Here's the report
---- Minecraft Crash Report ----
// Everything's going to plan. No, really, that was supposed to happen.

Time: 12/10/14 5:42 PM
Description: Unexpected error

java.lang.ArrayIndexOutOfBoundsException: 5
at mods.natura.blocks.trees.WillowBlock.func_149691_a(WillowBlock.java:47)
at net.minecraft.block.Block.func_149673_e(Block.java:554)
at net.minecraft.client.renderer.RenderBlocks.func_147793_a(RenderBlocks.java:8227)
at net.minecraft.client.renderer.RenderBlocks.func_147736_d(RenderBlocks.java:5993)
at net.minecraft.client.renderer.RenderBlocks.func_147784_q(RenderBlocks.java:4247)
at net.minecraft.client.renderer.RenderBlocks.func_147742_r(RenderBlocks.java:4268)
at net.minecraft.client.renderer.RenderBlocks.func_147805_b(RenderBlocks.java:257)
at net.minecraft.client.renderer.WorldRenderer.func_147892_a(WorldRenderer.java:181)
at net.minecraft.client.renderer.RenderGlobal.func_72716_a(RenderGlobal.java:1553)
at net.minecraft.client.renderer.EntityRenderer.func_78471_a(EntityRenderer.java:1187)
at net.minecraft.client.renderer.EntityRenderer.func_78480_b(EntityRenderer.java:1011)
at net.minecraft.client.Minecraft.func_71411_J(Minecraft.java:989)
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:887)
at net.minecraft.client.main.Main.main(SourceFile:148)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:134)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)

A detailed walkthrough of the error, its code path and all known details is as follows:

-- Head --
Stacktrace:
at mods.natura.blocks.trees.WillowBlock.func_149691_a(WillowBlock.java:47)
at net.minecraft.block.Block.func_149673_e(Block.java:554)
at net.minecraft.client.renderer.RenderBlocks.func_147793_a(RenderBlocks.java:8227)
at net.minecraft.client.renderer.RenderBlocks.func_147736_d(RenderBlocks.java:5993)
at net.minecraft.client.renderer.RenderBlocks.func_147784_q(RenderBlocks.java:4247)
at net.minecraft.client.renderer.RenderBlocks.func_147742_r(RenderBlocks.java:4268)
at net.minecraft.client.renderer.RenderBlocks.func_147805_b(RenderBlocks.java:257)
at net.minecraft.client.renderer.WorldRenderer.func_147892_a(WorldRenderer.java:181)
at net.minecraft.client.renderer.RenderGlobal.func_72716_a(RenderGlobal.java:1553)
at net.minecraft.client.renderer.EntityRenderer.func_78471_a(EntityRenderer.java:1187)

-- Affected level --
Details:
Level name: MpServer
All players: 1 total; [EntityClientPlayerMP['Prodkid'/314, l='MpServer', x=-129.47, y=95.94, z=-76.92]]
Chunk stats: MultiplayerChunkCache: 110, 110
Level seed: 0
Level generator: ID 00 - default, ver 1. Features enabled: false
Level generator options:
Level spawn location: World: (111,96,-53), Chunk: (at 15,6,11 in 6,-4; contains blocks 96,0,-64 to 111,255,-49), Region: (0,-1; contains chunks 0,-32 to 31,-1, blocks 0,0,-512 to 511,255,-1)
Level time: 86883413 game time, 87319623 day time
Level dimension: 0
Level storage version: 0x00000 - Unknown?
Level weather: Rain time: 0 (now: false), thunder time: 0 (now: false)
Level game mode: Game mode: creative (ID 1). Hardcore: false. Cheats: false
Forced entities: 16 total; [EntityItemFrame['entity.ItemFrame.name'/478, l='MpServer', x=-193.50, y=155.50, z=-79.06], EntityItemFrame['entity.ItemFrame.name'/479, l='MpServer', x=-193.50, y=155.50, z=-76.94], EntityMinecartEmpty['entity.MinecartRideable.name'/476, l='MpServer', x=-185.50, y=153.50, z=-55.50], EntityMinecartEmpty['entity.MinecartRideable.name'/474, l='MpServer', x=-187.50, y=153.50, z=-57.50], EntityMinecartEmpty['entity.MinecartRideable.name'/475, l='MpServer', x=-186.25, y=153.50, z=-56.75], EntityBoomerang['entity.weaponmod.boomerang.name'/472, l='MpServer', x=-85.16, y=82.16, z=-73.47], EntityHat['unknown'/3020, l='MpServer', x=-129.47, y=95.94, z=-76.92], EntityCow['Cow'/473, l='MpServer', x=-128.63, y=100.00, z=-18.69], EntityChicken['Chicken'/470, l='MpServer', x=-114.44, y=90.37, z=-85.84], EntityBoomerang['entity.weaponmod.boomerang.name'/471, l='MpServer', x=-81.94, y=83.08, z=-72.75], EntityTrail['unknown'/3046, l='MpServer', x=-129.47, y=95.94, z=-76.92], EntityPlayerChild['unknown'/2974, l='MpServer', x=-129.59, y=95.62, z=-77.03], EntityClientPlayerMP['Prodkid'/314, l='MpServer', x=-129.47, y=95.94, z=-76.92], EntityItem['item.item.egg'/485, l='MpServer', x=-74.69, y=87.30, z=-101.69], EntityChicken['Chicken'/484, l='MpServer', x=-73.09, y=94.00, z=-101.09], EntityPig['Pig'/483, l='MpServer', x=-120.19, y=103.00, z=-14.72]]
Retry entities: 0 total; []
Server brand: cauldron,craftbukkit,mcpc,fml,forge
Server type: Non-integrated multiplayer server
Stacktrace:
at net.minecraft.client.multiplayer.WorldClient.func_72914_a(WorldClient.java:373)
at net.minecraft.client.Minecraft.func_71396_d(Minecraft.java:2432)
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:916)
at net.minecraft.client.main.Main.main(SourceFile:148)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:134)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)

-- System Details --
Details:
Minecraft Version: 1.7.10
Operating System: Windows 7 (amd64) version 6.1
Java Version: 1.7.0_71, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 2246495680 bytes (2142 MB) / 2680160256 bytes (2556 MB) up to 14316732416 bytes (13653 MB)
JVM Flags: 3 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx15360m -XX:MaxPermSize=256m
AABB Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
FML: MCP v9.05 FML v7.10.25.1188 Minecraft Forge 10.13.0.1188 37 mods loaded, 36 mods active
mcp{9.05} Minecraft Coder Pack Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
FML{7.10.25.1188} Forge Mod Loader Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
Forge{10.13.0.1188} Minecraft Forge Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
ivtoolkit{1.0.1} IvToolkit Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
OpenEye{0.6} OpenEye Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
AIRI{3.0.0-1.7.10} AIRI Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
AliensVsPredator{3.9.14-1.7.10} AliensVsPredator Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
asielib{0.2.11} asielib Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
iChunUtil{4.0.0} iChunUtil Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
BackTools{4.0.0} BackTools Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
BiblioCraft{1.7.5} BiblioCraft Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
Mantle{1.7.10-165.4bc3343} Mantle Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
Natura{2.2.0} Natura Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
BiblioWoodsNatura{1.3} BiblioWoods Natura Edition Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
CarpentersBlocks{3.3.3} Carpenter's Blocks Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
chisel{2.1.0.0} Chisel Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
customnpcs{1.7.10b} CustomNpcs Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
wonderfulwands{1.4.1} Cyano's Wonderful Wands Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
props{1.10} Decocraft Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
flansmod{4.5.1} Flan's Mod Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
Hats{4.0.1} Hats Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
headcrumbs{1.2.7} Headcrumbs Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
mod_LATL{1.9} Lamps and Traffic lights Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
LightBridgesAndDoors{0.2.0} kris91268's Light Bridges and Doors Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
mod_MedievalWars{0.1} Medievalwars Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
cfm{3.4.4} §9MrCrayfish's Furniture Mod Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
rivalrebels{1.7.10A} Rival Rebels Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
mod_RoadWorks{2.0} Roadworks Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
SaintsCore{0.8} Saintscore Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
mod_Saintspack{0.8} Saintspack Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
secretroomsmod{@Version@} The SecretRoomsMod Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
statues{2.1.3} Statues Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
TrailMix{4.0.0} TrailMix Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
Trapcraft{v2.2.1a} Trapcraft Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
weaponmod{v1.14.3} Balkon's WeaponMod Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
yegamolchattels{1.1} Ye Gamol Chattels Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
asielibcore{} AsieLib CoreMod Unloaded->Disabled
Mantle Environment: Environment healthy.
Launched Version: 1.7.10-Forge10.13.0.1188
LWJGL: 2.9.1
OpenGL: Intel(R) HD Graphics Family GL version 3.1.0 - Build 8.15.10.2455, Intel
GL Caps: Using GL 1.3 multitexturing.
Using framebuffer objects because OpenGL 3.0 is supported and separate blending is supported.
Anisotropic filtering is supported and maximum anisotropy is 16.
Shaders are available because OpenGL 2.1 is supported.

Is Modded: Definitely; Client brand changed to 'fml,forge'
Type: Client (map_client.txt)
Resource Packs: []
Current Language: English (US)
Profiler Position: N/A (disabled)
Vec3 Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
Anisotropic Filtering: Off (1)

Do you get this crash only with natura and Mantle installed? also try updating forge while you are at it.

Try updating Forge to a relatively new build.

for the SMP are you using cauldron or forge?

cauldron. I realized i was running an old version of natura and mantle so I updated and it still occured. Heres the crash report. Same issue.
http://pastebin.com/xkhAgVqn

Still occurred with the latest build of forge. Seems to only happen in multiplayer and with all tree leaves.

Does this happen with both graphics settings?

It occurs in both fancy and fast loading. On any type of leaves.

Have you tried with just a forge server not cauldron?