Aboveground biomass


This paper compares aboveground forest structure and macronutrient stoichiometry over 5 15 years of hurricane induced secondary succession by species, life history groups, community 6 species composition, and geomorphic setting. Stem density continually increased after the 7 impact of the Category 4 hurricane Hugo and 15 years later, it was greater than pre-hurricane. 8 There were significant spatial and temporal differences in the number of species, the diversity 9 index per plot, forest structure, and biomass. The greatest compositional differences occurred 10 between the post-Hugo and the 15-year census. Prior to hurricane Hugo most plots had very 11 similar species composition and abundances, and thus occupied a small area in non-metric 12 multidimensional species space. Following the hurricane new species combinations occurred 13 and the location of plots was spread in multidimensional space. Diversity indices were 14 significantly different among geomorphic settings before and immediately after hurricane Hugo. 15 However, these differences were not observed again until the 15-year census where they returned 16 to pre-hurricane levels. Plant associations based on abundance, life history traits, and landscape 17 position had measurable differences in their structure, composition, aboveground nutrient 18 storage, and stoichiometry. However, these differences were reflected in a variety of ways at 19 different spatial scales. At the species level differences in macronutrient tissue concentrations 20 were apparent when comparing co-existing primary forests dominants, early successional 21 dominants, high-light and low-light species, and species whose stem densities are negatively 22 correlated. Community level differences were greater for forest structure and total nutrient 23 storage compared to the mass weighted concentrations of macronutrients. The largest differences observed were in Mg and can be attributed to the succession of pioneer species 2 following the hurricane. Over the entire 15-year period, the watershed average aboveground 3 stoichiometry was relatively consistent and this is linked to the biomass dominance of a few 4 species. The successional history recorded here also suggests that community level differences 5 in species composition, structure, and stoichiometry were well established after 10 to 15 years of 6 secondary succession.

Impacts of disturbance initiated by road construction in a subtropical cloud forest in the Luquillo Experimental Forest, Puerto Rico

Olander, Lydia P.; Scatena, F.N; Silver, Whendee L. 1998. Impacts of disturbance initiated by road construction in a subtropical cloud forest in the Luquillo Experimental Forest, Puerto Rico. Forest Ecology and Management 109 ;33-49.

The impacts of road construction and the spread of exotic vegetation, which are common threats to upper elevation tropical forests, were evaluated in the subtropical cloud forests of Puerto Rico. The vegetation, soil and microclimate of 6-month-old road®lls, 35-year-old road®lls and mature forest with and without grass understories were compared. Recent road®lls had higher light levels, soil temperatures, bulk densities, larger pools of exchangeable soil nutrients and higher soil oxygen concentrations; but lower soil moisture, soil organic matter and total soil N than the mature forest. On the 35-year-old road®lls, bulk density, soil pH and P pools were statistically similar to the mature forest while soil moisture, total N and base cations were different. The total aboveground biomass of 6-month-old road®lls was about 2 Mg/ha and dominated by a variety of monocot and herbaceous species. The 35-year-old road®ll areas had a biomass of 10.5 Mg/ha, 77% of which was nonwoody. Seedling density, tree density and total woody biomass were 12, 28 and 2% of mature forest sites, respectively. In these areas, where soils were disturbed during construction, accumulation of biomass is the slowest known for the LEF. It may take 200-300 years for biomass to attain mature forest levels. In areas that were not directly disturbed during construction, the road has had little effect on the vegetative composition beyond a 5±10 m zone immediately adjacent to the pavement. Although non-native monocots, one of which had been planted along the road 35 years earlier, were copious along the disturbed roadside, they were generally absent from the mature forest and only abundant in habitats of anthropogenic origin.

Changes in Structure, Composition, and Nutrients During 15 Yr of Hurricane-Induced Succession in a Subtropical Wet Forest in Puerto Rico

Heartsill Scalley, Tamara; Scatena, Frederick N.; Lugo, Ariel E.; Moya, Samuel; Estrada Ruiz, Carlos R. 2010. Changes in structure, composition, and nutrients during 15 years of hurricane-induced succession in a subtropical wet forest in Puerto Rico. Biotropica. 42(4): 455-463.

The trajectory of hurricane-induced succession was evaluated in a network of forest plots measured immediately before and 3 mo, 5, 10, and 15 yr after the direct impact of a Category 4 hurricane. Comparisons of forest structure, composition, and aboveground nutrients pools were made through time, and between species, lifehistory groups and geomorphic settings. The hurricane reduced aboveground biomass by 50 percent, causing an immediate decrease in stem density and diversity indices among all geomorphic settings. After 15 yr, basal area and aboveground biomass returned to pre-hurricane levels, while species richness, diversity indices, and stem densities exceeded pre-hurricane levels. Differences in species composition among geomorphic settings had not returned after 15 yr but differences in stem densities and structure were beginning to emerge. Significant differences were observed in the nutrient concentration of the three species that comprised the most aboveground biomass, and between species categorized as secondary high-light species and primary, low-light species. Species whose abundance was negatively correlated with the mature forest dominant also had distinct nutrient concentrations. When total aboveground nutrient pools were compared over time, differences in leaf nutrients among species were hidden by similarities in wood nutrient concentrations and the biomass dominance of a few species. The observed successional trajectory indicates that changes in species composition contributed to fast recovery of aboveground biomass and nutrient pools, while the influence of geomorphic setting on species composition occurs at time scales 415 yr of succession.
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