Effect of Grazing on Restoration of Endemic Dwarf Pine (Pinus Culminicola Andresen Et Beaman) Populations in Northeastern Mexico
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Effect of Grazing on Restoration of Endemic Dwarf Pine (Pinus culminicola Andresen et Beaman) Populations in Northeastern Mexico Javier Jime´nez,1,2 Enrique Jurado,1 Oscar Aguirre,1 and Eduardo Estrada1 Abstract lished: (1) seedlings protected from cattle plus small mam- A pilot experiment designed to test the effect of cattle, mals, (2) seedlings protected from cattle, and (3) seedlings small mammals, and elevation on the success of refores- with free access to cattle and small mammals. Seedling sur- tation of an endemic dwarf pine species in northeastern vival was approximately 50% in (1) after 4 years, but there Mexico was implemented. Pinus culminicola (Andresen et were no surviving seedlings with free access to cattle. Ele- Beaman) grows only in four high peaks in the Sierra Ma- vation in general did not account for variation in survival. dre Oriental and is under pressure from grazing, wildfires, Seedling growth was poor during the 4 years, which implies and human activities such as mining, road development for that seedlings remain susceptible to grazing and trampling timber extraction, and telecommunication and aerial navi- by cattle and small mammals. The implications for a large- gation devices. We planted and monitored 2-year-old seed- scale restoration program are discussed. lings at three elevations within the natural distribution range of this species at Cerro El Potosı´ in Nuevo Leo´n, Key words: cattle exclosure, grazing, Pinus culminicola, Mexico. At each elevation three treatments were estab- rehabilitation, seedling. Introduction above sea level and is the highest peak in Northern Restoration of endemic species should be done with Mexico (Garcı´a & Gonza´lez 1991). Due to its geographi- knowledge of the species biology as well as an understand- cal isolation and peculiar geological strata, it has many ing of the community organization (Gross et al. 1989; rare, endemic and endangered plant species (Rzedowski Bowles & Whelan 1994; Teketay 1997). Endangered spe- 1978). The vegetation types at the summit of Cerro El cies recovery is always difficult, and biologists need to use Potosı´ are alpine and subalpine prairie, Pinus culminicola the best tools, skills, and experience available. Hence, the (Pinaceae) matorral (shrubland), mixed forest of Pinus knowledge of the development of spatial pattern of the culminicola–P. hartwegii (Pinaceae), mixed forest of Pinus species in the communities under restoration allows for hartwegii–P. culminicola, mixed forest of Abies vejari a better understanding of the interactions between ani- (Pinaceae)–Pseudotsuga menziesii (Pinaceae)–Pinus hart- mals and plants in the ecosystem (Dale 2000). wegii–P. ayacahuite (Pinaceae), and forests of Pinus hart- Fragmentation and habitat loss are the main threats to wegii. Endemic and rare plant species in the area include the survival of most endangered species; hence, the in- Pinus culminicola, Juniperus sabinoides (Cupressaceae), clusion of dynamic processes of plant communities in res- Lupinus cacuminis (Fabaceae), Hackelia leontis (Boragi- toration plans would result in lower habitat loss and naceae), Erigeron potosinus (Asteraceae), Senecio hinto- fragmentation (Falk et al. 1996; Pickett et al. 1997; Tucker niorum (Asteraceae), and Arracacia schneideri (Apiaceae) & Murphy 1997; Huxel & Hastings 1999; Jime´nez et al. and the endangered plant species Ageratina potosina 1999). Lesica and Allendorf (1999) argue that a primary (Asteraceae), Astranthium beamanii (Asteraceae), Castilleja goal of restoration is the establishment of long-term viable bella (Scrophulariaceae), Stachys vulnerabilis (Lamia- populations that will restore ecosystem functions and pro- ceae), Poa mulleri (Poaceae), Potentilla leonine (Rosa- cesses, prevent erosion, and protect biological diversity. ceae), Trifolium schneideri (Fabaceae), Viola galeanaensis The protected natural area ‘‘Cerro El Potosı´’’ is located (Violaceae), and Arracacia. tolucensis (Apiaceae) (Mc- in the Sierra Madre Oriental, in the southern part of the Donald 1990; Garcı´a&Gonza´lez 1991). Some animal spe- State of Nuevo Leo´n, Mexico; it has an elevation of 3,670 m cies in the area are also considered endangered (Golden Eagle [Aquila chrysaetos], Maroon-fronted Parrot [Rhyn- chopsitta terrisi], Harris’ (Bay wing) Hawk [Parabuteo uni- 1 Facultad de Ciencias Forestales, Universidad Auto´ noma de Nuevo Leo´ n, cinctus], American Gold Finch [Carduelis tristis], Black bear Apartado Postal 89 67700 Linares, Nuevo Leo´ n, Me´xico [Ursus americanus eremicus]) or endemic (Painted Redstart 2 Address correspondence to J. Jime´nez, email [email protected] [Myioborus pictus], Carmen mountain shrew [Sorex milleri], Ó 2005 Society for Ecological Restoration International Flat headed myotis bat [Myotis planiceps], Coyote [Canis MARCH 2005 Restoration Ecology Vol. 13, No. 1, pp. 103–107 103 Effect of Grazing on Dwarf Pine Restoration latrans mearnsi]) (Guzma´n 1998; Garcı´a et al. 1999; Jime´nez Experiment et al. 2002). The experiment was laid out in December 1997 at three Dwarf pine (P. culminicola) was described by Andresen elevations and vegetation types: (1) high elevation at and Beaman (1961) as a new species endemic to Cerro El 3,500 m in Pinus culminicola matorral, (2) intermediate Potosı´. Later the same authors described the distribution elevation at 3,400 m in P. culminicola–P. hartwegii for- of the species as a total of 106 ha (Beaman & Andresen est, and (3) lower elevation at 3,300 m in P. hartwegii– 1966). In 1975 the species was also found in three other P. culminicola forest. At each elevation three square plots sites of the same Sierra (Sierra La Marta and Sierra La of 625 m2 were established for planting 2-year-old dwarf Viga in the state of Coahuila, and Cerro Pen˜aNevadain pine seedlings that had been grown in a seedling nursery. Nuevo Leo´n) with similar spatial patterns and altitudinal Three treatments were made for each plot: (1) small mam- distribution ranges to those determined for Cerro El Potosı´ mal plus cattle exclusion (chicken wire), (2) cattle exclu- (Riskind & Patterson 1975). In 1978 wildfires at Cerro El sion (barbed wire), and (3) free range. For each treatment Potosı´ burned 34% of the dwarf pine population (Garcı´a at each elevation, 110 seedlings were planted at a density 1989). During the past four decades, a reduction of the area of approximately 2 seedlings in each 10 m2. At the time formerly covered by dwarf pine has been observed, due to of planting, seedlings were approximately 100 mm tall and human impact involving timber extraction, road building, 5 mm in stem diameter. and land use change for the development of telecom- munication and aerial navigation infrastructure. A manga- nese mine was opened and later abandoned in the region Monitoring (Jime´nez et al. 1996). Recently (1998), several wildfires All planted seedlings were labeled so they could be drastically reduced the area formerly covered by dwarf distinguished from any naturally established seedlings. We pine at Cerro El Potosı´. Currently, only 30 ha of frag- monitored seedlings annually from November 1998 to mented dwarf pine area exist at Cerro El Potosı´, and these November 2001. Plant survival was determined by check- include many old trees with low seed production that are ing the position of each planted seedling. Stem diameter subject to cattle grazing (Jime´nez et al. 1999). The species and total height were measured for all surviving seedlings. is now considered endemic and is subject to special protec- To test whether grazing and elevation affected seedling sur- tion (Diario Oficial de la Federacio´ n 2000). There are no vival, we used a two-way analysis of variance (ANOVA). studies of P. culminicola populations in the other moun- To test whether elevation affected seedling growth in tains where it occurs; unfortunately these areas are not pro- diameter and height, we used one-way ANOVA. tected and are also subjected to grazing and wildfires. In spite of the uniqueness of the species, there are few published studies of the ecology of dwarf pine. Garza et al. (2002) described a high fungal diversity (51 species of mac- Results romycetes from 19 families and 42 genera) associated with P. culminicola. Aguirre et al. (2001) described the vegeta- Seedling Survival tion types of the area and examined the stem density pat- Both elevation and exclosure had an effect on seedling tern of P. culminicola and P. hartwegii and found the survival (p = 0.0016) for the duration of this experiment. former to be more abundant at higher elevations. In this Seedling mortality was high in all treatments, with only study we tested restoration techniques for P. culminicola, about 50% of seedlings surviving 4 years after planting in through replanting and the use of herbivore exclosures in the areas excluded for cattle and small mammals (Fig. 1). the protected natural area Cerro El Potosı´, within its natu- Seedling survival was significantly higher in areas ex- ral distribution range. cluded from both cattle and small vertebrates than in areas with cattle exclosures only. Survival was much lower where no exclosure was used (Fig. 1). Many seedlings in the free-range treatment were grazed and trampled, al- Methods though this did not happen uniformly to all seedlings. This implies that grazing is low and erratic in the area. How- Study Area ever, 2 years after planting, more than 80% of seedlings The study site is located at the top of the protected natural had died at the highest elevation. By the fourth year after area Cerro El Potosı´, in the south of the State of Nuevo planting, no free-range seedlings had survived at any ele- Leo´ n, Mexico (lat 24°320N, long 100°130W). This moun- vation. Where small mammals were not excluded, seed- tain is within the Sierra Madre Oriental range, between lings were found to be nibbled and occasionally had the Gulf Coastal Plain and the Mexican High Plateau. The broken stems. This damage was also present, although mountain top is exposed to high winds for most of the rarely, in the area excluded for cattle plus small mammals, year.