首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 0 毫秒
1.
One common problem encountered when restoring grasslands is the prominence of non-native plant species. It is unclear what effect non-native plants have on habitat quality of grassland passerines, which are among the most imperiled groups of birds. In 2004 and 2005, we compared patterns of avian reproduction and the mechanisms that might influence those patterns across a gradient of 13 grasslands in the Zumwalt Prairie in northeastern Oregon that vary in the degree of non-native plant cover (0.9–53.4%). We monitored the fate of 201 nests of all the breeding species in these pastures and found no association of percent non-native cover with nest densities, clutch size, productivity, nest survival, and nestling size. Regardless of the degree of non-native cover, birds primarily fed on Coleoptera, Orthoptera, and Araneae. But as percent non-native cover in the pastures increased, Orthoptera made up a greater proportion of diet and Coleoptera made up a smaller proportion. These diet switches were not the result of changes in terrestrial invertebrate abundance but may be related to decreases in percent bare ground associated with increasing cover of non-native vegetation. Measures of nest crypticity were not associated with cover of non-native vegetation, suggesting that predation risk may not increase with increased cover of non-native vegetation. Thus, the study results show that increased non-native cover is not associated with reduced food supplies or increased predation risk for nesting birds, supporting the growing body of evidence that grasslands with a mix of native and non-native vegetation can provide suitable habitat for native grassland breeding birds.  相似文献   

2.
放牧对草地群落与土壤特征的影响   总被引:2,自引:0,他引:2  
针对放牧干扰对草地生态系统的影响,采用回归分析和典型对应分析(CCA)方法,研究放牧对草地植物群落物种多样性与生产力、土壤碳氮含量与生物量关系的影响。结果表明:(1)与休牧草地相比,放牧草地的地上生物量降低31.63%,凋落物生物量降低134.29%;放牧草地的禾草类生物量提高19.77%,而杂草类生物量和豆科类生物量分别降低31.09%和23.42%。(2)当物种多样性指数小于1.3时,休牧草地的生产力明显高于放牧草地;当物种多样性指数大于1.3时,放牧草地的生产力高于休牧草地。(3)CCA分析显示,家畜主要通过影响群落地上生物量、凋落物质量和土壤容重进而影响土壤的碳氮含量。(4)当群落地上生物量小于100g·m-2时,休牧草地的土壤有机碳和全氮含量高于放牧草地,当群落地上生物量大于100g·m-2时,放牧草地则略高于休牧草地。(5)当群落地下生物量小于1 200g·m-2时,放牧草地土壤有机碳、全氮含量高于休牧草地;当地下生物量大于1 200g·m-2时,放牧草地则略低于休牧草地。  相似文献   

3.
A complex rotational grazing trial on a south-facing slope of chalk grassland at the Old Winchester Hill National Nature Reserve is briefly introduced. The responses of 23 numerous species of Auchenorrhyncha, and of species richness (S) and total abundance (N), from 1981 to 1985 are described. The greatest effects were those of variation between years, between positions on the hillside (top, middle and bottom) and between grazing plots within these positions. 10 (of the total of 23) species favoured the top of the slope, where the vegetation was significantly taller than in the middle or at the bottom. S, N and the numbers of 8 species were significantly lower on plots grazed in the year of sampling compared with ungrazed plots. Early (vs. late) grazing significantly reduced S, N and the abundance of two species, but increased the numbers of Macrosteles laevis. S, N and the abundance of 13 species was significantly and positively correlated with vegetation height measured early (May–June) and late (July–October); the numbers of 4 other species were so correlated with the latter height only. The significance of the results is discussed in relation to the management of grassland nature reserves for the maintenance of high invertebrate diversity. It is concluded that rotational management is an important and valuable system, but suggested that such systems should be as simple as possible whilst remaining adequate to achieve conservation objectives.  相似文献   

4.
鄂尔多斯沙地不同退牧年限植物群落多样性及变异性研究   总被引:2,自引:1,他引:2  
根据内蒙古鄂尔多斯退牧还草工程近30年的12个样地植被数据,将其按植被盖度分为半流动沙地(退牧5~10年)、半固定沙地(退牧15~20年)和固定沙地(退牧25~30年),以空间代替时间顺序采用α多样性指数(Simpson指数、Shannon-Wiener指数和Pielou指数)以及β变异性Sorenson指数的方法,分析了退牧年限与沙地植被群落多样性和变异性的关系.结果表明:(1)退牧20年为群落敏感期,Simpson指数和Shannon-Wiener指数在退牧30年间变化趋势相近,均匀度Pielou指数变化幅度较大,退牧15年物种分布最均匀,退牧20年时均匀度最小且随退牧年限先上升后下降;(2)草本层在退牧5~10年中Shannon-Wiener指数(0.99)和Pielou均匀度指数(1.25)较高,退牧15~20年后草本层逐渐被灌木半灌木层替代;(3)退牧5~20年的半流动与半固定沙地群落变异性大,退牧20~30年群落变异性相对较小;退牧5~20年,当地优势种油蒿(Artemisia ordosica)种群和羊柴(Hedysarum laeve)种群变异系数相近约为1.2,退牧30年左右油蒿变异系数是羊柴2倍多且油蒿种群发展较快.研究表明,退牧5~10年敏感期需禁牧管理,退牧15年灌木丛多样性和优势性较稳定宜采取轻度放牧管理,退牧30年左右,油蒿种群与羊柴种群种间竞争加剧,且前者有替代后者的趋势,管理时应注意防止群落组成结构单一化.  相似文献   

5.
6.
Abstract: Ponderosa pine (Pinus ponderosa) forests with Gambel oak (Quercus gambelii) are associated with higher bird abundance and diversity than are ponderosa pine forests lacking Gambel oak. Little is known, however, about specific structural characteristics of Gambel oak trees, clumps, and stands that may be important to birds in ponderosa pine-Gambel oak (hereafter pine-oak) forests. We examined associations among breeding birds and structural characteristics of Gambel oak at a scale similar in size to individual bird territories in pine-oak forests in northern Arizona and western New Mexico, USA. Avian species richness and occurrence of some bird species were associated with specific growth forms of Gambel oak. Estimated probability of Virginia's warblers (Vermivora virginiae), black-headed grosbeaks (Pheucticus melanocephalus), and red-faced warblers (Cardellina rubrifrons) occurring at points increased with increasing density of pole-sized Gambel oak 7–15 cm in diameter at breast height. We also found evidence that large Gambel oak trees (≥23 cm dbh) were associated with increased occurrence of yellow-rumped warblers (Dendroica coronata) at points. Some avian associations with oak were influenced by characteristics of ponderosa pines. For example, bird species richness was positively associated with the abundance of large Gambel oak when density of large pine trees ≥23 cm in diameter at breast height was low. Because large oak trees are rare and their numbers are thought to be declining, efforts should be made to retain and promote growth of additional oaks in this size class. Forest management practices that maintain forest openings, such as prescribed burning, could promote growth of pole-sized Gambel oak, which appears important to some bird species in pine-oak forests.  相似文献   

7.
Abstract: Livestock grazing is common and widespread throughout North America, yet few studies have evaluated its effects on small mammals. We studied small mammals in mixed-conifer forests and oak woodlands on the Cascade-Siskiyou National Monument in southern Oregon, USA, to 1) evaluate small-mammal microhabitat associations, 2) identify riparian-associated species, and 3) test the hypothesis that grazing does not influence small mammals after accounting for microhabitat associations. We live-trapped small mammals at 16 study sites and used logistic regression to model probability of capture on measured habitat characteristics at each trap station and to evaluate effects of grazing. Over 2 years, we trapped 1,270 individual small mammals representing 18 species. Odds of capturing western harvest mice (Reithrodontomys megalotis), dusky-footed woodrats (Neotoma fuscipes), and long-tailed voles (Microtus longicaudus) were lower (P < 0.05) on heavily versus lightly grazed sites. Odds of capture for deer mice (Peromyscus maniculatus) were lower (P < 0.05) on heavily versus lightly grazed sites in woodlands, but there was less difference in the odds of capture between grazing intensities in conifer forests. Odds of capturing Townsend's vole (Microtus townsendii) were lower on heavily versus lightly grazed riparian areas. Western harvest mice, long-tailed voles, and Townsend's voles were associated with, but not obligated to, riparian areas. Deer mice were ubiquitous, but captures were also higher (P < 0.05) in riparian areas compared with uplands. Siskiyou chipmunks (Tamias siskiyou) and piñon mice (Peromyscus truei) were associated with uplands (P < 0.05) rather than riparian areas. Trowbridge's shrews (Sorex trowbridgii), Siskiyou chipmunks, and bushy-tailed woodrats (Neotoma cinerea) were positively associated with coarse woody debris. Land managers should anticipate that small mammals associated with herbaceous or shrub cover, particularly in riparian areas, will decline when cattle remove this cover.  相似文献   

8.
Worldwide, savanna remnants are losing acreage due to species replacement with shade-tolerant midstory forest species as a response to decades of fire suppression. Because canopy closes grasses and other easily ignitable fuels decline, therefore, fire, when reintroduced after years of absence, is not always effective at restoring the open structure original to these communities. Our study sought to determine if managed grazing is an alternative tool for reducing shrub densities and restoring savanna structure without the impacts on soils and native vegetation observed with unmanaged grazing. We compared effects of fire and managed grazing on shrub and herb composition within degraded oak savanna and tallgrass prairie of the U.S. Upper Midwest using a randomized complete block design. The vegetation response to treatments differed by species and by vegetation type. Total shrub stem densities declined 44% in grazed and 68% in burned paddocks within savanna and by 33% for both treatments within prairie. Within savanna, cattle reduced stem densities of Rubus spp. 97%, whereas fire reduced Ribes missouriense stems 96%. Both fire and grazing were effective at reducing stem numbers for several other shrub species but not to the same degree. Native forbs were suppressed in grazed savanna paddocks, as were native grasses in grazed prairie paddocks along with a minor increase of exotic forbs. We did not observe changes in soil bulk density. We conclude that managed grazing can serve as a valuable supplement but not as a replacement to fire for controlling shrubs in these systems.  相似文献   

9.
封育和放牧条件下退化荒漠草地土壤种子库特征   总被引:19,自引:1,他引:18  
连续2年地不同退化程度天然干旱荒漠草原围封后群落的土壤种子库进行研究。结果显示,土壤种子库物种数、种子密度和植物生活型在年际间、封育与放牧样地间及退化梯度问均有明显差异。种子库物种数为封育高于放牧样地;退化梯度相比,物种数除2003年封育样地随退化程度加剧呈减少趋势外,放牧样地及2004年各样地均随退化程度加剧而增加。种子岸密度结果显示.2003年种子库密度明显高于2004年;各封育样地2年中土壤种子库密度显著或极显著(P<0.01)高于放牧样地;退化梯度相比种子库密度除2003年封育样地随退化程度加剧而急剧增加外,其余各样地种均随退化程度加剧而明显下降。植被生活型分析结果为,2003年以一年生草本植物种出现频率最高,各样地分别达94.0%~98.4%.多年生草本及灌木出现频率则很低,分别为1.59%~5.15%和0.03%~0.4%,2004年则为多年小草本植物种比例上升.且显示出封育高于放牧、退化程度愈轻增幅愈大的趋势。2年的结果显示种子库物种Shannon-Wiener多样性指数和Peilow均匀性系数均以封育低于放牧样地。种子库密度与地上植被盖度相关性分析表.2年结果中仅一年生草本和2003年灌木的土壤种子库密度与相应地上植被盖度之间具相关趋势和显著(P〈0.01)相关。  相似文献   

10.
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。  相似文献   

11.
The investigation dealt with the changes of the community structure as well as its cause of change, also with the quality of the artificial grassland sown with Elymus nutans at different time in the subalpine meadow in Gannan. The results are described as follows. 1. The aboveground biomass of E. nutans in the 2 year-old artificial grassland was highest and the index of grassland quality (IGQ) was highest in the 2 and 3 year-old communities, whereas it decreased in the other communities. IGQ was the lowest in the 7 year- o1d community. 2. The number and diversity of E. nutans species in the artificial grassland communities increased with the age increase of the communities but differed in their patterns of increase. 3. The decrease in biomass of E. nutans and IGQ correlated with the decrease of available phosphorus and not with the concentration of nitrogen in soil. The time for utilization of the artificial grassland with E. nutans could be lengthened by additional phosphorus supplement in soil.  相似文献   

12.
Prescribed fire is an important management tool for reducing the dominance of non‐native species in annual grasslands; both annual and perennial native species show strong vegetative responses in the subsequent growing season. However, although the post‐fire contribution of native species to the seed bank is assumed to be larger than in pretreatment years, the effects on seed quality, particularly viability and longevity, are not well understood. In this study, I germinated Nassella pulchra (purple needlegrass) seed that had been stored for 10 years after collection from target plants receiving treatment combinations of summer burning and grazing by sheep. Seeds from burned plants were larger and had higher germinability than seed from unburned plants. Seeds from plants that were both burned and grazed had the highest germination. The strong relationship between long‐term viability and seed size suggests greater maternal provisioning and increased seed quality subsequent to burning and grazing. I conclude that managing for seed quality may be a useful approach for conservation of native species in California's critically endangered grassland habitats.  相似文献   

13.
Recent losses and fragmentation of tallgrass prairie habitat to agriculture and urban development have led to corresponding declines in diversity and abundance of plants and birds associated with such habitat. Mowing and burning are alternative management strategies for restoring and rejuvenating prairies in fragmented landscapes, but their specific, comparative effects are the subjects of ongoing evaluation. We compared the responses of plant and bird communities on four sets of mowed, burned, and untreated sites of small (3–10 ha), fragmented tallgrass prairies at the DeSoto National Wildlife Refuge (DNWR), Iowa, U.S.A., during May–July in 1998 and 1999. Species richness and diversity of plants, resident grassland birds, and communities of birds associated with grassland edges (edge species) were independent of treatment. Although not affecting species richness and diversity in plant communities, mowed sites ranked lower in total plant coverage and total forb coverage than burned sites or untreated sites. In contrast, untreated sites had more coverage by shrubs, suggesting that mowing and burning did retard shrub encroachment. Overall, abundance and diversity of plants and birds were generally insensitive to management strategies. Small, fragmented sites of rare habitat may not respond in the short term to management treatments and may not be capable of supporting highly diverse communities, no matter how intensively manipulated. It is more probable that diversity of native prairie communities can be enhanced and restored only through long‐term efforts, acquisition of large land units capable of supporting stable populations, and deliberate reintroduction of species of high conservation value.  相似文献   

14.
Many herbaceous meadows are dominated by competitive non‐native grasses and subject to ungulate herbivory, ecological processes that shift the proportional biomass of plant groups in the community. Predicting the outcome of restoration is complicated because herbivory and competition can interact. We examined the relationship between herbivory by native black‐tailed deer and domestic sheep and dominance of non‐native grasses in Garry oak meadows, one of North America's most endangered habitat types. A 3‐year factorial experiment tested the effects of mowing and fencing on plant community biomass, categorized into eight groups by geographic origin (native/non‐native), growth form (annual/perennial), and plant type (forb/grass). To test if the rarity of native plant groups was related to herbivory, we estimated ungulate foraging preferences for each plant group. Mowing and fencing treatments interacted for annual and perennial non‐native grasses. Dominance was shifted from non‐native to native grasses only when both mowing and fencing were applied. Fencing increased the total biomass, whereas mowing had no overall effect; however, fencing alone did not affect any individual plant group. Mowing shifted dominance from grasses to forbs, although both native and non‐native forbs benefited from the increased light availability. We also noted that herbivore fecal pellet densities were greatest in the spring, which coincided with the peak season of their preferred plant group, native perennial forbs. Overall, applying both mowing and fencing was the most effective restoration treatment to increase native plant groups and biomass.  相似文献   

15.
桂林两江国际机场内草坪动物与鸟类关系   总被引:2,自引:0,他引:2  
2005年7月~2006年7月对桂林两江国际机场草坪动物及鸟类进行调查.共记录到鸟类9目23科48种,其中优势种是:田鹨、家燕、小云雀、棕背伯劳、黑卷尾、针尾沙锥、红隼、黑翅鸢;记录到昆虫13目76科,其中优势种有:直翅目、鞘翅目、双翅目、膜翅目、半翅目等昆虫和各种蜘蛛.鸟类数量和昆虫数量存在密切联系,鸟类数量峰值和昆虫数量峰值有部分重叠,说明昆虫数量对鸟类数量有影响.严格控制草坪昆虫数量能有效控制机场草坪的鸟类数量.蛙鼠类对草坪鸟类数量影响不大.  相似文献   

16.
ABSTRACT Livestock grazing in the shortgrass steppe of the Intermountain region of British Columbia may have a negative impact on ground‐nesting birds, but evidence of such an impact is lacking. We examined nest‐site selection and productivity of ground‐nesting Vesper Sparrows (Pooecetes gramineus) across sites with different grazing histories. From 2006 to 2008, we monitored Vesper Sparrow nests and measured vegetation characteristics known to be affected by grazing within nest patches. We used an information‐theoretic approach to test the relative importance of grazing‐affected vegetation variables as predictors of nest‐site selection, nest survival, and nestling condition. Vesper Sparrows selected nest sites with greater cover of late‐seral grass species that decrease in occurrence in response to grazing (i.e., “decreasers”) than was available in random patches in the same territories. Daily nest survival was also lower for nests surrounded by shorter vegetation (odds ratio = 1.12). However, “decreaser” cover was not associated with either of the two indices of productivity measured (daily nest survival probability and nestling condition). In addition, vegetation height, although an important driver of success, was not linked with nest‐site selection, and no vegetation‐cover variable was positively associated with productivity, despite nest concealment being central to our predictions. This suggests that predation risk for nests in areas with shorter vegetation was being elevated through some factor unrelated to concealment. Our results show that grazing reduced both the availability of suitable habitat for and nesting success of Vesper Sparrows, indicating that grazing could pose a threat to population persistence at a broader scale and could potentially contribute to observed declines. Additional research is needed to determine if grazing guidelines in the Intermountain region of British Columbia should be amended, better enforced, or both to prevent regional declines in populations of ground‐nesting grassland birds.  相似文献   

17.
丁小慧  宫立  王东波  伍星  刘国华 《生态学报》2012,32(15):4722-4730
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。  相似文献   

18.
黄土高原半干旱区退化草地恢复与利用过程研究   总被引:4,自引:0,他引:4  
草地退化表现为土壤和植被遭到彻底破坏,草地演替过程受到强烈抑制.实验采用长期(30年)封禁措施,定位监测退化草地从次生半裸地演变为近似原生植被(进展演替)的变化过程.结果表明,随着封禁时间的变化,退化草地恢复演替经历了4个阶段,群落盖度、植株密度、物种丰富度和多样性指数、地上生物量和地下生物量在草地群落恢复过程中逐渐增加,其特征变化出现的峰值均在封禁第20年(地下生物量峰值在第15年),其中地上生物量最高达520.5 g/m2;直到封禁的第20~25年,以本氏针茅为建群种的草原群落衰败退化现象明显,而大针茅种群密度剧增;在封禁的第26年以上以大针茅为优势的群落生长较为稳定,从目前群落演替进程看,大针茅有替代本氏针茅的趋势.另外,在草原沟道两侧以斑块状聚集分布有中旱生灌木,群落的演替进入了一个新的阶段.随着封禁时间的延续,退化草地从自然封禁恢复的0~26年,通过侵入-竞争-扩散-定居的几个演替阶段,目前形成以大针茅为建群种相对稳定的"亚顶级".虽然草地生物量有一定下降,但草地质量提高,物种多样性丰富,促进草地的进展演替.草地植物群落主要由禾本科、豆科和菊科组成;多年生植物、C3和旱生物种可以作为草地演替过程和植被恢复的指示物种.长期封育对草地物种更新和生态系统稳定性有负面影响,因此,合理的封育时间是草地生态恢复中非常重要的一个因素.本研究提出,在黄土区退化草地封育10~15年后可以开始进行合理的利用,例如通过两年一次刈割和轻度放牧(2只羊/hm2).本研究可为干旱区、半干旱区相似的退化草地恢复提供理论依据.  相似文献   

19.
To assess the potential for enhancing an existing stand of native perennial grasses on a California Coast Range Grassland site, we experimentally manipulated the seasonal timing and presence of grazing for 3 years (1994 through 1996) and of autumn burning for 2 years (1994 and 1995) and measured species cover for 6 years (1993 through 1998). We subjected the species matrix to classification (TWINSPAN) and ordination (CCA) and tested the ordination site scores as well as diversity indices with linear mixed effects models. Four distinct plant community groups emerged from the classification. Two of these were dominated by annual grasses and two by perennial grasses. No treatment effects were observed on diversity. For composition, temporal and spatial random effects were important mixed effects model parameters, as was the fixed effect covariate, pre‐treatment CCA site score, indicating the importance of random environmental variation and initial starting conditions. Incorporation of these random effects and initial condition terms made for more powerful tests of the fixed effects, grazing season, and burning. We found no significant burning effects. Grazing removal imparted a shift in plant community from more annual‐dominated toward more perennial‐dominated vegetation. Individual perennial grass species responded differently according to genus and species. Nassella spp. increased gradually over time regardless of grazing treatment. Nassella pulchra (purple needlegrass) increase was greatest under spring grazing and N. lepida (foothill needlegrass) was greatest with grazing removal. Danthonia californica (California oatgrass) had little response over time under seasonal grazing treatments, but increased with grazing removal. Under relatively mesic weather conditions it appears that grazing removal from Coast Range Grasslands with existing native perennial grass populations can increase their cover. However if N. pulchra is the sole existing population, spring season‐restricted grazing should be equally effective at enhancing cover of the native grass species.  相似文献   

20.
The decline in grasslands and other species‐rich early successional habitats on the coastal sandplains of the northeastern United States has spurred management to increase the area of these declining plant communities. We mechanically removed overstory oak and applied seed from a nearby sandplain grassland on the island of Martha’s Vineyard, Massachusetts, to evaluate this technique for creating an open oak community able to support sandplain herbaceous species. We compared vegetation structure and composition before and after clearing in an area of total tree removal (clearcutting), an area where 85% of tree basal area was removed (savanna cutting), and in adjacent coastal oak forest. Plant responses to clearcutting and savanna cutting were similar. Sandplain herbs colonized at high frequencies after seeding and increased herbaceous cover from less than 7% before clearing to 22–38% three growing seasons later. Pennsylvania sedge (Carex pensylvanica) increased in cover approximately 6‐fold, accounting for 84–90% of the increased herbaceous cover. Other native ruderals and exotic herbs reached 2 and less than or equal to 1%, cover, respectively, after three years. Species richness across cleared treatments increased from 30 to 79 species. All forest species were retained. Forest shrubs and trees initially declined from their dominant cover but rebounded after three years. Tree clearing plus seeding appeared to be a viable management practice for increasing cover of herbaceous sandplain species while causing minimal increases in exotic herbaceous cover. The long‐term persistence of sandplain herbs may require periodic disturbances that limit woody regrowth.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号