Analysis of the effects of extreme events such as heavy rainfall, drought, windstorms and forests on ecosystem processes has always been a great challenge. This challenge has increased in recent decades because environmental change (climate, land use, biotic) has altered both the frequency as well as the ecosystem response, to these events of these events. Long Term Ecological Research (LTER) sites provide unique opportunities for analysis of these challenging questions. At the Hubbard Brook LTER site in the northern hardwood forests of New Hampshire, we have been characterizing variable
Nitrogen (N) dynamics in terrestrial ecosystems are quite complex because of the high spatial and temporal variabilities together with its high turnover due to the high biological N demand by plants and microbes. To elucidate the N dynamics in intact terrestrial ecosystems, the use of the natural abundance of stable N and oxygen (O) isotopes has been carried out in many ways. The recent methodological progress (Sigman et al. 2001; Casciotti et al. 2002) now can allow us to measure not only N but also O isotope ratios with samples with quite tiny amounts (e.g. 20nmol-N).