No effect of invasive tree species on aboveground biomass increments of oaks and pines in temperate forests

Prunus serotina and Robinia pseudoacacia are the most widespread invasive trees in Central Europe.In addition,according to climate models,decreased growth of many economically and ecologically important native trees will likely be observed in the future.We aimed to assess the impact of these two neophytes,which differ in the biomass range and nitrogen-fixing abilities observed in Central European conditions,on the relative aboveground biomass increments of native oaks Qucrcus robur and Q.petraea and Scots pine Pinus sylvestris.We aimed to increase our understanding of the relationship between facilitation and competition between woody alien species and overstory native trees.We established 72 circular plots(0.05 ha)in two different forest habitat types and stands varying in age in western Poland.We chose plots with different abundances of the studied neophytes to determine how effects scaled along the quantitative invasion gradient.Furthermore,we collected growth cores of the studied native species,and we calculated aboveground biomass increments at the tree and stand levels.Then,we used generalized linear mixed-effects models to assess the impact of invasive species abundances on relative aboveground biomass increments of native tree species.We did not find a biologically or statistically significant impact of invasive R.pseudoacacia or P.serotina on the relative aboveground,biomass increments of native oaks and pines along the quantitative gradient of invader biomass or on the proportion of total stand biomass accounted for by invaders.The neophytes did not act as native tree growth stimulators but also did not compete with them for resources,which would escalate the negative impact of climate change on pines and oaks.The neophytes should not significantly modify the carbon sequestration capacity of the native species.Our work combines elements of the per capita effect of invasion with research on mixed forest management.

Assessing the invasion risk of botanical garden's exotic threatened collections to adjacent mountain forests: A case study of Cibodas Botanical Garden

A primary objective of botanical gardens is to conserve threatened plant species from different regions and countries.However,such ex-situ conservation practices for exotic plant species may pose a significant plant invasion risks.In this study,we predict the naturalization probability of exotic threatened plant species of Cibodas Botanical Garden(CBG) collections based on leaf trait(specific leaf area,SLA) or as a function of invasion risk assessment scoring system(Tropical Weed Risk Assessment Protocol,TWRAP).We found that SLA and TWRAP were positively correlated with naturalization probability.The TWRAP model produced higher predictive probabilities with larger uncertainty compared to SLA model.Parmentiera cereifera and Burretiodendron hsienmu are two species that have highest naturalization probability based on SLA model.Chamaedorea oblongata has the highest naturalization probability based on TWRAP model.From practical and management point of view,we recommend the simultaneous use of SLA-based and TWRAP-based invasive species risk assessment to estimate the naturalization risk of exotic threatened collections of botanical gardens to adjacent mountain forests.Finally,given the important conservation value of threatened exotic collection of botanical garden,we need to be aware with the invasion risks of these species.The threatened condition of a plant species is not only caused by its natural characteristics but also may be caused(in fact mostly confounding with) by external disturbance either natural catastrophic or human related activities.Thus,a threatened species may not necessarily a noninvasive species outside their natural distribution ranges.

Ecological Assessment on the Introduced Sonneratia caseolaris and S. apetala at the Mangrove Forest of Shenzhen Bay, China

yTwo exotic species, Sonneratia caseolaris (L.) Engl. and S. apetala B. Ham., were introduced to Futian Mangrove Forest Nature Reserve, Shenzhen Bay, in 1993 for afforestation. Winter cold caused frigid harm but did not appear to be an obstacle to the introduction. The cold tolerance of the parental and filial generation increased in several years. The two Sonneratia spp. could propagate by seeds and disperse in Shenzhen Bay. While the two species grew faster than indigenous species, at the same time they promoted the growth of indigenous species, but they could not replace indigenous mangrove species. Suitable habitat was more important than the distance from the source in the natural spreading for the two species. The niche of the two species did not overlap with the niche of indigenous species. The two species did not self regenerate, although they could disperse on localized area in Shenzhen Bay. Therefore, it was unlikely that the two species would pose ecological disaster.

Leaf thickness and elevation explain naturalized alien species richness in a tropical mountain forest: A case study from Mount Gede-Pangrango National Park,Indonesia

Exotic plant invasion is one of the major causes of species extinction.In many contexts,mountainous forests are the last refuge for native species.There are several inventory studies conducted in mountainous and tropical forests in Indonesia.However,there are no studies yet on the factors that explain the abundance and richness of surveyed naturalized alien species.This study investigated whether the number of individuals and abundanceweighted species richness(AWR) of naturalized alien plant species in the hiking-trail of Mount GedePangrango National Park(MGPNP) forest area correlated with leaf traits(specific leaf area(SLA) and leaf thickness) and environmental factors(elevation,slope,and normalized difference vegetation index(NDVI)).We showed that leaf thickness and habitat elevation explained the AWR variations of naturalized alien species.We did not detect any important effect of leaf traits and environmental factors on the number of individuals per exotic species per plot.The influence of leaf thickness and habitat elevation indicates the important role of both biotic and abiotic factors on exotic species to develop a high species richness and become an invasive species in the tropical mountain forest ecosystem.

The Research of Ecological Nutritional Organs of Invasive Plants Structural Characteristics

[Objective] The aim of this paper was to discuss the adaptability of ecological nutritional organs of invasive plants.[Method] By dint of high-definition display of plant tissue crystal method and paraffin section method,the vegetative organs root,stem and leaf cross-section of the organizational structure of Asteraceae Ambrosia trifida L.ragweed（Ambrosia trifida L.）in the suburbs of Changchun City in Jilin Province were inspected.[Result] The structural basis for ecological invasive plant Ambrosia trifida L.vegetative organs was mainly through strengthening the roots of water absorption and transporting function,increasing the water storage function of leaf and stem,reducing the water absorption of stem and leaf for plants to promote water absorption and to enhance the assimilation of leaves to achieve a variety of complex environmental conditions in the rapid growth and development in order to achieve an ecological invasion.[Conclusion] The study provided reference for the biological fundamental research of Ambrosia trifida L.

Invasive sequence and ecological niche of main insect borers of Larix gmelinii forest in Aershan, Inner Mongolia

After the outbreak of Dendrolimus superans Buter in 2002, many insect borers quickly invaded larch （Larix gmelinii Rupr.） forests in the Aershan of Inner Mongolia. Methods involved included setting sample plots, collecting adults in iron traps and measuring areas of galleries to study the invasive sequence, their ecological niche and the extent of the different effects by the main insect borers to their hosts. The results showed that the damage of D. superans weakened L. gmelinii, first Ips subelongatus Motschulsky invaded, followed by Acanthocinus carinulatus Gebler, Monochamus urussovi Fisher and M. sutor L. After the outbreak of D. superans, the average density of longhorn beetles per L. gmelinii tree increased. The ecological niche of Ips subelongatus stretches almost from the base to the top of the trunk. The number of insects in older stands of L. gmelinii is larger than those in middle aged stands. They do not damage healthy trees of L. gmelinii. The ecological niche of A. carinulatus is higher in dead L. gmelinii trees than in weak ones. The degree of damage is directly proportional with age and depth of bark. M. urussovi mainly damages trunks below 4 m in weak trees; in dead trees they can do damage up to 6 m in height. M. sutor mainly damages trunks below 5 m in weak L. gmelinii trees; in dead trees they cause damage up to 7 m. Again, the degree of damage is directly proportional with age. None of the three species of longhorn beetles damage healthy L. gmelinii and younger trees. Among the main insect borers, the degree of damage caused by I. subelongatus is more serious than that of other insects.

Potential effects of climate change on a marine invasion： The importance of current context

Species invasions threaten marine biodiversity globally. There is a concern that climate change is exacerbating this problem. Here, we examined some of the potential effects of warming water temperatures on the invasion of Western Atlantic habitats by a marine predator, the Indo-Pacific lionfish （Pterois volitans and P. miles）. We focussed on two temperature-dependent aspects of lionfish life-history and behaviour： pelagic larval duration, because of its link to dispersal potential, and prey consump- tion rate, because it is an important determinant of the impacts of lionfish on native prey. Using models derived from fundamental metabolic theory, we predict that the length of time spent by lionfish in the plankton in early life should decrease with warming temperatures, with a concomitant reduction in potential dispersal distance. Although the uncertainty around change in dispersal distances is large, predicted reductions are, on average, more than an order of magnitude smaller than the current rate of range expansion of lionfisli in the Caribbean. Nevertheless, because shorter pelagic larval duration has the potential to increase local re- tention of larvae, local lionfish management will become increasingly important under projected climate change. Increasing tem- perature is also expected to worsen the current imbalance between rates of prey consumption by lionfish and biomass production by their prey, leading to a heightened decline in native reef fish biomass. However, the magnitude of climate-induced decline is predicted to be minor compared to the effect of current rates of lionfish population increases （and hence overall prey consumption rates） on invaded reefs. Placing the predicted effects of climate change in the current context thus reveals that, at least for the lionfish invasion, the threat is clear and present, rather than future [Current Zoology 58 （1）： 1-8, 2012].

Soil fungi of three native tree species inhibit biomass production and shift biomass allocation of invasive Mikania micrantha Kunth

Soil microbes contribute to native plant species successful resistance against invasive plant.Three native tree species,Heteropanax fragrans (HF),Cinnamomum burmanii (CB),and Macaranga tanarius (MT) were effective in controlling the notorious invasive vine Mikania micrantha (MM).Biomass production and allocation patterns (shoot/root biomass ratio (shoot/root)) are important indicators of MM climbing coverage and competitive light-capturing capacity.An investigation was conducted to test the role of soil microbes associated with the three native tree species to inhibit MM biomass production and shift MM shoot/root.Rhizosphere soils originating from preculture HF,CB,MT,and MM plots were collected separately for use as inocula.The inocula were mixed with sterilized river sand at a 1:9 (w/w) ratio to grow MM.The fungicide carbendazim (methyl benzimidazol-2-ylcarbamate) was applied to half the treatments to kill pathogenic soil fungi.Two nutrient levels were established based on the natural soil nutrient concentration from a field stand invaded by MM.MM were grown from seeds in a glasshouse,harvested 15 weeks after sowing,and separated into shoot and root portions.Results showed that under interaction of soil origin and nutrient levels,MM biomass production was unchanged,but biomass allocation patterns were significantly different.MM biomass production grown in the three native tree soils under two nutrient levels was similar or higher than MM biomass production in MM conspecific soil,indicating the absence of species-specific pathogens that inhibited MM biomass production in native tree soils.However,in both conspecific and tree soils,MM biomass production was significantly reduced in the presence of pathogenic soil fungi,i.e.MM experienced significant fungal inhibition,demonstrating the pathogenic soil fungi promoted native tree resistence to MM.MM exhibited decreased shoot biomass allocation when cultivated in native tree soil relative to MM conspecific soil under field stand nutrient level conditions.Reduced resource allocation to shoot biomass could result in diminished capacity to climb,cover,and subsequent smother to native trees,and reduced surface area exposed to available light.Following fungicide application,significant biomass allocation differences disappeared,suggesting the native tree soil fungi were responsible for decreasing MM shoot biomass.The overall results indicated tree soil fungi serve an integral role in controlling invasive MM through fungal inhibition on MM biomass production,and shifts in MM biomass allocation patterns.

An invading annual plant benefits less from soil biota and has reduced competitive power with a resident grass

Aims Interactions between plants and their soil biota,arbuscular mycorrhizal fungi(AMF)in particular,may play a vital role in the establishment and the range expansion of exotic plants in new environments.However,whether there are post-introduction shifts in dependence on AMF and how dependency interacts with competition remains poorly understood.Methods We conducted a common garden greenhouse experiment to examine how native(USA)and invasive(China)populations of the plant species Plantago virginica,respond to soil biota,and whether these responses change in the presence of a competitor.Important Findings We found that while native populations consistently had a higher AMF colonization rate and benefited from AMF in both biomass and seed production,invasive populations received less benefit from AMF,and even showed reduced biomass with AMF in the presence of a competitor.This low mycorrhizal dependency in invasive populations correlated with greater suppression by an indigenous competitor for the invader.The different responses of the invasive and native populations to AMF suggest that alteration of mycorrhizal dependency has occurred during the invasion of P.virginica into China.Our findings suggest that this reduced dependency incurs a cost during interspecific competition.