Effects of Caragana microphylla plantations on organic carbon sequestration in total and labile soil organic carbon fractions in the Horqin Sandy Land,northern China

Afforestation is conducive to soil carbon(C) sequestration in semi-arid regions. However, little is known about the effects of afforestation on sequestrations of total and labile soil organic carbon(SOC) fractions in semi-arid sandy lands. In the present study, we examined the effects of Caragana microphylla Lam. plantations with different ages(12-and 25-year-old) on sequestrations of total SOC as well as labile SOC fractions such as light fraction organic carbon(LFOC) and microbial biomass carbon(MBC). The analyzed samples were taken from soil depths of 0–5 and 5–15 cm under two shrub-related scenarios: under shrubs and between shrubs with moving sand dunes as control sites in the Horqin Sandy Land of northern China. The results showed that the concentrations and storages of total SOC at soil depths of 0–5 and 5–15 cm were higher in 12-and 25-year-old C. microphylla plantations than in moving sand dunes(i.e., control sites), with the highest value observed under shrubs in 25-year-old C. microphylla plantations. Furthermore, the concentrations and storages of LFOC and MBC showed similar patterns with those of total SOC at the same soil depth. The 12-year-old C. microphylla plantations had higher percentages of LFOC concentration to SOC concentration and MBC concentration to SOC concentration than the 25-year-old C. microphylla plantations and moving sand dunes at both soil depths. A significant positive correlation existed among SOC, LFOC, and MBC, implying that restoring the total and labile SOC fractions is possible by afforestation with C. microphylla shrubs in the Horqin Sandy Land. At soil depth of 0–15 cm, the accumulation rate of total SOC under shrubs was higher in young C. microphylla plantations(18.53 g C/(m~2·a); 0–12 years) than in old C. microphylla plantations(16.24 g C/(m~2·a); 12–25 years), and the accumulation rates of LFOC and MBC under shrubs and between shrubs were also higher in young C. microphylla plantations than in old C. microphylla plantations. It can be concluded that the establishment of C. microphylla in the Horqin Sandy Land may be a good mitigation strategy for SOC sequestration in the surface soils.     

高寒沙地不同林龄中间锦鸡儿的水分利用策略

中间锦鸡儿是青海共和盆地高寒沙地的主要造林灌木树种之一。文中利用稳定同位素技术,测定共和盆地不同林龄(5a,9a,25a)中间锦鸡儿枝条木质部和土壤各层(10,20,30,50,100,150,200cm)水分的δD值、δ18O值,分析它们是否随林龄变化而选择性地利用不同深度的土壤水分;并通过测定不同林龄中间锦鸡儿叶片的δ13C值,分析比较它们的长期水分利用效率。结果表明:5a,9a和25a中间锦鸡儿均主要利用源自降雨的土壤浅层10-50cm的水分。3个林龄中间锦鸡儿的水分利用效率差异显著(P<0.05),5a中间锦鸡儿明显高于9a和25a中间锦鸡儿,9a和25a中间锦鸡儿水分利用效率类似。水分利用策略的分析结果表明,中间锦鸡儿在发育低龄期,采取提高水分利用效率的方法来应对干旱胁迫。25a中间锦鸡儿未发生明显退化。     

Soil exchangeable base cations along a chronosequence of Caragana microphylla plantation in a semi-arid sandy land,China

As a pioneer leguminous shrub species for vegetation re-establishment,Caragana microphylla is widely distributed in the semi-fixed and fixed sandy lands of the Horqin region,North China.C.microphylla plantations modify organic carbon(SOC),nitrogen(N) and phosphorus dynamics,bulk density and water-holding capacity,and biological activities in soils,but little is known with regard to soil exchange properties.Variation in soil exchangeable base cations was examined under C.microphylla plantations with an age sequence of 0,5,10,and 22 years in the Horqin Sandy Land,and at the depth of 0-10,10-20,and 20-30 cm,respectively.C.microphylla has been planted on the non-vegetated sand dunes with similar physical-chemical soil properties.The results showed that exchangeable calcium(Ca),magnesium(Mg),and potassium(K),and cation exchange capacity(CEC) were significantly increased,and Ca saturation tended to decrease,while Mg and K saturations were increased with the plantation years.No difference was observed for exchangeable sodium(Na) neither with plantation years nor at soil depths.Of all the base cations and soil layers,exchangeable K at the depth of 0-10 cm accumulated most quickly,and it increased by 1.76,3.16,and 4.25 times,respectively after C.microphylla was planted for 5,10,and 22 years.Exchangeable Ca,Mg,and K,and CEC were significantly(P<0.001) and positively correlated with SOC,total N,pH,and electrical conductivity(EC).Soil pH and SOC are regarded as the main factors influencing the variation in exchangeable cations,and the preferential absorption of cations by plants and different leaching rates of base cations that modify cation saturations under C.microphylla plantation.It is concluded that as a nitrogen-fixation species,C.microphylla plantation is beneficial to increasing exchangeable base cations and CEC in soils,and therefore can improve soil fertility and create favorable microenvironments for plants and creatures in the semi-arid sandy land ecosystems.     

Plantations of native shrub species restore soil microbial diversity in the Horqin Sandy Land,northeastern China

Caragana microphylla Lam., a leguminous shrub species, plays an important role in revegetation in the degraded ecosystems of the Horqin Sandy Land, Northeastern China. Large areas planted with this shrub have been artificially established as sand binders for soil protection, which might change the composition of soil bacterial communities with the development of sand dune stabilization. In this paper, we investigated the diversity and composition of native soil bacterial communities in the C. microphylla plantation for sand fixation using polymerase chain reaction with denaturing gradient gel electrophoresis（PCR-DGGE） to understand the influence of this plantation on sandy soil ecosystem development. We collected soil samples from plantations with an age sequence of 0, 9, 16, and 26 years, as well as from the natural community, to identify the differences among soil bacterial communities. The result showed that bacterial abundance and community composition in the sandy land were affected by the age of the C. microphylla plantation. Moreover, bacterial diversity decreased with increasing plantation age, and the composition of the bacterial community in the 26-year plantation was similar to that in the natural community. Phylogenetic analysis of bands excised from the DGGE gels showed that members of alpha Proteobacterium, gamma Proteobacterium, Gemmatimonadetes and Chloroflexi were dominant in the sandy land. The stabilization of moving sand dune and development of sand-fixed plantation resulted in an increase of soil fertility, which could drive the structural evolvement of soil bacterial community, and it needs over 20 years for the soil bacterial community to form a stable structure, similar to the case for the natural vegetation.     

库布齐沙地柠条根际土壤微生物生物量及其与土壤因子的关系

对库布齐沙地柠条根际、非根际土壤微生物生物量碳、氮分布状况及其与土壤因子的关系进行了研究。结果表明:柠条土壤生物量碳、氮含量的分布趋势均为根际土壤>非根际土壤>流沙,且以表层(0-10cm)最高,随土层加深,呈下降趋势;柠条土壤中微生物量碳、氮对土壤有机质、全氮的贡献率分别为1.55%-4.73%,5.61%-13.39%,微生物量碳氮比为3.10-7.22;微生物量碳氮间呈显著正相关,土壤全氮、有机质含量与土壤微生物生物量碳、氮相关性最大。     

科尔沁沙地小叶锦鸡儿人工林防风固沙及改良土壤效应研究

为探讨小叶锦鸡儿防风固沙、改良土壤养分状况和生物活性的能力,选取6年和11年生小叶锦鸡儿人工固沙林为对象,以流动沙丘为对照,研究不同年龄固沙林降低风速和风沙流结构特征、土壤有机质和N,P含量、土壤酶的活性以及微生物生物量C,N,P含量的变化特征.结果表明:在小叶锦鸡儿灌木林内,各个高度风速和输沙量均显著低于流动沙丘,防风固沙效果明显.随着小叶锦鸡儿固沙群落发育时间的增长,其综合防风性能提高,土壤有机质、N,P,K含量和生物活性逐渐得到改善.O～30 cm土层中磷酸单酯酶、蛋白酶、脲酶、蔗糖酶、硝酸还原酶、多酚氧化酶、脱氢酶的活性和土壤微生物生物量C,N和P含量均大幅度提高,其中O～10 cm土层增幅最大.土壤酶中蔗糖酶的活性增加最为迅速,6年和11年生固沙林O～10 cm 土层分别是流动沙丘的28.58倍和55.21倍.小叶锦鸡儿不仅具有较好的防风固沙性能,而且表现出强大的改善土壤养分和生物活性的能力,可作为优良的固沙植物材料在科尔沁沙地大面积推广应用.     

Persistence of four dominant psammophyte species in central Inner Mongolia of China under continual drought

Clarifying the persistence time of seedlings of dominant species under continual drought will help us understand responses of ecosystems to global climate change and improve revegetation efforts.Drought tolerance of four dominant psammophytic shrub species occurring in different environments was studied in the semi-arid areas of Inner Mongolian grasslands.Seedlings of Hedysarum laeve,Caragana korshinskii,Artemisia sphaerocephala and Artemisia ordosica were grown under four air temperature regimes(night/day:12.5/22.5℃,15/25℃,17.5/27.5℃ and 20/30℃)within climate(air temperature and humidity)controlled,naturally lit glasshouses with a night/day relative humidity of 70%/50%.Pots were watered to field capacity for each temperature treatment.Soil water condition was monitored by weighting each pot every day using an electronic balance.Date of seedling death for each treatment was recorded and the dead plants were harvested.Plant dry weights were determined after oven drying at 80℃ for 3 days.Two Artemisia species had higher growth rates than H.laeve and C.korshinskii,and the growth of all four species increased with increasing temperatures.The two Artemisia species had the highest leaf biomass increment,followed by C.korshinskii,and then H.laeve.Shoot biomass increment was higher for A.ordosica and C.korshinskii,intermediate for A.sphaerocephala and lowest for H.laeve.C.korshinskii had the highest root biomass increment.The final soil water content at death for all four species varied from 1% to 2%.C.korshinskii,A.sphaerocephala,H.laeve and A.ordosica survived for 25-43,24-41,26-41,and 24-37 days without watering,respectively.C.korshinskii,A.sphaerocephala,H.Laeve,and A.ordosica seedlings survived longer at the lowest temperatures(12.5/22.5℃)than at the highest temperatures(20/30℃)by 18,17,15 and 13 days,respectively.Increased climatic temperatures induce the death of seedlings in years with long intervals between rainfall events.The adaptation of seedlings to droughts should be emphasized in revegetation efforts in the Ordos Plateau,Inner Mongolia.     

吴起县退耕还林后主要植被类型土壤质量评价

为明确吴起县退耕还林后形成的主要植被类型土壤质量状况,文中以吴起县王洼子典型退耕植被作为研究对象,对比分析不同植被类型土壤理化性质差异,并综合主成分分析法、敏感性以及相关性分析法,建立了研究区土壤质量评价指标最小数据集.结果表明:1)不同植被类型间土壤物理、化学性质差异显著(P＜ 0.05);山桃×沙棘混交林在土壤孔隙...     

6种常用固沙植物的生态经济价值比较

通过分析小叶锦鸡儿(Caragana microphylla Lam)、中间锦鸡儿(Caragana in-termedia Kuang)、柠条锦鸡儿(Caragana korshinskii Kom)、塔落岩黄芪(Hedysarumleave Maxim)、细枝岩黄芪(Hedysarum scoparium Fisch)和山竹岩黄芪(Hedysarum fruti-cosum Pall)的光合作用、水分利用效率、生物量、营养成分、土壤改良作用和防风固沙作用,结果表明,岩黄芪属3种植物的生态经济价值明显优于锦鸡儿属3种植物。     

内蒙古西部干旱地区柠条开花结实特性及其果荚、种子发育研究

在柠条锦鸡儿、中间锦鸡儿和小叶锦鸡儿3种柠条中,中间锦鸡儿花期最短;小叶锦鸡儿和中间锦鸡儿的盛花期约在5月中下旬,并在5月下旬、6月上旬进入结实盛期,柠条锦鸡儿较前两者晚约半个月;种子采收前,92.42%的柠条锦鸡儿种子长度大于3mm,完全发育成熟,较小叶锦鸡儿高22.49%,较中间锦鸡儿高21.41%;3种柠条果荚长度均在20mm以上,但在20~30mm、30~40mm两个长度段上的比例分配有较大差距;3种柠条所有果荚的宽度均大于3 mm,但在3~6mm、6~9mm两个宽度段的构成比例有明显差异;柠条锦鸡儿花果总损失率最大,为82.37%;小叶锦鸡儿为75.96%;中间锦鸡儿为65.98%。     

风沙区不同土地利用类型的土壤水分灰色关联分析

运用灰色关联分析法,对宁夏风沙区盐池县马儿庄村4种不同土地利用类型土壤水分的垂直变化和月变化动态进行分析.结果表明:不同类型土壤水分垂直变化规律不尽相同,中层(30～70 cm)与深层(70～100 cm)土壤水分变化态势的相似程度均较高,但相似程度柠条>天然草场>甘草>苜蓿,表层(0～30 cm)与深层(70～100cm)的灰色关联度最小,土壤水分变化态势差异最大;从各月土壤水分灰色关联度来看,甘草8～10月份土壤水分灰色关联度较大,土壤水分变化态势的相似程度较高,7月份的差异明显;柠条在9月份的灰色关联度达到了最小,其他各月相似度逐渐增大;而苜蓿和天然草场土壤水分灰色关联度波动很大,变化趋势为大-小-大-小.灰色关联分析法可以较好地反映不同土地利用类型土壤水分变化趋势的相似或相异程度.     

Biological soil crust distribution in Artemisia ordosica communities along a grazing pressure gradient in Mu Us Sandy Land,Northern China

This study investigated the distribution pattern of biological soil crust (BSC) in Artemisia ordosica communities in Mu Us Sandy Land. Three experimental sites were selected according to grazing pressure gradient. In each experimental site, the total vegetation cover, A. ordosica cover, BSC cover, litter-fall cover, BSC degree of fragmentation, BSC thickness and soil properties were investigated in both fixed and semi-fixed sand dunes and simultaneously analyzed in the laboratory. The results showed that at the same grazing pressure, BSC cover and composition were significantly affected by the fixation degree of sand dunes. In addition, BSC cover in the fixed sand dunes was 83.74% on average, whereas it is proportionally dominated by 28% mosses, 21% lichens, and 51% algae. Meanwhile, BSC cover in the semi-fixed sand dunes was 23.54% on average, which is proportionally dominated by 6.3% mosses, 2.5% lichens, and 91.2% algae. Fine sand, organic matter, and total nitrogen (N) contents in the fixed sand dunes were all significantly higher than those in the semi-fixed sand dunes. Litter-fall cover decreased along the grazing pressure gradient, whereas BSC fragmentation degree increased. Fine sand content decreased along with the increase of grazing pressure, whereas medium sand content increased in both fixed and semi-fixed dunes. The organic matter and total N contents in the no grazing site were significantly higher than those in light and normal grazing sites. However, there were no significant differences between the light and normal grazing sites. In addition, there were also no significant differences in BSC thickness between the light and normal grazing sites in the fixed sand dunes. However, a significant decrease was observed in both BSC cover and thickness in the normal grazing site. The BSC in the semi-fixed dunes was more sensitive to disturbance.     

高寒沙区中间锦鸡儿人工林细根动态及其周转

通过对青海省治沙试验站3 a、5 a、10 a、16 a和30 a生的中间锦鸡儿(Caragana intermedia Kuang et H. C.Fu)人工林细根生物量的测定分析,了解其细根生物量的垂直分布和动态变化特征以及周转速率。结果表明:①中间锦鸡儿人工林约41%的活细根和39%的死细根分布在0~20 cm的土层,38%的活细根和死细根分布在20~40 cm的土层,21%的活细根和23%的死细根分布在40~60 cm的土层。②细根生物量表现出明显的季节动态性,活细根生物量峰值出现在6月和8月或者6月和9月,8月或9月达到最大值;死细根生物量峰值出现8月和9月,也是8月或9月达到最大值。③不同林龄人工林细根周转速率分别为:0. 53、0. 66、0. 56、0. 73、0. 78次·a^-1。④细根生物量和周转率均随林龄增大而增加,随土层加深而减小。     

腾格里沙漠南缘3种优势植物种子出苗对土壤类型和沙埋的响应

沙米（Agriophyllum squarrosum）、沙蒿（Artemisia sphaerocephala）和油蒿（Artemisia ordosica）分别是腾格里沙漠南缘不同植被演替阶段的3个优势物种,2009年5～6月在大田盆栽条件下,设计了2种土壤类型和0 cm,1 cm,2 cm,3 cm,4 cm,6 ...     

宁夏盐池沙地不同密度人工柠条林土壤水分时空变化分析

对宁夏盐池退化沙地不同密度的人工柠条林地的土壤水分时空特征进行分析。结果表明:1)林下土壤体积含水量随着深度的增加呈先增大后降低的趋势,在垂直剖面上可分为土壤水分速变层(0-20cm)、活跃层(20-80cm)、相对稳定层(80-100cm);2)土壤水分季节动态变化可划分为:积累期(4-5月);消耗期(6-9月);稳定期(10月至次年4月)3个时期;3)土壤体积含水量随人工林密度增加呈下降趋势,2490丛/hm2和1665丛/hm2可作为该区人工柠条林调控密度的参考依据。     

Soil properties and herbaceous characteristics in an age sequence of Haloxylon ammodendron plantations in an oasis-desert ecotone of northwestern China

Haloxylon ammodendron,a typical desert shrub with C4 pathway of photosynthesis,possessing a strong ability to adapt to an extreme drought environment,has a rapid growth rate in sandy lands and is widely used in sand-fixing shelter-forest systems in oasis-desert ecotones.To assess the effects of H.ammodendron plantation on the soil,we measured soil properties and herbaceous characteristics along a nearly 40-year chronosequence after H.ammodendron was planted in shifting sand dunes in an oasis-desert ecotone.Results showed that silt and clay fractions increased significantly in the topsoil.The accumulation rates of soil organic carbon(SOC),total nitrogen(TN) and total phosphorus(TP) were faster in the early stages(0–9 years) and slower in the late stages(9–39 years).The soil p H and electrical conductivity(EC) were higher than those in the non-vegetation dunes.Moreover,the soil properties in the topsoil(0–5 cm) showed larger variation scope than those in the deeper soil layers(5–20 cm).The significant relationships of the soil silt+clay content with the chemical properties mainly appeared in the topsoil.The wind erosion susceptibility of the soil,evaluated by erodible fraction(EF),decreased significantly with increasing H.ammodendron plantation age.Additionally,the annual pioneer herb,Agriophyllum squarrosum,was gradually substituted by the annual salt-tolerant herb,Bassia dasyphylla,with increasing plantation age.These results showed beneficial effects of H.ammodendron plantation on improving soil conditions.However,the dynamics of the herbaceous species also reminded us that the longterm effects of H.ammodendron plantation,especially on changes in vegetation composition,still need further evaluation.     

西宁盆地4种草本和灌木植物降盐效应试验研究

以西宁盆地长岭沟流域自建试验区为研究区,筛选出适宜当地气候条件下生长的2种灌木植物柠条锦鸡儿(Caragana korshinskii Kom.)、霸王[Zygophyllum xanthoxylon(Bunge)Maxim.]和2种草本植物细茎冰草(Agropyron trachycaulum cv.Slender)、紫花苜蓿(Medicago sativa Linn.)作为试验供试种,在试验区对4种植物采用单一种植和组合种植方式,探讨2种种植条件下植物根系在边坡地表以下垂直方向土体中K^+、Ca^2+、Na^+、Mg^2+、SO4^2-、Cl^-、HCO3^-、CO3^2-等8种易溶盐离子含量及其变化特征,评价了区内2种草本和2种灌木植物降低边坡土体盐分的能力。结果表明:单一种植细茎冰草、紫花苜蓿、柠条锦鸡儿、霸王对边坡土体中SO4^2-、Ca^2+、Na^+具有显著降低作用,草本与灌木组合Ⅰ(柠条锦鸡儿+紫花苜蓿+细茎冰草组合)和草本与灌木组合Ⅱ(霸王+紫花苜蓿+细茎冰草组合)对边坡土体中SO4^2-、Ca^2+、Mg^2+、K^+、Na^+表现出显著降低作用;紫花苜蓿的降盐效果相对较为显著、其次为柠条锦鸡儿和细茎冰草,霸王的降盐效果不及前者显著;草本与灌木组合Ⅱ的降盐效果相对显著于草本与灌木组合Ⅰ。     

低覆盖度柠条固沙林不同配置对植被修复的影响

低覆盖度行带式固沙林具有显著的防风固沙效果,已经在我国的半干旱地区广泛推广。针对内蒙古自治区呼和浩特市和林格尔县不同配置的柠条锦鸡儿人工林,进一步研究不同带间宽度带内植被自然恢复过程及物种多样性的差异,结果表明:(1)在覆盖度为20%左右时,合理的行带式格局分布的柠条锦鸡儿人工林带间植被的恢复效果优于随机分布格局的样地。(2)柠条行带式造林不宜太窄和盖度太大,会影响其林下物种丰富度。(3)宽的带间距带内物种丰富度与物种多样性和均匀度以及其生物量变化曲线呈现了两个高峰,出现在距柠条带6-8m左右,而窄的带间距带内只有一个高峰。因此,该地区柠条带宽度为12m-16m可以使其带内的草本物种多样性和生物量达到最大。     

Diversity of soil bacteria and fungi communities in artificial forests of the sandy-hilly region of Northwest China

Soil erosion is a serious issue in the sandy-hilly region of Shanxi Province, Northwest China. There has been gradual improvement due to vegetation restoration, but soil microbial community characteristics in different vegetation plantation types have not been widely investigated. To address this, we analyzed soil bacterial and fungal community structures, diversity, and microbial and soil environmental factors in Caragana korshinskii Kom., Populus tomentosa Carr., Populus simonii Carr., Salix matsudana Koidz, and Pinus tabulaeformis Carr. forests. There were no significant differences in the dominant bacterial community compositions among the five forest types. The alpha diversity of the bacteria and fungi communities showed that ACE (abundance-based coverage estimator), Chao1, and Shannon indices in C. korshinskii forest were significantly higher than those in the other four forest types (P<0.05). Soil organic matter, total nitrogen, and urease had a greater impact on bacterial community composition, while total nitrogen, β-glucosidase, and urease had a greater impact on fungal community composition. The relative abundance of beneficial and pathogenic microorganisms was similar across all forest types. Based on microbial community composition, diversity, and soil fertility, we ranked the plantations from most to least suitable as follows: C. korshinskii, S. matsudana, P. tabulaeformis, P. tomentosa, and P. simonii.     

Sand-fixing characteristics of Carex brunnescens and its application with straw checkerboard technique in restoration of degraded alpine meadows

Carex brunnescens(Pers.), a typical clonal species, is considered to be the only herb found to date that can develop on sand dunes in Maqu alpine region of northwestern China. However, the characteristics that C. brunnescens resists to harsh alpine environment have not been documented. In this study, we conducted a field investigation to determine the morphological, reproductive, and sand-fixing characteristics of C. brunnescens. Concomitantly, we transplanted the belowground rhizomes of C. brunnescens to sand dunes and compared the abilities to restore degraded alpine meadows among sand dunes that had no further treatment(SD+N), sand dunes that had straw checkerboard technique but no transplanted rhizomes of C. brunnescens(SD+SCT), and sand dunes that had both SCT and transplanted rhizomes of C. brunnescens(SD+SCT+P). We found that belowground vertical rhizomes and horizontal rhizomes(including branching rhizomes and main rhizomes) of C. brunnescens were highly developed and that population reproduction was dominated by horizontal rhizomes. C. brunnescens exhibited a significant sand-fixation effect under following conditions: population density was 145–156 ramets/m~2, vegetation cover was 31.2%–39.3%, total length of belowground rhizomes was 11,223 cm/m~2, total length of belowground first-order roots was 9161–10,524 cm/m~2, fresh weight of aboveground part was 198.5–212.6 g/m~2, and fresh weight of belowground part was 578.8–612.4 g/m~2. It should be particularly noted that SD+SCT+P treatment(sand dunes that had both straw checkerboard technique and transplanted rhizomes of C. brunnescens) was the best and SD+N(sand dunes that had no further treatment) was the worst in terms of following biotic indicators: total number of reproductive ramets, total number of belowground rhizomes, and fresh weight of aboveground and belowground parts of C. brunnescens, contents of soil organic carbon, available nitrogen, microbial biomass carbon, and microbial biomass nitrogen. It implies that applying SCT in sand dunes and transplanting belowground rhizomes to sand dunes with SCT could improve both soil fertility and growth of C. brunnescens. These results suggest that the SCT-promoted high reproductive abilities of belowground rhizomes of C. brunnescens can successfully facilitate the establishment of ramets and can thus be an effective strategy to restore degraded vegetation in Maqu alpine region of northwestern China.