Understanding of Coupled Terrestrial Carbon, Nitrogen and Water Dynamics—An Overview

Coupled terrestrial carbon (C), nitrogen (N) and hydrological processes play a crucial role in the climate system, providing both positive and negative feedbacks to climate change. In this review we summarize published research results to gain an increased understanding of the dynamics between vegetation and atmosphere processes. A variety of methods, including monitoring (e.g., eddy covariance flux tower, remote sensing, etc.) and modeling (i.e., ecosystem, hydrology and atmospheric inversion modeling) the terrestrial carbon and water budgeting, are evaluated and compared. We highlight two major research areas where additional research could be focused: (i) Conceptually, the hydrological and biogeochemical processes are closely linked, however, the coupling processes between terrestrial C, N and hydrological processes are far from well understood; and (ii) there are significant uncertainties in estimates of the components of the C balance, especially at landscape and regional scales. To address these two questions, a synthetic research framework is needed which includes both bottom-up and top-down approaches integrating scalable (footprint and ecosystem) models and a spatially nested hierarchy of observations which include multispectral remote sensing, inventories, existing regional clusters of eddy-covariance flux towers and CO2 mixing ratio towers and chambers

Adapting forest health assessments to changing perspectives on threats – a case example from Sweden

A revised Swedish forest health assessment system is presented. The assessment system is composed of several interacting components which target information needs for strategic and operational decision making and accommodate a continuously expanding knowledge base. The main motivation for separating information for strategic and operational decision making is that major damage outbreaks are often scattered throughout the landscape. Generally, large-scale inventories (such as national forest inventories) cannot provide adequate information for mitigation measures. In addition to broad monitoring programs that provide time-series information on known damaging agents and their effects, there is also a need for local and regional inventories adapted to specific damage events. While information for decision making is the major focus of the health assessment system, the system also contributes to expanding the knowledge base of forest conditions. For example, the integrated monitoring programs provide a better understanding of ecological processes linked to forest health. The new health assessment system should be able to respond to the need for quick and reliable information and thus will be an important part of the future monitoring of Swedish forests

Fine root classification matters : nutrient levels in different functional categories, orders and diameters of roots in boreal Pinus sylvestris across a latitudinal gradient

Background: Fine roots and their symbionts are the key drivers of processes such as nutrient cycling and belowground productivity. Their function depends on position in a branching hierarchy, with absorptive roots (responsible for resource acquisition), and transport roots. Aim: We examined how the different diameter cutoffs for root classification mirror concentrations of 11 different nutrients, plus Al in functionally different fine roots of Pinus sylvestris based on anatomical/ functional categorization and in relation to their biomass along a latitudinal gradient. Results: The C:N:P ratios for pooled roots ≤2 mm in diameter reflected the nutrient concentrations of transport roots. In contrast, the C:N:P ratios for all absorptive roots was best reflected by nutrient ratios in the 1st root order, and not by those in root <2 mm. These patterns were more clear along decreasing mean annual temperature, despite increasing contribution of absorptive roots in the fine root biomass. Higher biomass fraction of transport roots did not always mirror higher concentration of element accumulated. Narrowing the root diameter cutoffs to 0.5 mm provided more informative data about nutrient concentrations in the absorptive root pool than <2 mm cut-off. Conclusions: By analyzing nutrient concentration using ≤2 mm cut-off it is impossible to properly understand nutritional properties of roots with different functional attributes. Given that the diameter of fine root orders vary considerably even within a single species between stands, the diameter cutoffs for absorptive roots should be based on the characteristics of the studied species, and not on a fixed, universal diameter cutoff