Designing Timber Harvesting to Enhance New Zealand Falcon Populations

Previous breeding-season studies of threatened New Zealand falcons (Falco novaeseelandiae) in plantation forests have suggested that falcons benefit when harvesting creates a mosaic of differently aged stands, especially where young and mature tree stands are adjacent. Thus, changes in the rate and pattern of harvesting may affect habitat heterogeneity by altering the size and distribution of forest patches. We sought to determine guidelines for harvesting that would most benefit falcons by increasing the carrying capacity of the forest for falcons. We used radio-tracking to determine the home-range sizes of non-breeding falcons over 3 seasons and compared winter home-range overlap in the most-selected land cover types by falcons (mature-young edges and open patches) with other land cover types. The distribution of open patches and edges between mature stands and recently cleared areas affected falcon home ranges, home-range overlap, and the likelihood of nesting. Specifically, home ranges were smaller as the density of edges and percentage of open patch increased, and there was greater home-range overlap between individuals in the most-selected land cover types. Numbers of falcons decreased as the size of open patches increased, concomitant with a decrease in edge size, the number of edge borders, and the number of open patches. The likelihood of nesting also decreased as open patch size increased. Our results indicate that smaller open patches spread through a forest, maximizing the amount of mature-young edges, will favor smaller home ranges and therefore potentially greater numbers of falcons. We recommend harvesting protocols that ensure that open patches (0–3-yr-old stands) are <4 km² in size and retain at least small stands of mature pine to maintain a high density of edges. Similar protocols may increase the carrying capacity for other species occurring in managed systems involving fragmented landscapes or small reserves. © 2021 The Wildlife Society.     

Heathland management effects on carabid beetle communities: the relationship between bare ground patch size and carabid biodiversity

Carabid beetles were sampled by pitfall trapping on Brentmoor Heath, Surrey, UK during the summers of 2009 and 2010 to determine the effects of bare ground patch size on beetle abundance, richness and diversity. Four patch sizes were investigated: 1, 4, 25 and 100?m² as well as the adjacent mown and unmown areas. A range of environmental parameters relating to soil characteristics, stones and nearby vegetation were measured at each patch and control habitat in order to distinguish the effect of patch size. Results show that bare ground is a valuable habitat for carabids, but that the response of their abundance, richness and diversity to bare ground patch size depends on a large number of environmental variables on and around the patches. When all variables are taken into account, smaller patches appear to benefit carabid abundance, richness and diversity. In the presence of Molinia caerulea at the patch edges, however, larger patches were more beneficial. Given this dependence on environmental variables, the perfect patch size for conservation of biodiversity is likely to be site specific and the best approach may be to use a variety of patch sizes at a range of successional stages.     

Home-Range Size of the Bare-ear Marmoset (Callithrix argentata) at Alter do Chão,Central Amazonia,Brazil

We studied factors affecting variation in home-range size of four groups of bare-ear marmosets (Callithrix argentata) in patches of forest within a central Amazonian savanna. We determined relative use of different parts of the home range by radiotelemetry. We estimated fruit availability monthly in transects through each home range and mapped the habitats within the home range of each group. We determined the densities of gum- and fruit-producing trees in 18 50 × 50-m quadrats and related these data to the frequency of use by marmosets. Home-range size varied by a factor of 6 between groups, even though the study area covered <15 km ² and included only one major biome. Marmoset activity was concentrated in areas with many gum-producing trees. Monthly range size is positively correlated with fruit availability only for the group with the largest home range; the other groups appeared to be responding to other factors. Home-range sizes appeared to be limited by the size of the main patch of contiguous forest available to each group. Our findings suggest that conservation planning that does not consider the possibility of large differences among primate home-range sizes may be unsatisfactory.     

Effects of Spatial Scale of Soil Heterogeneity on the Growth of a Clonal Plant Producing Both Spreading and Clumping Ramets

Soil nutrients are commonly heterogeneously distributed at different spatial scales. Although numerous studies have tested the effects of soil nutrient heterogeneity on growth of clonal plants producing either spreading ramets or clumping ramets, no study has examined the effects on the growth of clonal plants producing both spreading and clumping ramets and how spatial scale affects such effects. To test these effects, clones of Buchloe dactyloides, a stoloniferous clonal plant that produces both clumping and spreading ramets, were grown in six heterogeneous environments with different patch sizes and one homogeneous environment containing the same quantity of nutrients. Total biomass, total number of ramets, number of clumping ramets, number of spreading ramets, spacer length, or root:shoot ratio of the whole plants did not differ significantly among the seven treatments. However, at the patch level there were significant effects of patch size by nutrient level on biomass, number of ramets, number of spreading ramets, and number of clumping ramets, and these four variables were significantly larger in the nutrient-rich patches than in the nutrient-poor patches in the heterogeneous treatment with the largest patch size, but not in the other five heterogeneous treatments with smaller patch sizes. Neither nutrient level nor patch size significantly affected spacer length or root:shoot ratio. Based on our results, we propose that B. dactyloides can efficiently exploit nutrient-rich patches by a plastic response of clumping ramets and spreading ramets at larger spatial scales of soil heterogeneity but not at smaller ones.     

Root responses to nutrient patches in grassland and forest

Differences between growth forms in root responses to experimentally created heterogeneity have been documented in many greenhouse and plot studies, but not in natural vegetation. Here we examined the response of roots to experimental nutrient patches in undisturbed grassland and forest at the northern edge of the North American Great Plains. Forest vegetation increases the spatial heterogeneity of soil resources, and we tested for differences between forest and grassland roots in response to patches. Ten minirhizotrons (clear tubes, 5 cm diameter, 180 cm long) were installed in both grassland and forest 3 years before the experiment. Minirhizotrons ran horizontally 10 cm beneath the soil surface. Patches of available nitrogen (N) were created over the tubes, using three concentrations (0, 3, 15 g N m⁻² yr⁻¹) and two patch sizes (1␣and 10 cm²). Root images were collected beneath patches over the course of a growing season. Root length was significantly greater in grassland than forest at the start and end of the growing season, but did not respond to N patches. Root production was also significantly greater in grassland than forest, and was significantly greater (about 20%) in high-N patches than in unfertilized patches. This increase, however, did not differ between vegetation types. Turnover did not vary with any treatment, and patch size had no effect on any response variable. Overall, differences caused by experimental patches were much smaller than differences between habitats, and did not vary between habitats. Realistic levels of experimentally imposed hetereogeneity in established vegetation may not be much greater than background levels, and field vegetation has extant root systems which respond to patches via uptake instead of growth. Both mechanisms should contribute to less root proliferation in field experiments than in greenhouse experiments.     

Aggregation of parasitism risk in an aphid-parasitoid system: Effects of plant patch size and aphid density

Few studies have linked density dependence of parasitism and the tritrophic environment within which a parasitoid forages. In the non-crop plant-aphid, Centaurea nigra–Uroleucon jaceae system, mixed patterns of density-dependent parasitism by the parasitoids Aphidius funebris and Trioxys centaureae were observed in a survey of a natural population. Breakdown of density-dependent parasitism revealed that density dependence was inverse in smaller colonies but direct in larger colonies (>20 aphids), suggesting there is a threshold effect in parasitoid response to aphid density. The CV² of searching parasitoids was estimated from parasitism data using a hierarchical generalized linear model, and CV²>1 for A. funebris between plant patches, while for T. centaureae CV²>1 within plant patches. In both cases, density independent heterogeneity was more important than density-dependent heterogeneity in parasitism. Parasitism by T. centaureae increased with increasing plant patch size. Manipulation of aphid colony size and plant patch size revealed that parasitism by A. funebris was directly density dependent at the range of colony sizes tested (50–200 initial aphids), and had a strong positive relationship with plant patch size. The effects of plant patch size detected for both species indicate that the tritrophic environment provides a source of host density independent heterogeneity in parasitism, and can modify density-dependent responses.     

Hydrophobic patches on the surfaces of protein structures

A survey of hydrophobic patches on the surface of 112 soluble, monomeric proteins is presented. The largest patch on each individual protein averages around 400 Ų but can range from 200 to 1,200 Ų. These areas are not correlated to the sizes of the proteins and only weakly to their apolar surface fraction. Ala, Lys, and Pro have dominating contributions to the apolar surface for smaller patches, while those of the hydrophobic amino acids become more important as the patch size Increases. The hydrophilic amino acids expose an approximately constant fraction of their apolar area independent of patch size; the hydrophobic residue types reach similar exposure only in the larger patches. Though the mobility of residues on the surface is generally higher, it decreases for hydrophilic residues with Increasing patch size. Several characteristics of hydrophobic patches catalogued here should prove useful in the design and engineering of proteins. © 1996 Wiley-Liss, Inc.     

Use of space and habitats by meadow voles at the home range,patch and landscape scales

Using capture/recapture methods, we examined the spatial usage patterns of Microtus pennsylvanicus within and between experimentally created habitat patches of three sizes (1.0, 0.25 and 0.0625 ha) and between a 20-ha fragmented and a 20-ha continuous habitat landscape. We tested the prediction that home ranges near patch edges would be qualitatively different from those in patch interiors, and that the edge:interior habitat ratio could be used to make predictions concerning the dispersion and spatial use of individuals occupying different sized patches and between landscapes with different habitat structure. We found adult females on patch edges to have larger and more exclusive home ranges, larger body sizes, longer residence times, and to reproduce at a higher frequency than those in patch interiors. These edge effects also appeared to be largely responsible for the greater proportion of larger, reproductive females we found in small than larger patches and in the fragmented than in the continuous habitat (control) landscape. The selection of higher quality edge habitats by dominant females and the relegation of sub-dominants to patch interiors provides an explanation for the observed differences in the distribution and performance of females over patches and between landscapes.     

Home range and habitat selection of spotted owls in the central Sierra Nevada

We studied home range and habitat selection of radio-marked adult California spotted owls (Strix occidentalis occidentalis) randomly selected from among the breeding population of owls in the central Sierra Nevada, California from June to October 2006. The most parsimonious home-range estimate for our data was 555 ha (SE = 100 ha). Home-range size was positively correlated with the number of vegetation patches in the home range (habitat heterogeneity). We used resource selection ratios to examine selection of vegetation types by owls within our study area. Owl home ranges contained a high proportion of mature conifer forest, relative to its availability, although the confidence interval for this estimate overlapped one. We also used resource selection functions (RSF) to examine owl foraging habitat selection. Relative probability of selection of foraging habitat was correlated with vegetation classes, patch size, and their interaction. Owls showed highest selection rates for large patches (>10 ha) of pole-sized coniferous forest. Our results suggested that spotted owls in the central Sierra Nevada used habitat that contained a high proportion of mature conifer forest at the home-range scale, but at a finer scale (foraging site selection) owls used other vegetation classes interspersed among mature forest patches, consistent with our hypothesis that spotted owls may use other forest types besides old growth and mature forests when foraging. Our study provides an unbiased estimate of habitat use by spotted owls in the central Sierra Nevada. Our results suggest that forest managers continue to protect remaining mature and old-growth forests in the central Sierra Nevada because owl home ranges contain high proportions of these habitats. However, our results also showed that owls used younger stands as foraging habitat so that landscape heterogeneity, with respect to cover types, may be an important consideration for management but we did not attempt to relate our findings to fitness of owls. Thus management for some level of landscape heterogeneity for the benefit of owls should proceed with caution or under an adaptive management framework. © 2011 The Wildlife Society.     

黄龙钙化滩流地物种-面积关系

黄龙沟钙化滩流地由于溪流的作用,在滩流地之间形成面积大小不一的植物群落斑块。这些小尺度斑块面积的大小对植物物种数量的影响尚不清楚。应用回归分析法和幂函数方程对黄龙沟钙化滩流地内的物种-面积关系进行了研究。结果表明黄龙沟钙化滩流地中斑块的大小对物种数(含兰科植物)具有强烈的影响,而调查的其他因子对总的植物物种数量的影响不显著。在所调查的环境因子中,斑块面积对物种数量的影响达到79.5%,即斑块越大,所包含的物种数量越多。兰科植物种类数量除了受斑块面积的影响外,还与距离林缘的距离有关(负相关)。物种-面积关系符合幂函数方程S=cA^Z的规律。不同的尺度下,z值略有差异,在中等尺度下 (1-10 m²)最大,为0.2616,较大尺度下(10-100 m²)的最小,z值为0.2050,小尺度下(<1 m²),z值为0.2382。表明中等尺度的斑块(1-10 m²)包含的物种数(含兰科植物)的增长速度最快,而在斑块面积大于10 m²时,物种数增长速度最小。     

根状茎型植物扁秆荆三棱对土壤养分异质性尺度和对比度的生长响应

土壤养分的空间异质性在自然界普遍存在, 而克隆植物被认为能很好地适应和利用土壤养分异质性。尽管尺度和对比度是异质性的两个重要属性, 但有关土壤养分异质性的尺度和对比度及其交互作用对克隆植物生长和分株分布格局影响的研究仍比较缺乏。在一个温室实验中, 根状茎型草本克隆植物扁秆荆三棱(Bolboschoenus planiculmis) (异名扁秆藨草(Scirpus planiculumis))被种植在由高养分斑块和低养分斑块组成的异质性环境中。实验为两种尺度处理(大斑块和小斑块)和两种对比度处理(高对比度和低对比度)交叉组成的4种处理组合。在每个处理中, 高养分和低养分斑块的总面积相同; 在所有4种处理中, 土壤养分的总量也完全相同。无论在整个克隆(植株)水平, 还是在斑块水平, 尺度、对比度及其交互作用对扁秆荆三棱的生物量、分株数、根状茎长和块茎数的影响均不显著。然而, 在斑块水平, 扁秆荆三棱在高养分斑块中的生物量、分株数、根状茎长和块茎数均显著高于低养分斑块, 而在高养分斑块中相邻分株间的距离(间隔物长)小于低养分斑块, 并且这种效应均不依赖于斑块尺度的大小和对比度的高低。因此, 在土壤养分异质性环境中, 扁秆荆三棱可以通过缩短间隔物长, 并可能通过提高根状茎的分枝强度, 把较多的分株和潜在分株放置在养分条件好的斑块中。这种响应格局体现出克隆植物的觅食行为, 有利于整个克隆对异质性资源的吸收和利用。然而, 该实验中的尺度和对比度对扁秆荆三棱分株的放置格局均没有显著效应。作者推测, 在一个更大的斑块尺度和(或)对比度范围内, 扁秆荆三棱对土壤养分异质性的响应可能不同。因此, 下一步的研究应涉及更广泛的尺度和对比度。     

Clonal growth strategies in simultaneously persistent and expanding <Emphasis Type="Italic">Trifolium repens</Emphasis> patches

Plants with clonal growth can generate patches dominated by a single species. In time, patches can change and may fragment, form a ring, dissolve or both persist and expand. For patches to maintain their original habitat and simultaneously increase in size, ramets or clonal fragments must both promote local persistence inside the patch and grow out of the patch into new habitats. This study analyses simultaneously expanding and persistent Trifolium patches in a nutrient-poor lawn that is frequently cut, and where the Trifolium is competitively superior to the grass species. Trifolium primary stolon growth strategies were analyzed in relation to their location (border, middle, and center) inside the patch, and according to patch size (small, medium, and large). It was hypothesized that different growth strategies inside a patch can explain both persistent and expanding patch of Trifolium, and that growth strategies were different between patch sizes. Primary Trifolium stolons had two different growth strategies inside and at the border of patches: (i) stolons at the border were long, grew fast, had few lateral stolons, and grew out of the patch, while (ii) stolons inside the patch were smaller, grew slowly, and had more lateral stolons and a wide range of growth directions. Growth strategies were not different between patch sizes. The directional growth and the high growth rate at the border will increase the patch size with time, while the growth strategy near the center consolidates the patch in space and time, by placing ramets inside the patch. Different growth strategies near the center and on the border result in Trifolium patches that are simultaneously persistent and on the increase. The results also indicate a division of labor among primary Trifolium stolons in a patch.     

Spatial heterogeneity and plant species richness at different spatial scales under rabbit grazing

Herbivores influence spatial heterogeneity in soil resources and vegetation in ecosystems. Despite increasing recognition that spatial heterogeneity can drive species richness at different spatial scales, few studies have quantified the effect of grazing on spatial heterogeneity and species richness simultaneously. Here we document both these variables in a rabbit-grazed grassland. We measured mean values and spatial patterns of grazing intensity, rabbit droppings, plant height, plant biomass, soil water content, ammonia and nitrate in sites grazed by rabbits and in matched, ungrazed exclosures in a grassland in southern England. Plant species richness was recorded at spatial scales ranging between 0.0001 and 150 m(2). Grazing reduced plant height and plant biomass but increased levels of ammonia and nitrate in the soil. Spatial statistics revealed that rabbit-grazed sites consisted of a mixture of heavily grazed patches with low vegetation and nutrient-rich soils (lawns) surrounded by patches of high vegetation with nutrient-poor soils (tussocks). The mean patch size (range) in the grazed controls was 2.1 +/- 0.3 m for vegetation height, 3.8 +/- 1.8 m for soil water content and 2.8 +/- 0.9 m for ammonia. This is in line with the patch sizes of grazing (2.4 +/- 0.5 m) and dropping deposition (3.7 +/- 0.6 m) by rabbits. In contrast, patchiness in the ungrazed exclosures had a larger patch size and was not present for all variables. Rabbit grazing increased plant species richness at all spatial scales. Species richness was negatively correlated with plant height, but positively correlated to the coefficient of variation of plant height at all plot sizes. Species richness in large plots (<25 m(2)) was also correlated to patch size. This study indicates that the abundance of strong competitors and the nutrient availability in the soil, as well as the heterogeneity and spatial pattern of these factors may influence species richness, but the importance of these factors can differ across spatial scales.     

Regional patch dynamics of Cirsium arvense and possible implications for plant‐animal interactions

Abstract. Plant population biology considers the dynamics of plant modules within stands. However, stands themselves may have considerable regional turnover in space and time. These changes in the number, distribution and size of plant stands generate a dynamic spatial pattern with important implications for the spatial and temporal dynamics of phytophagous insects using these plants as a host. During five successive years we studied the regional distribution and patch dynamics of the creeping thistle Cirsium arvense and the distribution of associated populations of the herbivore Urophora cardui (Diptera: Tephritidae), a specialist stem gall former. The study conducted was in a 15 km² heterogeneous, agricultural area in northeastern Bavaria. The distribution of the number of plants per patch was skewed with many more small C. arvense patches than large ones. During the five years of study, there was a 50% increase in the number of C. arvense patches, and a decrease in the mean number of plants per patch (= patch size) to less than half the patch size of the first year. Whilst patch size was randomly distributed in space, patch density showed a consistent, non‐random spatial pattern. Patch density was spatially auto‐correlated, with areas of high or low patch density having a characteristic dimension of ca. 1 km. Patch size was predictable in time and appeared to be regulated by size dependent processes, with the extinction probability of a patch being negatively correlated with its size. Correlated with the decline of C. arvense patch size during the study, the occupancy and total numbers of the herbivore U. cardui had a marked decrease, suggesting that the regional distribution of the stem gall former is not only influenced by patch number but more importantly by the mean patch size. With decreasing patch sizes, U. cardui was faced with an increasingly dynamic landscape due to higher extinction rates of small patches, although the mean distance between host plant patches decreased.     

How landscape scale changes affect ecological processes in conservation areas: external factors influence land use by zebra (Equus burchelli) in the Okavango Delta

Most large‐bodied wildlife populations in sub‐Saharan Africa only survive in conservation areas, but are continuing to decline because external changes influence ecological processes within reserves, leading to a lack of functionality. However, failure to understand how landscape scale changes influence ecological processes limits our ability to manage protected areas. We used GPS movement data to calculate dry season home ranges for 14 zebra mares in the Okavango Delta and investigated the effects of a range of landscape characteristics (number of habitat patches, mean patch shape, mean index of juxtaposition, and interspersion) on home range size. Resource utilization functions (RUF) were calculated to investigate how specific landscape characteristics affected space use. Space use by all zebra was clustered. In the wetter (Central) parts of the Delta home range size was negatively correlated with the density of habitat patches, more complex patch shapes, low juxtaposition of habitats and an increased availability of floodplain and grassland habitats. In the drier (Peripheral) parts of the Delta, higher use by zebra was also associated with a greater availability of floodplain and grassland habitats, but a lower density of patches and simpler patch shapes. The most important landscape characteristic was not consistent between zebra within the same area of the Delta, suggesting that no single foraging strategy is substantially superior to others, and so animals using different foraging strategies may all thrive. The distribution and complexity of habitat patches are crucial in determining space use by zebra. The extent and duration of seasonal flooding is the principal process affecting habitat patch characteristics in the Okavango Delta, particularly the availability of floodplains, which are the habitat at greatest risk from climate change and anthropogenic disturbance to the Okavango's catchment basin. Understanding how the factors that determine habitat complexity may change in the future is critical to the conservation of large mammal populations. Our study shows the importance of maintaining flood levels in the Okavango Delta and how the loss of seasonal floodplains will be compounded by changes in habitat configuration, forcing zebra to change their relative space use and enlarge home ranges, leading to increased competition for key resources and population declines.     

Spatial and Temporal Dynamics of a Restored Population of Oryza rufipogon in Huli Marsh, South China

Studying the process of population restoration is helpful for managing and preserving endangered species. A population of Oryza rufipogon (wild rice), an endangered species, was reintroduced in 1993 into Huli Marsh. We conducted a detailed survey over a 5‐year period (1997–2001) to evaluate the present status of the population and to further our understanding of its habitat requirements and the population model. The population was surveyed using 2 × 2–m quadrats in mid‐September of each year. In total, 2,683 quadrats were surveyed covering the whole O. rufipogon reserve during each survey. The population's spatial distribution was mapped, and the maps were used to examine the relationship between patch replacement and water depth. The individual number of O. rufipogon increased steadily from 1993 to 2001. The patch number, patch area, mean patch size, and largest patch size increased over this time period, and Korcak patchiness exponents decreased. On average, 83% of the patches persisted from one year to the next. There was a significant positive correlation between the initial patch size and the size the following year. The probability of patch disappearance decreased as patch size increased. Fifty‐eight percent of the patches were located at water depths between 20 and 30 cm. Water depth had no significant effect on the patch transition from O. rufipogon to other species. The loss and gain of O. rufipogon patches were statistically correlated with the patch areas in different water depths. Our results show that the population of O. rufipogon can successfully be reintroduced to the original habitat after appropriate environmental conditions have been restored. We recommend the following transplantation practices: transplant many smaller patches rather than a few larger patches, use transplant patch sizes of at least 20 m², and transplant into sites vegetated with species with different regeneration niches from the transplanted species.     

Interference competition in central place foragers: the effect of imposed waiting on patch-use decisions of eastern chipmunks, Tamias striatus

When central place foragers compete aggressively for patchyresources, subordinates may be preventedfrom collecting fooduntil a dominant has departed with its load. Extensions of centralplace foraging models predict that animals forced to wait ata patch should increase their load sizes and patch times aswellas their tendency to search for and switch to alternative patches.We tested these predictions usingeastern chipmunks, Tamias striatus,hoarding sunflower seeds collected from seed/vermiculite mixturesintrays placed 5-8 m from their burrows. By using her hand toprevent access to the patch, the experimentersubjected animalsto progressively increasing waiting times at two seed densities;another series of trialsat the same seed densities monitoreda similar number of trips without imposed waiting. As predicted,patch times and load sizes were higher in sessions with imposedwaiting than in control sessions. Loadsizes increased with trialnumber in experimental sessions but decreased or remained thesame in controlsessions. Chipmunks spent more of their timesearching for alternative patches during trials with imposedwaiting than during controls. They also started searching foralternative patches at lower levels of imposed waiting whenusing poor than when using rich patches. These results indicatethat the effects of interference on foraging decisions and onspatial overlap between individuals can be predicted by simpleeconomic models. Furthermore, the results suggest how resource-defensetactics can be predicted by the economic effects of interferenceon the foraging efficiency of the opponent.     

Soil heterogeneity affects ramet placement of Hydrocotyle vulgaris

Aims Soil heterogeneity is common in natural habitats. It may trigger foraging responses (placing more ramets and/or roots in nutrient-rich patches than in nutrient-poor patches) and further affect the growth of plants. However, the impact of soil heterogeneity on competitive interactions has been little tested.Methods We conducted a greenhouse experiment to investigate the effects of soil heterogeneity on intraspecific competition with a stoloniferous herb Hydrocotyle vulgaris. We grew one (without competition) or nine ramets (with competition) of H. vulgaris under a homogeneous environment and two heterogeneous environments differing in patch size (large or small patches). In the heterogeneous treatment, the soil consisted of the same number of nutrient-rich and nutrient-poor patches arranged in a chessboard manner, and in the homogeneous treatment, the soil was an even mixture of the same amount of the nutrient-rich and the nutrient-poor soil.Important findings Irrespective of intraspecific competition, H. vulgaris showed foraging responses to soil heterogeneity in the large patch treatment, e.g. it produced significantly more biomass, ramets, aboveground mass and root mass in the nutrient-rich patches than in the nutrient-poor patches. In the small patch treatment, foraging responses were observed when intraspecific competition was present, but responses were not observed when there was no competition. However, we find a significant effect of soil heterogeneity on neither overall growth nor competitive intensity of H. vulgaris. Our results suggest that foraging responses to soil heterogeneity may not necessarily be adaptive and intraspecific competition may not be influenced by soil heterogeneity.     

Woodland fragmentation affects space use of Eurasian red squirrels

When habitats become fragmented, variation in patch size and quality are expected to impose changes on the spacing pattern and social organization of animal populations. General theory predicts different possible responses including shrinking home ranges (fission response), increasing range overlap (fusion) and incorporation of multiple patches in the home range (expansion response) as fragmentation increases. We studied space use and social organization in a metapopulation of red squirrels (Sciurus vulgaris) in 15 woodland fragments differing in size and tree species composition. Home ranges and core areas of males were larger than females, and fragmentation had different and complex effects on the spacing pattern of both sexes. In food-supplemented patches, high densities led to increased intra-sexual overlap. In linear-shaped patches, squirrels used smaller home ranges and core areas and had lower male–male and male–female overlap levels, independent of patch quality or size. Home range and core area size of males increased with patch size, and male core areas overlapped extensively those of other males and females. Hence males seemed to show a fission response only in some patches. In contrast, home range and core area size of females was not related with patch size, but decreased with habitat quality, supporting predictions of a fusion response and intra-sexual defense of food-based core areas. Hence, where patch size and shape strongly affected space use of male red squirrels, social organization of females was only affected in small, food-supplemented patches, suggesting that the basic spatio-social organization of adult females is very resistant to fragmentation.