Calcium and Magnesium Dynamics in Litter in a Successional Forest Ecosystem, Under Hydroperiod

This study was part of the Manipulation of Moisture and Nutrient Availability in Young Regrowth Forests in Eastern Amazonia Project (MANFLORA). The experiment was designed in completely randomized blocks containing control and irrigated treatments during the dry period (5 mm of water/day), with four repetitions each. The monthly mean litter values ranged from 316.10 to 997.90 kg ha-1 month-1. The magnitude of this phenomenon can be explained by the functional role of the floristic structure, represented by the species Myrcia sylvatica (G. mey) DC., Myrcia bracteata (Rich) DC., Miconia ciliata (Rich) DC., Lacistema pubescens Mart., Lacistema aggregatum (Berg.) Rusby, Vismia guianensis (Aubl.) Choisy, Cupania scrobiculata Rich. and Ocotea guianensis Aubl., which constituted the determinant factors, associated with the hydroperiodic effect and ecosystem manipulation. The monthly mean of the analytical results of mass treatments were significant (P < 0.05), however, when compared annually there was no significance, which indicates seasonal influence, since the period of greatest deposition is the dry one, regardless of the water manipulation along the period studied. Only in time the mass values of Ca and Mg were not significant for treatment (P < 0.05). The amount of Ca was significantly (P < 0.05) higher than that of Mg.

Soil organic matter dynamics in changing forests: linking ecosystem manipulation experiments with soil inventories across Switzerland

<p>Forest soils are storing large quantities of carbon, but their quantitative role in sequestering C is less certain. In principal, soils developed over millennia are assumed to be ‘in equilibrium’ with minimal C stock changes. This concept is challenged by forest soil inventories (in Germany and France) indicate a substantial increase in soil C storage. However, soil organic matter (SOM) storage is susceptible to recent changes in forests - climate warming and droughts, increasing forest disturbances, and a more intensive forest management are all potentially increasing SOM turnover which may turn forest soils into C sources. Here, I will critically discuss the role in Swiss forest soils as C sinks by presenting data from 1000 soil profiles across environmental gradients and from flux measurements in large scale ecosystem manipulation experiments.</p><p>Swiss forests soils are among the C-richest soils in Europe storing on average 140 t C/ha. Analysis of 1000 forest soils show that these SOM stocks are caused by their high contents in potential SOM sorbents (pH, Al+Fe-oxides, Ca, clay), but also by the cool temperatures and high amounts of precipitation. Climate manipulation experiments suggest Swiss forest soils are vulnerable to loose C with expected climatic changes. A six year long soil warming experiment at treeline revealed soil C losses, while a 15 year long irrigation experiment in a dry forest induced C gains in the mineral soil, implying that a warmer and more frequent droughts will lead to C losses.</p><p>Switzerland - as other European mountainous areas – is currently experiencing a major change in land-use due to land abandonment, with the forests expanding by 3 to 4% per decade. Forest expansion affects a multitude of factors driving SOM cycling and storage, including the quantity and quality of organic matter inputs above and below the ground, a cooler and drier microclimate, and change in microbial diversity and activity. In contrast to the intuitive assumption that forests expansion leads to C gains in soils, measurements along an afforestation chronosequence of alpine grassland show that forest expansion leads to minimal changes in SOM stocks but a strong change in SOM quality. Soils gains in particulate organic matter with increasing forest age but lose C in mineral-associated organic matter. In support, reconstructing forest cover ages of 850 soil profiles showed that forest age and hence time since conversion into forest (predominantly from grasslands) did not significantly affect total SOM stocks, while other factors, especially physico-chemical soil characteristics and climate were more important. Overall, these results show that the inherently C rich forest soils in Switzerland are unlikely to gain additional C but rather loose it in response to the ongoing changes in climate and land-use. </p>

Falcon constructed artificial catchment for whole ecosystem manipulation how we build it and what are the first results

<p>Subsurface processes are often omitted in catchment studies here we presented artificial catchment as a new tool to study and budget these processes on catchment level.</p><p>Falcon is and artificial  catchment that build in Sokolov post mining sites Catchment consist from four separate micro catchments (pools) each ) 0.25ha in area and 2m in depth which are hydrologically isolated  and filled by post mining overburden. Two fields were levelled while in two was wave like surface was produced to mimic situation after heaping.  Leveled micro catchments were planted by alder (Alnus glutinosa).</p><p>Catchment allow to study meteorological variables, surface and subsurface runoff,  and other key ecosystem parameters (water table depth chemical composition of pore water, soil respiration, gas exchange between ecosystem and surrounding atmosphere using eddy tower etc.). First result show large erosion on waves then on levelled sites however large proportion of material eroded from flat site leave the site while in wave like surface most of it is trapped in depression between waves. Subsurface runoff form large proportion of total runoff in wavy sites than in flat sites. Stable water table established quickly in both types of catchments} few months after catchment establishment. Flat sites show higher initial diversity of plants.</p>

Understanding drought induced responses in leaf and root CO2 and VOC fluxes through position specific isotope labelling

<p>Climate change exerts increasing pressure on tropical rainforests enhancing their susceptibility to environmental stress. Plants' abilities to rapidly adjust their metabolism are critical for reducing the stress effects caused by extreme external conditions. Plants produce a wide spectrum of volatile organic compounds (VOCs) to cope with oxidative and thermal stress. The distribution and amount of VOC production thereby vary greatly not only among species but also organs, such as leaves and roots. Within the framework of our large-scale ecosystem manipulation experiment, Biosphere 2 Water, Atmosphere, and Life Dynamics (B2-WALD), we aimed to produce deeper insights into carbon partitioning between primary and secondary metabolism under drought stress, notably into CO<sub>2</sub> and VOCs.</p><p>In particular, we investigated how drought stress influences organ-specific carbon allocation between processes of primary and secondary metabolisms and to what extent allocation into secondary metabolism protects plants from drought. The tropical rainforest mesocosm in Biosphere 2, University of Arizona, provides a unique system for ecosystem manipulation studies. We implemented a drought stress experiment, excluding rainfall for two months. To investigate changes in carbon allocation, we performed labelling experiments with position-specific <sup>13</sup>C-labelled pyruvate on leaves and roots of several tropical tree and shrub species before and during the drought period. We used <sup>13</sup>CO<sub>2</sub> laser spectroscopy and high-sensitivity proton-transfer-reaction time-of-flight mass spectrometry to enable real-time analysis of metabolic pathways and carbon turnover, using leaf- and root-chambers to quantify fluxes.</p><p>Considering our preliminary results, net CO<sub>2 </sub>assimilation strongly declined under rain exclusion, due to stomatal closure. Consequently, respiration rates declined strongly in leaves as well as in roots. The response of VOC emissions, however, varied among organs. In leaves, we found that the emission of some VOCs declined under drought stress (acetone, monoterpenes), while other fluxes increased or stayed the same (isoprene). We will present detailed data on [1-13C]- and [2-13C]-pyruvate allocation within primary and secondary metabolism, such as decarboxylation processes and VOC-production. To our knowledge, this is the first time that real-time measurements of <sup>13</sup>C-labelled root VOC-emissions were conducted, enabling this comparative analysis of drought induced stress effects on leaf- and root-emissions.</p>