Interception loss, throughfall and stemflow chemistry in pine and oak forests in northeastern Mexico

Interception loss, gross precipitation, throughfall and stemflow solution c hemistry beneath pine (Pinus pseudostrobus Lindl.), oak (Quercus sp.) and p ine-oak natural forest canopies in northeastern Mexico were measured. Coeff icients of variation for throughfall were 12% in pine and oak canopies and 17% in the mixed pine-oak canopy. The variability of stemflow averaged 66, 126 and 73% for pine, oak and the mixed pine-oak canopies, respectively. Li near regression analysis of net versus gross precipitation for the three ca nopies showed highly significant correlations (r = 0.974-0.984). Total prec ipitation during the experimental period was 974 mm and estimated intercept ion loss was 19.2, 13.6 and 23% for the pine, oak and pine-oak canopies, re spectively. Stemflow did not occur following rainfall events of less than 4 mm and, in all canopies, stemflow represented a minimal proportion of gros s precipitation (0.60, 0.50 and 0.03% for pine, oak and pine-oak, respectiv ely). Throughfall pH in pine (6.2), oak (6.3) and pine-oak (6.3) canopies w as significantly more acidic than gross precipitation (6.6). Stemflow pH ra nged from 3.7 (pine) to 6.0 (oak). The pine-oak canopy registered the highe st throughfall and stemflow electrical conductivities, 104 and 188 muS cm(- 1), respectively. Net nutrient leaching of K, Mg, Na, Fe, Mn and Zn was sig nificantly higher from the pine-oak canopy than from the pure pine and oak canopies. Mean depositions of Ca and Cu in throughfall behaved similarly am ong the three types of canopies. A greater proportion of Zn in gross precip itation was absorbed by the oak canopy than by the pine and pine-oak canopi es. Enrichment factors beneath the pine-oak canopy relative to gross precip itation varied from 1.2 to 3.2 for macro-nutrients (Ca, K, Mg and Na) and f rom 1.4 to 3.1 for micro-nutrients (Cu, Fe, Mn and Zn). Stemflow deposition s of Ca, K, Mg and Cu were higher in the pine-oak canopy, whereas stemflow depositions of Na, Fe, Mn and Zn were higher in the pine canopy.