Alexander Tischer

Afforestation or intense pasturing improve the ecological and economic value of abandoned tropical farmlands

Increasing demands for livelihood resources in tropical rural areas have led to progressive clearing of biodiverse natural forests. Restoration of abandoned farmlands could counter this process. However, as aims and modes of restoration differ in their ecological and socio-economic value, the assessment of achievable ecosystem functions and benefits requires holistic investigation. Here we combine the results from multidisciplinary research for a unique assessment based on a normalization of 23 ecological, economic and social indicators for four restoration options in the tropical Andes of Ecuador. A comparison of the outcomes among afforestation with native alder or exotic pine, pasture restoration with either low-input or intense management and the abandoned status quo shows that both variants of afforestation and intense pasture use improve the ecological value, but low-input pasture does not. Economic indicators favour either afforestation or intense pasturing. Both Mestizo and indigenous Saraguro settlers are more inclined to opt for afforestation.

Land-use and soil depth affect resource and microbial stoichiometry in a tropical mountain rainforest region of southern Ecuador

Abstract Global change phenomena, such as forest disturbance and land-use change, significantly affect elemental balances as well as the structure and function of terrestrial ecosystems. However, the importance of shifts in soil nutrient stoichiometry for the regulation of belowground biota and soil food webs have not been intensively studied for tropical ecosystems. In the present account, we examine the effects of land-use change and soil depth on soil and microbial stoichiometry along a land-use sequence (natural forest, pastures of different ages, secondary succession) in the tropical mountain rainforest region of southern Ecuador. Furthermore, we analyzed (PLFA-method) whether shifts in the microbial community structure were related to alterations in soil and microbial stoichiometry. Soil and microbial stoichiometry were affected by both land-use change and soil depth. After forest disturbance, significant decreases of soil C:N:P ratios at the pastures were followed by increases during secondary succession. Microbial C:N ratios varied slightly in response to land-use change, whereas no fixed microbial C:P and N:P ratios were observed. Shifts in microbial community composition were associated with soil and microbial stoichiometry. Strong positive relationships between PLFA-markers 18:2n6,9c (saprotrophic fungi) and 20:4 (animals) and negative associations between 20:4 and microbial N:P point to land-use change affecting the structure of soil food webs. Significant deviations from global soil and microbial C:N:P ratios indicated a major force of land-use change to alter stoichiometric relationships and to structure biological systems. Our results support the idea that soil biotic communities are stoichiometrically flexible in order to adapt to alterations in resource stoichiometry.

Fire enhances phosphorus availability in topsoils depending on binding properties

Fire can have large effects on ecosystems, with phosphorus being highly important in this regard, especially when considering productivity in burned or adjacent ecosystems after fire. Unfortunately, existing data pose contradictions and methodological challenges to assessing P availability. Here, the impact of fire on topsoil available P was estimated using three different types of organic soil layers (raw humus from spruce, humus from beech, and peat) and two fire regimes (obtaining black carbon and ash). Our findings suggest a strong fire impact on P availability, by enhancing available P during burning to black carbon (~10-fold), and to ash (~2- to 7.5-fold) dependent on calcite content. Fire impact on P availability is on a similar order of magnitude as mineral weathering and annual P cycling/uptake in/by ecosystems. Furthermore, the proportion of available P in relation to total P depends on the origin of the organic soil layers. When related to the remaining mass after burning, as is commonly done, ...

Current Provisioning Services : Pasture Development and Use, Weeds (Bracken) and Management

This chapter reports on the historical expansion and current state of the pastures in the Rio San Francisco valley. Its major part is inhabited by the Mestizos, who do not have a long-standing pasture tradition. Three types of pastures were identified by the dominant grass species: the “pastos azules” (Holcus lanatus), the Yaragua pastures (Melinis minutiflora) and the dominating “pastos mieles” (Setaria sphacelata). The peculiarities, species composition, soil dynamics and agricultural values of these pastures are discussed. Except for the pastos azules on small flattenings in the otherwise steep slopes of the valley, pastures in the area suffer from invasion by aggressive weeds, mainly the tropical bracken fern. Abandonment of pastures is fostered by the use of fire to combat weeds and stimulate grass growth. This type of low-yield pasture farming is not sustainable. The earnings of livestock farming are not sufficient for subsistence. Diversification of the income portfolio is necessary.

Future Provisioning Services: Repasturisation of Abandoned Pastures, Problems, and Pasture Management

More and more pastures in the Rio San Francisco valley were and still are abandoned as a result of ecologically unbalanced pasture management, which promotes the invasion of weeds like bracken. Under the common pasture management, using fire as an agricultural tool, bracken by virtue of several ecophysiological traits can outcompete the grass. Competition of both species was investigated by the growth model SoBraCoMo. Vegetation development after burning of a bracken-infected pasture was followed by automated monitoring, using a balloon. To rehabilitate abandoned pastures, a three-step experiment was performed. Bracken control was followed by planting of the pasture grass Setaria sphacelata. Subsequently, different strategies for pasture management were examined. Fertilisation was crucial for the achievement of reasonable yields as well as for bracken suppression. Additionally, the prevention of negative nutrient balances of active pastures was investigated in an extended pasture fertilisation experiment (FERPAST). A specific combination of N and P is necessary to maintain soil productivity and to increase fodder quality.

Proteome data on the microbial microbiome of grasshopper feces

We present proteome data from the microbiota (feces) after a diet shift from a natural diverse to a monocultural meadow with Dactylis glomerata. The abundant grasshopper species, Chorthippus dorsatus, was taken from the wild and kept in captivity and were fed with Dactylis glomerata for five days. For phytophagous insects, the efficiency of utilization of hemicellulose and cellulose depends on the gut microbiota. Shifts in environmental and management conditions alter the presence and abundance of plant species which may induce adaptations in the diversity of gut microbiota. The mass spectrometry proteomics data have been deposited to the ProteomeXchange Consortium via the PRIDE partner repository with the dataset identifier PXD005126.