Soil formation under progressive accelerated succession of forest ecosystems in the North of Russia

The paper presents experimental data on restoration of soil, an ecosystem component. Each trial plot was treated differently. It is shown that the use of a combination of techniques, namely grass sowing and mineral and organic fertilization of soil, aimed at restoration of biological rotation of plants, radically intensifies the soil restoration. The developed organic-accumulating layer is the main indicator of successful soil restoration. The importance of soil as a structural element of an ecosystem is determined by its capacity to retain and accumulate nutrients thus ensuring stable conditions for self-restoration of ecosystem components.     

Relationships among soil fertility,native plant diversity and exotic plant abundance inform restoration of forb‐rich eucalypt woodlands

Aim Water and nutrient availability are major limits to productivity in semi‐arid ecosystems; hence, ecological restoration often focuses on conserving or concentrating soil resources. By contrast, nutrient enrichment can promote invasion by exotic annuals, leading to restoration approaches that target reduction of soil nutrients. We aimed to explore potential biodiversity trade‐offs between these approaches by investigating relationships among soil nutrients, exotic annuals and native plant diversity and composition. In particular, we investigated the hypothesis that native plant diversity in semi‐arid to temperate woodlands reflects the productivity–diversity hypothesis, leading to hump‐backed relationships with soil nutrients such that (1) native plant diversity declines with increasing nutrient enrichment and (2) native diversity is limited at the lowest levels of soil fertility. Location Fragmented, long‐ungrazed Eucalyptus loxophleba subsp. loxophleba (York gum)–Acacia acuminata (jam) woodlands in the wheatbelt of South‐Western Australia. Methods We conducted stratified surveys of floristic composition and topsoil nutrient concentrations in 112 woodland patches. We used generalized linear models, structural equation models and ordinations to characterize relationships among soil nutrients, rainfall, exotic annuals and patch‐scale (100 m²) native plant composition and diversity. Results Patch‐scale native plant diversity declined strongly with increasing exotic abundance. This was partly related to elevated soil nutrient concentrations, particularly total nitrogen and available phosphorus. By contrast, there was little evidence for positive correlations between soil nutrients and native diversity, even at very low soil nutrient concentrations. Main conclusions Minimizing weed invasions is crucial for maximizing native plant diversity in E. loxophleba woodlands and could include nutrient‐depleting treatments without substantially compromising the functional capacity of soils to maintain native plant richness and composition. More broadly we emphasize that understanding relationships among ecosystem productivity, plant diversity and exotic invasions in the context of associated theoretical frameworks is fundamental for informing ecological restoration.     

Ecosystem multifunctionality lowers as grasslands under restoration approach their target habitat type

Biodiversity is declining at a rapid pace and, with it, the ecosystem functions that support ecosystem services. To counter this, ecosystem restoration is necessary. While the relationship between biodiversity and ecosystem functioning has been studied in depth, the relationship between ecosystem restoration and ecosystem functioning is studied less. We performed an observational study in grasslands undergoing restoration management toward Nardus grassland. Eight ecosystem functions, representing flows of energy, matter or information between functional compartments, were measured across five successive restoration phases along the restoration gradient. The levels of functioning were then compared along the gradient for both the individual functions and a multifunctionality index. We hypothesized that plant richness increases when grasslands are more restored and this increase in biodiversity is paralleled by an increase in ecosystem functioning. In our study, the degraded grasslands, generally occurring on more nutrient-rich soils, were dominated by competitive fast-growing species, resulting in higher process rates and thus in higher, faster functioning. Likewise, more restored grasslands exhibited slower process rates and, thus, lower functioning. When studying ecosystem functioning, value judgments are easily made. Especially in a restoration context, high functioning does not necessarily equals well functioning, as this depends on the stakeholder perspective. We need to ask ourselves if a high functioning ecosystem is most desirable, especially in a restoration or conservation context. Policy frameworks will need to balance these goals.     

The temporal response of forest ecosystems to doubled atmospheric CO2 concentration

Vegetation responses to high [CO₂] include both direct photosynthetic effects and indirect effects associated with various plant and soil feedbacks. Synthesis of these direct and indirect effects requires ecosystem process models describing the cycling of carbon and essential mineral nutrients through plants and soils. Here we use the ecosystem model G'DAY to investigate responses to an instantaneous doubling of [CO₂]. The analysis indicates that the magnitude and even direction of the growth response to high [CO₂] can vary widely on different timescales, because responses on different timescales are determined by different ecosystem-level feedbacks and hence by different sets of key model parameters. Of particular importance are parameters describing the flexibility of plant and soil nitrogen to carbon (N:C) ratios; large responses occur if N:C ratios decline significantly at high [CO₂], with little or no response if N:C ratios are inflexible. According to G'DAY, the CO₂-response changes over time because responses on longer timescales are dictated by the N:C ratios of less rapidly cycled organic matter.     

Plant community and soil available nutrients drive arbuscular mycorrhizal fungal community shifts during alpine meadow degradation

Arbuscular mycorrhizal fungi (AMF) play an important role in maintaining the function and sustainability of grassland ecosystem, but they are also susceptible to environmental changes. In recent decades, alpine meadows on the Tibetan Plateau have experienced severe degradation due to the impact of human activities and climate change. But it remains unclear how degradation affects the AMF community, a group of functionally important root associated microorganisms, which potentially limit the development and application of microbial technologies in the restoration of degraded grasslands. In this study, we investigated AMF communities richness and composition in non-degraded (ND), moderately degraded (MD) and severely degraded (SD) alpine meadows on the Tibetan Plateau, and then explored their main biotic and abiotic determinants. Alpine meadow degradation significantly reduced plant community biomass, richness, soil organic carbon, total nitrogen, total phosphorus, available nitrogen and available phosphorus, but increased soil pH. AMF community composition and the iesdominant family and genera differed significantly among different degradation stages. Grassland degradation shifted the AMF community composition in favor of Claroideoglomus over Rhizophagus, and resulted in a marked loss of Glomeraceae and the dominance of Diversisporaceae. Alpine meadow degradation significantly increased AMF hyphal density and richness, likely working as a plant strategy to relieve nutrient deficiencies or loss as a result of degradation. The structural equation model showed that AMF community richness and composition were significantly influenced by plant community, followed by soil available nutrients. Soil available nutrients was the key contributor to the increased AMF hyphal density and richness during grassland degradation. Our findings identify the effects of alpine meadow degradation on AMF richness and highlight the importance of the plant community in shaping the AMF community during alpine meadow degradation. These results suggest that plant community restoration should be the primary goal for the ecological restoration of degraded alpine meadows, and these soil functional microorganisms should be simultaneously integrated into ecological restoration strategies and management.     

喀斯特不同植被恢复阶段土壤有机酸季节变化与有效氮磷的关系

植物分泌有机酸在提高土壤养分有效性方面起到重要作用。为了解喀斯特地区不同植被恢复阶段土壤有机酸含量季节性变化与氮磷有效性的关系,在灌木林和原生林各选择3种优势植物,测定雨季和旱季两个季节根际土和非根际土的有机酸含量、碳氮磷含量和比值、有效性氮磷含量及微生物生物量碳。结果表明:原生林植物根际土的草酸含量高于灌木林,而苹果酸和乙酸含量则低于灌木林;根际土草酸含量均高于非根际土;2个植被根际土和非根际土的草酸含量在雨季高于旱季,而苹果酸和乙酸含量则低于旱季;土壤草酸含量与有机碳、全氮、全磷和N∶P值呈显著正相关,与C∶N呈显著负相关;土壤有效氮和有效磷与草酸和微生物生物量碳呈显著正相关。上述结果表明,植物分泌有机酸的季节性变化与土壤养分状态和自身养分需求相关,而有机酸耦合微生物对养分有效性的提高具有积极的作用。因此,根际土的有机酸季节变化可能是喀斯特生态系统中植物适应土壤养分限制的一种重要机制。     

Advanced mine restoration protocols facilitate early recovery of soil microbial biomass,activity and functional diversity

Many ecosystem restoration programmes can take over 15 years to achieve ecosystem functioning comparable to that of an unmodified ecosystem, therefore a reliable shorter-term method of assessing and monitoring ecosystem recovery is needed to ensure that recovery is following an appropriate trajectory. Soil microbes respond to environmental change relatively quickly, and shifts in microbial communities can reflect the current status of their environment. As well as potentially acting as ‘indicator communities’, microbes play an integral role in restoring ecosystem functions. On an active opencast mine on New Zealand's West Coast, three main restoration methods are used, differing in cost and restoration effort. They range from most expensive (1) vegetation direct transfer (VDT), to (2) biosolids-amended stockpiles that are spread and replanted, and (3) untreated stockpiles that are spread and replanted. We assessed the impacts of these methods on soil microbial communities by measuring microbial biomass, dehydrogenase activity, community level physiological profile (CLPP) and functional diversity as measured by carbon substrate utilisation, where restored sites were 5 years old or less. These measures were compared to an unmodified reference ecosystem in the same location. Microbial activity and biomass were highest in pristine habitats, followed by VDT and biosolids-amended soils, then untreated stockpile soil. When compared to all other treatments untreated stockpiled soils had significantly different CLPPs and significantly reduced microbial biomass and activity; microbial biomass was an order of magnitude lower than in pristine soils. Functional diversity and richness did not differ between pristine, VDT and biosolids-amended soils, but were higher than in untreated stockpiled soils. CLPPs did not differ between pristine habitat soil and VDT soil but biosolids-amended and untreated stockpiled soils were significantly different to pristine soil. This study has shown that soil microbial communities are a valuable tool to assess restoration progress, and that ecosystem restoration can begin in a relatively short time following investment in appropriate restoration strategy, ultimately benefiting recolonisation by plants and animals.     

Mid‐term effects on ecosystem services of quarry restoration with Technosols under Mediterranean conditions: 10‐year impacts on soil organic carbon and vegetation development

The use of Technosols for the restoration of limestone quarries overcomes the usual “in situ” scarcity of soil and/or its poor quality. The use of mine spoils, improved with mineral and/or organic amendments, could be an efficient and environmentally friendly option. Properly treated sewage sludge from urban wastewater treatment plants could be a suitable organic amendment and fertilizer (rich in N and P) whenever its pollutant burden is low (heavy metals and/or organic pollutants). Its appropriate use could improve essential soil physical and chemical properties and, therefore, promote key ecosystem services of restored areas, such as biomass production and carbon sequestration, as well as biodiversity and landscape recovery. However, the mid‐term impacts of these restoration practices on soil functioning and their services have rarely been reported in the available literature. In this study we assess the mid‐term effects (10 years) of the use of sewage sludge as a Technosol amendment on soil organic carbon (SOC), nutrient status, and plant development in several restored quarries. Soils restored using sewage sludge showed a threefold increase in SOC compared to the corresponding unamended ones, despite the moderate sludge dosage applied (below 50 tonnes/ha). Plant cover was also higher in amended soils, and recruitment was not affected by sludge amendment at these doses. This study demonstrates that, used at an appropriate rate, sewage sludge is a good alternative for the valorization of mine spoils in quarry restoration, improving some important regulatory ecosystem services such as carbon sequestration, without compromising woody plant encroachment.     

Investigating the Vegetation–Soil Relationships on the Copper–Cobalt Rock Outcrops of Katanga (D. R. Congo), an Essential Step in a Biodiversity Conservation Plan

Plant communities of soils naturally enriched in copper and cobalt in Katanga (D. R. Congo) are critically threatened in the short term due to mining activities. For biodiversity conservation and ecosystem restoration purposes, there is an urgent need to acquire more knowledge on those plant communities including their diversity and their relationships to environmental factors. The classification of 62 vegetation plots located in 6 metal‐rich rocky hills in the Tenke Fungurume mining area resulted in 3 well‐defined steppic and steppic savanna communities. Canonical analysis showed that the community comprising the largest proportion of strictly endemic metallophytes (i.e. species that only occur on metal‐rich soils) developed in the soils with the most elevated concentrations of Cu and Co. However, contrasting species assemblages in the two other plant communities were explained by soil nutrients and percentage rocks in addition to heavy metal concentrations. The results of this study will assist with restoration efforts because they (1) provide a rigorous assessment of communities before a disturbance and (2) define essential edaphic conditions needed for the reestablishment of critical communities.     

喀斯特峰丛洼地不同生态系统的土壤肥力变化特征

基于喀斯特峰丛洼地坡耕地、草丛、灌丛、人工林、次生林、原生林6种典型生态系统的土壤主要养分、矿质养分和微生物这3组变量共计20个指标的调查、取样和分析,运用多重比较分析、主成分分析和典范相关分析探讨了其土壤肥力变化特征、主要影响因子及两两之间的相互关系。结果表明,喀斯特峰丛洼地土壤pH值为6.60—7.75,土壤主要养分、微生物种群数量和微生物生物量明显高于同纬度地区地带性红壤,矿质养分含量相对较低,其中SiO2、Al2O3、Fe2O3占矿质全量的90%以上。土壤肥力的总体趋势为原生林>次生林>灌丛>草丛>坡耕地>人工林。喀斯特石漠化地区实行林草结合的退耕还林还草模式更有利于土壤生态系统的环境改善,坡耕地应多施有机肥和氮肥,人工林应多施氮肥。原生林植物与养分之间达到了良好的平衡状态,主要应加强森林抚育管理,改善森林环境,保障植物、土壤养分及微生物之间的良好协调关系。确保土壤资源的合理利用,促进喀斯特峰丛洼地乃至整个西南喀斯特区域植被的迅速恢复和生态重建。     

Open‐cut mining impacts on soil abiotic and bacterial community properties as shown by restoration chronosequence

Open‐cut mining severely disrupts landforms and soils, preventing or impeding the restoration of preexisting or functional ecosystems because essential properties of the original soils cannot immediately or easily be reinstated. We examined the soil physicochemical and bacterial characteristics of 21 coal‐mined sites in subtropical Queensland, Australia, 3–23 years after establishment of native plant species relative to nonmined analogue sites. Soil disturbance significantly decreased total nitrogen, nitrate nitrogen, and especially total carbon (TC). The TC is projected to take 36 years to recover. Bacterial communities assessed by 16S ribosomal RNA sequencing showed greater species richness and evenness in rehabilitated as compared with nonmined soils, regardless of rehabilitation age. However, bacterial species composition was associated significantly with soil electrical conductivity, the plant density, and total stem cross‐sectional area of woody vegetation. The bacterial communities on rehabilitated sites became progressively more similar to those of nonmined analogue sites over time. This work demonstrates that if topsoils are conserved carefully during mining and supplemented by inorganic fertilizer addition, vigorous plant growth and changes in bacterial community composition can occur soon after plant establishment. This will mitigate the effects of soil disturbance and accelerate the return to the chemical and biological attributes of nonmined analogue soils.     

Multi‐nutrient vs. nitrogen‐only effects on carbon sequestration in grassland soils

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).     

Soil reconstruction after mining fails to restore soil function in an Australian arid woodland

The biogeochemical properties of soils drive ecosystem function and vegetation dynamics, and hence soil restoration after mining should aim to reinstate the soil properties and hydrological dynamics of remnant ecosystems. The aim of this study is to assess soil structure in two vegetation types in an arid ecosystem, and to understand how these soil properties compare to a reconstructed soil profile after mining. In an arid ecosystem in southeast Australia, soil samples were collected at five depths (to 105 cm) from remnant woodland and shrubland sites, and sites either disturbed or totally reconstructed after mining. We assessed soil physico‐chemical properties and microbial activity. Soils in the remnant arid ecosystem had coarse‐textured topsoils that overlay clay horizons, which allows water to infiltrate and avoid evaporation, but also slows drainage to deeper horizons. Conversely, reconstructed soils had high sand content at subsoil horizons and high bulk density and compaction at surface layers (0–20 cm). Reconstructed soils had topsoils with higher pH and electrical conductivity. The reconstructed soils did not show increased microbial activity with time since restoration. Overall, the reconstructed soil horizons were not organized in a way that allowed rainfall infiltration and water storage, as is imperative to arid‐zone ecosystem function. Future restoration efforts in arid ecosystems should focus on increasing sand content of soils near the surface, to reduce evaporative water loss and improve soil quality and plant health.     

严重退化生态系统不同恢复和重建措施的植物多样性与地力差异研究

对花岗岩区土壤严重退化生态系统（对照）及４种不同恢复和重建措施建筑多样性和地力研究结果表明,花岗岩区红壤严重退化生态系统（对照）植物多样地性极低,土壤肥力极差,生态环境极为恶劣,改为杨梅果园（措施Ａ）或多树种混交（措施Ｂ）后,植物多样性明显增大,林地土壤肥力得到一定程度恢复,生态系统朝着良性循环方向发展,采取封山育林（措施Ｃ）方法,林下植被层和群落多样性恢复最快,林地土壤肥力亦得到较快的恢复,保留     

Reviewing the contributions of macrofungi to forest ecosystem processes and services

Macrofungi are vital components of any forest ecosystem, performing different roles crucial to ecosystem functioning. Macrofungi play effective roles in ecosystem processes such as nutrient cycling. Ectomycorrhizal fungi and plant symbionts work together to accumulate, use and transfer essential nutrients, especially in nitrogen/phosphorus-limited environments. Pathogenic and predatory macrofungi exploit other resources such as plants and animals to obtain nutrients needed for growth. These groups of macrofungi also contribute to the species diversity of forest ecosystems. Saprotrophic macrofungi degrade available organic matter from dead plants and soil organic matter. Macrofungi also play an important role in carbon sequestration in the forest underground as well as in soil formation. Macrofungi remediate pollutants in the environment via extracellular enzymes. Mycelial networks that connect macrofungi to their symbiotic hosts and substrates enable most of these functions. Mycelial networks facilitate the absorption and transport of nutrients as well as the secretion of enzymes and other organic substances. Spore-producing bodies of macrofungi serve as a food source for wildlife. Fungal spores can act as aerosols in rain formation. All of these functions of macrofungi are necessary for maintaining biodiversity and healthy forest ecosystems. However, the contributions of macrofungi to ecosystem processes are often taken for granted or not fully recognized, offering key services that are easily overlooked in planning processes and policymaking. The present review summarizes the major roles of macrofungi in ecosystem functioning and services rendered, and the interrelationships between these functions and services in the forest ecosystems.     

鹤山退化草坡生态系统的自然恢复

研究了鹤山南亚热带退化草坡20a的自然恢复动态,发现群落虽有阳生乔木入侵,但仍处于草本和灌丛占优势的生物多样性较低的阶段;土壤中的有机质、水解氮、有效磷和有效钾等营养元素已基本恢复到同地带顶级森林群落的水平;虽然群落的空间结构与生物多样性尚未恢复,但其部分生态功能已经恢复,其中水土保持最先恢复,生产力等功能还需要较长的时间恢复;对于鹤山草坡这类一般退化生态系统来说,可能需要通过构建合适的人工林来加速生物多样性和生物量等指标的恢复过程,仅仅通过自然恢复是难以在较短的时间内迅速恢复其物质循环等功能的。     

Temporal Asynchrony in Soil Nutrient Dynamics and Plant Production in a Semiarid Ecosystem

A central goal of ecosystem ecology is to understand how the cycling of nutrients and the growth of organisms are linked. Ecologists have repeatedly observed that nutrient mineralization and plant production are closely coupled in time in many terrestrial ecosystems. Typically, mineralization rates of limiting nutrients, particularly of nitrogen, during the growing season determine nutrient availability while pools of mineral nutrients remain low and relatively constant. Although several previous reports suggest nitrogen mineralization has the potential to vary seasonally and out of phase with plant production, such a phenomenon has been poorly documented. Here we report results from a semiarid savanna ecosystem characterized by distinct temporal asynchrony in rates of soil nitrogen cycling and plant production. Periods of positive plant growth following the onset of rains coincide with periods of low N turnover rates, whereas higher rates occur late in the wet season following plant senescence and throughout dry seasons. Plant uptake from the substantial mineral N pool present early in the growing season is sufficient to explain most of the N allocation to aboveground plant biomass during the growing season, even in the absence of any wet-season mineralization. The mineral N pool is subsequently recharged by late wet- and dry-season mineralization, plus urine inputs at sites with high levels of ungulate activity. These findings suggest fundamental changes in the quality of substrates available to decomposers over a seasonal cycle, with significant implications for the partitioning of limiting nutrients by plant species, the seasonal pattern of nutrient limitations of aboveground production, and the effective use of N fertilizers in semiarid ecosystems.     

地下生态系统对生态恢复的影响

生态系统破坏与退化的加剧使生态恢复成为全球性的挑战课题,近年来生态恢复的研究已逐渐由地上向地下部分转移,地下部分对生态系统退化所起的作用、机理和过程已倍受关注。本文通过探讨恢复生态学的关键概念,从土壤、地下水循环、生物系统3个方面探讨了地下生态系统对生态恢复的作用机理和反馈机制。针对目前的研究现状,指出地下生态系统研究中存在的问题,并提出今后需要深入研究的几个方向:1)生态系统退化程度的诊断及其标准;2)基于诊断标准,针对不同退化生态系统类型选定恢复的目标植物群落,如何改善土壤性质,确定土壤性质的改善程度;确定地下水位及土壤含水量的阈值;如何有效选择、引入和接种土壤生物;3)生态系统地上和地下部分整合及恢复过程中监测指标的确定。     

科尔沁沙地封育恢复过程中植物群落特征变化及影响因素

封育是退化沙地植被恢复与生态重建的重要措施, 理解长期处于封育状态下不同类型沙地植物群落特征变化及其影响因素有利于沙地植被恢复和生态重建。该文基于对科尔沁沙地长期封育的流动沙丘(2005年封育)、固定沙丘(1985年封育)和沙质草地(1997年封育)连续多年(2005-2017年)的植物群落调查, 结合土壤种子库、土壤养分以及气象数据, 分析了植物群落特征变化及其对环境变化的响应。研究结果表明流动沙丘植被盖度显著增加, 群落生物量和物种多样性年际间波动变化, 但无明显趋势; 固定沙丘植物群落存在逆行演替趋势, 具体表现为群落生物量、灌木和半灌木以及豆科优势度显著下降, 而一年生和多年生杂类草优势度显著增加; 沙质草地群落物种丰富度和多年生禾草优势度存在降低趋势, 并且一年生杂类草优势度明显高于其他功能群, 群落存在退化现象。3类沙地土壤种子密度变化不显著, 而种子丰富度在流动沙丘显著增加, 在固定沙丘和沙质草地有下降趋势, 土壤养分仅有有效氮和有效磷含量增加。回归分析结果表明气温和降水是影响年内生物量积累的主要因素, 但对年际间群落生物量和物种丰富度变化影响不大。除趋势对应分析结果显示土壤种子库与植物群落之间存在很高的相似性, 典型相关分析结果表明沙质草地植物群落与土壤养分紧密相关, 而固定沙丘群落主要与土壤水分紧密相关。综合以上结果可知, 封育33年的固定沙丘群落和封育21年的沙质草地群落都存在退化现象, 而封育11年的流动沙丘群落正在缓慢恢复, 因此封育年限的设定对退化沙地植被恢复至关重要, 封育时间过长不仅不利于植物群落恢复, 反而会使群落发生逆行演替, 建议封育年限的设定应综合考虑植被退化程度、土壤养分状况、土壤种子库基础以及气候条件等因素的影响。     

植物对有机氮源的利用及其在自然生态系统中的意义

近来大量实验研究表明,许多植物能够在不经矿化的情况下直接吸收、利用环境介质中的生物有机氮,尤其氨基酸类。而且,有些植物利用氨基酸的效率可以与矿质氮源(NH4 、NO3)相当或更高。自然界植物赖以生存的土壤生境中同时存在多种有机氮和矿质氮养分,这是导致植物(至少部分植物)进化产生利用各种不同氮源能力的环境驱动力。土壤中的游离氨基酸尽管含量不高,但其周转快、通量大,理论上可远大于植物的氮需求。尽管植物在与土壤微生物的有机氮源竞争中处于根本性劣势,但土壤中氨基酸的巨大潜在通量和植物相对于微生物的生命周期仍可使植物在长期竞争中获取数量可观的氮。基于植物根对氨基酸的吸收能力、土壤中游离氨基酸库的大小和通量、植物与土壤微生物对氨基酸氮源的竞争以及有关的原位实验结果,近来许多研究者都认为植物有机氮营养在多种生态系统中是重要或潜在重要的。尤其是在一些极地、高山、亚高山、北方针叶林或泰加林生态系统中,由于低温等因素限制有机氮矿化,土壤氨基酸浓度常超过矿质氮(NH4 、NO3-)浓度,氨基酸可能代表着植物的一个主要氮源。认识到现实生态系统中植物对有机氮源利用的重要性意味着传统的矿质营养观念的更新,这将在很大程度上改变人们对某些重要生态过程的理解,并导致对若干生态学中心问题的再认识。研究以森林生态系统为例,阐述了我国开展该领域研究的科学意义和基本框架。