Effects of harvesting <Emphasis Type="Italic">Cyperus papyrus</Emphasis> in undisturbed wetland,Lake Naivasha,Kenya

In many parts of the world and especially in Africa, wetland plants are harvested to support livelihoods. As such, removal of biomass may have an impact on the standing biomass which could affect primary productivity, a fundamental biological process supporting trophic levels. In this study, the effects of harvesting on aerial biomass and shoot regeneration of Cyperus papyrus L. was investigated following 6 and 12 monthly harvesting regimes compared with un-harvested controls over a period of 3 years in an undisturbed site of Lake Naivasha. Our study revealed that the 6 monthly harvesting regime significantly affected aerial biomass production, culm (stem) density, culm diameter, culm height and clonal young shoot regeneration compared to the 12 monthly regime and the controls. This study recommends a harvesting regime that allows an adequate period for a full cycle of C. papyrus stems from young to senescence stage.     

Impact of winter reed harvesting and burning on the nutrient economy of reed beds

The fringing reeds (Phragmites australis (Cav.) Trin. ex Steud., Poaceae) at Lake Constance-Untersee were mown or burnt in winter thereby drastically reducing the addition of decomposable organic matter to the sediment. The purpose of this study was to test whether or not this management significantly decreased the contents of organic matter and nutrients in the surface sediment layer and if the oxygen conditions in the withinreed water body improved. Hypotheses were tested by monitoring 6 treated reed beds and 3 reference fields over a period of up to 4 years. The sediment/water system of reed beds was found to be well buffered against the removal of the current year's crop of dead Phragmites straw, because only slight, and mostly insignificant, differences between treated and untreated reeds were detected. Hence, the benefit of winter reed harvesting to reduce nutrient overloading of the reed-belts and the die-back of reeds remains dubious.     

How does plant population density affect the biomass of Ravenna grass?

Ravenna grass, Tripidium ravennae (L.) H. Scholz, is known to produce an abundance of biomass, but how plant density affects its biomass potential remains unknown. The objectives were to determine the effects of plant density on biomass yield; plant growth traits; biomass?carbon, nitrogen, and ash concentrations; heating value; nitrogen removal; and sucrose concentration in leaves and culms. The treatments consisted of five plant densities (1,250; 2,500; 5,000; 10,000; and 20,000 plants per hectare) in a randomized complete block design with four blocks. Plots were nonirrigated, unfertilized, and harvested once during the dormant season each year. Data were collected from 2015?2019. Dependent variables that varied with plant population density (p < .05) were biomass yield, number of reproductive culms per plant, reproductive culm diameter, reproductive culm sucrose concentration, and nitrogen removal with biomass. Biomass yield ranged from 5.6 to 16.3 Mg/ha for plant densities of 1,250–20,000 plants per hectare, respectively. Combined over years, nonlinear regression of the data showed the equation for biomass yield to plateau at 16.2 Mg/ha at a plant density of 10,640 plants per hectare. As plant density increased, the number of reproductive culms per plant, culm diameter, and culm sucrose concentration significantly decreased. At 1,250 plants per hectare, the number of reproductive culms per plant, culm diameter, and culm sucrose averaged 70, 10.2 mm, and 63.2 g/kg, respectively. Nitrogen removed with biomass significantly increased as biomass yield increased with plant density. At a density of 10,000 and 20,000 plants per hectare, the amount of nitrogen removed annually in the harvested biomass averaged 88 kg/ha. The data suggest that 10,000 plants per hectare would produce the greatest annual biomass yields; however, research is needed to determine the nutrient requirement for Ravenna grass to sustain biomass production at that density.     

Impact of Culm Harvest on Seed Production in a Monocarpic Bamboo

Successful regeneration of bamboos from seed is a key issue in the ecology of many tropical regions and the livelihoods of their inhabitants. The gregarious monocarpy of many bamboos may be driven by a need to satiate seed predators by seeding in abundance at infrequent intervals. In long‐lived clonal monocarps, seed production is expected to be positively related to the success of the clone in generating more and larger ramets during its lifetime. Ramification may be constrained by harvesting of culms, but it is unclear whether the reduction in productivity is proportional to the loss of reproductive biomass. We counted the seed produced by 661 culms (ramet stems) sampled from 90 clumps of the gregariously monocarpic bamboo Schizostachyum dullooa that is intensively harvested by villagers in northeastern India. The smallest clumps had fewer culms and few or no culms more than one year old. Seed production was indeed positively related to culm size and the number of culms in a clump. First‐year culms were markedly more productive than older culms after controlling for culm diameter and clump size. There was a negative effect of clump size on productivity per culm which may occur because clumps that had been harvested heavily were able to exploit resources retained in rhizomes from harvested culms. Nevertheless, small clumps produced much less seed than larger clumps, generating a risk of unknown magnitude that heavily harvested stands of monocarpic bamboos may be unable to satiate seed predators during their single opportunity for reproduction.     

Soil warming and CO2 enrichment induce biomass shifts in alpine tree line vegetation

Responses of alpine tree line ecosystems to increasing atmospheric CO₂ concentrations and global warming are poorly understood. We used an experiment at the Swiss tree line to investigate changes in vegetation biomass after 9 years of free air CO₂ enrichment (+200 ppm; 2001–2009) and 6 years of soil warming (+4 °C; 2007–2012). The study contained two key tree line species, Larix decidua and Pinus uncinata, both approximately 40 years old, growing in heath vegetation dominated by dwarf shrubs. In 2012, we harvested and measured biomass of all trees (including root systems), above‐ground understorey vegetation and fine roots. Overall, soil warming had clearer effects on plant biomass than CO₂ enrichment, and there were no interactive effects between treatments. Total plant biomass increased in warmed plots containing Pinus but not in those with Larix. This response was driven by changes in tree mass (+50%), which contributed an average of 84% (5.7 kg m^?2) of total plant mass. Pinus coarse root mass was especially enhanced by warming (+100%), yielding an increased root mass fraction. Elevated CO₂ led to an increased relative growth rate of Larix stem basal area but no change in the final biomass of either tree species. Total understorey above‐ground mass was not altered by soil warming or elevated CO₂. However, Vaccinium myrtillus mass increased with both treatments, graminoid mass declined with warming, and forb and nonvascular plant (moss and lichen) mass decreased with both treatments. Fine roots showed a substantial reduction under soil warming (?40% for all roots <2 mm in diameter at 0–20 cm soil depth) but no change with CO₂ enrichment. Our findings suggest that enhanced overall productivity and shifts in biomass allocation will occur at the tree line, particularly with global warming. However, individual species and functional groups will respond differently to these environmental changes, with consequences for ecosystem structure and functioning.     

Primary productivity of papyrus (Cyperus papyrus) in a tropical swamp; Lake Naivasha,Kenya

Papyrus (Cyperus papyrus) standing biomass and the primary productivity of undisturbed and previously harvested areas of papyrus was measured in Lake Naivasha swamp, Kenya. Papyrus culm density in undisturbed swamp was estimated to be 13·1±1·9 culms m⁻² and aerial biomass was 3602 g m⁻². In undisturbed swamp the aerial productivity was 14·1 g m⁻² day⁻¹ while the previously harvested swamp reached a peak of 21·0 g m⁻² after 6 months. The annual aerial production rate of papyrus in Lake Naivasha was estimated to be 5150 g m⁻² year⁻¹. To sustain yields of regularly harvested papyrus swamps, the harvest intervals should exceed 1 year.     

pH诱导絮凝-气浮收获雨生红球藻研究

为提高雨生红球藻(Haematococcus pluvialis)收获效率,文章发现一种通过pH调控诱导雨生红球藻絮凝-气浮收获方法。通过与自然沉降对比发现,在不添加混凝药剂的情况下,调节藻液的pH可以诱导雨生红球藻细胞自发团聚形成絮体,显著提高其沉降或气浮收获效率。pH小于3或大于11.5时,气浮可在2min内实现95%左右的收获效率,而自然沉降则需要30min,才能达到80%—90%的收获效率。气浮收获后的生物质含固率要显著高于沉降收获,当初始浓度为3.2 g/L时, pH诱导絮凝-气浮收获后的雨生红球藻生物质含固率可达到17%,实现了53倍浓缩。另外,与化学混凝剂(硫酸铝)和生物混凝剂(壳聚糖)混凝-气浮对比发现, pH诱导絮凝-气浮不仅可以实现传统药剂混凝-气浮的高收获效率,还可以有效避免混凝剂对生物质的污染(如金属离子残留等),且不会对雨生红球藻中虾青素提取产生影响。因此, pH调控诱导絮凝-气浮可以实现雨生红球藻的快速、高效和无污染收获,为雨生红球藻的收获提供新的解决方案。     

Management Impacts on Carbon Dynamics in a Sierra Nevada Mixed Conifer Forest

Forest ecosystems can act as sinks of carbon and thus mitigate anthropogenic carbon emissions. When forests are actively managed, treatments can alter forests carbon dynamics, reducing their sink strength and switching them from sinks to sources of carbon. These effects are generally characterized by fast temporal dynamics. Hence this study monitored for over a decade the impacts of management practices commonly used to reduce fire hazards on the carbon dynamics of mixed-conifer forests in the Sierra Nevada, California, USA. Soil CO₂ efflux, carbon pools (i.e. soil carbon, litter, fine roots, tree biomass), and radial tree growth were compared among un-manipulated controls, prescribed fire, thinning, thinning followed by fire, and two clear-cut harvested sites. Soil CO₂ efflux was reduced by both fire and harvesting (ca. 15%). Soil carbon content (upper 15 cm) was not significantly changed by harvest or fire treatments. Fine root biomass was reduced by clear-cut harvest (60–70%) but not by fire, and the litter layer was reduced 80% by clear-cut harvest and 40% by fire. Thinning effects on tree growth and biomass were concentrated in the first year after treatments, whereas fire effects persisted over the seven-year post-treatment period. Over this period, tree radial growth was increased (25%) by thinning and reduced (12%) by fire. After seven years, tree biomass returned to pre-treatment levels in both fire and thinning treatments; however, biomass and productivity decreased 30%-40% compared to controls when thinning was combined with fire. The clear-cut treatment had the strongest impact, reducing ecosystem carbon stocks and delaying the capacity for carbon uptake. We conclude that post-treatment carbon dynamics and ecosystem recovery time varied with intensity and type of treatments. Consequently, management practices can be selected to minimize ecosystem carbon losses while increasing future carbon uptake, resilience to high severity fire, and climate related stresses.     

Benthic macroinvertebrate biomass and wildfires: evidence for enrichment of boreal subarctic lakes

1 We quantified the effects of forest fire on littoral benthic macroinvertebrate biomass on a boreal subarctic plateau in Alberta, Canada. Water chemistry and benthos were collected from six lakes, 1 and 2 years following a 1995 fire which burned about 91% of their catchments (i.e. recently burnt lakes), and from four other lakes whose catchments burned between 1961 and 1985 (i.e. previously burnt lakes). Seven lakes whose catchments had not burned since at least 1957 served as reference systems.
2 Total benthic macroinvertebrate biomass and biomass of Chironomidae were 1.5‐ and 2‐fold (P<0.05) greater within recently burnt lakes than in reference systems, whereas the biomass of Oligochaeta (P=0.06) and Amphipoda (P=0.07) were marginally higher in burnt than reference lakes. Burnt lakes had greater colour (P<0.05) and marginally (P=0.06) higher concentrations of soluble reactive phosphorus than reference lakes.
3 Nutrient diffusing substrata deployed in a previously and a recently burnt lake indicated that littoral epilithic communities were co‐limited by the availability of phosphorus (P) and nitrogen (N), although co‐limitation was stronger in the previously burnt than the recently burnt lake. Epilithic chlorophyll a on natural stone surfaces in the recently burnt lake was also 3.5 times higher (P<0.05) than that from the previously burnt lake.
4 Among all 17 lakes, total benthic biomass and biomass of Chironomidae, Amphipoda and Nematoda, were significantly (P<0.05) or marginally (P=0.06) related to soluble reactive phosphorus (SRP) but not dissolved inorganic nitrogen or colour. These regressions explained between 11% and 64% of variation in benthic biomasses.
5 Linear regressions and second‐order polynomials explained 18% and 24% of the variation in concentrations of SRP and water colour with time since fire, respectively, and between 22% and 70% of variation in total biomass and biomass of the five dominant invertebrate groups. These analyses suggest that benthic biomasses continue to be elevated for about 15–20 years following fire before declining to pre‐disturbance levels.     

Optimization of Chlorella biomass harvesting by flocculation and its potential for biofuel production

Optimization of microalgal biomass harvesting is essential to produce effective and optimum outcomes that can contribute towards a feasible and economical harvesting technique. Two Chlorella species were used, namely, C. vulgaris and C. sorokiniana UKM3. Two essential factors affecting microalgal biomass harvesting via flocculation, namely, the initial pH of the microalgal broth and flocculant (chitosan) concentration were studied. The optimization process was conducted by using a response surface methodology (RSM) based on the model of face-centered-central composite design (FC-CCD). The potential for biofuel application of the harvested biomass was evaluated based on the production of fatty acid methyl esters (FAMEs) by transesterification. The quadratic models obtained from the RSM significantly fitted the experiment data as the p-values were less than 0.05. The initial pH of the microalgal suspension was found to have a more significant effect on the flocculation process than flocculant concentration. For C. vulgaris, the highest flocculant efficiency of 98.7% was obtained at a chitosan concentration of 0.2 g L^?1 and an initial pH of 12.0, whereas for C. sorokiniana UKM3, at 0.15 g L^?1 of chitosan and initial pH of 12.0 produced the highest efficiency of 97.1%. The harvested biomass of both species exhibited a high content of palmitic acid (C16:0) with 29.74 wt% and 11.81 wt% of dry biomass for C. vulgaris and C. sorokiniana UKM3, respectively. This study showed that Chlorella species can be harvested efficiently using the flocculation process and manifested an excellent potential for biodiesel production where palmitic acid (C16:0) is one of the main compounds for high-acid oil-biodiesel.

     

Effects of summer and winter harvesting on element phytoextraction efficiency of Salix and Populus clones planted on contaminated soil

The clones of fast-growing trees (FGTs) were investigated for phytoextraction of soil contaminated with risk elements (REs), especially Cd, Pb, and Zn. As a main experimental factor, the potential effect of biomass harvesting time was assessed. The field experiment with two Salix clones (S1 – (Salix schwerinii × Salix viminalis) × S. viminalis, S2 – S. × smithiana) and two Populus clones (P1 – Populus maximowiczii × Populus nigra, P2 – P. nigra) was established in April 2009. Shoots of all clones were first harvested in February 2012. After two further growing seasons, the first half of the trees was harvested in September 2013 before leaf fall (summer harvest) and the second half in February 2014 (winter harvest). Remediation factors (RFs) for all clones and all REs (except Pb for clone S1) were higher in the summer harvest. The highest annual RFs for Cd and for Zn (1.34 and 0.67%, respectively) were found for clone S2 and were significantly higher than other clones. Although no increased mortality of trees harvested in the summer was detected in the following season, the effect of summer harvesting on the phytoextraction potential of FGTs clones should be investigated in long-term studies.     

Winter hardiness of Miscanthus (I): Overwintering ability and yield of new Miscanthus ×giganteus genotypes in Illinois and Arkansas

Miscanthus ×giganteus (M×g) is an important bioenergy feedstock crop. However, biomass production of Miscanthus has been largely limited to one sterile triploid cultivar, M×g ‘1993‐1780’, which we demonstrate can have insufficient overwintering ability in temperate regions with cold winters. Key objectives for Miscanthus breeding include greater biomass yield and better adaptation to different production environments than M×g ‘1993‐1780’. In this study, we evaluated 13 M×g genotypes, including ‘1993‐1780’, in replicated field trials conducted for three years at Urbana, IL; Dixon Springs, IL; and Jonesboro, AR. Entries were phenotyped for first‐winter overwintering ability and plant hardiness (ratio of new tillers to old), yield in years 2 and 3, and first heading date, plant height, and culm number in years 1 and 2. We observed substantial variation for overwintering ability and biomass yield among the M×g genotypes tested and identified ones with better overwintering ability and/or higher biomass yield than ‘1993‐1780’. Most entries at Urbana were damaged during the first winter, whereas few or no entries were damaged at Dixon Springs or Jonesboro. However, M×g ‘Nagara’ was entirely undamaged during the first winter and produced high biomass yields at Urbana (19.7 Mg/ha in year 2 and 20.9 Mg/ha in year 3), whereas M×g ‘1993‐1780’ exhibited an overwintering loss of 29%, had severely damaged survivors (hardiness score of 25%), and reduced biomass yield (8.1 Mg/ha in year 2 and 16.2 Mg/ha in year 3), indicating that M×g ‘Nagara’ could be a better choice in hardiness zone 5 (average annual minimum air temperature of ?23.3 to ?28.9°C) or lower. In Dixon Springs, where M×g ‘1993‐1780’ was undamaged by the first winter, it yielded highest among all the entries (21.6 Mg/ha in year 3), though not significantly higher than M×g ‘Nagara’ (18.2 Mg/ha in year 3).     

Harvesting of the Kelp Ecklonia Maxima in South Africa Affects Its Three Obligate, Red Algal Epiphytes

In South Africa, more than 7000 t (f wt) of kelp (Ecklonia maxima) fronds are harvested annually to feed cultured abalone. Carpoblepharis flaccida, Gelidium vittatum and Polysiphonia virgata are conspicuous red algal epiphytes on older kelps and provide habitat and food for numerous animals. Over 4.5 y, we examined the effects of one destructive harvest of E. maxima on these 3 epiphytes. Two 20 × 20 m plots of kelp with similar epiphyte loads were demarcated. In one, all E. maxima sporophytes with stipes longer than 50 cm were harvested. The other plot served as a control. After 2.5 y the biomass of E. maxima in the harvested plot had recovered to control levels, but the epiphyte load (g epiphytes. Kg kelp⁻¹) was statistically lower in the harvested plot after 2.5 and 3.5 y, and only recovered after 4.5 y. While most commercial harvesters cut through the “heads” (primary blades) of the kelp, effectively killing them, a new, non-lethal method removes secondary blades 20–30 cm from their bases, leaving the meristems and primary blades intact. At 5 sites studied, G. vittatum and P. virgata were found almost entirely on stipes and primary blades, and harvesting only distal parts of secondary blades limited losses to about 50% of C. flaccida biomass. To protect epiphytes, non-lethal harvesting is recommended and permanent non-harvest zones have been established in addition to limiting kelp yields and disallowing harvesting in Marine Protected Areas.     

The effect of harvest date and duration of wound healing conditions on the susceptibility of damaged potato tubers to infection by Phoma exigua (gangrene)

In experiments extending over 3 yr, King Edward tubers harvested on various dates from early September until early November were uniformly wounded and kept at 15 ^oC and c. 95% r.h. for periods of up to 21 days for wounds to cure. When tubers were subsequently inoculated with Phoma exigua var.foveata and incubated at 5 ^oC for 12 wk, curing for 3 and 7 days decreased gangrene incidence to respectively c. 13 and 4% of the non-cured controls. When tubers were inoculated before curing and immediately after wounding, curing for 7 days decreased gangrene incidence to only c. 68% of the non-cured controls. Curing was also progressively less effective the later the date of harvesting, suggesting that there would be advantages in harvesting potato crops early in the autumn.     

Remediation of AMD Contaminated Soil by Two Types of Reeds

Acid mine drainage (AMD) adversely impacts many regions in the world. The interactions among citric acid (CA), rhizosphere bacteria and metal uptake in different types of Phragmites australis cultured in spiked AMD contaminated soil were investigated. Compared with non-contaminated reeds cultured under the same conditions, wild reeds harvested from a contaminated site accumulated more metals into tissues. Rhizosphere iron oxidizing bacteria (Fe(II)OB) enhanced the development of Fe plaque but had no significant impact on the formation of Mn and Al plaque on the root surface of either reeds. Plaque may restrain the accumulation of Fe and Mn into tissues of reeds. CA inhibited the growth of Fe(II)OB, reduced the formation of metal plaque and significantly elevated metal accumulations into both underground and aboveground biomass of reeds. The concentrations of Fe, Al and Mn were higher in belowground organs than aboveground tissues. The roots contained 0.28 ± 0.01 mg/g Mn, 3.09 ± 0.51 mg/g Al, 94.47 ± 5.75 mg/g Fe, while the stems accumulated 0.19 ± 0.01 mg/g Mn, 1.34 ± 0.02 mg/g Al, 10.32 ± 0.60 mg/g Fe in wild reeds cultured in soil added with 33,616 ppm CA. Further field investigations may be required to study the effect of CA to enhance phytoremediation of metals from real AMD contaminated sites.     

Nitrogen Fixation, Nodule Development, and Vegetative Regrowth of Alfalfa (Medicago sativa L.) following Harvest

Nitrogenase-dependent acetylene reduction, nodule function, and nodule regrowth were studied during vegetative regrowth of harvested (detopped) alfalfa (Medicago sativa L.) seedlings grown in the glasshouse. Compared with controls, harvesting caused an 88% decline in acetylene reduction capacity of detached root systems within 24 hours. Acetylene reduction in harvested plants remained low for 13 days, then increased to a level comparable to the controls by day 18.     

Standing crop and mineral content of reed,Phragmites australis (Cav.) Trin. exSteudel,in Sweden—Management of reed stands to maximize harvestable biomass

The mean above-ground biomass of reed,Phragmites australis, in closed South Swedish stands was found to be 1 kg dry weight. m^?2 in August. Leaves, which are shed in the autumn in contrast to culms that remain standing, represent 26% of the total shoot weight. Because part of the culm will be covered by water, ice and snow 0.5 kg dry weight. m^?2 is available for winter harvest. Nutrient concentrations in shoots decrease throughout summer and winter. Although part of the maximal summer standing stock of N, P and K is lost in shed leaves, 55%, 75% and 80%, respectively, can potentially be recycled to rhizomes. Nitrogen fertilization and removal of standing litter in winter can increase above-ground biomass production in reed stands. Reed culms, cut in winter with agricultural machinery or amphibious harvesters, have been tested as a fuel for heating purposes in Sweden     

Evaluation of electro‐coagulation–flocculation for harvesting marine and freshwater microalgae

Although microalgae are considered as a promising feedstock for biofuels, the energy efficiency of the production process needs to be significantly improved. Due to their small size and low concentration in the culture medium, cost‐efficient harvesting of microalgae is a major challenge. In this study, the use of electro‐coagulation–flocculation (ECF) as a method for harvesting a freshwater (Chlorella vulgaris) and a marine (Phaeodactylum tricornutum) microalgal species is evaluated. ECF was shown to be more efficient using an aluminum anode than using an iron anode. Furthermore, it could be concluded that the efficiency of the ECF process can be substantially improved by reducing the initial pH and by increasing the turbulence in the microalgal suspension. Although higher current densities resulted in a more rapid flocculation of the microalgal suspension, power consumption, expressed per kg of microalgae harvested, and release of aluminum were lower when a lower current density was used. The aluminum content of the harvested microalgal biomass was less than 1% while the aluminum concentration in the process water was below 2 mg L⁻¹. Under optimal conditions, power consumption of the ECF process was around 2 kWh kg⁻¹ of microalgal biomass harvested for Chlorella vulgaris and ca. 0.3 kWh kg⁻¹ for Phaeodactylum tricornutum. Compared to centrifugation, ECF is thus more energy efficient. Because of the lower power consumption of ECF in seawater, ECF is a particularly attractive method for harvesting marine microalgae. Biotechnol. Bioeng. 2011;108: 2320–2329. © 2011 Wiley Periodicals, Inc.     

Progressive effects of shading on experimental wetland communities over three years

To investigate how the composition of wetland communities changes over time in response to altered light regimes, experimental communities of five Carex and four grass species were subjected to artificial shading (continuous or seasonal) in a three-year field experiment. Shoot number and size was measured after six weeks, and shoot biomass was harvested five times during the experiment. Communities were initially dominated by three grass species in all treatments, but subsequently, the Carex species increased and reached dominance in the control plots, whereas grasses remained dominant in the shaded plots. Shading had no effect on the biomass of communities or of single species in the first year. In the second year, community biomass was still unaffected, but shading reduced the biomass of three Carex species and also reduced species diversity. In the third year, shading reduced community biomass and all Carex species, but not species diversity. The greater shade tolerance of the grasses could not be explained by differences in morphological plasticity: after six weeks of growth all species had increased shoot height in response to shade by 40–70%. Grasses were hardly more plastic than Carex species. We propose that the long-term success of the Carex species in full light was due to a high allocation of biomass to belowground parts, which may have reduced losses caused by repeated harvesting of shoots (a simulation of management in productive wet meadows). Shading probably caused the Carex plants to change their allocation pattern, and thus prevented their progressive increase.     

高原鼠兔刈割行为与栖息地植物群落的关系

采用观察法和样条法对不同栖息地高原鼠兔刈割植物的行为、相对频次、生物量百分比以及刈割植物与鼠兔冬季食物组成之间的关系进行了分析,并阐述了高原鼠兔刈割植物的生物学意义。结果表明:高原鼠兔刈割植物始于每年的6 月下旬,早于其它草原小型哺乳动物贮草时间。不同栖息地鼠兔对植物的刈割频次和生物量比例并非完全一致。在矮嵩草草甸,鼠兔刈割频次较高的为垂穗披碱草、二柱头藨草、甘肃棘豆、短穗兔耳草、铺散亚菊和鹅绒萎陵菜;这些植物生物量所占比例亦较高,仅短穗兔耳草比例较低;在垂穗披碱草草甸,鼠兔刈割频次较高的为垂穗披碱草和早熟禾;垂穗披碱草生物量较高;而在杂类草草甸,鼠兔主要刈割植物为铺散亚菊、大籽蒿、黄帚橐吾、长茎藁本和圆齿狗娃花,生物量比例较高的主要为铺散亚菊。相似性分析结果表明,不同栖息地间鼠兔刈割植物频次和生物量比例差异较大,相似性系数最大分别为0. 7862 和0. 6100, 最小仅为0.1422 和0. 1035,而同一栖息地间鼠兔刈割植物频次和生物量差异相对较小,相似性系数最高达0. 9203 和0. 8490,最小亦达到0. 6662 和0. 4440,表明栖息地变化对鼠兔刈割植物频次和比例有明显的影响作用。鼠兔刈割主要植物频次和生物量比例与冬季主要食物组成的相关分析结果表明,生物量比例与主要食物组成呈显著的正相关(r =0.8412,df = 6, P <0. 05),而刈割植物频次与主要食物相关不显著。