To evaluate the success of minimal versus maximal restoration intervention, the performance of recruits and transplants was assessed. To this end, performance of 15 native tree species was predicted using life-history, their origin (recruits or transplants) and 12 plant functional traits.
Overall 15 species recruited or planted, pioneers had higher performance than non-pioneer.Transplant shock in terms of survival and height growth rates was overcomeafter 5 years probably as a result of increases in diameter growthrates.
Maxtree Plant Models Vol 15
Tree species are divided in three groups to give recommendation for restoration: (1) Species in the Good recruiters group do not need to be transplanted; if seed sources are not close, we recommend direct seeding (i.e., Albizia purpusii, Cedrela odorata, Cecropia obtusifolia). (2) Species in the Good transplants group show very low or nil recruitment; they should be transplanted (i.e., Ochroma pyramidale, Ficus yoponensis, Cojoba arborea). (3) Species in the Poor transplants group should be transplanted but once a canopy has developed (i.e., Amphitecna tuxtlensis, Brosimum alicastrum, Bernoullia flammea).
Para evaluar el éxito de la intervención mínima en comparación con la máxima se midió el desempeño de reclutas y trasplantes. Con este fin se buscó explicar el desempeño de 15 especies de árboles nativos mediante su historia de vida, su origen (reclutas o trasplantes) y 12 caracteres funcionales.
Incluyendo las 15 especies evaluadas, las pioneras tuvieron mejor desempeño que las no-pioneras. El stress del trasplante terminó después de 5 años, probablemente debido al incremento en diámetro.
Las especies han sido divididas en tres grupos para dar recomendaciones sobre su uso en restauración: (1) Las especies del grupo Buenos reclutas no necesitan ser plantadas; si no hay fuentes de semillas cercanas se recomienda introducirlas por siembra directa (i.e., Albizia purpusii, Cedrela odorata, Cecropia obtusifolia). (2) Las especies del grupo Buenos trasplantes mostraron bajo o nulo reclutamiento, estas especies deben ser trasplantadas (i.e., Ochroma pyramidale, Ficus yoponensis, Cojoba arborea). (3) Las especies en el grupo Malos trasplantes pueden ser plantadas una vez que exista un dosel (i.e., Amphitecna tuxtlensis, Brosimum alicastrum, Bernoullia flammea).
Restoration actions may include different degrees of intervention to recover the structure and function of degraded tropical rain forest. Minimal intervention includes actions to stop disturbance so natural succession may take place whereas maximal intervention involves the establishment of restoration plantings (SER 2004, Morrison & Lindell 2011, Martínez-Garza et al. 2016). Many studies have quantified the natural recovery of vegetation of the rain forest after disturbance (e.g. Uhl 1987, Martínez-Ramos & García-Orth 2007) whereas other studies have evaluated the performance of tree species in plantings (e.g. Davidson et al. 1998, Hooper et al. 2002, Carpenter et al. 2004, dos Santos et al. 2006, Douterlungne et al. 2010). However, we are not aware of any study that compares the performance of naturally regenerating seedlings (i.e. recruits) and transplants in the same restoration setting to evaluate the success of minimal versus maximal restoration intervention.
Under minimal restoration intervention, natural succession takes place and pioneer species may establish. Pioneer tree species are those that colonize naturally in early successional environments, due to the high dispersal capacity of their small seeds and their rapid growth rates associated to high availability of resources (Swaine & Whitmore 1988, Whitmore 1989). Given that restoration plantings are expensive, pioneers are frequently selected because of high survival in such conditions (Davidson et al. 1998, dos Santos et al. 2006). On the other hand, late-successional non-pioneer species do not naturally recruit in early successional environments: they have large seeds dispersed by animals that do not cross open areas (Westoby 1998, & Howe 2003). However, some non-pioneers may perform as well as pioneers when transplanted to restoration areas in the tropics (Hooper et al. 2002, Carpenter et al. 2004) and they may arrive at older restoration plantings (De la Peña et al. 2013). Given that pioneer species naturally establish in early successional habitats, it is expected that they outperform non-pioneer species early in restoration settings. However, as succession takes place, may pioneers continue to outperform non-pioneers irrespective of their origin, recruited or transplanted?
When nursery-raised seedlings are transplanted, they may experience stress known as trans- plant shock. Transplant shock is defined as low survival and growth of seedlings transplanted to the field compared to naturally recruited seedlings (Close et al. 2005), usually due to the low contact between the roots of the seedlings and the soil (Burdett 1990). Transplant shock had been recorded in temperate forest (see for example, Bernier 1993); however, in the rain forest of Chiapas, Mexico, transplanted individuals realized higher survival than recruits established after direct seeding (Douterlungne et al. 2010). Transplant shock has never been evaluated for tropical tree species exposed to severely adverse environmental conditions of degraded areas; there, smaller recruits may be more affected by adverse soil conditions than larger transplants even after experiencing transplant shock.
Planning for restoration plantings in tropical rain forests involve the challenge of selecting appropriate species from around 53,000 species (Slik et al. 2015). Species selected for restoration plantings are usually those with high survival and growth rates in early successional environments (Vázquez-Yanes et al. 1999); however, evaluation of performance have been done for few species, mainly for forestry use (Evans & Turnbull 2004). Survival and growth of species in early successional environments may be predicted by their functional traits; a functional trait is a measurable property of the organisms that strongly influences its performance (McGrill et al. 2006). For example, in the cloud forest, transplanted species with large leaves and high dry matter content (Saldaña-Acosta et al. 2009) or in the rain forest, transplanted species with deep canopies (Martínez-Garza et al. 2013b) showed higher performance in restoration plantings. On the other hand, tree species that recruit naturally early in succession have functional traits associated to high dispersal capacity, as small seed size (Lohbeck et al. 2013). Also, seed size is related to establishment: larger seeds have higher establishment capacity (Coomes & Grubb 2003, Poorter et al. 2008). Plant strategies of both, transplants and naturally recruited trees include multiple functional traits (multivariate plant strategies; Weiher et al. 1999, Violle et al. 2007) which may coincide, so both successfully establish in early successional environments irrespective of their origin. Alternatively, individual functional traits that predict performance may be different among transplanted and naturally recruited trees, therefore individual traits may better predict performance of tree species than multivariate plant strategies.
Experimental settings. A 3 8 grid of 24 fenced plots (30 30 m, each plot separated by 35 m) was established along an altitudinal gradient in a 12-ha pasture of the agricultural colony of Ruiz Cortines in August 2006, adjacent to the LTBS. Barbed wire fences were held up by living poles of Gliricidia sepium (Jaq.) Kunz (Fabaceae) every two meters. Plots on the grid are within 500-1,200 m of the edge of the LTBS and 90 m from the nearby secondary forest. Standing trees within the 12 ha were cut in 2006 (Howe et al. 2010). From September to December 2006, 144 seedlings of each of 24 native tree species were transplanted to 16 of the 24 plots (see details in Martínez-Garza et al. 2013a). Seedlings were 4-7 months old at the time of planting, and their average height was 17.8 cm (range 5-40 cm across species). The entire area for the plantings was 0.92 ha (16 plots), and the area where natural recruitment could occur was 1.38 ha, includ- ing eight additional plots where no plantings were established.
Data collection. For this study, we selected 15 species following three criteria: 1) given that individuals were considered replicates, only species with more than 17 individuals across all plots were selected; 2) transplanted species that were also recorded as recruited and 3) a similar number of pioneer and non-pioneer species. We selected 11 species transplanted and eight registered as naturally recruited; four species had individuals from both origins (Table 1). A priori distinction between pioneer and non-pioneer species was based on the literature (Martínez-Ramos 1985, Popma et al. 1992, Ibarra-Manríquez & Oyama 1992). This study includes two censuses: June 2007 and 2011; at each census, we measured height and diameter at the base of all individuals transplanted and recruited of the 15 tree species selected. Growth rates were calculated as the difference between the first measurement and the last, divided by the number of months elapsed. Performance of all tree species transplanted (Martínez-Garza et al. 2013b) and richness and abundance of recruits (de la Peña-Domene et al. 2013) has been evaluated before. The present study adds an explicit comparison of survival and growth rates of recruits with a pertinent subset of the transplanted species (see above) and their functional traits.
Data Analysis. Performance of pioneer and non-pioneer species.- Two one-way analyses of variance (ANOVA) were carried out to test for differences in diameter and height growth between pioneer and non-pioneer species. The life history category was the independent variable. The proportion of survivors for each species at all the plots (seven pioneer species and eight non-pioneer species) was analyzed with a General Linear Model (GLM). For the analysis of growth rates, individuals were used as replicates (N = 319 pioneers and N = 277 non-pioneers): given that they were growing in mixed stands at each plot under variable soil conditions, we consider the performance of each plant to be independent. 2ff7e9595c
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