Successional Immobilization of Nutrients and Biologically Mediated Recycling in Tropical Forests

Abstract

A review of the literature shows a less-than-satisfactory number of detailed studies upon which can be based either a viable synthesis or a test of the major hypotheses on the relationship between nutrients and secondary succession in tropical forests. Data from several of the major works are summarized as an example of the state of our knowledge on the biological immobilization of nutrients. Less understood are processes associated with biologically mediated recycling in tropical forests. Reported examples of functional biological adaptations associated with the storage and/or cycling of nutrients are discussed within the context of theories proposed by others to suggest the most profitable future directions for research. THE PRIMARY PURPOSE OF THIS PAPER is to explore the state of our knowledge relative to both the biological immobilization of nutrients in tropical forest succession and to aspects of subsequent recycling within the more mature forest. Further, an attempt will be made to identify the subject area(s) where the most profitable gains in knowledge might be expected to originate. The few data summarized here are representative of the state of our knowledge, and, although thin and sparse in places, suggest that additional research will most likely result in a significant advancement in our knowledge. The literature dealing with the immobilization of nutrients in tropical forest succession appears bountiful but is, in fact, filled with significant gaps and frequently lacks the kinds of documentation that are requisite for synthesis. For instance, elemental concentrations of the tissues of tropical forest species have been presented in detail for successional species (Snedaker and Gamble 1969) and for species typical of later successional stages (Nye 1958, Ovington and Olson 1970, Stark 1971a and b, Golley et al. 1975). The concentrations of the nutrient elements are, in general, so uniform as to preclude identifying an overall trend associated with succession or a particular stage therein; documentation as to age, soil characteristics, local climate, etc. is either not adequately presented or is not suitably correlated with the measurements. Also, there is no basis for assessing spatial variability which could result in sampling artifacts. It is evident, however, that correlations are possible relating tissue concentrations with the mineral characteristics of the soils, and regional and climatic differences (vide Stark 1971a and b, Golley et al. 1975). Data also exist, along with some level of documentation correlating nutrient stocks with age of succession, but measurements are presented for too few ecosystem compartments and generally only the macronutrients are emphasized. A selection of these data is summarized in table 1. They reveal both significant gaps (measurements for wood biomass are rare even though it is the biomass compartment most closely correlated with the successional stage) and the lack of any significant trend in the stock of foliar nutrients. The data that are available do show the expected: that the total stock of nutrients biologically immobilized does increase with successional developinent as a result of an increasing wood biomass (see also Rodin and Bazilevich 1967). The quantity of nutrients immobilized in the leaves (table 1) does not increase due to an early stabilization in leaf biomass. Data and information on the micronutrients and trace metals are equally limited in the scope of coverage for tropical successional forests and also tropical forests, in general. The most complete data are reported by Golley et al. (1975), Odum and Pigeon (1970), Snedaker and Gamble ( 1 969), Snedaker et al. (1977), and Stark (197 lb), and selected data therefrom on the concentrations of these elements are summarized in table 2. These simply show a much greater variation among sites and successional stages than do the macronutrients and probably reflect both differences in the local surficial geology and the introduction of extraneous materials into the environment, as appears to be specifically the case for tropical mangrove forests. Differences among species in the concentrations of micronutrients and trace metals (vvide Snedaker and Gamble 1969, Ovington and Olson 1970) probably also reflect physiological differences among those species. Of course, one must always be aware of the variation which may be due solely to sampling and analytical techniques, particularly when making interstudy comparisons. 16 TROPICAL SUCCESSION 16-22 1980 This content downloaded from 157.55.39.211 on Tue, 09 Aug 2016 05:06:13 UTC All use subject to http://about.jstor.org/terms TABLE 1. Standing stock biomass (dry weight) and leaf compartment macronutrient inventories in selected tropical lowland successional and mature forests. Leaf compartment (gmis mr2) Vegetation Total age Vegetation biomassa (yrs) Location type (gms mr2) Biomass N P K Ca Mg Reference 1 Izabal, Heliconia 779 779b 9.1 0.5 14.2 2.6 6.8 Popenoe Guatemala fallow (unpublished) 1 Izabal, Mixed spp. 874 874e 11.7 0.9 10.0 5.5 6.0 Tergas 1965 Guatemala fallow 1 Izabal, Mixed spp. 836 706 14.4 1.1 8.3 7.0 4.8 Sncdaker 1970 Guatemala fallow 2 Belgian Mixed spp. 1323 787 10.5 1.2 10.2 ( 7.7 ) Bartholomew et al. Congo fallow 1953 2 Darien, Mixed spp. 1302 362 0.4 4.2 15.7 1.3 Golley et al. 1968 Panama fallow(1 2 Darien, Mixed spp. 2436 296 0.3 5.0 3.5 1.3 Golley et al. 1968 Panama fallowe 2 Guarin, Mixed spp. 1584 260 -Ewel 1968 (in Gamble Colombia fallow et al.) 2 Izabal, Mixed spp. 1419 953 -Snedaker 1970 Guatemala fallow 3 Izabal, Mixed spp. 2287 751 13.9 1.1 9.( 7.1 6.2 Snedaker 1970 Guatemala fallow 4 Guarin, Mixed spp. 4839 495 -Ewel 1968 (in Gamble Colombia fallow et al.) 4 Darien, Mixed spp 3794 594 0.7 8.3 8.0 1.8 Golley et al. 1968 Panama fallow 4 Izabal, Mixed spp 2711 845 13.3 0.8 9.2 6.2 5.4 Snedaker 1970 Guatemala fallow 5 Belgian Mixed spp 7668 563 12.5 0.7 7.9 ( 7.8 ) Bartholomew et al. Congo fallow 1953 5 Izabal, Mixed spp 3667 766 13.1 (.9 9.3 6.6 5.3 Snedaker 1970 Guatemala fallow 6 Izabal, Mixed spp 4467 778 27.6 2.6 19.3 20.9 6.1 Snedaker 1970 Guatemala fallow 6 Darien, Mixed spp 4245 655 -0.7 7.8 17.2 2.5 Golley et al. 1968 Panama fallowd 6 Benin, Acioa barteri 4609 419f 5.2 0.4 2.8 2.9 2.8 Nye and Greenland South fallow 1960 Nigeria 7 Izabal, Mixed spp 4666 1083 Snedaker 1970 Guatemala fallow 8 Belgian Mixed spp 12168 538 12.0 0.7 7.9 ( 8.7 ) Bartholomew et al. Congo fallow 1953 8 Izabal, Mixed spp 6589 1219 Snedaker 1970 Guatemala fallow 9 Izabal, Mixed spp 724