不同放牧强度下短花针茅荒漠草原植被-土壤系统有机碳组分储量特征

草地生态系统作为陆地生态系统的重要组成部分,在全球碳循环中发挥着重要作用。以内蒙古短花针茅荒漠草原不同放牧强度样地为研究对象,通过分析地上植物、凋落物、根系、土壤中有机碳和土壤轻组有机碳,研究草原植被-土壤系统有机碳组分储量的变化特征,从碳储量角度为合理利用草原提供指导。研究结果表明:(1)不同放牧强度荒漠草原地上植物碳储量为11.98—44.51 g/m~2,凋落物碳储量10.43—36.12 g/m~2,根系(0—40cm)碳储量502.30—804.31 g/m~2,且对照区(CK)均显著高于中度放牧区(MG)、重度放牧区(HG);(2)0—40cm土壤碳储量为7817.43—9694.16 g/m~2,其中轻度放牧区(LG)碳储量为9694.16 g/m~2,显著高于CK、HG(P0.05);(3)植被—土壤系统的碳储量为8342.14—10494.80 g/m~2,LGMGCKHG,有机碳主要储存于土壤当中,占比约90.54%—93.71%,适度放牧利用有利于发挥草地生态系统的碳汇功能;(4)土壤轻组有机碳储量为484.20—654.62 g/m~2,LG储量最高,表明适度放牧有助于草原土壤营养物质的循环和积累。     

放牧对荒漠草原克氏针茅种群和土壤生态化学计量特征的影响

该研究选取内蒙古荒漠草原,设计无牧区(NG)、中度放牧(MG)、重度放牧(HG)3个处理,测定分析不同放牧强度处理5年后,优势植物克氏针茅以及土壤的C、N、P营养元素的化学计量特征及其协同关系,以揭示放牧生态系统养分循环的影响机制,为区域草地的利用以及修复提供理论依据。结果表明:(1)轻度放牧下荒漠草原的物种多样性均显著高于中度和重度放牧条件(P<0.05)。(2)土壤中C、N含量以及C∶N、N∶P、C∶P,均随着放牧强度的增加呈先升高后降低的变化趋势,土壤P含量随放牧强度的增加而升高。(3)随放牧强度增加,克氏针茅地上部分C含量降低,N、P含量以及N∶P先升高后降低,C∶P则先减少后升高;克氏针茅地下部分的C、N含量以及N∶P一直呈增加的趋势,P含量先减少后升高,而C∶N、C∶P则是与P含量规律相反。(4)与地上部分各元素含量相比,克氏针茅地下部分各元素含量及其比值与土壤中各元素含量的相关性更高,说明放牧条件下荒漠草原优势植物的根系与其所处的土壤环境具有一定的协同变化能力。     

草原土壤微生物受放牧的影响及其季节变化

以内蒙古克什克腾旗西部的典型草原为对象,研究轻度放牧区(LG)、中度放牧区(MG)、重度放牧区(HG)土壤中的微生物数量、微生物生物量和土壤呼吸强度的季节变化以及放牧强度对它们的影响。结果表明,微生物数量、微生物生物量以及土壤的呼吸作用强度均有较明显的季节性变化,峰值均出现在8月份,而且三者之间具有极显著的正相关关系;轻度和中度放牧有利于土壤中的微生物数量、生物量的增加,而重度放牧则导致土壤中微生物数量和生物量的减少。     

氮和水分添加对内蒙古荒漠草原放牧生态系统土壤呼吸的影响

土壤呼吸是生态系统碳循环的重要组成部分,同时也是评价生态系统健康状况的重要指标,对于评估退化草地恢复过程中生态系统功能具有重要意义。该研究在内蒙古四子王旗短花针茅(Stipabreviflora)荒漠草原长期放牧实验平台上进行,该平台设置对照(CK)、轻度(LG)、中度(MG)和重度(HG) 4个放牧强度。通过在4个放牧处理区设置氮、水添加实验处理,探讨不同放牧强度背景下,氮、水补充对荒漠草原土壤呼吸过程的影响。结果表明:(1)历史放牧强度除2015年对土壤呼吸无显著影响,2016和2017年都有显著影响,放牧区3年平均土壤呼吸速率基本都高于对照区。此外,氮和水分添加显著增加了MG区土壤呼吸速率,HG区氮、水同时添加对土壤呼吸速率有显著增加作用;(2)无论是历史放牧强度,还是氮、水添加处理,都没有改变荒漠草原生长季土壤呼吸速率的季节动态变化趋势,土壤呼吸速率基本表现为单峰曲线模式,峰值出现在水热同期的7月份;(3)不同年份生长季土壤呼吸速率对氮、水处理的响应并不相同,氮添加至第3年产生显著影响。水分添加在平水年份(2015和2017年)对土壤呼吸产生显著影响,但在丰水年份(2016年)无显著影响。氮、水共同添加分别在CK、LG和HG区3年平均土壤呼吸速率显著高于单独加水处理,说明氮添加的有效性依赖于水分条件,两者表现为协同作用;(4)不同处理下荒漠草原土壤呼吸的温度敏感性(Q_(10))值介于1.13–2.41之间,平均值为1.71。在无氮、水添加时,放牧区的Q_(10)值都小于CK区,总体表现为CK MG LG HG;加水和氮水共同添加处理后, Q_(10)值都有明显增加,其中NW处理下Q_(10)值都增加到2.0以上。上述结果说明在过去受不同放牧强度影响的荒漠草原在停止放牧后的恢复过程中,土壤水分仍是影响土壤呼吸的主导环境因子,外源氮添加只有在满足一定水分供给的基础上才起作用,尤其是过去的重度放牧区土壤呼吸速率对氮、水补充的响应最为强烈。该研究结果可以为评估荒漠草原恢复过程中土壤呼吸速率受养分和水分影响提供基础资料和依据。     

氮和水分添加对内蒙古荒漠草原放牧生态系统土壤呼吸的影响

土壤呼吸是生态系统碳循环的重要组成部分, 同时也是评价生态系统健康状况的重要指标, 对于评估退化草地恢复过程中生态系统功能具有重要意义。该研究在内蒙古四子王旗短花针茅(Stipa breviflora)荒漠草原长期放牧实验平台上进行, 该平台设置对照(CK)、轻度(LG)、中度(MG)和重度(HG) 4个放牧强度。通过在4个放牧处理区设置氮、水添加实验处理, 探讨不同放牧强度背景下, 氮、水补充对荒漠草原土壤呼吸过程的影响。结果表明: (1)历史放牧强度除2015年对土壤呼吸无显著影响, 2016和2017年都有显著影响, 放牧区3年平均土壤呼吸速率基本都高于对照区。此外, 氮和水分添加显著增加了MG区土壤呼吸速率, HG区氮、水同时添加对土壤呼吸速率有显著增加作用; (2)无论是历史放牧强度, 还是氮、水添加处理, 都没有改变荒漠草原生长季土壤呼吸速率的季节动态变化趋势, 土壤呼吸速率基本表现为单峰曲线模式, 峰值出现在水热同期的7月份; (3)不同年份生长季土壤呼吸速率对氮、水处理的响应并不相同, 氮添加至第3年产生显著影响。水分添加在平水年份(2015和2017年)对土壤呼吸产生显著影响, 但在丰水年份(2016年)无显著影响。氮、水共同添加分别在CK、LG和HG区3年平均土壤呼吸速率显著高于单独加水处理, 说明氮添加的有效性依赖于水分条件, 两者表现为协同作用; (4)不同处理下荒漠草原土壤呼吸的温度敏感性(Q₁₀)值介于1.13-2.41之间, 平均值为1.71。在无氮、水添加时, 放牧区的Q₁₀值都小于CK区, 总体表现为CK 大于 MG 大于 LG 大于 HG; 加水和氮水共同添加处理后, Q₁₀值都有明显增加, 其中NW处理下Q₁₀值都增加到2.0以上。上述结果说明在过去受不同放牧强度影响的荒漠草原在停止放牧后的恢复过程中, 土壤水分仍是影响土壤呼吸的主导环境因子, 外源氮添加只有在满足一定水分供给的基础上才起作用, 尤其是过去的重度放牧区土壤呼吸速率对氮、水补充的响应最为强烈。该研究结果可以为评估荒漠草原恢复过程中土壤呼吸速率受养分和水分影响提供基础资料和依据。     

互花米草入侵下湿地土壤碳氮磷变化及化学计量学特征

为阐明外来物种入侵对生态系统的改变,对闽江河口区本土植物短叶茳芏和不同入侵年限的互花米草湿地土壤总碳(TC)、总氮(TN)、总磷(TP)含量进行了测定与分析.结果表明: 互花米草入侵后0～50 cm深度各层土壤TC、TN和TP含量均有不同程度的增加,其中TC、TN的变化比较一致,而TP的变化滞后;TC的增加引起土壤C/N持续增加,而TP是调节互花米草入侵过程中湿地土壤C/P和N/P的关键因子,C/P和N/P的变化基本一致.土壤TC、TN、TP的变化受到土壤盐度、容重、含水量和黏粒组成的影响,而它们之间计量比主要受土壤盐度、粒径组成的影响;C/N和C/P对互花米草湿地的土壤固碳效应具有良好的指示作用.互花米草入侵引起生物量和湿地生境改变,导致土壤碳氮磷含量及其生态化学计量比发生显著变化,且随入侵时间延长表现出不同的变化特征.     

放牧强度对华北农牧交错带典型草地土壤化学计量特征的短期影响

放牧是天然草地的主要利用方式之一,不同放牧强度可能通过影响家畜的选择性采食、凋落物输入和微生物的组成及结构等影响草地土壤化学计量特征。本研究通过在华北农牧交错带典型草地一个连续3年(2017—2019年)的生长季放牧试验,测定了土壤全碳(TC)、全氮(TN)、可溶性有机碳(DOC)和可溶性氮(DN)含量,以及土壤微生物生物量碳(MBC)和微生物生物量氮(MBN),分析这些参数间的化学计量特征,研究放牧强度对该地区草地土壤计量化学特征的影响。结果表明: 连续3年不同强度的放牧(1、2、4 sheep·0.2 hm^-2)对土壤TC含量没有显著影响,2019年中度放牧显著降低了10～20 cm土层中TN含量,轻度、中度和重度放牧显著提高10～20 cm层土壤的C/N。连续3年不同强度的放牧对土壤DOC、DN含量以及DOC/DN均没有显著影响,而DOC和DN含量在2019年呈现出随放牧强度增加而减少的趋势,表明持续高强度的放牧可能会引起土壤可溶性养分减少。随着放牧年限的增长,轻度放牧显著增加了土壤MBC,重度放牧显著降低了土壤MBC,而土壤MBN及MBC/MBN在不同放牧强度下变化不显著。     

长期不同放牧强度下荒漠草原建群种短花针茅(Stipa breviflora)叶片解剖结构变化

植物叶片解剖结构随放牧强度的变化而发生变化。以短花针茅荒漠草原长期(19年)固定监测放牧样地为研究区,以建群种短花针茅叶片作为实验材料,测量不同放牧强度(对照(CK)、轻度放牧(LG)、中度放牧(MG)、重度放牧(HG))下短花针茅叶片保护组织、输导组织、机械组织、同化组织有关的14个解剖结构指标,分析短花针茅叶片解剖结构随长期不同放牧强度的变化,从生理角度探讨荒漠草原植物对长期放牧的适应及响应。研究结果表明：(1)叶片层次上,短花针茅通过增加其叶片横切面面积和叶厚度去适应放牧干扰;(2)保护组织方面,与对照区相比,重度放牧区角质层厚度增加,但未达到差异显著性(P>0.05),角质层厚度占叶厚度比例随放牧强度的增加整体呈增加趋势;(3)输导组织方面,木质部面积随放牧强度的增加呈下降趋势,而韧皮部面积、主导管面积、维管束面积等指标均随放牧强度的增加呈增加趋势,但没有达到显著性(P>0.05);(4)机械组织方面,厚壁组织面积和厚壁组织占叶面积比例均随放牧强度的增加呈增加趋势;(5)同化组织方面,随着放牧强度的增加,短花针茅叶片叶肉组织面积显著增加(P<0.05)。可见,...     

宁夏荒漠草原优势植物生长及生物量分配对放牧干扰的响应

于2011年植物生长旺季(8月)在围封禁牧(NG)、轻度放牧(LG)、中度放牧(MG)和重度放牧(HG)区分别随机选取荒漠草原优势植物甘草(Glycyrrhiza uralensis)和牛心朴子(Cynanchum komarovii)各15株为研究对象,对比分析其生长特征、各植物构件生物量及生物量资源分配差异对不同放牧强度的响应机制,为退化草原的恢复演替提供依据。结果表明:(1)甘草株高和地径、牛心朴子株高均随放牧强度的增加呈先升高后下降的趋势,而且均在轻度放牧条件下最高,重度放牧时则显著降低。(2)甘草和牛心朴子的总生物量、茎生物量和叶生物量随着放牧强度的增加呈先升高后降低的趋势,且不同放牧强度间差异显著;甘草和牛心朴子根系生物量随放牧强度的加强变化趋势不同。(3)甘草和牛心朴子生物量分配的总体格局为:根叶茎;随着放牧强度的增加,甘草根生物量比呈先升高后降低趋势,茎生物量比呈下降的趋势,叶生物量比呈上升趋势,而牛心朴子根生物量比呈先下降后升高的趋势,茎生物量和叶生物量呈先增加后下降的趋势。研究认为,不同放牧强度下两种植物形态可塑性和生物量分配格局的差异反映出植物生态适应策略的不同。     

短花针茅叶片水分利用效率对放牧强度的响应及其影响因素

为明确植物的用水策略及适应性机制,以内蒙古四子王旗短花针茅荒漠草原为研究对象,设置对照(CK)、轻度放牧(LG)、中度放牧(MG)和重度放牧(HG)4个放牧梯度,其载畜率分别为每1 hm^(2)每年0、0.93、1.82和2.71个羊单位的放牧强度,调查建群种短花针茅的高度、盖度、密度、地上生物量以及土壤的理化性状,并且采用稳定碳同位素法和红外光合仪法对短花针茅水分利用效率进行了测定,旨在阐明短花针茅水分利用效率在不同放牧强度下的响应规律及其影响因素。结果显示:(1)放牧对短花针茅盖度、密度以及地上生物量的影响显著;随着载畜率的增大,有利于短花针茅的扩散使其分布面积增加,且在中度放牧条件下尤为明显。(2)随着放牧强度的增加,土壤水分含量较对照显著提高,土壤全氮含量呈先增加后减少的变化趋势,土壤速效钾呈现降低的变化趋势,而对土壤全碳含量和pH无显著影响,说明适度放牧能够提高土壤水分含量、促进土壤氮含量的积累,但放牧会导致土壤速效钾减少。(3)随着放牧强度的增大,短花针茅长期水分利用效率(WUE l)呈现“V”形变化趋势,而瞬时水分利用效率(WUE t)与内在水分利用效率(WUE i)总体呈降低的变化趋势。(4)相关分析显示,放牧强度与短花针茅密度、地上生物量呈显著正相关关系,土壤全氮含量与有机碳、pH、WUE i呈显著正相关关系,WUE t与WUE i呈显著正相关关系;短花针茅内在水分利用效率与土壤有机碳含量密切相关。研究表明,重度放牧导致短花针茅株丛破碎化,增加了种群的扩散面积,是短花针茅长期水分利用效率提高的直接原因;短花针茅瞬时水分利用效率随放牧强度的增加而降低可能是由其内在水分利用效率降低引起的。     

Impact of grazing on soil carbon and microbial biomass in typical steppe and desert steppe of Inner Mongolia

The potential of grazing lands to sequester carbon must be understood to develop effective soil conservation measures and sustain livestock production. Our objective was to evaluate the effects of grazing on soil organic carbon (SOC), total nitrogen (TN), microbial biomass carbon (MBC) in Typical steppe and Desert steppe ecosystems, which are both important grassland resources for animal grazing and ecological conservation in China, and to derive region-specific soil C changes associated with different stocking rates (ungrazed, UG; lightly grazed, LG; moderately grazed, MG; heavily grazed, HG). This study substantiated that significant higher SOC, TN and MBC appeared with the treatment of LG in typical steppe. From 2004 to 2010, grazing treatments increased soil carbon storage in desert steppe, which was partly due to the grazing history. The higher MBC concentration and MBC/SOC suggest a great potential for carbon sequestration in the desert steppe ecosystem. The greater MBC in desert steppe than typical steppe was mainly the result of higher precipitation and temperature, instead of soil substrate. The change of MBC and the strong positive relationships between MBC and SOC indicated that MBC in the soil was a sensitive index to indicate the dynamics of soil organic carbon in both steppes in Inner Mongolia of China.     

Response of Vegetation and Soil Carbon and Nitrogen Storage to Grazing Intensity in Semi-Arid Grasslands in the Agro-Pastoral Zone of Northern China

Overgrazing has been the primary cause of grassland degradation in the semi-arid grasslands of the agro-pastoral transition zone in northern China. However, there has been little evidence regarding grazing intensity impacts on vegetation change and soil C and N dynamics in this region. This paper reports the effects of four grazing intensities namely un-grazed (UG), lightly grazed (LG), moderately grazed (MG) and heavily grazed (HG) on vegetation characteristics and soil properties of grasslands in the Guyuan county in the agro-pastoral transition region, Hebei province, northern China. Our study showed that the vegetation height, canopy cover, plant species abundance and aboveground biomass decreased significantly with increased grazing intensity. Similarly, soil organic carbon (SOC) and total nitrogen (STN) in the 0–50 cm were highest under UG (13.3 kg C m⁻² and 1.69 kg N m⁻²) and lowest under HG (9.8 kg C m⁻² and 1.22 kg N m⁻²). Soil available nitrogen (SAN) was significantly lower under HG (644 kg N hm⁻²) than under other treatments (725–731 kg N hm⁻²) in the 0–50 cm. Our results indicate that the pasture management of “take half-leave half” has potential benefits for primary production and livestock grazing in this region. However, grazing exclusion was perhaps the most effective choice for restoring degraded grasslands in this region. Therefore, flexible rangeland management should be adopted in this region.     

Effects of livestock grazing intensity on soil arbuscular mycorrhizal fungi and glomalin-related soil protein in a mountain forest steppe and a desert steppe of Mongolia

Arbuscular mycorrhizal fungi (AMF) are important components of the grassland ecosystems in terms of plant phosphorus uptake and accumulation of glomalin-related soil protein (GRSP). Though Mongolian grasslands are seriously degraded by livestock grazing, the effects of grazing on soil AMF and GRSP remain unclear. Here, we examined community composition and diversity of AMF as well as amount of GRSP at three different grazing intensities: lightly grazed (LG), moderately grazed (MG), and heavily grazed (HG) under two different types of grassland, mountain forest steppe at Hustai and desert steppe at Mandalgobi. The diversity and biomass of AMF-host and non-AMF plants strongly affected the overall AMF community composition and its diversity. When we separately analyzed the factors affecting soil AMF diversity at Hustai and Mandalgobi, decrease in the shoot biomass of Poaceae plants at Hustai and decreases in the species number and shoot biomass of AMF-host plants at Mandalgobi were significantly correlated with AMF diversity. GRSP decreased with increasing grazing intensity, which was significantly correlated with soil pH and total root biomass at Hustai. The decrease in plant biomass caused by grazing thus led to GRSP reduction. Our results showed that change in soil AMF community caused by livestock grazing were associated with change in the biomass and diversity of functional vegetation groups such as Poaeceae, AMF-host and non-AMF plants, indicating the importance to focus on such functional vegetation groups to evaluate the effect of grazing on AMF.

     

Moderate grazing promotes the root biomass in Kobresia meadow on the northern Qinghai–Tibet Plateau

Grazing is an important modulator of both plant productivity and biodiversity in grassland community, yet how to determine a suitable grazing intensity in alpine grassland is still controversy. Here, we explore the effects of different grazing intensities on plant biomass and species composition, both at community level and functional group level, and examines the productivity–species richness relationship under four grazing patterns: no grazing (CK), light grazing (LG), moderate grazing, (MG) and heavy grazing (HG), attempt to determine a suitable grazing intensity in alpine grassland. The results were as follows. The total aboveground biomass (AGB) reduced with increasing grazing intensity, and the response of plant functional groups was different. AGB of both sedges and legumes increased from MG to HG, while the AGB of forbs reduced sharply and the grass AGB remained steady. There was a significant positive relationship between productivity and species richness both at community level and functional group level. In contrast, the belowground biomass (BGB) showed a unimodal relationship from CK to HG, peaking in MG (8,297.72 ± 621.29 g/m²). Interestingly, the grassland community tends to allocate more root biomass to the upper soil layer under increasing grazing intensities. Our results suggesting that moderate levels of disturbance may be the optimal grassland management strategy for alpine meadow in terms of root production.     

放牧对呼伦贝尔草地植物和土壤生态化学计量学特征的影响

放牧通过畜体采食、践踏和排泄物归还影响草地群落组成、植物形态和土壤养分,植物通过改变养分利用策略适应环境变化。通过分析呼伦贝尔草原放牧和围封样地中的群落植物和土壤的碳氮磷养分及化学计量比,探讨放牧对生态系统化学计量学特征和养分循环速率的影响机制。结果如下:(1)群落尺度上,放牧和围封草地植物叶片C、N和P的含量没有显著差异;但是在种群尺度上,放牧草地植物叶片N含量显著高于围封草地;(2)放牧草地土壤全C、全N、有机C、速效P含量,低于围封草地,硝态N含量高于围封草地;土壤全P和铵态N指标没有显著差异;(3)放牧草地植物C∶N比显著低于围封草地,植物残体分解速率较快,提高了生态系统养分循环速率。     

Above and belowground net primary productivity of grassland influenced by supplemental water and nitrogen in Inner Mongolia

While water availability determines grassland productivity in semiarid regions, nutrient availability is the main limiting factor under wet conditions. An experiment was conducted in 2008 at two sites in Inner Mongolia with histories of heavy grazing (HG) and moderate grazing (MG) to study the interactive effects of water and nitrogen on above- and belowground net primary productivity (ANPP and BNPP), biomass partitioning, and plant species composition. The study comprises two water treatments (no irrigation and irrigated when soil water content was below 70% of the field capacity), and two nitrogen (N) levels (0 and 100 kg N ha^?1). Mean values of ANPP at the peak biomass time reached 1,028?±?95 SD g m^?2 at the HG site and 568?±?32 SD g m^?2 at the MG site in irrigated and fertilized treatment. Nitrogen use efficiency (NUE) was significantly higher at irrigated plots compared to rain-fed plots at both HG and MG sites. Water use efficiency (WUEt) based on total water input and ANPP decreased with irrigation at the HG site. Meanwhile, N application significantly increased WUEt, WUEp (based on precipitation), and WUEi (based on irrigation water) at both sites. BNPP was significantly higher at irrigated plots compared to rain-fed plots at both HG and MG sites, and it tended to decrease with N addition. However, the fraction of belowground to total biomass (f _BNPP = BNPP/(ANPP+BNPP) decreased with the addition of supplemental resources and exhibited a negative correlation with ANPP. Species diversity remained lower at the HG site compared to the MG site; it decreased with the addition of supplemental resources at the latter site. The annual Salsola collina contributed the most to the total biomass under irrigation. Based on global climate models, more frequent extreme climates are predicted in the future, which can result in changes in resource availabilities. Therefore, our research results have important implications for predicting the production and other properties of grassland ecosystems.