Tree Diversity and Dynamics of the Forest of Seu Nico, Viçosa, Minas Gerais, Brazil

Abstract Background To understand future changes in community composition due to global changes, the knowledge about forest community dynamics is of crucial importance. To improve our understanding about processes and patterns involved in maintaining species rich Neotropical ecosystems, we provide here a dataset from the one hectare Forest of Seu Nico (FSN) Dynamics Plot from Southeastern Brazil. New information We report diameter at breast height, basal area and height measurements of 2868 trees and treelets identified from two census spanning over a nine-year period. Furthermore, soil properties and understory light availability of all 100 10 x 10m subplots from the one hectare FSN Dynamics Plot during the second census are given.


Introduction
Global changes such as habitat destruction, fragmentation and climate change threaten species richness and diversity of tropical forests (Wright 2010, Gastauer and Meira Neto 2013b, Magnago et al. 2014. To outline and understand their influences on tropical forest communities, long term monitoring studies, so-called community dynamics, are necessary (Losos and Leigh 2004, Wright 2005, Ernest et al. 2009).
Among tropical forests, the Brazilian Atlantic Forest is one of the most diverse terrestrial ecosystems (Stehmann et al. 2009). Due to its high degree of endemism and endangered status it is considered a biodiversity hotspot (Myers et al. 2000). Once covering up to 1,500,000 km (Câmara 2005), only about 11 % of the original Brazilian Atlantic Forest remains, most of it as small secondary forest patches (Ribeiro et al. 2009). Species rich old-growth forests such as the Forest of Seu Nico (FSN) in the Viçosa municipality, Minas Gerais, Brazil are extremely rare and poorly studied (Campos et al. 2006, Gastauer and Meira Neto 2013a, Gastauer and Meira Neto 2013b. The aim of this data paper is to distribute dynamics data from the FSN Dynamics Plot in order to increase knowledge about community composition and maintenance in the Brazilian Atlantic Forest. criterion was measured and the absolute height of trees was estimated. For multiple stem individuals, we calculated basal area at breast height for all shoots, summed these areas up and calculated from that the pooled circumference. dbh was computed from circumference assuming circular cross section of stems. Specimens not recognized during field surveys were collected, deposited in the Herbarium of the Federal University of Viçosa (VIC) and identified with the help of material from the VIC, by consultation of specialists and/or literature. Species names were checked using the Taxonomic Name Resolution Service (TNRS) as proposed by Boyle et al. (2013); species classification follows Angiosperm Phylogeny Group III (2009).
During the second census, three soil samples were collected in each plot following a standardized protocol. For each sample four to five sampling points were defined, their systematic arrangement within each plot is shown in Gastauer and Meira Neto (2013b). At each sampling point, the organic layer was removed and a soil block of 10 × 10 × 20 cm (length × width × depth) was collected. Blocks from the same sample were mixed before 500 g were weighed, stored in a plastic bag and transported to the lab. Immediately after arrival at the lab, the soil samples were air-dried.
The following parameters were analyzed in the laboratories of the Soil Department of the Federal University of Viçosa: soil acidity as pH (extraction with water); the concentrations of phosphorus, potassium (both Mehlich 1 extraction), calcium, magnesium, and aluminum (extracted with 1 mol/L KCl); interchangeable bases; the effective cation exchange capacity as well as the cation exchange capacity at pH 7; and the saturation of bases, aluminum and remnant phosphorus.
Additionally, the understory light availability was analyzed by hemispherical photography during the second census. A digital camera (Nikon Coolpix 5700) was combined with an adapter and a fish-eye lens (Nikon FC-E9). For photography, the camera was mounted on a tripod. Within each plot, one photo was taken from plot´s center at an altitude of one meter above soil level. As direct light affects data interpretation and analysis, hemispherical photos were taken only when sky was perfectly overcast. Canopy openness, i.e. the percentage of open sky seen from beneath a forest canopy, as well as the amount of direct, diffuse and total solar radiation transmitted by the canopy were calculated by the software Gap Light Analyzer 2.0 (Frazer 1999).

Taxonomic coverage
Description: Altogether 2868 trees belonging to 228 (morpho-)species from 54 families and 139 genera were sampled during both censuses (Table 1). Due to the lack of appropriate material (e.g., fruits or flowers) to provide a definite identification, 25 morphospecies remain partially or completely unidentified. 2143 individuals that were still present were resampled during the second census. Although species richness and diversity declined from the first to the second census (Gastauer & Meira-Neto 2013), they are still outstanding for the region ( In terms of basal area, Moraceae is the most abundant family, while Fabaceae head the ranking in terms of species richness and Myrtaceae in number of individuals (Table 3).
Ficus and Pseudopiptadenia are the most abundant genera in terms of basal area, while Siparuna, Protium and Sorocea are represented with the highest number of individuals and Ocotea, Psychotria and Casearia are most species-rich genera (Table 4). Three genera 2 Table 1.
FSN plot census history.   The largest tree in the sample is a Ficus gomelleira (dbh of 2.08 m), three further trees show a dbh lager than 1 m (Ceiba speciosa, Sterculia curiosa and Astronium graveolens) which explains the high rank of these species in terms of basal area (

Temporal coverage
Notes: see Table 1 Usage rights

Additional information Environmental data coverage
Minimum and maximum values of canopy openness differ by the factor 4.5, effective leaf area index show a twofold variation. Higher variation (factor 10) was observed for direct radiation than for diffuse radiation (factor 4), so that total radiation varies by factor 6 within the 100 subplots (Table 7). Nevertheless, influence of canopy openness or amount of radiation on tree species distribution has not yet been evaluated.  Minimum and maximum values of soil acidity, remnant phosphorus, cation exchange capacity at pH 7, nitrogen availability and organic material differ by the factor 1.4 to 2 among the 100 subplots; effective cation exchange capacity, potential soil acidity and phorphorus availability by factors between 2 and 3; potassium availability by factor 10 and saturation of bases, saturation of aluminium and availability of magnesium by factors up to 60. Aluminium saturation ranges from 0 to 95.1%, while aluminium and calcium availability range from 0 to 2.89 and 3.66 cmol /dm , respectively (Table 7). Nevertheless, soil variation explains only around 13% of species distribution within the 100 plots (Gastauer and Meira Neto 2013b).
As shown by Gastauer and Meira Neto (2013b), soil acidity increases with availability of potassium, calcium, magnesium as well as nitrogen. Furthermore, saturation of bases, effective cation exchange capacity, remnant phosphorus and nitrogen correlate positively with soil acidity, which decreases with increasing availability of aluminium. Phosphorus availability, on contrast, correlates positively with organic matter. Soil acidity does not correlate with percentage of canopy openess, but is correlated weakly with the amount of total solar radiation transmitted by the canopy (Gastauer 2012): The higher soil acidity, more light reaches understory. Aluminium availability, on the other hand, is significantly correlated with percentage of canopy openess and total solar radiation transmitted by the canopy. Percentage of canopy openess and total solar radiation transmitted by canopy is not correlated to number of individuals or species per plot, but pH correlates positively with per plot basal area and negatively with number of species and individuals per plot.
As outlined in Gastauer and Meira Neto (2013b), there is a soil gradient from south to north within the FSN dynamics plot. Southern subplots are more acidic, i.e., show lower soil acidity, have lower nitrogen, potassium and phosphorus contents, lower calcium and magnesium availability, a higher aluminium availability and lower saturation of bases as well as a lower effective cation exchange capacity than northern plots.
Due to correlations between soil properties and understory light availability, the percentage of canopy openess as well as the amount of solar radiation transmitted by canopy are higher in southern than in northern plots (

Description of the Darwin Core Archive containing dataset
Column labels and descriptions of further Darwin Core Archive files from both datasets are given at  Table 8.
Canopy openness and total understory radiation (mean and standard deviations) in northern and southern subplots from the FSN dynsamics plot. P is significance level of difference according to a two-tailed t-test. Table 9.