The peninsula effect on bird species in native eucalypt forests in a wood production landscape in Australia

The peninsula effect – a decrease in species richness from the base to the tip of a peninsula – has been tested for a diverse range of taxa at continental and regional scales. We investigated the peninsula effect at a local scale by examining bird species occurrence in riparian strips (peninsulas) of native eucalypt forest within a radiata pine plantation in the Tumut region, south-eastern Australia. Peninsulas were elongated but 'blind' extensions of a core area of native eucalypt forest. Birds were surveyed by the area search method, within 1.0-ha quadrats established along peninsulas ( n =14), in October and November 2002. Data were analysed using generalized linear mixed models. A significant decrease in bird species richness from the base towards the tip of the peninsulas was observed. The proportion of large bird species recorded per quadrat showed a significant decrease from the base towards the tip of the peninsulas. This pattern was not observed for small birds. Several species were more abundant at the base of the peninsulas than away from the core area of eucalypt forest. The peninsula effect can occur locally in landscape mosaics. Factors leading to the observed patterns of species occurrence may be distinct from those proposed in investigations of the peninsula effect with a biogeographical (macroscale) context. In our microscale study, foraging incursions of individual birds from the core area of native forest through peninsulas were a major factor giving rise to higher bird species richness in the more basal portions of peninsulas.     

Assessment and monitoring of damage from insects in Australian eucalypt forests and commercial plantations

Abstract   This paper presents a review of recent developments in the assessment and monitoring of health in Australian eucalypt forests and plantations of pine and eucalypt species, with an emphasis on damage caused by herbivorous insects. The diverse range of interests and priorities amongst Australian stakeholders of native forests and plantations influences the scale, resolution and accuracy of results sought, and this in turn influences how the assessment data are collected, analysed and reported. The authors discuss sampling systems that include extensive ground-based surveys, permanent plots and airborne technologies being developed in Australia. In all cases, there is an appreciation that the assessment protocols should be objective, repeatable and cost effective. Significant progress has been made in the application of digital, remotely sensed imagery to detect and classify damaged forest canopies. The success of this approach depends, in part, on a sound understanding of the progression of symptoms at the leaf, tree crown and stand scale, especially those symptoms that influence spectral reflectance behaviour.     

Spatially modelling native vegetation condition

Summary   The assessment of vegetation condition is seen as an increasingly important requirement for effective biodiversity conservation in Australia. Condition assessments that operate at the scale of the site are well established. However, there is a need for mapped representations of vegetation condition at regional scales to: (i) assist with regional planning and target setting; (ii) provide regional context for site-based assessment; and (iii) monitor the change in vegetation condition at multiple scales. This paper describes a methodology for converting site condition data collected in plots into maps of vegetation condition across entire regions using a predictive statistical modelling framework (Generalized Additive Modelling) combined with a GIS. The research demonstrates how explanatory variables including topographic position, terrain roughness, landscape connectivity and remote sensing derived indices can be used to map the condition of native vegetation at the scale of a subcatchment. The inclusion of indices derived from remotely sensed imagery (SPOT4) as explanatory variables in the modelling is a novel component of this research. Although the methodology generates statistically and ecologically plausible models of vegetation condition, there are nevertheless limitations associated with the way plot data were collected and some of the explanatory variables, which impacts upon model utility. We discuss how these problems can be minimized when embarking upon studies of this type. We demonstrate how maps produced from exercises such as this could be used for conservation planning and discuss the limitations of these data for monitoring.     

Evaluation of a visual assessment method for tree condition of eucalypt floodplain forests

Summary For decades the floodplain forests of the River Murray have endured the effects of prolonged water stress. This has resulted in significant crown dieback and loss of condition. The Living Murray (TLM) initiative aims to restore the ecological health of six Icon Sites along the River. The two eucalypts River Red Gum (Eucalyptus camaldulensis) and Black Box (Eucalyptus largiflorens) that dominate the forests at five of the six Icon Sites are undergoing widespread decline. To enable effective management and restoration of these forests, we developed a standardised tree condition assessment method. Named the TLM tree condition assessment method, it utilises visual assessment of a range of tree crown variables (extent and density of the foliage in the crown, epicormic growth, new tip growth, reproductive activity, leaf die‐off, mistletoe infestation) and measurements of bark condition, diameter at breast height and dominance class. This article describes the TLM tree condition assessment method and assesses it for consistency between multiple observer teams after limited training. The level of observer agreement between six teams each comprised of two observers was assessed for seven of the ten variables. Intra‐class correlation was used to compare scores of 30 River Red Gum trees assessed on Gunbower Island on the River Murray. The level of agreement for all variables was statistically significant with six of seven variables having correlation coefficients over R = 0.5. The TLM tree condition assessment method was found to provide accurate estimates of a range of tree variables that can be used to determine tree condition. The TLM tree condition assessment method provides a valuable monitoring tool that can be used to assess management interventions, such as management flooding and silvicultural thinning.     

Seasonality of canopy invertebrate communities in eucalypt forests of eastern and western Australia

Abstract Chemical knockdown procedures were used to sample canopy arthropods at 3 month intervals over 1 year at two sites, one in eastern Australia and the other in western Australia. Samples were taken from narrow-leaved ironbark, Eucalyptus crebra, and grey box, Eucalyptus moluccana, in the east and from jarrah, Eucalyptus marginata, and marri, Eucalyptus calophylla, in the west. Arthropods were more abundant on trees in eastern Australia and exhibited different seasonal patterns from those in the west. Members of different functional groups exhibited different seasonal patterns, with some herbivorous groups responding to times of leaf production, decomposers and fungus feeders responding to high moisture availability, and predators/parasites responding to the abundance of food items. Seasonal variability was slightly higher in the west, possibly reflecting the greater seasonal amplitude in rainfall. In the eastern forest, proportionately more taxa peaked in spring or summer and declined to minimum numbers in winter. In the western forest several taxa attained peak numbers in autumn, winter or spring, while others declined to minimum values in winter or summer. The phenological patterns of canopy arthropods appear to be linked to the condition of the host plant and/or to climatic factors. Comparison of the western Australian data to those from a second year of sampling at a time when rainfall was greater and fell later into the season indicated that variability in arthropod numbers between years can be as great as that between seasons. Implications of the variability in seasonal and annual patterns of canopy invertebrate communities are discussed in relation to the need for long-term sampling and in relation to evaluating the impact of disturbance on forest communities.     

联合星载ICESat-GLAS波形与多光谱Landsat-TM影像的森林郁闭度估测

森林郁闭度的空间分布是评价森林生产力和分解率的一个重要指标.本研究以吉林汪清林区为研究区,分别利用星载激光雷达ICESat-GLAS波形数据和多光谱遥感Landsat-TM影像对该区的森林郁闭度进行估测,然后采用多元线性回归和BP神经网络两种方法对GLAS数据和TM数据进行联合,共同估测了森林郁闭度.结果表明:单一遥感数据估测森林郁闭度时,GLAS数据的模型决定系数为0.762,TM数据的模型决定系数为0.598.将GLAS数据和TM数据联合后估测森林郁闭度时,多元线性回归模型的复决定系数为0.841,BP神经网络模型的仿真精度为0.851.表明ICESat-GLAS数据与Landsat-TM影像联合能够发挥多源遥感数据的优势,提高森林郁闭度的估测精度,并为后续的空间区域内森林郁闭度的连续制图提供可靠的方法.     

Comparison of contemporary mating patterns in continuous and fragmented Eucalyptus globulus native forests

While habitat fragmentation is a central issue in forest conservation studies in the face of broad-scale anthropogenic changes to the environment, its effects on contemporary mating patterns remain controversial. This is partly because of the inherent variation in mating patterns which may exist within species and the fact that few studies have replication at the landscape level. To study the effect of forest fragmentation on contemporary mating patterns, including effective pollen dispersal, we compared four native populations of the Australian forest tree, Eucalyptus globulus . We used six microsatellite markers to genotype 1289 open-pollinated offspring from paired fragmented and continuous populations on the island of Tasmania and in Victoria on mainland Australia. The mating patterns in the two continuous populations were similar, despite large differences in population density. In contrast, the two fragmented populations were variable and idiosyncratic in their mating patterns, particularly in their pollen dispersal kernels. The continuous populations showed relatively high outcrossing rates (86–89%) and low correlated paternity (0.03–0.06) compared with the fragmented populations (65–79% and 0.12–0.20 respectively). A greater proportion of trees contributed to reproduction in the fragmented ( de/d ≥ 0.5) compared with the continuous populations ( de/d  =   0.03–0.04). Despite significant inbreeding in the offspring of the fragmented populations, there was little evidence of loss of genetic diversity. It is argued that enhanced medium- and long-distance dispersal in fragmented landscapes may act to partly buffer the remnant populations from the negative effects of inbreeding and drift.     

Ground monitoring the light–shadow windows of a tree canopy to yield canopy light interception and morphological traits

Monitoring the light–shadow windows of a tree via a grid system on the ground was performed on sunny summer days at high spatial resolution using a custom‐built, inexpensive scanner. The measurements were taken with two goals: (1) to quickly and remotely quantify the overall, short‐wave solar radiation (300–1100 nm) intercepted by the tree canopy, and (2) to yield such crown geometric traits as shape, size and the number of theoretical canopy leaf layers (leaf layer index, LLI) in relation to the section orthogonal to sunbeam direction (sun window). The ground readings at each measurement over the day were used to project a digitized shadow image. Image processing was applied and the intercepted radiation was calculated as the difference from the corresponding incoming radiation above the canopy. Tree‐crown size and shape were profiled via computer imaging by analysing the different shadow images acquired at the various solar positions during the day. It is notable that these combined images yielded the crown features without having to parameterize such canopy characteristics as foliage extension and spatial distribution.     

Diversity of canopy and understorey spiders in north-temperate hardwood forests

1 We characterized and compared diversity patterns of canopy and understorey spiders (Arachnida: Araneae) on sugar maple ( Acer saccharum Marsh.) and American beech ( Fagus grandifolia Ehrh.) in hardwood forests of southern Québec, Canada.
2 We sampled canopies of 45 sugar maple and 45 American beech trees and associated understorey saplings in mature protected forests near Montréal. Samples were obtained by beating the crown foliage at various heights and by beating saplings around each tree.
3 Eighty-two species were identified from 13 669 individuals. Forty-eight species and 3860 individuals and 72 species and 9809 individuals were collected from the canopy and the understorey, respectively.
4 Multivariate analyses (NMDS ordination and NPMANOVA) showed the composition of canopy and understorey assemblages differed significantly, and canopy assemblages differed between tree species. Rank-abundance distribution models fitted to the canopy and understorey data indicated that different mechanisms structure the assemblages in both habitats. Three abundant spider species were significantly more common in the canopy; ten species were collected significantly more often in the understorey.
5 The forest canopy was shown to be an important reservoir for spider diversity in north-temperate forests.     

辽东栎冠层光合生理特性的空间异质性

冠层作为林木与环境因子相互作用最为直接的部分,研究冠层光合作用是分析森林生产力的基础。以北京东灵山辽东栎为对象,利用Li-6400便携式光合仪测定了不同冠层不同方向部位叶片的光合速率和光响应曲线,研究了叶片光合生理特性在冠层空间上的变化。结果表明：在不同冠层和不同方向上,饱和光合速率、光补偿点、光下暗呼吸和表观量子效率均存在差异,随着冠层下降以及从南至北,大多数光合生理特性指标表现出递减趋势。进一步的通径分析结果得出,光强、水气压亏缺、温度是影响不同层次光合速率的主要因子。冠层光合特性的空间异质性研究,对于在冠层水平上揭示植物固碳能力和估算植物生产力具有很重要的意义。     

Spatial distribution of phytomass carbon in Indian forests

A spatial analysis of phytomass carbon (C) in Indian forests for the period (1988–94) at the district‐level is reported. District‐level forest phytomass C (1988, 1994) was computed by combining remote sensing‐based forest area inventories on 1:250 000 scale, field inventories of growing stock volume by the Forest Survey of India (FSI), and crown density‐based biomass expansion factors. The estimates of forest area inventory, forest phytomass C density, and forest phytomass C pools (1988–94) were linked to the district boundary coverage of India in ARC/INFO Geographic Information System (GIS). Of the total 386 districts examined, only 17 districts had more than 75% forest cover (as percent of their geographic area) in 1988. Estimated district‐level forest phytomass C densities ranged from 4.3 to 206.8 MgC ha^?1*. At the national level, forest phytomass C pool was estimated to be 3871.2 and 3874.3 TgC# in 1988 and 1994, respectively. Although the aggregated national estimates were similar, the district‐level change analysis indicated a decrease of 77.8 TgC and an increase of 81 TgC (1988–94). The highest decrease of 10.4 TgC was observed in Vishakapatnam district (Andhra Pradesh) while largest increase of 9.8 TgC in Bastar district (Madhya Pradesh) resulting from deforestation and afforestation activities, respectively. At the national level, the total forest cover decreased by ～0.6 Mha, however, the district‐level spatial analysis indicated an increase of 1.07 Mha, and decrease of 1.65 Mha forest cover during 1988–94 period. Although, this is the first district level phytomass C analysis of Indian forests, the aggregated results at state‐level were close to the earlier estimates. The spatial analysis identified the districts that have undergone significant changes in their forest phytomass C during the study period. This improved understanding of forest phytomass C pools is important to sustainable development and conservation of forests, mitigation strategies for C sequestration, and accurate estimation of contribution of land use changes to C emission in India.     

Using Satellite Images to Classify and Analyze the Health of Hemlock Forests Infested by the Hemlock Woolly Adelgid

A method is described to classify stands of eastern hemlock by health condition, at the landscape level, using remote sensing. The hemlock woolly adelgid has been a major cause of hemlock decline in Connecticut since 1985, resulting in varying degrees of defoliation in the region. A 1985 Landsat Thematic Mapper (TM) image was classified to develop a base line of once healthy hemlock stands. Radiance normalization and non-hemlock masking techniques were used to pre-process a 1995 TM image. Several techniques were used to transform the 1995 TM image; each was followed by cluster analysis to separate hemlocks into four levels of tree vigor. We evaluated 600 trees at 150 sites across the study area using the USFS Crown Condition Rating Guide. These field data were used to measure the accuracy of various health classification techniques. The Modified Soil Adjusted Vegetation Index-2 (MSAVI₂) transform provided the best overall accuracy, 82.1%, for classifying hemlock according to tree vigor. Non-parametric statistics were used to determine if there were any significant variations in distribution of hemlock pixels by health class in association with features in the landscape. Several features were found to be statistically significant at a confidence level of 0.001. These were aspect of slope, hydrology group (infiltration rate), depth to bedrock, soil order, drainage class (hydraulic conductivity), and surface texture.     

Scaling gross ecosystem production at Harvard Forest with remote sensing: a comparison of estimates from a constrained quantum-use efficiency model and eddy correlation

Two independent methods of estimating gross ecosystem production (GEP) were compared over a period of 2 years at monthly integrals for a mixed forest of conifers and deciduous hardwoods at Harvard Forest in central Massachusetts. Continuous eddy flux measurements of net ecosystem exchange (NEE) provided one estimate of GEP by taking day to night temperature differences into account to estimate autotrophic and heterotrophic respiration. GEP was also estimated with a quantum efficiency model based on measurements of maximum quantum efficiency (Qmax), seasonal variation in canopy phenology and chlorophyll content, incident PAR, and the constraints of freezing temperatures and vapour pressure deficits on stomatal conductance. Quantum efficiency model estimates of GEP and those derived from eddy flux measurements compared well at monthly integrals over two consecutive years (R²= 0–98). Remotely sensed data were acquired seasonally with an ultralight aircraft to provide a means of scaling the leaf area and leaf pigmentation changes that affected the light absorption of photosynthetically active radiation to larger areas. A linear correlation between chlorophyll concentrations in the upper canopy leaves of four hardwood species and their quantum efficiencies (R²= 0–99) suggested that seasonal changes in quantum efficiency for the entire canopy can be quantified with remotely sensed indices of chlorophyll. Analysis of video data collected from the ultralight aircraft indicated that the fraction of conifer cover varied from < 7% near the instrument tower to about 25% for a larger sized area. At 25% conifer cover, the quantum efficiency model predicted an increase in the estimate of annual GEP of < 5% because unfavourable environmental conditions limited conifer photosynthesis in much of the non-growing season when hardwoods lacked leaves.