FOLIAR AMINO-ACID ACCUMULATION AS AN INDICATOR OF ECOSYSTEM STRESS FOR FIRST-YEAR SUGAR MAPLE SEEDLINGS

Accumulation of certain plant foliar amino adds (arginine, glutamine, and proline) can be used as indicators of anthropogenic and natural st ressors, such as atmospheric deposition and mineral nutritional imbala nces, which result in decreased plant growth. in this study a number o f factors were evaluated to assess the use of foliar amino acid accumu lation as indicators of sugar maple seedling stress tit two sugar mapl e dominated forests in Michigan. These factors were: (i) first-year su gar maple (Acer saccharum Marshall) seedling growth, (ii) N and P nutr ition, (iii) soluble foliar and root total amino acid concentrations, and (iv) concentrations of foliar arginine, glutamine, and proline. Th e most southern site (Wellston), which was exposed to high atmospheric deposition and had high available soil P and seedling foliar P, had g reater seedling growth. Foliar glutamine, arginine, and proline were g reater at the most northern site (Alberta), which received lesser amou nts of atmospheric deposition, but also had lower levels of available soil phosphorus, seedling foliar phosphorus, less seedling growth, and greater canopy closure. These results suggest that since atmospheric deposition is high in nitrogen, even the low levels of deposition at A lberta may be interacting with ecological variables such as, available soil phosphorus, light, or moisture to result in N/P imbalances and c onsequently higher arginine and glutamine concentrations in seedling f oliage.