The CADE (Competition and Diversity Experiment) was established in January 2018, representing the tropical-subtropical forest ecotone in southern China. It contains two sub-experiments: a competition experiment, which is designed to measure the niche overlap and fitness difference between tree species, and a BEF experiment, focusing on species diversity effect on a variety of ecosystem functions. The main goal of CADE is to explore the coexistence mechanisms underlying the biodiversity-ecosystem functioning (BEF).

Aerial view of CADE (November 2020)

Design
Competition experiment
The Competition experiment includes 4 species and consists of 6 blocks (48 m × 28 m), with 84 plots (4 m × 4 m) in each block. Following the response surface design, every plot contains 2 species at four different densities (25, 36, 64, and 100 saplings per plot) and five abundance proportions (A: B = 1:0, 3:1, 1:1, 1:3, 0:1). The tree saplings were planted at the equal planting distance of 0.8, 0.67, 0.5, and 0.4 m in the densities of 25, 36, 64, and 100 saplings per plot, respectively.

Response surface design.

Layout of the Competition experiment.

BEF experiment
The BEF experiment consists of 8 blocks (32 m × 20 m), with 40 plots (4 m × 4 m) in each block. Each plot was planted with 64 tree saplings of 1, 2, 4 or 8 species. In each block, a monoculture for each of the 8 species, 18 different 2-species mixtures, 12 different 4-species mixtures and 2 plots with all 8 species were planted. Species combinations in 2 and 4-species plots were randomly selected. The saplings were planted at an equal planting distance of 0.5 m in each plot.

Layout of the BEF experiment.

Site characteristics

name	CADE-BEF	CADE-Competition
location	Heerkou
former land use	Cropland, planted with rice, peanut and vegetable	Cropland (block 1-4) and orange groves (block 5 and 6)
altitude (m)	50
soil type	Red Sandy Loam, Ferrosol (FAO)
area (m2)	5102	8064
no of plots	320	504
plot size (m2)	16	16
no of trees planted	20 480	27 300
planting date	2017
diversity variables	species richness	-
diversity gradient	1, 2, 4, 8 sp.	-
size species pool	8	4
species pool	Erythrophleum fordii, Pinus massoniana, Castanopsis fissa, Castanopsis carlesii, Schima superba, Elaeocarpus sylvestris, Ilex rotunda, Cinnamomum camphora	Erythrophleum fordii, Pinus massoniana, Castanopsis fissa, Castanopsis carlesii
contact person	Chengjin Chu (储诚进)

Research

The CADE was designed to answer the following questions (but not limited to, actually):

1. How do neighbour competition and soil nutrient affect the growth and mortality of the trees?
2. How does species diversity affect ecosystem functions, such as primary production, herbivory damage and soil microbial community structure?
3. Do species coexistence determinants (niche difference and fitness difference) affect the direction and magnitude of the BEF relationships?

Extra information

For more information on the CADE, send an e-mail to the contact person or explore the publications.

• Messier C, Bauhus J, Sousa-Silva R, Auge H, Baeten L, Barsoum N, Bruelheide H, Caldwell B, Cavender-Bares J, Dhiedt E, Eisenhauer N, Ganade G, Gravel D, Guillemot J, Hall JS, Hector A, Hérault B, Jactel H, Koricheva J, Kreft H, Mereu S, Muys B, Nock CA, Paquette A, Parker JD, Perring MP, Ponette Q, Potvin C, Reich PB, Scherer-Lorenzen M, Schnabel F, Verheyen K, Weih M, Wollni M, Zemp DC (2021) For the sake of resilience and multifunctionality, let's diversify planted forests! Conservation Letters e12829 - https://doi.org/10.1111/conl.12829
• Shen Z, Li Y, Chen Z, Zhang B, Zhong Y, Xi N, Zhu X, Lin W, He Q, Luo W, Liu S, Wei W, Liu H, Jiang Y, Wang W, Chen D, Xiao J, Tang H, Li B, Chu C, Wang Y (2021) Neighborhood effects and environmental variables drive sapling growth in a young subtropical tree plantation. Forest Ecology and Management 483(1): 118929 - https://doi.org/10.1016/j.foreco.2021.118929
• Shen Z, Li Y, Chen Z, Xi N, Luo W, He Q, Liu S, Lin W, Zhu X, Fang S, Wang Y, Li B, Chu C (2020) Species identity and initial size rather than neighborhood interactions influence survival in a response-surface examination of competition. Frontiers in Plant Science 11: 1212 - https://doi.org/10.3389/fpls.2020.01212

Aerial view of CADE (November 2020)