Positive associations between the cushion plant Arenaria polytrichoides (Caryophyllaceae) and other alpine plant species increase with altitude in the Sino-Himalayas

Question: Does the facilitative effect of cushion plants increase with elevation as a result of increases in environmental harshness? Does this hypothesis apply in the Sino-Himalayan Mountains? Location: Lakaka Pass on the Baima Snow Mountains (28°20′N, 99°05′E), SW China. Methods: We evaluated the spatial association of several plant species with the cushion plant Arenaria polytrichoides (Caryophyllaceae) at two elevations (4500  m and 4700 m) in the study site and monitored temperature, moisture and nutritional status of soil beneath and outside the cushions. Results: While 14 species grow more frequently associated with the cushions at the higher elevation, at the lower site only three species were positively associated with cushions. Eleven of the species that occurred at both elevations changed their spatial association from neutral or negative with cushions at the lower site to positive at the higher elevation site. Substrate temperatures were rather similar between the cushions and areas of bare ground. Cushions maintained higher moisture than areas of bare ground at both elevations. Soils beneath cushions contained significantly more available nitrogen and potassium compared to open areas at the higher elevation. Conclusions: Our results show that facilitation by A. polytrichoides cushions increases with elevation in the Sino-Himalayan region. This facilitation effect of A. polytrichoides cushions is probably due to the improved nutrient availability provided by cushion plants in the higher elevation, and these conditions probably permit increased plant recruitment, growth and survival.

[1]  Hang Sun,et al.  The Bracts of Saussurea velutina (Asteraceae) Protect Inflorescences from Fluctuating Weather at High Elevations of the Hengduan Mountains, Southwestern China , 2009 .

[2]  L. Cavieres,et al.  Spatial patterns in cushion-dominated plant communities of the high Andes of central Chile: How frequent are positive associations , 2008 .

[3]  L. Cavieres,et al.  Facilitation of the non-native Taraxacum officinale by native nurse cushion species in the high Andes of central Chile: are there differences between nurses? , 2007 .

[4]  J. Travis,et al.  Facilitation in plant communities: the past, the present, and the future , 2007 .

[5]  P. Marquet,et al.  Ecosystem engineering facilitates invasions by exotic plants in high‐Andean ecosystems , 2007 .

[6]  F. Pugnaire,et al.  Facilitation in Plant Communities , 2007 .

[7]  Ángela Sierra-Almeida,et al.  Microclimatic Modifications of Cushion Plants and Their Consequences for Seedling Survival of Native and Non-native Herbaceous Species in the High Andes of Central Chile , 2007 .

[8]  H. Ouyang,et al.  Interactions between root andshoot competition among fourplant species inanalpine meadow ontheTibetan Plateau , 2006 .

[9]  Aníbal Pauchard,et al.  Nurse effect of the native cushion plant Azorella monantha on the invasive non-native Taraxacum officinale in the high-Andes of central chile , 2005 .

[10]  J. Boettinger,et al.  Canopy vs. soil effects of shrubs facilitating tree seedlings in Mediterranean montane ecosystems , 2005 .

[11]  J. Iriondo,et al.  Patch Dynamics and Islands of Fertility in a High Mountain Mediterranean Community , 2004 .

[12]  Tara A. Forbis.  Seedling demography in an alpine ecosystem. , 2003, American journal of botany.

[13]  M. Arroyo,et al.  Nurse effect of Bolax gummifera cushion plants in the alpine vegetation of the Chilean Patagonian Andes , 2002 .

[14]  C. Lortie,et al.  Positive interactions among alpine plants increase with stress , 2002, Nature.

[15]  P. Choler,et al.  FACILITATION AND COMPETITION ON GRADIENTS IN ALPINE PLANT COMMUNITIES , 2001 .

[16]  F. Davies,et al.  Effect of potassium on drought resistance of Hibiscus rosa-sinensis cv. Leprechaun: Plant growth, leaf macro- and micronutrient content and root longevity , 2001, Plant and Soil.

[17]  M. Aizen,et al.  Species associations and nurse plant effects in patches of high‐Andean vegetation , 1999 .

[18]  Terry V. Callaghan,et al.  The balance between positive and negative plant interactions and its relationship to environmental gradients : a model , 1998 .

[19]  J. Stöcklin,et al.  Seed rain, seedling establishment and clonal growth strategies on a glacier foreland , 1996 .

[20]  W. Bowman,et al.  Physiological and production responses of plant growth forms to increases in limiting resources in alpine tundra: implications for differential community response to environmental change , 1995, Oecologia.

[21]  M. Bertness,et al.  Positive interactions in communities. , 1994, Trends in ecology & evolution.

[22]  James C. Schardt,et al.  CONSTRAINTS OF NUTRIENT AVAILABILITY ON PRIMARY PRODUCTION IN TWO ALPINE TUNDRA COMMUNITIES , 1993 .

[23]  J. Macmahon,et al.  Alpine Seedling Establishment: The Influence of Disturbance Type , 1990 .

[24]  I. Bradbury,et al.  The Effect of Phosphorus and Potassium on Transpiration, Leaf Diffusive Resistance and Water-Use Efficiency in Sitka Spruce (Picea sitchensis) Seedlings , 1977 .

[25]  F. Maestre,et al.  On the relevance of facilitation in alpine meadow communities: An experimental assessment with multiple species differing in their ecological optimum , 2008 .

[26]  R. Callaway.  Positive interactions and interdependence in plant communities , 2007 .

[27]  Ángela Sierra-Almeida,et al.  Positive interactions between alpine plant species and the nurse cushion plant Laretia acaulis do not increase with elevation in the Andes of central Chile. , 2006, The New phytologist.

[28]  M. Arroyo,et al.  Positive associations between the cushion plant Azorella monantha (Apiaceae) and alpine plant species in the Chilean Patagonian Andes , 2004, Plant Ecology.

[29]  C. Körner,et al.  High elevation pioneer plants are sensitive to mineral nutrient addition , 2002 .

[30]  P. D. Körner.  Alpine Plant Life , 1999, Springer Berlin Heidelberg.