The restoration of species-rich heathland communities in the Netherlands

The wet heathland communities of the Ericetum tetralicis and the Cirsio-Molinietum have declined in the Netherlands due to acidification, eutrophication and lowering of the water table. To investigate the prospects of restoration of both communities, the effects of sod cutting and hydrological measures on vegetation and soil chemistry were studied in two nature reserves where these plant communities occurred decades ago. The combination of sod cutting and hydrological measures has restored several rare, groundwater dependent heathland communities. Sod cutting has restored the Ericetum tetralicis, but not the Cirsio-Molinietum. This might be due to the absence of viable seeds of characteristic species of the Cirsio-Molinietum and/or the absence of optimal site conditions, especially high phosphorus concentrations in the top soil. The high phosphorus concentrations might be a consequence of high mineralization rates and/or prolonged inundation with iron-poor water and the decreased flux of iron-rich groundwater into the topsoil. Restoration of the Cirsio-Molinietum only seems possible when sod cutting is carried out together with hydrological measures that counter prolonged inundation and reinforce the discharge of base and iron-rich groundwater.     

哈泥泥炭地落叶和常绿两类灌木对氮磷输入增加响应的对比

大气氮沉降及磷输入正影响泥炭地的生态过程,而其重要植物成分灌木对氮磷输入如何响应尚鲜有研究。在哈泥泥炭地,通过连续6年的人工氮、磷添加后对3种落叶灌木和3种常绿灌木生长状况进行测定,研究泥炭地两种类型灌木对氮磷输入的响应。落叶灌木(多度和盖度下降,高度上升)与常绿灌木(多度、盖度和重要值下降)对氮输入增加的响应存在差异,对磷输入增加的响应一致。从物种的角度看,存在种间差异,施氮抑制落叶灌木金露梅和笃斯越桔的生长,其多度和盖度均下降,对落叶灌木油桦有促进作用,使其高度、盖度和重要值增加。施氮仅对常绿灌木甸杜产生了影响,降低了其多度和重要值,对常绿灌木小叶杜鹃和狭叶杜香无影响。施磷缓解了部分灌木的养分限制,提高了落叶灌木油桦的盖度、常绿灌木小叶杜鹃的高度和重要值以及常绿灌木甸杜的多度。同时,氮磷对落叶灌木存在交互作用,未施氮肥和低浓度施氮时,施磷对落叶灌木的高度和重要值无影响,在高浓度施氮情况下,施磷使落叶灌木的高度和重要值增加,即氮和磷只有在一定比例下才会促进灌木植物的生长。研究表明,氮磷输入可影响泥炭地灌木间的竞争平衡,使落叶灌木油桦获得生长优势,抑制其他灌木的生长,进而对泥炭地的植被格局产生深远影响。     

森林土壤氮素可利用性的影响因素研究综述

近几十年来 ,人类对木材、纤维和其他森林资源需求的急剧增加 ,对森林的集约化经营管理成为必然趋势。由于大部分森林生态系统缺乏Ｎ素 ,因此施肥成为经济有效的途径。但是 ,由于森林中的Ｎ肥利用效率低于农业系统 ,且Ｎ肥生产成本较高 ,易造成环境中多余Ｎ素的污染 ,所以需要更有效的经营管理方法。要改进这类方法 ,则必须很好地理解全球各种森林生态系统的Ｎ素循环和Ｎ素可利用性[3 1] 。可利用性养分 (ａｖａｉｌａｂｌｅｎｕｔｒｉｅｎｔ)是指土壤中易被植物吸收同化的养分元素或化合物的数量[4 0 ] ,可以理解为植物利用土壤中易吸收和…     

Water use efficiency and carbon isotope composition of plants in a cold desert environment

Summary The effects of the availabilities of water and nitrogen on water use efficiency (WUE) of plants were investigated in a sagebrush steppe. The four species studied wereArtemisia tridentata (shrub),Ceratoides lanata (suffrutescent shrub),Elymus lanceolatus (rhizomatous grass), andElymus elymoides (tussock grass). Water and nitrogen levels were manipulated in a two-by-two factorial design resulting in four treatments: control (no additions), added water, added nitrogen, and added water and nitrogen. One instantaneous and two long-term indicators of WUE were used to testa priori predictions of the ranking of WUE among treatments. The short-term indicator was the instantaneous ratio of assimilation to transpiration (A/E). The long-term measures were 1) the slope of the relationship between conductance to water vapor and maximum assimilation and 2) the carbon isotope composition (¹³C) of plant material. Additional water decreased WUE, whereas additional nitrogen increased WUE. For both A/E and ¹³C, the mean for added nitrogen alone was significantly greater than the mean for added water alone, and means for the control and added water and nitrogen fell in between. This ranking of WUE supported the hypothesis that both water and nitrogen limit plant gas exchange in this semiarid environment. The short- and long-term indicators were in agreement, providing evidence in support of theoretical models concerning the water cost of carbon assimilation.     

源库比改变对玉米生育后期茎鞘贮存物质含量及产量的影响

通过对吐丝授粉期两种密度条件下的两个不同类型玉米品种剪1／2叶、剪1／2穗和断1／2根的研究发现：剪叶、断根减源后植株体内可溶性糖浓度下降2．19％～38．6％,剪穗缩库后可溶性糖浓度上升23．17％～38．5％,而单株生产力降低4．1％～40．94％。试验表明：玉米产量的形成与源库关系的协调性有关。     

An Exotic Tree Alters Decomposition and Nutrient Cycling in A Hawaiian Montane Forest

We evaluated the effects of the exotic tree Fraxinus uhdei on decomposition dynamics and nutrient turnover in a montane Hawaiian rainforest. We used reciprocal transplants of litterbags between forests dominated by Fraxinus and by the native Metrosideros polymorpha to distinguish between endogenous (litter quality) and exogenous (for example, microclimate, nutrient availability, microbial and invertebrate communities) effects of Fraxinus on mass loss and nutrient dynamics of decomposing litter. Fraxinus produced greater quantities of litter that was thinner, had higher N and P concentrations, and lower concentrations of lignin and soluble polyphenols. Microbes decomposing Fraxinus litter produced fewer enzymes involved in N and P acquisition and more of those involved in cellulose degradation. Differences in litter quality and microbial activity resulted in a strong effect of litter type on rates of mass loss, whereby Fraxinus litter decomposed and released nutrients at nearly twice the rate of Metrosideros litter (k=0.82 versus 0.48), regardless of site of decomposition. Although site of decomposition had no effect on rates of litter mass loss, Fraxinus litter decomposed under a Fraxinus canopy mineralized approximately 20% less P after one year than Fraxinus litter decomposed under a Metrosideros canopy. Furthermore, Fraxinus litter decomposed under a Fraxinus canopy immobilized greater amounts of N and P in the early stages of decay, suggesting that the large amounts of N and P in Fraxinus litterfall have raised nutrient availability to decomposers in the forest floor. Greater immobilization of N and P under a Fraxinus canopy may act as a governor on rates of nutrient cycling, limiting the degree to which Fraxinus invasion accelerates N and P cycling in this system.     

Use of wild and cultivated foods by chimpanzees at Bossou,Republic of Guinea: feeding dynamics in a human‐influenced environment

Increased human population growth and more conversions of natural habitat to agricultural land have resulted in greater proximity between humans and nonhuman primate species. Consequent increases in resource competition including crop‐raiding are a by‐product of both natural resources becoming less available and the nutritional benefits of cultivated foods becoming more known to the nonhuman primates. Chimpanzees at Bossou in the Republic of Guinea, West Africa, consume 17 different types of cultivated foods that are grown extensively throughout their small, fragmented home range. Direct observations of feeding behavior conducted over an 18‐month period revealed that during specific months crops account for up to one quarter of chimpanzee feeding time, with higher overall crop‐raiding levels throughout the periods of wild fruit scarcity. Some cultivated foods, especially sugar fruits, are mostly fallback foods, whereas others, such as rice pith (Oryza sp.) and maize (Zea mays), are consumed according to their availability even when wild foods are abundant. These findings highlight the importance of both crop choice by farmers and a thorough understanding of the ecology of resident primate species when establishing land management techniques for alleviating human–primate conflict. Am. J. Primatol. 71:636–646, 2009. © 2009 Wiley‐Liss, Inc.     

Adaptation of plant‐mycorrhizal interactions to moisture availability in prairie restoration

The strength and direction of plant response to inoculation with arbuscular mycorrhizal fungi (AM fungi) is dependent on both abiotic and biotic contexts, often generating patterns of AM fungal mediation of plant adaptation. However, knowledge of plant‐community level effects of these interactions in grassland restoration is limited. We conducted a field inoculation experiment by inoculating five plant species native to a drier prairie and five plant species native to a moister prairie with mycorrhizal fungal communities from each prairie type. Species were paired by genus or family to account for phylogenetic effects. The inoculated plants were transplanted to study plots seeded with a restoration seed mix. Plots were manipulated to create either moister or drier conditions similar to environments of the plant species and mycorrhizal communities. In both transplanted and seeded plant species, we found that only drier prairie‐range species benefited from moisture‐regime matched AM fungal inoculum. Other seeded prairie plant species demonstrated a negative response to inoculation, likely due to the earlier successional stage of these species. Additionally, nonseeded plants benefited from inoculation in different ways: native nonseeded plants had highest cover with drier prairie inoculum in drier conditions, while nonnative plants had highest cover with moister prairie‐origin inoculum. These results suggest that use of local AM fungi may be particularly important in restorations at drier sites, even at relatively small differences in moisture availability. Further, specific knowledge of relative responsiveness of seeded plant species and nonseeded plant species to AM fungal inoculation will be useful in planning restorations.     

Seasonal life cycles and resource uses of flower- and fruit-feeding drosophilid flies (Diptera: Drosophilidae) in central Japan

Seasonal life cycles and resource uses of flower- and fruit-feeding drosophilids (Diptera: Drosophilidae) were studied from low to high altitudes in central Japan to understand their adaptation to seasonal changes of environmental conditions. Drosophila unipectinata and D. oshimai specialized to flowers, D. suzukii and D. subpulchrella depended almost on fruits, while D. lutescens , D. rufa , D. auraria , D. biauraria and D. sternopleuralis used both of them. It was assumed that D. unipectinata moved from low to high altitudes in June while D. oshimai , D. suzukii and D. subpulchrella in July. Migration of D. unipectinata is considered as a means to avoid summer heat or exploit early-summer resources at high altitudes. On the other hand, D. oshimai , D. suzukii and D. subpulchrella have the capacity to pass the summer at low altitudes, and therefore their migration is assumed as a means to escape from resource-poor conditions in summer at low altitudes or exploit resources at high altitudes. The generalist species, D. lutescens , D. rufa , D. auraria , D. biauraria and D. sternopleuralis , would not perform such extensive movements between low and high altitudes. They may pass the summer at low or mid altitudes depending on accidentally fallen immature fruits and/or some other resources such as decayed leaves.     

森林采伐方式对森林景观的影响模拟——以大兴安岭呼中林区为例

干扰对森林景观变化的影响是一个长期的过程,传统的定位观测很难探究大空间尺度上干扰对森林景观的长期影响,模型模拟是目前常用的研究方法.本研究采用空间直观景观模型(LANDIS),模拟大兴安岭呼中林区在无采伐、皆伐、渐伐和择伐共4种预案下300年内森林景观的长期动态变化.选取落叶松和白桦为典型代表,以平均斑块面积、物种面积比例、聚集度以及年龄结构为指标,探讨不同采伐方式对森林景观的长期影响.结果表明:采伐降低了落叶松的面积比例,提高了白桦的面积比例,不同采伐方式之间差异不明显;采伐降低了落叶松的聚集度,提高了白桦的聚集度,皆伐预案高于其他预案;采伐在模拟前期降低了落叶松的平均斑块面积,提高了白桦的平均斑块面积;采伐提高了落叶松和白桦的中幼龄林比例,皆伐预案下白桦中幼龄林面积增加最明显.采伐使森林生态景观破碎化,皆伐预案下森林景观破碎化最为严重.建议,在采伐强度相同的条件下,尽量采用择伐方式,降低森林采伐对森林生态系统的影响,进而促进森林生态系统健康稳定的发展.     

Resource availability,mating opportunity and sexual selection intensity influence the expression of male alternative reproductive tactics

The expression of alternative reproductive tactics can be plastic and occur simultaneously depending on cues that vary spatially or temporally. For example, variation in resources and sexual selection intensity is expected to influence the pay‐off of each tactic and shape the decision of which tactic to employ. Males of the nuptial gift‐giving spider Pisaura mirabilis can adopt three tactics: offering a genuine prey gift, a ‘worthless’ non‐nutritious gift or no gift. We hypothesized that resources and/or male body condition, and mating opportunity and sexual selection intensity, vary over the course of the mating season to shape the co‐existence of alternative traits. We measured these variables in the field over two seasons, to investigate the predictions that as the mating season progresses, (i) males become more likely to employ a gift‐giving tactic, and (ii) the likelihood of switching from worthless to genuine gifts increases. Prey availability increased over the season and co‐varied with the propensity of males to employ the gift‐giving tactic, but we found no support for condition‐dependent gift giving. Males responded to an increase in female availability by increasing their mating effort (gift production). Furthermore, the frequency of genuine gift use increased with sexual selection intensity, consistent with the assumption that sperm competition intensity increases with time. Our results suggest that the frequency of alternative tactics is shaped by seasonal changes in ecological factors and sexual selection. This leads to relaxed selection for the gift‐giving tactic early in the season when females are less choosy and resources more scarce, and increased selection for genuine gifts later in the season driven by mating opportunity and risk of sperm competition.     

Dispersal patterns of an Australian gall-forming thrips and its host tree (Oncothrips tepperi and Acacia oswaldii )

Abstract. 1. Clark and Evans' nearest-neighbour method was used to evaluate the distribution pattern of Acacia oswaldii and Oncothrips tepperi populations.
2. A random distribution pattern was supported statistically for both the host trees and trees that were parasitised by O. tepperi .
3. It is therefore likely that dispersal distances of colonising thrips are large enough to be able to traverse the 1 km² study site.     

Effects of oxygen concentration during incubation and broiler breeder age on embryonic heat production,chicken development,and 7-day performance

Older breeder flocks produce eggs with a relatively larger yolk and thereby a higher nutrient availability than young breeder flocks. To optimise nutrient utilisation and embryonic development throughout incubation and posthatch period, embryos originating from older breeder flocks may require a higher oxygen availability. The current study investigated effects of broiler breeder flock age and incubational oxygen concentration on embryonic metabolism and chicken development until 7-day posthatch. Similar sized eggs of a young (28–32 week) or old (55–59 week) Cobb 500 breeder flock were incubated at one of three oxygen concentrations (17%, 21% or 25%) from day 7 of incubation until 6 h after emergence from the eggshell. Posthatch, chickens were reared until 7 days of age. Egg composition at the start of incubation, heat production during incubation, and embryo or chicken development at embryonic day (ED)14 and ED18 of incubation, 6 h after hatch and day 7 posthatch were evaluated. An interaction was found between breeder age and oxygen concentration for yolk-free body mass (YFBM) at ED18. A higher oxygen concentration increased YFBM in the old breeder flock, whereas no difference was found between 21 and 25% oxygen in the young breeder flock. Yolk size was larger in the old compared to the young flock from ED0 until 6 h after hatch. Breeder flock age did not affect YFBM at ED14 and 6 h after hatch nor daily embryonic heat production, but there were some effects on relative organ weights. Chickens of the old compared to the young breeder flock showed a higher weight gain at day 7, but at a similar feed conversion ratio (FCR). A higher oxygen concentration during incubation stimulated embryonic development, especially between 17% and 21% of oxygen, in both flock ages_. Although this growth advantage disappeared at 7 days posthatch, a low oxygen concentration during incubation resulted in a higher FCR at 7 days posthatch. Results indicated that breeder flock age seemed to influence body development, with an advantage for the older breeder flock during the posthatch period. Oxygen concentrations during incubation affected body development during incubation and FCR in the first 7 days posthatch. Although an interaction was found between breeder flock age and oxygen concentration at ED18 of incubation, there was no strong evidence that nutrient availability at the start of incubation (represented by breeder flock ages) affected embryo and chicken development at a higher oxygen concentration.     

The influence of plants on concentration and fractionation of Zn, Pb, and Cu in salt marsh sediments (Tagus Estuary, Portugal)

Sediment cores were collected from two sites of the Tagus estuary salt marshes which differed in degree of metal contamination. At each site, six 60-cm-long cores were taken, three from a non-vegetated intertidal zone, and one from each of areas colonized by salt marsh plants, Spartina maritima, Halimione portulacoides and Arthrocnemum fruticosum, respectively. Total concentrations and concentrations in sequential extractions of Zn, Pb, and Cu were determined in several sediment layers. Sediment slices containing most of the roots (5–15-cm depth) were enriched in metals in comparison with other depths in the core and with non-vegetated cores. Additionally, metals in sediment slices with roots were preferentially linked to the residual fraction. These results are evidence that aquatic plant roots can have a strong influence on metal concentration and speciation in sediments. Since metals become immobilized in vegetated sediments, the preservation of salt marshes or the creation of artificial wetlands could be considered as an efficient natural means for maintaining ecosystem health or restoring ecosystem quality.     

A Dynamical Model of Biological Population Under the Variation of Resource and Its Numerical Analysis

1IntroductionTheLogisticequationofpopulationgroanisaclassicalmodeld~bingthePOPulationdy~cs,itisconSiderasthefundamentalthaiofPOPulationd~cs(May,1974).Inthebeisticmodel,thegrowth~ourofpopulationdependsonthebiolodedspeCies'intrinsicrateofincreaseandthe~lugCapaCityofenvironxnent.Therearetwoqueshonswoadinvestigatingfabler.First,dasapopulationreachitSintrinsicrateonlywhenthePOPulatonsizeisequaltozero?hand,isthe~lugcapadtyofenvironmentaconStantwhichcanbedet~nedinadvance?Infact,anypopulationc…     

Effects of microplastics and biochar on soil cadmium availability and wheat plant performance

Biochar is a promising amendment to promote cadmium (Cd) sorption and fixation in agricultural soil, where microplastics are emerging contaminants in soil. Herein, a greenhouse pot experiment was conducted to elucidate the effects on Cd availability in a soil–plant system by biochar and fresh/aged microplastics application. The fresh microplastics led to an obvious increase in soil Cd availability and Cd uptake by wheat plant, while the aged microplastics increased the available Cd in soil but had no effect on Cd uptake by wheat plant, which was likely attributed to the blocking effect of the aged microplastics on Cd transportation from the soil to the wheat plant. Unexpectedly, biochar had increased Cd availability and Cd uptake. The increased soil soluble Cd was because of both decreased soil pH and elevated dissolved organic matter (DOM) content resulted by biochar addition. Also, the unchanged Cd adsorption of the soil was likely responsible for the increased tested soil Cd availability. In addition, the combined effects of a greater decrease in soil pH, an increase in soil DOM content, and a reduction in Cd adsorption after the addition of microplastics to biochar-amended soil resulted in a significant increase (ranging from 2.63% to 47.73%) in Cd availability compared to soil treated with biochar alone. Moreover, fresh microplastics inhibited wheat growth, and greater inhibition effect was observed for their aged ones. The biochar elevated the wheat biomass; however, the coexistence of microplastics and biochar decreased the wheat plant biomass compared with biochar alone, due to the negative influence of microplastics in plant growth.     

Evolution of Mating Systems in Island Populations of Campanula microdonta: Pollinator Availability Hypothesis

Abstract Island populations of Campanula microdonta and mainland Honshu populations of C. punctata have several different mating systems: self-incompatible (SI) and therefore obligately outcrossing in mainland Honshu and Oshima Island; self-compatible (SC) and largely outcrossing in the northern islands of Toshima and Niijima; and SC and predominantly inbreeding southern ones of Miyake and Hachijo. Several features possibly associated with the mating systems are described. A hypothesis is proposed that the mean and variance of pollinator availability together with inbreeding depression could explain the observed patterns of mating system as the results of evolution.