鼎湖山不同演替阶段森林土壤水分时空变异研究

土壤水分作为森林生态系统水分蓄库的主体,森林土壤水分储量及其时空动态与变异对揭示区域植被恢复与气候变化背景下的森林生态系统水文过程响应与服务功能变化机制具有重要意义。本研究以南亚热带地区典型森林植被演替序列马尾松人工林（Pinus massoniana coniferous forest,PF）-马尾松针阔叶混交林（mixed Pinus massoniana/broad-leaved forest,MF）-季风常绿阔叶林（monsoon evergreen broad-leaved forest,MEBF）为研究对象,依托中国生态系统研究网络森林样地建设与监测统一规范对鼎湖山森林生态系统定位站站区内分布的上述森林类型土壤水分的长期定位观测（2005-2015年）,通过分析各演替阶段森林土壤不同土层（0-15、15-30、30-45、45-60、60-75和75-90 cm）土壤体积含水量观测数据,探究该区域森林植被恢复过程中的土壤水分变化及其时空变异。结果表明：在雨热同期且干湿季明显的南亚热带地区,鼎湖山森林土壤储水量及其时间动态受降雨量的影响显著,森林土壤层对降雨具有强烈的调蓄和稳定作用,伴随PF→MF→MEBF自然演替进程,调蓄水分能力逐步增强。林型间,由初期阶段PF到顶级群落MEBF,森林土壤水分储量逐渐提高,且演替后期林型相对于早期林型,土壤储水量均呈现为较小的年际与年内变幅。干、湿季而言,干季时林型间的土壤储水量差异大于湿季,干季时MEBF和MF土壤含水量分别是PF的1.33倍和1.11倍。从土壤含水量的干、湿季期间变异来看,不同林型各土层土壤含水量的变异系数大小均表现为干季大于湿季;垂直剖面方向上,突出表现为无论干湿季MEBF各层土壤含水量变异均比其他两种林型较为缓和,充分体现了MEBF优越的土壤水分时空调配能力。整体上,伴随PF→MF→MEBF自然演替进程,土壤水分储量及其稳定性逐步提升。     

Impacts of cattle grazing on forest structure and raptor distribution within a neotropical protected area

Uncontrolled cattle grazing is frequent in protected areas across the tropics but its effect on habitat structure and biodiversity is poorly known. We used generalized additive models to examine the precise relationships between cattle grazing intensity, vegetation structure, and raptor occurrence and richness across 39 1-km² plots within the North West Biosphere Reserve, Peru. Cattle grazing was widespread and intensity was negatively correlated with average canopy height and percentage of vegetation cover at 5–15 m. Raptors were influenced by cattle density but they were probably more strongly influenced by canopy and sub-canopy characteristics. Raptor species responded differently to increasing cattle density: presence of species that hunted or searched for food in open habitats increased with cattle density, while presence of range restricted species that hunted from perches, and declining species decreased. Moderate cattle densities (20–60 cows km^?2) may actually benefit some raptor species and help to maintain the high raptor diversity in the study area. Reserve authorities should, however, act to reduce cattle densities in some areas, which can exceed 120 cows km^?2, that seriously affect some key raptor species, and cause forest to be converted to permanent cattle pasture.     

Temporal and vertical drosophilid (Insecta; Diptera) assemblage fluctuations in a neotropical gallery forest

The drosophilids of a gallery forest in the Brazilian savanna were investigated to identify the temporal and vertical patterns in the community structure of these insects. Twelve monthly collections were performed (December 2007 to November 2008) in three vertical strata of the forest (0, 4 and 8 m heights) using 30 traps baited with fermented banana. The drosophilid assemblage was composed of 61 species (7,623 individuals), experienced temporal fluctuations and was vertically stratified. Both the diversity and abundance of the flies were very low during the dry season, a time when the assemblages were dominated by the exotic species Drosophila simulans, whereas the community showed an increased abundance and richness of neotropical species and showed vertical stratification in the wet season. Rare species were found primarily at the ground level (flies usually associated with neotropical forests) or in the canopy, which harbors species currently associated with open vegetation, little-studied neotropical species and most likely several new species. These changes, which reflect drosophilid adaptations to different environments, involve a shifting of the ecological niches occupied by the flies in the forest over time. This process of change is termed niche construction. Thus, we conclude that this complex and dynamic community structure, which is related to the interaction of several environmental factors associated with different forest environments, contributes to the high diversity of gallery forests in the Brazilian savanna.     

Temporal and spatial variability in soil food web structure

Heterogeneity is a prominent feature of most ecosystems. As a result of environmental heterogeneity the distribution of many soil organisms shows a temporal as well as horizontal and vertical spatial patterning. In spite of this, food webs are usually portrayed as static networks with highly aggregated trophic groups over broader scales of time and space. The variability in food web structure and its consequences have seldom been examined. Using data from a Scots pine forest soil in the Netherlands, we explored (1) the temporal and spatial variability of a detrital food web and its components, (2) the effect of taxonomic resolution on the perception of variability over time and across space, and (3) the importance of organic matter quality as an explanatory factor for variability in food web composition. Compositional variability, expressed using the Bray‐Curtis similarity index, was measured over 2.5 years using a stratified litterbag design with three organic horizons per litterbag set. Variability in community composition and organic matter degradation increased over time in the litter horizon only. Seasonal variation in community composition was larger than variation between samples from the same season in different years. Horizontal spatial variability in community composition and organic matter degradation was relatively low, with no increase in variability with increasing distance between samples. Vertically, communities and organic matter degradation was more different between the non‐adjacent litter and humus horizons than between adjacent layers. These findings imply that soil food webs, at least in temperate forest plantations, are more variable than is currently appreciated in experiments and model studies, and that organic matter turnover might be an important factor explaining variability in community composition. Species composition was more variable than functional group composition, which implies that aggregated food webs will seem less sensitive to local temporal and spatial changes than they in fact are.     

Temporal and spatial mapping of red grouper Epinephelus morio sound production

The goals of this project were to determine the daily, seasonal and spatial patterns of red grouper Epinephelus morio sound production on the West Florida Shelf (WFS) using passive acoustics. An 11 month time series of acoustic data from fixed recorders deployed at a known E. morio aggregation site showed that E. morio produce sounds throughout the day and during all months of the year. Increased calling (number of files containing E. morio sound) was correlated to sunrise and sunset, and peaked in late summer (July and August) and early winter (November and December). Due to the ubiquitous production of sound, large‐scale spatial mapping across the WFS of E. morio sound production was feasible using recordings from shorter duration‐fixed location recorders and autonomous underwater vehicles (AUVs). Epinephelus morio were primarily recorded in waters 15–93 m deep, with increased sound production detected in hard bottom areas and within the Steamboat Lumps Marine Protected Area (Steamboat Lumps). AUV tracks through Steamboat Lumps, an offshore marine reserve where E. morio hole excavations have been previously mapped, showed that hydrophone‐integrated AUVs could accurately map the location of soniferous fish over spatial scales of <1 km. The results show that passive acoustics is an effective, non‐invasive tool to map the distribution of this species over large spatial scales.     

Temporal and spatial variability in soil nutrient status of a former beach plain

As part of a research project on the variation in life-history characteristics within a population of Plantago major L. ssp. pleiosperma, seasonal and spatial variability in the availability of macronutrients (N, P, and K) were examined on a small scale in the 0–25 cm soil depth at a primary beach plain site, embanked since 1966. On the basis of distinct differences, among other things, in plant biomass, an a priori division into three different types of microhabitat occurring in a mosaic distribution pattern was made: an overall low-lying area (subsite 1) with slightly elevated patches of 0.5 to 1.5 m in diameter (subsite 2) and rather large patches, 20 to 40 m in diameter, of sea buckthorn shrubs, with small and relatively open spots (subsite 3) in the transitional zone from lower area into scrub. All three subsite types were studied within a total area of approximately 2000 m². Three methods of analysis were applied: an inventory survey (sampling once at the start of the growing season), an analysis of the seasonal variation (sampling at approximately monthly intervals during the period April-November), and an assessment of nitrogen mineralization potentials in the laboratory (sampling once at the beginning of the growing season). All three procedures clearly demonstrated the occurrence of differences in the availability of nutrients over very short distances, i.e. a pronounced spatial variability among subsites. Particularly the availability of N and P appeared to have increased at the subsites 2 and 3, when compared to subsite 1. This small-scale differentiation in soil properties has occurred in an essentially homogeneous parent material (e.g. in texture and carbonate content) over a period of about 20 years. Besides a spatial variability, statistically significant temporal fluctuations were observed in the availability of N, P, and K. Relative fluctuations of mineral N (as indicated by the range/mean ratio) were especially large at the subsites 2 and 3.     

Environmental controls of temporal and spatial variability in CO2 and CH4 fluxes in a neotropical peatland

Tropical peatlands play an important role in the global storage and cycling of carbon (C) but information on carbon dioxide (CO₂) and methane (CH₄) fluxes from these systems is sparse, particularly in the Neotropics. We quantified short and long‐term temporal and small scale spatial variation in CO₂ and CH₄ fluxes from three contrasting vegetation communities in a domed ombrotrophic peatland in Panama. There was significant variation in CO₂ fluxes among vegetation communities in the order Campnosperma panamensis > Raphia taedigera > Cyperus. There was no consistent variation among sites and no discernible seasonal pattern of CH₄ flux despite the considerable range of values recorded (e.g. ?1.0 to 12.6 mg m^?2 h^?1 in 2007). CO₂ fluxes varied seasonally in 2007, being greatest in drier periods (300–400 mg m^?2 h^?1) and lowest during the wet period (60–132 mg m^?2 h^?1) while very high emissions were found during the 2009 wet period, suggesting that peak CO₂ fluxes may occur following both low and high rainfall. In contrast, only weak relationships between CH₄ flux and rainfall (positive at the C. panamensis site) and solar radiation (negative at the C. panamensis and Cyperus sites) was found. CO₂ fluxes showed a diurnal pattern across sites and at the Cyperus sp. site CO₂ and CH₄ fluxes were positively correlated. The amount of dissolved carbon and nutrients were strong predictors of small scale within‐site variability in gas release but the effect was site‐specific. We conclude that (i) temporal variability in CO₂ was greater than variation among vegetation communities; (ii) rainfall may be a good predictor of CO₂ emissions from tropical peatlands but temporal variation in CH₄ does not follow seasonal rainfall patterns; and (iii) diurnal variation in CO₂ fluxes across different vegetation communities can be described by a Fourier model.     

The relationship between population density, habitat position and habitat breadth within a neotropical forest bird community

We examined the relationship between local abundance, habitat position and habitat breadth across bird species in a large Atlantic forest reserve in Brazil. This appears to be the first such study for any rainforest taxon. Habitat position for a species was its mean foraging height, along with the mean scores on three principal habitat axes for census stations at which it was recorded. Habitat breadth was the standard deviation of recorded foraging heights and the standard deviations of "positive" station scores on the habitat axes. We also examined differences in habitat position and breadth between endemic and wide-ranging taxa and amongst dietary groups. Amongst 31 species for which density estimation was possible, there were no correlations between local abundance and breadth of habitat use on any of the habitat axes. Breadth of habitat used did not vary with degree of endemism, but herbivores used a greater breadth of habitats on the axis describing canopy closure than did omnivores. Habitat position did not vary with endemic status, but herbivores preferred higher-biomass habitats than faunivores, and higher foraging heights than either faunivores or omnivores. Local abundance was linked weakly to habitat position with commoner species tending to forage in the lower strata of open-canopied areas. The 31 most commonly recorded species tended to occupy "middle-range" habitat positions, while 28 rarer species occupied habitats toward one or other end of the vegetation axes. These results suggest an association between the local abundance of a species and its habitat position, and especially its preference for common or mid-range habitats, rather than with its ability to utilise a wide range of habitats.     

天津沿海水鸟群落格局分析

2007年1～12月,利用样点法对天津沿海水鸟进行调查.共观察到水鸟6目11科71种,其中古北界40种,东洋界1种,广布种30种;鸟类居留型以旅鸟为主,有部分夏候鸟、冬候鸟和留鸟.水鸟群落格局时空差异明显,时间格局表现为季节变化较大,种数、数量及多样性均以春秋季高于冬夏季;空间格局表现为种数和Shannon-Weaner指数(H')均以青坨子最高,数量以北大港水库最多,均匀度指数(E)以唐家河口最高,4个群落参数的最小值均出现在滨海大道和独流减河.     

Temporal and spatial variability in nearshore bacterioplankton communities of Lake Michigan

The spatial and temporal variability of bacterial communities were determined for the nearshore waters of Lake Michigan, an oligotrophic freshwater inland sea. A freshwater estuary and nearshore sites were compared six times during 2006 using denaturing gradient gel electrophoresis (DGGE). Bacterial composition clustered by individual site and date rather than by depth. Seven 16S rRNA gene clone libraries were constructed, yielding 2717 bacterial sequences. Spatial variability was detected among the DGGE banding patterns and supported by clone library composition. The clone libraries from deep waters and the estuary environment revealed highest overall bacterial diversity. Betaproteobacteria sequence types were the most dominant taxa, comprising 40.2–67.7% of the clone libraries. BAL 47 was the most abundant freshwater cluster of Betaproteobacteria , indicating widespread distribution of this cluster in the nearshore waters of Lake Michigan. Incertae sedis 5 and Oxalobacteraceae sequence types were prevalent in each clone library, displaying more diversity than previously described in other freshwater environments. Among the Oxalobacteraceae sequences, a globally distributed freshwater cluster was determined. The nearshore waters of Lake Michigan are a dynamic environment that experience forces similar to the coastal ocean environment and share common bacterial diversity with other freshwater habitats.     

Pollen dispersal and representation in a neotropical rain forest

Results of 3 years of pollen trapping on Barro Colorado Island, Panama, are presented. Minimum pollen dispersal distances are estimated for the most abundant pollen taxa. Dispersal distances for some taxa appear to be as low as 5 m, while for other taxa at least 50% of the trapped pollen had travelled more than 40 m. No consistent pattern of spatial variation was reflected in the pollen rain, however, samples close to large canopy gaps had exceptional abundances of 'disturbance' taxa. A preliminary analysis of the representation of canopy components indicates that as much as 19% of pollen caught in the traps was derived from large tree species.     

Landslide early succession in a neotropical dry forest

Early succession on large landslides in highly humanized areas that have a tropical dry climate is not well studied. This study documented vegetation recovery during the first 4 years after disturbance at a landslide on Casita Volcano, Nicaragua. We aimed to determine the main pathways and causes of change in community features, such as richness, biovolume, and species composition and verify the role played by environmental heterogeneity. Data consisting on number, covers and mean height of woody species and several abiotic factors related to fertility and stability of substrates were obtained from permanent plots in previously defined zones. Pathways of early succession were highly contingent on abiotic heterogeneity and landscape context and were mainly controlled by abiotic factors associated with fertility of substrates, and incidence of human disturbances. Those results might form the basis of a model of early succession on landslides located in densely populated areas within tropical dry ecosystems. Our results suggest that, rather than focusing research on large-scale disturbances, the study of succession in landslides of the type that occurred on Casita Volcano must point towards the response of ecosystems to a much more complex disturbance regime, in which human-induced disturbances play a major role.     

Temporal and spatial variability of an invasive toxigenic protist in a North American subtropical reservoir

The toxigenic marine flagellate Prymnesium parvum was first recorded in Lake Texoma, OK-TX, USA, an impoundment of the Red and Washita Rivers, following a massive fish kill in January 2004. Results of a 4.5-year monitoring program, spanning five bloom periods, revealed that Prymnesium abundances in the lake were temporally and spatially variable—densities were higher in winter, near-shore, and in Red River-associated sampling sites; the largest blooms were in Lebanon Pool, a large backwater basin often disconnected from the main reservoir. Prymnesium blooms appeared to have been fueled by high nutrient concentrations, and winter-spring densities were positively correlated with chlorophyll a, conductivity, total phosphorus, total nitrogen, and microzooplankton biomass, and negatively correlated with molar total nitrogen:total phosphorus and cladoceran and total crustacean zooplankton biomass. Comparison of Prymnesium densities with hydrological data suggested that Prymnesium blooms in Lebanon Pool were highest when the pool was disconnected from the main reservoir; no bloom occurred in the winter of 2004–2005, the only year since the 2003–2004 invasion in which Lebanon Pool and Lake Texoma were connected during the winter months.     

Modeling the spatial distribution and fruiting pattern of a key tree species in a neotropical forest: methodology and potential applications

Background

The movement patterns of wild animals depend crucially on the spatial and temporal availability of resources in their habitat. To date, most attempts to model this relationship were forced to rely on simplified assumptions about the spatiotemporal distribution of food resources. Here we demonstrate how advances in statistics permit the combination of sparse ground sampling with remote sensing imagery to generate biological relevant, spatially and temporally explicit distributions of food resources. We illustrate our procedure by creating a detailed simulation model of fruit production patterns for Dipteryx oleifera, a keystone tree species, on Barro Colorado Island (BCI), Panama.

Methodology and Principal Findings

Aerial photographs providing GPS positions for large, canopy trees, the complete census of a 50-ha and 25-ha area, diameter at breast height data from haphazardly sampled trees and long-term phenology data from six trees were used to fit 1) a point process model of tree spatial distribution and 2) a generalized linear mixed-effect model of temporal variation of fruit production. The fitted parameters from these models are then used to create a stochastic simulation model which incorporates spatio-temporal variations of D. oleifera fruit availability on BCI.

Conclusions and Significance

We present a framework that can provide a statistical characterization of the habitat that can be included in agent-based models of animal movements. When environmental heterogeneity cannot be exhaustively mapped, this approach can be a powerful alternative. The results of our model on the spatio-temporal variation in D. oleifera fruit availability will be used to understand behavioral and movement patterns of several species on BCI.     

荒漠人工固沙植被区土壤水分的时空变异性

表层土壤水分具有高度的时间和空间变异性.研究的目的:(1)揭示沙坡头人工固沙植被区浅层土壤水分的时空变异性特征;(2)确定驱动土壤水分变异的主要环境因子.在人工固沙植被区内一个4500m2的网格样地上每隔10m设置取样点,在连续7个月的时间内 (2005年4～10月),每隔15d用时域反射仪测量各样点表层以下15cm和30cm深度的土壤容积含水量.结果表明,该区网格尺度上浅层土壤水分的分布具有明显的空间变异性,其变异性随着土壤水分含量的降低而减小;相对海拔是驱动土壤水分空间变异的主要环境因子,其作用在降雨后尤为显著,且其对土壤下层的影响比上层更明显;植被和土壤水分含量的相关性时间序列与相对海拔一致--降雨使其相关性增加;土壤质地(土壤粒径分布)和土壤水分含量的相关性时间序列特征与植被和相对海拔相反,且其对土壤上层的影响比下层更明显.因此,在沙坡头荒漠人工固沙植被区,降雨后的短暂湿润期,地形和植被是驱动浅层土壤水分变异的主要影响因子,而随着降雨之后土壤逐渐变干,土壤质地的影响变得更加明显.     

Microhabitat associations and seedling bank dynamics in a neotropical forest

We conducted a rigorous test of tropical tree seedling microhabitat differentiation by examining microhabitat associations, survival and growth of established seedlings of ten tropical tree species representing a four-factor gradient in seed size. Eight microhabitat variables describing soil and light conditions were measured directly adjacent to each of 588 seedlings within twelve 10×100 m belt transects at Paracou, French Guiana, and at 264 reference points along the transects. From these measurements, we defined three principal components describing soil richness, soil softness and canopy openness. Six of ten species (in 9 of 30 total cases) were distributed non-randomly with respect to microhabitat along at least one principal component. However, few species demonstrated clear microhabitat specialization. All shifts in distribution relative to reference points were in the same direction (richer, softer soil). Furthermore, of 135 pairwise comparisons among the species, only 7 were significantly different. More than three-fourths of all seedlings (75.3%) survived over the 2-year monitoring period, but survival rates varied widely among species. In no case was the probability of survival influenced by any microhabitat parameter. Relative height growth rates for the seedlings over 2 years varied from –0.031 cm cm^–1 year^–1 (Dicorynia guianensis, Caesalpiniaceae) to 0.088 cm cm^–1 year^–1 (Virola michelii, Myristicaceae). In only 4 of 30 cases was height growth significantly associated with one of the three principal components. Because the conditions in this study were designed to maximize the chance of finding microhabitat differentiation among a group of species differing greatly in life history traits, the lack of microhabitat specialization it uncovered suggests that microhabitat partitioning among tropical tree species at the established seedling stage is unlikely to contribute greatly to coexistence among these species.     

Comparative analysis of temporal and spatial variability in above-ground production in a deciduous forest and prairie

Production patterns of tallgrass prairie and adjacent eastern deciduous forest were summarized for a five to seven year period. Each system responded differentially to annual or growing season rainfall and solar energy (measured by pan water evaporation). Overall, forest productivity was negatively correlated with annual precipitation; the prairie exhibited no relationship with precipitation. These differences probably reflect the lack of water limitation of the forest and the "downstream" position of the forest.
Wood and seed production in the forest were the most variable components measured in our study. Neither variable was related to forest foliage production. Seed production in the prairie was also variable within and between years but was related to prairie foliage production. Prairie seed production was not correlated with seed production of the forest.
The two ecosystems respond differentially and independently of each other within the range of climatic variation observed here. Such differences have potential significance to consumers who use both systems for habitat or resources.     

Temporal and spatial partitioning of water resources among eight woody species in a Hawaiian dry forest

Lowland dry forests are unique in Hawaii for their high diversity of tree species compared with wet forests. We characterized spatial and temporal partitioning of soil water resources among seven indigenous and one invasive dry forest species to determine whether the degree of partitioning was consistent with the relatively high species richness in these forests. Patterns of water utilization were inferred from stable hydrogen isotope ratios (δD) of soil and xylem water, zones of soil water depletion, plant water status, leaf phenology, and spatial patterns of species distribution. Soil water δD values ranged from –20‰ near the surface to –48‰ at 130 cm depth. Metrosideros polymorpha, an evergreen species, and Reynoldsia sandwicensis, a drought-deciduous species, had xylem sap δD values of about –52‰, and appeared to obtain their water largely from deeper soil layers. The remaining six species had xylem δD values ranging from –33 to –42‰, and apparently obtained water from shallower soil layers. Xylem water δD values were negatively correlated with minimum annual leaf water potential and positively correlated with leaf solute content, an integrated measure of leaf water deficit. Seasonal patterns of leaf production ranged from dry season deciduous at one extreme to evergreen with near constant leaf expansion rates at the other. Species tapping water more actively from deeper soil layers tended to exhibit larger seasonality of leaf production than species relying on shallower soil water sources. Individuals of Myoporum sandwicense were more spatially isolated than would be expected by chance. Even though this species apparently extracted water primarily from shallow soil layers, as indicated by its xylem δD values, its nearly constant growth rates across all seasons may have been the result of a larger volume of soil water available per individual. The two dominant species, Diospyros sandwicensis and Nestegis sandwicensis, exhibited low leaf water potentials during the dry season and apparently drew water mostly from the upper portion of the soil profile, which may have allowed them to exploit light precipitation events more effectively than the more deeply rooted species. Character displacement in spatial and temporal patterns of soil water uptake was consistent with the relatively high diversity of woody species in Hawaiian dry forests. Received: 20 May 1999 / Accepted: 2 March 2000     

Modeling decay rates of dead wood in a neotropical forest

Variation of dead wood decay rates among tropical trees remains one source of uncertainty in global models of the carbon cycle. Taking advantage of a broad forest plot network surveyed for tree mortality over a 23-year period, we measured the remaining fraction of boles from 367 dead trees from 26 neotropical species widely varying in wood density (0.23–1.24 g cm⁻³) and tree circumference at death time (31.5–272.0 cm). We modeled decay rates within a Bayesian framework assuming a first order differential equation to model the decomposition process and tested for the effects of forest management (selective logging vs. unexploited), of mode of death (standing vs. downed) and of topographical levels (bottomlands vs. hillsides vs. hilltops) on wood decay rates. The general decay model predicts the observed remaining fraction of dead wood (R ² = 60%) with only two biological predictors: tree circumference at death time and wood specific density. Neither selective logging nor local topography had a differential effect on wood decay rates. Including the mode of death into the model revealed that standing dead trees decomposed faster than downed dead trees, but the gain of model accuracy remains rather marginal. Overall, these results suggest that the release of carbon from tropical dead trees to the atmosphere can be simply estimated using tree circumference at death time and wood density.