Plant Community Properties Research Articles

COMMUNITY- AND ECOSYSTEM-LEVEL CHANGES IN A SPECIES-RICH TALLGRASS PRAIRIE RESTORATION

Changes in the plant community and ecosystem properties that follow the conversion of agriculture to restored tallgrass prairies are poorly understood. Beginning in 1995, we established a species-rich, restored prairie chronosequence where ∼3 ha of agricultural land have been converted to tallgrass prairie each year. Our goals were to examine differences in ecosystem properties between these restored prairies and adjacent agricultural fields and to determine changes in, and potential interactions between, the plant community and ecosystem properties that occur over time in the restored prairies. During the summers of 2000–2002, we examined species cover, soil C and N, potential net C and N mineralization, litter mass, soil texture, and bulk density across the 6- to 8-year-old prairie chronosequence and adjacent agricultural fields in southern Minnesota. We also established experimentally fertilized, watered, and control plots in the prairie chronosequence to examine the degree of nitrogen limitation on aboveground and belowground net primary production (ANPP and BNPP). Large shifts in functional diversity occurred within three growing seasons. First-year prairies were dominated by annuals and biennials. By the second growing season, perennial native composites had become dominant, followed by a significant shift to warm-season C4 grasses in prairies ≥3 yr old. Ecosystem properties that changed with the rise of C4 grasses included increased BNPP, litter mass, and C mineralization rates and decreased N mineralization rates. ANPP increased significantly with N fertilization but did not vary between young and old prairies with dramatically different plant community composition. Total soil C and N were not significantly different between prairie and agricultural soils in the depths examined (0–10, 10–20, 20–35, 35–50, 50–65 cm). We compared the results from our species-rich prairie restoration to published data on ecosystem function in other restored grasslands, such as Conservation Reserve Program (CRP) and old-field successional sites. Results suggest that rapid changes in functional diversity can have large impacts on ecosystem-level properties, causing community- and system-level dynamics in species-rich prairie restorations to converge with those from low-diversity managed grasslands.

The effects of landscape attributes and plant community on soil chemical properties in rangelands

This study addressed the effect of landscape attributes and plant community type on the spatial distribution of soil chemical properties in an alpine rangeland in a semiarid area of Iran. To identify the effects of landscape attributes on soil chemical properties, the present study collected and analyzed information from air photos, satellite images, field survey, and the laboratory using statistical analyses. Land stratification allowed the study area to be subdivided into Land Unit Tracts (LUT), according to specified criteria including landform attributes (slope, aspect, and altitude), and vegetation type. A factorial model on the basis of a completely randomized design was used to analyze the data collected from 234 LUT. The interrelationships between soil chemical properties and landscape attributes were investigated and interpreted based on statistical analysis and expert knowledge. Most chemical properties of the 0- to 10-cm topsoil including EC, OC%, total N%, P, and K significantly related to slope gradient. Soil chemical properties including the grouping described as nutrient elements (CEC, N, P, K, and OC), and pH significantly related to aspect of slope. In addition lower soil temperature and less moisture evaporation on a north-facing slope (shady aspect) resulted in less organic matter decomposition and consequently more organic carbon and total nitrogen accumulation in the soil. Consequently, the soil nutrient pool and general fertility on north-facing slopes was greater than on south-facing slopes. The interdependency of landscape attributes, plant community, and soil chemical properties led to a variety of species, vegetation types, and plant communities existing in the study area. In this research, vegetation type was highly significantly related to all the determined soil chemical properties except for cation exchange capacity.

Effects of anthropogenic disturbance on plant diversity and community structure of a sacred grove in Meghalaya, northeast India

This study analyses the effects of anthropogenic disturbance on plant diversity and community attributes of a sacred grove (montane subtropical forest) at Swer in the East Khasi Hills district of Meghalaya in northeast India. The undisturbed, moderately disturbed and highly disturbed stands were identified within the sacred grove on the basis of canopy cover, light interception and tree (cbh ≥ 15 cm) density. The undisturbed forest stand had >40% canopy cover, >50% light interception and a density of 2103 trees per hectare, whereas the highly disturbed stand had <10% canopy cover, <10% light interception and 852 trees per hectare. The moderately disturbed stand occupied the intermediate position with respect to these parameters. The study revealed that the mild disturbance favoured species richness, but with increased degree of disturbance, as was the case in the highly disturbed stand, the species richness markedly decreased. The number of families of angiosperms was highest (63) in the undisturbed stand, followed by the moderately (60) and highly disturbed (46) stands. The families Rubiaceae, Asteraceae and Poaceae were the dominant families in the sacred forest. Rubiaceae was represented by 11, 14 and 10 species in the undisturbed, moderately disturbed and highly disturbed stands, respectively, whilst the family Asteraceae had 16 species in the moderately disturbed stand and 14 species in the highly disturbed stand. The number of families represented by a single species was reduced significantly from 33 in the undisturbed stand to 23 in the moderately and 21 in the highly disturbed stand. The similarity index was maximum (71%) between the undisturbed and moderately disturbed stand and minimum (33%) between the undisturbed and highly disturbed stands. The Margalef index, Shannon diversity index and evenness index exhibited a similar trend, with highest values in the moderately disturbed stand. In contrast, the Simpson dominance index was highest in the highly disturbed stand. There was a sharp decline in tree density and basal area from the undisturbed (2103 trees ha−1 and 26.9 m2 ha−1) to the moderately disturbed (1268 trees ha−1 and 18.6 m2 ha−1) and finally to the highly disturbed (852 trees ha−1 and 7.1 m2 ha−1) stand. Density–girth curves depicted a successive reduction in number of trees in higher girth classes from the undisturbed to the moderately and highly disturbed stands. The log-normal dominance–distribution curve in the undisturbed and moderately disturbed stands indicated the complex and stable nature of the community. However, the short-hooked curve obtained for the highly disturbed stand denoted its simple and unstable nature.

Characteristics of Plant Community and Soil Properties in the Plantation Chronosequence of Caragana microphylla in Horqin Sandy Land

Characteristics of Plant Community and Soil Properties in the Plantation Chronosequence of Caragana microphylla in Horqin Sandy Land

RELATIONSHIPS AT THE ABOVEGROUND–BELOWGROUND INTERFACE: PLANTS, SOIL BIOTA, AND SOIL PROCESSES

Interactions at the aboveground-below ground interface provide important feedbacks that regulate ecosystem processes. Organisms within soil food webs are involved in processes of decomposition and nutrient mineralization, and their abundance and activity have been linked to plant ecophysiological traits such as species identity and the quality and quantity of plant tissue. We tested aboveground-below ground diversity relationships in a naturally developed plant community of native tallgrass prairie by taking soil samples from beneath naturally established grass tillers of chosen characteristics (e.g., homogeneous vs. heterogeneous plant combinations or C-4 vs. C-3 photosynthetic pathway) without imposing any disturbances to existing plant-soil relationships. The goal of this study was to elucidate the consequences, for soil microbiota (microflora phospholipid fatty acids, protozoa, and nematode functional groups) and for C and N mineralization, of plant community properties such as species richness, resource quality, resource heterogeneity, species identity, and presence of exotics. None of the biotic or abiotic soil variables was related to plant resource heterogeneity. Protozoa were not responsive to any of the plant community traits. Some bacterial and nematode groups were affected by plant characteristics specific to a particular plant species, but no uniform pattern emerged. Invasive and native plants generally were similar with respect to soil variables tested in this study. The lack of clear responses of soil variables to plant community traits indicates that idiosyncratic effects dominate both at the plant and soil biotic level and that generalized plant and soil diversity effects are hard to predict.

Do species evenness and plant density influence the magnitude of selection and complementarity effects in annual plant species mixtures?

Abstract Plant species richness influences primary productivity via mechanisms that (1) favour species with particular traits (selection effect) and (2) promote niche differentiation between species (complementarity). Influences of species evenness, plant density and other properties of plant communities on productivity are poorly defined, but may depend on whether selection or complementarity prevails in species mixtures. We predicted that selection effects are insensitive to species evenness but increase with plant density, and that the converse is true for complementarity. To test predictions, we grew three species of annuals in monocultures and in three‐species mixtures in which evenness of established plants was varied at each of three plant densities in a cultivated field in Texas, USA. Above‐ground biomass was smaller in mixtures than expected from monocultures because of negative ‘complementarity’ and a negative selection effect. Neither selection nor complementarity varied with species evenness, but selection effects increased at the greatest plant density as predicted.

Arbuscular mycorrhizal propagule densities respond rapidly to ponderosa pine restoration treatments

1 Mycorrhizae form a critical link between above-ground plants and the soil system by influencing plant nutrition, nutrient cycling and soil structure. Understanding how mycorrhizae respond to disturbances may lead to important advances in interpreting above-ground plant recovery. 2 The inoculum potential for arbuscular mycorrhizae (AM) and ectomycorrhizal (EM) fungi was investigated in thinned-only, thinned and prescribed burned (both restoration treatments) and unthinned and unburned control stands in northern Arizona ponderosa pine forests. The relationships between mycorrhizal fungal propagule densities and plant community and soil properties were quantified. 3 The relative amount of infective propagules of AM fungi was significantly higher in samples collected from both restoration treatments than their paired controls (unthinned and unburned stands). In contrast, the same restoration treatments had no significant effect on the relative amount of infective propagules of EM fungi. 4 The relative amount of infective propagules of AM fungi was significantly positively correlated with graminoid cover and herbaceous understorey species richness and negatively correlated with overstorey tree canopy cover and litter cover. 5 Synthesis and applications. These results indicate that population densities of AM fungi can rapidly increase following restoration treatments in northern Arizona ponderosa pine forests. This has important implications for restoring the herbaceous understorey of these forests because most understorey plants depend on AM associations for normal growth. These results also can be applied to other ecosystems that are in a state of restoration or where the role of fire is just beginning to be understood.

Mechanisms for locating resources in space and time: Impacts on the abundance of insect herbivores

AbstractHerbivorous insects have the problem both of locating appropriate host plants and ensuring that the plant‐feeding stages of their life cycles are synchronized with the times when those hosts provide a high‐quality food resource. Because the taxonomic range of potential hosts is generally narrow, and the temporal window when those hosts are suitable is often relatively short, developmental (especially diapause) and dispersal mechanisms may be critical factors in determining whether or not a species population is successful in a particular plant community. The present paper considers the impact of diapause and dispersal mechanisms on the ability of insect herbivores to cope with two attributes of their host plants: (i) the diversity of the plant community within which the hosts are located; and (ii) the seasonal predictability of host suitability. Some common dispersal mechanisms used by insect herbivores are much more appropriate to low‐diversity than to high‐diversity plant communities and, similarly, some diapause cues are appropriate only to highly predictable plant phenology. Both agriculture and silviculture characteristically manipulate both these attributes of plant communities, that is, in order to make the human use of plants more efficient, cultivation strategies normally both reduce plant species diversity (often to a condition approaching monoculture) and increase the predictability of plant developmental patterns. Consequently, major pest species in managed systems may not be those that are most common in natural systems, and may be difficult to predict in advance.

Plant community responses to Scotland's changing environment

Summary The ecological dangers of global climatic change are frequently discussed in relation to their threat to biodiversity. Oceanic Scotland, however, differs in many respects from else- where, both in the nature of the current climatic change and the biodiversity of the flora on which it reacts. Scottish habitats, such as those in the more peripheral regions, are rarely rich in species and biodiversity may not be a relevant concept for assessing the impact of environmental change. In species-poor habitats ecosystem health may be a more useful measure of potential survival capacity than species wealth. Examination of the homeo-static properties of plant communities, and their ability to withstand environmental change, could provide a more practical method of predicting which sections of the Scottish flora are at risk from climatic change as well as indicating possible remedial action. Case histories from coastal, wetland, forest and mountain sites are discussed in terms of their present ecological robu...

Diversity &amp; Ecosystem Resilience

ECOLOGY The relationship between biodiversity and ecosystem function has been a subject of intense debate among ecologists, especially in recent months. Most of the experimental work on this subject has compared the functional attributes of artificial plant communities constructed with different numbers of species. Griffiths et al. extend these studies to soil microbial communities, in which—rather than constructing communities of different species number—they compare function after reducing diversity by fumigation with chloroform. After recovery of the populations of the remaining species, Griffiths et al. assessed community attributes such as nitrification, denitrification, decomposer activity, and response to added nutrients. No clear pattern emerged: some functions (decomposition) were enhanced by decreased diversity, while others (nitrification) were depressed. However, the low-diversity communities were consistently less able to recover from an applied perturbation. The implications are that there is some redundancy with respect to function among species in the higher-diversity communities, but that loss of species leads to loss of stability in these soils. In a theoretical study, Ives et al. examine how such increased resilience to perturbation might arise from increased diversity in complex ecological communities. Their models indicate that such stability arises not from species number per se , but from the diversity across species of responses to environmental fluctuations. — AMS OIKOS 90 , 279 (2000); Ecol. Lett. 3 , 399 (2000).

Structure and composition of oligohaline marsh plant communities exposed to salinity pulses

The response of two oligohaline marsh macrophyte communities to pulses of increased salinity was studied over a single growing season in a greenhouse experiment. The plant communities were allowed a recovery period in freshwater following the pulse events. The experimental treatments included: (1) salinity influx rate (rate of salinity increase from 0 to 12 g l −1); (2) duration of exposure to elevated salinity; and (3) water depth. The communities both included Sagittaria lancifolia L.; the codominant species were Eleocharis palustris (L.) Roemer and J.A. Schultes in community 1 and Schoenoplectus americanus (Pers.) Volk. ex Schinz and R. Keller in community 2. Effects of the treatments on sediment chemical characteristics (salinity, pH, redox potential, and sulfide and ammonium concentrations) and plant community attributes (aboveground and belowground biomass, stem density, leaf tissue nutrients, and species richness) were examined. The treatment effects often interacted to influence sediment and plant communities characteristics following recovery in fresh water. Salinity influx rate per se, however, had little effect on the abiotic or biotic response variables; significant influx effects were found when the 0 g l −1 (zero influx) treatment was compared to the 12 g l −1 treatments, regardless of the rate salinity was raised. A salinity level of 12 g l −1 had negative effects on plant community structure and composition; these effects were usually associated with 3 months of salinity exposure. Water depth often interacted with exposure duration, but increased water depth did independently decrease the values of some community response measures. Community 1 was affected more than community 2 in the most extreme salinity treatment (3 months exposure/15-cm water depth). Although species richness in both communities was reduced, structural changes were more dramatic in community 1. Biomass and stem density were reduced in community 1 overall and in both dominant species. Structural changes in community 2 consisted of reduced biomass and stem density in the community overall and in S. lancifolia; S. americanus was not affected by salinity. In this most extreme treatment, community 2 tended to change to a monospecific S. americanus stand while community 1 was reduced to a few surviving stems of secondary species. Our results suggest that vegetation recovery or establishment of new species following a temporary increase in soil water salinity will vary with exposure duration and water depth.

Soil Properties of Boreal Riparian Plant Communities in Relation to Natural Succession and Clear-Cutting, Peace River Lowlands, Wood Buffalo National Park, Canada

Thirteen study sites on the floodplain and terraces ofthe lower Peace River, Wood Buffalo National Park,Canada, were examined for the effects of naturalforest succession and logging on physical and chemicalsoil properties. The principal changes in substratecharacteristics along the natural successional pathwaywere (i) development of a forest floor and (ii) burialof organic layers by floodwater deposition. Thephysical soil parameters of the forest floor andmineral soil were closely related to floodingfrequency, soil texture, stand closure, and forestfloor build-up. Significant differences in a number ofchemical soil properties between early (Barren Silt,Establishing) and late (Mature, Old-growth)successional stages were evident. The rising influenceof the developing plant community on chemical soilparameters was obvious. Organic carbon, totalnitrogen, cation exchange capacity, exchangeablecalcium, magnesium and potassium and extractablephosphorus level of forest floor and mineral soilswere highest in Mature sites; whereas pH and basesaturation were lowest. Physical and chemical soilproperties at three clear-cut sites were compared tosix undisturbed Mature/Old-growth stands. Removingvegetation had an effect on the physical soilproperties. A significant decrease in forest floornitrogen, cation exchange capacity, calcium andphosphorus occurred due to clear-cutting. Nosignificant change of chemical soil parameters wasobserved in the mineral soil at 0–20 cm depthfollowing harvesting. Significant impacts on chemicalsoil characteristics appeared to be limited to theforest floor. The absence of post-cutting sitepreparations makes the study area a useful benchmarkfor comparison with logged and scarified borealriparian sites elsewhere.

Changes in community and population responses across a forest‐field gradient

The ground‐layer vegetation of a forest‐old field edge gradient was sampled to determine the effects of the edge on spatial patterns of plant species and community attributes. Species showed individualistic responses to the forest edge, with peak abundance at different spatial positions relative to the edge. Principal components analysis resulted in three axes which explained a total of 63.2% of the variation within the data set. The first two PCA axes were related to distance to the forest edge. The third separated plots into those that were dominated by Solidago canadensis. and those that were dominated by Solidago juncea. All population and community‐level attributes varied along the edge gradient. Species richness, Shannon‐Wiener diversity, and total percent cover increased from the forest to the edge, with slight declines 60 m from the edge in the field. Among‐plot heterogeneity was higher at the edge than in either the forest or the field. Exotic species had peak abundance within 20 m of the edge inside the forest and are restricted to the edge. Most population and community‐level attributes showed edge responses on both sides of the edge. This emphasizes the need to study edges as gradients that include both disturbed and undisturbed habitats.

Community attributes of atlantic white cedar (Chamaecyparis thyoides) swamps in disturbed and undisturbed Pinelands watersheds

We assessed the effect of regional watershed conditions on plant community attributes, scedbed and seedling density, and environmental conditions in New Jersey Pinelands Atlantic white cedar (Chamaecyparis thyoides) swamps under three disturbance regimes (high, moderate, and low). High regional watershed disturbance, defined by the percentage basin cover of combined residential and agricultural development, was associated with elevated pH, specific conductance, and nutrient concentrations in surface waters adjacent to our study sites. High disturbance sites generally had lower understory species richness and differed from other sites in overall understory species composition. High canopy red maple (Acer rubrum) cover and high canopy closure were also associated with swamps in high disturbance basins. Because other environmental variables did not differ significantly between disturbance types and red maple is a common associate, of cedar throughout the Pinelands, differences in species richness and composition may be related to canopy conditions rather than the effects of watershed disturbance. Regional differences in biogeography may also be a factor. We found no exotic species in our study sites. Only one species considered uncharacteristic of the Pinelands was associated with high disturbance basin sites. Unlike previous, similar studies in the Pinelands, the high disturbance sites did not support a unique group of plants. AlthoughSphagnum cover (typically, associated with optimal cedar seedbed conditions) was lowest in disturbed basin sites, there were no significant differences in overall seedbed conditions and cedar seedling density. Cedar swamps located a distance from upgradient watershed disturbances and not affected by overbank flooding seem to be buffered from the impacts of these regional disturbances.

Livestock Grazing: Animal and Plant Biodiversity of Shortgrass Steppe and the Relationship to Ecosystem Function

We synthesized published and unpublished data from long-term grazing treatments in North American shortgrass steppe on diversity and abundance of plants, lagomorphs, rodents, birds, aboveground and belowground macroarthropods, microarthropods, and nematodes. The relatively small response of the plant community to grazing provides an opportunity to address some broad questions concerning relationships among responses of structural and functional aspects of systems in general. Are there consistencies in diversity and abundance responses to grazing among groups of organisms? Are some groups more sensitive than others, or do responses mirror that of vegetation? Are the responses in terms of biodiversity related to ecosystem-level functional responses? Diversity, abundance, dominance, and dissimilarity responses to long-term grazing were highly variable across classes of organisms. Some groups of consumers displayed large differences among treatments even though differences in plant community attributes were relatively minor. Some responses were large even when comparing ungrazed to lightly or lightly to moderately grazed treatments. Birds appear to be particularly responsive to grazing. Differences among treatments in richness within groups other than plants and birds were relatively minor, especially when compared to large declines in abundance of some groups with increasing grazing intensity. For the well-studied groups (plants and birds), shifts in species in terms of 'quality' factors, such as exotic, endemic, and rare, generally suggest that livestock grazing may be more similar to conditions in recent evolutionary time in this particular system than would conditions resulting from the removal of the exotic, domestic grazers that appear to functionally serve as a surrogate to bison. Trophic structure composition did not vary greatly across grazing treatments. Further, large effects of grazing on some consumer groups did not translate into similarly large effects on ecosystem processes such as primary production or soil nutrient pools and cycling rates.

Insects, plants and succession: advantages of long-term set-aside

Countryside quality over much of Britain depends on agricultural policies, important among which is the set-aside programme in which area based payments are made to encourage farmers to take arable land out of food production. Decisions between long-term and short-term set-aside will influence the future age profile of communities on uncultivated land, affecting their conservation value and their role as sources of pests, natural enemies and pollinators for nearby crops. Because long-term studies of set-aside in Britain are not yet available, other evidence is used to review the successional changes to be expected in a 10 year period of natural regeneration after ploughing. Succession is considered in terms of ecological attributes of plant and insect communities, rather than lists of individual species, so that the concepts are more generally applicable. In a landscape increasingly affected by disturbance, in which some groups of plant and insect species of long-established vegetation are already decreasing, long-term unploughed set-aside offers an opportunity to establish and protect patches of undisturbed perennial herbaceous vegetation and their associated fauna, helping common species to remain common and ecologically important species to remain functional.

Higher plant terpenoids: A phytocentric overview of their ecological roles

Characteristics of higher plant terpenoids that result in mediation of numerous kinds of ecological interactions are discussed as a framework for this Symposium on Chemical Ecology of Terpenoids. However, the role of terpenoid mixtures, either constitutive or induced, their intraspecific qualitative and quantitative compositional variation, and their dosage-dependent effects are emphasized in subsequent discussions. It is suggested that little previous attention to these characteristics may have contributed to terpenoids having been misrepresented in some chemical defense theories. Selected phytocentric examples of terpenoid interactions are presented: (1) defense against generalist and specialist insect and mammalian herbivores, (2) defense against insect-vectored fungi and potentially pathogenic endophytic fungi, (3) attraction of entomophages and pollinators, (4) allelopathic effects that inhibit seed germination and soil bacteria, and (5) interaction with reactive troposphere gases. The results are integrated by discussing how these terpenoids may be contributing factors in determining some properties of terrestrial plant communities and ecosystems. A terrestrial phytocentric approach is necessitated due to the magnitude and scope of terpenoid interactions. This presentation has a more broadly based ecological perspective than the several excellent recent reviews of the ecological chemistry of terpenoids.

An Analytical Approach to the Expression of Light Intensity in Plant Communities

An instance that plant communities can not always be considered as a homogeneous layer is shown through applying Fresnel's formulae to plant communities in order to obtain albedo from extinction coefficient. Another expression of plant communities is presented with construction of a simple model of plant communities employing vector relations. It is shown from investigation of increase in intensity of light by a leaf that the equation relating amount of increase in averaged intensity with incident averaged intensity is expressed by use of LAI. Similarly, increase in averaged intensity by stem is expressed by use of area of longitudinal section per unit area. Extension of these equations to conditions of plant communities where leaves and stems are continuously distributed in the vertical direction is attempted by employment of probability density functions of leaves and stems in each height. Integrating the differential equation under the assumptions that the distribution of leaves with respect to height is continuous and that the probalility density function of leaves depends only on the angle of leaves making with z-axis, intensity of light is expressed by a simple exponential function in each direction of incident beam. Extinction coefficient of a beam as a function of angle of incidence and of leaf arrangement is not generally monotonic. This property of extinction functions causes a trapping of radiation incident on plant communities with slanting leaves. On the basis of the extinction coefficent for a beam, the extinction coefficient of isotropic incident radiation is computed in the system with horizontal leaves and with vertical leaves. The computed extinction eoefficients in this manner are, respectively, 1 for the former and 0.5-0.4 for the latter system.The value in the former system approximates those experimentally obtained. A difference between the experimental and the computed extinction coefficient is considered as a result of neglect of reflection from and transmission through leaves of light. Reflection from plant communities is computed readily in the system with horizontal leaves, leading to the expression of albedo depending upon angle of incidece. In this case, it is also found that intensities of reflection can exceed those by a leaf in directions of the greater zenith angles of reflection.In order to verify these results on the extinction of a beam, shortwave radiation falling on a horizontal plane is measured in paddy fields with tube pyranometers just above and below the layers where most leaves are of horizontal habit. Observed diurnal variations of the ratios of shortwave radiation in the paddy fields to incident shortwave radiation are similar to those computed from the equation of light intensity. Quantitative comparisons of the observed dependence of extinction coefficients on incident angle with the computed are possible by use of observed shortwave and diffuse incident radiation and of the extinction coefficient for diffuse incident radiation, showing that the expression of light intensity of a beam in plant communities is a good approximation at least for the smaller zenith angles of sun. When the ratio of the averaged intensity of diffuse incident radiation to direct solar radiation is remained small, a linear relaionship between albedo and secant of zenith angle of sun is found from observations of albedo in paddy fields with upright leaves. Validity of the computed results encourages one to analyse communities of lowland rice. The analysis is based on a series expansion of logarithm of intensity ratio in terms of extinction functions. Results of the analyses show some characteristics due to difference in density. An extent, to which the computed result is valid, is inferred through a result of analyzing reflection from paddy field.The detailed description apprears in ISOBE, S. (1962): Preliminary Studies on Physical Properties of Plant Communities. Bull. Nat. Inst. Agr. Sci., se