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In coastal ecosystems, water availability is limited because of the high soil salinity influenced by sea water intrusion, high soil noncapillary porosity, and significant seasonal fluctuation of precipitation. Therefore, water availability is a key determinant of plant growth and distribution in coastal ecosystems. Tamarix chinensis Lour. and Ziziphus jujuba var. spinosa Hu are two coexisting shrub species growing on Chenier Island in the Yellow River Delta (YRD), China. Our aim was to investigate how the water-use strategies of the two species respond to variations in soil moisture to improve understand of their adaptations to drought stress and their coexistence mechanism. During the growing season, the oxygen stable isotope signatures ([delta][sup.18]O) were measured for soil water in different soil depths (0-20, 20-40,40-60, and 60-100 cm), shallow groundwater, and xylem water. The proportional contributions of potential water sources for the two species were calculated by using the IsoSource mixing model. The results showed that the [delta][sup.18]O values of the two species showed a clear seasonal difference. When soil moisture was high and air temperature was low, T. chinensis mainly used water from soil depths of 60-100 cm, while Z. jujuba mainly used water from soil depths of 0-40 cm. When soil moisture was low or air temperature was high, T. chinensis mainly used the saline shallow groundwater, while Z. jujuba mainly used water from soil depths of 20-100 cm. When there was a large amount of precipitation, both T. chinensis and Z. jujuba mainly absorbed water from soil depths of 20-40 cm. Tamarix chinensis and Z. jujuba had different water-use patterns during the growing season, which reflected their adaptations to seasonal fluctuations in soil water content within a water-limited coastal ecosystem, while the niche differentiation in water use of the two species clarifies their coexistence mechanism. Key words: water-use strategies, water resource, coexisting shrubs, coastal zone, Yellow River Delta. Dans les ecosystemes cotiers, la disponibilite de l'eau du sol est reduite a cause de la salinite elevee du sol qui est influencee par l'intrusion de l'eau de mer, de la porosite non capillaire elevee du sol et de la fluctuation saisonniere de la precipitation. Par consequent, la disponibilite de l'eau est un facteur determinant pour la croissance et la repartition des plantes dans les ecosystemes cotiers. Tamarix chinensis Lour. et Ziziphus jujuba var. spinosa Hu sont deux especes d'arbuste qui coexistent et croissent sur l'ile Chenier dans le delta du fleuve Jaune en Chine. Notre objectif consistait a etudier de quelle facon les strategies d'utilisation de l'eau des deux especes reagissent aux variations de l'humidite du sol dans le but d'ameliorer notre comprehension de leur adaptation au stress cause par la secheresse et de leur mecanisme de coexistence. Durant la saison de croissance, la signature de l'isotope stable de l'oxygene ([delta][sup.18]O) a ete mesuree dans l'eau du sol a differentes profondeurs (0-20, 20-40, 40-60, et 60-100 cm), dans les eaux souterraines peu profondes et dans le xyleme. La contribution proportionnelle des sources d'eau potentielles a ete calculee chez les deux especes en utilisant le modele de melange IsoSource. Les resultats indiquent qu'il y a une difference saisonniere claire entre les deux especes d'apres les valeurs de [delta][sup.18]O. Lorsque l'humidite du sol est elevee et la temperature de l'air est basse, T. chinensis utilise surtout l'eau du sol a une profondeur de 60-100 cm tandis que Z. jujuba utilise surtout l'eau du sol a une profondeur de 0-40 cm. Lorsque l'humidite du sol est reduite et que la temperature de l'air est elevee, T. chinensis utilise surtout les eaux souterraines peu profondes et salines tandis que Z. jujuba utilise surtout l'eau du sol a une profondeur de 20-100 cm. Lorsqu'une forte precipitation survient, les deux especes absorbent surtout l'eau du sol situe a 20-40 cm de profondeur. Tamarix chinensis et Z. jujuba ont differents profils d'utilisation de l'eau durant la saison de croissance correspondant a leur adaptation aux fluctuations saisonnieres de la teneur en eau du sol dans un ecosysteme cotier limite en eau, tandis que la differentiation de niche entre les deux especes sur la base de l'utilisation de l'eau clarifie leur mecanisme de coexistence. [Traduit par la Redaction] Mots-cles : strategies d'utilisation de l'eau, ressource hydrique, coexistence de deux arbustes, region cotiere, delta du fleuve Jaune., Introduction Coastal ecosystems are the most dynamic and productive ecosystems in the world (Perez-Ruzafa et al. 2011; Grootjans et al. 1997; Bakun et al. 2015) and are sensitive to climate [...]

Abstract: Many studies report mixed results on the influence of invasive plants on native animals, partly due to uncertainties about habitat preference and reproductive performance in native animals before and [...]

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

It has been shown that the spatial configuration of a green area can strongly influence its cooling effect. However, the specific correlation has not been sufficiently studied. To systematically clarify the correlation between the spatial configuration and the cooling effect of green areas, 25 idealized scenarios are designed and simulated using the microclimate model ENVI-met. These 25 scenarios represent green areas with five different spatial configurations (integrated green area, sparse dotted green areas, dense dotted green areas, belt-shaped green areas parallel to wind direction, and belt-shaped green areas vertical to wind direction) and five vegetation types (trees with big canopies, trees with small canopies, hedges and shrubs, 50 cm grass, and 10 cm grass). The human thermal comfort of each scenario is evaluated by means of physiologically equivalent temperature (PET) using Rayman. The results reveal the influence of the fragmentation degree (quantified by the patch density and edge density), shape complexity (quantified by the land shape index), orientation of green belt, and vegetation type on the cooling effect of a green area. The spatial configuration and the vegetation type of green areas were found jointly affecting the efficiency of the green areas’ cooling effect. The highest cooling effect appears at 2 pm, reaching 6.3 K in the scenario of belt-shaped green areas parallel to the wind direction and with big canopy trees. The conclusions of this paper can provide suggestions for the climate-adaptive design and planning of urban green areas in the future. [ABSTRACT FROM AUTHOR]

Abstract: Increases in the cover or density of woody plants (encroachment) and overgrazing by European livestock are 2 major drivers of ecosystem structure and function in drylands and are often associated with land degradation. Although the effects of encroachment and overgrazing on vascular plants are relatively well known, little is known about their effects on arthropods such as ants. We examined ant community composition at sites ranging in shrub cover in a wooded dryland in eastern Australia, testing the notion that increasing shrub cover and grazing intensity would alter ant assemblages and functional group composition. We used ants because they are abundant, diverse, and respond to small‐scale environmental changes. Increasing shrub cover had no effect on ant richness, diversity, or evenness but increased the abundance of Subordinate Camponotini. Larger shrubs tended to have greater ant richness, and abundance of Cold Climate Specialists, but fewer Generalized Myrmicinae and Hot Climate Specialists. More intense grazing was associated with greater ant richness, diversity, and evenness; a greater abundance of Hot Climate Specialists and Dominant Dolichoridae; and lower abundance of Subordinate Camponotini. Our study indicates that changes in grazing intensity had stronger effects on ant richness than any increase in shrub cover. The effects of grazing likely resulted from changes in soil surface complexity such as barer ground associated with grazing‐induced degradation. [ABSTRACT FROM AUTHOR]

We explore the possibility of extending the national forest inventory-based point data of understory presence using region-wide, disparate lidar data for the southeastern USA. For this, we developed a simple inferential model that helps to understand the basic underlying relationships and associations between lidar predictor metrics and forest understory shrub presence over a wide range of forest types and topographic conditions. The model (a least absolute shrinkage and selection operator-based logistic regression model) had fair predictive performance (accuracy = 62%, kappa = 0.23). Hence, we were able to propose a set of biophysically meaningful predictor variables that represent understory (4), canopy (3), topographic conditions (1), and sensor characteristics (1). The single most important predictor variable was the understory layer canopy density, which is the ratio of lidar returns in the understory to those near the ground. Hence, we demonstrate that the interplay of several factors affects understory vegetation condition. Overall, our work highlights the potential value of using lidar to characterize understory conditions. [ABSTRACT FROM PUBLISHER]

Phenology indicates the response of ecosystem dynamics to climate change. Shrubs are an important component of alpine forests, and play a key role in forest ecosystem function, especially in semiarid alpine regions. In 2015, we observed the dynamics of phenology in five shrub communities along an elevation gradient (2600-3300 m) in the Qilian Mountains. Our results showed that the length of the growing season decreased from 153 days for Caragana tangutica to 150 days for Berberis diaphana, 149 days for Potentilla fruticosa L., 144 days for Caragana jubata (Pall.) Poir., and 134 days for Salix gilashanica C. Wang et P. Y. Fu. The accumulated temperature of the five shrub communities during the growing season varied from 1735.4 °C for C. tangutica to 1051.3 °C for C. jubata. The beginning of the growing season was earlier at lower, than at higher, elevations, while the end of the growing season was later at lower, than at higher, elevations. Elevation and aspect were two important environmental factors that affected shrub phenology. In our study, low temperature, coinciding with the occurrence of early frost, particularly in higher elevations, was the key factor in promoting end-of-season shrub growth cessation. [ABSTRACT FROM AUTHOR]

In urban landscape planning, using or not-using fruitful trees and shrubs as part of urban agriculture is a significant challenge. This study evaluated the important factors affecting cultivation of fruitful shrubs and trees in urban landscapes. It also utilized these factors in developing effective strategies for cultivation of these groups of plants in landscaping of the metropolitan city of Mashhad, Iran. It would be crucial for urban landscape managers and decision-makers to understand the relative importance of the affecting factors and to develop effective planning strategies for using these groups of plants in urban landscaping. To support their decision making process, a SWOT analysis approach was applied. Twelve factors and their relative weighting were examined through focus group interviews. This was followed by a semi-structured questionnaire survey with landscape decision makers in the city of Mashhad. The results suggested a range of SWOT strategies among which Strength-Threat (ST) strategies were the most important strategies. These ST strategies should be applied in productive cultivation of trees and shrubs in landscape development in the city of Mashhad. One of the main strategies which might be applicable for urban agriculture development in developing countries is using germplasms of native fruit trees with low water requirements. Using native species leads to sustainable use of local water and soil resources that are critical in these countries, such as the countries in the Middle East, on the benefit of employing more labors that are relatively cheap. This can also improve satisfaction of the society with reduction in unemployment rates. [ABSTRACT FROM AUTHOR]

Climate projections forecast more extreme interannual climate variability over time, with an increase in the severity and duration of extreme drought and rainfall events. Based on bioclimatic envelope models, it is projected that changing precipitation patterns will drastically alter the spatial distributions and density of plants and be a primary driver of biodiversity loss. However, many other underlying mechanisms can impact plant vital rates (i.e., survival, growth, and reproduction) and population dynamics. In this study, we developed a size-dependent integral projection model ( IPM) to evaluate how interannual precipitation and mollusk herbivory influence the dynamics of a Hawaii endemic short-lived shrub, Schiedea obovata (Caryophyllaceae). Assessing how wet season precipitation effects population dynamics it critical, as it is the timeframe when most of the foliar growth occurs, plants flower and fruit, and seedlings establish. Temporal variation in wet season precipitation had a greater effect than mollusk herbivory on S. obovata population growth rate [ABSTRACT FROM AUTHOR]

Stemflow is known as a highly localized point input of rainwater and solutes around tree/shrub bases where roots are concentrated, thus having considerable effects on hydrology and biogeochemistry of vegetated ecosystems. Stemflow shows a pronounced inter-specific variation due to morphological differences among species, while the intra-specific variation of stemflow has been poorly explored. We systematically examined the effects of shrub morphological metrics on intra-specific funnelling efficiencies by quantifying the stemflow of nine shrubs of Caragana korshinskii within a water-limited arid desert ecosystem of northern China. Stemflow volume was used to compare the absolute amount of stemflow generated by shrubs of varying size, and funnelling ratio was used to assess their funnelling efficiencies. Both rainfall depth and shrub morphological metrics significantly affected stemflow volume, while funnelling ratio was more associated with shrub morphology. Under the same rainfall condition, smaller shrubs produced lower volumes of stemflow, while gaining access to rainfall via higher funnelling ratio than larger shrubs. Our findings highlight a large variation in funnelling efficiency among individual shrubs within the same species, and in particular, smaller shrubs might profit more from sporadic small rainfall events than larger shrubs. [ABSTRACT FROM AUTHOR]

Abstract.--There is a need for a consolidated source of information on native vegetation seed collection and germination strategies in southern California. Published literature on these methods is often experimental, species-specific, [...]

Background: Understanding how landscape factors, including suites of geographic and environmental variables and both historical and contemporary ecological and evolutionary processes shape the distribution of genetic diversity is a primary goal of landscape and conservation genetics and may be particularly consequential for species involved in ecological restoration. In this study, we examine the factors that shape the distribution of genetic variation in a leguminous shrub (Caragana microphylla) important for restoration efforts on the Mongolian Plateau in China. This region houses several major bioclimatic gradients and C. microphylla is an important restoration species because it stabilizes soils and prevents advancing desertification on the Inner Mongolia Plateau caused by ongoing climate change. Results: We assembled an expansive genomic dataset, consisting of 22 microsatellite loci, four cpDNA regions and 5788 genome-wide SNPs from ten populations of C. microphylla. We then applied ecological niche modelling and linear and non-linear regression techniques to investigate the historical and contemporary forces that explain patterns of genetic diversity and population structure in C. microphylla on the Inner Mongolia Plateau. We found strong evidence that both geographic and environmental heterogeneity contribute to genetic differentiation and that the spatial distribution of genetic diversity in C. microphylla appears to result partly from the presence of a glacial refugium at the southwestern edge of its current range. Conclusions: These results suggest that geographic, environmental and historical factors have all contributed to spatial genetic variation in this ecologically important species. These results should guide restoration plans to sustain genetic diversity during plant translocations. [ABSTRACT FROM AUTHOR]

Background and aims: The encroachment of halophytic shrubs including tamarisk into saline meadows is accelerating with global warming in the northern Tarim Basin, Xinjiang, China. However, the role of tamarisk in the spatial heterogeneity of soil resources in different desertification stages remains unclear. Methods: The influences of tamarisk on soil resources were assessed via soil salinity and soil organic matter (SOM) measurements under tamarisk canopies and in interspaces. Geostatistical methods were applied to compare the spatial heterogeneity of these soil properties in three regions representing different desertification stages: 1) a meadow with shrubs, 2) a shrubland and 3) shrub duneland. Results: The highest coefficient of variation (CVs) of the soil analytes and most developed 'resource islands' were observed in the shrubland. The overall variation of most of the soil variables was lower in the shrub duneland than in the shrubland and similar to that in the meadow with shrubs. The distribution of SOM and most soil salinity ions were moderately spatially dependent in the meadow with shrubs but highly spatially dependent in the shrubland and shrub duneland. The autocorrelation distances of the most of soil salinity ions were approximately 6- to 15- fold and 2- to 4-fold highest than the tamarisk shrub size in the meadow with shrubs and shrubland, respectively. In contrast, the distribution range of total soil salinity (TSS) and soil K, Na and Cl in the shrub duneland were 1/5 ~ 2/3 of the tamarisk size. Conclusions: 1) Compared with the effect of tamarisk on soil resource heterogeneity in the meadow with shrubs, that in the shrubland was enhanced due to the larger shrub size and more open and scattered canopy in the latter.2) Although the largest shrub size were observed in the shrub duneland, the role of tamarisk in redistributing soil resources was overriden by those of physical processes due to the loose canopy. 3) The spatial heterogeneity of soil resources is determined by not only tamarisk but also environmental factors, such as the connectivity of bare areas and topography. [ABSTRACT FROM AUTHOR]

Both overabundant ungulates and invasive shrubs negatively impact forest floor plants, but few studies have investigated their interaction. We tested for direct effects and interactions of white-tailed deer, Odocoileus virginianus , and the invasive shrub, Lonicera maackii , on forest floor plant richness and composition in five sites in southwest Ohio. In each site a deer exclosure and an unfenced plot (each 20 × 20 m) were established in 2010; in half of each plot all L. maackii was removed. Each spring and summer, 2011–2014, percent cover of each plant species in 50 × 20 cm subplots was recorded. Herb layer species richness was greater where L. maackii was removed, and this effect tended to be stronger where deer were excluded. Species composition in the spring was not affected by treatments, whereas summer species composition (in one year) was affected by L. maackii treatment. Cover of graminoids, spring herbs, and vines were lower where L. maackii was intact, whereas cover of shrubs and tree seedlings were lower, and cover of bare ground higher, where deer had access. Our findings reveal that deer and L. maackii negatively impact different components of the forest herb layer. However, the combined effects on species richness tended to be antagonistic (less than additive), possibly due to deer browse reducing the cover of this invasive shrub. This suggests that the diversity of the herb layer will be enhanced more by both removal of invasive shrubs and reduction of the deer population than by either management action alone. [ABSTRACT FROM AUTHOR]

Aims Global change projections predict biodiversity changes and increased drought intensity in the Mediterranean Basin in the decades to come. This will presumably affect plant performance, plant community composition and ecosystem functioning. Shrublands are widespread in the Mediterranean area, yet we have no clear understanding of shrubland responses to the combined effects of increased drought and changes in plant diversity. Location Natural Mediterranean shrubland, Marseille, south France. Methods A rainfall manipulation experiment was conducted to examine the performance of four dominant shrub species in response to increased drought. The study assemblages spanned a gradient of four shrub richness levels (mono-, bi-, tri- and tetra-specific plant mixtures) and 15 different shrub combinations. Throughout the 2 yr of non-destructive experiments (2012-2014), we measured plant litter fall, stand necromass and plant cover of the four dominant plant species: Cistus albidus, Quercus coccifera, Rosmarinus officinalis and Ulex parviflorus. Results Increasing shrub richness levels in the plant community led to higher litter production by all four species and a decrease in dry shoots for Quercus and Ulex. Shrub species responses were affected by the rain exclusion treatment, but the effects were mainly dependent on shrub richness level. In mono-specific plots, aggravated drought conditions led to a decrease in litter fall of Cistus, Rosmarinus and Ulex and an increase in necromass of all four species. In general, these negative drought effects disappeared as number of shrub species in the community increased. Under rain exclusion treatment, Rosmarinus cover decreased in mono-specific plots whereas Quercus cover increased in bi-specific plots and Rosmarinus cover increased in tetra-specific plots. We observed two drought tolerance patterns, with Quercus and Rosmarinus being more tolerant species and Ulex and Cistus less tolerant. Conclusions The magnitude of drought effects on shrub performance is species-specific, and plant species combination-dependent. High shrub richness levels modulate the negative impacts of aggravated drought conditions. Our results point to a probable shift of interspecific relationships in response to water shortage. As drought impacts are not mediated in low-diversity communities, species-specific responses to drier conditions could lead to shifts in plant community composition favouring the most drought-resistant species, i.e. Quercus and Rosmarinus. Maintaining high diversity appears critical to mediate drought effects for less resistant species ( Cistus and Ulex in our study). [ABSTRACT FROM AUTHOR]

Shrub densification has been widely reported across the circumpolar arctic and subarctic biomes in recent years. Long-term analyses based on dendrochronological techniques applied to shrubs have linked this phenomenon to climate change. However, the multi-stemmed structure of shrubs makes them difficult to sample and therefore leads to non-uniform sampling protocols among shrub ecologists, who will favor either root collars or stems to conduct dendrochronological analyses. Through a comparative study of the use of root collars and stems of Betula glandulosa, a common North American shrub species, we evaluated the relative sensitivity of each plant part to climate variables and assessed whether this sensitivity is consistent across three different types of environments in northwestern Québec, Canada (terrace, hilltop and snowbed). We found that root collars had greater sensitivity to climate than stems and that these differences were maintained across the three types of environments. Growth at the root collar was best explained by spring precipitation and summer temperature, whereas stem growth showed weak and inconsistent responses to climate variables. Moreover, sensitivity to climate was not consistent among plant parts, as individuals having climate-sensitive root collars did not tend to have climate-sensitive stems. These differences in sensitivity of shrub parts to climate highlight the complexity of resource allocation in multi-stemmed plants. Whereas stem initiation and growth are driven by microenvironmental variables such as light availability and competition, root collars integrate the growth of all plant parts instead, rendering them less affected by mechanisms such as competition and more responsive to signals of global change. Although further investigations are required to determine the degree to which these findings are generalizable across the tundra biome, our results indicate that consistency and caution in the choice of plant parts are a key consideration for the success of future dendroclimatological studies on shrubs. [ABSTRACT FROM AUTHOR]

Tall-shrub expansion into low-statured communities, a hallmark of recent vegetative change across tundra ecosystems, involves three major genera: Alnus, Betula and Salix. Which genus expands most into tundra landscapes will determine ecosystem properties., We show that Alnus and Salix shrubs segregate thermal space (elevation × insolation) and colonize tundra landscapes differently in response to climate warming, thereby replacing different tundra types., Vegetative change estimated from repeat photography should account for hill-slope. Methodologically, slope determines surface area estimated from orthophotos as projected pixel area times secant of pixel slope. Ecologically, the change in thermally responsive vegetative area is sensitive to terrain steepness, scaling as the cosecant of hill-slope, so that studies should expect more shrub expansion in areas of shallow slopes than steep slopes., Repeat aerial photography in Alaska's Chugach Mountains from 1972 to 2012 orthorectified on a high-resolution lidar digital elevation model indicated tall Salix was rare in 1972 and colonized warmer slopes by 2012. Tall Alnus colonized steeper, cooler slopes both by 2012 and by 1972. Salix and forest colonized similar thermal space. Colonization probability for both shrub genera was maximized at intermediate elevations., Alnus colonization adjacent to dwarf-shrub tundra was twenty times as likely as Salix colonization. Salix colonization adjacent to low-shrub/herbaceous tundra was three times as likely as Alnus colonization. Replacement of dwarf-shrub tundra by Alnus and of low-shrub/herbaceous communities by Salix will affect herbivores and soil properties., Good agreement between observations of plant functional type and multinomial predictions in a thermal space defined by elevation and insolation suggested that these two variables were sufficient for forecast modelling. Spatially explicit, climate-driven generalized linear multinomial and random forest classification models in available thermal space forecast surface areas of forest, Alnus, Salix and tundra over a range of warming, modelled as upward shifted isotherms, including expected IPCC scenarios. Both modelling approaches indicated that shrubs may respond nonlinearly to warming., Synthesis. The provision of taxon-specific coefficients for climate-driven, spatially explicit models using high-resolution digital elevation models is necessary for accurately forecasting vegetative change due to climate warming in montane and arctic regions. [ABSTRACT FROM AUTHOR]

Copyright of Fire Ecology is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We quantified the fine root length density of Lonicera maackii (Amur honeysuckle) and native trees at two depths on transects away from individuals of this invasive shrub and tested whether the invasive shrub L. maackii reduced water availability for other forest plants by either of two mechanisms: (1) intercepting rainwater during light rain events or (2) absorbing large amounts of water through its fine roots. To test the two hypothesized mechanisms, we selected plots near large L. maackii shrubs and control plots away from any large L. maackii shrubs in the forest understory. Within each plot we placed a trenched and an untrenched subplot and measured soil water content in each. We also measured precipitation above and below L. maackii canopies. We found that within 2 m of large maackii shrubs, this shrub accounted for a large fraction (22-25%) of the fine roots in the top 12 cm of soil. Reduced throughfall and soil moisture below shrubs supported the hypothesis that L. maackii competes with tree seedlings by interception. Findings were inconclusive regarding the hypothesis of competition by water uptake., INTRODUCTION Invasive plant species often cause deleterious effects on local communities, particularly by reducing native plant species diversity (Vila et al., 2011). However, the individual mechanisms underlying these reductions in [...]

Aims: We evaluated the combined effects of litter type, UV radiation, and soil water on litter decomposition processes in denuded areas of the arid Patagonian Monte. Methods: We conducted a manipulative experiment with litterbags with litter dominated by evergreen shrubs (ES), and litter dominated by perennial grasses and evergreen shrubs (PG) placed on undisturbed upper soil blocks from denuded areas. We subjected soil blocks with litterbags to near ambient and attenuated UV radiation levels, and low and high soil water levels. We evaluated litter mass loss and changes in N, soluble phenolic and lignin contents during 420 days. Results: PG litter decomposed faster than ES litter, and UV radiation and soil water enhanced decomposition of both litter types. PG litter immobilized N while ES litter released N. During decomposition, soluble phenolic content decreased while lignin content did not vary in both litter types. Conclusions: Our results highlighted that abiotic and biotic controls differed between mass loss and N release/immobilization. We found additive effects of the studied factors on mass loss while litter chemistry controlled microbial N release or immobilization from decaying litter. Further studies should explore the effects of these factors on species or functional groups shifts in microorganism communities. [ABSTRACT FROM AUTHOR]

Freezing resistance through avoidance or tolerance of extracellular ice nucleation is important for plant survival in habitats with frequent subzero temperatures. However, the role of cell walls in leaf freezing resistance and the coordination between leaf and stem physiological processes under subzero temperatures are not well understood. We studied leaf and stem responses to freezing temperatures, leaf and stem supercooling, leaf bulk elastic modulus and stem xylem vessel size of six Patagonian shrub species from two sites (plateau and low elevation sites) with different elevation and minimum temperatures. Ice seeding was initiated in the stem and quickly spread to leaves, but two species from the plateau site had barriers against rapid spread of ice. Shrubs with xylem vessels smaller in diameter had greater stem supercooling capacity, i.e., ice nucleated at lower subzero temperatures. Only one species with the lowest ice nucleation temperature among all species studied exhibited freezing avoidance by substantial supercooling, while the rest were able to tolerate extracellular freezing from −11.3 to −20 °C. Leaves of species with more rigid cell walls (higher bulk elastic modulus) could survive freezing to lower subzero temperatures, suggesting that rigid cell walls potentially reduce the degree of physical injury to cell membranes during the extracellular freezing and/or thaw processes. In conclusion, our results reveal the temporal–spatial ice spreading pattern (from stem to leaves) in Patagonian shrubs, and indicate the role of xylem vessel size in determining supercooling capacity and the role of cell wall elasticity in determining leaf tolerance of extracellular ice formation. [ABSTRACT FROM AUTHOR]

One of the prominent compositional features of thermophilous deciduous forests of southern Europe is their richness in secondary woody species (AWS). To date, no studies have focused on the diversity and contribution to the ecosystem functions and socio-economic benefits provided by these species. Here, we first characterized species richness and diversity for three main functional groups of AWS, sporadic trees, shrubs and vines, in 53 representative stands of central Italy. Secondly, we explored variations in AWS diversity and composition along a four-level gradient of species richness of dominant trees under comparable site conditions. The 40 AWS taxa recorded showed a remarkable taxonomic singularity at both the genus and the family rank. Dominant tree species richness had no significant effect on AWS species richness and composition, while Shannon diversity of AWS, especially shrubs, was associated with cover of the dominant trees. Each AWS possessed, on average, ca. five ability traits over a total of 13 considered that contributed to important ecosystem functions or expected socio-economic benefits such as wood and food production, conservation of genetic resources (wild crop relatives) and ornamentals. This highlights the key role of AWS, and in particular of sporadic trees, for enhancing multifunctionality of thermophilous deciduous forests. [ABSTRACT FROM PUBLISHER]

The pervasive pattern of aggregated tree distributions in natural communities is commonly explained by the joint effect of two clustering processes: environmental filtering and dispersal limitation, yet little consensus remains on the relative importance of the two clustering processes on tree aggregations. Different life stages of examined species were thought to be one possible explanation of this disagreement, because the effect of environmental filtering and dispersal limitation are expected to increase and decrease with tree life stages, respectively. However, few studies have explicitly tested these expectations. In this study, we evaluated these expectations by three different methods (species-habitat association test based on Poisson Clustering model and spatial point pattern analyses based on Heterogeneous Poisson model and the jointly modeling approach) using 36 species in a 20-ha subtropical forest plot. Our results showed that the percentage of species with significant habitat association increased with life stages, and there were fewer species affected by dispersal limitation in later life stages compared with those in earlier stages. Percentage of variance explained by the environmental filtering and dispersal limitation also increases and decreases with life stages. These results provided a promising alternative explanation on the existing mixed results about the relative importance of the two clustering processes. These findings also highlighted the importance of plant life stages for fully understanding species distributions and species coexistence. [ABSTRACT FROM AUTHOR]

Woody plant encroachment in grasslands is a world-wide concern. Assertions that abiotic stress reduction facilitates encroachment are not universally supported. To devise restoration and management strategies, the ability of stress reduction, in the context of co-occurring biotic land-use legacies, needs to be assessed to predict shrub cover., We determined whether legacy-induced reduction in Carex stricta (a potential facilitator of shrub encroachment and attractor of animal dispersers) and an increase in herbaceous invaders (potential competitors) altered the ability of stress reduction to predict woody plant cover in ploughed and never-ploughed plots within 11 Wisconsin (USA) calcareous fens. We hypothesized that drier conditions (low saturation stress) and higher nutrient availability associated with ploughing would be associated with high woody plant cover; that higher cover of herbaceous invaders associated with ploughing would predict low woody plant cover, and C. stricta cover predicts high woody plant cover in saturated, never-ploughed plots. Restricted maximum-likelihood (REML) multiple regression was used to determine the importance of interactions among ploughing, saturation, nutrients and the two biotic legacies in predicting woody richness and cover, as well as cover by dispersal syndromes and individual species., Unexpectedly, encroachment by animal-dispersed species was higher in never-ploughed plots, while wind-dispersed species had no relationship with ploughing. Animal-dispersed species cover decreased with saturation stress in never-ploughed plots, only. Carex cover was associated with increased encroachment by animal-dispersed species, mainly in never-ploughed highly saturated plots. Herbaceous-invasive cover was associated with decreased encroachment. Wind-dispersed species cover declined with increasing saturation stress, with responses varying among species., Synthesis and applications. The results suggest that the impacts of stress reduction on encroachment are not uniform and are modified by biotic legacies. We suggest that impacts of restoring stressful abiotic conditions on encroachment may not be known until the impacts on competitors and facilitators are understood. [ABSTRACT FROM AUTHOR]

Species with fire stimulated reproduction (fsr) are common in Mediterranean climate ecosystems. We investigated how season of, and time since, fire affects seed production in Podocarpus drouynianus F. Muell., a dioecious resprouting coniferous shrub endemic to the jarrah ( Eucalyptus marginata Sm.) forests of southwestern Australia, and if the now largely managed fire regime in these forests poses a risk to its persistence. We hypothesised that, like other species showing fsr, seed production in P. drouynianus would be limited to the first few years following fire and seed set would be lower after spring burns. Mature plants regenerated rapidly from buried stem tissue (lignotuber) after fire, producing abundant sporophylls in autumn 12-18 months later. Stands burnt in autumn showed peak seed production 1 year later, while for those burned in spring, peak seed production was delayed until the second autumn after fire. Limited seed production occurred for up to 3 years following fire, but no seed production was observed in longer unburnt (>10 years since fire) stands. While we did not observe a significant impact of fire season on seed production, seed weight and viability were lower for spring-burnt plants. Population-level effects associated with plant density may also have negative impacts on P. drouynianus demography, with females within a small population burnt in autumn producing very few seeds 12 months following fire. Interactions between climate change, fire regimes and fire management practices need to be considered in order to best safeguard the long-term persistence of this conifer species. [ABSTRACT FROM AUTHOR]

Evaluating the interactions of woody plants has been a major research topic of ecological investigations in arid ecosystems. Plant-plant interactions can shift from positive (facilitation) to negative (competition) depending on levels of environmental stress and determine the spatial pattern of plants. The spatial distribution analysis of plants via different summary statistics can reveal the interactions of plants and how they influence one another. An aggregated distribution indicates facilitative interactions among plants, while dispersion of species reflects their competition for scarce resources. This study was aimed to explore the intraspecific interactions of eshnan (Seidlitzia rosmarinus) shrubs in arid lands, central Iran, using different summary statistics (i.e., pair correlation function g(r), O-ring function O(r), nearest neighbour distribution function D(r), spherical contact distribution function Hs(r)). The observed pattern of shrubs showed significant spatial heterogeneity as compared to inhomogeneous Poisson process (α=0.05). The results of g(r) and O(r) revealed the significant aggregation of eshnan shrubs up to scale of 3 m (α=0.05). The results of D(r) and Hs(r) also showed that maximum distance to nearest shrub was 6 m and the distribution of the sizes of gaps was significantly different from random distribution up to this spatial scale. In general, it was concluded that there were positive interactions between eshnan shrubs at small scales and they were aggregated due to their intraspecific facilitation effects in the study area. [ABSTRACT FROM AUTHOR]

We sampled shrub canopy volume (height times area) and environmental factors (soil wetness, soil depth of thaw, soil pH, mean July air temperature, and typical date of spring snow loss) on 471 plots across five National Park Service units in northern Alaska. Our goal was to determine the environments where tall shrubs thrive and use this information to predict the location of future shrub expansion. The study area covers over 80,000 km2 and has mostly tundra vegetation. Large canopy volumes were uncommon, with volumes over 0.5 m3/m2 present on just 8% of plots. Shrub canopy volumes were highest where mean July temperatures were above 10.5°C and on weakly acid to neutral soils (pH of 6 to 7) with deep summer thaw (>80 cm) and good drainage. On many sites, flooding helped maintain favorable soil conditions for shrub growth. Canopy volumes were highest where the typical snow loss date was near 20 May; these represent sites that are neither strongly wind-scoured in the winter nor late to melt from deep snowdrifts. Individual species varied widely in the canopy volumes they attained and their response to the environmental factors. Betula sp. shrubs were the most common and quite tolerant of soil acidity, cold July temperatures, and shallow thaw depths, but they did not form high-volume canopies under these conditions. Alnus viridis formed the largest canopies and was tolerant of soil acidity down to about pH 5, but required more summer warmth (over 12°C) than the other species. The Salix species varied widely from S. pulchra, tolerant of wet and moderately acid soils, to S. alaxensis, requiring well-drained soils with near neutral pH. Nearly half of the land area in ARCN has mean July temperatures of 10.5 to 12.5°C, where 2°C of warming would bring temperatures into the range needed for all of the potential tall shrub species to form large canopies. However, limitations in the other environmental factors would probably prevent the formation of large shrub canopies on at least half of the land area with newly favorable temperatures after 2°C of warming. [ABSTRACT FROM AUTHOR]

Copyright of Western North American Naturalist is the property of Monte L. Bean Life Science Museum and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The expansion (or encroachment) of shrubs in forests and woodlands is generally considered a serious threat to biodiversity. The effects of shrub expansion on forest fauna, however, are poorly understood and likely to depend on the availability of key resources in shrub-encroached forest. Coranderrk Bushland, like many conservation reserves in south-eastern Australia, is considered threatened by the spread of an indigenous shrub. We investigated the associations between cover of Yarra burgan ( K unzea leptospermoides ( Myrtaceae)), vegetation structure and the occurrence of terrestrial native mammals within the reserve, basing our predictions on prior knowledge of burgan growth habits and fauna habitat preferences. We quantified burgan cover and other potentially important habitat attributes using structure surveys, and used motion-sensing cameras to detect terrestrial mammals. Dense burgan cover was associated with less grass, a sparser understorey, and more cryptogams, dead trees and coarse woody debris. However, there was no evidence that these changes negatively affected native mammals: burgan cover had little influence on the occurrence of any species except swamp wallabies ( W allabia bicolor), which occurred in all areas of the reserve but shifted from sites with high burgan cover during the day to sites with low cover at night. Our findings contrast with those from grassland shrub-expansion studies, where fauna generally show strong responses to shrub cover. The effects of shrub expansion on forest fauna may be mitigated by the greater pre-existing structural diversity in forests or the longer time required for structural changes to be fully realized. The large quantities of dead wood in areas with high shrub cover may also provide compensatory resources for small mammals, while the proximity to un-encroached areas may enable large herbivores to move between dense shelter and forage. Shrub-encroached forests clearly provide resources for some native fauna, and management strategies need to consider the potential impacts of shrub removal on these taxa. [ABSTRACT FROM AUTHOR]

Question Shrub invasions often alter ground layer vegetation but the permanence of these changes is sometimes unclear. We asked: (i) do affected communities recover to their former state when invading species decline; (ii) do plant species density and composition change through the successional sequence of shrub invasion, dominance and decline; and, if yes, (iii) is change dependent on the scale of observation? Location Yanakie Isthmus, Wilsons Promontory National Park, southeastern Victoria, Australia. Methods We use a nested quadrat approach along a chronosequence of invasion states (uninvaded, invaded, senescent) to document composition and diversity of coastal grassy woodland in response to invasion by the range-expanding native shrub Leptospermum laevigatum (Myrtaceae) across multiple spatial scales. Non-metric multidimensional scaling and species-area curves were used to assess changes in vegetation and the ability of invaded communities to return to 'uninvaded' states after the senescence of Leptospermum. Results Shrub invasion did not lead to a decline in total species density. However, there was a significant shift in species composition, suggesting species replacement. Canopy gaps created by Leptospermum senescence had significantly higher species density at a large scale of observation (256 m2), but not at any of the smaller scales. Species composition within Leptospermum gaps was initially highly variable and significantly dissimilar to that prior to gap creation. With increasing time-since-gap creation, floristic composition became less varied and more similar to the uninvaded state, but the oldest gaps were still compositionally different to the uninvaded state. These results were coupled with decreases in light, soil nitrate and soil moisture following invasion, and an increase in those variables following the creation of tree-fall gaps. Conclusions Community composition was positively influenced by the creation of gaps within an otherwise shrub-dominated ecosystem. Gaps represent the removal of potential inhibitory influences created by the dominant species and permit the return of the system to that more similar the uninvaded state. Gaps also increased heterogeneity in the landscape that promoted species diversity in an otherwise uniform landscape. These patterns were scale-invariant. [ABSTRACT FROM AUTHOR]

Stable isotope studies on stable isotope ratios of hydrogen and oxygen in water within plants provide new information on water sources and water use patterns under natural conditions. In this study, the sources of water uptake for two typical xerophytic shrubs, Caragana korshinskii and Artemisia ordosica, were determined at four different-aged revegetated sites (1956, 1964, 1981, and 1987) in the Tengger Desert, a revegetated desert area in China. Samples from precipitation, soil water at different soil layers, and xylem water from each species were collected in 2013. The proportion of plant water sources derived from different potential sources was determined using oxygen (δ18O) and hydrogen (δD) stable isotope analysis combined with a multiple-source linear mixing model. Results showed that the local meteoric water line (LMWL) at Shapotou was as follows: δD = 7.39δ18O + 3.91 (R2 = 0.93; n = 26). The vertical distribution of soil water content in older vegetation areas (1956a and 1964a) was much lower than that in relatively younger vegetation areas (1981a and 1987a). Mean soil water δD and δ18O values varied with depth, and the variation decreased as the age of the revegetated site increased. In general, C. korshinskii and A. ordosica mainly tapped water from the upper soil layer (10-100 cm) during the wet seasons. With increasing sand stabilization age, the proportion of water sources from shallow soil water decreased, whereas deep soil moisture utilization increased. During the dry season, C. korshinskii and A. ordosica showed evident hierarchical utilization of soil water in different soil layers. Small rainfall events did not significantly affect the water source of C. korshinskii and A. ordosica. However, large rainfall events not only complemented the deep soil moisture, but also recharged the shallow soil water after a few days, and the proportion of soil water source from deep soil layer increased from 2% ± 0.7% to 10% ± 1.4% for both plants. [ABSTRACT FROM AUTHOR]

The studies included cultural landscapes of simple (agricultural land) and complex (forest) structure in Wielkopolska., The goal of the studies was to define biocoenotic function of marginal habitats such as - shrubs, field border, road borders, and forest edges - structural elements of agricultural landscape making suitable habitats for parasitoid hymenoptera of subfamily Pimplinae (Hymenoptera, Ichneumonidae), The authors wanted to establish: which of marginal habitats are most attractive for Pimplinae;, which of these habitats are similar to forest habitats, due to the qualitative and quantitative structure of parasitoid hymenoptera communities living there; and, whether linear marginal habitats (like road sides) can fulfil the function of ecological corridors for parasitoid hymenoptera, between agricultural and forest habitats., , The species diversity of Pimplinae in all the habitats of agricultural landscape and forest environment (national park) was similar., On the forest edges (high heterogeneity landscape), the communities of Pimplinae were most numerous. In the low heterogeneity landscape, the greatest species diversity occurred in shrubs. The majority of Pimplinae populations living in agricultural landscape and forest showed great similarity in their qualitative structure and less similarity in their quantitative structure., The conclusion can be made that marginal habitats of agricultural landscape make attractive environment for parasitoids of Pimplinae and that vegetation alongside roads can make function as ecological corridors. [ABSTRACT FROM AUTHOR]

Water is a major limiting factor in desert ecosystems. In order to learn how plants cope with changes in water resources over time and space, it is important to understand plant-water relations in desert region. Using the oxygen isotopic tracing method, our study clarified the seasonal changes in the water use strategies of three co-occurring desert shrubs. During the 2012 growing season, δ18O values were measured for xylem sap, the soil water in different soil layers between 0 and 300 cm depth and groundwater. Based on the similarities in δ18O values for the soil water in each layer, three potential water sources were identified: shallow soil water, middle soil water and deep soil water. Then we calculated the percentage utilization of potential water sources by each species in each season using the linear mixing model. The results showed that the δ18O values of the three species showed a clear seasonal pattern. Reaumuria songarica used shallow soil water when shallow layer was relatively wet in spring, but mostly took up middle soil water in summer and autumn. Nitraria tangutorum mainly utilized shallow and middle soil water in spring, but mostly absorbed deep soil water in summer and autumn. Tamarix ramosissima utilized the three water sources evenly in spring and primarily relied on deep soil water in summer and autumn. R. songarica and N. tangutorum responded quickly to large rainfall pulses during droughts. Differential root systems of the three species resulted in different seasonal water use strategies when the three competed for water. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Indirect effects of trophic interactions on biodiversity can be large and common, even in complex communities. Previous experiments with dominant understory Piper shrubs in a Costa Rican rain forest revealed that increases in herbivore densities on these shrubs caused widespread seedling mortality as a result of herbivores moving from Piper to seedlings of many different plant genera. We tested components of the Janzen-Connell hypothesis by conducting focused studies on the effects of specialist and generalist Piper herbivores on local seedling diversity. Whereas specialist herbivores are predicted to increase mortality to neighboring seedlings that are closely related to the source plant, true generalists moving from source plants may cause density-dependent mortality of many species, and possibly increase richness if new species replace abundant species that have been thinned by herbivores. Therefore, we hypothesized that seedling richness would be greater in understory control plots created in patches of Piper that had normal densities of generalist herbivores compared to plots from which we removed generalist herbivores manually from all Piper shrubs. After 15 months, generalist-herbivore-removal plots had >40% fewer seedlings, >40% fewer species, and 40% greater seedling evenness, on average, than control plots with generalist herbivores intact. Using a complementary approach in unmanipulated plots in four forests, we used path analysis to test for a positive association between seedling diversity and herbivore damage on Piper species. In unmanipulated plots, for both generalist and specialist herbivores, our data were significant fits to the causal model that Piper herbivores decrease evenness and increase plant species richness, corroborating the experimental results. Because herbivores changed how individuals were apportioned among the species and families present (lower evenness), one interpretation of these associations between herbivores on Piper shrubs and local seedling richness is that high seedling mortality in dominant families allowed the colonization or survival of less common species. If interspecific or apparent competition allowed for a relative increase in species richness, then the Janzen-Connell hypothesis may extend its predictions to generalist seedling predators. We speculate that apparent competition may explain some of the deviations from neutral model predictions, especially at small scales. Key words: apparent competition; biodiversity; herbivory; Janzen-Connell hypothesis; seedling mortality; tropical rain forest.

In ecological communities, the outcome of plant plant--interactions represents the net effect of positive and negative interactions occurring above and below ground. Untangling these complex relationships can provide a better understanding of mechanisms that underlie plant--plant interactions and enhance our ability to predict population, community, and ecosystem effects of biotic interactions. In forested ecosystems, tree seedlings interact with established vegetation, but the mechanisms and outcomes of these interactions are not well understood. To explore such mechanisms, we manipulated above- and belowground interactions among tree seedlings, shrubs, and trees and monitored seedling survival and growth of six species (Pinus banksiana, Betula papyrifera, P. resinosa, Quercus rubra, P. strobus, and Acer rubrum) in mature pine-dominated forest in northern Minnesota, USA. The forest had a moderately open canopy and sandy soils. Understory manipulations were implemented in the forest interior and in large gaps and included removal of shrubs(no interactions), tieback of shrubs (belowground), removal of shrubs with addition of shade (aboveground), and unmanipulated shrubs (both below-and aboveground). We found that shrubs either suppressed or facilitated seedling survival and growth depending on the seedling species, source of interaction (e.g., above-or belowground), and ecological context (e.g., gap or forest interior). In general, shrubs strongly influenced survival and growth in gaps, with more modest effects in the forest interior. In gaps, the presence of shrub roots markedly decreased seedling growth and survival, supporting the idea that belowground competition may be more important in dry, nutrient-poor sites. Shrub shade effects were neutral for three species and facilitative for the other three. Facilitation was more likely for shade-tolerant species. In the forest interior, shrub shade negatively affected seedling survival for the most shade-intolerant species. For several species the net effect of shrubs masked the existence of both positive and negative interactions above and below ground. Our results highlight the complexity of plant-plant interactions, demonstrate that outcomes of these interactions vary with the nature of resource limitation and the ecophysiology of the species involved, and suggest that ecological theory that rests on particular notions of plant-plant interactions (e.g., competition) should consider simultaneous positive and negative interactions occurring above and below ground. Key words: competition; Corylus cornuta; facilitation; North American pine forest; plant species interactions; positive and negative effects; shade tolerance.

There is increasing recognition that overall interactions among plant species are often the net result of both positive and negative effects. However, the positive influence of other plants has rarely been examined using detailed demographic methods, which are useful for partitioning net effects at the population level into positive and/or negative effects on individual vital rates. This study examines the influence of microhabitats created by the native shrubs Artemisia tridentata and Purshia tridentata on the demography of the invasive annual grass Bromus tectorum in the Great Basin Desert, California, USA. Shrub understory environments differed significantly from intershrub space and were characterized by higher soil fertility and less extreme microclimates. There existed a strong spatial association between B. tectorum and the shrubs across four years, with more than double the density of B. tectorum in shrub microhabitats compared to intershrub space. Periodic matrix models were used to calculate population growth ([lambda]) and reproductive potential (RP, expected lifetime fecundity of seedlings) of B. tectorum in different microhabitats over two years. Modeled population growth was significantly increased in shrub microhabitats in the first of two years. This was primarily due to increased seedling establishment in Artemisia microhabitats, rather than effects during the growing season. In the following year, B. tectorum individuals in shrub microhabitats had a significantly greater reproductive potential than those in intershrub microhabitats, indicating shrub facilitation during the growing season. Loop analysis revealed an interacting effect of year and microhabitat on B. tectorum life history pathway elasticity values, demonstrating a fundamental influence of spatiotemporal factors on which life history pathways are important and/or possible. Life table response experiment (LTRE) analysis showed that increased survival and growth rates positively contributed to population growth in both years under Purshia, but only in the second year under Artemisia. This research provides evidence that the positive effects of native shrubs on B. tectorum can be strong enough to produce net positive effects at the population level, although positive effects were variable. In this study, a rigorous demographic approach was particularly useful in partitioning overall interactions into positive and negative components. Key words: Artemisia tridentata; Bromus tectorum; California, USA; facilitation; Great Basin Desert; invasive species; life table response experiment; loop analysis; LTRE; periodic matrix models; positive interactions; Purshia tridentata.

Mediterranean-type climate regions are highly biodiverse and predicted to be particularly sensitive to climate change. Shrubs of the mediterranean-type climate region of South Africa are highly threatened, and their response to water stress has been comparatively little studied. Resistance to water stress induced xylem cavitation ([P.sub.50]) and xylem specific hydraulic conductivity ([K.sub.s) were measured in 15 shrub species from fynbos and succulent karoo communities of South Africa. Species displayed a fivefold variation in cavitation resistance ([P.sub.50] of -1.9 to -10.3 MPa) with succulent karoo species displaying greater interspecific variability in [P.sub.50] than fynbos species. Principal components analysis (including [P.sub.50], minimum seasonal water potential, [K.sub.s], and xylem density) showed the response to water stress in fynbos species to be similar to chaparral species from the mediterranean-type climate region of California. The data suggest convergence of community and species-specific water stress 'strategies' between these mediterranean-type climate regions with respect to their xylem traits. On the basis of the current study and reported plant death and dieback in these regions, woody species within the fynbos may be more susceptible to climate warming and drying than those within the succulent karoo that appear to be utilizing more diverse xylem strategies in response to water stress. Key words: cavitation resistance; chaparral; dioecious; fynbos; mediterranean-type climate; Mojave Desert; succulent karoo; water relations; xylem density. doi: 10.3732/ajb.0800424

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Riparian ecosystems are among the most degraded systems in the landscape, and there has been substantial investment in their restoration. Consequently, monitoring restoration interventions offers opportunities to further develop the science of riparian restoration, particularly how to move from small-scale implementation to a broader landscape scale. Here, we report on a broad range of riparian revegetation projects in two regions of south-western Victoria, the Corangamite and Glenelg-Hopkins Catchment Management Areas. The objectives of restoration interventions in these regions have been stated quite broadly, for example, to reinstate terrestrial habitat and biodiversity, control erosion and improve water quality. This study reports on tree and shrub composition, structure and recruitment after restoration works compared with remnant vegetation found regionally. Within each catchment, a total of 57 sites from six subcatchments were identified, representing three age-classes: <4, 4-8 and >8-12 years after treatment, as well as untreated (control) sites. Treatments comprised fencing to exclude stock, spraying or slashing to reduce weed cover, followed by planting with tube stock. Across the six subcatchments, 12 reference (remnant) sites were used to provide a benchmark for species richness, structural and recruitment characteristics and to aid interpretation of the effects of the restoration intervention. Vegetation structure was well developed in the treated sites by 4-8 years after treatment. However, structural complexity was higher at remnant sites than at treated or untreated sites due to a higher richness of small shrubs. Tree and shrub recruitment occurred in all remnant sites and at 64% of sites treated >4 years ago. Most seedling recruitment at treatment sites was by Acacia spp. This assessment provides data on species richness, structure and recruitment characteristics following restoration interventions. Data from this study will contribute to longitudinal studies of vegetation processes in riparian landscapes of south-western Victoria. [ABSTRACT FROM AUTHOR]