Data from: Precipitation, soils, NPP, and biodiversity: resurrection of Albrecht's Curve

Climate and soils are widely recognized as major drivers of virtually all
properties of ecosystems and communities. However, despite major advances
in the understanding of soil formation and ecosystem dynamics, the effects
of climate on soil properties are not widely appreciated. Understanding
the effects of water availability on the rates of chemical and biological
processes that affect soil formation can help clarify the global patterns
of soil fertility, which affect agricultural and forest productivity, as
well as biodiversity. Empirical tests of Albrecht's conceptual model
of soil development and degradation using global climate and soil datasets
and soil chronosequences confirm that soil total exchangeable bases (TEB),
phosphorus, nitrogen and other components of soil fertility, along with
plant productivity generally decline on older soils and under wetter
conditions as precipitation exceeds potential evapotranspiration. The
basic pattern of soil fertility in relation to water availability is a
unimodal curve, with a maximum near or below a water balance of zero
(annual precipitation - annual potential evapotranspiration). Analysis of
global data by sub-regions reveals significant differences between
temperate and tropical soil fertility distributions, as well as
significant differences between continents. The low levels of soil
nutrients (e.g., TEB, P, N) and plant productivity found on ancient soils
or highly weathered soils in regions with high precipitation suggest that
the positive effects of low productivity on plant diversity that have been
observed at local and regional scales may also occur at the global scale.