We measured litter quality, N mineralization, air and soil temperatures, soil moisture, and aboveground net primary production (ANPP) at 18 plots in three forest types typical of full-stature forests found on western slopes of the Cordillera de Piuchué (CP) on Isla de Chiloé in southern Chile. The primary objectives were to examine the range of net N mineralization across forest types that have different vegetation and litter composition, assess probable controls on mineral N production and leaching, and to determine if the relationship between N mineralization and ANPP was similar to that observed in cool temperate northern hemisphere forests. Average annual litter lignin/N ratios were high in the evergreen montane broadleaf forest plots (50:1) and very high in the montane conifer plots (80:1). Net N mineralization during the summer months was correspondingly low (1.2 and 2.2 kg ha À1 , respectively). The high litter lignin content and associated low rate of N mineralization can explain the extremely low concentrations of mineral N in soils and upland streams of this region. In the broadleaf evergreen coastal forest plots, lignin/N ratio was lower (23:1) and N mineralized was considerably greater over the same measurement period than in the montane forest plots (14 kg ha À1). In contrast to findings in many cool temperate northern hemisphere forests, ANNP in the broadleaf forest type was high (average 11.1 Mg ha À1 yr À1) in spite of the low net N mineralization rates, and ANPP and net N mineralized were not correlated. Net N mineralization was best correlated with litter quality, soil temperature, and soil moisture content, and ANPP was best correlated with growing degree days. Site Description Isla de Chiloé is located off the coast of southern Chile. Low mountains of the CP run the length of the island's west
We studied broadleaf and needle-leaf forests along an elevation gradient (600-1200 m) at Whiteface Mountain, New York, to determine relationships among temperature, mineral N availability, and aboveground net primary productivity (ANPP) and controls on the latter two variables. We measured net N mineralization during the growing season, annual litterfall quantity and quality, aboveground woody biomass accumulation, and soil organic matter quality. Inorganic N deposition from cloudwater markedly increases mineral N availability above 1000 m in this region. Consequently, mineral N availability across the climosequence remains relatively constant because N mineralization decreases with increasing elevation. Across this climosequence, air temperature (as growing season degree-days) exerted the most control on ANPP. Nitrogen mineralization was most strongly related to soil growing season degree-days and less so to lignin to N ratios in litter. ANPP was correlated with N mineralization but not with mineral N availability. Combining our data with those from similar studies in other boreal and cool temperate forests shows that N mineralization and ANPP are correlated at local, regional, and interbiome scales. Regarding the persistent question concerning cause and effect in the N mineralization -forest productivity relationship, our data provide evidence that at least in this case, forest productivity is a control on N mineralization. We studied broadleaf and needle-leaf forests along an elevation gradient (600-1200 m) at Whiteface Mountain, New York, to determine relationships among temperature, mineral N availability, and aboveground net primary productivity (ANPP) and controls on the latter two variables. We measured net N mineralization during the growing season, annual litterfall quantity and quality, aboveground woody biomass accumulation, and soil organic matter quality. Inorganic N deposition from cloudwater markedly increases mineral N availability above 1000 m in this region. Consequently, mineral N availability across the climosequence remains relatively constant because N mineralization decreases with increasing elevation. Across this climosequence, air temperature (as growing season degree-days) exerted the most control on ANPP. Nitrogen mineralization was most strongly related to soil growing season degree-days and less so to lignin to N ratios in litter. ANPP was correlated with N mineralization but not with mineral N availability. Combining our data with those from similar studies in other boreal and cool temperate forests shows that N mineralization and ANPP are correlated at local, regional, and interbiome scales. Regarding the persistent question concerning cause and effect in the N mineralization -forest productivity relationship, our data provide evidence that at least in this case, forest productivity is a control on N mineralization. Résumé :Nous avons étudié des forêts de feuillus et de résineux le long d'un gradient altitudinal (600-1200 m) à Whiteface Mountain dans l'État de New York pou...
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