长江中下游滩地植被与钉螺孳生关系的研究

对由莎草、苔草、狗牙根为优势种组成的杂草群落植被类型、由多种苔草、荻、为优势种组成的苔草、荻群落植被类型和由芦苇、菱笋、蒌蒿及蓼类为优势种组成的芦苇群落植被类型３种长江中下游滩地主要群落植被类型进行了钉螺密度与植被高度、钉螺密度与植被盖度之间的关系。结果表明：杂草群落植被类型,钉螺生存最适宜的植被高度为２２．０５ｃｍ、范围为１５～４７ｃｍ,钉螺生存最适宜的植被盖度为６５．２８％、范围为３５％～９０％;苔草、荻群落植被类型,钉螺生存最适宜的植被高度为２２．６９ｃｍ、范围为２０～３３ｃｍ,钉螺生存最适宜的植被盖度为６７．８０％、范围为３５％～９５％;芦苇群落植被类型,钉螺生存最适宜的植被高度为６４．８２ｃｍ、范围为７２～７８ｃｍ,钉螺生存最适宜植被盖度为６３．９５％、范围为１％～１００％。这一研究结果对通过生态工程措施控制植被因子,实现抑螺防病的策略提供科学依据     

氮素添加对科尔沁沙质草地物种多样性和生产力的影响

物种多样性和生产力是生态系统结构和功能的重要指标.以科尔沁沙质草地为对象,通过对其进行不同梯度的氮素添加处理,研究氮素添加对沙质草地生态系统物种组成、物种多样性和生产力的影响.结果表明：氮素添加改变了群落物种组成和群落中的优势种,使植被的高度和盖度增加,植被的透光率减小;随着氮素水平的增加,群落中物种丰富度减小,物种多样性降低;不同水平的氮素添加均显著增加了(P<0.01)群落地上生物量;物种丰富度与植被透光率呈线性正相关(P<0.01),与植被盖度呈线性负相关关系(P<0.01),说明长期的氮沉降与人为氮素输入将影响沙地生态系统的物种组成、物种多样性以及生产力.     

内蒙古贺兰山啮齿动物群落多样性及其与环境因子关系

啮齿动物群落结构可以反映生态环境特征。本研究对处于阿拉善荒漠区呈“孤岛”状态的内蒙古贺兰山国家级自然保护区内啮齿动物的种类、分布型及群落多样性进行系统研究。将内蒙古贺兰山划分为五种生境类型,于2013年春、夏、秋3季共布设有效铗日18748个,捕获啮齿动物235只,分属2目5科11属13种。在整体研究区域,阿拉善黄鼠（Spermophilus alashanicus）为优势种。明确了喜湿型是本研究区域的主要分布型,占捕获啮齿动物的54%,并且在中低海拔区域,随着海拔的升高,喜湿型所占比例增加。受“边缘效应”的影响,山地荒漠和荒漠草原生境以及山地草原灌丛生境的啮齿动物群落多样性指数高于其他生境,除环境因素外,啮齿动物群落的多样性受两种因素的影响,既可随群落内物种数量的增加而增大,同时又受制于群落内部物种分布的均匀程度。冗余分析结果表明,植被高度、植被盖度、灌木（乔木）高度和海拔4个环境因子是决定啮齿动物群落结构最主要的环境因子,其中植被盖度与群落多样性呈负相关,随着植被盖度的增加,多样性指数随之减低。     

放牧管理模式对高寒草甸鼢鼠鼠丘群落演替的影响

高寒草甸放牧利用下高原鼢鼠(Eospalax baileyi)等危害的发生是草地管理的关键难题,分析放牧管理模式对鼢鼠鼠丘植被群落演替的影响能为草地管理提供重要依据。研究选择划区轮牧(RG)、生长季休牧(GSG)、连续放牧(CG)和禁牧(PG)4种放牧管理模式,以及各模式下不同年限鼠丘(一年(ZM1)、两年(ZM2)、三年(ZM3)和多年鼠丘(ZMM))与对照(CM)草地。分析不同放牧管理模式对鼠丘植被群落特征和生物量等的影响,结果发现:PG和GSG下所有年限鼠丘的植被高度、地上生物量均高于RG和CG;RG和GSG下ZM1和ZM2物种Shannon-wiener指数均高于对照样地物种Shannon-wiener指数。主成分分析表明:RG下地上生物量和物种丰富度指数是影响鼠丘植被群落演替的重要因子,PG下地上生物量、盖度、Shannon-wiener指数和均匀度指数是鼠丘植被群落演替的重要因子,CG下物种丰富度和重要值是影响鼠丘植被群落演替的重要指标,GSG下Shannon-wiener指数、盖度和高度是影响鼠丘植被群落演替的重要指标。可见,不同放牧制度对鼠丘植被群落演替的影响不同,禁牧和生长季休牧管理模式能够较好地恢复鼠丘植被群落演替。     

新疆阜康地区植物群落物种多样性及其测度指标的比较

对新疆阜康绿洲荒漠过渡带植被,分别采用重要值、盖度、多度计测了9种物种多样性指数,并进行了对比分析。结果表明：①对新疆阜康绿洲荒漠过渡带植被类型,以重要值和盖度为测度指标优于多以度为指标计测群落多样性指数;②对9个指数的主成分分析（PCA）表明,3个多样性指数中,Shannon-Wiener指数受丰富影响最大,其次是McIntosh指数,而Simpson指数与丰富度关系较远。     

鄂尔多斯高原植物群落多样性时空变化特点

作者利用1999年和2000年野外植物群落调查资料,结合李博(1990)的植物群落调查结果,分析了鄂尔多斯高原植物群落多样性的时空变化特点。鄂尔多斯高原主要植物群落类型有23类,不同植被类型的群落多样性表现出一定的差异性,其中丰富度指数的差异不显著,而Simpson指数和Shannon-Wiener指数及群落盖度的差异明显。中东部典型草原表现为高多样性高盖度;西鄂尔多斯荒漠草原和草原化荒漠物种多样性较高,但盖度较低;毛乌素沙地植物群落物种多样性低,但盖度较高。从1986年到2000年,该地区典型草原群落、荒漠草原和沙地植被的群落多样性指数都有下降趋势;典型草原和草原化荒漠的群落盖度有所增加,荒漠草原有所下降。以上结果表明,沙地植被和草原化荒漠生物多样性已经得到了一定的保护,但还有待加强,而荒漠草原的保护亟待引起重视。     

高原兔夏季卧栖地生境利用关键因子分析

研究阿尔金山国家级自然保护区高山草甸和高山荒漠区高原兔Lepus oiostolus夏季生境卧息地利用的主要影响因子,为高原兔的科学管理提供依据。2011—2013年夏季,累计调查高原兔卧息地5 m×5 m样方32个,另外在附近相同生境类型中设置对照样方33个。记录样方所在地的植物种数、植被盖度、植被高度、土壤硬度以及距道路的距离等指标。结果表明,卧息地和对照样方在植物种数、土壤硬度等方面差异有统计学意义(P<0.05),而在隐蔽级、植被高度、植被密度等方面差异有高度统计学意义(P<0.01)。Vanderloeg和Scavia选择指数Ei、选择系数Wi分析显示高原兔卧栖地偏好选择高度在30 cm以上、植被盖度大于30%且密度小于80株/m2,隐蔽级在10 cm以上,土质较软(6~9 kg/cm2)的小生境。主成分分析表明影响高原兔卧息地利用的主要因子依次是:植被密度(-0.898),植被盖度(-0.812)和隐蔽级(0.764)。高原兔偏爱植被高度更高、植物密度更低、隐蔽级更高、土壤较软的小生境。我们的结果为高原兔的科学管理提供了重要依据。     

阿尔泰山两河源牧区草地群落生物量及物种多样性

群落生物量和物种多样性是表征草地生态系统数量特征的重要指标。该研究以新疆阿尔泰山南麓两河源放牧区草地为研究对象,利用样方法对两河源不同放牧区的草地植被进行调查,分析研究区生物量和物种多样性变化,探讨二者与环境因子之间的关联性,为草地群落物种保护以及草地可持续利用提供理论依据。结果表明：(1) 两河源不同牧区间群落盖度、高度、植株密度、地上生物量和单位盖度生物量存在差异。(2) 两河源牧区草地群落地上生物量与群落盖度、植株密度呈显著正相关关系(P<0.05),且地上生物量主要受草地群落盖度的影响;不同牧区的物种多样性指数有一定差异,但物种分布相对均匀。(3)两河源牧区草地群落生物量及物种多样性主要受气温和降水的影响。     

北京野鸭湖湿地地表甲虫群落组成与空间分布格局

2007年4–10月在北京野鸭湖湿地两种保存较好的湿地植被类型和3种主要的退化植被类型中设立了32个样地, 采用陷阱法调查地表甲虫群落的组成, 并在科级水平上探讨了湿地退化及植被类型变化对地表甲虫群落组成的影响。整个采样周期共采集甲虫标本42科, 其中步甲科和隐翅虫科为优势科, 蚁形甲科、肖叶甲科和薪甲科为亚优势科。在所研究的5种植被类型中, 湿地景观保存较好的芦苇(Phragmites communis)带与球穗莎草(Cyperus glomeratus)带的甲虫群落活动密度、科丰富度和Shannon-Wiener多样性指数(H’)均无显著差异, 而上述两种植被类型的甲虫活动密度以及球穗莎草带的甲虫科丰富度均显著高于3种退化的植被类型。对地表甲虫群落组成与9个环境因子进行的典范对应分析(CCA)表明, 32个样地在CCA排序图中的分布与植被类型之间存在明显的对应关系, 土壤含水量、植物盖度、植物生物量和枯落物盖度是影响地表甲虫群落组成及空间分布的主要环境因子。相关和回归分析结果也显示, 甲虫群落的活动密度与土壤含水量、植物生物量和植物盖度均极显著或显著正相关, 科丰富度与植物生物量显著正相关, 多样性指数(H’)与植物盖度极显著负相关; 其中土壤含水量的变化能够解释甲虫群落活动密度总方差的57%。此外, 通过主成分分析获得了反映土壤含水量、植物生物量和植物盖度综合作用的环境变量WBC (Water-Biomass-Coverage)。依据地表甲虫活动密度与WBC的关系, 可将5种植被类型分为彼此差异极显著的3组。研究结果表明保持良好的湿地景观对于保护湿地甲虫具有重要意义。     

繁殖期荒漠鸟类群落与自然植被的相关格局

为探讨植被结构和物种组成对鸟类群落多度分布的影响,于2010年5～8月,在阜康地区所涵盖的显域植被梯度带(梭梭、琵琶柴及蒿属荒漠)内分别布设3～4条样线,调查繁殖鸟类群落多度分布及植被参数.借助平均高度和盖度反映植被结构,平均物种数目反映植物组成.从鸟类群落中抽取显著正相关鸟种组合及狭分布鸟种组合,将不同的鸟类组合与植...     

Measuring succession: methods for establishing long-term vegetation monitoring sites

Successional stages are often characterized by dominant plant species (species with the highest cover) and their effect on the structure and function of an area through time. However, the plant species determining the ecosystem properties and plant community dynamics may not be the dominant, especially when it is exotic. Understanding plant community dynamics in ecosystems that are uncharacterized and/or affected by invasive plant species requires a data-driven approach and proper placement of monitoring plots. To generate robust datasets on vegetation change through time, monitoring plot placement must consider the scale of ecological variation for both vegetation and soils and plots would ideally be replicated within similar ecological site types to quantify the consistency of successional transitions. We characterized soil and vegetation across and within seven floodplains affected by Russian olive (Elaeagnus angustifolia L.) along the Yellowstone River in southeastern Montana, USA. Using modern Classification and Regression Trees (CART) and multivariate net differentiation, we identified five distinct plant community types, or classes, characterized by their tertiary woody plant cover, not the primary species, Russian olive. Our findings indicate that Russian olive communities differ across space, and these riparian areas can be classified into distinct plant community types. Characterizing plant community types via this analytical approach should allow practitioners to modify management decisions and forecast succession within relevant plant communities.     

A plant diversity×water chemistry experiment in subalpine grassland

Plant diversity has been shown to drive important ecosystem functions such as productivity. At the same time, plant diversity and species composition are altered in alpine ecosystems by human impacts such as skiing. Therefore, we investigated impacts of decreased species richness and ski piste treatments on ecosystem functions in subalpine grassland.Species richness manipulations were combined with nutrient input from snow cover treated with snow additives that are commonly used on ski pistes. Three different species richness levels containing 1, 3 or 9 species randomly selected from a larger pool plus unmanipulated meadow plots were treated with four water types to simulate melt water. One water type contained the snow additive ammonium nitrate. Invasion into the communities was prevented by weeding during 2 years and allowed in three subsequent years.Higher species richness increased plant cover and biomass and decreased their variation. The number of functional groups in a plant assemblage had a positive effect on plant growth. Ammonium nitrate strongly increased biomass and plant cover after a single application but decreased species richness in originally diverse meadow plots. There was no significant interaction between species richness and water-type treatments.After the cessation of weeding, the species richness of different plot types converged within 3 years due to invasion. Nevertheless, relationships between initial species richness and plant cover remained positive.The results suggest that the diversity and species composition of alpine vegetation are important factors influencing cover and biomass, in particular during re-colonization of bare ground after disturbances such as ski-piste construction. In slow-growing alpine vegetation, initially positive diversity effects may remain even after successional convergence of species richness due to invasion. The negative effect of ammonium nitrate on species richness suggests the snow additives should only be used with care.     

Plant responses to nutrient addition and predictive ability of vegetation N:P ratio in an austral fen

1. Previous studies of the N:P ratio in wetland plants have been carried out in northern hemisphere wetlands where atmospheric nitrogen deposition is higher. There is little research on foliar N:P ratio as a potential indicator of nutrient limitation in vegetation communities in southern hemisphere wetlands. This study aimed to redress this knowledge gap and answer the following questions: how well does the plant tissue nitrogen to phosphorus (N:P) ratio predict wetland plant community nutrient limitation, as indicated by vegetation standing stocks and below-ground biomass, in southern hemisphere fens? Secondly, what are the impacts of realistic upper levels of farm nutrient run-off on natural montane fen vegetation?
2. Low (35 kg ha⁻¹ year⁻¹) and high (70 kg ha⁻¹ year⁻¹) levels of nitrate-N or ammonium-N with and without P (20 kg ha⁻¹ year⁻¹) were added to 81 vegetation plots over a period of 2.75 years. Species composition, plant nutrient status, and above-ground live vegetation standing stocks were assessed after 3 years, and below-ground biomass after 2 years.
3. Plant tissue analysis suggested the community was N limited or N and P co-limited; we found greater standing stocks of vegetation in plots treated with 70 kg ha⁻¹ year⁻¹ ammonium-N, indicating N limitation. No difference between other treatments was found in above-ground standing stocks or below-ground biomass. Plant species cover increased in both high N treatments, consistent with N limitation. These changes in plant species cover were accompanied by significant decreases in species richness in both high N treatments. Native species dominated the vegetation and this was unaffected by nutrient addition (90% cover).
4. This is one of the first studies to test and find support for the N:P ratio in southern hemisphere wetlands. Observed declines in species richness after N fertilisation in an N-limited fen suggests increased N may pose risks to austral wetlands. Responses by plant communities (changes in composition, biomass) to lower levels of nutrient addition may require longer periods of fertilisation to be apparent in slow growing ecosystems.

     

Resource availability and plant diversity explain patterns of invasion of an exotic grass

Aims In this study, we examine two common invasion biology hypotheses—biotic resistance and fluctuating resource availability—to explain the patterns of invasion of an invasive grass, Microstegium vimineum.Methods We used 13-year-old deer exclosures in Great Smoky Mountains National Park, USA, to examine how chronic disturbance by deer browsing affects available resources, plant diversity, and invasion in an understory plant community. Using two replicate 1 m 2 plots in each deer browsed and unbrowsed area, we recorded each plant species present, the abundance per species, and the fractional percent cover of vegetation by the cover classes: herbaceous, woody, and graminoid. For each sample plot, we also estimated overstory canopy cover, soil moisture, total soil carbon and nitrogen, and soil pH as a measure of abiotic differences between plots.Important findings We found that plant community composition between chronically browsed and unbrowsed plots differed markedly. Plant diversity was 40% lower in browsed than in unbrowsed plots. At our sites, diversity explained 48% and woody plant cover 35% of the variation in M. vimineum abundance. In addition, we found 3.3 times less M. vimineum in the unbrowsed plots due to higher woody plant cover and plant diversity than in the browsed plots. A parsimonious explanation of these results indicate that disturbances such as herbivory may elicit multiple conditions, namely releasing available resources such as open space, light, and decreasing plant diversity, which may facilitate the proliferation of an invasive species. Finally, by testing two different hypotheses, this study addresses more recent calls to incorporate multiple hypotheses into research attempting to explain plant invasion.     

Spontaneous and initiated succession on unvegetated slopes in the abandoned lignite‐mining area of Goitsche,Germany

Abstract. In this study, we examined the colonization of unvegetated, dry slopes in the lignite‐mining area of Goitsche, Germany. The plots, characterized by different habitat conditions, were studied from 1994–2000. The vegetation development on treated plots was compared to untreated plots showing spontaneous succession. For initial treatments we used fresh plant clippings from a species‐rich sandy grassland (Armerion elongatae) mowed at the end of July. Soil seed bank samples, taken at the beginning of the experiments and cultivated for 18 months, confirmed that the vegetation development on the slopes started with primary succession. Because seed rain is considered to be an important factor in primary succession, we also studied the diaspore input during the first year. The hospitable Quaternary substrate of Site I (pH = 4.1–4.7, 92 % sand) supports fast vegetation development on treated and untreated plots. On treated plots, we have identified plant assemblages similar to initial stages of the Armerion elongatae community. On control plots, Coryne‐phorion communities have established spontaneously. At Site II (mixed Quaternary and Tertiary substrate, pH = 3.0–3.5,40 % sand) the total cover and number of psammophytic species was low. Treated plots showed development towards ruderal sandy grassland, but the establishment of Calamagrostis epigejos would eventually lead to monodominant stands. Untreated control plots showed basically the same pattern, however the development was slower. At Site III (pH = 1.8–2.8, 34 % sand), the hostile Tertiary substrate impeded the succession on both treated and untreated plots because low pH and therefore high amounts of Al³⁺ produced elemental toxicity to plants. The application of plant clippings accelerated the vegetation development in sites with a pH exceeding 3. On plots with the initial treatment, vegetation cover and total number of species were higher than on untreated plots. The application of fresh plant clippings from areas with similar habitat conditions appears to be a viable alternative to traditional restoration methods.     

Revegetation of an artificial cut-slope by seeds dispersed from the surrounding vegetation

We examined a method for revegetation of cut-slopes in Tochigi, Japan, using only natural plant dispersal from the surrounding vegetation. We examined plant establishment in six plots in a cut-slope in bedrock (inclination: 65°, direction: S45°W) treated with various types of netting and fertilizer. We surveyed the plant communities, individual trees, and seed rain on the cut-slope, as well as the plant community on the undisturbed upper slope. Revegetation method using polyethylene netting with fertilizer and water-retention material was the most effective. The resulting plant community was dominated by Pinus densiflora, with a cover of 49.0±11.4% after 5 years. This plant community consisted of 19 species, including ten tree species and a density of 26.2 trees/m². Revegetation method using palm-fiber netting with fertilizer also resulted in high plant cover after five years, although little revegetation grew on this plot in the earlier years. The roughness of the palm fiber may have inhibited revegetation. Application of fertilizer was essential for the success of this natural revegetation method. In addition, the revegetated plant community was strongly influenced by seed rain from the vegetation of the upper slope. The number of trees that became established was much lower than the number of tree seeds that were dispersed, possibly because of the absence of soil. We recommend that soil is allowed to accumulate or that a base of material to facilitate plant growth is added. Successful revegetation was achieved even under the harsh conditions of this cut-slope.     

Termite- and Mulch-Mediated Rehabilitation of Vegetation on Crusted Soil in West Africa

The rehabilitation of vegetation on structurally crusted soils by triggering termite activity through mulch was studied on three soil types in northern Burkina Faso, West Africa. A split-plot design was used in a fenced environment for the experiment. Insecticide (Dieldrin) was used at a rate of 500 g a.i. (active ingredient)/ha to create nontermite and termite plots. Three mulch types consisting of straw (Pennisetum pedicellatum), woody material (Pterocarpus lucens), and a composite mulch (straw and woody material) applied at a rate of 3, 6, and 4 tons/ha, respectively, were used to trigger termite activity. The grasses and woody species on the plots were surveyed. Nontermite plots responded weakly to mulch treatments, but even in the first year vegetation established on termite + mulch plots. Termite activity resulted in the increase of plant cover, plant species number, phytomass production, and rainfall use efficiency. Infiltrated water use efficiency and plant diversity were not statistically different among treatments during the first 2 years but were in the third. Woody species established only on termite plots. The three types of mulch plots showed greater vegetation development than bare plots, which remained bare throughout the experiment. Analysis of the termite and mulch interaction indicated that mulch plots without termites did not perform better than bare plots, especially in the case of woody plant regeneration. Vegetation rehabilitation was best with composite and straw mulches with termites, followed by woody mulch with termites; it was worst on bare plots.     

Timing of white-tailed deer browsing affects wetland plant communities

White-tailed deer (Odocoileus virginianus Zimm.) have the potential to alter plant community composition and successional trajectory by browsing differentially on forb, graminoid, and woody species. The objective of this study was to determine if seasonal elimination of deer browsing changed wetland plant community composition and structure. We established 66 deer exclosure plots in two wetland vegetation communities in Canaan Valley, West Virginia, USA. Plots were established in April 2005 and monitoring was conducted in June and October, 2005–2007 to obtain data on both early and late species. Composition differed between control and treatment plots in Solidago spp.–Rubus hispidus L. communities in late-protected plots (enclosed July–October) when data were gathered in October. Community composition also varied in early-protected plots (enclosed April–July) when data were gathered in June. Forb cover increased in treatment plots in Solidago spp.–Rubus hispidus communities. Composition differed in Populus tremuloides Michx. communities in late-protected and continuously protected plots. There was no increase in cover by any wetland indicator status categories after 2 years of protection. Timing of browse played an influential role in the effect that white-tailed deer have on wetland plant communities. Our results suggest that reducing browsing pressure seasonally can increase forb species cover.     

Relationships between seed banks and spatial heterogeneity of North American alvar vegetation

Abstract. This is the first quantitative study of seed bank characteristics in North American alvar habitats. We assessed seed bank density, species richness, and species composition in 75 plots distributed among five alvar sites in Bruce Peninsula National Park, Ontario, Canada, each of which displayed areas of high and low vegetation cover within the alvar and a fully forested perimeter area. Forested habitats immediately adjacent to alvar patches contained minimal seed banks for species restricted to the alvar patches. Open alvars contained less than 1% seeds from woody forest species. This suggests that forest is not invading adjacent alvar habitat via seeds and that adjacent forest does not contain a reservoir of alvar seeds. When compared to areas on the alvar with high vascular plant cover, areas with low cover contained a slightly smaller viable seed bank, but seed banks from high and low vegetation cover plots had similar species composition and species richness. High vegetation cover plots had slightly higher mean and maximum soil depths compared with low cover plots, but no differences in other physical and chemical parameters. Thus, spatial heterogeneity in plant cover is associated only weakly with heterogeneity in below‐ground factors. Despite the availability of seed and soil resources, vegetation dynamics are constrained in areas with low plant cover, and thus alvar community development seems to respond non‐linearly to resource availability.     

Soil feedback does not explain mowing effects on vegetation structure in a semi-natural grassland

Due to its ability to create aboveground conditions that favour plant diversity, mowing is often used to preserve the high conservation value of semi-natural species-rich grasslands. However, mowing can also affect belowground conditions. By decreasing plant carbon supply to soil, mowing can suppress the activity of soil decomposers, diminish plant nutrient availability and thus create a feedback on plant growth. In this study, we first documented the effects of three-year mowing on plant community structure in a species-rich grassland. We found that mowing decreased the total areal cover of woody plants and increased the total cover of leguminous forbs. At the species level, mowing further increased the cover of two non-leguminous forbs, Prunella vulgaris and Sagina procumbens. Mowing did not affect the species number, diversity or evenness of the plant community. To study whether any of these effects could be explained by mowing-induced changes in the soil, and particularly by reduced nutrient availability, we then collected soil from different treatment plots and monitored the growth of nine plant species in these soils in a greenhouse. Plant growth did not differ between soils collected from mowed and unmowed plots, suggesting that our mowing regimes did not impose such changes in soil decomposer activity and nutrient supply that would feedback on plant growth. Moreover, each of the nine species responded equally to the different nutrient availability in different parts of the grassland, which indicates that even if mowing had reduced plant nutrient supply, this would not have led to changes in plant community structure. It appears that those changes in aboveground vegetation that we recorded after three years of mowing were purely due to the aboveground effects, such as frequent cutting of woody plants and enhanced light availability for low-growing forbs.