Soil‐nutrient availability under a global‐change scenario in a Mediterranean mountain ecosystem

Changes in rainfall availability will alter soil‐nutrient availability under a climate‐change scenario. However, studies have usually analyzed the effect of either drier or wetter soil conditions, despite the fact that both possibilities will coexist in many climatic regions of the world. Furthermore, its effect may vary across the different habitats of the ecosystem. We experimentally investigated the effect of three contrasting climatic scenarios on different carbon (C), nitrogen (N), and phosphorus (P) fractions in soil and microbial compartments among three characteristic habitats in a Mediterranean‐type ecosystem: forest, shrubland, and open areas. The climatic scenarios were dry summers, according to the 30% summer rainfall reduction projected in the Mediterranean; wet summer, simulating summer storms to reach the maximum historical records in the study area; and current climatic conditions (control). Sampling was replicated during two seasons (spring and summer) and 2 years. The climatic scenario did not affect the nutrient content in the litter layer. However, soil and microbial nutrients varied among seasons, habitats, and climatic scenarios. Soil‐nutrient fractions increased with lower soil‐moisture conditions (dry scenario and summer), whereas microbial nutrients increased under the wet summer scenario and spring. This pattern was consistent both studied years, although it was modulated by habitat, differences being lower with denser plant cover. Holm oak seedlings, used as live control of the experiment, tended to increase their N and P content (although not significantly) with water availability. Thus, the results support the idea that higher rainfall boosts microbial and plant‐nutrient uptake, and hence nutrient cycling. By contrast, a rainfall reduction leads to an accumulation of nutrients in the soil, increasing the risk of nutrient loss by leaching or erosion. These results show that the projected climate change will have significant effects on nutrient cycles, and therefore will have important implications on the ecosystem functioning.     

Sporadic rainy events are more critical than increasing of drought intensity for woody species recruitment in a Mediterranean community

The understanding of the impact of extreme climatic events under a global climate change scenario is crucial for the accurate forecast of future plant community dynamics. We have experimentally assessed the effect of drier and wetter summer conditions on the recruitment probabilities and the growth of seedlings from eight woody species representative of the most important functional groups in the community, pioneer shrubs, mid-successional shrubs and trees, across the main habitats in the study area (open habitat, shrubland, and forest). Our hypothesis proposes that wet summer conditions would represent a good opportunity for tree species regeneration, enhancing both forest maintenance and expansion. A drier summer scenario, on the other hand, would limit forest regeneration, and probably hinder the colonization of nearby habitats. We found a habitat effect on the emergence, survival, and final biomass, whereas different climate scenarios affected seedling survival and biomass. A wet summer boosted growth and survival, whereas greater drought reduced survival only in some cases. These results were modulated by the habitat type. Overall, shrub species presented higher survival and growth and were less affected by more severe drought, whereas some tree species proved to be extremely dependent on wet summer conditions. We conclude that the reduction in frequency of wet summers predicted for the coming decades in Mediterranean areas will have greater consequences for species recruitment than will increased drought. The different response of the species from the various functional groups has the potential to alter the composition and dominance of future plant communities.     

Oak seedling survival and growth along resource gradients in Mediterranean forests: implications for regeneration in current and future environmental scenarios

Understanding seedling performance across resource gradients is crucial for defining the regeneration niche of plant species under current environmental conditions and for predicting potential changes under a global change scenario. A 2‐year field experiment was conducted to determine how seedling survival and growth of two evergreen and two deciduous Quercus species vary along gradients of light and soil properties in two Mediterranean forests with contrasting soils and climatic conditions. Half the seedlings were subjected to an irrigation treatment during the first year to quantify the effects on performance of an alteration in the summer drought intensity. Linear and non‐linear models were parameterized and compared to identify major resources controlling seedling performance. We found both site‐specific and general patterns of regeneration. Strong site‐specificity was found in the identity of the best predictors of seedling survival: survival decreased linearly with increasing light (i.e. increasing desiccation risk) in the drier site, whereas it decreased logistically with increasing spring soil water content (i.e. increasing waterlogging risk) in the wetter site. We found strong empirical support for multiple resource limitation at the drier site, the response to light being modulated by the availability of soil resources (water and P). Evidence for regeneration niche partitioning among Quercus species was only found at the wetter site. However, at both sites Quercus species shared the same response to summer drought alleviation through water addition: increased first‐year survival but not final survival (i.e. after two years). This suggests that extremely dry summers (i.e. the second summer in the experiment) can cancel out the positive effects of previous wetter summers. Therefore, an increase in the intensity and frequency of summer drought with climate change might cause a double negative impact on Quercus regeneration, due to a general reduction in survival probability and the annulment of the positive effects of (infrequent) ‘wet’ years. Overall, results presented in this study are a major step towards the development of a mechanistic model of Mediterranean forest dynamics that incorporates the idiosyncrasies and generalities of tree regeneration in these systems, and that allow simulation and prediction of the ecological consequences of resource level alterations due to global change.     

Microclimate Impacts Survival and Prevalence of Phytophthora ramorum in Umbellularia californica,a Key Reservoir Host of Sudden Oak Death in Northern California Forests

Phytophthora ramorum, an invasive pathogen and the causal agent of Sudden Oak Death, has become established in mixed-evergreen and redwood forests in coastal northern California. While oak and tanoak mortality is the most visible indication of P. ramorum’s presence, epidemics are largely driven by the presence of bay laurel (Umbellularia californica), a reservoir host that supports both prolific sporulation in the winter wet season and survival during the summer dry season. In order to better understand how over-summer survival of the pathogen contributes to variability in the severity of annual epidemics, we monitored the viability of P. ramorum leaf infections over three years along with coincident microclimate. The proportion of symptomatic bay laurel leaves that contained viable infections decreased during the first summer dry season and remained low for the following two years, likely due to the absence of conducive wet season weather during the study period. Over-summer survival of P. ramorum was positively correlated with high percent canopy cover, less negative bay leaf water potential and few days exceeding 30°C but was not significantly different between mixed-evergreen and redwood forest ecosystems. Decreased summer survival of P. ramorum in exposed locations and during unusually hot summers likely contributes to the observed spatiotemporal heterogeneity of P. ramorum epidemics.     

Contrasting climate influences on Nothofagus pumilio establishment along elevational gradients

Predicted warmer temperatures and more frequent extreme climatic events in the southern Andes may affect the dynamics of the Patagonian forests. These environmental changes may differentially alter the probability of Nothofagus pumilio establishment across its altitudinal range of distribution. We monitored fruit fall, seedling emergence and survival at altitudinal distribution range of N. pumilio forests in Santa Cruz (49°22′ S—72°56′ W), Argentina. Fruit fall, seedling emergence and survival were tested in relation to drought, based on the SPEI (Standardized Precipitation Evapotranspiration Index), interacting with elevation. Fruit fall was consistently higher at low elevation and the abundance of fruits was not affected by drought intensity. Density of new-born seedlings was?~?9 to 24 times lower at low- than at high-elevation plots in our first observations (2014 and 2016), characterized by warm-dry climatic conditions in spring-early summers. In contrast, seedling abundance was?~?1.5 times larger at low elevations during relatively cold-wet growing seasons. Survival probability was explained by the interaction between SPEI and elevation. At low elevation and in dry periods, survival probability was lower (CI 54–72%) than in wet periods (CI 68–84%) but at high elevation similar survival was registered even with positive or negative SPEI values. Our results show interacting effects of elevation and drought on tree establishment at the elevation limits, with positive and negative drought effects at high and low elevations, respectively. Predicted increase of extreme drought events during the XXI century could be detrimental for N. pumilio establishment at dry, low-elevation forests.

     

Temporal dynamics of ectomycorrhizal fungal communities in Shorea siamensis forest fragments

Investigating the dynamics of ectomycorrhizal fungal (EMF) communities in seasonally dry tropical forests is essential for sustainable management and for understanding the resilience of this forest type in future climate change scenarios. EMF communities in secondary forest fragments with Shorea siamensis as a single host tree species in central Thailand were sampled seasonally for 2.5 y. Ten EMF taxa were identified from ectomycorrhizal morphotypes, with/tomentella-thelephora and/russula-lactarius as the dominant taxa. Seasonal differences in EMF diversity were not detected; the dominant morphotypes were present in both seasons and their abundance varied. Most EMF taxa exhibited wide environmental ranges and only a few taxa were correlated with soil moisture. Seasonal dynamics of ectomycorrhizal colonization was likely influenced by climatic factors and the phenology of host species. Together, these results suggested that climatic variation may have a long-term and subtle influence on the composition of ectomycorrhizal communities.     

Habitat variability in the effects of predation and microclimate on mycophagous fly communities

Ant predation and soil moisture have direct and interactive effects on the abundance and community structure of mycophagous flies Here, we replicated an experiment across three climatically different habitat types to describe how these small-scale processes (microclimate and predation) are affected by macroclimatic variability at a larger spatial scale (among habitats) Each week for eight weeks during the summer of 1993, 18 Agaricus bisporus mushrooms were placed on dry, moist, or wet potting soil, within predator access or predator exclusion treatments cups, at six sites in the piedmont of South Carolina, USA Two sites were moist hemlock ravines and four sites were dry ridgetops Mushrooms and soil were collected after one week and fly metamorphs were counted and sorted by species We described the effects of ant predation, soil moisture, site and week on the frequency of host use, metamorph abundance, and Simpson's diversity All three measures were affected by macroclimatic differences among sites and across weeks At wet sites and during rainy weeks, more mushrooms were used, more metamorphs emerged, and the communities were more diverse than at dry sites or during dry periods The small-scale effect of soil moisture was strongly affected by large-scale macroclimatic conditions In dry ridgetop sites and in dry weeks, abundance and diversity increased with increasing soil moisture In moist sites or dunng rainy weeks, however, soil moisture was unimportant and had no effect on abundance or community structure Predation was unaffected by large-scale differences in climate, but was affected by small-scale differences in soil moisture, becoming more intense as soil moisture increased This research demonstrates that the effect of climate on predation is a scale-dependent phenomenon, and that microclimatic effects are mediated by climatic conditions at larger spatial scales We relate these findings to hierarchical theory and hypotheses concerning the relative effects of tolerances, competition, and predation under different levels of environmental stress     

Does distance from the sea affect a soil microarthropod community?

Coastal sand dunes are dynamic ecosystems characterized by strong abiotic gradients from the seashore inland. Due to significant differences in the abiotic parameters in such an environment, there is great interest in biotic adaptation in these habitats. The aim of the present study, which was conducted in the northern Sharon sand-dune area of Israel, was to illustrate the spatial changes of a soil microarthropod community along a gradient from the seashore inland. Soil samples were collected from the 0–10 cm depth at five locations at different distances, from the seashore inland. Samples were taken from the bare open spaces during the wet winter and dry summer seasons. The soil microarthropod community exhibited dependence both on seasonality and sampling location across the gradient. The community was more abundant during the wet winter seasons, with an increasing trend from the shore inland, while during the dry summers, such a trend was not observed and community density was lower. The dominant groups within soil Acari were Prostigmata and Endeostigmata, groups known to have many representatives with adaptation to xeric or psammic environments. In addition, mite diversity tended to be higher at the more distant locations from the seashore, and lower at the closer locations, a trend that appeared only during the wet winters. This study demonstrated the heterogeneity of a soil microarthropod community in a coastal dune field in a Mediterranean ecosystem, indicating that the gradient abiotic parameters also affect the abundance and composition of a soil microarthropod community in sand dunes.     

Spring water deficit and soil conditions matter more than seed origin and summer drought for the establishment of temperate conifers

In anticipation of more severe summer droughts, forestry in temperate Europe is searching for drought-resistant ecotypes of native tree species that might maintain ecosystem services in the future. We investigated how spring precipitation and soil conditions interact with summer drought and affect the establishment of conifer seedlings from different climatic origin. Emergence, establishment and subsequent performance of seedlings originating from autochthonous, Central Alpine, continental Eastern European, and Mediterranean Pinus sylvestris and Picea abies populations were studied in the dry Alpine Rhine valley, Switzerland, at three sites with differing soil water holding capacities and in 3 years with contrasting weather conditions. In addition to this natural inter-annual variation, precipitation was manipulated within sites with throughfall reduction roofs. Seedling establishment and growth were principally affected by the spring weather in the year of emergence. In years with average to positive spring water balance, seedlings grown at the site with the highest water holding capacity had 2–5 times more aboveground biomass than seedlings grown at sites with less favourable soils. Effects of seed origin were marginal and only detectable at the drier sites: contrary to our expectations, seedlings from the Central Alpine Rhone valley, where the climatic spring water deficit is large, outperformed those from the Mediterranean. Consequently, plantation of non-native populations from dryer origin will mitigate the effects of increased summer drought at driest sites only, while the inter-annual variability of spring precipitation will continue to enable temperate conifers to regenerate on a wide range of forest soils independent of seed origin.     

Characteristics of soil animal community in the subalpine/alpine forests of western Sichuan during onset of freezing

Seasonal freeze–thaw cycle is a common phenomenon in the subalpine/alpine forest region, and may have a significant influence on the structure and function of soil animal community. To understand the characteristics and dynamics of soil animal community as well as its response to repeated freeze–thaw events in this region during onset of freezing, a field experiment was conducted to investigate the composition, abundance, and diversity of soil fauna in primary fir (Abies faxoniana) forest, fir and birch (Betula albosinensis) mixed forest and secondary fir (A. faxoniana) forest, which were three representative forests in the subalpine and alpine forest region in western Sichuan. Soil samples were collected from November 3 to November 27, 2008, which was defined as onset of freezing based on the simultaneous monitoring of soil temperature. Soil macrofauna were picked up by hand in the fields. Mesofauna were separated and collected from the soil samples by Baermann and Tullgren methods, respectively. By preliminary identification, 40,942 individuals were collected, which belonged to 7 phyla, 15 classes and 25 orders in the three sampling forests. 16,557, 14,669 and 9716 individuals were found in primary forest, mixed forest and secondary forest, respectively. In comparison with the mineral soil layer, the soil organic layer had higher density and groups of soil fauna. Furthermore, following the repeated freeze–thaw events, density and groups of soil fauna experienced a distinct decrease in both soil organic layer and mineral soil layer, and this trend in soil organic layer was more significant in the primary forest, owing to higher intense and more frequent freeze–thaw cycles in soil organic layer of the primary forest. The results revealed that soil animals were sensitive bio-indicators to environmental changes, such as repeated freeze–thaw events and dry–wet cycle. Meanwhile, the results also implied that the dynamics of the structure and function of soil animal community during the onset of freezing was of ecological significance to understand the wintertime ecological process in soils.     

A multispecies approach to manage effects of land cover and weather on upland game birds

Loss and degradation of grasslands in the Great Plains region have resulted in major declines in abundance of grassland bird species. To ensure future viability of grassland bird populations, it is crucial to evaluate specific effects of environmental factors among species to determine drivers of population decline and develop effective conservation strategies. We used threshold models to quantify the effects of land cover and weather changes in "lesser prairie‐chicken" and "greater prairie‐chicken" (Tympanuchus pallidicinctus and T. cupido, respectively), northern bobwhites (Colinus virginianus), and ring‐necked pheasants (Phasianus colchicus). We demonstrated a novel approach for estimating landscape conditions needed to optimize abundance across multiple species at a variety of spatial scales. Abundance of all four species was highest following wet summers and dry winters. Prairie chicken and ring‐necked pheasant abundance was highest following cool winters, while northern bobwhite abundance was highest following warm winters. Greater prairie chicken and northern bobwhite abundance was also highest following cooler summers. Optimal abundance of each species occurred in landscapes that represented a grassland and cropland mosaic, though prairie chicken abundance was optimized in landscapes with more grassland and less edge habitat than northern bobwhites and ring‐necked pheasants. Because these effects differed among species, managing for an optimal landscape for multiple species may not be the optimal scenario for any one species.     

Patterns of Richness and Abundance in a Tropical African Leaf‐litter Herpetofauna1

I compared species richness and habitat correlates of leaf‐litter herpetofaunal abundance in undisturbed and selectively logged forests, and an abandoned pine plantation in Kibale National Park, Uganda. I sampled 50 randomly located 25 m² litter plots in each area during the wet and dry seasons in 1997. Ten anuran, five lizard, and three snake species were captured in plots over the study. Assemblage composition was most similar at logged and unlogged sites. The logged forest herpetofauna had higher species richness and abundance than the unlogged forest, but diversity was greater in the unlogged forest due to greater evenness. In contrast, the pine plantation site had the highest richness, abundance, and evenness of the three study sites, but species composition was distinct from the other areas. Herpetofaunal densities were significantly lower in all three areas during the dry season than in the wet season. During the dry season, soil moisture, litter mass, topography, shrub cover, and number of fallen logs were significant positive predictors of herpetofaunal presence in litter plots, but only soil moisture was significant in the wet season. The interaction of moisture and topography appears to be important in determining seasonal patterns of litter herpetofaunal distribution. Comparison of litter herpetofaunal studies across the tropics have shown that mid‐elevation faunas generally support fewer species than lowland faunas. Compared with other tropical mid‐elevation litter faunas, Kibale supports an intermediate number of species, but at lower densities than observed at any other mid‐elevation site reported in the literature.     

The phenology of Onitis alexis (Coleoptera: Scarabaeidae) in the Araluen Valley: Survival in a marginal environment

The introduced African dung beetle, Onitis alexis Klug, has become established in the warmer regions of Australia. The south-eastern limit of its current distribution is Moruya, NSW, and the Araluen Valley 50 km inland. At Araluen newly emerged beetles are present in dung in late spring, summer and autumn. Egg-laying starts 1-2 weeks after emergence and continues throughout the summer and autumn, as indicated by the presence of parous females in the population and of broods under experimental pads. Eggs laid in December/January produce adults in late summer and autumn, those laid from February to April produce adults in the following spring and summer. In the laboratory, mortality of larvae is high in cold (0–16°C), wet conditions and their development is delayed in warm (25°C and 27°C), dry conditions. This delay was confirmed in the field during the summer drought of 1982-83 when predicted times of emergence (based on day-degree summation in the soil) always preceded the observed emergence time of the local population, as well as preceding the emergence of beetles developing from eggs laid at known times. Follicle resorption in adult females was related directly to increasing age and to rainfall. Dung collected from hayed-off pasture did not affect fecundity, but caused larval mortality. Adults survived the winters at Araluen in some years, and immatures survived best during dry winters, being facilitated in this by a cold-induced larval diapause. Onitis alexis larvae can survive wet or dry summers, and cold dry winters (down to about 0°C) but not wet winters. This seems to be the major factor limiting the southern distribution of the species.     

Rainfall seasonality and drought performance shape the distribution of tropical tree species in Ghana

Tree species distribution in lowland tropical forests is strongly associated with rainfall amount and distribution. Not only plant water availability, but also irradiance, soil fertility, and pest pressure covary along rainfall gradients. To assess the role of water availability in shaping species distribution, we carried out a reciprocal transplanting experiment in gaps in a dry and a wet forest site in Ghana, using 2,670 seedlings of 23 tree species belonging to three contrasting rainfall distributions groups (dry species, ubiquitous species, and wet species). We evaluated seasonal patterns in climatic conditions, seedling physiology and performance (survival and growth) over a 2‐year period and related seedling performance to species distribution along Ghana's rainfall gradient. The dry forest site had, compared to the wet forest, higher irradiance, and soil nutrient availability and experienced stronger atmospheric drought (2.0 vs. 0.6 kPa vapor pressure deficit) and reduced soil water potential (?5.0 vs. ?0.6 MPa soil water potential) during the dry season. In both forests, dry species showed significantly higher stomatal conductance and lower leaf water potential, than wet species, and in the dry forest, dry species also realized higher drought survival and growth rate than wet species. Dry species are therefore more drought tolerant, and unlike the wet forest species, they achieve a home advantage. Species drought performance in the dry forest relative to the wet forest significantly predicted species position on the rainfall gradient in Ghana, indicating that the ability to grow and survive better in dry forests and during dry seasons may allow species to occur in low rainfall areas. Drought is therefore an important environmental filter that influences forest composition and dynamics. Currently, many tropical forests experience increase in frequency and intensity of droughts, and our results suggest that this may lead to reduction in tree productivity and shifts in species distribution.     

欧亚大陆植被生态系统平均中心时空偏移的情景模拟

欧亚大陆复杂多样的植被生态系统在全球气候变化的驱动下,其时空分布格局将发生系列的偏移变化,进而对欧亚大陆"一带一路"沿线国家和地区的生态环境产生重要影响。如何从全球气候变化驱动的角度来实现欧亚大陆植被生态系统时空偏移趋势的模拟分析,已成为"一带一路"沿线国家和地区生态环境研究的热点科学问题之一。在对HLZ生态系统模型进行改进和构建植被生态系统平均中心时空偏移分析模型的基础上,基于欧亚大陆的气候观测数据(1981—2010年)和CMIP5 RCP2.6、RCP4.5和RCP8.5三种情景数据(2011—2100年),实现欧亚大陆植被生态系统平均中心时空偏移趋势的模拟分析。结果表明:欧亚大陆植被生态系统平均中心主要分布在欧亚大陆的中部和南部地区;3种气候情景下,欧亚大陆的亚热带干旱森林、暖温带湿润森林、亚热带有刺疏林、亚热带潮湿森林、冷温带潮湿森林、寒温带湿润森林、冷温带湿润森林、亚热带湿润森林、暖温带干旱森林、亚极地/高山湿润苔原和极地/冰原等植被生态系统的平均中心偏移幅度大于其他植被生态系统类型;欧亚大陆植被生态系统在RCP8.5情景下的植被生态系统平均中心偏移幅度大于其他两种情景;在2011—2100年期间,3种气候变化情景下,欧亚大陆植被生态系统平均中心整体上将呈向北偏移的变化趋势。     

Enhanced summer warming reduces fungal decomposer diversity and litter mass loss more strongly in dry than in wet tundra

Many Arctic regions are currently experiencing substantial summer and winter climate changes. Litter decomposition is a fundamental component of ecosystem carbon and nutrient cycles, with fungi being among the primary decomposers. To assess the impacts of seasonal climatic changes on litter fungal communities and their functioning, Betula glandulosa leaf litter was surface‐incubated in two adjacent low Arctic sites with contrasting soil moisture regimes: dry shrub heath and wet sedge tundra at Disko Island, Greenland. At both sites, we investigated the impacts of factorial combinations of enhanced summer warming (using open‐top chambers; OTCs) and deepened snow (using snow fences) on surface litter mass loss, chemistry and fungal decomposer communities after approximately 1 year. Enhanced summer warming significantly restricted litter mass loss by 32% in the dry and 17% in the wet site. Litter moisture content was significantly reduced by summer warming in the dry, but not in the wet site. Likewise, fungal total abundance and diversity were reduced by OTC warming at the dry site, while comparatively modest warming effects were observed in the wet site. These results suggest that increased evapotranspiration in the OTC plots lowered litter moisture content to the point where fungal decomposition activities became inhibited. In contrast, snow addition enhanced fungal abundance in both sites but did not significantly affect litter mass loss rates. Across sites, control plots only shared 15% of their fungal phylotypes, suggesting strong local controls on fungal decomposer community composition. Nevertheless, fungal community functioning (litter decomposition) was negatively affected by warming in both sites. We conclude that although buried soil organic matter decomposition is widely expected to increase with future summer warming, surface litter decay and nutrient turnover rates in both xeric and relatively moist tundra are likely to be significantly restricted by the evaporative drying associated with warmer air temperatures.     

Response of soil nematode community structure and diversity to long-term land use in the black soil region in China

Soil nematodes are sensitive to environmental changes and are used widely as indicators of soil conditions. The community structure and diversity of soil nematodes were studied in different long-term land use regimes in the black soil area in Northeast China. The land use regimes were maintained for 22?years, and included crop land (CL), grass land (GL) and bare land (BL). Soil samples were taken throughout the growing season, and nematodes were extracted and identified. A total of 39 nematode genera with relative abundance over 0.1?% were identified. Heterodera was the dominant genus in CL; Boleodorus was the dominant genus in GL, and Boleodorus, Eucephalobus and Filenchus were the dominant genera in BL. Land use had a significant effect on abundance of all soil nematode tropic groups and ecological indices. Sampling time had an effect on soil nematode abundance, but only on three of the eight nematode ecological indices MI (maturity index of free-living nematode), CI (channel index) and EI (enrichment index). SR (species richness index) was highest in GL where plant species diversity was also high. The CI was the highest in BL among three land uses, which means the soil food web dominated, with fungal decomposition channels in BL. Soil nematode community structure and diversity was shown to be an effective and informative tool for analyzing ecological aspects of land use in black soil regions. The data are inconclusive as to whether the effect of land use on soil nematode parameters is direct, or indirect via inducing changes in soil physicochemical properties.     

Diversity and altitudinal distribution of Chrysomelidae (Coleoptera) in Peregrina Canyon,Tamaulipas, Mexico

The Chrysomelidae (Coleoptera) is a highly speciose family that has been poorly studied at the regional level in Mexico. In the present study, we estimated species richness and diversity in oak-pine forest, Tamaulipan thorny scrub and in tropical deciduous forests in Peregrina Canyon within the Altas Cumbres Protected Area of the northeastern state of Tamaulipas, Mexico. Sampling of Chrysomelidae consisted of five sweep net samples (200 net sweeps) within each of three sites during four sample periods: early dry season, late dry season, early wet season, and late wet season. Species were identified and total numbers per species were recorded for each sample. A total of 2,226 specimens were collected belonging to six subfamilies, 81 genera and 157 species of Chrysomelidae from the study area. Galerucinae was the most abundant subfamily with 1,828 specimens, representing 82.1% of total abundance in the study area. Lower abundance was recorded in Cassidinae (8.5%), Eumolpinae (3.6%), Cryptocephalinae (2.2%), Chrysomelinae (2.2%), and finally Criocerinae (1.3%). The highest species richness was also presented in the subfamily Galerucinae with 49% of the total obtained species followed by Cassidinae (20%), Cryptocephalinae (9.7%), Eumolpinae (9.7%), Chrysomelinae (6.5%) and Criocerinae (5.2%). The most common species were Centralaphthona fulvipennis Jacoby (412 individuals), Centralaphthona diversa (Baly) (248), Margaridisa sp.1 (219), Acallepitrix sp.1 (134), Longitarsus sp.1 (104), Heterispa vinula (Erichson) (91), Epitrix sp.1 (84) and Chaetocnema sp.1 (72). Twenty-two species were doubletons (1.97% of total abundance) and 52 were singletons (2.33%). The estimated overall density value obtained was 0.0037 individuals/m2. The greatest abundance and density of individuals were recorded at the lowest elevation site. However, alpha diversity increased with increasing altitude. Similarity values were less than 50% among the three sites indicating that each site had distinct species assemblages of Chrysomelidae. The highest abundance was obtained during the late dry season, whereas diversity indices were highest during the early wet season. The present work represents the first report of the altitudinal variation in richness, abundance, and diversity of Chrysomelidae in Mexico. These results highlight the importance of conservation of this heterogeneous habitat and establish baseline data for Chrysomelidae richness and diversity for the region.     

Effect of Sowing Season,Plant Cover,and Climatic Variability on Seedling Emergence and Survival in Burned Austrocedrus chilensis Forests

Fire is the most important disturbance factor in Cypress (Austrocedrus chilensis) forests in Patagonia, Argentina. This ecosystem recovers poorly after fire, and direct sowing could be a potentially useful restoration practice. To evaluate the effect of season of sowing, post‐fire plant cover (PC), and climatic variability on seedling emergence and survival, three direct sowing studies were established in two burned cypress stands: Trevelin (xeric conditions) and El Bolsón (mesic conditions). Two studies were conducted in winter (2000 and 2001) and one in spring (2001). Precipitation was higher than the mean during the 2000–2001 growing season and lower during 2001–2002. At both sites, emergence and survival were much higher for winter‐ than for spring‐sown seedlings. In the xeric stand, emergence and survival of winter‐sown seedlings increased with medium and high PC values, after the humid and dry summers, respectively. However, most spring‐sown seedlings did not emerge, and those that did were short‐lived. Because of the more favorable growing conditions in the mesic stand, PC had no effect on emergence and only favored first year survival of winter‐sown seedlings after the dry summer. Spring‐sown seedlings showed no association with PC in the mesic site, probably because the first summer was exceptionally humid. We speculate that shading plants exert a positive effect on cypress seedling establishment, likely by reducing the stress from high temperatures and low water availability. Sowing of small patches under the protection of understory vegetation could be useful in restoring burned cypress stands.     

Linking increasing drought stress to Scots pine mortality and bark beetle infestations

In the dry Swiss Rhone Valley, Scots pine forests have experienced increased mortality in recent years. It has commonly been assumed that drought events and bark beetles fostered the decline, however, whether bark beetle outbreaks increased in recent years and whether they can be linked to drought stress or increasing temperature has never been studied. In our study, we correlated time series of drought indices from long-term climate stations, 11-year mortality trends from a long-term research plot, and mortality probabilities modeled from tree rings (as an indicator of tree vitality) with documented occurrences of various bark beetle species and a buprestid beetle, using regional Forest Service reports from 1902 to 2003 and advisory cases of the Swiss Forest Protection Service (SFPS) from 1984 to 2005. We compared the historical findings with measured beetle emergence from a 4-year tree felling and breeding chamber experiment. The documented beetle-related pine mortality cases increased dramatically in the 1990s, both in the forest reports and the advisory cases. The incidents of beetle-related pine mortality correlated positively with spring and summer temperature, and with the tree-ring based mortality index, but not with the drought index. The number of advisory cases, on the other hand, correlated slightly with summer drought index and temperature, but very highly with tree-ring-based mortality index. The tree-ring-based mortality index and observed tree mortality increased in years following drought. This was confirmed by the beetle emergences from felled trees. Following dry summers, more than twice as many trees were colonized by beetles than following wet summers. We conclude that increased temperatures in the Swiss Rhone Valley have likely weakened Scots pines and favored phloeophagous beetle population growth. Beetles contributed to the increased pine mortality following summer drought. Among the factors not addressed in this study, changed forest use may have also contributed to increased beetle populations and Scots pine mortality, whereas air pollution seems to be of lesser importance.