Edward A. Martinko

Diverse and Contrasting Effects of Habitat Fragmentation

Different components of an ecosystem can respond in very different ways to habitat fragmentation. An archipelago of patches, representing different levels of fragmentation, was arrayed within a successional field and studied over a period of 6 years. Ecosystem processes (soil mineralization and plant succession) did not vary with the degree of subdivision, nor did most measures of plant and animal community diversity. However, fragmentation affected vertebrate population dynamics and distributional patterns as well as the population persistence of clonal plant species. The results highlight the dangers of relying on broad community measures in lieu of detailed population analyses in studies of fragmented habitats.

INTERRELATIONSHIPS AMONG LANDSCAPES, NDVI, AND STREAM WATER QUALITY IN THE U.S. CENTRAL PLAINS

During late spring through summer of 1994 and 1995, 290 randomly selected stream sites in Nebraska, Kansas, and Missouri were sampled once for several parameters including conductivity, turbidity, total phosphorus, nitrate-nitrite nitrogen, the index of biotic integrity, and a habitat index. Based on landscape data from watersheds that were delineated for each sampling location, interrelationships were examined between these water quality parameters and land use/land cover, the normalized difference vegetation index (NDVI), and vegetation phenological metrics derived from the NDVI. Statistically signif- icant relationships were found between NDVI values and the derived metrics with the stream condition parameters ( r values to 0.8, a5 0.05). The NDVI or vegetation pheno- logical metrics (VPMs) were more highly correlated to the selected stream condition pa- rameters than were the land use/land cover proportions. Knowledge of the general land use/land cover setting within the watersheds, however, was important for interpreting these relationships. The most common variables associated with the stream data were early spring NDVI values or VPMs associated with the date of onset of greenness. These results dem- onstrate the utility of NDVI and VPMs as broad-scale environmental indicators of watershed conditions.

Discriminating between cool season and warm season grassland cover types in northeastern Kansas

This study assesses the ability of multitemporal Landsat Thematic Mapper (TM) data and the normalized difference vegetation index (NDVI) to spectrally separate grazed cool season and warm season grassland cover types in Douglas County, Kansas. Biophysical data collected during the summer of 1997 suggest that differences in the per cent of total living vegetation cover, per cent of senescent vegetation, and proportion of forb cover between the two grassland cover types could make cool season and warm season grassland cover types spectrally distinct. The results show that the two grassland cover types were spectrally different in several spring (May) and mid-summer (July) bands, but not in any fall (September) bands. Furthermore, the two grassland cover types could be discriminated with a high level of accuracy. Accuracy assessments of the three single dates showed that the mid-summer (July) image and NDVI discriminated between the grassland cover types most accurately (81.8%). The multitemporal TM and NDVI data did not improve the spectral discrimination of the two grassland cover types over the mid-summer image or NDVI and had classification accuracy levels of 63.6% and 68.2%, respectively.

Identifying historical and recent land-cover changes in Kansas using post-classification change detection techniques

Abstract Statewide land-cover change detection analysis provides a useful tool for conservation planning and environmental monitoring and addresses issues of habitat fragmentation and urban sprawl. Furthermore, land-cover data offer a historical and recent perspective on landscape dynamics. To this end, the first alliance level land-cover map of Kansas (Kansas Vegetation Map) recently completed by the KARS Program was compared to Küchlers Potential Natural Vegetation map and the 1993 Kansas Land Cover Patterns map. The post-classification change detection technique was used along with co-occurrence matrices to identify areas and directions of land-cover change. Comparisons showed that the land cover of Kansas has changed drastically since European settlement. Over 48% of the land is now cultivated and native vegetation types such as tallgrass and shortgrass prairie have been reduced dramatically in area. There are, however, millions of ha of these vegetation types remaining in Kansas. Comparisons between the two recent land-cover maps reveal that over 80% of the land in Kansas has remained unchanged in the five years between map development. Recent land-cover changes include conversion of grassland to cropland, cropland to grassland, and grassland to woodland. Many areas changing from cropland to grassland have been identified as land being enrolled in the Conservation Reserve Program (CRP). Post-classification change detection analysis also shows that forest and woodland types have increased over the five-year period and over 1 million ha of grassland have been converted to cropland. The magnitude of increases in woodland and forest is questionable, however, and may be due to registration errors and classification methodologies used to generate the land-cover maps.

A multivariate analysis of biophysical parameters of tallgrass prairie among land management practices and years.

Six treatments of eastern Kansas tallgrass prairie – native prairie, hayed, mowed, grazed, burned and untreated – were studied to examine the biophysical effects of land management practices on grasslands. On each treatment, measurements of plant biomass, leaf area index, plant cover, leaf moisture and soil moisture were collected. In addition, measurements were taken of the Normalized Difference VegetationIndex (NDVI), which is derived from spectral reflectance measurements. Measurements were taken in mid-June, mid-July and late summer of 1990 and 1991. Multivariate analysis of variance was used to determine whether there were differences in the set of variables among treatments and years. Follow-up tests included univariate t-tests to determine whichvariables were contributing to any significant difference. Results showed a significant difference (p < 0.0005) among treatments in the composite of parameters during each of the months sampled. In most treatment types, there was asignificant difference between years within each month. The univariate tests showed, however, that only some variables, primarily soil moisture, were contributing to this difference. We conclude that biomass and % plant cover show the best potential to serve as long-term indicators of grassland condition as they generally were sensitive to effects ofdifferent land management practices but not to yearlychange in weather conditions. NDVI was insensitive to precipitation differences between years in July for most treatments, but was not in the native prairie. Choice of sampling time is important for these parameters to serve effectively as indicators.

Investigating Grazing Intensity and Range Condition of Grasslands in Northeastern Kansas Using Landsat Thematic Mapper Data

Abstract Grazing changes plant species composition of grassland ecosystems by selective removal and trampling. Grazing also alters soil physical and biogeochemical properties and can dramatically change hydrologic processes that can impact water budgets and quality. For these reasons, practical means are needed to assess grazing management practices and its impacts upon the land. This study examines whether a grazing intensity and range condition gradient can be detected in spectral reflectance characteristics of grasslands in northeastern Kansas. Multitemporal Landsat Thematic Mapper (TM) data, the normalized difference vegetation index (NDVI), and field data collected concurrent with the TM overpasses, were used in the analysis. Correlation analysis was used to examine relationships between spectral data and biophysical data. Next, the study sites within each grassland type were classified into three spectrally similar clusters. Grazing intensity, range condition, and biophysical characteristics were summarized for each spectral cluster and compared. The results suggest that NDVI may be used as a surrogate for living biomass for both grassland types and may be useful for predicting grazing intensity in native warm season grasslands. And while there appeared to be relationships between total living and non‐living cover, and TM NIR and MIR bands, there were no direct relationships between spectral characteristics and grazing intensity or range condition.

Effect of succession and habitat area on wandering spider (Araneae) abundance in an experimental landscape.

Abstract Terrestrial communities are strongly affected by habitat area and successional stage. As generalist predators, spiders represent an important community component that may be particularly sensitive to these landscape features. We used pitfall traps to sample ground-dwelling, cursorial spider abundance at 2 successional stages on an experimentally fragmented old-field site in northeastern Kansas. The site, established in 1984, includes replicate habitat patches undergoing secondary succession separated by a matrix of low turf maintained by regular mowing. Spiders were collected from traps located in large (5000 m2) and small (32 m2) patches during 1988 and 1990 (early succession), and 2005 (mid-succession). Total numbers collected were about 20% lower in 2005 than in 1988 and 1990. However, in all 3 yr significantly more spiders were collected by traps in large patches than by traps in small patches. The positive density–area relationship did not differ among years (no significant patch-size by year interaction), despite substantial change in patch vegetation during the 17 yr spanned by this study. The results for patch size are similar to those obtained in a study of insects sampled by sweep-net transects at the same site, which contrast with the negative density–area relationship reported for some small mammal species. The form of the density–area relationship may be determined by the size of the animals relative to the spatial scale of habitat fragmentation.

Rapporteur’s Report

The task of defining ecosystem health is difficult because of the complex nature of ecosystems and the multitude of problems that must be considered. The initial section, therefore, sets the stage by considering the definition of ecosystem health, its relationship to and comparison with the health services, its relationship to the delivery of ecosystem services, and its utility in communicating with the public.