1. Biodiversity and climate gradients. Latitudinal gradient in the Andean western slope (Lima-Piura). Reserved Forest Area Irma Franke
Pitajo de Ceja Blanca, Ochthoeca leucophrys,
Ave common in cloud forests of the western slope dry
is considered one of the most important causes of the great biological richness in Andean region is the compression of climatic ranges along climatic gradients ( Braun et al. 2002). In addition, d entered the large climatic gradients, variable terrain and slope and aspect of the slopes and the microrelief create a diverse topography that interacts with solar radiation, wind and precipitation, creating a multitude of habitats called "geodiversity" .
Due to its geographical location and topography, the Peruvian territory is dominated by climatic gradients, both latitudinal and altitudinal. Altitudinal gradients tend to have greater influence than latitudinal gradients in biodiversity that is developed along it. However, l to western slopes of the Andes from central Peru and the north end is a region that stands out because both climatic gradients, altitudinal and latitudinal are striking.
Although s and have been several analysis of the distribution of organisms that live along climatic gradients (Pearson & Pearson, Ralph 1978, Patterson et al. 1996, Patterson et al. 1998), the main characteristics of these gradients are rarely reported. For this region of Peru, l to western slopes of the Andes from central Peru and the north end especially in the band between 2500 and 3000 m , where are located the dry forests of fog, it has been analyzed main climatic gradients of variables and the distribution of organisms, allowing for interesting comparisons.
Latitudinal gradient in Climate Western Slope Andina (Lima-Piura).
climate variables that most clearly represent the climatic gradients of precipitation and temperature. As these variables are presented in the western slopes of the Andes from Lima to Piura?.
Precipitation
The climatic latitudinal gradient of precipitation that occurs in Slope western Andean between the northwest on the border with Ecuador and central Peru is especially strong in three areas:
1) Annual Total Precipitation . The Total Annual Rainfall decreases markedly from north to south following the pattern of a sigmoid curve, from amounts exceeding 1000 mm in the extreme north to values \u200b\u200bbetween 150 and 500 mm in central Peru. The reduction is significantly more pronounced in the coastal strip at high altitudes (Figure 1) (Valencia 1990). Following the outline of 2800 m altitude, where are located the dry forests of fog, the total annual rainfall decreases from 1400 mm near the border with Ecuador to about 300 mm to 12 degrees latitude, Zárate Forest location (Franke 1994).
Figure 1. Annual precipitation of 215 weather stations located in Western Slope the Andes of Peru (Valencia 1990).
2) Seasonality. Although the full extent of the wettest time gradient corresponds to the months from December to April (Fig. 2), altitudinal strip between 2500 and 3000 m the proportion of annual precipitation falls during these months increases 60% in northern Peru to 80% in central Peru (Franke 1994). As a result, northern dry season is quite short and not very steep, becoming more extensive and marked to the south. North of Ancash pattern Annual precipitation is usually bimodal, with a maximum rainfall peak in March and a secondary peak in September / October.
Figure 2. Gradient of the seasonality of climate in the area between 2200 and 3000 m in altitude between Piura and Lima (Franke 1994).
3) Niño (ENSO). The impact of El Niño (ENSO) is strong throughout this region of Peru, although the intensity of their effect varies. In the north of Peru to about 7 degrees south latitude, annual rainfall has marked variations between years, mainly due to this phenomenon. Is the area where its effects are more profound. In central Peru the total annual rainfall is more constant. Only affected by more intense ENSO events, although there are quite dry years (Valencia 1990).
Average Annual Temperature.
In general, temperatures in the western slopes of the Andes are lower than would be expected in these latitudes (Johnson 1976). The average annual temperature has its highest values \u200b\u200bin the bottom of the slope of the far north and decreases towards higher altitudes and towards the south. The temperature gradients are far less drastic than the rainfall gradient and as a result both gradients, altitudinal and latitudinal are properly represented by straight lines. The altitudinal gradient is relatively strong and similar in all the area between Piura and Lima, consisting of a reduction of 0.4 º C each 100 m altitude. The latitudinal gradient is less marked 0.17 º C per degree of latitude (Valencia 1990). Following the outline of 2800 m, where they are located in the cloud forests dry, the average annual temperature decreases 9.6 ° C at the north end to 8.4 º C in central Peru.
As a result of latitudinal variations in relation to rainfall in northern organisms not only have more water in the south, but this is available for a more extensive year and is quite variable from year to year. In contrast, in relation to temperature, the regime that varies little latitudinal are subject to a certain altitude.
Latitudinal Biodiversity Gradient in Western Slope Andina (Lima-Piura).
The sharp climatic gradient of the western slope between Lima and Piura is clearly a gradient in organisms that live along it. In the dry cloud forest, located between 2500 and 3000 m along this gradient, both studies have been conducted in various aspects of vegetation (Valencia 1990) and birds (Franke 1991, 1994) showing the correlation between environmental gradients and agencies.
cloud forest vegetation dry
A feature of the vegetation of the dry cloud forests of the western slope that clearly reflects the precipitation gradient is related to its structure. 4 layers can be recognized along the gradient. However, the maximum height of emergent trees reaching 22 m in the forests of north and decreases to 12 m in the forests of central Peru. The main canopy also decreases approximately 13 m in the north 7 m in central Peru. In addition, northern main canopy is generally continuous but not dense, whereas in the forests of central Peru is usually more dense but not continuous. The basal layer is richer south, due to the more open nature of these forests. Lianas and epiphytes are more numerous in the north. Structural latitudinal variations of the forests are linked to variations in species composition, with dominance of different species in the forests of North and South (Valencia 1990).
Figure 3. Latitudinal variation in the structure of the cloud forest's dry western slopes of the Andes between Piura and Lima (Valencia 1990).
Strata: a = emergent trees, b = main canopy, c = shrubs and small trees and d = basal layer.
Figure 4. Profile Huamba forest, Piura (4 º 41'S).
Clm= Clusia aff. multiflora ; Gy1= Gynoxis sp1; Hedyosmum scabrum ; Il1= Ilex sp1; La2=Lauraceae sp2; Loh= Lomatia hirsuta ; Mlo= Meliosma sp1; Mic= Miconia cajanumana ; ; My1= Myrcianthes sp1; Ms2= Myrsine sp2; Pa1= Palicourea sp1; Poo= Podocarpus oleifolius ; Sy2= Symplocos sp2; Sy1= Symplocos sp1; Te1= Ternstroemia sp1; Vas= Vallea stipularis ; Wer= Weinmannia reticulata (Valencia 1990) .
Figure 5. Profile Forest Chinaman, Lambayeque (6 º 06'S).
Caa = Carica aprica ; Clf = Clusia flaviflora; incarum Cti = Citronella ; Dei = Delostoma integrifolium, Mic = cajanumana Miconia, Myrsine MS1 = sp1; My2 = Myrcianthes sp2; MY3 = Myrcianthes sp3, PI3 = Piper sp3, Ra2 = Randia sp2, SO3 = Solanum sp3; Ty1 = THYMELACEAE sp1, VI1 = Viburnum sp1 (Valencia 1990).
Figure 6. Profile Forest Zárate, Lima (11 ° 55'S).
Bef = Berberis flexuosa; Cid = Citharexylum dentatum; Dus = Duranta sprucei ; MyQ = Myrcianthes quinqueloba ; Gold = Oropanax oroyanus; amblophyllum Soa = Solanum.
Avifauna of cloud forests dry.
The number of bird species in dry cloud forests decreases markedly from north to south, from 102 species in the northwest to 56 species in central Peru (Figure 7). This decrease from north to south and follows a sigmoid pattern is correlated significantly (r = 0.8723, P> 0.001) with decreasing precipitation gradient (Franke 1991, 1994). Without doubt, this pattern is due to the direct effect of precipitation on forest characteristics resulting from the latitudinal pattern of precipitation.
Figure 7. Latitudinal variation in number of bird species in the dry forests of fog. a) Total number of birds, b) birds with distribution ranging from Ecuador to the south (Franke 1991).
The avifauna of the dry forests of fog is made up of two main groups of birds. The first group of birds is distributed from Ecuador to the south. The second group of birds endemic species. The distribution of these birds identified five areas of replacement of taxa: 1) Tambo River area in Piura, 2) Call and Chugur area and the deep valley of the river Chancay (high Reque River) in Cajamarca, 3) deep valleys Jequetepeque river valleys and Chicama, 4) The Santa River valley in Ancash and 5) Pativilca River Valley. (Figure 8)
Figure 8. Latitudinal distribution of nine related groups of birds living in the cloud forests are replaced dry along the western slopes of the Peruvian Andes from Lima to Piura.
Ann = Anairetes nigrocristatus; reguloides Anr = Anairetes , Op = Ochthoeca piurae , Ol = Ochthoeca leucophrys , Cap = Cranioleuca antisiensis palamblae ; Cab = Cranioleuca antisiensis baroni ; Caz = Cranioleuca antisiensis zaratensis ; ACP = Aglaeactis curpipennis parvulus; Acc = Aglaeactis curpipennis parvulus; Lpc = Lepthastenura pileata cajabambae; Lpp = Lepthastenura pileata pileata; Dh = Diglossa humeralis; Db = Diglossa brunneiventris; Ass = Atlapetes Seebohm; An = Atlapetes Nation; Sn = nigroceps Saltator, Saltator Sa = aurantiirostris; If = Synallaxis elegantior; Sz = Synallaxis Zimmerer. Areas Shaded = main areas of replacement of species or subspecies (Franke 1991, 1994).
replacement areas of taxa correspond to the deepest valleys and / or comprehensive Western Slope. these valleys are barriers to have produced enough isolation between populations of birds of the western slopes that led to the development of distinct species or subspecies?
References
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Franke, I. 1991. Disjunct bird distributions along the west slope of the
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Pearson, O.P. & C. Pearson-Ralph (1978) The diversity and abundance of vertebrates along an altitudinal gradient in Peru . Memorias del Museo de Historia Natural "Javier Prado" (Perú) 18: 1-97
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