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Publisher Copyright: © 2022 Northern forest soils are a major carbon (C) reservoir of global importance. To estimate how the C balance in these soils will change, the roles of tree roots and soil microbes in C balance should first be decoupled. This study determined how the activity of heterotrophs and tree roots together with root-associated microbes in the rhizosphere varies in coniferous forest soils in boreal, hemiboreal, and temperate climates along a latitudinal gradient using a trenching approach. We created experimental plots without living tree roots, measured soil respiration (CO2 efflux) from these and from unmanipulated plots using the chamber technique, and partitioned the efflux into root-rhizosphere (RR) and heterotrophic (RH) respiration. The share of RR in ecosystem gross primary production (GPP) decreased from north to south in the Scots pine (Pinus sylvestris L.) and the Norway spruce (Picea abies (L.) Karst.) forests, with the exception of a mixed site, where the share of RR in GPP varied strongly between the years. RR per ground area and per root biomass were mainly independent of climate within the gradient. RH per ground area increased from north to south with temperature, while RH per soil C did not change with temperature. Soil moisture did not significantly affect the respiration components in the northernmost site, whereas soil moisture was positively connected with RH and negatively with RR in other Scots pine sites and positively connected with RR in pure Norway spruce stands. The dynamic ecosystem model LPJ-GUESS was able to capture the seasonal dynamics of RH and RR at the sites, but overall accuracy varied markedly between the sites, as the model underestimated RH in the southern site and RR elsewhere. Our study provides knowledge about the nature of soil respiration components. The valuable insights can be used in more accurate land-ecosystem modelling of forest ecosystems.

This paper presents a multi-site (>20) analysis of the relative and absolute energy balance (EB) closure at European FLUXNET sites, as a function of the stability parameter xi, the friction velocity u., thermally-induced turbulence, and the time of the day. A focus of the analysis is the magnitude of EB deficits for very unstable conditions. A univariate analysis of the relative EB deficit as function of xi alone (both for individual sites and a synthesis for all sites), reveals that the relative EB deficit is larger for very unstable conditions (xi < -1.0) than for less unstable conditions (-0.02 > xi >= -1.0). A bivariate analysis of the relative EB deficit as function of both xi and u., however, indicates that for situations with comparable u. the closure is better for very unstable conditions than for less unstable conditions. Our results suggest that the poorer closure for very unstable conditions identified from the univariate analysis is due to reduced u. under these conditions. In addition, we identify that the conditions characterized by smallest relative EB deficits (elevated overall turbulence, mostly during day time) correspond to cases with the largest absolute EB deficits. Thus, the total EB deficit at the sites is induced mostly under these conditions, which is particularly relevant for evapotranspiration estimates. Further, situations with the largest relative EB deficits are generally characterized by small absolute EB deficits. We also find that the relative EB deficit does generally not correspond to the regression line of absolute EB deficit with the net radiation because there is a (positive or negative) offset. This can be understood from theoretical considerations. Finally, we find that storage effects explain a considerable fraction of the large relative (but small absolute) nocturnal EB deficits, and only a limited fraction of the overall relative and absolute EB deficits. (C) 2010 Elsevier B.V. All rights reserved.

Depressive disorders belong to the most frequent psychiatric disorders in Western Europe and the U.S.A. and are associated with high recurrence rates, high resistance to therapy, morbidity and mortality [1-4]. Currently, depressions have a share of 6.1% in total DALYs (DALY = Disability-Adjusted Life Year = as measure for disease burden), and thus are ranked at the 4th place in worldwide causes of disease [4]. It is expected that unipolar de‐ pression will become the main health-related cause of death in developed countries by 2020 [5,6]. In the E.U. alone, 18.5 million people have been diagnosed with major depression [7].

[1] Heterogeneity in small-scale subsurface flow processes does not necessarily lead to complex system behavior at larger scales. Here we use the simple dynamical systems approach recently proposed by Kirchner (WRR, 2009) to analyze, characterize, and simulate streamflow dynamics in the Swiss Rietholzbach catchment. The Rietholzbach data set used here provides 32 years of continuous and high-quality observations, which include a soil moisture profile and unique observations of storage changes and evapotranspiration measured by a weighing lysimeter. Streamflow recession at the daily time scale shows a marked seasonal cycle and is fastest in summer due to the higher evapotranspiration losses. The discharge sensitivity function linking storage and discharge is nonlinear and slightly downward-curving in double-logarithmic space. Small diurnal discharge fluctuations prevent application of the approach at the hourly resolution for low-discharge conditions. The vast majority of runoff peaks can be explained by storage variations, except peaks that follow events with extreme precipitation intensity (30–40 mm h−1). Storage change dynamics inferred from streamflow variations compare well to observations from the lysimeter and simulations with a land surface model but become very uncertain under dry conditions. Good results can be obtained when the discharge sensitivity function is calibrated on a monthly time scale to avoid the effect of the diurnal discharge fluctuations. Our analysis highlights the importance of evapotranspiration for catchment hydrology, as it is the main driver of changes in streamflow at Rietholzbach for 21% of the time.