Plant Traits and Soil Chemical Variables During a Secondary Vegetation Succession in Abandoned Fields on the Loess Plateau

Species dynamics in terms of both plant biological traits, ecological strategies and species richness as well as soil chemical variables during a secondary succession in abandoned fields on the Loess Plateau along a temporal sere from 3 a to 149 a were studied. The results indicated that (I) Soil total C and N increased while soil pH, total K and Na decreased with years since abandonment. No noticeable trend was found in the case of soil P along the successional sere. On the other hand, total CaO of the surface layer (0 - 10 cm) decreased, but that of the two deeper layer, (20 - 30 cm, 40 - 50 cm) increased with years since abandonment. Soil C, N, K and P decreased, while Na, CaO and soil pH increased with increasing soil depth. (2) Species richness peaked at both mid-stage of the successional sere and the intermediate portion of soil chemical variables gradient. (3) An ideal dominant species in the early successional stage were annuals with stable seed pool, CR-life strategy, S-regeneration strategy, and strong competitive ability on relatively poor soil, while perennials capable of intensive lateral spread and colonal ability, requiring high nutrient supply, and having Clife strategy would be the dominant species in the subsequent stages. Plant traits, such as perennial-life history, C-, CR-, SC-, SR-, S- and R-life strategies, W-, S-, Bs- VBs- and V-regeneration strategies, were over- represented throughout the whole sere among the other species. (4) Some traits, such as C-, SC-life strategies, ability of clonality, perennial-life history, well-developed lateral spread ability, V- and VBs-regeneration strategies, seed animal. dispersal mode, flowering time of autumn, fruit types of legumen and nut, were more or less correlated with increased soil total C, N and K, while S-, SR-, R-, CR-life strategies, annual-, biannual-life history, non-clonal ability, S-regeneration strategy, poor lateral spread ability, and fruit types of utricle, capsule were associated with increased soil total Na, CaO and pH. The results suggested that steppes should be the dominant native vegetation coinciding with the large-scaled eco-climatic conditions on the Loess Plateau.

Ecological stoichiometric comparison of plant-litter-soil system in mixed-species and monoculture plantations of Robinia pseudoacacia,Amygdalus davidiana,and Armeniaca sibirica in the Loess Hilly Region of China

We examined how afforestation patterns impact carbon(C),nitrogen(N),and phosphorus(P)stoichiometry in the plant-litter-soil system.Plant leaf,branch,stem,and root,litter,and soil samples were collected from mixedspecies plantations of Robinia pseudoacacia with Amygdalus davidiana(RPAD),R.pseudoacacia with Armeniaca sibirica(RPAS),and monocultures of R.pseudoacacia(RP),A.davidiana(AD),and A.sibirica(AS)in the Loess Hilly Region.The results showed that in mixed-species plantations,R.pseudoacacia had lower leaf N and P concentrations than in monocultures,while both A.davidiana and A.sibirica had higher leaf N and P concentrations.Soil P limited tree growth in both afforestation models.Mixing R.pseudoacacia with A.davidiana or A.sibirica reduced N-limitation during litter decomposition.Average soil total N and P concentrations were higher in RPAS than in RPAD,and both were higher than the corresponding monocultures.The average soil C:N ratio was the smallest in RPAS,while the average soil C:P ratio was larger in RPAS than in RP.A positive correlation between N and P concentrations,and between C:N and C:P ratios,was found in litter and all plant organs of mono-and mixedstands.Alternatively,for N concentration and C:N ratio,the correlations between plant(i.e.,leaf,branch,root)and litter and between plant and soil were inverse between plantation types.RPAD has an increased litter decomposition rate to release N and P,while RPAS has a faster rate of soil N mineralization.RPAD was the best plantation(mixed)to improve biogeochemical cycling,as soil nutrient restrictions,particularly for P-limitation,on trees growth were alleviated.This study thus provides insights into suitable tree selection and management by revealing C:N:P stoichiometry in the plant-litter-soil system under different afforestation patterns.

Effects of warming and clipping on plant and soil properties of an alpine meadow in the Qinghai-Tibetan Plateau, China

Climate warming and livestock grazing are known to have great influences on alpine ecosystems like those of the Qinghai-Tibetan Plateau （QTP） in China. However, it is lacking of studies on the effects of warming and grazing on plant and soil properties in these alpine ecosystems. In this study, we reported the related research from manipulative experiment in 2010-2012 in the QTP. The aim of this study was to investigate the individual and combined effects of warming and clipping on plant and soil properties in the alpine meadow ecosystem. Infrared radiators were used to simulate climate warming starting in July 2010, while clipping was performed once in Octo- ber 2011 to simulate the local livestock grazing. The experiment was designed as a randomized block consisting of five replications and four treatments： control （CK）, warming （W）, clipping （C） and warming＋clipping combination （WC）. The plant and soil properties were investigated in the growing season of the alpine meadow in 2012. The results showed that W and WC treatments significantly decreased relative humidity at 20-cm height above ground as well as significantly increases air temperature at the same height, surface temperature, and soil temperature at the depth of 0-30 cm. However, the C treatment did not significantly decrease soil moisture and soil temperature at the depth of 0-60 cm. Relative to CK, vegetation height and species number increased significantly in W and WC treatment, respectively, while vegetation aboveground biomass decreased significantly in C treatment in the early growing season. However, vegetation cover, species diversity, belowground biomass and soil properties at the depth of 0-30 cm did not differ significantly in W, C and WC treatments. Soil moisture increased at the depth of 40-100 cm in W and WC treatments, while belowground biomass, soil activated carbon, organic carbon and total nitrogen increased in the 30-50 cm soil layer in W, C and WC treatments. Although the initial responses of plant and soil properties to experimental warming and clipping were slow and weak, the drought induced by the down- ward shift of soil moisture in the upper soil layers may induce plant belowground biomass to transfer to the deeper soil layers. This movement would modify the distributions of soil activated carbon, organic carbon and total nitrogen However, long-term data collection is needed to further explain this interesting phenomenon.

Degradation leads to dramatic decrease in topsoil but not subsoil root biomass in an alpine meadow on the Tibetan Plateau, China

Understanding the effects of degradation on belowground biomass(BGB)is essential for assessment of carbon budget of the alpine meadow ecosystem on the Tibetan Plateau,China.This ecosystem has been undergoing serious degradation owing to climate change and anthropogenic activities.This study examined the response of the vertical distribution of plant BGB to degradation and explored the underlying mechanisms in an alpine meadow on the Tibetan Plateau.A field survey was conducted in an alpine meadow with seven sequential degrees of degradation in the Zoige Plateau on the Tibetan Plateau during the peak growing season of 2018.We measured aboveground biomass(AGB),BGB,soil water content(SWC),soil bulk density(SBD),soil compaction(SCOM),soil organic carbon(SOC),soil total nitrogen(STN),soil total phosphorus(STP),soil available nitrogen(SAN),and soil available phosphorus(STP)in the 0-30 cm soil layers.Our results show that degradation dramatically decreased the BGB in the 0-10 cm soil layer(BGB0-10)but slightly increased the subsoil BGB.The main reason may be that the physical-chemical properties of surface soil were more sensitive to degradation than those of subsoil,as indicated by the remarked positive associations of the trade-off value of BGB0-10 with SWC,SCOM,SOC,STN,SAN,and STP,as well as the negative correlation between the trade-off value of BGB0-10 and SBD in the soil layer of 0-10 cm.In addition,an increase in the proportion of forbs with increasing degradation degree directly affected the BGB vertical distribution.The findings suggest that the decrease in the trade-off value of BGB0-10 in response to degradation might be an adaptive strategy for the degradation-induced drought and infertile soil conditions.This study can provide theoretical support for assessing the effects of degradation on the carbon budget and sustainable development in the alpine meadow ecosystem on the Tibetan Plateau as well as other similar ecosystems in the world.

Response of plant physiological parameters to soil water availability during prolonged drought is affected by soil texture

Soil water deficit is increasingly threatening the sustainable vegetation restoration and ecological construction on the Loess Plateau of China due to the climate warming and human activities.To determine the response thresholds of Amygdalus pedunculata(AP)and Salix psammophila(SP)to soil water availability under different textural soils,we measured the changes in net photosynthetic rate(Pn),stomatal conductance(Gs),intercellular CO2 concentration(Ci),leaf water potential(ψw),water use efficiency(WUE)and daily transpiration rate(Td)of the two plant species during soil water content(SWC)decreased from 100%field capacity(FC)to 20%FC in the sandy and loamy soils on the Loess Plateau in the growing season from June to August in 2018.Results showed that Pn,Gs,WUE and Td of AP and SP remained relatively constant at the beginning of soil water deficit but decreased rapidly as plant available soil water content(PASWC)fell below the threshold values in both the sandy and loamy soils.The PASWC thresholds corresponding to Pn,Gs and Ci of AP in the loamy soil(0.61,0.62 and 0.70,respectively)were lower than those in the sandy soil(0.70,0.63 and 0.75,respectively),whereas the PASWC thresholds corresponding to Pn,Gs and Ci of SP in the loamy soil(0.63,0.68 and 0.78,respectively)were higher than those in the sandy soil(0.58,0.62 and 0.66,respectively).In addition,the PASWC thresholds in relation to Td and WUE of AP(0.60 and 0.58,respectively)and SP(0.62 and 0.60,respectively)in the loamy soil were higher than the corresponding PASWC thresholds of AP(0.58 and 0.52,respectively)and SP(0.55 and 0.56,respectively)in the sandy soil.Furthermore,the PASWC thresholds for the instantaneous gas exchange parameters(e.g.,Pn and Gs)at the transient scale were higher than the thresholds for the parameters(e.g.,Td)at the daily scale.Our study demonstrates that different plant species and/or different physiological parameters exhibit different thresholds of PASWC and that the thresholds are affected by soil texture.The result can provide guidance for the rational allocation and sustainable management of reforestation species under different soil conditions in the loess regions.

不同干扰强度高原鼠兔对高寒草甸土壤温室气体通量变化的影响

高原鼠兔通过取食植物、排泄粪尿及掘土等行为对土壤理化性质及土壤微生物产生广泛干扰,进而可能会影响高寒草甸土壤温室气体排放。本研究选择高密度组(H)、低密度组(L)、对照组(CK)3种鼠兔干扰强度的高寒草甸为研究对象,揭示温室气体排放速率对不同高原鼠兔干扰强度的响应规律及主要调控因素。结果表明,H组高寒草甸土壤CO_(2)排放速率为596.66 mg·(m^(2)·h)^(-1),显著低于CK组的695.45 mg·(m^(2)·h)^(-1)(P<0.05)。高原鼠兔干扰强度、地上生物量、土壤pH和土壤含水量是影响CO_(2)排放速率的主要调控因素。H组高寒草甸CH_(4)吸收速率为-43.46mg·(m^(2)·h)^(-1),显著低于L组的4.92mg·(m^(2)·h)^(-1)(P<0.05),H和L组高寒草甸N_(2)O排放速率分别为8.03、-2.39μg·(m^(2)·h)^(-1),均显著高于CK组的-16.69μg·(m^(2)·h)^(-1)(P<0.05)。土壤硝态氮和铵态氮含量、pH和含水量是影响CH_(4)吸收和N_(2)O排放的重要因素。因此,高原鼠兔干扰强度是影响温室气体排放速率的因素之一,进一步研究高原鼠兔对高寒草甸土壤温室气体排放速率的影响具有重要意义。

黄土丘陵区典型小流域不同植被恢复方式土壤理化性质差异及其影响因素

黄土高原不同小流域由于环境特点和植被恢复方式的不同,导致其生态效益存在地带性差异。为了研究不同环境和植被恢复方式下土壤理化性质的差异性及影响机制,选取黄土高原两个小流域不同植被恢复方式(油松人工林、侧柏人工林和自然恢复对照)作为研究对象,对比分析植被恢复方式和环境特点对土壤养分储量和水分状况,以及植被生长状态等生态恢复效益的影响和贡献。结果表明:(1)吉县自然恢复下全氮含量最高,均值为0.79g/kg;有机碳均值含量表现为定西油松最高,吉县对照次之,其均值分别是16.91g/kg,13.46g/kg;全磷含量和全钾含量最高的是吉县油松样地和定西的侧柏样地,其均值为2.40g/kg和23.43g/kg。(2)土壤速效氮、速效磷、速效钾的含量,吉县的油松样地、侧柏样地和自然对照样地分别高于定西2.89%,81.03%和7.49%。(3)基于主成分分析(PCA)和方差分解(VP)结果,在不同小流域影响土壤养分和水分含量的主要因素有所差异。其中吉县和定西小流域影响土壤养分的主要因素分别为土壤物理性质和植被属性,解释度分别为79.92%、55.3%;而土壤含水量主要受降水量和土壤-植被共同影响,其解释度分别为87.06%、43.53%。综上结果表明,多雨条件的吉县地区植被适合自然恢复,而相对干旱的定西地区植被则适合人工恢复。考虑黄土高原植被恢复的人工和自然恢复方式,结果证明不同小流域的降水量与土壤含水量等环境特点影响植被生长状态和植被恢复的生态效益,可为因地制宜的科学植被恢复策略提供数据和理论支持。

植被与土壤特征对青藏高原不同程度退化草地的响应

高寒草地作为青藏高原高寒生态系统的重要组分之一,其退化已严重影响到高原的可持续发展和草地恢复重建。搜集了2004—2022年间关于青藏高原高寒草地退化的64篇研究结果,包含土壤有机碳、生物量和多样性指数等16个指标的1403组数据,运用meta分析解析了草地退化对土壤理化性质、植被生产力和物种多样性的影响,并对重度退化草地的土壤理化性质和植物生物量进行线性回归分析。结果表明:随着草地退化的加剧,土壤有机碳、全氮、全磷、有效氮、有效磷、有效钾、土壤含水量、地上生物量、地下生物量和植被高度显著下降;土壤容重显著上升;土壤pH、全钾在各个退化阶段没有明显差异;Shannon多样性指数、Pielou均匀度指数和Margalef丰富度指数整体呈下降趋势。土壤有机碳、全氮、全磷、有效氮、有效磷、有效钾和土壤含水量与地上生物量、地下生物量存在显著的正相关;土壤容重与地上生物量、地下生物量呈显著的负相关;土壤pH与地上生物量、地下生物量呈负相关。因此,青藏高原高寒草地退化通过改变土壤理化性质而改变地上群落多样性和生物量,为阐明植被与土壤特征对草地退化的响应机制以及高寒退化草地的恢复提供了科学依据。

青藏高原高寒草地不同植物功能群与土壤碳同位素特征及影响因素

青藏高原海拔高、面积广,是全球范围内最典型的高寒地区之一,探究青藏高原高寒草地植物和土壤碳稳定同位素组成(δ^(13)C)特征及其控制要素,对深刻理解高寒生态系统碳循环过程具有重要意义。研究采集并测定了青藏高原不同区域135个草地样点中的植物和土壤碳稳定同位素自然丰度,探讨了不同植物功能群和表层(0—10 cm)土壤δ^(13)C特征及其与气候、土壤因素的关系。结果表明:(1)杂类草δ^(13)C显著低于禾本科、莎草科和豆科植物δ^(13)C(P<0.05)。表层土壤δ^(13)C与禾本科、莎草科、豆科植物δ^(13)C呈显著正相关(P<0.05),与杂类草δ^(13)C无显著相关关系,且表层土壤δ^(13)C对三种植物功能群δ^(13)C的敏感性为禾本科>豆科>莎草科。(2)在影响禾本科、莎草科、豆科植物和表层土壤δ^(13)C的环境因子中,气候因子的相对贡献率均大于土壤因子,气候因子中太阳辐射相对贡献率最大,杂类草δ^(13)C与气候和土壤因子均不存在显著相关关系。研究表明,太阳辐射是决定高寒草地生态系统植物和表层土壤δ^(13)C的主要因子。研究可为青藏高原高寒草地植物和土壤δ^(13)C特征与有机碳动态循环提供数据支撑和理论参考。

人工林种植和生长对黄土高原生态系统固碳和水文调节功能的影响——基于遥感时序分析证据

随着生态恢复工程的进展,黄土高原人工林种植面积不断增加,黄土高原人工林生态系统服务功能的响应变化仍存在争议。基于黄土高原人工林的时空分布和种植年份信息,从生态系统净初级生产力(NPP)、蒸散发(ET)以及土壤含水率(SMC)三个维度评估黄土高原地区人工林生态系统固碳和水文调节服务功能的动态变化及其对天然林和整个区域生态系统功能的影响,并进一步研究2000—2020年间人工林林龄对生态系统服务功能的影响。天然林的NPP相对于整个区域的百分比基本保持不变,维持在21%左右;而人工林的NPP相对于整个区域的百分比显著增加,并在2009年超过了天然林,成为黄土高原NPP增加的主要来源。人工林占整个区域的ET百分比和SMC百分比均显著增加,分别由不到2%增长至13.9%、1.5%上升至11.8%。至2015年,黄土高原人工林的ET和SMC已经逐步趋于稳定。随着林龄增大,SMC变化速率和变化量不断下降。ET与林龄成正相关,而SMC与林龄负相关,表明具有不同年龄结构的人工林将有效减弱树木生长所引起的土壤干旱的影响。尽管黄土高原人工林林龄与NPP、ET和SMC变化速率和变化量之间存在显著相关性(P<0.01),但由于现阶段此地区人工林多为幼龄林和中龄林,未来这种显著相关关系是否持续有待进一步研究。

黄土高原典型草本植物根系分布特征及其对土壤理化性质的影响研究

为控制黄土高原严重的水土流失,我国实施了大规模的植被恢复,生态环境得到改善。阐明植被恢复过程中不同根系类型对土壤性质的影响差异,有利于完善黄土高原植被恢复优选模式的系统性研究,为黄土高原后续生态恢复提供参考。本研究选取黄土高原自然恢复优势种长芒草(须根系)和铁杆蒿(直根系)为研究对象,以退耕一年的裸地为对照,测定根系特征与土壤理化性质,分析不同直径下根系分布规律及其与土壤理化性质的关系。结果表明:1)长芒草和铁杆蒿根系特征差异显著,须根系长芒草极细根(直径,D<0.5 mm)根长密度(RLD)和根表面积密度(RSAD)占比较高,分别为94.73%和90.20%。直根系铁杆蒿主根优势明显,表现出较高的根质量密度(RMD)、平均直径(RD)和根体积密度(RVD)。其中,铁杆蒿粗根RLD(16.28%)和RSAD(32.85%)的占比明显高于长芒草。2)与裸地相比,长芒草与铁杆蒿显著改善土壤结构,提高土壤稳定性。长芒草与铁杆蒿根系主要聚集在0~20cm土层,对表层土壤的理化性质影响最大。其中,铁杆蒿群落土壤团聚体稳定性和土壤持水性最高,土壤团聚体平均重量直径(2.04 mm)、毛管持水量(24.69%)及饱和含水量(34.93%)分别是裸地的4.33、1.36和1.31倍。长芒草群落土壤有机质含量(7.23 g·kg^(-1))最高。3)植物根系特征显著影响土壤性质,细根RLD与RSAD对土壤理化性质的影响最显著。细根RLD和RSAD与土壤容重显著负相关(P<0.05),与土壤孔隙度显著正相关(P<0.05),极细根(D<0.5 mm)与有机质含量极显著正相关(P<0.01)。主成分分析结果显示,长芒草与铁杆蒿改善土壤性质的差异主要体现在土壤团聚体平均重量直径(MWD)、有机质含量(SOM)和土壤含水量(SWC)。

高原鼠兔干扰对高寒草甸植物物种多样性与土壤生态化学计量比间关系的影响

植物物种多样性和土壤生态化学计量比间的关系,是草地植物群落结构维持的关键。高原鼠兔干扰虽被证实能够影响植物物种多样性、土壤有机碳、全氮和全磷的含量,但是否影响高寒草甸植物物种多样性和土壤生态化学计量比间的关系,尚不清楚。本研究以甘南和青海湖流域为对象,采用配对设置样地的方法,分析了高原鼠兔干扰对高寒草甸植物物种多样性和土壤生态化学计量比间关系的影响。结果表明:高原鼠兔干扰显著增加了物种丰富度指数、土壤有机碳、全氮和全磷含量,以及土壤C∶N和C∶P(P<0.05),但没有显著影响物种多样性指数、物种均匀度指数和土壤N∶P。高原鼠兔干扰增加了物种丰富度指数和物种多样性指数与土壤C∶N间的正相关性(P<0.05),减弱了物种丰富度指数与土壤C∶P间的正相关性(P<0.01);物种多样性指数与土壤C∶P间的关系从高原鼠兔未干扰生境的对数关系转变为干扰生境的二次函数关系(P<0.05),而物种丰富度指数与土壤N∶P间的关系从高原鼠兔未干扰生境的不显著相关,改变为干扰生境的显著负相关二次函数(P<0.01);物种多样性指数与土壤N∶P间的关系从未干扰生境的显著正相关二次函数(P<0.05),变为干扰生境的不显著相关,这确证了高原鼠兔干扰能够改变植物物种多样性与土壤生态化学计量比间的关系,为全面解释高原鼠兔干扰下草地植物群落结构的维持提供了基础信息。

白草塬植被恢复后沟头草本植物多样性与土壤因子的关系

[目的]探究黄土塬沟头在植被恢复后的草本植物多样性变化与土壤因子间的关系,为该区沟头水土保持效益评估提供科学依据。[方法]以农地沟头为对照,选择不同植被恢复年限(5,13,18,22 a)的白草塬草地沟头,调查和测定了各植被恢复年限沟头的草本植物多样性和表层土壤(0—10 cm和10—25 cm)的土壤性质因子。[结果]随植被恢复年限的增长,Patrick丰富度指数呈现先增大后稳定的变化趋势;Shannon-Wiener指数呈现持续上升的趋势,植被恢复18 a和22 a时的Shannon-Wiener指数高于恢复13 a,但没有显著性差异;Pielou均匀度指数呈现增加—降低—再增加的波动趋势,且在恢复22 a时达到最大值(0.89)。白草塬沟头0—10 cm和10—25 cm的土壤容重均在恢复22 a时达到最小值,较农地分别显著降低13.1%和17.8%(p<0.05);0—10 cm和10—25 cm的土壤有机质含量、水稳性团聚体含量、团聚体平均重量直径和饱和导水率均随植被恢复年限的增加而显著增加,两土层的土壤因子在各植被恢复年限上呈现出显著性差异。相关性分析显示草本植物多样性指标与容重间呈负相关关系,与土壤有机质、水稳性团聚体、团聚体平均重量直径以及饱和导水率呈显著正相关(p<0.05)。冗余分析表明土壤团聚体含量与草本植物多样性变化密切相关。[结论]植被恢复显著提高了沟头草本植物多样性,可改善表层土壤性质,在稳固沟头过程发挥重要作用。

Soil water depletion depth by planted vegetation on the Loess Plateau

Evapotranspiration of much planted vegetation exceeds precipitation, and this can deplete soil water and cause a deep dry layer in the soil profile, which is a serious obstacle to sustainable land use on the Loess Plateau, China. This study aimed to determine water depletion depth of planted grassland, shrub, and forest in a semiarid area on the Loess Plateau. Soil moisture of five vegetation types was measured to >20 m in depth. The vegetation types were crop, natural grasse, seven-year-old planted alfalfa (Medicago sativa L.), 23-year-old planted caragana (Caragana microphylla Lam.) shrub, and 23-year-old planted pine (Pinus tabulaeformis L) forest land. Through comparing moisture of planted alfalfa grass, caragana shrub, and pine forest to crop and natural grassland, the depth and amount of soil water consumed by grassland, caragana brush and pine forest was determined. The depth of soil water depleted by alfalfa, caragana brush, and pine forest reached 15.5, 22.4 and 21.5 m, respectively.

EFFECTIVENESS OF PLANT ROOTS TO INCREASE THE ANTI-SCOURABILITY OF SOIL ON THE LOESS PLATEAU

The recent study results show that the intensification ability of plant roots to the anti-scourability of soil mainly depends on the distribution and twining of effective root density in the soil profile, and the physical basis of effective root density is the number of

不同种植方式下黄土塬区土壤水分变化特征

【目的】从土壤水分变化的角度探究不同种植方式对黄土塬区水资源的影响,以期为雨养旱作农业的可持续发展、水资源的高效利用以及水分管理措施的改进提供理论依据。【方法】选取长武塬区三种不同种植方式下的土壤水分为研究对象,通过对2014—2017年对0~300 cm土层土壤含水量进行监测,分析单作小麦、单作玉米和小麦-玉米轮作三种种植方式下0~300 cm土壤剖面水分垂直分布特征、土壤水分季节变化特征和土壤干燥化指数。【结果】结果表明:(1)不同种植方式下,剖面上的土壤水分垂直分布动态表现出一定的层次性,活跃层分别为单作玉米0~60 cm,单作小麦0~30 cm,麦玉轮作0~10 cm,最大耗水深度从大到小依次为麦玉轮作,单作小麦和单作玉米。(2)三种种植方式都将在大量消耗期内引发土壤含水量下降,生育期内平均月储水量从大到小依次为单作玉米(607.7 mm),单作小麦(554.5 mm)和麦玉轮作(474.6 mm)。(3)三种种植方式都将造成短期土壤干燥化,其中麦玉轮作干燥化指数最高,为187.5,其次是单作小麦186.5,最低是单作玉米162.3。【结论】研究认为,不同种植方式下土壤水分的垂直分布动态表现出一定的层次性,且土壤水分具有明显的季节性波动变化特征,相比降雨和含水量变化,储水量变化更为滞后;土壤干燥化指数能够反映不同种植方式的水分利用状况,且受降雨量的影响较大,麦玉轮作方式将最不利于土壤水分的恢复。因此,在黄土塬区开展农业生产时,应合理选择种植方式,减少对土壤水分的消耗和破坏,以达到高效利用水资源的目的。

PRELIMINARY STUDY ON MECHANISM OF PLANT ROOTS TO INCREASE SOIL ANTISCOURIBILITY ON THE LOESS PLATEAU

The effects of the root system of trees, shrubs and grasses on the hydraulic andphysical properties of soil and their interrelation with increasing soil anti--scouribility byroots are quantitatively demonstrated in this paper for the first time. Based on the analysisof the leading factors of roots to increase the soil anti--scouribility, a mathematical modelon increasing soil anti-scouribility by roots is established. The value in application of themodel is to explain the mechanism of roots to increase the soil anti-scouribility and toevaluate the increasing effects of soil anti-scouribility by roots in different layers of soilThe calculated results of the values in soil anti--scouribility intensified by roots at variousintensities of rainfall and slopes of the model have higher precision, all of the meanmaximum deviations between the estimated and observed values being less than 1.417 s/g.

Reasonable management of perennial planting grassland contributes to positive succession of soil microbial community in Sanjiangyuan of Qinghai-Tibetan Plateau,China

Grassland reconstruction is a major approach to alleviate the‘black beach’in Sanjiangyuan of the Qinghai-Tibetan Plateau.It is vital to understand how to manage the planting grassland after reconstruction.And which artificial grassland management pattern is more likely to restore the degraded grassland of‘black beach?’To provide the scientific basis for the restoration of‘black beach’,we investigated the changes in vegetation characteristics,soil physicochemical properties and soil microbial community structure of planting grassland under different management patterns,and explored the effect of the management patterns on community succession of planting grassland.In this study,vegetation characteristics and soil physicochemical properties were measured by field investigation and laboratory analyses,respectively.Soil microbial community composition was determined by high-throughput sequencing techniques.The results showed that there were significant differences in vegetation characteristics,soil physicochemical properties and soil microbial community structure of the planting grassland under different management patterns.Actinobacteria and Basidiomycota were mainly controlled by vegetation plant species diversity,aboveground biomass(AGB)and soil organic carbon(SOC).Shannon-Wiener index,AGB and SOC peaked and the relative abundance of amplicon sequence variants annotated by Actinobacteria and Basidiomycota were significantly enriched under the management pattern of the planting once treatment.Additionally,the soil had the highest bacterial diversity and the lowest fungal diversity under the planting once treatment,becoming a‘bacterial’soil.These vegetation characteristics and soil environment were more conducive to overall positive community succession,indicating that the planting once treatment is the most reasonable management pattern for restoring the‘black beach’.

木里煤矿生态环境修复治理模式

木里煤矿位于青海省海西州木里镇,区域属于高寒草甸覆盖区,生态环境脆弱,为了解决高原高寒矿区生态脆弱、敏感,易遭破坏且难于恢复问题,采用以渣山地形地貌重塑技术、高原湖泊水系连通技术、冻土层保护、稀缺煤炭资源保护技术、土壤重构技术、自然生态集排水系统构建技术、高原植被重建技术为核心的高原高寒煤矿开采生态环境修复治理技术,对木里煤矿区露天采坑、渣山及裸露煤层进行了修复治理,实现了2 a复绿,这种集合了水系连通、土壤重构、封填煤层重塑冻土层及草七步法的高原高寒煤矿开采区生态环境修复治理模式对于高海拔高寒矿山环境修复具有重要实践意义。

Plant functional groups mediate effects of climate and soil factors on species richness and community biomass in grasslands of Mongolian Plateau

Aims Functional group composition of a plant community is mainly driven by environmental factors and is one of the main determinants of grassland biodiversity and productivity.Therefore,it is important to understand the role of plant functional groups(PFGs)in mediating the impact of environmental conditions on ecosystem functions and biodiversity.Methods We measured plant biomass and species richness(SR)of grasslands in 65 sites on the Mongolian Plateau and classified 157 perennial herbaceous plants into two main PFGs(namely grasses and forbs).Using the random forest model and ordinary least squares regression,we identified that environmental factors(i.e.aridity index,soil total nitrogen[STN]and pH)were significantly related to the SR and aboveground biomass(AGB)of PFGs.We then used structural equation modeling to explore the relationship between the identified environmental factors and community SR and biomass,and the role of PFGs in driving this relationship.Important Findings We found that aridity index had unimodal relationships with both AGB and SR of the PFGs and the whole community.All SR and biomass metrics were significantly related to STN and pH.The relationship between aridity index and community biomass was mediated by an increase in the AGB of grasses.The influence of STN and pH on community SR was mainly due to their regulation in the SR of forbs.Our results indicate that community composition and the identity of the PFGs play a key role in linking environmental factors to ecosystem functioning.