Aluminum in the opal silica reticule of phytoliths: a new tool in palaeoecological studies

X-ray microanalysis was employed to screen biogenic plant silica extracted from the aboveground tissues of 20 species (Gramineae, Cyperaceae, Ericaceae, and Coniferae) occurring in subalpine and alpine grasslands, heaths, and woodlands on siliceous bedrock in the Valaisan Swiss Alps. Among the taxa investigated, only woody species produced a high proportion of phytoliths containing aluminum in the form of aluminosilicates. This difference between the chemical composition of wood and that of herbaceous phytoliths has important implications for the sourcing of phytoliths. As applications for palaeoenvironmental studies can be expected to be far-reaching, the potential of this microanalytical technique is discussed.     

Analysis of nitrogen saturation potential in Rocky Mountain tundra and forest: implications for aquatic systems

We employed grass and forest versions of the CENTURY model under a range of N deposition values (0.02–1.60 g N m^–2 y^–1) to explore the possibility that high observed lake and stream N was due to terrestrial N saturation of alpine tundra and subalpine forest in Loch Vale Watershed, Rocky Mountain National Park, Colorado. Model results suggest that N is limiting to subalpine forest productivity, but that excess leachate from alpine tundra is sufficient to account for the current observed stream N. Tundra leachate, combined with N leached from exposed rock surfaces, produce high N loads in aquatic ecosystems above treeline in the Colorado Front Range. A combination of terrestrial leaching, large N inputs from snowmelt, high watershed gradients, rapid hydrologic flushing and lake turnover times, and possibly other nutrient limitations of aquatic organisms constrain high elevation lakes and streams from assimilating even small increases in atmospheric N. CENTURY model simulations further suggest that, while increased N deposition will worsen the situation, nitrogen saturation is an ongoing phenomenon.     

Structure and Function of Silica Bodies in the Epidermal System of Grass Shoots

Silica (SiO₂.nH₂O) is deposited in large quantities in the shootsystems of grasses. In the leaf epidermal system, it is incorporatedinto the cell wall matrix, primarily of outer epidermal walls,and within the lumena of some types of epidermal cells. This biogenic silica can be stained specifically with methylred, crystal violet lactone, and silver amine chromate. At theultrastructural level, the silica in lumens of silica cells,bulliform cells and long epidermal cells is made up of rodsabout 2.5 µm in length and 0.4µm in width. Ultimateparticles in the rods range from 1 to 2 nm in diameter. In contrast,silica in the cell wall matrix of trichomes and outer wallsof long epidermal cells is not rod-shaped, but rather, formsroughly spherical masses. Detailed analyses are presented on the frequencies of occurrenceof the different types of epidermal cells that contain silicain the leaves of representative C₃ and C₄ grasses. The C₄ grasseshave higher frequencies of bulliform cell clusters, silica cells,and long epidermal cells, whereas the C₃ grasses have higherfrequencies of trichomes. No correlation was found in the frequencyof occurrence of silica bodies in bulliform cells for C₃ grassesas compared with C₄ grasses. Of all the grasses examined, Coix,Oryza, and Eleusine had the highest densities of such bodies,and some taxa had no silica bodies apparent in their bulliformcells. The idea that silica bodies in bulliform cells and silica cellsmight act as "windows’ and trichomes might function as‘light pipes’ to facilitate light transmission throughthe epidermal system to photosynthetic mesophyll tissue belowwas tested. The experimental data presented do not support eitherof these hypotheses. C₂ and C₄ grasses, biogenic silica, light pipes, window hypothesis, silica staining, silica ultrastructure     

Environmental drivers of subalpine and alpine fen vegetation in the Southern Rocky Mountains,Colorado, USA

Fens are widely distributed wetlands worldwide and provide vital habitat for plant and animal species in mountainous regions. Alpine fens are rare in the Rocky Mountains and concentrated in the San Juan Mountains where broad regions at high elevation have relatively level topography and suitable climate to favor peat accumulation. Studies of montane and boreal peatlands have identified water chemistry as a main driver of vegetation composition. This study investigated whether similar drivers of vegetation composition are important for alpine and subalpine fens in the San Juan Mountains of Colorado, USA. Water chemistry variables were most important in structuring subalpine and alpine fen vegetation. However, these variables explained considerably less variation in alpine than subalpine fen vegetation. In addition, lower variance of water chemistry in alpine fens did not lead to lower beta diversity of vegetation in alpine than in subalpine fens. Although alpine and subalpine fen vegetation supports similar beta diversity, key differences occur in the environmental drivers of their vegetation composition.     

川西亚高山流域水碳平衡研究

森林生态系统的产水量与固碳效益之间存在着一种可交易的平衡关系。基于WaSSI-C水碳耦合模型和趋势分析, 研究了1982-2006年川西杂古脑河上游22个子流域内不同植被类型空间分布对水碳平衡的影响并分析了其水碳耦合关系, 发现: 1)针叶林主导的流域在生长季增加土壤水分入渗的功能明显高于其他植被类型, 但不足以补偿其高蒸散带来的水分消耗, 因而其年平均土壤含水量明显低于高山草甸和混交林类型; 且森林土壤含水量随着森林覆盖率的升高而降低。2) 25年的土壤水分蓄变量的平均值, 高山草甸流域为-44 mm, 混交林为-18 mm, 针叶林为-5 mm, 说明川西亚高山植被的整体维持稳定产水量及其潜力在下降, 其中高山草甸流域下降趋势尤为显著。3)流域产流量和净生态系统生产力具有显著负相关性, 且不同植被组成对固碳和产水效益的转化具有重要影响: 高山草甸主导的子流域具有较高的产水量和较低的固碳能力, 常绿针叶林主导的子流域具有较高固碳能力和较低产水量, 且森林覆盖率越高, 产水量越低。三种植被类型的净生态系统生产力在研究期间均呈现上升趋势, 且高山草甸的上升趋势显著。     

Trade-offs between water yield and carbon sequestration for sub-alpine catchments in western Sichuan,China

Aims There is increasing concern on the trade-off between carbon sequestration and water yield of forest ecosystems. Our objective was to explore the effects of vegetation composition on water and carbon trade-off in the sub-alpine watersheds of western Sichuan during 1982-2006.Methods The WaSSI-C, which is an eco-hydrological model with coupled water and carbon cycles, was employed to calculate the key components in water balance and carbon sequestration for the 22 sub-catchments in the upper reaches of Zagunao River. Spearman’s Rho trend analysis was used to examine the trends in runoff and net ecosystem productivity. Important findings Compared with either subalpine meadow or mixed forest dominated catchments, the conifer-dominated catchments had much higher water loss due to high evapotranspiration, and the loss was not offset by its higher soil water infiltration during the growing season. The change in soil water storage for subalpine meadow, mixed forest and coniferous forest are -44 mm, -18 mm and -5 mm, respectively, which indicated significant decline in soil water storage and thus water yield particularly in alpine meadow catchments. Significant negative relationship was found between runoff and net ecosystem productivity, the alpine meadow as the dominant vegetation type showed high water yield and low carbon sequestration, and the conifer-dominant and mixed forest vegetation showed low water yield and high carbon sequestration, moreover, the higher the forest coverage, the lower the water yield. Upward trends in net ecosystem productivity were observed in the three vegetation types during the study period and the alpine meadow type was significant.     

Assessment of Hedysarum theinum Krasnob. (Fabaceae) population status in Altai

The status of 22 Hedysarum theinum cenopopulations (CPs) located in subalpine and alpine vegetation belts in Kazakhstan and Altai Republic is assessed by a complex of traits. It is detected that conditions of the subalpine belt (12 CPs), where the point sum of organismal and population traits vary from high to average values, are the most favorable for this species. The pessimal state, characterized by the smallest values of most species parameters, is determined in the alpine vegetation belt at an altitude of about 2000 m above sea level in Rudnyi Altai (Kazakhstan) and a shrub community at the junction of alpine and subalpine belts on the edge of the H. theinum area in Russian Altai. A reactive-tolerant type of H. theinum population strategy is detected.     

Trade-offs between water yield and carbon sequestration for sub-alpine catchments in western Sichuan,China北大核心CSCD

Aims: There is increasing concern on the trade-off between carbon sequestration and water yield of forest ecosystems. Our objective was to explore the effects of vegetation composition on water and carbon trade-off in the sub-alpine watersheds of western Sichuan during 1982-2006. Methods: The WaSSI-C, which is an eco-hydrological model with coupled water and carbon cycles, was employed to calculate the key components in water balance and carbon sequestration for the 22 sub-catchments in the upper reaches of Zagunao River. Spearman's Rho trend analysis was used to examine the trends in runoff and net ecosystem productivity. Important findings: Compared with either subalpine meadow or mixed forest dominated catchments, the conifer-dominated catchments had much higher water loss due to high evapotranspiration, and the loss was not offset by its higher soil water infiltration during the growing season. The change in soil water storage for subalpine meadow, mixed forest and coniferous forest are -44 mm, -18 mm and -5 mm, respectively, which indicated significant decline in soil water storage and thus water yield particularly in alpine meadow catchments. Significant negative relationship was found between runoff and net ecosystem productivity, the alpine meadow as the dominant vegetation type showed high water yield and low carbon sequestration, and the conifer-dominant and mixed forest vegetation showed low water yield and high carbon sequestration, moreover, the higher the forest coverage, the lower the water yield. Upward trends in net ecosystem productivity were observed in the three vegetation types during the study period and the alpine meadow type was significant.     

Relationships between temperature responses and bacterial community structure along seasonal and altitudinal gradients

In this study, soil bacterial communities and the temperature responses (Q10) of substrate-induced respiration were compared between an alpine dry meadow and a subalpine forest in the Colorado Rocky Mountains. Bacterial communities in three seasons from each environment were described with 16S rRNA gene clone libraries. The main goal of this comparison was to relate phylogenetic differences among bacterial communities with variation in soil respiratory temperature sensitivities along seasonal and altitudinal gradients. The warmer, lower elevation, subalpine forest soil exhibited large seasonal variations in Q10. Subalpine Q10 values were highest in summer, and were higher than alpine values in all seasons except winter. Q10 in alpine soils were consistently low throughout the year. Alpine and subalpine bacterial communities both varied seasonally, and were markedly distinct from each other. Based on Fst analysis, subalpine communities from colder times of year were more similar to the alpine communities than were subalpine summer communities. Principle component analysis of the pairwise genetic distances (Fst) between communities produced two factors that accounted for 69% and 22% of the total variance in the data set. These factors demonstrated a significant relationship between bacterial community structure and temperature response when regressed on log-transformed Q10 data.     

Contrasting long-term alpine and subalpine precipitation trends in a mid-latitude North American mountain system,Colorado Front Range,USA

Background: Long-term climate trends in mountain systems often vary strongly with elevation.

Aims: To evaluate elevation dependence in long-term precipitation trends in subalpine forest and alpine tundra zones of a mid-continental, mid-latitude North American mountain system and to relate such dependence to atmospheric circulation patterns.

Methods: We contrasted 59-year (1952–2010) precipitation records of two high-elevation climate stations on Niwot Ridge, Colorado Front Range, Rocky Mountains, USA. The sites, one in forest (3022 m a.s.l.) and the other in alpine tundra (3739 m), are closely located (within 7 km horizontally, ca. 700 m vertically), but differ with respect to proximity to the mountain-system crest (the Continental Divide).

Results: The sites exhibited significant differences in annual and seasonal precipitation trends, which depended strongly on their elevation and distance from the Continental Divide. Annual precipitation increased by 60 mm (+6%) per decade at the alpine site, with no significant change at the subalpine site. Seasonally, trends at the alpine site were dominated by increases in winter, which we suggest resulted from an increase in orographically generated precipitation over the Divide, driven by upper-air (700 hPa) north-westerly flow. Such a change was not evident at the subalpine site, which is less affected by orographic precipitation on north-westerly flow.

Conclusions: Elevation dependence in precipitation trends appears to have arisen from a change in upper-air flow from predominantly south-westerly to north-westerly. Dependence of precipitation trends on topographic position and season has complex implications for the ecology and hydrology of Niwot Ridge and adjacent watersheds, involving interactions among physical processes (e.g. snowpack dynamics) and biotic responses (e.g. in phenologies and ecosystem productivity).     

High-altitude multi-taskers: bumble bee food plant use broadens along an altitudinal productivity gradient

We use an extensive historical data set on bumble bee host choice collected almost 50 years ago by L. W. Macior (Melanderia 15:1–59, 1974) to examine how resource partitioning by bumble bees varies over a 2,700-m altitudinal gradient at four hierarchical scales: individual, colony, species and community. Bumble bee behavior, resource overlap between castes, and plant-bumble bee networks change with altitude in accordance with tightening temporal constraints on flowering and colony growth in alpine habitats. Individual bees were more likely to collect pollen from multiple sources at high altitude. Between-caste foraging niche overlap increased with altitude. Similarly, alpine forager networks were more highly nested than either subalpine or montane networks due to increased asymmetric specialization. However, interspecific resource partitioning showed a more complex spatial pattern with low niche overlap at intermediate altitude (subalpine) compared to montane (disturbed) and alpine (unproductive) sites. Results suggest that spatial variation in interspecific resource partitioning is driven by a shift in the behavior of long-tongued bumble bees. Long-tongued bumble bees specialized in the subalpine but generalized in montane and alpine zones. Our reanalysis of Macior’s data shows that bumble bee behavior varies substantially with altitude influencing plant-bumble bee interaction networks. Results imply that pollination services to alpine host plants will change dramatically as subalpine species with unique foraging strategies move upward under global warming.     

Relationship between Degree of Dominance and Species Richness in Grass Communities with Different Productivities

The aim of this study is to test the assumption that the relationship between the degree of dominance and local species richness may be different in grass communities with different productivities. Alpine, subalpine, and low-mountain grasslands, as well as subalpine mires, alpine communities of low-snow habitats and those with long-term snow cover, steppe communities, and the grass layer of low-mountain forest communities of the Western Caucasus and Ciscaucasia, are used as objects of research. The data on the phytomass of 419 plots with an area of 0.25 m² are studied. The results show that, the higher the mean productivity of communities is, the closer the relationship between the degree of dominance and species richness is, and the closest relationship is observed in meadow communities. Possible causes of these relationships are considered. It is reasonably suggested that this may be due to the features of the organization of plant communities with high and low productivity (in particular, high or low intensity of interspecific competition).     

Biogenic Opal in Three Species of Gramineae

Particulate biogenic opaline silica is concentrated in cellwalls, intercellular deposits and cell lumina of all portionsof the above-ground plant body of three species of PanicoidGramineae,Andropogon gerardi, Sorgastrum nutans and Panicumvirgatum. Morphologically distinct opal phytoliths form notonly in long cells, short cells, trichomes, stomatal elementsand bulliform cells of the epidermis but also within the cellularstructure of mesophyll, vascular, and sclerenchyma tissues.Roots and rhizomes contain measurable quantities of opalinesilica, and phytoliths develop in epidermal long cells, saddle-shapedshort cells, vascular cells, and intercellular deposits. A morphologicallyunique plate-phytolith, formed by silicification of the innertangential wall of the endodermis, is present in the roots ofall three species. Differences in the quantity of opaline silicaoccur between species and between parts of the same species.The amount of opal deposited in the soil annually by root systemsand above-ground parts is approximately equal in magnitud Andropogon gerardi, Sorgastrum nutans, Panicum virgatum, opaline silica deposition     

Effects of grazing exclusion on species composition in high-altitude grasslands of the Central Alps

Our study examines the effects of grazing exclusion on low-productive subalpine and alpine grasslands of the Central Alps (UNESCO Biosphere Park Gurgler Kamm, Obergurgl, Austria). A long-term exclusion experiment was established in 2000 in the subalpine, the lower, and the upper alpine zone. With exception of the subalpine zone, domestic herbivores have been grazing during the whole growing season. In grazed and exclosure plots species frequencies were recorded for 7 years. We analysed exclosure effects on species number, community composition, life forms, and functional groups.Species richness did not decrease significantly within the exclosures, but changes in species composition occurred in each zone, although some were transitory in nature. The dynamic trends of the plots were significantly explained by the ‘treatment×year’ effect along the whole altitudinal gradient, but the effects decreased considerably with altitude. In the subalpine and upper alpine exclosures, stress-tolerators, species of low or no nutritive value, and mosses showed a decreasing trend, whereas tall grasses (subalpine exclosures), competitors, and species with high or medium nutritive values (lower alpine exclosures) tended to increase.Overall, our 7-year study revealed that several functional groups reacted to grazing, according to our main expectations. We suggest that these effects will intensify in the long term.     

Virtual issue: Alpine and subalpine plant communities: importance of plant growth,reproduction and community assemblage processes for changing environments

Natural plant communities are exposed to environmental changes such as global warming and increased human activities. It is thought that alpine and subalpine ecosystems with cool climatic conditions are sensitive to environmental changes. This virtual issue introduces multidisciplinary research at alpine and subalpine plant communities. The articles include research on (1) species diversity, vegetation and biomass, (2) species assembly, (3) climate and growth of alpine plants, (4) reproduction of alpine plants, (5) differences of growth traits among coexisting species, (6) vegetation changes by human activities and overgrazing of deer, and (7) differentiation of growth traits among ecotypes in relation to climatic conditions. These thirteen articles provide valuable information for future research on the effects of environmental changes on alpine and subalpine plant communities.     

天山北坡植物土壤生态化学计量特征的垂直地带性

生态化学计量工作专注于植物与土壤的元素比例关系及其环境解释等问题上,还需要分析在连续环境梯度上元素比例关系的变化规律以进一步加深已有的认识。受水热梯度的影响,植被与土壤在天山北坡均存在明显的垂直地带性,这为探讨植物土壤生态化学计量特征的垂直带谱提供了有利条件。在天山中段北坡海拔1000—3840m范围内,按海拔梯度对植物和土壤分别采样,测定其C、N、P含量。结果表明:(1)随海拔的升高,植物C、N、P含量及其计量比变化规律各不相同,C含量随海拔变化保持不变,仅山地针叶林显著低于亚高山灌丛草甸、高山垫状植被和山前灌木(P0.05);N含量、C∶P、N∶P随海拔先升高后降低,山地针叶林和亚高山灌丛草甸显著高于山地荒漠草原、山地草原、高山垫状植被(P0.05);P含量、C∶N则是随海拔先降低后升高,高山垫状植被显著高于其他植被类型,山地荒漠草原、山前灌木和高山草甸显著高于山地草原、针叶林和亚高山灌丛草甸(P0.05)。(2)从生活型角度,乔木、灌木和草本C、N含量、C∶N差异不显著,灌木P含量、C∶P、N∶P显著高于草本(P0.05);乔木和灌木更受P限制,草本更受N限制。(3)随海拔的升高,土壤C、N、P含量、C∶P、N∶P均先升高后降低,其中山地针叶林和亚高山灌丛草甸均显著高于山地荒漠草原和山地草原(P0.05),土壤C∶N表现为一直降低,山地荒漠草原显著高于其他植被类型(P0.05)。(4)植物C、N、P及计量比与土壤相关性分析中,仅植物C∶P与土壤C∶P相关性显著,且植物C、N、P含量与土壤相关系数小于植物C∶P、N∶P与土壤相关系数。在垂直地带性上,土壤主要通过生态化学计量比影响植物的生长。     

短期氮添加对祁连山亚高山草地生产力及植物多样性的影响

全球氮沉降速率的急剧增加已显著地改变了生态系统的生产力及稳定性,特别是在受N限制较严重的亚高山草地生态系统。虽然氮沉降增加对草地生产力和植物多样性影响的研究报道已经很多,但是氮素沉降的生态系效应因气候区、草地系统类型、加氮水平、氮肥类型和试验时间长短等不同而差别很大。为了评估氮沉降增加对亚高山草地植物物种多样性和生产力的影响,通过在祁连山中部亚高山草地设置不同氮添加水平（0、2、5、10、15、25 g N m^-2 a^-1和50 g N m^-2 a^-1）的短期氮沉降增加模拟试验,探讨了生产力和物种多样性对不同水平氮添加的响应。结果显示：氮添加增加了禾本科（垂穗披碱草、赖草和草地早熟禾）和莎草科（矮嵩草）的地上生产力及其在群落生产力中所占的比例,主要表现在氮添加增加了禾本科和莎草科的株高和株数,降低了其他科（鹅绒委陵菜和葛缕子）的株高和株数;与生产力相比,植物多样性对氮添加的响应较慢,总体随着氮添加量的增加呈下降趋势但未达到显著水平;植物多样性与生产力呈显著的负相关关系。研究结果表明氮添加有助于提高禾本科和莎草科的生产力,进而提高群落生产力,但其他科的植物会被逐渐替代,导致群落植物物种多样性降低。研究结果可为我国亚高山草地的持续性管理提供一定的理论基础。     

Sources of dissolved and particulate organic material in Loch Vale Watershed,Rocky Mountain National Park,Colorado, USA

The sources of both dissolved organic carbon (DOC) and particulate organic carbon (POC) to an alpine (Sky Pond) and a subalpine lake (The Loch) in Rocky Mountain National Park were explored for four years. The importance of both autochthonous and allochthonous sources of organic matter differ, not only between alpine and subalpine locations, but also seasonally. Overall, autochthonous sources dominate the organic carbon of the alpine lake, while allochthonous sources are a more significant source of organic carbon to the subalpine lake. In the alpine lake, Sky Pond, POC makes up greater than one third of the total organic matter content of the water column, and is related to phytoplankton abundance. Dissolved organic carbon is a product of within-lake activity in Sky Pond except during spring snowmelt and early summer (May–July), when stable carbon isotope ratios suggest a terrestrial source. In the subalpine lake, The Loch, DOC is a much more important constituent of water column organic material than POC, comprising greater than 90% of the spring snowmelt organic matter, and greater than 75% of the organic matter over the rest of the year. Stable carbon isotope ratios and a very strong relation of DOC with soluble Al_(tot) indicate DOC concentrations are almost entirely related to flushing of soil water from the surrounding watershed during spring snowmelt. Stable carbon isotope ratios indicate that, for both lakes, phytoplankton is an important source of DOC in the winter, while terrestrial material of plant or microbial origin contributes DOC during snowmelt and summer.     

高寒草毡层基本属性与固碳能力沿水分和海拔梯度的变化

高寒草毡层是高原寒区自然植被下形成的松软而坚韧且耐搬运的表土层,认识其生态功能是促进草牧业生产休养保护和工程施工主动利用的前提。通过对青藏高原东部若尔盖高原植被的广泛调查,在布设沼泽、退化沼泽、沼泽化草甸、湿草甸、干草甸和退化草甸水分梯度群落样地,以及亚高山草甸、亚高山灌丛草甸、高山灌丛草甸和高山草甸海拔梯度群落样地的基础上,通过对不同类型群落样地草毡层容重、土壤颗粒组成和土壤有机碳(SOC)含量的测定分析,比较了水分和海拔梯度下草毡层固碳能力。结果表明,草毡层厚度平均为30cm,沼泽湿地草毡层容重最小,SOC含量在300g/kg以上;退化草甸容重最高,SOC含量显著下降。不同群落草毡层SOC密度在10—24kg C/m~2之间,随着土壤水分有效性的降低而降低;高山灌丛草甸草毡层SOC密度比草甸高15%。研究得出,保持草毡层稳定的质量含水量阈值为30%,SOC含量阈值为30g/kg;高寒植被草毡层在沼泽到草甸的退化演替中,容重、紧实度变大,有机碳含量减少,碳密度和碳储量下降;灌丛草甸的固碳能力大于草甸,但灌丛草甸的生产功能降低;保持可持续发展的草地生产能力,维护固碳生态功能,需要防止草毡层退化,抑制草甸向灌丛草甸演替。     

土壤肥力和物种属性决定亚高寒草甸实验群落的生产力

生物多样性与生态系统功能之间的关系及其形成的内在机制还存在很多争议。为了揭示植物群落生产力形成的生态学机制, 采用盆栽方法探讨了物种多样性、物种属性以及施肥水平与植物群落生产力之间的关系。研究结果显示: 在不施肥和每盆施5.0 g磷酸二铵的条件下, 随着物种多样性的增加, 地上生物量增加不显著; 在每盆施10.0 g磷酸二铵的条件下, 随着物种多样性的增加, 地上生物量显著增加。相对于中华羊茅(Festuca sinensis)而言, 垂穗披碱草(Elymus nutans)和垂穗鹅观草(Roegneria nutans)对群落生产力的贡献较大, 但在不同施肥水平和播种密度下, 其影响不完全相同。这表明物种多样性对群落生产力的影响随着土壤肥力的变化而变化; 并且植物群落生产力受组成群落的物种属性影响较大, 而物种属性又与特定时间和特定生境下资源的利用方式相联系。在高肥力水平下, 物种多样性之所以对群落生产力具有正效应, 可能是因为高肥力水平增加了可利用的生态位空间, 最终仍体现在物种组合上。因此, 植物群落的生产力与物种多样性之间没有必然的联系, 而与土壤肥力和土壤肥力决定的物种属性有关。