Temporal and spatial variation in soil resources in a deciduous woodland

1 Plants can respond to nutrient-rich patches by proliferation of roots or by increased rates of ion uptake; such patches are therefore considered to be an important source of nutrients for plant growth. However, little is known about the spatial and temporal heterogeneity of nutrient concentration at scales that are applicable to the development of root systems of herbaceous perennial plants. 2 A woodland site in North Yorkshire (UK) was studied to measure the scale and extent of nutrient heterogeneity. Phosphate, nitrate, ammonium, pH and soil moisture were measured by destructive soil coring over a period of 2 years, and phosphate, nitrate and ammonium were also measured at a smaller scale using Rhizon Soil Solution Samplers. 3 Soil moisture was relatively constant at 0.6 g g(-1) fresh soil weight. Temporal variation was found in all other variables, but the timing of peaks in nutrient concentration was not predictable. 4 Soil coring showed differences in phosphate, ammonium and nitrate concentrations at a scale of over 2 m, which may be too large a scale to affect individual herbaceous perennial plants but might be important for trees. However, the soil solution sampling showed two- to fivefold differences in nitrate and ammonium at scales of 20 cm; the root systems of many herbaceous plants will spread over such distances. 5 Peaks in nutrient concentration that occurred in localized areas lasted no more than 4 weeks. Therefore if these nutrient-rich patches are to be utilized by plants, their roots must respond rapidly. 6 The study showed that localized nutrient-rich areas may form an important source of nutrients for plants in some natural habitats, especially when the general levels of nutrient availability are low. Hence the patchy nature of the soil should be considered in root foraging and population studies.