Variation in wolf spider (Araneae: Lycosidae) distribution and abundance in response to the size and shape of woodland fragments

The wolf spider (Lycosidae) community of open paddocks and five different configurations of woodland habitat in the wheatbelt of New South Wales, Australia, was sampled by nocturnal spotlighting. A total of 16 species was detected amongst the 2769 individuals that were sufficiently mature to allow identification, and 80% of these individuals were accounted for by just three species. There were no significant differences in the spider community among any of the woodland configurations, but the community of all five configurations differed significantly from that of open paddocks. However, only three species differed significantly in abundance between paddocks and the woodland configurations. Two species, Venator spenceri and Sp. C appeared to be less common in paddocks than in the woodland habitats, while Sp. A was more abundant in the paddocks. The percentage cover of thistles, medium grass and high grass, as well as the total abundance of Callitris glaucophylla were the habitat variables that best explained variation in the wolf spider community between woodland sites. Of these, thistle cover had the strongest correlation suggesting that disturbance, rather than cover per se, might be an important determinant of wolf spider communities. This study indicates that habitat fragmentation, at the spatial scale associated with current agricultural practices, may not be presenting a threat to generalist ground predators such as wolf spiders.     

Are spiders reacting to local or landscape scale effects in Hungarian pastures?

Declines of West-European farmland biodiversity have been associated with intensive agricultural practices, Central and Eastern European grasslands still harbour a diverse and unique arthropod community. However, our understanding of the effects of farmland management both at local and landscape levels is rather limited there. A paired field approach was used to compare extensively (0.5 cows/ha) and intensively (>1 cows/ha) grazed pastures in 42 fields in three distinct biogeographic regions within Hungary. Spiders belonging to the hunting and web-building communities were sampled using funnel traps. We found no management effect either on richness and abundance or on species composition, which shows that both forms of grazing management at the intensity levels studied support valuable spider fauna. At the local scale plant and litter cover were the two most important variables that significantly affected the communities overall, meaning both the hunting and to some degree the web-building communities. No significant landscape effects were found in the analyses on spider richness and abundance, but community structure was affected by two landscape level factors (grassland patch density and grassland percentage). We suggest that to protect the valuable spider and other fauna of these regions, the recently launched national agri-environmental program should be further supported and enlarged to maintain and reintroduce the traditional grazing management on these semi-natural grasslands.     

Landscape and patch-level factors influence bird communities in an urbanized tropical island

As human population continues to increase and intensification of human land use escalates, it is important to address the role of urban forest patches in supporting bird communities. We related bird species richness and community assemblage to landscape- and patch- level factors in 40 forest patches in the densely populated metropolitan area of San Juan, Puerto Rico. In total, 54 bird species were observed including 26 resident, 10 endemic, 12 migratory, and 6 introduced species. Patch size, level of urbanization in the surrounding matrix, and vertical heterogeneity of forest patches were the most important variables in explaining species richness. Patch size had the highest predictive power in explaining species richness for all groups except migrants, which were best predicted by patch-level factors (vegetation heterogeneity). The degree of matrix urbanization was correlated negatively with endemic species richness, but positively with introduced species. Endemic species were particularly sensitive to landscape factors (patch size, matrix urbanization, and canopy texture). Introduced species richness was not dependent on any patch-level factors. Eight species were relatively unaffected by urbanization, whereas two species were only found in large forest patches, and two species were sensitive to urban development. Seven species demonstrated a preference for small patches. Recommendations for land managers and conservation agencies to maintain a high bird species richness and diversity include: (1) preserve both large and small forest patches, (2) limit urban development near forest patches, (3) manage forest patch structure to maintain vertical heterogeneity, and (4) maintain forest patches with different vegetation types.     

Determinants of bird community composition on patches in the suburbs of Paris, France

The ecological processes responsible for the spatial assemblages of breeding bird communities in urban landscapes are more and more investigated. Indeed, understanding these processes is imperative to plan relevant management policies. We investigated breeding bird communities on 67 patches in the suburbs of Paris, France. We examined the role of patch characteristics and geographic distance between patches in determining similarity between bird assemblages. To do this, we proposed a new SØrensen similarity index based on estimators of change in community composition taking into account the detection probability of species. The patch occupancy by sedentary and migratory species was also estimated to compare their sensitivity to urbanization. Patches close to each other supported more similar bird assemblages, suggesting an effect of the spatial distribution of patches on bird dispersal and a posteriori on local community composition. Accounting for spatial location of patches, bird assemblage similarity was related to the similarity of the surrounding level of urbanization but not to the similarity of patch size or to the similarity of patch vegetation. The mean estimated occupancy rate of sedentary species was higher than that of migratory species in the whole study area. While sedentary species occupied patches surrounded by both moderate and high levels of urbanization, migratory ones primarily occupied patches surrounded by moderate levels of urbanization. Human choices in degrees, styles, and extent of urbanization, including designation and design of patches within an urban matrix, affect the composition of local bird communities.     

Effects of habitat degradation on the abundance, richness and diversity of raptors across Neotropical biomes

Population growth and human development result in biodiversity loss and biological homogenization not only in developed countries, but increasingly in the less developed countries as well. In those countries, where urbanization and agricultural intensification occur at a faster rate than in developed countries, habitat degradation appears to be the leading cause of wildlife loss. During the breeding seasons of 2002–2005 we conducted road surveys across five biomes of Argentina to detect variations in raptor community attributes as potential indicators of broad scale habitat degradation. Abundance of individuals, richness and diversity of species were calculated to assess the effects of habitat transformation and patch size on these community attributes. Raptor communities strongly varied in relation to habitat transformations, with lower abundance of individuals, richness and diversity of species in more transformed landscapes. Small patches of natural vegetation and locations in which natural and cultivated lands where interspersed showed lower richness and diversity of raptors than large patches. Fragmentation was the main cause of reductions in abundance of individuals. Although the relative contribution of our two estimates of habitat degradation to abundance, richness and diversity of raptors varied among biomes, these community attributes proved useful as predictors of habitat degradation. This was especially true in habitats where raptor communities are more complex although overall patterns remained constant across biomes, from forests to deserts. Taking into account current trends of habitat transformation (drastic increments in monocultures, urban areas, and habitat patchiness), the conservation of raptor communities in these biomes could be seriously compromised. In terms of species-specific responses of raptors to habitat degradation, a rapid process of homogenization can be expected, resulting in only a few winner species within a general scenario of losers.     

Small isolated aspen stands enrich bird communities in southwestern ponderosa pine forests

Small aspen stands are disappearing from the landscape in the Southwest, so it is important to understand their contribution to the avian community. We sampled birds in 53 small, isolated aspen stands and 53 paired plots within the ponderosa pine forest in northern Arizona, during the 1996 and 1997 breeding seasons. Bird species richness and abundance were higher in aspen than in pine. However, bird species richness and abundance did not vary with size of the aspen patch or isolation index. In addition, direct ordination of species distributions with habitat factors suggested no distinct avian communities. This suggests that aspen stands do not harbor separate populations, but rather are locations where the regional avifauna reaches high local density and richness and may be crucial to birds in years of resource scarcity. Thus it is important for avian conservation to maintain many aspen stands across the landscape, encompassing a diversity of vegetation structure and composition.     

A multi-scale analysis of species-environment relationships: rare moths in a pitch pine-scrub oak (Pinus rigida-Quercus ilicifolia) community

Community level analyses of species-environment relationships can provide critical information for conservation planners. A comprehensive analysis of the factors that influence species distributions should include variables measured at multiple scales because species-environment relationships are known to vary with the scale of observation. The pitch pine-scrub oak (Pinus rigida-Quercus ilicifolia) communities, or pine barrens, of the northeastern USA are severely threatened by development and fire suppression. They also provide critical habitat for many species of rare moths. We used partial canonical correspondence analysis to assess the relative effects of three levels of environmental variables (plot, patch, and landscape) on the distribution and abundance of 10 species of rare moths in a pine barrens community in southeastern Massachusetts, USA. We also used a set of spatial variables to quantify and partial out the effects of spatial autocorrelation of species composition among sampling locations. All three levels of environmental factors combined, independent of spatial factors, accounted for virtually half (48.4%) of the total variation in the moth community. Sequential partitioning of the variance explained by each level of environmental factors indicated that landscape level factors explained more than twice as much variance as plot and patch level factors. Another environmental model that included only landscape level variables explained 53% of the total variation in the moth community. Patch density and percentage of the landscape comprised of open and sparse canopy, scrub oak habitats were the most significant variables. These results suggest that the presence of scrub oak habitat within relatively large, heterogeneous landscape mosaics may be more important for the maintenance of many rare pine barrens associated moth populations than plot or patch level characteristics.     

Agricultural landscape modification increases the abundance of an important food resource: Mistletoes, birds and brigalow

Agricultural landuse alters landscape pattern, with important consequences for native species. Complex responses to changes in landscape pattern may be observed for species with strong inter-specific relationships. We investigate how the abundance of an ecologically important food resource, the grey mistletoe (Amyema quandang), is influenced by the interactive influences of human-modified landscape pattern, bird disperser abundance and host condition. Mistletoe abundance was estimated in brigalow (Acacia harpophylla) dominated remnants in three separate study areas with differing landscape patterns. Negative binomial generalised linear models of mistletoe abundance were tested with combinations of seven explanatory variables: study area, landscape connectivity and edge contrast, patch shape, bird disperser abundance, brigalow foliage cover and basal area of standing dead trees. Ranking of model averaged parameter estimates showed that study area, bird disperser abundance, patch shape, dead trees and connectivity had the strongest influence on A. quandang abundance. Mistletoe abundance apparently increased with landscape modification, particularly in narrow linear patches, but may be limited by the availability of seed dispersers and host condition. Given high landscape modification and ongoing degradation, management should be targeted towards maintaining brigalow remnant condition to ensure bird and mistletoe populations can be supported in the long-term.     

Determinants of leaf litter patchiness in mixed species New Jersey pine barrens forest and its possible influence on soil and soil biota

 We have identified the importance of ground layer ericaceous shrub density as a determinant of leaf litter patch size in upland oak/pine communities of the New Jersey pine barrens. Litter patch area is directly proportional to the number of ericaceous stems. This observation has been confirmed by experimentation where leaf litter patches accumulated under artificial stems for a period of 2 years. Leaf litter patches of different sizes contain differing proportions of leaf species. Large patches contain a significantly higher proportion of oak leaves than small patches. Difference in physical structure of large and small patches, due to leaf species composition and due to differential leaf chemistries, result in differences in soil characteristics and soil biota under the patches. Soil moisture and organic matter content of upper soil layers are greater under large litter patches than under small ones. We have preliminary evidence that these changes influence the community structure of ectomycorrhizae developing under patches of different sizes. Received: 12 April 1999     

The use of zooplankton in a biomonitoring program to detect lake acidification and recovery

A detailed review of the zooplankton literature found strong evidence that lake acidification consistently causes declines in crustacean and rotifer species richness, the relative abundance of cyclopoids and daphnids, and the relative abundance of 16 particular zooplankton species. Five species were found to consistently increase as lake pH declines. Inconsistent effects were observed on crustacean biomass and mean organism size. Biomonitoring response variables recommended to detect incipient community changes include the relative abundance of pH sensitive species, overall crustacean and rotifer community composition plotted in abundance ordination space, crustacean and rotifer species richness, and the relative abundance of acid tolerant species. If acidification effects have been detected using the above response variables, then more detailed monitoring to understand the functional characteristics of affected systems (e.g. crustacean biomass, rotifer biomass and/or overall community size spectra) is appropriate. A lake selection procedure is recommended to maximize the number of systems containing sensitive species, and ensure a set of reference systems whose acidity is unlikely to change significantly.     

The effect of the surrounding landscape matrix on mangrove bird community assembly in north Australia

Mangroves are highly threatened ecosystems yet their community ecology is poorly understood. We examined the ecological determinants of bird community assemblage in floristically depauperate mangroves. Birds were surveyed using line transect methods. Large mangrove patches supported fewer species than smaller patches. Patches did not comprise nested species subsets and the bird species richness of several small patches combined was greater than a single large area. The number of mangrove dependent species in a patch was area-dependent suggesting these species may be resource limited, although there was no species density compensation. There was a clear effect of the surrounding habitat, with matrix species accounting for ∼45% of bird species in a patch. Patches surrounded by tropical savanna were relatively species-poor, while regardless of size, patches including monsoon rainforest were relatively species rich. Null model analysis of non-random assemblage structure (nestedness and species co-occurrence) revealed no deterministic structure to the overall mangrove species assemblage. These analyses described a random pattern of bird distribution and with no evidence of density compensation this suggests that competition is a weak structuring force of mangrove bird assemblages. The lack of nestedness and the random co-occurrence of species are consistent with the matrix-dependence of bird community composition. Conservation plans should treat mangrove patches as part of a habitat mosaic and incorporate many smaller mangrove patches rather than just big ones. Consideration of the nature, extent and diversity of the surrounding matrices is vital in managing and conserving mangrove bird communities.     

Resource use and rarity among frugivorous birds in a tropical rain forest on Sulawesi

Relatively few studies have focussed on the relationship between resource use and rarity. Rare species could differ from common species in two ways: rare species may utilise resources that are themselves rarer or rare species may utilise a narrower range of resources than common species (i.e., they are more specialised). I investigated the relationship between local abundance and patterns of food resource use for an assemblage of 19 frugivorous birds in the tropical lowland rain forest of Sulawesi, Indonesia. Over a 10-month period I collected data on two measures of rarity, the local abundance and monthly variability in local abundance of each bird species, together with data on their feeding ecology including dietary specialisation, resource availability, resource overlap and habitat use. These measures produced 18 ecological variables, 17 of which I correlated with the two measures of rarity using univariate correlations and minimum adequate multiple regression models. These were carried out using the original data and independent contrasts that controlled for potential phylogenetic bias. Both measures of rarity were most strongly correlated with measures of resource availability. In both the original data and independent contrasts regression models of the temporal variability in bird abundance, only temporal fruit availability was included as a significant predictor. In the regression models of bird abundance, the strongest significant predictor was the amount of rare fruit in the diet (a negative relationship). Both models also included measures of resource specialisation, however, these were not significant in the absence of the measure of resource availability. On Sulawesi, rare frugivorous birds utilise rare resources. Specialisation, however, might be an important factor in species persistence once they become rare. The generality of the findings need to be tested.     

Habitat configuration affects colonisation of epifauna in a marine algal bed

Habitat fragmentation is a threat to the preservation of both terrestrial and marine biodiversity. While terrestrial systems have been well studied, relatively few studies have considered how changes to the spatial arrangement of habitats affect fauna in marine systems. In this study, sampling and manipulative experiments examined the effects of varying the size and isolation of habitat patches on the abundance of mobile invertebrates inhabiting an algal dominated rocky reef. Variation in the size of naturally occurring patches of the brown alga Sargassum linearifolium did not impact upon the abundance of any taxonomic groups, with the exception of polychaete worms, which were most abundant in small patches. When habitat patch size and isolation were manipulated, the abundance of colonising isopods increased with increasing isolation from contiguous habitat. Amphipods and ostracods colonised small patches to greater numbers than large patches. Sampling of the matrix was undertaken to examine the rarely tested assumption that the area between habitat patches is not a potential source of colonists to the habitat in question. The matrix was found to support a strikingly different community of invertebrates than did the algal habitats and thus was unlikely to be a source of colonists to isolated algal patches. The increased abundance on small and isolated patches for some taxa are inconsistent with traditional predictions of the effects of reduced habitat patch sizes and indicate that patchy landscapes should not necessarily be considered poor habitats. The variation in responses among taxonomic groups suggests that a range of patch sizes may be necessary to maintain species diversity.     

Do regional gradients in land-use influence richness, composition and turnover of bird assemblages in small woods?

Small patches of natural or semi-natural habitat have an important role in the conservation of biodiversity in human-dominated environments. The values of such areas are determined by attributes of the patch as well as its context in the surrounding land mosaic. There is a need for better understanding of the ways in which assemblages are influenced by patch context and the scale over which this occurs. Here we examine the influence of regional environmental gradients on the richness, annual turnover and composition of breeding bird species in small woods in south-eastern England. Regional gradients were defined independently of woods by an ordination of attributes for 5 km × 5 km landscape units across a 2100 km² region. Patch-level attributes, particularly area, were the most important predictors for most bird variables. For woodland migrants and woodland-dependent species, variables representing the context of each wood, either at a local or regional scale, explained significant additional variance in species richness after accounting for wood area, but did not do so for species turnover. Significant context effects for woodland-dependent species related to the extent of hedges and woodland cover in the local vicinity (<1 km radius), whereas for woodland seasonal migrants the best predictors of richness after patch area were two regional environmental gradients. The initial cue to settlement for migrants may be at a coarse regional scale, with selection for suitable landscapes that have a greater extent of woodland cover. Edge species showed different responses: they were influenced by the diversity of structural features in woods, and were a more-dominant component of the avifauna in isolated woods in open fenland environments of the region. Significant relationships between coarse regional gradients (25 km² units) and bird assemblages in small woods (0.5-30 ha) suggest that population and community processes in the avifauna operate across a broader scale than local patch neighbourhoods. They also highlight the importance of adopting a landscape or regional perspective on potential changes to land-use in rural environments, and on the conservation management of small reserves.     

Values of village fengshui forest patches in biodiversity conservation in the Pearl River Delta, China

Chinese village fengshui forests (VFF) are small remnant forest patches that coexist with natural villages. The indigenous residents protect the forest patches under traditional Chinese geomancy beliefs (namely fengshui). However, the VFF community features and conservation values and relationships with the indigenous people remain poorly understood. In this study, we evaluated tree species diversity conservation of regional VFF patches by sampling a 1200 m² transect within each patch. We also tested our hypothesis that patch size did not significantly impact interior forest community features of well-protected VFF patches. Thirty-two well-protected VFF patches in the Pearl River Delta, China were investigated. The average coefficient of similarity between transects (CS) was employed to evaluate community heterogeneity. Five forest community parameters (tree species richness per 1200 m², tree stem density, tree basal area density, Shannon–Wiener diversity index (SWI), and Simpson diversity index (SI)) were measured and compared with regional well-developed evergreen broadleaved, coniferous and coniferous-broadleaved mixed forests. The relationships between the five parameters versus patch size and elevation were analyzed. A total of 266 tree species comprised of 57 families were recorded in 32 transects, of which 258 (97%) species were indigenous and eight (3%) were exotic. Ten tree species were endangered, rare or nationally protected by the Chinese government, and 57 species were endemic to China. The average CS was 0.38; and the average five forest community parameter values were as follows: 46.8 for tree species richness; 3403 plants/ha for stem density, 49.1 m²/ha for basal area, 4.04 for SWI and 0.90 for SI. These values were consistent with well-developed evergreen broadleaved forests and greater than coniferous and coniferous-broadleaved forests. No significant correlation was detected between the five community parameters and patch area or elevation. We conclude that VFF patches preserve abundant tree species and heterogeneous habitats, which are important for maintaining regional biodiversity. The interior community features of VFF patches were not significantly affected by patch size. We recommend protection of both large and small VFF patches, which can be substantially enhanced by the preservation of associated traditional relic village cultures.     

Nested plant and fungal communities; the importance of area and habitat quality in maximizing species capture in boreal old-growth forests

Knowledge of the distribution of rare species is crucial for species conservation in fragmented habitats. Species communities often exhibit nestedness, i.e. species in species-poor sites comprise a subset of richer ones. Thus, rare species are confined to species-rich sites. We evaluate whether plant and fungal communities in 46 old-growth spruce forest patches (0.17-12 ha) exhibit nestedness. The question whether a single large patch or several small patches capture most species (i.e. the SLOSS-issue) is evaluated in combination with species saturation analyses. All species groups exhibited significant nestedness. Area was generally related to nestedness, i.e. rare species were over-represented in the largest patches. Species saturation analysis indicated that large patches accumulated more Red-list species in patch interiors than small patches. Thus, rare and Red-list species were best captured in large patches. However, nestedness also emerged in equal sized sample plots, i.e. rare species were over-represented in high quality habitats. Thus, small habitats of high quality should not be neglected in a conservation perspective.     

Warming favours small-bodied organisms through enhanced reproduction and compositional shifts in belowground systems

The increased prevalence of smaller-bodied species under warmer conditions (community downsizing) is hypothesized as an ecologically critical consequence of climate change, leading to changes in trophic transfer efficiency, and rates of nutrient and energy flux within ecosystems. This study used 100 intact peat-soil mescosms to measure changes in belowground biodiversity under three manipulated climate variables: elevated temperature, elevated CO₂, and altered water table. Changes in species richness, abundance, community composition and body size spectra were used to determine whether climate change factors led to community downsizing, and elucidate any underlying mechanisms. Warming was the primary driver of compositional shifts in belowground fauna communities with the strongest effect among the smaller-bodied, non-sexually reproducing species. Increases in abundance driven by enhanced reproduction in small-bodied species rather than an increased extinction-rate among large-bodied predators was the basis of the observed downsizing. The overall consequences of warming-induced changes in belowground systems on ecosystem function are still unclear. However, as body size is intricately linked to metabolism, observed community downsizing suggests reductions in food web trophic transfer efficiency with consequences for nutrient and energy dynamics in belowground systems.     

The influence of patch area and connectivity on avian communities in urban revegetation

Landscape restoration through revegetation is being increasingly used in the conservation management of degraded landscapes. To effectively plan restoration programs information is required on how the landscape context of revegetation influences biodiversity gains. Here, we investigate the relative influence of patch area and connectivity on bird species richness and abundance within urban revegetation patches in Brisbane, Australia. We carried out bird surveys at 20 revegetation sites, and used hierarchical partitioning and model selection to test the relative importance of patch area (the area of revegetation including all directly connected remnant vegetation) and landscape connectivity (the vegetated area connected by less than 10 m, 20 m, 30 m, 40 m and 50 m cleared gaps). We controlled for a number of possible confounding variables within the hierarchical partitioning procedure. Both the hierarchical partitioning and model selection procedures indicated that connectivity had an important influence on bird species richness. Patch area in combination with connectivity were important influencing factors on overall bird abundance. We also carried out the hierarchical partitioning procedure for bird abundance data within a range of feeding guilds, yielding results specific to species groups. Overall our data suggest that greater connectivity enhances the habitat area that colonists can arrive from (resulting in greater species richness), whereas increased patch area allows for increased abundance by expanding the habitat available to species already present in a patch. A combined approach where connectivity and overall habitat area is enhanced across the landscape is likely to be necessary to meet long-term conservation objectives.     

管理措施及土壤因子对5种农田生境地表蜘蛛群落多样性的影响

以往的研究表明有机管理有利于生物多样性保护,但在不同农业生境类型中是否都存在这个结论呢?基于此问题,本研究在一个多生境的有机管理农场与一个相邻的多生境常规集约化管理农区,采用陷阱法进行蜘蛛取样,对比有机和常规管理措施下大棚菜地、果园、稻田田埂、露天田块及农田边界等5种生境类型的农田蜘蛛多样性的差异,并分析土壤因子对蜘蛛多样性的影响。研究发现:1)有机管理与常规管理的蜘蛛物种数没有显著差异,但有机管理的果园中蜘蛛个体数比常规管理的果园中多139%,且差异显著。同一管理措施下,仅常规管理农田区的农田边界蜘蛛个体数和物种数分别显著高于其他生境均值104%和59%。2)有机管理农场比常规管理农田的蜘蛛物种组成差异略大,且在有机管理下不同生境间的蜘蛛群落组成差异更明显。3)土壤因子中有机质、全氮、全磷含量等对蜘蛛群落结构有显著影响,但对蜘蛛个体数和物种数没有显著影响,仅土壤Cu含量和蜘蛛个体数呈显著负相关。在本研究中虽然有机管理和土壤因子对蜘蛛多样性有一定影响,但不同生境间管理强度、植被结构等差异对蜘蛛多样性的影响更大。因此,发展多种农业生境类型的有机农业可提升物种β多样性。同时,在常规集约化管理农区,保留农田边界等半自然生境、适当减少化肥和农药等投入、降低农田内部的管理强度、防止土壤重金属污染等措施均有助于保护蜘蛛多样性。     

Seedling recruitment and survival of two desert grasses in the monte of Argentina

In the Monte Austral Neuquino, Argentina, vegetation is arranged in patches. Understanding the mechanisms involved in their distribution is critical for preventing desertification. The working hypothesis was that vegetation patches reduce environmental stress on the plants. Plant patches were classified into four microenvironments: windward; below the dominant shrubs (subcanopy); vegetation at the patch periphery (canopy edge) and bare patch interspaces (open). We determined seedling survival of the dominant species in each microenvironment, using a marking method of seedlings established from sown seeds. In addition, we measured the environmental characteristics in the four microenvironments, and associated them with seedling survival. Study species were the perennial grasses Leymus erianthus (Phil.) Dubcovsky, Stipa neaei Nees ex Steudel and Poa ligularis Nees ex Steudel, and the shrubs Larrea divaricata Cav. and Atriplex lampa Gill ex Moquin. Results supported the hyphothesis only for L. erianthus and S. neaei (but not for the other three species that showed higher seedling survival in the subcanopy than in the patch interspaces after 1 year from sowing). This study determined that (1) reduced environmental stress does not guarantee seed germination and seedling survival of a given species in the plant community and (2) seedling establishment will not be possible for any species of the plant community in the patch interspaces under the study conditions in the region. This is mostly because soil temperatures can reach up to 50°C in the patch interspaces in years of scanty precipitation during late spring and summer. Copyright © 2010 John Wiley & Sons, Ltd.