre production, and in some areas they are the only forest cover. Here we investigate the potential role of exotic plantations in supporting native forest-dwelling carabid beetles in regions that have experienced extensive deforestation. On the Canterbury Plains of New Zealand, more than 99% of the previous native forest cover has been lost, and today exotic pine (Pinus radiata) plantations are the only forest habitat of substantial area. Carabids were caught with pitfall traps in native kanuka (Kunzea ericoides) forest remnants and in a neighbouring pine plantation, grassland and gorse (Ulex europaeus) shrubland. A total of 2,700 individuals were caught, with significantly greater abundance in traps in young pine, grassland and gorse habitats than in kanuka and older pine. Rarefied species richness was greatest in kanuka, a habitat that supported two forest specialist species not present in other habitat types. A critically endangered species was found only in the exotic plantation forest, which also acts as a surrogate habitat for most carabids associated with kanuka forest. The few remaining native forest patches are of critical importance to conservation on the Canterbury Plains, but in the absence of larger native forest areas plantation forests are more valuable for carabid conservation than the exotic grassland that dominates the region.

Forest Plantations and Biodiversity: A Fresh Perspective

Abstract We examined the worldwide literature on biodiversity in forest plantations for the indicator organism assessed, species composition (native versus exotic), tree species diversity, and appropriateness of the comparisons made. Fifty percent of the studies used invertebrates, 36% birds, 6% mammals, and 6% vascular plants as bioindicators. We found that 76% of the existing literature compares exotic plantation forests to native/natural forests, 9% of studies compare native plantations to native/natural forests, and 3% examine plantations to plantations. Lower biodiversity in plantation forest compared to other forests was reported by 94% of the reviewed studies. However, some studies indicate higher biodiversity in plantation forests compared to other land uses such as agriculture. We argue that much of the literature reporting lower biodiversity in plantation forests is based on inappropriate comparisons. We suggest more appropriate approaches to assessing the effects of plantation forests on biodiversity.

Parasitoids and predators of the endemic defoliator Pseudocoremia suavis (Butler) (Lepidoptera: Geometridae: Ennominae)

Pseudocoremia suavis is an endemic looper with a history of damaging outbreaks in exotic plantation forests in New Zealand. Little is known of the natural enemies of this pest, or what role they might play in the regulation of populations. Here we compile a list of parasitoids and predators of this species, including the results of recent collections of larval parasitoids at Eyrewell Forest, a pine plantation in North Canterbury. Thirteen primary parasitoids, two hyperparasitoids and 11 predators are recorded. The dominant parasitoid reared from larval collections made at Eyrewell Forest in this study was Aleiodes declanae. This species was also dominant during P. suavis outbreaks at Eyrewell Forest during the 1950s and 1960s, along with the pupal parasitoids Aucklandella conspirata, A. pyrastis, and Zealachertus longus. Previously unpublished information on the biology of the parasitoids and predators gathered during this study and during previous outbreaks of P. suavis is included.

Discrimination of native and exotic forest patterns through shape irregularity indices: An analysis in the landscapes of Galicia, Spain

Landscapes resulting from human activity may be expected to present simpler shapes than more natural landscapes. In the case of forest landscapes, the boundaries of native forest patches may be more irregular than those of exotic forest plantations. There is however a lack of quantitative results to this respect, and it is not clear which shape indices are more adequate for such discrimination. In this study, we analysed the shape of a large number of forest classes in the region of Galicia (Spain) using the Spanish Forest Map at a scale 1:50 000 as the spatial information source. We considered a set of fifteen shape irregularity indices including those that have been commonly used in landscape ecology studies. We found systematic differences in the shape of the analysed forest classes, with native forests presenting both more complex and elongated boundaries than exotic forests. We suggest that these differences are due to the combined effects of human action and other topographical and hydrological factors. The only index that perfectly discriminated both types of forest was the mean circumscribing circle index. Other six indices provided also a significantly good discrimination: density of shape characteristic points, area-weighted mean perimeter-area ratio, area-weighted mean contiguity index, mean shape index, perimeter-area fractal dimension and mean largest axis index. Comparisons of pure and mixed forests with the same dominant species indicated that an increase in tree species richness is in general associated with more irregular boundaries in the forest. Discarding indices on the basis of a high statistical correlation may not be an adequate procedure to retain the best-performing indices. Finally, we discussed several limitations of some frequently used indices that may be relevant to prevent an improper characterization of landscape shape.

Land-use change alters New Zealand’s terrestrial carbon budget: uncertainties associated with estimates of soil carbon change between 1990–2000

In New Zealand, afforestation and reforestation of grazing land give rise to large (relative to national CO2 emissions) vegetation carbon (C) sinks. These land-use changes may, however, lead to losses of mineral soil C. Full C accounting may, therefore, require including mineral soil C losses if credits are awarded for vegetation C. To monitor soil C stocks and changes, we developed an IPCC-based soil Carbon Monitoring System (CMS) in which New Zealand is stratified by soil type, climate, land-use and an erosivity index (slope × precipitation). Georeferenced soil C data were used to assign steady-state soil C stocks to various combinations of these factors (cells). We then used a General Linear Model to compare soil C between cells, and derived land-use effects (LUEs) from this analysis that quantify soil C changes that accompany land-use change. These LUEs were used to predict soil C changes resulting from land-use change between 1990–2000. We tested the CMS by comparing predicted soil C stocks, and changes in these stocks, against more detailed soil C data. Overall, soil C estimates obtained from the CMS are consistent with detailed, stratified soil C measurements at specific sites and over larger regions. However, for grazing-land to exotic-forest conversions, estimates of soil C changes are higher and more variable than those based on paired-site studies. Nationally, soil C losses of 0.9 ± 0.4 Tg C yr−1 for all land-use changes over the period 1990–2000 appear likely, with uncertainties arising mainly from estimates of changes in the areas involved, and LUE values for cells with limited soil C data. Changes in soil C in reforested land are likely to be small, but precise area changes, soil C data and detailed paired-site studies are lacking for this key land-use change. By contrast, biomass C accumulation in new exotic plantation forests (afforestation) and native reforestation are 6–9 Tg C yr−1, with C accumulation by afforestation being well quantified. Detailed site studies, process-based modelling and improved area-change estimates are needed to further reduce uncertainties in land-use-change effects on soil C. Our approach could be adapted to countries with country-specific land-use issues different from those in the IPCC default methodology.

Soil nitrogen mineralisation changes rapidly when pine is planted into herbicide-treated pasture—the first two years of growth

The conversion of hill country pastures to exotic forest plantations has occurred rapidly in New Zealand over the last 10 years. This land-use change affects properties of the mineral soil, especially nitrogen (N) cycling. Here we studied the changes in soil in situ N mineralisation, in leaching, and microbial biomass, when Pinus radiata D. Don is planted into pasture; sheep were used to reduce pasture herbage before planting, and then herbicide was used to control the rank growth of grass around the trees. Total net N mineralisation in soil (0–100 mm) under pasture was 325 kg/ha.year. Net N mineralisation in the herbicide-treated areas was about double that under pasture or rank grass in the first 2 months. The concentration of nitrate-N in soil solution in the herbicide-treated areas was then 81 mg/L, compared with &lt;2 mg/L under pasture. During this time, the pH under the pine trees decreased very rapidly as nitrification increased. Soil nitrification and nitrate leaching were enhanced for 15 months after application of herbicide. After this 15-month period, soil total carbon (C) was slightly lower (P &lt; 0.10) under trees than rank grass, whereas microbial C and N were markedly lowest (P &lt; 0.05) under the trees. Over this period, about 18 kg N/ha was leached to 250 mm in the tree-planted area. The data also give additional insights into processes that occur when soil cores in buried bags are used to estimate N mineralisation.

2003 Daniel McAlpine Memorial Lecture Increasing threat of diseases to exotic plantation forests in the Southern Hemisphere: lessons from Cryphonectria canker

Plantation forestry in the Southern Hemisphere has grown dramatically in the last hundred years. This has largely been due to the exceptional growth and performance of exotic species, particularly Pinus, Eucalyptus and Acacia. It is generally recognised that the success of these plantations has, at least in part, been due to the separation of the trees from their natural enemies. In this regard, the trees have performed similarly to weeds. Indeed, in some situations, species regarded as highly desirable for forestry are also recognised as noxious weeds. The artificial barrier between exotic plantation species and their pathogens is, however, crumbling. Despite intensive efforts to exclude pests and pathogens from countries now dependent on plantations of exotic trees, new and seriously damaging incursions are occurring with increasing frequency. Cryphonectria canker of Eucalyptus caused by Cryphonectria cubensis provides an important and interesting example and is used in this paper to illustrate emerging trends. These include evidence to suggest that native pathogens, previously thought to be relatively host specific and non-threatening, are adapting to infect exotic plantation trees. Other than the damage that these pathogens are causing to exotics, they now pose a serious threat to the same or related tree species in their areas of origin. This tremendous threat is only just being recognised and it is little understood. This is, at least in part, due to a poor understanding of the taxonomy and ecology of even some of the better known tree pathogens. Intensive efforts will be required to protect the sustainability of exotic plantation forestry. They will also be needed to ensure that ‘new pathogens’ do not lead to destruction of the same or related tree species in their areas of origin.

First report of the pitch canker fungus, Fusarium circinatum, on pines in Chile

Pitch canker, caused by Gibberella circinata (Fusarium circinatum), is currently regarded as one of the most serious diseases of pines in the world. The disease was first discovered in the south-eastern United States in the early 1900s and subsequently, has caused sporadic occurrences of severe disease in that area. More recently, the disease appeared in California where it is currently causing a serious epidemic on native Pinus radiata, which is of international concern (Gordon et al., 2001). Pinus radiata forms the basis of extensive areas of exotic forest plantation in many countries in the Southern Hemisphere. For this reason, pitch canker is viewed as one of the greatest threats to globally relevant forest industries in these areas. Consequently, various international programmes have been established in an attempt to reduce this threat (Devey et al., 1999). During the course of recent surveys in the Concepción area of Chile, dying P. radiata plants have been discovered in both containerized and open rooted clonal hedges. Plants appear to die rapidly and typically display resin exudation from the root collar areas and pitch-soaked wood associated with these lesions. Isolations from symptomatic tissue have consistently yielded cultures of Fusarium belonging to the Fusarium subglutinans species complex. Isolates have sterile hyphal coils strongly reminiscent of F. circinatum. Single conidial cultures paired with mating tester strains of the ‘H’ mating population (Britz et al., 1999) consistently showed sexual compatibility. To further confirm their identity, a PCR-RFLP test based on histone H3 gene sequences (Steenkamp et al., 1999) was used on six isolates to compare them with members of the F. subglutinans species complex. This technique reliably distinguishes F. circinatum from other species in this complex. Results confirmed morphological comparisons and mating compatibility tests showing that the fungus associated with dying plants in Chile is F. circinatum. Although F. circinatum is causing damage to P. radiata plants in Chilean nurseries, it has as yet, not been found on trees in plantations. In this sense, the situation is similar to that in South Africa, where the pathogen causes serious damage to seedlings in nurseries but is not associated with typical symptoms of pitch canker. The fact that P. radiata is highly susceptible to infection by F. circinatum and that this tree forms the basis of the local forestry is of significant concern. This concern is heightened by the fact that various insect pests of P. radiata are present in Chile that are capable of providing infection sites for the pitch canker fungus. Consequently, various strategies linked to tree breeding and selection have been established to minimise the long-term threat of pitch canker in Chile.

Genetic variability of Pisolithus isolates associated with native hosts and exotic eucalyptus in the western Mediterranean region.

• Genetic diversity and host specificity of Pisolithus is reported here in exotic (Eucalyptus) and native hosts in the western Mediterranean region. • Polymorphism in the internal transcribed spacer (ITS) sequences of the nuclear rDNA of Pisolithus was analysed. Sequences for 17 isolates associated with native Mediterranean hosts and Eucalyptus were compared with those in the GenBank DNA database using distance and parsimony methods. • Bootstrap analysis showed clustering of all Pisolithus isolates associated with Mediterranean hosts. The ITS sequences suggest the occurrence of several ecological species adapted to exploit different soil types (basic, acid and clayey slate-derived soils), with specificity for particular indigenous hosts. Isolates from eucalypt plantations in Brazil, Kenya and the Mediterranean grouped together with eucalypt-associated Australian isolates. Transfer to native hosts did not occur; the host specificity range of these exotic strains might prevent out-competition and interbreeding with local species. • Pisolithus spp. in eucalypt plantations in the Mediterranean basin are of Australian origin; the co-introduction of the ectomycorrhizal fungi might explain the success of these exotic forest plantations.

Conservation of the greater glider (Petauroides volans) in remnant native vegetation within exotic plantation forest

AbstractA field‐validated metapopulation model of patch occupancy was used to examine the persistence of greater gliders (Petauroides volans) in patches of remnant native eucalypt forest in south‐eastern Australia. The model was based on a system of eucalypt patches embedded within a plantation forest of exotic radiata pine (Pinus radiata) at Buccleuch State Forest, New South Wales. The probability of local extinction in occupied patches was a function of patch size. The probability of colonization of empty patches was a function of the size and proximity of occupied patches. The results of the simulations suggested that suitable habitat should occupy approximately 10% (or more) of the total landscape to ensure the persistence of greater gliders. Rates of patch occupancy were maximized when suitable habitat was clustered into larger patches. Patches &lt;3 ha in area were predicted to be of limited value as habitat for greater gliders. The predictions of the model are consistent with the observed persistence of greater gliders in the eucalypt patch system. The system of unlogged eucalypt patches within the pine plantation is a useful model of a network of small to medium‐sized conservation reserves. Principles of reserve design can have value even in somewhat degraded and highly modified landscapes. The results demonstrate that reserved patches of native forest embedded within intensively logged forest can have significant conservation value, with important implications for the design and establishment of new softwood plantations.

Conservation of the greater glider (Petauroides volans) in remnant native vegetation within exotic plantation forest

A field-validated metapopulation model of patch occupancy was used to examine the persistence of greater gliders (Petauroides volans) in patches of remnant native eucalypt forest in south-eastern Australia. The model was based on a system of eucalypt patches embedded within a plantation forest of exotic radiata pine (Pinus radiata) at Buccleuch State Forest, New South Wales. The probability of local extinction in occupied patches was a function of patch size. The probability of colonization of empty patches was a function of the size and proximity of occupied patches. The results of the simulations suggested that suitable habitat should occupy approximately 10% (or more) of the total landscape to ensure the persistence of greater gliders. Rates of patch occupancy were maximized when suitable habitat was clustered into larger patches. Patches <3 ha in area were predicted to be of limited value as habitat for greater gliders. The predictions of the model are consistent with the observed persistence of greater gliders in the eucalypt patch system. The system of unlogged eucalypt patches within the pine plantation is a useful model of a network of small to medium-sized conservation reserves. Principles of reserve design can have value even in somewhat degraded and highly modified landscapes. The results demonstrate that reserved patches of native forest embedded within intensively logged forest can have significant conservation value, with important implications for the design and establishment of new softwood plantations.

Soil carbon storage in plantation forests and pastures: land-use change implications

Afforestation may lead to an accumulation of carbon (C) in vegetation, but little is known about changes in soil C storage with establishment of plantation forests. Plantation forest carbon budget models often omit mineral soil C changes from stand-level C budget calculations, while including forest floor C accumulation, or predict continuous soil C increases over several rotations. We used national soil C databases to quantify differences in soil C content between pasture and exotic pine forest plantations dominated by P. radiata (D. Don), and paired site studies to quantify changes in soil C with conversion of pasture to plantation forest in New Zealand. Overall, mineral soil C to 0.10 m was 20–40% lower under pine for all soil types (p < 0.01) except soils with high clay activity (HCA), where there was no difference. Similar trends were observed in the 0.1–0.3 m layer. Moreover, mineral soil C to 0.1 m was 17–40% lower under pine than pasture in side-by-side comparisons. The only non-significant difference occurred at a site located on a HCA soil (p < 0.08). When averaged across the site studies and the national databases, the difference in soil C between pasture and pine was about 16 t C ha-1 on non-HCA soils. This is similar to forest floor C averaged across our individual sites (about 20 t C ha-1). The decrease in mineral soil C could result in about a 15% reduction in the average C sequestration potential (112 t C ha-1) when pasture is converted to exotic plantation forest on non-HCA soils. The relative importance of this change in mineral soil C will likely vary depending on the productivity potential of a site and harvest impacts on the forest floor C pool. Our results emphasize that changes in soil C should be included in any calculations of C sequestration attributed to plantation forestry.