Sarah C. Goslee

Plant species diversity, ecosystem function, and pasture management : A perspective

Grassland farmers face many challenges in pasture management including improving sustainability, reducing inputs of fertilizers and pesticides, and protecting soil resources. In this paper we provide our perspective on managing plant diversity within and among pastures as one tool to aid producers in meeting these challenges. Pasture ecosystems can be highly diverse, with a complex array of organisms contributing to ecosystem functioning. Within the broad range of plant and animal biodiversity in pastures, plant species diversity may be the most amenable to manipulation or management. Reported benefits of plant diversity in grasslands include: increased forage production, greater ecosystem stability in response to disturbance, and reduced invasion by exotic species such as weeds. Some view diversity as a sort of insurance policy where different species contribute in their own time or can take the place of species that fail from stress or mismanagement. Using mixtures of several forages in pastures, in som...

Behavior of vegetation sampling methods in the presence of spatial autocorrelation

Spatial autocorrelation in vegetation has been discussed extensively, but little is yet known about how standard plant sampling methods perform when confronted with varying levels of patchiness. Simulated species maps with a range of total abundance and spatial autocorrelation (patchiness) were sampled using four methods: strip transect, randomly located quadrats, the non-nested multiscale modified Whittaker plot and the nested multiscale North Carolina Vegetation Survey (NCVS) plot. Cover and frequency estimates varied widely within and between methods, especially in the presence of high patchiness and for species with moderate abundances. Transect sampling showed the highest variability, returning estimates of 19–94% cover for a species with an actual cover of 50%. Transect and random methods were likely to miss rare species entirely unless large numbers of quadrats were sampled. NCVS plots produced the most accurate cover estimates because they sampled the largest area. Total species richness calculated using semilog species-area curves was overestimated by transect and random sampling. Both multiscale methods, the modified Whittaker and the NCVS plots, overestimated species richness when patchiness was low, and underestimated it when patchiness was high. There was no clear distinction between the nested NCVS or the non-nested modified Whittaker plot for any of the measures assessed. For all sampling methods, cover and especially frequency estimates were highly variable, and depended on both the level of autocorrelation and the sampling method used. The spatial structure of the vegetation must be considered when choosing field sampling protocols or comparing results between studies that used different methods.

Correlation analysis of dissimilarity matrices

Distance-based methods have been a valuable tool for ecologists for decades. Indirectly, distance-based ordination and cluster analysis, in particular, have been widely practiced as they allow the visualization of a multivariate data set in a few dimensions. The explicitly distance-based Mantel test and multiple regression on distance matrices (MRM) add hypothesis testing to the toolbox. One concern for ecologists wishing to use these methods lies in deciding whether to combine data vectors into a compound multivariate dissimilarity to analyze them individually. For Euclidean distances on scaled data, the correlation of a pair of multivariate distance matrices can be calculated from the correlations between the two sets of individual distance matrices if one set is orthogonal, demonstrating a clear link between individual and compound distances. The choice between Mantel and MRM should be driven by ecological hypotheses rather than mathematical concerns. The relationship between individual and compound distance matrices also provides a means for calculating the maximum possible value of the Mantel statistic, which can be considerably less than 1 for a given analysis. These relationships are demonstrated with simulated data. Although these mathematical relationships are only strictly true for Euclidean distances when one set of variables is orthogonal, simulations show that they are approximately true for weakly correlated variables and Bray–Curtis dissimilarities.

Plant community associations of two invasive thistles

We assessed the field-scale plant community associations of Carduus nutans and C. acanthoides, two similar, economically important invasive thistles. Several plant species were associated with the presence of Carduus thistles while others, including an important pasture species, were associated with Carduus free areas. Thus, even within fields, areas invaded by Carduus thistles have different vegetation than uninvaded areas, either because some plants can resist invasion or because invasion changes the local plant community. Our results will allow us to target future research about the role of vegetation structure in resisting and responding to invasion.

Pastureland Conservation Effects Assessment Project: Status and expected outcomes

The Conservation Effects Assessment Project (CEAP) is a multiagency scientific effort to quantify environmental outcomes of conservation practices applied to private agricultural lands. The program is anticipated to help shape future conservation policies, programs, and practices. The integrated landscape approach will focus on enhanced ecological resilience and sustainable agricultural production, both of which are essential to maintaining livelihoods and meeting global food needs (Nowak and Schnepf 2010). Principal components of CEAP include (1) detailed syntheses of scientific conservation literature; (2) a national assessment of conservation effects on ecosystem services; and (3) detailed investigations of conservation practices at various scales, including paddock, landscape, and water-shed levels. The CEAP effort on grazing lands began in rangeland in 2006 (Weltz et al. 2008) with a synthesis of the scientific literature on key rangeland conservation practices (Briske forthcoming). A CEAP effort on pastureland, primarily in the eastern and central United States, began in 2008. A literature synthesis documenting the science behind key conservation practices (Nelson forthcoming) revealed that scientific support exists for most conservation practices on pastureland, but critical knowledge, data, and technology gaps remain, including the following: Comprehensive assessments of effects of grazing management on a broad suite of…

Spatial prediction of invasion success across heterogeneous landscapes using an individual-based model

The limited resources available for managing invasive plant species in native ecosystems and the magnitude of the problem make it essential that we develop methods to prioritize sites for management efforts. We used the individual-based simulation model ECOTONE in conjunction with climate and soil texture data to identify grassland site types where the invasive perennial forb Acroptilon repens is likely to be successful, and to create a threat map indicating the most vulnerable regions of Colorado. Acroptilon repens has the potential to become most abundant in dry areas with fine-textured soils. This information can be used to direct management efforts towards the areas at greatest risk, allowing the most effective use of limited resources. The most common approach for identifying invasible regions has been to extrapolate from the locations of existing invasions to find similar sites. Two major drawbacks to this method are the lack of consideration of the role of the existing plant community in inhibiting or facilitating invasion, and the assumption that the invading species is at equilibrium with the environment. The combination of an individual-based simulation model and a geographic information system provides a flexible tool to investigate the community and regional dynamics of invasive plant species.

Pasture monitoring at a farm scale with the USDA NRCS pasture condition score system

The Pasture Condition Score (PCS) system, developed by the USDA Natural Resources Conservation Service, is a monitoring and assessment tool for pastureland enrolled in conservation programs. Ten indicators of vegetation and soil status are rated on a 1 to 5 scale and are summed to give an aggregate score, which is interpreted for management recommendations. Information is lacking, however, on how PCS results vary within and among environments and farms. We applied the PCS on two farms in Pennsylvania (one dairy, one beef), two dairy farms in New York, and an organic dairy in Maryland. All pastures (25 to 63 per farm) on each farm were evaluated according to PCS methodology in spring, summer, and autumn of 2004, 2005, and 2006. Aggregate PCS scores ranged from 30 to 40 (indicating some improvements were needed to pasture management) and were relatively stable within management recommendation categories across seasons in 2004 and 2006. The PCS scores in 2005, however, plummeted (below 25 to 30—indicating major management changes to prevent degradation) on the Pennsylvania and Maryland farms because of drought. Pastures used for heifers and dry cows or as wintering areas often had lower scores than other pastures. Typically, these pastures were on less productive soils, steep slopes, and were stocked intensively. There was much overlap among individual score categories for some indicators, which suggests that fewer but broader score categories (e.g., low, medium, high) would simplify the system for farmers. The monitoring workload could be reduced by assessing representative subsets of pastures managed similarly or in similar landscape positions instead of all pastures on a farm.

An ecologically based landscape classification system for monitoring and assessment of pastures

The pastures and haylands of the United States have substantial potential to contribute to national goals for sustainably increasing food production (Nelson 2012). Realizing this potential will require technologies and management strategies that are tailored to the agroecosystems of the region, are economically viable, enhance the environment, and are sufficiently flexible to adapt to climate change. Forage production is the foundation for pasture-based dairy and livestock production, including low input and organic systems, and contributes to confined animal feeding operations through hay production. Pastures often include a diverse mixture of numerous forage species, the identities of which depend on complex interactions between soil, climate, landscape, and management (Goslee and Sanderson 2010). Plant species composition affects not only plant productivity and length of grazing season, but also animal intake, production, and greenhouse gas emissions. An applied understanding of these complex relationships is lacking in current pasture classifications, even though an ecologically based framework is needed to support management practices that sustain biological integrity and enhance plant and animal productivity while minimizing adverse environmental impacts (Sanderson et al. 2011). Effective ecosystem management requires that we simplify the complex natural world enough that we can understand how to manage it while at the…

An integrated approach to grazingland ecological assessments and management interpretations

In the United States, grazinglands have been separated into categories such as rangelands and pasturelands and have traditionally been assessed using different methods and indicators. The term grazingland refers to areas producing forage from native or introduced plants and harvested directly by animals without reference to land tenure or other land uses (Allen et al. 2011). The largest area of grazingland in the United States occurs west of the 100th meridian, in water-limited rangelands (Briske 2011). The eastern portion of the country, where water is not a limiting factor, contains substantial areas of improved pastures (Sanderson et al. 2012). Together, these grazinglands represent a substantial proportion, nearly 22% (Jin et al. 2013), of agricultural lands in the United States (figure 1) and contribute many ecosystem goods and services that help support human well-being (Nelson et al. 2012). When taking into account the dichotomy in grazingland terminology, it is important to note that for some parts of the United States, and many parts of the world, the difference between pasturelands and grazinglands is less clear and land considered a pasture to some might be considered an intensively managed rangeland to others. Here we follow the Allen et al. (2011) definitions for…

Establishment and Seedling Growth of Sawgrass and Cattail from the Everglades

Loveless (1959) described the vegetation of the Everglades as being predominantly sawgrass (Cladium jamaicense), with 65–70% cover. In wetter areas, the vegetation consists of wet prairie communities, and the deepest areas, known as sloughs, contain emergent and aquatic species (Davis 1994; see Chap. 4). Cattail (Typha domingensis) is native to the Everglades, but historical populations were low (Chap. 12). Historically, the Everglades was a low-nutrient system, especially deficient in phosphorus, because it received nutrients mainly from rainwater (Chap. 2). Few plant species are capable of growing in such a wet, infertile habitat. In some areas of the Everglades, particularly the Water Conservation Areas (WCAs), the vegetation is changing. Both sloughs and sawgrass stands are being invaded and replaced by cattails, especially near the water inflows from the Everglades Agricultural Area (EAA), and some sloughs in other areas are being filled in by sawgrass (Richardson et al. 1999). In WCA-2A, sawgrass has decreased from 95% cover to only 61% between 1973 and 1991 (Jensen et al. 1995). This change is correlated with increased nutrient loadings, and also with increased hydroperiod (Urban et al. 1993; Craft et al. 1995). Changes in the frequency of fire and other disturbances may also be a contributing factor. Cattail encroachment is not unique to the Everglades. Wilcox et al. (1985) observed the invasion of cattail into a sedge wetland at Indiana Dunes National Lakeshore. Cattail increased with increased water levels. Colonies became established by seed, and spread vegetatively. Cattail in Indiana was the most successful in stabilized elevated water levels. This could be similar to the process occurring in the Everglades, although there is the added complication of nutrient enrichment. There are many potential consequences of a shift from sawgrass to cattail, both to the Everglades itself and on a larger scale. The native plant community is being altered, and accompanying changes in associated plant species, periphyton, and in the fauna have been reported (SFWMD 1992, 2003, 2004, 2005). In addition, different decomposition characteristics of the two species lead to different rates of peat accretion and different peat characteristics (Chap. 3). Peat accumulates faster in cattail areas because of the higher productivity, but the peat is finer and less