甘肃马鹿冬季放牧践踏作用及其对土壤理化性质影响的评价

确定了草地上路径的密度,宽度,深度和土壤容重等5项放牧家畜践踏作用的观测指标,用该5个指标构建了2个践踏综合指数,定量了甘肃马鹿冬季季放牧的相对践踏强度,其可信度和可行性较高,定义了放牧践踏强度,根据冬季牧场载畜量和践踏综合指数确定了甘肃马鹿的绝对践踏强度和放牧强度。草地生长季土壤水分随践踏增强而减少,对放牧践踏的敏感性随着生长季推移逐渐降低。0－40cm土层全氮和速效氮含量,以及0－20cm土层速效磷,全盐和有机质含量,随践踏强度增加而减少,0－20cm土层全磷呈逐渐增多趋势,0－40cm土层水分和速效氮含量对践踏的敏感性随土层加深而上升,0－30cm土层全氮含量对家畜践踏的敏感性高于0－10cm土层,0－10cm土层速效磷含量对践踏的敏感性高于10－20cm土层。土壤子系统对放牧践踏作用的耐受性表现为土壤理化性状之间相互关系的稳定性,冬季牧场践踏强度梯度上,土壤质量综合指数的变化存在拐点,对应着草地从稍形过牧到明显过牧和短花针茅在群落中的次优势种地位。     

内蒙古温带草原不同放牧强度和围栏封育对凋落物分解的影响

放牧和围封通过影响植物群落结构和土壤微环境来调控草地生态系统的碳循环。该研究在内蒙古温带草原设置轻度放牧后围封、轻度放牧、重度放牧后围封、重度放牧4种样地, 通过测定干旱年(2011年)和湿润年(2012年)地上、地下凋落物产量、质量及其分解速率和土壤养分含量, 分析不同放牧强度对凋落物形成和分解的影响, 以及围栏封育对生态系统恢复的作用。结果表明: 重度放牧地上凋落物产量和分解速率均高于轻度放牧。干旱年轻度放牧样地地下凋落物产量和分解速率高于重度放牧, 湿润年相反。短期围封显著提高了凋落物产量, 轻度放牧样地围封后地上凋落物分解速率和养分循环加快, 而重度放牧样地围封后地上凋落物分解减慢。因此, 与重度放牧相比, 轻度放牧草地的恢复更适合采用围栏封育措施; 而重度放牧草地的恢复可能还需辅以必要的人工措施。降水显著促进地上、地下凋落物形成和分解。地下凋落物的生产和分解受降水年际波动影响较大, 重度放牧草地对降水变化的敏感度比轻度放牧草地高。地上凋落物分解速率与凋落物N含量显著正相关, 与土壤全N显著负相关, 与地上凋落物C:N和木质素:N相关性不大; 地下凋落物分解速率与凋落物C、C:N和纤维素含量显著负相关。该研究结果将为不同放牧强度的草地生态系统恢复和碳循环研究提供理论依据。     

放牧对内蒙古典型草原大针茅凋落物中土壤动物组成及其分解功能的影响

放牧是影响草地生态系统中土壤动物组成和凋落物分解的重要因素.2010—2012年,选择内蒙古锡林郭勒盟白音锡勒牧场境内的禁牧草地、放牧草地和沙地为研究样地,以凋落物袋法研究了大针茅凋落物分解过程中主要理化特性以及其中土壤动物群落的变化特征.共采集到土壤动物67056头52类,隶属于5门8纲,其中螨类23科,昆虫19科.大针茅凋落物的初始有机质含量为92.5%,分解780 d后分别降至40.0%(禁牧草地)和41.3%(放牧草地),差异不显著;凋落物残留率分别降低至50.0%(禁牧草地)和23.0%(放牧草地),差异显著.放牧影响下,大针茅残留凋落物中土壤动物多度显著降低.将大针茅凋落物置入沙地环境,有机质分解速率无显著变化,但凋落物残留率显著降低,螨类群落组成发生显著变化.在内蒙古典型草原环境下,放牧显著改变了植物凋落物中的土壤动物群落组成和多度,但凋落物中有机质分解速率未发生显著变化;半干旱地区土壤动物的凋落物分解功能较为微弱.     

放牧家畜组合对高寒草地植物群落特征及生产力的影响

为明晰中等放牧强度下不同放牧家畜组合如何调控高寒草地地上净初级生产力,进而提高高寒草地管理水平,本研究以青藏高原东端高寒草地为对象,设置中等放牧强度下不同放牧家畜组合样地(牦牛、藏羊单独放牧及1∶2混合放牧)和不放牧样地,分析了不同放牧家畜组合下高寒草地植物群落特征、土壤理化性质及地上净初级生产力变化。结果表明：不同放牧家畜组合对物种丰富度与多样性指数无显著影响,但显著降低高寒草地植物群落的高度与盖度,并改变功能群重要值占比;藏羊单独放牧显著增加高寒草地土壤速效氮、磷含量以及土壤容重;放牧弱化高寒草地植物多样性对地上净初级生产力的调控作用并加强土壤环境因子的作用强度;牦牛、藏羊混合放牧时高寒草地地上净初级生产力、家畜采食量均最高。为提升高寒草地管理水平,建议基于中等放牧强度进行牦牛、藏羊适宜比例的混合放牧,采用植被-家畜-土壤耦合管理方式以实现高寒草地生态功能维持与可持续利用。     

放牧对全球草地生态系统碳氮磷化学计量特征影响的Meta分析

为明确全球尺度下放牧管理措施对草地生态系统碳(C)、氮(N)、磷(P)化学计量特征的影响,提高草地生态系统管理水平,本研究选取国内外83篇中英文文献进行Meta分析,并通过亚组分析探讨了放牧家畜组合(羊单牧、牛单牧和牛羊混牧)和放牧强度(轻度、中度、重度)对草地生态系统叶片、凋落物、根系,以及土壤C、N、P化学计量特征的影响。结果表明: 放牧会显著降低叶片和凋落物C含量、C/N、C/P,增加N、P含量及N/P;显著降低根系和土壤C、N含量,C/P和N/P,增加P含量和C/N。叶片、凋落物化学计量特征变化对牛、羊单独放牧响应更为明显,而根系、土壤化学计量特征变化则对混牧响应更为明显,重度放牧会对草地生态系统化学计量特征产生更大的影响。放牧会降低土壤N含量,增加P含量,表明放牧对草地N、P含量的影响路径不同。进一步研究N、P含量变化对放牧活动不平衡响应机制,将放牧方式、强度的影响纳入草地生态系统预测、管理模型,能够有效提高草地生态系统管理水平。     

放牧对草地的作用

从牧草生长、种群、群落、土壤和生态系统5个方面分析了放牧的作用、机理与途径。放牧改变牧草的物质与能量分配格局,多途径地诱导牧草的补偿性生长,取决于放牧制度等因素。放牧还改变种间竞争格局、调控种群更新,以及群落结构和功能。介绍了草地健康管理的阈限双因子法,讨论了稳定态一过渡态假说和草地灌丛化。家畜对土壤有直接和间接两种作用途径,作用效果与放牧强度、季节、地形有密切关系,重点分析了放牧对土壤C贮量的作用机制。阐述了提高放牧系统生产力的系统耦合机制,以及放牧对生态系统物质循环的影响。根据放牧生态学的发展趋势和我国放牧管理现状,提出7项值得深入研究的问题。     

模拟践踏和降水对高寒草甸土壤养分和酶活性的影响

为明晰牦牛和藏羊践踏对高寒草甸的分异影响,通过2年模拟践踏和降水双因子控制试验,研究了践踏和降水对高寒草甸土壤养分和酶活性的影响。研究结果表明,践踏处理提高了0—20 cm土层土壤速效氮和速效钾含量,降低了0—20 cm全磷、脲酶和0—10 cm速效磷、碱性磷酸酶和有机质含量,且适度践踏促进了全氮的矿化。随降水强度的增加,0—30 cm土层土壤全氮和0—20 cm全磷和脲酶活性呈单峰曲线的变化态势,在平水下达到峰值;降水显著降低了0—30 cm土层土壤速效氮、磷、钾和0—10 cm土层土壤全钾含量,对土壤有机质含量无显著影响(P0.05)。同一放牧强度下,藏羊践踏区的土壤养分和酶活性优于牦牛践踏区,但差异不显著(P0.05)。综合可得,家畜的践踏作用促进了土壤氮和钾的矿化,抑制了磷的累积且加速了表层土壤有机质的耗竭,降低了土壤脲酶和碱性磷酸酶活性;适度降水提高了土壤全氮、全磷含量及酶活性,降水过多则相反。适度的家畜践踏与降水相耦合下草地土壤的养分循环和酶活性要优于重度践踏和不践踏小区。在对草地的适度放牧利用前提下,应注重土壤含水量和放牧畜种对草地的影响。草地干旱或土壤含水量过高时,应适当减少放牧畜种中牦牛比例增加藏羊比例,以期使草地得到健康可持续发展。     

模拟践踏和降水对高寒草甸土壤养分和酶活性的影响

为明晰牦牛和藏羊践踏对高寒草甸的分异影响,通过2年模拟践踏和降水双因子控制试验,研究了践踏和降水对高寒草甸土壤养分和酶活性的影响。研究结果表明,践踏处理提高了0—20 cm土层土壤速效氮和速效钾含量,降低了0—20 cm全磷、脲酶和0—10 cm速效磷、碱性磷酸酶和有机质含量,且适度践踏促进了全氮的矿化。随降水强度的增加,0—30 cm土层土壤全氮和0—20 cm全磷和脲酶活性呈单峰曲线的变化态势,在平水下达到峰值;降水显著降低了0—30 cm土层土壤速效氮、磷、钾和0—10 cm土层土壤全钾含量,对土壤有机质含量无显著影响(P0.05)。同一放牧强度下,藏羊践踏区的土壤养分和酶活性优于牦牛践踏区,但差异不显著(P0.05)。综合可得,家畜的践踏作用促进了土壤氮和钾的矿化,抑制了磷的累积且加速了表层土壤有机质的耗竭,降低了土壤脲酶和碱性磷酸酶活性;适度降水提高了土壤全氮、全磷含量及酶活性,降水过多则相反。适度的家畜践踏与降水相耦合下草地土壤的养分循环和酶活性要优于重度践踏和不践踏小区。在对草地的适度放牧利用前提下,应注重土壤含水量和放牧畜种对草地的影响。草地干旱或土壤含水量过高时,应适当减少放牧畜种中牦牛比例增加藏羊比例,以期使草地得到健康可持续发展。     

草地利用方式对土壤呼吸和凋落物分解的影响

草地利用方式影响植被群落结构和土壤微环境, 制约草地生态系统碳循环。该文通过测定温带草原在放牧、割草、围封3种利用方式下湿润年(2012年)和干旱年(2011年)的凋落物产量、质量及其分解速率和土壤碳通量, 分析了草地利用方式对土壤呼吸和凋落物的影响, 探讨了凋落物对土壤呼吸的贡献机制。结果表明: 在干旱年份, 放牧样地土壤呼吸最大, 分别达到割草和围封样地的1.5倍和1.29倍; 在湿润年份, 割草样地土壤呼吸最大, 为309 g C∙m^-2∙a^-1, 明显高于放牧样地和围封样地。不论干旱年还是湿润年, 围封样地凋落物产量都大于放牧样地和割草样地。3种利用方式下湿润年土壤呼吸和凋落物分解均比干旱年增强。因此, 水分是温带草原植物生长和生态系统碳循环的主要限制因子, 草地利用方式则显著影响凋落物生产和分解。进一步分析表明, 经过两年的分解, 同一样地内凋落物质量C:N下降, N含量和木质素:N升高, 土壤呼吸与凋落物产量、凋落物分解速率以及木质素:N正相关, 而与凋落物C:N负相关。     

放牧对草地枯落物分解和土壤动物群落及其相互关系的影响

在草地生态系统中,枯落物作为介导土-草界面过程的重要环节,主要调控地上-地下生态系统物质循环与能量流动,其分解对土壤食物网和土壤生物营养结构具有显著影响。土壤动物是枯落物与土壤之间物质循环与能量流动的重要媒介,是枯落物分解与养分释放过程的主要调节者。近年来,国内外学者对枯落物分解与土壤动物多样性的研究逐步深入,取得大量的研究成果。本文通过综述国内外文献,从放牧对枯落物分解过程的影响、放牧对土壤动物的影响及放牧对枯落物分解与土壤动物关系的影响等三个方面,总结分析了放牧通过采食、践踏和排泄行为改变枯落物分解,间接影响土壤动物多样性,从而降低了土壤微食物网的复杂性。另外,食草动物对草地枯落物分解和土壤动物关系的影响复杂,且这种关系往往对放牧强度、放牧季节、家畜种类等做出响应,进而会影响到整个生态系统的结构和功能。     

Nest predation and trampling as management risks in grazed coastal meadows

Livestock grazing is an important management tool of agri-environment schemes initiated within the European Union to maintain and restore biodiversity of grassland birds. However, grazing can affect bird populations negatively by depressing reproduction through nest trampling and increasing nest predation. These effects are, however, considered low when using recommended stocking rates. By simulating wader nests, we experimentally quantify and examine the causes of variation in trampling rates on managed Baltic coastal meadows. Secondly, we examine whether livestock presence increases nest predation of one management target, the critically endangered southern dunlin (Calidris alpina schinzii). Trampling rates of experimental nests were high. Only 21% of nests would have survived a three week incubating period early in the grazing season. Trampling rates were most severe at the onset of grazing and decreased with time. Thus, timing of grazing plays a crucial role in determining breeding success on managed meadows. Predation rates of dunlin nests were moderate and did not depend on livestock presence suggesting that incubating dunlin are not disturbed by cattle. While grazing is vital in habitat restoration and in conserving grassland biodiversity, our results suggest that grazing may also threaten the viability of populations if negative effects are underestimated. Therefore, management plans, especially for endangered species, should not only rely on general recommendations on stocking rates but instead planners need to evaluate the significance of negative effects in terms of local conditions (timing of breeding and grazing, space use of cattle and birds, measured trampling rates) and adjust grazing practises accordingly.     

水源圈研究进展

在干旱、半干旱区草场上,由于饮水的需求导致牲畜经常性地集中在水源点周围,从而使草地生态系统以水源点为中心呈梯度退化,形成水源圈.按照放牧影响程度的大小,以水源点为中心由内向外可将水源圈划分为“牺牲带”、过渡带和自然带3部分,水源圈内的植被、土壤等对放牧的响应也呈梯度变化.由于水源圈内存在着“天然的放牧梯度”,使其成为研究放牧对植被、土壤的影响和自然资源保护及其可持续利用的绝佳场所.本文对水源圈的概念、研究的发展历程和研究方法等进行了综述,并对国内研究现状进行了评述,以促进干旱、半干旱区草场的科学管理和可持续利用.     

放牧践踏对黄蒿功能性状的影响

植物功能性状是构成植物个体的基础,从性状角度揭示植物个体特征的变化机制尤为重要。该研究以半干旱沙质草地优势草本植物黄蒿为研究对象,探讨不同践踏强度在生长季早期对其功能性状的影响。结果表明：(1)在群落水平上,放牧践踏显著降低了生长季早期植物群落高度;而在个体水平上,黄蒿株高不是响应放牧践踏的敏感性状。(2)黄蒿的叶长、叶宽随践踏强度增加呈先增加后减少的趋势,在中度践踏强度下达到最高;茎直径随践踏强度的增加而增加;根系和全株性状随践踏强度增加无显著差异。(3)黄蒿的叶片长度、叶片宽度、单叶面积随叶片厚度的增加而减小,且叶片与一级根数目、根茎叶生物量之间均呈显著正相关关系;放牧践踏会影响黄蒿茎直径,但对其他表型性状没有显著影响;在生长发育过程中,黄蒿通过不同表型性状的非对称变化进行性状之间的权衡,践踏强度的增加对生长季早期黄蒿根茎叶生物量积累的影响很小。研究认为,黄蒿在生长季早期对放牧践踏具有较强的抵抗力,这对生长季早期半干旱沙地放牧压力的选择和物种保护具有重要的指导意义。     

水源圈研究进展

在干旱、半干旱区草场上,由于饮水的需求导致牲畜经常性地集中在水源点周围,从而使草地生态系统以水源点为中心呈梯度退化,形成水源圈.按照放牧影响程度的大小,以水源点为中心由内向外可将水源圈划分为“牺牲带”、过渡带和自然带3部分,水源圈内的植被、土壤等对放牧的响应也呈梯度变化.由于水源圈内存在着“天然的放牧梯度”,使其成为研究放牧对植被、土壤的影响和自然资源保护及其可持续利用的绝佳场所.本文对水源圈的概念、研究的发展历程和研究方法等进行了综述,并对国内研究现状进行了评述,以促进干旱、半干旱区草场的科学管理和可持续利用.     

Effects of experimental and real land use on seedling recruitment of six fen species

Seedling emergence and early establishment of six fen species differing in seed mass and growth form were investigated under experimental land use with changed vegetation structure and under real land use in a calcareous fen. Seeds of all six species were sown in plots with different experimental land-use treatments: summer and autumn mowing with or without litter removal, trampling and abandonment. Additionally, emergence and survival of experimentally sown seeds was investigated under real land use on adjacent sites managed by mowing, grazing, intense trampling or abandonment.On abandoned plots and on plots without litter removal of the land-use experiment, emergence rates of all species were negatively affected either by high litter and moss cover or by tall canopy. No differences were found between autumn and summer mowing. Gap creation by experimental trampling did not increase germination rate. Under real land use, establishment of seedlings of most species was positively affected by litter cover and tall canopy. Trampling, in contrast, had a severe negative effect on seedling survival.The investigated species differed in their germination ability which was tested in the germination chamber and in their response to land use. Succisa pratensis with the highest seed mass germinated well in the chamber and in the field more or less regardless of land use. The low germination rate of Parnassia palustris in the germination chamber indicated a limitation of viable seeds. In the field, however, seedling emergence was additionally limited by microsite availability. Seeds of Serratula tinctoria and Primula farinosa germinated well in the germination chamber, but seedling recruitment in the field was hampered in the presence of a high litter or moss cover. Seeds of Tofieldia calyculata and Pinguicula vulgaris were strongly dependent on the availability of suitable microsites in the field. They hardly germinated under natural conditions, in spite of a high number of germinable seeds in the germination chamber.     

Nest success and cause-specific nest failure of grassland passerines breeding in prairie grazed by livestock

Livestock grazing is a widespread source of habitat modification, and may affect populations of ground-nesting grassland birds by influencing rates of nest failure. Nesting attempts can fail for various reasons, and determining risk of failure from specific causes associated with livestock grazing would enhance development of range management practices in areas managed for threatened grassland bird populations. Domestic livestock may influence nest failure by affecting vegetation structure, numerical or functional responses of predators, or directly by trampling nests. We hypothesized stocking rate may influence nest fate because it affects the amount and distribution of remaining vegetation, and the number of large herbivores to which nests are exposed. In 2007 and 2008, we evaluated nest fates for savannah sparrows and horned larks under 4 stocking rates experimentally applied in 40-ha paddocks in northeastern Oregon, USA. In addition to stocking rate, we evaluated variables such as vegetation structure and predator abundance and activity to help clarify mechanisms responsible for nest failure. We used a discrete competing risks framework to estimate daily probability of nest survival and failure from specific causes. These algorithms, implemented in a stand-alone graphical user interface-driven model, allow incorporation of covariates within an information theoretic approach to model inference. Although stocking rate influenced vegetation structure, the only nest failures related to stocking rate were from trampling. Trampling events were too infrequent to test for treatment effects (only 1 nest of each species), but occurred in the moderate and high stocking treatments. Additional variables were related to variation in nest failure from predation, but we found no support for the hypothesis that these causes of failure were affected by stocking rate. For savannah sparrows, daily probability of nest success (95% CI) = 0.97 (0.96–0.98); predation = 0.018 (0.008–0.028); and trampling = 0.001 (0.000–0.004). For horned larks, daily probability of nest success = 0.96 (0.95–0.98); predation = 0.029 (0.012–0.045); and trampling = 0.003 (0.000–0.007). Our results suggest grasslands managed for livestock may generally be compatible with grassland songbird conservation, at least for the species and stocking rates examined here. The most effective conservation strategies for improving nest success will involve decreasing risk of nest predation. However, we found no evidence that management of stocking rate is an effective method for doing so. © 2012 The Wildlife Society.     

Livestock disturbances in Mediterranean temporary ponds: A mesocosm experiment with sheep manure and simulated trampling

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Nest trampling and ground nesting birds: Quantifying temporal and spatial overlap between cattle activity and breeding redshank

Conservation grazing for breeding birds needs to balance the positive effects on vegetation structure and negative effects of nest trampling. In the UK, populations of Common redshank Tringa totanus breeding on saltmarshes declined by >50% between 1985 and 2011. These declines have been linked to changes in grazing management. The highest breeding densities of redshank on saltmarshes are found in lightly grazed areas. Conservation initiatives have encouraged low‐intensity grazing at <1 cattle/ha, but even these levels of grazing can result in high levels of nest trampling. If livestock distribution is not spatially or temporally homogenous but concentrated where and when redshank breed, rates of nest trampling may be much higher than expected based on livestock density alone. By GPS tracking cattle on saltmarshes and monitoring trampling of dummy nests, this study quantified (i) the spatial and temporal distribution of cattle in relation to the distribution of redshank nesting habitats and (ii) trampling rates of dummy nests. The distribution of livestock was highly variable depending on both time in the season and the saltmarsh under study, with cattle using between 3% and 42% of the saltmarsh extent and spending most their time on higher elevation habitat within 500 m of the sea wall, but moving further onto the saltmarsh as the season progressed. Breeding redshank also nest on these higher elevation zones, and this breeding coincides with the early period of grazing. Probability of nest trampling was correlated to livestock density and was up to six times higher in the areas where redshank breed. This overlap in both space and time of the habitat use of cattle and redshank means that the trampling probability of a nest can be much higher than would be expected based on standard measures of cattle density. Synthesis and applications: Because saltmarsh grazing is required to maintain a favorable vegetation structure for redshank breeding, grazing management should aim to keep livestock away from redshank nesting habitat between mid‐April and mid‐July when nests are active, through delaying the onset of grazing or introducing a rotational grazing system.