Seasonal variations in plant species effects on soil N and P dynamics.

It is well established that plant species influence ecosystem processes, but we have little ability to predict which vegetation changes will alter ecosystems, or how the effects of a given species might vary seasonally. We established monocultures of eight plant species in a California grassland in order to determine the plant traits that account for species impacts on nitrogen and phosphorus cycling. Plant species differed in their effects on net N mineralization and nitrification rates, and the patterns of species differences varied seasonally. Soil PO4- and microbial P were more strongly affected by slope position than by species. Although most studies focus on litter chemistry as the main determinant of plant species effects on nutrient cycling, this study showed that plant species affected biogeochemical cycling through many traits, including direct traits (litter chemistry and biomass, live-tissue chemistry and biomass) and indirect traits (plant modification of soil bioavailable C and soil microclimate). In fact, species significantly altered N and P cycling even without litter inputs. It became particularly critical to consider the effects of these multiple traits in order to account for seasonal changes in plant species effects on ecosystems. For example, species effects on potential rates of net N mineralization were most strongly influenced by soil bioavailable C in the fall and by litter chemistry in the winter and spring. Under field conditions, species effects on soil microclimate influenced rates of mineralization and nitrification, with species effects on soil temperature being critical in the fall and species effects on soil moisture being important in the dry spring. Overall, this study clearly demonstrated that in order to gain a mechanistic, predictive understanding of plant species effects on ecosystems, it is critical to look beyond plant litter chemistry and to incorporate the effects of multiple plant traits on ecosystems.

[1]  M. Firestone,et al.  Plant and soil nitrogen dynamics in California annual grassland , 1988, Plant and Soil.

[2]  V. Eviner.  PLANT TRAITS THAT INFLUENCE ECOSYSTEM PROCESSES VARY INDEPENDENTLY AMONG SPECIES , 2004 .

[3]  P. Bottner,et al.  Modelling the effect of active roots on soil organic matter turnover , 1999, Plant and Soil.

[4]  J. Pastor,et al.  Nitrogen mineralization dynamics in grass monocultures , 1993, Oecologia.

[5]  D. Tilman,et al.  Species effects on nitrogen cycling: a test with perennial grasses , 1990, Oecologia.

[6]  F. Stuart Chapin,et al.  Functional Matrix: A Conceptual Framework for Predicting Multiple Plant Effects on Ecosystem Processes , 2003 .

[7]  M. Mack,et al.  The Effects of Exotic Grasses on Litter Decomposition in a Hawaiian Woodland: The Importance of Indirect Effects , 2003, Ecosystems.

[8]  P. Templer,et al.  Soil microbial biomass and nitrogen transformations among five tree species of the Catskill Mountains, New York, USA , 2003 .

[9]  M. Mack,et al.  EXOTIC GRASSES ALTER CONTROLS OVER SOIL NITROGEN DYNAMICS IN A HAWAIIAN WOODLAND , 2003 .

[10]  F. Chapin,et al.  Biogeochemical interactions and biodiversity. , 2003 .

[11]  F. Chapin,et al.  Substrate limitations to microbial activity in taiga forest floors , 2001 .

[12]  W. Bowman,et al.  Original Articles: Differential Influence of Plant Species on Soil Nitrogen Transformations Within Moist Meadow Alpine Tundra , 1998, Ecosystems.

[13]  Peter M. Vitousek,et al.  Effects of plant composition and diversity on nutrient cycling , 1998 .

[14]  D. Binkley,et al.  Foliage litter quality and annual net N mineralization: comparison across North American forest sites , 1997, Oecologia.

[15]  I. Burke,et al.  Contingent effects of plant species on soils along a regional moisture gradient in the Great Plains , 1997, Oecologia.

[16]  K. Giller,et al.  Driven by Nature: Plant Litter Quality and Decomposition , 1996 .

[17]  S. Hobbie.  Direct and Indirect Effects of Plant Species on Biogeochemical Processes in Arctic Ecosystems , 1995 .

[18]  J. C. Hickman,et al.  The Jepson Manual: Higher Plants of California , 1993 .

[19]  D. Binkley,et al.  Relationships Between Litter Quality and Nitrogen Availability in Rocky Mountain Forests , 1993 .

[20]  S. Hobbie.  Effects of plant species on nutrient cycling. , 1992, Trends in ecology & evolution.

[21]  R. Coupland,et al.  Natural grasslands : introduction and Western Hemisphere , 1992 .

[22]  C. Bakker,et al.  Root turnover as determinant of the cycling of C, N, and P in a dry heathland ecosystem , 1992 .

[23]  F. Berendse,et al.  Nitrogen mineralization in heathland ecosystems dominated by different plant species , 1992 .

[24]  D. Coleman,et al.  Rhizosphere effect on soil organic matter decomposition , 1991 .

[25]  Jerry M. Melillo,et al.  Predicting long-term patterns of mass loss, nitrogen dynamics, and soil organic matter formation from initial fine litter chemistry in temperate forest ecosystems , 1990 .

[26]  I. Burke.  Control of Nitrogen Mineralization a Sagebrush Steppe Landscape , 1989 .

[27]  B. R. Taylor,et al.  Nitrogen and Lignin Content as Predictors of Litter Decay Rates: A Microcosm Test , 1989 .

[28]  Neil K. McDougald,et al.  Correlation of degree-days with annual herbage yields and livestock gains. , 1988 .

[29]  J. Blair.  Nitrogen, sulfur and phosphorus dynamics in decomposing deciduous leaf litter in the southern appalachians , 1988 .

[30]  H. Marschner.  Mineral Nutrition of Higher Plants , 1988 .

[31]  J. Aber,et al.  Forest Litter Decomposition in Relation to Soil Nitrogen Dynamics and Litter Quality , 1985 .

[32]  P. Bottner.  Response of microbial biomass to alternate moist and dry conditions in a soil incubated with 14C- and 15N-labelled plant material , 1985 .

[33]  K. Cleve,et al.  Nutrient cycling in relation to decomposition and organic-matter quality in taiga ecosystems , 1983 .

[34]  W. Williams,et al.  Effect of Sulfur Fertilization oil Three Annual Range Species I. Laughlin Soil Experiment 1 , 1983 .

[35]  John F. Muratore,et al.  Nitrogen and Lignin Control of Hardwood Leaf Litter Decomposition Dynamics , 1982 .

[36]  W. McGill,et al.  Comparative aspects of cycling of organic C, N, S and P through soil organic matter , 1981 .

[37]  Milton B. Jones,et al.  SOIL PHOSPHORUS TESTS ON CALIFORNIA SUBCLOVER‐ANNUAL GRASS PASTURES , 1980 .

[38]  V. Meentemeyer,et al.  Macroclimate and Lignin Control of Litter Decomposition Rates , 1978 .

[39]  H. Heady.  VEGETATIONAL CHANGES IN THE CALIFORNIA ANNUAL TYPE , 1958 .

[40]  M. W. Talbot,et al.  Fluctuations in the Annual Vegetation of California , 1939 .