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1.
长芒草(Stipa bungeana)群系是欧亚大陆草原区东南部的主要针茅草原类型之一, 中国特有群系类型, 以黄土高原及其周边为集中分布区。由于农业开垦等人为活动, 其天然植被保存不多, 现有分布破碎化严重或处于不稳定的演替阶段。该文利用2013-2019年在全国范围内调查的108个样地的数据, 对长芒草群系的地理分布、物种组成、生态特征和群落分类做了详细的描述和研究。结果表明: 长芒草群系在陕北、宁南、陇东、陇中、晋北、阴山南部黄土丘陵和鄂尔多斯高原的分布较为集中, 通常发育在黄绵土或栗钙土上, 海拔高度在(1) 631-3 174 (4 098) m之间。108个样地内共记录到种子植物37科109属214种, 大多为偶见种或稀有种, 生活型组成以地面芽植物或多年生杂类草居多, 水分生态类型以旱生, 尤其是中旱生和典型旱生植物居多, 区系地理成分以东亚成分、东古北极成分和亚洲中部成分较多。群落的高度、盖度、生物量及物种丰富度变化幅度均较大, 这些与生境的湿润程度和干扰状况密切关联。长芒草群系划分为7个群丛组, 37个群丛。  相似文献   

2.
封育是天然草地管理的一种有效措施,利于草地生产力提高和退化草地恢复。该研究通过对青藏高原高寒草甸放牧和封育草地物种多样性、植被构成、植物种生态位特征、草地演替度等分析,解析高寒草甸植物种间关系及草地演替方向。结果表明:(1)封育显著降低了草地群落植物物种数以及α和β多样性指数,显著增加了草地1年生植物种数、地面芽植物种数和地上生物量。(2)放牧草地地上生物量以莎草科(59.7%)和禾本科(23.9%)为主,封育草地地上生物量以禾本科(85.0%)为主;放牧草地优势种为矮嵩草(Kobresia humilis)和线叶嵩草(K.capillifolia),封育草地优势种为垂穗披碱草(Elymus nutans)和早熟禾(Poasp.)。(3)放牧和封育草地的群落植物种重要值均与各自的生态位宽度变化规律一致。(4)草地植物种间竞争主要发生在不同科属植物种之间,封育增加了群落植物种整体生态位重叠值和植物种间竞争。(5)草地群落演替度为封育地放牧地,封育群落处于较稳定状态。研究认为,封育促进了高寒草甸由莎草+杂类草群落向禾草+杂类草群落演替。  相似文献   

3.
无定型碳酸钙对植物生长具有重要意义,草原-荒漠过渡区主要建群植物体内无定型碳酸钙含量特征目前尚不明确。本文测定了宁夏哈巴湖国家级自然保护区和宁夏吴忠市红寺堡区主要植物叶片碳酸钙含量。结果表明:草本植物碳酸钙含量之间有显著差异,而灌木碳酸钙含量之间没有差异显著;对于草本植物,演替初期建群植物沙蓬(Agriophyllum squarrosum)和猪毛菜(Salsola collina)、演替中期建群植物赖草(Aneurolepidium dasystachys)和白草(Pennisetum centrasiaticum)、演替后期建群植物长芒草(Stipa bungeana)和糙隐子草(Cleistogenes squarrosa),随进展演替,不同演替阶段植物碳酸钙含量逐渐降低;典型草原演替后期建群种体内碳酸钙含量显著高于荒漠草原演替后期建群种;油蒿(Artemisia ordosica)幼龄阶段叶片碳酸钙含量显著高于成龄和老龄阶段,沙冬青(Ammopiptanthus mongolicus)、小叶锦鸡儿(Caragana microphylla)和紫穗槐(Amorpha frutic...  相似文献   

4.
本文应用多样性指数、聚类分析等数学方法,研究了不同放牧强度下高寒灌丛群落特征的变化,用主分量分析方法,研究了不同放牧强度下高寒灌丛的演替规律。多样性分析结果表明,植物多样性指数在放牧强度为C组的草场达到最大。聚类分析结果,当相关系数R≥0.90 时,以重要值为特征的植物聚合为10类,它们分别属于植物群落不同演替阶段的建群种、优势种和伴生种。主分量分析表明,5个不同放牧强度的高寒灌丛群落聚合为3类,A和B组草场属于以灌木和杂类草为优势植物的2层结构的植物群落,C组草场属于以灌木为建群植物、杂类草和耐牧的莎草为共优势植物的2层结构的植物群落,D和E组草场属于以灌木为建群植物、禾草和莎草为共优势植物的3层结构的植物群落。  相似文献   

5.
该文比较研究了内蒙古羊草草原和大针茅草原放牧演替系列经过20a (1985~2005年) 放牧, 利用群落组成与结构的变化分析了这两个放牧演替系列上15个植物群落的变化趋势, 并依此探讨长期放牧对草原生态系统结构和功能的影响。结果表明:在大针茅 (Stipa grandis) 牧压梯度系列上, 群落仍以大针茅群系为主, 冷蒿 (Artemisia frigida) 为建群种的群落消失;在羊草 (Leymus chinensis) 牧压梯度系列上, 羊草和冷蒿不再是建群种, 被西伯利亚羽茅 (Achnatherum sibiricum) 、大针茅、冰草 (Agropyron cristatum) 和糙隐子草 (Cleistogenes squarrosa) 所替代。综合两个牧压梯度系列的研究结果得出以下基本结论:长期过度放牧进一步加速了草原群落的退化进程, 但退化草原具有较高的恢复弹性, 控制放牧使部分群落得到一定程度的恢复。同一植物群落时间变化, 或不同演替阶段的植物群落在空间序列上的位移程度主要取决于放牧史和利用强度。过去20a中, 特别是2003年以来草原管理政策的改变并没有导致该区域草地的整体退化, 而是在一定程度上有利于草地的恢复。  相似文献   

6.
祁连山金露梅灌丛草甸群落结构及主要种群的点格局分析   总被引:3,自引:0,他引:3  
金露梅灌丛草甸是青藏高原高寒草地生态系统的重要组分之一,采用Ripley的K(t)函数分析方法,对放牧和封育条件下主要种群的分布格局和种间关系及金露梅灌丛群落动态变化进行了研究.结果表明:(1)经过6年的围栏封育,金露梅灌丛草甸主要种群的空间分布格局表现出从均匀或随机分布向随机或聚集分布转变的趋势,聚集强度随围封尺度增大而增加,随放牧的干扰而降低,聚集分布有利于种群发挥功能群整体效应.(2)围栏内不同功能群之间主要呈显著正关联;围栏外的禾草与杂类草、莎草与杂类草之间均呈显著负关联,出现种间资源竞争,且随着尺度的增大负关联逐渐增强,不同物种的生态位差异明显.(3)围栏内外种群点格局分布都具有明显的尺度依赖性,植物间相互作用和外界放牧干扰是影响物种不同尺度下空间格局变化的主要原因,点格局的变化驱动了群落结构的变化.可见,长期夏季放牧抑制了高寒金露梅灌丛草甸禾草和莎草植物的分株和生长,促进了杂类草的生长,金露梅灌丛草甸呈现出退化的趋势,围栏封育有利于草地生态系统的恢复演替.  相似文献   

7.
陕北黄土区生态修复过程中植物群落物种多样性变化   总被引:17,自引:0,他引:17  
根据18块典型样地的植被调查数据,采用时空互代和对比分析法,从演替时间、生态修复模式和坡向3个方面研究了陕西省吴起县生态修复过程中植物群落物种多样性特征.结果表明:在25年自然演替序列中,退耕封育群落依次经历了猪毛菜、猪毛蒿、达乌里胡枝子、铁杆蒿和白羊草5种类型,建群种表现为1年生向多年生、低级向高级的演替趋势.其间,物种种类、Margalef指数、Simpson指数、Shannon-Wiener指数和Pielou指数均呈二次函数变化,说明黄土区退化生态系统在消除外界压力后,通过自然恢复可达到高级、稳定状态,但速度缓慢.地形条件和恢复年限一致时,4种主要修复模式形成的群落中,草本层的Margalef指数、Shannon-Wiener指数和Pielou指数表现为退耕封育>退耕还草>退耕还林>荒山造林,Simpson指数则相反.与退耕封育模式相比,退耕还草和退耕还林模式在相同恢复期内形成的草本群落,虽然多样性指数较低,但更接近自然演替后期阶段,说明人工修复模式能加快演替进程.在相同恢复年限内,阴坡退耕封育群落的Margalef指数、Shannon-Wiener指数和Pielou指数明显大于阳坡,且群落类型更接近演替后期阶段,说明阳坡生态修复的本底条件更差,植被自然演替速率更缓慢.  相似文献   

8.
自然生态系统中植物物种多样性是否随功能多样性变化而影响初级生产力的问题存在很大争议。在高寒矮嵩草草甸,对不同放牧强度、不同利用格局和土壤资源水平的4种生境(Ⅰ.畜圈:重度放牧、资源丰富;Ⅱ.牧道:中度放牧、资源适中;Ⅲ.人工草地:轻-中度放牧、资源贫乏;Ⅳ.封育草地:不放牧、资源贫乏)中物种多样性与功能多样性的变化及其对初级生产力的影响进行了研究。结果表明:物种多样性在牧道生境最高,符合中度干扰理论的预测;人工草地物种多样性低但功能多样性却最高;封育草地物种多样性和功能多样性均较高;物种多样性与地上生物量呈正相关,而功能多样性则与地上生物量呈负相关。表明功能多样性不随物种多样性而变化,二者可能在一定程度上是相互独立地作用于生产力的。群落生产力和生物多样性受生境资源、物种特征、放牧历史和放牧强度等因素的综合影响。  相似文献   

9.
陈蔚  王维东  蒋嘉瑜  刘任涛 《生态学报》2022,42(11):4401-4414
在半干旱草地,关于放牧和封育管理对草地植物枯落物分解及其与土壤动物互作关系的研究一直是该区域生态系统物质循环与生态恢复过程研究的重要科学问题。以放牧和封育样地中赖草(Leymus secalinus)、牛枝子(Lespedeza potaninii)及其混合枯落物为研究对象。于2017年9月、2018年5月和9月、2019年5月和9月,采用2种不同孔径(30目和250目)网袋量化中小型土壤动物的作用,调查了宁夏半干旱草地枯落物碳、氮和磷元素分解与土壤动物群落分布及其对放牧和封育样地的响应规律。结果显示:(1)封育样地中,枯落物碳元素最终残留率均表现为3种枯落物处理间无显著差异;但250目网孔中枯落物氮、磷元素最终残留率和30目网孔中氮元素最终残留率均表现为牛枝子显著高于赖草和混合物,而后两者间无显著差异;仅30目网孔中磷元素最终残留率表现为牛枝子和混合物显著高于赖草,而前两者间无显著差异。放牧样地中,250目网孔的碳、磷元素最终残留率和30目网孔中的氮、磷元素最终残留率均表现为牛枝子显著高于混合物,而赖草居中;氮元素最终残留率表现为牛枝子显著高于赖草和混合物,后两者间无显著差异。(2)...  相似文献   

10.
放牧干扰下若尔盖高原沼泽湿地植被种类组成及演替模式   总被引:3,自引:0,他引:3  
韩大勇  杨永兴  杨杨  李珂 《生态学报》2011,31(20):5946-5955
以若尔盖高原退化沼泽植被为研究对象,应用多重比较、双因素方差分析、物种累积曲线、PCA排序、方差分解等方法分析了不同放牧压力、放牧季节下物种丰富度、多度、生活型组成、群落演替的变化。结果表明:不同放牧季节物种丰富度格局不尽相同,其中6、9、10月在各牧压梯度间无显著差异,7、8月均以极重度和极度阶段(中生草甸)的最高,原生沼泽的最低。在物种累积速率上,沿牧压梯度以极重度和极度阶段的最高,沿放牧季节以7、8月最高;双因素方差分析结果进一步表明物种丰富度与放牧季节无显著关系,但与放牧压力关系显著。放牧压力和放牧季节共解释了物种多度总方差的47.6%,其中放牧压力解释了50.1%,放牧季节以及二者方差交集均为负值;沿牧压梯度,沼泽植被逆向演替模式倾向于沼泽→草甸,沼泽化草甸阶段不明显,但是演替方向未发生变化,建群种替代规律为:乌拉草→木里苔草→栗褐苔草,生活型组成中直立型植物比例较少,莲座型和匍匐型植物增加。总之,放牧季节对物种丰富度无显著影响,但在一定程度上改变了其牧压梯度格局,降低了物种累积速率。放牧压力改变了群落物种丰富度、生活型组成和演替模式,但放牧可能仅为沼泽植物群落物种多样性格局和演替的驱动力之一。  相似文献   

11.
群落组成结构的异质性是群落动态的主要属性。本研究采用样线、样方调查方法,基于物种频度与幂函数法则,分析了内蒙古克氏针茅草原围栏封育和自由放牧条件下群落物种结构与空间异质性的变化。结果表明:在围栏外和围栏内不同利用方式下,物种均呈现集中分布;从水分生态型、生活型、生育型、种子传播型和植物科属等不同功能群类别来看,旱生植物和中旱生植物广泛分布,生活型以多年生草本植物为主,依靠重力传播种子的植物占有相对较大的比例,达到60%以上,禾本科、百合科、菊科和豆科等适牧植物具有相对优势;在围栏保护状态下,物种多样性增加,群落异质性降低,放牧退化草原开始向群落状况良好的草原类型演替。  相似文献   

12.
《农业工程》2020,40(6):425-431
Livestock grazing is one of the main factors of vegetation and soil degradation in arid and semi-arid rangelands of Iran and causes changes in diversity, vegetation, litter and soil characteristics. Therefore, this study has been conducted aimed to examine the effects of exclosure and livestock grazing on vegetation and soil. For this purpose, two grazing areas of medium and high grazing intensity and two exclosure areas (Non-grazing livestock) with duration of 8 and 11 years were selected for sampling. Then, we identified plant species, percentage of coverage of each species, measurement of diversity indices, species similarity and soil chemical properties including electrical conductivity (mho), acidity, organic matter(%), organic carbon (%), nitrogen (%), phosphorus (mg/L) and bulk density (gr/cm3) in each area and they were compared using variance analysis. The results showed that exclosure significantly at 5% level reduced organic matter percentage, electrical conductivity and organic carbon percentage, but it caused a significant increase in soil bulk density at 1% level. Similarity of plant species due to the reduction of livestock grazing intensity and increasing exclosure duration. The results also indicate Livestock grazing increased Coverage of plant family such as Poaceae, Zygophyllacea in the area due to the increase of plant species such as Peganum harmala and Poa bulbosa (non-pleasant species of class III). Based on the results, despite increasing the diversity of plant species in the area over time, increasing diversity does not increase dominant species of the area, as well as companion species increased in the composition of vegetation. It concluded that exclusion has a significant effect on vegetation improvement, vegetation cover percentage, diversity, palatability and litter percentage in the region.  相似文献   

13.
Questions: Is plant species richness, diversity and above‐ground standing biomass enhanced after establishing exclosures on communal grazing lands? What factors influence the effectiveness of exclosures to restore degraded native vegetation in Tigray, Ethiopia? Location: Northern Ethiopia. Methods: We used a space‐for‐time substitution approach to detect changes in plant species richness, diversity and above‐ground standing biomass after conversion of communal grazing lands to exclosures. We selected replicated (n=3) 5‐, 10‐, 15‐ and 20‐year‐old exclosures and paired each exclosure with an adjacent communal grazing land to ensure that soil and terrain conditions were as similar as possible among each pair. Results: All exclosures displayed higher plant species richness, diversity and biomass than the communal grazing lands. Differences in plant species richness and biomass between an exclosure age and adjacent communal grazing land were higher in oldest than in youngest exclosures. In exclosures, much of the variability in plant species composition and biomass was explained by a combination of edaphic (total nitrogen, phosphorus, texture and soil pH) and site (precipitation and altitude) variables (R2=0.72–0.82). Edaphic and site variables also explained much of the variability in plant species composition in communal grazing lands (R2=0.76–0.82). Our study shows that all exclosures are at an early stage of succession. The increase in economically important indigenous shrub and tree species with exclosure age suggests that, with time, a valuable afromontane forest may develop. Conclusions: Establishment of exclosures on communal grazing lands is a viable option to restore degraded native vegetation. However, before expanding exclosures, the ecological consequences of additional exclosures should be investigated as further expansion of exclosures could increase grazing pressure on remaining grazing areas. Furthermore, consideration of edaphic and site variables will help optimize selection of areas for establishment of exclosures and enhance natural regeneration in exclosures in the future.  相似文献   

14.
It is becoming more apparent that species richness alone many not be sufficient to fully understand ecosystem resilience but that functional diversity (diversity of species having similar effects on an ecosystem process) may be more relevant. In particular, response diversity (diversity of species that respond differently to disturbance) within functional groups (FG) is suggested to be critical for resilience. We assess for the first time the use of response diversity as a measure of resilience in an empirical study. Our experimental design consisted of sites with three disturbance intensities during a grazing exclosure period and the same sites, 1 year later, after grazing. Plant FGs were identified based on effect traits related to nutrient cycling and soil retention, and species richness within groups was assessed during exclosure and after grazing. To assess if response diversity could predict loss of species richness (resilience analysis), response diversity was calculated only during the exclosure period, based on traits related to grazing tolerance. We also assessed the contribution of richness to response diversity during exclosure (redundancy analysis). Response diversity was significantly and highly correlated with species richness within FGs during disturbance. That is, FGs with the lowest response diversity were the most affected, disappearing when disturbance appeared. Richness within FGs during exclosure was not significantly correlated with response diversity, showing that higher richness does not ensure resilience. We conclude that response diversity can be used to predict which FGs are more resilient, and hence, less vulnerable to future disturbance.  相似文献   

15.
The purpose of this study was to clarify the effect of grazing exclosures on the recovery and rehabilitation of overgrazed steppe vegetation on varying slope aspects in the Loess Plateau of northwest China. The annual precipitation in the area studied was 400–480 mm. Soil samples were taken on nine slopes in the five-year exclosure and on five slopes outside the exclosure after a vegetation survey; they were then analyzed chemically. Mean number of species recorded per 0.25 m2 was lower on the south-facing slope than all other slopes. The reverse trend was observed for aerial biomass. Species diversity estimated by information content was higher in the grazing zone than in a 3200-ha protected zone within an exclosure. From species ordination by principal component analysis, species with lower coverage in the grazing zone were Poa sphondylodes, Roegneria purpurascens, Hierochloe odorata, and Potentilla bifurca, which are all recognized as indicator species for rehabilitation efforts. In the soil surface layer, calcium contents were low, and the total contents of carbon and nitrogen were high on the north-facing slope in the exclosure. The protection by exclosure of overgrazed steppe was seen to be effective because the accumulation of soil organic matter increased and water balance improved.  相似文献   

16.
围栏禁牧对内蒙古典型草原群落特征的影响   总被引:13,自引:0,他引:13  
采用样方法对内蒙古典型草原区围封26 a(E26)7、a(E7)2、a(E2)和未围封(G)样地的植物多样性、群落高度、盖度、地上与地下生物量进行实地调查分析,以研究围栏禁牧对草原植物群落特征的影响.结果表明:围封26a样地具有最高的丰富度指数和多样性指数,围封相对于放牧在一定程度上可以维持和保护植物多样性和丰富度.围封7 a样地的多样性指数与未围封样地(G)以及围封2 a样地(E2)无显著差异,说明放牧导致了该区植物多样性的降低,但围封并未显示出使其恢复的趋势;从自由放牧样地到围封样地,退化指示植物糙隐子草(Cleistogenessquarrosa)以及一年生植物猪毛菜(Salsola collina)、刺穗藜(Chenopodium aristatum)等的比重和出现频率呈减少的趋势;围封2 a样地的地上现存量显著低于围封7 a样地,而围封26 a样地相对于围封7 a样地又表现出显著减小的结果.说明围封在一定时期内可显著提高草地生产力,但围封时间过长将不利于其维持较高的生产力.  相似文献   

17.
We examined whether terrestrial vertebrates affected the arbuscular mycorrhizal fungal spore communities and mycorrhizal inoculum potential (MIP) of a tropical rain forest soil by comparing plots where terrestrial vertebrates had been excluded for 3 years to adjacent control plots. We extracted spores from soil using sucrose density gradient centrifugation and assayed MIP by growing seedlings of maize ( Zea mays ) and a rain forest tree ( Flindersia brayleana ) in intact soil cores from exclosure and control plots. Control plots had significantly higher spore abundance, species richness and diversity than exclosures. Spore community composition also differed significantly between exclosure and control plots. Seedlings of both plant species grown in control cores had significantly higher arbuscular-mycorrhizal colonization than those grown in exclosure cores. This study suggests that loss of vertebrates could alter rates of mycorrhizal colonization with consequences for community and ecosystem properties.  相似文献   

18.
Hyperaccumulation of Ni by plants is hypothesized to function as an elemental defense against herbivores and pathogens. Laboratory experiments have documented toxic effects to herbivores consuming high-Ni plant tissues, but this paper reports the first experiment to examine the defensive effectiveness of Ni hyperaccumulation under field conditions. The experiment was conducted at an ultramafic soil site naturally inhabited by the Ni hyperaccumulator Streptanthus polygaloides (Brassicaceae). Experimental treatments examined the response of herbivores to hyperaccumulated Ni, using exclosure and insecticide treatments to divide herbivores into groups based primarily upon herbivore size. Three soils (Ni-amended greenhouse soil, unamended greenhouse soil, ultramafic soil), three exclosure treatments (exclosure, control exclosure, no exclosure), and a systemic insecticide treatment were combined in a fractional factorial experimental design. Streptanthus polygaloides plants were grown in a greenhouse for 2 mo, transplanted into the field by inserting potted plants into holes dug on the experimental site, and periodically examined for herbivore damage during a 41-d period. Initial surveys showed greater amounts of insect damage to plants with low tissue Ni levels, confirming the defensive effect of Ni against some insect herbivores, but large herbivores (probably vertebrates) later consumed entire plants regardless of plant Ni status. We concluded that Ni was not an effective defense against these large herbivores, probably because their diets mix high-Ni S. polygaloides foliage with that of associated non-hyperaccumulating species. We suggest that such dietary dilution is one mechanism whereby some herbivores can circumvent elemental plant defenses.  相似文献   

19.
为明确围栏封育对温带典型草原群落物种种间关系的影响, 运用方差比率法、基于2 × 2列联表的χ2检验、Ochiai指数、Spearman相关分析, 对位于内蒙古锡林郭勒盟太仆寺旗封育6年的围封样地及围栏外样地的主要优势种及伴生种进行了种间关联和相关性分析。同时运用生态位宽度指数分析围栏内外物种对环境资源的利用能力及种间竞争情况。结果表明: 1) 基于2 × 2列联表的χ2检验结果表明围栏内9个种对显著正联结, 4个种对显著负联结(p ≤ 0.05), 围栏外有19个种对显著正联结, 8个种对显著负联结; Spearman秩相关分析表明围栏内有10个种对显著正相关, 16个种对显著负相关, 围栏外有12个种对显著正相关, 30个种对显著负相关。χ2检验和Spearman检验结果表明围栏内群落处于稳定发展状态, 而围栏外群落处于退化阶段。2)围栏内外的优势种Ochiai指数都较高, 但χ2检验并不显著, 表明优势种之间的关联程度高, 但存在相对独立的分布格局。3)围栏内主要优势种的生态位宽度大于围栏外, 说明围栏封育保护了主要优势种的生长。  相似文献   

20.
Exotic plant invasions and chronic high levels of herbivory are two of the major biotic stressors impacting temperate forest ecosystems in eastern North America, and the two problems are often linked. We used a 4-ha deer exclosure maintained since 1991 to examine the influence of a generalist herbivore, white-tailed deer (Odocoileus virginianus), on the abundance of four exotic invasive (Rosa multiflora, Berberis thunbergii, Rubus phoenicolasius and Microstegium vimineum) and one native (Cynoglossum virginianum) plant species, within a 25.6-ha mature temperate forest dynamics plot in Virginia, USA. We identified significant predictors of the abundance of each focal species using generalized linear models incorporating 10 environmental and landscape variables. After controlling for those predictors, we applied our models to a 4-ha deer exclusion site and a 4-ha reference site, both embedded within the larger plot, to test the role of deer on the abundance of the focal species. Slope, edge effects and soil pH were the most frequent predictors of the abundance of the focal species on the larger plot. The abundance of C. virginianum, known to be deer-dispersed, was significantly lower in the exclosure. Similar patterns were detected for B. thunbergii, R. phoenicolasius and M. vimineum, whereas R. multiflora was more abundant within the exclosure. Our results indicate that chronic high deer density facilitates increased abundances of several exotic invasive plant species, with the notable exception of R. multiflora. We infer that the invasion of many exotic plant species that are browse-tolerant to white-tailed deer could be limited by reducing deer populations.  相似文献   

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