提高碳汇潜力：量化树种和造林模式对碳储量的影响

全球气候变化背景下,造林再造林固定的碳可以抵消温室气体减限排量。通过造林再造林增加森林面积可以增加林业碳汇,在土地面积有限的情况下,提高造林质量——在有限的造林面积上固定更多的碳是十分必要的。树种和造林模式的选择是增加森林生态系统碳汇的重要管理决策。文章综述了树种和造林模式对生态系统的碳储量的影响。树种从生物量的积累,凋落物和土壤碳储存,以及木材密度、碳贮存量等几个方面探讨其对生态系统碳库的影响。混交林能充分利用立地条件、改善树木营养状况,并且可以减少病虫害和森林火灾。同时分析了我国在森林经营方面存在的问题和改善途径,以期为该领域的研究提供参考。     

Variation partitioning of species data matrices: estimation and comparison of fractions

Establishing relationships between species distributions and environmental characteristics is a major goal in the search for forces driving species distributions. Canonical ordinations such as redundancy analysis and canonical correspondence analysis are invaluable tools for modeling communities through environmental predictors. They provide the means for conducting direct explanatory analysis in which the association among species can be studied according to their common and unique relationships with the environmental variables and other sets of predictors of interest, such as spatial variables. Variation partitioning can then be used to test and determine the likelihood of these sets of predictors in explaining patterns in community structure. Although variation partitioning in canonical analysis is routinely used in ecological analysis, no effort has been reported in the literature to consider appropriate estimators so that comparisons between fractions or, eventually, between different canonical models are meaningful. In this paper, we show that variation partitioning as currently applied in canonical analysis is biased. We present appropriate unbiased estimators. In addition, we outline a statistical test to compare fractions in canonical analysis. The question addressed by the test is whether two fractions of variation are significantly different from each other. Such assessment provides an important step toward attaining an understanding of the factors patterning community structure. The test is shown to have correct Type I. error rates and good power for both redundancy analysis and canonical correspondence analysis.     

Spatial error propagation when computing linear combinations of spectral bands: The case of vegetation indices

The collection of accurate and timely information on land use, crops, forest and vegetation are increasingly based on remote sensing spectral measurements produced by satellites. The most recent spacecrafts like the Earth Observing 1 (EO-1) produce a rich source of information being endowed with hyperspectral sensors that can provide up to 200 or more channels. In many instances such a multivariate signal has to be reduced to just one single value per pixel representing a particular characteristic of land. Linear combinations of bands are the general form of many indices. Since each individual image used to construct indices contains errors, when combined they produce a propagation of errors, a process that can distort a final output map. In this paper we measure the extent of error propagation when building linear vegetation indices. We consider three types of indices: the difference vegetation index (DVI), selected Kauth-Thomas indices (SBI, GVI and WET), and principal components, using benchmarking examples taken from the remote sensing literature. The main implication emerging from these examples is that the SBI and the first principal component are the indices more prone to error propagation. The formalization presented here allows a user to derive measures of error propagation in cases where technical characteristics of a sensor and physical characteristics of a landscape are known. These results can help a user to choose between alternative vegetation indices, and to associate a measure of reliability with such indices.     

Enzyme activities and allozyme polymorphism in two genetic types (or sibling species) of the genus Marenzelleria (Polychaeta: Spionidae) in Europe

Two populations of Marenzelleria spp. from the North Sea and the Baltic Sea that had already been characterized by allozyme electrophoresis and found genetically different in 1994 were again examined in 1997. The genetic identity (I = 1.0) examined in 1994 and 1997 shows that the structures of the populations of genetic Type I in the North Sea (Ringkobing Fjord) and genetic Type II in the Baltic Sea (Darss–Zingst Bodden chain) are stable. Three diagnostic gene loci that were determined additionally (citrate synthase, one locus; alanine aminotransferase, two loci) support the hypothesis of the existence of two sibling species of the genus Marenzelleria in Europe. In addition, the activities of ten electrophoretically separated enzyme systems were measured in the worms immediately after removal from their habitat and after they had been kept in the laboratory for 2 months. Under both conditions four enzymes showed significant differences between genetic types. The higher activity of the alanine aminotransferase of the North Sea worms (Type I) is discussed in the context of the different preferred salinities of the two Marenzelleria sibling species. Received: 21 January 1999 / Accepted: 13 July 1999     

Colonization of Europe by two American genetic types or species of the genus Marenzelleria (Polychaeta: Spionidae). An electrophoretic analysis of allozymes

Allozyme electrophoresis was conducted in an attempt to identify the origin ofMarenzelleria sp. found in the North Sea and Baltic Sea. The analysis covered eight enzymes with ten loti from nine populations found on the North American Atlantic toast, these populations in the North Sea and five populations in the Baltic. The North Sea spionids correspond to the Type IMarenzelleria from North American coastal waters between Barnstable Harbor (Massachusetts) and Cape Henlopen (Delaware). Nei's genetic distance between these North American populations and those from the North Sea wasD = 0.010 to 0.020. TheMarenzelleria sp. found in the Baltic Sea very probably stems from North American populations of Type II found from the region of Chesapeake Bay (Trippe Bay) south to the Currituck Sound (North Carolina). The genetic distance between these North American populations and the Baltic populations isD = 0.000 to 0.001. The invaders appear to have lost little of their genetic variation while colonizing the North and Baltic Seas. Probably, both colonizing events tan be attributed to large numbers of individuals reaching Europe simultaneously on one or more occasions. In addition, aMarenzelleria Type III was found by electrophoresis among specimens from Currituck Sound (North Carolina), rohere it is sympatric withMarenzelleria Type II. Salinity is discussed as an important factor for the establishment ofMarenzelleria Type I in the North Sea and Type II in the Baltic Sea.     

Does displacement of spawning time occur in the sibling species Cerastoderma edule and C. lamarcki?

The spawning cycles of the sibling species Cerastoderma edule (L.) and C. lamarcki (Reeve) were studied in allopatric and sympatric Danish populations from 1978–1980. The results do not support earlier findings of reproductive character displacement in sympatric populations of the two species. New records of hybrid formation and intermediate forms are presented and discussed.     

冀东铁矿2种恢复模式植被演替过程中群落结构及生物多样性比较研究

油松（Pinus tabulaeformis）耐低温、干旱和贫瘠,是我国北方温性针叶林中分布最广的森林群落,也是我国北方广大地区最主要的本土造林树种之一,火炬（Rhus typhina Linn.）根萌蘖力强,耐寒、耐旱、耐盐碱,是一种适应周围环境能力极强的外来引入种树种。采用空间代替时间的方法,以冀东铁矿不同年份种植的人工火炬林和人工油松林群落为研究对象,采用样方法进行调查取样,分析了2种恢复模式不同演替阶段群落结构的变化,群落动态,同时采用Pielou均匀度指数、Margalef丰富度指数、Shannon-Wiener多样性指数分析了物种多样性在群落演替过程中的动态变化,在此基础上,对比分析了2种恢复模式在生态效益方面的优劣。主要结果如下：1）短期来看,火炬可以迅速提高植被盖度,增加生物量,但是,长期来看,随着火炬的快速萌集繁殖和林分的郁闭,林下草本急剧减少,形成火炬单优群落,而不能形成稳定的顶级群落。2）短期来看,油松生长缓慢,其生态效益远小于火炬群落,但是油松群落经过11年的演替形成了乔-灌-草3层结构,群落结构逐渐完善。3）演替初期火炬群落优势种以猪毛蒿（Artemisia scoparia）、狗尾草（Setaria viridis）等耐干旱的植物为主,演替后期林下物种迅速减少以至大量消失;油松群落经过11年的恢复,群落草本层植物种数逐渐增大,从一年生先锋植物占优势过渡到以白羊草（Bothriochloa ischaemun）和硬质早熟禾（Poa sphondylodes）为建群种,并出现了黄刺玫（Rosa xanthina）和胡枝子（Lespedeza bicolor）等多年生灌木。4）演替初期Margalef丰富度指数、Pielou均匀度指数和Shannon-Wiener指数表现为：火炬群落﹥油松群落,演替后期则相反,这主要是由群落内种间竞争关系和水热环境的差异造成。4）综合植物群落盖度、物种多样性和群落未来的演替趋势,火炬长期的生态效益远不及油松树种。     

Voluntary conservation of endangered species: when does no regulatory assurance mean no conservation?

Voluntary conservation agreements are becoming increasingly important in implementing the Endangered Species Act on private land. We analyze when such agreements arise and what level of conservation they generate in the presence of uncertainty about future conservation benefits and irreversibility of habitat loss and species extinction. Our results suggest that the likelihood of an agreement and the resulting conservation levels depend on the background threat of regulation, the cost advantage offered by voluntary agreements, and the availability of assurances regarding future regulation. Under conditions likely to hold in practice, conservation agreements that offer assurances may generate higher levels of conservation and higher net social benefits than agreements that do not offer assurances. However, the resulting level of conservation will not be optimal, and may be lower than that attainable under regulation.     

Activity budgets in two species of bee flies (Lordotus: Bombyliidae,Diptera): a comparison of species and sexes

Summary This study compares time budgets of males and females of two sympatric species of bee flies, Lordotus pulchrissimus and L. miscellus. These species occur synchronously in sand dune habitat on the north shore of Mono Lake, Mono Co., California, and feed almost exclusively on the flowers of a composite shrub, Chrysothamnus nauseosus. The two closely related species, with similar ecological requirements and in an identical environment, allocate time and energy in very different ways, even when accomplishing the same ecological goals. L. pulchrissimus males and females engage respectively in aggressive interactions and feeding primarily in the morning. In contrast, L. miscellus males and females intersperse brief periods of resting with flying when defending territories and feeding, and they keep up these activities until later in the day. Similarly within species, males are involved in aggressive interactions for a shorter period each day, and females feed over a longer period. Flies in all sex-species classes but male pulchrissimus allocate their time energetically in similar ways. Male pulchrissimus spend more time each day in energetically costly activities; they engage in continuous hovering flight and intense interactions in aerial aggregations. While male miscellus feed little, male pulchrissimus spend a large portion of their time feeding, approximately as much as females, contrary to the expectation that males should be foraging-time minimizers. This study corroborates the conclusions of previous studies on bee-fly communities by showing that nectar and pollen are important resources for adult bee flies, at least for some species: Individuals of these two species spend a large proportion of their adult lifetimes feeding.     

Bayesian estimation of species relative abundances and habitat preferences using opportunistic data

We develop a new statistical procedure to monitor relative species abundances and their respective preferences for different habitat types, using opportunistic data. Following Giraud et al. (Biometrics 72(2):649–658, 2015), we combine the opportunistic data with some standardized data in order to correct the bias inherent to the opportunistic data collection. Species observations are modeled by Poisson distributions whose parameters quantify species abundances and habitat preferences, and are estimated using Bayesian computations. Our main contributions are (i) to tackle the bias induced by habitat selection behaviors, (ii) to handle data where the habitat type associated to each observation is unknown, (iii) to estimate probabilities of selection of habitat for the species. As an illustration, we estimate common bird species habitat preferences and abundances in the region of Aquitaine (France).     

Uptake of seven metals by two macrophytes species: potential for phytoaccumulation and phytoremediation

Aquatic macrophytes can be used in the studies of quality of water ecosystems and in monitoring of metals and other pollutants. The aim of this study was to assess concentration levels, accumulation and distribution of seven metals in selected plant parts of Typha angustifolia L. and Iris pseudacorus L., in comparison with sediment and water samples of a reservoir. Metal content in the samples was determined by optical emission spectrometry (ICP-OES iCAP 6500). The concentrations of all examined metals were higher in the sediment than in the water samples. In plants, metal concentrations depended on plant species and organs. The roots/rhizomes were primary organs for metal concentration and accumulation. T. angustifolia L. accumulated Mn and Cu, and I. pseudacorus L. accumulated Cd and Cu in the fruits. T. angustifolia L. hyperaccumulated As. The values of enrichment coefficients and translocation factors were: 0 to 3.31 and 0 to 2.39, respectively. The plant species investigated absorb, translocate and accumulate metals in their organs differently, which provides advantages in combining them for remediation of wasted aquatic ecosystems.     

Karyotypes in two species of the genusHippocampus (Pisces: Syngnatiformes)

Diploid modal numbers of chromosomes 2n=48 forHippocampus ramulosus and 2n=44 forH. hippocampus, collected in the Gulf of Palermo in May 1985, are established. No sex-linked heteromorphic pairs are observed in the two species analyzed. The karyotype ofH. hippocampus seems to be a derived condition.     

Lipid biochemistry and reproductive biology in two species of Gammaridae (Crustacea: Amphipoda)

Gammarus oceanicus Segerstråle, 1947 and Echinogammarus marinus (Leach, 1815) were sampled during the breeding season from Oslofjord in 1984, and their lipid composition examined in relation to reproductive condition. In G. oceanicus, female lipid content increased as the ovary matured. Both the amount of lipid stored and the rate of accumulation were greater in spring than in winter. Spring eggs contained 12.4 g lipid, of which 63% was triacylglycerol and 27% phospholipid. Both fractions decreased steadily during embryonic development. Winter eggs contained 19.2g lipid, of which 52% was triacylglycerol and 43% phospholipid. During the early stages of embryonic development the amount of phospholipid decreased sharply, whereas that of triacylglycerol increased, suggesting that some of the fatty acid released from phospholipid was sequestered temporarily as triacylglycerol. When newly spawned, both winter and spring eggs were richer in monoenoic fatty acids than adult amphipods and these acids were the major fuel consumed during development. 6 fatty acids were utilised more slowly than 3 acids, and egg carotenoid pigment content remained constant. Female E. marinus increased in lipid content as the ovary matured. Spring eggs contained 14.7 g lipid when newly spawned and this increased to 16.6 g during the early stages of development. This increase was entirely triacylglycerol, which declined in later stages; the source of the extra lipid was unclear. Eggs contained very little phospholipid or sterol, and both of these components remained at a steady low level during development. E. marinus eggs were not significantly rich in thonoenoic acids compared with adults, and saturated, monoenoic and polyenoic acids were utilised about equally during development. Both adults and eggs were rich in 20.46, which was utilised at a slower rate than the 3 polyunsaturated acids during embryonic development; again, egg carotenoid pigment content remained constant. In both species there was a decrease in the size of the egg (and as a result, of the newly hatched juvenile), but an increase in total reproductive output (i.e., the total weight of the egg clutch) per female as the breeding season proceeded. The reproductive output of an individual female is probably related to food availability during the period of ovarian maturation, whereas the size of an individual egg is dictated largely by feeding conditions for the juveniles once they are independent of the female. The different patterns of lipid utilisation during development found in this study emphasize the flexibility of response in the reproductive biology of gammarid amphipods. It is not yet possible, however, to relate the differing patterns in a simple way either to egg size or total female reproductive output. Two outstanding problems are the source of extra triacylglycerol during the early stages of development of E. marinus and the metabolic cost of brooding eggs.     

Reproductive effort and r-and K-selection in two species of Lacuna (Gastropoda: Prosobranchia)

The growth and spawning of Lacuna pallidula and L. vincta were measured in the laboratory over 7 months. In both cases, there were significant differences between the mean number of eggs per batch or weight of egg batches from females of the same species and also between rates of spawning by females of the same species. The reproductive effort of L. vincta, estimated by the ratio total spawn weight: body weight and by the time taken to exceed body weight in cumulative spawn, is approximately twice that of L. pallidula. L. vincta has a long-lived planktotrophic larva, while L. pallidula has direct, lecithotrophic development, and therefore in this instance planktotrophic development seems to be more expensive to the parent than lecithotrophic development. Published work on two Pacific seastars leads to the opposite conclusion, and it is suggested that the paradox can be resolved in terms of r-K-selection theory. In both cases, the r-selected species has a higher reproductive effort, notwithstanding that the snail is planktotrophic and the seastar lecithotrophic in development.     

Predatory behavior and chemical communication in two Metapone species (Hymenoptera:Formicidae)

Summary. Colonies of two species of Metapone (M. madagascarica, M. new species.) were collected in Madagascar and established in laboratory nests. It could be demonstrated that both species are specialist predators of termites (Cryptotermes kirbyi). During hunting the ants sting the termites and thereby paralyze and preserve the prey alive. In this way prey can be stored in the ant nest for extended periods. During foraging and colony emigrations the ants lay chemical trails with poison gland secretions. Among the seven compounds identified in the venom only methyl pyrrole-2-carboxylate elicits trail following behavior in both Metapone species. Received 11 February 2002, accepted 23 February 2002.     

Territory quality and territorial behavior in two sympatric species of hummingbirds

Summary Changes in territorial behavior of blackchinned hummingbirds (Archilochus alexandri) in response to experimental changes in territory quality were investigated using artificial feeders and simultaneous, pair-wise observations of owners. Some of the responses of A. alexandri were similar to those documented by a previous study of the Anna's hummingbird (Calypte anna): A. alexandri defending rich territories spent more time on their territories, encountered a greater percentage of intruders, and chased more intruders than did A. alexandri defending poor territories. In contrast to C. anna, A. alexandri supplemented chases with energetically inexpensive threat vocalizations more extensively when territory quality was increased. This difference may be related to A. alexandri's more tenuous control of rich territories. When both species were observed on very poor territories, A. alexandri chased a greater percentage of intruders, consumed a greater proportion of available food, and obtained a greater net energy gain from their territories. When observed simultaneously on territories with ad lib food, both species defended highly exclusive territories but A. alexandri suffered higher intrusion pressure and spent more time and energy in defense. These interspecific differences in territorial behavior may facilitate sympatric coexistence of the two species through aggressive partitioning of flower patches according to productivity: the greater payoff received by C. anna on rich territories and A. alexandri on poor territories should favor a corresponding monopolization of rich areas by C. anna and poor areas by A. alexandri.     

Uptake and elimination kinetics of triphenyltin hydroxide by two fish species

The uptake from water and the elimination of carbon‐14 radiolabelled triphenyltin hydroxide ([¹⁴C]TPTH) was studied in two fish species: guppy (Poecilia reticulata) and rainbow trout larvae (Salmo gairdneri). During all the experiments no steady state in fish was found. TPTH was rapidly taken up, while elimination was very slow. Uptake and elimination rate constants (k ₁ and k ₂, respectively), and a bioconcentration factor were estimated, assuming first order kinetics.

During eight days of exposure of guppy to TPTH an uptake rate constant k ₁ of 70±7L/kg.d and an elimination rate constant k ₂ of 0.005 ±0.029d ^‐1 was found. This resulted in a biconcentration factor of at least 2.1 × 10³L/kg (wet weight). Comparable results were obtained during a 30 days exposure experiment with guppy: k ₁ was 41±2L/kg.d, k ₂ 0.014 + 0.002d^‐1, and the bioconcentration factor was estimated to be 2.9 × 10³ L/kg (wet weight).

Four days exposure of rainbow trout larvae resulted in a it, of 22+ 2 L/kg.d, and a k ₂ of 0.031 ±0.007d^‐1. Using these k, and k ₂ values it was estimated that the biconcentration factor exceeds 650 L/kg (wet weight).