Winners and losers in a long-term study of vegetation change at Moor House NNR: Effects of sheep-grazing and its removal on British upland vegetation

We analysed data collected between 1954 and 2000 from nine long-term experiments designed to assess the effects of sheep-grazing versus no-sheep-grazing at Moor House NNR, an Environmental Change Network site. The experiments were set up between 1954 and 1972 across a range of vegetation types typical of much of upland Britain. Data from this type of experiment are often difficult to analyse and we describe the procedures undertaken to prepare the data for analysis. We fitted the resultant data to the British National Vegetation Classification and used ordination techniques to assess the relative positions of the experiments to each other. Finally, we used Generalized Linear Mixed-effects Modelling within a Bayesian framework to model change of species taxonomic/physiognomic groups through time in both sheep-grazed and ungrazed treatments across all nine experiments; variables included species diversity, Shannon–Weiner index and derived data on occurrence and abundance of species groups based on taxonomy and physiognomy. Hurdle analysis was used to model the species groups; this analysis separated the change through time in both probability of occurrence (binomial distribution) and abundance (Poisson distribution).In the sheep-grazed plots (the “business-as-usual” treatment hence here designated the “control”) there was a reduction in species diversity and a decrease in abundance of vascular plants, grasses, lichens, liverworts and mosses; whereas herbs, sedges and shrubs increased. When probability of occurrence was considered, there was a reduction in number of presences of both lichens and liverworts. Thus, the status quo management of continuous sheep-grazing, even though reduced since 1972, has resulted in a marked change in species composition of these plant communities, with some winners and some losers, but overall they support the concept of biotic homogenization. It is likely that some of these changes were driven by external factors such as elevated atmospheric nutrient deposition. Removal of sheep grazing had some positive benefits; with the herbs, mosses, sedges and shrubs increasing, but faster reductions in grasses and liverworts. Sedges + rushes were stable. It suggested that future monitoring schemes might use either the probability of occurrence of liverworts and lichens, or the abundance of lichens, liverworts, grasses and mosses as sensitive indicators of change in upland Britain.Moreover, during the period that Moor House has been protected as a nature reserve some key plant species groups have declined in spite of reductions in grazing pressure. To reverse this trend requires some form of interventionist management. In order to increase the diversity of vascular plants some form of disturbance will probably be needed, but for bryophytes and lichens this remains a research question. If the results from these small-scale experiments are replicated at the landscape scale a reduction of sheep grazing pressure, for example in rewilding schemes, will have little effect on species composition over a 28–44 year period.     

Seasonal and management influences on bacterial community structure in an upland grassland soil

Floristically diverse Nardo-Galion upland grasslands are common in Ireland and the UK and are valuable in agricultural, environmental and ecological terms. Under improvement (inputs of lime, fertiliser and re-seeding), they convert to mesotrophic grassland containing very few plant species. The effects of upland grassland improvement and seasonality on soil microbial communities were investigated at an upland site. Samples were taken at five times in one year in order to observe seasonal trends, and bacterial community structure was monitored using automated ribosomal intergenic spacer analysis (ARISA), a DNA-fingerprinting approach. Differences in soil chemistry and bacterial community structure between unimproved and improved grassland soils were noted. Season was also found to cause mild fluctuations in bacterial community structure, with soil samples from colder months (October and December) more correlated with change in ribotype profiles than samples from warmer months. However, for the majority of seasons clear differences in bacterial community structures from unimproved and improved soils could be seen, indicating seasonal influences did not obscure effects associated with improvement.     

The impact of pests and diseases on the herbage yield of permanent grassland at eight sites in England and Wales

Plots at each of eight widespread permanent pasture sites below 300 m and representative of large areas of long established grassland in England and Wales, were treated with an insecticide plus molluscicide, a fungicide or nematicide treatment. Populations of various invertebrates and the occurrence of foliar fungal diseases were assessed. Leaf blotch (Drechslera) was the most common disease, but neither this nor other foliar fungal diseases were prevalent until late in the growing season. The fungicide treatment did not control diseases satisfactorily. The fungicide and nematicide treatment had little effect on total annual herbage yield. Leatherjackets, crambids, slugs and frit fly larvae were present, usually in low numbers, at most sites. The insecticide and molluscicide treatment increased yield by 11% on average across all sites and years. Losses caused by pests to UK grasslands were estimated to be over £500 million per year.     

Effects of scale-dependent factors on herbaceous vegetation patterns in a wetland,northern Japan

Herbaceous vegetation was examined in an Otanoshike wetland in northern Japan to clarify the relationships between vegetation patterns and environmental factors with different scales. Alders (Alnus japonica) have recently invaded and might modify the herbaceous vegetation. In total, 150 50×50cm plots were established on the transitional areas between alder thickets and grassy marshland. Cover was measured for the vascular plant taxa, and canopy area, number of stumps, number of mounds, water depth, elevation difference, litter thickness, soil organic matter, and soil pH were measured in each plot. TWINSPAN cluster analysis classified four vegetation groups: (i), grasslands represented by Phragmites australis, Trientalis europaea, Lythrum salicaria, and Hosta rectifolia; (ii), Calamagrostis langsdorfii, and Polygonum thunbergii grasslands with Spiraea salicifolia; (iii), reed swamp dominated by Phragmites australis, and (iv), marshland dominated by Carex lyngbyei. Canonical correspondence analysis indicated that water depth primarily divided vegetation groups 1–2 and 3–4. Alder established in drier sites mostly by re-sprouting, and the canopy affected light and soil conditions on the ground surface. The second axis of canonical correspondence analysis was related to the canopy area and soil pH, and explained the vegetation differentiation between groups 1 and 2, and groups 3 and 4. In conclusion therefore, scale-dependent or hierarchical variables affected the vegetation patterns in different ways, that is, the herbaceous vegetation was first differentiated by water depth that was corresponding to alder establishment on a large scale, and subsequent light and soil conditions were second determinants on a small scale.     

The populations of fish in tributaries of the River Eden on the Moor House National Nature Reserve,northern England

The population dynamics of trout (Salmo trutta L.) were studied in two high-altitude streams flowing westwards into the River Eden in northern England. The results from one (Knock Ore Gill), which is accessible to spawners from downstream, were compared with published data from an isolated population in a nearby stream which flows eastward into the River Tees. The Knock Ore Gill trout had a population density of 0.4–0.9 fish m^–2, a biomass of 12.4 g m^–2, annual production of 12–14 g m^–2 year^–1 and an instantaneous mortality rate of 0.97 year^–1. Comparable values from the Tees tributary were 0.2, 3.3, 2.3 and 0.66 respectively. The Knock Ore Gill population also contrasted with that of the Tees tributary in having reliable recruitment from year to year. These differences were related to differences in the chemistry and spate characteristics of the two streams and to the fact that immigrants from downstream were responsible for over 30% of the annual oviposition in Knock Ore Gill.     

Canonical analysis of asymmetric matrices: two applications from a study of chalk grassland in the south of England

Gower's (1977) method for the canonical analysis of asymmetric matrices (CAA) where the same entities index both the rows and the columns is described. This technique displays the indexing entities in a series of orthogonal planes of decreasing importance in such a way as to preserve the pattern of the asymmetry between them. The analysis is applied to a half-diallel experiment and to some leaf-overtopping data, both from a study of the control of relative abundance of perennials in chalk grassland. The results suggest a common source for the asymmetry in the very different interference and overtopping data, namely that of leaf height. It is concluded that relative abundance in the field may be determined, in part, by leaf height through aboveground interference between plants.Nomenclature follows Tutin et al., 1964–1980. Flora Europaea, Vols 1–5. Cambridge University Press, Cambridge.I am particularly indebted to the Nature Conservancy Council for permission to carry out the field experiment on the Aston Rowant N.N.R., and to do field work at Castle Hill N.N.R.We are grateful to R. A. Kempton for permission to use his methodology in the analysis of the half-diallel experiment prior to publication. This work was carried out while J.M. was in receipt of a Research Studentship from the Natural Environment Research Council, and L.G. was in receipt of an internal Research Studentship from Trinity College, Cambridge.     

Tree species distribution in canopy gaps and mature forest in an area of cloud forest of the Ibitipoca Range,south-eastern Brazil

The tree community of both canopy gaps and mature forest was surveyed in a 5 ha plot of cloud forest in the Ibitipoca Range, south-eastern Brazil, aiming at: (a) comparing the tree community structure of canopy gaps with that of three strata of the mature forest, and (b) relating the tree community structure of canopy gaps with environmental and biotic variables. All saplings of canopy trees with 1–5 m of height established in 31 canopy gaps found within the plot were identified and measured. Mature forest trees with dbh 3 cm were sampled in four 40×40 quadrats laid on the four soil sites recognised in the local soil catena. All surveyed trees were identified, measured and distributed into three forest strata: understorey (<5 m of height), sub-canopy (5.1–15 m) and canopy (15.1–30 m). The following variables were obtained for each gap: mode of formation, age, soil site, slope grade, size, canopy openness and abundance of bamboos and lianas. A detrended correspondence analysis indicated that the tree community structure of gaps in all soil sites was more similar to that of the mature forest understorey, suggesting that the bank of immatures plays an important role in rebuilding the forest canopy and that gap phases may be important for understorey shade-tolerant species. There was evidence of gap-dependence for establishment for only one canopy tree species. Both canonical correspondence analysis and correlation analysis demonstrated for a number of tree species that the distribution of their saplings in canopy gaps was significantly correlated with two variables: soil site and canopy openness. The future forest structure at each gap is probably highly influenced by both the present structure of the adjacent mature forest and the gap creation event.     

Environmental gradients determining the distribution of benthic macroinvertebrates in Lake Takkobu, Kushiro wetland, northern Japan

Effects of environmental variables on the distribution of benthic macroinvertebrates inhabiting sediments were studied at 25 sites along the shoreline of Lake Takkobu in the Kushiro wetland of northern Japan in summer 2003. During the last decade, the lake’s status has undergone a drastic shift from clear water dominated by submerged macrophytes to turbid water dominated by phytoplankton. The canonical correspondence analysis showed that four environmental variables explained the significant variation in the macroinvertebrate species composition: submerged plant biomass, bottom sediment organic matter content (OMC), distance from the mouth of the Takkobu River, and bottom-layer pH. Five species of Chironomidae [Chironomus sp. (except plumosus group), Psectrocladius sp., Corynoneura sp., Parachironomus sp. arcuatus group, and Zavreliella sp.] occurred in sites with relatively lower pH and a high submerged plant biomass, whereas three species of Tubificidae (Tubifex tubifex, Aulodrilus limnobius and Aulodrilus sp.) and two of Chironomidae (Nanocladius sp. and Monodiamesa sp.) occurred in sites with high pH and little vegetation. The three Tubificidae species also preferred organic-rich sediments. Irrespective of aquatic vegetation, Sphaerium sp. (Bivalvia) and Monodiamesa sp. (Chironomidae) occurred in low-OMC sites, whereas Tanypus sp. (Chironomidae) preferred high-OMC sites. The number of macroinvertebrate taxa showed the highest correlation with the number of submerged plants, suggesting that macroinvertebrate species richness was related mostly to submerged plant species diversity in this lake. The quantity and species richness of submerged plants and OMC are thus important determinants of the community structure of macroinvertebrates inhabiting sediments in Lake Takkobu.     

Holocene vegetation and land-use history in the environs of Lake Kahala, northern Estonia

Pollen profiles, based cores taken in Lake Kahala and from the adjoining mire, were used to establish general vegetation history and to reconstruct the extent and types of land-use over most of the Holocene. Modern pollen deposition was studied using moss polsters and the results were used in the interpretation of the fossil pollen data in terms of former land-use practices. The modern-day samples are from settlements, hay meadow and pasture, and overgrown pasture. Indications of human activity can be traced back to the Stone Age. At ca. 6400 cal. B.C., the first indications of possible woodland utilisation by humans are recorded. This may have involved grazing within the forests. From 4200 cal. B.C. onwards, animal husbandry with changing intensity was practised. Arable farming, involving cereals, was introduced to the area at ca. 1800 cal. B.C., but it was only at ca. 500 cal. B.C. that it assumed an important role in the farming economy.Secale cereale (rye) was introduced during the Roman Iron Age, intensive rye cultivation started at the end of the Iron Age, at ca. cal. A.D. 800. Ever increasing farming pressures triggered the formation of openalvars. Open landscape similar to that of today has persisted, with minor forest regeneration phases, since at least 500 cal. B.C.     

Energy dynamics in the C4 species dominated montane subtropical grassland at Nilgiri Biosphere Reserve, the Western Ghats, India

The energy dynamics in Thiashola grassland, a montane subtropical vegetation in Nilgiri Biosphere Reserve, the Western Ghats, India is studied for a period of one year. The study revealed that the energy content in unit biomass of C₃ and C₄ species has not varied significantly. However, the C₄ species in total due to higher net primary production, entrapped 8.5 times greater solar energy (28.82 kcal/m²/day) than that of their C₃ counterparts. Of the total energy fixed, the C₃ and C₄ species, respectively channeled 4.07 kcal/m²/day and 13.3 kcal/m²/day to the aboveground standing live compartment. The transfer rate of energy to standing dead compartment from standing live part were 3.22 kcal/m²/day and 10.36 kcal/m²/day for C₃ and C₄ species, respectively and both the C₃ and C₄ together transferred 4.81 kcal/m²/day of energy from standing dead to litter compartment. The total dissipation of energy from the system is determined to be 4401.11 kcal/m²/yr and the surplus quantity of 38.37% of energy is accumulated in the aboveground parts of both C₃ and C₄ species which indicates the availability of substantial amount of energetic fodder to the wild herbivores in the Thiashola grassland.     

Energy dynamics in the C4 species dominated montane subtropical grassland at Nilgiri Biosphere Reserve, the Western Ghats, India

The energy dynamics in Thiashola grassland, a montane subtropical vegetation in Nilgiri Biosphere Reserve, the Western Ghats, India is studied for a period of one year. The study revealed that the energy content in unit biomass of C₃ and C₄ species has not varied significantly. However, the C₄ species in total due to higher net primary production, entrapped 8.5 times greater solar energy (28.82 kcal/m²/day) than that of their C₃ counterparts. Of the total energy fixed, the C₃ and C₄ species, respectively channeled 4.07 kcal/m²/day and 13.3 kcal/m²/day to the aboveground standing live compartment. The transfer rate of energy to standing dead compartment from standing live part were 3.22 kcal/m²/day and 10.36 kcal/m²/day for C₃ and C₄ species, respectively and both the C₃ and C₄ together transferred 4.81 kcal/m²/day of energy from standing dead to litter compartment. The total dissipation of energy from the system is determined to be 4401.11 kcal/m²/yr and the surplus quantity of 38.37% of energy is accumulated in the aboveground parts of both C₃ and C₄ species which indicates the availability of substantial amount of energetic fodder to the wild herbivores in the Thiashola grassland.     

A numerical analysis of the mesoscale distribution patterns of vascular plants in the subarctic Kevo Nature Reserve, northern Finland

Different numerical techniques were used to detect and describe the major ecological-biogeographical patterns of vascular plant distributions at the meso-scale level in a subarctic region in Finland. The distribution patterns of 231 native taxa in 362 1 km² grid squares of the Kevo Nature Reserve were analysed by two-way indicator species analysis and detrended correspondence analysis, and were subsequently related to twenty-eight geographical, topographical, geological, and vegetational variables using simple discriminant functions and canonical correspondence analysis with associated Monte Carlo permutation tests.
The floristic variation detected reflects variations in environmental factors operative at the regional and local scales. No major broad-scale coherent geographical patterns were detected; instead, the spatial distribution of the grids with a similar floristic composition shows a scattered distribution. All the numerical techniques reveal a major gradient from alpine areas to lowland sites with rivers and rocky outcrops, and the most important explanatory variables for predicting the main floristic variation are all associated with altitude. The floristic patterns represented by the second ordination gradient mainly correlate with the abundance of mires. Partial ordinations indicate that both the geographical and geological variables explain relatively little of the species distributional patterns.
Although the meso-scale approach reveals much about the plant-environment relationships in the study area, the floristic variation appears to be determined mainly by fine-scale factors. In the most heterogeneous grids, the grid size used fails to detect accurately the ecological patterns of the species present.     

毛乌素沙地植被不同恢复阶段植物群落物种多样性、功能多样性和系统发育多样性

进入21世纪以来, 中国荒漠化恢复取得显著成效, 荒漠化、沙化土地面积持续减少, 植被覆盖度大幅提升, 但关于植被恢复过程中生物多样性如何变化的研究不足, 这制约着对荒漠化恢复成效的全面评估。本文基于群落调查和叶功能性状(叶片厚度、叶片干物质含量、比叶面积和叶片密度)的测定, 分析了毛乌素沙地不同恢复阶段(半固定沙地、固定沙地、结皮覆盖沙地和草本植物覆盖沙地)的植物群落物种多样性、功能多样性和系统发育多样性特征。结果表明: (1)多数叶功能性状的系统发育信号不显著, 表明环境因子对研究区植物功能性状的塑造作用很强。(2)对于α多样性, 结皮覆盖沙地的物种多样性(Shannon-Wiener多样性, H)、物种丰富度(S)、功能丰富度(FRic)及系统发育多样性(PD)指数均显著低于其他恢复阶段, 而其他3个阶段间无显著差异; 这些指数间均显著正相关, 表明物种多样性、功能多样性和系统发育多样性在植被恢复过程中协同变化。(3) β多样性指数随恢复阶段间隔增加而逐渐增大, 表明物种组成、功能属性及系统发育关系随植被恢复持续变化, 且半固定沙地到固定沙地的群落物种组成、功能属性及系统发育关系更替最快, 导致群落间差异最大。(4)固定沙地、结皮覆盖沙地和草本植物覆盖沙地群落系统发育结构均趋向于发散, 表明竞争排斥是群落构建的主要驱动力; 而半固定沙地群落系统发育结构无一致规律, 表明群落构建可能受到生境过滤和竞争排斥的综合作用。研究结果可为植被建设与管理提供参考, 为毛乌素沙地生态保育和生物多样性的保护提供科学依据。     

Palynological evidence for 19th century grazing-induced vegetation change in the southern Sierra Nevada, California, U.S.A.

Aim Stratigraphic pollen records are used to assess historic vegetation changes that have transpired in a North American mountain meadow since the introduction of Old World livestock species in the middle 1800s. Location Monache Meadows is located on the Kern Plateau in the Sierra Nevada mountain range, California, U.S.A. It is situated along the upper reaches of the South Fork Kern River in the southernmost drainage basin of the Sierra Nevada. Methods Short core samples of meadow sediments were extracted from five locations throughout Monache Meadows. These five samples are classified according to topographic position within the meadow – two upper meadow sites and three lower meadow sites. Stratigraphic analyses of fossil pollen from each core were used to assess vegetation composition before the introduction of European livestock (pre1850) and throughout the historic period (1850–present). The historic period geochronology is based on ²¹⁰Pb dating of selected strata from each core. Results Riccia was a dominant taxon in the upper meadow before the introduction of grazing; Salix seems to have been more abundant in the lower meadow. Both Riccia and Salix decreased dramatically by c.1900, coeval with marked increases in Artemisia (upper meadow) and Cyperaceae (upper and lower meadows). Main conclusions Changes in meadow vegetation occurring during the latter part of the 19th century at Monache Meadows are attributed primarily to the introduction of European livestock (sheep and cattle). Other factors that may have contributed to the observed shifts in composition and dominance include changes in native herbivore populations and decreased fire frequency as a result of 20th century fire suppression policies.     

Stable carbon isotope analysis of soil organic matter illustrates vegetation change at the grassland/woodland boundary in southeastern Arizona,USA

In southeastern Arizona, Prosopis juliflora (Swartz) DC. and Quercus emoryi Torr. are the dominant woody species at grassland/woodland boundaries. The stability of the grassland/woodland boundary in this region has been questioned, although there is no direct evidence to confirm that woodland is encroaching into grassland or vice versa. We used stable carbon isotope analysis of soil organic matter to investigate the direction and magnitude of vegetation change along this ecotone. ¹³C values of soil organic matter and roots along the ecotone indicated that both dominant woody species (C₃) are recent components of former grasslands (C₄), consistent with other reports of recent increases in woody plant abundance in grasslands and savannas throughout the world. Data on root biomass and soil organic matter suggest that this increase in woody plant abundance in grasslands and savannas may increase carbon storage in these ecosystems, with implications for the global carbon cycle.     

Effects of climatic and edaphic factors on arbuscular mycorrhizal fungi in the rhizosphere of Hippophae rhamnoides in the Loess Plateau, China

In order to investigate the effects of climatic and edaphic factors on arbuscular mycorrhizal (AM) fungi in the rhizosphere of Hippophae rhamnoides in the Loess Plateau, spore density, mycorrhizal colonization and gene diversity were analyzed by using the methods of microscopy and polymerase chain reactiondenaturing gradient gel electrophoresis (PCR-DGGE) respectively. The results showed that H. rhamnoides could form strong symbiotic relationships with AM fungi. There existed obvious differences in AM fungal colonization among five sampling sites in the Loess Plateau (P < 0.05). Correlation analysis showed that AM fungal colonization and spore density were closely related with climatic and edaphic factors. 42 different species (band types) were found in the DGGE gel. Based on analysing the position and intensity of AM fungal DGGE bands, the gene diversity indices, including species richness, evenness, Simpsom’s and Shannon-Weiner index, showed significant differences among five sampling sites (P < 0.05). All the AM species could be classified into four groups in the biplot of canonical correspondence analysis (CCA), and each group had various responses to climatic and edaphic factors. Monte Carlo random test indicated that soil available phosphorus (F = 2.26, P = 0.025) and spore density (F = 1.76, P = 0.006) were the dominating factors affecting AM fungal communities. In conclusion, AM fungal colonization and community diversity in the rhizosphere of H. rhamnoides showed obvious spatial heterogeneity among the different areas of the Loess Plateau, and climatic and edaphic conditions were important factors affecting the AM fungal communities. Therefore, screening and application of AM fungal strains in the Loess Plateau need to fully consider the local climatic and edaphic conditions.