Lipid concentration and composition in xylem sap of woody angiosperms from a tropical savanna and a seasonal rainforest

Lipids may play an important role in preventing gas embolisms by coating nanobubbles in xylem sap.Few studies on xylem sap lipids have been reported for temperate plants,and it remain unclear whether sap lipids have adaptational significance in tropical plants.In this study,we quantify the lipid composition of xylem sap for angiosperm species from a tropical savanna(seven species)and a seasonal rainforest(five species)using mass spectrometry.We found that all twelve species studied contained lipids in their xylem sap,including galactolipids,phospholipids and triacylglycerol,with a total lipid concentration ranging from 0.09 to 0.26 nmol/L.There was no difference in lipid concentration or composition between plants from the two sites,and the lipid concentration was negatively related to species’open vessel volume.Furthermore,savanna species showed little variation in lipid composition between the dry and the rainy season.These results support the hypothesis that xylem sap lipids are derived from the cytoplasm of individual conduit cells,remain trapped inside individual conduits,and undergo few changes in composition over consecutive seasons.A xylem sap lipidomic data set,which includes 12 tropical tree species from this study and 11 temperate tree species from literature,revealed no phylogenetic signals in lipid composition for these species.This study fills a knowledge gap in the lipid content of xylem sap in tropical trees and provides additional support for their common distribution in xylem sap of woody angiosperms.It appears that xylem sap lipids have no adaptive significance.

Influence of Human Activity Intensity on Habitat Quality in Hainan Tropical Rainforest National Park,China

Due to long-term human activity interference,the Hainan Tropical Rainforest National Park(HTRNP)of China has experienced ecological problems such as habitat fragmentation and biodiversity loss,and with the expanding scope and intensity of human activity impact,the regional ecological security is facing serious challenges.A scientific assessment of the interrelationship between human activity intensity and habitat quality in the HTRNP is a prerequisite for achieving effective management of ecological disturbances caused by human activities and can also provide scientific strategies for the sustainable development of the region.Based on the land use change data in 2000,2010,and 2020,the spatial and temporal variations and the relationship between habitat quality(HQ)and human activity intensity(HAI)in the HTRNP were explored using the integrated valuation of ecosystem services and trade-offs(InVEST)model.System dynamics and land use simulation models were also combined to conduct multi-scenario simulations of their relationships.The results showed that during 2000–2020,the habitat quality of the HTRNP improved,the intensity of human activities decreased each year,and there was a negative correlation between the two.Second,the system dynamic model could be well coupled with the land use simulation model by combining socio-economic and natural factors.The simulation scenarios of the coupling model showed that the harmonious development(HD)scenario is effective in curbing the increasing trend of human activity intensity and decreasing trend of habitat quality,with a weaker trade-off between the two compared with the baseline development(BD)and investment priority oriented(IPO)scenarios.To maintain the authenticity and integrity of the HTRNP,effective measures such as ecological corridor construction,ecological restoration,and the implementation of ecological compensation policies need to be strengthened.

A test of the mycorrhizal-associated nutrient economy framework in two types of tropical rainforests under nutrient enrichments

Shifts in tree species and their mycorrhizal associations driven by global change play key roles in biogeochemical cycles. In this paper, we proposed a framework of the mycorrhizal-associated nutrient economy(MANE), and tested it using nutrient addition experiments conducted in two tropical rainforests. We selected two tropical rainforests dominated by arbuscular mycorrhizal(AM) and ectomycorrhizal(ECM) trees, and established eighteen20 m×20 m plots in each rainforest. Six nitrogen(N) and phosphorus(P) addition treatments were randomly distributed in each rainforest with three replicates. We examined the differences in soil carbon(C) and nutrient cycling, plant and litter productivity between the two rainforests and their responses to 10-year inorganic N and P additions. We also quantified the P pools of plants, roots, litter, soil and microbes in the two rainforests. Overall,distinct MANE frameworks were applicable for tropical rainforests, in which soil C, N and P were cycled primarily in an inorganic form in the AM-dominated rainforest, whereas they were cycled in an organic form in the ECMdominated rainforest. Notably, the effects of mycorrhizal types on soil P cycling were stronger than those on C and N cycling. The intensified N and P deposition benefited the growth of AM-dominated rainforests instead of ECMdominated rainforests. Our findings underpin the key role of mycorrhizal types in regulating biogeochemical processes, and have important implications for predicting the ecological consequences of global changes.

Characteristics of typhoon disturbed gaps in an old-growth tropical montane rainforest in Hainan Island, China

Disturbances that create gaps can shape the structure and function of forests. However, such disturbance regimes in Asian tropical montane rainforests remain largely unquantified. Least studied are typhoon disturbances that are attributable to climate change. We investigated gap characteristics in terms of size, age, and gap-maker to quantify the gap disturbance regimes in an intact old-growth tropical montane rainforest on Hainan Island, China. The intensity of typhoons has increased since 1949, and typhoon winds blow mostly (45.5%) from the northeast corner of Hainan Island, resulting in a higher frequency of gaps in the northeast. A total of 221 gap-makers (trees that fell to create canopy gaps) and 53 gaps were observed in a 3.16 ha old-growth rainforest. Most canopy gaps (85%) were < 200 m(2). The average size of canopy gaps was smaller in the rainforest than in other tropical forests, while the average size of expanded gaps was similar to those in other tropical forests. The maximum age of gaps was 23.5 years indicating that gaps had more rapid turnover than other parts of tropical forests. The frequency distribution of gap-makers followed a lognormal distribution with a distinctive peak at three gap-makers, which was different from the inverse J-shaped curve typical of other tropical forests. Gaps were recorded mainly on slopes between 20A degrees and 35A degrees and wood density of gap-makers was between 0.6 and 0.7 g cm(-3). Our results suggest that small-scale disturbance was the dominant agent of gap formation in this old-growth rainforest that is subject to increasing typhoon disturbances.

Responses of soil CH_(4) fluxes to nitrogen addition in two tropical montane rainforests in southern China

Background:Atmospheric nitrogen(N)deposition is projected to increase in the next few decades,which may have a marked impact on soil-atmosphere CH_(4) fluxes.However,the impacts of increased atmospheric N depositions on soil CH_(4) flux in tropical rainforests are still poorly understood.From January 2015 to December 2018,a field experiment was conducted in a primary tropical montane rainforest(PTMR)and a secondary tropical montane rainforest(STMR)in southern China to quantify the impact of N additions at four levels(N0:0 kg N⋅ha^(-1)⋅year^(-1);N25:25 kg N⋅ha^(-1)⋅year^(-1);N50:50 kg N⋅ha^(-1)⋅year^(-1);N100:100 kg N⋅ha^(-1)⋅year^(-1)on soil CH_(4) flux.Results:Four years of measurements showed clear seasonal variations in CH_(4) flux in all treatment plots for both forest types(PTMR and STMR),with lower rates of soil CH_(4) uptake during the wet season and higher rates of soil CH_(4) uptake during the dry season.Soil CH_(4) uptake rates were significantly and negatively correlated with both soil temperature and soil moisture for both forest types.Annual CH_(4) uptake for the N0 plots from the PTMR and STMR soils were2.20 and1.98 kg N⋅ha^(-1)⋅year^(-1),respectively.At the PTMR site,mean CH_(4) uptake compared with the N0 treatment was reduced by 19%,29%,and 36%for the N25,N50,and N100 treatments,respectively.At the STMR site,mean CH_(4) uptake compared with the N0 treatment was reduced by 15%,18%,and 38%for the N25,N50,and N100 treatments,respectively.High level N addition had a stronger inhibitory impact on soil CH_(4) uptake than did the low level N addition.Conclusion:Our data suggest that soil CH_(4) uptake in tropical rainforests is sensitive to N deposition.If atmospheric N deposition continues to increase in the future,the soil CH_(4) sink strength of tropical rainforests may weaken further.

Pollination Biology of Ficus hispida in the Tropical Rainforests of Xishuangbanna, China

Ficus hispida L. (Moraceae) is a remarkable species in the ecosystem of tropical rainforests in Xishuangbanna, China. The figs and fig_pollination wasps (Chalcidoidae: Agaonidae) are highly co_evolved mutualists that depend completely on each other for propagating descendants. Pollination of all fig species is done by fig wasps; their unique symbiotic associates, the fig wasps, cannot develop in anywhere except in the fig syconia. The present paper reports on the biology and flowering phenology of F. hispida , as well as the propagation character and pollination behavior of the fig wasps (Ceratosolen solmsi marchali Mayr) based on our observations in the rainforests of Xishuangbanna, southern Yunnan of China. F. hispida is a dioecious tree that annually blossoms and bears fruits 6-8 times, with four to five fruit_bearing peaks. The male trees produce pollen and provide fig wasps with reproductive havens, while the female trees produce fig seeds after pollination by the female wasps. Pollen of F. hispida cannot escape from the dehiscent anthers until they are disturbed by fig wasps. The female wasps open the anthers and collect pollen with their antennal scrapes, mandibles and legs, and then carry pollen to the female receptive syconia where fertilization takes place. Meanwhile, some of the female wasps lay eggs in the male receptive syconia. It takes about 3-67 min to search for the receptive syconia for pollination, and 15-23 h to enter the female receptive syconia. The number of female wasps entering a syconium has close relation with the impregnation and seed_bearing rate of female flowers, as well as the oviposition and reproduction rate of the fig wasps themselves. F. hispida is endowed with a relatively high level of seed bearing (54.1%-82.5%, average 73.8 %). The wasp oviposition rate on the male flowers is between 72.3% and 93.8% with a mean of 84.4%.

Research on Landscape Construction of the Tropical Rainforest Scenic Area ——A Case Study of Yanuoda Rainforest Scenic Area in Sanya City, Hainan Province

With its unique attractiveness, abundant natural and tourism resources, tropical rainforest plays a significant role in improving global climatic conditions and protecting the diversity of species, thus how to protect and properly utilize resources in the development of tropical rainforest is the top issue to be discussed. With the study case of Yanuoda Rainforest Scenic Area in Sanya, the landscape design principles and creation techniques of tropical scenic areas are to be discussed in this paper.

THE FLORISTIC CHARACTERISTICS OF THE TROPICAL RAINFOREST IN XISHUANGBANNA

ＴＨＥ ＦＬＯＲＩＳＴＩＣ ＣＨＡＲＡＣＴＥＲＩＳＴＩＣＳ ＯＦ ＴＨＥ ＴＲＯＰＩＣＡＬ ＲＡＩＮＦＯＲＥＳＴ ＩＮ ＸＩＳＨＵＡＮＧＢＡＮＮＡ ＺｈｕＨｕａ（朱华）（ＸｉｓｈｕａｎｇｂａｎｎａＴｒｏｐｉｃａｌＢｏｔａｎｉｃａｌＧａｒｄｅｎ，ｔｈｅ...

THE TROPICAL RAINFOREST VEGETATION IN XISHUANGBANNA

The tropical rainforest in Xishuangbanna,Yunnan Province of China,is introduced in detail in this paper.Situated at the northern margin of tropical mainland SE Asia and controlled by monsoon climate,the region has been climatically at the lower limits for tropical rainforests,however true tropical rainforests exist and develop luxuriantly in the region.The reasons for this are discussed.In general phytocoenological characteristics such as vertical stratification,life form spectrum,species riches etc.the tropical rainforest in Xishuangbanna is very similar to the typical tropical rainforest in equatorial region,but it is characterized by a clear change of physiognomy between different season.As occurred at the latitudinal and altitudinal limits of tropical rainforest,the flora of the rainforest is endowed with the nature of northern margin of tropical zone of SE Asia and is transitional toward the flora of subtropical forest of China.In recent years the region has been opened up to use in a large scale and the primary forests,eseialy rainforests,have been severely destroyed,The conserva.tion and rsercho lo the ropiranr rnforest are very ugent and have io be doneat once.

Population distribution and threats to sustainable management of selected non-timber forest products in tropical lowland rainforests of south western Nigeria

Uncontrolled harvesting of non-timber forest products （NTFPs） poses a serious risk of extermination to several of these species in Nigeria. Yet, there is a paucity of information on the distribution, population status and sustainable management of NTFPs in most of the tropical lowland rainforests. We, therefore, assessed the population, distribution and threats to sustainable management of NTFPs within the tropical lowland rainforests of Omo and Shasha Forest Reserves, south western Nigeria. Data were obtained through inventory surveys on five top priority species including： bush mango （Irvingia gabonensis （Aubry-Lecomte ex O’Rorke） Baill）, African walnut （Tetracarpidium conophorum （Mull. Arg.） Hutch. ＆ Dalziel syn. Plukenetia conophora）, chew-stick （Massularia acuminata （G. Don） Bullock）, fever bark （Annickia chlorantha Setten ＆ P.J.Maas syn. Enantia chloranta） and bush pepper （Piper guineense Schumach. ＆ Thonn.）. Purposive and stratified random sampling techniques were used for the inventory. Each forest reserve was stratified into three, viz： less disturbed natural forest （for areas that have been rested for at least ten years）, recently disturbed natural forest （for areas that have suffered one form of human perturbation or the other in the last five years）, and plantation forest （for areas carrying forest plantation）. Data were collected from eighteen 10 m × 500 m belt transects located in the above strata. The species were generally fewer in both plantation and recently disturbed natural forest than the less disturbed natural forest, suggesting that forest disturbances （habitat modification） for other uses may have an effect on the occurrence and densities of the NTFPs. Exceptions to this trend were found for P. guineense and T. conophorum, which were fairly common in both plantation and recently disturbed natural forest. Among three tree NTFP species （i.e. I. gabonensis, M. acuminata and A. chlorantha）, only I. gabonensis showed a significant difference in overall DBH size classes for both reserves （t=？2.404; df =21; p=0.026）. Three tree NTFP species in both reserves further showed differences from the regular patterns of distribution of trees. The fairly regular reverse J-shaped size class distribution observed for M. acuminata in the study sites, however, suggests a recuperating population. In general, destructive harvesting of species, logging operations, low population size, narrow distribution ranges and habitat degradation are the major threats to the population of NTFPs in the study area. The implications of our findings for sustainable management of NTFPs in the study area are discussed and recommendations are made for a feasible approach towards enhancing the status of the species.

The carbon fluxes in different successional stages:modelling the dynamics of tropical montane forests in South Ecuador

Background： Tropical forests play an important role in the global carbon（C） cycle.However, tropical montane forests have been studied less than tropical lowland forests, and their role in carbon storage is not well understood.Montane forests are highly endangered due to logging, land-use and climate change.Our objective was to analyse how the carbon balance changes during forest succession.Methods： In this study, we used a method to estimate local carbon balances that combined forest inventory data with process-based forest models.We utilised such a forest model to study the carbon balance of a tropical montane forest in South Ecuador, comparing two topographical slope positions（ravines and lower slopes vs upper slopes and ridges）.Results： The simulation results showed that the forest acts as a carbon sink with a maximum net ecosystem exchange（NEE） of 9.3 Mg C？（ha？yr）-1during its early successional stage（0–100 years）.In the late successional stage, the simulated NEE fluctuated around zero and had a variation of 0.77 Mg C？（ha？yr）–1.The simulated variability of the NEE was within the range of the field data.We discovered several forest attributes（e.g., basal area or the relative amount of pioneer trees） that can serve as predictors for NEE for young forest stands（0–100 years） but not for those in the late successional stage（500–1,000 years）.In case of young forest stands these correlations are high, especially between stand basal area and NEE.Conclusion： In this study, we used an Ecuadorian study site as an example of how to successfully link a forest model with forest inventory data, for estimating stem-diameter distributions, biomass and aboveground net primary productivity.To conclude, this study shows that process-based forest models can be used to investigate the carbon balance of tropical montane forests.With this model it is possible to find hidden relationships between forest attributes and forest carbon fluxes.These relationships promote a better understanding of the role of tropical montane forests in the context of global carbon cycle, which in future will become more relevant to a society under global change.

Assessing Tropical Deforestation and Biodiversity Loss in the Cross River Rainforest of Nigeria

The Cross River Rainforest of South Eastern Nigeria is one of Africa’s last remaining areas of pristine tropical high forest, extremely rich in a wide variety of flora and fauna species, and is among the twenty five biodiversity hotspots in the world. The forest has important biophysical properties which affect local, regional and global environmental quality. Using a combination of document research, GIS report, field observations, interviews and focus group discussions, the study reveals that the ecological integrity of this forest is being seriously threatened by a myriad of human activities, such as unsustainable agricultural practices, illegal logging, population explosion/expansion of human settlements, construction of highways, mining activities, and high unemployment/pressure on natural resources. All the above factors have combined to impact heavily on the depletion and extinction of valuable flora and fauna species in the region. Rigorous research-based innovative forestry and biodiversity policies and programmes, forest restoration initiatives, community-based forest management, and sustainable land use practices are recommended to save the Cross River Rainforest from total destruction.

Blood and Gastrointestinal Parasites of Chickens and Turkeys Reared in the Tropical Rainforest Zone of Southeastern Nigeria

The blood and gastrointestinal (GI) parasites of chickens and turkeys reared in Owerri, Southeastern Nigeria were studied. Out of 5600 birds, 5040 (90%) were chickens and 560 (10%) were turkeys. Of these birds, 672 (12%) were infected with blood parasites, of which 448 (8.9%) were chickens and 224 (40%) turkeys. The blood parasites found in chickens were Leucocytozoon sp., with a prevalence rate of 448 (8.9%) occurring in both male and female chickens examined. Plasmodium sp. was found in the turkeys and it gave a prevalence of 224 (40%). 1792 (32%) of the birds were infected with faecal parasites, out of which, 1456 (28.9%) were chickens and 336 (60%) turkeys examined. Ascaridia sp. infected 1232 (24.4%) of the chickens and 336 (60%) of the turkeys were examined. The only cestode observed was Raillietina spp., which infected 224 (4.4%) of the chickens, but none in the turkeys. Generally, low blood and faecal infections were observed in the chickens, while infections in the turkeys were slightly higher.

Evaluating the addition of radar with optical data for vegetation mapping in a montane region in Sri Lanka

The use of freely-available multi-source imagery for mapping vegetation in montane terrain is important for many developing countries that do not have the funding for high-resolution data capture.Radar images are also now freely available and include Sentinel-1 in dual polarisation,and PALSAR-2.These images can penetrate cloud cover and provide the advantage of acquiring data in a cloudy tropical region.This research evaluated whether the addition of radar with optical and topographic data improves classification accuracy in a montane region in Sri Lanka.Six classification experiments were designed based on different combinations of image data to test whether radar data improved land cover classification accuracy compared with optical data alone.Random forest classifier in the Google Earth Engine has been utilised to classify the tropical montane vegetation.The results indicate that radar or optical data alone cannot obtain satisfactory results.However,when combining radar with optical data the overall accuracy increased by approximately 5%,and by an additional 2%when topography data were added.The highest accuracy(92%)was achieved with multiple imagery,and adding the vegetation indices improved the model slightly by 0.3%.In addition,feature importance analysis showed that radar data makes a significant contribution to the classification.These positive outcomes demonstrate that freely-accessible multi-source remotely-sensed data have impressive capability for vegetation mapping,and support the monitoring and managing of forest ecological resources in tropical montane regions.

Phyllosphere eukaryotic microalgal communities in rainforests:Drivers and diversity

Phyllosphere algae are common in tropical rainforests,forming visible biofilms or spots on plant leaf surfaces.However,knowledge of phyllosphere algal diversity and the environmental factors that drive that diversity is limited.The aim of this study is to identify the environmental factors that drive phyllosphere algal community composition and diversity in rainforests.For this purpose,we used single molecule real-time sequencing of full-length 18S rDNA to characterize the composition of phyllosphere microalgal communities growing on four host tree species(Ficus tikoua,Caryota mitis,Arenga pinnata,and Musa acuminata) common to three types of forest over four months at the Xishuangbanna Tropical Botanical Garden,Yunnan Province,China.Environmental 18S rDNA sequences revealed that the green algae orders Watanabeales and Trentepohliales were dominant in almost all algal communities and that phyllosphere algal species richness and biomass were lower in planted forest than in primeval and reserve rainforest.In addition,algal community composition differed significantly between planted forest and primeval rainforest.We also found that algal communities were affected by soluble reactive phosphorous,total nitrogen,and ammonium contents.Our findings indicate that algal community structure is significantly related to forest type and host tree species.Furthermore,this study is the first to identify environmental factors that affect phyllosphere algal communities,significantly contributing to future taxonomic research,especially for the green algae orders Watanabeales and Trentepohliales.This research also serves as an important reference for molecular diversity analysis of algae in other specific habitats,such as epiphytic algae and soil algae.

海南热带雨林国家公园优先保护物种名录及其在国家公园管理中的应用

海南热带雨林国家公园是全国首批唯一地处热带且生物多样最高的国家公园。生物多样性保护是国家公园建设的重要任务,海南热带雨林国家公园极其丰富的物种为保护工作带来了机遇和挑战。确定生物多样性保护的优先性是在生物多样性资源分布不均、受胁程度不同以及人力、物力有限的情况下缓解当前生物多样性丧失的有效手段。为有序地开展生物多样性保护和推动国家公园建设,海南热带雨林国家公园在全国率先开展优先保护物种名录遴选工作,拟定了包含脊椎动物、植物和大型真菌在内的《海南热带雨林国家公园优先保护物种名录》。研究总结名录的遴选方法与结果,阐明名录对国家公园建设和生物多样性保护的重要作用,为我国的国家公园建设提供海南样本。

水生态系统韧性视角下热带雨林地区的蓝绿空间评价——以五指山市南圣河为例

热带雨林地区因特殊的气候特点及空间特征,河流蓝绿空间面临的雨洪压力与人类社会活动压力较大,其韧性建设对于整个生境具有关键性影响。国内外研究聚焦于韧性承洪实践与韧性评估量化,鲜有基于不同生态压力冲击对河流蓝绿空间开展多维韧性评价。文章以南圣河为对象,基于雨洪等自然灾害的脉冲式压力与人类社会对生态系统施加的慢性压力两类情境,构建水生态系统的“压力-脉冲-韧性”模型,通过“构建理论模型―叠合双维承压评价―解析吻合/冲突点―探析韧性策略”的逻辑方法实现特定地域蓝绿空间的评价与优化。研究发现:1)生态系统服务价值越高,调节功能越高,蓝绿空间韧性越强。2)突发性脉冲方面,在极端日降雨量增加情景下,河流水系的缓冲半径与水源类型密切相关,水库受到水安全威胁的风险大于河流,地表的径流曲线数值(简称CN)一般与历史经验相关。3)慢发性压力方面,韧性压力与城市人口密切相关,人口越密集,韧性压力越大;且不同季候的游憩密度与丰枯期存在分异,丰水期雨洪威胁大,游憩密度低,枯水期雨洪威胁小,游憩密度高。

海南热带雨林国家公园重要地质遗迹特征及综合评价

海南热带雨林国家公园内地质遗迹资源是热带雨林内自然资源和自然环境极其重要的组成部分,地质遗迹所赋存的地质环境,是热带雨林生物多样性的基础条件。推进地质遗迹资源的科学保护和合理利用是建设海南热带雨林国家公园的重要内容之一。基于对海南热带雨林国家公园全面系统的地质遗迹调查评价工作,依据《地质遗迹调查规范》(DZ/T 0303-2017),笔者等系统的总结了海南热带雨林国家公园内重要地质遗迹资源的特征和分布,对其科学价值和美学价值进行了定性和定量综合分级评价。研究结果表明:海南热带雨林国家公园内地质遗迹类型多样,以基础地质和地貌景观大类为主,包括重要化石产地类、岩土体地貌类、水体地貌类以及火山地貌类4类,古生物群化石产地、岩溶地貌、侵入岩地貌、碎屑岩地貌、瀑布、火山岩地貌6个亚类,共计21处重要地质遗迹点。其中,世界级地质遗迹点的有1处,省级地质遗迹点17处,省级以下地质遗迹点3处。通过对海南热带雨林国家地质公园地质遗迹评价,为国家公园内地质遗迹资源保护和利用提供基础资料和思路。

海南尖峰岭热带山地雨林60 hm2大样地幼苗物种组成及数量特征

【目的】分析海南尖峰岭热带山地雨林60 hm^(2)大样地幼苗物种组成、分布及数量特征变化规律,更深入了解热带森林群落物种组成和自然更新过程,为进一步探究幼苗分布与生长的影响因素提供参考依据。【方法】在海南尖峰岭典型热带山地雨林,基于2012年建立的1块60 hm^(2)动态监测大样地,连续7年监测其中290个样站(每个样站3个1 m^(2)小样方)的幼苗生长规律,区分幼苗的生活型、菌根类型和物种优势度,分析其物种组成及数量动态变化特征。【结果】2013—2019年共记录到幼苗个体234种60750株,包括4种生活型(乔木、灌木、藤本和草本)和3种菌根类型(丛枝菌根类型AM、外生菌根类型ECM、内生和外生混合类型AM&ECM)。优势物种九节和厚壳桂幼苗广泛分布,其重要值、植株数量和出现频度均在所有物种幼苗中占据前2位。各幼苗样方物种数量分布不均匀,较大部分幼苗物种仅有稀少的植株数量。【结论】海南尖峰岭热带山地雨林幼苗物种组成丰富,存在大量稀有物种,研究结果对了解时间和空间尺度上幼苗的物种组成、分布及数量特征变化以及探究其影响因素具有重要参考价值。

宿主身份与叶性状对海南热带山地雨林樟科和壳斗科植物叶内生真菌群落的影响

为了揭示植物身份与叶性状在叶内生真菌群落构建中的作用,笔者使用Illumina Miseq测序平台检测海南尖峰岭热带山地雨林中优势植物叶内生真菌群落的物种组成,并探讨宿主身份和叶性状对叶内生真菌群落物种组成的影响。本研究共检测到来自8种樟科和7种壳斗科植物的叶内共生真菌的1539567条真菌的ITS2序列,并将它们划分为5471个真菌分类单元(Operational Taxonomic Units,OTUs),隶属于8个门、30个纲、108个目、281个科、892个属。其中,子囊菌是叶内生真菌的最大类群,占所测真菌序列数的94.5%。单株樟科植物叶内生真菌物种数805±32OTUs显著高于壳斗科植物554±41 OTUs。相比之下,Shannon-Wiener、Simpson多样性指数在两科植物的叶内生真菌间均无显著差异。偏冗余分析(partial redundancy analysis)结果表明,宿主科、属、种身份对叶内生真菌群落组成有显著的影响。去除植物性状的效应后,宿主科、属、种身份能够独立解释叶内生真菌群落物种组成的变异量分别达到2.9%、15.7%、33.7%。去除宿主植物身份的影响后,叶性状在总体上能够解释叶内生真菌群落物种组成的变异量达到21.3%(P=0.003),其中,叶钙含量、比叶面积、叶氮含量和叶钾含量对叶内生真菌群落物种组成有显著影响。上述结果表明,宿主身份和叶性状是热带山地雨林叶内生真菌群落构建的重要驱动因子。