荒漠土壤因子和DSE定殖对克隆植物入侵的响应

克隆植物,尤其是游击型克隆植物,具有很强的扩展能力,通过克隆扩展可侵入到不同生境斑块。克隆植物入侵可能会影响入侵地土壤营养状况和微生物群落。为了探明克隆植物入侵对DSE(dark septate endophytes)活动和土壤理化性质的影响,于2013年6月在克隆植物羊柴(Hedysarum laeve)和沙鞭(Psammochloa villosa)群落空地沿根状茎延伸方向设置样方,分别于6月、8月和10月在样方内分0—10、10—20、20—30、30—40、40—50 cm土层采集土样和根样,研究了不同采样时间羊柴和沙鞭群落空地DSE和土壤理化性质时空变化。结果表明,从6月到10月,随时间后延,克隆植物逐渐侵入群落空地,沙鞭入侵群落空地数和分株数高于羊柴。羊柴群落空地根系DSE定殖率随采样时间后延,逐渐降低,最大值在6月;沙鞭群落空地根系DSE定殖率随采样时间后延,逐渐升高,最大值在10月。随着克隆植物入侵,入侵地土壤中可利用的营养物质含量显著提高,羊柴入侵提高了入侵群落空地土壤碱解N、有效P和速效K含量,沙鞭入侵提高了入侵群落空地土壤碱解N和有效P含量。相关性分析表明,羊柴群落空地DSE定殖率与土壤p H值和电导率显著正相关,沙鞭群落空地DSE定殖率与土壤p H值极显著负相关,与电导率、碱解N和有效P极显著正相关。克隆植物入侵使得土壤环境更有利于克隆植物自身生长,为荒漠植被恢复提供了前提。     

Spatial dynamics of dark septate endophytes in the roots and rhizospheres of Hedysarum scoparium in northwest China and the influence of edaphic variables

Spatial dynamics of DSE in the roots and rhizospheres of Hedysarum scoparium Fisch. et Mey. and soil factors were investigated at seven arid and semi-arid locations in northwest China in July 2015. Sampling sites were found to have a significant influence on the morphology, components, distribution, and infection of DSE in the roots of H. scoparium. Of nine DSE species isolated from H. scoparium roots, five are reported here for the first time from desert ecosystems. Hyphal infection in roots was positively correlated with soil urease and phosphatase activity. The presence of microsclerotia in roots was positively correlated with soil ammonium, and negatively correlated with soil organic matter and pH. We conclude that DSE infection is spatially predictable, and is influenced by nutrient availability and enzymatic activity. This research provides a basis for further understanding the ecological functions of DSE, and their roles in the promotion of vegetation restoration and in reducing erosion and desertification in arid ecosystems.     

荒漠沙蒿根围AM真菌和DSE的空间分布

2009年7月在内蒙古黑城子北、多伦县城东和正蓝旗元上都遗址3个样地分别从0-10 cm、10-20 cm、20-30cm、30-40 cm和40-50 cm 5个土层采集沙蒿(Artemisia sphaerocephala)根围土壤和根样,系统研究了沙蒿根围AM真菌和DSE(Dark septate endophytes)的空间分布及与土壤因子的相关性。结果表明,沙蒿根系能被AM真菌高度侵染形成典型的I-型(Intermediate type)丛枝菌根,并发育形成泡囊和丛枝结构, 并与DSE形成良好的共生关系,样地生态条件和采样深度对AM真菌分布和活动有显著影响。黑城子样地孢子密度最高,元上都样地泡囊定殖率最高,不同样地间丛枝、菌丝、总定殖率和DSE定殖率无显著差异。孢子密度峰值出现在0-10cm表层土,并随土壤剖面深度增加而降低;泡囊定殖率峰值出现在10-20cm土层;AM真菌其他结构定殖率及DSE定殖率在各土层间差异不显著或变化无规律。孢子密度与AM真菌不同结构定殖率无显著相关性,与各土壤因子极显著正相关。泡囊定殖率与脲酶和碱性磷酸酶极显著负相关,与酸性磷酸酶显著负相关。菌丝定殖率、总定殖率及DSE定殖率与各土壤因子均无显著相关性。土壤碱解N和有机C与脲酶、酸性磷酸酶和碱性磷酸酶极显著正相关;土壤速效P与碱性磷酸酶极显著正相关,与脲酶显著正相关。对沙蒿根系AM真菌和DSE真菌分布和定殖规律的研究,可进一步明确AM真菌和DSE的生态功能,为利用菌根生物技术促进荒漠植被恢复和生态重建提供依据。     

Stemflow in two xerophytic shrubs and its significance to soil water and nutrient enrichment

Shrub canopies are expected to funnel substantial amounts of intercepted rainwater with enriched nutrients as stemflow to shrub base in the desert ecosystems characterized by limited water and nutrients. However, lacking are quantitative studies on the water and nutrient enrichment of stemflow at the shrub basal area. In this study, stemflow were quantified for two xerophytic shrubs (Caragana korshinskii and Artemisia ordosica) in a revegetated desert ecosystem of Shapotou area in northwestern China. We also measured the ion concentrations of total nitrogen (TN), total phosphors (TP), NH₄ ⁺–N, NO₃ ^?–N, Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl^?, SO₄ ^2? and the pH and electric conductivity (EC) in stemflow, throughfall and bulk precipitation. Results indicated that stemflow accounted for 8.8 and 2.8 % of the gross rainfall for C. korshinskii and A. ordosica, respectively. Individual stemflow linearly increased with increasing rainfall depth. Stemflow increased with rainfall intensity when rainfall intensity was less than 2 mm h^?1 but showed decreased tendency thereafter. An antecedent precipitation of 1.3 and 1.6 mm was necessary for stemflow initiation for C. korshinskii and A. ordosica, respectively. The mean (confidence intervals, α = 0.05) funneling ratio was 82 (17) for C. korshinskii and 26 (7) for A. ordosica. Ion concentrations in stemflow were higher than in throughfall, and the concentration of most of the ions measured were significantly higher (p < 0.05) in stemflow than in bulk precipitation, with a nutrient enrichment ratio ranged 122.8–1677.0 for C. korshinskii and 12.6–1306.0 for A. ordosica among measured ions, respectively. Overall, the larger funneling ratios and enrichment ratios for the two shrubs suggest that stemflow plays a significant positive role in soil water replenishment and nutrient enrichment at deeper soil profile of root zone in the revegetated ecosystems under arid desert conditions.     

荒漠北沙柳根系丛枝菌根真菌和黑隔内生真菌定殖状况

为利用土壤共生真菌资源促进荒漠植被恢复和生态重建, 分别于2013年6月、8月和10月, 从内蒙古元上都地区采集北沙柳(Salix psammophila)根围0-10、10-20、20-30、30-40和40-50 cm共5个土层的土壤样品, 系统研究了丛枝菌根真菌(AMF)和黑隔内生真菌(DSE)的时空分布及其与土壤因子的相关性。结果表明: AMF和DSE的平均定殖率分别为77%和84%, 说明北沙柳根系能与这两类真菌形成良好的共生关系。AMF和DSE的分布和定殖具有明显的时空异质性, 并与土壤因子密切相关。AMF和DSE的平均定殖率均表现为10月> 8月> 6月。土壤深度对AMF和DSE的定殖率有显著影响, AMF和DSE定殖率的最大值分别在0-20 cm和0-10 cm土层。双因子方差分析表明, 月份和土层对AMF和DSE的定殖率以及土壤因子具有显著的交互效应。主成分分析表明, 土壤湿度、pH值、碱性磷酸酶、易提取球囊霉素是内蒙古荒漠环境中AMF和DSE定殖的主要影响因子。     

Spatio-temporal dynamics of arbuscular mycorrhizal fungi associated with glomalin-related soil protein and soil enzymes in different managed semiarid steppes

Temporal and spatial patterns of arbuscular mycorrhizal fungi (AMF) and glomalin and soil enzyme activities were investigated in different managed semiarid steppes located in Inner Mongolia, North China. Soils were sampled in a depth up to 30 cm from non-grazed, overgrazed, and naturally restored steppes from June to September. Roots of Leymus chinense (Trin.) Tzvel. and Stipagrandis P. Smirn. were also collected over the same period. Results showed that overgrazing significantly decreased the total mycorrhizal colonization of S. grandis; total colonization of L. chinensis roots was not significantly different in the three managed steppes. Nineteen AMF species belonging to six genera were isolated. Funneliformis and Glomus were dominant genera in all three steppes. Spore density and species richness were mainly influenced by an interaction between plant growth stage and management system (P?P?相似文献   

荒漠植物油蒿根围AM真菌的时空分布

 2006年5、8和10月分别从陕西榆林沙生植物园样地油蒿(Artemisia ordosica)根围分0～10、10～20、20～30、30～40和40～50 cm 5个土层采集土壤样品, 系统研究了AM真菌的时空分布。结果表明, AM真菌孢子密度和丛枝定殖率随时间呈递减趋势; 泡囊定殖率随时间变化先降后升, 在10月出现最高值; 菌丝定殖率随时间变化先升后降, 8月出现最高值; AM真菌孢子密度和定殖率的最大值分别出现在5月的0～10和20～30 cm土层。实验站中土壤因子对AM真菌时空分布有显著影响, 土壤速效N、速效P和有机质与孢子密度呈极显著正相关, 土壤速效K与菌丝定殖率呈极显著正相关, 和总定殖率成显著正相关。     

蒙古沙冬青伴生植物AM真菌的空间分布

进一步探究荒漠植物与AM(arbuscular mycorrhiza)真菌共生关系及其生态适应性,为以蒙古沙冬青为建群种适生区的植被恢复与生态改良提供依据。于2013年6月在内蒙古荒漠带选取以蒙古沙冬青为建群种的3个样地乌海、磴口和阿拉善,从每个样地选择2种主要伴生植物,按0—10、10—20、20—30、30—40、40—50 cm共5个土层采集土样和根样,研究了蒙古沙冬青伴生植物AM真菌空间分布及其与土壤因子的关系。从梭梭(Haloxylon ammodendron)、油蒿(Artemisia ordosica)、柠条锦鸡儿(Caragana korshinskii)和蒙古扁桃(Amygdalus mongolica)4种伴生植物根围土壤共分离鉴定4属25种AM真菌,其中球囊霉属(Glomus)14种,无梗囊霉属(Acaulospora)7种,管柄囊霉属(Funneliformis)3种,盾巨孢囊霉属(Scutellospora)1种,优势菌种为网状球囊霉(Glomus reticulatum),AM真菌属种分布具有不均衡性和地域性。4种伴生植物根系均能与AM真菌形成I-型(intermediate type)丛枝菌根,其共生程度和定殖规律具有明显空间异质性。AM真菌种数随土层深度增加而下降。AM真菌最大定殖率在10—30 cm土层,最大孢子密度在10—20 cm土层。相关性分析表明,AM真菌菌丝与土壤有机C极显著正相关(P0.01),与易提取球囊霉素(EEG)显著负相关(P0.05);孢子密度与有机C、碱性磷酸酶极显著负相关(P0.01),与碱解N极显著正相关(P0.01)。主成分分析表明,土壤有效P、酸性磷酸酶、碱性磷酸酶和总球囊霉素(TEG)等土壤因子能综合反映内蒙古荒漠带营养状况。TEG和EEG平均含量分别为4.76 mg/g和1.62 mg/g,占土壤有机C平均含量为61.26%和20.8%,说明在贫瘠荒漠环境中球囊霉素是土壤有机碳库重要来源和组成部分。     

沙坡头地区沙冬青AM真菌的时空分布

2007年5月、8月和10月分别从宁夏沙坡头地区豆科植物沙冬青(Ammopiptanthus mongolicus)根围分0-10cm,10-20cm,20-30cm,30-40cm和40-50cm5个土层采集土壤样品。研究了AM真菌时空分布及与土壤因子的相关性,在分离的3属12种AM真菌中,球囊霉属(Glomus)6种,无梗囊霉属(Acaulospora)4种,盾巨孢囊霉属(Scutellospora)2种,3属12种AM真菌在3个时期均有分布。AM真菌定殖率与孢子密度有明显的时空分布规律,并与土壤因子关系密切。孢子密度和泡囊定殖率在8月份最高,丛枝、菌丝和总定殖率10月份最高。土壤采样深度对孢子密度和定殖率有显著影响,AM真菌最高定殖率和最大孢子密度均出现在0-30cm浅土层。孢子密度与土壤有机质、碱解N极显著正相关,与pH显著正相关;菌丝、总定殖率与pH、碱解N和速效P极显著正相关。在评估荒漠生态系统和沙冬青形成菌根的能力时,AM真菌孢子密度、菌根不同结构的定殖程度是十分有用的指标。     

西北荒漠带细枝岩黄耆AM真菌与DSE真菌时空分布研究

为探明细枝岩黄耆Hedysarum scoparium根系丛枝菌根真菌（arbuscular mycorrhizae,AM）和深色有隔内生真菌（dark septate endophytes,DSE）定殖特征及其生态地理分布,充分理解菌根共生体在植物生长和植被恢复中的功能,本研究连续3年采集我国西北荒漠带不同样地细枝岩黄耆0-30cm土层土壤样品和根样,不同样地细枝岩黄耆均能被AM和DSE侵染,形成AM典型结构菌丝、泡囊和丛枝,DSE典型结构深色有隔菌丝和微菌核。细枝岩黄耆根系AM真菌定殖高于DSE定殖,但极端干旱条件下DSE定殖优于AM真菌定殖。AM真菌定殖率不同年际间表现为2016年最高,同一年份不同样地,除乌海、沙坡头样地,菌丝定殖率自东向西呈降低趋势。DSE真菌定殖率,在同一样地不同年份：乌海样地2016年定殖率显著高于2015年和2017年,在同一年份不同样地：2015年沙坡头样地DSE菌丝定殖率、总定殖率显著高于其他样地,而2016、2017年鄂尔多斯样地最高。NMDS分析结果显示,AM和DSE真菌定殖不同年际间差异显著。相关性分析表明,AM真菌定殖率与DSE定殖率显著正相关;土壤温度与AM定殖显著负相关;有机碳、速效磷、磷酸酶、湿度与AM定殖显著正相关;DSE菌丝定殖率、定殖强度仅与酸性磷酸酶正相关。本研究比较分析西北荒漠带不同样地AM和DSE定殖与土壤因子的相关性,有助于充分理解菌根共生体在植物生长和植被恢复中的功能和意义。     

西北旱区甘草深色有隔内生真菌物种多样性及空间分布

为探明西北旱区甘草Glycyrrhiza uralensis根系深色有隔内生真菌（dark septate endophytes,DSE）生态分布和定殖状况,于2018年7月分别从甘肃安西、民勤和宁夏沙坡头地区采集甘草不同灌丛范围0-10cm和20-30cm土壤和根系样品,系统研究不同样地甘草灌丛内外DSE生态分布及其与土壤因子的相关性。结果表明,不同样地甘草均能被DSE高度侵染,形成典型深色有隔菌丝和微菌核结构。不同样地DSE定殖率差异显著,安西DSE总定殖率（43.34%）显著低于民勤（90%）和沙坡头（88.34%）样地。相关性分析表明,DSE定殖率主要与土壤速效磷、有机碳和碱性磷酸酶显著相关。共分离鉴定11属13种DSE,即Acrocalymma vagum、Alternaria longissima、Alternaria chlamydospora、Alternaria chlamydosporigena、Paraphoma chrysanthemicola、Darksidea alpha、Niesslia aemula、Tricharina ochroleuca、Acremonium nepalense、Fusarium solani、Preussia sp.、Leptosphaeria oraemaris和Ulocladium sp.。其中Acrocalymma vagum是甘草根系DSE优势菌种,为民勤和沙坡头共有种,而安西样地DSE物种多样性最高,共7种。主成分分析表明,安西DSE物种组成在0-10cm和20-30cm不同灌丛范围存在显著差异;单因素方差分析显示,安西和沙坡头DSE菌丝定殖率在距主干0-10cm显著高于20-30cm,说明荒漠环境灌丛覆盖对DSE真菌群落存在显著影响。方差分解结果表明,DSE定殖受样地空间分布、灌丛覆盖和土壤因子共同影响（74.91%）,而DSE种类组成更多依赖于样地异质性（84.46%）和土壤养分（87.82%）的作用。研究不同荒漠环境DSE定殖和群落组成差异,有助于充分理解DSE在旱区植物生长和植被恢复中的功能和意义。     

塞北荒漠草原柠条锦鸡儿AM真菌的空间分布

为了探明塞北荒漠草原AM真菌生态分布规律,于2013年6月选取河北沽源县二牛点、内蒙古上都镇和青格勒图嘎查3个样地,按照0—10 cm、10—20 cm、20—30 cm、30—40 cm、40—50 cm 5个土层分别采集柠条锦鸡儿(Caragana korshinskii)根围土壤样品,研究了AM真菌空间分布特征及其与土壤因子的相关性。结果表明,柠条锦鸡儿根系能与AM真菌共生形成疆南星型丛枝菌根,AM真菌孢子密度和定殖率与样地和采样深度密切相关。二牛点孢子密度最大,3个样地孢子密度最大值均在0—10 cm土层,并随土层加深而减少;3个样地菌丝定殖率依次为上都镇青格勒图嘎查二牛点,峰值均在0—10 cm土层;泡囊定殖率青格勒图嘎查显著低于其他样地,但土层间无规律性变化;丛枝样地间定殖状况差异明显,变化趋势为青格勒图嘎查上都镇二牛点;AM真菌总定殖率和定殖强度最大值在上都镇。孢子密度与土壤有机C、全N、易提取球囊霉素和总球囊霉素极显著正相关,与p H值显著正相关,与速效P显著负相关;菌丝定殖率与土壤p H值、速效P、全N和酸性磷酸酶显著负相关;泡囊和丛枝定殖率与土壤碱解N和碱性磷酸酶具有极显著相关性;总球囊霉素和易提取球囊霉素与脲酶显著正相关,与碱解N、全N、碱性磷酸酶和酸性磷酸酶极显著正相关。主成分分析表明,酸性磷酸酶、总球囊霉素、全N、碱性磷酸酶、有机C是影响荒漠土壤营养状况的主要因子。总球囊霉素和易提取球囊霉素平均含量分别为3.19 mg/g和1.17 mg/g,占土壤有机C平均含量比为7.77%和3.83%,占土壤全N平均含量比为20.81%和9.57%。多元线性回归表明,总球囊霉素和易提取球囊霉素与土壤有机C和全N具有显著线性相关关系。研究球囊霉素与土壤有机C和N的比例关系可进一步明确AM真菌的生态功能,对荒漠土壤C库和N库研究具有重要意义。     

Linking thaw depth with soil moisture and plant community composition: effects of permafrost degradation on alpine ecosystems on the Qinghai-Tibet Plateau

Background and aims

The warming of the planet in recent decades has caused rapid, widespread permafrost degradation on the Qinghai–Tibet Plateau. These changes may significantly affect soil moisture content and nutrient supply, thereby affecting ecosystem structure and function. This study aimed to describe the dynamic changes in thaw depth, assess the relationship between thaw depth and soil moisture content, and analyze the changes in species composition and water-use efficiency in response to permafrost degradation.

Methods

We surveyed species composition, thaw depth, ground temperature, soil moisture, nutrient content, and foliar stable carbon isotope compositions to gain insights into the response of alpine grassland ecosystems to permafrost degradation on the Qinghai-Tibet Plateau.

Results

Moisture content of the surface layer decreased with increasing thaw depth. The correlation between thaw depth and surface soil moisture content was strongest in June and decreased in July and August. The strongest correlation occurred at a depth of 20 cm to 30 cm. The dominant species shifted from Cyperaceae in alpine meadow to mesoxerophytes in alpine steppe before finally shifting to xerophytes in alpine desert steppe. Thaw depth correlation was significantly negative with organic C content (r?=??0.49, P?<?0.05) and with total N content (r?=??0.62, P?<?0.01). The leaf δ¹³C of Carex moorcroftii increased with increasing thaw depth and followed a linear relationship (R ²?=?0.85, P?=?0.008).

Conclusions

Permafrost degradation decreases surface soil moisture and soil nutrient supply capacity. Increasing permafrost degradation decreases the number of plant families and species, with hygrophytes and mesophytes gradually replaced by mesoxerophytes and xerophytes. The water-use efficiency of plants improved in response to increasing water stress as surface layers dried during permafrost degradation. Permafrost on the Qinghai–Tibetan Plateau is expected to further degrade as global warming worsens. Therefore, more attention should be dedicated to the response of alpine ecosystems during permafrost degradation.     

Water integration patterns in two rhizomatous dune perennials of different clonal fragment size

In clonal plants, a clonal fragment is a basic unit. There may exist clonal integration that is often regarded adaptive. By definition, a larger clonal fragment comprises more interconnected ramets and/or occupies a larger area of the habitat. When the habitat is so heterogeneous in terms of essential resources that the resources the whole clonal fragment needs can be captured only in a limited number of microhabitats, a large clonal fragment may require extensive and/or intensive clonal integration. Therefore, we hypothesize that in an environment where the resources are distributed in a highly heterogeneous way, a species forming large clonal fragments possesses more extensive and/or intensive clonal integration gaining essential resources than that forming small ones.This hypothesis was tested in a field experiment with two rhizomatous species growing in inland-dune habitats with high heterogeneity of water resource, one (Psammochloa villosa) forming large clonal fragments and the other (Hedysarum laeve) forming small ones. In P. villosa, tracer-(water-soluble acid fuchsin)-labeled water could be transported along the rhizome at a velocity of about 0.93 m per hour and 4 ramets per hour, which was much faster than that in H. laeve. Similarly, the acid fuchsin-labeled water was transported to a longer length in the rhizomes (3.96 m vs. 1.12 m) and to more ramets (14 vs. 3) in P. villosa than in H. laeve. In P. villosa, the acid fuchsin-labeled water reached the ends of the rhizomes and all ramets along the rhizomes were dyed purple. In H. laeve, however, the acid fuchsin-labeled water could not reach the rhizome tips and along the rhizomes only some ramets were labeled. The results suggest that P. villosa is an extensive and intensive integrator, whereas H. laeve is a restrictive and less intensive integrator, supporting the hypothesis. The possible mechanisms and the ecological implications of the findings were discussed.     

北方两省农牧交错带沙棘根围AM真菌与球囊霉素空间分布

2009年7月在内蒙古和河北两省农牧交错带沙棘(Hippophae rhamnoides L)集中分布区选取3个典型样地,分别从0-10cm、10-20cm、20-30cm、30-40cm和40-50cm土层采集沙棘根围土壤样品,研究了沙棘根围AM真菌与球囊霉素空间分布及与土壤因子的相关性。结果表明,沙棘能与AM真菌形成良好的疆南星型(Arum-type)丛枝菌根。AM真菌定殖率和孢子密度与样地生态条件密切相关。大梁底村和多伦东样地AM真菌不同结构定殖率及孢子密度无明显差别,但均显著高于黄柳条村样地,只在大梁底村发现丛枝定殖;孢子密度在3个样地均随土层加深而降低,不同结构定殖率在大梁底村随土层加深而降低,其他2个样地无明显变化规律;AM真菌最高定殖率和最大孢子密度均出现在0-30cm浅土层。根围土壤总球囊霉素(TEG)和易提取球囊霉素(EEG)含量在3个样地均随土层加深而降低。相关性分析表明,孢子密度与菌丝定殖率、泡囊定殖率和总定殖率极显著正相关。AM真菌菌丝、泡囊和总定殖率与土壤pH值、有机C、碱解N和速效P含量、脲酶和碱性磷酸酶活性极显著正相关,丛枝定殖率与土壤碱解N含量和脲酶活性显著正相关。多元线性回归方程表明,AM真菌不同定殖结构和土壤因子对TEG和EEG含量贡献不同,对于TEG:菌丝>孢子>泡囊;有机C>速效P>酸性磷酸酶>pH值,对于EEG:泡囊>孢子>菌丝;有机C>速效P。结果建议,AM真菌孢子密度、菌丝定殖程度和土壤球囊霉素含量在一定程度上能综合反应土壤AM真菌群落、有机C动态和养分循环进程,可以作为土壤质量及功能评价的新指标进一步深入研究。     

新疆沙冬青AM和DSE真菌的空间分布

2012年6月从新疆阿图什市选取康苏、膘尔托阔依(阳)、膘尔托阔依(阴)和上阿图什4个样地,采集新疆沙冬青(Ammopiptanthus nanus)根围0—10、10—20、20—30、30—40和40—50cm5个土层土壤样品,研究了新疆沙冬青AM和DSE真菌定殖规律以及土壤因子的生态作用。结果表明,AM和DSE真菌平均总定殖率分别为83.2%和53.22%,说明AM和DSE真菌能与新疆沙冬青根系形成良好共生关系。AM和DSE真菌具有明显空间异质性,AM总定殖率最大值在20—30cm土层,样地间表现为康苏=上阿图什膘尔托阔依(阳)膘尔托阔依(阴);DSE土层间无规律性变化,样地间为膘尔托阔依(阳)膘尔托阔依(阴)康苏上阿图什。相关性分析表明,AM菌丝、泡囊和总定殖率与DSE定殖率极显著负相关,AM定殖强度与DSE菌丝和总定殖率显著负相关,丛枝定殖率与DSE菌丝和总定殖率极显著正相关,说明两者间存在生态位竞争。土壤速效P、总球囊霉素和酸性磷酸酶与AM总定殖率极显著正相关,pH与AM总定殖率显著负相关;脲酶与DSE极显著正相关,pH和碱解N与DSE显著负相关。     

荒漠草原区4种植物群落土壤种子库特征及其土壤理化性质

土壤种子库作为地上植被更新的潜在种源,在植被自然恢复和演替过程以及生态系统建设中起着重要作用。以宁夏盐池县荒漠草原区4种植物群落为研究对象,通过对封育16年后植物群落土壤理化性质的变化与其土壤种子库的特征之间的关系的探讨,揭示荒漠草原植物群落的土壤种子库分布特征和演替趋势,以及土壤质量的改变如何影响土壤种子库特征。研究结果表明：（1）不同植物群落土壤种子库物种组成及种子密度不同,同一物种在不同植物群落土壤种子库中出现时种子密度也存在差异;禾本科、菊科、藜科植物种在4种植物群落土壤种子库中出现比例均较高,分别占到26.19%、21.43%和19.05%,占总物种数的66.7%;灰绿藜、冰草、碱蓬在4种植物群落土壤种子库中均有出现。（2）4种植物群落土壤种子库中多年生植物和一年生植物种子居多,灌木、半灌木植物种较少。（3）4种植物群落土壤种子库中物种数和种子密度均表现为：芨芨草群落 > 苦豆子群落 > 油蒿群落 > 盐爪爪群落;且随着土层的加深,4种植物群落土壤种子库中物种数和种子密度均呈递减趋势。（4）4种植物群落土壤种子库中Shannon-Wiener指数、Simpsin指数、Pielou指数和Patrick指数均表现为芨芨草群落 > 苦豆子群落 > 油蒿群落 > 盐爪爪群落。此外,芨芨草群落土壤种子库与油蒿群落土壤种子库相似性最高,油蒿群落与盐爪爪群落的最低。（5）土壤种子库物种多样性特征指数与土壤pH、含水量、碱解氮呈正相关,与土壤电导率呈负相关,其中土壤pH和电导率对种子库物种多样性的影响较大。荒漠草原封育以后,土壤种子库中植物种数、种子密度和物种多样性均呈增加趋势,且以多年生植物和一年生植物种子居多;禾本科和豆科植物的物种数和种子密度大于菊科和藜科,这表明围封后牧草品质改善,植物群落正向演替。     

Soil Moisture Rather than Soil Nutrient Regulates the Belowground Bud Bank of Rhizomatous Species <i>Psammochloa villosa</i> in Arid Sand Dunes

In arid and semi-arid sand dune ecosystems, belowground bud bank plays an important role in population regeneration and vegetation restoration. However, the responses of belowground bud bank size and composition to sand burial and its induced changes in soil environmental factors have been rarely studied. In arid sand dunes of Northwestern China, we investigated belowground bud bank size and composition of the typical rhizomatous psammophyte Psammochloa villosa as well as three key soil environmental factors (soil moisture, total carbon and total nitrogen) under different depths of sand burial. Total buds and rhizome buds increased significantly with increasing burial depth, whereas tiller buds first increased and then decreased, with a peak value at the depth of 20–30 cm. Soil moisture increased significantly with sand burial depth, and was positively correlated with the number of all buds and rhizome buds. Soil total carbon concentration first increased and then decreased with sand burial depth, and total nitrogen concentration was significantly lower under deep sand burial than those at shallow depths, and only the number of tiller buds was positively correlated with soil total nitrogen concentration. These results indicate that soil moisture rather than soil nutrient might regulate the belowground bud bank of P. villosa, and that clonal psammophytes could regulate their belowground bud bank in response to sand burial and the most important environmental stress (i.e., soil moisture). These responses, as the key adaptive strategy, may ensure clonal plant population regeneration and vegetation restoration in arid sand dunes.     

Dark septate endophyte and arbuscular mycorrhizal status of vegetation colonizing a bottomland hardwood forest after a 100 year flood

Levels of arbuscular mycorrhizal (AM) colonization and dark septate endophyte (DSE) colonization were assessed in the vegetation recolonizing a remnant bottomland hardwood forest in north central Texas following a 100 year flood. Thirty seven plant species representing 21 dicotyledonous and 2 montocotyledonous families established following floodwater recession. AM and/or DSE were found in all species. AM colonization was found in 31 out of the 37 species assessed including both monocotyledonous families (Poaceae and Cyperaceae) and 17 out of 21 dicotyledonous families (Acanthaceae, Asteraceae, Boraginaceae, Cucurbitaceae, Euphorbiaceae, Lamiaceae, Loganiaceae, Lythraceae, Malvaceae, Onagraceae, Pedaliaceae, Ranunculaceae, Sapindaceae, Scrophulariaceae, Solanaceae, Verbanaceae and Violaceae). DSE were found in 31 out of 37 species assessed including both monocotyledonous families and 15 out of 21 dicotyledonous families (Amaranthaceae, Asteraceae, Boraginaceae, Brassicaceae, Cucurbitaceae, Euphorbiaceae, Lamiaceae, Lythraceae, Malvaceae, Pedaliaceae, Phytolaccaceae, Polygonaceae, Ranunculaceae, Sapindaceae, Scrophulariaceae and Violaceae). There were no detectable differences in AM or DSE colonization levels among wetland indicator groups (p > 0.05). Levels of DSE colonization were negatively correlated with vesicular colonization and hyphal colonization for the obligate wetland species. There were no other significant relationships between AM and DSE colonization detected. Spearman rank order correlation coefficients did not differ significantly among wetland indicatory category for any level of AM or DSE colonization.     

荒漠草原不同植物根际与非根际土壤养分及微生物量分布特征

通过对宁夏荒漠草原6种地带性优势物种长芒草、蒙古冰草、甘草、牛心朴子、黑沙蒿和苦豆子植物根际与非根际土壤养分和微生物量分布特征进行研究,探讨不同植物根际养分的富集的相关性和差异性。研究结果表明:6种植物根际土壤养分和微生物量均表现出明显的富集效应,根际富集率大小依次为菊科(黑沙蒿)豆科(苦豆子、甘草)禾本科(长芒草、蒙古冰草)萝藦科(牛心朴子);全磷(TP)在根际和非根际中无显著差异(P0.05),其它土壤养分及理化指标在根际中均表现出显著富集(P0.05),土壤养分中以有机碳(SOC)的富集作用最为明显;土壤有效态养分较全量养分对植物根际微小的变化响应更为灵敏;不同荒漠植物根际与非根际SOC与全氮(TN)呈极显著线性关系(P0.01),TN与碱解氮之间呈极显著线性关系(P0.01),TP与有效磷(AP)没有显著的相关性(P0.05)。荒漠植物土壤有效养分在根际存在一定的富集,灌木和豆科植物的根际效应的大于禾本科植物,它们通过降低根际pH值可以提高根际养分,有利于在脆弱环境下对土壤养分的有效利用。