Growth Traits and the Trade-Offs for Tree Species with Arbuscular Mycorrhizal Fungi in a Tropical Rain Forest Edge at Los Tuxtlas,Mexico

The effect of arbuscular mycorrhizal fungi on seedling growth across the rain forest-pasture edge has not received much attention. In a tropical rain forest in eastern Mexico, the seedlings of light demanding (Ficus insipida), nonsecondary light demanding (Lonchocarpus cruentus) and shade tolerant species (Nectandra ambigens, Coccoloba hondurensis) were grown and transplanted to a forest edge with three inoculation treatments (AM fungus spores and colonized roots, spores, and no inoculum). For all species, stem height, stem diameter, total dry weight, leaf area and net assimilation rate were higher in the pasture. Stem height, stem diameter and root/shoot were higher for L. cruentus, and leaf area ratio, specific leaf area and net assimilation rate were higher for F. insipida;the lowest values of almost all variables were recorded for N. ambigens. L. cruentus and C. hondurensis with mycorrhizae had the highest values for root/shoot and net assimilation rate, respectively. The lowest values of root/shoot and net assimilation rate were observed for nonlight-demanding species in the forest. There were clear trade-offs for the pioneer species between survival and growth, and in underground biomass allocation and assimilation for nonsecondary light demanding, but there was not for the shade-tolerant species.

Application of Lattice Boltzmann Method to Simulate Forest Edge

This study is focused on the forest edge flow by using numerical method.To model the effects of a forest canopy on airflow,source terms are introduced into the governing equations.The lattice Boltzmann method in conjunction with the standard k-εmodel is applied to solve the turbulent wind field.In order to perform the simulation on non-uniform grids,the Taylor series expansion and least square based lattice Boltzmann method(TLLBM)is adopted to improve the accuracy and computational efficiency.The present method and code are verified with an earlier forest edge simulation.A series of forest canopies are established to explore the impacts of canopy morphology on wind field.These canopies cover 3 canopy architectures and the Leaf Area Index(LAI)ranges from 2.0 to 4.0.The further study is carried out by adjusting the canopy foliage amount and the canopy architecture.The present study demonstrates the potential of lattice Boltzmann method to simulate the high Re number forest edge flow.The impacts of canopy morphology on zero plane displacement,aerodynamic roughness length,friction wind velocity,permeability coefficient,wall-shear stress are illustrated in detail.The results show that the canopy sub-layer wind field,especially the wind velocity profiles within and above the forest canopy,are mainly determined by canopy morphology.

A seed rain community in a reforested post-agricultural field and adjacent secondary forest of Mount Papandayan Nature Reserve,West Java,Indonesia

Understanding the mechanisms and barriers to the restoration of degraded land,especially post agriculture,will help provide protocols on effective ways of restoration into functional ecosystems.One of the barriers in early stages of forest restoration is the arrival and availability of propagules.Seed rain and factors affecting it(i.e.,distance to the forest edge,species diversity and surrounding vegetation)were measured in a reforested post-agricultural field and in an adjacent secondary forest.Multivariate g lm analysis was used on the seed rain community data and univariate lm analysis on the most abundant seed captured(i.e.,Schima wallichii(DC.)Korth.).After 8 months of seed rain collection,there was a total of 3596 seeds from eight tree species.Seeds were more abundant and more diverse in the secondary forest(74.9%,8 species)compared to the reforested field(24.1%,2 species).There was a limitation on seed dispersal in reforested field from the adjacent forest.The abundance of S.wallichii seeds determined by the dominance of adult trees(136 trees/ha in the forest and 115 trees/ha in the reforested field).Our study suggests,that after 7 years of planting,the reforested field has received limited seed rain and has not yet recovered.

Fraying around the edges:negative effects of the invasive Tradescantia zebrina Hort.ex Bosse(Commelinaceae)on tree regeneration in the Atlantic Forest under different competitive and environmental conditions

Aims Invasive plants modify the structure and functioning of natural en-vironments and threat native plant communities.Invasive species are often favored by human interference such as the creation of arti-ficial forest edges.Field removal experiments may clarify if invasive plants are detrimental to native plant regeneration and how this is related to other local factors.We assessed the joint effect of envir-onment and competition with the invasive Tradescantia zebrina on tree species recruitment in an Atlantic Forest fragment.Methods We carried out the experimental study in the Iguaçu National Park,located in southern Brazil,using 30 plots distributed across five invaded sites during 6 months.We counted T.zebrina leaves and recorded the abundance and height of tree recruits over time under contrasting environmental(forest edge vs.forest interior)and removal(all aboveground biomass,only T.zebrina removal,and control)treatments.We analyzed the effects of environment and re-moval treatment using generalized linear mixed models.Important Findings The invasive species performed better at the forest edge than in the interior.The higher competitive pressure of T.zebrina led to higher mortality and lower height of tree recruits.Invader removal favored tree recruitment,especially in the forest interior.Our study shows that T.zebrina hampers woody species regeneration in tropical Atlantic Forests,especially at the forest edge.

Distribution and effects of tree leaf litter on vegetation composition and biomass in a forest–grassland ecotone

Aims After abandonment of grasslands,secondary succession leads to the invasion by woody species.This process begins with the accumulation of tree litter in the forest–grassland ecotone.Our objectives were to determine the relationships between litter amounts and vegetation composition and cover along natural forest–grassland ecotones and to experimentally study the initial effects of tree litter accumulation on grassland vegetation and on microsite conditions.Methods We established 11 transects varying from 12 to 15 m in length in different forest–grassland ecotones in the Lahn-Dill highlands,Germany,and measured the mass and cover of tree litter and the cover and composition of vegetation at five sequential positions along each transect by using 1 m2 plots with five replications.In a field experiment,we established plots subjected to different litter amounts(0,200 and 600g m^(−2))and evaluated changes in grassland vegetation,soil temperature and soil nutrient availability below the litter layer.Important Findings Tree litter amounts decrease from 650 to 65g m^(−2) across the forest–grassland ecotone.Vegetation changed from shrubs and annual species(adapted to more stressful conditions)in the forests edge to grasses,rosettes and hemirosette species(with higher competitive abilities)in the grassland.These anthropogenic forest–grassland ecotones showed abrupt edges,and the two adjacent ecosystems were characterized by different species pools and functional groups.In the field experiment,the presence of a litter layer reduced vegetation biomass and cover;the species richness was only reduced in the treatment with high litter(600g m^(−2)).Additionally,adding litter on top of vegetation also reduced thermal amplitude and the number of frost days,while increasing the availability of some nutrients,such as nitrogen and aluminium,the latter being an indicator of soil acidification.Adding a tree litter layer of 600g m^(−2) in grassland areas had strong effects on the composition and diversity of grassland vegetation by reducing the cover of several key grassland species.In,or near,forest edges,litter accumulation rapidly changes established vegetation,microsite conditions and soil nutrients.

Distribution of ground-dwelling beetles （Coleoptera） across a forest-clearcut ecotone in Wolong Natural Reserve, southwestern China

The influence of edge effect on ground-dwelling beetles （Coleoptera） across a forest-clearcut ecotone was studied in Wolong Natural Reserve, southwestern China. During the field research, a total of 30 739 beetles were collected with pitfall traps along transects, which extending 100 m from the edge into the forest interior and 100 m into the clearcut. Of the collection, Carabidae comprised 92%, Staphylinidae 3%, Curculionidae 2%, and Tenebrionidae 2%, and these four families can be considered as abundant groups. Family richness, Shannon diversity and equitability display a significant decrease from forest interior, edge to clearcut. Based on the family composition and abundance, ground-dwelling beetles of the forest interior can be separated from those in the clearcut by Principal coordinate analysis ordination, and beetle assemblages in the forest edge were more similar to forest assemblages than to those found in the clearcut by cluster analysis. Seasonal dynamics of family richness showed a monotone peak in the middle season, with a highest value in the forest interior and a lowest value in the clearcut. Family abundance showed two peaks in the middle season, always with more individuals in the clearcut than in the forest interior or in the edge. Multiple linear regression analyses showed that the cover of shrub and litter were the two most important factors in determining family richness, Shannon diversity, equitability and abundance. Our results show that the forest edge and clearcut have obviously different composition and diversity of ground-dwelling beetles from forest interior at the family level. However, more edges have been formed due to increasing forest fragmentation （clearcutting or logging）, so it is necessary to preserve large and intact forest to protect the diversity of ground-dwelling beetles in Wolong Natural Reserve.We are indebted to Dr Jari Niemel^i and Dr Tibor Magura for constructive suggestions on the experiment and provid- ing important references. We are grateful to Mrs Xiao-Ping Zhou, Jin-Yan Huang, Shi-Qiang Zhou, Yuan-Jun Jiang, Shu-Ming Fan, Guo-You Li and You-Qian Yang （Wolong Natural Reserve, Wenchuan County, Sichuan Province） for assistance in field experiments. This study was supported in part by a State Key Basic Research and Development Plan from the Ministry of Science and Technology of China （G2000046800）, National Natural Science Foundation of China （No. 30570215）, a grant to the senior author （No. D/3684-1） of International Foundation for Sciences