Abstract
We analyze here how much carbon is being accumulated annually by secondary tropical dry forests (TDFs) and how structure, composition, time since abandonment, and climate can influence the dynamics of forest carbon accumulation. The study was carried out in Santa Rosa National Park in Guanacaste province, Costa Rica and Mata Seca State Park in Minas Gerais, Brazil. Total carbon storage and carbon accumulation were obtained for both sites from the sum of the aboveground carbon and belowground carbon gain plus the annual litterfall. Carbon accumulation of these TDFs varied from 2.6 Mg C ha−1 y−1 to 6.3 Mg C ha−1 y−1, depending on the age of the forest stands. Time since abandonment and number of stems per plot were the best predictors for carbon storage, annual carbon gains, and losses. Mortality rates and carbon losses were also associated with seasonal climate variability. We found significant correlations between tree mortality, carbon losses and mean seasonal temperature, mean seasonal precipitation, potential evapotranspiration, and the Oceanic Niño Index. Carbon dynamics in tropical dry forests are driven by time since abandonment and forest structure; however, rising temperature and El Niño Southern Oscillation (ENSO) events can have a significant impact on tree mortality and carbon losses. Depending on their location and land-use history, some dry forests are more impacted by climatic extremes than others, and differences between secondary stages are expected.
Highlights
The current extent of tropical dry forests (TDFs) has been reduced globally by 48.5%and 66% in the Neotropics [1]
We quantified biomass and carbon dynamics in two TDFs over a 12-year period along a successional gradient to address the following questions: (i) How much carbon is being accumulated annually by secondary TDFs of different ages?; (ii) How do structure, composition, and time since abandonment influence the dynamics of forest carbon accumulation?; (iii) How does climate affect mortality, and carbon accumulation across stand ages? We addressed these questions in two TDFs, representing two extremes in the spectrum of TDFs along a precipitation gradient
For the linear relationship between the annual carbon losses from at eachJune site separated by successional stage and the seasonal climatic variables (MSP, mean seasonal seasonal temperature (MST)), we found significant losses, we found significant correlations with MST, PET, and ONI in the month relationships (p < 0.05) for the Mata Seca State Park (MSSP) only with increasing MST (Figure 5)
Summary
The current extent of tropical dry forests (TDFs) has been reduced globally by 48.5%and 66% in the Neotropics [1]. The current extent of tropical dry forests (TDFs) has been reduced globally by 48.5%. The few remnants of TDFs that used to be large continuous tracts of forest cover in lowlands and submontane areas are highly fragmented patches under high anthropogenic pressure [1]. Secondary TDFs are increasingly dominant in tropical regions, and they currently occupy more area than old-growth forests [2,3]; it remains unclear how these secondary TDFs cope with current and predicted climate change. In the case of TDFs, changes in climate, forest structure, and diversity loss would add even more stress to these highly fragmented, threatened, disturbed, and understudied ecosystems [1,4,5,6]. Tropical secondary dry forests are important aboveground and belowground carbon reservoirs [7,8,9].
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