Biomass and primary-production of herbaceous plant communities in the Amazon floodplain

The increase in biomass of different aquatic and terrestrial herbaceous plant communities was measured during various growth periods in the Amazon floodplain near Manaus. Maximum biomass varied from 4–11.2 t ha^–1 dry weight in mixed annual terrestrial communities to 6–23 t ha^–1 in aquatic annual species (Paspalum repens, Oryza perennis, Luziola spruceana and Hymenachne amplexicaulis) and 15.6–57.6 t ha^–1 in communities of the perennial species Paspalum fasciculatum. Cumulative biomass of 3 successively growing annual species reached 30 t ha^–1 a^–1. Net primary production is considerably higher than maximum biomass. Paspalum fasciculatum reached 70 t during a growth period of 8 months. If one considers for annual species a monthly loss of 10–25% of the biomass, then net primary production in areas with three successive macrophyte communities and a cumulative maximum biomass of 30 t ha^–1 is estimated to reach up to 50 t ha^–1 a^–1. Annual P/B ratio may reach about 3.     

Climate change may alter genetic diversity of Duchesnea indica,a clonal plant species

Climate change may alter the genetic diversity of plants. However, the relationship between genetic diversity in clonal plant species and climate change is unclear. To address this, we examined a representative clonal plant species, Duchesnea indica. We used microsatellite markers to analyze the genetic diversity of the species and used a correlation analysis to infer the relationship between climatic suitability and genetic diversity by using Maxent modeling. Then, we used a geographical information system approach to evaluate the change in genetic diversity of D. indica under climate change scenarios. There was a significantly negative relationship between climatic suitability and the genetic diversity of the clonal plant species. Using a proxy of genetic diversity, we found that climate change may alter the genetic diversity and even lead to a reduction in regional genetic diversity in D. indica. Annual precipitation, in particular, contributes to these changes in genetic diversity. Hence, climatic factors can be used as indicators of genetic diversity for clonal plant species, and studies should examine the impact of climate change on the maintenance of genetic diversity in plant species.     

根茎禾草沙鞭的克隆生长在毛乌素沙地斑块动态中的作用

毛乌素沙地沙化景观是由众多不同类型和大小的斑块镶嵌而成的,许多生态学过程影响着这些斑块的动态,根茎禾草沙鞭的克隆生长就是其中之一.通过对有沙鞭生长的3块1hm2风蚀样地的野外调查和染料饲喂实验,研究了沙鞭的克隆生长在毛乌素沙化景观斑块动态中的作用.每块样地均被划分为625个4m×4m的格子,在3块样地的流沙斑块出现的植物中,沙鞭占据了最多的格子数.沙鞭根茎扩展的主要方向是从半固定斑块到流沙斑块,染料饲喂实验测量了沙鞭扩展到风蚀流沙斑块中的分株数、根茎分枝数、根茎长度和地上生物量.将不同斑块土壤含水量和沙鞭根茎在土壤中的分布进行比较发现,在沙鞭根茎分布集中的地下30～50cm处,流沙斑块的土壤含水量显著地高于半固定斑块.这一研究结果表明沙鞭的克隆生长在风蚀流沙斑块的固定和演变中起着非常重要的作用.     

Population-biomass dynamics and the absence of - 3/2 self-thinning in the clonal weed Salvinia molesta

Abstract In the field, the population density (n) of crowded, living ramets of Salvinia molesta ranged from 2500 m ^?2 in nutrient-poor water to more than 30 000 m^?2 in nutrient-rich water. Biomass of living shoots (B) in some localities exceeded 600 gm^?2 dry weight (150 tonnes ha^?1 fresh weight) and shoots plus roots of living and floating dead material exceeded 1600 gm^?2 dry weight (400 tonnes ha^?1 fresh weight). The ultimate limit B= 10⁵n^0.5 suggested by previous authors was not exceeded. The highest n and smallest ramets occurred in nutrient-rich water and B was a linear function of n. Field experiments confirmed no effect of n, but a strong effect of nutrient availability, on ramet weight. In a glasshouse experiment, ramet populations did not ‘self-thin’ along the log log B-n trajectory of slope -0.5, which has been suggested for aclonal plants, but followed trajectories having slopes closer to +1.0 before halting at the ambient B-n limit. Nutrient concentrations in the plants increased during the experiment, causing ramet size to decrease and slopes of log log B-n trajectories to depart from +1.0 by amounts which reflected the degree to which nutrient concentration had changed. Under constant conditions, mean ramet size is expected to remain constant and log log B-n trajectories to travel in a straight line of slope +1.0 to the ambient B-n limit. This behaviour of salvinia, whose ramets consist of a single structural module, is contrasted with that expected of clonal plants whose ramets are made up of multiple structural modules. A logistic model explained the increases in n and biomass of living and dead ramets when ramets were assumed to have constant longevity, constant time to decay, and when both the B-n limit and size of ramets were dependent on nitrogen content of the plant. There was no indication that physiological integration within phenets halted production of new ramets when carrying capacity was reached and new ramets continued to be produced on top of older ramets. Rates of ramet mortality were equal to, and dependent on, rates of ramet natality.     

Shoot growth dynamics and size-dependent shoot fate of a clonal plant,Festuca rubra, in a mountain grassland

The relation of the within-season and between-season patterns of shoot growth were compared in a clonal grass with long-lived shoots,Festuca rubra, in a mown mountain grassland. The growth rate of shoot length from spring to summer in a year was almost constant for each shoot irrespective of spring shoot length each year. The annual shoot growth rate from spring to spring was negatively correlated with the shoot length in the first spring. Shoots of different length and age therefore tended to converge over time to a population of identical shoot size, suggesting an equalizing effect of growth pattern on size structure. Shoot size (shoot length and number of leaves) influenced the fates of shoots. Larger shoots showed an increased incidence of both flowering and formation of intravaginal daughter shoots and a decreased incidence of death in the subsequent time period. The fates of shoots were independent of their age. Although the negatively size-dependent springto-spring annual shoot growth rate acted to decrease shoot size variation, the remaining variation within the shoot population was still sufficient to generate different fates of shoots. These fates were not related to the previous life history of individual shoots. There was a significantly positive effect of the shoot size at initiation on its life expectancy. This was mainly attributable to the positively size-dependent survival rate of shoots in the early stage (<1 year old) of shoot life history. Later on (> 1 year old), shoot size had little effect on the survival rate of shoots. Once small young shoots have survived this early stage (< 1 year old) in life history, they can grow vigorously, little affected by competition regardless of shoot size, and converge to a stable size structure of shoots of similar size. Only shoot size in the early stage ( < 1 year old) of life history is important for the persistence of a shoot population.     

A new species of Anchoviella (Clupeiformes: Engraulidae) from the western Amazon River in Peru,with comments on congeners in the Peruvian Amazon River

Anchoviella hernanni sp. nov. is described from the upper Amazon River basin, in tributaries of the Marañon, Ucayali and Madre de Dios river drainages that drain the Peruvian Andes. The new taxon can be distinguished from all congeners except Anchoviella jamesi, Anchoviella manamensis and Anchoviella perezi, by having 12–15 gill rakers in the lower branch of the first gill arch (v·16–35) and from those species by the distance between verticals through the posterior margin of the orbit to the posterior margin of the upper jaw 9·5–14·8% head length; L_H (v. up to 6·0% L_H). An updated identification key of all freshwater species of Anchoviella and morphological comparisons between all species of the genus occurring in Peru are provided.     

Stochastic simulation of clonal growth in the tall goldenrod,Solidago altissima

Summary As clonal plants grow they move through space. The movement patterns that result can be complex and difficult to interpret without the aid of models. We developed a stochastic simulation model of clonal growth in the tall goldenrod, Solidago altissima. Our model was calibrated with field data on the clonal expansion of both seedlings and established clones, and model assumptions were verified by statistical analyses.When simulations were based on empirical distributions with long rhizome lengths, there was greater dispersal, less leaf overlap, and less spatial aggregation than when simulations were based on distributions with comparatively short rhizome lengths. For the field data that we utilized, variation in rhizome lengths had a greater effect than variation for either branching angles or rhizome initiation points (see text). We also found that observed patterns of clonal growth in S. altissima did not cause the formation of fairy rings. However, simulations with an artificial distribution of branching angles demonstrate that fairy rings can result solely from a plant's clonal morphology.Stochastic simulation models that incorporated variation in rhizome lengths, branching angles, and rhizome initiation points produced greater dispersal and less leaf overlap than deterministic models. Thus, variation for clonal growth parameters may increase the efficiency of substrate exploration by increasing the area covered and by decreasing the potential for intraclonal competition. We also demonstrated that ramet displacements were slightly, but consistently lower in stochastic simulation models than in random-walk models. This difference was due to the incorporation of details on rhizome bud initiation into stochastic simulation models, but not random-walk models. We discuss the advantages and disadvantages of deterministic, stochastic simulation, and random-walk models of clonal growth.     

Nutrient addition does not increase the benefits of clonal integration in an invasive plant spreading from open patches into plant communities

• One benefit of clonal integration is that resource translocation between connected ramets enhances the growth of the ramets grown under stressful conditions, but whether such resource translocation reduces the performance of the ramets grown under favourable conditions has not produced consistent results. In this study, we tested the hypothesis that resource translocation to recipient ramets may reduce the performance of donor ramets when resources are limiting but not when resources are abundant.
• We grew Mikania micrantha stolon fragments (each consisting of two ramets, either connected or not connected) under spatially heterogeneous competition conditions such that the developmentally younger, distal ramets were grown in competition with a plant community and the developmentally older, proximal ramets were grown without competition. For half of the stolon fragments, slow‐release fertiliser pellets were applied to both the distal and proximal ramets.
• Under both the low and increased soil nutrient conditions, the biomass, leaf number and stolon length of the distal ramets were higher, and those of the proximal ramets were lower when the stolon internode was intact than when it was severed. For the whole clone, the biomass, leaf number and stolon length did not differ between the two connection treatments. Connection did not change the biomass of the plant communities competing with distal ramets of M. micrantha.
• Although clonal integration may promote the invasion of M. micrantha into plant communities, resource translocation to recipient ramets of M. micrantha will induce a cost to the donor ramets, even when resources are relatively abundant.

     

Shoot population dynamics of persisting clones of<Emphasis Type="Italic"> Miscanthus sinensis</Emphasis> in the warm-temperate region of Japan

The population dynamics of annual shoots in four clonal patches of Miscanthus sinensis was surveyed in terms of clone persistence. Over a study period of 3 years, a stable net shoot number was attained through a balanced replacement of old shoots by tillering 2–3 times a year. The birth rate was significantly correlated with the average monthly temperature. This suggests that a warm climate advances the date of tillerings, and shoots become taller as they emerge earlier. Five cohorts were identified, corresponding to shoots that were born in spring, early summer, summer, autumn and early winter. The autumn cohorts were more numerous and had a greater longevity than the other cohorts; they were thus were best suited for overwintering and, consequently, maintaining the population from one generation to the next. The shoots of earlier cohorts grew too tall to survive the cold of winter, which might cause freezing injury, while later cohorts shoots excelled in overwintering because of their shortness. However, if the delayed shoots are very short, they will also have difficulty in surviving the early season of growth. Therefore, M. sinensis shoots have an optimum size for survival.     

Assemblage structure and dynamics of terrestrial birds in the southwest Amazon: a camera‐trap case study

Habitat spatial distribution, seasonal variation, and activity patterns influence changes in vertebrate assemblages over time. Terrestrial birds play major roles in the dynamics of tropical forests, but there are few effective methods to study these species due to their cryptic coloration and elusive behavior. We used camera‐trap data collected during 16 mo (February 2017–June 2018) to describe the terrestrial avifauna in southeastern Peru, assess to what extent the composition of terrestrial avifauna changes among seasons and across two major habitats (terra firme and floodplain forests), and determine daily activity patterns of terrestrial birds. We used overlap analyses to examine temporal co‐occurrence between ecologically similar and sympatric species. Camera traps recorded 16 species, including eight species in the family Tinamidae. Capture rates were highest for Pale‐winged Trumpeters (Psophia leucoptera; Psophiidae) and Gray‐fronted Doves (Leptolila rufaxilla; Columbidae). Species composition did not differ between habitats or seasons, and capture rates between habitats only differed for White‐throated Tinamous (Tinamus guttatus). Overlaps of activity patterns were high between ecologically similar species and species found in terra firme habitats (White‐throated Tinamous and Cinereous Tinamous, Crypturellus cinereus) and in both habitat types (Pale‐winged Trumpeters and Gray‐fronted Doves). Low numbers of captures of possibly locally rare or less abundant species hindered a complete analysis of spatial and seasonal patterns of terrestrial bird assemblages. We suggest a greater sampling effort and greater spatial replication to better understand the spatial and seasonal dynamics of the terrestrial avifauna. Further studies that assess the mechanisms that allow the coexistence of sympatric tinamous would be valuable, both in our study area and elsewhere. The use of camera traps in long‐term monitoring projects proved to be an effective tool for monitoring terrestrial birds, identifying cryptic and often rare animals to species level, and providing valuable ecological information at species and community levels.     

Origins and genetic conservation of tropical trees in agroforestry systems: a case study from the Peruvian Amazon

Hundreds of native tree species are currently found in extensive agroforestry ecosystems in the Peruvian Amazon, forming an important reservoir of biodiversity. To further promote conservation, farmers are encouraged to supplement intra-specific genetic diversity in these populations with seed collected from local forests. For some tree species, however, this approach may be inappropriate, as stands of these taxa already found on-farm may not be of local origin. Despite this issue being of importance for conservation, little information is available on the history of cultivated trees in the region, a situation that we here rectify for the important fruit tree Inga edulis. Based on nuclear SSR and chloroplast DHPLC analyses of closely geographically matched natural and planted stands at five sites, it appears that cultivated material of I. edulis is primarily of non-local origin, indicating that conservation based on new wide-scale infusions from local wild stands into farms may be inappropriate in the region. Although nuclear and chloroplast diversity were both lower in planted stands, values were still relatively high (∼80 and 70% of natural stands, respectively), indicating that when farmers plant trees, good collection practice of seed from already cultivated I. edulis should be an effective means for ensuring long-term conservation on farms.     

Integration in the clonal plant <Emphasis Type="Italic">Eriophorum angustifolium</Emphasis>: an experiment with a three-member-clonal system in a patchy environment

A clonal plant in heterogeneous environments is usually expected to profit from resource exchange via a clonal network where ramets placed in contrasting environments can specialise so to acquire the most abundant resources. An experiment was designed using the three member clonal system of Eriophorum angustifolium, which consisted of one parent ramet growing in a resource poor environment and two offspring: one was limited in growth by nutrients while the other was light limited; the contrast in availability of limited resources between the offspring ramets was high, medium or none, with the system either connected or severed. The total resource availability was the same in all treatments. We proposed four possible scenarios for the system: offspring ramets will share resources via the deficient parent ramet, and the whole clone will profit from the contrasting environment (scenario 1); offspring ramets will support exclusively the parent ramet, and the whole clone will profit from a homogeneous environment (scenario 2); offspring ramets will stop the export of the limiting resource to the parent ramet, with split and connected treatments not differing (scenario 3); and offspring ramets will exhaust the carbon stored in the biomass of the parental ramet; offspring ramet will profit from connection (scenario 4). In the experiment, the limiting resources were sent to the strongest sink (scenario 2). The parent ramet growing in a deficient environment received the highest support in the treatment where both offspring ramets were growing in the same conditions (no-contrast treatment). Production of new shoots, but not biomass of whole clone, was supported in a homogenous environment. The experiment revealed that multiple stresses might prohibit free exchange of limiting resources via the clonal network and supports the idea that experimental studies on more complex clones are essential for understanding the costs and benefits of clonal growth.     

Determinants of growth of the flammable grass,Triodia scariosa: Consequences for fuel dynamics under climate change in the Mediterranean region of South Eastern Australia

Environmental conditions may influence the presence and strength of competitive interactions between different life forms, thereby shaping community composition and structure, and corresponding fuel dynamics. Woodland and shrubland communities of the Mediterranean climate region of South Eastern Australia contain a varied mixture of herbaceous and woody plants. The ratio of herbaceous to woody plants changes along gradients of temperature, moisture and soil fertility. This study aimed to experimentally examine the relative importance of, and interactions between environmental controls (moisture and soil fertility) on the balance of dominant herbaceous (Triodia scariosa) and woody plants (e.g. Acacia ligulata and Leptospermum coriaceum) and their ultimate effects on fuel and fire regimes. The results suggest that environmental determinants of the growth of T. scariosa are likely to be more important than interactions with shrubs in controlling the distribution of T. scariosa. The growth of T. scariosa was consistently higher under hot temperatures and on the less fertile yellow sands, which dominate the south of the region. The results suggest that there is strong potential for the distribution and abundance of T. scariosa to be altered in the future with changes in temperature associated with climate change. The distribution of soil types across the Mediterranean climate region of South Eastern Australia may be predisposed to favour the southerly expansion of T. scariosa‐dominated communities in the future under a warmer climate.     

Platycarpum vriesendorpiae sp. nov., a second new species of Tribe Henriquezieae (Rubiaceae) from nutrient‐poor soils in the Peruvian Amazon

The new species Platycarpum vriesendorpiae N. Dávila (Rubiaceae, Henriquezieae) is described from Peru, where it is restricted to white‐sand forests and peatlands in the Tapiche and Blanco River watersheds in southeastern Loreto Region. The new species is generally similar to P. acreanum Rogers of western Brazil in its phyllotaxy, leaf pubescence, and fruit shape and size. However, P. vriesendorpiae differs in its triangular stipules that are 2‐ or 3‐angled at the base and in its smaller corolla.     

Physical and chemical post-dam alterations in the Jamari River, a hydroelectric-developed river of the Brazilian Amazon

The regulation of the Jamari River advanced peak floods by 1–2 months and increased dry-season discharges from 60 to 200 m³ s^–1, resulting in water levels approximately 1 m above those recorded before regulation. Daily variation in water level associated with fluctuations in electricity production by the dam propagated to the lower reaches of the tributary Candeias River. Dissolved oxygen (DO), temperature, pH, and conductivity measured over 1.5 years on three locations along the regulated and two free-flowing rivers indicated important alterations in the case of oxygen concentrations. DO levels shifted from saturated (7–8 mg l^–1) during the flood season (when the spillways were open releasing epilimnetic water) to hypoxic (1.5–3 mg l^–1) during the dry season (when the floodgates were closed and only hypolimnetic water used to run the turbines was feeding the river). Fluctuations in water level and variation in dissolved oxygen tended to be greater at the site closest to the dam, gradually attenuating downstream. Mitigation of the downstream effects of river regulation would require modifications in the operation of the dam.     

Genetic variation of Calycophyllum spruceanum in the Peruvian Amazon Basin, revealed by amplified fragment length polymorphism (AFLP) analysis

An understanding of the level, structure and origin of genetic variation within and among populations of tropical trees is essential for devising optimum management strategies for their sustainable utilization and conservation. Here, amplified fragment length polymorphism (AFLP) analysis was used to partition genetic variation within and among nine populations of the predominantly riverine tree, Calycophyllum spruceanum , sampled across a wide geographical range along river tributaries of the Peruvian Amazon Basin. Analysis of molecular variance ( AMOVA ) employed 65 AFLP markers and revealed most variation among individuals within populations (91%), although variation among populations was highly significant ( P < 0.001). Calculation of genetic distances and nested AMOVA indicated a degree of structuring among populations based on geographical proximity, although clustering did not depend on geographical distance alone. No firm evidence was obtained for unidirectional seed dispersal by water playing an important role in determining genetic structure over the geographical range sampled. Implications of data for optimising genetic management of the species are discussed and areas for further study identified.     

Effects of clonal variation of the host plant,interspecific competition,and climate on the population size of a folivorous thrips

Summary The effects of clonal variation, interspecific competition, and climate upon the population size of Apterothrips secticornis was assessed by a series of observations and experimental manipulations. Three clones of the host plant, Erigeron glaucus, consistently supported different numbers of thrips during monthly censuses. When rosettes of the three clones were transplanted to a common garden, relative numbers of thrips on the clones remained the same as those observed where the clones grew in situ. The presence or absence of other hervivores had no effect on thrips numbers in the common garden. Plume moth caterpillars and thrips were observed to co-occur less often than expected in the field but this was caused by differences in habitat selection by these two species rather than being the result of interspecific competition. Populations of thrips were affected by climate, but analyses suggest that the host clone was a more important factor.     

百山祖常绿阔叶林灌草层物种组成和 分布的10年动态

森林群落的动态受多方面因素的影响。林下的草本植物和木本植物幼苗幼树对于森林的更新及动态具有重要作用。为了解百山祖常绿阔叶林群落下层植物物种组成和分布的动态变化, 我们分析了2003-2013年间百山祖5 ha森林动态样地灌草层物种(包括DBH < 1 cm的木本植物和所有草本植物)在物种重要值、α多样性以及物种分布等方面的变化。结果表明: (1) 10年间, 群落灌草层植物个体数减少了28.7%, 其中草质藤本植物个体数下降比例最大(76.9%), 而乔木的幼苗和幼树下降比例最小(14.4%); (2)整个灌草层的物种数明显下降, 同时乔木的幼苗和幼树及直立灌木的均匀度均下降, 而草本植物均匀度有所上升; (3)除短尾柯(Lithocarpus brevicaudatus)、叶萼山矾(Symplocos phyllocalyx)、显脉野木瓜(Stauntonia conspicua)和福建悬钩子(Rubus fujianensis)等植物重要值逆势上扬外, 直立灌木物种重要值10年间的变化值与其在2003年时的重要值呈显著正相关, 而其余各类生活型植物都显示, 初始重要值越高的物种在10年后下降幅度越大; (4)物种分布与生境类型的相关性变化复杂, 除与山谷生境正相关的物种数量增加外, 研究期间与生境存在显著相关性的物种数都有所减少; (5) 10年来仅陡坡处物种多样性指数没有显著下降。总体来说, 百山祖常绿阔叶林灌草层群落仍未达到顶极状态, 2003-2013年间正缓慢向顶极群落演替。群落内部的种间和种内竞争应是当前群落动态的主导因素。