INTEGRATING RESOURCE HETEROGENEITY AND PLANT PLASTICITY - MODELING NITRATE AND PHOSPHATE-UPTAKE IN A PATCHY SOIL ENVIRONMENT

Citation
Rb. Jackson et Mm. Caldwell, INTEGRATING RESOURCE HETEROGENEITY AND PLANT PLASTICITY - MODELING NITRATE AND PHOSPHATE-UPTAKE IN A PATCHY SOIL ENVIRONMENT, Journal of Ecology, 84(6), 1996, pp. 891-903
Citations number
65
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Ecology
Journal title
ISSN journal
0022-0477
Volume
84
Issue
6
Year of publication
1996
Pages
891 - 903
Database
ISI
SICI code
0022-0477(1996)84:6<891:IRHAPP>2.0.ZU;2-O
Abstract
1 We used the Barber-Cushman model of nutrient uptake to simulate the importance of soil heterogeneity and root plasticity for nitrate (NO3- ) and phosphate (P) uptake. Model inputs included root physiological p arameters and soil characteristics obtained from five years of field s tudies in the sagebrush steppe. At an intensively sampled field site t he average variation in soil P and NO; around individual plants was 3- fold and 12-fold (3 x and 12 x, respectively), the range of soil varia bility used in our simulations. 2 In soil patches three-fold enriched in P (3 x), simulated P uptake was three to four times greater than in soil of background P concentrations (1 x). The importance of soil het erogeneity and root plasticity was even more pronounced for NO3-. In 1 2 x soil patches, NO3- uptake was 7-20 times greater than at 1 x, depe nding on simulation conditions. Plasticity (root proliferation and inc reased uptake kinetics) accounted for up to 75% of NO3- and over 50% o f P acquired from enriched soil patches. Even without plasticity, nutr ient uptake increased substantially in enriched patches because of hig her soil-solution concentrations. 3 Using the same model we simulated P and NO3- uptake for an actual 0.25-m(2) soil area in the field. Plan t acquisition of P in this area was 28% higher with root plasticity th an without, equally attributable to root proliferation and increased u ptake kinetics. Plant NO3- uptake was 61 % greater with plasticity, du e almost exclusively to increased uptake capacity of roots. 4 We also simulated P and NO3- uptake in hypothetical soil arrays containing an equivalent quantity of nutrient distributed homogeneously or heterogen eously. A plant without plasticity always acquired less P or NO3- in t he heterogeneous arrays than in the homogeneous arrays. With plasticit y, it acquired more nutrients in three of four cases compared to the h omogeneous 'control'. 5 We present these simulations as a way to integ rate field experiments, generate and test hypotheses, and stimulate di scussion. Given that heterogeneity is the norm rather than the extreme , our simulations highlight the importance of soil heterogeneity and r oot plasticity for both nutrient acquisition and plant competition in the field.