On the Nature of Environmental Gradients: Temporal and Spatial Variability of Soils and Vegetation in the New Jersey Pinelands

Abstract

Summary1 Environmental variability can occur over various spatial scales, ranging from small patches at the scale of individual plants to long gradients over hundreds of metres. 2 In the New Jersey Pinelands, different species in the diverse shrub understorey of pitch pine (Pinus rigida Mill.) forests are patterned at these various scales. 3 Soil moisture, extractable NH 4 -N and N mineralization rate vary in complex ways, with the scale of spatial patterning changing over time and with depth in the soil profile. Moisture in both mineral and organic horizons, and NH 4 -N in the organic horizon, have patterns that are more stable over time than the mineralization rate in either horizon, or the NH 4 -N concentrations in the mineral horizon. 4 Vegetation patterns, as captured in principal components analysis, were poorly explained by any of the soil properties. Only the more temporally stable properties showed any relationship with vegetation patterns. 5 These results suggest that environmental gradients reflect patterns of environmental variation in four dimensions. Variation in the vertical dimension and over time is as pronounced and important as variation in the horizontal dimensions. 6 Many methods used to analyse vegetation implicitly assume temporal and spatial stability of environmental properties. Our results suggest that a more complex, fourdimensional assessment of environmental variation should be incorporated into models of vegetation-environment relationships.

Temporal dynamics of soil water balance components in a karst range in southeastern Spain: estimation of potential recharge

“…In nearby areas with similar climate, the maximum E occurs in May (Domingo et al, 1999). The seasonal pattern of variation in y, high in spring and late autumn and characteristically low in summer when plants actively take up soil water, is well known (Henninger et al, 1976;Ehrenfeld et al, 1997;Gehrels et al, 1998).…”

Influence of Tree Spacing on Soil Nitrogen Mineralization and Availability in Hybrid Poplar Plantations

“…However, it was not clear whether and how the rate of N mineralization in soil is related to the growing periods of trees above-ground. Most studies suggest that N mineralization was enhanced during the growing season [14,30], which was, in part, attributed to higher temperature coupled with greater soil moisture in the growing season [31,32]. Zhang et al [33] found that 85% of total annual nitrification and 90% of annual N mineralization took place during the growing season.…”

Nitrogen mineralization processes of soils from natural saline-alkalined wetlands, Xianghai National Nature Reserve, China

“…Nitrogen mineralization varies both spatially (Connell et al 1995;González-Prieto et al 1996) and temporally (Aber et al 1993;Ehrenfeld et al 1997). Knowledge of the temporal variations in N mineralization rates in any ecosystem is important because close coupling between N mineralization and plant primary production allows ecosystems to conserve and use N more efficiently.…”