TY - ABST

T1 - Off-season uptake of nitrogen in temperate heath vegetation

AU - Andresen, Louise Christoffersen

AU - Michelsen, Anders

PY - 2004

Y1 - 2004

N2 - Off-season ecosystem processes is becoming an area of increasing interest, beingimportant when considering annual nitrogen and carbon budgets. The general assumption thatphysiological activity in soil microorganisms as well as vegetation is low during winter maynot be justified. In this field study we show that northern temperate coastal heath vegetationhas a significant uptake potential for nitrogen, both in the form of ammonium and as glycine,throughout the non-growing season.We used 15N ammonium and 2*(13C)15N glycine as nutrient tracer. This was injectedinto the soil two times during winter and once at spring. The winter temperatures were similarto those of average winter in the northern temperate region of Europe, with only few days ofsoil temperatures below zero and a winter mean of 2.4 °C. The vegetation, consisting of theevergreen dwarf shrub Calluna vulgaris (L.), the deciduous dwarf shrub Salix arenaria (L.)and the graminoids Carex arenaria (L.) and Deschampsia flexuosa (L.), showed root uptakeof both forms of nitrogen, both one day after labelling and after a month. Translocation of thelabelled nitrogen to shoots was generally evident after one month and increased as springapproached, with different translocation strategies in the three plant functional types.Furthermore, shoot total nitrogen concentration increased in all plant types, but only thegraminoids and, eventually, S. arenaria showed shoot growth during winter. Our studysuggests that plant nitrogen uptake can cause increasing nitrogen concentration in shoot tissuefrom fall to spring.To our knowledge this is one of the first studies of plant nitrogen uptake during nongrowingseason at a temperate heath. Our results show that the nitrogen uptake is in the sameorder of magnitude as summer uptake in other types of ecosystems in the temperate/borealregion. These results suggest that plant nitrogen uptake during winter should be included inthe annual nitrogen budgets of heath ecosystems, and that the view of plant nutrient uptake aslow in this climatic region during winter should be revised. Furthermore, these results shouldbe taken into account when ecosystem responses to climatic changes such as warming areevaluated.

AB - Off-season ecosystem processes is becoming an area of increasing interest, beingimportant when considering annual nitrogen and carbon budgets. The general assumption thatphysiological activity in soil microorganisms as well as vegetation is low during winter maynot be justified. In this field study we show that northern temperate coastal heath vegetationhas a significant uptake potential for nitrogen, both in the form of ammonium and as glycine,throughout the non-growing season.We used 15N ammonium and 2*(13C)15N glycine as nutrient tracer. This was injectedinto the soil two times during winter and once at spring. The winter temperatures were similarto those of average winter in the northern temperate region of Europe, with only few days ofsoil temperatures below zero and a winter mean of 2.4 °C. The vegetation, consisting of theevergreen dwarf shrub Calluna vulgaris (L.), the deciduous dwarf shrub Salix arenaria (L.)and the graminoids Carex arenaria (L.) and Deschampsia flexuosa (L.), showed root uptakeof both forms of nitrogen, both one day after labelling and after a month. Translocation of thelabelled nitrogen to shoots was generally evident after one month and increased as springapproached, with different translocation strategies in the three plant functional types.Furthermore, shoot total nitrogen concentration increased in all plant types, but only thegraminoids and, eventually, S. arenaria showed shoot growth during winter. Our studysuggests that plant nitrogen uptake can cause increasing nitrogen concentration in shoot tissuefrom fall to spring.To our knowledge this is one of the first studies of plant nitrogen uptake during nongrowingseason at a temperate heath. Our results show that the nitrogen uptake is in the sameorder of magnitude as summer uptake in other types of ecosystems in the temperate/borealregion. These results suggest that plant nitrogen uptake during winter should be included inthe annual nitrogen budgets of heath ecosystems, and that the view of plant nutrient uptake aslow in this climatic region during winter should be revised. Furthermore, these results shouldbe taken into account when ecosystem responses to climatic changes such as warming areevaluated.

M3 - Conference abstract in journal

JO - Oecologia

JF - Oecologia

SN - 0029-8519

Y2 - 19 April 2004 through 23 April 2004

ER -