Effects Of Canopy Coverage And Altitude On The Growth, Palatability And Nutrition Of Staple Food Bamboo For Giant Pandas

The giant panda (Ailuropoda melanoleuca) is one of the world’s most treasured endangered herbivore species, the main food of the endangered giant panda is totally dependent on a few understory bamboos, and its dietary specialization is one of the impacts to exacerbate the endangerment. Fargesia denudata is one of the dwarf bamboos and it is the main selection of feeding by giant pandas in Wanglang Nature Reserve in the northwest Sichuan, China. Palatability and nutrition of dwarf bamboos play the key roles in an evaluation of forage, however, effects on the palatability and nutrition to the giant pandas in various circumstance conditions are not clear yet. To characterize the effects of canopy coverage and altitude on growth, palatability and nutrition of Fargesia denudata, three altitudes (2380,2776 and 3170 m) and three canopy coverage (closed canopy, gap edge and gap center) were established, and bamboo shoots (BS), annual stems (AS), annual leaves (AL), perennial stems (PS), and perennial leaves (PL) of Fargesia denudata were sampled.The densities, withered shoots, height, basal diameter, leaf area, biomass, tannins, total phenols, crude fibre, crude protein, crude fat and crude ash, et al. were analyzed with observation of environmental gradient in this paper. This study could make a contribution to establish corridors of habitat patches and the conservation effectiveness of the giant panda reserves and the main results indicat:(1) It had no significant difference between closed canopy and gap edge in bamboo shoots, but both of the canopy coverages were higher than gap center, and altitude had no significant influence in bamboo shoots and withered bamboo shoots. The highest bamboo density, height and basal diameter was in closed canopy(176.00±8.00 plant·m-2), the gap edge of altitude 2776 m (312.21±10.50 cm)and the gap center of altitude 2776m (1.01±0.05 cm), respectively. Leaf area (4.44±0.42 cm2) was the highest in closed canopy of 2776 m, it explained that bamboos would increase leaves to gain more light in the dark environment. The biomass of bamboos were stems> leaves, of which the highest biomass of stem and leaf were under the gap center in altitude 3170 m (65.35±11.14 g·plant-1)and 2776 m (10.25±0.99 g·plant-1), respectively. Furthermore, the bamboo biomass of per area was highest in altitude 2776 m, it had no significant difference between the gap edge and gap center, and both of the canopy coverages were significantly higher than closed canopy. Therefore, it was benefit for the growth of bamboos in a mid-altitude and appropriate light condition.(2) The moisture of bamboo in shoots was more than stems and leaves, and the highest growth rate was 71.22±0.72% under the closed canopy of altitude 2776 m. The concentration of tannins were lower in young bamboo organs than older, the concentration of tannins in different organs were bamboo shoots< stems< leaves, perennial leaves> annual leaves, and the tannin concentrations increased with age. The lowest tannin concentrations of bamboo shoots were 0.13±0.01 mg·g-1, the highest concentration of perennial leaves were 1.41±0.18 mg·g-1, and the tannin concentrations in annual leaves of Fargesia denudata growed in the closed canopy was 181.10% lower than the gap center. The concentration of total phenols in different organs were also bamboo shoots< stems< leaves, the lowest concentration of total phenols of bamboo shoots were 1.00±0.27 mg·g-1, and the highest total phenol concentrations of perennial leaves were 3.54±0.19 mg·g-1. Meanwhile, it revealed that the total phenol concentrations of five organs growed in the altitude 2776 m were the lowest. The concentration of crude fibres in different organs were bamboo shoots< leaves< stems, and it increased with age. The lowest crude fibre concentration was 28.74±0.45% under the gap edge of altitude 2776 m, and it had no significant difference between closed canopy and gap edge. Furthermore, the interaction between altitude and canopy coverage had obvious relation in the tannin concentrations of all the organs, the crude fibres and total phenols in young organs of Fargesia denudata.(3) The crude protein, crude fat and crude ash had the same regular, leaves> shoots> stems, young> old, but the cellulose of bamboos was different from others, the cellulose of stems> leaves> shoots. The annual leaves of bamboos under the gap edge of altitude 2776 m, it had the highest crude protein (7.73±1.09a%), crude fat (2.78±0.15%) and crude ash (3.28±0.16%), respectively. But the cellulose (35.09±2.25%) of perennial stems was the highest under the gap edge of altitude 2776 m. It had more obvious relation between altitude and the nutritional concentrations than canopy coverage and the nutritional concentrations. Moreover, the interaction between altitude and canopy coverage had the significant effects on the young bamboos, example of bamboo shoots.In all, the concentrations of tannins and total phenols were both lower in mid-altitude (2776 m) and closed canopy, which showed a better palatability, and the concentrations of crude protein, crude fat, crude ash and cellulose were higher in closed canopy or gap edge and altitude 2776 m, which showed a better nutritional value.