Nutrient dynamics in singleleaf pinyon (Pinus monophylla Torr & Frem.) needles

Area of Science:

• Plant physiology
• Forest ecology
• Nutrient cycling

Background:

• Singleleaf pinyon pine (Pinus monophylla) are long-lived trees.
• Needle retention can exceed 18 years.
• Understanding nutrient dynamics in long-lived conifers is crucial for forest health.

Purpose of the Study:

• To quantify nutrient retranslocation from senescing needles in singleleaf pinyon pine.
• To determine if retranslocation meets the nutrient demands of new needles.
• To characterize the role of older foliage as a nutrient reserve.

Main Methods:

• Analysis of nutrient concentrations and amounts in needles of varying ages.
• Calculation of nutrient retranslocation percentages at needle abscission.
• Comparison of retranslocated nutrients with estimated demands of new needles.

Main Results:

• Nutrient retranslocation supplied only 2-13% of the nitrogen, phosphorus, potassium, iron, copper, and magnesium required by new needles.
• Needle weight and accumulation of Ca, Mg, Fe, Zn, P, and Mn increased with age.
• No consistent trend was observed for nitrogen content with needle age.

Conclusions:

• Nutrient capital in existing foliage serves as a long-term nutrient reserve for singleleaf pinyon pine.
• Nutrient retranslocation from older needles is insufficient to support new needle development.
• This study highlights the conservative nutrient use strategy in long-lived pinyon pines.