Bulk leaf δ18O and δ13C reflect the intensity of intraspecific competition for water in a semi-arid tussock grassland |
| |
Authors: | DAVID A. RAMÍ REZ,JOSÉ I. QUEREJETA,& JUAN BELLOT |
| |
Affiliation: | Departamento de Ciencias Ambientales, Universidad de Castilla-La Mancha, Ap. 45071, Toledo, Spain,;Departamento de Conservación de Suelos y Aguas, Centro de Edafología y Biología Aplicada del Segura-Consejo Superior de Investigaciones Científicas (CEBAS-CSIC), Campus Universitario de Espinardo E-30100, Murcia, Spain and;Departamento de Ecología, Universidad de Alicante, Ap. 99-E- 03080, Alicante, Spain |
| |
Abstract: | We investigated the extent to which plant water and nutrient status are affected by intraspecific competition intensity and microsite quality in a monodominant tussock grassland. Leaf gas exchange and stable isotope measurements were used to assess the water relations of Stipa tenacissima tussocks growing along a gradient of plant cover and soil depth in a semi-arid catchment of Southeast Spain. Stomatal conductance and photosynthetic rate decreased with increasing intensity of competition during the wet growing season, leading to foliar δ 18O and δ 13C enrichment. A high potential for runoff interception by upslope neighbours exerted strong detrimental effects on the water and phosphorus status of downslope S. tenacissima tussocks. Foliar δ 15N values became more enriched with increasing soil depth. Multiple stepwise regression showed that competition potential and/or rhizosphere soil depth accounted for large proportions of variance in foliar δ 13C, δ 18O and δ 15N among target tussocks (57, 37 and 64%, respectively). The results presented here highlight the key role that spatial redistribution of resources (water and nutrients) by runoff plays in semi-arid ecosystems. It is concluded that combined measurement of δ 13C, δ 18O and nutrient concentrations in bulk leaf tissue can provide insight into the intensity of competitive interactions occurring in natural plant communities. |
| |
Keywords: | Stipa tenacissima δ 13C δ 15N δ 18O drought stress plant competition runoff redistribution |
|
|