Edge effects and forest water use: A field study in a mixed deciduous woodland

A field study was carried out in a mixed deciduous forest in order to measure the spatial variability of evapotranspiration in relation to distance from the nearest forest edge. Throughfall was collected in storage gauges in a transect across the edge. Transpiration was measured at the tree scale by means of the sap flux technique. Thermal dissipation probes were inserted into the hydro-active sapwood of 12–16 sample trees at a time covering four species. The sample trees were located close to a north- and a south-facing forest edge and between 3 and 69 m away from the nearest edge. The probes were moved to new trees about once a month and in total 71 trees were sampled. Sap flux densities were compared with potential evaporation and scaled up to the stand through multiplication with sapwood area per unit ground area. No significant edge effect on interception evaporation could be detected but there was a large influence on stand transpiration which increased towards the edge. In ash (Fraxinus excelsior L.), this increase resulted mainly from enhanced sap flux density (by 33–82%, depending on the size class) in trees located at the edge, whereas in oak (Quercus robur L.) the sap flux density was similar in edge and inner trees and an effect was only found at the stand scale in the way that the total basal area, per unit ground area, was larger near the forest edge than in the forest interior. Hawthorn (Crataegus monogyna L.) and field maple (Acer campestre L.), which occurred mainly in the understorey, were only weakly affected by the proximity to an edge. At the stand scale the total seasonal transpiration varied between 354 mm in the forest interior (>45 m away from the edge) and 565 mm at the forest edge (<15 m away from the edge), whilst the potential evaporation over the same period was 571 mm. This corresponds to Priestley–Taylor coefficients of 0.78 in the interior and 1.25 at the edge, whilst intermediate numbers were found for the area between the edge and inner zones. Using these results to calculate the average water loss per unit ground area of hypothetical woodlands of various sizes, it is shown that the edge effect dominates the water use of small forests and becomes negligible only for woodlands larger than 100 ha.     

朝阳地区油松人工林天然更新的主要类型

采用标准地调查方法对朝阳地区油松人工林天然更新进行了研究,将其归纳为疏林林下更新、林缘更新、侵蚀沟更新、林隙更新和动物传播种子更新5种类型。不同坡向疏林地油松天然更新幼树株数差异明显;侵蚀沟内油松天然更新明显优于正常坡面;阴坡林隙更新良好,阳坡林隙基本不能进行天然更新;油松林缘更新幼树主要分布于距林缘20 m以内;动物传播种子天然更新多以散生天然油松幼树形式存在。     

The response of small mammals to natural and human-altered edges associated with Afromontane forests of South Africa

An increase in edge area reduces the effective size of habitat fragments and thus the area available for habitat-interior specialists. However, it is unclear how edge effects compare at different ecotones in the same system. We investigated the response of a small mammal community associated with Afromontane forests to edge effects at three different habitat transitions: natural forest to grassland (natural edge, structurally different vegetation types), natural forest to mature plantation (human-altered edge, structurally similar vegetation types) and natural forest to harvested plantation (human-altered edge, structurally different vegetation types). We predicted that edge effects should be less severe at natural ecotones and at similarly structured contiguous vegetation types than human-altered ecotones and differently structured contiguous vegetation types, respectively. We found that forest species seemed to avoid all habitat edges in our study area. Surprisingly, natural edges supported a less diverse small mammal community than human-altered forest edges. However, edge effects were observed deeper into native forests surrounded by mature alien plantations (and more so at harvested plantations) than into native forests surrounded by native grasslands. The net effect of mature plantations was therefore to reduce the functional size of the natural forest by creating a larger edge. We suggest that when plantations are established a buffer zone of natural vegetation be left between natural forests and newly established plantations to mitigate the negative effects of plantation forestry.     

Morphological variation along the sea-land gradient: trees in a subtropical maritime woodland

As long-lived sessile organisms, trees demonstrate morphological variability in response to the environmental conditions encountered in a particular local habitat. However, the detection of such variation on a small spatial scale may not be straightforward. In this study we investigated the morphological variation of trees along the edge–interior gradient of a small subtropical-temperate coastal woodland in Amakusa, western Kyushu, Japan. The woodland was located on a narrow sand-spit surrounded by the sea, thus exposed to intense marine influences. In three dominant tree species, Quercus glauca, Ligustrum japonicum, and Pittosporum tobira, the tendency of multi-stemming was significantly greater on the seaward edge of the woodland and declined towards the interior. Furthermore, tree height and size (cross-sectional area at breast height) declined and canopy openness increased towards the woodland edge. In Q. glauca and L. japonicum, shoot growth was more pronounced in the interior than on the edge (i.e. shorter shoots with wider spacing in the latter habitat). Thus, spatial variation in tree structure manifested clearly as shorter height with greater multi-stemming tendencies and greater canopy openness (more spacing among branches/shoots) towards the woodland edge where more light is available and the effects of sea wind and salt spray are greater.     

Enhanced transpiration in response to wind effects at the edge of a blue gum (Eucalyptus globulus) plantation

In Australia, tree planting has been widely promoted to alleviate dryland salinity and one proposed planting configuration is that of strategically placed interception belts. We conducted an experiment to determine the effect of tree position in a belt on transpiration rate. We also assessed how much the effect of tree position can be explained by advection and environmental conditions. Daily transpiration rates were determined by the heat pulse velocity technique for four edge and 12 inner trees in a 7-year-old Tasmanian blue gum (Eucalyptus globulus) plantation in South Australia. Various climatic variables were logged automatically at one edge of the plantation. The relationship between daily sap flow and sapwood area was strongly linear for the edge trees (r2 = 0.97), but only moderately correlated for the inner trees (r2 = 0.46), suggesting an edge effect. For all trees, sap flow normalized to sapwood area (Qs) increased with potential evaporation (PE) initially and then became independent as PE increased further. There was a fairly close correlation between transpiration of the edge and inner trees, implying that water availability was partially responsible for the difference between inner and edge trees. However, the ratio of edge tree to inner tree transpiration differed from unity, indicating differences in canopy conductance, which were estimated by an inverse form of the Penman-Monteith equation. When canopy conductances were less than a critical value, there was a strong linear relationship between Qs of the edge and inner trees. When canopy conductances of the edge trees were greater than the critical value, the slope of the linear relationship was steeper, indicating greater transpiration of the edge trees compared with the inner trees. This was interpreted as evidence for enhancement of transpiration of the edge trees by advection of wind energy.     

Stomatal conductance, transpiration and sap flow of tropical montane rain forest trees in the southern Ecuadorian Andes

We investigated tree water relations in a lower tropical montane rain forest at 1950-1975 m a.s.l. in southern Ecuador. During two field campaigns, sap flow measurements (Granier-type) were carried out on 16 trees (14 species) differing in size and position within the forest stand. Stomatal conductance (g(s)) and leaf transpiration (E(l)) were measured on five canopy trees and 10 understory plants. Atmospheric coupling of stomatal transpiration was good (decoupling coefficient Omega = 0.25-0.43), but the response of g(s) and E(l) to the atmospheric environment appeared to be weak as a result of the offsetting effects of vapor pressure deficit (VPD) and photosynthetic photon flux (PPF) on g(s). In contrast, sap flow (F) followed these atmospheric parameters more precisely. Daily F depended chiefly on PPF sums, whereas on short time scales, VPD impeded transpiration when it exceeded a value of 1-1.2 kPa. This indicates an upper limit to transpiration in the investigated trees, even when soil water supply was not limiting. Mean g(s) was 165 mmol m(-2) s(-1) for the canopy trees and about 90 mmol m(-2) s(-1) for the understory species, but leaf-to-leaf as well as tree-to-tree variation was large. Considering whole-plant water use, variation in the daily course of F was more pronounced among trees differing in size and crown status than among species. Daily F increased sharply with stem diameter and tree height, and ranged between 80 and 120 kg day(-1) for dominant canopy trees, but was typically well below 10 kg day(-1) for intermediate and suppressed trees of the forest interior.     

Species diversity of broad-leaved trees in Cryptomeria japonica plantations in relation to the distance from adjacent broad-leaved forests

The species diversity of broad-leaved trees in relation to the distance from a broad-leaved forest was investigated in Cryptomeria japonica plantations with crown snow damage near the Japan Sea in central Japan. The number and diversity of species and stem density decreased with distance from the broad-leaved forest in maturing gap stands (51–58 years old; >10 years after crown snow damage), but not in recent gap stands (34–42 years old; <10 years after crown snow damage), and increased with improved light conditions in the interior of recent gap stands, but not in that of maturing gap stands. The stem densities of tall and small tree species and woody lianas were greater in the interior of recent gap stands than in maturing gap stands. Woody lianas, which are characteristically shade intolerant, had a high stem density in the interior of recent gap stands. In contrast, the stem density of shrubs was greater in maturing gap stands than in recent gap stands, irrespective of distance. Shade-tolerant shrubs had a high stem density in maturing gap stands. Wind-dispersed and frugivore-dispersed species were concentrated at the edges of maturing gap stands, but some frugivore-dispersed species, which may persist in soil seed banks, occurred in the interior of recent gap stands. Gravity-dispersed species tended to occur both at the plantation edge and in the interior. The differences in the occurrence patterns of broad-leaved trees in the two types of stands reflected the difference in the effect of both the distance from the adjacent broad-leaved forest and the light conditions related to canopy gaps, with the time since gap formation in a region where crown snow damage often occurs.     

Tree-grass relationships in open eucalypt woodlands of northeastern Australia: influence of trees on pasture productivity, forage quality and species distribution

Pasture yield, quality and species distributions were compared between zones around live and killed eucalypt trees at two woodland sites in northeast Queensland which differed markedly in soil fertility. Trees affected pasture quality and yield on an individual tree basis: N concentration and dry matter digestibility tended to be higher under trees than in inter-tree areas at both sites and pasture yields declined with distance from killed trees at the lower fertility site. However, the distribution of individual species did not vary markedly with distance from trees. Trees also affected pasture yield on a woodland basis: yields were greater where the trees were killed than under intact woodland. Soil under trees had higher levels of organic carbon and greater litter cover than soil in inter-tree areas. However, pasture yields did not generally reflect this fertility gradient since growth was limited by moisture availability due to drought conditions during the study period. Pasture N concentration was higher under trees that in inter-tree areas since plants under trees produced a similar amount of biomass as plants in inter-tree areas, but had access to higher nutrient levels. Trees appeared to have a greater effect on soil nutrient availability at the low fertility site. Live trees depressed pasture yields to a lesser degree at the low fertility site, demonstrating that the effects of trees on soil water availability (on a woodland scale) are less important when soil nutrients are more limiting to growth. These results indicate that, while removing trees may enhance pasture productivity, this benefit may be offset by a reduction in pasture quality. Given the beneficial effect of trees on soil nutrients, tree removal may also have longer term implications for soil nutrient dynamics. This revised version was published online in August 2006 with corrections to the Cover Date.     

Mammal movements and foraging at remnant woodlands inside coniferous forest landscapes

Temporary or spatially restricted resources may affect population densities over more or less wide areas in the surrounding landscape or region. They may affect more than one trophic level by facilitation of predation. Areas of influence may differ between species. Such effects of mast-seeding in confined oak–hazel woodlands were examined for a guild of mainly seed-eating mammals and their predators. The mammals were tracked in snow in winter and the foraging of granivorous small mammals was assessed by experimental seed supplies in spring and autumn. Movements and foraging at various locations in and around the woodlands were distinguished from large-scale influences in the surrounding conifer forest landscape. Roe deer moved more abundantly inside the woodlands than in the conifer forest 50 m away and, less clearly, this was also the case for granivorous small mammals. Squirrels were particularly common at the edges while brown hares were somewhat less common at these edges. The edge effects appear therefore species-specific. Brown hares, squirrels, voles and granivorous small mammals were generally less common in the coniferous forest more than 500 m from the woodlands than in the coniferous forest 50 m from the woodlands. The most common generalist predator, the red fox, was as a mean equally common at all locations. However, it demonstrated a spatio-temporal variation in movements related to hare and, to a lesser extent, squirrel occurrence at open woodland sites. In order to sustain several mammalian species in conifer forest landscapes, not only granivorous ones, resource patches of oak and hazel should be retained, regenerated and, if possible, expanded. Such hot spots often need particular management.     

The decreased competition in expanding versus mature juniper woodlands is counteracted by adverse climatic effects on growth

World-wide deforestation is being reversed in Mediterranean continental areas, where abandonment of traditional practises favours the expansion of valuable habitats, like Juniperus thurifera woodlands. We hypothesised that pre-existing trees facilitate establishment in expanding woodlands, whereas in mature woodlands, competition leads to patch disaggregation. We compared the imprint of these processes on growth, demographic and spatial structure of expanding and mature J. thurifera woodlands. We selected plots where we geopositioned, aged and quantified the morphological characteristics of all trees. In the mature woodland, trees arranged in clumps and randomly in the expanding woodland. Competition negatively affected growth, was greater in the mature woodland and led to disaggregation of juvenile clumps. Differences in growth between the mature and the expanding woodland disappeared in climatically unfavourable years, suggesting that adverse climate constrains growth more in expanding than in mature woodlands. We suggest that change in the dispersal agents and a decrease of facilitation underlay differences in spatial patters between the expanding and the mature woodland. Observed effective recruitment in less than 30?years into the expanding woodland evidenced that propagule arrival and sapling survival do not constrain woodland expansion. Furthermore, growth of juveniles established in these new areas is favoured by reduced intra-specific competition. However, we expect growth in expanding woodlands to be negatively impacted by climate change. We conclude that under current global change scenario, conservation of J. thurifera woodlands is favoured by changes in land use, but greater frequency and severity of drier than usual episodes could hamper natural reforestation.     

Length and classification of natural and created forest edges in boreal landscapes throughout northern Sweden

Forest edges have numerous implications for structure and function of forest ecosystems. Previous studies on edge quantity have used broad classifications. However, edge influence is driven by the contrast in vegetation structure between adjoining ecosystems, and thus we need detailed site-specific data to assess the role of edges in forests. We studied the variability of sharp edges in 28 boreal landscapes (4 km × 4 km) across an 830 km gradient throughout northern Sweden. Our objectives were: (1) to compare the length of natural and created edges, (2) to classify edges in detail by edge origin, maintenance and forest attributes, and (3) to examine relationships between length of edge and landscape variables. Data were collected using stereo-interpretation of high spatial resolution colour infrared aerial photographs, in combination with line intersect sampling and plots. The length of edge varied from 12 to 102 m ha⁻¹ among landscapes, with an overall mean of 54 m ha⁻¹. Created edges dominated most landscapes (mean 33 m ha⁻¹) and had greater variability than natural edges (mean 21 m ha⁻¹). Maintained edges (e.g. roads, agricultural land) were more abundant than regenerating edges caused by logging. Thirty percent of total edges adjoined narrow linear features. Seventy percent adjoined wider patches and showed high variability (35 classes). Overall, high-contrast edges towards mature forest dominated, i.e. ones that may experience strong edge influence. The amount of edge increased with percent of landscape affected by disturbance, and decreased with latitude and elevation. This study shows that edges are both abundant and highly variable in boreal forests and that forestry is the main driver behind edge creation. Detailed classification of edges based on site-specific forest and patch attributes may help to estimate edge influence at landscape level, and can guide experimental design for examining the impact of edges on structure and function of forest ecosystems.     

Effects of active pasture,teak (Tectona grandis) and mixed native plantations on soil chemistry in Costa Rica

In this study soil samples were taken from the O/A and B horizons of undisturbed forest, active pasture, and 8- to 12-year-old teak and mixed native plantations. Samples were analyzed for K, Ca, Mg, soil organic carbon, pH, exchangeable acidity, bulk density, and compared with a fertility equation. Bulk density was significantly lower in the undisturbed forest than other land uses, suggesting that after approximately 10 years of growth neither plantation lowered bulk density significantly from that of the active pasture. Teak plantations had significantly higher Mg and K (B horizon) and Ca (O/A horizon) concentrations than the undisturbed forest. This trend suggests that exchangeable base concentrations increase when land use changes from undisturbed forest to pasture, then pasture to plantation, with the most pronounced effect of this in teak plantations exhibiting more high fertility plots than other land uses. Soil organic carbon concentration was similar for all land uses except for a significantly lower concentration in teak plantations than in active pasture (O/A horizons). These results suggest that teak plantations may be advantageous for increasing soil fertility but, with respect to restoration of undisturbed forest conditions, present significant deviations in soil chemistry. Options for improved plantations soil management are discussed.     

The confluence of landscape context and site-level management in determining Midwestern savanna and woodland breeding bird communities

Species distributions are determined by complex interplays between multi-scale factors. Conservation management, however, often occurs at a single scale of the site level. This is true for bird communities of restored savannas and mixed woodlands in the central U.S. In this region, many historic open-canopy oak savanna habitats have become closed canopy mixed woodlands due to loss of landscape-scale disturbance from fire and grazing. Site-level management efforts return some mixed woodland habitats back to savanna through fire and mechanical thinning. Savanna and woodland historically formed complex mosaic landscapes at the ecotone between prairies and Eastern deciduous forests and now exist within landscapes that vary in amount of open (e.g., perennial grassland and row crop agriculture) and woodland habitat. To understand the interplay between site and landscape level factors in savanna restoration, we sampled the breeding bird community in four combinations of site and landscape: restored savanna in open landscapes, restored savanna in woodland landscapes, and closed canopy woodland in both landscapes. We found that the outcome of site-level savanna restoration depended on the surrounding landscape. Compared to other treatment types, restored savannas in open landscapes supported a distinctive bird community characterized by high species richness, bird abundance, and percent of ground feeders, shrub nesters, and edge species. Both savanna and woodland sites in the open landscape had a higher percent of species of conservation concern, while at both site and landscape levels, woodland was associated with a higher percent of area sensitive species and habitat specialists. Our results suggest savanna restoration efforts should focus on sites that exist either in open country or on edges where closed canopy forest meets open country. This strategy would combine site and landscape level benefits of savanna restoration for avian diversity, while also preserving the conservation benefits of large tracts of intact forest.     

The “sun-effect”: microclimatic alterations predispose forest edges to bark beetle infestations

Bark beetle dispersal and host selection behaviour are a complex and poorly understood process, resulting in specific spatio-temporal infestation patterns in forests. Aerial images from the Bavarian Forest National Park (Germany) provide a high-resolution, that is, tree-scale data set for the period 2001–2010, including information about Ips typographus (Col., Curculio., Scolytinae) infestation, the application of sanitary logging, natural forest edges and the area of living spruce susceptible to bark beetle infestation. We combined methods of GIS and image analysis to investigate the infestation probabilities at three types of forest edges under spatial and temporal aspects and compared them to the corresponding probabilities at the stand interior. Our results showed a pronounced infestation predisposition of such edge trees delimiting infestation patches cleared by sanitary logging measures, in particular at the south-facing edge sector. In contrast, edges adjacent to non-cleared infestation were revealed as less attractive for subsequent infestations, but nonetheless more attractive than permanent forest edges or the stand interior. Additionally, we measured near-bark surface air temperature to determine microclimatic differences at those edge- or non-edge sites and related them to predisposition results. Finally, our study emphasized favourable microclimatic conditions—summarized as the “sun-effect”—as a decisive factor enhancing the local infestation probability at recent forest edges in multiple ways. Both insect- and host tree-related reactions to suddenly altered microclimate are supposed to bias arbitrary colonization behaviour at patch and tree level, thereby mainly explaining observed infestation patterns. From the forester’s point of view, our results may contribute to precise bark beetle risk assessment and thus facilitate decision making in forest management.     

Observations of evapotranspiration in a break of slope plantation susceptible to periodic drought stress

Break of slope (BOS) plantations are advocated as a means of water table control in areas where groundwater flows through colluvial deposits overlying low permeability bedrock. It is also believed that BOS plantations can supplement their water use requirements by exploiting shallow groundwater at the breaks in topographic slope. We compared measurements of BOS plantation and pasture evapotranspiration during spring, when the weather was warm and soils moist, and late summer when drought conditions prevailed. Microlysimeters and ventilated chambers were used to determine pasture and plantation floor evaporation, and heat pulse sensors were used to determine transpiration of the plantation. In spring, pasture evapotranspiration was 65% of that of the plantation, whereas, in summer, pasture evapotranspiration was equivalent to only 35% of that of the plantation. Rainfall interception by the canopy of the plantation was twice that of the pasture, reinforcing the notion that trees can help reduce groundwater recharge and alleviate dryland salinity and waterlogging. During the summer drought period, daily plantation transpiration was only 20% of that measured during spring, suggesting that the plantation was not utilizing groundwater supplies but was instead drawing from soil water supplies. This hypothesis was supported by the comparison of relative abundances of the isotopes of water ((2)H and (18)O) in soil and wood samples. We conclude that the BOS plantation is not behaving in the manner predicted, and our findings raise doubts about the predicted advantages of establishing plantations in break of slope positions.     

城市森林规划中的城市森林分类——以新疆阿克苏市为例

文章以阿克苏城市森林规划为例,提出了城市森林规划"二分法",论述了其必要性和应采取的分类原则,并详述了"二分法",即针对用地的林地分类和针对树木的植被分类的具体应用。       

Enhanced transpiration by riparian buffer trees in response to advection in a humid temperate agricultural landscape

Riparian buffers are designed as management practices to increase infiltration and reduce surface runoff and transport of sediment and nonpoint source pollutants from crop fields to adjacent streams. Achieving these ecosystem service goals depends, in part, on their ability to remove water from the soil via transpiration. In these systems, edges between crop fields and trees of the buffer systems can create advection processes, which could influence water use by trees. We conducted a field study in a riparian buffer system established in 1994 under a humid temperate climate, located in the Corn Belt region of the Midwestern U.S. (Iowa). The goals were to estimate stand level transpiration by the riparian buffer, quantify the controls on water use by the buffer system, and determine to what extent advective energy and tree position within the buffer system influence individual tree transpiration rates. We primarily focused on the water use response (determined with the Heat Ratio Method) of one of the dominant species (Acer saccharinum) and a subdominant (Juglans nigra). A few individuals of three additional species (Quercus bicolor, Betula nigra, Platanus occidentalis) were monitored over a shorter time period to assess the generality of responses. Meteorological stations were installed along a transect across the riparian buffer to determine the microclimate conditions. The differences found among individuals were attributed to differences in species sap velocities and sapwood depths, location relative to the forest edge and prevailing winds and canopy exposure and dominance. Sapflow rates for A. saccharinum trees growing at the SE edge (prevailing winds) were 39% greater than SE interior trees and 30% and 69% greater than NW interior and edge trees, respectively. No transpiration enhancement due to edge effect was detected in the subdominant J. nigra. The results were interpreted as indicative of advection effects from the surrounding crops. Further, significant differences were document in sapflow rates between the five study species, suggesting that selection of species is important for enhancing specific riparian buffer functions. However, more information is needed on water use patterns among diverse species growing under different climatic and biophysical conditions to assist policy and management decisions regarding effective buffer design.     

Role of woody perennials in animal agroforestry

Two main roles are identified in the review: the productive one, where woody perennials yield a material output (fuel, fodder, etc.), and the ‘service’ type, with no tangible product (shelter, nutrient recycling, etc.). In their productive role trees and shrubs may supply fodder in browsing systems, or industrial material, wood products and food in forest and plantation grazing systems. Service roles, rarely divorced from productive ones, arise mainly from relationships between woody perennials and the herbaceous vegetation growing in their vicinity. As a fodder source, the relatively low productivity and palatability of high protein content foliage from most woody perennials would indicate a supplementary role, particulary during dry seasons in arid and semiarid zones. In these type of lands pod-bearing trees seem to have a greater potential for improving fodder production in silvopastoral systems. The negative effect of trees on pasture production in forest and plantation grazing is compensated by their contribution to the system through other products. Available data would support the potential of certain species of woody perennials to foster pasture growing underneath, mainly through soil enrichment. Windbreaks can also indirectly benefit pasture growth, by decreasing water loss from the soil. It is postulated that research efforts in animal agroforestry should be focused on woody perennials for browsing systems, particularly on pod-bearing trees having beneficial effects on the herbaceous layer growing underneath.     

Tropical reptiles in pine forests: Assemblage responses to plantations and plantation management by burning

Worldwide, the land area devoted to timber plantations is expanding rapidly, especially in the tropics, where reptile diversity is high. The impacts of plantation forestry and its management on native species are poorly known, but are important, because plantation management goals often include protecting biodiversity. We examined the impact of pine (Pinus caribaea) plantations, and their management by fire, on the abundance and richness of reptiles, a significant proportion of the native biodiversity in tropical northern Australia, by (i) comparing abundance and diversity of reptiles among pine plantations (on land cleared specifically for plantation establishment), and two adjacent native forest types, eucalypt and Melaleuca woodlands, and (ii) comparing reptile abundance and richness in pine forest burnt one year prior to the study to remove understorey vegetation with pine forest burnt two years prior to the study. We also examined the influence of fire on reptile assemblages in native vegetation, by comparing eucalypt woodland burnt two years prior to the study and unburnt for eight years. To quantify mechanisms driving differences in reptile richness and abundance among forest types and management regimes, we measured forest structure, the temperatures used by reptiles (operative temperature) and solar radiation, at replicate sites in all forest types and management regimes. Compared to native forests, pine forests had taller trees, lower shrub cover in the understorey, more and deeper exotic litter (other than pine), and were cooler and shadier. Reptile assemblages in pine forests were as rich as those in native forests, but pine assemblages were composed mainly of species that typically use closed-canopy rainforest and prefer cooler, shadier habitats. Burning did not appear to influence the assemblage structure of reptiles in native forest, but burning under pine was associated with increased skink abundance and species richness. Burned pine was not warmer or sunnier than unburned pine, a common driver of reptile abundance, so the shift in lizard use after burning may have been driven by structural differences in understorey vegetation, especially amounts of non-native litter, which were reduced by burning. Thus, burning for management under pine increased the abundance and richness of lizard assemblages using pine. Pine plantations do not support the snake diversity common to sclerophyllous native forests, but pine may have the potential to complement rainforest lizard diversity if appropriately managed.     

Linking leaf and tree water use with an individual-tree model

We tested the ability of a model to scale gas exchange from leaf level to whole-tree level by: (1) measuring leaf gas exchange in the canopy of 10 trees in a tall Eucalyptus delegatensis RT Baker forest in NSW, Australia; (2) monitoring sap flow of the same 10 trees during the measurement week; and (3) using an individual-tree-based model (MAESTRA) to link the two sets of measurements. Photosynthesis and stomatal conductance components of the model were parameterized with the leaf gas exchange data, and canopy structure was parameterized with crown heights, dimensions and leaf areas of each of the measurement trees and up to 45 neighboring trees. Transpiration of the measurement trees was predicted by the model and compared with sap flow data. Leaf gas exchange parameters were similar for all 10 trees, with the exception of two smaller trees that had relatively low stomatal conductances. We hypothesize that these trees may have experienced water stress as a result of competition from large neighboring trees. The model performed well, and in most cases, was able to replicate the time course of tree transpiration. Maximum rates of transpiration were higher than measured rates for some trees and lower than measured rates for others, which may have been a result of inaccuracy in estimating tree leaf area. There was a small lag (about 15-30 minutes) between sap flow and modeled transpiration for some trees in the morning, likely associated with use of water stored in stems. The model also captured patterns of variation in sap flow among trees. Overall, the study confirms the ability of models to estimate forest canopy transpiration from leaf-level measurements.