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Abundancia y riqueza de especies de plntulas en proximidad al bosque en los rompevientos de Caitas, Costa Rica
Abundance and species richness of seedlings in proximity to forest in windbreaks of Caitas, Costa Rica
Windbreaks are important to agricultural landscapes as well as biodiversity. They may preserve crops and livestock, harbor a diverse seed bank, as well as serve as corridors for forest animals. I examined species richness and density of seedlings within the understory of windbreaks
connected to a forest. It was expected that closer proximity to forests would have higher species richness and seedling densities. A total of 220 seedlings were observed spanning across 35 different species and 23 families. The plant families of Lauraceae, Myrtaceae, and Solanaceae
were found to have the greatest number of species diversity. Viburnum costaricanum, family Caprifoliaceae, and Conostegia xalapensis, family Melastomataceae, were found to have the two highest abundances of individual species. It was also observed that bird dispersed species, and medium growth tree species were the most abundant. Linear regressions confirmed that species
richness increases with closer proximity to the forest, as well as abundance with closer proximity to the forest. This study suggests that attaching windbreaks to forest increases seedling diversity and abundance on the agricultural landscape. The study also proposes that there may be a limit to
the distance that animals travel into the windbreaks, which forms a gradient of seedling growth. Therefore, the location of windbreaks is of vital importance.
Los rompe-vientos son importantes tanto para la agricultura como para la biodiversidad. Estos pueden preservar la agricultura y la ganadera, albergar un banco diverso de semillas, as como servir de corredores para los animales del bosque. Examin la riqueza de especies y la densidad de las plntulas en el sotobosque de los rompe-vientos conectados al bosque. Se espera que con una mayor cercana a los bosques vaya a ver una mayor riqueza de especies y densidad de plntulas. Un total de 220 plntulas fueron observadas, ests perteneciente a 35 especies diferentes en 23 familias. Las familias Lauraceae, Myrtaceae y Solanaceae presentaron una mayor diversidad. Viburnum costaricanum (Caprifoliaceae) y Conostegia xalapensis (Melastomastaceae) presentaron la mayor abundancia. Tambin se observ que las especies dispersadas por aves y las especies de rboles de tamao mediano son las ms abundantes. Las regresiones lineales confirman que la riqueza de especies aumenta con la proximidad al bosque, as como la abundancia es mayor cerca del bosque. Este estudio sugiere que los rompe-vientos conectados al bosque aumentan la diversidad y abundancia de las plntulas en paisajes agrcolas. El estudio adems propone que puede haber una distancia lmite en la cual los animales viajan en el rompe-vientos, lo que forma un gradiente de crecimiento de plntulas. Por lo tanto, la ubicacin de los rompe-vientos es de suma importancia.
Text in English.
Windbreaks, shelterbelts, etc.
Rompe vientos, corta vientos, etc
Diversidad de especies
Tropcical Ecology Fall 2010
Ecologa Tropical Otoo 2010
t Monteverde Institute : Tropical Ecology
Abundance and species richness of Seedlings in proxim ity to forest in windbreaks of C aitas, Costa Rica Rebecca Brey Student University of Wisconsin Madison ABSTRACT Windbreaks are important to agricultural landscapes as well as biodiversity. They may p reserve crops and livestock, harbor a diverse seed bank, as well as serve as corridors for forest animals. I examined species richness and density of seedlings within the understory of windbreaks connected to a forest. It was expected that closer proximity to forest would have higher species richness and seedling densities. A total of 220 seedlings were observed spanning across 35 different species and 23 families. The plant families of Lauraceae, Myrtaceae, and Solanaceae were found to have the greatest nu mber of species diversity. Viburnum costaricanum, family Caprifoliaceae, and Conostegia xalapensis family Melastomataceae, were found to have the two highest abundances of individual species. It was also observed that bird dispersed species, and medium gr owth tree species were the most abundant. Linear regressions confirmed that species richness increases with closer proximity to the forest, as well as abundance with closer proximity to the forest. This study suggests that attaching windbreaks to forest i ncreases seedling diversity and abundance on the agricultural landscape The study also propose s that there may be a limit to the distance that animals travel into the windbreaks whic h form s a gradient of seedling growth. Therefore, the location of windbr eaks is of vital importance. RESUMEN Los corta vientos son importantes tanto para la agricultura como para la biodiversidad. Estos pueden preservar cultivos y ganado, albergar un banco diverso de semillas, as como servir de corredor para animales. Exami n la riqueza de especies y densidad de plntulas en el sotobosque de corta vientos conectados al bosque. Un total de 220 plntulas se observaron, ests pertenecientes a 35 especies diferentes en 23 familias. Las familias Lauraceae, Myrtaceae y Solanacea e presentaron una mayor diversidad. Viburnum costaricanum (Caprifoliaceae) y Conostegia xalapensis (Melastomastaceae) presentarn la mayor abundancia. Se observ adems que las especies dispersadas por aves, y especies de rboles de tamao mediano son la s ms abundantes. Regresiones lineales confiran que la riqueza de especies aumenta con la proximidad al bosque, as como la abundancia es mayor cerca del bosque. Este estudio sugiere que corta vientos conectados al bosque aumentan la diversidad y abundan cia de plntulas en paisajes agrcolas. El estudio adems propone que puede haber una distancia lmite en la cual los animales viajan en el corta vientos, lo que forma un gradiente de crecimiento de plntulas. Por lo tanto, la ubicacin de los corta vien tos es de suma importancia.
INTRODUCTION Human modifications to the environment are undeniable. A net loss of approximately 7 11 million km 2 has occurred in the last 300 years mainly for timber extraction and agricultural expansion (Foley et a l 2005). C urrently one of the largest terrestrial biomes is croplands and pastures, making up nearly 40% of land surface; even more, human activities comprise one third to one half of global ecosystem production (Foley et a l 2005). This means that one third to one half of the land transformations and usage is due to activities humans deem necessary, such as farming, logging, etc. In other words, human The structure and functioning of ecosystems are changed by human land use, as we ll as the interactions of the ecosystem with other systems such as water, atmosphere, and adjacent land (Vitousek et a l 1997). The Monteverde region, which includes Caitas, has experienced a variety of land transformations (Burlingame 2000). Land has sw itched between forests, pastures, and croplands several times throughout the last 6 0 years (Burlingame 2000). Currently Monteverde is perceived as a farming and conservation community (Griffith et al. 2000). Strong winds during the dry season can have dam aging effects on farm productivity, such as soil erosion, pasture and crop stress, which can indirectly decreases milk and crop yields on a farm (Burlingame 2000). To combat this, projects centering on the creation of windbreak s were started about 25 years ago (Harvey 2000 b ). One main purpose windbreaks serve to benefit agriculture is by protecting cattle and crops from the strong winds that could otherwise be damaging or cause injury (Nielson & DeRosier 2000). Over the course of these projects, more than a million trees have been planted in windbreaks, and over 70% of farms participated in the projects (Griffith et a l 2000). Windbreaks also have other benefits, such as doubl ing as natural fencing and provid ing refuge by acting as corridors to birds, insec ts, and small mam mals which are often known to be popular pollinators and seed dispersers of species in these regions (Harvey 2000 a,b; Brandle et al. 2004). These corridors may also connect diversity preserve biodivers ity by lowering rates of species extinction (Hobbs 1992). Windbreaks also help to increase the diversity of the farms by serving as protection, habitats, and stepping stones for plant and animal species (Schroth et al. 2004). Diversity is an important fac tor in agricultural systems for more than just food production. It helps recycle nutrients, regulate microclimates, water processes; diversity also may suppress unwanted species, and remove harmful chemicals (Altieri 1999). In 1995 Harvey surveyed windbrea ks for species richness and abundance of seeds and seedlings in the understory of windbreaks in the Monteverde region. She found that windbreaks can enhance the seed bank by attracting seed dispersing birds from the forest in comparison to pastures Howev er she also found that seed disposition in proximity to the forest did not have a clear pattern (Harvey 2000b). Her study was one of the first to explore the effectiveness of windbreaks in preserving biodiversity; my study was created as a likeness to Har examined species richness and density of seedlings located within the understory of windbreaks connected to forest. Since Harvey surveyed the seedlings/windbreaks at a young age (6 years), I thought it would be interesting to examine the n ow older windbreaks for richness and density.
METHODS Seedlings were examined in three different windbreaks connected to a forest fragment on the Bella Cruz farm in Caitas, Costa Rica. Square plots were made of PVC piping with sides of 0.85 meters. B eginning where the windbreak me t the forest plots were placed down the windbreak at 10 meter intervals (Figure 1) FIGURE 1. Diagram of my study site at the Bella Cruz farm in Caitas, Costa Rica The vertical lines represent the windbreak. The numbers 1, 2, and 3 to the right of the lines correspond to the number of the windbreak. The numbers trailing down the number, lower numbers are closer to the forest. Within each plot, w oody seedling observations were made I exclud ed grasses, vines, lianas, and other non woody seedlings; my goal was to survey the tree species within the windbreaks because t he trees have a greater importance for biodiversity and regeneration properties of windbreaks. Woody plant samples were collecte d and numbered, with the abundance of each recorded. Samples were later taken to a Monteverde, Costa Rica plant expert for identification. The n umber of samples taller than 0.85 meters was also noted. A total of 64 plots were examined, 17 in the first win dbreak, 20 in the second, and 27 in the third. Number of plots per windbreak varied with the length of the windbreak, as plots were placed down the entire length. RESULTS Species Richness Combining the three windbreaks there was a net of 220 seedlings obs erved spanning 35 different species. Lauraceae was the family that had the largest number of different species, six total. The next families found to have a large number of different species were Myrtaceae and Solanaceae with four and three respectively (T able 1) The two most common individual species were Viburnum costaricanum of the family Caprifoliaceae with 35 % and Conostegia xalapensis
of the family Melastomataceae with 14 % of the samples. No other individual species made up more than 9 % with the majority composing less than 5 % each. TABLE 1. S pecies of seedlings collected in three windbreaks connected to a small forest frag ment Caitas, Costa Rica. Growth Form abbreviations are as follows: Tl= Large tree/Canopy, Tm=Medium tree/subcanopy, Ts= Small tree/understory, E=Epiphyte, S=Shrub. Disperser abbreviations are as follows: B=Bird, CH=Bat, EX=Explosive, G=Gravity, M=Mammal, W=Wind. Other Observations Of the 35 presumed different species of seedlings observed, 33 were identified to species. Fr om species data it was determined that 65 % of the species are dispersed by only birds, but 71 % can be dispersed by birds, while the remaining 29 % dispersed by other methods such as exploding wind, mammals, or bats (Table 1, Fig. 4 ). Birds disperse Viburn um costaricanum and Conostegia xalapensis the two most commonly observed species. Species also varied in their growth forms. Tree seedlings made up the greatest abundance growth form with 94 % Of the various types of trees, medium/sub canopy trees were t he most common seedlings followed by lar ge/canopy tree seedlings (Table 1, Fig. 5 ).
FIGURE 4. Percentages of Dispersal Modes for observed seedling species. FIGURE 5. Percentage distribution of seedling species growth forms.
Highest species richness wa s found within 50 meters from the forest with 22 different species. Moving away from the forest, 17 different species were found in the plots 51 100 meters from the forest, 11 different species were found 101 150 meters from the forest and 15 species wer e found in the plots 151 270 meters from the forest Richness decreased significantly (F=11.7506, df=1 62 p = 0.001) as distance f rom the forest increased (Fig. 2 ). FIGURE 2. Distribution of species richness per plot as distance from the windbreaks co nnection to the forest increases. Sixteen percent of the change in species richness can be accounted for by the distance from the forest. Canitas, Monteverde, Costa Rica.
Abundance Of the 220 seedlings observed, 60 % of them were found within 100 meters of where the windbreak connected to the forest. The remaining 40 % were found between 101 meters and 270 meters. Abundance of seedlings decreased significantly (F=15.8, df=1 62 p = 0.0002) as the distance f rom the forest increased (Fig. 3 ). FIGURE 3. Distri bution of seedling abundance as distance from the windbreaks connection to the forest increases. Twenty percent of the change in species richness can be accounted for by the distance from the forest Caitas, Monteverde, Costa Rica. DISCUSSION The Laurac eae family possibly had the largest number of individual species because it is a large family whose highest abundance and diversity (69 species in Monteverde ) occurs commonly in the cloud forests of Costa Rica (Haber et a l 2000). Therefore since it has a large occurrence in the area already, it is more likely to have high seedling diversity and/or abundance in addition Another reason the Lauraceae family may have high diversity in windbreaks is because nearly all the species are dispersed by birds (Haber et al. 2000). This is important because birds often use windbreaks for perches and refuge (Nielson & DeRosier 2000). Myrtaceae and Solanaceae are close seconds because they are commonly dispersed by bird species as well (Haber et al. 2000). Myrtaceace als o has relatively high diversity (31 species in Monteverde) in tropical forests
especially those at mid elevations (Haber et al. 2000), such as tropical lower montane wet forests in Caitas, Costa Rica. However Viburnum costaricanum of the family Caprifo liaceae and Conostegia xalapensis of the family Melastomataceae made up the largest percent of seedlings. This may be because they are both distributed by a large variety of birds. Conostegia xalapensis has a small fruit that contains a large amount of sma ll see ds this high amount of seeds increases dispersal capabilities, and may account for its increased frequency of occurrence within windbreaks (Haber et al. 2000 Zuchowski 2007). Viburnum costaricanum also has a small fruit however there is only one se ed per fruit, therefore dispersal is still dictated by its small fruit size; also, it is possible that the seed has greater germination capabilities which again increa ses overall seedling abundance (Haber et al. 2000). Another reason these two species wer e the most abundant could be due to their capability to be used as natural fencing (Haber et al. 2000). This multiple functionality increases the benefits to farmers, and it may be possible that these species were planted at some point for lower growth wi ndbreak and natural fencing, and have since thrived. Natural fencing was observed in the windbreaks, however the trees were not typed to see if they were Viburnum costaricanum or Conostegia xalapensis Greater species richness and seedling abundance incre asing with increased proximity to the forest may be explained by windbreak usage. It has been observed that birds use windbreaks as corridors. They may be optimal foraging habitats for insectivorous birds because of their large edges, or as was investigate d in this study, a refuge where fruit and seedeaters may consume their meal (Nielson & DeRosier 2000). However while birds are undeniably using windbreaks as corridors, if they are coming from the forest, it is reasonable to presume that there may be a l imit as to how far the birds travel. This theory may also be applicable to other seed distributors such as rodents. Animals may only leave the forest to a certain extent therefore creating a gradient, which results in higher species richness closer to th e forest and since there is higher traffic at the connection between windbreak and forest there is a greater likelihood that seeds will be distributed there whether as a result of be ing dropped, defecated, or deposited in other ways ; therefore, resultin g in higher seedling abundance with closer proximity to the forest. Medium/sub canopy tree seedlings are most common in windbreaks possibly because they are better adapted to a variety of conditions. Windbreaks have a multitude of different climatic condi tions. The seedlings must be tolerant to whatever conditions arise. Possible extreme conditions may include sun, shade, strong winds, extreme rain, and dry weather In the forest, sub canopy trees are adaptive to their conditions, in that they grow in the shade, and do what they need to there, however if a light gap appears, they benefit more. They are also tailored to function under the new conditions the light gap brings such as wind, rain, and increased drying. In conclusion, t his study found highest a bundance and species richness with closer proximity to forest, which suggests that attaching windbreaks to forest increases species richness and abundance of seedlings The study also proposes that there may be a limit to the distance that animals travel i nto the windbreaks which allows for the creation of a gradient of seedling growth. Therefore the location of windbreaks is of vital importance to conservation and farmers.
ACKNOWLEDGEMENTS Special thanks to my advisor Pablo Allen for his guidance and assistance throughout the entire project, as well as the Bella Cruz family for allowing me to use the windbreaks on their farm. A tremendous thank you goes out to Willow and Bill Zuchowski and their knowledge of Monteverdian plants for identifying my samp les. Many thanks also to Moncho for his patience and helpfulness with my many questions. LITERATURE CITED Altieri M.A. 1999. The ecological role of biodiversity in agroecosystems. Agriculture, Ecosystems & Environment, 74: 19 31. Brandle J.R., L. Hodge s, and X.H. Zhou. 2004. Windbreaks in North American agricultural systems. Agroforestry Systems, 61: 65 78. Burlingame, L.J. 2000. Conservation in the Monteverde Zone: Contributions of Conservation Organizations. In: Monteverde, N.M. Nadkarni and N.T. Whe elwright, ed. Oxford University Press, Oxford, NY, pp. 365 366. Foley, J.A., R. DeFries, G.P. Asner, C. Barford, G. Bonan, S.R. Carpenter, F.S. Chapin, M.T. Coe, G.C. Daily, H.K. Gibbs, J.H. Helkowski, T. Holloway, E.A. Howard, C.J. Kucharik, C. Monfreda, J.A. Patz, I.C. Prentice, N. Ramankutty, and P.K. Snyder. 2005. Global Consequences of Land Use. Science, 309: 570 574. Griffith K., D. Peck, and J. Stuckey. 2000. Agriculture in Monteverde: Moving Toward Sustainability. In: Monteverde, N.M. Nadkarni and N .T. Wheelwright, ed. Oxford University Press, Oxford, NY, pp. 397. Haber, W.A., W. Zuchowski, and Erick Bell. 2000. An Introduction to Cloud Forest Trees Monteverde, Costa Rica. Mountain Gem Publications, Monteverde de Puntarenas, Costa Rica, pp. 82, 96, 1 56. Harvey, C.A. 2000 a Colonization of Agricultural Windbreaks of Forest Trees Effects of Connectivity and Remnant Trees. Ecological Applications, 10: 1762 1773. Harvey, C.A. 2000 b Windbreaks E nhance Seed Dispersal into Agricultural Landscapes in Montev erde, Costa Rica. Ecological Applications, 10: 155 173. Hobbs, R.J. 1992. The Role of Corridors in Conservation: Solution or Bandwagon?. Tree. Vol. 7 no.11: 389. Neilson, K. and D. DeRosier. 2000. Windbreaks as corridors for birds. In: Monteverde, N.M. Nad karni and N.T. Wheelwright, ed. Oxford University Press, Oxford, NY, pp. 448 450. Schroth, G., G.A.B. da Fonseca, C.A. Harvey, H.L. Vasconcelos, C. Gascon, and A.N. Izac. 2004. Introduction: The Role of Agroforestry in Biodiversity Conservation in Tropical Landscapes. In: Agroforestry and Biodiversity Conservation in Tropical Landscapes, G. Schroth, G.A.B. da Fonseca, C.A. Harvey, C. Gascon, H.L. Vasconcelos, and A.N. Izac, ed. Island Press, Washington, DC, Pp. 1. Vitousek, P.M., H.A. Mooney, J. Lubchenco, Science, 277: 494 499. Zuchowski, W. 2007. Tropical Plants of Costa Rica. Zona Tropical, San Jose, Costa Rica, pp. 55.