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1.
We studied the relationships among plant and arbuscular mycorrhizal (AM) fungal diversity, and their effects on ecosystem function, in a series of replicate tropical forestry plots in the La Selva Biological Station, Costa Rica. Forestry plots were 12 yr old and were either monocultures of three tree species, or polycultures of the tree species with two additional understory species. Relationships among the AM fungal spore community, host species, plant community diversity and ecosystem phosphorus-use efficiency (PUE) and net primary productivity (NPP) were assessed. Analysis of the relative abundance of AM fungal spores found that host tree species had a significant effect on the AM fungal community, as did host plant community diversity (monocultures vs polycultures). The Shannon diversity index of the AM fungal spore community differed significantly among the three host tree species, but was not significantly different between monoculture and polyculture plots. Over all the plots, significant positive relationships were found between AM fungal diversity and ecosystem NPP, and between AM fungal community evenness and PUE. Relative abundance of two of the dominant AM fungal species also showed significant correlations with NPP and PUE. We conclude that the AM fungal community composition in tropical forests is sensitive to host species, and provide evidence supporting the hypothesis that the diversity of AM fungi in tropical forests and ecosystem NPP covaries.  相似文献   

2.
Plant or community longevity can strongly influence soil fertility, yet it is seldom among the functional traits considered in studies of biodiversity and ecosystem functioning. For 11 years we tracked the influences of plant longevity, life-form richness, and tree species identity on 12 soil chemical properties in model ecosystems on an allophanic Andisol in the humid lowlands of Costa Rica. The design employed three levels of plant longevity: 1 year and 4 years (trees cut without biomass removal and replanted to same species), and uncut; two levels of life-form diversity (tree alone, or tree plus palm plus giant perennial herb); and three eudicot, non-nitrogen (N)-fixing tree species. The site’s Andisol proved remarkably resistant to treatment-induced loss of fertility. Although the magnitude of changes was low, most properties declined during the early phases of plant growth, then stabilized or increased. The greatest declines occurred in stands of shortest life span, where organic matter inputs were low and leaching rates were high. In contrast, massive depositions of organic matter every 4 years sustained or augmented surface-soil cation concentrations, pH, organic carbon (SOC), and extractable phosphorus (P). An increase in diversity from one life form to three led to more SOC and calcium (Ca), whereas potassium (K) decreased due to a species effect: high K uptake by the giant herb. The most notable tree-species effects concerned P: It increased under the species that had the highest litterfall and may facilitate apatite weathering; it decreased under the species of highest tissue-N concentrations. Through its effects on soil exposure and organic matter returns, plant longevity exerted greater influence on more soil properties than either diversity or species identity.  相似文献   

3.
施秀珍  王建青  黄志群  贺纪正 《生态学报》2022,42(15):6092-6102
森林是陆地生态系统的重要组成部分,其巨大的生产力和生态服务功能对人类的生存和发展至关重要。森林树种多样性增加能够显著提高森林生产力,关于树种多样性如何影响地下生物多样性及生态功能逐渐受到国内外学者的广泛关注。从土壤微生物及其介导的元素生物地球化学循环这一视角出发,综述了树种多样性对土壤细菌和真菌多样性、群落结构及功能的影响,提出需要进一步深入研究的方向。总体来说,树种多样性有利于增加土壤细菌生物量和多样性,是预测病原性真菌和菌根真菌多样性及群落结构的重要生物因子。树种多样性能增加土壤有机碳储量,增强森林土壤的甲烷氧化能力,并提高土壤磷周转速率及有效磷含量。关于树种多样性对森林土壤氮循环的影响需考虑多样性假说和质量比假说的相对贡献。今后应加强树种多样性对多个营养级之间相互作用的研究;关注树种多样性对生态系统多功能的影响;加强学科交叉,引入微生物种群动态模型和气候模型等模型预测方法,研究树种多样性对全球气候变化的应对机制,以期促进地上植物多样性与地下生态系统功能关系的研究,增强森林生态系统应对未来全球环境变化的能力。  相似文献   

4.
资源互补效应对多样性——生产力关系的影响   总被引:3,自引:0,他引:3       下载免费PDF全文
 许多有关物种多样性-生态系统功能关系的观察、理论和实验研究都表明, 在局域尺度范围内, 植物种多样性对生态系统生产力存在正效应。 然而, 对于促成这种关系的潜在生态学机制却缺乏足够的了解。 该实验利用9种一年生栽培牧草, 采用各物种单播及混播的方法, 构建不同多样性梯度的实验群落, 对物种多样性与生态系统生产力的关系及资源互补效应对系统生产力的影响进行了研究。 结果表明, 在一年生植物群落内,植物种多样性在一定程度内对系统生产力存在正效应, 物种多样性与生产力呈二次函数关系, 关系式为y = -98.449x2 + 1 039.2 x - 42.407, (R2 = 0.423 1)。 各物种在资源利用、生长速度和竞争能力等功能特征方面存在较大差异, 最高产物种和最低产物种间产量相差5.8倍。 在同一多样性梯度内, 不同物种组合的群落间生产力和互补效应也存在较大差异, 说明物种的成分对生态系统生产力也有重要影响。 同时,在混播群落中程度不同地存在着资源的互补性利用, 说明物种多样性对系统生产力有增强作用, 但相关分析表明, 互补效应和物种多样性间不存在显著相关关系。互补效应的4种计算方法所反映的资源互补程度有所不同, 每种方法各有利弊, 在对系统的多样性效应作用机制进行评价时, 应根据具体情况, 同时采用几种方法, 以利于对资源互补效应做出恰当的估测。  相似文献   

5.
Studies examining the influence of biodiversity on ecosystem functioning have rarely considered water turnover, the quantitatively most important biogeochemical flux in ecosystems and a process with high sensitivity to climate warming. With a tree sapling experiment consisting of three diversity levels (1, 3, 5 species), 11 different species combinations and two soil moisture levels (moist and dry), we examined the influence of tree species diversity and species identity on stand transpiration (T) under ample and restricted water supply. We further asked whether growth in mixture leads to adaptive responses in the hydraulic system and water loss regulation in plants with heterospecific neighbors compared to plants in monoculture. In moist soil, T was on average ~11% higher in the mixtures than in the monocultures (significant net diversity effect), which can mostly be attributed to a selection effect. Overyielding in T was highest in mixtures when Tilia cordata and/or Fraxinus excelsior were present. Both species developed larger leaf areas (LA) and sapwood areas (SA) in monocultures than the other species and furthermore increased LA and SA from the monocultures to the mixtures. Thus, inherent species differences in LA and hydraulics, but also neighbor effects on these traits determined T to a large extend. In dry soil, the diversity effect on T was not larger but slightly smaller, which is not in agreement with other published studies. We conclude that differences between pure and mixed sapling assemblages in stand water consumption and drought response are mainly caused by species identity effects, while species diversity seems to be less influential.  相似文献   

6.
Recent research has shown that genetic variation can directly impact community and ecosystem level processes. Populus tremuloides (trembling aspen) is an extremely widespread and genetically diverse tree species important to many North American forest ecosystems. Using leaf litter from five genotypes grown in a common garden under two nutrient treatments, we tracked litter decomposition in a natural aspen stand for 1 year. Here we show that aspen leaf litter decomposes and releases carbon, nitrogen, and sulfur in relation to its genetic identity. In a secondary experiment, we show that the genetic diversity of aspen litter mixtures can influence decomposition, however weakly so. Overall, nutrient treatments influenced leaf litter decomposition the most, followed by genetic identity, and then by genetic diversity (if at all in some cases). In this widespread, genetically diverse, and dominant species, genetic variation within a single species is important to ecosystem functioning. The relatively weak effect of genetic diversity on the processes measured here does not preclude its importance to ecosystem functioning, but does suggest that genetic identity and composition are more important than genetic diversity per se.  相似文献   

7.
Studies of biodiversity–ecosystem function in treed ecosystems have generally focused on aboveground functions. This study investigates intertrophic links between tree diversity and soil microbial community function and composition. We examined how microbial communities in surface mineral soil responded to experimental gradients of tree species richness (SR ), functional diversity (FD ), community‐weighted mean trait value (CWM ), and tree identity. The site was a 4‐year‐old common garden experiment near Montreal, Canada, consisting of deciduous and evergreen tree species mixtures. Microbial community composition, community‐level physiological profiles, and respiration were evaluated using phospholipid fatty acid (PLFA ) analysis and the MicroResp? system, respectively. The relationship between tree species richness and glucose‐induced respiration (GIR ), basal respiration (BR ), metabolic quotient (qCO 2) followed a positive but saturating shape. Microbial communities associated with species mixtures were more active (basal respiration [BR ]), with higher biomass (glucose‐induced respiration [GIR ]), and used a greater number of carbon sources than monocultures. Communities associated with deciduous tree species used a greater number of carbon sources than those associated with evergreen species, suggesting a greater soil carbon storage capacity. There were no differences in microbial composition (PLFA ) between monocultures and SR mixtures. The FD and the CWM of several functional traits affected both BR and GIR . In general, the CWM of traits had stronger effects than did FD , suggesting that certain traits of dominant species have more effect on ecosystem processes than does FD . Both the functions of GIR and BR were positively related to aboveground tree community productivity. Both tree diversity (SR ) and identity (species and functional identity—leaf habit) affected soil microbial community respiration, biomass, and composition. For the first time, we identified functional traits related to life‐history strategy, as well as root traits that influence another trophic level, soil microbial community function, via effects on BR and GIR .  相似文献   

8.
Human activities have greatly increased the availability of biologically active forms of nutrients [e.g., nitrogen (N), phosphorous (P), potassium (K), magnesium (Mg)] in many soil ecosystems worldwide. Multi‐nutrient fertilization strongly increases plant productivity but may also alter the storage of carbon (C) in soil, which represents the largest terrestrial pool of organic C. Despite this issue is important from a global change perspective, key questions remain on how the single addition of N or the combination of N with other nutrients might affect C sequestration in human‐managed soils. Here, we use a 19‐year old nutrient addition experiment on a permanent grassland to test for nutrient‐induced effects on soil C sequestration. We show that combined NPKMg additions to permanent grassland have ‘constrained’ soil C sequestration to levels similar to unfertilized plots whereas the single addition of N significantly enhanced soil C stocks (N‐only fertilized soils store, on average, 11 t C ha?1 more than unfertilized soils). These results were consistent across grazing and liming treatments suggesting that whilst multi‐nutrient additions increase plant productivity, soil C sequestration is increased by N‐only additions. The positive N‐only effect on soil C content was not related to changes in plant species diversity or to the functional composition of the plant community. N‐only fertilized grasslands show, however, increases in total root mass and the accumulation of organic matter detritus in topsoils. Finally, soils receiving any N addition (N only or N in combination with other nutrients) were associated with high N losses. Overall, our results demonstrate that nutrient fertilization remains an important global change driver of ecosystem functioning, which can strongly affect the long‐term sustainability of grassland soil ecosystems (e.g., soils ability to deliver multiple ecosystem services).  相似文献   

9.
Chan  F.  Menge  B. A.  Nielsen  K.  & Lubchenco  J. 《Journal of phycology》2003,39(S1):8-9
Net primary production in marine ecosystems ultimately reflects the inputs of nutrients and the efficiency with which nutrients are acquired and used by phytoplankton in growth. In contrast to our understanding of the linkages between nutrient loading and production, the influence of nutrient use efficiency (NUE) on cross-system variations in coastal productivity remains unclear. Nutrient use efficiency at the ecosystem scale is the product of the per capita efficiency of nutrient use in phytoplankton growth and the efficiency with which phytoplankton communities are able to assimilate limiting nutrient(s). We measured the relative dominance of ecosystem N pools by phytoplankton biomass as an index of NUE across 56 inner-shelf sites. These sites were distributed across a strong geographic range of upwelling intensity and productivity along the coasts of Oregon, California and New Zealand. We also compiled an extensive dataset of published NUE values in coastal and oceanic sites in order to assess cross-system patterns and differences in NUE. Our results indicate that exceptional rates of productivity in inner-shelf upwelling systems arise as a consequence of near dominance of ecosystem N pools by phytoplankton biomass. Elevated rates of NUE nevertheless appear to be a transient phenomenon in marine systems. Cross-shelf transects across upwelling fronts off the Oregon coast reveal a temporal pattern of intense phytoplankton blooms and decline that reflects the eventual dominance of ecosystems N pools by detrital and dissolved organic N pools. Our findings suggest that NUE may play a central role in governing the productivity of marine ecosystems.  相似文献   

10.
In species-poor communities, genetic diversity potentially plays an important role for ecosystem functioning, though this is still largely unexplored in marine and estuarine ecosystems. We studied how genetic diversity (sensu genotypic diversity and/or allelic richness) affects ecosystem functioning in marine habitat-forming plant communities. First, we conducted a 15-month field experiment in the highly seasonal Baltic Sea and established mono- and polycultures of different genotypes and genotype combinations of Zostera marina. Second, we reviewed existing literature and performed a meta-analysis of 12 studies including this study. We found no evidence of positive genetic diversity effects on shoot production in the field experiment, but diversity enhanced community stability over time. The literature review revealed that a majority of the included studies observed positive effects of genetic diversity on ecosystem functions such as primary production and nutrient uptake. The results from the meta-analysis support the hypothesis that genetic diversity effects on productivity are stronger during or after periods of stress. These diversity effects were also more positive in the field compared to mesocosm studies. Our results indicate that genetic diversity has positive effects on ecosystem functioning, particularly during increased environmental stress. Thus, local genetic diversity should be preserved especially in species-poor ecosystems, where it potentially provides insurance against environmental change.  相似文献   

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