| The effects of human activity on the environment are increasing worldwide. Changes in land and fossil fuel use have significantly altered our atmosphere, land, and water. Terrestrial ecosystem uptake is somewhere between ∼2.5–5 gigatons of carbon each year. Understanding the ecological patterns and processes that control terrestrial carbon uptake is vital to developing sound policies that would help temper future environmental impacts of human activity. This research focuses on providing ground-based measurements of leaf area index (LAI) and net primary production (NPP) for validation of NASA's Terra satellite and the Moderate Resolution Image Spectrometer (MODIS).; The objective of this study was to use a cyclic sampling design to compare the spatial patterns of LAI and NPP in five biomes in North America. The cyclic sampling design increased the sampling efficiency by optimizing the placement of plots so they were distributed more efficiently for geostatistical analyses. At the northern Wisconsin site, LAI differed significantly among the five cover types and averaged 3.45, 3.57, 3.82, 3.99 and 1.14 for northern hardwoods, aspen, forested wetlands, upland conifers, and grass, respectively; the overall mean LAI was 3.51 (S.E. ± 0.89). Aboveground NPP for the northern Wisconsin site for aspen, hardwoods, mixed, upland conifers, nonforested wetlands, and forested wetlands were 7.8, 7.2, 5.7, 4.9, 5.0, and 4.5 t·drymass·ha −1·yr−1, respectively; the overall mean aboveground NPP was 5.8 t·drymass·ha−1·yr −1. There were significant (p ≤ 0.01) spatial patterns in wood, foliage, and understory NPP components and total aboveground NPP (p ≤ 0.03) at the northern Wisconsin site. The geostatistical mean LAI in 2000 were 3.6 (S.E. ± 0.2), 5.0 (S.E. ± 0.2), 2.0 (S.E. ± 0.2) and 3.8 (S.E. ± 0.2) for an agroecosystem, a temperate mixed forest, a tallgrass prairie and an evergreen needleleaf forest, respectively. Land-cover type, slope and aspect explained a significant amount of the observed spatial variation in LAI; management practices were significant contributors at three sites. The ranges of spatial autocorrelation for LAI were found to be between 81 m to 412 m. These results show that field based measurements can be used to quantify the natural variations in LAI and NPP across a diverse group of landscapes. |
