e-journal

Causes for the unimodal pattern of biomass and productivity in alpine grasslands along a large altitudinal gradient in semi-arid regions

---

Abstract
Questions: How can we understand the limitations to plant growth at high altitudes? Our aimwas to test the hypotheses that for alpine grasslands along a large altitudinal gradient in semi-arid regions, plant growth is mainly limited by drought at low altitudes but by low temperature at high altitudes, resulting in a
unimodal pattern of biomass and productivity associated with an optimal combination of temperature and precipitation. Such knowledge is important to understanding the response of alpine ecosystems to climate change.
Location: We conducted a 5-yr livestock exclosure experiment along the southfacing slope of the Nyaiqentanglha Mountains, central Tibetan Plateau.
Methods: We measured above- and below-ground biomass, species richness, leaf d13C and water potential, and related climate and soil variables across 42 fenced and unfenced quadrats near seven HOBO weather stations along the slope. The vegetation changed from alpine steppe-meadow at 4390–4500 m to alpinemeadow at 4600–5210 m.
Results: Total above- and below-ground biomass across fenced and unfenced quadrats increased with increasing altitude up to 4950–5100 m, and then decreased above 5100 m. Altitudinal trends in leaf d13C and water potential of dominant species also showed a unimodal pattern corresponding to that of vegetation biomass. Total above- and below-ground biomass as well as sedge above-ground biomass all showed a quadratic relationship with mean temperatures and the ratio of growing season precipitation (GSP) to
5 °C accumulated
temperature (AccT; R2 = 0.830.88, P < 0.001). In general, above- and below-ground biomass increased with increasing water availability when the GSP/AccT ratio was lower than the threshold level of 0.80–0.84, but
decreased when the GSP/AccT ratio was higher than this threshold level. No significant relationship was found between residuals of above-ground biomass and species richness after removing the effects of climate factors on both stand variables.
Conclusions: The results support our hypotheses, further suggesting a threshold ofwater limitation that is consistent with themodel prediction over the Tibetan Plateau. Species richness per se appears to weakly affect community-level productivity. The response of alpine grasslands to climate warming may vary with altitude because of altitudinal shifts in factors limiting plant growth.

Keywords: Alpine grassland; Biomass; Functional groups; Leaf water potential; Net primary productivity;
Plant–climate interactions; Species richness

---

Ketersediaan

Tidak ada salinan data

Informasi Detail

Judul Seri

Journal of Vegetation Science

No. Panggil

-

Penerbit

: International Association for Vegetation Science., 2013

Deskripsi Fisik

Journal of Vegetation Science 24 (2013) 189–201

Bahasa

English

ISBN/ISSN

-

Klasifikasi

-

Tipe Isi

-

Tipe Media

-

Tipe Pembawa

-

Edisi

-

Subjek

PERTANIAN.

Info Detail Spesifik

-

Pernyataan Tanggungjawab

agus

Versi lain/terkait

Lampiran Berkas

Komentar

---

Anda harus masuk sebelum memberikan komentar