Browsing by Subject "Regenwald"

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Agent-based modeling of human-environment interactions in a smallholder agricultural system in the Atlantic Forest (Ribeira Valley, SP, Brazil)
(2021) Munari, Lucia Chamlian; Berger, Thomas
Shifting cultivation systems (SCSs) have been practiced all over the tropics for centuries as the primary subsistence strategy for smallholders. However, since the mid-20th century, SCSs have been submitted to changes, driven by a combination of geographic, economic, socio-political, and demographic factors. Consequently, land use changes lead to agricultural intensification and the replacement of more profitable and permanent practices. The implementation of forest conservation policies (FCPs) is one of the changing drivers to SCSs. They have been designed to reduce or eliminate it, criminalize traditional practices, restrict resources access, displace locals, and increase inequalities and land conflicts. In Brazil, SCSs have been practiced by smallholders and indigenous groups, including Quilombolas, descendants of African enslaved who rebelled against the Portuguese regime. After the abolition of slavery, they remained spread over the country without any state legitimation. Their recognition and rights to ancestors land were possible only in 1988, with the Brazilian Constitution. The Ribeira Valley (Southeastern Brazil) is home to dozens of Quilombos, one of the most significant Atlantic Forest remnants, and high biodiversity. Its first Quilombos were formed in the 18th century and relied on SCS to survive, relatively isolated, up to the 1950s. However, in the context of SCS changes, Quilombos are under a transitional process in different dimensions, including constraints to their traditions by FCPs, generating conflicts. Inspired by this challenging scenario, the Thesis goals are to evaluate Quilombolas’ socioeconomic conditions and the perception of FCPs implementation and integrate two modeling tools. The tools will model the impact of agricultural transitions on family wealth, income, landscape structure, and tree community β diversity and model the impact of FCPs over the equal economic and ecological dimensions. Socioeconomic data were gathered in 2017 in 14 communities through interviews of 164 farmers. Quilombolas’ perception of FCPs and constraints for agricultural practice were investigated. The modeling implementation used MPMAS (Mathematical Programming-based Multi-Agent Systems) to simulate land use change in agriculture and forestry. MPMAS was integrated (through land use maps) with a Generalized Dissimilarity Modeling tool (GDM) to predict beta diversity as a function of environmental variation. The modeling exercise was implemented for Pedro Cubas territory, a Quilombo with 52 households located in Eldorado (SP). A combination of primary and secondary data from different sources was used, including a socioeconomic census of 2014 and a collection of tree data in 2016. Five economic/political scenarios were created for comparisons, with a baseline and four different counterfactual situations, varying in market access and FCPs versions. Seven yield curve scenarios and 30 Sobol’ repetitions were combined, totalizing 1050 simulations. A tradeoff analysis was applied over the political scenarios. MPMAS sensitivity/uncertainty analyses revealed variation on staples consumptions among yield curve scenarios, the sensitivity of income to different parameters, and each income source relevance. The GDM calibration highlighted the importance of climate predictors for tree species, indicating vulnerability to potential climate variability. Results revealed that only 32% of the families were practicing SCS in 2017, but it was still relevant for food security. 83% of the interviewees were unsatisfied with the FCPs, especially the timing of issuing the licenses for SCS. The political scenarios comparison indicates that agricultural intensification caused an improvement in average income. Still, it was accompanied by economic inequality, diminished rotation of plots, lower diversity of habitats, and a less permeable landscape structure (on fallows and because of the emergence of pasture and perennial areas). GDM results showed a significant change in landscape structure/tree community for at least 10% of the territory in the last decades. Regarding FCPs implementation, scenario comparison showed that well-being conditions improved when FCPs were excluded, although more ecological impacts occur. However, such effects refer to only 2.6% of the territory where 90% is covered by mature forest, and GDM indicates that the total ß diversity would not be significantly affected. The tradeoff analysis showed that FCPs are significant for conservation in the present context when perennials and pasture areas occur. In the isolated scenario case, when SCS is the only economic activity, a combination of good well-being and conservation performances was found, suggesting it is causing even lower environmental impacts. I recommend more flexible policies for SCS implementation in the Quilombos in general, for the potential of improving well-being conditions by impacting a small share of the territories. FCPs flexibilization would be even more relevant to the communities that don’t have access to alternatives to SCS.
Radial tree growth dynamics and xylem anatomy along an elevational gradient in the El Sira Mountains, Peru
(2019) Niessner, Armin; Küppers, Manfred
The explicit purpose of this study was to (1) characterize climate and vegetation along the western slope of the Cerros del Sira (Peru), (2) evaluate radial tree growth along this slope in response to seasonal rainfall anomalies, (3) reveal how the meteorological environment controls tree radial stem growth, and (4) to investigate how xylem anatomy relates to dynamics of tree growth. From May 2011 until September 2015, radial stem growth of 67 trees was monitored using point-dendrometers, and meteorological parameters were measured within five sites along an elevational gradient. Additionally, tree dimensions (stem diameter, stem height) and xylem anatomical traits (mean vessel diameter, vessel frequency, cumulative vessel area and potential hydraulic conductivity) were determined. The transect extends from lowland terra firme forests (ca. 250 m asl) over submontane forests, late and mid successional montane cloud forests up to exposed elfin forests (ca. 2200 m asl). Continuous rainfall records for remote tropical areas are extremely rare and measurements along this transect are also incomplete. Monthly rainfall estimates by the TRMM PR satellite ("product 3B42") were highly correlated with rain gauge observations, although they underestimate rainfall at high elevations. Different intra-annual tree growth patterns could be identified within each elevational forest type, showing species/individuals with seasonally independent continuous or alternating growth patterns and strictly seasonal growth. Stem growth at each site was typically higher during rainy seasons, except for in the elfin forest. The rainy season from October 2013 to March 2014 was extraordinarily dry, with only 73 % of long-term mean precipitation received, which resulted in reduced tree radial growth rates, again with the exception of the elfin forest. Different analytical approaches revealed that precipitation is the main growth-controlling factor at lower elevations, especially during rainy seasons. Growth within montane and cloud forests positively correlates to solar radiation. Tree growth within the elfin forest is only weakly correlated to meteorological parameters, but dry conditions during dry seasons promote growth. It was hypothesized that (1) individuals/species with large vessel diameters and low vessel frequencies have higher radial growth rates, but are more vulnerable to relatively dry periods. Therefore, (2) they are more likely to grow seasonally and predominantly during rainy seasons, (3) their growth during the exceptionally dry rainy season 2013/14 was more constrained, and (4) their growth is generally closer correlated to meteorological parameters. Larger trees tend to have larger vessel diameters, which positively relates to radial growth rates, and they also tend to grow more seasonal. As hypothesized, trees having large vessel diameters are more sensitive to droughts, as indicated by stronger positive correlations with rainfall and negative with solar radiation. However, in mountainous forests, relations between xylem anatomical traits and tree growth dynamics seem to be more complex. In late-successional cloud forests, growth of trees with large vessel diameter is positively, while of trees with small vessel diameter negatively related to solar radiation. Sensitivity to the dry rainy season 2013/14, expressed as relative reduction in growth compared to "normal" rainy seasons, could not be explained by xylem anatomical traits, contradicting the preceded hypothesis. Tropical lowland rainforest species, especially individuals with large vessels, will likely suffer from increasing drought frequencies and intensities. How montane forest ecosystems will react to a (globally) changing climate is rather uncertain, especially in exposed elfin forests. Results of this study suggest that species of late-successional tropical montane forests may profit from higher temperatures. While montane tropical rain forests may also suffer from prolonged droughts, exposed ridges covered by elfin forests still receive plenty of precipitation and may benefit from receiving more solar radiation for photosynthesis and, thus, grow faster.