Assessment of long-term tallgrass prairie restoration in Manitoba, Canada

Ecological restoration is important in mitigating degradation and habitat loss of tallgrass prairie in North America. In 2002, we assessed the progress of a long-term tallgrass prairie restoration initiated in 1987 in southern Manitoba (Canada). Nine restoration and three reference sites were examined, as was a neighbouring site of future restoration that is now used for agriculture. Vegetation diversity, species composition, and associated soil properties were compared among restoration and reference sites, and changes associated with restoration identified. Restoration had a substantial effect on diversity and species composition, although restoration sites had significantly lower native and higher exotic diversity than reference sites. Overall and native diversity decreased over time, as both exotic and seeded native species were lost from the restoration sites. Particularly vulnerable were native forb species, which represent much of the diversity of prairie habitats. Forb presence was negatively associated with that of warm season native grasses, especially Andropogon gerardii (big bluestem). Similarity of restoration and reference vegetation increased over time, particularly for seeded native graminoids. When species that had been seeded elsewhere and had colonized restorations were examined, similarity between restoration and reference also increased with time, suggesting that older sites may be self-propagating. No significant differences in soil properties variables were observed among restoration sites, indicating that changes in these factors are slow relative to vegetation changes. Although time-since-restoration had a substantial impact on diversity and species composition, this habitat will require ongoing restoration.     

Snake species distributions and temperate grasslands: A case study from the American tallgrass prairie

Many snake species are declining globally, yet data unavailability in temperate grasslands hinders snake conservation in one of the world’s most endangered biomes. To encourage and inform the conservation of snakes in these regions, I examined snake species diversity and abundance during 2 years of a mark-recapture study at 22 sites located in six American tallgrass prairie preserves in northern Illinois, USA. I emphasized landscape-scale relationships after accounting for covariance with environmental factors at both finer (microhabitat) and broader (regional) scales. A total of 120 snakes representing seven species was captured using drift fence arrays associated with funnel traps and sheet metal cover. The low numbers and diversity of snakes captured, when compared to historic evidence, indicate that since the 1930s Midwestern snake populations have declined. Non-metric multidimensional scaling and Mantel tests demonstrate that differences in snake species composition in remnant and degraded prairies are discernable along gradients of urban and agricultural land cover. However, different patterns of abundance for individual snake species indicate that the relative importance of specific landscape factors differ among species, which has significant conservation implications. Here, I recommend that conservationists use a species-specific approach to manage snake populations. I also stress the need for thorough inventory of snake populations and studies of snake-habitat relationships to advance our understanding of snake ecology and conservation within the little studied temperate grassland habitats of South America and eastern Eurasia.     

Exploitation of Annual and Perennial Herbaceous Species for the Rehabilitation of a Sand Quarry in a Mediterranean Environment

Commercial seeds are widely used for re‐vegetation interventions in Mediterranean areas. These seeds mostly consist of species and varieties of non‐local provenance. The current practice relies mainly on forage or turf and fast growing species, even if it is often inefficient. Twenty‐two local populations or commercial varieties of annual and perennial species belonging to the botanical families Leguminosae, Graminaceae and Compositae were evaluated in a 4‐year field experiment in order to investigate their potential in terms of establishment and persistence in the re‐vegetation of an inactive sand quarry. Native species showed better performances than commercial varieties and encouraged further actions for the valorisation of local plant biodiversity. Among legumes, the best adapted species was the perennial Lotus cytisoides that showed high persistence in combination with other positive traits. A few annual species, that is, Melilotus indica, Trifolium subterraneum and Ornithopus sativus performed well and persisted until the end of the experiment. Among perennial grasses, Cynodon dactylon survived to drought and low soil nutrients. Both native annual grasses Lolium rigidum and Aegilops geniculata performed very well during the first 2 years of experiments. Both forbs, the perennial Cichorium intybus and the annual Chrysanthemum coronarium did not guarantee a satisfactory persistence. Some native species were evidenced, which may play an important role in the re‐vegetation of sand quarries and have good potential to be further characterized before introduction in the seed market. Copyright © 2013 John Wiley & Sons, Ltd.     

Labile, recalcitrant, and microbial carbon and nitrogen pools of a tallgrass prairie soil in the US Great Plains subjected to experimental warming and clipping

Carbon (C) and nitrogen (N) fluxes are largely controlled by the small but highly bio-reactive, labile pools of these elements in terrestrial soils, while long-term C and N storage is determined by the long-lived recalcitrant fractions. Changes in the size of these pools and redistribution among them in response to global warming may considerably affect the long-term terrestrial C and N storage. However, such changes have not been carefully examined in field warming experiments. This study used sulfuric acid hydrolysis to quantify changes in labile and recalcitrant C and N fractions of soil in a tallgrass prairie ecosystem that had been continuously warmed with or without clipping for about 2.5 years. Warming significantly increased labile C and N fractions in the unclipped plots, resulting in increments of 373 mg C kg⁻¹ dry soil and 15 mg N kg⁻¹ dry soil, over this period whilst clipping significantly decreased such concentrations in the warmed plots. Warming also significantly increased soil microbial biomass C and N in the unclipped plots, and increased ratios of soil microbial/labile C and N, indicating an increase in microbial C- and N-use efficiency. Recalcitrant and total C and N contents were not significantly affected by warming. For all measured pools, only labile and microbial biomass C fractions showed significant interactions between warming and clipping, indicating the dependence of the warming effects on clipping. Our results suggest that increased soil labile and microbial C and N fractions likely resulted indirectly from warming increases in plant biomass input, which may be larger than warming-enhanced decomposition of labile organic compounds.     

Historical influences on the vegetation and soils of the Martha’s Vineyard, Massachusetts coastal sandplain: Implications for conservation and restoration

Both disturbance history and previous land use influence present-day vegetation and soils. These influences can have important implications for conservation of plant communities if former disturbance and land use change species abundances, increase colonization of nonnative plant species or if they alter soil characteristics in ways that make them less suitable for species of conservation interest. We compared the plant species composition, the proportion of native and nonnative plant species, and soil biogeochemical characteristics across seven dominant land use and vegetation cover types on the outwash sandplain of Martha’s Vineyard that differed in previous soil tillage, dominant overstory vegetation and history of recent prescribed fire. The outwash sandplain supports many native plant species adapted to dry, low nutrient conditions and maintenance of native species is a management concern. There was broad overlap in the plant species composition among pine (Pinus resinosa, P. strobus) plantations on untilled soils, pine plantations on formerly tilled soils, scrub oak (Quercus ilicifolia) shrublands, tree oak (Q. velutina, Q. alba) woodlands, burned tree oak woodlands, and sandplain grasslands. All of these land cover categories contained few nonnative species. In contrast, agricultural grasslands had high richness and cover of nonnative plants. Soil characteristics were also similar among all of the woodland, shrubland and grassland land cover categories, but soils in agricultural grasslands had higher pH, extractable Ca²⁺ and Mg²⁺ in mineral soils and higher rates of net nitrification. The similarity of soils and significant overlap in vegetation across pine plantations, scrub oak shrublands, oak woodlands and sandplain grasslands suggests that the history of land use, current vegetation and soil characteristics do not pose a major barrier to management strategies that would involve conversion among any of these vegetation types. The current presence of high cover of nonnative species and nutrient-enriched soils in agricultural grasslands, however, may pose a barrier to expansion of sandplain grasslands or shrublands on these former agricultural lands if native species are not able to outcompete nonnative species in these anthropogenically-enriched sites.     

锌对不同基因型玉米缺锌后的恢复效果及胚乳在缺锌中的作用

用溶液培养法研究不同Zn浓度对玉米缺Zn后恢复效果及胚乳在缺Zn中作用结果表明,不同基因型玉米缺Zn后恢复所需的适宜Zn浓度不同,敏感品种比非敏感品种要求更高的Zn浓度。缺Zn后恢复所需适宜Zn浓度高于正常培养所需适宜Zn浓度,低浓度Zn(0.1μmol/L)无恢复作用(生物量)。带上胚乳使敏感品种在缺Zn、低Zn下受抑程度(缺Zn与供Zn生物量差值)提高,而非敏感品种受抑程度反而减小。缺Zn与低Zn培养时体内P含量提高,胚乳可缓解这种影响。缺Zn后再供Zn可使体内Zn含量提高,而P含量降低,玉米对Zn产生奢侈吸收,使体内Zn含量超过正常供Zn水平,表明缺Zn后植物对Zn的要求提高。0.1μmol/L Zn恢复对“吉单120”玉米Zn含量无明显影响,但“辽单22”玉米Zn含量显著提高,这表明非敏感品种比敏感品种利用低Zn的能力更强。     

Effects of microsite, water, weeding, and direct seeding on the regeneration of native and alien species within a Hawaiian dry forest preserve

Tropical dry forests are among the most endangered ecosystems in the world in general and in Hawaii in particular. To investigate the regeneration ecology of native and alien dry forest species on the island of Hawaii, we used a factorial experiment with microsite (sub-canopy vs. inter-canopy), water (supplemental vs. ambient), and weeding (alien species removed vs. not removed) treatments, and also seeded six native woody species into each plot at the start of the experiment. At the end of the 21-month study, the biomass of the volunteer native and alien species (i.e. unplanted species consisting mainly of relatively fast-growing shrubs) was nearly three and 13 times that of the seeded species, respectively. The biomass of the native volunteers was greater in the inter-canopy plots, greater for the seeded species in the sub-canopy plots, and did not differ significantly within this treatment for the alien species. Few species survived in the ambient water plots, resulting in greater biomass in the watered plots for all species. There were no significant differences in the biomass of the native species within the weeded vs. non-weeded plots; on the contrary, we found consistently positive correlations between the abundance of the seeded species and the volunteer native and alien species. Thus it may be possible to restore Hawaii's degraded dry forests by manipulating these naturally recruiting species to create microsites favorable for the eventual re-establishment of the endangered native canopy tree flora.     

退化喀斯特植被恢复对土壤微生物数量及群落功能多样性的影响

采集不同恢复阶段的土壤样品,采用微生物培养法研究了退化喀斯特植被恢复对土壤微生物数量、群落功能多样性的影响。研究结果表明随着退化喀斯特植被的恢复,土壤微生物数量增加,表现为乔木群落阶段灌木群落阶段草本群落阶段裸地阶段。土壤微生物群落代谢功能分析表明:植被恢复往往导致较高的平均颜色变化率、物种丰富度和功能多样性。乔木群落阶段的平均诱导底物利用率最高,明显地与其他3个恢复阶段不同。总之,植被恢复使得土壤微生物数量增加,碳源平均利用率增强。因此,创造了更好的土壤条件更有利于退化喀斯特植被的恢复。     

Effects of habitat degradation on the abundance, richness and diversity of raptors across Neotropical biomes

Population growth and human development result in biodiversity loss and biological homogenization not only in developed countries, but increasingly in the less developed countries as well. In those countries, where urbanization and agricultural intensification occur at a faster rate than in developed countries, habitat degradation appears to be the leading cause of wildlife loss. During the breeding seasons of 2002–2005 we conducted road surveys across five biomes of Argentina to detect variations in raptor community attributes as potential indicators of broad scale habitat degradation. Abundance of individuals, richness and diversity of species were calculated to assess the effects of habitat transformation and patch size on these community attributes. Raptor communities strongly varied in relation to habitat transformations, with lower abundance of individuals, richness and diversity of species in more transformed landscapes. Small patches of natural vegetation and locations in which natural and cultivated lands where interspersed showed lower richness and diversity of raptors than large patches. Fragmentation was the main cause of reductions in abundance of individuals. Although the relative contribution of our two estimates of habitat degradation to abundance, richness and diversity of raptors varied among biomes, these community attributes proved useful as predictors of habitat degradation. This was especially true in habitats where raptor communities are more complex although overall patterns remained constant across biomes, from forests to deserts. Taking into account current trends of habitat transformation (drastic increments in monocultures, urban areas, and habitat patchiness), the conservation of raptor communities in these biomes could be seriously compromised. In terms of species-specific responses of raptors to habitat degradation, a rapid process of homogenization can be expected, resulting in only a few winner species within a general scenario of losers.     

施氮量与栽插密度对超级早稻中早22产量的影响

以超级早稻中早22为材料,采用裂区设计,研究了不同施氮量与栽插密度组合对其产量的影响.结果表明,施氮量和栽插密度及其互作对产量的影响均达显著水平.在中、低施氮水平下,不同密度间产量差异很小,而在高氮水平下,适当降低密度有利高产.在0～195 kg/hm<'2>施氮范围内,有效穗数、生物产量、产量、氮素积累总量、最高茎蘖...     

Management effects on the vegetation and soil seed bank of calcareous grasslands: An 11-year experiment

Calcareous grasslands, most of which are man made and therefore depend on some kind of human interference for their maintenance, are among the most species-rich communities on Earth at a small scale. For many centuries, most of these grasslands have been used as extensive pasture. However, after 1900, and particularly from 1940 onwards, livestock grazing has declined throughout Europe leading to the abandonment of low intensity grasslands over large areas. To conserve the remaining grasslands or to restore recently abandoned grasslands, better insights about the effects of grassland management on above and belowground species diversity are needed. Here, we describe the results of an 11-year experiment to investigate the role of grassland management (grazing, mowing and abandonment) in determining species composition and diversity both in the aboveground vegetation and the seed bank of a calcareous grassland in Belgium. Species diversity declined by about 60% 11 years after abandonment, from 29 species m⁻² to as few as 12 species m⁻². Plots that were grazed remained constant in species richness, whereas mown sites lost about 20% of their original species. Abandoned plots were largely dominated by a few grass species, in particular Festuca rubra. Concomitant with changes in the aboveground vegetation, both the number of species found in the seed bank and seed density (number of seeds m⁻²) had changed significantly 11 years after abandonment. Species diversity and seed density were significantly lower in abandoned plots than in grazed or mown plots. We conclude that abandonment of calcareous grasslands may lead to rapid decline of plant species diversity both in the aboveground vegetation and in the seed bank. As a result, seed banks probably have a limited role to play in the restoration of recently abandoned grasslands.     

不同禾本科牧草与组合秸秆混合饲料的营养特性及利用效率研究

利用体外产气技术研究了青贮玉米秸秆与稻秆组合(50∶50)与7种禾本科牧草二次组合时体外发酵特性。结果表明,不同比例组合产气量、理论最大产气量、产气速率及产气延滞时间变化趋势不同;青稻与皇竹草或黑麦草按25∶75的比例组合时的组合效应明显好于其他组合;粗蛋白及中性洗涤可溶物与产气量及产气速率间极显著(P<0.001)正相关,而中性洗涤纤维及酸性洗涤纤维则与之呈极显著(P<0.001)的负相关关系。生产实践中应针对低质粗饲料营养特性,适当添补易发酵或高蛋白牧草,提高粗饲料利用效率。     

种植密度和播种方式对盐碱地花生生长发育、产量及品质的影响

以耐盐品种‘花育25号’为材料,通过田间小区试验,设置18.0万穴·hm~(-2)(M1)、19.6万穴·hm~(-2)(M2)、21.4万穴·hm~(-2)(M3)、23.5万穴·hm~(-2)(M4)、26.0万穴·hm~(-2)(M5)5个单粒精播播种方式下的种植密度和双粒穴播播种方式下的11.6万穴·hm~(-2)(M6)、13.0万穴·hm~(-2)(M7)、14.7万穴·hm~(-2)(M8)3个种植密度,研究种植密度和播种方式对盐碱地花生主要农艺性状、产量和品质的影响,探讨盐碱地花生适宜的种植密度和播种方式。结果显示,1)土壤盐碱胁迫较大程度地抑制了花生植株的生长发育,与非盐碱地花生相比,盐碱地花生主茎高和侧枝长明显降低,仅分别为25.6 cm和29.0 cm左右。2)单粒精播方式下,在19.6~26.0万穴·hm~(-2)范围内,主茎高和侧枝长在饱果期前随种植密度的增加显著降低;荚果膨大前和饱果期后,单粒精播方式下一、二次分枝数显著高于双粒穴播,且在M2~M4密度范围内,其基部茎长随密度增大而缩短但差异不显著。基部茎长和茎粗的变化主要发生在结荚期前,且以茎的伸长速度快于横截面积增大速度,生育后期基部茎长和茎粗均趋于稳定。3)盐碱地花生叶片和茎+叶柄光合产物快速积累期主要在花针期和荚果膨大期,叶片最大生长速率(Vm)只有茎+叶柄Vm的一半,叶片快速生长早于茎+叶柄5 d左右,且双粒穴播方式下叶片和茎+叶柄最大生长速率出现的时间(Tm)明显滞后于单粒精播方式。单粒精播方式下盐碱地花生地上部营养器官Vm随种植密度增加表现为"抛物线型"变化,M4处理下的叶片和茎+叶柄的Vm最大,分别为0.492 5 g·株-1和0.878 3 g·株-1。4)种植密度对盐碱地花生各生育时期光合产物的积累影响较为显著,但对各时期各器官中分配率的影响差异较小。盐碱地花生光合产物分配规律与非盐碱地花生基本一致,生育前期光合产物主要分配在茎和叶片等营养器官中,至饱果期约1/3以上的光合产物分配于荚果中。5)种植密度对单粒精播方式下荚果产量有显著影响,但对各处理下的籽仁可溶性糖、蛋白质、脂肪和油酸/亚油酸(O/L)等影响不大。中轻度盐碱土区,采用单粒精播的播种方式时,适宜的种植密度为19.0~23.5万株·hm~(-2)。     

Experimental analysis of the effect of exotic and native plant species on the structure and function of soil microbial communities

Invasions of exotic plant species are among the most pervasive and important threats to natural ecosystems, however, the effects of plant invasions on soil processes and the soil biota have rarely been investigated. We grew two exotic and a native under-story plant species in the same mineral soil from a non-invaded forest stand in order to test whether observed differences in the field could be experimentally produced in the greenhouse. We characterized changes in the soil microbial community structure (as indexed by PLFAs) and function (as indexed by enzyme activities and SIR), as well as changes in potential nitrogen mineralization rates. We found that the invasion of two very dissimilar exotic species into the under-story of deciduous forests in eastern North America can rapidly cause changes in most of the studied soil properties. At the end of the three-month incubation, soils under the exotic species had significantly different PLFA, enzyme and SIR profiles than both initial soils and soils where native shrubs had been grown. We also observed a significant increase in pH and nitrification rates under one of the exotic plants. Such changes in the soil are potentially long-term (e.g. changes in soil pH) and are therefore likely to promote the re-invasion of these and other exotics. Both management of exotic plant invasions and the restoration of native communities must take into account exotic species effects on the soil.     

Mixed-species bird flocks from Brazilian Atlantic forest: the effects of forest fragmentation and seasonality on their size, richness and stability

The effects of forest fragmentation on species richness, size and stability of bird mixed-species flocks were studied during rainy and dry seasons at nine Atlantic Forest fragments in Minas Gerais state, southeastern Brazil. Two distinct kinds of mixed-species flocks were identified at the study area: heterogeneous flock and understory flocks. The first type of association was observed in all forest fragments and was composed mainly of canopy and midstory species, but may include a few understory species. Understory flocks were composed mainly of understory species and were detected in only three forest fragments. Forest fragment area and season significantly affected species richness, size and stability of heterogeneous flocks. Moreover, species richness in heterogeneous flocks was correlated with total species pool in forest fragments. Species richness and size of understory flocks were different among the three forest fragments, but season influenced only flock size. Understory flock stability differed neither among forest fragments nor between seasons. The red-crowned ant-tanager Habia rubica was the nuclear and leader species of understory flocks, and determined the occurrence of this association in forest fragments. Our results show that forest fragmentation can affect species’ interactions in foraging associations, and that conservation plans for the region should preserve nuclear species of mixed-species flocks and their preferred habitats.     

谷豆分带种植对谷子生理过程的影响

谷豆分带种植,能改变田间小气候,使气温升高,光照增强,CO₂浓度增大,从而引起谷子体内一系列 生理变化,扩大了绿叶面积,减小了气孔阻力,有利于光合作用和蒸腾作用的进行;促进了呼吸作用,加强了根系活性,提高了植株对光能和水分的利用率;增加了体内干物质积累量,加速了物质向穗部运转,提高了收获指数,因而能高产高效。     

Effects of removing the litter and humic layers on heathland establishment following plantation removal

We investigated ways of optimising the establishment of Calluna vulgaris-dominated heathland vegetation following removal of pines from afforested heathland using a randomised block experiment. Removal of the litter layer, or both the litter and humic layers, resulted in a higher initial establishment rate of C. vulgaris compared to in the control plots. The effect of adding heathland clippings suggested that the rate of establishment of C. vulgaris was limited by seed availability in plots from which both the litter and humic layers had been removed, but not in those from which just the litter layer had been removed. Removal of both the litter and humic layers did, though, result in a long-term reduction in the depth of the humic layer, a lower loss-on-ignition and lower level of nitrate and total nitrogen compared to in the control plots. The optimal method for establishing heathland vegetation at a site will depend on: (1) whether there is a viable seedbank of C. vulgaris and other desirable heathland species present; (2) the importance of quickly establishing a high cover of desirable heathland species; (3) the likely long-term effects of soil nitrogen levels on the maintenance of C. vulgaris dominance; (4) the practicality of removing and disposing of the litter and humus layers.     

Effects of land management on the abundance and richness of spiders (Araneae): A meta-analysis

Human land use, through forest management and conversion of natural habitats into agroecosystems, has often resulted in loss of biodiversity. Spiders are important predators in terrestrial ecosystems, biological control agents against pests in agroecosystems and forests, and useful indicators due to their sensibility to changes in habitat structure and microclimate. Effects of land use on spiders have been reviewed several times but existing reviews are narrative and usually focused on one single kind of management. We summarize the impacts of land use on spider abundance and species richness using meta-analysis. The main ecosystems where the effect of management on spiders has been studied were forests, agroecosystems and rangelands (including meadows and grasslands). Although our survey retrieved studies from all parts of the world and climatic zones, a dominance of studies from temperate habitats in Europe and North America was evident. The meta-analysis showed negative effects on spider species richness and abundance for agroecosystems and rangelands, but were less evident for forests. From 10 kinds of land management identified, all but forest plantation showed effects on spider richness or abundance. These land management scenarios affected either species richness (forest fragmentation and logging, farmland abandonment, and miscellaneous management including plowing, cutting and fire), or spider abundance (forest fragmentation, forest fire, conventional farming, insecticides, grazing, and farmland abandonment), but not both. Edge effects had contrasting effects depending on the ecosystem, affecting spider species richness in agroecosystems and abundance in rangelands and forests. Direct destruction of spiders or negative effects on habitat heterogeneity or prey populations were the most likely causes of the negative effects detected.     

基于主导功能的国土空间生态修复分区的原理与方法

国土空间规划是统筹区域资源开发利用和生态保护格局、促进空间治理体系现代化、服务生态文明建设和国家现代化战略的重大举措,国土生态修复是针对区域空间格局失调、资源利用低效、生态功能受损的国土空间进行综合整治与生态修复的活动和过程,是编制和实施国土空间规划的重点内容,生态修复分区则是合理编制国土空间生态修复规划和科学高效开展生态修复的重要前提。通过分析区域国土、生态、经济等主导功能的分区定位与内涵特征,依据“生命共同体理论”、“三生协调理论”、“适宜性管理”等国土空间规划与生态文明建设的基本理论,基于“自上而下”和“自下而上”相结合,提出了基于主导功能型区划的国土空间生态修复分区的思路与方法：1）摸清自然资源本底,完成一级生态功能基础分区;2）评价区域生态功能状况,完成二级生态修复格局分区;3）明确生态修复重点区域,完成三级生态修复模式分区。通过在江西省国土空间生态修复分区进行实践应用,可将江西省生态修复区划分为5个大区,以及24个亚区、70个修复小区,研究可为江西实施生态修复工程和国土空间管治提供决策依据。该方法归纳起来有以下4点特征：一是突出主导功能;二是遵循生态规律;三是适配空间尺度;四是强化上下衔接。研究对于国土空间生态修复规划编制、实施和生态管控具有积极的意义,可为国土空间整体保护、系统修复、综合整治与推进美丽中国建设提供科技支撑。