Bunch Grass Research Articles

Efficient utilization of winter nitrogen sources by soil microorganisms and plants in a temperate grassland

In seasonal snow-covered regions, the soil microbial community remains highly active, enabling nitrogen (N) mineralization processes to occur even during the winter. Therefore, winter N accumulation is likely to be a primary N source for plant growth in the subsequent spring. However, the availability of winter N resources (i.e., ammonium and nitrate N) to soil microorganisms and plants in temperate grasslands remains unclear. Here, we applied 15NH4Cl and K15NO3 tracers before autumn-winter freezing, and then investigated the retention of both 15N tracers in soil microorganisms and different plants during the winter and spring period in a typical steppe. The results showed that approximately 33 % and 27 % of 15NH4Cl and K15NO3 tracers were immobilized by soil microorganisms, while little had been uptake by plants during winter. In the subsequent spring, soil retained 32 % and 34 %, microorganisms immobilized 5.1 % and 5.2 %, plant acquired 40 % and 28 % of the 15NH4Cl and K15NO3 tracers, respectively. At a temporal scale, perennial bunch grasses first acquired 15N in the winter-spring transition, followed by perennial rhizome grasses and forbs in early spring, while legumes utilized little 15N. In contrast, the 15N absorption capacity of perennial rhizome grasses and perennial forbs was similar to that of bunch grasses. Additionally, only dominant bunch grasses showed a preference for ammonium N over nitrate N, while other plant species did not exhibit a clear preference for different forms of N. Our results suggest that the temporal differentiation of N utilization between plants and microorganisms enhances the availability of winter N sources. Importantly, the differences among plant species in the timing and quantity of winter N resource utilization contribute to species coexistence in temperate grasslands. This study highlights the crucial role of winter N accumulation as a primary N source for plant growth in temperate grasslands. Understanding the availability of winter N sources for plant and microbial growth is essential for predicting plant community dynamics and species coexistence in these ecosystems.

Responses in species diversity in the Hulunbuir grassland to phosphorus addition under nitrogen-limiting and non-limiting conditions.

The phenomenon of nitrogen deposition resulting in species loss in terrestrial ecosystems has been demonstrated in several experiments. Nitrogen (N) and phosphorus (P), as major nutrients required for plant growth, exhibit ecological stoichiometric coupling in many ecosystems. The increased availability of nitrogen can exacerbate the ecological effects of phosphorus. To reveal the ecological effects of phosphorus under nitrogen-limiting and non-limiting conditions, we conducted a controlled N-P interaction experiment over 5 years in the Hulunbuir meadow steppe, where two nitrogen addition levels were implemented: 0g N·m-2·a-1 (nitrogen-limiting condition) and 10g N·m-2·a-1 (nitrogen-non-limiting condition), together with six levels of phosphorus addition (0, 2, 4, 6, 8, and 10g P·m-2·a-1). The results showed that nitrogen addition (under nitrogen-non-limiting conditions) significantly decreased species diversity in the steppe community, which was exacerbated under phosphorus addition. Under nitrogen-limiting conditions, phosphorus addition had no marked impact on species diversity compared to the control; however, there were substantial differences between different levels of phosphorus addition, exhibiting a unimodal change. Under both experimental nitrogen conditions, the addition of 6g P·m-2·a-1 was the threshold for affecting the community species diversity. Nitrogen addition reduced the relative biomass of legumes, bunch grasses, and forbs, but substantially increased the relative biomass of rhizomatous grasses. In contrast, phosphorus addition only markedly affected the relative biomass of forbs and rhizomatous grasses, with the former showing a unimodal pattern of first increasing and then decreasing with increasing phosphorus addition level, and the latter exhibiting the opposite pattern. The different responses of rhizomatous grasses and other functional groups to nitrogen and phosphorus addition were observed to have a regulatory effect on the changes in grassland community structure. Phosphorus addition may increase the risk of nitrogen deposition-induced species loss. Both nitrogen and phosphorus addition lead to soil acidification and an increase in the dominance of the already-dominant species, and the consequent species loss in the forb functional group represents the main mechanism for the reduction in community species diversity.

Vegetation patterns associated with nutrient availability and supply in high-elevation tropical Andean ecosystems

Abstract. Plants absorb nutrients and water through their roots and modulate soil biogeochemical cycles. The mechanisms of water and nutrient uptake by plants depend on climatic and edaphic conditions, as well as the plant root system. Soil solution is the medium in which abiotic and biotic processes exchange nutrients, and nutrient concentrations vary with the abundance of reactive minerals and fluid residence times. High-altitude ecosystems of the tropical Andes are interesting for the study of the association between vegetation, soil hydrology, and mineral nutrient availability at the landscape scale for different reasons. First of all, because of low rock-derived nutrient stocks in intensely weathered volcanic soils, biocycling of essential nutrients by plants is expected to be important for plant nutrient acquisition. Second, the ecosystem is characterized by strong spatial patterns in vegetation type and density at the landscape scale and hence is optimal to study soil-water–vegetation interactions. Third, the area is characterized by high carbon stocks but low rates of organic decomposition that might vary with soil hydrology, soil development, and geochemistry, all interconnected with vegetation. The páramo landscape forms a vegetation mosaic of bunch grasses, cushion-forming plants, and forests. In the nutrient-depleted nonallophanic Andosols, the plant rooting depth varies with drainage and soil moisture conditions. Rooting depths were shallower in seasonally waterlogged soils under cushion plants and deeper in well-drained soils under forest and tussock grasses (>100 cm). Vegetation composition is a relevant indicator of rock-derived nutrient availability in soil solutions. The soil solute chemistry revealed patterns in plant-available nutrients that were not mimicking the distribution of total rock-derived nutrients nor the exchangeable nutrient pool but clearly resulted from strong biocycling of cations and removal of nutrients from the soil by plant uptake or deep leaching. Soils under cushion plants showed solute concentrations of Ca, Mg, and Na of about 3 times higher than forest and tussock grasses. Differences were even stronger for dissolved Si with solute concentrations that were 16 times higher than forest and 6 times higher than tussock grasses. Amongst the macronutrients derived from lithogenic sources, P was a limiting nutrient with very low solute concentrations (<1 µM) for all three vegetation types. In contrast K showed greater solute concentrations under forest soils with values that were 2 to 3 times higher than under cushion-forming plants or tussock grasses. Our findings have important implications for future management of Andean páramo ecosystems where vegetation type distributions are dynamically changing as a result of warming temperatures and land use change. Such alterations may lead not only to changes in soil hydrology and solute geochemistry but also to complex changes in weathering rates and solute export downstream with effects on nutrient concentrations in Andean rivers and high-mountain lakes.

Association Analysis of Tiller-Related Traits with EST-SSR Markers in Psathyrostachys juncea.

Psathyrostachys juncea is a long-lived perennial Gramineae grass with dense basal tillers and soft leaves. It is used widely in cold and dry areas of Eurasia and North America to establish grazing pasture and is even used as an ideal plant for revegetation and ecological restoration. Plant architecture, especially tillering traits, is critical for bunch grasses in breeding programs, and these traits in plants are mostly quantitative traits. In this study, the genetic diversity, population structure, and linkage disequilibrium of 480 individual lines were analyzed using 127 pairs of the EST-SSR marker, and a significant association between ten plant-architecture-related traits of P. juncea and molecular markers was found. The results of the genetic diversity analysis showed that the number of observed alleles was 1.957, the number of effective alleles was 1.682, Shannon's information index was 0.554, observed heterozygosity was 0.353, expected heterozygosity was 0.379, and the polymorphism information content was 0.300. A total of 480 individual lines were clustered into five groups based on population genetic structure, principal coordinate analysis, and unweighted pair group method with arithmetic mean analysis (UPGMA). The linkage disequilibrium coefficient (r2) was between 0.00 and 0.68, with an average of 0.04, which indicated a relatively low level of linkage disequilibrium among loci. The results of the association analysis revealed 55 significant marker-trait associations (MTA). Moreover, nine SSR markers were associated with multiple traits. This study provides tools with promising applications in the molecular selection and breeding of P. juncea germplasm.

Fecal metabarcoding of the endangered Pacific pocket mouse (Perognathus longimembris pacificus) reveals a diverse and forb rich diet that reflects local habitat availability.

Information on diet breadth and preference can assist in understanding links between food resources and population growth and inform habitat restoration for rare herbivores. We assessed the diet of the endangered Pacific pocket mouse using metabarcoding of fecal samples and compared it to plant community composition in long-term study plots in two populations on Marine Corps Base Camp Pendleton, San Diego County, CA. Fecal samples (n = 221) were collected between spring 2016 and fall 2017 during monthly live-trap surveys. Concurrently, percent cover and plant phenology were measured in plots centered on trap locations. Fecal samples were sequenced with paired-end reads of the internal transcribed spacer 2 region of the nuclear ribosomal gene, and the resulting amplicons were matched to a regionally specific database. Seventy-three plant taxa were detected, which were mostly forbs and perennial herbs (70-90%). Diet composition differed between populations, years, seasons, and plots. Overall, diet and local habitat composition in plots were significantly correlated. However, we detected some differences in above-ground seed availability and proportion in fecal samples that indicate diet preferences for some forbs, perennial herbs, and native bunch grasses over perennial shrubs and non-native grasses. This is the first study of PPM to pair plant phenology surveys with diet metabarcoding to estimate resource selection, and results suggest that managing habitat for diverse native forb communities and reducing non-native grass cover may be beneficial for this critically endangered species.

Methods of Cultivation and Crop Productivity in Rain-fed Mechanized Schemes in Sennar State, Sudan

The objective of this study was to obtain baseline informationabout the methods of cultivation and crop productivity in the RainfedMechanized Schemes (RMS) in Sennar State. Forty farmers were selectedfrom Eldindir, Singa and Sennar localities. The data collected was in theform of questionnaires, meetings and group discussion with farmers. Thequestionnaire was designed to obtain information about the area perscheme, areas allocated for cultivation, cultural practices, crops grown,and their yields. SSPS software programme was used for data analysis.The results revealed that the largest scheme areas were at Singa followedby EL Dindir and the smallest areas were at Sennar. Farmers at Sennarallocate all the area for crop cultivation, whereas at EL dindir and Singa,53.4 and 66.7% of the farmers allocate area for cropping and the rest forforest, respectively. Sorghum and millet are grown in all localaties, whilesesame and sunflower are grown only at EL dindir and Singa localities.Land preparation in all locations started by clearance of trees andperennial bunch grasses. Sowing is by wide level disc planter in ELDindir and Singa, while in Sennar, sowing is by seed broadcast andridging. In all localities weeding is manually after two or three weeksfrom sowing and some farmers use herbicides in combination withmanual weeding. None of the farmers use fertilizers and pesticides. Noproper crop rotation is applied in all localities. All farmers harvestsorghum and millet manually and mechanical threshing, while sesame isharvested manually and sunflower mechanically. The yields of all growncrops are low and not exceeding an average of 414, 252, 207 and 255 kgseeds per feddan for sorghum, millet, sesame and sunflower,respectively.

Compensatory dynamics drive grassland recovery from drought

Abstract Grasslands are expected to experience droughts of unprecedented frequency and magnitude in the future. Characterizing grassland responses and recovery from drought is therefore critical to predict the vulnerability of grassland ecosystems to climate change. Most previous studies have focused on ecosystem responses during drought while investigations of post‐drought recovery are rare. Few studies have used functional traits, and in particular bud or clonal traits, to explore the mechanisms underlying grassland responses to and recovery from drought. To address this issue, we experimentally imposed a four‐year drought in a C3‐dominated grassland in northeastern China and monitored recovery for 3 years post‐drought. We investigated the immediate and legacy effects of drought on total above‐ground net primary productivity (ANPP), ANPP of functional groups (rhizomatous grasses, bunch grasses and forbs), and how the legacy effects were driven by plant species diversity, clonal traits and vegetative traits. We found that drought progressively reduced total ANPP over the 4‐year period. The reductions in total ANPP in the first and third drought years were caused by the decrease in ANPP of bunch grasses only, while that of the second year was caused by declines in ANPP of bunch grasses and forbs, and the fourth year decline was linked to all three functional groups. The post‐drought recovery of ANPP, which occurred despite the continued loss of plant species diversity, was mainly driven by rapid recovery of rhizomatous and bunch grasses, which compensated for the slow response by forbs. The rapid post‐drought recovery of these grasses can be attributed to their relatively large, intact bud and shoot densities post‐drought, as well as the recovery of plant height and specific leaf area. The rapid recovery of grasses possibly restricted the growth and distribution of forbs, resulting in reduced forb ANPP and, consequently, lower species diversity during the recovery period. Synthesis. These results highlight the potential for positive legacy effects of drought on ANPP as well as the important and complementary roles of plant reproductive and vegetative traits in mediating ecosystem recovery from drought in a C3‐dominated grassland.

Antibacterial and Anticancer Effects of Silver Nanoparticles Synthesised using Eragrostis tef and Vitellaria paradoxa Seeds Extract

The present study aims to investigate the biosynthesis of silver nanoparticles using the aqueous extract of the Eragrostis tef (teff or annual bunch grass) and Vitellaria paradoxa (Shea Butter Tree) seeds extract and investigate their antimicrobial and anticancer activities. In order to synthesise the silver nanoparticles, aqueous extract of the plant was prepared and introduced into a 1mM silver nitrate solution. The synthesised AgNPs were characterised using various instrumental techniques including ultraviolet-visible spectroscopy, Fourier transformed infrared spectroscopy (FTIR), scanning electron microscope (SEM). Surface Plasmon Resonance (SPR) for AgNPs using E. tef and V. paradoxa seeds extract was observed at 40 nm. The synthesised AgNPs of E. tef and V. paradoxa was found with diameter of 12.59- 34.60 nm, 29.05- 83.94 nm respectively. The antibacterial result against the experimental pathogens was found to range from 12-22 mm and from 13-19 mm using AgNPs of E. tef, V. paradoxa seed extracts respectively. In addition the result show that there was clear effect on Acinetobacter baumannii from hospital sewage isolates. Toxic effect of AgNPs against cancer cell were 77.12 (concentration of AgNPs was 75%) of E. tef and 77.23 (concentration of AgNPs was 50%) of V. paradoxa.

Analysis of controlling genes for tiller growth of Psathyrostachys juncea based on transcriptome sequencing technology

BackgroundTillering is a complicated process in plant and is a significant trait that affects biomass and seed yield of bunch grass Psathyrostachys juncea, a typical perennial forage species. To clarify the regulatory mechanisms of tillering in P. juncea and to explore related candidate genes could be helpful to improve the seed and forage yield of perennial gramineous forages. We selected the tiller node tissues of P. juncea for transcriptome sequencing to determine the differentially expressed genes (DEG) between dense and sparse tillering genotypes. The metabolic pathway was studied, candidate genes were screened, and reference genes stability were evaluated.ResultsThe results showed that approximately 5466 DEGs were identified between the two genotypes with dense and sparse tillers of P. juncea, which significantly differed in tiller number. Tillering regulation pathways analysis suggested that DEGs closely related to the biosynthesis of three plant hormones, namely auxin (IAA), cytokinin (CTK), and strigolactones (SLs), while “biosynthesis of lignin” and “nitrogen metabolism” have remarkable differences between the dense and sparse tillering genotypes. Meanwhile, the reference gene Actin1, having the best stability, was screened from twelve genes with highest expression level and was used in verification of ten tillering related candidate genes.ConclusionsThe tillering mechanism of perennial grass P. juncea was expounded by transcriptome analysis of tiller node tissues. We demonstrated that dense-tillering genotypes may be distinguished by their low expression patterns of genes involved in SL, IAA, and high expression patterns of genes involved in CTK biosynthesis at the tillering stage, and nitrogen metabolism and lignin biosynthesis can also affect the number of tillers. Furthermore, the expression level of ten tillering related candidate genes were verified using Actin1 as reference gene. These candidate genes provide valuable breeding resources for marker assisted selection and yield traits improvement of P. juncea.

Short-term responses of herbaceous vegetation to bush clearing in semi-arid rangelands of South Africa

Bush thickening reduces herbaceous species diversity and forage production, leading to a decline in grazing capacity. Hence, altering the micro-climate and woody-grass competition in bush-encroached rangelands using bush clearing is instrumental for the restoration of herbaceous vegetation. The short-term recovery potential of herbaceous species composition, basal cover and biomass production was assessed following bush clearing at Makapaanstad, North West province, South Africa. The mean density was 6908 woody plants ha−1, with Vachellia tenuispina encroaching at 6301 plants ha−1. Paired observations were conducted in bush-cleared sites (where woody plants were cut using saws, with stumps treated with picloram at 1% concentration) and uncleared sites (where the woody cover was left intact). Forty-nine different herbaceous species were recorded, with grasses being more abundant in cleared (62%) than in uncleared sites (50%). Herbaceous species showed interspecific responses, with Brachiaria eruciformis and Panicum coloratum colonising in cleared sites, whereas the frequency of other species remained comparable between cleared and uncleared sites. Graminoids, largely bunch grasses, had a significantly greater basal cover in cleared (496 cm2 m−2) compared to uncleared (301 cm2 m−2) sites. Likewise, total biomass production was significantly (p = 0.05) higher in cleared (760 kg DM ha−1) than in uncleared (636 kg DM ha−1) sites. The principal component analysis (PCA) showed that most herbaceous species were associated with soils having high total nitrogen and nitrite. Seedlings of forbs (r2 = 0.81), grasses (r2 = 0.97) and succulents (r2 = 0.98) were highly associated with nitrate-rich soils. Our results revealed that even at a short term, bush clearing is important for the restoration of herbaceous vegetation.

Effects of land use on the hydrologic regime, vegetation, and hydraulic conductivity of peatlands in the central Peruvian Andes

The vegetation, geographic distribution, and pastoralist uses of peatlands in the central Andes have been extensively studied over the past 20 years. However, little information exists to characterize the hydrologic processes that support these groundwater-dependent ecosystems or the hydrologic alterations occurring due to human activities or climate changes. This lack of information significantly limits our understanding of how the central Andean Puna, one of the world's most threatened ecoregions, may be altered by increasing temperature and water extraction for human use. In addition, these peatlands provide critical pasture for native and domestic livestock and carbon storage, but overgrazing is an important modifier of their ecological trajectories.We analyzed three groundwater-fed fen peatlands with differing hydrologic regimes, annual precipitation, land use, and vegetation composition. Water table depth was a key factor significantly contributing to differences in soil hydraulic conductivity (p < 0.05) and vegetation composition (p < 0.05). Saturated hydraulic conductivity (K) varied from 0.57 m day−1 to 0.03 m day−1 for the horizontal component (Kh) and 0.07 to 0.002 m day−1 for the vertical component (Kv). The principal differences in K were in the seasonally unsaturated upper soil layers at 0–75 cm depth. The annual deepening in the water table and Distichia muscoides dominance drive the variability in K for these layers. Those drivers were themselves correlated but can individually modify K, increasing the decomposition rate and porosity (WT deepening) and altering the initial peat structure (D. muscoides dominance). Three vegetation communities were identified, one in sites with the deepest water tables, the lowest hydraulic conductivities, and dominance of Werneria pygmaea and Plantago rigida. The second community, dominated by bunch grasses in the genus Calamagrostis, occurred in areas with the most variable water table and medium hydraulic conductivity. The third community occurred in the most hydrologically stable areas, with the shallowest water table, highest hydraulic conductivities, and was dominated by Distichia muscoides. The study peatlands appear to have originated as the third community – groundwater-supported fens dominated by Distichia muscoides cushion and pool communities. However, modern hydrologic changes caused by human land uses and climate variability have caused a divergence in the vegetation, and in the more disturbed sites created higher decomposition rates in the shallow peat layers, and differences in soil structure.

Post-Fire Effects on the Globally Imperiled Chapin Mesa Milkvetch (Astragalus schmolliae), 2001–2019

Chapin Mesa milkvetch (Astragalus schmolliae) is an endemic, obligate pinon-juniper̴ woodland species that occupies approximately 2500 ha in southwest Colorado. In 2002 a crown fire burned 38% of the known distribution in Mesa Verde National Park. Initially, Chapin Mesa milkvetch (CMM) responded positively to the 2002 burn, increasing in density compared to unburned areas. Nine years post-fire (2011), the density in burned areas was nearly twice that of unburned transects. By 2013, the pattern had reversed, and by 2019, the juvenile and adult population in the burned area was reduced to half that of unburned (0.046 plants/m2 vs. 0.089 plants/m2). Recruitment of CMM in burned areas in 2019 was near zero: 4 seedlings in 63 burned transects vs. 6079 seedlings in 105 unburned transects. The downward trend in CMM density in the burn is likely associated with intensified competition from the dense grass cover. Prior to the burn, the grass cover in the to-be-burned area was qualitatively similar to that in present day unburned areas, which is 15%, almost exclusively muttongrass (Poa fendleriana), a shallow-rooted bunch grass. In 2019, cheatgrass (Bromus tectorum) and western wheatgrass (Pascopyrum smithii), seeded in 2002, dominated the cover in the burn, averaging 45% cover, collectively. Management practices that assist the recovery of burned pinon-juniper̴ woodland (and therefore CMM), as well as preserving the remaining old-growth pinon-juniper̴ stands, are likely key to CMM long-term survival.

Responses of grass productivity traits to bush clearing in semi-arid rangelands in North-West Province of South Africa

Woody plant encroachment threatens herbaceous plant productivity in many rangelands globally. We evaluated the impact of bush clearing on grass tiller, leaf and biomass production, and tuft sizes in the Kgomo-kgomo and Makapaanstad rangelands in North-West Province, South Africa. In each rangeland, the number of tillers and leaves, tuft sizes and biomass of eight dominant grass species were recorded in bush-cleared and uncleared treatments. The treatment and species interacted significantly (P &lt; 0.001) for tiller and leaf production and tuft sizes. Bush clearing increased tiller production of bunch grasses but not stoloniferous grasses. At Kgomo-kgomo, bunch grasses (Panicum maximum (Jacq.) and Urochloa mosambicensis (Hack.) Dandy] had three to six times more tillers and leaves per plant in the cleared than uncleared treatment. At Makapaanstad, only annual bunch grasses [Brachiaria eruciformis (Sibth. &amp; Sm.) Griseb and Tragus berteronianus (Schult.)] attained twice as many tillers and leaves per plant in the cleared compared to uncleared treatment. Biomass was 1776 ± 159 and 696 ± 159 g m−2 in cleared and uncleared treatments respectively at Kgomo-kgomo and 1358 ± 258 and 1089 ± 258 g m−2 at Makapaanstad. The tufts of bunch grasses were nearly twice as large in the cleared compared with the uncleared treatment at Kgomo-kgomo, whereas only stoloniferous grass tufts increased at Makapaanstad. Overall, bush clearing improved grass productivity and performance, but the responses varied by species.

Vicuña Dung Piles For Self‐Orientation

Photo 1. Vicuña dung pile in sleeping territory mounted up for weighing. Dung piles function to keep insiders in, not outsiders out. Note the downhill clump of Excrement-Influenced Vegetation (EIV) of unpalatable bunch grass “Peccoy” (Stipa ichu), successional stage EIV-1 from nutrients and organic matter having washed downhill. Additional EIV-1 clumps in right background. Pampa Galeras National Vicuña Reserve, Peru (4,100 m elevation). Photo credit: William L. Franklin. Photo 2. Vicuña territorial male chasing and attacking neighboring adult females that have accidentally trespassed into his year-round, defended feeding territory. Members of neighboring family groups typically smell dung piles as they approach boundaries for self-orientation to stay within their own territory. Photo credit: William L. Franklin. Photo 3. Young Vicuña females at sunset moving to their nighttime sleeping territory that is typically at a higher elevation where nighttime temperatures are warmer and avoids lower valleys where predators often hunt. Photo credit: William L. Franklin. Photo 4. The Andean Vicuña, close to extinction in the 1960s, has now recovered in part due to the protection and rational utilization of the species by indigenous peoples who live-capture the animals to shear and market their extremely fine and valuable wool. Photo credit: William L. Franklin. Photo 5. Young non-territorial Vicuña males in an all-male group moving between feeding sites. Adults weigh between 38 and 46 kg, being monomorphic with no difference between males and females. Photo credit: William L. Franklin. These photographs illustrate the article “Vicuña dung gardens at the edge of the cryosphere: Comment” by William L. Franklin published in Ecology. https://doi.org/10.1002/ecy.3522

氮水添加对放牧背景下荒漠草原生产力的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 氮水添加对放牧背景下荒漠草原生产力的影响 DOI: 10.5846/stxb202011112916 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金地区基金(31960246,31860138);内蒙古农牧业创新基金项目(2020CXJJM11);内蒙古科技计划项目(2019GG015) Influence of nitrogen and water addition on the primary productivity of Stipa breviflora in a desert steppe under different grazing intensities Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:水分与氮素作为干旱和半干旱草原生产力的共同限制性因子在退化草原的生态快速修复过程中备受关注。以不同放牧强度背景下的短花针茅荒漠草原为研究对象,开展围封模拟放牧利用实验,同时添加氮素和水分。通过分析历史放牧强度与年份对生产力的影响,以及添加氮素和水分对不同功能群植物生物量的作用,探讨放牧强度对短花针茅草原生产力的内在作用机制,以及如何实现荒漠草原资源合理开发和可持续利用。研究结果显示,降雨量与放牧强度决定着短花针茅草原的植物群落结构。氮素和水分添加可分别提升11%-29%和12%-32%的群落地上生物量,且二者存在显著的交互作用。不同功能群植物的地上生物量对氮素与水分添加的响应存在差异,多年生丛生禾草对氮素和水分添加响应最敏感。氮素与水分添加可显著提高多年生丛生禾草的地上生物量,但与自然降水量相关。氮素添加对地上生物量的影响在正常降雨和稍旱年份作用显著,而水分添加在干旱年份作用显著。在正常降雨年份,以半灌木植物为优势种的轻度放牧背景以添加水分对提升生产力最宜,以多年生丛生禾草和半灌木为共优种的中度放牧背景和以多年生丛生禾草为优势种的重度放牧以同时添加水分和氮素对提升生产力最为宜;在干旱年份不同放牧强度背景下均以同时添加水分和氮素对提升生产力最为宜。我们的结果表明了养分与资源的改善有利于退化短花针茅草原的快速恢复和可持续生产。 Abstract:Nitrogen and water as a co-limitation of primary productivity in steppe has attracted much attention in the rapid restoration of the degraded grassland. In this study, we take desert steppe of Stipa breviflora under different grazing intensities as study object, and simulation grazing, nitrogen addition, and water addition were carried out at the fenced site. By analyzing the effects of historical grazing intensity, year, nitrogen addition, and water addition on total aboveground biomass and plant biomass of different functional groups, we discovered the regulation mechanism of sustainable utilization of Stipa breviflora in a desert steppe under different grazing intensities. The results showed that rainfall and grazing intensity determined the structure of plant community in the desert steppe of Stipa breviflora. Nitrogen addition and water addition enhanced total aboveground biomass by 11%-29% and 12%-32%, respectively, with significantly interaction. The response of plant growth to nitrogen and water addition was different in different functional groups, and perennial bunch grasses were most sensitive to nitrogen and water addition. Nitrogen addition and water addition significantly increased aboveground biomass affecting the perennial bunch grasses, but associated with rainfall. The effect of nitrogen addition on aboveground biomass was significant in normal rainfall and lightly dry years, while water addition was significant in dry years. In normal rainfall years, water addition to increase productivity is most appropriate in the light grazing grassland which is with semi-shrubs as dominant species, while combined nitrogen and water addition to enhance productivity is most appropriate in the moderate grazing grassland which is with semi-shrubs and perennial bunch grasses as co-dominant species, and in the heavy grazing grassland which is with perennial bunch grasses as dominant species. In dry years, combined nitrogen and water addition to increase productivity is most appropriate in grassland under different grazing intensities. Our results show that the improvement of nutrients and resources is beneficial to the rapid recovery and sustainable production of the degraded Stipa breviflora steppe. 参考文献 相似文献 引证文献

Spatial Distribution of Lissorhoptrus oryzophilus (Coleoptera: Curculionidae) in Rice.

Rice water weevil, Lissorhoptrus oryzophilus Kuschel (Coleoptera: Curculionidae), is a destructive insect pest of rice in the United States. The pruning of rice roots by L. oryzophilus larvae can cause up to 25% yield loss. Currently, insecticidal seed treatments are used in the Louisiana rice industry as a pre-emptive means of controlling this weevil species. Our objective was to gain a better understanding of the spatial distribution of L. oryzophilus in Louisiana rice fields. Thirteen untreated commercial rice fields in Louisiana were mapped using GPS software, and surveyed for L. oryzophilus larvae over two years (2017 and 2018). An ANOVA, spatial interpolation, hotspot analysis, and multiple linear regression were used to determine where populations of L. oryzophilus were concentrated and whether distributions of the pest were related to edge effects. The results showed that L. oryzophilus larvae are typically aggregated along the edges of rice fields, with populations decreasing toward the center of rice fields. Lissorhoptrus oryzophilus densities were 3.3- and 2.2- fold greater along field edges than in field centers in 2017 and 2018, respectively. Hotspot spatial analysis revealed 59% and 32% of low-density clusters occurred at or near field centers, respectively. Multiple linear regression revealed larval densities decline with increasing distance from overwintering sites and alternative habitats (such as tree lines and levees containing bunch grasses and other alternative noncrop plants). These results suggest potential for insecticidal seed treatments to be applied selectively within rice fields to control this pest.

To bulk or not to bulk? Intense genetic differentiation of seed dormancy among Stipa lagascae (Poaceae) genotypes accessed and multiplied in arid Tunisia

Many ecological restoration projects involving wild dryland grasses work with bulk‐harvested seed, yet bulking may lead one to overlook and lose genetic variation that turns out to be crucial for restoration success, including specific dormancy breakdown requirements (conditional dormancy) and genetic variation in these. This article reports on the genetic variation of conditional seed dormancy of Stipa lagascae Roem. &amp; Schult. (Poaceae), a winter‐growing bunch grass with high‐grazing value, native to the circum‐Mediterranean areas but threatened with extinction. This grass is a cleistogamous inbreeder whose population remnants exhibit a fine‐grained genetic structure in many ecological traits. Seed from different lineages was obtained at the end of a seed increase program that chose not to bulk seed during seed sourcing, seed increase, nor seed harvesting for final use. Over a period of 3 years, three germination trials were run with seed coming from 15 to 20 different seed lineages and harvested over different years in two related seed increase plots. Seed lineage was the single most important factor explaining differences in conditional dormancy. Seed weight did not add much to explain these differences. The singularity of behavior of each lineage was conserved over the different harvests. Young seed exhibits the strongest differentiation in conditional dormancy. To restore genetically diversified populations of this inbreeding grass, restoration practitioners should avoid to bulk seed during sourcing and seed increase, because unique seed lineages get easily lost unseen. However, seed for final use could be bulk harvested if seed is used when still conditionally dormant.

Where Have the Native Grasses Gone?: What a Long-Term, Repeat Study Can Tell Us about California’s Native Prairie Landscapes

Much of the foothill and valley areas of coastal southern California are covered by stands of non-native grasses with occasional scattered patches of native bunch grasses. For decades, the dominant view held that these native bunchgrasses, particularly Stipa pulchra, once covered these lands and that grazing practices were a key cause of their decline. The so-called bunchgrass dominant paradigm (BDP) put forth by Clements influenced thinking on grassland ecology and biogeography for decades until it was discredited. Recent research suggests that grazing and related disturbances might have supported native bunchgrasses, but results are mixed and most studies cover only a short time frame. This research uses a long-term, repeat study design to analyze and compare data from three surveys of 15 permanent quadrats in La Jolla Valley, California, to determine changes in grassland cover over 34 years. A unique aspect of the study is that the site was selected by researchers precisely because it contained excellent ‘relic’ stands of Stipa pulchra (in accordance with the BDP) and the baseline study was conducted shortly after the area was released from grazing and placed under conservation management. We compared data on species frequency and percent cover collected using the same sampling routine for three periods: 1981, 1994, and 2015, to document the shifts in vegetation. We found that native grass cover decreased dramatically (especially on the valley floor), exotic grass cover fluctuated widely over time, while both native and exotic forb cover increased over time. The findings support the notion that prior grazing management practices may have supported the former stands of Stipa pulchra.

Peatlands of the Central Andes Puna, South America

The Andean puna is the highest elevation mountain and plateau region in the western hemisphere, extending from northern Peru to central Chile and Argentina, with vast areas above 4,250 m elevation. The Atacama Desert on the western side of the Andes is the world’s most arid region, and this aridity extends across the mountains. The upland vegetation is mostly continuous in the more humid north but becomes more and more patchy and barren composed only of bunch grasses in the central and southern region. Extensive upland talus, moraines, and colluvial deposits of the mountains produces perennial ground water flow systems that support thousands of peatlands and other wetlands that are regionally termed “bofedales” or “vegas”. The peatlands are dominated by several species in the family Juncaceae, most famously Distichia muscoides, that forms dense clonal cushions that characterize the alpine peatlands and landscapes. Being close to the equator, the growing season extends across the entire year, and continuous growth of the cushion plants have produced high carbon accumulation rates and peat bodies 7-10 m thick in many areas. The region supports unique plants and animals, and ecosystems, and the wetlands are threatened by overuse for livestock grazing, and climate changes that could reduce water provision may lead to some bofedales completely drying.

Influence of Beef Cattle Stocking Density on Utilization of Vegetative Communities in a Late-Spring, Early-Summer Native Bunchgrass Prairie

This study evaluated the influence of cattle stocking density on the use of botanical communities on a native bunchgrass prairie. In each of two years, 192 cow-calf pairs and 48 yearling heifers were randomly selected for the following grazing treatments: 1) control, no livestock grazing; 2) low stocking, 0.36 animal units (AU) ∙ ha-1; 3) moderate stocking, 0.72 AU ∙ ha-1; and 4) high stocking, 1.08 AU ∙ ha-1 for a 42-day grazing period. Thirty-six monitoring sites were established uniformly along a grid in each paddock. Standing crop and relative preference data for cattle collected from the treatment area were used to develop the following vegetation community classifications: 1) &gt; 20% introduced; 2) &gt; 40% native bunchgrass with &gt; 50% Idaho fescue (Festuca idahoensis); 3) &gt; 40% native bunch grass with &lt; 50% Idaho fescue; 4) &gt; 50% Forb; and 5) other. Utilization for each community type was collected at the end of the grazing period. High stocking density paddocks had higher utilization across all vegetation classifications compared to other stocking densities (P ≤ 0.04). Moderate stocking density paddocks were utilized 11.5% more than low paddocks, however, utilization of introduced vegetative communities, Idaho fescue dominated bunchgrass communities, and forb dominated communities did not differ in use (P ≥ 0.13). Use of monitoring to actively adjust stocking densities based on differential community utilization may improve the sustainable grazing of sensitive communities because conventional stocking rate calculations based on total productivity do not account for the selective grazing behavior of cattle.